Loss Per Share (Tables)

6 Months Ended

Jun. 30, 2021

Dilutive Shares Which Could Exist Pursuant to Exercise of Outstanding Stock Instruments and Which were not Included in Calculation

Dilutive shares which could exist pursuant to the exercise of outstanding stock instruments and which were not included in the calculation because their affect would have been anti-dilutive are as follows:

	June 30, 2021 (shares)		June 30, 2020 (shares)
Warrants to purchase shares of common stock		11,357,964		12,538,204
Options to purchase shares of common stock		4,919,725		3,737,575
Shares of common stock issuable upon conversion of convertible note payable		2,049,428		—
Shares of common stock issuable upon conversion of preferred stock		510,424		514,602
	18,837,541		16,790,381