Helicos Biosciences (NASDAQ: HLCS), the Cambridge, MA-based maker of genetic analysis instruments, said today in a regulatory filing that president Steve Lombardi has resigned. Lombardi’s exit was official as of February 11 from his full-time job and from his position on the board of directors. Helicos didn’t say why Lombardi is leaving, but noted that it wasn’t because of a disagreement with the company over operations, policies, or practices. Lombardi will continue to earn his salary through August 31, at his annual base rate of $375,000. Lombardi had been CEO of Helicos from August 2008 to December 2008, when he was replaced in the company’s top job by Ronald Lowy.