Developer Carter Winstanley has spent the last 22 years working to build up a life science hub in New Haven. Two decades later, 300 George is at capacity, and two subsequent Winstanley bioscience buildings — 25 Science Park and 100 College St., home of Alexion Pharmaceuticals — are also full. This spring, he plans to kick off construction on a second, $100 million bioscience tower at 101 College St., set to open in 2023, and he is finalizing deals with major tenants. Winstanley initially planned to break ground on the project last August, but delays due to COVID-19 have pushed back the start date until spring. Construction is expected to take two years. When he looks ahead to the next 10 years, Winstanley envisions an additional 5 million square feet of privately developed commercial life science space springing up around the medical school and hospital.