In December 2007, we closed the sale of our facility and associated real property for a purchase price of $109.0 million. Concurrent with the sale, we retired the entire $47.7 million in mortgage debt previously outstanding with respect to the facility and associated real property and received cash of $61.0 million, net of transaction costs and debt retirement. The ultimate result of this real estate sale was a net deferred gain of $39.1 million, of which the remaining balance was $8.0 million as of December 31, 2018, and which we recognized as a cumulative-effect adjustment to equity upon adoption of Topic 842 on January 1, 2019.

Upon closing of the sale of the facility and associated real property, we entered into an agreement (the original lease) to lease back our corporate headquarters, comprised of two buildings located in San Diego, California, for a term of 12 years. In 2008 through 2011, we entered into a series of subsequent amendments to the original lease, whereby we vacated one of the two buildings and continued to occupy one building (the existing premises). In June 2017, we entered into an amendment to the original lease (the amended lease), whereby we extended its term through December 31, 2029. In August 2019, we entered into an amendment (the 2019 amendment) to the amended lease, whereby we agreed to lease 80,282 square feet of additional office space (the expanded premises) in San Diego, California, for a term of 12 years, and to extend the total term of the original lease to a coterminous date of July 31, 2031.

Under the terms of the 2019 amendment, we will take possession of the expanded premises on a tranche-by-tranche basis as office space currently occupied by third-party tenants becomes available through 2021. Commencing on each applicable tranche lease commencement date and continuing throughout the term of the lease, we will be obligated to pay base annual rent (subject to an annual fixed percentage increase) and our then-applicable portion of the operating expenses and taxes attributable to the expanded premises. Additionally, we will continue to be obligated to pay base annual rent (subject to an annual fixed percentage increase), operating expenses, and taxes attributable to the existing premises.

The 2019 amendment includes two options to extend the term of the lease for a period of 10 years each. We were not reasonably certain to exercise either of these options at lease commencement. As such, neither option was recognized as part of the associated operating lease ROU asset or liability. In connection with the amended lease, in lieu of a cash security deposit, Wells Fargo Bank, N.A. (Wells Fargo) issued a $3.0 million letter of credit on our behalf, which is secured by a deposit of equal amount.

In May 2018, we entered into an agreement to lease 44,718 square feet of office space in San Diego, California, which commenced on July 1, 2018, for a term of 10 years and 10 months. Under the terms of the lease, we pay base annual rent (subject to an annual fixed percentage increase), plus property taxes, and other normal and necessary expenses, such as utilities, repairs, and maintenance. Certain incentives were included in the lease, including $4.2 million in tenant improvement allowances and twelve months of rent abatement. In lieu of a cash security deposit, Wells Fargo issued a $1.0 million letter of credit on our behalf, which is secured by a deposit of $0.7 million. We do not have the right to extend the lease or right of first offer for future rental of adjacent office space owned by the landlord.

For the nine months ended September 30, 2019, our operating lease cost was $5.9 million and cash paid for amounts included in the measurement of lease liabilities for operating cash flows from operating leases was $5.5 million. As of September 30, 2019, we reported operating lease ROU assets and operating lease liabilities of $62.0 million and $82.6 million, respectively. Further, as of September 30, 2019, our operating leases had a weighted average remaining lease term of 11.43 years and a weighted average discount rate of 5.84%.

At September 30, 2019, the approximate future minimum lease payments under operating leases were as follows:

(in thousands)	Operating Leases
Year Ending December 31,
2019 (3 months remaining)	$	2,142
2020		8,431
2021		9,026
2022		9,302
2023		9,586
Thereafter		77,068
Total operating lease payments		115,555
Less accreted interest		(32,914	)
Total operating lease liabilities		82,641
Less current operating lease liabilities		(8,159	)
Noncurrent operating lease liabilities	$	74,482

Note: Amounts presented in the table above exclude $47.4 million of non-cancelable future minimum lease payments for operating leases that have not yet commenced.