Impact of granulocyte colony-stimulating factors on cytokine release syndrome during bispecific antibody initiation in relapsed/refractory multiple myeloma

Bispecific antibody (BsAb) treatment in multiple myeloma can be associated with adverse events including cytokine release syndrome (CRS), cytopenias, and infections. While granulocyte colony-stimulating factors (G-CSF) can be used to treat neutropenia, little is known about their safety during the BsAb initiation period and whether G-CSF can increase the risk of CRS. To assess the impact of G-CSF on risk of CRS, we included all patients with multiple myeloma who received at least one dose (step-up doses [SUD] and first treatment dose [FTD]), of commercial teclistamab, elranatamab, or talquetamab between November 2022 and April 2024 at Memorial Sloan Kettering Cancer Center ( N = 186). Exposure to G-CSF was defined as administration of at least one dose of filgrastim from 48 h before up to 7 days after BsAb SUD or FTD, or one dose of peg-filgrastim between 7 days prior to up to 7 days after BsAb SUD or FTD. Of the 186 patients, 22 were classified as G-CSF exposed. CRS occurred in 16/22 (73%) patients with G-CSF exposure vs 76/164 (46%) of non-exposed. All CRS was grade 1 (56%) or grade 2 (44%) and the majority occurred prior to G-CSF was given (16/22 patients). The median absolute neutrophil count (ANC) at time of G-CSF exposure was 0.5 × 10 9 /L (0.4–0.7). There was a trend towards increased risk of CRS after G-CSF exposure, although not significant (hazard ratio [HR] 1.7, 95% confidence interval [CI] 0.6–4.7, p = 0.3). These results suggest that G-CSF administration can be considered for neutropenia during BsAb initiation.