CVS Caremark has entered into an agreement to buy Apria Healthcare Group’s Coram infusion therapy business for approximately $2.1 billion in cash, the two companies announced Wednesday. Sullivan & Cromwell is advising first-time M&A client CVS, while Simpson Thacher & Bartlett is serving as outside counsel to Apria, which is owned by private equity giant and longtime Simpson Thacher client The Blackstone Group.

Once completed, the purchase will give CVS—which owns 7,600 pharmacies, as well as a mail-order prescription operation—a business that provides more than 20,000 patients each month with intravenous and tube-feeding treatments for conditions including immune and nutritional deficiencies, rheumatoid arthritis and multiple sclerosis, according to a CVS press release. Apria will continue to own a respiratory therapy business after the deal closes.

Denver-based Coram is estimated to generate about $1.4 billion in revenue in its first 12 months under CVS ownership. The deal, which is subject to regulatory approval, is expected to close in the first quarter of next year. CVS said in its release that it does not anticipate any material impact on its 2014 finances as a result of the acquisition, which the company expects will add between 3 and 5 cents to its adjusted earnings per share in 2015.

S&C landed the lead outside counsel role for Woonsocket, R.I.–based CVS, which often turns to Davis Polk & Wardwell on M&A deals. Several past transactions on which Davis Polk has advised CVS include its $25 billion merger with Caremark in 2006; its $2.7 billion acquisition of Longs Drug Stores in 2008; and its purchase earlier this year of Brazilian retailer Drogaria Onofre for an undisclosed sum in the company’s first-ever international deal.

Reached Wednesday, S&C partner Matthew Hurd, who served as the lead M&A lawyer for CVS on the Apria matter, said his firm grabbed the assignment through its relationship with CVS general counsel Thomas Moriarty, who joined the company last year. Hurd and an S&C team had previously been hired by Moriarty when he was general counsel of Medco, which S&C advised on its $29.1 billion sale to Express Scripts in 2011.

Hurd, who specializes in health care–related transactions, said he “would certainly hope” that Moriarty will continue to send deal work S&C’s way and that it has been “thrilling” to work with CVS for the first time.

“It’s always exciting to be involved with a major client undertaking a project as strategic as this one,” Hurd says. “It gets to where they want to be as health care evolves over time.” As part of that evolutionary process, Hurd says, health care services like those offered by Coram are increasingly provided in people’s homes in a way that keeps them out of hospitals and assisted living facilities.

The S&C deal team also includes finance partner Neal McKnight and special counsel Michael Torkin, executive compensation and employee benefits partner Matthew Friestedt, tax partner Ronald Creamer Jr., intellectual property special counsel Spencer Simon, environmental special counsel Matthew Brennan, and associates Ari Blaut, Guy Inbar, Nicholas Krainak, Joyce Kwok, Alice Lee, Anca Mihaela Paraian, Collette Shin and Michael Snypes Jr.

In addition, Dechert partner Michael Cowie is advising CVS on antitrust aspects of the deal. (Cowie also secured antitrust approval on the Medco/ Express Scripts deal.)

Hurd said the firm has been busy with health care–related M&A deals this year, including its representation of Bayer HealthCare in its $1.1 billion acquisition of birth control maker Conceptus and its representation of Amgen in its $10.4 billion purchase of Onyx Pharmaceuticals.

Simpson Thacher’s ties to Apria date back to 2008, when the firm advised Blackstone on its purchase of the health care services company for approximately $1.6 billion. M&A partner and Simpson Thacher chairman William Dougherty advised on both that deal and the Coram sale (Dougherty was not immediately available to comment Wednesday).

Other Simpson Thacher lawyers advising on the deal are banking and credit partner Alden Millard, capital markets partner Igor Fert, tax partner Gary Mandel, executive compensation and employee benefits partner Gregory Grogan, antitrust partner Joseph Tringali and senior counsel Michael Naughton, environmental senior counsel Michael Isby and associates Ellen Frye, Daniel Kay, Kevin Lehpamer, Jennifer Pepin, Marcela Robledo, Jodi Sackel, Jason Vollbracht, Erik Wang and Benjamin Wells.

Simpson Thacher has long-standing ties to Blackstone, whose chief legal officer, John Finley, is a former Simpson Thacher executive committee member. Finley joined Blackstone in 2010, replacing former Simpson colleague Robert Friedman as the private equity firm’s top in-house lawyer.

Robert Holcombe is Apria’s general counsel.