548P - Progression-free survival (PFS) and overall survival (OS) in advanced/recurrent (AR) mismatch repair deficient/microsatellite instability–high or proficient/stable (dMMR/MSI-H or MMRp/MSS) endometrial cancer (EC) treated with dostarlimab in the GARNET study

Background

Dostarlimab is a programmed death 1 (PD-1) inhibitor approved in the EU as a monotherapy in patients (pts) with dMMR/MSI-H AR EC that has progressed on or after platinum-based chemotherapy; and in the US as a monotherapy in pts with dMMR AR EC that has progressed on or after platinum-based chemotherapy or dMMR solid tumors that have progressed on or after prior treatment, with no satisfactory alternative treatment options. We report on PFS and OS in 2 expansion cohorts of the GARNET trial that enrolled pts with EC.

Methods

GARNET is a multicenter, open-label, single-arm phase 1 study. Pts were assigned to cohort A1 (dMMR/MSI-H EC) or A2 (MMRp/MSS EC) based on local immunohistochemistry assessment. Pts received 500 mg of dostarlimab IV every 3 weeks for 4 cycles, then 1000 mg every 6 weeks until disease progression, discontinuation, or withdrawal. PFS and OS are secondary efficacy endpoints.

Results

153 pts with dMMR/MSI-H and 161 pts with MMRp/MSS EC were enrolled and treated. The efficacy-evaluable population included 143 pts with dMMR/MSI-H EC and 156 pts with MMRp/MSS EC with measurable disease at baseline and ≥6 mo of follow-up. Median follow-up was 27.6 mo for dMMR/MSI-H and 33.0 mo for MMRp/MSS EC (Table). For pts with dMMR/MSI-H EC, median PFS (mPFS) was 6.0 mo, with 3-year estimated PFS rate of 40.1%. With 37.3% of pts experiencing an event, mOS was not reached; estimated 3-year OS was >50%. For pts with MMRp/MSS EC, mPFS was 2.7 mo. mOS was 16.9 mo with 68.9% of pts experiencing an event. Safety has been previously reported. Table: 548P

Datacut: 1 Nov 2021. NR, not reached

Conclusions

Dostarlimab demonstrated durable antitumor activity in dMMR/MSI-H and MMRp/MSS AR EC. dMMR/MSI-H was associated with longer PFS and OS than MMRp/MSS as expected.

Clinical trial identification

NCT02715284.

Editorial acknowledgement

Writing and editorial support, funded by GlaxoSmithKline (Waltham, MA, USA) and coordinated by Heather Ostendorff-Bach, PhD, of GlaxoSmithKline, was provided by Shannon Morgan-Pelosi, PhD, and Jennifer Robertson, PhD, of Ashfield MedComms, an Ashfield Health company (Middletown, CT, USA).

Legal entity responsible for the study

GlaxoSmithKline.

Funding

GlaxoSmithKline.

Disclosure

A.V. Tinker: Financial Interests, Institutional, Sponsor/Funding: AstraZeneca; Financial Interests, Personal, Other: AstraZeneca, Eisai, GlaxoSmithKline. B. Pothuri: Financial Interests, Institutional, Funding: AstraZeneca, Celsion, Clovis Oncology, Eisai, Genentech/Roche, Karyopharm, Merck, Mersana, Takeda Pharmaceuticals, Tesaro/GSK; Financial Interests, Personal, Other: Arquer Diagnostics, AstraZeneca, Atossa, Clovis Oncology, Deciphera, Elevar Therapeutics, Imab, Mersana, Tesaro/GSK, Merck, Sutro Biopharma, Tora, GOG Partners; Financial Interests, Personal, Advisory Board: Arquer Diagnostics, AstraZeneca, Atossa, Deciphera, Clovis Oncology, Eisai, Elevar Therapeutics, Imab, Merck, Mersana, Sutro Biopharma, Tesaro/GSK, Toray; Financial Interests, Personal, Leadership Role: GOG Partners, NYOB Society Secretary, SGO Clinical Practice Committee Chair, SGO COVID-19 Taskforce Co-Chair. L. Gilbert: Financial Interests, Institutional, Funding: Alkermes, AstraZeneca, Clovis, Esperas, IMV, ImmunoGen Inc, Karyopharm, Merck Sharp & Dohme, Mersana, Novocure GmbH, OncoQuest Pharmaceuticals, Pfizer, Roche, Tesaro; Financial Interests, Personal, Other: Merck, Alkermes, AstraZeneca, Eisai, Eisai-Merck, GlaxoSmithKline. R. Sabatier: Financial Interests, Institutional, Funding: AstraZeneca, Eisai; Financial Interests, Personal, Other: AstraZeneca, GlaxoSmithKline, Novartis, Pfizer, Roche; Non-Financial Interests, Personal, Other: AstraZeneca, Bristol Myers Squibb, GlaxoSmithKline, Pfizer, Roche. J. Brown: Financial Interests, Personal, Advisory Role: Caris, Clovis, Eisai, GlaxoSmithKline; Financial Interests, Personal, Funding: GlaxoSmithKline, Genentech. S. Ghamande: Financial Interests, Personal, Advisory Role: Seattle Genetics; Financial Interests, Personal, Speaker’s Bureau: GlaxoSmithKline; Financial Interests, Institutional, Funding: Abbvie, Advaxis, Bristol Myers Squibb, Clovis, Genentech, GlaxoSmithKline, Merck, Roche, Seattle Genetics, Takeda. C. Mathews: Financial Interests, Institutional, Research Grant: Astellas, AstraZeneca, Deciphera, Moderna, GSK, Regeneron, Seattle Genetics; Financial Interests, Personal, Advisory Board: IMAB biopharma. D. O'Malley: Financial Interests, Personal, Advisory Board: AstraZeneca, Tesaro/GSK, Immunogen, Ambry, Janssen/J&J, Abbvie, Regeneron, Amgen, Novocure, Genentech/Roche, GOGFoundation, Iovance, Eisai, Agenus, Merck, SeaGen, Novartis, Mersana, Clovis, Elevar, Takeda, Toray, INXMED, SDP Oncology (BBI), Arquer Diagnostics, Roche Diagnostics MSA, Sorrento, Corcept Therapeutics, Celsion Corp; Financial Interests, Personal, Funding: AstraZeneca, Tesaro/GSK, Immunogen, Janssen/J&J, Abbvie, Regeneron, Amgen, Novocure, Genentech/Roche, VentiRx, Array Biopharma, EMD Serono, Ergomed, Ajinomoto Inc, Ludwig Cancer Research, Stemcentrx, Inc, Cerulean Pharma, GOGFoundation, Bristol-Myers Squibb Co, Serono Inc, TRACON Pharmaceuticals, Yale University, New Mexico Cancer Care Alliance, INC Research, Inc, inVentiv Health Clinical, Iovance, PRA Intl, Eisai, Agenus, Merck, GenMab, SeaGen, Mersana, Clovis, SDP Oncology (BBI); Financial Interests, Personal, Other: Myriad Genetics, Tarveda. V. Boni: Financial Interests, Personal, Advisory Board: OncoArt, Guidepoint Global; Financial Interests, Personal, Speaker’s Bureau: Solti; Financial Interests, Personal, Other: START, Loxo, IDEAYA Biosciences; Financial Interests, Institutional, Research Grant: Sanofi, Seattle Genetics, Loxo, Novartis, CytomX Therapeutics, Pumo Biotechnology, Kura Oncology, GlaxoSmithKline, Roche/Genentech, Bristol-Myers Squibb, Menarini, Synthon, Janssen Oncology, Merck, Lilly, Merus, Pfizer, Bayer, Incyte, Merus, Zenith Epigenetics, Genmab, AstraZeneca, Seattle Genetics, Adaptimmune, Alkermes, Amgen, Array BioPharma, Boehringer Ingelheim, BioNTech AG, Boston Biomedical. A. Gravina: Financial Interests, Personal, Other: Gentili, Pfizer. S. Banerjee: Financial Interests, Personal, Advisory Board: Amgen, Genmab, Immunogen, Mersana, Merck Sereno, MSD, Roche, Tesaro, AstraZeneca, GSK, Oncxerna; Financial Interests, Personal, Invited Speaker: Clovis, Pfizer, Tesaro, AstraZeneca, GSK, Takeda, Amgen, Medscape, Research to Practice, Peerview; Financial Interests, Personal, Stocks/Shares: PerciHealth; Financial Interests, Institutional, Research Grant: AstraZeneca, GSK, Tesaro; Non-Financial Interests, Principal Investigator, Phase II clinical trial Global lead, ENGOTov60/GOG3052/RAMP201: Verastem; Non-Financial Interests, Principal Investigator, ENGOT-GYN1/ATARI phase II international trial (academic sponsored): Astrazeneca; Non-Financial Interests, Advisory Role: Epsilogen; Non-Financial Interests, Other, Member of membership committee: ESGO; Non-Financial Interests, Advisory Role, Medical advisor to UK ovarian cancer charity: Ovacome Charity; Non-Financial Interests, Other, Received research funding from UK based charity I have provided medical advice (non-remunerated): Lady GardenFoundation Charity. R. Miller: Financial Interests, Personal, Other: AZD, Clovis Oncology, Ellipses, GlaxoSmithKline, MSD, Shionogi, AZD, GlaxoSmithKline; Financial Interests, Personal, Speaker’s Bureau: AZD, Clovis Oncology, GSK, Roche. J. Pikiel: Financial Interests, Personal, Other: Amgen, Clovis Oncology, GlaxoSmithKline, Incyte, Novartis, Odonate Therapeutics, Pfizer, Regeneron, Roche. M.R. Mirza: Financial Interests, Personal, Advisory Board: AstraZeneca, Biocad, GSK, Karyopharm, Merck, Roche, Zailab; Financial Interests, Personal, Invited Speaker: AstraZeneca, GSK, Karyopharm; Financial Interests, Personal, Stocks/Shares: Karyopharm; Financial Interests, Institutional, Research Grant: GSK, AstraZeneca, ultimovacs, Apexigen; Financial Interests, Institutional, Invited Speaker: Deciphera; Non-Financial Interests, Advisory Role: Ultimovacs, Apexigen. T. Duan: Financial Interests, Personal, Full or part-time Employment: GlaxoSmithKline. G. Antony: Financial Interests, Personal, Full or part-time Employment: GlaxoSmithKline. S. Zildjian: Financial Interests, Personal, Full or part-time Employment: GlaxoSmithKline. E. Zografos: Financial Interests, Personal, Full or part-time Employment: GlaxoSmithKline. J. Veneris: Financial Interests, Personal, Full or part-time Employment: GlaxoSmithKline. A. Oaknin: Financial Interests, Personal, Advisory Board: AstraZeneca, Clovis Oncology, Deciphera Pharmaceuticals, Genmab, GSK, Immunogen, Mersana Therapeutics, PharmaMar, Roche, Tesaro, Merck Sharps & Dohme de España, SA, Agenus, Sutro, Corcept Therapeutics, EMD Serono, Novocure, prIME Oncology, Sattucklabs, Itheos, Eisai, F. Hoffmann-La Roche,; Financial Interests, Personal, Other, Travel and accomodation: AstraZeneca, PharmaMar, Roche; Financial Interests, Institutional, Funding: Abbvie Deutschland, Advaxis Inc., Aeterna Zentaris, Amgen, Aprea Therapeutics AB, Clovis Oncology Inc, EISAI limited LTD, F. Hoffmann –La Roche LTD, Regeneron Pharmaceuticals, Immunogen Inc, Merck, Sharp & Dohme de España SA, Millennium Pharmaceuticals Inc, PharmaMar SA, Tesaro Inc., Bristol Myers Squibb; Non-Financial Interests, Leadership Role, Executive Board member as a Co-Chair: GEICO; Non-Financial Interests, Leadership Role, Phase II Committee and Cervix Cancer Committee Representative on behalf of GEICO: GCIG; Non-Financial Interests, Officer, Chair of Gynaecological Track ESMO 2019. Scientific Track Member Gynaecological Cancers ESMO 2018, ESMO 2020, ESMO 2022. Member of Gynaecological Cancers Faculty and Subject Editor Gyn ESMO Guidelines.: ESMO; Non-Financial Interests, Member: ESMO, ASCO, GCIG, SEOM, GOG.