A Randomized Phase 0 Trial Of The Mitochondria! Inhibitor Me344 Or Placebo Added To The Antiangiogenic (Aa) Bevacizumab In Early Her2-Negative Breast Cancer (E-Hernebc).

3100 Background: We have shown that when Aas induce vascular normalization (VN), tumors escape upregulating mitochondrial metabolism. Mitochondrial inhibition with ME344 induced synergy with various Aas. We also found that VN could be traced by showing a 10% decrease in tumor FDG-PET SUV from day (d) 0 to d8 of Aa. We studied the activity of adding ME344 or placebo to Bev (Ki67 decrease) in E-HERNEBC in a phase 0 randomized trial. As a secondary objective we measured the activity of the combination in patients (Pts) showing VN according to FDG-PET. Methods: Untreated E-HERNEBC Pts with T > 1cm, any N, M0 underwent a baseline FDG-PET (d1) and received a single dose of Bev (15mg/kg) prior to randomization (1:1) to arm A (FDG-PET on d8 followed by ME344 10 mg/kg IV on d8, d15 and d21) or Arm B (FDG-PET on d8 followed by placebo on d8, d15 and d21). Tumors were biopsied on d0 and 28. A 40 Pts sample size was powered to detect a 30% relative difference between arms in digitally acquired Ki67 decrease from d0 to d28 (alpha 0.05, beta 0.2). Results: Arm A: 20 Pts; Arm B: 21 Pts. Baseline characteristics were in arm A vs B: age 58.4(41.5-75.3) vs 53.6(39-82.8); T1(30%)/T2(60%)/T3(10%) vs T1(52%)/T2(48%)/T3(0%); N0(80%)/N1(20%) vs N0(81%)/N1(19%); ER+(75%)/TNBC(25%) vs ER+(71.4%)/TNBC(28.6%); Ki67 31.6% (3.6%-70%) vs 25.2% (1.2% - 81.5%). PET-SUV decreased > 10% from d0 to d8 in 6/20 (arm A) and 6/21 (arm B) Pts. Two G3 adverse events (blood pressure) were reported (1/arm) and deemed related to Bev. Results of the primary endpoint: table. Conclusions: ME344 showed significant biologic activity, enhancing the effect in Ki67 decrease vs placebo when added to Bev in E-HERNEBC. The activity was greater in TNBC. A trend for greater activity in patients experiencing VN according to FDG-PET was observed. Clinical trial information: NCT02806817. [Table: see text]