Under terms of the deal, Astra will make an upfront payment of $50 million to the world's largest biotechnology company, and the companies will share costs and profits on the drugs for a variety of autoimmune, inflammatory and respiratory diseases.

The collaboration will provide Amgen with additional resources to help advance its product portfolio and give Astra access to new medicines at a time when its own pipeline is relatively barren and it is facing competition from cheap generic versions of its big-selling antipsychotic drug Seroquel.

The deal comes as Amgen's longtime chief executive, Kevin Sharer, is preparing to step down next month.

"We have a lot of things that we want to move forward and there are financial constraints everywhere with how much you can do," Joe Miletich, Amgen's senior vice president for research and development, said in a telephone interview.

"We get some financial relief for moving these assets forward and we can tap into some strong areas of expertise that AstraZeneca has," Miletich added.

Astra has extensive experience selling respiratory treatments, which would be a new area for Amgen.

Sanford Bernstein biotech analyst Geoffrey Porges questioned the selection of AstraZeneca as Amgen's partner and the partnering strategy itself.

"It's hard to see what AstraZeneca brings to the table other than cash and the ability for Amgen to maintain their share buybacks and dividends," Porges said, conceding that Astra does provide some global commercial reach that Amgen lacks.

"The fact that Amgen has to partner yet another one of their strategic initiatives isn't really going to fill investors with very much confidence," said Porges, who was critical of Amgen's decision to collaborate with Watson Pharmaceuticals Inc on the development of generic biotech drugs, or biosimilars.

Recent AstraZeneca setbacks with experimental medicines for depression, ovarian cancer and diabetes have hurt investor confidence in the company's ability to rejuvenate its pipeline internally. In an interview last month, research chief Martin Mackay told Reuters that Astra was actively seeking deals, "including potential peer-to-peer and biotech deals.

AstraZeneca expects revenue to fall by more than 10 percent in 2012 and it has twice cut its 2014 outlook, with new drugs expected to contribute a lot less than initial estimates.

The most advanced of the five drugs to be shared by Amgen and Astra is brodalumab, which is about to begin Phase III clinical trials for psoriasis, and is also being tested for psoriatic arthritis and asthma.

The others, all at a much earlier stage of development, are AMG 139 for Crohn's disease; AMG 181 for ulcerative colitis and Crohn's; AMG 557 for lupus; and AMG 157 for asthma.

Under current plans, about 65 percent of the costs through 2014 will be funded by AstraZeneca, after which the companies will split costs equally. Amgen will book sales globally and retain a low single-digit royalty for brodalumab and a mid single-digit royalty for the rest of the portfolio. After 2014, the companies will share profits equally.

Astra will take the lead for development and commercial strategy of AMG 139, AMG 157 and AMG 181, while Amgen will lead the development and commercial strategy for brodalumab and AMG 557, the companies said. There will be a joint collaboration committee with representatives of both companies on all five projects.

The cost sharing will enable Amgen to fund some other projects that it might otherwise have been forced to abandon, Miletich said.

"We still have many more things that we're still moving on our own, and this actually will help free some resources so we can continue to innovate in bringing some of the programs in our earlier pipeline along in a way that might not have been possible if we were funding these all on our own," Miletich said.

(Reporting By Bill Berkrot; Editing by Phil Berlowitz and Richard Chang)

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