Checkpoint inhibitors assessment in oropharynx cancer (CIAO): Safety and interim results

6008 Background: Anti-PD-1/PD-L1 are active in metastatic oropharynx squamous cell carcinoma (OPC). Durvalumab (durva) and tremelimumab (tremi) target respectively PD-L1 and CTLA-4, which in combination may be synergistic. Here we report the safety and interim results of durva vs. durva+tremi prior to surgery in a window of opportunity trial in OPC. Methods: Pts were randomized 1:1 to durva 1500 mg or durva 1500 mg + tremi 75 mg IV Q4W x 2 cycles. The primary objective was to quantify pre- and post-treatment differences in CD8+ tumor infiltrating lymphocytes for the two arms. Secondary objectives included safety, toxicity, ORR by RECIST, fraction of patients undergoing surgery at 8 wks, and percentage viable tumor cells in the surgical specimen. Serial pre- and post-treatment blood and tumor specimens were collected for ongoing correlative analyses. Results: 28 pts enrolled: median age 64y, 27 (96%) male, 19 (68%) newly diagnosed, most (63%) at stage IVA (AJCC 7th Ed), 9 (32%) had locoregional recurrence, 24 (86%) p16 positive, and 22 (79%) had ≤ 10 PPY smoking history. Median follow-up was 7.6 months. The most common AEs were fatigue (36%), leukopenia/lymphopenia (25%), transaminitis (25%), and rash (21%). Grade 3 AEs occurred in 4 (14%) pts: 2 elevated lipase, 1 diarrhea, and 1 hepatitis, all were manageable. There were no grade >3 AEs. ORR was 43%: 50% had SD (including 29% tumor shrinkage in 1 pt). Treatment effect in the surgical specimen was observed in 19 (79%) of 24 evaluable pts; 2 pts had major pathologic response (≤ 10% viable tumor) at the primary site. Efficacy was equivalent in both arms. The 2 pts with PD and 1 pt with SD were switched to chemotherapy after durva +/- tremi before resection; interestingly, each achieved a pCR in the primary. Most pts (57%) didn’t receive radiotherapy after surgery. There was a statistically significant association between ORR and treatment effect (p=0.014). The median percentage of viable tumor in the primary was 37.5% in pts with PR, and 82.5% in SD (p=0.003). Conclusions: Durva +/- tremi prior to surgery was well tolerated in OPC pts. Activity is encouraging with treatment effect seen in 79% of pts. The primary endpoint and complete efficacy data will be presented. Clinical trial information: NCT03144778.