Actinium Announces Positive Full Data Results From the Pivotal Phase 3 SIERRA Trial in Patients with Active, Relapsed or Refractory Acute Myeloid Leukemia - Iomab-B met the primary endpoint of durable Complete Remission

Actinium Announces Positive Full Data Results

From the Pivotal Phase 3 SIERRA Trial in Patients with Active, Relapsed or Refractory Acute Myeloid Leukemia

Iomab-B met the primary endpoint of durable Complete Remission (dCR) of 6-months following initial complete remission after BMT with

high statistical significance (p-value of <0.0001), 22% of patients achieved dCR in the Iomab-B arm compared to 0% in the control

In patients achieving 6-month dCR with Iomab-b, 1-year survival of 92% and 2-year survival of 60% was achieved; median overall survival

(OS) has not been reached in these patients

Iomab-B demonstrated significant improvement in Event Free Survival (EFS) with a Hazard Ratio = 0.22, p<0.0001

Iomab-B doubled 1-year survival and median overall survival compared to control arm patients who did not crossover

Iomab-B was well tolerated with a favorable safety profile - 4 times lower rate of sepsis than control arm

Company to host conference call and webcast on Saturday, February 18, 2023 at 6:00 PM EST to highlight full SIERRA results

NEW YORK, NY - February 18, 2023 -

Actinium Pharmaceuticals, Inc. (NYSE AMERICAN: ATNM) (Actinium or the Company), a leader in the development of targeted radiotherapies,

today announced positive results for the primary and secondary endpoints from its pivotal Phase 3 SIERRA trial of Iomab-B in patients

age 55 and above with active relapsed or refractory acute myeloid leukemia (r/r AML). Iomab-B met the primary endpoint of durable Complete

Remission (dCR) of 6-months following initial complete remission following BMT with a high degree of statistical significance (p<0.0001).

Additionally, Iomab-B produced a significant and clinically meaningful improvement in the secondary endpoint of Event-Free Survival (EFS),

with a 78% reduction in the probability of an event (Hazard Ratio=0.22, p<0.0001). Iomab-B doubled 1-year survival compared to the

control arm excluding cross over patients (26.1% vs 13.1%) as well as median overall survival (6.4 months vs. 3.2 months). Iomab-B was

well tolerated with four times lower rates of sepsis (6.1% vs 28.6%) and lower rates of febrile neutropenia, mucositis and acute graph

versus host disease (aGVHD). Iomab-B enabled unprecedented access to BMT with 100% engraftment in patients receiving a therapeutic dose

of Iomab-B compared to 18% of patients in the control arm and Iomab-B produced a 75% post-BMT Complete Remission (CR) rate compared to

6.3% post-BMT CR in the control arm. These high rates of access and post-BMT CR enabled the highly significant primary endpoint results.

The full SIERRA results were presented in the late-breaker session at the 2023 Tandem Meetings: Transplantation & Cellular Therapy

Meetings of the American Society for Transplantation and Cellular Therapy (ASTCT) and the Center for International Blood & Marrow

Transplant Research (CIBMTR).

Investor Conference Call and Webcast Details:

M.D., VP, Clinical Development - BMT & Cellular Therapy

Avinash Desai, M.D.,

Chief Medical Officer

Chief Commercial Officer

will be available on the Actinium's website (click here) after the event.

Dr. Sergio Giralt, Deputy Head, Division of Hematologic

Malignancies, Attending Physician, Adult BMT Service at Memorial Sloan Kettering Cancer Center, stated, "The SIERRA trial results

are an exciting advancement for older patients with active r/r AML and will be practice changing in how we treat these patients. I am

thrilled to see a high percentage of Iomab-B patients who achieved durable remissions reaching the critical 2-year survival mark. Significant

improvement in event-free survival and overall survival, with an excellent safety profile in the SIERRA trial, demonstrate the potential

of Iomab-B becoming a new standard of care for active, r/r AML."

SIERRA Trial Results

The pivotal Phase 3 SIERRA trial is a 153-patient,

randomized, multi-center, controlled trial, where Iomab-B is compared to the control arm that allowed physician's choice of over

20 available agents including chemotherapies and/or targeted therapies such as Venetoclax (Bcl-2), FLT3 inhibitors, IDH inhibitors and

Mylotarg. The control arm reflects current best practices for the treatment of r/r AML patients. SIERRA was conducted at 24 of the leading

BMT centers in the United States and Canada. SIERRA enrolled older, heavily pre-treated patients with active disease and high-risk characteristics

who would not be offered BMT in standard practice outside of a clinical trial and therefore have dismal survival outcomes of two to three

Iomab-B Patient Characteristics:

BMT Access and Engraftment:

All patients receiving the therapeutic dose of

Iomab-B were able to access BMT with 100% engraftment. Patients in the Iomab-B arm were able to access a BMT without having to first attain

a CR, consequently they were able to access BMT in half the time compared to the control arm as those patients need to attain a CR prior

to BMT, which is the norm per current practice.

Primary Endpoint - dCR 6-months After

Secondary Endpoints - Event Free Survival and Overall Survival:

Dr. Avinash Desai, Chief Medical Officer of Actinium,

said, "We are excited that Iomab-B met the primary endpoint and produced positive results across all SIERRA trial endpoints with

improved safety compared to control arm in such a difficult patient population. In routine clinical BMT practice, patients enrolled on

SIERRA would never be considered for transplant and often have dismal outcomes. Iomab-B provides unprecedented BMT access and improved

outcomes with better tolerability - opening the promise of better transplant outcomes for the entire universe of relapsed and refractory

AML patients. These results clearly demonstrate Iomab-B's practice expanding opportunity as more patients will be able to access

transplant and upon reaching the 100-day post-transplant mark they can return to their referring hematologist for long-term care. We look

forward to launching an early access program, completing our BLA submission and initiating life cycle management activities to bring Iomab-B

to as broad a patient population as possible."

Sandesh Seth, Actinium's Chairman and CEO,

added, "These positive SIERRA results will help to establish Iomab-B as a new standard of care for r/r AML. Iomab-B is a very attractive

option for patients due to its excellent safety and strong efficacy profile. It will enable physicians to provide a treatment intervention

with potential long-term survival outcomes and will help bring more patients to curative BMTs. We truly believe that Iomab-B enables potentially

better value to be unlocked by getting more patients safely to an effective BMT and by increasing the length and quality of life for patients

who otherwise would have dismal outcomes using currently available options. The commercial opportunity for Iomab-B is attractive as the

majority of relapsed/refractory patients cannot be treated with a BMT today and Iomab-B can enable them to access this potentially curative

treatment. These patients comprise of over half of all AML patients. In addition, the lack of current or visible competition for Iomab-B

and the concentration of BMT centers imply that successful commercialization of this high-value treatment can be achieved with a streamlined,

efficient organization that is sparing to the balance sheet. We look forward to establishing this practice expanding treatment as the

standard of care and to updating on our plans to file the BLA and progress toward this goal."

About Iomab-B and the Pivotal Phase 3 SIERRA

Iomab-B is a first-in-class targeted radiotherapy

intended to improve patient access to potentially curative BMT by simultaneously and rapidly depleting blood cancer, immune and bone marrow

stem cells that uniquely express CD45. Multiple studies have demonstrated increased survival in patients receiving BMT, however, an overwhelming

majority of patients with blood cancers do not receive BMT as current approaches do not produce a remission, which is needed to advance

to BMT, or are too toxic. Studied in over 400 patients, prior studies with Iomab-B have demonstrated nearly universal access to BMT, increased

survival and tolerability in multiple clinical trials including the recently completed pivotal Phase 3 SIERRA trial in patients with active

(leukemic blasts >5%), relapsed or refractory acute myeloid leukemia (r/r AML) age 55 and above.

Iomab-B met the primary endpoint of durable Complete

Remission (dCR) of 6 months after initial remission post-BMT in the pivotal Phase 3 SIERRA trial with high statistical significance (p<0.0001).

Iomab-B produced a 75% post-BMT CR rate (44/59 patients), which is 12-times greater than the post-BMT rate of 6.3% (4/64 patients) in

the control arm. Patients receiving Iomab-B had a 78% lower probability of an event, defined as not achieving a CR/CRp, crossover, not

receiving a BMT, relapse or death, with a Hazard Ratio of 0.22 (p<0.0001). Iomab-B doubled 1-year overall survival with 26.1% compared

to 13.1% in the control arm for patients who did not crossover as well as median overall survival with 6.4 months vs 3.2 months. Overall

survival statistics are confounded by the crossover arm. Crossover patients had a 35.8% 1-year overall survival rate. Due to its targeted

nature, Iomab-B was well tolerated with four times lower rates of sepsis compared to the control arm (6.1% vs. 28.6%) and lower rates

of BMT associated adverse events including febrile neutropenia, mucositis and graft versus host disease (GVHD). Actinium intends to submit

a Biologics License Application (BLA) seeking approval for Iomab-B in 2023 to address patients age 55+ with r/r AML who cannot access

BMT with currently available therapies. Iomab-B has been granted Orphan Drug Designation from the U.S. Food and Drug Administration (FDA)

and has patent protection into 2037.

The pivotal Phase 3 SIERRA (Study of Iomab-B in

Elderly relapsed or refractory AML) is a 153-patient, randomized, multi-center clinical trial, studying Iomab-B compared to the control

arm of physician's choice of salvage therapy. Control arm options included chemotherapies like cytarabine and daunorubicin and targeted

agents such as a Bcl-2 inhibitor (Venetoclax), FLT3 inhibitors and IDH 1/2 inhibitors. The SIERRA control arm reflects real-world treatment

of r/r AML patients with over 20 agents used alone or in combination as no standard of care exists for this patient population. The SIERRA

trial enrolled patients at 24 leading transplant centers in the United States and Canada that perform over 30% of AML BMTs.

Developed at the Fred Hutchinson Cancer Research

Center, a pioneer in the field of BMT, Iomab-B is supported by data in six disease indications including leukemias, lymphomas and multiple