August 15, 2025 – In a statement issued today, Pfizer announced the results of their Phase 3 THRIVE-131 study evaluating inclacumab. Although inclacumab was generally well tolerated in THRIVE-131, the study results concluded that inclacumab “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.” The Medical and Research Advisory Committee (MARAC) of the Sickle Cell Disease Association of America, Inc. (SCDAA) would like to express its disappointment in hearing this news. While we recognize that not all therapies will be approved, this report does present a setback to the sickle cell disease community. It underscores the need for further research and clinical trials to find a universal cure for this rare disease.
Sickle cell disease (SCD) is a rare condition that affects over 100,000 Americans and millions across the world. Progress has been made in the treatment of the disease since the approval of hydroxyurea 1997 but it has been slow and far and few between. In addition to hydroxyurea, only two other medications are currently available to treat sickle cell patients: L- glutamine and crizanlizumab. These disease modifying therapies have successfully addressed such major complications as acute pain crisis and acute chest syndrome, among others. Still individuals continue to report issues such as fatigue, chronic pain and other symptoms that result in poor quality of life. Recently approved cell and gene therapies are available and are potentially curative but are costly and require a significant time commitment for the transplant procedure.
MARAC recognizes that while the Pfizer study did not achieve the anticipated outcomes, we applaud those individuals who participated in this and other in clinical trials. Had the therapy achieved its primary clinical trial endpoint, it would have been promising. MARAC encourages the pharmaceutical industry and the Food and Drug Administration (FDA) to work with the sickle cell community to continue to search for therapies that not only address the clinical outcomes often evaluated in sickle cell studies but also explore outcome measures and endpoints that address patient-reported outcomes that impact quality of life.
SCDAA has also joined with a community of sickle cell disease advocacy organizations with this response.
