Athenahealth shares rose 3.6 percent, to $156.53, in early trading on Wednesday, giving the company a market value of $6.3 billion.
Athenahealth, based in the Boston suburb of Watertown, provides billing and other digital services for 114,000 medical providers and stores more than 110 million patient records. It grew out of a company that Mr. Bush started in 1997.
Mr. Bush, 49, is a nephew of President George H.W. Bush and a cousin of President George W. Bush. His resignation and Athenahealth’s decision to potentially put itself up for sale comes a month after Elliott unveiled its hostile bid. In making the offer, the hedge fund argued that strategic miscues had left the company dramatically undervalued.
Athenahealth initially tried to defend itself against Elliott’s offensive. But pressure mounted as other shareholders, including Janus Henderson and ClearBridge, pushed the company to consider purchase offers. Both Janus and ClearBridge criticized Athenahealth’s management.
As the fight escalated, court papers surfaced indicating that in 2005, Mr. Bush had physically and verbally abused his former wife. News reports about the episode prompted Mr. Bush to publicly apologize last month.