Greystar’s 465,000-square-foot 74M office-lab tower in Somerville. Image courtesy of Elkus Manfredi Architects

Demand for life science space declined in the second quarter as the lab vacancy rate in Greater Boston hit 14.3 percent, according to a brokerage report.

The industry hub of Cambridge has the lowest vacancy rate of any local submarket at 8.5 percent, up from 6.4 percent in the first quarter, Cushman & Wakefield reported.

Nearly 1.2 million square feet of lab space in new developments have been completed since January, of which 38 percent has been leased. Approximately 35 percent of the nearly 15 million square feet in development is preleased.

Greater Boston has over 35 million square feet of lab space, of which nearly 15 percent is currently being marketed for lease.

“We believe leasing activity will rebound and normalize over the coming quarters, as Greater Boston will always be a market that life science companies depend on to flourish and thrive due to our deep pool of talent,” Cushman & Wakefield Vice Chairman Connor Barnes said in a statement.

More than two-thirds of the new projects under construction in Cambridge are preleased, compared with 63 percent in Boston’s central business district, the report said.

Major developments under construction include BioMed Realty’s Assembly Innovation Park and Greystar’s 74M lab tower in Somerville, and Boston Global Investors’ 10 World Trade development in Boston’s Seaport District.