Stock Incentive Plans - Schedule of Options Activity (Details) - 2008 Plan, 2016 Plan, and 2018 Inducement Incentive Award Plan - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2023	Dec. 31, 2022
Employees
Number of Options
Beginning balance (in shares)	15,578,412
Granted (in shares)	5,477,200
Forfeited (in shares)	(1,207,712)
Ending balance (in shares)	19,847,900	15,578,412
Vested (in shares)	8,956,975
Vested and expected to vest (in shares)	18,564,837
Weighted-average exercise price
Beginning balance (in dollars per share)	$ 3.44
Granted (in dollars per share)	1.15
Forfeited (in dollars per share)	2.84
Ending balance (in dollars per share)	2.85	$ 3.44
Vested (in dollars per share)	3.92
Vested and expected to vest (in dollars per share)	$ 2.93
Weighted-average remaining contractual term
Outstanding, term	7 years 11 months 4 days	7 years 6 months 25 days
Vested, term	6 years 8 months 4 days
Vested and expected to vest, term	7 years 10 months 2 days
Aggregate intrinsic value
Outstanding	$ 1	$ 4
Vested	1
Vested and expected to vest	$ 1
Non-employee consultants
Number of Options
Beginning balance (in shares)	266,239
Ending balance (in shares)	266,239	266,239
Vested (in shares)	266,239
Vested and expected to vest (in shares)	266,239
Weighted-average exercise price
Beginning balance (in dollars per share)	$ 8.05
Ending balance (in dollars per share)	8.05	$ 8.05
Vested (in dollars per share)	8.05
Vested and expected to vest (in dollars per share)	$ 8.05
Weighted-average remaining contractual term
Outstanding, term	4 years 6 months 29 days	5 years 29 days
Vested, term	4 years 6 months 29 days
Vested and expected to vest, term	4 years 6 months 29 days
Aggregate intrinsic value
Outstanding	$ 0	$ 0
Vested	0
Vested and expected to vest	$ 0