Cambridge-based Generation Bio Co. will build out a 104,000-square-foot biomanufacturing facility in Waltham after signing a $104 million lease.

The company said it plans to spend $45 million to build out the space at 41 Seyon St.

Fort Worth, Texas-based TPG Group’s Alloy life science platform bought the property for $340 million in January as part of 600,000-square-foot Waltham portfolio, with plans to add R&D-ready space for life science companies. The 41 Seyon St. property, located in the CenterPoint complex that also includes 43 Foundry Ave., was originally a Raytheon Corp. R&D and manufacturing facility and later converted into office space.

In an SEC filing, Generation Bio said the 12-year lease includes total payments of $104 million commencing on or about Sept. 1, 2022. The lease calls for monthly base rent of $437,500, and includes a $26 million construction allowance.

Newmark Managing Director Matt Malatesta represented ownership in the lease transaction.

Generation Bio is researching genetic medicines for diseases including hemophilia.