LEASES	6 Months Ended
LEASES	Jun. 30, 2021
Leases [Abstract]
LEASES	LEASES On January 14, 2020, the Company entered into a non-cancelable real property lease agreement for 61,282 square feet of laboratory and office space at 75 Hayden Avenue in Lexington, Massachusetts (the “75 Hayden Avenue” lease). The original term commenced during the fourth quarter of 2020 and is for 125 months with options to extend for two additional successive periods of five years thereafter. On July 1, 2020, the Company entered into an amendment to the 75 Hayden Avenue lease (the “75 Hayden Amendment”). The 75 Hayden Amendment expanded the square footage leased under the 75 Hayden Avenue lease by 30,446 square feet to contain a total of  91,728 rentable square feet and increased the monthly base rent by an average of $0.2 million per month. The term for the additional space under the 75 Hayden Amendment commenced for accounting purposes during the second quarter of 2021 and is for 118.5 months with options to extend for two additional successive periods of five years thereafter. Payments for the extensions are not included in measurement of the right-of-use (“ROU”) asset and lease liability, as it is not reasonably certain that the Company will exercise its options to extend the lease term. The aggregate total fixed rent for the 75 Hayden Amendment is approximately $21.3 million with the annual fixed rental payments increasing from $1.9 million to $2.6 million during the amended term. The Company recognized an ROU asset and a lease liability of approximately $17.2 million and $15.3 million, respectively, in the three months ended June 30, 2021 related to the 75 Hayden Amendment. The interest rate implicit in the lease agreement is not readily determinable, and as such, the Company utilizes its incremental borrowing rate to calculate the lease liability, which is the rate incurred to borrow, on a collateralized basis for a similar term, an amount equal to the lease payments in a similar economic environment at the time the asset is made available to the Company.

Dicerna Pharmaceuticals Inc 10-Q