High Responses Rates with Single Agent Belantamab Mafodotin in Relapsed Systemic AL Amyloidosis

Introduction: Systemic AL amyloidosis, a rare incurable plasma cell disorder, has no approved treatments at relapse. Belantamab mafodotin is an antibody-drug conjugate which targets BCMA antigen approved for relapsed refractory myeloma. We report our results using belantamab mafodotin monotherapy for the treatment of patients with relapsed refractory AL amyloidosis including those traditionally excluded from clinical trials (eGFR70 years. Eighteen (67%) had λ AL-type and nine (33%) κ AL-type. A median of two organs were involved at baseline (range 1-4) with renal and cardiac involvement in 20 (74%) and 15 (56%) respectively (3 each for Mayo stage IIIa and stage IIIb). The median time from AL amyloidosis diagnosis to first administration of belantamab mafodotin was 69 (range 5-174) months (~6 years) with a median of 3 prior lines of treatment (range 2-6). Prior drug class exposure included proteasome inhibitors (100%), immunomodulatory drugs (81%) and anti-CD38 antibody (81%) therapy. Ten patients (37%) had undergone prior melphalan-conditioned autologous stem cell transplantation. At the time of first belantamab mafodotin dose, the median involved free light chain concentration was 118mg/l (range 31-1778), eGFR was 40 ml/min (range 7 - 120) and a third (9/27) with an eGFR