The combination of encorafenib, binimetinib, and nivolumab demonstrated superior progression-free survival compared to standard immunotherapy in patients with BRAF V600-mutant melanoma brain metastases, according to results from the phase 2 SWOG S2000 trial presented at the 2025 ASCO Annual Meeting.
The study showed that patients treated with the triplet combination (n = 16) achieved a median progression-free survival of 6.2 months (95% CI, 3-14.4) compared with 1.5 months (95% CI, 0.7-1.7) for those receiving nivolumab plus ipilimumab (n = 15; HR, 0.47; 1-sided 90% CI, 0-0.82; P = .04). The 6-month PFS rates were 54% (95% CI, 27%-75%) and 20% (95% CI, 5%-42%), respectively.
Significant Intracranial Activity
The triplet regimen demonstrated particularly impressive intracranial activity, with a median intracranial PFS of 8.7 months (95% CI, 3-19.4) compared to 1.5 months (95% CI, 0.7-1.7) in the doublet arm (HR, 0.39; 1-sided 90% CI, 0-0.68; P = .01).
Intracranial response rates were substantially higher with the triplet therapy at 75% (95% CI, 54%-96%) versus 13% (95% CI, 0%-31%) with nivolumab plus ipilimumab. One patient in each arm achieved an intracranial complete response, while all other responses were partial in both groups.
"In this still difficult-to-treat patient population, a triplet regimen may be therapeutically useful but is still in need of further study," said lead study author Zeynep Eroglu, MD, of Moffitt Cancer Center in Tampa, Florida.
Study Design and Patient Population
SWOG S2000 enrolled patients at least 18 years of age with melanoma brain metastases of at least 0.5 cm who had symptomatic disease, defined as neurological symptoms and/or the need for steroids. All patients harbored BRAF V600 mutations and were treatment-naive in the metastatic setting.
Patients were randomly assigned to receive either encorafenib at 450 mg once daily plus binimetinib at 45 mg twice daily and nivolumab at 480 mg every 4 weeks, or nivolumab at 480 mg every 4 weeks plus ipilimumab at 1 mg/kg every 3 weeks for 4 cycles. Treatment continued for up to 2 years or until disease progression or unacceptable toxicity.
The median age was 66.9 years in the triplet arm and 60.8 years in the doublet arm. Most patients were male (63% vs 80%) and White (94% vs 80%), with the majority harboring BRAF V600E mutations (56% vs 87%). Corticosteroid use was reported in 38% and 47% of patients, respectively.
Overall Response and Safety Profile
Among evaluable patients, the overall response rate was 67% (95% CI, 43%-91%) in the triplet arm (n = 15) compared to 14% (95% CI, 0%-33%) in the control arm (n = 14). Progressive disease occurred in 13% of triplet-treated patients versus 79% in the control group.
Grade 3/4 treatment-related adverse events occurred in 69% of patients receiving the triplet versus 75% of those on the doublet regimen. Treatment discontinuation due to adverse events was reported in 19% and 32% of patients, respectively, while dose modifications were required in 75% and 32% of patients.
Clinical Implications
The 18-month overall survival rates were similar between groups at 36% (95% CI, 13%-60%) for the triplet and 37% (95% CI, 12%-62%) for the doublet (HR, 1.21; 95% CI, 0.49-2.98; P = .66).
Eroglu noted that the trial faced challenges in enrolling highly symptomatic patients and was not designed to compare the triplet with sequential targeted therapy and immunotherapy approaches. She emphasized that more research and improved guidelines are needed for optimal treatment of this patient population, who have historically had poor outcomes with immunotherapy.
As the first randomized study in this challenging clinical setting, SWOG S2000 provides important evidence that triplet regimens incorporating BRAF/MEK inhibitors with immunotherapy warrant further investigation in patients with symptomatic melanoma brain metastases.
