Pexidartinib is an investigational novel, oral small molecule that selectively inhibits a primary growth driver of abnormal cells in the synovium that causes TGCT called colony stimulating factor-1 receptor (CSF-1R).
It has not been approved by the FDA or any other regulatory authority for uses under investigation.
Apart from the breakthrough therapy designation, the FDA has also granted orphan drug designation to pexidartinib for the treatment of PVNS and GCT-TS
Plexxikon CEO Gideon Bollag said: "The responses seen in our ongoing phase 1 study provided initial proof-of-concept that selective CSF-1R inhibition with pexidartinib may safely and effectively reduce tumor burden in patients with TGCT, providing the rationale to move directly into a phase 3 clinical trial.
"This Breakthrough Therapy Designation represents another significant milestone in our commitment to develop novel targeted agents that address unmet medical needs in rare conditions such as TGCT."
The European Commission has also granted orphan designation to pexidartinib to treat TGCT, which is a rare non-metastatic tumor that affects the synovium-lined joints, bursae and tendon sheaths causing swelling, pain, stiffness and reduced mobility.
Daiichi Sankyo and Plexxikon are evaluating pexidartinib in several other potential clinical indications including glioblastoma, melanoma, ovarian and breast cancer as well as in combination with anti-PD-1 therapy, pembrolizumab, for advanced melanoma and other multiple solid tumors.