PD-L1 expression predicts efficacy in the phase II SPiReL trial with MVP-S, pembrolizumab, and low-dose CPA in R/R DLBCL.

BACKGROUND

Patients with relapsed/refractory diffuse large B-cell lymphoma (R/R DLBCL) have limited treatment options.

METHODS

R/R DLBCL patients, who were mostly ineligible for ASCT due to age or comorbidities, were treated with maveropepimut-S (MVP-S, previously DPX-Survivac) a survivin directed T cell educating therapy, pembrolizumab, and intermittent low-dose cyclophosphamide.

FINDINGS

We identified, using univariate analysis, a subset of patients with enhanced ORR, PFS and DOR. Patients with baseline CD20+/PD-L1 expression had an ORR of 46% (6/13) and the disease control rate was 10/13 (77%). The PFS and OS of the positive CD20+/PD-L1 patients were 7.1 months and 17.4 months, whereas in the intent-to-treat (ITT) population of 25 enrolled patients, the ORR was 28% (7/25), median PFS and OS were 4.2 months and 10.1 months respectively. A total of 6/7 clinical responders occurred in CD20+/PD-L1 patients. The regimen was well-tolerated, requiring only minor dose modifications and one discontinuation. Grade 1 or 2 injection site reactions occurred in 14/25, (56%). Statistically significant associations were also seen between PFS and; injection site reactions; and ELISpot response to survivin peptides, both identifying the mechanistic importance of specific immune responses to survivin.

INTERPRETATION

This immunotherapy combination was found to be active and safe in this clinically challenging patient population.