But California-based PDL BioPharma Inc, which makes Nuvion, known generically as visilizumab, said later tests showed the drug did not work well.

The phase I safety study showed Nuvion helped 45 percent of patients with a severe version of the condition to avoid surgery, a team at the University of North Carolina reported.

"The patients in this study were people for whom all other standard medical therapies had failed and they were so severely ill they had to be hospitalized," said Dr. Scott Plevy, an associate professor of medicine, microbiology and immunology who led the study.

"Historically, almost all patients in this group will ultimately require surgery to remove their large intestine."

The company said in August it stopped development of the drug because it did not work well enough in later, phase 3 trials.

"Often a drug candidate can look promising in early uncontrolled studies, yet more data in phase III can often reveal that the drug ultimately isn't safe or efficacious in that particular indication. This was the case for Nuvion," the company's Kathleen Rinehart said in an e-mail.

Writing in the journal Gastroenterology, Plevy noted that more than 500,000 Americans have ulcerative colitis, which causes diarrhea and painful inflammation and sores in the lining of the rectum and colon.

For the study, 32 patients were given intravenous infusions of visilizumab on two consecutive days. Higher doses caused dangerous side-effects such as a drop in blood pressure, fever, nausea and vomiting but a lower dose reduced these symptoms.

After 30 days, 85 percent of the patients showed clinical improvement, Plevy said, and 41 percent of these reported their symptoms had disappeared.