A Texas doctor leaked confidential research to the makers of the popular diabetes drug Avandia weeks before a study was published tying the drug to higher heart risks, the scientific journal Nature reported Wednesday, according to The Associated Press. Dr. Steven Haffner, of the University of Texas Health Science Center at San Antonio, broke confidentiality rules for medical journal peer reviewers when he gave the Avandia study to GlaxoSmithKline PLC 17 days before it was published in the New England Journal of Medicine, the Nature report says. The study, linking Avandia to a 43 percent greater risk of heart attacks, got widespread attention, led the federal Food and Drug Administration to issue a safety alert, and caused the company's stock to drop. The study was led by Cleveland Clinic cardiology chief Dr. Steven Nissen. Haffner admitted faxing the study to a Glaxo employee he worked with on an earlier Avandia study, says the report published online Wednesday in the news section of Nature. «Why I sent it is a mystery. I don't really understand it. I wasn't feeling well. It was bad judgment,» Nature quotes Haffner as saying. It's not clear that Glaxo took any action after getting the confidential information. Most scientific journals have outside scientists, «peer reviewers,» who study research to be sure it is solid before it is published. The leak came to light last summer, when Glaxo officials informed the Senate Finance Committee that Haffner had sent them the study, according to a letter released Wednesday by Republican Sen. Charles Grassley, the panel's ranking member. Grassley wants Glaxo to explain what it did after learning that the negative study was imminent. Glaxo spokeswoman Nancy Pekarek told Nature that the company did not offer any input to Haffner on the study and, to her knowledge, did not inform the New England Journal of the breach, the Nature article says. Spokesmen for the New England Journal would not say what if any actions had been taken against Haffner. «We consider the peer-review process to be confidential. Any breach of ethics by a reviewer would be taken very seriously by the editors, but would be handled as a private matter,» says a statement from the journal. Last year, the journal restricted future publishing rights of another peer reviewer, Columbia University's Dr. Martin Leon. He had discussed confidential results of another controversial study, involving angioplasty and heart stents, before its scheduled publication.