Note 2 - Summary of Significant Accounting Policies (Tables)

9 Months Ended

12 Months Ended

Sep. 30, 2019

Dec. 31, 2018

Notes Tables

Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block]


	As of December 31, 2018
		Level 1			Level 2			Level 3			Total
Financial liabilities
Warrant liability		$	—		$	—		$	140		$	140
Total financial liabilities		$	—		$	—		$	140		$	140


		As of December 31, 2017
		Level 1			Level 2			Level 3			Total
Financial liabilities:
Warrant liability		$	—		$	—		$	42		$	42
Total financial liabilities		$	—		$	—		$	42		$	42


		As of December 31, 2018
		Level 1			Level 2			Level 3			Total
Financial liabilities:
Warrant liability		$	—		$	—		$	140		$	140
Total financial liabilities		$	—		$	—		$	140		$	140

Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block]


		Nine Months Ended September 30,
		2018			2019
Fair value, beginning of period		$	42		$	140
Change in fair value of preferred stock warrants			1			94
Exchange of warrants upon Merger			—			(234)
Fair value at end of period		$	43		$	—

		Nine Months Ended September 30,
		2018			2019
Fair value, beginning of period		$	—		$	—
Embedded derivative liability from the issuance of Notes			864			—
Change in value of embedded derivatives			(211)			—
Fair value at end of period		$	653		$	—


		Years Ended
		December 31,
		2017			2018
Fair value, beginning of period		$	54		$	42
Preferred stock warrants – exercised			(8)			—
Change in fair value of preferred stock warrants			(4)			98
Fair value at end of period		$	42		$	140


		Years Ended
		December 31,
		2017			2018
Fair value, beginning of period		$	—		$	—
Embedded derivative liability from the issuance of Notes			—			864
Change in value of embedded derivatives			—			(211)
Termination of the embedded derivative liability due to the extinguishment of the related Notes			—			(653)
Fair value at end of period		$	—		$	—