Shares of BioScrip Inc. soared 32% toward a 4-year high in premarket trade Friday, after the company announced a deal to merge with privately held Option Care Enterprises Inc., a provider of home and alternate treatment site infusion therapy services owned by funds affiliated with Walgreens Boots Alliance Inc. /zigman2/quotes/203410933/composite WBA -2.00% and private-equity firm Madison Dearborn Partners LLC (MDP). BioScrip's stock is halted for news until 7:30 a.m. Eastern. Under terms of the agreement, BioScrip will issue new shares to Option Care's shareholder and Walgreens and MDP will own about 80% of the combined publicly traded company. BioScrip's market capitalization was about $446.9 million as of Thursday's close. "This is a compelling and complementary fit of two leading players in the U.S. infusion market," said BioScrip Chief Executive Daniel Greenleaf. "Together, we will be able to provide a diverse set of life-improving and cost-effective services to more patients across the United States." BioScrip's stock has rallied 31% over the past 12 months, while the SPDR Health Care Select Sector ETF /zigman2/quotes/205918244/composite XLV -0.42% has gained 6.9% and the Dow Jones Industrial Average /zigman2/quotes/210598065/realtime DJIA -0.92% has tacked on 3.4%.