Note 10 - Shareholders' Equity

12 Months Ended

Dec. 31, 2021

Notes to Financial Statements

Stockholders' Equity Note Disclosure [Text Block]

Note 10 — Stockholders' Equity

Common Stock Purchase Agreement

On  October 24, 2019, the Company entered into a Common Stock Purchase Agreement with Ninteenth Investment Company LLC, an affiliate of Mubadala Investment Company PJSC (the “Purchaser”).  During the year ended  December 31, 2021, the Company issued an additional 797,450 shares of Company common stock to the Purchaser pursuant to the terms of the Common Stock Purchase Agreement.

At-the-Market Program

In  August 2021, the Company entered into an at-the-market sales agreement with Virtu Americas LLC (“Virtu”) pursuant to which the Company  may sell shares of Company common stock from time to time through Virtu acting as sales agent, for aggregate proceeds of up to $50 million.  During the year ended  December 31, 2021, the Company sold approximately 0.2 million shares for proceeds, net of placement fees, of approximately $0.6 million.

Common Stock Warrants

During the year ended  December 31, 2021, Common Stock Warrants were exercised by certain holders of Series A Preferred Stock and Series B Preferred Stock.  In connection with the exercises of Common Stock Warrants, the Company issued an aggregate of approximately 1.5 million shares of Company common stock.