13. Defined Contribution Plan

The Company began sponsoring a 401(k) Plan in 2017, which provides that eligible employees can elect to contribute to the 401(k) Plan, subject to certain limitations, on a pretax basis. The Company matches up to 50% of the first 4% of each employee’s contribution. During the year ended December 31, 2021, expenses recognized for the 401(k) Plan was $0.4 million, while the amount was immaterial for the years ended December 31, 2020 and 2019.