Pharmaceutical company GSK announced Monday that its cancer-fighting drug Jemperli has successfully achieved the main objective of a mid-stage clinical trial, demonstrating a clinically meaningful rate of patients showing no detectable traces of cancer for at least one year following treatment for a particular form of locally advanced rectal cancer.
The drug, known scientifically as dostarlimab, is being evaluated against rectal cancer tumors that have a specific genetic flaw — they are unable to properly repair DNA damage. According to GSK, this tumor subtype accounts for roughly 5% to 10% of the approximately 730,000 rectal cancer cases diagnosed globally each year.
The current standard treatment for this type of cancer typically involves a combination of chemotherapy, radiation therapy, and surgery. These treatments can result in serious long-term consequences for patients, including permanent colostomy bag use and infertility.
Because these tumors accumulate mutations due to their inability to fix DNA damage, they tend to respond strongly to immunotherapy treatments like Jemperli. The interim results from the Phase II AZUR-1 trial also indicated that the drug’s safety and tolerability were consistent with what had been observed in earlier studies involving solid tumors.
Jemperli is already approved for use in the United States and United Kingdom for certain subtypes of endometrial cancer. The drug brought in $1.1 billion in sales in 2025, and GSK considers it a key component of its long-term goal of surpassing £40 billion (approximately $53.52 billion) in annual sales by 2031.
The U.S. Food and Drug Administration has granted Jemperli both Breakthrough Therapy and Fast Track designations. GSK said it intends to present the new trial data to regulatory agencies around the world for their review.
