Merck, one of the world’s largest drugmakers, agreed to buy Seattle-based biotechnology company Immune Design for $300 million in cash.

The deal’s price tag, at $5.85 per share, amounted to a more than 300 percent premium on the stock’s price at the previous day’s close. Shares of the company skyrocketed on the news.

“Scientists at Immune Design have established a unique portfolio of approaches to cancer immunization and adjuvant systems designed to enhance the ability of a vaccine to protect against infection, which could meaningfully improve vaccine development,” Dr. Roger M. Perlmutter, president of Merck Research Laboratories, said in a statement.

Merck said the acquisition would boost its capabilities in vaccine development for infectious diseases and cancer. The deal is expected to close early in the second quarter of this year.

Immune Design, which first debuted as a public company in 2014, develops therapies to fight diseases using the body’s immune system. The company is developing an immunotherapy treatment for non-Hodgkin’s lymphoma, as well as vaccines for peanut allergies and the respiratory syncytial virus. It also owns the Glaas and Zvex immunotherapy technologies.

“Merck has a rich history of discovery and innovation and a strong track record of developing meaningful therapeutics and vaccines,” Immune Design CEO Dr. Carlos Paya said in a statement. “We believe this agreement creates shareholder value by positioning our technologies and capabilities for long-term success with a leading, research-driven biopharmaceutical company.”

Immune Design restructured last year after abandoning the development of a cancer drug that treated relapsed synovial sarcoma. Immune Design was named the 18th-largest biotech in the Seattle area with 55 employees in 2017 by the Puget Sound Business Journal.