January 12, 2026 – Merck Healthcare KGaA, Darmstadt, Germany, which operates as Merck Serono in the United States and Canada, announced today that the U.S. Food and Drug Administration (FDA) has officially accepted the New Drug Application (NDA) for pimicotinib for the systemic treatment of tenosynovial giant cell tumor (TGCT). The application is based on the primary results and long-term follow-up data from the global Phase III MANEUVER study, which confirmed that pimicotinib delivers profound and durable tumor responses, bringing clinically meaningful efficacy improvements to patients.

Basis for the New Drug Application

This NDA is supported by the primary results and long-term follow-up data from the global Phase III MANEUVER study. The trial demonstrated that at Week 25 of treatment, once-daily oral administration of pimicotinib achieved a statistically significant and substantial improvement in the primary endpoint of Objective Response Rate (ORR) – as assessed by the Blinded Independent Review Committee (BIRC) per the Response Evaluation Criteria in Solid Tumors version 1.1 (RECIST v1.1) – compared with the placebo group. Meanwhile, the study observed statistically significant and clinically meaningful improvements across all key secondary endpoints related to patient-reported outcomes (PROs) in TGCT, including increased active joint range of motion and physical function, as well as reduced joint stiffness and pain symptoms in patients.

About Tenosynovial Giant Cell Tumor (TGCT)

TGCT is a rare, locally aggressive neoplasm arising within or around joints. It causes progressive swelling and stiffness in the affected joints, accompanied by impaired mobility, which severely impacts patients’ daily activities and quality of life. The disease predominantly affects otherwise healthy individuals. If left untreated or if the disease recurs, TGCT may cause irreparable damage to bones, joints and surrounding tissues. Currently in clinical practice, beyond surgical resection, there remains an urgent unmet need for treatment options with well-established efficacy and favorable tolerability that can both induce tumor shrinkage and alleviate patients’ pain while restoring joint function.

In December 2025, the National Medical Products Administration (NMPA) of China approved pimicotinib for the treatment of symptomatic adult patients with TGCT for whom surgical resection is likely to result in functional limitations or severe complications. At present, marketing applications for the drug are also under regulatory review by health authorities in other countries and regions.

About the MANEUVER Study

The pivotal global Phase III MANEUVER study is a three-part, randomized, double-blind, placebo-controlled clinical trial designed to evaluate the efficacy and safety of pimicotinib in patients with TGCT who require systemic therapy and have no prior exposure to Colony-Stimulating Factor 1/Colony-Stimulating Factor 1 Receptor (CSF-1/CSF-1R) targeted therapy. Conducted by Abbisko Therapeutics, the study enrolled a total of 94 patients, with 45 in China, 28 in Europe, and 21 in the United States and Canada.

In the double-blind Part 1 of the study, 94 patients were randomized in a 2:1 ratio: 63 patients received oral pimicotinib at a dose of 50 mg once daily, and 31 patients received placebo, with a 24-week treatment period for both groups. The primary endpoint was the ORR in the intent-to-treat (ITT) population at Week 25 of treatment, as assessed by the BIRC per RECIST v1.1. Secondary endpoints included Tumor Volume Score (TVS), relative joint range of motion, joint stiffness measured by the Numeric Rating Scale (NRS), pain intensity measured by the Brief Pain Inventory (BPI), and physical function assessed by the Patient-Reported Outcomes Measurement Information System-Physical Function (PROMIS-PF) module.

Eligible patients who completed the double-blind Part 1 were able to enter the open-label Part 2 for up to 24 weeks of subsequent treatment; patients who finished Part 2 could then proceed to the open-label extension study phase (Part 3) for continued treatment and safety follow-up.

About Pimicotinib (ABSK021)

Independently developed by Abbisko Therapeutics, pimicotinib is a novel, oral, highly selective and potent small-molecule inhibitor of CSF-1R. It has been approved in China for the treatment of symptomatic adult patients with TGCT for whom surgical resection is likely to result in functional limitations or severe complications. The drug has been granted Breakthrough Therapy Designation (BTD) by the FDA for the treatment of inoperable TGCT, and PRIority MEdicines (PRIME) designation by the European Medicines Agency (EMA). Merck KGaA, Darmstadt, Germany holds the exclusive global commercialization rights to pimicotinib.