Rapid Readout: Safety and Efficacy of CD37-Targeting Naratuximab Emtansine plus Rituximab in Diffuse Large B-Cell Lymphoma and Other Non-Hodgkin’s B-Cell Lymphomas

This program is supported by Debiopharm.

OncLive® Rapid Readout from Safety and Efficacy of CD37-Targeting Naratuximab Emtansine plus Rituximab in Diffuse Large B-Cell Lymphoma and Other Non-Hodgkin’s B-Cell Lymphomas – a Phase 2 Study

Segment Description: Moshe Yair Levy, MD, discusses the safety and efficacy in a phase 2 trial that focused on naratuximab emtansine plus rituximab for the treatment of B-cell lymphomas, as presented at the 63rd ASH Annual Meeting in 2021. (Abstract 526)

Segment Body Content:

• Naratuximab emtansine (nara, Debio 1562, formerly IMGN529) is an antibody-drug conjugate (ADC) consisting of a humanized anti-CD37 antibody, K7153A, conjugated via a thioether-based linker to a cytotoxic maytansinoid, DM1. CD37, a lymphocyte surface marker, is highly expressed in B-NHL.
• A Phase 1 monotherapy study of nara revealed a good safety profile and promising efficacy (22% overall response rate [ORR] in DLBCL at all doses). In preclinical models of B-NHL, nara demonstrated synergistic antitumor activity when combined with rituximab (RTX).
• The aim of this open-label Phase 2 study was to evaluate the safety and efficacy of nara + RTX and to characterize pharmacokinetics (PK) and pharmacodynamics (PDy) in patients (pts) with relapsed and/or refractory (R/R) B-NHL.

Methods

• R/R B-NHL pts who were not candidates for stem cell transplant, with 1-6 prior lines of treatment, were recruited to two study parts.
• In Part 1, which included a safety run-in followed by an expansion, pts received 0.7 mg/kg nara in combination with 375 mg/m2 RTX every 3 weeks (Q3W).
• In Part 2, only R/R DLBCL pts were included. Pts were assigned either to the Q3W regimen (cohort A), or to a weekly regimen of 0.4, 0.2, and 0.2 mg/kg nara administered on days 1, 8 and 15 of 21-day cycles combined with 375 mg/m2 RTX on day 1 (cohort B).
• Six cycles of treatment were administered with possible extension. Primary endpoints were safety and ORR. PK and PDy evaluations included ADC and DM1 catabolites’ systemic levels and receptor occupancy on peripheral blood mononuclear cells (PBMCs), to investigate CD37 target engagement.
• Pts from cohorts A and B were requested to fill in the FACTLym quality of life questionnaire (QoL). Pts with double/triple hit lymphoma, bulky disease, and up to 6 prior lines of treatment for DLBCL were allowed. There was no limit on life expectancy.
• Pts were considered efficacy evaluable (EE) if they had one baseline and at least one post-baseline tumor assessment or an assessment of clinical progression. Tumor assessment by CT was acceptable. The follow-up period was up to 1 year after last pt first dose (NCT02564744).

Results

• 100 pts were enrolled in the study: 80 DLBCL, 14 follicular lymphoma (FL) and 6 mantle cell lymphoma (MCL) pts; 81 pts (81%) experienced grade ≥ 3 treatment emergent adverse events, the most common being neutropenia 54 (54%), leukopenia 19 (19%), lymphopenia 17 (17%), and thrombocytopenia 12 (12%). Of the 80 DLBCL pts, 10 (12.5%) were primary refractory, 24 (30%) were refractory to last line, 62 (78%) had Ann Arbor stage III/IV, and 35 (44%) had received at least 2 prior systemic cancer therapies.
• The ORR in the 76 EE DLBCL pts was 44.7%, with 24 (31.6%) complete responses (CR) and 10 (13.2%) partial responses (PR). In addition, 9 (11.8%) stable disease (SD) and 33 (43.4%) progressive disease (PD) were observed.
• 30 pts were efficacy evaluable in each of the two major cohorts (A and B) of Part 2, enrolling mainly relapsed pts. ORR was 50% in each cohort (CR rate: 43.3% in cohort A; 33.3% in cohort B). In Part 1, 16 DLBCL pts were EE, of which 6 were primary refractory and 10 were refractory to last line. ORR in this group was 25%.
• Median duration of response (mDoR) in the 76 evaluable DLBCL pts was not reached (lower 95% confidence interval [CI] 12 months). Median duration of follow-up in responders was 15 months (95% CI 9-18 months).
• In the 14 FL pts, the ORR was 57%: 5 CR, 3 PR, 3 SD, and 3 PD; the mDoR in this population was not reached (lower 95% CI: 19 months), with a median duration of follow-up of 21.8 months (95% CI 19.1 – not reached).
• Of the 6 MCL pts, 4 were efficacy evaluable: 2 CR and 2 PD. Due to the low number of pts, the DoR curves are not presented. PK levels were sufficient to fully engage the CD37 target on PBMCs. A relationship between PK exposure and efficacy was identified. Data showed acceptable systemic release of cytotoxic DM1 and catabolites.
• DLBCL responders in cohorts A and B demonstrated on average a clinically meaningful improvement of 3 points (standard deviation: 6.6) in the Lymphoma Subscale of the FACT-Lym QoL.

Conclusions

• The combination of nara + RTX resulted in good OR and CR rates, durable responses, a manageable safety profile, and full CD37 target engagement. Consequently, nara + RTX could be considered an attractive option for the treatment of R/R B-NHL. The treatment was well tolerated and contributed to the pts’ well-being, as demonstrated by the QoL results.