Pembrolizumab appears to have clinical benefit in patients with relapsed or refractory primary mediastinal large B-cell lymphoma (rrPMBCL), according to data from the phase 1B KEYNOTE-013 and phase 2 KEYNOTE-170 trials. The results of both trials were recently reported in the Journal of Clinical Oncology.

The KEYNOTE-013 trial (ClinicalTrials.gov identifier: NCT01953692) included an expansion cohort of 21 patients with rrPMBCL who received pembrolizumab. In response to the findings of the KEYNOTE-013 trial, the KEYNOTE-170 trial was conducted and evaluated pembrolizumab in 53 patients with rrPMBCL.

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Overall, the KEYNOTE-013 trial had 7 patients (33%) achieve a complete response (CR) and 3 (14%) achieve a partial response (PR), totaling to an objective response rate (ORR) of 48%. Among the patients enrolled in the KEYNOTE-170 trial, 7 (13%) achieved a CR and 17 (32%) achieved a PR, contributing to an ORR of 45%.

To date, none of the patients who achieved a CR has experienced disease progression.

Patients on the KEYNOTE-013 trial had a median progression-free survival (PFS) of 10.4 months (95% confidence interval [CI], 3.4 months to not reached) and median overall survival (OS) of 31.4 months (95% CI, 4.9 months to not reached). Patients in the KEYNOTE-170 trial had a median PFS of 5.5 months (95% CI, 2.8-12.1 months) and a median OS that had not been reached (95% CI, 7.3 months to not reached).

The proportion of grade 3 or grade 4 treatment-related adverse events was similar between the KEYNOTE-013 and KEYNOTE-170 trials (24% vs 23%, respectively), with the most common event being neutropenia in both trials (14% vs 13%, respectively). No patient deaths were attributed to treatment.

In addition, severity of the 9p24 aberration was correlated with PD-L1 expression, and PD-L1 expression was significantly correlated with better PFS.

“Pembrolizumab is associated with high response rate, durable activity, and a manageable safety profile in patients with rrPMBCL,” the study authors wrote in conclusion.

Disclosure: The study was supported by Merck Sharp & Dohme, a subsidiary of Merck & Co, Kenilworth, NJ. Some of the authors also disclosed financial relationships with the pharmaceutical industry; for a full list of disclosures, please refer to the original study.

Reference

Armand P, Rodig S, Melnichenko V, et al. Pembrolizumab in relapsed or refractory primary mediastinal large B-cell lymphoma [published online October 14, 2019]. J Clin Oncol. doi: 10.1200/JCO.19.01389