Note 9 - Net Loss Per Share Attributable to Common Stockholders (Tables)

6 Months Ended

Jun. 30, 2019

Notes Tables

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

	Three Months Ended June 30,				Six Months Ended June 30,
	2019		2018		2019		2018
Outstanding stock options		3,658,280		4,447,226		3,658,280		4,447,226
Outstanding ESPP shares		-		-		-		-
Convertible preferred stock		21,771,032		22,112,775		21,771,032		22,112,775
		25,429,312		26,560,001		25,429,312		26,560,001