125 Lincoln St. Boston

Greater Boston life science leasing hit a lull in the fourth quarter amid the nation’s largest lab development boom.

The region’s lab market had 99,000 square feet of negative absorption while construction of 3.9 million square feet of life science facilities is under way and another 18.4 million square feet are proposed, according to research by brokerage Avison Young.

West Cambridge led the region in 2020 with 255,000 square feet of net absorption during 2020. The market-wide vacancy rate ended 2020 at 5 percent, and asking triple-net rents range from $32.24 in the Route 495 submarket to $104.28 in East Cambridge.

Traditional office landlords and developers are looking to the life science sector for growth opportunities while office leasing stalls during the pandemic, contributing to the growing lab pipeline. Former office buildings switching to lab-ready designs include Boston Global Investors’ 401 Congress St. and Oxford Property Group’s proposed 125 Lincoln St. tower.

Greater Boston’s 3.9-million-square-foot lab construction pipeline is 1 million square feet larger than any other U.S. market, according to Avison Young. The region’s research hospitals and biotech startups continue to attract strong investment, receiving over $10 billion in National Institutes of Health and venture capital funding in 2020, up from $7.2 billion in 2019.