Clinical trial in progress: Phase II trial of defactinib (VS-6063) combined with VS-6766 (CH5126766) in patients with metastatic uveal melanoma.

TPS9588 Background: Despite successful treatment of primary uveal melanomas (UM), up to 50% of patients subsequently develop systemic metastasis, with the liver involved in up to 90% of patients. Currently there is no US FDA-approved treatment for metastatic uveal melanoma (MUM). Activating mutations in genes encoding alpha subunits of the heterotrimeric G proteins, GNAQ and GNA11, are found in 80-90% of UM. Recent information suggests that GNAQ/GNA11-oncogenic signaling involves a non-canonical pathway conferring the activation of YAP1, distinct from the activation of PLCβ and PKC-MEK-ERK, which may explain the failure of MEK inhibitors in MUM patients. Focal Adhesion Kinase (FAK) is a tyrosine kinase that provides a direct link between Gαq and tyrosine phosphorylation networks controlling YAP and UM growth. Interestingly, UM represents the human cancer harboring the highest level of FAK overexpression. Recent kinome-wide CRISPR-Cas9 screens revealed that FAK and RAF/MEK co-targeting may provide a new network-based precision therapeutic strategy for MUM treatment. Methods: This is an investigator-initiated, prospective, single arm, single-institution, phase II trial evaluating the combination of a FAK inhibitor (defactinib, VS-6063) with a RAF/MEK inhibitor (VS-6766, CH5126766) for the treatment of patients with metastatic uveal melanoma [NCT04720417]. The primary endpoint of the study is disease control rate (DCR) of 50% including complete response (CR), partial response (PR), and stable disease (SD) as determined by RECIST criteria version 1.1. Secondary endpoints include progression free survival, overall survival, and causality of adverse events. Exploratory endpoints include analysis of the pharmacodynamic profile, mechanism of resistance to the combination, and investigation of circulating free DNA as a biomarker. The efficacy of this combination treatment will be assessed using the Simon’s two stage design. In stage I, a total number of 8 patients are accrued and if there are 2 or fewer overall responses among these 8 patients, further enrollment of patients may be stopped with the conclusion that DCR cannot be 50% or greater. Otherwise, an additional 10 patients will be accrued in stage II, resulting in a total sample size of 18 patients. Patients at 18 years or older with metastases from uveal melanoma will be eligible (any line of therapy). Defactinib (200 mg) will be administered orally twice a day in combination with VS-6766 (3.2 mg) administered orally twice a week for 3 weeks, in 28-day cycles. Dose modification will be considered based on toxicity. Treatment will be continued until maximum clinical benefit is obtained; disease progression or the development of intolerable side effects. Enrollment to stage 1 began in February 2021. Clinical trial information: NCT04720417.