Photo courtesy of Jonathan Azize Photography

Developers of the first major life science building in Somerville’s Boynton Yards have recapitalized the property in a $478-million deal with a San Francisco investor joining the ownership.

The 289,000-square-foot 101 South St. property is the first phase of a 1.3 million-square-foot, master-planned development in the transforming neighborhood which awaits the completion of the MBTA Green Line Extension in March.

San Francisco-based TPG Real Estate Partners joined the ownership team, a joint venture of DLJ Real Estate Capital Partners and Leggat McCall Properties, which broke ground on the 9-story tower in 2019 with construction financing from Bank OKZ.

Companies backed by Cambridge-based biotech investor Flagship Pioneering have leased 280,000 square feet, according to DLJ Real Estate.

A second lab tower in the Boynton Yards project, known as 808 Windsor, broke ground in December with $246 million in construction financing.

TPG Real Estate Partners’ life science platform, Alloy Properties, previously acquired the Gauge and Centerpoint campuses in Waltham and 20 and 34 Crosby Drive in Bedford.

Flush with cash from venture capital investors, life science companies continued to expand throughout Greater Boston and added 5.2 million square feet of positive absorption during 2021, according to a report released this week by CBRE. Leasing velocity hit a peak of 2.4 million square feet in the fourth quarter.

Eighteen early-stage companies that received a collective $2.6 billion in venture capital funding leased 1 million square feet in the fourth quarter, according to CBRE.

Average lab rents topped $97 per square foot on a triple-net basis, with East Cambridge leading the pack at nearly $126 per square foot.

Correction 3:17 p.m., Jan. 11, 2022: This report has been updated with additional leasing information and to clarify that DLJ Real Estate and Leggat McCall Properties retained an ownership position in 101 South St.