Osivelotor

NEW YORK, NY, USA I August 15, 2025 I Pfizer Inc. (NYSE: PFE) today announced results from the Phase 3 THRIVE-131 study evaluating inclacumab, an investigational P-selectin inhibitor, in patients 16 years of age and older with sickle cell disease (SCD). The study did not meet its primary endpoint of significant reduction in the rate of vaso-occlusive crises (VOCs) in participants receiving inclacumab versus placebo every 12 weeks over 48 weeks. Inclacumab was generally well tolerated in THRIVE-131. The most commonly reported treatment-emergent adverse events in either group were 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,” said Michael Vincent, M.D., Ph.D., Chief Inflammation & Immunology Officer, Pfizer. “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. We remain focused on our mission of bringing much-needed treatments to patients with sickle cell disease. We are deeply grateful to the participants and investigators for their contributions to this important work. Their efforts are invaluable in informing future sickle cell research.” Analyses of the data will be shared with the scientific and patient community in due course. Pfizer remains committed to the sickle cell community and is actively progressing next steps for its broader SCD portfolio, including OXBRYTA® (voxelotor) and osivelotor. Updates on OXBRYTA ® and osivelotor will be provided as they become available. About THRIVE-131 The Phase 3 THRIVE-131 ( NCT04935879 ) study was a 48-week, global, randomized, double-blind, placebo-controlled study evaluating the efficacy and safety of inclacumab, an investigational monoclonal antibody that selectively targets P-selectin for the treatment of patients with SCD. The study enrolled 241 participants 16 years and older with SCD who experienced between two and 10 VOCs in the previous year. Participants were randomized 1:1 to receive intravenous inclacumab or placebo every 12 weeks for 48 weeks. The primary endpoint measured the rate of VOCs with inclacumab compared to placebo during the 48-week treatment period. Participants from THRIVE-131 were eligible to enroll in THRIVE-133 OLE, an open-label extension study to evaluate the long-term safety of inclacumab. For more information on THRIVE-131 (NCT04935879), go to ClinicalTrials.gov . About Pfizer’s Sickle Cell Portfolio In September 2024, Pfizer withdrew all lots of OXBRYTA® (voxelotor) in all approved markets based on the totality of clinical and real-world data, which suggested an imbalance in VOCs and fatal events at that time, requiring further evaluation. Pfizer has since completed its OXBRYTA data assessment review and shared this information with the FDA and EMA. Pfizer is committed to publishing a comprehensive analysis that includes additional OXBRYTA data and analyses this year. Osivelotor is being evaluated in a Phase 3 clinical trial, studying the efficacy and safety of a next-generation hemoglobin S polymerization inhibitor, as a potential chronic treatment for SCD. Enrollment is currently paused due to a partial clinical hold issued by the FDA at the end of last year. Updates on the Phase 2/3 clinical trial of osivelotor will be shared as available. About Sickle Cell Disease SCD is a lifelong, debilitating inherited blood disorder in which hemoglobin S polymerization leads to red blood cell sickling resulting in vascular inflammation and hemolytic anemia. Vascular inflammation, together with sickled red blood cells, can lead to acute pain crises, or VOCs, and progressive end organ damage. Complications of SCD begin in early childhood and are associated with shortened life expectancy. Early intervention and treatment of SCD have shown potential to modify the course of this disease, reduce symptoms and events, prevent long-term organ damage, and extend life expectancy. Historically, there has been a high unmet need for therapies that address the root cause of SCD and its acute and chronic complications. While rare in developed countries, there are an estimated 6.5 – 9 million people living with SCD globally. 1 SCD occurs particularly among those whose ancestors are from sub-Saharan Africa, though it also occurs in people of Hispanic, South Asian, Southern European and Middle Eastern ancestry. 1,2 About Pfizer: Breakthroughs That Change Patients’ Lives At Pfizer, we apply science and our global resources to bring therapies to people that extend and significantly improve their lives. We strive to set the standard for quality, safety and value in the discovery, development and manufacture of health care products, including innovative medicines and vaccines. Every day, Pfizer colleagues work across developed and emerging markets to advance wellness, prevention, treatments and cures that challenge the most feared diseases of our time. Consistent with our responsibility as one of the world’s premier innovative biopharmaceutical companies, we collaborate with health care providers, governments and local communities to support and expand access to reliable, affordable health care around the world. For 175 years, we have worked to make a difference for all who rely on us. We routinely post information that may be important to investors on our website at www.Pfizer.com . In addition, to learn more, please visit us on www.Pfizer.com and follow us on X at @Pfizer and @Pfizer_News , LinkedIn , YouTube and like us on Facebook at www.facebook.com/Pfizer/ 1 GBD 2021 Sickle Cell Disease Collaborators. Global, regional, and national prevalence and mortality burden of sickle cell disease, 2000-2021: a systematic analysis from the Global Burden of Disease Study 2021 [published correction appears in Lancet Haematol. 2023 Aug;10(8):e574. doi: 10.1016/S2352-3026(23)00215-6.]. Lancet Haematol. 2023;10(8):e585-e599. doi:10.1016/S2352-3026(23)00118-7 2 Adigwe OP, Onoja SO, Onavbavba G. A Critical Review of Sickle Cell Disease Burden and Challenges in Sub-Saharan Africa. J Blood Med. 2023;14:367-376. Published 2023 May 31. doi:10.2147/JBM.S406196 SOURCE: Pfizer