Abstract CT162: A phase II basket trial of dual anti-CTLA-4 and anti-PD-1 blockade in rare tumors (DART) SWOG S1609: the clear cell ovarian, endometrial, cervical cancer cohorts
Authors: Chae Young Kwang , Ryan Christopher W. , Aung Naing , Robinson William R. , Othus Megan , Sharon Elad , O'Malley David M. , Backes Floortje J. , Blanke Charles D. , Eskander Ramez N. , Kurzrock Razelle 
Published: April 2023

Background: Dual checkpoint inhibition with anti-PD-1 and anti-CTLA4 checkpoint inhibitors have proven to be efficacious in numerous malignancies. This study presents the first results of ipilimumab and nivolumab in the clear cell gynecologic cancer cohorts of the SWOG S1609 Dual Anti-CTLA-4 & Anti-PD-1 blockade in Rare Tumors (DART) trial.

Methods: DART is a prospective, open-label, multicenter/multi-cohort phase 2 clinical trial of ipilimumab (1mg/kg IV every 6wk) plus nivolumab (240mg IV every 2wk). The primary endpoint was objective response rate (ORR) (RECIST v1.1) (confirmed CR and PR); progression-free survival (PFS), overall survival (OS), stable disease (SD) &gt;6 months, and toxicity are secondary endpoints.

Results: Evaluable patients were as follows: clear cell ovarian cancer (N=19); clear cell endometrial cancer (N=8); clear cell cervical (N=5) (median ages, 53, 66, and 59 years; cohorts 46, 45, and 42, respectively) In the clear cell ovarian cancer cohort, ORR was 21.1% [CR, 15.8%, n=3; PR, 5.3%, n=1]; clinical benefit rate (CBR) (includes stable disease ≥6 months) was 31.6% (6/19 patients). Among three patients with confirmed CR, two patients showed 100% regression (with ongoing response at 36+ months and 37+ months respectively), and the other patient showed 67% regression (due to lymph node &lt; 1.0cm), but eventually progressed after 722 days. One confirmed PR patient achieved 75% regression (ongoing response at 53+ months). Of note, three patients achieved unconfirmed PR; one showed 34% regression (5 months); another, 38% (51.5+ months); and another, 58% regression (5 months). The ORR when including unconfirmed PR is 36.8% (7/19). Median PFS was 3.7 months (95% confidence interval (CI); 1.7-∞). Median OS was 21.7 months (6.4-∞). In the clear cell endometrial cancer cohort, ORR was 0%; CBR, 25% (2/8 patients). Of note, one patient achieved unconfirmed PR with 69% regression (4 months). The ORR when including unconfirmed PR is 12.5% (1/8). Median PFS was 2.0 months (95% confidence interval; 1.8-na). Median OS was 4.3 months (4.2-na). In the clear cell cervical cancer cohort, ORR was 0%; CBR, 20.0% (1/5 patients). Median PFS was 2.2 months (95% CI; 1.9-na). Median OS was 23.6 months (95% CI; 15.3-na). The most common adverse events, in the three cohorts combined, were nausea (37.5%, n=12), fatigue (34.4%, n=11), anorexia (31.2%, n=10), hypothyroidism (31.2%, n=10), and pruritus (28.1%, n=9). Grade 3-4 adverse events were reported in 17 cases (53.1%) with no grade 5 adverse events.

Conclusion: Ipilimumab plus nivolumab in 19 clear cell ovarian cancer patients resulted in an ORR of 21.1% and CBR of 31.6%, with two durable CRs ongoing at 3+ years; CBR was 25% and 20%, respectively, in clear cell endometrial and cervical cohorts, with no objective responses, albeit with only 8 and 5 patients per cohort. Correlative studies to determine response/resistance markers are ongoing. Further prospective studies in rare gynecologic malignancies are warranted.

Citation Format: Young Kwang Chae, Christopher W. Ryan, Naing Aung, William R. Robinson, Megan Othus, Elad Sharon, David M. O'Malley, Floortje J. Backes, Charles D. Blanke, Ramez N. Eskander, Razelle Kurzrock. A phase II basket trial of dual anti-CTLA-4 and anti-PD-1 blockade in rare tumors (DART) SWOG S1609: the clear cell ovarian, endometrial, cervical cancer cohorts [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr CT162.