WEDNESDAY, Aug. 21 (HealthDay News) -- An experimental drug may help some people who have inflammatory bowel disease that has failed to respond to current medications, two new clinical trials find.

The drug, called vedolizumab, is being developed to treat the two main forms of inflammatory bowel disease (IBD) -- ulcerative colitis and Crohn's disease. Both arise when the immune system launches an abnormal attack on the lining of the digestive tract, leading to chronic inflammation and symptoms such as abdominal cramps, diarrhea and rectal bleeding.

In the new trials, reported in the Aug. 22 issue of the New England Journal of Medicine, researchers found that vedolizumab worked in some cases where standard IBD medications had failed.

The drug was more effective for colitis than for Crohn's, however, and an expert not involved in the studies said he suspects vedolizumab might be approved for colitis first.

Overall, the results are "very exciting," said Dr. Fabio Cominelli, chief of gastroenterology and liver disease at Case Western Reserve University School of Medicine, in Cleveland.

"This is a potential new weapon in our armamentarium," said Cominelli, who wrote an editorial that accompanied the reports.

The two studies included more than 2,000 patients with either colitis or Crohn's who had failed to get enough relief from standard medications, which include immune-system suppressors such as corticosteroids, azathioprine (brand name Imuran) and mercaptopurine (Purinethol).

About half of the patients had also tried the most recently developed drugs for IBD, known as anti-TNF agents. Those drugs -- infliximab (Remicade), adalimumab (Humira) and certolizumab (Cimzia) -- are given intravenously, and block an inflammatory protein called tumor necrosis factor (TNF).

In one trial, nearly 900 colitis patients were given two infusions of either vedolizumab or a placebo, two weeks apart. After six weeks, 47 percent of the vedolizumab patients had a "clinical response," or a meaningful drop in their symptoms.

Those patients were then randomly assigned to either stay with the drug -- getting infusions every four weeks or every eight weeks -- or receive placebo infusions.

After a year, 42 percent to 45 percent of the vedolizumab patients were in remission, compared with 16 percent of the placebo group.