Blackstone Group agreed to buy landlord BioMed Realty Trust Inc. for $4.8 billion, betting on growth in real estate demand from the life sciences and biotechnology industries.

The world’s largest private equity investor in real estate will pay $23.75 a share in cash, according to a statement Thursday. That’s about 24 percent more than BioMed’s closing share price on Sept. 22, the day before Bloomberg reported that the San Diego-based real estate investment trust was working with Morgan Stanley to explore a sale.

Health-care spending is rising quickly in the United States, boosting demand for laboratory space that can accommodate pharmaceutical developers and manufacturers.

The transaction is valued at about $8 billion, including debt. The deal, which is supported by BioMed’s entire board of directors, is expected to close in the first quarter, subject to approval by shareholders.

BioMed “owns an exceptional collection of office buildings catering to life-science tenants in gateway markets including Boston-Cambridge, San Francisco, San Diego and Seattle,” said Nadeem Meghji, co-head of U.S. real estate acquisitions for Blackstone.