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Equity Incentive Plans - Summary of Changes in Options Outstanding and Related Exercise Prices for Company's Common Stock Options Issued (Detail) - 2006 Plan and 2010 Plan [Member]
$ / shares in Units, $ in Thousands
12 Months Ended
Dec. 31, 2021
USD ($)
$ / shares
shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Number of Outstanding Options, Outstanding, Beginning balance | shares 4,255,371
Number of Outstanding Options, Granted | shares 1,761,962
Number of Outstanding Options, Forfeited or canceled | shares (622,088)
Number of Outstanding Options, Expired | shares (22,042)
Number of Outstanding Options, Outstanding, Ending balance | shares 5,373,203
Number of Outstanding Options, Vested and expected to vest at December 31, 2020 | shares 5,187,332
Number of Outstanding Options, Exercisable at December 31, 2020 | shares 3,980,138
Weighted Average Exercise, Outstanding, Beginning balance | $ / shares $ 3.41
Weighted Average Exercise, Granted | $ / shares 0.39
Weighted Average Exercise, Forfeited or canceled | $ / shares 2.14
Weighted Average Exercise, Expired | $ / shares 284.00
Weighted Average Exercise, Outstanding, Ending balance | $ / shares 1.42
Weighted Average Exercise, Vested and expected to vest at December 31, 2020 | $ / shares 1.46
Weighted Average Exercise, Exercisable at December 31, 2020 | $ / shares $ 1.77
Weighted Average Remaining Contractual Term (in years), Options Outstanding Ending Balance 7 years 3 months 21 days
Weighted Average Remaining Contractual Term (in years), Vested and expected to vest at December 31, 2020 7 years 2 months 23 days
Weighted Average Remaining Contractual Term (in years), Exercisable at December 31, 2020 6 years 6 months 29 days
Aggregate Intrinsic Value, Outstanding, Ending balance | $ $ 146
Aggregate Intrinsic Value, Vested and expected to vest at December 31, 2020 | $ 131
Aggregate Intrinsic Value, Exercisable at December 31, 2020 | $ $ 34