BACKGROUND: Modern radiotherapy is associated with dermatitis (RD) in approximately one-third of patients treated for breast cancer. There is currently no standard for treating RD. OBJECTIVE: The objective of this study was to determine whether LUT014, a topical BRAF inhibitor which paradoxically activates mitogen-activated protein kinase, can safely improve RD. METHODS: A phase I/II study was designed to first follow a small cohort of women with grade 2 RD regarding toxicity and response. Then, 20 patients were randomized to compare LUT014 to vehicle relative to safety and response (measured with common terminology criteria for adverse events, Dermatology Life Quality Index). RESULTS: No substantial toxicity (eg, 0 serious adverse event) was associated with LUT014. All 8 women receiving LUT014 achieved treatment success (5-point Dermatology Life Quality Index reduction at day 14) compared to 73% (8/11) on the placebo arm (P = .591). The time to complete recovery was shorter in the treatment arm. LIMITATIONS: The sample size was limited. Only 2 hospitals were included. CONCLUSIONS: Topical LU014 is tolerable and may be efficacious for grade 2 RD.

Treatment of cancer with EGFR inhibitors is limited by on-target skin toxicities induced by inhibition of the MAPK pathway. BRAF inhibitors are known to paradoxically activate the MAPK downstream of EGFR, which we confirmed using human skin keratinocytes. We then conducted a phase I clinical trial testing the hypothesis that topical therapy with the BRAF inhibitor LUT014 could improve skin toxicities induced by EGFR inhibitors. Ten patients with metastatic colorectal cancer who had developed acneiform rash while being treated with cetuximab or panitumumab were enrolled in three cohorts. LUT014 was well tolerated, and there were no dose-limiting toxicities. The acneiform rash improved in the 6 patients who started with grade 2 rash in the low and intermediate cohorts. We conclude that topical LUT014 is safe and efficacious in improving rash from EGFR inhibitors, consistent with the mechanism of action inducting paradoxical MAPK activation. SIGNIFICANCE: BRAF inhibitor topical therapy could avoid dose reductions of EGFR inhibitors, locally treating the main dose-limiting skin toxicity of this class of agents.This article is highlighted in the In This Issue feature, p. 2113.