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Biogen to buy Nightstar Therapeutics in $800 mln cash deal

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March 4 (Reuters) - Biogen Inc said on Monday it will buy Nightstar Therapeutics Plc for about $800 million in cash as the company looks to tap into a potentially lucrative gene therapy market.

Biogen's offer of $25.50 per share, represents a premium of 68 percent to Nightstar's Friday close of $15.16.

Gene therapy, an emerging field of biotechnology, uses specially engineered viruses, or viral vectors, to deliver genetic material into defective cells, in hopes of improving or potentially even curing an inherited condition.

London-based gene therapy company Nightstar is focused on adeno-associated virus (AAV) treatments for inherited retinal disorders.

"Ophthalmology is an emerging growth area for Biogen," said Michel Vounatsos, Biogen's chief executive officer. "Nightstar would accelerate our entry into ophthalmology by contributing two mid- to late-stage gene therapy assets."

Biogen said it plans to fund the acquisition through available cash.

Last week, Sarepta Therapeutics Inc beefed up its gene therapy portfolio through the purchase of its partner Myonexus Therapeutics Inc, while Swiss drugmaker Roche Holding AG said it was buying U.S.-based gene therapy specialist Spark Therapeutics Inc for $4.3 billion.

Goldman, Sachs & Co is acting as financial adviser to Biogen and Centerview Partners was Nightstar's financial adviser. (Reporting by Rishika Chatterjee and Subrat Patnaik in Bengaluru; Editing by Shounak Dasgupta)