Daiichi Sankyo's Turalio becomes first FDA-approved therapy for tenosynovial giant cell tumour

The FDA on Friday announced that it has approved Daiichi Sankyo's CSF1 inhibitor Turalio (pexidartinib) for the treatment of adults with symptomatic tenosynovial giant cell tumour (TGCT) associated with severe morbidity or functional limitations, and not responsive to improvement with surgery. Richard Pazdur, acting director of the Office of Hematology and Oncology Products in the FDA's Center for Drug Evaluation and Research, said "surgery is the primary treatment option, but some patients are not eligible...and tumours can recur, even after the procedure," adding that the decision makes Turalio "the first FDA-approved therapy to treat this rare disease." 

Approval was based on data from the randomised Phase III ENLIVEN trial of 120 patients with symptomatic advanced TGCT for whom surgical removal of the tumour would be associated with potential worsening of functional limitations or severe morbidity. The primary efficacy endpoint was the overall response rate (ORR) analysed after 25 weeks of treatment.  

According to the FDA, results showed that a significant 38% of Turalio-treated patients achieved an ORR, versus no responses for those in the placebo group. Specifically, the complete and partial response rates were 15% and 23%, respectively, the FDA said. The agency noted that 22 out of 23 responders who had been followed for at least six months after the initial response maintained their response for six or more months, while all 13 of the responders who were monitored for at least a year following the initial response maintained their response for 12 or more months. 

More recently, Daiichi Sankyo presented long-term pooled results from the trial at this year's American Society of Clinical Oncology (ASCO) conference showing that the best overall response with Turalio at a median treatment duration of 17 months was 54% when measured by RECIST 1.1 and 64% by Tumor Volume Score (TVS). The company said at the time that the median duration of response had not yet been reached. 

An FDA advisory committee in May voted 12 to 3 that the benefits of Turalio outweighed its risks in the treatment of adults with symptomatic TGCT. The same panel also voted against recommending approval of Daiichi Sankyo's FLT3 inhibitor quizartinib in acute myeloid leukaemia (for related analysis, see ViewPoints: Daiichi Sankyo hopes to roll past FDA snub). 

The FDA, which assessed the Turalio filing under a priority review, previously granted the CSF1 inhibitor breakthrough therapy and orphan drug designations. Daiichi Sankyo acquired Turalio, formerly known as PLX3397, via its purchase of Plexxikon in 2011. 

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