Janowski, Wojciech

7516 Background: With the growing use of anti-CD38 therapies in early multiple myeloma (MM) management, there is a need for data in patients previously exposed to anti-CD38 therapy to guide decision making. In the Phase 3 IRAKLIA trial (NCT05405166), patients with relapsed/refractory MM (RRMM) received the anti-CD38 monoclonal antibody isatuximab (Isa) subcutaneously (SC) delivered via an innovative on-body injector (OBI) or intravenously (IV), with pomalidomide and dexamethasone (Pd). In this post hoc analysis, we examined outcomes in IRAKLIA patients with vs without prior anti-CD38 exposure. Methods: RRMM patients ≥18 years with ≥1 prior line of therapy including lenalidomide and a proteasome inhibitor were randomized to receive Isa SC (n=263) or IV (n=268) weekly in Cycle 1, then every 2 weeks, with Pd. Patients with prior anti-CD38 exposure <9 months (mos) before randomization or intolerance to anti-CD38 were excluded. Refractory patients were defined as those who failed to achieve minimal response on treatment or had progression within 60 days after last dose. Patients receiving Isa SC or IV were pooled. Results: Overall, 67 patients (12.6%) had prior anti-CD38 exposure with a median washout period of 20.2 mos, of which 26 (38.8%) were anti-CD38 refractory. Baseline characteristics were largely consistent between patients with or without prior anti-CD38 exposure; the median follow-up for the overall population was 12 mos. Patients with prior anti-CD38 exposure had an overall response rate (ORR) of 52.2%, 12-mo progression-free survival (PFS) rate of 40.6%, and median PFS of 8.5 mos. In patients without prior exposure, an ORR of 73.5%, 12-mo PFS of 68.8%, and non-estimable (NE) median PFS were reported. Anti-CD38 non-refractory vs refractory patients had an ORR of 48.8% vs 57.7%, 12-mo PFS of 38.9% vs 42.2%, and median PFS of 9.0 vs 7.5 mos. Patients with a longer washout period (>median of 20.2 mos) had an ORR of 63.6%, 12-mo PFS of 61.8% and NE median PFS, whereas patients whose prior anti-CD38 therapy ended more recently (≤median of 20.2 mos) had an ORR of 41.2%, 12-mo PFS of 19.2%, and median PFS of 6.7 mos. The safety profile of Isa + Pd was similar in patients with vs without prior anti-CD38 exposure. Conclusions: Isa + Pd demonstrated clinical benefit across anti-CD38–naïve, anti-CD38–exposed, and anti-CD38–refractory patients. A washout period >median of 20.2 mos resulted in outcomes comparable to those in anti-CD38–naïve patients, and outcomes were consistent between anti-CD38–exposed and anti-CD38–refractory patients after a >9-mo washout period. Efficacy of Isa + Pd in patients with prior anti-CD38 exposure from the IRAKLIA trial presents an opportunity to address an unmet need in a difficult-to-treat patient population. Clinical trial information: NCT05405166 .

TPS8064 Background: Multiple myeloma (MM) remains an incurable disease. Combinations of established agents, including proteasome inhibitors (PIs), immunomodulatory drugs (IMiDs), and anti-CD38 antibodies, are used in all lines of therapy, but re-exposure to previously received classes of therapy is associated with decreasing response rates and duration of response (Moreau et al. 2021). BCMA-targeted agents have recently been approved for the treatment of patients with RRMM whose disease has been exposed or become refractory to PIs, IMIDs and anti-CD38 antibodies (triple-class exposed or refractory MM). Although effective, the majority of patients who respond to anti-BCMA agents eventually relapse. Proven salvage therapies for these patients are currently lacking and represent a new unmet medical need. Cevostamab is an immunoglobulin G1-based T-cell-engaging bispecific antibody that targets Fc receptor-homolog 5 (FcRH5) on myeloma cells and CD3 on T cells. Dual binding results in T-cell activation and potent killing of MM cells. In an ongoing Phase I study (GO39775; NCT03275103), cevostamab monotherapy showed promising activity in heavily pre-treated patients with RRMM, including those with prior exposure to anti-BCMA agents (Trudel et al. 2021). Methods: CAMMA 2 (CO43476; NCT05535244) is an open-label, multicenter Phase I/II trial evaluating cevostamab monotherapy in patients with RRMM who are triple-class refractory and have previously received an anti-BCMA agent. Prior anti-BCMA antibody-drug conjugates or chimeric antigen receptor (CAR) T cells are permitted in Cohorts A1 and B1, while prior anti-BCMA bispecific antibodies are allowed in Cohorts A2 and B2. In A1 and A2, cevostamab is administered by intravenous infusion and is initiated with step dosing (0.3mg on Cycle [C] 1 Day [D] 1 and 3.3mg on C1D2, D3, or D4 depending on the emergence and resolution of cytokine release syndrome [CRS] after the initial administration), with the target dose of 160mg given on C1D8 and on D1 of each subsequent 21-day cycle. Patients are hospitalized for the C1 administrations only and treatment is continued until disease progression or unacceptable toxicity occurs. CRS is managed per protocol based on the clinical presentation and may involve corticosteroid and tocilizumab treatment. Primary objectives are evaluation of efficacy (primary endpoint: objective response rate by investigator assessment using IMWG criteria) and safety. Secondary objectives include assessment of quality of life, pharmacokinetics, pharmacodynamics, and immunogenicity. Cohorts B1 and B2 will evaluate the efficacy and safety of cevostamab at the recommended Phase II dose in this setting. As of February 2023, enrolment into Cohorts A1 and A2 is ongoing. Clinical trial information: NCT05535244 .