Daratumumab, lenalidomide, and dexamethasone in Japanese patients with transplant-ineligible newly diagnosed multiple myeloma: a phase 1b study

Lenalidomide and dexamethasone (Rd) treatment is common for patients with newly diagnosed multiple myeloma (NDMM) ineligible for autologous stem-cell transplantation. Daratumumab plus Rd (D-Rd) is effective and well tolerated for treating relapsed or refractory multiple myeloma. In this ongoing phase 1b trial, transplant-ineligible Japanese patients with NDMM received daratumumab (16 mg/kg intravenously every week for 8 weeks, every 2 weeks for 16 weeks, then every 4 weeks until disease progression) plus Rd (R 25 mg on Days 1-21 of 28-day cycle; d 40 mg weekly). The primary objective was to evaluate D-Rd tolerability and safety in Japanese patients with NDMM. Secondary objectives included daratumumab pharmacokinetics and response rate. During the dose-limiting toxicity (DLT) evaluation period, two DLTs occurred in seven (28.6%) patients, indicating D-Rd tolerability. At an 11.0-month median follow-up (interim analysis), grade 3/4 treatment-emergent adverse events occurred in six (85.7%) patients, including lymphopenia (71.4%), leukopenia (57.1%), and neutropenia (42.9%). Three (42.9%) patients experienced infusion-related reactions (IRRs). All IRRs were grade 2, occurred during the first daratumumab infusion, and resolved within 24 h. Pharmacokinetic findings were comparable to those in previous studies. A 100% overall response rate was achieved. These findings suggest D-Rd is tolerable in Japanese patients with transplant-ineligible NDMM. ClinicalTrials.gov identifier NCT02918331.