Note 9 - Stockholders' Equity	9 Months Ended
Sep. 30, 2020
Notes to Financial Statements
Stockholders' Equity Note Disclosure [Text Block]	9. Stockholders’ Equity *Common Stock* Registered Direct Offering On July 23, 2020, the Company completed a registered direct offering in which it issued and sold 9,433,962 shares of its common stock at a price of $1.06 per share. The total net proceeds from this offering were approximately $10.0 million, after deducting estimated expenses payable by the Company of $49,000. No underwriter or placement agent participated in the offering. ATM Agreement The Company has entered into a Controlled Equity Offering^SM Sales Agreement, or the ATM Agreement, with Cantor Fitzgerald & Co., or Cantor, as agent, pursuant to which the Company may offer and sell, from time to time through Cantor, shares of the Company’s common stock having an aggregate offering price of up to $40.0 million. On May 9, 2019, the Company increased the aggregate offering amount of shares of the Company’s common stock which may be offered and sold under the ATM Agreement by $40.0 million, for a total of $80.0 million. There were no shares of common stock sold pursuant to the ATM Agreement during the three months ended September 30, 2020. During the nine months ended September 30, 2020, the Company issued and sold 876,800 shares of common stock pursuant to the ATM Agreement, respectively, for which the Company received net proceeds of approximately $1.5 million. As of September 30, 2020, the Company has the ability to sell $43.8 million of the Company’s common stock under the ATM Agreement. *New and Amended* *Stock Plans* 2020 Equity Incentive Plan On June 16, 2020, at the 2020 Annual Meeting of Stockholders of the Company, the Company’s stockholders, upon the recommendation of the Company’s Board of Directors, approved the Company’s 2020 Equity Incentive Plan, or the 2020 EIP. As of June 16, 2020, no more awards may be granted under the 2011 Equity Incentive Plan, or the 2011 EIP, although all outstanding stock options and other stock awards previously granted under the 2011 EIP will continue to remain subject to the terms of the 2011 EIP. The initial aggregate number of shares of the Company’s common stock issuable pursuant to stock awards under the 2020 EIP was 5,500,000 shares. In addition, the share reserve will be increased by the number of returning shares, if any, as such shares become available from time to time under the 2006 Plan and the 2011 EIP, for an additional number of shares not to exceed 14,892,170 shares. The term of any option granted under the 2020 EIP is determined on the date of grant but shall not be longer than 10 years. The Company issues new shares for settlement of vested restricted stock units and exercises of stock options. The Company does not have a policy of purchasing its shares relating to its stock-based programs. Amended and Restated 2011 Employee Stock Purchase Plan Additionally, on June 16, 2020, the Company’s stockholders, upon the recommendation of the Company’s Board of Directors, approved the Amended and Restated 2011 Employee Stock Purchase Plan, or the Amended 2011 ESPP, which increased the aggregate number of shares of the Company’s common stock reserved for issuance under the 2011 Employee Stock Purchase Plan, or ESPP, to 4,900,000 shares, subject to adjustment for certain changes in the Company’s capitalization, and removed the “evergreen” provision from the ESPP.

Note 9 - Stockholders' Equity

9 Months Ended

Sep. 30, 2020

Stockholders' Equity Note Disclosure [Text Block]

9. Stockholders’ Equity

Common Stock

Registered Direct Offering

On July 23, 2020, the Company completed a registered direct offering in which it issued and sold 9,433,962 shares of its common stock at a price of $1.06 per share. The total net proceeds from this offering were approximately $10.0 million, after deducting estimated expenses payable by the Company of $49,000. No underwriter or placement agent participated in the offering.

ATM Agreement

The Company has entered into a Controlled Equity Offering^SM Sales Agreement, or the ATM Agreement, with Cantor Fitzgerald & Co., or Cantor, as agent, pursuant to which the Company may offer and sell, from time to time through Cantor, shares of the Company’s common stock having an aggregate offering price of up to $40.0 million. On May 9, 2019, the Company increased the aggregate offering amount of shares of the Company’s common stock which may be offered and sold under the ATM Agreement by $40.0 million, for a total of $80.0 million.

There were no shares of common stock sold pursuant to the ATM Agreement during the three months ended September 30, 2020. During the nine months ended September 30, 2020, the Company issued and sold 876,800 shares of common stock pursuant to the ATM Agreement, respectively, for which the Company received net proceeds of approximately $1.5 million. As of September 30, 2020, the Company has the ability to sell $43.8 million of the Company’s common stock under the ATM Agreement.

New and Amended Stock Plans

2020 Equity Incentive Plan

On June 16, 2020, at the 2020 Annual Meeting of Stockholders of the Company, the Company’s stockholders, upon the recommendation of the Company’s Board of Directors, approved the Company’s 2020 Equity Incentive Plan, or the 2020 EIP.

As of June 16, 2020, no more awards may be granted under the 2011 Equity Incentive Plan, or the 2011 EIP, although all outstanding stock options and other stock awards previously granted under the 2011 EIP will continue to remain subject to the terms of the 2011 EIP.

The initial aggregate number of shares of the Company’s common stock issuable pursuant to stock awards under the 2020 EIP was 5,500,000 shares. In addition, the share reserve will be increased by the number of returning shares, if any, as such shares become available from time to time under the 2006 Plan and the 2011 EIP, for an additional number of shares not to exceed 14,892,170 shares. The term of any option granted under the 2020 EIP is determined on the date of grant but shall not be longer than 10 years. The Company issues new shares for settlement of vested restricted stock units and exercises of stock options. The Company does not have a policy of purchasing its shares relating to its stock-based programs.

Amended and Restated 2011 Employee Stock Purchase Plan

Additionally, on June 16, 2020, the Company’s stockholders, upon the recommendation of the Company’s Board of Directors, approved the Amended and Restated 2011 Employee Stock Purchase Plan, or the Amended 2011 ESPP, which increased the aggregate number of shares of the Company’s common stock reserved for issuance under the 2011 Employee Stock Purchase Plan, or ESPP, to 4,900,000 shares, subject to adjustment for certain changes in the Company’s capitalization, and removed the “evergreen” provision from the ESPP.