10-K

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 10-K

(Mark One)

For the fiscal year ended December 31, 2023

Commission File Number 001-39460

KYMERA THERAPEUTICS, INC.

(Exact name of Registrant as specified in its Charter)

200 Arsenal Yards Blvd., Suite 230Watertown, Massachusetts 02472

(Address of principal executive offices) (Zip Code)

Registrant’s telephone number, including area code: (857) 285-5300

Securities registered pursuant to Section 12(b) of the Act:

Title of each class Trading Symbol(s) Name of each exchange on which registered

Common Stock, par value $0.0001 per share KYMR The Nasdaq Global Market

Securities registered pursuant to Section 12(g) of the Act: None

Indicate by check mark if the Registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act. Yes ☒ NO ☐

Indicate by check mark if the Registrant is not required to file reports pursuant to Section 13 or 15(d) of the Act. YES ☐ No ☒

Indicate by check mark whether the Registrant: (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the Registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. Yes ☒ NO ☐

Indicate by check mark whether the Registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter period that the Registrant was required to submit such files). Yes ☒ NO ☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

Large accelerated filer ☒ Accelerated filer ☐

Non-accelerated filer ☐ Smaller reporting company ☐

Emerging growth company ☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Indicate by check mark whether the registrant has filed a report on and attestation to its management’s assessment of the effectiveness of its internal control over financial reporting under Section 404(b) of the Sarbanes-Oxley Act (15 U.S.C. 7262(b)) by the registered public accounting firm that prepared or issued its audit report. ☒

If securities are registered pursuant to Section 12(b) of the Act, indicate by check mark whether the financial statements of the registrant included in the filing reflect the correction of an error to previously issued financial statements. ☐

Indicate by check mark whether any of those error corrections are restatements that required a recovery analysis of incentive-based compensation received by any of the registrant’s executive officers during the relevant recovery period pursuant to §240.10D-1(b). ☐

Indicate by check mark whether the Registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act). YES ☐No ☒

The aggregate market value of the registrant’s common stock, $0.0001 par value per share, held by non-affiliates of the registrant, based on the last sale price of the Common Stock at the close of business on June 30, 2023, was $1,012.8 million. Shares of common stock held by each executive officer and director and by each other person who may be deemed to be an affiliate of the registrant have been excluded from this computation. The determination of affiliate status for this purpose is not necessarily a conclusive determination for other purposes.

The number of shares of Registrant’s Common Stock outstanding as of February 16, 2024 was 61,111,678.

DOCUMENTS INCORPORATED BY REFERENCE

Portions of the registrant’s Proxy Statement for its 2024 Annual Meeting of Stockholders, which the registrant intends to file with the Securities and Exchange Commission not laterthan 120 days after the registrant’s fiscal year ended December 31, 2023, are incorporated by reference into Part III of this Annual Report on Form 10-K

Table of Contents

Page

PART I

Item 1. Business 3

Item 1A. Risk Factors 59

Item 1B. Unresolved Staff Comments 108

Item 1C. Cybersecurity 109

Item 2. Properties 109

Item 3. Legal Proceedings 109

Item 4. Mine Safety Disclosures 109

PART II

Item 7A. Quantitative and Qualitative Disclosures About Market Risk 125

Item 8. Financial Statements and Supplementary Data 125

Item 9A. Controls and Procedures 132

Item 9B. Other Information 134

Item 9C. Disclosure Regarding Foreign Jurisdiction that Prevents Inspections 134

PART III

Item 10. Directors, Executive Officers and Corporate Governance 135

Item 11. Executive Compensation 135

Item 14. Principal Accounting Fees and Services 135

PART IV

Item 15. Exhibits, Financial Statement Schedules 136

SUMMARY OF THE MATERIAL AND OTHER RISKS ASSOCIATED WITH OUR BUSINESS

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We are a biopharmaceutical company with a limited operating history and have not generated any revenue to date from drug sales, and may never become profitable.

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We have incurred significant operating losses since inception and anticipate that we will incur continued losses for the foreseeable future.

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We will need to raise substantial additional funding. If we are unable to raise capital when needed or on attractive terms, we would be forced to delay, scale back or discontinue some of our product candidate development programs or future commercialization efforts.

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We are very early in our development efforts and our IRAK4, STAT3 and MDM2 programs are still in early clinical development. If we are unable to advance them through the clinic for safety or efficacy reasons or commercialize our product candidates or experience significant delays in doing so, our business will be materially harmed.

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We cannot be certain of the timely completion or outcome of our preclinical testing, including our STAT6 and TYK2 programs. In addition, the results of preclinical studies may not be predictive of the results of clinical trials and the results of any early-stage clinical trials we commence may not be predictive of the results of later-stage clinical trials.

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Our approach to the discovery and development of product candidates based on our PegasusTM platform is novel and unproven, which makes it difficult to predict the time, cost of development, and likelihood of successfully developing any products.

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Business interruptions resulting from any pandemic or geopolitical conflict could cause a disruption to our supply chain or the development of our product candidates and adversely impact our business.

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We may not be successful in our efforts to identify or discover additional product candidates or we may expend our limited resources to pursue a particular product candidate or indication and fail to capitalize on product candidates or indications that may be more profitable or for which there is a greater likelihood of success.

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If we experience delays or difficulties in the initiation or enrollment of patients in clinical trials, our receipt of necessary regulatory approvals could be delayed or prevented.

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Our current or future product candidates may cause adverse or other undesirable side effects that could delay or prevent their regulatory approval, limit the commercial profile of an approved label, or result in significant negative consequences following marketing approval, if any.

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Even if we receive regulatory approval for any of our current or future product candidates, we will be subject to ongoing obligations and continued regulatory review, which may result in significant additional expense.

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We rely, and expect to continue to rely, on third parties to conduct our ongoing and planned clinical trials for our current and future product candidates. If these third parties do not successfully carry out their contractual duties, comply with regulatory requirements or meet expected deadlines, we may not be able to obtain marketing approval for or commercialize our current and potential future product candidates and our business could be substantially harmed.

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If we are unable to obtain and maintain patent and other intellectual property protection for our technology and product candidates or if the scope of the intellectual property protection obtained is not sufficiently broad, our competitors could develop and commercialize technology and drugs similar or identical to ours, and our ability to successfully commercialize our technology and drugs may be impaired.

SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

This Annual Report on Form 10-K, or Annual Report, contains forward-looking statements which are made pursuant to the safe harbor provisions of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended. All statements other than statements of historical facts contained in this Annual Report are forward-looking statements. In some cases, you can identify forward-looking statements by terminology such as “may”, “will”, “should”, “expects”, “intends”, “plans”, “anticipates”, “believes”, “estimates”, “predicts”, “potential”, “continue” or the negative of these terms or other comparable terminology. These statements are not guarantees of future results or performance and involve substantial risks and uncertainties. Forward-looking statements in this Annual Report include, but are not limited to, express or implied statements about:

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the initiation, timing, progress, results, and cost of our research and development programs, and our current and future preclinical and future clinical studies, including statements regarding the timing of initiation and completion of studies or trials and related preparatory work, the period during which the results of the trials will become available, and our research and development programs;

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our ability to continue to construct PegasusTM, our drug discovery platform, and to enable a rational and effective drug discovery and development engine;

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the timing and the success of preclinical development efforts for STAT6 and TYK2 and clinical studies under our IRAK4, STAT3 and MDM2 programs;

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our plans to submit investigational new drug applications to the U.S. Food and Drug Administration, or FDA for current and future product candidates;

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the subsequent initiation of planned clinical trials;

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our ability to identify research priorities and apply a risk-mitigated strategy to efficiently discover and develop product candidates, including by applying learnings from one program to other programs and from one modality to our other modalities;

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our potential ability to manufacture our drug substances, delivery vehicles, and product candidates for preclinical use, for clinical trials and on a larger scale for commercial use, if approved;

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the ability and willingness of our third-party strategic collaborators to continue research and development activities relating to our development candidates and product candidates;

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our ability to obtain funding for our operations necessary to complete further development and commercialization of our product candidates;

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our ability to obtain and maintain regulatory approval of our product candidates;

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our ability to commercialize our products, if approved;

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the pricing and reimbursement of our product candidates, if approved;

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the implementation of our business model, and strategic plans for our business, product candidates, and technology;

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the scope of protection we are able to establish and maintain for intellectual property rights covering our product candidates and technology;

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estimates of our future expenses, revenues, capital requirements, and our needs for additional financing;

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the potential benefits of strategic collaboration agreements, our ability to enter into strategic collaborations or arrangements, and our ability to attract collaborators with development, regulatory and commercialization expertise;

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future agreements with third parties in connection with the commercialization of product candidates and any other approved product;

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the size and growth potential of the markets for our product candidates, and our ability to serve those markets;

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our financial performance;

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the rate and degree of market acceptance of our product candidates;

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regulatory developments in the United States and foreign countries;

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our ability to contract with third-party suppliers and manufacturers and their ability to perform adequately;

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our ability to produce our products or product candidates with advantages in turnaround times or manufacturing cost;

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the success of competing therapies that are or may become available;

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our ability to attract and retain key scientific or management personnel;

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the impact of laws and regulations;

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developments relating to our competitors and our industry;

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the effect of any pandemics or geopolitical conflicts, including mitigation efforts and economic effects, on any of the foregoing or other aspects of our business operations, including but not limited to our preclinical studies and future clinical trials; and

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other risks and uncertainties, including those listed under the caption “Risk Factors.”

Any forward-looking statements in this Annual Report reflect our current views with respect to future events and with respect to our future financial performance, and involve known and unknown risks, uncertainties and other factors that may cause our actual results, performance or achievements to be materially different from any future results, performance or achievements expressed or implied by these forward-looking statements. Factors that may cause actual results to differ materially from current expectations include, among other things, those described under Part I, Item 1A, “Risk Factors” and elsewhere in this Annual Report. Given these uncertainties, you should not place undue reliance on these forward-looking statements. Except as required by law, we assume no obligation to update or revise these forward-looking statements for any reason, even if new information becomes available in the future.

All of our forward-looking statements are as of the date of this Annual Report only. In each case, actual results may differ materially from such forward-looking information. We can give no assurance that such expectations or forward-looking statements will prove to be correct. An occurrence of or any material adverse change in one or more of the risk factors or risks and uncertainties referred to in this Annual Report or included in our other public disclosures or our other periodic reports or other documents or filings filed with or furnished to the Securities and Exchange Commission, or the SEC, could materially and adversely affect our business, prospects, financial condition and results of operations. Except as required by law, we do not undertake or plan to update or revise any such forward-looking statements to reflect actual results, changes in plans, assumptions, estimates or projections or other circumstances affecting such forward-looking statements occurring after the date of this Annual Report, even if such results, changes or circumstances make it clear that any forward-looking information will not be realized. Any public statements or disclosures by us following this Annual Report that modify or impact any of the forward-looking statements contained in this Annual Report will be deemed to modify or supersede such statements in this Annual Report.

We may from time to time provide estimates, projections and other information concerning our industry, the general business environment, and the markets for certain diseases, including estimates regarding the potential size of those markets and the estimated incidence and prevalence of certain medical conditions. Information that is based on estimates, forecasts, projections, market research or similar methodologies is inherently subject to uncertainties, and actual events, circumstances or numbers, including actual disease prevalence rates and market size, may differ materially from the information reflected in this Annual Report. Unless otherwise expressly stated, we obtained this industry, business information, market data, prevalence information and other data from reports, research surveys, studies and similar data prepared by market research firms and other third parties, industry, medical and general publications, government data, and similar sources, in some cases applying our own assumptions and analysis that may, in the future, prove not to have been accurate.

PART I

Item 1. Business.

We are a biopharmaceutical company focused on discovering and developing novel small molecule therapeutics that selectively degrade disease-causing proteins by harnessing the body’s own natural protein degradation system. Our proprietary targeted protein degradation, or TPD, platform, which we refer to as PegasusTM, allows us to discover highly selective small molecule protein degraders with activity against disease-causing proteins throughout the body. We believe that our small molecule protein degraders have unique advantages over existing therapies and allow us to address a large portion of the human genome that was previously intractable with traditional modalities. We focus on biological pathways that have been clinically validated but where key biological nodes/proteins have not been drugged or are inadequately drugged. To date, we have utilized our PegasusTM platform to design novel protein degraders focused in the areas of immunology-inflammation and oncology, and we continue to apply our platform’s capabilities to additional therapeutic areas. We have a mission to drug all target classes in human cells using TPD.

Our current clinical stage programs are IRAK4, STAT3, and MDM2, which each address high impact targets within biologically-proven pathways, providing the opportunity to treat a broad range of immuno-inflammatory diseases, hematologic malignancies, and/or solid tumors. Our programs exemplify our focus on addressing high impact targets that have been elusive to conventional modalities and that drive the pathogenesis of multiple serious diseases with significant unmet medical needs. Our disclosed preclinical programs target STAT6 and TYK2, two proteins in well-validated pathways where we believe our degrader technology has the potential to offer unique advantages as compared to competing therapies. Both programs are currently in IND-enabling studies.

With respect to our IRAK4 program, we are collaborating with Sanofi S.A, or Sanofi, on the development of drug candidates targeting IRAK4 outside the oncology and immuno-oncology fields. We are developing KT-474, a highly active and selective, orally bioavailable IRAK4 degrader, for the treatment of interleukin-1 receptor/toll-like receptor or IL-1R/TLR-driven immunology-inflammation conditions and diseases with high unmet medical need, including hidradenitis suppurativa, or HS, an inflammatory skin disease, as well as atopic dermatitis, or AD, and potentially other indications. We have completed our Phase 1 trial of KT-474, which included cohorts of healthy volunteers, as well as patients with HS and AD. Phase 2 clinical trials of KT-474, conducted by Sanofi, are initially investigating its potential in HS and AD. The clinical trials for both indications have been initiated, and patient dosing is ongoing.

With respect to our clinical oncology programs, we are evaluating KT-333, a STAT3 degrader, in a Phase 1 clinical trial in patients with relapsed/refractory liquid and solid tumors, including aggressive lymphomas. Patient enrollment and dosing are ongoing in the Phase 1a portion of the trial, and we expect to present additional clinical data in 2024. In September 2023, we announced that the FDA, granted KT-333 Fast Track Designation for the treatment of relapsed/refractory peripheral T cell lymphoma, an indication for which we have previously received Orphan Drug Designation. Our Phase 1 clinical trial of KT-253, our MDM2 degrader, was initiated in March 2023. The study is evaluating the safety, tolerability, pharmacokinetics/pharmacodynamics, and clinical activity of ascending doses of KT-253 in adult patients with relapsed or refractory high grade myeloid malignancies, acute lymphocytic leukemia, or ALL, lymphomas, and solid tumors. Patient enrollment and dosing are ongoing in the Phase 1a portion of the trial, and we provided initial safety, proof-of-mechanism and proof-of-concept data in November of 2023. We expect to present additional clinical data in 2024. In June 2023, KT-253 was granted orphan drug designation by the FDA for the treatment of acute myeloid leukemia. In November 2023, we announced the decision to discontinue the development of our KT-413 (IRAKIMiD) program, despite reaching expected degradation levels and a lack of dose-limiting toxicities, in order to focus resources to support our growing immunology pipeline.

Our Strategy

Our mission is to discover, develop and commercialize novel and transformative therapies that improve the lives of patients with serious diseases. We have a unique target selection strategy that is focused on undrugged/inadequately drugged targets where targeted protein degradation (TPD) is the only or best unlocking drug modality. Our first in class programs target proteins that have strong genetics and clinical pathway validation and serve areas with large clinical and commercial opportunities. TPD is a disease-agnostic technology, and we are currently advancing this modality across several disease areas, with a primary focus in immunology as well as selected key therapeutic targets in oncology. Our goal is to leverage our leading capabilities in TPD and to become a fully integrated biopharmaceutical company with a pipeline of novel degrader medicines.

We intend to achieve this goal by pursuing the following strategic objectives:

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Advance our existing clinical pipeline. We have advanced four programs into human clinic testing, including our current ongoing clinical stage programs which target IRAK4, STAT3 and MDM2. We believe these programs have the potential to treat multiple immuno-inflammatory and/or oncology indications. Our clinical pipeline is consistent with our target selection strategy that focuses on undrugged or inadequately drugged targets in validated pathways.

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Build a broad and diverse pipeline of novel protein degraders. Guided by our drug development principles, innovative platform capabilities, and the learnings from our clinical-stage programs, we continue to identify therapeutic targets that have disruptive therapeutic potential and are well-suited for a TPD approach. Our two most advanced pre-clinical programs, STAT6 and TYK2, reflect our increased pipeline focus on immunology. These programs target significant and well-validated opportunities in which we believe our technology has the potential to deliver biologic-like activity with the convenience of an oral pill.

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Expand and protect our proprietary know-how and intellectual property. We have developed a broad patent estate protecting our intellectual property, which we intend to expand to further protect the drug candidates we develop and our platform. Our intellectual property includes proprietary know-how as well as a broad series of patents.

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Pursue synergistic collaboration opportunities. To further our goal of delivering transformative therapies to the broadest patient populations, we intend to become a fully integrated biopharmaceutical company. In addition to our ongoing collaboration with Sanofi, we expect to leverage additional strategic partnerships that can contribute complementary capabilities in discovery, development and commercialization in disease areas both within and outside of our core areas of therapeutic focus.

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Build our organizational capabilities . We continue to build capabilities across our organization, including expertise in key therapeutic areas and functions. We view these capabilities as a strategic advantage, and as critical to our objective to become a fully-integrated biotechnology company.

Background of Targeted Protein Degradation

Proteins are responsible for the structure, function and regulation of tissues and organs. Cells in the body continuously synthesize and degrade proteins, maintaining an equilibrium called protein homeostasis. Most diseases are the result of aberrant protein behavior driven by activation, mutation, or downregulation of the protein itself, or by the gene responsible for the transcription and translation of that particular protein. With a deepened molecular understanding of various diseases and the characterization of the full human genome, research efforts have increasingly focused on the development of medicines to address malfunctioning proteins responsible for oncologic, auto-immune, cardio-metabolic, neurodegenerative, and rare genetic diseases.

The ‘druggable’ genome challenge

Several therapeutic modalities have been developed over the years to address aberrant protein activity. These have included small molecule inhibitors of protein function, therapeutic antibodies, oligo-based therapeutics such as RNA interference therapeutics, antisense oligonucleotides, or ASO, and other genetic therapies.

Some of these modalities have had a tremendous impact on the treatment of diseases and quality of life of patients, and several others, while earlier stage, offer potential. However, these traditional modalities face specific challenges that limit their therapeutic impact and reach. Some of the limitations of existing modalities include the following:

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Traditional small molecule therapeutics are unable to block the function of proteins without a catalytic or substrate binding site and cannot block proteins with dual function, as such are not effective against transcription factors, scaffolding and adaptor proteins, many of which play a key role in certain diseases.

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Therapeutic antibodies are generally too large to penetrate cells and are therefore typically limited to protein targets that are extracellular, or outside of the cell, whereas most proteins are inside the cell. They also have to be dosed parenterally and can be costly and complex to develop and manufacture.

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Oligo-based therapeutics are capable of drugging proteins elusive to small molecules in some cases but have significant drug delivery challenges with dosing and in achieving systemic distribution, greatly limiting the breadth of diseases they are able to address effectively. These therapeutics can also be costly and complex to develop and manufacture.

As a result of these limitations, we believe that only 20% of the full human genome has been effectively drugged to date. New therapeutic modalities which can overcome some of these challenges are necessary to expand the drugged proteome/genome and provide new efficacious medicines to patients in need. We believe that TPD is such a modality.

Targeted Protein Degradation

One of the methods that cells use to control the balance between the synthesis of new proteins and the degradation and disposal of damaged and/or misfolded proteins, is ubiquitin-proteasome system, or UPS. The discovery of ubiquitin-mediated protein degradation provided important insights into specific processes like cellular division and DNA repair and led to the discovery of UPS’ critical roles in various cellular pathways, including the cell cycle, signaling pathways, the regulation of gene expression, and responses to oxidative stress. The discovery of the UPS also revealed a new modality to harness this cellular process for the treatment of diseases.

As shown below in figure 1, the UPS comprises a series of finely orchestrated enzymatic sequences that ultimately lead to protein polyubiquitination and degradation by the proteasome in cells. Protein ubiquitination is a cellular process involving an enzymatic cascade consisting of ubiquitin-activating enzymes (E1), ubiquitin-conjugating enzymes (E2), and ubiquitin-protein ligases (E3). In humans, there are two classes of ubiquitin activating E1 enzymes, more than 30 E2 enzymes, and approximately 600 E3 ligases.

The E3/E2/ubiquitin ligase complex (shown in blue) binds to a substrate protein (shown in orange) to mediate the transfer of ubiquitin, which leads to degradation of the target protein through the proteasome.

Targeted protein degradation is a new modality that co-opts this innate cellular process. The core of the TPD modality consists of a small molecule that we refer to as a heterobifunctional degrader. The role of this heterobifunctional degrader molecule is to mediate a “new” interaction through the formation of a ternary complex between a disease-causing protein and an E3 ligase. The E3 liaise tags the protein target for degradation by attaching a series of ubiquitin, and the proteasome recognizes the tagged protein and degrades it into small peptides.

Forming an efficient ternary complex, as shown in step 2 in the figure below, is a critical step in TPD, and its formation, function, and effect on cellular and in vivo systems is vital to the success of the degradation and its impact on disease. In addition, the degrader molecule needs to be able to effect degradation in a variety of different cell types and contexts and have the right pharmaceutical properties to be therapeutically dosed to patients.

As shown in step 3 and step 4 in the figure below, after the degrader facilitates the ubiquitination of the target protein, and as the protein is degraded by the proteasome, the molecule separates from the protein, and is able to form another ternary complex to conduct the degradation process again. This iterative mechanism is catalytic, which results in increased potency even at lower concentrations, another key differentiator from other modalities such as small molecule inhibitors and therapeutic antibodies.

Figure 1

Due to the unique advantages of TPD, this transformative modality is capable of targeting proteins traditionally undrugged by small molecules. Specifically, TPD can target proteins without a catalytic function such as scaffolding proteins and transcription factors, with small molecule-like drug properties that can potentially be dosed orally and distributed systemically unlike oligo-based therapeutics such as RNAi’s. TPD molecules also are amenable to existing small molecule manufacturing principles which are less costly than other therapeutic modalities. Because of the catalytic nature of the degradation process, we believe the modality has the potential to be therapeutically effective with smaller amounts of drug substance and less frequent dosing than traditional therapeutics.

The use of small molecules to affect protein homeostasis has been clinically and commercially validated by multiple drugs over the past two decades. Drugs such as bortezomib and fulvestrant have been understood to inhibit the proteasome and target the estrogen receptor for proteasome-dependent degradation, respectively. More recently, immunomodulatory imide drugs such as lenalidomide and pomalidomide have been understood on a post-hoc basis to direct the degradation of a series of transcription factors via the UPS.

These immunomodulatory drugs have validated the concept of using the UPS to degrade proteins and elicit a pharmacological and therapeutic effect in disease settings. However, unlike earlier approaches in this field, TPD takes this proven concept further to prospectively target the degradation of a wider range of proteins through the rational design of heterobifunctional degraders which coordinate the discreet binding of target proteins and E3 ligases to drive the desired protein degradation.

An important factor for the efficiency of a degrader is the specificity and affinity to the targeted E3 ligase. The various E3 ligases have different distribution and cellular localization profiles that are important factors when considering which E3 ligase to use for a particular disease protein target. There are approximately 600 E3 ligases that occur in nature, but to date only a handful of these E3 ligases have been evaluated for therapeutic purposes, leaving a substantial portion of the genome available for targeting.

Our PegasusTM Platform

Our proprietary drug discovery platform, called Pegasus, enables us to rationally design targeted protein degraders that have the potential to drug all target classes in the cell. Our approach is rooted in an understanding of the relationship between E3 ubiquitin ligases and target proteins, which allows us to identify the properties that make a target both ligandable and degradable, and determine how multiple factors impact potency, selectivity, pharmacokinetics (PK) and pharmacodynamics (PD). We have built extensive capabilities and knowledge that contributes to the development of our preclinical and clinical pipeline.

Our proprietary chemistry expertise enables the design and optimization of both E3 ligase and target protein binders, with artificial intelligence (AI) enabled insights, allowing for the opportunity to design of targeted protein degraders with optimal pharmaceutical properties. Additionally, we utilize our E3 ligase Whole-Body Atlas includes the expression profiles of approximately 600 unique E3 ligases. Using this Atlas, we are able to match target proteins with appropriate E3 ubiquitin ligases based on expression, distribution, intracellular localization and biology, a process that is enabled with our machine learning-based algorithms. We continue to utilize our Quantitative System Pharmacology Model, which measures and predicts a diverse set of parameters that impact target protein levels, based on an understanding of PK/PD, both in vitro and in vivo, and across healthy and diseased tissues and cell types. We have also focused on identifying novel tissue restricted or selective E3 ligases, beyond traditional cereblon/IMiD interactions, that enable the design of molecules that target both undrugged and un-ligandable proteins through small molecule interactions.

Our Therapeutic Pipeline

Our pipeline includes immunology and oncology programs in various stages of clinical and preclinical development. Our immunology programs include IRAK4, STAT6 and TYK2. Our oncology pipeline includes STAT3 and MDM2. We also have multiple programs in earlier stages of development, not depicted here, and are exploring targets in therapeutic areas outside of oncology and immunology.

The following table summarizes our publicly-disclosed clinical and near-term clinical stage pipeline.

Figure 2

1 KT-474 (SAR444656) partnered with Sanofi, with Kymera option to participate in the development and commercialization, and 50/50 profit split, in the United States. Double digit tiered royalties in ROW;

2 Current indications: HS and AD. Other diseases shown, where IL-1R/TLR pathway has been implicated in pathogenesis, are additional potential opportunities;

3 Assessment of STAT3 I/I opportunity is ongoing.

Our Immunology programs: IRAK4, STAT6 and TYK2

IRAK4

We are developing KT-474, a highly active and selective, orally bioavailable IRAK4 degrader, for the treatment of IL-1R/TLR-driven immunology-inflammation conditions and diseases with high unmet medical need. The initial indications being pursued include HS and AD. We have chosen to pursue IRAK4 degradation due to the well-validated role of the IL-1R/TLR pathway in immunology and inflammation and the potential advantage that drugging a single node of multiple different mediators of inflammation has over other approaches focused on targeting one of many cytokines that stimulate the IRAK4 node. IRAK4 is a critical node in the IL-1R/TLR signaling pathway, which is dependent on both IRAK4’s kinase activity and scaffolding function. We have observed through our in vitro and in vivo studies that KT-474 induces IRAK4 degradation, impacting both the kinase and the scaffolding functions, and therefore can efficiently and selectively block IL-1R/TLR-mediated inflammation in a way we believe to be superior to IRAK4 kinase inhibitors. We therefore believe KT-474 has the potential to improve outcomes over current treatment options as well as other drugs currently in development. We are collaborating with Sanofi on the development of drug candidates targeting IRAK4 outside of oncology and immuno-oncology fields. Sanofi recently advanced KT-474 into two Phase 2 clinical trials in patients with HS and AD, and the first patients were dosed in each trial in the fourth quarter of 2023. See the section entitled “Business— Collaborations—Collaboration Agreement with Sanofi" appearing elsewhere in this Annual Report for more information.

STAT6

We are developing degraders that target STAT6, an essential transcription factor specific to the IL-4/IL-13 signaling pathway and the central driver of Type 2 inflammation in allergic diseases. STAT6 is a genetically validated target and we believe the pathway has been clinically validated by approved IL-4/IL-13-targeting biologics, such as dupilumab. In preclinical studies, KT-621, our first-in-class oral STAT6 degrader, demonstrated full inhibition of the IL-4/IL-13 pathway in all relevant human cell contexts evaluated with strong picomolar potency similar or superior to pathway biologics such as dupilumab. KT-621 also demonstrated strong activity in multiple preclinical efficacy studies. In addition, at low oral doses, KT-621 demonstrated nearly full in vivo STAT6 degradation and was well-tolerated in multiple preclinical toxicity studies. KT-621 has been developed as a once daily oral small molecule degrader which we believe has the potential to have broad activity across multiple diseases, which may include atopic dermatitis, asthma, chronic obstructive pulmonary disorder, eosinophilic esophagitis and chronic rhinosinusitis with nasal polyps, among others. We expect to initiate a Phase 1 clinical trial in the second half of 2024.

TYK2

We are developing degraders that target TYK2, a member of the Janus Kinase or JAK family required for Type I interferon or IFN, interleulin-12, or IL-12 and interleulin-23, or IL-23 signaling. TYK2 is a genetically- and clinically-validated target in autoimmune and inflammatory diseases. TYK2 has a well-established scaffolding function that plays a key role in cytokine receptor surface expression and activation. In preclinical studies, KT-294, our first-in-class oral TYK2 degrader, demonstrated picomolar to nanomolar potencies across all relevant human cell contexts evaluated, representing what we believe is the only approach to TYK2 targeting that has the potential to recapitulate the human loss-of-function biology of nearly full pathway inhibition of Type I IFN, IL-12 and IL-23, while also sparing interleukin-10, or IL-10. Degradation of TYK2 has the potential to overcome the challenges of small molecule inhibitors, which have limitations due to lack of selectivity, limited target engagement, and/or lack of potent activity against Type I IFN. KT-294 has been developed as a once daily oral small molecule degrader with a potential biologics-like activity profile, which we believe has the potential to address conditions such as inflammatory bowel disease, psoriasis, psoriatic arthritis and lupus, among others. We expect to initiate a Phase 1 clinical trial in the first half of 2025.

Our Oncology programs: STAT3 and MDM2

STAT3

indications through the targeting of a single genetically and clinically validated pathway. While the JAK-STAT pathway has been partially addressed with several clinically successful JAK-targeting agents, we believe there are currently no drugs that specifically affect STAT3 broadly across all the relevant cell types. Small molecule STAT3 dimerization inhibitors targeting the SH2 domain have been in development, but significant challenges remain: first, homology of SH2 domains among all STAT family members impacts the ability to achieve specificity for STAT3, and second, inability to block dimerization independent transcriptional activities of STAT3. For these reasons, we believe that STAT3 degraders may provide a transformative solution to the development of targeted and selective drugs to address multiple STAT3 dependent pathologies. We are currently evaluating our STAT3 degrader, KT-333, in a Phase 1 clinical trial in patients with relapsed/refractory liquid and solid tumors, including aggressive lymphomas. Patient enrollment and dosing are ongoing in the Phase 1a dose escalation portion of the trial, and we expect to provide additional clinical data in 2024.

MDM2

We are developing degraders that target MDM2 for the treatment of solid tumors and hematological malignancies. MDM2 is the crucial regulator of the most common tumor suppressor, p53, which remains intact (or wild type) in close to 50% of cancers. Unlike small molecule inhibitors, our MDM2 degrader, KT-253, has been shown preclinically to have the ability to overcome the MDM2 feedback loop and rapidly induce apoptosis, even with brief exposures. We initiated a Phase 1 clinical trial of KT-253 in May 2023, which is designed to evaluate the safety, tolerability, PK/PD and clinical activity in adult patients with liquid and solid tumors. Patient enrollment and dosing are ongoing in the Phase 1a dose escalation portion of the trial, and we expect to provide additional clinical data in 2024.

Our Approach to Target Selection

To realize on the promise of TPD, we have taken a unique and differentiated approach to target selection, which has several key tenets that guide our research and development efforts, as seen in Figure 3. We focus on undrugged or inadequately drugged targets, such as transcription factors and scaffolding proteins, within pathways with clear clinical validation and validation through human genetics/causal biology. We identify targets where TPD is the best or the only solution, with a strong degrader rationale and line of sight to demonstrating superiority of our modality over existing drugs within these pathways. Additionally, we focus on areas of significant patient need and large commercial opportunities.

Figure 3

Clinical Immunology: IRAK4

Summary

We are developing KT-474, a highly active and selective, orally bioavailable IRAK4 degrader, for the treatment of IL-1R/TLR-driven immuno-inflammatory conditions and diseases with high unmet medical need, including HS, AD and others. We have chosen to pursue IRAK4 degradation due to the well-validated role of the IL-1R/TLR pathway in immunology and inflammation and the potential advantage that drugging a single node of multiple different mediators of inflammation has over other approaches focused on targeting one of many cytokines that stimulate the IRAK4 node. IRAK4 is a critical node in the IL-1R/TLR signaling pathway, which is dependent on both IRAK4’s kinase activity and scaffolding function. We have observed through our in vitro and in vivo studies that KT-474 induces IRAK4 degradation, impacting both the kinase and the scaffolding functions, and therefore can selectively block IL-1R/TLR-mediated inflammation in a way we believe to be superior to IRAK4 kinase inhibitors. We therefore believe KT-474 has the potential to improve outcomes over current treatment options as well as other drugs currently in development. The KT-474 Phase 1 trial, which included healthy volunteers and HS and AD patients, was completed in October 2022. We are collaborating with Sanofi on the development of drug candidates targeting IRAK4 outside of oncology and immuno-oncology fields. Sanofi has advanced KT-474 into Phase 2 clinical trials in patients with HS and AD, both which were initiated in the fourth quarter of 2023. See the section entitled “Business—Collaborations—Collaboration Agreement with Sanofi” appearing elsewhere in this Annual Report for more information.

Biology and Mechanism of Action

IRAK4 is a key component of the myddosome, a multiprotein complex involved in innate immunity that mediates signaling through TLRs and IL-1Rs. The IRAK4 protein is ubiquitously expressed across multiple different tissue types, including skin, lymphoid tissue, bone marrow, gastrointestinal tract, and lung.

The function of IRAK4 is dependent both on its kinase activity and on its scaffolding function, which are required for the assembly of the myddosome complex following TLR or IL-1R engagement and MYD88 activation. While the kinase function is primarily responsible for the phosphorylation events in the IRAK4-JNK axis, the scaffolding function is primarily responsible for the NF-KB activation and downstream gene traction of several key pro-inflammatory cytokines and chemokines.

We believe IRAK4 degradation is superior to IRAK4 kinase inhibition as our preclinical data suggests that it is critical to block both the kinase activity and scaffolding functions of the IRAK4 protein, which requires removal, as opposed to just inhibition, of the protein. IL-1 family cytokines, including IL-1a, IL-1ß, IL-18, IL-36, and IL-33, have been implicated in a variety of different immunology-inflammation conditions and diseases. As both TLRs and IL-1Rs are involved in the production and response to all of these IL-1 family cytokines, IRAK4 targeting with a single small molecule degrader could impact multiple different cytokines and chemokines and thereby provide a transformative approach to the treatment of IL-1R/TLR-driven diseases.

Figure 4

Development Opportunities

We estimate that more than 150 million people in the US, Europe and Japan suffer from TH1-driven diseases. There are numerous cutaneous, rheumatic and gastrointestinal immunology-inflammation disease indications for which pathogenesis involves IL-1 family cytokines as well as TLR stimulation. These present opportunities where we believe a highly efficient and selective IRAK4 degrader would provide significant advantages over both currently approved treatment options and those in clinical development. We are initially prioritizing HS and AD, autoimmune dermatologic conditions where there is clinical proof of concept for targeting cytokines impacted by the IL-1R/TLR pathway but for which there continues to be a high level of unmet need. There are many other diseases where the IL-1R/TLR pathway has been implicated in pathogenesis and could be additional potential opportunities targeting respiratory, GI and rheumatology.

Hidradenitis Suppurativa

HS is a chronic, destructive, painful and debilitating inflammatory skin disease affecting up to 1% of both the U.S. and global population. Patients with HS have numerous painful, draining nodules and abscesses, usually within skin folds, that are characterized by inflammation and bacterial colonization. Currently HS is treated symptomatically with corticosteroids, antibiotics and surgery. The only FDA-approved treatment for HS is the anti-TNF antibody adalimumab, which provides some benefit to approximately 50% of patients with moderate-to-severe disease but is not curative. Thus, there remains a high unmet need for better therapies for the treatment of HS.

Bacterial activation of TLRs, as well as the production of IL-1a, IL-1ß, and IL-36 by keratinocytes and inflammatory cells leading to inflammation characterized by high levels of TNF-a, IL-6, and IL-17, are central to the pathogenesis of HS. Monoclonal antibodies targeting individual cytokines such as IL-1a (bermekimab), IL-1a/ß receptor (anakinra), and IL-17 (secukinumab and bimekizumab) have shown preliminary clinical activity in HS and provide clinical validation for targeting the IL-1R/TLR pathway in HS. As such, an IRAK4 degrader which acts on multiple cytokines as well as TLRs has the potential to offer a significant advantage over the single-cytokine-targeting agents currently being developed.

Atopic Dermatitis

AD is a chronic, pruritic inflammatory skin disease that occurs most frequently in children but also affects adults. In the major global markets, the diagnosed prevalence of AD is estimated over 60 million patients, with approximately 40%, or 24 million, falling into the moderate-to-severe category. AD follows a chronic relapsing course over month to years, with dry skin and severe pruritus as the primary symptoms, sometimes accompanied by skin thickening from chronic scratching and fissuring. AD is treated symptomatically with topical therapies, including emollients, corticosteroids, and phosphodiesterase inhibitors. The leading FDA-approved systemic treatment is the IL-4Ra targeting antibody dupilumab, though only approximately 40% of moderate-to-severe disease patients met the primary endpoint in its Phase 3 trials, leaving a significant percentage of patients who are currently underserved.

Furthermore, there is evidence that IL-18 and IL-1 are both involved in the generation of inflammation in both AD and other autoimmune and inflammatory diseases, including eosinophilic asthma and chronic rhinosinusitis. Single-cytokine-targeting monoclonal antibodies against IL-18 (GSK1070806) and IL-1a (bermekimab)have shown preliminary clinical activity in AD while a monoclonal antibody against IL-1a/b (lutikizumab) has shown preliminary clinical activity in HS. Thus, we believe the ability of an IRAK4 degrader to impact the production of both IL-18 and IL-1, through complete TLR signaling blockade, and the cellular response to both cytokines, through complete IL-1R signaling blockade, provides a compelling mechanistic rationale for development in AD and HS and other autoimmune and inflammatory diseases.

Clinical Studies and Data

In December 2021, we completed dose escalation in the Single Ascending Dose, or SAD and Multiple Ascending Dose, or MAD portions of the KT-474 Phase 1 trial in healthy volunteers. The trial evaluated safety, tolerability and pharmacokinetics in 105 healthy volunteers. The SAD portion consisted of single doses ranging from 25 to 1600 mg. The MAD portion consisted of escalating doses ranging from 50 mg to 200 mg that were administered for 14 consecutive days. Highlights of the healthy volunteer portion of the trial included robust (>95%) and sustained IRAK4 degradation with single and multiple daily doses (Figure 5) and broad inhibition of ex vivo TLR-mediated cytokine induction (Figure 6). KT-474 was generally well-tolerated across all dose groups.

Figure 5

Figure 6

Following the healthy volunteer portion of the trial, we completed a single dose, food-effect cohort to establish the dose for the patient cohort, or Part C, of the KT-474 Phase 1 trial, which included HS and AD patients and which was completed in October 2022. The HS and AD patient cohort was an open label study in 21 patients with HS and AD. The patients were administered a 75 mg daily dose taken with food, which we estimated would be equivalent exposure to 100 mg fasted, one of the doses in our SAD/MAD trial. The patient cohort dose of 75 mg was administered for 28 consecutive days.

The KT-474 plasma PK at the 75 mg once daily, or QD dose (in the fed state) in patients was comparable to healthy volunteers in the MAD portion of the Phase 1 clinical trial who received 100 mg once daily in the fasted state, the MAD cohort which we refer to as MAD3. Additionally, mean Cmax (6-hour post dose concentration) and Ctrough (pre-dose concentration) levels at steady state in Part C were in line with MAD3 levels at Day 14, and the mean half-life of 44 hours was within the range observed in MAD (34-59 hours). Additionally, KT-474 concentrations in plasma led to a comparable level of IRAK4

degradation in healthy volunteers and HS/AD patients. Specifically, at concentrations above 3 ng/mL degradation was generally above 80% in both populations. Additionally, IRAK4 levels in PBMC in patients with evaluable samples were near the lower limit of quantification at Day 28.

KT-474 demonstrated high skin exposure in the skin of evaluable HS and AD patients, as shown below in Figure 7.

Figure 7

Additionally, baseline IRAK4 levels in skin lesions of evaluable HS and AD patients were approximately twice the levels of healthy volunteers. By Day 28 of dosing, the mean IRAK4 level in skin lesions of AD and HS patients was reduced to approximately the same level as healthy subjects, as shown below in Figure 8.

Figure 8

KT-474 was generally well-tolerated. There were no serious adverse events, no drug-related infections, and no adverse events observed leading to dose interruption or discontinuation. A modest, non-adverse QTc prolongation, consistent with that observed by Day 7 in the MAD portion of the healthy volunteer study, was also observed in the patient cohort but spontaneously resolved back to baseline with continued dosing during the 28-day dosing period.

To determine whether KT-474 had a systemic anti-inflammatory effect in HS and AD patients, plasma levels of IL-6, CRP, SAA and IL-1b were measured at baseline and at various times during and after the 28-day treatment period. In patients whose baseline levels were greater than the upper limit of normal, the evaluable patients showed suppression of all 4 analytes, with mean maximum reductions through Day 42 ranging from 41 to 63%. The patient cohort also evaluated how systemic IRAK4 degradation in blood and skin would affect the expression of proinflammatory genes known to be relevant to either AD or HS. In AD, affected genes included the Th2 cytokine IL-5, the inflammasome NLRP3, as well as CXCL1 and IL-2RB. Genes affected in HS included IL-1 family cytokines IL-1 and IL-36A, mediators of Th1 inflammation such as IFN-g and GZMB, the Th17 cytokine IL-17A, and drivers of innate immunity such as IL-8 and CSF3. The downregulation was substantial with many genes inhibited more than 90% in both diseases.

Figure 9

†log2(fold change): -1 = 50% decrease, -2 = 75% decrease, -3 = 87.5% decrease.

Part C included exploratory clinical endpoints used for HS and AD. The endpoints were chosen to assess the effect of KT-474 treatment on the burden of skin disease as well as on symptoms such as pain and pruritus that impact quality of life for HS and AD patients. In AD patients, as shown in Figure 10, there was a mean 37% reduction in skin lesions as measured using the Eczema Area and Severity Index (EASI) score, with reductions in individual patients of up to 76%. Maximum reduction was seen by Day 28 and was maintained at Day 42.

Figure 10

As shown in Figure 11, mean peak pruritus in AD patients over the past week or past 24 hours was reduced by 52% and 63%, respectively, with maximum reductions occurring by Day 42. Peak pruritus responders, defined as ≥4 Unit reduction in peak pruritus over the past week or past 24 hours, were seen in 57% and 71% of AD patients, respectively, with responses sustained after Day 28.

Figure 11

The Validated Investigator’s Global Assessment, or vIG, of disease severity improved in 2 of 7 AD patients and remained stable in the others out to Day 42.

In HS patients, the efficacy analyses were performed in all patients, which included two patients with very severe disease. In addition, efficacy analyses were also performed in a subset of HS patients that only had moderate to severe disease, which was the target population for this study. The AN count was reduced by up to an average of 46% in all HS patients and by an average of 51% in the moderate to severe subset, with reductions in individual patients of up to 100% and with maximum reduction occurring by Day 42. The proportion of patients achieving an AN count of 0, 1 or 2 at Day 28 was 42% in all HS patients and 50% in those with moderate to severe disease. HiSCR50 response is defined as a 50% or greater reduction in AN count and no increase in abscesses or draining fistulas. As shown in Figure 12, at Day 42, the proportion of HiSCR50 responders was 42% in all HS patients and 50% in those with moderate to severe disease.

Figure 12

HiSCR75 response, defined as 75% or greater reduction in AN count, was seen in 25% of all HS patients and 30% of those with moderate to severe disease.

Symptoms of pain and pruritus were also measured. As shown in Figure 13, there was a 49 to 55% mean reduction in the Pain Numerical Rating Scale, or NRS, in all HS patients and in those HS patients with moderate to severe disease, respectively, with maximum reduction occurring between Days 28 and 42. Pain NRS30 response is defined as at least a 30% reduction and at least one unit reduction from baseline in Pain NRS. As also shown in Figure 13, the Pain NRS responder rate was 50% in all HS patients and 60% in those HS patients with moderate to severe disease, sustained after Day 28.

Figure 13

There also was a mean reduction in peak pruritus of 62% in all HS patients and 68% in those HS patients with moderate to severe disease, with maximum reduction by Day 42 in all HS patients and by Day 28 in those with moderate to severe disease. Additionally, the Physician’s Global Assessment of disease severity improved in 5 HS patients, including clearing of disease in 1 patient with moderate disease at baseline, and remained stable in the other evaluable patients out to Day 42.

Clinical Development Plan

In the fourth quarter of 2023, the first patients were dosed in the Phase 2 clinical trials of KT-474 in HS and AD.

The Phase 2 clinical trial in HS, or ZEN, is a double blind, placebo-controlled, 2-arm randomized trial consisting of a KT-474 oral tablet, or placebo, once-daily. The primary outcome measure is percent change from baseline in total abscess and inflammatory nodule (AN) count. Select secondary outcome measure include proportion of patients achieving HiSCR50, AN Count ≤2; absolute change from baseline in HIS4; proportion of patients with improvement in Hurley Stage, AN50; change from baseline in reported daily worst pain HS-Skin Pain-NRS; and proportion of participants achieving at least 30% reduction and at least 1 unit reduction in daily worst pain using HS-Skin Pain-NRS.

The Phase 2 clinical trial in AD, or ADVANTA, is a double blind, placebo-controlled, 3-arm randomized trial consisting of a KT-474 dose 1 oral tablet, a KT-474 dose 2 oral tablet, or placebo, once-daily. The primary outcome measure is percent change from baseline in EASI. Select secondary outcome measure include proportion of participants with vIGA-AD of 0 or 1 and a reduction from baseline of ≥2 points; proportion of participants achieving EASI-50 EASI-75 EASI-90; proportion of participants with reduction of weekly average of daily PP-NRS by ≥4 points from baseline; percent change from baseline in weekly average of daily PP-NRS; and absolute change from baseline in weekly average of daily PP-NRS.

Topline data from the two ongoing trials is expected in the first half of 2025. Additionally, Kymera and Sanofi are evaluating opportunities to expand in indications beyond HS and AD.

Preclinical Immunology: STAT6 and TYK2

STAT6

Summary

Biology and Mechanism of Action

STAT6 is the specific transcription factor required for IL-4 and 13 cytokine signaling. There are two types of IL-4 receptors, type I consisting of IL-4 receptor alpha and gamma C, and type II with IL-4 receptor alpha and IL-13 receptor alpha 1. IL-4 signals through both type I and II receptors and IL-13 signals through type II only. Upon IL-4 or IL-13 binding to the receptor, the downstream activated JAK kinases phosphorylate and activate STAT6, leading to allergic TH2 inflammation.

Figure 14

STAT6 regulated cytokines are clinically validated targets for allergic diseases as demonstrated by the clinical efficacies of the biologics targeting IL-4 and IL-13 signaling. Unlike JAK inhibitors, which are activated by multiple cytokine pathways, STAT6 is specifically activated by IL-4 and 13 cytokines, which supports STAT6 as a means to selectively block IL-4 and 13 signaling. The pathogenic role of STAT6 is also supported by human genetics showing that gain of function mutations of STAT6 cause severe early onset allergic diseases in human. Additionally, STAT6 knockout in mice is protective in multiple allergic disease models, and those mice develop normally and are viable and fertile.

Development Opportunities

We estimate that more than 150 million people in the US, Europe and Japan suffer from TH2-driven diseases. There are existing pathway therapeutics that have validated many of these diseases, including atopic dermatitis, prurigo nodularis, Asthma, COPD, chronic rhinosinusitis with nasal polyps, eosinophilic esophagitis and others.

We believe that STAT6 degradation has the potential to demonstrate full pathway inhibition comparable to biologics, but with the benefit of a simple, daily, oral profile. The preference that many patients may have for an oral option could allow us to access many more patients worldwide than current injectable biologics, potentially transforming the treatment paradigm of TH2 diseases.

Preclinical Studies and Data

Our lead STAT6 degrader, KT-621, is an extremely potent degrader of STAT6. As shown in Figure 15, KT-621 demonstrated picomolar degradation potencies across all the disease relevant human primary cell types that were studied, making KT-621 one of the most potent heterobifunctional degraders we have designed and tested at Kymera. We demonstrated STAT6 degradation across hematopoietic cells which are involved in all TH2 diseases; epithelial cells, including keratinocytes and lung epithelial cells, which are involved in skin and respiratory indications; smooth muscle cells from the lung and esophagus, which are involved in respiratory and GI indications; and vascular endothelial cells which are involved in inflammatory cell infiltration in all TH2 diseases.

Figure 15

We also demonstrated dose-dependent degradation across both Hematopoietic cells and tissue cells, as shown below in Figure 16.

Figure 16

We use mass spectrometry to measure the degradation selectivity profile of all our programs, including STAT6. The following figure is a volcano plot that depicts the degradation selectivity of KT-621. As shown in the figure, at concentrations as high as 100 times the DC90 of KT-621, STAT6 is the only protein that KT-621 degraded out of the approximately 10,000 proteins that were detected by mass spectrometry. Specifically, no other STAT proteins were degraded, demonstrating the very high degradation selectivity of KT-621.

Figure 17

We tested KT-621 for functional selectivity against all the other STAT proteins in cytokine assays, which are shown below in the tables and graphs. Consistent with the observed proteomics selectivity, KT-621 only inhibited STAT6 function, and did not impact any other STAT proteins, as shown in the flat dose response curves, further demonstrating the high functional selectivity of KT-621.

Figure 18

KT-621 was also evaluated in TH2 functional assays to assess its impact on IL-4 and 13 signaling. Specifically, we measured IL-4 and 13 induced TARC release assays in human PBMC, IL-4 and 13 induced CD23 expression assays in human CD19 B cells (which is a B cell activation marker and correlates with IgE class switch) and IL-13 induced periostin release assays in human bronchial and esophageal smooth muscle cells. We chose TARC, IgE and periostin as PD biomarkers as they are all well-established biomarkers that are used in the clinic for TH2 diseases. We also compared the ability of KT-621 to

block the pathways with dupilumab. As shown below in Figure 19, in our preclinical testing, KT-621 fully blocked the IL-4/IL-13 pathway in human TH2 functional assays with IC50’s lower than dupilumab.

Figure 19

We also evaluated KT-621 by assessing levels of degradation in vivo. In our studies, KT-621 robustly degraded STAT6 across multiple preclinical species including mouse, rat, dog and non-human primates. Specifically, KT-621 was able to achieve dose-dependent deep degradation of STAT6 with low oral doses. In Figure 20, we depict KT-621’s in vivo degradation in dogs, illustrating dose-dependent degradation. We tested doses ranging from 0.2 to 12.8 mpk, with doses between approximately 1 and 3 mpk leading to maximal STAT6 degradation near depletion. Additionally, in our studies KT-621 demonstrated rapid degradation onset, notably within just a few hours following a single oral dose. These results, and other PK/PD studies we have completed, suggest the potential for low and developable efficacious doses of KT-621 in humans.

Figure 20

We also evaluated the degradation of STAT6 in key disease relevant tissues in non-human primates. The following Figure 21 illustrates that KT-621, dosed at 10 mpk for 14 days, degraded STAT6 across key disease-relevant tissues, including blood, spleen, skin and lung.

Figure 21

The above degradation represented dosing at the lowest dose level in our dose range finding safety study. In that study, we dosed as high as 300 mpk daily for 14 days and reached concentrations that were above 40-fold of our efficacious concentration. At all dose levels in our study, including the highest dose level, KT-621 was well tolerated with no adverse events or relevant findings.

In preclinical models of the skin and lung, we assessed the in vivo activity of KT-621. First, we assessed KT-621 in a two-week atopic dermatitis model induced by topical application of low-calcemic vitamin D3 analog MC903. The model utilized IL-4/IL-4Rα humanized mice which allowed response to dupilumab and enabled us to compare preclinical activity. KT-621 was dosed once daily orally for 11 days at 2, 8, and 32 mpk. These doses led to ~70%, 80% and 90% degradation, respectively, in the spleen as illustrated in Figure 22. In this preclinical study, dupilumab was dosed 4 times subcutaneously, at 25 mpk twice weekly, a level expected to ensure constant IL-4Rα saturation with full IL-4/13 blockade. We estimated that dose to be equivalent to 300 mg every other week in humans, which is the highest approved dose regimen in humans.

Figure 22

As illustrated in Figure 23, the prominent TH2 inflammation demonstrated by the elevated total serum IgE in the PO vehicle and the SubQ IgG4 control groups, compared to the no MC903 group. In contrast, KT-621 robustly and dose dependently inhibited IgE elevation to levels that were comparable to dupilumab, in this preclinical study. Of note, the KT-621 dose that led to 90% STAT6 degradation produced similar activity in this preclinical model to an IL-4Rα saturating dose of dupilumab, indicating full IL-4 and IL-13 blockade by KT-621 in vivo.

Figure 23

* Significance to PO vehicle (MC903); # Significance to SC IgG4 25 mpk BIW

We assessed KT-621 in a one-month lung inflammation model induced by intranasal house dust mite (HDM) administration, which we believe is considered to be the most relevant preclinical model of TH2 inflammation. Unlike ovalbumin, which is commonly used in mouse models but does not induce airway inflammation in humans, house dust mite is a real-world allergen that can induce asthma in humans. The intranasal HDM model has a dominant TH2 inflammation and was used for the preclinical development of dupilumab. Similar to the skin model previously described, we used the IL4/IL4Rα humanized mice. KT-621 was dosed once daily orally for 31 days at the same three dose levels, 2, 8 and 32 mpk, leading to 72, 85 and 91% degradation in the spleen, respectively, consistent with the previous skin model. Dupilumab was dosed 9 times subcutaneously twice weekly at 25 mpk, meant to ensure constant IL-4Rα saturation with full IL-4/IL-13 blockade, and similarly equivalent to that of the highest approved dose of 300 mg every other week in humans.

As illustrated in Figure 24, the dominant TH2 inflammation was demonstrated by the greatly elevated IgE in the serum, TARC and periostin release in the bronchoalveolar lavage, and eosinophil recruitment to the lung. All are well-established TH2 biomarkers. KT-621 showed robust inhibition at all three dose levels. In this preclinical study, KT-621 blocked TH2 inflammation in vivo equally or better than an IL-4Rα saturating dose of dupilumab in the intranasal HDM asthma model for all these TH2 measures.

Figure 24

*Significance to PO vehicle (HDM); # Significance to SC IgG4 Ctrl 25 mpk

Clinical Development Plan

Our lead STAT6 degrader, KT-621, is currently in IND enabling studies. We expect to begin a Phase 1 clinical trial in the second half of 2024, and to report the Phase 1 results in 2025.

TYK2

Summary

We are developing highly potent and selective degraders of TYK2, a member of the JAK family required for Type I interferon, or IFN, IL-12 and IL-23 signaling with both genetic and clinical validation in autoimmune and inflammatory diseases.

Biology and Mechanism of Action

As seen in Figure 25, TYK2, a member of the JAK family of kinases, binds the IL-12, IL-23 and Type I IFN receptors to recruit and phosphorylate signal transducer and activation of transcription (STAT) transcription factors. Additionally, TYK2 has a well-established scaffolding function that plays a key role in cytokine receptor surface expression and activation. A loss of function variant is protective in autoimmune diseases and an allosteric inhibitor (deucravacitnib) of TYK2 as well as multiple biological agents targeting IL-12, IL-23 and IFN-α have been approved for the treatment of multiple autoimmune diseases, making TYK2 a highly validated target.

Figure 25

Degradation of TYK2, which can fully recapitulate the human knockout biology by completely removing the protein, has the potential to overcome the challenges of small molecule inhibitors, which have limitations due to lack of selectivity, limited target engagement, and/or lack of potent activity against Type I IFN. TYK2 degraders therefore have the potential to achieve full pathway inhibition of Type I IFN, IL-12 and IL-23 while sparing IL-10 in a once daily oral pill with a potential biologics-like activity profile.

Development Opportunities

We estimate that more than 20 million people in the US, Europe and Japan suffer from Type I IFN and IL-12/IL-23 mediated diseases. There are numerous indication opportunities across multiple immunological therapeutic areas including dermatology, gastroenterology, rheumatology, and CNS. The potential for TYK2 to be effective across multiple indications is supported by pathway biologics and TYK2 small molecule inhibitors. We believe that TYK2 degradation differentiates from inhibition and has the potential to demonstrate full pathway inhibition comparable to biologics, but with the benefit of a daily, oral profile.

Preclinical Studies and Data

We have developed a highly potent and selective TYK2 degrader, KT-294. In Figure 26, our proteomics data demonstrates KT-294, a highly selective picomolar TYK2 degrader, recapitulates TYK2 human deficiency biology and fully inhibits Type I IFN and IL-12/23 signaling and spares IL-10/IL-22. In particular, KT-294 is extremely selective over the JAK family members.

Figure 26

In Figure 27, we achieved picomolar degradation in human PBMC and keratinocytes and low nM inhibition of our functional assays across a range of cell types. We have potent preclinical efficacy on the IL-23 and IL-12 signaling pathways in PBMCs and potent inhibition on the Type I IFN pathway in PBMCs and also in specific B-cell assays. We demonstrated that we spare the IL-10 and IL-22 pathways completely.

Figure 27

IL-10 has essential roles in intestinal homeostasis such as epithelial repair and mucosal healing, which is important in diseases such as Inflammatory Bowel Disease, or IBD. In fact, loss of function mutations of IL-10 cause early onset refractory colitis in humans. In Figure 28, we show western blots demonstrating that when TYK2 is not present in a cell, we can induce pSTAT3 with IL-10, showing TYK2 is not necessary for IL-10 signaling. We also show the TYK2 small molecule inhibitor, deucravacitinib, can block that pathway signaling exclusively due to its ability to inhibit JAK1, and not through TYK2.

Figure 28

In Figure 29, we have an assay where we induce phospho-STAT3 in monocytes with IL-10, in this context our degrader has no effect on pSTAT3 because it doesn’t inhibit the IL-10 pathway. However, in contrast, deucravacitinib potently inhibits the IL-10 signaling as shown with the decrease of the orange data points.

Figure 29

Similarly in Figure 30, we have monocytes where we use IL-10 to suppress LPS induced TNF-α. KT-294 has no effect on IL-10 suppression of LPS induced TNF-α release, however deucravacitinib inhibits IL-10’s function of suppressing LPS induced TNF-α release and see an increase in TNF-α, which is demonstrated by the orange data points.

Figure 30

Additionally, we compared KT-294 to TAK-279, an investigational TYK2 inhibitor that is selective over JAK, and as a result spares IL-10. In our experiment, we used a concentration of TAK-279 that was expected to fully occupy TYK2 and a concentration of KT-294 that was expected to fully degrade TYK2 to assess if there were any biological differences between the two compounds. The concentrations were determined based on the IC95 of the IFNα pSTAT2 assay which is the most difficult TYK2-related cytokine assay to inhibit. RNAseq data show KT-294 has superior inhibition of the IFN pathway signature genes, as illustrated in the 21 gene signature score in Figure 31. Differences in the innate immune pathway, as shown in Figure 32, were observed. We believe this is due to the fact KT-294 fully removes the protein, and all possible scaffolding functions, phenocopying human knockout. Based on clinical findings, TAK-279 does not achieve clinical exposures of more than about 77nM with 35mg repeat dosing, which is close to the TAK-279 Phase 3, 30 mg dose. At clinically relevant exposures, we believe it is likely that TAK-279 will not reach these levels of pathway inhibition shown by KT-294 in figure 31.

Figure 31

Figure 32

KT-294 achieved dose dependent deep degradation of TYK2 in vivo with low oral doses. Specifically, in non-human primates, or NHP, upon repeat daily low oral doses, KT-294 can degrade TYK2 in a dose responsive manner and reach full degradation of TYK2, providing a path to pharmacological target engagement, as shown in figure 33.

Figure 33

Clinical Development Plan

We expect to initiate a Phase 1 clinical trial of our TYK2 degrader, KT-294, in the first half of 2025 and to report data in 2025.

Clinical Oncology: STAT3 and MDM2

STAT3

Summary

We are developing our selective STAT3 degraders for the treatment of hematological malignancies and solid tumors. We are also exploring the potential for STAT3 degradation in autoimmune diseases. STAT3 is a transcription factor activated through a variety of different cytokine and growth factor receptors via JAKs, as well as through oncogenic fusion proteins and mutations in STAT3 itself. We believe the diverse functions of STAT3 in tumor biology, evasion of immune surveillance by tumor cells, and inflammation and fibrosis provide opportunities to address a wide variety of high unmet need disease indications through the targeting of a single genetically and clinically validated pathway. While the JAK-STAT pathway has been partially addressed with several clinically successful JAK-targeting agents, we believe there are currently no drugs that specifically affect STAT3 broadly across all the relevant cell types. Small molecule STAT3 dimerization inhibitors targeting the SH2 domain have been in development, but significant challenges remain. Homology of SH2 domains among all STAT family members impacts the ability to achieve specificity for STAT3, and an inability to block dimerization independent transcriptional activities of STAT3. For these reasons, we believe that STAT3 degraders may provide a transformative solution to the development of targeted and selective drugs to address multiple STAT3 dependent pathologies. We are currently evaluating our STAT3 degrader, KT-333, in a Phase 1 clinical trial in patients with relapsed/refractory liquid and solid tumors, including aggressive lymphomas. Patient enrollment and dosing are ongoing in the Phase 1a portion of the trial, and we expect to provide additional clinical data in 2024.

Biology and Mechanism of Action

STAT3 (signal transducer and activator of transcription 3) is a transcription factor and a member of the STAT protein family. In response to cytokines and growth factors, STAT3 is phosphorylated by receptor-associated serine/threonine kinases, and phosphorylated STAT3, or p-STAT3, then forms dimers that translocate into the nucleus, bind to DNA, and regulate transcription of a wide variety of genes involved in oncogenesis, inflammation and fibrosis. STAT3 is frequently mutated and activated in numerous cancers, including clinically aggressive hematologic malignancies with high unmet medical need. Mechanistically, aberrant activation of STAT3 has been directly linked to the promotion of cancer cell survival, proliferation, and metastasis. In addition, STAT3 regulates the crosstalk between tumor, stroma, and immune cells to promote an immunosuppressive tumor microenvironment. STAT3 activation by IL-6 and TGF-ß is also involved in the pathogenesis of autoimmunity and fibrosis. These various roles of STAT3 in disease pathogenesis make it an attractive target for drug development in cancer and autoimmune and fibrotic diseases.

Figure 34

Small molecule inhibitors against JAK family kinases, such as JAK1, JAK2, JAK3, and TYK2, have been approved for the treatment of autoimmune diseases such as rheumatoid arthritis, psoriatic arthritis, and ulcerative colitis and target the JAK2/STAT5 pathway. In oncology, JAK inhibitors have been approved for hematological malignancies with mutations leading to activation of the JAK2/STAT5 pathway, including primary myelofibrosis and polycythemia vera, and for acute graft

versus host disease. JAK inhibitors block signaling of a number of cytokines and growth factors and reduce activation not only of STAT3 but also STAT1 and STAT5 in response to these stimuli. For modulating anti-tumor effects, this broad activity may have conflicting consequences. In particular, the inhibition of STAT1 activity dampens anti-tumor immune responses by cytolytic T cells and antigen presenting cells, thereby counteracting a productive immune response that could be achieved by inhibition of STAT3 alone. As a result, JAK inhibitors have not shown clinical activity in cancer beyond the myeloproliferative neoplasms. The broad activity of JAK inhibitors is also associated with class-specific adverse effects. By targeting STAT3 selectively, these immunosuppressive and safety liabilities associated with broader STAT1 and STAT5 inhibition through JAK inhibition may be avoided while also effectively addressing JAK-dependent and independent activation of STAT3. Monoclonal antibodies directed against pro-inflammatory cytokines such as IL-6 or their receptors IL-6R have also been approved for select autoimmune diseases. However, autoimmune and fibrotic diseases and certain cancers are often regulated by multiple cytokines. As such, targeting STAT3 has the potential to be more effective since it is involved in signaling by not just IL-6, but also by TGF-ß and cytokines such as IL-12, IL-2 and IL-15. Consequently, targeting STAT3 directly has the potential to block multiple signaling pathways that converge on STAT3 and reverse pathological processes that contribute to a tumor-permissive microenvironment.

Development Opportunities

The multiple effects of a STAT3 degrader on oncogenesis, tumor cell resistance to tyrosine kinase inhibitors and chemotherapy, and evasion of immune surveillance provide multiple development opportunities in hematologic malignancies and solid tumors.

Hematologic Malignancies

Oncogenic STAT3 mutations and/or STAT3 pathway activations are highly common in peripheral T-cell lymphoma, or PTCL and cutaneous T-cell lymphoma, or CTCL. Every year, approximately 8,000 patients are diagnosed with PTCL and approximately 6,000 patients are diagnosed with CTCL across major global markets. STAT3 mutations and pathway activations along with responsiveness of PTCL subsets and CTCL to immune checkpoint inhibitors point to a dependency on STAT3 in these indications and therefore the opportunity to develop a STAT3 degrader as a monotherapy. The standard of care for first-line treatment of PTCL is the combination of brentuximab vedotin, a CD30-directed antibody-drug conjugate, and chemotherapy. The majority of PTCL patients, including ALK-ALCL, PTCL-Not Otherwise Specified, AITL and NK/T lymphoma subtypes, eventually progress and die of their disease. For patients with refractory/relapsed disease, current treatment options are limited and approved therapies pralatrexate and romidepsin have shown limited efficacy. High prevalence of STAT3 mutations (approximately 13-38%) and STAT3 pathway activation (up to 90%) is found in these refractory/relapsed PTCL subsets with high unmet need. Given the documented effect of STAT3 downregulation on levels of programmed death-ligand 1, or PD-L1, we expect our STAT3 degrader to have a dual effect in these patients. In CTCL patients with advanced stage disease and the highest levels of STAT3 activation, there are no curative therapies and no standard of care. Antibody-drug conjugates, HDAC inhibitors, and immune checkpoint inhibitors have some activity and are used upfront or in refractory/relapsed patients, but there remains a high unmet need for an effective therapeutic with both tumor-intrinsic as well as immunomodulatory antitumor effects.

STAT3 pathway activation is also present in virtually all patients with T- and NK-cell large granular lymphocytic leukemia, and up to 70% of patients have oncogenic STAT3 mutations. These findings are highly indicative of STAT3 dependency, which is further supported by the preliminary clinical activity of JAK inhibitors in these patients. STAT3 activation is also commonly observed in AML and in DLBCL even though STAT3 mutations are infrequent. PD-L1 overexpression in DLBCL has been linked to worse disease outcomes and responses to anti-PD-1/PD-L1 drugs have been reported in these patients. Given STAT3 has downstream impact on PD-1/PD-L1, we believe that a STAT3 degrader has the potential to achieve profound clinical effects both as a monotherapy and in combination with other active drugs.

Solid Tumors

Cancers that are responsive to anti-PD-1/PD-L1 immune checkpoint inhibitors (ICIs) and tyrosine kinase inhibitors (TKIs), including non-small cell lung cancer, or NSCLC, head and neck squamous cell carcinoma, or HNSCC, breast cancer and colorectal cancer, are compelling development opportunities due to the established role of STAT3 in solid tumor resistance to ICIs and TKIs. Specifically, STAT3 degraders have the potential to improve responses upfront in combination with these modalities or overcome acquired resistance as add-on therapy in second line.

Clinical Studies and Data

In 2022, we initiated our Phase 1 clinical trial of KT-333 to evaluate the safety, tolerability, PK/PD and clinical activity of KT-333 dosed weekly on Days 1, 8 and 15 of 28-day cycles in adult patients with relapsed and/or refractory lymphomas, leukemias and solid tumors. Figure 35 below shows the details of the trial.

Figure 35

In December 2023, we presented clinical data from the Phase 1 clinical trial of KT-333 in a poster session at the 2023 American Society of Hematology (ASH) Annual Meeting and Exposition. The poster provided an interim update with a data cut-off as of October 18, 2023. As of that date, twenty-nine patients, with median age of 65 years, had been treated across five dose levels (DL1-5) with a mean of eight doses, including five with cutaneous T-cell lymphoma (CTCL), two with large granular lymphocytic leukemia, or LGL-L, one each with peripheral T-cell lymphoma, or PTCL, B-cell and Hodgkins’s lymphoma, and nineteen with a variety of solid tumor malignancies. Overall, the data demonstrated early signs of antitumor activity at doses that were generally well-tolerated and associated with substantial STAT3 knockdown in blood and tumor.

The following table highlights the demographics of the 29 patients that were treated across 5 dose levels as of the October 18, 2023, data cut-off.

Figure 36

‡ = anal; appendiceal; cholangiocarcinoma; colon adenocarcinoma; colorectal (4); duodenal; endometrial; head and neck (3); ovarian, pancreatic (2), peritoneal, rectal and renal; ⌂ = anaplastic T-cell lymphoma; Data cut-off: 18 October 2023.

KT-333 was generally well tolerated with primarily Grade 1 and 2 adverse events which included constipation, fatigue, nausea and anemia. The only KT-333 related adverse events that were Grade 3 or higher were stomatitis, arthralgia, and decreased weight in one patient each. Two dose-limiting toxicities (DLTs), stomatitis and arthralgia, occurred in LGL-L patients at DL5 and no DLTs were observed in solid tumor/lymphoma patients. Based on these findings, the study protocol was revised to continue dose escalation in solid tumor and lymphoma patients separately from patients with leukemia, including LGL-L and T-cell prolymphocytic leukemia, or T-PLL patients.

To demonstrate proof-of-mechanism, STAT3 degradation was evaluated in peripheral blood in cycles 1 and 2 using targeted mass spectrometry as shown in Figure 37. Mean maximum degradation of STAT3 in PBMCs post KT-333 infusion increased from 70% to 84% between dose levels 1 and 5 respectively. Percent change in STAT3 represents mean percent change of two STAT3 peptides from baseline. Up to 96% maximum knockdown of STAT3 protein was observed in PBMCs from patient in dose level 4. Recovery of STAT3 protein was observed between doses.

Figure 37

As shown in Figure 38, pathway engagement in tumor was demonstrated through semiquantitative analysis of multiplex immunofluorescence data which showed a 69% decrease in STAT3 positive cells and 87% reduction in phospho STAT3 positive cells in a CTCL biopsy ~ 24 hours post KT-333 infusion compared to baseline.

Figure 38

We observed clinical activity in 3 of 5 CTLC patients, including 2 partial responses and 1 stable disease. We also observed 1 partial response in Classic Hodgkin lymphoma, or cHL. Collectively, these results demonstrated single agent activity in liquid tumors that was supported by preclinical data. In solid tumors, where preclinically no strong single agent activity was observed, a pattern of more prolonged stable disease, or SD in Head & Neck tumors was observed with a total of 4 patients. The following tables highlight the response data as of the October 18, 2023, data cut-off.

Figure 39

*Mucoepidermoid carcinoma of parotid gland (C7+), sinonasal adenocarcinoma (C5), cholangiocarcinoma (C3), renal cell cancer (C3+).

Figure 40

* Received steroids during 1st week of C1 to treat symptoms arising from Sezary Syndrome; ¥ Discontinued d/t AE (Gr. 2 squamous cell carcinoma of skin); discontinued d/t PI discretion (stable disease at discontinuation); HNC1 = Mucoepidermoid carcinoma of parotid gland; HNC2 = Sinonasal adenocarcinoma.

KT-333 resulted in substantial reduction of STAT3, pSTAT3 and SOCS3 in a CTCL patient tumor with concomitant induction of IFNγ-stimulated genes, suggestive of positive immunomodulatory response in the tumor microenvironment that both clinically and preclinically has been shown to enhance the activity of anti-PD-1 drugs, supporting potential expansion into combinations of KT-333 and anti-PD-1 agents. An interferon gamma signature predictive of sensitivity to anti-PD-1 therapy was induced in the tumor biopsy of a cutaneous T-cell lymphoma (CTCL) patient following treatment on the Phase 1 trial, indicating the potential of KT-333 to synergize with PD-1 antibody therapy.

Figure 41

Figure 42

Clinical Development Plans

The Phase 1a dose escalation portion of the trial is ongoing. We expect to provide additional clinical data in 2024.

MDM2

Summary

We are developing degraders that target MDM2 for the treatment of solid tumors and hematological malignancies. KT-253 targets MDM2, the crucial regulator of the most common tumor suppressor, p53. p53 remains intact (wild type) in close to 50% of cancers, meaning that it retains its ability to modulate cancer cell growth. While small molecule inhibitors (SMIs) have been developed to stabilize and upregulate p53 expression, they have been found to induce a feedback loop that increases MDM2 protein levels, which can repress p53 and limit their efficacy. In preclinical studies, KT-253 has shown the ability to overcome the MDM2 feedback loop and rapidly induce cancer cell death with brief exposures, providing the opportunity for an improved efficacy and safety profile. In May 2023, we began dosing in a Phase 1 clinical trial of KT-253. The study is designed to evaluate the safety, tolerability, PK/PD and clinical activity of KT-253 in adult patients with liquid and solid tumors. KT-253 has achieved clinical proof-of-mechanism in the Phase 1 trial and shown signs of anti-tumor activity in liquid and solid tumor types. Patient enrollment and dosing are ongoing in the Phase 1a portion of the trial, and we expect to provide additional clinical data in 2024.

Biology and Mechanism of Action

The murine double minute 2 (MDM2) oncoprotein is the major E3 ligase which controls the tumor suppressor p53. p53 is a transcription factor that regulates cellular responses to stress and guides cell fate decisions such as cell cycle arrest, DNA repair, senescence, and apoptosis and functional in close to 50% of cancers, both liquid and solid, and many p53 functional cell lines are dependent on MDM2 overexpression for p53 suppression and survival. Stabilization and upregulation of p53 by removal of MDM2 by degradation can cause cells to undergo cell death and/or cell cycle arrest. While MDM2 small molecule inhibitors have shown clinical activity in a variety of tumor types, the activity has been limited as a result of the inhibition of MDM2 leading to a feedback loop, as shown in Figure 43. This feedback loop results in upregulation of MDM2 protein expression, which in turn makes it more difficult for occupancy-driven small molecules to inhibit MDM2. As a result, small molecule inhibitors have had a more modest effect on p53 upregulation which often leads to cell cycle arrest rather than apoptosis, thereby limiting the efficacy of MDM2/p53 small molecule inhibitors. This feedback loop also necessitates more chronic exposure to drug to maintain modest MDM2 inhibition in tumors, potentially leading to toxic effects on normal cells that limits the safety and tolerability of these inhibitors. Degraders have the potential to overcome the MDM2 feedback loop by completely removing the protein in a catalytic manner. This enables the development of highly potent drugs that are able to induce strong p53 upregulation and an irreversible acute apoptotic response in tumor cells with just brief exposures, thereby maximizing efficacy and improving the safety profile by allowing time for the recovery of normal cells.

Figure 43

Development Opportunities

The large numbers of p53wt cell lines dependent on MDM2, as seen in Figure 44, gives a high-level view of the potential breadth of opportunities in oncology for a potent and well tolerated agent for this pathway. These tumor cell types include but are not limited to cancers which have amplification and over expression of MDM2. De-stabilization of p53 by MDM2 enables cells to survive by blocking both cell cycle arrest and apoptosis. While the opportunities are very diverse, we plan to focus our development efforts on tumors which are most susceptible to the acute apoptotic response elicited by our degraders, where we believe we will be able to achieve the greatest therapeutic index and efficacy. Our initial disease areas of interest are hematological malignancies and solid tumor indications where preclinically we see that MDM2 degradation leads to an acute apoptotic response predictive of clinical activity with intermittent dosing.

Figure 44

For hematological malignances, KT-253 has potential monotherapy and combination opportunities in Acute Myeloid Leukemia (AML), and potential opportunities across Myelofibrosis, Myelodysplastic Syndrome (MDS), Acute Lymphocytic Leukemia (ALL) and TP53WT lymphomas. For solid tumors, KT-253 has monotherapy opportunities across a subset of adult and pediatric tumors, to be informed by emerging gene signature with potential for a tumor-agnostic development path. We are assembling a comprehensive preclinical and clinical dataset examining the factors impacting in vivo response to intermittent dosing with KT-253 across multiple different solid and liquid tumor types in order to derive patient selection biomarkers for the next stage of development after Phase 1a.

Preclinical Studies and Data

KT-253’s potent p53 stabilization, with brief exposures, drives apoptosis in cancer cells. In Figure 45, KT-253 demonstrated greater than 200-fold improvements in both in vitro cell growth inhibition and apoptosis than small molecule inhibitors.

Figure 45

Unlike small molecule inhibitors, KT-253 removes the protein, which can overcome the p53-dependent feedback loop that upregulates MDM2 production. As seen in Figure 46, MDM2 levels are increased by the small molecule inhibitor (feedback loop), impairing p53 stabilization.

Figure 46

In preclinical models, 4-hour target coverage by KT-253 was sufficient to induce apoptosis, as shown in Figure 47. These data support an intermittent dosing schedule of KT-253 can drive efficacy while increasing therapeutic index.

Figure 47

KT-253 potently degrades MDM2 leading to pathway impact and antitumor activity superior to a small molecular inhibitor in preclinical models. Targeted proteomic analysis of RS4;11 (ALL) tumors demonstrated robust degradation of MDM2 one hour post dosing and associated pathway activation biomarkers including p53 and GDF15, as show in Figure 48.

Figure 48

Figure 49 shows sustained tumor regressions in MV4;11 (AML) CDX models after a single 3 mg/kg KT-253 dose. Additionally, KT-253 demonstrated robust anti-tumor activity in MCC models. No efficacy was observed with the clinically relevant dosing regimen of the small molecule inhibitor (DS-3032).

Figure 49

Clinical Studies and Data

The Phase 1 trial, began dosing patients in May 2023, is evaluating the safety, tolerability, PK/PD, and clinical activity of KT-253 in patients with relapsed or refractory high grade myeloid malignancies, including AML, ALL, lymphoma and solid tumors. Patients in the Phase 1 dose escalation study will receive intravenous doses of KT-253 administered once every 3 weeks. The open-label study is intended to identify the recommended Phase 2 dose, and is comprised of two arms, with ascending doses of KT-253 in each arm. The first arm consists of patients with lymphomas and advanced solid tumors and the second arm consists of patients with high grade myeloid malignancies and ALL.

Figure 50

As of the October 20, 2023, data cut-off date, a total of 9 patients with solid tumors had been enrolled onto dose levels 1-3 of Arm A and received a mean of 2.3 cycles with a range of 1 to 6 cycles. The data from Arm A of the ongoing Phase 1a trial demonstrated KT-253 clinical proof-of-mechanism and initial signs of clinical activity in the first 2 dose levels in patients. Clinical response results for all patients within a dose cohort were available for dose level 1. Based on exposures we did not expect this dose level to be clinically active, however, we observed that among the 3 solid tumor patients treated on dose level 1, there was 1 confirmed partial response after 4 cycles with treatment continuing after 6 cycles, 1 confirmed stable disease after 4 cycles with the patient subsequently discontinued from the study after 6 cycles for lack of response, and 1 patient with disease progression after cycle 1, as seen in Figure 51. The patient with the partial response had Merkel Cell Carcinoma, or MCC, metastatic to abdominal lymph nodes and skin who had previously been treated with chemotherapy as well as multiple different immune checkpoint inhibitors.

Figure 51

There were no dose-limiting toxicities across dose levels 1-3. As of the data cut-off date, the most common drug-related adverse events. or AE’s, occurring in 2 or more patients included Grade 1/2 nausea and Grade 1 diarrhea. One patient at dose level 1 had a serious adverse event, or SAE, of Grade 3 hypotension during cycle 4 that was due to diminished oral intake deemed related to study drug. Treatment included IV fluids and the patient remains on study without dose reduction or recurrence of hypotension. As of the data cut-off date, there were no neutropenia or thrombocytopenia AEs even in patients who had received up to 6 cycles of therapy.

Clinical Development Plan

The KT-253 Phase 1a trial is an open label dose escalation study where adult patients with relapsed or refractory high grade myeloid malignancies, ALL, lymphomas and solid tumors receive IV doses of KT-253 once every 3 weeks. The study is intended to evaluate safety, tolerability, PK/PD and initial clinical activity and identify the recommended Phase 2 dose. It is comprised of two arms with ascending doses of KT-253 in each arm. Arm A is in patients with advanced solid tumors and lymphomas and Arm B is in patients with relapsed or refractory high grade myeloid malignancies, including AML, and ALL. The first patient was dosed in May 2023 and the first 2 dose levels in Arm A have been fully enrolled, with enrollment ongoing. Enrollment onto Arm B has also been initiated following demonstration of on-target pharmacology in the first 2 dose levels of Arm A. The Company expects to share additional clinical data in 2024.

Collaboration Agreement with Sanofi (formerly Genzyme Corporation)

On July 7, 2020, we entered into a collaboration agreement, or the Original Sanofi Agreement, with Genzyme Corporation, a subsidiary of Sanofi, to co-develop drug candidates directed to two biological targets. The Original Sanofi Agreement became effective during the third quarter of 2020.

On November 15, 2022, we entered into an Amended and Restated Collaboration and License Agreement with Sanofi, or the Amended Sanofi Agreement, which amended the Original Sanofi Agreement to revise certain research terms and responsibilities set forth under the Original Sanofi Agreement. The Amended Sanofi Agreement also specifies details around the timing and number of Phase 2 trials required under the terms of the collaboration. The Amended Sanofi Agreement became effective on December 5, 2022. The Original Sanofi Agreement, as amended by the Amended Sanofi Agreement, is referred to herein as the Sanofi Agreement.

Under the Sanofi Agreement, Kymera grants to Sanofi a worldwide exclusive license to develop, manufacture and commercialize certain lead compounds generated during the collaboration directed against IRAK4 and one additional undisclosed target in an undisclosed field of use. Such license is exercisable on a collaboration target-by-collaboration target basis only after a specified milestone. For compounds directed against IRAK4, the field of use includes diagnosis, treatment, cure, mitigation or prevention of any diseases, disorders or conditions, excluding oncology and immune-oncology.

Pursuant to the Sanofi Agreement, with respect to both targets we are responsible for discovery and preclinical research and conducting a phase 1 clinical trial for at least one degrader directed against IRAK4 plus up to three back up degraders, the costs of which will be borne by us, except in certain circumstances. With respect to both targets, Sanofi is responsible for development, manufacturing, and commercialization of product candidates after a specified development milestone occurs with respect to each collaboration candidate.

In addition, pursuant to the Sanofi Agreement, Sanofi will grant to us an exclusive option, or Opt-In Right, exercisable, at our sole discretion, on a collaboration target-by-collaboration target basis that will include the right to (i) fund 50% of the United States development costs for collaboration products directed against such target in the applicable field of use and (ii) share equally in the net profits and net losses of commercializing collaboration products directed against such target in the applicable field of use in the United States. In addition, if we exercise our Opt-In Right, Sanofi will grant to us an exclusive option, applicable to each collaboration target, which upon exercise will allow us to conduct certain co-promotion activities in the field in the United States.

In consideration for the exclusive licenses granted to Sanofi under the Sanofi Agreement, Sanofi paid to us an upfront payment of $150.0 million. In addition to the upfront payment, under the agreement we were eligible to receive certain development milestone payments of up to $1.48 billion in the aggregate, of which more than $1.0 billion relates to the IRAK4 program, upon the achievement of certain developmental or regulatory events. We will also be eligible to receive certain commercial milestone payments up to $700.0 million in the aggregate, of which $400.0 million relates to the IRAK4 program, which are payable upon the achievement of certain net sales thresholds. We will further be eligible to receive tiered royalties for each program on net sales ranging from the high single digits to high teens, subject to low-single digits upward adjustments in certain circumstances.

The Sanofi Agreement, unless earlier terminated, will expire on a product-by-product basis on the date of expiration of all payment obligations under the Sanofi Agreement with respect to such product. We or Sanofi may terminate the agreement upon the other party’s material breach or insolvency or for certain patent challenges. In addition, Sanofi may terminate the agreement for convenience or for a material safety event upon advance prior written notice, and we may terminate the agreement with respect to any collaboration candidate if, following Sanofi’s assumption of responsibility for the development,

commercialization or manufacturing of collaboration candidates with respect to a particular target, Sanofi ceases to exploit any collaboration candidates directed to such target for a specified period.

Additionally, in December 2022, Sanofi provided us with written notice of its intention to take KT-474 into Phase 2 clinical trials. In the fourth quarter of 2023, the Company achieved two milestones of $40.0 million and $15.0 million relating to the dosing of the first patient in the Phase 2 clinical trial for the first and second indications, respectively. As of December 31, 2023, the Company had received the $40.0 million milestone with the $15.0 million included within the accounts receivable on the consolidated balance sheet.

In September 2023, the Company and Sanofi mutually agreed to cease activities related to the undisclosed target and we are no longer eligible for the milestone and royalty payments associated with the second target.

Manufacturing / Supply Chain

We do not own or operate manufacturing facilities for the production of our drug candidates and currently have no plans to build our own clinical or commercial scale manufacturing capabilities. We currently engage with third-party contract manufacturing organizations, or CMOs, for the manufacture of our drug candidates for preclinical studies, and we intend to continue to do so in the future. We rely on and expect to continue to rely on third-party manufacturers for the production of both drug substance and finished drug product. We have engaged third-party manufacturers to supply the drug substances for our drug candidates and a third-party manufacturer to develop and manufacture finished drug products that we are using in our clinical trials. We currently obtain our supplies from these manufacturers on a purchase order basis and do not have long-term supply arrangements in place. Should any of these manufacturers become unavailable to us for any reason, we believe that there are a number of potential replacements, although we may incur some delay in identifying and qualifying such replacements.

All of our drug candidates are organic compounds of low molecular weight, generally called small molecules, but which are larger than traditional small molecule therapeutics. We have selected these compounds not only on the basis of their potential efficacy and safety, but also because we anticipate an ease of synthesis and cost of goods. We have produced drug substances and drug products for use in our clinical trials and continue to refine our production processes. The drug substance and drug product processes are amenable to scale-up and do not require unusual equipment in the manufacturing process. To adequately meet our needs for late-stage clinical and commercial manufacturing, our suppliers will need to scale their production, or we will need to secure alternate suppliers.

Competition

The biotechnology industry is extremely competitive in the race to develop new products. While we believe we have significant competitive advantages with our years of expertise in targeted protein degradation, clinical development expertise, and intellectual property position, we currently face and will continue to face competition for our development programs from companies that use targeted protein degradation or targeted protein degradation development platforms, and from companies focused on more traditional therapeutic modalities such as small molecules and antibodies. The competition is likely to come from multiple sources, including larger pharmaceutical companies, biotechnology companies, and academia.

Companies developing small molecule protein degraders therapies for patients, include, but are not limited to, Arvinas, Inc., C4 Therapeutics, Inc., Nurix Therapeutics, Inc., and Foghorn Therapeutics, Inc. Further, several large pharmaceutical companies have disclosed preclinical investments in this field. Our competitors will also include companies that are or will be developing other targeted protein degradation methods as well as small molecule, antibody, or gene therapies for the same indications that we are targeting. In addition to competitors we face in developing small molecule protein degraders, we will also face competition in the indications we expect to pursue with our IRAK4, STAT6, TYK2, STAT3, and MDM2 programs. Many of these indications have approved standards of care which may include more traditional therapeutic modalities. In order to compete effectively with these existing therapies, we will need to demonstrate that our protein degrader therapies are favorable to existing therapeutics.

Intellectual Property

Our success depends in part on our ability to secure intellectual property protection for our product candidates and future products, as well as our platform protein degradation technologies and any other relevant inventions and improvements that are considered commercially important to our business. Our success also depends on our ability to defend and enforce our

intellectual property rights, preserve the confidentiality of our proprietary information, and operate without infringing, misappropriating or otherwise violating the valid and enforceable patents and proprietary rights of third parties.

As with other biotechnology and pharmaceutical companies, our ability to secure and maintain intellectual property protection for our product candidates, future products, and other proprietary technologies will depend on our success in obtaining effective patent coverage and enforcing those patents if granted. However, we cannot guarantee that our pending patent applications, and any patent applications that we may in the future file, will result in the issuance of patents, or that any issued patents we may obtain will provide sufficient proprietary protection from competitors. Any issued patents that we obtain may be challenged, invalidated, or circumvented by third parties.

In addition to patents, we also rely on trade secrets, know-how and continuing technological innovation to develop and maintain our competitive position. We seek to protect our proprietary technology, in part, through confidentiality agreements and invention assignment agreements with our employees, consultants, scientific advisors, contractors and potential collaborators.

Patent Portfolio

Our intellectual property includes a portfolio of wholly owned patent families covering our platform E3 ligase ligand technology and our novel bifunctional degrader product candidates, including claims to compositions of matter, pharmaceutical compositions, methods of use, methods of treatment, and other related compounds and methods. Our intellectual property portfolio is in its very early stages, and, as of December 31, 2023, included 19 granted U.S. patents, about 100 U.S. patent applications, about 25 international patent applications, five granted foreign patents, and about 449 foreign patent applications. Our patent portfolio is generally organized into two categories: (1) platform E3 ligase ligand patent families and (2) protein degrader patent families, including various target-specific degrader patent families.

Platform E3 Ligase Ligand Patent Families

Our platform E3 ligase ligand patent families are wholly owned and include four patent families directed to novel ligands for the cereblon E3 ubiquitin ligase, as well as methods of treatment and other related methods. As of December 31, 2023, our platform E3 ligase ligand patent families included three granted U.S. patents, five U.S. patent applications, and three patent applications in Europe. Any U.S. or foreign patents resulting from these applications, if granted and all appropriate maintenance fees paid, are expected to expire between 2038 and 2044, absent any patent term adjustments or extensions.

Protein Degrader Patent Families

Our protein degrader patent families are wholly owned and are directed to novel bifunctional degrader compounds that are useful in affecting ubiquitination of a target protein, as well as methods of treatment and other related methods. As of December 31, 2023, our protein degrader patent families included two granted U.S. patent, five U.S. patent applications and about 19 foreign patent applications filed in foreign jurisdictions, such as Australia, Canada, Europe, Israel, Japan, Mexico, New Zealand, and the Russian Federation. Any U.S. or foreign patents resulting from these applications, if granted and all appropriate maintenance fees paid, are expected to expire between 2038 and 2043, absent any patent term adjustments or extensions.

Target-Specific Degrader Patent Families

Our target-specific degrader patent families are wholly owned and focus protection around degrader compounds that are designed to target specific proteins for degradation, as well as methods of treatment and other related methods. Such targets include, for example, IRAK (interleukin-1 receptor-associated kinases) and STAT (signal transducers and activators of transcription). As of December 31, 2023, our target-specific degrader patent families included 14 granted U.S. patents, about 87 U.S. patent applications, about 22 international patent applications, three granted foreign patents, and about 423 patent applications filed in foreign jurisdictions, such as Australia, Brazil, Canada, China, Eurasia, Europe, Israel, India, Japan, Mexico, New Zealand, Singapore, South Africa, and Taiwan. Any U.S. or foreign patents resulting from our target-specific degrader patent families, if granted and all appropriate maintenance fees paid, are expected to expire between 2038 and 2044, absent any patent term adjustments or extensions.

IRAK-Specific Patent Families

Our IRAK-specific patent families are wholly owned and include patent families covering degrader compounds that are designed to specifically target IRAK for degradation and patent families covering novel IRAK ligands. As of December 31, 2023, our IRAK-specific patent families included 11 granted U.S. patents, about 34 U.S. patent applications, about eight international patent applications, three granted foreign patents and about 293 patent applications filed in foreign jurisdictions,

such as Australia, Argentina, Brazil, Canada, China, Europe, Eurasia, Gulf Cooperation Council, Israel, India, Japan, Mexico, New Zealand, Singapore, South Africa, and Taiwan. Any U.S. or foreign patents resulting from our IRAK-specific patent families, if granted and all appropriate maintenance fees paid, are expected to expire between 2038 and 2044, absent any patent term adjustments or extensions.

With respect to the KT-474 product candidate, as of December 31, 2023, we own three granted U.S. patent, eight pending U.S. patent applications, five pending international patent applications, one granted foreign patent and about 128 patent applications filed in foreign jurisdictions, such as Australia, Brazil, Canada, China, Europe, Israel, India, Japan, South Korea, Mexico, New Zealand, Singapore, South Africa, and Taiwan, each with claims directed to compositions of matter covering KT-474 and/or methods of making or using KT-474. Any U.S. or foreign patents resulting from these patent families, if granted and all appropriate maintenance fees paid, are expected to expire between 2039 and 2044, absent any patent term adjustments or extensions.

STAT-Specific Patent Families

Our STAT-specific patent families are wholly owned and focus on degrader compounds that are designed to specifically target signal transducers and activators of transcription (STAT) for degradation. As of December 31, 2023, our STAT-specific patent families included two granted U.S. patent, about 18 U.S. patent applications, three international patent applications, and about 49 patent applications filed in foreign jurisdictions, such as Australia, Canada, China, Eurasia, Europe, India, Israel, Japan, South Korea, Mexico, and Taiwan. Any U.S. or foreign patents resulting from our STAT-specific patent families, if granted and all appropriate maintenance fees paid, are expected to expire between 2040 and 2044, absent any patent term adjustments or extensions.

Other Target-Specific Patent Families

As of December 31, 2023, we own one granted U.S. patent, about 31 U.S. patent applications, 10 international patent applications and about 81 patent applications filed in Australia, Argentina, Brazil, Canada, China, Europe, Gulf Cooperation Council, Israel, India, Japan, Mexico, New Zealand, Singapore, South Africa, and Taiwan which focus on degrader compounds designed to specifically target other proteins. Any U.S. or foreign patents resulting from these patent families, if granted and all appropriate maintenance fees paid, are expected to expire between 2040 and 2044, absent any patent term adjustments or extensions.

The term of individual patents may vary based on the countries in which they are obtained. Generally, patents issued from applications filed in the United States are effective for 20 years from the earliest effective non-provisional filing date. In certain cases, a patent term can be extended to recapture a portion of the term effectively lost as a result of the FDA regulatory review period. The Hatch-Waxman Act permits a patent term extension of up to five years beyond the expiration of the patent, though the total patent term, including any extension, must not exceed 14 years following FDA approval. A patent can only be extended once, such that, if a single patent is applicable to multiple products, it can only be extended based on one product.

The duration of patents outside of the United States varies in accordance with provisions of applicable local law, but typically is also 20 years from the earliest effective national filing date.

Similar patent term extension provisions are available in Europe and other foreign jurisdictions to extend the term of a patent covering an approved drug. When possible, we expect to apply for patent term extensions for patents covering our product candidates and their methods of use.

Trademarks

We have and intend to file applications for trademark registrations in connection with our product candidates and other technologies in various jurisdictions, including the United States.

We have applied to register both the KYMERA mark and the KYMERA THERAPEUTICS mark in the United States, Europe, and Canada. We also filed applications in the same jurisdictions for the mark IRAKIMiD, for pharmaceutical and medical preparations and therapeutics, as well as diagnostic reagents, for the treatment of oncology, autoimmune, immune-oncology and other related diseases. In addition, we filed applications for E3 HUMAN ATLAS and E3 LIGASE WHOLE BODY ATLAS in connection with pharmaceutical research and development and drug development and discovery services. All of our European Union trademarks in existence as of December 31, 2020 were automatically cloned onto the United Kingdom register due to “Brexit.”

Most recently, we filed an application for our K & Design mark in the United States, and we plan to file European Union, United Kingdom, and Canada applications based on our U.S. priority date in that application in due course.

Government Regulation

The FDA and other regulatory authorities at federal, state and local levels, as well as in foreign countries, extensively regulate, among other things, the research, development, testing, manufacture, quality control, import, export, safety, effectiveness, labeling, packaging, storage, distribution, record keeping, approval, advertising, promotion, marketing, post-approval monitoring and post-approval reporting of drugs. We, along with our vendors, contract research organizations and contract manufacturers, will be required to navigate the various preclinical, clinical, manufacturing and commercial approval requirements of the governing regulatory agencies of the countries in which we wish to conduct studies or seek approval of our product candidates. The process of obtaining regulatory approvals of drugs and ensuring subsequent compliance with appropriate federal, state, local and foreign statutes and regulations requires the expenditure of substantial time and financial resources.

In the U.S., the FDA regulates drug products under the Federal Food, Drug, and Cosmetic Act, or FD&C Act, as amended, its implementing regulations and other laws. If we fail to comply with applicable FDA or other requirements at any time with respect to product development, clinical testing, approval or any other legal requirements relating to product manufacture, processing, handling, storage, quality control, safety, marketing, advertising, promotion, packaging, labeling, export, import, distribution, or sale, we may become subject to administrative or judicial sanctions or other legal consequences. These sanctions or consequences could include, among other things, the FDA’s refusal to approve pending applications, issuance of clinical holds for ongoing studies, suspension or revocation of approved applications, warning or untitled letters, product withdrawals or recalls, product seizures, relabeling or repackaging, total or partial suspensions of manufacturing or distribution, injunctions, fines, civil penalties or criminal prosecution.

The process required by the FDA before our product candidates are approved as drugs for therapeutic indications and may be marketed in the U.S. generally involves the following:

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completion of extensive preclinical studies in accordance with applicable regulations, including studies conducted in accordance with good laboratory practice, or GLP, requirements;

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completion of the manufacture, under current Good Manufacturing Practices, or cGMP, conditions, of the drug substance and drug product that the sponsor intends to use in human clinical trials along with required analytical and stability testing;

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submission to the FDA of an IND application, which must become effective before clinical trials may begin;

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approval by an institutional review board, or IRB, or independent ethics committee at each clinical trial site before each trial may be initiated;

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performance of adequate and well-controlled clinical trials in accordance with applicable IND regulations, good clinical practice, or GCP, requirements and other clinical trial-related regulations to establish the safety and efficacy of the investigational product for each proposed indication;

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submission to the FDA of a NDA;

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a determination by the FDA within 60 days of its receipt of an NDA, to accept the filing for review;

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satisfactory completion of one or more FDA pre-approval inspections of the manufacturing facility or facilities where the drug will be produced to assess compliance with cGMP requirements to assure that the facilities, methods and controls are adequate to preserve the drug’s identity, strength, quality and purity;

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potential FDA audit of the clinical trial sites that generated the data in support of the NDA;

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payment of user fees for FDA review of the NDA; and

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FDA review and approval of the NDA, including consideration of the views of any FDA advisory committee, prior to any commercial marketing or sale of the drug in the U.S.

Preclinical Studies and Clinical Trials for Drugs

Before testing any drug in humans, the product candidate must undergo rigorous preclinical testing. Preclinical studies include laboratory evaluations of drug chemistry, formulation and stability, as well as in vitro and animal studies to assess safety and in some cases to establish the rationale for therapeutic use. The conduct of preclinical studies is subject to federal

and state regulations and requirements, including GLP requirements for safety/toxicology studies. The results of the preclinical studies, together with manufacturing information and analytical data must be submitted to the FDA as part of an IND. An IND is a request for authorization from the FDA to administer an investigational product to humans and must become effective before clinical trials may begin. Some long-term preclinical testing may continue after the IND is submitted. The IND automatically becomes effective 30 days after receipt by the FDA, unless the FDA, within the 30-day time period, raises concerns or questions about the conduct of the clinical trial, including concerns that human research patients will be exposed to unreasonable health risks, and imposes a full or partial clinical hold. FDA must notify the sponsor of the grounds for the hold and any identified deficiencies must be resolved before the clinical trial can begin. Submission of an IND may result in the FDA not allowing clinical trials to commence or not allowing clinical trials to commence on the terms originally specified in the IND.

The clinical stage of development involves the administration of the product candidate to healthy volunteers or patients under the supervision of qualified investigators, generally physicians not employed by or under the trial sponsor’s control, in accordance with GCP requirements, which include the requirements that all research patients provide their informed consent for their participation in any clinical trial. Clinical trials are conducted under protocols detailing, among other things, the objectives of the clinical trial, dosing procedures, subject selection and exclusion criteria and the parameters and criteria to be used in monitoring safety and evaluating effectiveness. Each protocol, and any subsequent amendments to the protocol, must be submitted to the FDA as part of the IND. Furthermore, each clinical trial must be reviewed and approved by an IRB for each institution at which the clinical trial will be conducted to ensure that the risks to individuals participating in the clinical trials are minimized and are reasonable related to the anticipated benefits. The IRB also approves the informed consent form that must be provided to each clinical trial subject or his or her legal representative and must monitor the clinical trial until completed. The FDA, the IRB or the sponsor may suspend or discontinue a clinical trial at any time on various grounds, including a finding that the patients are being exposed to an unacceptable health risk. There also are requirements governing the reporting of ongoing clinical trials and completed clinical trials to public registries. Information about applicable clinical trials, including clinical trial results, must be submitted within specific timeframes for publication on the www.clinicaltrials.gov website.

A sponsor who wishes to conduct a clinical trial outside of the United States may, but need not, obtain FDA authorization to conduct the clinical trial under an IND. If a foreign clinical trial is not conducted under an IND, FDA will nevertheless accept the results of the study in support of an NDA if the study was conducted in accordance with GCP requirements, and the FDA is able to validate the data through an onsite inspection if deemed necessary.

Clinical trials to evaluate therapeutic indications to support NDAs for marketing approval are typically conducted in three sequential phases, which may overlap.

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Phase1—Phase 1 clinical trials involve initial introduction of the investigational product into healthy human volunteers or patients with the target disease or condition. These studies are typically designed to test the safety, dosage tolerance, absorption, metabolism and distribution of the investigational product in humans, excretion the side effects associated with increasing doses, and, if possible, to gain early evidence of effectiveness.

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Phase2—Phase 2 clinical trials typically involve administration of the investigational product to a limited patient population with a specified disease or condition to evaluate the drug’s potential efficacy, to determine the optimal dosages and dosing schedule and to identify possible adverse side effects and safety risks.

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Phase3—Phase 3 clinical trials typically involve administration of the investigational product to an expanded patient population to further evaluate dosage, to provide statistically significant evidence of clinical efficacy and to further test for safety, generally at multiple geographically dispersed clinical trial sites. These clinical trials are intended to establish the overall risk/benefit ratio of the investigational product and to provide an adequate basis for product approval and physician labeling.

In March 2022, the FDA released a final guidance entitled “Expansion Cohorts: Use in First-In-Human Clinical Trials to Expedite Development of Oncology Drugs and Biologics,” which outlines how drug developers can utilize an adaptive trial design commonly referred to as a seamless trial design in early stages of oncology drug development (i.e., the first-in-human clinical trial) to compress the traditional three phases of trials into one continuous trial called an expansion cohort trial. Information to support the design of individual expansion cohorts are included in IND applications and assessed by FDA. Expansion cohort trials can potentially bring efficiency to drug development and reduce development costs and time.

Post-approval trials, sometimes referred to as Phase 4 clinical trials or post-marketing studies, may be conducted after initial marketing approval. These trials are used to gain additional experience from the treatment of patients in the intended therapeutic indication and are commonly intended to generate additional safety data regarding use of the product in a clinical setting. In certain instances, the FDA may mandate the performance of Phase 4 clinical trials as a condition of approval of an NDA.

Progress reports detailing the results of the clinical trials, among other information, must be submitted at least annually to the FDA. Written IND safety reports must be submitted to the FDA and the investigators fifteen days after the trial sponsor determines the information qualifies for reporting for serious and unexpected suspected adverse events, findings from other studies or animal or in vitro testing that suggest a significant risk for human volunteers and any clinically important increase in the rate of a serious suspected adverse reaction over that listed in the protocol or investigator brochure. The sponsor must also notify the FDA of any unexpected fatal or life-threatening suspected adverse reaction as soon as possible but in no case later than seven calendar days after the sponsor’s initial receipt of the information.

Concurrent with clinical trials, companies usually complete additional animal studies and must also develop additional information about the chemistry and physical characteristics of the product candidate and finalize a process for manufacturing the drug product in commercial quantities in accordance with cGMP requirements. The manufacturing process must be capable of consistently producing quality batches of the product candidate and manufacturers must develop, among other things, methods for testing the identity, strength, quality and purity of the final drug product. Additionally, appropriate packaging must be selected and tested, and stability studies must be conducted to demonstrate that the product candidate does not undergo unacceptable deterioration over its shelf life.

U.S. Marketing Approval for Drugs

Assuming successful completion of the required clinical testing, the results of the preclinical studies and clinical trials, together with detailed information relating to the product’s chemistry, manufacture, controls and proposed labeling, among other things, are submitted to the FDA as part of an NDA requesting approval to market the product for one or more indications. An NDA is a request for approval to market a new drug for one or more specified indications and must contain proof of the drug’s safety and efficacy for the requested indications. The marketing application is required to include both negative and ambiguous results of preclinical studies and clinical trials, as well as positive findings. Data may come from company-sponsored clinical trials intended to test the safety and efficacy of a product’s use or from a number of alternative sources, including studies initiated by investigators. To support marketing approval, the data submitted must be sufficient in quality and quantity to establish the safety and efficacy of the investigational product to the satisfaction of the FDA. FDA approval of an NDA must be obtained before a drug may be marketed in the U.S.

The FDA reviews all submitted NDAs before it accepts them for filing and may request additional information rather than accepting the NDA for filing. The FDA must make a decision on accepting an NDA for filing within 60 days of receipt, and such decision could include a refusal to file by the FDA. Once the submission is accepted for filing, the FDA begins an in-depth substantive review of the NDA. The FDA reviews an NDA to determine, among other things, whether the drug is safe and effective for the indications sought and whether the facility in which it is manufactured, processed, packaged or held meets standards designed to assure the product’s continued safety, quality and purity. Under the goals and polices agreed to by the FDA under the Prescription Drug User Fee Act, or PDUFA, the FDA targets ten months, from the filing date, in which to complete its initial review of a new molecular entity NDA and respond to the applicant, and six months from the filing date of a new molecular entity NDA for priority review. The FDA does not always meet its PDUFA goal dates for standard or priority NDAs, and the review process is often extended by FDA requests for additional information or clarification.

Further, under PDUFA, as amended, each NDA must be accompanied by a user fee. The FDA adjusts the PDUFA user fees on an annual basis. Fee waivers or reductions are available in certain circumstances, including a waiver of the application fee for the first application filed by a small business. Additionally, no user fees are assessed on NDAs for products designated as orphan drugs, unless the product also includes a non-orphan indication.

The FDA also may require submission of a Risk Evaluation and Mitigation Strategy, or REMS, program if it believes that a risk evaluation and mitigation strategy is necessary to ensure that the benefits of the drug outweigh its risks. The REMS program could include use of risk evaluation and mitigation strategies like medication guides, physician communication plans, assessment plans and/or elements to assure safe use, such as restricted distribution methods, patient registries or other risk-minimization tools.

The FDA may refer an application for a novel drug to an advisory committee. An advisory committee is a panel of independent experts, including clinicians and other scientific experts, which reviews, evaluates and provides a recommendation as to whether the application should be approved and under what conditions. The FDA is not bound by the recommendations of an advisory committee, but it considers such recommendations carefully when making decisions.

Before approving an NDA, the FDA typically will inspect the facility or facilities where the product is manufactured. The FDA will not approve an application unless it determines that the manufacturing processes and facilities are in compliance with cGMP requirements and adequate to assure consistent production of the product within required specifications. Additionally, before approving an NDA, the FDA may inspect one or more clinical trial sites to assure compliance with GCP and other requirements and the integrity of the clinical data submitted to the FDA.

After evaluating the NDA and all related information, including the advisory committee recommendation, if any, and inspection reports regarding the manufacturing facilities and clinical trial sites, the FDA may issue an approval letter, or, in some cases, a complete response letter. A complete response letter generally contains a statement of specific conditions that must be met in order to secure final approval of the NDA and may require additional clinical or preclinical testing in order for the FDA to reconsider the application. Even with submission of this additional information, the FDA ultimately may decide that the application does not satisfy the regulatory criteria for approval. If and when those conditions have been met to the FDA’s satisfaction, the FDA will typically issue an approval letter. An approval letter authorizes commercial marketing of the drug with specific prescribing information for specific indications.

Even if the FDA approves a product, depending on the specific risk(s) to be addressed it may limit the approved indications for use of the product, require that contraindications, warnings or precautions be included in the product labeling, require that post-approval studies, including Phase 4 clinical trials, be conducted to further assess a drug’s safety after approval, require testing and surveillance programs to monitor the product after commercialization or impose other conditions, including distribution and use restrictions or other risk management mechanisms under a REMS, which can materially affect the potential market and profitability of the product. The FDA may prevent or limit further marketing of a product based on the results of post-marketing studies or surveillance programs. After approval, some types of changes to the approved product, such as adding new indications, manufacturing changes and additional labeling claims, are subject to further testing requirements and FDA review and approval.

Orphan Drug Designation and Exclusivity

Under the Orphan Drug Act of 1983, the FDA may grant orphan designation to a drug intended to treat a rare disease or condition, which is a disease or condition that affects fewer than 200,000 individuals in the U.S., or if it affects more than 200,000 individuals in the U.S., there is no reasonable expectation that the cost of developing and making the product available in the U.S. for the disease or condition will be recovered from sales of the product. Orphan designation must be requested before submitting an NDA. Orphan designation does not convey any advantage in or shorten the duration of the regulatory review and approval process, though companies developing orphan products are eligible for certain incentives, including tax credits for qualified clinical testing and waiver of application fees.

If a product that has orphan designation subsequently receives the first FDA approval for the disease or condition for which it has such designation, the product is entitled to a seven-year period of marketing exclusivity during which the FDA may not approve any other applications to market the same therapeutic agent for the same indication, except in limited circumstances, such as a subsequent product’s showing of clinical superiority over the product with orphan exclusivity or where the original applicant cannot produce sufficient quantities of product. Competitors, however, may receive approval of different therapeutic agents for the indication for which the orphan product has exclusivity or obtain approval for the same therapeutic agent for a different indication than that for which the orphan product has exclusivity. Orphan product exclusivity could block the approval of one of our products for seven years if a competitor obtains approval for the same therapeutic agent for the same indication before we do, unless we are able to demonstrate that our product is clinically superior. If an orphan designated product receives marketing approval for an indication broader than what is designated, it may not be entitled to orphan exclusivity. Further, orphan drug exclusive marketing rights in the U.S. may be lost if the FDA later determines that the request for designation was materially defective or the manufacturer of the approved product is unable to assure sufficient quantities of the product to meet the needs of patients with the rare disease or condition.

In September of 2022, KT-333, Kymera’s STAT3 degrader in development for relapsed and/or refractory lymphomas and solid tumors, was granted its second orphan drug designation by the U.S. Food and Drug Administration for the treatment of cutaneous T-cell lymphoma (CTCL), following its orphan drug designation for peripheral T-cell lymphoma (PTCL) in June of 2022. In June 2023, KT-253, Kymera’s MDM2 degrader in development for hematological malignancies and solid tumors, was granted orphan drug designation by the FDA for the treatment of acute myeloid leukemia. These designations provide incentives to encourage the development of medicines for rare diseases.

Expedited Development and Review Programs for Drugs

The FDA maintains several programs intended to facilitate and expedite development and review of new drugs to address unmet medical needs in the treatment of serious or life-threatening diseases or conditions. These programs include Fast Track designation, Breakthrough Therapy designation, Priority Review, Accelerated Approval and platform technology designation and the purpose of these programs is to either expedite the development or review of important new drugs to get them to patients earlier than under standard FDA development and review procedures.

A new drug is eligible for Fast Track designation if it is intended to treat a serious or life-threatening disease or condition and demonstrates the potential to address unmet medical needs for such disease or condition. Fast Track designation provides increased opportunities for sponsor interactions with the FDA during preclinical and clinical development, in addition to the

potential for rolling review once a marketing application is filed, meaning that the agency may review portions of the marketing application before the sponsor submits the complete application, as well as Priority Review, discussed below.

In addition, a new drug may be eligible for Breakthrough Therapy designation if it is intended to treat a serious or life-threatening disease or condition and preliminary clinical evidence indicates that the drug may demonstrate substantial improvement over existing therapies on one or more clinically significant endpoints, such as substantial treatment effects observed early in clinical development. Breakthrough Therapy designation provides all the features of Fast Track designation in addition to intensive guidance on an efficient drug development program beginning as early as Phase 1, and FDA organizational commitment to expedited development, including involvement of senior managers and experienced review staff in a cross-disciplinary review, where appropriate.

Any product submitted to the FDA for approval, including a product with Fast Track or Breakthrough Therapy designation, may also be eligible for additional FDA programs intended to expedite the review and approval process, including Priority Review designation and Accelerated Approval. A product is eligible for Priority Review if it has the potential to provide a significant improvement in safety or effectiveness in the treatment, diagnosis or prevention of a serious disease or condition. Under priority review, the FDA must review an application in six months compared to ten months for a standard review.

Additionally, products are eligible for Accelerated Approval if they can be shown to have an effect on a surrogate endpoint that is reasonably likely to predict clinical benefit, or an effect on a clinical endpoint that can be measured earlier than an effect on irreversible morbidity or mortality which is reasonably likely to predict an effect on irreversible morbidity or mortality or other clinical benefit, taking into account the severity, rarity or prevalence of the condition and the availability or lack of alternative treatments.

Accelerated Approval is usually contingent on a sponsor’s agreement to conduct additional post-approval studies to verify and describe the product’s clinical benefit and, under the Food and Drug Omnibus Reform Act of 2022, or FDORA, the FDA is now permitted to require, as appropriate, that such trials be underway prior to approval or within a specific time period after the date of approval for a product granted accelerated approval. Under FDORA, the FDA has increased authority for expedited procedures to withdraw approval of a drug or indication approved under Accelerated Approval if, for example, the confirmatory trial fails to verify the predicted clinical benefit of the product. In addition, for products being considered for accelerated approval, the FDA generally requires, unless otherwise informed by the Agency, that all advertising and promotional materials that are intended for dissemination or publication within 120 days following marketing approval be submitted to the agency for review during the pre-approval review period, and that after 120 days following marketing approval, all advertising and promotional materials must be submitted at least 30 days prior to the intended time of initial dissemination or publication.

Under FDORA, a platform technology incorporated within or utilized by a drug or biological product is eligible for designation as a designated platform technology if (1) the platform technology is incorporated in, or utilized by, a drug approved under an NDA; (2) preliminary evidence submitted by the sponsor of the approved or licensed drug, or a sponsor that has been granted a right of reference to data submitted in the application for such drug, demonstrates that the platform technology has the potential to be incorporated in, or utilized by, more than one drug without an adverse effect on quality, manufacturing, or safety; and (3) data or information submitted by the applicable person indicates that incorporation or utilization of the platform technology has a reasonable likelihood to bring significant efficiencies to the drug development or manufacturing process and to the review process. A sponsor may request the FDA to designate a platform technology as a designated platform technology concurrently with, or at any time after, submission of an IND application for a drug that incorporates or utilizes the platform technology that is the subject of the request. If so designated, the FDA may expedite the development and review of any subsequent original NDA for a drug that uses or incorporates the platform technology.

Even if a product qualifies for one or more of these programs, the FDA may later decide that the product no longer meets the conditions for qualification or the time period for FDA review or approval may not be shortened. Furthermore, Fast Track designation, Breakthrough Therapy designation, Priority Review and Accelerated Approval do not change the scientific or medical standards for approval or the quality of evidence necessary to support approval but may expedite the development or review process.

Pediatric Information and Pediatric Exclusivity

Under the Pediatric Research Equity Act, or PREA, as amended, certain NDAs and certain supplements to an NDA must contain data to assess the safety and efficacy of the drug for the claimed indications in all relevant pediatric subpopulations and to support dosing and administration for each pediatric subpopulation for which the product is safe and effective. The FDA may grant deferrals for submission of pediatric data or full or partial waivers. The FD&C Act requires that a sponsor who is planning to submit a marketing application for a drug that includes a new active ingredient, new indication, new dosage form, new dosing regimen or new route of administration submit an initial Pediatric Study Plan, or PSP, within 60 days of an end-of-Phase 2 meeting or, if there is no such meeting, as early as practicable before the initiation of the Phase 3 or Phase 2/3 trial.

The initial PSP must include an outline of the pediatric study or studies that the sponsor plans to conduct, including study objectives and design, age groups, relevant endpoints and statistical approach, or a justification for not including such detailed information, and any request for a deferral of pediatric assessments or a full or partial waiver of the requirement to provide data from pediatric studies along with supporting information. The FDA and the sponsor must reach an agreement on the PSP. A sponsor can submit amendments to an agreed-upon initial PSP at any time if changes to the pediatric plan need to be considered based on data collected from preclinical studies, early phase clinical trials and/or other clinical development programs.

A drug can also obtain pediatric market exclusivity in the U.S. Pediatric exclusivity, if granted, adds six months to existing exclusivity periods for all formulations, dosage forms, indications of the active moiety and patent terms. This six-month exclusivity, which runs from the end of other exclusivity protection, may be granted based on the voluntary completion of a pediatric trial or of multiple pediatric trials in accordance with an FDA-issued “Written Request” for such trials, provided that at the time pediatric exclusivity is granted there is not less than nine months of term remaining.

U.S. Post-Approval Requirements for Drugs

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KYMR · 10-K · period ended 2023-12-31

Item 1. Business.

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