Organization and Basis of Presentation - Additional Information (Details)			1 Months Ended	3 Months Ended	6 Months Ended		12 Months Ended
	Aug. 15, 2018	Jul. 16, 2018	Aug. 31, 2018 USD ($) $ / shares shares	Mar. 31, 2019 shares	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)
Organization And Basis Of Presentation [Line Items]
Number of securities called by each warrant or right | shares			1
Conversion ratio	0.5	0.0467
Accumulated deficit | $					$ (88,278,737)		$ (72,762,428)
Net cash used in operating activities | $					(12,868,425)	$ (9,753,921)	19,900,000
Cash and cash equivalents | $					$ 15,294,526		$ 16,522,729
Common Stock
Organization And Basis Of Presentation [Line Items]
Number of units sold (shares) | shares				748,427
Number of securities called by each IPO unit | shares			1
Common warrants
Organization And Basis Of Presentation [Line Items]
Number of securities called by each IPO unit | shares			1
Initial Public Offering
Organization And Basis Of Presentation [Line Items]
Number of units sold (shares) | shares			3,864,000
Offering price per unit | $ / shares			$ 6.125
Net cash proceeds after deducting underwriting discounts and commissions | $			$ 19,400,000
Underwriters' discounts and commissions | $			2,200,000
Offering expenses | $			$ 2,100,000
Number of common stock issuable upon conversion of convertible preferred stock (shares) | shares			2,850,280
Conversion of preferred stock warrants into common stock warrants | $			$ 84,676
Fair value of warrants | $			$ 400,000
Percentage of offering price per unit			100.00%
Initial Public Offering | Common Stock
Organization And Basis Of Presentation [Line Items]
Outstanding convertible promissory notes and accrued interest converted, amount | $			$ 14,900,000
Outstanding convertible promissory notes and accrued interest converted, shares | shares			3,239,294
Initial Public Offering | Maximum
Organization And Basis Of Presentation [Line Items]
Issuance of warrants to underwriters to purchase of common stock | shares			115,920
Underwriters Over-Allotment Option
Organization And Basis Of Presentation [Line Items]
Number of units sold (shares) | shares			504,000