Poster Presentation Clinical Oncology Society of Australia Annual Scientific Meeting 2023

Dostarlimab for Primary Advanced or Recurrent (A/R) Endometrial Cancer (EC): Outcomes by Blinded Independent Central Review (BICR) of the RUBY trial (#174)

Matthew A. Powell 1 , Sakari Hietanen 2 , Robert L. Coleman 3 , Bradley J. Monk 4 , Oleksandr Zub 5 , David M. O’Malley 6 , Lucy Gilbert 7 , Iwona Podzielinski 8 , Roberto Angioli 9 , Dana Chase 10 , Ashish Banerjee 11 , Dirk Bauerschlag 12 , Destin Black 13 , Annemarie Thijs 14 , Sudarshan Sharma 15 , Michael A. Gold 16 , Kari L. Ring 17 , Zangdong He 18 , Shadi Stevens 19 , Brian Slomovitz 20 , Mansoor R. Mirza 21
  1. National Cancer Institute-sponsored NRG Oncology; Washington University School of Medicine, St. Louis, Missouri, USA
  2. Turku University Hospital and FICAN West, Turku, Finland
  3. US Oncology Research, The Woodlands, Texas, USA
  4. HonorHealth Research Institute, University of Arizona College of Medicine, Phoenix; Creighton University School of Medicine, Phoenix, Arizona, USA
  5. Chernihiv Regional Oncology Hospital, Chernihiv, Ukraine
  6. Ohio State University; James Comprehensive Cancer Center, Columbus, Ohio, USA
  7. McGill University Health Centre, Montreal, Quebec, Canada
  8. Parkview Health, Fort Wayne, Indiana, USA
  9. University di Roma – Campus Biomedico, Rome, Italy
  10. David Geffen School of Medicine at UCLA, Los Angeles, California, USA
  11. GSK, Point Cook, VICTORIA, Australia
  12. University Hospital Schleswig-Holstein, Campus Kiel, Kiel, Germany
  13. LSU Health Shreveport, and Willis-Knighton Physician Network, Shreveport, Louisiana, USA
  14. Catharina Hospital, Eindhoven, the Netherlands
  15. AMITA Adventist Hinsdale Hospital, Hinsdale, Illinois, USA
  16. Oklahoma Cancer Specialists and Research Institute, Tulsa, Oklahoma, USA
  17. University of Virginia Health System; Emily Couric Clinical Cancer Center, Charlottesville, Virginia, USA
  18. GSK, Collegeville, Pennsylvania, USA
  19. GSK, London, UK
  20. Mount Sinai Medical Center; Florida International University, Miami Beach, Florida, USA
  21. Copenhagen University Hospital; Nordic Society of Gynaecologic Oncology-Clinical Trial Unit, Copenhagen, Denmark

Aims: The RUBY trial evaluated the efficacy and safety of dostarlimab+standard of care (SOC) carboplatin paclitaxel (CP) versus CP alone in A/R EC. The primary endpoint of PFS by investigator assessment (INV; RECIST v1.1) was significantly longer with dostarlimab+CP than placebo+CP in the mismatch repair deficient/microsatellite instability-high (dMMR/MSI-H) and overall populations. Here we present the secondary efficacy endpoints by BICR.

Methods: RUBY is a phase 3, global, randomized, double-blind, multicenter, placebo-controlled study (Funded by Tesaro: NCT03981796, GSK: 213361). Patients with primary advanced stage III or IV or first recurrent EC were randomized (1:1) to receive dostarlimab 500 mg or placebo, plus carboplatin AUC 5 and paclitaxel 175 mg/m2 Q3W (6 cycles), followed by dostarlimab 1000 mg or placebo, monotherapy Q6W for up to 3 years. Secondary endpoints by BICR assessment (RECIST v1.1) were PFS, ORR, DOR, and DCR in the dMMR/MSI-H and overall populations.

Results: Of the 494 patients randomized (dostarlimab+CP: 245; placebo+CP: 249), 47.8% had recurrent disease, 18.6% and 33.6% had primary stage III and IV disease, respectively. PFS by BICR was longer with dostarlimab+CP than placebo+CP in the dMMR/MSI-H (HR 0.29; 95% CI 0.158–0.543) and overall populations (HR 0.66; 95% CI 0.517–0.853). ORR and DCR by BICR were similar between the two arms in the two populations. mDOR by BICR was NE (95% CI 13.1–NE) with dostarlimab+CP and 6.9 (5.5–10.1) months with placebo+CP in the dMMR/MSI-H population; 12.9 (8.2–NE) with dostarlimab+CP and 6.7 (5.7–8.3) months with placebo+CP in the overall population. Safety was previously reported.

Conclusions: Dostarlimab+CP showed clinically meaningful improvement in BICR-assessed PFS versus CP alone, in the two populations. HRs for BICR- - and INV-assessed PFS were consistent; benefits seen in all BICR-assessed endpoints were consistent with INV. Dostarlimab+CP represents a new SOC for patients with primary A/R EC.

Originally presented at 2023 ASCO Annual Meeting (10.1200/JCO.2023.41.16_suppl.5503). Permission granted by Wolters Kluwer.