By Tristan Manalac

The FDA has approved GSK’s Jemperli (dostarlimab-gxly) for the treatment of primary advanced or recurrent endometrial cancer, the company announced Monday.
The label expansion covers a combination regimen of Jemperli, carboplatin and paclitaxel, followed by Jemperli as a single agent. Monday’s approval also only applies to patients who are mismatch repair deficient (dMMR), as confirmed by an FDA-approved test, or who have high microsatellite instability (MSI-H).
Jemperli is the first immuno-oncology treatment and PD-1 inhibitor to be authorized for frontline use in this patient population, according to GSK.
The expanded approval “redefines the treatment landscape for patients with dMMR/MSI-H primary advanced or recurrent endometrial cancer,” for whom chemotherapy alone has been the standard of care, though many patients still see disease progression, Hesham Abdullah, GSK’s senior vice president and global head of oncology development, said in a statement.
Jemperli is an anti-PD-1 antibody that was first approved in April 2021 for recurrent or advanced dMMR endometrial carcinoma. The treatment works by disrupting the interaction between the PD-1 receptor with its corresponding ligands, thereby enabling the immune system to detect and attack the tumor.
In June 2023, the FDA accepted GSK’s supplemental Biologics License Application seeking to push Jemperli to the frontline setting. The regulator gave GSK Priority Review and set a target action date of September 23, making Monday’s approval nearly two months ahead of schedule.
The FDA’s speedy decision was backed by an interim analysis of data from the first part of the Phase III RUBY trial, which showed that over a median follow-up of at least 25 months, the Jemperli regimen significantly improved progression-free survival (PFS). Patients with dMMR/MSI-H disease treated with the treatment combination also saw a 71% drop in the risk of disease progression or death.
Monday’s regulatory win puts Jemperli slightly ahead of Keytruda, which still remains approved only for later lines of treatment in endometrial cancer.
In March 2023, however, data from the Phase III NRG-GY018 study suggested that Merck’s blockbuster PD-1 blocker still keeps its edge over Jemperli. Keytruda elicited a 70% improvement in PFS, but it achieved this effect over only 12 months of follow-up.
In the subset of patients who were MMR-proficient, Jemperli reduced the risk of disease progression or death by 24% in 24 months, while Keytruda achieved a 46% reduction in 12 months.
Neither RUBY nor NRG-GY018 are head-to-head trials, and important differences in their respective methodologies make cross-study comparisons inconclusive.