By Yasmeen Abutaleb

WASHINGTON, Jan 31 (Reuters) - Two Democratic U.S. senators said they have fresh concerns over clinical trials conducted by Philip Morris International Inc as it seeks U.S. clearance to market its iQOS electronic tobacco product as less risky than cigarettes, according to statements both senators provided to Reuters.

Senator Dick Durbin of Illinois and Richard Blumenthal of Connecticut cited reports that showed problems with the trials that supported Philip Morris's application to the U.S. Food and Drug Administration, including a Reuters investigation published in December.

The Reuters story identified shortcomings in the training and professionalism of some of the lead investigators in the clinical trials. Former Philip Morris employees and contractors also described irregularities in those experiments. (https://www.reuters.com/investigates/special-report/tobacco-iqos-science/) and (http://www.reuters.com/investigates/section/pmi)

"Reuters' reporting, and the serious concerns raised by FDA's advisory committee, make clear that this product fails to meet the requirements set out under the Tobacco Control Act for modified risk claims," Durbin said in a statement.

A Senate Democratic aide said that Blumenthal plans to send a letter to FDA Commissioner Scott Gottlieb regarding the new concerns.

In October, Blumenthal, Durbin and two other Democratic senators wrote to the agency urging a thorough review of the iQOS product, warning that tobacco companies "have a long history of making false claims about the risks their products pose."

"I have serious concerns over reports that clinical trials for this product have been severely lacking in quality and sophistication. FDA must learn from past mistakes and thoroughly scrutinize all supporting materials submitted by (Philip Morris International)," Blumenthal said in a statement to Reuters.

An FDA official said the agency generally cannot comment on a pending product application. Philip Morris officials could not immediately be reached.

IQOS is a sleek, penlike device that heats tobacco but does not ignite it, an approach Philip Morris says produces far lower levels of harmful chemicals than regular cigarettes. It is used by nearly 4 million people in 30 markets outside the United States.

The company has spent more than $3 billion developing new smoking platforms like iQOS.

Last week, outside advisors to the FDA dealt a blow to Philip Morris's ambitions for iQOS, saying the company should not be allowed to claim the product is less risky than cigarettes based on the available data.

The recommendation is nonbinding and the FDA could still allow Philip Morris to make such a claim. Some analysts think the agency might ask for additional data to do so.

Philip Morris said at the time it was confident in its ability to address the advisors' questions about iQOS.

The iQOS application is seen as a test of tobacco regulation under the Trump administration.

FDA's Gottlieb has proposed an approach to tobacco policy that would reduce nicotine in cigarettes to "non-addictive" levels while fostering development of lower-risk alternatives for people who cannot quit smoking.

Critics have said the approach risks rushing to market products that may later prove harmful, and could jeopardize efforts to prevent younger Americans from picking up a tobacco habit. (Reporting by Yasmeen Abutaleb; Editing by Michele Gershberg)