A sequential cohort study evaluating single-agent KappaMab and KappaMab combined with lenalidomide and low-dose dexamethasone in relapsed and/or refractory kappa light chain-restricted multiple myeloma (AMaRC 01-16).

KappaMab (KM; formerly MDX-1097) is a monoclonal antibody specific for the kappa myeloma antigen (KMA), a cell-surface antigen expressed on malignant plasma cells in kappa-restricted multiple myeloma (κMM), some lymphomas, occasional tonsillar B cells and in vitro activated B cells, but not on normal B cells in bone marrow. Phase I/IIa studies of single-agent KM confirmed a favourable toxicity profile and evidence of anti-myeloma activity. Ex-vivo studies demonstrating upregulation of KMA by lenalidomide, and enhanced effector-cell cytotoxicity provided the rationale for this phase IIb study where KM or KM in combination with lenalidomide and dexamethasone (KM-Rd) was administered in relapsed, refractory κMM patients. In addition, outcomes for a real-world matched case-control cohort from the Australian and New Zealand Myeloma and Related Diseases Registry (MRDR) who received Rd were compared to the KM-Rd cohort. KM-Rd demonstrated an overall response rate of 82.5% which compared favourably to the Rd-MRDR cohort of 45.1%. Both single-agent KM and KM-Rd regimens were well tolerated, with the KM-Rd safety profile similar to patients given only Rd in other clinical settings. Based on the excellent safety profile and significant efficacy, further clinical trials escalating the KM dose and pairing KM with other standard-of-care treatments are planned.