Intermittent treatment with vorinostat in patients with BRAFi/MEKi-resistant BRAFV600-mutated melanoma is well tolerated. Although the primary endpoint of this study was not met, durable antitumor responses were observed in a minority of patients (9%).
Patients with BRAFi/MEKi-resistant BRAFV600-mutated melanoma were treated with vorinostat 360 mg once daily for 14 days followed by BRAFi/MEKi. The primary endpoint was an objective response rate of progressive lesions of at least 30% according to Response Evaluation Criteria in Solid Tumors 1.1. Secondary endpoints included progression-free survival, overall survival, safety, pharmacokinetics of vorinostat, and translational molecular analyses using ctDNA and tumor biopsies.
The development of resistance limits the clinical benefit of BRAF and MEK inhibitors (BRAFi/MEKi) in BRAFV600-mutated melanoma. It has been shown that short-term treatment (14 days) with vorinostat was able to initiate apoptosis of resistant tumor cells. We aimed to assess the antitumor activity of sequential treatment with vorinostat following BRAFi/MEKi in patients with BRAFV600-mutated melanoma who progressed after initial response to BRAFi/MEKi.
Of the 26 patients with progressive BRAFi/MEKi-resistant BRAFV600-mutated melanoma receiving treatment with vorinostat, 22 patients were evaluable for response. The objective response rate was 9%, with one complete response for 31.2 months and one partial response for 14.9 months. Median progression-free survival and overall survival were 1.4 and 5.4 months, respectively. Common adverse events were fatigue (23%) and nausea (19%). ctDNA analysis showed emerging secondary mutations in NRAS and MEK in eight patients at the time of BRAFi/MEKi resistance. Elimination of these mutations by vorinostat treatment was observed in three patients.
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