Antitumor activity of pembrolizumab plus dinaciclib in patients with diffuse large B cell lymphoma: the phase 1b KEYNOTE-155 study.

Introduction: KEYNOTE-155 (NCT02684617) evaluated the antitumor activity of pembrolizumab (pembro) plus dinaciclib in patients (pts) with relapsed/refractory (rr) CLL, MM, and DLBCL. Here we present data from an interim analysis of safety and efficacy in pts with rrDLBCL. Method(s): In this phase 1b, two-part, non-randomized, open-label study, pts with rrDLBCL who received >=2 prior therapies were enrolled into a dose-evaluation phase (two 21-day [d] cycles of pembro 200 mg [d1] and dinaciclib 7 mg/m2 [d1], 10 mg/m2 [d8] in cycle 1 and 14 mg/m2 [d1, d8] from cycle 2 onwards). The DLBCL expansion cohort was opened for the signal-detection phase (>=30 patients) if <=4 pts had dose-limiting toxicities (DLTs) during dose-evaluation. Treatment continued up to 35 cycles or until progression (PD) or unacceptable toxicity. Response was assessed every 3 cycles for DLBCL (Revised Response Criteria for Malignant Lymphoma 2007). Pts who discontinued before PD were followed Q12W until PD, new anticancer treatment, or death. The primary endpoint was safety and tolerability. Secondary endpoints included ORR by investigator, DOR, PFS, and OS. Efficacy and safety were assessed in all pts who received >=1 dose of pembrolizumab or dinaciclib. Result(s): As of Apr 25, 2018, 38 pts with rrDLBCL were enrolled and treated. Median age was 64.5 years (range, 39-85), 22 (58%) pts had ECOG PS 1, and 22 (58%) had >=3 prior therapies. After median follow-up of 2.79 mo (range, 1.5-6.8), 36 (95%) pts discontinued treatment: 21 (55%) PD, 12 (32%) by physician decision (10 [26%] clinical progression, 1[3%] logistics, 1 [3%] new therapy), 2 (5%) pt decision, and 1 (3%) AE. Median time on treatment was 51d (range, 1-471). Among 12 pts in all disease cohorts enrolled in the dose-evaluation phase, DLTs occurred in 1 of 6 (17%) evaluable pts (grade 4 thrombocytopenia) with rrDLBCL. Of 38 pts with rrDLBCL, 24 (63%) had a treatment-related AE. Common treatment-related AEs were decreased platelets (21%), l