Sintilimab (anti-PD-1 antibody) combined with high-dose methotrexate, temozolomide, and rituximab (anti-CD20 antibody) in primary central nervous system lymphoma: a phase 2 study

Primary central nervous system lymphoma(PCNSL)is a rare and frequently fatal lymphoma subtype.The programmed death-1(PD-1)pathway has emerged as a potential therapeutic target,but the effectiveness of PD-1 antibody sintilimab in combination with immunochemotherapy as a frontline treatment for PCNSL remains to be determined.In this phase 2 trial(ChiCTR1900027433)with a safety run-in,we included patients aged 18–70 with newly diagnosed PCNSL.Participants underwent six 21-day cycles of a SMTR regimen,which includes sintilimab(200 mg,Day 0),rituximab(375 mg/m2,Day 0),methotrexate(3.0 g/m2,Day 1 or 1.0 g/m2 for patients aged≥65 years),and temozolomide(150 mg/m2/d,Days 1–5).Among 27 evaluable patients,the overall response rate(ORR)was 96.3%(95%confidence interval:81–99.9%),with 25 complete responses.At a median follow-up of 24.4 months,the medians for duration of response,progression-free survival(PFS),and overall survival were not reached.The most common grade 3–4 treatment-related toxicities were increased levels of alanine aminotransferase(17.9%)and aspartate aminotransferase(14.3%).Additionally,baseline levels of interferon-αand the IL10/IL6 ratio in cerebrospinal fluid emerged as potential predictors of PFS,achieving areas under the curve of 0.88 and 0.84,respectively,at 2 years.Whole-exome sequencing revealed a higher prevalence of RTK-RAS and PI3K pathway mutations in the durable clinical benefit group,while a greater frequency of Notch and Hippo pathway mutations in the no durable benefit group.These findings suggest the SMTR regimen is highly efficacious and tolerable for newly diagnosed PCNSL,warranting further investigation.