9. Leases

In February 2025, the Company entered into a Second Amendment (the “Winter Street Amendment”) which will terminate the lease entered into by the Company in 2022 for space at 840 Winter Street, Waltham, Massachusetts (the “840 Winter Lease”) on or before June 30, 2028. In connection with the Winter Street Amendment, the Company paid the landlord lease modification

payments totaling $78.0 million in three installments, with $34.0 million paid in February 2025, $30.0 million paid in April 2025 and $14.0 million paid in January 2026. In conjunction with the Winter Street Amendment, also in February 2025, the Company entered into a lease agreement (the “Tech Square Lease”) with the same landlord as the 840 Winter Lease, for office and laboratory space located at 400 Technology Square, Cambridge, Massachusetts (“400 Tech Square”).

Under the terms of the Tech Square Lease and subsequent amendments, the Company will lease approximately 125,000 square feet of office and laboratory space at 400 Tech Square. In addition, the Tech Square Lease will expand to include an additional 23,000 square feet of office and laboratory space at 400 Tech Square representing the 5th floor (the “Additional Tech Square Premises”) when such space becomes available.

The initial term of the Tech Square Lease is twelve years and three months beginning in September 2026 (the “Rent Commencement Date”). The Company’s obligation to pay rent will start in December 2026. The Company has an option to extend the Tech Square Lease for an additional term of five years. As of the Rent Commencement Date, the base rent under the Tech Square Lease will be $108.00 per square foot per year, plus certain operating expenses, and taxes. The base rent is subject to scheduled annual increases of 3% in July of each rent year. In addition, the Company is entitled to receive up to $410.00 per square foot of tenant improvement allowances. The Company has recorded $51.4 million of prepaid rent related to the Tech Square Lease within “Prepaid expenses and other current assets” in the condensed consolidated balance sheet as of June 30, 2026.

In April 2026, as part of its efforts to streamline its real estate portfolio, the Company amended its lease for 130 Brookline Street in Cambridge, Massachusetts to shorten the term from mid-2031 to December 31, 2026, in exchange for a $3.9 million fee payable in two equal installments, due in July 2026 and January 2027. This transaction resulted in a reduction of the 130 Brookline Street right-of-use asset from the remeasurement of the lease liability of approximately $2.1 million.

Excluded from the Future Operating Lease Payments table above is $189.1 million related to the Tech Square Lease, which had not yet commenced as of June 30, 2026. The Tech Square Lease is expected to commence in the third quarter of 2026.