April 22 (HealthDay News) -- Cimzia (certolizumab pegol) has been approved by the U.S. Food and Drug Administration to treat adults with moderate-to-severe Crohn's disease who haven't responded to conventional therapies.

Crohn's, an inflammatory bowel disease, has no known cause or cure. Affecting more than 1 million people worldwide, it has symptoms including diarrhea, fever, bleeding, malnutrition, narrowing of the colon, obstructions, cramps and abdominal pain.

Cimzia, an injected drug, can cause side effects including headache, upper respiratory infection, abdominal pain, nausea and reactions at the injection site.

Because the drug affects the immune system, people taking Cimzia are at increased risk of life-threatening infections. The drug also blocks tumor necrosis factor, which may contribute to the onset of lymphoma and other cancers, the FDA said.

Maker UBC Inc., of Smyrna, Ga., will be required to perform post-marketing studies that evaluate the drug's long-term safety, the agency said.