CD19 4-1BBL (RO7227166) a Novel Costimulatory Bispecific Antibody Can be Safely Combined with the T-Cell-Engaging Bispecific Antibody Glofitamab in Relapsed or Refractory B-Cell Non-Hodgkin Lymphoma

Background RO7227166 is a bispecific monoclonal antibody that simultaneously targets CD19 on B-cells and 4-1BB on T-cells and other immune cells. In the presence of a T-cell receptor signal and strictly dependent on CD19 crosslinking, RO7227166 provides a strong co-stimulation to T-cells via 4-1BB agonism. RO7227166 is therefore not exhibiting single-agent activity. Our preclinical and clinical data demonstrated 4-1BB upregulation on immune cells by glofitamab and in our in vivo humanized lymphoma xenograft mouse models the combination of glofitamab plus RO7227166 showed increased anti-tumor efficacy mediated by increased infiltration of activated CD8 T-cells within the tumor. We therefore hypothesized that RO7227166 would boost the anti-tumor activity of glofitamab in patients (pts) with B-cell non-Hodgkin lymphoma (B-NHL). Methods We report data from the first-in-human study BP41072 (NCT04077723), a multicenter open label Phase 1 trial investigating the safety, tolerability, pharmacokinetics (PK), pharmacodynamics and preliminary antitumor activity of RO7227166 in combination with glofitamab (part II of the study) in relapsed/refractory (R/R) B-NHL pts. Pts received 1000mg obinutuzumab 7 days prior to first glofitamab administration to mitigate cytokine release syndrome (CRS). Glofitamab was then dosed following a step-up regimen in cycle 1 (C1), from cycle 2 day 1 (C2D1) on, every 3 weeks (Q3W) for up to 12 cycles. First RO7227166 dose was given on C2D8 and from C3 onwards on the same day as glofitamab. RO7227166 dose escalation was guided by an mCRM EWOC model with overdose control. Response rates were reported based on the Lugano criteria. Results As of June 7, 2022, a total of 46 pts with R/R aggressive B-NHL (diffuse-large B-cell lymphoma [DLBCL]) and 24 pts with R/R indolent B-NHL (23 follicular lymphoma [FL], 1 marginal zone lymphoma [MZL]) received RO7227166 doses ranging from 360µg up to 33mg. So far the dose level with the expected maximum efficacy is not yet reached. Pts had a median age of 66 years, 44.3% were female, with ECOG of 0 (62.9%) or 1 (37.1%). Approximately half of pts had Stage IV disease (44.3%), 18.6% pts had bulky disease (at least one lesion > 6cm), 27.1% had prior CAR-T therapy. Median prior lines of therapy was 3 (range 1-7), with 40% refractory to last prior therapy, 21.4% primary refractory and 12.9% refractory to CAR-T. Across 70 safety evaluable pts, 67 (95.7%) had adverse events (84.3% pts grade 1, 64.3% pts grade 2, 44.3% pts grade 3, 8.6% pts grade 4 and 4.3% pts grade 5). Grade 5 events were pneumocystis jirovecii pneumonia which qualified as dose-limiting toxicity (n=1) and septic shock (n=1) and COVID-19 infection (n=1) which were both assessed as not related to study medications. The most frequent adverse event was CRS with 63 events occurring in 38 (54.3%) pts (maximum grade 1 in 37,1% pts, and maximum grade 2 in 17,1% pts, according to ASTCT score). Of all 63 events (including multiple events for some pts), 55 were related to glofitamab alone (87,3%), 5 events to glofitamab and RO7227166 (8%, all grade 1) and 3 events related to RO7227166 alone (4.8%, all grade 1). Overall the safety profile was mainly driven by glofitamab (Hutchings, et al. 2021) and we are yet to detect an additive safety signal from RO7227166 when combined with glofitamab. RO7227166 exposure increased dose-dependently across the investigated doses. Furthermore, preliminary pharmacodynamic analysis showed further expansion of primed and activated CD8, and effector memory T-cells in the periphery, which supports the expected mode of action of RO7227166 in combination with glofitamab. Of the 56 response-evaluated subjects, pts with DLBCL achieved a best overall response rate (BORR) of 67% and a complete response rate (CRR) of 39%, while the BORR and CRR for patients with FL was 91% and 73%. Summary This is the first study demonstrating that glofitamab can be safely combined with a costimulatory bispecific antibody (RO7227166) in R/R B-NHL. No new safety signals or signs of increased immune-related AEs were detected and the overall safety profile was consistent with that reported from single-agent glofitamab. At doses explored, combination therapy maintains efficacy similar to glofitamab single-agent, and dose escalation continues with additive benefit of the combination expected at higher doses.