Welireg/Belzutifan (MK-6482) + Keytruda/Pembrolizumab (MK-3475) (HIF-2α/PD-1 Blockade)

2026-02-28 — Merck (NYSE: MRK) reported late-breaking Phase 3 LITESPARK-022 results at the 2026 ASCO Genitourinary Cancers Symposium evaluating adjuvant KEYTRUDA® (pembrolizumab) plus WELIREG® (belzutifan) vs KEYTRUDA plus placebo in patients with clear cell renal cell carcinoma (RCC) after nephrectomy.

At the first pre-specified interim analysis (median follow-up 28.4 months), the combination significantly improved disease-free survival (primary endpoint), reducing risk of recurrence or death by 28% (HR 0.72; 95% CI 0.59–0.87; p=0.0003). Median DFS was not reached; 24‑month DFS was 80.7% with the combination vs 73.7% with KEYTRUDA alone. Overall survival remains under evaluation.

Safety was consistent with known profiles; Grade ≥3 TEAEs were higher with the combination (52.1% vs 30.2%), notably anemia (12.1% vs 0.5%) and hypoxia (4.6% vs 0%).

Merck said the FDA accepted priority review supplemental applications for WELIREG plus KEYTRUDA/KEYTRUDA QLEX™ in adjuvant RCC, with a PDUFA target date of June 19, 2026—supporting potential label expansion and a new adjuvant regimen beyond pembrolizumab monotherapy.