The Company leases approximately 19,900 square feet of office space in Cambridge, Massachusetts under a lease that began in May 2018 and is scheduled to expire on June 14, 2022 (the “Lease”), as discussed further below. Upon adoption of ASC 842, the Company recorded a right-of-use asset and corresponding lease liability for the Lease on January 1, 2019, by calculating the present value of lease payments, discounted at 6%, the Company’s estimated incremental borrowing rate annually, over the 2-year remaining term.

The Company adopted ASC 842 as of January 1, 2019 using the effective date method, in which the Company did not restate prior periods. Upon adoption, the Company elected the package of practical expedients permitted under the transition guidance within ASC 842, which among other things, allowed it to carry forward the historical lease classification. The Company does not allocate consideration in its leases to lease and non-lease components and does not record leases on its balance sheets with terms of 12 months or less.

The Company uses its estimated incremental borrowing rate, which is derived from information available at the lease commencement date, in determining the present value of lease payments. The Company’s incremental borrowing rate represents the rate of interest that it would have to pay to borrow over a similar term an amount equal to the lease payments in a similar economic environment.

The adoption of ASC 842 on January 1, 2019 resulted in the recognition of approximately $9,692,000 of right-of-use asset and $9,347,000 of lease liabilities on the Company’s balance sheet. The adoption did not have a material net impact on the Company’s consolidated statements of operations and comprehensive loss or accumulated deficit. The Company will review the classification of newly entered leases as either an operating or a finance lease and recognize a related right-of-use asset and lease liability on its balance sheet upon commencement.

On January 18, 2018, the Company entered into an operating lease agreement for its laboratory and office space in Cambridge, Massachusetts for the period from May 1, 2018 through April 30, 2021 (the “Laboratory and Office Lease”). The lease contains escalating payments during the lease period. Upon execution of this lease agreement, the Company prepaid three months of rent, two of which will be held in escrow and credited against future rent payments and the other of which was applied to the first month’s rent. The Company also prepaid seven and one-half months’ rent pursuant to an amendment to the lease agreement executed on June 18, 2018. These amounts were recorded to deposits and prepaid expenses, respectively, at December 31, 2018. On June 18, 2018, the Company entered into an amendment to the Laboratory and Office Lease that provided the Company with a reduction in rental fees for its office and laboratory space in exchange for prepayment of a portion of the fees. This amendment was effective beginning on May 15, 2018.

The monthly rent payment due under the Laboratory and Office Lease, as amended, was $330,550 until April 2021 and increased to $375,174 for the remainder of the term.

On September 20, 2018, the Company entered into an operating lease for additional laboratory space at 21 Erie Street, Cambridge, Massachusetts for the period from October 15, 2018 through April 14, 2021 (the “Additional Laboratory Lease”). The lease contains escalating payments during the lease period. The monthly rental rate under the Additional Laboratory Lease was $72,600 for the first 12 months and $78,600 for the remainder of the term. Upon execution of this lease agreement, the Company prepaid 12 months’ rent pursuant to the lease agreement executed on September 20, 2018.

On September 19, 2019, the Company entered into a second amendment to the Additional Laboratory Lease that removed one holding room from the additional laboratory space. The amendment was effective beginning on October 1, 2019. The monthly rental rate under the Additional Laboratory Lease decreased from $78,600 to $58,995 for the remainder of the lease term. The partial termination of the lease did not change the classification of the lease and remained accounted for as an operating lease. The weighted-average discount rate remained the same at 6%. The Company accounted for the lease modification under ASC 842 that removed one holding room by electing Approach 1, which remeasured the right-of-use asset on the basis of the amount of the liability change. The modification of the partial termination resulted in a reduction to right-of-use asset and lease liability of $335,465 and $327,079, respectively. The difference of $8,386 was recorded as a loss to the right-of-use asset as of December 31, 2020.

On June 24, 2020, the Company entered into a second amendment to the Laboratory and Office Lease. Pursuant to the amendment (1) the term of the lease was extended to June 14, 2022 and (2) the monthly rental rate for the last 14 months of the lease term was increased to $375,174. The Company determined that the amendment should be accounted for as a lease modification applicable under ASC 842, not as a separate contract, with an effective date of lease modification of May 14, 2020. At the effective date of modification, the Company recorded an adjustment to the right-of-use asset and lease liability in the amount of approximately $4,826,000.

On July 20, 2020, the Company entered into a third amendment to the Additional Laboratory Lease. Pursuant to the amendment, the term of the lease was extended to June 14, 2022. The Company determined that the amendment should be accounted for as a lease modification applicable under ASC 842, not as a separate contract, with an effective date of lease modification of August 4, 2020, when the agreement was fully executed. At the effective date of modification, the Company recorded an adjustment to the right-of-use asset and lease liability in the amount of approximately $813,000.

At September 30, 2021, the Company recorded approximately $3,369,000 to operating lease right-of-use asset, and approximately $3,633,000 to the short-term operating lease liability. At September 30, 2021, the remaining lease term was 1 year for both leases. At December 31, 2020, the Company recorded approximately $6,774,000 to operating lease right-of-use asset, and approximately $4,777,000 and $2,369,000 to short- and long-term operating lease liability, respectively. At December 31, 2020, the remaining lease term was 1.46 years for both leases. As of September 30, 2021 and December 31, 2020, a security deposit of approximately $177,000 is included in deposits on the Company’s consolidated balance sheet.

Future minimum lease payments under these leases at September 30, 2021 are as follows:

Year	(in thousands)
2021		1,312
2022		2,408
Total lease payment	$	3,720
Less: present value discount		(87	)
Total	$	3,633

Total rent expense of approximately $1,223,000 and $1,212,000 was included in the consolidated statement of operations and other comprehensive loss for the three months ended September 30, 2021 and 2020, respectively, and $3,668,000 and $3,372,000 for the nine months ended September 30, 2021 and 2020, respectively. Other information pertaining to the Company’s operating leases for the three and nine months ended September 30, 2021 is summarized in the table below.

Other information (in thousands)	Three Months Ended September 30, 2021		Nine Months Ended September 30, 2021
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$	1,285	$	3,744
Operating lease cost	$	1,225	$	3,670
Weighted average discount rate	6.0%		6.0%
Weighted average remaining lease term	0.71 year		0.71 year