Stock-Based Awards - Summary of Stock Option Activity (Detail) - $ / shares	6 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Shares, Beginning balance	3,320,706
Number of Shares, Granted	1,771,000
Number of Shares, Canceled	(401,754)
Number of Shares, Ending balance	4,689,952	3,320,706
Number of Shares, Options exercisable	1,879,181	1,415,900
Number of Shares, Options vested and expected to vest	4,587,708	3,264,851
Weighted Average Exercise Price, Beginning balance	$ 3.87
Weighted Average Exercise Price, Granted	0.72
Weighted Average Exercise Price, Exercised	0.00
Weighted Average Exercise Price,Canceled	6.54
Weighted Average Exercise Price, Forfeited	0.00
Weighted Average Exercise Price, Ending balance	2.45	$ 3.87
Weighted Average Exercise Price, Options exercisable	3.68	5.56
Weighted Average Exercise Price, Options vested and expected to vest	$ 2.48	$ 3.89
Weighted-Average Remaining Contractual Term, Outstanding	8 years 6 months	7 years 4 months 24 days
Weighted Average Remaining Contractual Term, Options exercisable	7 years 7 months 6 days	5 years 2 months 12 days
Weighted Average Remaining Contractual Term, Options vested and expected to vest	8 years 6 months	7 years 4 months 24 days