The USA’s Sepracor yesterday announced a delay in the filing of its second-quarter results with the Securities and Exchange Commission until it has completed an internal review of its employee stock option practices, and said it will restate earnings back to 2003 under an investigation by the US government into the matter.

Earlier this year, the maker of sleep drug Lunesta (eszopiclone) admitted that it was among a list of companies under scrutiny by the SEC for a practice known as ‘backdating’, ie. pushing back the date of a stock option to a time when the stock price was lower, thereby potentially artificially inflating the return at the time of sale.

But investors seemed unconcerned on the news, which failed to take away from Lunesta’s billion-dollar-plus sales potential; Sepracor’s shares grew just under 3% to close at $48.34 last night.