Isatuximab (Isa) subcutaneous (SC) via an on-body injector (OBI) vs isa intravenous (IV), plus pomalidomide and dexamethasone (Pd) in relapsed/refractory multiple myeloma (RRMM): East asia subgroup results from the randomized, non-inferiority, phase

Abstract Background: Intravenous (IV) isatuximab plus pomalidomide and dexamethasone (Isa-Pd) is approved for treatment in patients with relapsed/refractory multiple myeloma (RRMM) based on the ICARIA-MM study. Subcutaneous (SC) administration of Isa offers potential advantages such as shorter administration duration and greater patient comfort compared with IV routes. Isa SC via an on-body injector (OBI), an investigational wearable bolus injector, demonstrated safety and efficacy in a Phase 1b study in patients with RRMM. The IRAKLIA trial (NCT05405166) was the first Phase 3 trial evaluating the non-inferiority of Isa-Pd SC via an OBI vs Isa-Pd IV in patients with RRMM. Here, we report the findings of the IRAKLIA trial in the East Asian subgroup with RRMM. Methods: This global, multicenter, open-label study enrolledpatients aged ≥18 years with RRMM who had received ≥1 prior line of therapy (LOT) including lenalidomide and a proteasome inhibitor (PI). Patients were randomized 1:1 to Isa SC (1400 mg) or Isa IV (10 mg/kg) weekly in Cycle (C)1, then every 2 weeks in addition to P (4 mg orally daily, Day [D]1-21) and d (40 mg orally [20 mg if age ≥75 years] weekly). Treatment was administered in 4-week cycles and continued until disease progression, unacceptable toxicity, or patient withdrawal. Co-primary endpoints included overall response rate (ORR) and observed Isa concentration before dosing (Ctrough) at steady state (predose at C6D1). Key secondary endpoints included rate of very good partial response or better (≥VGPR), Ctroughlevel Cycle 2 Day 1 (C2D1), infusion reaction incidence, and patient satisfaction rate based on the patient experience and satisfaction questionnaire (PESQ) at C5D15. Results: The East Asian subgroup consisted of 105 patients from China (Mainland, n=82 and Taiwan, n=1) and Japan(n=22) (SC, n=50; IV, n=55). Baseline characteristics of the East Asian subgroup were generally balanced between the two arms and generally comparable to the overall global population (median age 62 years; median 2 prior LOT; 29.5% high-risk cytogenetics; 82.9% refractory to lenalidomide; 7.6% prior exposure to daratumumab). After a median of 13.0 months follow-up, ORR in the SC and IV arm was 74.0% and 70.9%, respectively (relative risk [95% CI] = 1.044 [0.815 – 1.335]). The mean (SD) of Ctroughat C6D1 was 502 (232) µg/mL for SC arm and 282 (123) µg/mL for IV arm. The geometric mean ratio (90% CI) comparing SC to IV for Ctrough at steady state was 1.756 (1.346 – 2.290). The ≥VGPR rates were 58.0% for SC and 50.9% for IV (relative risk [95% CI] = 1.139 [0.798 – 1.631]). The mean(SD) of C2D1 Ctroughlevel was 420 (161) µg/mL for the SC arm and 262 (111) µg/mL for IV arm. The geometric mean ratio (90% CI) comparing SC to IV for Ctrough at C2D1 was 1.673 (1.321 to 2.120). The infusion reaction incidence was 0% and 21.8% for SC and IV, respectively. Grade ≥3treatment-emergent adverse events were observed in 82.0% and 87.3% of patients in the SC and IV arms, respectively. Treatment discontinuation rates were 6% for the SC arm and 12.7% for the IV arm. Injection site reactions (ISRs) occurred in 4% (2/50) of patients in the SC arm and in 0.21% (2/964) of SC injections (all Grade 1), with 99.3% of SC injections completed successfully. Isa SC patients expressed higher satisfaction with their injection method, with 64.0% of patients reporting “satisfied” or “very satisfied” vs 52.7% of Isa IV patients (odds ratio [95% CI] = 1.594 [0.728 – 3.489]). Conclusions: The efficacy, safety and pharmacokinetic results between Isa SC vs IV + Pd in the East Asian population from the IRAKLIA study were consistent with the results of the overall global population, in which non-inferiority of ORR, Ctrough at C6D1, ≥VGPR and Ctrough at C2D1 was demonstrated and statistically significantly fewer infusion reactions and higher patient satisfaction were also noted for SC vs IV. These results support the potential use of Isa SC delivered via OBI in East Asian patients and demonstrate the potential of this delivery method to improve patient experience and practice efficiency.