(311) Belantamab Mafodotin Individual Patient Dosing in Patients With Relapsed/Refractory Multiple Myeloma Treated in the Phase 3 DREAMM-7 and DREAMM-8 Clinical Trials

Background: : Belantamab mafodotin (belamaf) is an antibody-drug conjugate that targets B-cell maturation antigen, which is present on the surface of multiple myeloma cells. Robust clinical efficacy was observed with belamaf combinations (belamaf +bortezomib [V]+dexamethasone [d] vs daratumumab [D]+Vd in DREAMM-7 [NCT04246047] and belamaf+pomalidomide [P]+d vs PVd in DREAMM-8 [NCT04484623]) in patients (pts) with relapsed/refractory multiple myeloma. Dose modifications were used to manage belamaf-associated adverse events, which affected the dose and dosing frequency over time, resulting in belamaf median relative dose intensity (mRDI) of 51.0% and 52.5% for BVd and BPd, respectively.

Objective: : Given the mRDI of belamaf in DREAMM-7/DREAMM-8, differences between protocol planned belamaf dosing and actual belamaf dosing (per weekly aggregate individual pt dosing [IPD] and RDI based on pt data) from DREAMM-7/DREAMM-8 were quantified to help inform costs as part of a budget impact model (BIM).

Methods: : A BIM was developed to estimate the cost of belamaf over 3 years, including an analysis of the weekly number of pts on treatment, administered doses, and administration frequency during DREAMM-7 and DREAMM-8. Per protocol, BVd-treated pts in DREAMM-7 were to receive belamaf 2.5 mg/kg Q3W and BPd-treated pts in DREAMM-8 were to receive belamaf 2.5 mg/kg for cycle 1, then 1.9 mg/kg Q4W thereafter. The aggregate IPD and mRDI of daratumumab in the DREAMM-7 comparator, DVd, were also assessed.

Results: : Per protocol-planned dosing, BVd-treated pts were planned to receive 18/17/17 belamaf doses and 49.6/46.8/46.8 belamaf vials in year (Y) 1/Y2/Y3; aggregated IPD data showed pts actually received 9/7/6 doses and 22.1/13.6/11.5 vials (24.3/22.9/22.9 vials per mRDI) in Y1/Y2/Y3. BPd-treated pts were planned to receive 13/13/13 belamaf doses and 27.9/27.2/27.2 belamaf vials per year for Y1/Y2/Y3; aggregated IPD data showed pts actually received 6/3/3 doses and 13.5/6.8/8.5 vials (14.6/14.3/14.3 vials per mRDI) in Y1/Y2/Y3. For daratumumab in DVd, both the IPD and RDI (mRDI 97%) remained stable and similar to the planned dose from initiation through Y3. The impact of belamaf dose modifications on total cost of care will be reported.

Conclusions: : Both IPD and RDI measures of belamaf dosing in the BVd and BPd combinations resulted in substantially lower values than the planned protocol dosing, indicating that use of these measures would provide a more accurate view of costs associated with BVd and BPd treatment as part of a budget impact assessment.

Sponsorship:: GSK