Swiss pharmaceutical giant Roche says it will buy US-based lung disease treatment developer InterMune in a deal worth $US8.3 billion.

Swiss pharmaceutical company Roche says it will buy a California-based developer of treatments for lung diseases, InterMune Inc, in a deal worth $US8.3 billion ($A8.98 billion).

Roche said on Sunday the companies had reached an agreement under which Roche will acquire InterMune in an all-cash transaction, paying $US74.00 per InterMune share.

That’s a premium of 38 per cent over InterMune’s closing price on Friday.

The Swiss firm says the acquisition the biotechnology company, based in Brisbane, California, “will allow Roche to broaden and strengthen its respiratory portfolio globally.”