Pfizer’s Experimental SCD Drug Fails in Phase 3 Study

Rare Daily Staff

Pfizer said its experimental sickle cell disease therapy, inclacumab, failed to meet its primary endpoint of a significant reduction in vaso-occlusive crises among participants receiving the therapy compared with those receiving placebo.

The setback follows Pfizer’s decision in September 2024 to withdraw all lots of Oxbryta from approved markets after clinical and real-world data suggested an imbalance in vaso-occlusive crises and fatal events, warranting further evaluation. Pfizer acquired Oxbryta through its $5.4 billion acquisition of Global Blood Therapeutics in 2022. The company has since completed a data assessment review for Oxbryta and shared its findings with regulators in the United States and Europe.

Pfizer is evaluating a separate experimental therapy, osivelotor, as a potential chronic treatment for sickle cell disease. Enrollment in a phase 3 study is currently paused due to a partial clinical hold issued by the Food and Drug Administration at the end of last year.

The company said it remains committed to the sickle cell community and is advancing next steps for its broader portfolio of therapies for the disease, including Oxbryta and osivelotor.

The Phase 3 THRIVE-131 study was a 48-week, global, randomized, double-blind, placebo-controlled trial assessing the efficacy and safety of inclacumab. Investigators enrolled 241 participants age 16 and older who had experienced two to 10 vaso-occlusive crises in the previous year. Participants were assigned in a 1:1 ratio to receive intravenous inclacumab or placebo every 12 weeks for 48 weeks.

Inclacumab was generally well tolerated in the THRIVE-131 study. The most commonly reported treatment-emergent adverse events in either group included anemia, arthralgia, back pain, headache, malaria, sickle cell anemia with crisis, and upper respiratory tract infection.

“While the THRIVE-131 results did not meet our expectations, we remain committed to better understanding these results and sharing them with the medical and sickle cell community in the interest of advancing our collective understanding of sickle cell disease,” said Michael Vincent, chief inflammation and immunology officer at Pfizer. “We remain focused on our mission of bringing much-needed treatments to patients with sickle cell disease.”