NEW YORK – GlaxoSmithKline yesterday announced that new data from its ongoing Phase I/II GARNET study evaluating the anti-PD-1 monoclonal antibody dostarlimab showed the drug provided clinically meaningful results among women with recurrent or advanced mismatch repair-deficient (dMMR) endometrial cancer who had disease progression during or after a platinum-based treatment regimen.
The data were accepted as a late-breaking abstract and presented as part of the Society of Gynecologic Oncology's 2020 virtual congress.
Out of 71 patients with dMMR endometrial cancer who had measurable disease at baseline and at least six months of follow-up by the data cutoff, 42 percent demonstrated objective response, 58 percent demonstrated disease control, 13 percent had a complete response, and 30 percent had a partial response. The median duration of response — which was the study's second primary endpoint, along with objective response rate — had not been reached by the time of the data cutoff.
The data are based on patients treated with 500 mg of dostarlimab once every three weeks for four doses, followed by 1,000 mg of dostarlimab once every six weeks until disease progression. The interim analysis also demonstrated that dostarlimab was well-tolerated, and that its adverse events reflected that of other anti-PD-1 therapies. Only 2 percent of the 104 patients evaluated in the safety population of the study had to discontinue treatment with dostarlimab, and there were no deaths associated with the treatment.
"There are limited treatment options for women with advanced or recurrent endometrial cancer, and prognosis of these patients is poor," GARNET's primary investigator Ana Oaknin of Vall d'Hebron Institute of Oncology in Barcelona, said in a statement. "The results observed in the GARNET trial indicate the potential of dostarlimab to offer a new treatment option for women with this challenging disease."
GSK has previously shared that it hopes to develop dostarlimab in a tissue-agnostic fashion. This would potentially position the drug as a competitor to pembrolizumab (Merck's Keytruda). In addition to the GARNET study, GSK is also investigating dostarlimab in the Phase III RUBY study for women with recurrent or primary advanced endometrial cancer in combination with chemotherapy, as well for patients with advanced solid tumors in combination with other therapeutic agents.