REGENXBIO Inc. Leases Disclosure

6. Leases

9804 Medical Center Drive

In November 2018, the Company entered into an operating lease, which has been amended from time to time, for approximately 186,000 square feet of office, laboratory and manufacturing space at 9804 Medical Center Drive in Rockville, Maryland (the 9804 Medical Center Drive Lease), which now serves as the Company’s corporate, research and manufacturing headquarters. The initial construction of the building was performed by the landlord and the lease commenced in September 2020 upon delivery of the leased premises to the Company to make additional improvements to the building. Monthly payments under the lease began in September 2021 and escalate annually in accordance with the lease agreement. The lease expires in September 2036, subject to extension and termination options held by the Company. The Company has an option to extend the term of the lease for up to 10 additional years and an option to terminate the lease, with payment of an early termination fee, after 12 years from the delivery of the leased premises to the Company. As of December 31, 2024, the Company’s extension and termination options under the 9804 Medical Center Drive Lease were excluded from the measurement of the right-of-use assets and lease liabilities as they were not reasonably certain of exercise. As required by the 9804 Medical Center Drive Lease, the Company has provided the landlord with an irrevocable letter of credit of $1.1 million which the landlord may draw upon in the event of any uncured default by the Company under the terms of the lease.

Pursuant to the 9804 Medical Center Drive Lease, the Company received a $19.5 million tenant improvement allowance from the landlord to perform improvements to the leased premises. The tenant improvement allowance was recorded as a reduction of the right-of-use assets for the lease and is amortized on a straight-line basis as a reduction of lease expense over the term of the lease. The

Company began occupation of a portion of the facility upon the completion of its construction in 2021. The remaining portion of the building, primarily associated with the manufacturing facility, was activated upon the completion of its construction in 2022. As of December 31, 2024, the Company had recorded property and equipment at cost of $132.6 million related to the buildout at 9804 Medical Center Drive, of which $131.6 million was placed in service and $1.0 million has not yet been placed in service.

As of December 31, 2024, the Company had recorded right-of-use assets of $42.9 million and lease liabilities of $69.0 million related to the 9804 Medical Center Drive Lease.

9712 Medical Center Drive

In March 2015, the Company entered into an operating lease for office space at 9712 Medical Center Drive in Rockville, Maryland (the 9712 Medical Center Drive Lease). The lease term commenced in April 2015, and monthly payments under the lease began in October 2015 and escalate annually in accordance with the lease agreement.

The 9712 Medical Center Drive Lease has been amended from time to time to include additional office and laboratory space at an adjacent building located at 9714 Medical Center Drive and extend the term of the lease, which expires in February 2027, subject to extension options held by the Company. The Company has an option to extend the term of the lease for three additional years, as well as an option to extend the lease term to be coterminous with the 9804 Medical Center Drive Lease, which expires in September 2036. As of December 31, 2024, the Company’s extension options under the 9712 Medical Center Drive Lease were excluded from the measurement of the right-of-use assets and lease liabilities as they were not reasonably certain of exercise. The Company received a $0.4 million tenant improvement allowance from the landlord which was recorded as a reduction of the right-of-use assets for the lease and is amortized on a straight-line basis as a reduction of lease expense over the term of the lease.

As of December 31, 2024, the Company had recorded right-of-use assets of $3.2 million and lease liabilities of $3.6 million related to the 9712 Medical Center Drive Lease.

New York Lease and Sublease

In May 2016, the Company entered into an operating lease for office space in New York, New York (the New York Lease), which has since been amended to include additional office space and extend the term of the lease. The lease term commenced in July 2016 and expires in April 2027. The Company received a $0.7 million tenant improvement allowance from the landlord which was recorded as a reduction of the right-of-use assets for the lease and is amortized on a straight-line basis as a reduction of lease expense over the term of the lease. As required by the New York Lease, the Company has provided the landlord with an irrevocable letter of credit of $0.2 million which the landlord may draw upon in the event of any uncured default by the Company under the terms of the lease.

In March 2024, the Company entered into an agreement to sublease its office space under the New York Lease (the New York Sublease) to a third-party subtenant. The sublease term commenced in April 2024 and expires in April 2027 concurrent with the expiration of the New York Lease. Monthly payments under the New York Sublease commenced in July 2024 and escalate annually in accordance with the sublease agreement. As of December 31, 2024, total undiscounted future minimum lease payments to be received by the Company over the term of the New York Sublease were $1.2 million. The Company recognized sublease income of $0.3 million under the New York Sublease during the year ended December 31, 2024.

The New York Sublease is classified as an operating lease and the Company was not relieved of its primary obligation under the New York Lease. The Company continues to account for the New York Lease as it did prior to the commencement of the sublease.

As a result of the New York Sublease, the Company determined an impairment indicator was present as of March 31, 2024 related to the long-lived asset group subject to the sublease, which included the right-of-use asset under the New York Lease, leasehold improvements and other property and equipment allocable to the New York Sublease. The Company concluded the carrying value of the asset group as of March 31, 2024 was not recoverable, as it exceeded the sum of the estimated undiscounted cash flows to be generated by the assets over their remaining lives. The Company estimated the fair value of the asset group as of March 31, 2024 using a discounted cash flow method, which incorporated unobservable inputs including the net identifiable cash flows over the term of the New York Sublease and an estimated borrowing rate of a market participant subtenant. The estimated fair value of the asset group as of March 31, 2024 represents a Level 3 nonrecurring fair value measurement. The Company concluded the carrying value of the asset group of $3.4 million exceeded its estimated fair value of $1.3 million as of March 31, 2024. As such, the Company recognized impairment losses of $2.1 million during the year ended December 31, 2024 on the long-lived asset group associated with the New York Sublease. The impairment losses were allocated to the various assets within the long-lived asset group based on their

relative carrying values and consisted of $1.4 million recorded to the right-of-use assets and $0.7 million recorded to property and equipment. No material impairment losses on long-lived assets were recorded during the years ended December 31, 2023 and 2022.

As of December 31, 2024, the Company had recorded right-of-use assets of $0.6 million and lease liabilities of $2.2 million related to the New York Lease.

Other Leases

In October 2022, the Company entered into an operating lease for office space in Washington, D.C. (the DC Lease). The lease term commenced in October 2022 and expires in October 2027. The Company has an option to extend the term of the lease for five additional years. As of December 31, 2024, the Company’s extension option under the DC Lease was excluded from the measurement of the right-of-use assets and lease liabilities as it was not reasonably certain of exercise. The Company recorded the right-of-use assets and lease liabilities related to the DC Lease upon its commencement in October 2022. As of December 31, 2024 the Company had recorded right-of-use assets of $4.0 million and lease liabilities of $4.0 million related to the DC Lease.

The Company leases additional office, laboratory and warehousing space, as well as laboratory and other equipment, under operating leases with various expiration dates through 2029, including leases which have been executed but have not yet commenced.

Operating Lease Information

All of the Company’s leases are classified as operating leases. The following table summarizes the Company’s lease costs and supplemental cash flow information related to its operating leases (in thousands):

Cash paid for amounts included in operating lease liabilities for the years ended December 31, 2024, 2023 and 2022 includes zero, $0.1 million and $1.3 million, respectively, received by the Company during the period under its tenant improvement allowances, which were deemed in-substance lease payments and included in the calculation of the lease liability. Short-term lease expense for the years ended December 31, 2024, 2023 and 2022 was not material and is included in operating lease cost in the table above. Variable lease cost under the Company’s operating leases includes items such as common area maintenance, utilities, taxes and other charges.

The table above excludes future minimum lease payments for leases which were executed but had not yet commenced as of December 31, 2024, the total of which were not material.