Abbisko Therapeutics' pimicotinib has shown positive results in a Phase 3 clinical trial for the treatment of tenosynovial giant cell tumor (TGCT). The MANEUVER study revealed that 54% of patients treated with pimicotinib experienced tumor shrinkage, compared to only 3.2% in the placebo group, meeting the trial's primary endpoint. This study offers a potential new treatment option for patients with this rare condition.
Understanding TGCT and Current Treatment Landscape
Tenosynovial giant cell tumor is a rare condition primarily driven by the overexpression of colony stimulating factor-1 receptor (CSF-1R). This overexpression leads to the proliferation of cells like microglial cells and macrophages, resulting in joint pain, stiffness, and potential irreversible damage to joints and bones. Current treatment approaches mainly involve surgery, which can be challenging for some patients. Pexidartinib (Turalio), a CSF-1R blocker by Daiichi Sankyo, is an existing systemic therapy but requires twice-daily administration and carries the risk of side effects such as hepatotoxicity.
MANEUVER Study Details and Results
The MANEUVER study was a randomized, double-blind, placebo-controlled trial involving 94 patients with TGCT across Europe, China, and North America. These patients had not previously received CSF-1R blocking treatments. Patients were administered 50 mg of pimicotinib daily. In addition to the primary endpoint of tumor shrinkage, the pimicotinib group also demonstrated significant improvements in secondary endpoints, including reduced stiffness and pain. The drug was reported to be well-tolerated among the participants.
Expert Commentary
Niu Xiaohui, a study investigator and director of the Bone and Soft Tissue Tumour Diagnosis and Research Centre at Beijing Jishuitan Hospital, stated that the data from the MANEUVER study, combined with the convenience of once-daily oral administration and pimicotinib's selective inhibition of CSF-1R, could establish a new treatment paradigm for TGCT patients.
Pimicotinib's Potential and Future Development
Merck KGaA holds the commercial rights for pimicotinib in mainland China, Hong Kong, Macau, and Taiwan, having acquired these rights from Abbisko in a deal valued at $70 million upfront in 2023. Abbisko is also exploring the potential of pimicotinib in treating solid tumors, chronic graft-versus-host disease, and advanced pancreatic cancer.
Competitive Landscape
Pexidartinib (Turalio) received its first approval in the U.S. in 2019, based on a 38% overall response rate (ORR) in Phase 3 trials. Another contender, Deciphera's vimseltinib, achieved a 40% ORR in a Phase 3 trial for TGCT treatment last year. While CSF-1R blockers have faced challenges in clinical trials for other tumor types, pimicotinib's selective inhibition and promising results in TGCT offer a potential advancement in this specific area.
