In April 2019, the Company entered into a lease for its corporate headquarters in Pasadena, California. The 91 month office building lease between the Company and 177 Colorado Owner, LLC is for approximately 24,000 square feet of office space located at 177 E. Colorado Blvd, Pasadena, California. The increased capacity of this new office space compared to the Company’s prior corporate headquarters will accommodate increased personnel as the Company’s pipeline of drug candidates expands and moves closer to market. Lease payments began on September 30, 2019 and are estimated to total approximately $8.7 million over the term. The lease expires on April 30, 2027. The Company has paid approximately $3.5 million for leasehold improvements, net of tenant improvement allowances. The lease contains an option to renew for one term of five years. The exercise of this option was not determined to be reasonably certain and thus was not included in lease liabilities on the Company’s Consolidated Balance Sheet at December 31, 2020. On October 23, 2020, the Company signed a lease expansion to add an additional approximately 24,000 square feet of office space at the same location for its corporate headquarters. The lease commencement date is expected to be in July 2021, after certain leasehold improvements are completed, and the lease expires in April 2027. The lease payments for the expansion are expected to total $6.9 million. The Company anticipates paying approximately $4.0 million of leasehold improvements, net of tenant improvement allowances. The increased capacity of this additional office space compared to the Company’s current corporate headquarters will accommodate increased personnel as the Company’s pipeline of drug candidates expands and moves closer to market.

In January 2016, the Company entered into a lease for its research facility in Madison, Wisconsin. The lease was for approximately 60,000 square feet of office and laboratory space and had an expiration date of September 30, 2026. The lease was amended in January 2019 and May 2020 to expand the rentable square feet by an additional 40,000 total square feet and extended the lease expiration date to September 30, 2031. Lease payments are estimated to total approximately $26.2 million for the term. The Company anticipates paying approximately $11.0 million of leasehold improvements for the additional 40,000 square feet, net of tenant improvement allowances. The lease contains two options to renew for two terms of five years. The exercise of these options were not determined to be reasonably certain and thus was not included in lease liabilities on the Company’s Consolidated Balance Sheet at December 31, 2020. In November 2020 and December 2020, two amendments were signed to expand the rentable square space by an additional 10,743 square feet and these amendments added a total of approximately $1.2 million of lease payments for the remainder of the term.

In March 2020, the Company entered into a sublease agreement (the “Sublease”) with Halozyme, Inc. for additional research and development facility space in San Diego, California. The Sublease provides additional space needed to accommodate the recent growth of the Company’s personnel and discovery efforts. The sublease is for approximately 21,000 rentable square feet. The term of the Sublease commenced on April 1, 2020 and will end on January 14, 2023. Sublease payments are estimated to total approximately $2.0 million over the term.

Operating lease cost during the three months ended December 31, 2020 and 2019 was $0.9 million and $0.5 million, respectively. Variable lease costs for the three months ended December 31, 2020 and 2019 was $0.2 million and $0.2 million, respectively. There was no short-term lease cost during the three months ended December 31, 2020 and 2019.

The following table presents maturities of operating lease liabilities on an undiscounted basis as of December 31, 2020:

	(in thousands)
2021 (remainder of fiscal year)	$	2,379
2022		3,853
2023		3,406
2024		3,269
2025		3,358
2026 and thereafter		15,331
Total	$	31,596
Less imputed interest	$	(10,728	)
Total operating lease liabilities (includes current portion)	$	20,868

Cash paid for the amounts included in the measurement of the operating lease liabilities on the Company’s Consolidated Balance Sheet and included in Other changes in operating assets and liabilities within cash flows from operating activities on the Company’s Consolidated Statement of Cash Flow for the three months ended December 31, 2020 and 2019 was $0.7 million and $0.3 million, respectively. The weighted-average remaining lease term and weighted-average discount rate for all leases as of December 31, 2020 was 9.2 years and 8.4%, respectively.