Private equity firm Veritas Capital and hedge fund Elliott Management are buying Athenahealth Inc. for about $5.7 billion, the U.S. health care software maker said on Monday.

The all-cash deal values Athenahealth at $135 per share, representing a premium of 12.2 percent to the stock’s closing price on Friday.

Athenahealth had been under pressure from Elliott to sell itself since the hedge fund acquired a stake in the company last year. Elliott made an unsolicited offer of $160 per share to buy Athenahealth in May.

The Watertown-based company, whose cloud-based software is used to track revenue from patients, physicians and hospitals, has cut jobs and overhauled its management over the past year as part of a restructuring effort.

Former General Electric CEO Jeff Immelt is currently its chairman.

Once the deal is complete, Athenahealth will merge with Virence Health, the former GE Healthcare unit that Veritas acquired earlier this year, the companies said in a joint statement.

A deal for Athenahealth represents the largest deal to date for Elliott’s private equity arm, Evergreen.

Athenahealth’s founder and CEO Jonathan Bush, a nephew of former U.S. President George H.W. Bush, stepped down in June following a newspaper report alleging he had assaulted his former wife 14 years earlier.