Prothena’s Phase III AL Amyloidosis Trial Fails to Meet Primary Endpoint

Prothena Corporation’s Phase III AFFIRM-AL trial evaluating birtamimab for Mayo Stage IV amyloid light-chain (AL) amyloidosis did not meet its primary endpoint of overall survival, prompting the company to discontinue the therapy’s development and halt the trial’s open-label extension. The global, double-blind, placebo-controlled study enrolled 207 newly diagnosed, treatment-naïve patients.

Secondary endpoints, including the six-minute walk test and SF-36 physical component scores, were also unmet. Patients in the treatment arm received 24 mg/kg birtamimab every 28 days alongside standard bortezomib chemotherapy, with daratumumab use allowed.

Despite the results, birtamimab was generally safe and well-tolerated. Prothena plans to announce cost-cutting measures and business strategy updates soon. The company continues to develop treatments targeting neurodegenerative and amyloid-related diseases like ATTR amyloidosis, Parkinson’s, and Alzheimer’s.

28-05-2025