The FDA is looking for stronger overall survival data to back Actinium’s application for Iomab-B, an investigational therapy that will allow acute myeloid leukemia patients to receive bone marrow transplants.
Actinium Pharmaceuticals on Monday announced that it is seeking partnership opportunities for its investigational targeted radiotherapy Iomab-B, which the company is developing as an induction and conditioning therapy for patients with relapsed or refractory acute myeloid leukemia.
The decision comes after the FDA rejected Actinium’s Biologics License Application (BLA) for Iomab-B, citing the need for another trial—one that would establish the treatment’s overall survival (OS) benefit when pitted against a standard reduced-intensity conditioning regimen.
CEO Sandesh Seth in a statement said that Actinium is “disappointed” that the data backing Iomab-B “are not deemed adequate by the FDA to support a BLA filing despite meeting the primary endpoint with statistical significance.”
Actiniums remains “committed” to Iomab-B and will find the “best development path forward” for the conditioning therapy candidate, including finding a development partner, Seth said.
Iomab-B is a first-in-class targeted radiotherapy that works by selectively and rapidly depleting CD45-positive blood cancer, immune and bone marrow stem cells, according to Actinium’s website. This mechanism of action makes bone marrow transplantation available to more patients. The procedure, while otherwise potentially curative, first requires remission which makes it inaccessible to most patients.
To support its BLA, Actinium conducted the Phase III SIERRA study, a pivotal, randomized trial that enrolled more than 150 patients with relapsed or refractory acute myeloid leukemia. SEIRRA compared Iomab-B versus a physician’s choice of salvage therapy, such as cytarabine, daunorubicin and venetoclax.
In October 2022, Actinium published topline data from SIERRA, touting that 100% of patients treated with Iomab-B eventually qualified for a bone marrow transplant and engraftment in these patients did not experience delays. However, in the control group, 82% of patients failed to reach durable complete remission and were ineligible to undergo the transplant procedure.
Iomab-B also hit SIERRA’s primary endpoint of durable complete remission of six months after initial remission and bone marrow transplant, compared to conventional care. The effect was statistically significant, with a p-value less than 0.0001, according to Actinium’s October 2022 announcement.
SIERRA also demonstrated an overall favorable OS trend for Iomab-B but because the study allowed control patients to cross over and receive the active treatment, its OS analysis was ultimately confounded.
In denying Actinium’s BLA, the FDA pointed to the need for stronger OS data before the biotech can refile its application. The proposed additional trial will not allow patient crossover to better assess Iomab-B’s effects on patient survival, according to Actinium.
