Pexidartinib Designated Breakthrough Therapy for Rare Tumor

Daiichi Sankyo and Plexxikon announced that the Food and Drug Administration (FDA) has granted Breakthrough Therapy designation to the investigational agent pexidartinib (formerly PLX3397) for the treatment of tenosynovial giant cell tumor (TGCT) where surgical removal of the tumor would be associated with potentially worsening functional limitation or severe morbidity.

TGCT, a group of neoplasms including pigmented villonodular synovitis (PVNS) and giant cell tumor of the tendon sheath (GCT-TS), is a rare, usually non-metastatic tumor that affects the synovium-lined joints, bursae, and tendon sheaths, resulting in swelling, pain, stiffness and reduced mobility in the affected joint or limb. Currently, there is no FDA-approved systemic therapy for TGCT, with the primary treatment being surgery to remove the tumor.

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The Breakthrough Therapy designation was based on results from an extension cohort of a single-arm, multicenter, Phase 1 study that assessed the safety and efficacy of pexidartinib. The Phase 3 ENLIVEN study is currently enrolling patients with symptomatic TGCT for whom surgical tumor removal would be associated with potentially worse outcomes.

The FDA has previously granted pexidartinib Orphan Drug designation for the treatment of PVNS and GCT-TS.

Pexidartinib is a novel, investigational, oral small molecule colony stimulating factor-1 receptor (CSF-1R) inhibitor.

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