A phase 2 clinical trial of regorafenib in patients with advanced pretreated melanoma (RegoMel).

9518 Background: A majority of advanced melanoma patients (pts) will eventually progress despite treatment with PD-(L)1/CTLA-4/LAG-3 immune checkpoint- and BRAF-/MEK-inhibitors (BRAF-/MEKi; restricted to BRAF V600 -mutant pts). Retrospective case observations indicate activity of regorafenib (REGO) in this setting (1). Methods: This single center, prospective, two-stage, phase 2 clinical trial, investigates REGO 80 mg QD (continuous dosing) in pts with advanced melanoma refractory to standard of care treatment. Objective response rate (ORR, by RECIST v1.1) served as the primary endpoint. The sample size (n=16) was determined according to a Simon’s two-stage minimax statistical design; the trial is considered positive if 3 or more responses are observed. Response assessments are performed every 6 weeks (q6w) during the first 24w, and q12w thereafter. Secondary endpoints are safety, progression free survival (PFS) and overall survival (OS). REGO treatment beyond first progression was permitted if considered to be of potential clinical benefit. Database lock was on Jan 9 th , 2024. Results: From Oct 2022 to Sep 2023, 16 pts were enrolled (9 male, med age 61y; AJCC stage IIIC: 1; IV-M1a: 1; -M1c: 12, -M1d: 2, ECOG PS 0-1: 100%). Oncogenic driver mutations were identified in BRAF V600 : 7-, KIT: 3-, NF1: 3-, NRAS Q61K : 2-, RAF fusion: 1 pt. The ORR was 31% (: 5 partial responses (PR) - 4 confirmed in 3 KIT-,and 1 BRAF V600 -mut pt; and 1 unconfirmed in a BRAF V600 -mut pt). One KIT-mut pt had previously progressed on imatinib. The median duration of response (DoR) was 29.7w (range 12-44). The disease control rate (DCR) was 56%. The median time on REGO monotherapy was 12.3w 95% CI 2.3-22.3, treatment is ongoing in 3 pts. At first progression, 6 BRAF V600 -mut pts continued REGO in association with BRAF-/MEKi, in 5 response evaluable pts there is an ORR of 40% (2 PR with DoR of 24w and 30w) and DCR of 80%. At database lock, 11 pts were alive with a median follow up of 48.4w (range 24-63), 13 pts have progressed on REGO monotherapy (median PFS 11.9w 95% CI 3.5-20.3; median OS was not reached). There were no grade ≥ 4 treatment related adverse events (TRAE); 56% of pts had at least one grade 3 TRAE, including hypertension (n=3) and maculo-papular rash (n=2). There was one toxicity-related REGO discontinuation. Conclusions: This phase 2 clinical trial on REGO monotherapy in advanced pretreated melanoma patients met its primary endpoint and demonstrated significant anti-tumor activity in KIT-mutant melanoma patients. In BRAF V600 -mutant melanoma, continuation of REGO in combination with BRAF-/MEK-inhibitors demonstrated promising activity in patients who previously progressed on BRAF-/MEK-inhibitors for which further prospective investigation is ongoing. 1. Dirven I. et al. ESMO Meeting 2023. Clinical trial information: NCT05370807 .