7. STOCKHOLDERS’ EQUITY

Authorized shares

We are authorized to issue up to 33.3 million shares of common stock with a par value of $0.0001 per share, 0.8 million shares of class C special stock with a par value of $0.0001 per share, and 1.7 million shares of undesignated preferred stock with a par value of $0.0001 per share at December 31, 2017.

There were 11.7 million and 11.6 million shares of common stock issued and outstanding as of December 31, 2017 and 2016, respectively.

There were 11 thousand shares of class C special stock issued and outstanding as of December 31, 2017 and 2016. Each share of class C special stock entitles its holder to one vote per share. Each share of class C special stock is exchangeable, at the option of the holder, for one share of our common stock, at an exchange price of $90.00 per share, subject to adjustment upon certain capitalization events. Holders of class C special stock are not entitled to receive dividends or to participate in the distribution of our assets if we were to liquidate, dissolve, or wind-up the company. The holders of class C special stock have no cumulative voting, preemptive, subscription, redemption, or sinking fund rights.

There were no shares of undesignated preferred stock outstanding as of December 31, 2017 and 2016.

Stock Repurchase Program

In October 2015, our Board of Directors authorized a program to repurchase up to $25.0 million of our outstanding common stock through December 31, 2016. The authorization allows for repurchases to be conducted through open market or privately negotiated transactions. Shares acquired under the stock repurchase program are returned to the status of authorized but unissued shares of common stock. The stock repurchase program could be suspended, modified, or discontinued at any time at our discretion.

In January 2016, we purchased 65 thousand shares under the stock repurchase program for $2.5 million. The repurchased shares were returned to the status of authorized but unissued shares of common stock. This program terminated on December 31, 2016.

Warrants

Warrants to purchase an aggregate of 2.1 million shares of our common stock were outstanding and exercisable as of December 31, 2017:

Issue Date	Number of Underlying Shares of Common Stock (in thousands)		Per Share Exercise Price		Expiration Date
December 4, 2014		1,799	$	96.21	March 1, 2020
December 5, 2014		270	$	96.21	March 1, 2020

All outstanding warrants are classified as equity. No warrants were granted, exercised, or expired unexercised during the year ended December 31, 2017 and 2016.

No warrants were issued or exercised during the year ended December 31, 2015. Warrants to purchase 405 thousand shares of common stock expired during the year ended December 31, 2015.