Dostarlimab (Jemperli) FDA Approval for Rectal Cancer: Trials, Uses, and What It Means

GSK's Jemperli is the first immunotherapy approved for dMMR rectal cancer, offering some patients a path around surgery, radiation, and chemo.

On October 19, 2026, the U.S. Food and Drug Administration granted accelerated approval to dostarlimab, sold by GSK as Jemperli, for a specific form of rectal cancer. It is the first immunotherapy cleared to treat this disease before surgery, and for some patients it can replace surgery, radiation, and chemotherapy altogether.

What Is Dostarlimab?

Dostarlimab is a PD-1 inhibitor, a type of immunotherapy. Cancer cells can flip a molecular “off switch” called PD-1 to hide from the immune system; the drug blocks that switch so the body’s T cells recognize the tumor and attack it. It belongs to the same class as Merck’s Keytruda and Bristol Myers Squibb’s Opdivo.

The drug is not new. The FDA first approved it in 2021 for a form of endometrial cancer, and it later picked up a broader use in certain advanced solid tumors. What ties those uses together is a biomarker. Dostarlimab works in tumors that are mismatch repair deficient (dMMR) or microsatellite instability-high (MSI-H), meaning their DNA-repair machinery is broken. These tumors carry so many mutations that the immune system, once unleashed, sees them clearly. Only about 5-10% of rectal cancers fall into this category.

What the FDA Approved

The approval covers adults with previously untreated, stage II or III dMMR/MSI-H locally advanced rectal cancer, confirmed by an FDA-authorized test. Patients take dostarlimab on its own, 500 mg by IV infusion every three weeks for nine cycles, roughly six months of treatment.

The standard approach to this cancer is hard on the body. Standard care means chemotherapy, radiation, and an operation, and the surgery alone can permanently affect bowel and bladder control and sexual function, sometimes leaving a patient with a colostomy bag. The new indication gives doctors a drug-only option that, when it works, spares patients all three.

The Clinical Trials Behind the Approval

The first study made headlines in 2022, when researchers at Memorial Sloan Kettering reported that every patient in an early group of 12 participants saw their tumor disappear on dostarlimab alone. Published in the New England Journal of Medicine, the study grew to about 50 patients, and roughly 93% had a complete response lasting at least a year, with none needing chemoradiation or surgery. That near-perfect result drove the excitement, but it came from a single center and a small group.

The approval rests on a larger trial, AZUR-1, which enrolled 154 patients across multiple sites. Its numbers are strong but more measured than the headlines. By independent review, 47% of patients had a sustained complete response at 12 months, and about 79% saw their tumors shrink. Investigators reviewing the same scans put the complete-response figure at 68%. Most patients who responded needed no further treatment, and after a median follow-up of just over two years, none of the responders had relapsed.

What Dostarlimab Means for Patients

For the right patient, the payoff is organ preservation. Someone who would otherwise schedule surgery and weeks of radiation may instead finish six months of infusions and move into active monitoring, a “watch-and-wait” approach with regular scans and scopes. If the cancer stays gone, they keep their rectum and the everyday functions that surgery often removes.

The approval does not promise this result for everyone. Some patients on the trial still needed surgery or added therapy, and because this is an accelerated approval, the FDA is requiring follow-up studies to confirm the benefit holds over time. Still, for a group that has long faced a punishing treatment path, a drug-only option is a meaningful shift.

What the Approval Means for the Industry

The decision reinforces a few trends already reshaping oncology.

Treatment is moving toward molecular signatures over tumor location. The whole approval hinges on a dMMR/MSI-H test, which strengthens the case for routine biomarker screening and the companion-diagnostics business that supports it.

It is also a rare case of doing less. Most cancer launches add a drug on top of existing care; this one can remove surgery, radiation, and chemo for responders. That improves outcomes and quality of life, but it complicates trial design and cuts into surgical and radiation-oncology volumes.

The approval came fast. The FDA cleared it about four months ahead of its February 2027 target date, through its priority review and a newer national priority voucher program. For GSK, the drug carves out a defensible niche in a PD-1 market dominated by Keytruda and Opdivo, where neither rival holds this specific indication. Rectal cancer affects roughly 770,000 people worldwide each year; the dMMR/MSI-H slice is small, but it is now served by a branded, premium therapy.