An experimental immunotherapy drug is a potentially effective treatment for patients with bladder cancer who no longer respond to current therapies, researchers reported at the Society of Urologic Oncology meeting in Dallas.

In a late-stage study involving 112 patients whose cancers were not responding to the Bacillus Calmette Guerin - a vaccine used for bladder cancer - nearly 75% experienced complete cancer remission upon treatment with CG Oncology’s cretostimogene. Many of them remained cancer-free beyond two years, researchers reported.

At the start of the trial, the cancer had not invaded the muscle of the bladder wall in any of the patients. A year later, that was still true for 97%.

Most participants did not need to have their bladder surgically removed, and the treatment was well tolerated with minimal serious side effects, according to the researchers.

"These findings address a significant unmet need for bladder cancer patients and could improve their quality of life," study leader Mark Tyson, MD of the Mayo Clinic in Rochester, Minnesota said in a statement.

"We now know this treatment can be both effective and safe, potentially reducing the need for bladder removal surgery and providing a much-needed alternative for patients with limited options."

Cretostimogene has received fast track and breakthrough therapy designations from the FDA, typically awarded to therapies the agency sees as a potential major advance.

“Based upon the latest data, we are confident that cretostimogene is well positioned to address an unmet need for patients... if approved by the FDA,” CG Oncology President Ambaw Bellete said in a statement.