UnitedHealth Group Inc.'s OptumRx Inc. will merge with Michigan-based specialty pharmacy Diplomat Pharmacy Inc.

OptumRx will acquire Diplomat's outstanding common stock for $4.00 per share through a cash tender offer and assumption of outstanding debt. Based on an outstanding share count of 75,770,397 as of Nov. 8, the per-share price implies a stock valuation of $303.1 million.

Diplomat provides specialized infusion therapies in all 50 states and the District of Columbia. It had launched a strategic review with a view to a possible sale or merger in August, having seen its shares plunge more than 56% in a day when it announced Feb. 22 that it would delay its fourth-quarter and full-year 2018 financial results.

It later recorded a full-year 2018 loss attributable to the company of $302.3 million, mainly driven by a $262 million noncash impairment charge within its pharmacy benefit management segment and a $46 million noncash impairment charge related to its specialty segment.

The deal was unanimously approved by the specialty pharmacy's board.