An institutional investor that was once one of Allscripts Healthcare Solutions' largest shareholders has divested itself of virtually all its stock in the Chicago-based health IT firm. Atlanta-based Invesco Ltd., owned more than 12.7 million shares as of Sept. 30, 2011, roughly 7 percent of Allscripts. But its holdings have shrunk to just under 200,000 shares, or 0.1 percent of outstanding shares, as of Wednesday, according to a filing with the Securities and Exchange Commission.

Invesco unloaded most of its shares in the first half of 2012, during which Allscripts was in crisis after weak first quarter, a vote of no-confidence in then-CEO Glen Tullman—which he survived—and a call for his resignation by the company's largest shareholder. Mr. Tullman eventually resigned in December. Allscripts stock closed at $11.22 a share on Wednesday, down more than 40 percent from a year ago, when it was $18.79.