Pfizer’s Sickle Cell Therapy Fails Phase III Trial, Future Uncertain

Pfizer’s investigational sickle cell disease therapy, inclacumab, has failed to meet the primary endpoint in its Phase III THRIVE-131 trial (NCT04935879). The study, which enrolled patients aged 16 and older, aimed to show a significant reduction in vaso-occlusive crises (VOCs) over 48 weeks but did not achieve this goal. While the drug was generally well tolerated, common adverse events included anaemia, back pain, headache, and upper respiratory infections. Pfizer said it will share detailed analyses with the scientific and patient community.

Inclacumab remains under evaluation in the THRIVE-133 OLE study (NCT05348915), focused on long-term safety. GlobalData projects potential global sales of $267 million by 2031 if the therapy secures approval.

The setback adds to Pfizer’s challenges in the sickle cell space, following the 2024 withdrawal of Oxbryta and an FDA clinical hold on its osivelotor program. Meanwhile, competitors like Vertex and CRISPR’s Casgevy are slowly gaining traction despite high treatment costs.

18-08-2025