Pre-Clinical Assessment of SAR442257, a CD38/CD3xCD28 Trispecific T Cell Engager in Treatment of Relapsed/Refractory Multiple Myeloma.

Current treatment strategies for multiple myeloma (MM) are highly effective, but most patients develop relapsed/refractory disease (RRMM). The anti-CD38/CD3xCD28 trispecific antibody SAR442257 targets CD38 and CD28 on MM cells and co-stimulates CD3 and CD28 on T cells (TCs). We evaluated different key aspects such as MM cells and T cells avidity interaction, tumor killing, and biomarkers for drug potency in three distinct cohorts of RRMM patients. We found that a significantly higher proportion of RRMM patients (86%) exhibited aberrant co-expression of CD28 compared to newly diagnosed MM (NDMM) patients (19%). Furthermore, SAR442257 mediated significantly higher TC activation, resulting in enhanced MM killing compared to bispecific functional knockout controls for all relapse cohorts (Pearson's r = 0.7). Finally, patients refractory to anti-CD38 therapy had higher levels of TGF-ß (up to 20-fold) compared to other cohorts. This can limit the activity of SAR442257. Vactoserib, a TGF-ß inhibitor, was able to mitigate this effect and restore sensitivity to SAR442257 in these experiments. In conclusion, SAR442257 has high potential for enhancing TC cytotoxicity by co-targeting CD38 and CD28 on MM and CD3/CD28 on T cells.

Ex Vivo Efficacy of SAR442257 Anti-CD38 Trispecific T-cell Engager in Multiple Myeloma Relapsed After Daratumumab and BCMA-targeted Therapies.

T cell-engaging antibodies (TCEs) are showing promising efficacy in relapsed/refractory multiple myeloma, even in patients that relapsed after B-cell maturation antigen (BCMA)-targeted therapy. Patients with multiple myeloma may have compromised T-cell health unaccounted for by preclinical models. Here, we use Myeloma Drug Sensitivity Testing (My-DST) for ex vivo measurement of anti-multiple myeloma cytotoxicity for the trispecific CD38/CD28xCD3 TCE SAR442257 through activation of the patients' own endogenous T cells to inform clinical development of the compound in multiple myeloma. My-DST incubates primary mononuclear cells in humanized media for 48 hours followed by flow cytometry for multiple myeloma cell viability with or without drug treatment. SAR442257 was tested on 34 samples from patients with multiple myeloma across disease settings. Potential biomarkers, T-cell dependence, and degranulation were assessed. SAR442257 was effective at low dose in My-DST cultures. High ex vivo response rates were observed in primary aspirates taken from patients with multiple myeloma at diagnosis, with modestly reduced response in multiple myeloma recently treated with anti-CD38 mAbs. SAR442257 was highly effective in patients relapsing after BCMA therapy. The CD38/CD28xCD3 trispecific format was substantially more effective than a conventional bispecific CD38/CD3 antibody format and CD38 mAbs. Anti-multiple myeloma cell cytotoxicity was dependent on the presence of endogenous T cells. Surface CD38 expression was the strongest biomarker of TCE response. My-DST is capable of measuring T cell-dependent killing using the multiple myeloma patient's own bone marrow-derived T cells. SAR442257 shows promise for multiple myeloma and may be best suited for patients declared resistant to both CD38 mAbs and BCMA-targeted therapy. SIGNIFICANCE: This study introduces the use of My-DST to measure and characterize sensitivity to anti-CD38 T-cell engager SAR442257 in primary samples using matched endogenous T cells. Preclinical testing in samples from patients with diverse treatment history supports further testing in post-chimeric antigen receptor T-cell multiple myeloma.

Isatuximab in combination with carfilzomib and dexamethasone in 1q21+ patients with relapsed/refractory multiple myeloma: Long-term outcomes in the Phase 3 IKEMA study.

Gain/amplification of 1q21 (≥3 copies), a chromosomal abnormality frequently observed in multiple myeloma, can negatively affect prognosis, due to its involvement in resistance to anti-myeloma therapy and disease progression. In this updated subgroup analysis of the randomized, Phase 3 IKEMA study (NCT03275285) in relapsed/refractory multiple myeloma (RRMM), we evaluated progression-free survival (PFS) and depth of response with the anti-CD38 antibody isatuximab plus carfilzomib-dexamethasone (Isa-Kd) versus Kd, in 1q21+ patients and related subgroups, at long-term follow-up (44.2 months). Our analysis included patients with 1q21+ (≥3 copies, with/without high-risk chromosomal abnormality [HRCA]), isolated 1q21+ (≥3 copies, without HRCA), gain(1q21) (3 copies, with/without HRCA), and amp(1q21) (≥4 copies, with/without HRCA). PFS benefit was achieved with Isa-Kd versus Kd in patients with 1q21+ (HR 0.58, 95% CI: 0.37-0.92), with isolated 1q21+ (HR 0.49, 95% CI: 0.27-0.92), with gain(1q21), or amp(1q21), consistent with the overall population and prior interim 1q21+ subgroup analyses. Median PFS with Isa-Kd versus Kd was 25.8 versus 16.2 months in 1q21+ patients and 38.2 versus 16.2 months in patients with isolated 1q21+. Clinically meaningful, higher rates of very good partial response or better, complete response or better (≥CR), minimal residual disease (MRD) negativity, and MRD negativity and ≥CR were reached with Isa-Kd versus Kd in patients with 1q21+, isolated 1q21+, gain(1q21), or amp(1q21). In Isa-Kd and Kd, the MRD negativity and ≥CR rate was 29.3% versus 15.4% in 1q21+ patients, 36.2% versus 12.9% in patients with isolated 1q21+, 27.9% versus 13.5% in patients with gain(1q21), and 31.3% versus 20.0% in patients with amp(1q21), respectively. In conclusion, addition of Isa to Kd in triplet combination therapy has shown PFS benefit and deeper responses, compared with Kd, in 1q21+ patients at higher risk of progression, including patients with isolated 1q21+, gain(1q21), and amp(1q21), thus supporting Isa-Kd an effective treatment option for patients with RRMM.