FDA Grants Fast Track Status to Muzastotug for Some Colorectal Cancers

The U.S. Food and Drug Administration (FDA) has granted fast track designation to muzastotug when used in combination with Keytruda (pembrolizumab) to treat adult patients with microsatellite stable metastatic colorectal cancer without current or active liver metastases, according to a news release from Adagene Inc.

“Receiving fast track designation marks an important milestone for Adagene and further validates the promise of our SAFEbody technology to unlock CTLA-4 biology in a fundamentally safer and more effective way,” Peter Luo, chief executive officer and president of R&D at Adagene, said in the news release.

The fast track designation is supported by early clinical evidence showing encouraging efficacy with deep and durable responses and a favorable safety profile in a heavily pretreated patient population. Fast track is intended to speed development and review of treatments for serious conditions with unmet medical need and allows for more frequent interactions with the FDA, including the possibility of rolling review.

Luo continued, “We are deeply encouraged by the responses we are seeing with muzastotug in combination with [Keytruda] and believe this therapy has the potential to reshape the treatment paradigm by offering patients an opportunity for extended survival with an improved quality of life. We look forward to sharing updated topline phase 1b/2 clinical data over the next few months as we continue advancing this program with urgency and purpose.”

Muzastotug is an investigational immunotherapy known as a masked anti-CTLA-4 SAFEbody, a type of antibody designed to help the immune system attack cancer. CTLA-4 is a protein that can limit immune responses, and tumors can use it to avoid being targeted. Muzastotug is engineered to become active mainly inside the tumor microenvironment, the area surrounding the tumor, which may reduce side effects in the rest of the body while preserving its antitumor activity.

Future Trials That Will Muzastotug Treatment

The planned phase 2 and phase 3 trials were reviewed with the US Food and Drug Administration, which confirmed the study designs and goals. Future trials will enroll late-line patients with microsatellite stable colorectal cancer, meaning a common subtype that typically does not respond well to immunotherapy, who do not have cancer spread to the liver. Patients with peritoneal metastasis, cancer involving the lining of the abdomen, will be included.

In the phase 2 dose-optimization portion, patients will be randomly assigned to receive either 10 milligrams (mg) per kilogram or 20 mg per kilogram of muzastotug in combination with pembrolizumab, another immunotherapy. The treatment will use an induction-maintenance approach, which starts with more intensive treatment followed by ongoing therapy, with no set limit on how long muzastotug can be given. Each group will enroll up to 30 patients, and there will be no group receiving muzastotug alone.

For phase 3, the FDA agreed with the use of a standard-of-care control group, meaning patients will receive the current usual treatment for this cancer type. A muzastotug-only group will not be required. The main goal of the phase 2 trial will be overall response rate, which measures the percentage of patients whose tumors shrink or disappear. Additional goals include duration of response, or how long the cancer stays controlled, progression-free survival, the length of time before the cancer grows or spreads, and overall survival, the length of time patients live after starting treatment. In phase 3, overall survival will be the primary endpoint, with progression-free survival, duration of response and overall response rate as secondary measures.

Reference

1. “Adagene Announces FDA Fast Track Designation for Muzastotug (ADG126),” by Adagene Inc. News Release; Dec. 16, 2025.

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