Abstract CT161: A phase II basket trial of dual anti-CTLA-4 and anti-PD-1 blockade in rare tumors (DART) SWOG S1609: the non-epithelial ovarian tumor cohort
Authors: Chae Young Kwang , Othus Megan , Patel Sandip Pravin , Wilkinson Kelly J. , Whitman-Purves Emily M. , Lea Jayanthi , Schallenkamp John M. , Adra Nabil , Appleman Leonard J. , Alden Mitchell , Pepin Jessica Thomes , Ellerton John A. , Poklepovic Andrew , Walter Adam , Rampurwala Murtuza M. , Robinson William R. , Chung Liam Il-Young , McLeod Christine M. , Chen Helen X. , Sharon Elad , Streicher Howard , Ryan Christopher W. , Blanke Charles D. , Kurzrock Razelle 
Published: April 2023

Background: Dual checkpoint inhibition with Anti-PD-1 and anti-CTLA4 checkpoint inhibitors have proven to be effective in several malignancies but their potential role in numerous rare solid cancers is yet to be established. This study presents the first results of ipilimumab and nivolumab in the non-epithelial ovarian tumor cohort (#13) 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 intravenously every 6 weeks) plus nivolumab (240mg intravenously every 2 weeks). This cohort included several histologies grouped for statistical analysis. The primary endpoint was objective response rate (ORR) (RECIST v1.1) (confirmed complete (CR) and partial responses (PR)); progression-free survival (PFS), overall survival (OS), stable disease (SD) &gt;6 months, and toxicity are secondary endpoints.

Results: Seventeen evaluable patients (median age, 64 years) were analyzed. The subtypes of non-epithelial ovarian cancer were: granulosa cell (47%, n=8), carcinosarcoma or malignant mixed Mullerian tumor (MMMT; 35%, n=6), one each for Wolffian duct, yolk sac, and Sertoli-Leydig cell. There were 2 responses in the 8 patients with granulosa cell (ORR of 25% in the granulosa cell tumors): 1CR (79% regression [due to lymph node &lt; 1.0cm], 59 month PFS, juvenile type) and 1 PR (79% regression, 51+ month PFS, adult type). 6/8 patients remain alive (PFS 52-1774 days). In contrast, carcinosarcomas showed no responses. One patient with Sertoli-Leydig cell tumor had a 22% response and 341 day PFS. Overall ORR was 12% (2/17), clinical benefit rate (CBR; no progression &gt; 6months) of 29.4%. The median PFS was 3.5 months, median OS was 42.5 months. The most common adverse events were fatigue (52.9%, n=9) and hypothyroidism (35.3%, n=6). Grade 3-4 adverse events occurred in 47.1% of patients (n=8). There were 3 adverse events (17.6%) that led to discontinuation, of which 2 (11.8%) were grade 3-4. There were no grade 5 adverse events.

Conclusion: Ipilimumab plus nivolumab in non-epithelial ovarian cancer resulted in an ORR of 12% (with 2 of 8 patients with granulosa ovarian tumors showing a durable CR and PR [both, &gt;4 years)) and CBR of 29.4%, with durable responses seen. In contrast there were no responses in the carcinosarcoma group. One patient with Sertoli Leydig cell tumor suggested a possible benefit. Correlative studies to determine response and resistance markers are ongoing. Expanded prospective studies in granulosa tumor but not carcinosarcoma are warranted.

Citation Format: Young Kwang Chae, Megan Othus, Sandip Pravin Patel, Kelly J. Wilkinson, Emily M. Whitman-Purves, Jayanthi Lea, John M. Schallenkamp, Nabil Adra, Leonard J. Appleman, Mitchell Alden, Jessica Thomes Pepin, John A. Ellerton, Andrew Poklepovic, Adam Walter, Murtuza M. Rampurwala, William R. Robinson, Liam Il-Young Chung, Christine M. McLeod, Helen X. Chen, Elad Sharon, Howard Streicher, Christopher W. Ryan, Charles D. Blanke, Razelle Kurzrock. A phase II basket trial of dual anti-CTLA-4 and anti-PD-1 blockade in rare tumors (DART) SWOG S1609: the non-epithelial ovarian tumor cohort [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 CT161.