UPDATE 1-Celgene to buy Juno Therapeutics for $9 billion

(Adds details on deal, background, share move)

Jan 22 (Reuters) - Celgene Corp said on Monday it would pay about $9 billion in cash to acquire the rest of Juno Therapeutics Inc and gain access to Juno's experimental gene therapy to treat cancer.

The $9 billion represents an offer $87 per share to Juno's shareholders and the deal, agreed by both boards, is expected to close in the first quarter of 2018.

Shares of Juno rose 26.8 percent to $86.01 in premarket trading. Shares of Celgene were marginally up.

The acquisition will add JCAR017, Juno's experimental treatment for a type of blood cancer, to Celgene's lymphoma program.

The drug is expected to be approved in 2019 and could bring in peak sales of about $3 billion worldwide, the companies said.

In 2015, Celgene paid $93 per Juno share for 9.7 percent of the company.

J.P. Morgan Securities LLC is the financial adviser for Celgene and Morgan Stanley & Co for Juno.

Proskauer Rose LLP and Hogan Lovells will be the legal counsel for Celgene and Skadden, Arps, Slate, Meagher and Flom LLP for Juno. (Reporting by Tamara Mathias and Manas Mishra in Bengaluru; Editing by Arun Koyyur)