Exposure-response analyses for belantamab mafodotin in combination with bortezomib and dexamethasone in patients with relapsed/refractory multiple myeloma from DREAMM-6 Arm B and DREAMM-7

BACKGROUND: Belantamab mafodotin, bortezomib and dexamethasone (BVd) demonstrated clinical activity in the phase I/II DREAMM-6 (Arm B) study and significant clinical benefit in the phase III DREAMM-7 study for patients with relapsed/refractory multiple myeloma (RRMM) and ≥1 prior line of therapy. METHODS: Population pharmacokinetic-derived Cycle 1 (C1) belantamab mafodotin exposures were used to evaluate exposure-efficacy/exposure-safety relationships across multiple doses and schedules for benefit-risk assessment. RESULTS: Belantamab mafodotin C1 exposure was positively associated with response endpoints and grade ≥2/ ≥3 ophthalmic exam findings (OEFs), but not grade ≥2/ ≥3 ocular adverse events (oAEs) or best-corrected visual acuity (BCVA) worsening to 20/50 or worse in both eyes. Probability of very good partial response or better (≥VGPR) was higher than grade ≥3 oAEs/BCVA worsening in both eyes across C1 exposures; efficacy improved at higher C1 exposures without increased OEF risk. Model-based benefit-risk assessment showed a belantamab mafodotin starting dose of 1.9 mg/kg instead of 2.5 mg/kg would result in lower probability of ≥VGPR without reduction in BCVA worsening in both eyes/grade ≥3 oAEs. CONCLUSIONS: An initial belantamab mafodotin dose of 2.5 mg/kg for BVd yields deeper responses with minimal change in safety outcomes versus 1.9 mg/kg for patients with RRMM.