UPDATE 1-US warns Roche, Shire on misleading drug promotions

* Genentech cited for Rituxan, Shire for bowel drugs

* Shire says stopped using materials

* Genentech says working to remove materials

WASHINGTON, May 5 (Reuters) - U.S. regulators have warned Roche Holding AG ROG.VX unit Genentech and Shire Plc SHP.L about misleading promotions for cancer and bowel drugs, letters released on Wednesday said.

In an April 29 letter, the Food and Drug Administration said promotional materials from Genentech made unsupported efficacy claims for cancer drug Rituxan and left out important risk information.

“The overall effect of these misleading presentations undermines the communication of important risk information, thereby misleadingly suggesting that Rituxan is safer than has been demonstrated,” the FDA said of the materials, which were aimed at doctors.

Genentech spokesman Edward Lang said the company would work to remove all the offending materials.

The FDA released two letters to Shire objecting to sales materials for drugs to treat ulcerative colitis, a painful bowel inflammation.

The agency said a Shire brochure developed for doctors overstated effectiveness and omitted certain information about one drug, Lialda. Another written promotion for doctors made unsupported efficacy claims for the company’s Pentasa drug.

Shire spokesman Matt Cabrey said the company has stopped using the promotions cited by the FDA and is working with the agency to resolve the issues raised in the letters.

Editing by Richard Chang