Pfizer’s sickle cell disease (SCD) drug has flunked a key phase 3 test, the latest blow to the pharma’s $5.4 billion acquisition of Global Blood Therapeutics.
Pfizer acquired the P-selectin inhibitor, called inclacumab, as part of the buyout of GBT in 2022. For its part, GBT had gained the asset from Roche four years earlier.
Pfizer set about evaluating inclacumab in pair of phase 3 studies, dubbed Thrive. The Big Pharma terminated one of those trials, which was examining the safety and efficacy of inclacumab in reducing vaso-occlusive crisis (VOCs) experienced by patients with SCD, back in March 2024, citing “slow recruitment” of patients.
At the time, Pfizer insisted that the termination didn’t impact the company's plans to get inclacumab approved in 2026.
But, in a short press release Friday, Pfizer revealed that the other Thrive study missed its primary endpoint of demonstrating a significant reduction in VOCs compared to placebo at 48 weeks.
Inclacumab was generally well tolerated, Pfizer added, with the most commonly reported treatment-emergent adverse events being anemia, arthralgia, back pain, headache, malaria, sickle cell anemia with crisis and upper respiratory tract infection.
“We recognize this news is disappointing for the sickle cell community, and we share their disappointment,” Michael Vincent, M.D., Ph.D., chief inflammation and immunology officer at Pfizer, said in the Aug. 15 release.
“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,” Vincent added. “We remain focused on our mission of bringing much-needed treatments to patients with sickle cell disease.”
It's only the latest setback to Pfizer’s GBT-acquired portfolio. The biggest prize from the acquisition was the approved SCD drug Oxbryta, but Pfizer was forced to pull the drug from markets worldwide last year based on clinical information that the company said “now indicates the overall benefit of Oxbryta no longer outweighs the risk.”
With the future of both inclacumab and Oxbryta uncertain, the last untainted GBT legacy asset in Pfizer’s SCD portfolio is an HbS polymerization inhibitor called osivelotor, which is currently in phase 3 development.
The biggest positive developments in the SCD space in recent years has been from gene therapies, notably Vertex Pharmaceuticals and CRISPR Therapeutics’ Casgevy as well as bluebird bio’s Lyfgenia.