Merck’s Pimicotinib Accepted for Priority Review in China, Offering Hope for Patients with TGCT
Merck, a prominent global science and technology company, announced a significant milestone in its oncology portfolio as the Center for Drug Evaluation (CDE) under China’s National Medical Products Administration (NMPA) officially accepted the company’s application for the marketing authorization of pimicotinib, a novel oral treatment targeting tenosynovial giant cell tumor (TGCT). The acceptance, which follows the CDE’s grant of Priority Review status in May, represents an accelerated regulatory pathway for what may become the first approved systemic therapy for TGCT in China.
A New Treatment Option for a Debilitating Joint Tumor
TGCT is a rare, debilitating condition that primarily affects young and middle-aged adults, often striking individuals in their prime working years. It is characterized by non-malignant but locally aggressive tumors that grow in the synovium of joints, tendon sheaths, and bursae. The tumor growth leads to a cascade of painful and disabling symptoms including joint swelling, stiffness, chronic pain, reduced range of motion, and eventual joint destruction. These effects significantly impair daily functioning and quality of life, and surgical removal—the current mainstay of treatment—carries a high risk of recurrence.
Although TGCT is not classified as cancer, the aggressive nature of the tumor, especially in its diffuse form, has long necessitated a safe, effective systemic treatment. In this context, the potential approval of pimicotinib could address a large and unmet medical need, especially in China where treatment options remain limited.
Pimicotinib: A Promising CSF-1R Inhibitor
Pimicotinib is an investigational small molecule developed by Abbisko Therapeutics Co., Ltd. It acts as a colony stimulating factor-1 receptor (CSF-1R) inhibitor, which targets a key pathway involved in the formation and growth of TGCT. CSF-1R is a tyrosine kinase receptor expressed on macrophages and other myeloid-lineage cells that plays a crucial role in the recruitment of inflammatory cells to the tumor environment.
In preclinical and early clinical studies, pimicotinib has demonstrated potent activity in suppressing tumor progression, with a promising safety and tolerability profile. These attributes have earned the compound Breakthrough Therapy Designation (BTD) from China’s NMPA—recognition reserved for drugs that show substantial clinical improvement over existing therapies in serious conditions.
“With the acceptance of our application for pimicotinib and the initiation of the priority review, we aim to offer patients in China the first approved systemic therapy for TGCT, addressing a tremendous unmet need in this country,” stated Hong Chow, Head of China and International, Healthcare Business of Merck. “Pimicotinib has demonstrated the ability to not only shrink tumors that affect their joints but also improve outcomes like mobility, pain, and stiffness, highlighting its potential to be a best-in-class treatment for TGCT. In parallel, we are working to file a New Drug Application (NDA) to the U.S. Food and Drug Administration, with additional filings planned in other markets.”
Groundbreaking Phase 3 Results from the MANEUVER Study
Merck’s marketing authorization application in China is supported by compelling data from Part 1 of the global Phase 3 MANEUVER trial, a pivotal study designed to evaluate the safety and efficacy of pimicotinib in adults with symptomatic TGCT requiring systemic treatment.
In this placebo-controlled, double-blind study, patients who received once-daily pimicotinib showed a statistically significant improvement in the primary endpoint—objective response rate (ORR) assessed by a blinded independent review committee (BIRC)—compared to those on placebo. At week 25, the ORR was 54.0% in the pimicotinib group versus 3.2% in the placebo arm (p<0.0001), highlighting the drug’s robust antitumor activity.
In addition to the primary endpoint, pimicotinib also delivered statistically significant and clinically meaningful improvements across multiple key secondary endpoints, including:
- Active range of motion: Many patients reported enhanced mobility in the affected joint(s), allowing greater independence in daily activities.
- Pain and stiffness reduction: Pimicotinib led to a noticeable decline in reported joint pain and stiffness, which are major contributors to quality-of-life impairment in TGCT patients.
- Physical function: Measured through patient-reported outcome tools, the treatment demonstrated improvements in functional scores related to walking, lifting, and general limb use.
The results were presented at the 2025 American Society of Clinical Oncology (ASCO) Annual Meeting, where they generated significant attention among oncologists, rheumatologists, and musculoskeletal disease experts. The promising efficacy, combined with a manageable safety profile, positions pimicotinib as a front-runner in the systemic treatment of TGCT, where previously limited or no approved options were available in many regions.
Strategic Significance of the China Filing
Merck’s decision to prioritize the Chinese market for pimicotinib’s launch underscores the company’s expanding oncology footprint in Asia, particularly in the world’s second-largest pharmaceutical market. The fast-track acceptance and priority review by the NMPA reflect a growing alignment between clinical urgency and regulatory responsiveness in China, especially for novel therapies that show transformative potential.
According to industry analysts, TGCT affects thousands of individuals in China, yet few are diagnosed promptly, and even fewer are able to access innovative treatments. The availability of a systemic therapy like pimicotinib may not only change clinical practice but could also drive earlier diagnosis and intervention.
Beyond China: Global Expansion Plans
Merck is actively preparing for additional regulatory submissions beyond China. A New Drug Application (NDA) to the U.S. FDA is in the pipeline, and subsequent filings in other regions including the European Union, Japan, and Latin America are expected to follow.
The global development and commercial rights to pimicotinib are held by Abbisko Therapeutics, with Merck serving as the partner for certain regions, including China. The collaboration marks another strategic partnership for Merck as it broadens its immunology and oncology pipeline through alliances with biotech innovators.
A New Chapter in TGCT Management
If approved, pimicotinib would become the first systemic therapy for TGCT in China, potentially redefining the treatment landscape for this rare but impactful disease. Its acceptance under Priority Review status accelerates the regulatory timeline and reinforces the growing emphasis on innovative therapies for underserved conditions.
The combination of strong clinical efficacy, patient-reported functional improvements, and regulatory momentum signals a transformative moment in TGCT care. For Merck, the progress of pimicotinib is a testament to its commitment to delivering science-driven, patient-centered solutions—and for patients, it may mark the beginning of a new era in symptom relief, joint preservation, and improved quality of life.
As Hong Chow emphasized, “We are proud to bring forward a therapy that has the potential to be truly life-changing for people with TGCT. We look forward to working closely with regulators, clinicians, and patients to ensure pimicotinib becomes available as swiftly and broadly as possible.”
