IMPEDE

Results: At the time of data cut-off, 15 patients were enrolled. Median age was 68 years (range, 54-79) and 3 were African American. Disease was refractory to lenalidomide in all patients, and refractory to both bortezomib and lenalidomide in 3 patients. Six patients were previously exposed to anti-CD38 mAb. Eleven (73%) patients had presence of high-risk cytogenetics including del 17p, t (4;14), t (14;16) and 1q gain/amp. All 6 patients in in the safety lead-in cohort completed at least 2 cycles of treatment (DLT window), while the remaining patients completed at least 1 cycle of treatment. The median follow up was 8.5 months (1-16.6). None of the patients experienced DLT in the safety lead-in phase. Grade 3-4 treatment emergent adverse events (TEAEs) occurred in 15 (100%) of patients with most common being lymphopenia (93%), neutropenia (93%) and leucopenia (40%). Grade 3-4 infections occurred in 1(7%) patient. No grade 5 TEAEs occurred. Infusion related reactions occurred in 1 patient, maximum grade 2. All patients were evaluable for response with an ORR of 80% (12/15) (6 VGPR or better, 6 PR), and 100% in anti-CD38 mAb naive. The 12-month PFS rate was 67% (45%-99%). 5 patients discontinued the study (4 due to disease progression and 1 withdrew consent). Lymphocyte subpopulations showed a decrease in relative and absolute NK cells and an increase in monocytes (Figure 1 A, B). NK cell cytolytic activity was maintained in patient samples obtained over the course of the study (Figure 1C).

Conclusions: This is the first ever report combining two different mAbs with dual targeting of CD38 and SLAMF7 in RRMM. The results demonstrate that Isa-EloPD combination is both safe and feasible with high frequency and durability of responses. Despite an anticipated reduction in number, NK cell cytotoxicity remain unaffected with the combination. The study is ongoing and results from additional patients and longer follow up will be presented.