Pimicotinib (previously known as ABSK-021) is being developed to treat TGCT by targeting a protein that drives the growth of the tumor, known as the colony stimulating factor 1 (CSF1). It is being developed by Merck KgaA and EMD Serono for the treatment of TGCT. Pimicotinib is an oral (50 mg) daily medication that is designed to block CSF1 at the cell source. As an investigational drug, pimicotinib has not been approved by the United States Food and Drug Administration (FDA) or in Europe, Canada, Australia. However, on December 21, 2025, pimicotinib was approved for symptomatic adult patients with TGCT in China. It is expected that pimicotinib will rollout in other countries upon approvals.
The pivotal Phase 3 study, known as MANEUVER, tested the effectiveness and long-term safety of an investigational drug, pimicotinib, as a potential new treatment for TGCT. This pivotal study was randomized where patients received pimicotinib or a placebo (look alike sugar pill) for 6 months. After 6 months, patients on placebo were given the chance to "crossover" and receive pimicotinib and patients receiving pimicotinib were allowed to continue receiving it.
Published findings from the trial show that 94 TGCT patients (45 in China, 46 in Europe and North America) received 50 mg of pimicotinib once daily. All patients had symptomatic TGCT and were at least 18 years of age. Unlike other trials in TGCT, MANEUVER enrolled patients with both diffuse and localized TGCT. Sixty percent (60%) of patients had prior surgeries. At 25 weeks, 54% of patients had significant tumor shrinkage, defined as those who have 30% or more shrinkage in their TGCT, after 6 months of treatment with pimicotinib (1). Of those with significant shrinkage, 41% had shrinkage within 13 weeks. The tumor shrinkage also increased with longer treatment out to 12 months (Of those patients that remained on for 12 months of pimicotinib treatment, 76% of patients had 30% or more TGCT shrinkage). At 25 weeks of treatment, 65% of patients that received pimicotinib also had significant reductions in stiffness, pain, and improved range of motion.
Majority of side effects have been mild-to-moderate. According to their recent publication, all patients had some side effect. The most common side effects include itching, facial swelling, rash, swelling around the eyes, fatigue, nausea, and headaches which were reported in more than 10% of all patients receiving pimicotinib (1). Six percent of patients had increases in blood pressure. Additional lab abnormalities were seen such as creatinine kinase, liver enzymes like AST/ALT, LDH, and alpha-HBDH, although patients were not symptomatic due to lab changes. Nearly 8% of patients changed dose due to side effects and 2% discontinued treatment due to side effects.
