FDA Fast Tracks SynOx's Emactuzumab for TGCT

DUBLIN, Ireland and OXFORD, United Kingdom, April 14, 2025—SynOx Therapeutics Limited, a biopharmaceutical company in the advanced stages of clinical development, made an important announcement regarding its lead candidate, emactuzumab. This drug has received Fast Track Designation (FTD) from the United States Food and Drug Administration (FDA) for treating Tenosynovial Giant Cell Tumours (TGCT) in patients who are not candidates for surgery or would not gain benefits from surgical options.

Emactuzumab is a monoclonal antibody designed to inhibit the CSF-1 receptor (CSF-1R), which plays a significant role in the growth of TGCT. This promising therapy is currently undergoing evaluation in the TANGENT study, a global and multi-centre Phase 3 trial. This trial is randomized, double-blind, and placebo-controlled, underscoring the rigorous approach taken in assessing emactuzumab's efficacy and safety.

TGCT is a rare, non-cancerous, yet aggressively proliferating tumor affecting the synovium, tendon sheaths, and bursa membranes, primarily around joints such as the knee, hip, and ankle. The tumor's growth is driven by an overproduction of CSF-1, leading to chronic disability for patients. Symptoms include joint pain, stiffness, and a restricted range of motion, significantly impacting patients' quality of life. Data from Phase 1/2 clinical studies have shown that emactuzumab facilitates a rapid and robust reduction in tumor size, along with a sustained response and a manageable safety profile. The drug has also received Orphan Medicinal Project designation from the European Medicines Agency.

Dr. Elyse Seltzer, Chief Medical Officer of SynOx Therapeutics, highlighted the impact of TGCT on patients and the pressing need for innovative treatment options. She emphasized that clinical findings thus far suggest that emactuzumab could substantially fulfill unmet patient needs by providing an effective and rapid treatment that allows patients to effectively manage their condition. Dr. Seltzer expressed anticipation for the completion of the TANGENT study and the potential commercial availability of emactuzumab.

Fast Track Designation by the FDA is an important regulatory milestone intended to accelerate the development and review of drugs targeting serious conditions with unmet medical needs. This designation facilitates enhanced communication and collaboration between the FDA and drug developers, potentially expediting the review process and bringing vital treatments to patients more swiftly.

TGCT, formerly known as pigmented villonodular synovitis (PVNS), affects the soft tissues around joints and tendons. According to the WHO classification, TGCTs are categorized as fibrohistiocytic tumors and are further classified based on their growth pattern and location. These tumors can be locally destructive and aggressive, resulting in significant pain, stiffness, and loss of joint function, which can severely reduce patients' quality of life. Although surgery is a common treatment approach, over 50% of patients with diffuse TGCT experience recurrence within three years. Untreated, the condition can lead to joint deformity and even necessitate arthrodesis or amputation in extreme cases.

Emactuzumab targets the CSF-1 receptor, which is activated by the cytokine CSF-1, commonly expressed on macrophages and other immune cells. Initially developed by Roche, emactuzumab has demonstrated significant effectiveness in TGCT clinical trials, showing a notable response rate and improving patient functionality while maintaining a favorable safety profile. The potential utility of emactuzumab in other diseases driven by macrophages is under active exploration by SynOx.

SynOx Therapeutics Limited, situated in Dublin and Oxford, focuses on the development of emactuzumab and other therapies targeting CSF-1-related and macrophage-driven disorders. The company is led by a team of experienced professionals with a history of successful product development and commercialization, supported by premier life science investors. Emactuzumab's journey through clinical trials continues as SynOx pursues further research and potential expansion into additional therapeutic areas.