Fore Bio’s plixorafenib receives FDA Breakthrough Therapy status for BRAF-mutated glioma

Fore Biotherapeutics, a registration-stage oncology company headquartered in Philadelphia, Pennsylvania, announced that the FDA has granted Breakthrough Therapy Designation (BTD) to plixorafenib (FORE8394), a BRAF-targeted small-molecule kinase inhibitor functioning as both a dimer and paradox breaker, for the treatment of adult patients with BRAF V600E-mutated high-grade glioma (HGG). The company describes this as the first BTD awarded to a targeted therapy for HGG.

The designation adds to previously received Fast Track Designation for BRAF Class 1 and Class 2 alterations and Orphan Drug Designation (ODD) for primary brain and central nervous system (CNS) malignancies, and confers more frequent FDA engagement, senior reviewer involvement, and eligibility for rolling and priority review of a future marketing application.

The FDA based its decision on data from approximately 25 patients enrolled across the completed Phase I/IIa clinical trial and the ongoing Phase II FORTE basket study, which evaluates plixorafenib monotherapy across recurrent or progressive BRAF V600 primary CNS tumors — including HGG, low-grade gliomas (LGG), and other primary brain and spinal cord tumors in adults and children. Phase I/IIa results, presented at ASCO 2023 and SNO 2023, showed a 67% overall response rate (ORR) in a pre-specified subgroup of MAPK inhibitor-naive patients with BRAF V600-mutated primary CNS tumors, with a clinical benefit rate (CBR) exceeding 75%. In a broader V600-altered, MAPK inhibitor-naive population, plixorafenib achieved a 42% response rate, a median duration of response (mDOR) of 17.8 months, and a CBR above 70%. The drug-related adverse event discontinuation rate across tumor types was below 2%.

Within FORTE, the BRAF V600E CNS basket met its pre-specified interim efficacy analysis in Q3 2025, with the Independent Data Monitoring Committee (IDMC) supporting continuation based on responses assessed by blinded independent central review (BICR). Topline data from the CNS basket are expected by the end of 2026, and Fore has stated that a positive primary analysis would support a New Drug Application (NDA) submission under the Accelerated Approval pathway.

The FORTE Master Protocol is a global Phase II registration-intended trial operating under a Bayesian adaptive design, with four sub-protocol baskets covering recurrent or progressive BRAF V600 primary CNS tumors, solid tumors with BRAF fusions, and rare BRAF V600-mutated solid tumors.

Research context

Approved BRAF inhibitors — including vemurafenib, dabrafenib, and encorafenib — were developed primarily for melanoma and carry a class liability: paradoxical MAPK pathway activation in cells with wild-type BRAF or RAS mutations, which can drive tumor growth and necessitates co-administration of a MEK inhibitor to suppress this effect. That combination requirement introduces additional toxicity and, in CNS tumors, may be complicated by differential blood-brain barrier penetration between agents.

Plixorafenib is engineered to address both limitations. Its dimer-breaking mechanism disrupts the BRAF dimerization that underlies paradoxical activation, and its paradox-breaker profile allows monotherapy use without the MEK inhibitor dependency that characterizes earlier-generation BRAF inhibitors. Whether this translates to more durable responses in HGG — where rapid resistance emergence has limited prior BRAF-targeted approaches — remains to be established from the full FORTE dataset.

The competitive landscape in BRAF-mutated CNS tumors is evolving. Dabrafenib plus trametinib received FDA approval in 2022 for BRAF V600E-mutated low-grade glioma in pediatric patients aged 1 year and older, but HGG in adults lacks an approved targeted option in the BRAF-altered setting. Tovorafenib (DAY101), a RAF inhibitor developed by Day One Biopharmaceuticals, received FDA approval in 2024 for pediatric low-grade glioma with BRAF alterations, further establishing BRAF as a validated target in CNS oncology — though again in a distinct population and histologic grade from plixorafenib’s current BTD indication.