Officials with the FDA have approved pexidartinib (Turalio, Daiichi Sankyo) for the treatment of certain patients with symptomatic tenosynovial giant cell tumor (TGCT), according to a press release.
 
TGCT, also called pigmented villondular synovitis or giant cell tumor of the tendon sheath, is a rare, non-malignant tumor that affects small and large joints. With this approval, pexidartinib is the first therapy indicated to treat the rare and debilitating tumor.
 
Pexidartinib is an oral therapy that inhibits colony stimulating factor-1 receptor (CSFR1R) which is a primary growth driver of abnormal cells in the synovium that cause TGCT, according to Daiichi Sankyo.
 
The approval is based on results from the phase 3 ENLIVEN study, the first placebo-controlled study of a systemic therapy in patients with TGCT, which evaluated patients with symptomatic TGCT for whom surgical removal of the tumor would be associated with potentially worsening functional limitation or severe morbidity. In the first part of the study, 120 patients were randomized to receive either pexidartinib at 1000 mg per day for 2 weeks followed by 800 mg per day for 22 weeks or a placebo. The second part of the trial includes a long-term portion in which patients could continue or start to receive pexidartinib.
 
According to the data:
  • The primary endpoint of tumor response rate by Response Evaluation Criteria v1.1 in Solid Tumors (RECIST) was 38% (95% Cl: 27%, 50%) in pexidartinib-treated patients and 0% (95% Cl: 0%, 6%) for placebo-treated patients at week 25.
  • Overall response rate by tumor volume score was 56% (95% Cl: 43%, 67%) in patients randomized to the pexidartinib arm and 0% in patients randomized to the placebo arm at week 25.
  • The analysis of mean change from baseline in range of motion at week 25 demonstrated a statistically significant improvement in patients treated with pexidartinib compared with a placebo. 
“The FDA approval of Turalio represents a paradigm shift in the treatment of carefully selected TGCT patients who face significant disease morbidity and for whom surgery is not an option,” lead study author William D. Tap, MD, chief of the Sarcoma Medical Oncology Service at Memorial Sloan Kettering Cancer Center, said in a statement. “We now have a new oral treatment option that can have a meaningful clinical benefit in select patients, including a reduction in tumor size.”
 
Pexidartinib comes with a Boxed Warning for hepatotoxicity due to the risk of serious and potentially fatal injury. Because of this risk, pexidartinib will be available only through the Risk Evaluation and Mitigation Strategy Program.
 
Reference
 
FDA Approves Daiichi Sankyo’s Turalio (pexidartinib) for the Treatment of Select Patients with TGCT, a Rare and Debilitating Tumor [news release]. Daiichi Sankyo. https://www.daiichisankyo.com/media_investors/media_relations/press_releases/detail/007041.html. Accessed August 5, 2019.