The lymphocyte/monocyte ratio predicts the efficacy of isatuximab plus pomalidomide in multiple myeloma patients

Isatuximab, an anti-CD38 antibody, has been widely used in treatments for patients with relapsed/refractory multiple myeloma (MM). Despite its high efficacy, not all patients achieve a lasting therapeutic response with isatuximab. We tried to identify biomarkers to predict the effectiveness of isatuximab by focusing on the host's immune status before treatment. We retrospectively analyzed the cases of 134 relapsed/refractory MM patients in the Kansai Myeloma Forum database who had received only a first isatuximab treatment. Among the 134 patients, an isatuximab, pomalidomide and dexamethasone (Isa-PD) regimen, isatuximab, carfilzomib and dexamethasone (Isa-KD) regimen and isatuximab and/or dexamethasone (Isa-D) regimen were used in 112, 15 and 7 patients, respectively. The median age at treatment, number of prior treatment regimens, and progression-free survival (PFS) were 71, 6, and 6.54 months, respectively. Multivariate analysis showed that the PFS under the Isa-PD regimen was longer in patients with higher lymphocyte/monocyte ratio (LMR ≥ 4), fewer prior treatment regimens (< 6), and no use of prior daratumumab treatment. The OS under the Isa-PD regimen was longer in patients with higher white blood cell counts (WBC counts ≥ 3000/μL) and higher LMR. The PFS under the Isa-D regimen was longer in patients with fewer prior treatment regimens in univariate analysis, but no parameters were correlated with PFS/OS under the Isa-KD regimen. We found that the patients with higher LMR (≥ 4) could obtain longer PFS and OS under the Isa-PD regimen. Other cohort studies of isatuximab treatment might be necessary to substantiate our results.