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Clinical trials: Non-immunologic

Session: Rapid Report: Session I

CTNI-52 - Survival Outcomes in Recurrent Glioblastoma (rGBM) Patients Treated with a Single Intra-tumoral Administration of Bizaxofusp, an IL-4R-targeting Toxin, in a Phase IIb Trial

Friday, November 17, 2023
7:58 PM - 8:02 PM PT
Location: Exhibit Hall A/B
Non-CME
Background: Bizaxofusp (MDNA55) is an IL4R-targeting toxin in development for recurrent (r)GBM, a universally fatal disease with mOS of 6-9 months. IL-4R is overexpressed in GBM and surrounding tumor microenvironment, with high expression associated with poor clinical outcome.

Method: Efficacy and safety were evaluated in a single-arm, open-label, multi-center Ph2 study using convection-enhanced delivery of Bizaxofusp. The primary endpoint of mOS was compared to results from a blinded eligibility-matched external control arm (ECA). OS was defined as time from relapse to death/censor. IL-4R expression was determined by immunohistochemistry of available archival tumor tissues from both arms.

Results: Bizaxofusp showed an acceptable safety profile at doses of up to 240 μg. Forty-four subjects were treated with Bizaxofusp per protocol; 81 ECA subjects met the eligibility criteria of the study. The Bizaxofusp group had a significantly longer mOS (12.85 months compared to 7.7 months for ECA; HR, 0.62; 95% CI, 0.42-0.89). Amongst the unmethylated MGMT and high IL-4R sub-groups, subjects treated with Bizaxofusp had significantly longer mOS when compared to the ECA. Eleven patients (25%) treated with Bizaxofusp survived >24 months; 3 patients were still alive (29.9, 32.8 and 40.1 months) at last follow-up. High IL-4R expression was associated with improved survival (mOS, 15.8 versus 9.8 months; HR, 0.7; 95% CI, 0.39-1.46) at all doses. However at high doses (180 μg) subjects with low IL-4R expression had significantly longer survival versus low dose Bizaxofusp (mOS, 15.4 versus 9.1 months; HR, 0.28; 95% CI, 0.09-0.91).

Conclusion: In patients with rGBM, a single treatment of Bizaxofusp resulted in significantly improved OS compared to eligibility-matched ECA. High-dose Bizaxofusp was equally effective irrespective of IL4R expression. A Phase 3 registration trial will use a novel hybrid design with a propensity-matched ECA comprising two-thirds of the control arm, setting a new precedent for GBM clinical trials.