The agency approved the drug in April for dMMR recurrent or advanced endometrial cancer that has progressed during or following treatment with a platinum-containing regimen. The labeling notes that dMMR status for both indications must be determined through an FDA-approved test.
The accelerated approval “may be contingent upon verification and description of clinical benefit in a confirmatory” trial, the labeling says.
The new indication was based results from 209 patients in the GARNET trial. In that trial, the objective response rate was 41.6% across dMMR endometrial and other solid tumors. The complete response rate was 9.1%.
The median duration of response was 34.7 months. For 95% of patients who responded to treatment, the duration of response was 6 months or longer, according to a press release from the maker, GlaxoSmithKline.
In mismatch repair deficiency, tumors contain abnormalities that affect the proper repair of DNA. Prevalence in the United States is estimated to be 14%. The deficiency is particularly common in endometrial, colorectal, and other gastrointestinal cancers, the company said.
The drug was administered in GARNET as a 500-mg intravenous infusion every 3 weeks in four doses, followed by 1,000 mg once every 6 weeks until disease progression or unacceptable toxicity.
Common adverse events included fatigue/asthenia (42%), anemia (30%), diarrhea (25%), and nausea (22%). The most common grade 3 or 4 adverse reactions included anemia, fatigue/asthenia, increased transaminases, sepsis, and acute kidney injury.
As with other PD-1/PD-L1 blockers, there’s also a possibility of severe and fatal immune-mediated adverse reactions in any organ system either during or after treatment, including immune-mediated pneumonitis, colitis, and hepatitis.
GlaxoSmithKline said it’s studying dostarlimab in earlier lines of treatment for endometrial cancer and in combination with other agents for other advanced/metastatic cancers.
A version of this article first appeared on Medscape.com.