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45 Summer Street
Eli Lilly is deepening its stake in Boston’s Seaport District by securing a new lease that grants the company exclusive control of the 645 Summer Street building. The Indianapolis‑based firm has added 75,000 sq ft, bringing its total occupancy to 150,000 sq ft and making it the sole tenant of the two‑story laboratory complex.
The structure, erected in 1966 and updated in 2019, formerly housed gene‑editing startup Akouos, which Lilly bought in 2022. Akouos had occupied half the space before the acquisition. The expanded site now operates as Lilly Harborside Research & Development Labs, according to the Boston Business Journal.
The move expands Lilly’s growing Seaport presence, which already includes the 12‑story, 346,000‑sq‑ft Lilly Seaport Innovation Center on Necco Street that opened in 2024. That hub serves as the company’s primary center for genetic‑medicine research and hosts the East Coast branch of its Gateway Labs incubator.
Allison Howell, Lilly’s associate director of R&D communications, confirmed the lease, noting that “as Lilly’s Seaport footprint expands across these two sites, the need for additional space became critical.” She added that the facilities focus on RNA and DNA‑based therapies and on discovering new drug targets for conditions such as diabetes, obesity, cardiovascular disease, neurodegeneration, chronic pain, immunology, and hearing disorders.
The 2024 opening of the Seaport Innovation Center marked a strategic shift from Cambridge to Boston’s waterfront, solidifying Lilly’s role in one of the city’s fastest‑growing life‑sciences clusters.
