Efficacy of Combined CD38 and PD1 Inhibition with Isatuximab and Cemiplimab for Relapsed/Refractory NK/T-Cell Lymphoma

• Isatuximab and cemiplimab combined therapy shows durable responses and manageable safety in relapsed/refractory NK/T-cell lymphoma.

• Structural variations disrupting the 3’-UTR of PD-L1 and high PD-L1 expression were related with response to this combination therapy.

This study aimed to assess the efficacy and safety of combining cemiplimab, an anti-PD1 antibody, with isatuximab, an anti-CD38 antibody, in relapsed or refractory extranodal NK/T-cell lymphoma (R/R ENKTL). The hypothesis was that CD38 blockade could enhance the antitumor activity of PD1 inhibitors. Eligible patients received cemiplimab (250 mg on days 1 and 15) and isatuximab (10 mg/kg on days 2 and 16) intravenously every four weeks for six cycles. Responders then received cemiplimab (350 mg) and isatuximab (10 mg/kg) every three weeks for up to 24 months. The primary endpoint was the complete response (CR) rate based on the best response. Out of 37 patients enrolled, the CR rate was 51% (19/37), exceeding the primary endpoint of 40%, and the objective response rate was 65% (24/37). After a median follow-up of 30.2 months (95% CI: 25.6-34.8 months), the median progression-free survival was 9.5 months (95% CI: 1.4-17.6 months), while the median overall survival had not yet been reached. Patients achieving CR received a median of 28 cycles (range: 4-33), and the median duration of response for responders (n = 24) was 29.4 months (95% CI: 15.4-43.4 months). Structural variations disrupting the 3'-UTR of PD-L1 and high PD-L1 expression were observed in responders. Most adverse events were mild (grade 1-2), with grade ≥3 events (32%) and no treatment-related deaths. The combination of isatuximab and cemiplimab demonstrated sustained antitumor activity and a manageable safety profile in R/R ENKTL. This phase II trial is registered at www.clinicaltrials.gov as #NCT04763616.