Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Income Taxes [Line Items]
Deferred income tax expense (benefit)	$ 0	$ 0
Deferred tax assets change in valuation allowance	30,401,000	32,066,000
Deferred tax assets, operating loss carryforwards, domestic	312,967,000	$ 213,991,000
Deferred tax assets, operating loss carryforwards, not subject to expiration	295,224,000
Payroll tax liability capped per year	250,000
Income tax reconciliation tax credit research	$ 250,000
Income tax credit carryforward expiration period	20 years
Research and development tax credits	2.00%	2.30%
Percentage of cumulative changes in ownership interest subject to annual limitation	50.00%
Period of cumulative changes in ownership interest	3 years
U.S. federal [Member]
Income Taxes [Line Items]
Research and development tax credits carryforwards	$ 6,234,000	$ 3,677,000
Australia [Member]
Income Taxes [Line Items]
Income tax reconciliation tax credit research	$ 1,210,000	589,000
Australia [Member] | Maximum [Member]
Income Taxes [Line Items]
Research and development tax credits	43.50%
Orphan Drug Credit [Member] | U.S. federal [Member]
Income Taxes [Line Items]
Research and development tax credits carryforwards	$ 1,959,000
Expiration Through 2037 [Member]
Income Taxes [Line Items]
Deferred tax assets, operating loss carryforwards, subject to expiration	17,743,000
Expiration Through 2039 [Member]
Income Taxes [Line Items]
Deferred tax assets, operating loss carryforwards, state	290,500,000	201,642,000
Expiration Through 2033 [Member] | State [Member]
Income Taxes [Line Items]
Research and development tax credits carryforwards	$ 1,959,000	$ 894,000