Summary of Significant Accounting Policies (Tables)

3 Months Ended

Mar. 31, 2017

Accounting Policies [Abstract]

Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table Text Block]

The stock-based compensation expense recorded for the three months ended March 31, 2017 and 2016 is as follows:

	Three Months Ended March 31,
	2017		2016
Research and development	$	94	$	87
General and administrative		967		1,044
Total stock-based compensation expense	$	1,061	$	1,131

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

The following table sets forth the outstanding potentially dilutive securities that have been excluded in the calculation of diluted loss per share attributable to common stockholders (in common stock equivalent shares):

	March 31,
	2017		2016
Series A convertible preferred stock		—		400,000
Series B convertible preferred stock		—		454,581
Convertible promissory notes		—		533,031
Common stock purchase warrants		829,284		710,487
Restricted stock unit		855,430		—
Common stock options		1,502,300		1,556,867
Total		3,187,014		3,654,966