First-in-class oral ERK1/2 inhibitor Ulixertinib (BVD-523) in patients with advanced solid tumors: Final results of a phase I dose escalation and expansion study.

Abstract

2508 Background: Aberrant MAPK pathway activation is known to be an oncogenic driver in many solid tumors, making ERK inhibition an attractive therapeutic strategy. Ulixertinib is an oral ERK1/2 inhibitor that demonstrated potent activity in vitro and tumor regression in BRAF and RAS mutant xenograft models. Methods: This multi-center phase I trial enrolled patients (pts) with advanced solid tumors. Dose escalation utilized an accelerated 3+3 design; expansion cohorts included BRAF or NRAS mutant melanoma and other BRAF or MEK mutant cancers. Study objectives were to characterize dose limiting toxicities (DLTs), maximum tolerated dose (MTD), toxicity profile, pharmacokinetics, pharmacodynamics and preliminary anti-tumor activity by RECIST 1.1. Results: A total of 135 pts were enrolled. Dose escalation enrolled 27 pts (10-900 mg BID) and established the MTD and recommended phase 2 dose (RP2D) of 600 mg BID. DLTs included rash, diarrhea, elevated AST, and elevated creatinine. Drug exposure was dose proportional up to the RP2D, which provided near-complete inhibition of ERK activity in whole blood. In the 108 pt expansion cohort, there were no drug related deaths; however, 32% of pts required a dose reduction. The most common adverse events were rash (49%), diarrhea (47%), fatigue (41%), and nausea (37%). In addition to 3 pts with partial responses during escalation (11%), an additional 9 of 83 (11%) evaluable pts at expansion had a partial response: 1 melanoma pt refractory to prior BRAFi/MEKi treatment, 3 NRAS mutant melanoma pts, 2 pts with BRAF V600E mutant lung cancers including response in brain metastases, 1 with BRAF V600E mutant glioblastoma multiforme, 1 with BRAF G469A head & neck cancer, and 1 with BRAFL485W gallbladder cancer. The duration of response ranged from 2 to 24+ months. Conclusions: Ulixertinib at 600 mg twice a day has an acceptable safety profile and has produced durable responses in pts with NRAS mutant melanoma, BRAF V600 and non-V600 mutant solid tumors including melanoma, glioblastoma multiforme, lung cancers with brain metastases, gallbladder and head & neck cancers. These data support further clinical development of ulixertinib. Clinical trial information: NCT01781429.