What You Should Know
- The FDA has approved the immunotherapy drug Jemperli (dostarlimab) for some people with newly diagnosed stage II or III rectal cancer, giving them a chance to avoid treatments that can permanently affect bowel, bladder, and sexual function.
- The approval only covers tumors with a DNA repair problem called dMMR or MSI-H. That’s about 3% of these cancers, so a tumor test should come first, ideally before any treatment begins.
- In the main study, about 7 in 10 people were able to skip surgery, radiation, and chemotherapy with Jemperli alone, given as an IV infusion every three weeks for about six months.
- So far, no one whose tumor disappeared has had cancer come back, though people still need regular scans and checkups to watch for any return.
- People who didn’t fully respond could still get standard treatment, and for most of them, it worked. Serious side effects were uncommon, and only 2% of patients stopped treatment because of them.
On October 19, 2026, the U.S. Food and Drug Administration approved dostarlimab (brand name Jemperli), made by GSK, for some people with newly diagnosed rectal cancer.
Read MoreWho This Approval Is For
The approval covers adults who haven’t had any treatment yet and whose cancer is stage II or III. At these stages, the cancer has grown into nearby tissue or reached nearby lymph nodes, the small glands that help fight infection. It hasn’t spread to distant organs. Doctors call this “locally advanced” rectal cancer.The tumor must also be mismatch repair deficient (dMMR) or microsatellite instability-high (MSI-H). A lab test on your tumor tissue shows this.
According to the FDA, only about 3% of locally advanced rectal cancers fall into this group, so most people with rectal cancer won’t qualify. The only way to know is to be tested.
Ask your doctor whether your tumor has been checked for dMMR or MSI-H, ideally before you start any treatment.
What dMMR and MSI-H Mean
Every time a cell divides, it copies its DNA, and mistakes happen. Normally, a built-in repair system fixes them.
In dMMR or MSI-H tumors, that system is broken. Errors pile up, causing cancer cells to produce unusual proteins that your immune system can spot. That makes these tumors especially likely to respond to immunotherapy, which is treatment that helps your own immune system fight cancer.
Some people with these tumors have Lynch syndrome, an inherited condition that raises the risk of several cancers. In the study, 23% of patients had it, though most were never tested. If your tumor is dMMR or MSI-H, ask whether genetic testing makes sense for you and your family.
How Jemperli Works
Cancer cells can hide from the immune system by pressing a “brake” on immune cells, a protein called PD-1. Jemperli blocks PD-1, so your immune cells can attack the cancer.
In the main study, patients got the drug through an IV every three weeks, for up to nine doses over about six months.
Standard treatment can affect bowel, bladder, and sexual function, as well as fertility, according to the FDA. Some people end up with a permanent colostomy, an opening in the belly where stool leaves the body into a bag. Avoiding all of that is what makes this approval matter.
“Standard treatment for rectal cancer has major life-changing effects. For certain types of rectal cancer, this approval represents a groundbreaking option that avoids surgery, radiation, and chemotherapy,” said Dr. Angelo de Claro, director of the FDA’s Oncology Center of Excellence, in the agency’s announcement.
What the Main Study Found
The approval is based on early results from AZUR-1, a study of 154 patients at 40 hospitals in 10 countries, published in the journal Annals of Oncology.
After treatment, doctors checked for any remaining tumor using endoscopy (a thin tube with a camera), MRI, and CT scans. If they found no sign of cancer, that’s called a clinical complete response.
After a median of about two years, meaning half the patients were followed longer than that:
- 71% of patients were treated with Jemperli alone and skipped surgery, radiation, and chemotherapy.
- Of patients whose tumors disappeared, 98% stayed cancer-free on their tests for at least a year. The other 2% chose surgery anyway, and no cancer was found.
- No one whose tumor disappeared has had cancer come back so far.
“Watching tumors melt away on imaging… is like watching magic,” Dr. Hornstein says.
What If Jemperli Doesn’t Fully Work?
The answer here is reassuring. Forty patients went on to standard treatment, and for most of them it still worked. Overall, 93% of all patients had no signs of their cancer growing at their last check.
The researchers concluded that trying Jemperli first didn’t seem to reduce people’s chance of receiving standard treatment later.
What’s still uncertain
These results are early. The study had no comparison group, so Jemperli wasn’t tested side by side against standard treatment.
The trial’s main goal was measured by independent reviewers who didn’t know the patients. So far, they’ve confirmed a lasting complete response in 47% of the patients they could fully assess, compared with 68% by the patients’ own doctors. The researchers say the reviewers often took months longer to confirm a response, so many patients haven’t been followed long enough to count yet. They expect the number to rise.
The FDA gave Jemperli accelerated approval, which lets a promising drug reach patients early. The company must keep following patients to show the benefit lasts.
Side Effects
Because Jemperli boosts your immune system, it can sometimes attack healthy organs. The FDA notes that these reactions can be severe or even fatal.
In the study, about 1 in 4 patients had an immune-related side effect, most often an underactive thyroid. Serious immune side effects happened in 3% of patients, and only 2% stopped treatment because of side effects. According to the FDA, the most common side effects overall were fatigue, rash, diarrhea, and itching.
What follow-up looks like
Skipping surgery doesn’t mean skipping checkups. In the study, people who avoided surgery had endoscopy and scans every four months for the first two years, then every six months through year five. These visits are how doctors catch any cancer that returns early.
What This Means for You
“This should be widespread and used in all practice settings,” Dr. Hornstein adds.
The first step is a test. If you’ve just been diagnosed with stage II or III rectal cancer, ask whether your tumor has been checked for dMMR or MSI-H before treatment begins. If your tumor isn’t dMMR or MSI-H, standard treatment remains the proven path, and it works for many people. If it is, this approval gives you and your doctor an important new option to discuss. If your tumor isn’t dMMR or MSI-H, standard treatment remains the proven path, and it works for many people.
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