ITEM 1A. RISK FACTORS

In analyzing our company,

you should consider carefully the following risk factors, together with all of the other information included in this Annual Report on

Form 10-K. Factors that could cause or contribute to differences in our actual results include those discussed in the following

subsection, as well as those discussed below in “Management’s Discussion and Analysis of Financial Condition and Results

of Operations” and elsewhere throughout this Annual Report on Form 10-K. The following are material factors that make an investment

in our company speculative or risky. The risks and uncertainties described below are not the only ones we face. Additional risks not

currently known to us or other factors not perceived by us to present significant risks to our business at this time also may impair

our business operations.

Summary of Risk Factors

We are providing the following

summary of the risk factors contained in this Annual Report on Form 10-K to enhance the readability and accessibility of our risk factor

disclosures. We encourage you to carefully review the full risk factors contained in this Annual Report on Form 10-K in their entirety

for additional information regarding the material factors that make an investment in our securities speculative or risky. These risks

and uncertainties include, but are not limited to, the following:

Risks Related to Our Business

We are a clinical-stage company and have

generated no revenue from commercial sales to date.

We are a clinical-stage biopharmaceutical

company with a limited operating history. We have no products approved for commercial sale and have not generated any revenue from product

sales to date. We will encounter risks and difficulties frequently experienced by early-stage companies in rapidly evolving fields. If

we do not address these risks successfully, our business will suffer.

We have incurred net losses in every year

since our inception and anticipate that we will continue to incur net losses in the future.

We are not profitable and

have incurred losses in each period since our inception. As of December 31, 2022 and December 31, 2021, we had an accumulated deficit

of $288.8 million and $255.7 million, respectively. We reported a net loss of $33.0 million and $24.8 million for the years ended December

31, 2022 and 2021, respectively. We expect to continue to operate at a net loss as we continue our research and development efforts, continue

to conduct clinical trials and develop manufacturing, sales, marketing and distribution capabilities. There can be no assurance that the

products under development by us will be approved for sale in the United States or elsewhere. Furthermore, there can be no assurance that

if such products are approved, they will be successfully commercialized, which would have an adverse effect on our business prospects,

financial condition and results of operation.

If we fail to obtain additional financing,

we will be unable to continue or complete our product development and you will likely lose your entire investment.

As of the date of filing this

report, we expect that our existing resources will be more than sufficient to fund our planned operations for more than 12 months following

the date of this report.

Our business or operations

may change in a manner that would consume available funds more rapidly than anticipated and substantial additional funding may be required

to maintain operations, fund expansion, develop new or enhanced products, acquire complementary products, business or technologies or

otherwise respond to competitive pressures and opportunities, such as a change in the regulatory environment or a change in preferred

cancer treatment modalities. However, we may not be able to secure funding when we need it or on favorable terms or indeed on any terms.

In addition, from time to time, we may not be able to secure enough capital in a timely enough manner which may cause the generation of

a going-concern opinion from our auditors which can and may impair our stock market valuation and also our ability to finance on favorable

terms or indeed on any terms.

To raise additional capital,

we may in the future offer additional shares of our common stock or other securities convertible into or exchangeable for our common stock.

We cannot assure you that we will be able to sell shares or other securities in any other offering at a price per share that is equal

to or greater than the price per share paid by investors, and investors purchasing shares or other securities in the future could have

rights superior to existing stockholders.

If we cannot raise adequate

funds to satisfy our capital requirements, we will have to delay, scale back or eliminate our research and development activities, clinical

studies or future operations. We may also be required to obtain funds through arrangements with collaborators, which arrangements may

require us to relinquish rights to certain technologies or products that we otherwise would not consider relinquishing, including rights

to future product candidates or certain major geographic markets. We may further have to license our technology to others. This could

result in sharing revenues which we might otherwise have retained for ourselves. Any of these actions may harm our business, financial

condition and results of operations.

The amount of funding we will

need depends on many factors, including the progress, timing and scope of our product development programs; the progress, timing and scope

of our preclinical studies and clinical trials; the time and cost necessary to obtain regulatory approvals; the time and cost necessary

to further develop manufacturing processes and arrange for contract manufacturing; our ability to enter into and maintain collaborative,

licensing and other commercial relationships; and our partners’ commitment of time and resources to the development and commercialization

of our products.

We have limited access to the capital markets

and even if we can raise additional funding, we may be required to do so on unfavorable terms.

We have limited access to

the capital markets to raise funds. The capital markets have been unpredictable in the recent past for radioisotope and other oncology

companies and unprofitable companies such as ours. In addition, it is generally difficult for development-stage companies to raise capital

under current market conditions. The amount of capital that a company such as ours is able to raise often depends on variables that are

beyond our control. As a result, we may not be able to secure financing on terms attractive to us, or at all. If we are able to consummate

a financing arrangement, the amount raised may not be sufficient to meet our future needs. If adequate funds are not available on acceptable

terms, or at all, our business, including our technology licenses, results of operations, financial condition and our continued viability

will be materially adversely affected.

We are highly dependent on the success of

Iomab-B and the SIERRA trial and we may not be able to complete the necessary clinical development or our development efforts may not

result in the data necessary to receive regulatory approval.

We have completed patient

enrollment in the pivotal Phase 3 SIERRA trial (Study of Iomab-B in Elderly Relapsed or Refractory AML), a 153-patient multi-center randomized

trial that will compare outcomes of patients who receive Iomab-B and a BMT to those patients receiving physician’s choice of salvage

chemotherapy, defined as conventional care, as no standard of care exists for this patient population. We have announced that Iomab-B

met the primary endpoint of dCR in the SIERRA trial with statistical significance (p<0.0001). The SIERRA trial may be unsuccessful

and fail to demonstrate a safety and efficacy profile that is necessary to receive favorable regulatory approval. Even if Iomab-B receives

favorable regulatory approval, we may not be successful in securing adequate reimbursement or establishing successful commercial operations.

Any or all of these factors could have a material adverse impact on our business and ability to continue operations.

We may be unable to establish sales, marketing

and commercial supply capabilities.

We do not currently have,

nor have we ever had, commercial sales and marketing capabilities. If any of our product candidates become approved, we would have to

build and establish these capabilities in order to commercialize our approved product candidates. The process of establishing commercial

capabilities will be expensive and time consuming. Even if we are successful in building sales and marketing capabilities, we may not

be successful in commercializing any of our product candidates. Any delays in commercialization or failure to successfully commercialize

any product candidate may have material adverse impacts on our business and ability to continue operations.

Our business could be adversely affected

by the effects of health epidemics, including the global COVID-19 pandemic.

The global health crisis caused

by the novel coronavirus COVID-19 pandemic and its resurgences has and may continue to negatively impact global economic activity, which,

despite vaccination efforts, remains uncertain and cannot be predicted with confidence. In addition, highly transmissible new variants

of COVID-19 have spread globally. The full impact of such variants cannot be predicted at this time, and could depend on numerous factors,

including vaccination rates among the population, the effectiveness of COVID-19 vaccines and boosters against the COVID-19 variants and

the response by governmental bodies and regulators. Given the ongoing and dynamic nature of the circumstances, it is difficult to predict

the impact of the COVID-19 pandemic on our business.

Many countries around the

world have imposed quarantines and restrictions on travel and mass gatherings and could reinstitute such policies in response to future

COVID-19 outbreaks. In such a scenario, our ability to continue to operate our business may also be limited. Such events may result in

a period of business, supply and drug product manufacturing disruption, and in reduced operations, any of which could materially affect

our business, financial condition and results of operations. In response to COVID-19, we implemented hybrid working for our office-based

staff, while our research staff has been actively working in our laboratory throughout the pandemic and thus far have not experienced

a significant disruption or delay in our operations as it relates to the clinical development, preclinical development of manufacturing

of our drug candidates. Although we are adhering to health and safety protocols, an outbreak of COVID-19 at our facilities could nonetheless

cause shutdowns of facilities and a reduction in our workforce, which could cause a disruption or delay in such operations. New outbreaks

may further divert the attention and efforts of the medical community to coping with COVID-19, and may disrupt the marketplace in which

we operate and may have a material adverse effect on our operations.

A continuation or worsening

of the levels of market disruption and volatility seen in the recent past could have an adverse effect on our ability to access capital,

which could in the future negatively affect our liquidity. In addition, a recession or market correction resulting from the spread of

COVID-19 could materially affect our business and the value of our common stock.

We believe our earlier

stage CD33 clinical trials will continue to recruit and enroll patients given the acute nature of relapsed or refractory AML. The

continuation of the pandemic could adversely affect our planned clinical trial operations, including our ability to conduct the

trials on the expected timelines and recruit and retain patients and principal investigators and site staff who, as healthcare

providers, may have heightened exposure to COVID-19 if their geography is impacted by the pandemic. Further, the continuation and/or

resurgence of the COVID-19 pandemic could result in delays in our clinical trials due to prioritization of hospital resources toward

the pandemic, restrictions in travel, potential unwillingness of patients to enroll in trials at this time, or the inability of

patients to comply with clinical trial protocols if quarantines or travel restrictions are reinstated that impede patient movement

or interrupt healthcare services. In addition, we rely on independent clinical investigators, contract research organizations and

other third-party service providers to assist us in managing, monitoring and otherwise carrying out our preclinical studies and

clinical trials, and the pandemic may affect their ability to devote sufficient time and resources to our programs or to travel to

sites to perform work for us, which may result in delays or hinder our ability to collect data from our clinical trials.

Additionally, COVID-19 may

result in delays in receiving approvals from local and foreign regulatory authorities, delays in necessary interactions with IRB’s

or Institutional Review Boards, local and foreign regulators, ethics committees and other important agencies and contractors due to limitations

in employee resources or forced furlough of government employees.

We continue to monitor

the impacts of COVID-19 on the global economy and on our business operations. However, the ultimate impact from COVID-19 on our

business operations and financial results during 2023 will depend on, among other things, the ultimate severity and scope of the

pandemic, including the new variants of the virus, and whether governmental and private travel restrictions and public concerns

about public gatherings are reinstated. We are not able to fully quantify the impact that these factors had on our financial

results during 2022 and will have in 2023.

Our business is subject to cybersecurity

risks.

Our operations are increasingly

dependent on information technologies and services. Threats to information technology systems associated with cybersecurity risks and

cyber incidents or attacks continue to grow, and include, among other things, storms and natural disasters, terrorist attacks, utility

outages, theft, viruses, phishing, malware, design defects, human error, and complications encountered as existing systems are maintained,

repaired, replaced, or upgraded. Risks associated with these threats include, among other things:

● theft or misappropriation of funds;

● damage to our reputation with our potential partners, patients and the market;

● exposure to litigation;

● increased costs to prevent, respond to or mitigate cybersecurity events.

Although we utilize various

procedures and controls to mitigate our exposure to such risk, cybersecurity attacks and other cyber events are evolving and unpredictable.

Moreover, we have no control over the information technology systems of third parties conducting our clinical trials, our suppliers, and

others with which our systems may connect and communicate. As a result, the occurrence of a cyber incident could go unnoticed for a period

time.

We have cybersecurity insurance

coverage in the event we become subject to various cybersecurity attacks, however, we cannot ensure that it will be sufficient to cover

any particular losses we may experience as a result of such cyberattacks. Any cyber incident could have a material adverse effect on our

business, financial condition and results of operations.

Risks Related to Regulation

The FDA or comparable foreign regulatory

authorities may disagree with our regulatory plans and we may fail to obtain regulatory approval of our product candidates.

Our products are subject to

rigorous regulation by the FDA and numerous other federal, state and foreign governmental authorities. The process of seeking regulatory

approval to market an antibody radiation-conjugate product is expensive and time-consuming, and, notwithstanding the effort and expense

incurred, approval is never guaranteed. If we are not successful in obtaining timely approval of our products from the FDA, we may never

be able to generate significant revenue and may be forced to cease operations. In particular, the FDA permits commercial distribution

of a new antibody radiation-conjugate product only after a BLA for the product has received FDA approval. The BLA process is costly, lengthy

and inherently uncertain. Any BLA filed by us will have to be supported by extensive data, including, but not limited to, technical, preclinical,

clinical trial, chemistry, manufacturing and controls (“CMC”) and labeling data, to demonstrate to the FDA’s satisfaction

the safety and efficacy of the product for its intended use. The lengthy approval process as well as the unpredictability of future clinical

trial results may result in our failing to obtain regulatory approval to market our product candidates, which would significantly harm

our business, results of operations and prospects. In addition, even if we were to obtain approval, regulatory authorities may approve

any of our product candidates for fewer or more limited indications than we request, may not approve the price we intend to charge for

our products, may grant approval contingent on the performance of costly post-marketing clinical trials, or may approve a product candidate

with a label that does not include the labeling claims necessary or desirable for the successful commercialization of that product candidate.

Any of the foregoing scenarios could materially harm the commercial prospects for our product candidates.

In June 2012, we acquired

rights to apamistamab, a clinical stage anti-CD45 monoclonal antibody with safety and efficacy data in more than 300 patients in need

of a BMT. Iomab-B is our product candidate that links I-131 to apamistamab that is being studied in the pivotal Phase 3 SIERRA trial.

Product candidates utilizing apamistamab would require BLA approval before they can be marketed in the United States. We are also evaluating

Iomab-ACT, which uses a lower dose I-131 for lymphodepletion prior to CAR-T or adoptive cell therapy. We are currently evaluating clinical

trials that would use our construct for lymphodepletion. Our CD33 Alpha program studying Actimab-A (lintuzumab-Ac-225) product candidate

is also being studied in several Phase 1 trials under our sponsorship and investigator-initiated trials in patients with r/r AML. Product

candidates utilizing the lintuzumab antibody would require BLA approval before they can be marketed in the United States. We are in the

early stages of evaluating other product candidates consisting of conjugates of Ac-225 with human or humanized antibodies for pre-clinical

and clinical development in other types of cancer. The FDA may not approve these products for the indications that are necessary or desirable

for successful commercialization. The FDA may fail to approve any BLA we submit for new product candidates or for new intended uses or

indications for approved products or future product candidates. Failure to obtain FDA approval for our products in the proposed indications

would have a material adverse effect on our business prospects, financial condition and results of operations.

The approval process in the

United States and in other countries could result in unexpected and significant costs for us and consume management’s time and other

resources. The FDA and other foreign regulatory agencies could ask us to supplement our submissions, collect non-clinical data, conduct

additional clinical trials or engage in other time-consuming actions, or it could simply deny our applications. In addition, even if we

obtain approval to market our products in the United States or in other countries, the approval could be revoked, or other restrictions

imposed if post-market data demonstrates safety issues or lack of effectiveness. We cannot predict with certainty how, or when, the FDA

or other regulatory authorities will act. If we are unable to obtain the necessary regulatory approvals, our financial condition and cash

flow may be materially adversely affected, and our ability to grow domestically and internationally may be limited. Additionally, even

if we obtain approval, regulatory authorities may approve any of our product candidates for fewer or more limited indications that we

request. The Company’s products may not be approved for the specific indications that are most necessary or desirable for successful

commercialization or profitability.

We have not demonstrated that any of our

products are safe and effective for any indication and will continue to expend substantial time and resources on clinical development

before any of our current or future product candidates will be eligible for FDA approval, if ever.

We expect that a substantial

portion of our efforts and expenditures over the next few years will be devoted to development of our existing and contemplated biological

product candidates. Accordingly, our business currently depends heavily on the successful development, FDA approval, and commercialization

of such candidates, which may never receive FDA approval or be successfully commercialized even if FDA approval is received. The research,

testing, manufacturing, labeling, approval, sale, marketing, and distribution of our biological product candidates are, and will remain,

subject to extensive regulation by the FDA and other regulatory authorities in the United States and other countries, as applicable. We

are currently not permitted to market any of our current or future product candidates in the United States until we receive FDA approval

(of each) via the BLA process. To date, we have two product candidates in clinical development and have not-yet submitted a BLA for any

of our candidates and, for many such candidates, do not expect to be in a position to do so for the foreseeable future, as there are numerous

developmental steps that must be completed before we can prepare and submit a BLA.

In the United States, the

FDA regulates pharmaceutical and biological product candidates under the FDCA and the Public Health Service Act (“PHSA”),

as well as their respective implementing regulations. Such products and product candidates are also subject to other federal, state, and

local statutes and regulations. The process of obtaining regulatory approvals and the subsequent compliance with appropriate federal,

state, local, and foreign statutes and regulations requires the expenditure of substantial time and financial resources. The process required

by the FDA before a drug or biological product may be marketed in the United States generally involves the following:

● FDA review and approval, or denial, of the BLA.

Before testing any biological

product candidate in humans, the product candidate enters the preclinical testing stage. Preclinical tests include laboratory evaluations

of product chemistry, toxicity and formulation, as well as animal studies to assess the potential safety and activity of the product candidate.

The conduct of the preclinical tests must comply with federal regulations and requirements including GLPs. The clinical trial sponsor

must submit the results of the preclinical tests, together with manufacturing information, analytical data, any available clinical data

or literature and a proposed clinical protocol, to the FDA as part of the IND. Some preclinical testing may continue even after the IND

is submitted. The IND automatically becomes effective 30 days after receipt by the FDA, unless the FDA raises concerns or questions regarding

the proposed clinical trials and places the trial on a clinical hold within that 30-day time period. In such a case, the IND sponsor and

the FDA must resolve any outstanding concerns before the clinical trial can begin. The FDA may also impose clinical holds on a biological

product candidate at any time before or during clinical trials due to safety concerns or non-compliance. If the FDA imposes a clinical

hold, trials may not recommence without FDA authorization and then only under terms authorized by the FDA. Accordingly, we cannot be sure

that submission of an IND will result in the FDA allowing clinical trials to begin or that, for those that have already commenced under

an active IND, that issues will not arise that suspend or terminate such trials.

Clinical trials involve the

administration of the biological 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. 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

to be used to monitor subject safety, including stopping rules that assure a clinical trial will be stopped if certain adverse events

should occur. Each protocol and any amendments to the protocol must be submitted to the FDA as part of the IND. Clinical trials must be

conducted and monitored in accordance with the FDA’s regulations composing the GCP requirements, including the requirement that

all research subjects provide informed consent. Further, each clinical trial must be reviewed and approved by an independent institutional

review board, or IRB, at or servicing each institution at which the clinical trial will be conducted. An IRB is charged with protecting

the welfare and rights of trial participants and considers such items as whether the risks to individuals participating in the clinical

trials are minimized and are reasonable in relation to anticipated benefits. The IRB also approves the form and content of the informed

consent that must be signed by each clinical trial subject or his or her legal representative and must monitor the clinical trial until

completed. Human clinical trials are typically conducted in three sequential phases that may overlap or be combined:

Post-approval clinical trials,

sometimes referred to as Phase 4 clinical trials, may be conducted after initial marketing approval. These clinical trials are used to

gain additional experience from the treatment of patients in the intended therapeutic indication, particularly for long-term safety follow-up.

After the completion of clinical

trials of a biological product, FDA approval of a BLA must be obtained before commercial marketing of the biological product. The BLA

must include results of product development, laboratory and animal studies, human trials, information on the manufacture and composition

of the product, proposed labeling and other relevant information. The FDA may grant deferrals for submission of data, or full or partial

waivers. The testing and approval processes require substantial time and effort and there can be no assurance that the FDA will accept

the BLA for filing and, even if filed, that any approval will be granted on a timely basis, if at all. Before approving a BLA, the FDA

will inspect the facilities at which the product is manufactured. The FDA will not approve the product 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 a BLA, the FDA will typically inspect one or more clinical sites to assure that the clinical

trials were conducted in compliance with IND trial requirements and GCP requirements. To assure cGMP and GCP compliance, an applicant

must incur significant expenditure of time, money and effort in the areas of training, record keeping, production, and quality control.

Notwithstanding the submission

of relevant data and information, the FDA may ultimately decide that the BLA does not satisfy its regulatory criteria for approval and

deny approval. Data obtained from clinical trials are not always conclusive and the FDA may interpret data differently than we interpret

the same data. We cannot predict with any certainty if or when we might submit a BLA for regulatory approval for our product candidates

or whether any such BLA will be approved by the FDA. Human clinical trials are very expensive and difficult to design and implement, in

part because they are subject to rigorous regulatory requirements. For example, the FDA may not agree with our proposed endpoints for

any clinical trial we propose, which may delay the commencement of our clinical trials. The clinical trial process is also lengthy and

requires substantial time and effort.

In December 2015, the FDA

cleared our IND filing for Iomab-B and we have completed patient enrollment of a randomized, controlled, pivotal Phase 3 clinical trial

under such IND to study Iomab-B in patients 55 years of age or older with relapsed or refractory AML. The Phase 3 SIERRA trial met its

primary endpoint with high statistical significance with positive results for secondary endpoints and exploratory endpoints and it is

expected to form the basis for a BLA for Iomab-B for use in preparing and conditioning AML patients for a BMT. Additionally, there are

physician IND trials at the FHCRC that have been conducted or are currently ongoing at FHCRC with Iomab-B (for other target indications)

and the apamistamab antibody (formerly known as BC8) we licensed. We have other clinical trials ongoing and others that we have planned

but not-yet commenced, for our other drug candidate Actimab-A under our own sponsorship and investigator-initiated trials ongoing. Except

for Iomab-B (for patients with AML), we expect that the clinical trials we need to conduct to be in a position to submit BLAs for our

product candidates currently in-development will take, at least, several years to complete. Moreover, failure can occur at any stage of

the trials, and we could encounter problems that cause us to abandon or repeat clinical trials. Also, the results of early preclinical

and clinical testing may not be predictive of the results of subsequent clinical trials. A number of companies in the biopharmaceutical

industry have suffered significant setbacks in advanced clinical trials due to lack of efficacy or adverse safety profiles, notwithstanding

promising results in earlier studies. And, preclinical and clinical data are often susceptible to multiple interpretations and analyses.

Many companies that have believed their product candidates performed satisfactorily in preclinical studies and clinical trials have, nonetheless,

failed to obtain marketing approval of their products. Success in preclinical testing and early clinical trials does not ensure that later

clinical trials, which involve many more subjects, and the results of later clinical trials may not replicate the results of prior clinical

trials and preclinical testing. Any failure or substantial delay in our product development plans may have a material adverse effect on

our business.

We may encounter substantial delays in our

clinical trials or may not be able to conduct our trials on the timelines we expect.

We cannot predict whether

we will encounter problems with any of our ongoing or planned clinical trials that will cause us or regulatory authorities to delay, suspend,

or discontinue clinical trials or to delay the analysis of data from ongoing clinical trials. Any of the following could delay or disrupt

the clinical development of our product candidates and potentially cause our product candidates to fail to receive regulatory approval:

● delays in enrolling patients into clinical trials;

● a lower than anticipated retention rate of patients in clinical trials;

We may suspend, or the FDA

or other applicable regulatory authorities may require us to suspend, clinical trials of a product candidate at any time if we or they

believe the patients participating in such clinical trials, or in independent third-party clinical trials for drugs based on similar technologies,

are being exposed to unacceptable health risks including but not limited to unacceptable or suboptimal factors related to toxicity, clinical

efficacy, imbalances in safety and efficacy profiles or for other reasons.

Further, individuals involved

with our clinical trials may serve as consultants to us from time to time and receive stock options or cash compensation in connection

with such services. If these relationships and any related compensation to the clinical investigator carrying out the study result in

perceived or actual conflicts of interest, or the FDA concludes that the financial relationship may have affected interpretation of the

study, the integrity of the data generated at the applicable clinical trial site may be questioned and the utility of the clinical trial

itself may be jeopardized. The delay, suspension or discontinuation of any of our clinical trials, or a delay in the analysis of clinical

data for our product candidates, for any of the foregoing reasons, could adversely affect our efforts to obtain regulatory approval for

and to commercialize our product candidates, increase our operating expenses and have a material adverse effect on our financial results.

Clinical trials may also be

delayed or terminated as a result of ambiguous or negative interim results. In addition, a clinical trial may be suspended or terminated

by us, the FDA, the IRBs at the sites where the IRBs are overseeing a trial, or a data safety monitoring board, or DSMB (Data Safety Monitoring

Board)/DMC (Data Monitoring Committee), overseeing the clinical trial at issue, or other regulatory authorities due to a number of factors,

including:

● unforeseen safety issues; or

● lack of adequate funding to continue the clinical trial.

Modifications to our product candidates

may require federal approvals.

The BLA application is the

vehicle through which the company may formally propose that the FDA approve a new pharmaceutical for sale and marketing in the United

States. Once a particular product candidate receives FDA approval, expanded uses or uses in new indications of our products may require

additional human clinical trials and new regulatory approvals, including additional IND and BLA submissions and premarket approvals before

we can begin clinical development, and/or prior to marketing and sales. If the FDA requires new approvals for a particular use or indication,

we may be required to conduct additional clinical studies, which would require additional expenditures and harm our operating results.

If the products are already being used for these new indications, we may also be subject to significant enforcement actions.

Conducting clinical trials

and obtaining approvals is a time-consuming process, and delays in obtaining required future approvals could adversely affect our ability

to introduce new or enhanced products in a timely manner, which in turn would have an adverse effect on our business prospects, financial

condition and results of operation.

Clinical trials necessary to support approval

of our product candidates are time-consuming and expensive.

Initiating and completing

clinical trials necessary to support FDA approval of a BLA for Iomab-B, Actimab-A, and other product candidates, is a time-consuming and

expensive process, and the outcome is inherently uncertain. Moreover, the results of early clinical trials are not necessarily predictive

of future results, and any product candidate we advance into clinical trials may not have favorable results in later clinical trials.

We worked with the FDA to develop the SIERRA clinical trial to test the safety and efficacy of Iomab-B in patients with relapsed or refractory

AML who are age 55 and above prior to a BMT. This trial is designed to support a BLA filing for marketing approval by the FDA. In addition

to clinical data, a BLA filing encompasses preclinical, CMC, labeling and other information. Even if the clinical data from the SIERRA

trial is positive, there can be no assurances that the BLA filing we produce will meet all of the FDA’s requirements or that they

will not request additional information or studies, which may delay the FDA’s review or we may not be able to produce. We have also

worked with the FDA to develop a regulatory pathway for lintuzumab-Ac-225 in patients with high-risk MDS that consists of a dose-confirming

Phase 1 trial that can be followed by a randomized, controlled pivotal trial that could support a BLA filing. To date, we have not initiated

this clinical trial and we may never elect or be able to do so. There can be no assurance that the data generated during the trial, or

any trial, will meet our chosen safety and effectiveness endpoints or otherwise produce results that will eventually support the filing

or approval of a BLA. Even if the data from this trial are favorable, the data may not be predictive of the results of any future clinical

trials.

Preliminary, Interim, and “top-line”

data from our clinical trials that we announce or publish from time to time may change as more patient data become available and are subject

to audit and verification procedures that could result in material changes in the final data.

From time to time, we

may publicly disclose preliminary, interim, and top-line data from our clinical trials, which is based on a preliminary analysis of then-available

data, and the results and related findings and conclusions are subject to change as more patient data become available or following a

more comprehensive review of the data related to the particular study or trial. For example, in October 2022 we announced that Iomab-B

met the primary endpoint of dCR in the SIERRA trial with statistical significance (p<0.0001). We also make assumptions, estimations,

calculations and conclusions as part of our analyses of data, and we may not have received or had the opportunity to fully and carefully

evaluate all data. Our clinical trials may be open label studies and certain of our clinical development and or operations staff may review

interim or preliminary safety or efficacy data during routine data collection, cleaning and analysis from time to time. Interim or preliminary

results that we report may differ from future results of the same studies, or different conclusions or considerations may qualify such

results once additional data have been received and fully evaluated. Preliminary, interim or top-line data also remain subject to audit

and verification procedures that may result in the final data being materially different from the top-line, interim or preliminary data

we previously published. As a result, top-line, interim and preliminary data should be viewed with caution until the final data are available.

From time to time, we may

also disclose interim data from our preclinical studies and clinical trials. Interim data from clinical trials that we may complete are

subject to the risk that one or more of the clinical outcomes may materially change as patient enrollment continues and more patient data

become available. Adverse differences between interim data and final data could significantly harm our business prospects. Further, disclosure

of interim data by us or by our competitors could result in volatility in the price of our common stock.

Further, others, including

regulatory agencies, may not accept or agree with our assumptions, estimates, calculations, conclusions or analyses or may interpret or

weigh the importance of data differently, which could impact the value of the particular program, the approvability or commercialization

of the particular product candidate or product and our company in general. In addition, the information we choose to publicly disclose

regarding a particular study or clinical trial is based on what is typically extensive information, and you or others may not agree with

what we determine is material or otherwise appropriate information to include in our disclosure.

If the interim, top-line or

preliminary data that we report differ from final results, or if others, including regulatory authorities, disagree with the conclusions

reached, our ability to obtain approval for, and commercialize, our product candidates may be harmed, which could harm our business, operating

results, prospects or financial condition.

Our clinical trials may fail to demonstrate

adequately the efficacy and safety of our product candidates, which would prevent or delay regulatory approval and commercialization.

Even if our clinical trials

are completed as planned, we cannot be certain that their results will support our product candidate claims or that the FDA or foreign

authorities will agree with our conclusions regarding them. Success in pre-clinical studies and early clinical trials does not ensure

that later clinical trials will be successful, and we cannot be sure that the later trials will replicate the results of prior trials

and pre-clinical studies. The clinical trial process may fail to demonstrate that our product candidates are safe and effective for the

proposed indicated uses. If FDA concludes that the clinical trials for Iomab-B, Actimab-A, or any other product candidate for which we

might seek approval, have failed to demonstrate safety and effectiveness, we would not receive FDA approval to market that product candidate

in the United States for the indications sought. In addition, such an outcome could cause us to abandon the product candidate and might

delay development of others. Any delay or termination of our clinical trials will delay or preclude the filing of any submissions with

the FDA and, ultimately, our ability to commercialize our product candidates and generate revenues. It is also possible that patients

enrolled in clinical trials will experience adverse side effects that are not currently part of a product candidate’s profile.

The intellectual property related to antibodies

we have licensed has expired or likely expired.

The key patents related to

the humanized antibody, lintuzumab, which we use in our Actimab-A product candidate have expired. It is generally possible that others

may be eventually able to use an antibody with the same sequence, and we will then need to rely on additional patent protection covering

alpha particle drug products comprising Ac-225. Our final drug construct, Actimab A, consists of the lintuzumab antibody labeled with

the isotope Ac-225. We currently own issued and pending patents relating to methods of manufacturing Actimab-A, methods of treatment using

Actimab-A and production of the Ac-225 isotope. In addition, we possess trade secrets and know how related to the manufacturing and use

of isotopes. Any competing product based on the lintuzumab antibody is likely to require several years of development before achieving

our product candidate’s current status and may be subject to significant regulatory hurdles but such development by others is nevertheless

a possibility that could negatively impact our business in the future. We own 4 issued U.S. patents, 1 issued Canadian patent, 1 issued

European patent (validated as a national patent in several countries) and 1 issued Japanese patent that relate to the composition of our

Iomab-B product candidate. Patent applications relating to Iomab-B are also pending in the U.S. and internationally. We have and may continue

to file patents related to Iomab-B that can provide barriers to entry but there is no certainty that these patents will be granted or

such granting thereof will adequately prevent others from seeking to replicate and use the apamistamab antibody or the construct. Our

patent portfolio includes pending applications related to radioimmunoconjugate composition, formulation administration, and methods of

use in treating solid or liquid cancers. This subject matter includes composition, administration, and methods of treatment for our product

candidates Actimab-A and Iomab-B. Any competing product based on the antibody used in Iomab-B is likely to require several years of development

before achieving our product candidate’s current status and may be subject to significant regulatory hurdles but such development

by others is nevertheless a possibility that could negatively impact our business in the future.

Our CD33 program clinical trials are testing

the same drug construct.

Our CD33 program is comprised

of several clinical trials including investigator-initiated trials in AML that are studying the same drug construct consisting of lintuzumab-Ac-225.

Negative results from any of these trials could negatively impact our ability to enroll or complete our other trials studying lintzumab-Ac-225.

Additionally, negative outcomes including safety concerns, may result in the FDA discontinuing other trials utilizing lintuzumab-Ac-225.

We may be unable to obtain a sufficient

supply of isotopes to support clinical development or at commercial scale.

Iodine-131 is a key component

of our Iomab-B drug candidate. We currently source medical grade I-131 from three suppliers including two leading global manufacturers.

Currently, there is sufficient supply of I-131 to support additional trials we may undertake utilizing I-131 and for commercialization

of Iomab-B. We continually evaluate I-131 manufacturers and suppliers and intend to have multiple qualified suppliers prior to the commercial

launch of Iomab-B. While we consider I-131 to be commoditized and obtainable through several suppliers, there can be no guarantee that

we will be able to secure I-131 or obtain I-131 on terms that are acceptable to us.

Actinium-225 is a key component

of our Actimab-A product candidate, technology platform, preclinical R&D programs and other drug candidates that we might consider

for development with the Ac-225 payload. There are adequate quantities of Ac-225 available today to meet our current needs via our present

supplier, the Department of Energy (“DOE”). The Ac-225 currently supplied to Actinium’s clinical trials from the DOE

is derived from the natural decay of thorium-229 from so-called ‘thorium-cows’ and is able to produce sufficient quantities

that are several multiples of the amount of Ac-225 we require to supply our clinical programs through to early commercialization phase.

The DOE is also producing Ac-225 from a recently developed alternative route for Ac-225 production via a linear accelerator that is currently

being evaluated by Actinium. Initial preclinical and modelling results have indicated that the linear accelerator sourced Ac-225 does

not impact labelling efficiency and expected distribution. In accordance with representations made by the DOE, the capacity of Ac-225

from this route is expected to be sufficient to supply all of Actinium’s pipeline and commercial Ac-225 needs and support new program

expansion by not just Actinium but also other companies that are developing Ac-225 based products. Additional routes of Ac-225 production

are being pursued by the DOE including the generation of new thorium cows and production via a cyclotron. The cyclotron production method

for Ac-225 production leverages Actinium’s proprietary technology and know-how and presents an additional path towards production

of high-quality Ac-225 at a scale that would be able to satisfy commercial needs. In addition, we are aware of at least ten other government

and non-government entities globally including the U.S., Canada, Russia, Belgium, France and Japan that have, or expect to have ability

to supply Ac-225 or equipment for its production within the timeframes relevant to the potential first commercial approval of our Ac-225-based

drug candidate.

Our contract for supply of

this isotope from the DOE must be renewed yearly, and we renewed our contract to extend through the end of 2023. While we expect this

contract will continue to be renewed at the end of its term as it has since 2009, there can be no assurance that the DOE will renew the

contract or that change its policies that allow for the sale of isotope to us. Failure to acquire sufficient quantities of medical grade

Ac-225 would make it impossible to effectively complete clinical trials and to commercialize any Ac-225 based drug candidates that we

may develop and would materially harm our business.

Our ability to conduct clinical

trials to advance our drug candidates is dependent on our ability to obtain the radioisotopes I-131, Ac-225 and other isotopes we may

choose to utilize in the future. Currently, we are dependent on third party manufacturers and suppliers for our isotopes. These suppliers

may not perform their contracted services or may breach or terminate their agreements with us. Our suppliers are subject to regulations

and standards that are overseen by regulatory and government agencies and we have no control over our suppliers’ compliance to these

standards. Failure to comply with regulations and standards may result in their inability to supply isotopes and could result in delays

in our clinical trials, which could have a negative impact on our business. We have developed intellectual property, know-how and trade

secrets related to the manufacturing process of Ac-225. While we have manufactured medical grade Ac-225 of a purity compared to the cyclotron

sourced material in the past, this activity was terminated due to operating cost reasons and we currently do not have experience in manufacturing

medical grade Ac-225 and may not obtain the resources necessary to establish our own manufacturing capabilities in future. Our inability

to build out and establish our own manufacturing facilities would require us to continue to rely on third party suppliers as we currently

do. However, based on our current third-party suppliers and potential future suppliers of Ac-225 we expect to have adequate isotope supply

to support our current ongoing clinical trials, current and planned preclinical R&D activities and commercialization should our drug

candidates receive regulatory approval.

If we encounter difficulties enrolling patients

in our clinical trials, our clinical development activities could be delayed or otherwise adversely affected.

The timely completion of clinical

trials in accordance with their protocols depends on our ability to enroll a sufficient number of patients who remain in the trial until

its conclusion. We may experience difficulties in patient enrollment in our clinical trials for a variety of reasons, including:

● the size and nature of the patient population;

● the patient eligibility criteria defined in the protocol;

● the proximity of patients to trial sites;

● the design of the trial;

● competing clinical trials for similar or alternate therapeutic treatments;

● our ability to obtain and maintain patient consents; and

In addition, refractory patients,

which several of our trials are enrolling, participating in clinical trials are seriously and often terminally ill and therefore may not

complete the clinical trial due to reasons including comorbid conditions or occurrence of adverse medical events related or unrelated

to the investigational products, or death. Even if we are able to enroll a sufficient number of patients in our clinical trials, delays

in patient enrollment will result in increased costs or affect the timing of our planned trials, which could adversely affect our ability

to advance the development of our product candidates.

FDA may take actions that would prolong,

delay, suspend, or terminate clinical trials of our product candidates, which may delay or prevent us from commercializing our product

candidates on a timely basis.

There can be no assurance

that the data generated in our clinical trials will be acceptable to FDA or that if future modifications during the trial are necessary,

that any such modifications will be acceptable to FDA. Certain modifications to a clinical trial protocol made during the course of the

clinical trial have to be submitted to the FDA. This could result in the delay or halt of a clinical trial while the modification is evaluated.

In addition, depending on the quantity and nature of the changes made, FDA could take the position that some or all of the data generated

by the clinical trial is not usable because the same protocol was not used throughout the trial. This might require the enrollment of

additional subjects, which could result in the extension of the clinical trial and the FDA delaying approval of a product candidate. If

the FDA believes that its prior approval is required for a particular modification, it can delay or halt a clinical trial while it evaluates

additional information regarding the change.

Any delay or termination of

our current or future clinical trials as a result of the risks summarized above, including delays in obtaining or maintaining required

approvals from IRBs, delays in patient enrollment, the failure of patients to continue to participate in a clinical trial, and delays

or termination of clinical trials as a result of protocol modifications or adverse events during the trials, may cause an increase in

costs and delays in the filing of any submissions with the FDA, delay the approval and commercialization of our product candidates or

result in the failure of the clinical trial, which could adversely affect our business, operating results and prospects. Lengthy delays

in the completion of our Iomab-B clinical trials would adversely affect our business and prospects and could cause us to cease operations.

We have obtained orphan drug designation

from FDA for two of our current product candidates and intend to pursue such designation for other candidates and indications in the future,

but we may be unable to obtain such designations or to maintain the benefits associated with any orphan drug designations we have received

or may receive in the future.

We have received orphan drug

designation for Iomab-B and Actimab-A for treatment of AML in both the United States and the EU. Under the Orphan Drug Act, the FDA may

grant orphan designation to a drug or biologic intended to treat a rare disease or condition, which is a disease or condition that affects

fewer than 200,000 individuals in the United States, or if it affects more than 200,000 individuals in the United States, there is no

reasonable expectation that the cost of developing and making available a drug or biologic for this type of disease or condition will

be recovered from sales in the United States for that drug or biologic. Similarly, the EMA grants orphan drug designation to promote the

development of products that are intended for the diagnosis, prevention, or treatment of a life-threatening or chronically debilitating

condition affecting not more than five in 10,000 persons in the EU.

Orphan drug designation neither

shortens the development time or regulatory review time of a drug or biologic nor gives the drug or biologic any advantage in the regulatory

review or approval process. In the United States, orphan drug designation entitles a party to financial incentives, such as opportunities

for grant funding towards clinical trial costs, tax advantages, and application fee waivers. In addition, if a product candidate receives

the first FDA approval for the indication for which it has orphan designation, such product is entitled, upon approval, to seven years

of orphan-drug exclusivity, during which the FDA may not approve any other application to market the same drug for the same indication,

unless a subsequently approved product is clinically superior to orphan drug or where the manufacturer is unable to assure sufficient

product quantity in the applicable patient population. In the EU, orphan drug designation entitles a party to financial incentives such

as reduction of fees or fee waivers and ten years of market exclusivity following drug or biological product approval. This period may

be reduced to six years if the orphan drug designation criteria are no longer met, including where it is shown that the product is sufficiently

profitable not to justify maintenance of market exclusivity.

Even if we obtain (or have

obtained) orphan drug designation for certain product candidates, we may not be the first to obtain marketing approval for such candidates

for the applicable indications due to the uncertainties inherent in the development of novel biologic products. And, an orphan drug candidate

may not receive orphan-drug exclusivity upon approval if such candidate is approved for a use that is broader than the indication for

which it received orphan designation. In addition, exclusive marketing rights in the United States may be lost if the FDA later determines

that the request for designation was materially defective or if the manufacturer is unable to assure sufficient quantities of the product

to meet the needs of patients with the rare disease or condition.

Finally, even if we successfully

obtain orphan-drug exclusivity for an orphan drug candidate upon approval, such exclusivity may not effectively protect the product from

competition because (i) different drugs with different active moieties can be approved for the same condition; and (ii) the FDA or EMA

can also subsequently approve a subsequent product with the same active moiety and for the same indication as the orphan drug if the later-approved

drug if deemed clinically superior to the orphan drug.

Even if we receive regulatory approval of

our product candidates, we will be subject to ongoing regulatory obligations and continued regulatory review.

Any regulatory approvals that

we receive for our product candidates will require surveillance to monitor the safety and efficacy of the product candidate. The FDA may

also require a REMS in order to approve our product candidates, which could entail requirements for a medication guide, physician communication

plans or additional elements to ensure safe use, such as restricted distribution methods, patient registries and other risk minimization

tools. In addition, if the FDA or a comparable foreign regulatory authority approves our product candidates, the manufacturing processes,

labeling, packaging, distribution, adverse event reporting, storage, advertising, promotion, import, export and recordkeeping for our

product candidates will be subject to extensive and ongoing regulatory requirements. These requirements include submissions of safety

and other post-marketing information and reports, registration, as well as continued compliance with cGMPs and GCPs for any clinical trials

that we conduct post-approval. In addition, the FDA could require us to conduct another study to obtain additional safety or biomarker

information. Later discovery of previously unknown problems with our product candidates, including adverse events of unanticipated severity

or frequency, or with our third-party suppliers or manufacturing processes, or failure to comply with regulatory requirements, may result

in, among other things:

● fines, warning letters or holds on clinical trials;

● injunctions or the imposition of civil or criminal penalties.

The FDA’s and other

regulatory authorities’ policies may change, and additional government regulations may be enacted that could prevent, limit or delay

regulatory approval of our product candidates. We cannot predict the likelihood, nature or extent of government regulation that may arise

from future legislation or administrative action, either in the United States or abroad. If we are slow or unable to adapt to changes

in existing requirements or the adoption of new requirements or policies, or if we are not able to maintain regulatory compliance, we

may lose any marketing approval that we may have obtained, and we may not achieve or sustain profitability.

Coverage and reimbursement may be limited

or unavailable in certain market segments for our product candidates which could limit our sales of our product candidates, if approved.

The commercial success of

our product candidates in both domestic and international markets will be substantially dependent on whether third-party coverage and

reimbursement is available for patients that use our products. However, the availability of insurance coverage and reimbursement for newly

approved cancer therapies is uncertain, and therefore, third-party coverage may be particularly difficult to obtain even if our products

are approved by the FDA as safe and efficacious. Patients using existing approved therapies are generally reimbursed all or part of the

product cost by Medicare or other third-party payors. Medicare, Medicaid, health maintenance organizations and other third-party payors

are increasingly attempting to contain healthcare costs by limiting both coverage and the level of reimbursement of new drugs, and, as

a result, they may not cover or provide adequate payment for these products. Submission of applications for reimbursement approval generally

does not occur prior to the filing of a BLA for that product and may not be granted until many months after BLA approval. In order to

obtain coverage and reimbursement for these products, we or our commercialization partners may have to agree to a net sales price lower

than the net sales price we might charge in other sales channels. The continuing efforts of government and third-party payors to contain

or reduce the costs of healthcare may limit our revenue. Initial dependence on the commercial success of our products may make our revenues

particularly susceptible to any cost containment or reduction efforts.

Healthcare legislative reform measures intended

to increase pressure to reduce prices of pharmaceutical products paid for by Medicare or, otherwise, affect the federal regulation of

the U.S. healthcare system could have a material adverse effect our business, future revenue, if any, and results of operations.

In the United States, there

have been a number of legislative and regulatory initiatives focused on containing the cost of healthcare. The Affordable Care Act, for

example, substantially changed the way healthcare is financed by both governmental and private insurers. The Affordable Care Act contains

a number of provisions that could impact our business and operations, primarily, once we obtain FDA approval to commercialize one of our

product candidates in the United States, if ever, and may also affect our operations in ways we cannot currently predict. Affordable Care

Act provisions that may affect our business include, among others, those governing enrollment in federal healthcare programs, reimbursement

changes, rules regarding prescription drug benefits under health insurance exchanges, expansion of the 340B program, expansion of state

Medicaid programs, fees and increased discount and rebate obligations, transparency and reporting requirements, and fraud and abuse enforcement.

Such changes may impact existing government healthcare programs, industry competition, formulary composition, and may result in the development

of new programs, including Medicare payment for performance initiatives, health technology assessments, and improvements to the physician

quality reporting system and feedback program.

There have been significant

judicial, administrative, executive, and legislative initiatives to modify, limit, replace, or repeal the Affordable Care Act since its

enactment. For example, former President Trump issued several Executive Orders and other directives designed to delay the implementation

of certain provisions of the Affordable Care Act or otherwise circumvent some of the requirements for health insurance mandated by the

ATNM US Equity

ATNM · 10-K · period ended 2022-12-31

ITEM 1A. RISK FACTORS

ATNM US Equity☆

ATNM · 10-K · period ended 2022-12-31

ITEM 1A. RISK FACTORS

ATNM US Equity