AnaptysBio, Inc. announced that GSK has received U.S. Food and Drug Administration (FDA) approval for JEMPERLI (dostarlimab-gxly) plus carboplatin and paclitaxel (chemotherapy) for the treatment of adult patients with mismatch repair deficient (dMMR)/microsatellite instability-high (MSI-H) primary advanced or recurrent endometrial cancer. The supplemental Biologics License Application (sBLA) supporting this new indication received Priority Review and was approved ahead of the Sept. 23, 2023 Prescription Drug User Fee Act action date.

This approval is supported by interim analysis results from Part 1 of GSK?s Phase 3 RUBY trial. The dual-primary endpoints in Part 1 are investigator-assessed progression-free survival (PFS) and overall survival (OS). The statistical analysis plan included pre-specified analyses of PFS in the dMMR/MSI-H and intent-to-treat (ITT) populations and OS in the overall population.

Part 1 of the RUBY trial continues to assess the dual-primary endpoint of OS in the ITT population. JEMPERLI was discovered by AnaptysBio and licensed to TESARO, Inc., now a part of the GSK group of companies, under a Collaboration and Exclusive License Agreement signed in March 2014. GSK is responsible for the ongoing development and commercialization of JEMPERLI.

AnaptysBio is entitled to receive milestones and tiered royalties of 8% for net sales of JEMPERLI below $1 billion and 12% up to 25% of net sales above $1 billion. In 2021, AnaptysBio monetized with Sagard Healthcare Royalty Partners certain commercial milestones and royalties for net sales of JEMPERLI below $1 billion up to a certain amount of receivables before such receivables revert back to AnaptysBio. The sBLA supporting this new indication was reviewed under the FDA Oncology Center of Excellence Project Orbis Framework, which allowed for concurrent submission to and review by US and other international regulatory authorities.

As part of Project Orbis, the application remains under review in Australia, Canada, Switzerland, Singapore and the United Kingdom. A marketing authorization application is also under review by the European Medicines Agency. RUBY is a two-part global, randomized, double-blind, multicenter Phase 3 trial of patients with primary advanced or recurrent endometrial cancer.

Part 1 is evaluating dostarlimab plus carboplatin-paclitaxel followed by dostarlimab versus carboplatin-paclitaxel plus placebo followed by placebo. Part 2 is evaluating dostarlimab plus carboplatin-paclitaxel followed by dostarlimab plus niraparib versus placebo plus carboplatin-paclitaxel followed by placebo. The dual-primary endpoints in Part 1 are investigator-assessed PFS based on the Response Evaluation Criteria in Solid Tumors v1.1 and OS.

The statistical analysis plan included pre-specified analyses of PFS in the dMMR/MSI-H and ITT populations and OS in the overall population. Pre-specified exploratory analyses of PFS in the mismatch repair proficient (MMRp)/microsatellite stable (MSS) population and OS in the dMMR/MSI-H populations were also performed. RUBY Part 1 included a broad population, including histologies often excluded from clinical trials and had approximately 10% of patients with carcinosarcoma and 20% with serous carcinoma.

In Part 2, the primary endpoint is investigator-assessed PFS. Secondary endpoints in Part 1 and Part 2 include PFS per blinded independent central review, overall response rate, duration of response, disease control rate, patient-reported outcomes, and safety and tolerability. JEMPERLI is a programmed death receptor-1 (PD-1)-blocking antibody that binds to the PD-1 receptor and blocks its interaction with the PD-1 ligands PD-L1 and PD-L2.

JEMPERLI is being investigated in registrational enabling studies, as monotherapy and as part of combination regimens, including in women with recurrent or primary advanced endometrial cancer, women with stage III or IV non-mucinous epithelial ovarian cancer, and in patients with other advanced solid tumors or metastatic cancers. In the U.S., JEMPERLI is indicated for adult patients with mismatch repair-deficient (dMMR) recurrent or advanced endometrial cancer, as determined by an FDA-approved test, that has progressed on or following a prior platinum-containing regimen in any setting and are not candidates for curative surgery or radiation, and in combination with carboplatin and paclitaxel for the treatment of adult patients with primary advanced or recurrent endometrial cancer that is dMMR, as determined by an FDA-approved test, or microsatellite instability-high (MSI-H). The sBLA supporting this new indication received Breakthrough Therapy designation from the FDA.

JEMPERLI is also indicated in the U.S. for patients with dMMR recurrent or advanced solid tumors, as determined by an FDA-approved test, that have progressed on or following prior treatment and who have no satisfactory alternative treatment options. The latter indication is approved in the U.S. under accelerated approval based on tumor response rate and durability of response. Continued approval for this indication in solid tumors may be contingent upon verification and description of clinical benefit in a confirmatory trial(s).