Pimicotinib (ABSK021), an investigational CSF-1R inhibitor, has shown promising results in the Phase 3 MANEUVER trial for patients with tenosynovial giant cell tumor (TGCT). The study met its primary endpoint, demonstrating a significant improvement in objective response rate (ORR) compared to placebo. These findings suggest that pimicotinib could offer a new treatment paradigm for this rare and debilitating condition.
The MANEUVER trial (NCT05804045) was a three-part, double-blind, randomized study designed to evaluate the efficacy and safety of pimicotinib versus placebo in patients with TGCT who were eligible for systemic therapy and had not previously received CSF-1 or CSF-1R-targeting therapies. In the first part of the trial, 94 patients were randomized in a 2:1 ratio to receive either pimicotinib at 50 mg once daily (n = 63) or a matched placebo (n = 31) for 24 weeks. The study included patients from China (n = 45), Europe (n = 28), and the US and Canada (n = 21).
Primary and Secondary Endpoints
The primary endpoint of the trial was ORR at 25 weeks, assessed using RECIST v1.1 criteria by blinded independent central review. Key secondary endpoints included tumor volume score, active range of motion, stiffness (measured by Numeric Rating Scale - NRS), pain (measured by Brief Pain Inventory - BPI), and physical functioning (measured by Patient-Reported Outcomes Measurement Information System - PROMIS criteria).
Significant Improvement in ORR
The results of the MANEUVER trial showed a statistically significant improvement in ORR with pimicotinib compared to placebo. At 25 weeks, the ORR was 54.0% in the pimicotinib arm versus 3.2% in the placebo arm (P < .0001). This clinically meaningful difference highlights the potential of pimicotinib to address the unmet needs of TGCT patients.
Improvements in Patient-Reported Outcomes
In addition to the primary endpoint, the study also demonstrated statistically significant and clinically meaningful improvements in secondary endpoints related to patient outcomes. The mean change in stiffness by NRS from baseline was -3.00 with pimicotinib compared to -0.57 with placebo (P < .0001). Similarly, the mean change in pain by BPI from baseline was -2.32 and 0.23 in the pimicotinib and placebo arms, respectively (P < .0001).
Safety Profile
The safety profile of pimicotinib in the MANEUVER trial was consistent with prior reports. There were no signs of cholestatic hepatoxicity observed. In the pimicotinib arm, 1.6% (n = 1) and 7.9% (n = 5) of patients experienced treatment-emergent adverse effects resulting in treatment discontinuation and dose reduction, respectively.
Impact on TGCT Patients
TGCT primarily affects young and middle-aged adults, causing swelling, pain, stiffness, and limited mobility in the joints. These symptoms can significantly impact patients' ability to perform daily activities, affecting their work and social lives. According to Niu Xiaohui, MD, professor and director of the Bone and Soft Tissue Tumor Diagnosis and Research Centre at Beijing Jishuitan Hospital, pimicotinib, with its once-daily oral administration and selective inhibition of CSF-1R, has the potential to establish a new treatment paradigm for patients with TGCT.
Pimicotinib has received breakthrough therapy designation from the FDA, the China National Medical Products Administration, and priority medicine designation from the European Medicines Agency for the treatment of TGCT.
