BIOS-01. EFFICACY AMONG THERAPEUTICALLY EFFECTIVE ABSORBED DOSE PATIENTS IN RESPECT-GBM PHASE I OF RHENIUM-186 NANOLIPOSOME (¹⁸⁶RNL) IN RECURRENT GLIOBLASTOMA (RGBM) COMPARED TO AN EXTERNAL CONTROL ARM (ECA)

ReSPECT-GBM is a Phase 1/2 study of ¹⁸⁶RNL administered by convection enhanced delivery (CED) in patients with rGBM. In Phase I, 15 of 24 patients have achieved a therapeutic absorbed dose defined as > 100 Gy. Based on prior work establishing the comparability of a bevacizumab (Bev) comparator to inform early-phase CED study results, OS of the 15 TAD patients were compared to a Bev ECA.

Recent Bev-treated rGBM clinical trial patients meeting the same eligibility criteria as patients in the ReSPECT-GBM study were identified from the Medidata Enterprise Data Store of aggregated and deidentified patient-level historical clinical trial data. Propensity score (PS) methods were used to select the ECA and align the baseline characteristics of the Bev patients to the ReSPECT TAD cohort. OS estimates were generated using the weighted Kaplan-Meier method and compared with a weighted 2-sample 2-sided log-rank test at α = 0.05 based on a data cut-off of December 2022.

Baseline characteristics of the ReSPECT TAD and ECA patients were well-aligned after PS modeling. Although not achieving statistical significance due to small sample sizes (median OS 12.2 vs 10.1 months, hazard ratio 0.63, 95% CI: 0.26, 1.52), comparison of OS between the ReSPECT TAD and ECA patients demonstrate consistently longer OS at each 6-month interval: 6 months: 85.1% vs 73.3%, 12 mos: 51.1% vs 30.3%, 18 months: 30.6% vs 25.4%, 24 months: 30.6% vs 3.5%.

Single-arm studies can be challenging to interpret. By comparing the ReSPECT-GBM outcomes to an ECA of similar patients with balanced baseline characteristics, we can better appreciate the treatment effect of ¹⁸⁶RNL administered via CED. The current results are encouraging, and updated results reflecting current follow-up will be presented at the meeting.