Note 8 - Net Loss Per Share Attributable to Common Stockholders (Tables)

9 Months Ended

Sep. 30, 2019

Notes Tables

Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table Text Block]

	Three Months Ended September 30,				Nine Months Ended September 30,
	2019		2018		2019		2018
Outstanding stock options		772,847		4,597,226		772,847		4,597,226
Outstanding ESPP shares		-		26,642		-		26,642
Convertible preferred stock		21,771,032		22,112,775		21,771,032		22,112,775
		22,543,879		26,736,643		22,543,879		26,736,643