Preclinical data demonstrated that combining an anti–programmed cell death 1 (PD-1) inhibitor with a cyclin-dependent kinase 9 (CDK9) inhibitor provided enhanced antitumor activity with no significant toxicities, suggesting this combination may be a potential therapeutic option. The multicohort, phase 1 KEYNOTE-155 study evaluated the safety and antitumor activity of the PD-1 inhibitor pembrolizumab plus the CDK9 inhibitor dinaciclib in patients with relapsed or refractory (rr) chronic lymphocytic leukemia (CLL), diffuse large B-cell lymphoma (DLBCL) and multiple myeloma (MM). Patients enrolled were ≥18 years of age with a confirmed diagnosis of CLL, DLBCL, or MM. The study included 2 phases: a dose-evaluation phase to determine dose-limiting toxicities and a signal-detection phase. Patients received pembrolizumab 200 mg every 3 weeks plus dinaciclib 7 mg/m2 on day 1 and 10 mg/m2 on day 8 of cycle 1 and 14 mg/m2 on days 1 and 8 of cycles 2 and later. Primary endpoint was safety, and a key secondary endpoint was objective response rate (ORR). Seventy-two patients were enrolled and received ≥1 dose of study treatment (CLL, n = 17; DLBCL, n = 38; MM, n = 17). Pembrolizumab plus dinaciclib was generally well tolerated and produced no unexpected toxicities. The ORRs were 29.4% (5/17, rrCLL), 21.1% (8/38, rrDLBCL), and 0% (0/17, rrMM), respectively. At data cutoff, all 72 patients had discontinued treatment, 38 (52.8%) because of progressive disease. These findings demonstrate activity with combination pembrolizumab plus dinaciclib and suggest that a careful and comprehensive approach to explore anti–PD-1 and CDK9 inhibitor combinations is warranted. This trial was registered at www.clinicaltrials.gov as NCT02684617.

Immunoglobulin light-chain (AL) amyloidosis is a plasma cell disorder characterized by progressive organ dysfunction secondary to deposition of organized immunoglobulin light-chain aggregates. Achievement of rapid and deep normalization of involved immunoglobulin free light chains is necessary to maximize chances of reversibility of organ dysfunction, which, in turn, results in improved quality and length of life. There are no US Food and Drug Administration (FDA)–approved therapies for patients with relapsed AL amyloidosis. B-cell maturation antigen–targeting (BCMA)-bispecific T-cell engagers teclistamab and elranatamab have shown high activity and acceptable safety profile in patients with relapsed and/or refractory multiple myeloma, leading to their FDA approval. Herein, we report on safety and efficacy of elranatamab for patients with relapsed and/or refractory AL amyloidosis. We treated 9 consecutive patients with advanced-stage AL amyloidosis with single-agent elranatamab, observing a 100% overall response and 67% complete response rate, including minimal residual disease negativity, with expected toxicities. Median time to hematological response was 9 days (range, 6-24), with deep suppression in involved free light chains observed within 1 cycle of therapy, translating in cardiac and renal responses at 3 to 6 months. These data support prospective studies exploring elranatamab for patients with relapsed AL amyloidosis.