Roche will pay $74 a share, representing a 38% premium over InterMune’s (ITMN) closing price on Friday. The deal has been approved by the boards of both companies.

The deal, which is expected to be accretive to earnings by 2016, will give the Swiss pharmaceutical giant access to InterMune’s innovative therapies in pulmonology and fibrotic diseases, expanding its respiratory treatments portfolio.

InterMune’s portfolio has “medical differentiation that fits very well with our pulmonary portfolio,” Roche CEO Severin Schwan told CNBC.

InterMune’s standout treatment, pirfenidone, is expected to launch in the U.S. this year. The medicine treats idiopathic pulmonary fibrosis (IPF), which causes progressive scarring of the lungs leading to loss of function.

IPF has no real treatment options available, and patients with the disease live only 2-to-4 years, on average, after diagnosis. Until now, a lung transplant has been the only treatment that has helped improve patients’ lifespans.

The potential approval of the drug will solve “significant unmet medical needs” and could prove to be a billion-dollar treatment, said Liisa Bayko, an analyst with JMP Securities.

It’s rare for a big pharmaceutical company to buy a drug prior to U.S. Food and Drug Administration approvals, but a series of tests have proved pirfenidone’s efficacy. The FDA labeled the drug a “breakthrough therapy” in July after an additional round of Phase 3 trials revealed a proven mortality benefit.

“This is an asset that is very de-risked,” said Bayko. “With a mortality benefit in hand, it’s hard to see any reason the FDA wouldn’t approve this drug.”

The drug had been delayed in the U.S. market after the FDA recommended an additional Phase 3 trial to confirm its efficacy in 2010. The results were part of a new drug application submitted to the FDA in May, and final approvals are expected in late November.

Pirfenidone is currently marketed in the EU and Canada under the brand name Esbriet.

Roche will be able to leverage its back-office operations to prioritize the drug’s launch, leveraging its established sales and marketing teams to push the drug out to the U.S. market after approvals. These synergies make the drug worth more in the hands of Roche, said Bayko. InterMune CEO Dan Welch seems to agree.

“Roche shares our passion and commitment to the IPF community and to ensuring that pirfenidone is available as quickly as possible to patients in the United States, pending FDA approval,” he said.