Immunotherapy-based combinations including pembrolizumab plus lenvatinib are the standard of care for patients with first-line clear-cell renal cell carcinoma, but these combinations are not well characterised in non-clear-cell renal cell carcinoma. We aimed to assess the activity and safety of pembrolizumab plus lenvatinib as a first-line treatment for patients with advanced non-clear-cell renal cell carcinoma.

KEYNOTE-B61 is a single-arm, phase 2 trial being conducted at 48 sites (hospitals and cancer centres) in 14 countries (Australia, Canada, France, Hungary, Ireland, Italy, Poland, South Korea, Russia, Spain, Türkiye, Ukraine, the UK, and the USA). Adult patients (aged ≥18 years) with previously untreated stage IV non-clear-cell renal cell carcinoma and a Karnofsky performance status of 70% or higher were eligible for enrolment. All enrolled patients received pembrolizumab 400 mg intravenously every 6 weeks for up to 18 cycles (2 years) plus lenvatinib 20 mg orally once daily or until disease progression, unacceptable toxicity, or withdrawal; lenvatinib could be continued beyond 2 years. The primary endpoint was the proportion of patients with a confirmed objective response as per adjusted Response Evaluation Criteria in Solid Tumours (version 1.1) assessed by independent central review. Activity and safety were analysed in all patients who received at least one dose of study treatment (the as-treated population). This trial is registered with ClinicalTrials.gov (NCT04704219) and is no longer recruiting participants but is ongoing.

Between Feb 23, 2021, and Jan 21, 2022, 215 patients were screened; 158 were enrolled and received treatment. Median age at baseline was 60 years (IQR 52-69), 112 (71%) of 158 patients were male, 46 (29%) were female, 128 (81%) were White, 12 (8%) were Asian, three (2%) were Black or African American, and 15 (9%) were missing data on race. As of data cutoff (Nov 7, 2022), median study follow-up was 14·9 months (IQR 11·1-17·4). 78 of 158 patients had a confirmed objective response (49%; 95% CI 41-57), including nine (6%) patients with a confirmed complete response and 69 (44%) with a confirmed partial response. Grade 3-4 treatment-related adverse events occurred in 81 (51%) of 158 patients, the most common of which were hypertension (37 [23%] of 158), proteinuria (seven [4%]), and stomatitis (six [4%]). Serious treatment-related adverse events occurred in 31 (20%) of 158 patients. Eight (5%) patients died due to adverse events, none of which was considered related to the treatment by the investigators (one each of cardiac failure, peritonitis, pneumonia, sepsis, cerebrovascular accident, suicide, pneumothorax, and pulmonary embolism).

Pembrolizumab plus lenvatinib has durable antitumour activity in patients with previously untreated advanced non-clear-cell renal cell carcinoma, with a safety profile consistent with that of previous studies. Results from KEYNOTE-B61 support the use of pembrolizumab plus lenvatinib as a first-line treatment option for these patients.

Merck Sharp & Dohme (a subsidiary of Merck & Co, NJ, USA), and Eisai.