Amgen Inc. on Monday announced a collaboration with generic drugmaker Watson Pharmaceuticals Inc. to develop and sell “biosimilar” versions of biotech cancer drugs.

The Thousand Oaks biotech, which has been aggressive in protecting its own products from generic competitors, said the collaboration with Watson, a Parsippany, N.J. company, would create drugs to be sold under an Amgen/Watson label.

“The pairing of Amgen’s 30 years of experience … together with Watson’s substantial generics and specialty pharmaceutical experience and complementary commercial and distribution capabilities provides great potential …” said Robert A. Bradway, Amgen’s chief operating officer.

Under the collaboration, Amgen will lead the development, manufacturing and initial commercialization of the products. Watson initially would receive royalties and sales milestones from product revenue, and contribute up to $400 million in co-development costs. It also will contribute expertise about the products’ commercialization and marketing.

Scott Foraker, head of Amgen’s new biosimilar group, said the company already has identified several drugs that are scheduled to go off patent in the second half of this decade. In addition to the Watson collaboration, Amgen also is developing several biosimilar drugs on its own, he said.

Amgen is known its blood-strengthening products, which treat anemia, infection and inflammation. Watson’s products include drugs for hypertension, antidepressants and oral contraceptives.

Amgen shares earlier closed up 12 cents, or less than 1 percent, to $60.17 on the Nasdaq.