Introduction/Background Dostarlimab+carboplatin-paclitaxel demonstrated PFS and OS benefits vs carboplatin-paclitaxel in patients with primary advanced or recurrent endometrial cancer (pA/rEC). Here, we report on the management of immune-related adverse events (irAEs) in the RUBY (NCT03981796) trial.

Methodology Patients with pA/rEC were randomized 1:1 to dostarlimab 500 mg, or placebo, plus carboplatin AUC 5 and paclitaxel 175 mg/m2 Q3W for 6 cycles, followed by dostarlimab 1000 mg, or placebo, Q6W for up to 3 years. AEs were assessed according to CTCAE v4.03. irAEs were defined as CTCAE grade ≥2 from a predefined list.

Results The safety population included 487 patients who received ≥1 dose of treatment (241 dostarlimab+carboplatin-paclitaxel; 246 placebo+carboplatin-paclitaxel). irAEs related to dostarlimab or placebo were reported by 38.2% in the dostarlimab+carboplatin-paclitaxel arm and 15.4% in the placebo+carboplatin-paclitaxel arm; grade ≥3 irAEs related to dostarlimab or placebo were reported by 12.4% and 3.3%, respectively (table 1). Only 7.9% and 3.7% of patients discontinued dostarlimab or placebo because of an irAE, respectively; there were no irAE-related deaths. Of those experiencing irAEs in the dostarlimab+carboplatin-paclitaxel arm, 63.5% were treated with steroids, immunosuppressants and/or thyroid therapy; 73.6% resolved (median resolution, 10.0 days). Of the 36.5% patients not receiving steroids, immunosuppressants and/or thyroid therapy, 80.0% resolved (median resolution, 8.0 days). Management and resolution frequency were similar in the placebo+carboplatin-paclitaxel arm (table 1).

Conclusion In the RUBY trial, most irAEs were mild and resolved. Few patients discontinued dostarlimab because of irAEs. The irAE profile observed in the dostarlimab+carboplatin-paclitaxel arm showed similar trends as that observed with dostarlimab monotherapy.

Disclosures Clinical trial registration: NCT03981796

Encore Statement: Data presented on behalf of the original authors with their permission. Previously presented at the International Gynecologic Cancer Society (IGCS) Congress 2023; 5–7 November 2023; Seoul, Korea. Final publication number: 248. Zoltán Novák et al. Reused with permission.

Disclosures: This study (NCT03981796) was sponsored by GSK, Waltham, MA, USA.

Third-party medical writing support: Writing and editorial support, funded and coordinated by GSK (Waltham, MA, USA), was provided by Shannon Morgan-Pelosi, PhD, and Jennifer Robertson, PhD, of Ashfield MedComms, an Inizio company.

COI: Dr Novak reports honoraria from Sofmedica, AstraZeneca, and MSD; support for attending meetings from Sofmedica and Preglem; participation on a Data Safety Monitoring Board or Advisory Board from AstraZeneca and Richter Gedeon; stock options from Richter Gedeon; and receipt of equipment, materials, drugs, medical writing, gifts or other services from AstraZeneca.

Dr Savarese reports institutional funding and provision of study materials from GSK and MSD; institutional funding and provision of study material for other clinical trials from GSK and MSD; honoraria from GSK and MSK; support for attending meetings and/or travel from GSK, MSK, and Pharmamar; and advisory board honoraria from Eisai and MSD.

Dr Kommoss reports grants from GSK; consulting fees from AstraZeneca, Eisai, GSK, MSD, and Roche; and participation on a Data Safety Monitoring Board or Advisory Board from AstraZeneca, GSK, MSD, and Roche.

Dr Cantuaria reports consulting fees from GSK; and she holds a patent on an anti-tumor lipid molecule that is early stage of development.

Dr Boere reports institutional research grant from GSK; and institutional advisory board meeting fees from AstraZeneca and GSK.

Dr Gilbert reports institutional grants from Alkermes, AstraZeneca, Clovis, Esperas, IMV, ImmunoGen Inc, Karyopharm, Merck Sharp & Dohme, Mersana, Novocure GmbH, OncoQuest Pharmaceuticals, Pfizer, Roche, and Tesaro; consulting fees from Merck; honoraria from Alkermes, AstraZeneca, Eisai, Eisai-Merck, and GSK.

Dr Holloway reports honoraria from GSK, AstraZeneca, Clovis, Eisai Inc, and Merck.

Dr E. Miller reports advisory board meeting fees from AstraZeneca, GSK, and Tempus; honoraria from OncLive and Opinions in Gyn Malignancies; and support for attending meetings from Opinions in Gyn Malignancies and OncLive.

Dr Powell reports consulting fees from GSK, Tesaro, Merck, Eisai, SeaGen, Clovis Oncology, and AstraZeneca.

Dr Mirza reports consulting fees from AstraZeneca, Biocad, GSK, Karyopharm, Merck, Roche, Zailab; speakers’ bureau fees from AstraZeneca and GSK; research funding (to institution) from Apexigen, AstraZeneca, Deciphera (trial chair), GSK, and Ultimovacs; and personal financial interest in Karyopharm (stocks/shares, member of Board of Directors).

Dr McCourt reports personal royalties <$200 annually from UpToDate; and personal honoraria of $200 from the Washington University OB/Gyn annual symposium.

Dr Diaz, Dr Fleming, Dr Gill, Dr Gold, Dr Herrstedt, Dr R. Miller, and Dr Pennington have nothing to disclose.

Dr Dabrowski and Dr Stevens are employees of GSK.