UPDATE 3-U.S. FDA warns J&J unit over antibiotic studies

* FDA: unit did not properly monitor records, researchers

* J&J says letter concerns ceftobiprole

* Shares of J&J little changed in afternoon trade (Adds company comment, updates share price, byline)

WASHINGTON, Aug 18 (Reuters) - U.S. health regulators have warned Johnson & Johnson's JNJ.N drug development unit over its failure to properly oversee two clinical trials for an experimental antibiotic for treating skin infections.

The U.S. Food and Drug Administration, in a letter released on Tuesday, cited “objectionable conditions” that included a failure to properly monitor the studies and ensure researchers followed the study plan, among other issues.

“We conclude that you did not adhere to the applicable statutory requirements and FDA regulations governing the conduct of clinical investigations,” the agency said in a letter to Johnson & Johnson Pharmaceutical Research & Development (J&J PRD).

The FDA withheld details about the drug in question and the clinical trial sites, but a spokesman for the J&J unit confirmed it involved ceftobiprole.

“We will continue to work with the agency to address their concerns,” said J&J PRD spokesman Ernie Knewitz.

Most such warnings are handled without further regulatory action, but the FDA can impose fines, product seizures and other penalties.

J&J had hoped to market the drug in the United States to combat skin infections. But in November 2008 the FDA declined to approve it and asked the company to further investigate issues at some trial sites and overall monitoring of its studies.

It was not clear from the warning letter when the FDA conducted its investigation. But J&J PRD’s Knewitz said it received its first notice from the agency June 12, 2008 and sent a response to the agency later that month.

The unit sent two more responses in September 2008, but the company’s responses were “inadequate,” the FDA wrote.

Among other issues, the company did not ensure that researchers conducting the studies were properly trained and experienced, the letter said.

J&J chose a doctor at one site despite finding “that the investigator ‘is not recommended’ for lack of compliance in completing regulatory documents,” according to the FDA.

Knewitz said the two studies of the drug were being conducted at 150 sites worldwide and that “a handful of sites were identified by the agency as having issues.”

The FDA posted the letter on its websitehere .

The agency earlier this month announced efforts to streamline its warning letter process. FDA Commissioner Margaret Hamburg said the agency aimed to warn companies more quickly about inspection problems as well as make it clearer when it felt the problems were resolved.

Shares of Johnson & Johnson were off 2 cents to $59.80 in Tuesday afternoon trading on the New York Stock Exchange. (Reporting by Susan Heavey; Editing by Gerald E. McCormick and Tim Dobbyn)