Additional Balance Sheet Detail - Schedule of Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Balance Sheet Related Disclosures [Abstract]
External research and development	$ 1,779	$ 437
Payroll and benefits	1,511	1,448
Professional services	168	254
Capital lease obligation, current portion	49	46
Restricted stock liability, current portion	15	18
Property and equipment purchases		174
Other	61	120
Total accrued expenses and other current liabilities	$ 3,583	$ 2,497

Accrued liabilities and other current liabilities.

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- Definition

Accrued property and equipment purchases.

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- Definition

Accrued research and development expenses.

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- Definition

Accrued restricted stock liability, current.

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Carrying value as of the balance sheet date of obligations incurred through that date and payable for professional fees, such as for legal and accounting services received. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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Amount of capital lease obligation due within one year or the normal operating cycle, if longer.

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Total of the carrying values as of the balance sheet date of obligations incurred through that date and payable for obligations related to services received from employees, such as accrued salaries and bonuses, payroll taxes and fringe benefits. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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Amount of liabilities classified as other, due within one year or the normal operating cycle, if longer.

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