In an interview with CNBC at the annual meeting of the American Diabetes Association in Chicago, Nissen said, "My job is as a scientist," with an "obligation to publish" data suggesting a drug may be unsafe.

Nissen conducted a meta-analysis -- published in May in the New England Journal of Medicine -- that he said showed patients taking GlaxoSmithKline's diabetes drug Avandia have a higher risk of heart attack.

The Cleveland Clinic cardiologist said he began his research on Avandia with "no preconceived notions. This was not a political effort, this was a scientific effort," he said.

Nissen likened his frequent role as vocal critic of a string of widely prescribed drugs to "wearing a target on my back that says, 'Shoot at me.'" But he added he would proceed the same way again in his warnings about Avandia. "In the end, science will prevail," Nissen said.

Glaxo maintains Nissen's analysis was "premature" and that conclusions on Avandia's heart safety should await the results of a large-scale trial the company is conducting on its drug, the CNBC report said.