Actinium Showcases Improved TP53 Patient Outcomes with Iomab-B at EHA 2024

Actinium Pharmaceuticals, Inc. recently shared promising results from the Phase 3 SIERRA trial for their drug Iomab-B at the 2024 European Hematology Association (EHA) Hybrid Congress in Madrid, Spain. The trial, focused on older patients with active relapsed or refractory acute myeloid leukemia (r/r AML), demonstrated significant benefits for those receiving an Iomab-B led bone marrow transplant (BMT) compared to standard care.

In the SIERRA trial, which involved 153 patients aged 55 and above, the primary endpoint was durable complete remission. Notably, only patients who received an Iomab-B led BMT achieved this endpoint, showing a one-year survival rate of 92% and a two-year survival rate of 69%, both statistically significant improvements in event-free survival. The study also included high-risk patients with factors like TP53 mutations, advanced age, complex cytogenetics, and previous therapies.

One of the key presentations at the EHA congress focused on outcomes for patients with TP53 mutations, which are often linked to poor treatment responses. Among the 24% of patients in the trial with this mutation, those who received Iomab-B (either initially or via cross-over) were the only ones to achieve complete or durable complete remission. The median overall survival for these TP53 mutated patients was 5.49 months with Iomab-B, compared to just 1.66 months for those who did not receive the drug, highlighting Iomab-B's efficacy (hazard ratio=0.23, p=0.0002).

Further analysis showed that TP53 negative patients receiving Iomab-B had a median overall survival of 6.37 months, while TP53 positive patients had a median of 5.72 months, illustrating Iomab-B's potential to overcome the adverse effects of TP53 mutations.

Another key presentation covered long-term efficacy results of Iomab-B in the SIERRA trial. It was noted that all patients on the Iomab-B arm underwent a BMT, whereas only 18% of those in the control arm did. Remarkably, 75% of patients treated with Iomab-B achieved complete remission, compared to just 6.3% in the control group. The durable complete remission rate was 22% in the Iomab-B group, with none in the control arm, meeting the primary endpoint with high statistical significance (p-value<0.0001). Among those achieving durable complete remission, the one-year survival rate was 92%, and the two-year survival rate was 69%, with the median overall survival not yet reached.

Moreover, Iomab-B was well tolerated with a favorable safety profile, showing lower incidences of sepsis and mucositis among patients who received the drug.

Actinium Pharmaceuticals, Inc., recognized for developing targeted radiotherapies, plans to further advance Iomab-B for other blood cancers and explore next-generation conditioning candidates like Iomab-ACT to enhance cell and gene therapy outcomes. The company's pipeline includes the pre-BLA & MAA (EU) Iomab-B, a conditioning agent for BMT, and Actimab-A, a therapeutic agent in the National Cancer Institute CRADA pivotal development path, both aimed at improving survival rates for patients with relapsed and refractory acute myeloid leukemia.

The SIERRA trial's findings underscore the potential of Iomab-B to significantly improve outcomes in high-risk AML patients, particularly those with TP53 mutations, offering new hope for a population with historically limited treatment options.