U.S. biotechnology company Biogen Inc. plans to acquire British clinical-stage gene therapy company Nightstar Therapeutics PLC for around $800 million in cash.

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

Biogen said that Nightstar Therapeutics will advance the company’s entry into ophthalmology by contributing two mid- to late-stage gene therapy assets.

Biogen noted that it intends to finance the transaction through available cash.