Actinium Pharmaceuticals is no longer planning to move forward with its iodine-based drug independently after the FDA said a new clinical trial would be needed to apply for approval.
Actinium was developing its lead asset, Iomab-B, as a conditioning agent for certain acute myeloid leukemia patients before they get a bone marrow transplant. “The FDA has now determined that demonstrating an overall survival benefit in a randomized head-to-head trial is required,” Actinium wrote in a Monday press release.
Actinium’s shares $ATNM fell 70% Monday morning.
In its pivotal study, SIERRA, the company measured durable complete remission for its primary endpoint. At six months, 44 of 59, or 75% of patients who received Iomab-B achieved initial remission compared to four of 64 in the control arm, meeting the endpoint of the study.
Actinium said that it presented additional SIERRA analyses to the FDA that looked at the drug’s impact on overall survival. “However, the FDA has now determined that the analyses from the SIERRA trial do not adequately support a BLA filing for Iomab-B and requires an additional clinical study,” the company wrote.
The agency recommended that a crossover should not be used in the new study. Nearly 60% of patients in the SIERRA trial crossed over to the treatment arm from the control arm, confounding the overall survival analysis, according to Actinium.
The FDA also proposed that the new study compare the Iomab-B conditioning regimen for bone marrow transplant with a standardized reduced intensity conditioning regimen as a control. The previous study’s control arm had allowed different conditioning regimens and physician’s choice of salvage therapies.
Actinium said that following further discussions with the FDA around specifics of the new clinical trial, the company plans to look for a US partner for the experimental drug. Moving forward, Actinium said it plans on focusing on its early-stage candidates Actimab-A and Iomab-ACT, as well as preclinical work.
Radiopharmaceuticals have been a hot area for the biopharma industry lately, where large pharma companies have spent over $8 billion to acquire startups over the last year. However, Actinium’s approach with Iomab-B — developing it as a radiotherapy conditioning agent — is different from the other companies that are primarily focused on developing treatments for solid tumor cancers.