Under the merger agreement, which has now been approved by the boards of both companies, InterMune shareholders will receive a cash price of $74 per share. According to the announcement, this means that they will receive a 38% increase on InterMune's closing price on 22 August 2014 and a 63% increase on its closing price on 12 August 2014.
In a statement, Roche said that the deal would allow the company to "broaden and strengthen its respiratory portfolio globally".
"We are very pleased that we have reached this agreement with InterMune," said Roche's chief executive, Severin Schwan.
"Our offer provides significant value to InterMune's shareholders and this acquisition will complement Roche's strengths in pulmonary therapy. We look forward to welcoming InterMune employees into the Roche Group and to making a difference for patients with idiopathic pulmonary fibrosis, a devastating disease," he said.
InterMune's work focuses on the research, development and commercialisation of innovative treatments for lung diseases. Its particular focus is on the treatment of idiopathic pulmonary fibrosis (IPF), which it describes as a "progressive, irreversible, unpredictable and ultimately fatal" lung disease. Its lead drug is called pirfenidone and has been approved for the treatment of IPF in the EU and Canada, with US regulatory approval pending.
Under the terms of the merger agreement, Roche will begin tendering for InterMune's existing shares no later than 29 August 2014 while InterMune has filed a 'recommendation statement' containing the board's unanimous recommendation that InterMune's shareholders tender their shares to Roche. The transaction is expected to close by the end of this year.
The total value of healthcare mergers and acquisitions globally had reached €163bn by April this year, representing the highest year-to-date figures since records were first compiled in 2007, according to market analysts Dealogic. Last month, US firm AbbVie announced that it was to purchase UK company Shire for $54bn.