The U.S. Food and Drug Administration (FDA) has accepted a New Drug Application for pimicotinib, a promising oral therapy for the treatment of tenosynovial giant cell tumor. The application was submitted by EMD Serono, the healthcare business of Merck KGaA, Darmstadt, Germany, following encouraging results from the global Phase 3 MANEUVER clinical trial. This development represents a significant milestone for patients living with this rare and often debilitating tumor, particularly those who have limited options beyond surgery.
Tenosynovial giant cell tumor, commonly referred to as TGCT, is a rare condition that affects joints and surrounding tissues. While it is generally not life threatening, it can be highly aggressive locally and severely impact mobility, function, and quality of life. The FDA acceptance of pimicotinib brings renewed attention to the urgent need for effective and well tolerated systemic therapies in this space.
Tenosynovial giant cell tumor is a rare tumor that develops in or around joints, tendon sheaths, and bursae. It is caused by the overexpression of colony stimulating factor 1, which attracts inflammatory cells and leads to tumor growth. TGCT most commonly affects younger to middle aged adults who are otherwise healthy and active.
Symptoms of TGCT often include joint swelling, stiffness, pain, and reduced range of motion. Over time, untreated or recurrent disease can cause irreversible damage to bones, cartilage, and surrounding soft tissues. In many cases, patients struggle with daily activities, work responsibilities, and overall physical function.
Surgery has historically been the primary treatment option. However, surgical resection is not always feasible and recurrence rates can be high. Some patients face significant functional limitations or morbidity following surgery, highlighting the need for effective systemic treatments.
Pimicotinib, also known as ABSK021, is an orally administered small molecule inhibitor that selectively targets the colony stimulating factor 1 receptor. By inhibiting CSF 1R signaling, pimicotinib reduces the recruitment and survival of inflammatory cells that drive TGCT tumor growth.
The drug was developed by Abbisko Therapeutics and is designed for once daily oral administration. Its targeted mechanism allows it to address the underlying biology of TGCT rather than simply managing symptoms.
Pimicotinib has already received regulatory recognition. It has been granted Breakthrough Therapy Designation by the U.S. Food and Drug Administration and Priority Medicines designation from the European Medicines Agency. In December 2025, it was approved in China for adults with symptomatic TGCT when surgery may lead to severe morbidity or functional limitation.
On January 12, 2026, EMD Serono announced that the FDA had accepted its New Drug Application for pimicotinib as a systemic treatment for patients with tenosynovial giant cell tumor in the United States. FDA acceptance means the application is complete and will undergo a full regulatory review to determine whether the drug should be approved.
According to the company, the application is supported by primary and longer term follow up data from the global Phase 3 MANEUVER study. The trial demonstrated deep and durable tumor responses, along with meaningful improvements in patient reported outcomes.
David Weinreich, Global Head of Research and Development and Chief Medical Officer for the healthcare business of Merck KGaA, emphasized the importance of this development. He noted that pimicotinib has the potential to significantly advance care for people living with TGCT by reducing tumor burden and alleviating symptoms such as pain and stiffness.
The MANEUVER study was a pivotal global Phase 3 clinical trial designed to evaluate the efficacy and safety of pimicotinib in patients with TGCT who required systemic therapy and had not received prior CSF 1 or CSF 1R targeted treatment.
The trial was a randomized, double blind, placebo controlled study conducted across China, Europe, the United States, and Canada. A total of 94 patients were enrolled in the double blind portion of the study and randomized in a 2 to 1 ratio to receive either pimicotinib 50 mg once daily or placebo for 24 weeks.
The primary endpoint was objective response rate at week 25, assessed by a blinded independent review committee using RECIST version 1.1 criteria. Secondary endpoints included tumor volume score, range of motion, stiffness, pain, and physical function as measured by validated patient reported outcome tools.
Pimicotinib demonstrated a statistically significant improvement in objective response rate compared with placebo at week 25. Importantly, patients experienced not only tumor shrinkage but also clinically meaningful improvements in symptoms that directly affect daily life.
Secondary endpoints showed improvements in active range of motion and physical function, as well as reductions in stiffness and pain. These findings suggest that pimicotinib addresses both structural disease and patient quality of life.
Longer term data presented at the ESMO Congress 2025, with a median follow up of 14.3 months, showed that objective response rates continued to increase over time among patients who started pimicotinib from the beginning of the study.
After completing the double blind phase, eligible patients could enter an open label treatment phase for up to 24 additional weeks. Those who completed this phase were then able to enroll in an open label extension for extended treatment and safety monitoring.
This design allowed researchers to assess the durability of response and long term safety of pimicotinib, both of which are critical for a chronic condition such as TGCT.
For patients living with tenosynovial giant cell tumor, treatment decisions often involve difficult tradeoffs. Surgery can be effective but may lead to joint damage, reduced mobility, or repeated procedures due to recurrence. Until recently, there have been limited systemic options that offer both efficacy and tolerability.
Pimicotinib represents a potential shift in the treatment landscape. By targeting the underlying CSF 1R pathway, it offers a non surgical option that may reduce tumor burden while improving pain, stiffness, and physical function. This is especially important for patients whose tumors are inoperable or for whom surgery would result in significant morbidity.
If approved by the FDA, pimicotinib could become an important option for patients in the United States who currently have few alternatives beyond repeated surgeries or watchful waiting.
Merck KGaA, Darmstadt, Germany, holds worldwide commercialization rights for pimicotinib. In the United States and Canada, the drug is being developed and commercialized through EMD Serono.
In addition to FDA review in the United States, regulatory applications are currently under review in other international markets. The approval in China by the National Medical Products Administration in December 2025 marks the first global approval for pimicotinib and provides real world momentum for its broader adoption.
EMD Serono is the healthcare business of Merck KGaA, Darmstadt, Germany, in the United States and Canada. The company focuses on developing treatments for difficult to treat conditions such as cancer, multiple sclerosis, and infertility. With a history spanning more than 350 years, Merck KGaA operates across healthcare, life science, and electronics, employing over 62,000 people worldwide.
In 2024, Merck KGaA reported global sales of €21.2 billion, underscoring its role as a leading science and technology company committed to advancing innovation and patient care.
The FDA acceptance of the pimicotinib New Drug Application marks an important step forward in the treatment of tenosynovial giant cell tumor. While final approval is still pending, the robust clinical data from the MANEUVER study provide strong evidence of the drug’s potential benefit.
For patients, clinicians, and caregivers, this development offers hope for a future where TGCT can be managed more effectively with targeted, well tolerated therapies that improve both clinical outcomes and quality of life.
EMD Serono, Inc. press release
This article is for informational and educational purposes only and does not constitute medical advice. It is not intended to diagnose, treat, cure, or prevent any disease. Always seek the advice of a qualified healthcare professional with any questions regarding a medical condition or treatment.
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