Description of Capital Stock

Exhibit 4.1

Description of the Company’s Common Stock Registered

Under Section 12 of the Exchange Act of 1934

The following is a description of the common stock, $0.0001 par value per share (“Common Stock”) of Sunesis Pharmaceuticals, Inc. (the “Company”), which is the only security of the Company registered pursuant to Section 12 of the Securities and Exchange Act of 1934, as amended.  The following summary describes the material terms of our Common Stock. The description of our Common Stock is based on the provisions of our amended and restated certificate of incorporation, our amended and restated bylaws and the applicable provisions of the Delaware General Corporation Law (the “DGCL”). This information may not be complete in all respects and is qualified entirely by reference to our amended and restated certificate of incorporation, our amended and restated bylaws and the DGCL. For a complete description of the terms and provisions of the Company’s capital stock, including its Common Stock, refer to our amended and restated certificate of incorporation and our amended and restated bylaws, both of which are filed as exhibits to our Annual Report on Form 10-K filed with the Securities Exchange Commission on March 10, 2020. Capitalized terms used but not defined herein have the meanings given them our amended and restated certificate of incorporation.

Common Stock

The Company is authorized to issue up to 400,000,000 shares of Common Stock. The holders of Common Stock are entitled to one vote for each share held of record on all matters submitted to a vote of the stockholders and do not have cumulative voting rights with respect to the election of directors. Generally, all matters to be voted on by stockholders must be approved by the holders of a majority of the Common Stock and Preferred Stock (voting together as a single class on an as-if converted basis), or, in the case of the election of directors, a plurality, represented at a meeting at which a quorum is present. Subject to preferences that may be applicable to the outstanding shares of Preferred Stock, the holders of Common Stock are entitled to receive ratably such dividends as may be declared by the board of directors out of funds legally available therefor. Upon the liquidation, dissolution or winding up of the Company, holders of our Common Stock are entitled to share ratably in all assets legally available for distribution to stockholders remaining after payment of liabilities and the liquidation preferences of outstanding shares of Preferred Stock. Holders of Common Stock have no preemptive rights and no right to convert their Common Stock into any other securities. There are no redemption or sinking fund provisions applicable to our Common Stock.

Anti-Takeover Effects of Provisions of Charter Documents and Delaware Law

Charter Documents

In accordance with our amended and restated certificate of incorporation, our board of directors is divided into three classes, with staggered three-year terms. Only one class of directors is elected at each annual meeting of our stockholders, with the other classes continuing for the remainder of their respective three-year terms. Because our stockholders do not have cumulative voting rights, in the case of the election of directors, holders of a plurality of the Common Stock represented at a meeting at which a quorum is present will be able to elect all of our directors. Our amended and restated certificate of incorporation and our amended and restated bylaws provide that all actions taken by the holders of Common Stock must be effected at a duly called meeting of stockholders and not by a consent in writing, and that only our board of directors, chairman of the board, chief executive officer, or president (in the absence of a chief executive officer) or holder of greater than 10% of our Common Stock may call a special meeting of stockholders. Our amended and restated certificate of incorporation requires a 66- 2/3% stockholder vote for the amendment, repeal or modification of certain provisions of our amended and restated certificate of incorporation and our amended and restated bylaws relating to the absence of cumulative voting, the classification of our board of directors, the requirement that stockholder actions be effected at a duly called meeting, and the designated parties entitled to call a special meeting of the stockholders.

The classification of our board of directors, the lack of cumulative voting and the 66- 2/3% stockholder voting requirements make it more difficult for our existing holders of our Common Stock to replace our board of directors as well as for another party to obtain control of us by replacing our board of directors. Since our board of directors has the power to retain and discharge our officers, these provisions could also make it more difficult for existing holders of our Common Stock or another party to effect a change in management.

In addition, the authorization of undesignated Preferred Stock makes it possible for our board of directors to issue shares of Preferred Stock with voting or other rights or preferences that could impede the success of any attempt to change our control.

Our amended and restated certificate of incorporation authorizes our board of directors to issue up to 10,000,000 shares of our Preferred Stock, of which, as of December 31, 2019: (i) 5,000,000 are designated Series A Preferred Stock, none of which are issued and outstanding as, (ii) 30,000 are designated as Series B Preferred Stock, none of which are issued and outstanding, (iii) 3,000 are designated as Series C Preferred Stock, none of which are issued and outstanding, (iv) 2,500 are designated as Series D Preferred Stock, 1,381 of which are issued and outstanding, (v) 17,000 are designated as Series E Preferred Stock, 10,000 of which are issued and outstanding and (vi) 8,333 are designated as Series F Preferred Stock, all of which are issued and outstanding. For a complete description of the terms and provisions of the Company’s Preferred Stock, refer to our amended and restated certificate of incorporation and our amended and restated bylaws, both of which are filed as exhibits to this Annual Report on Form 10-K.

These provisions may have the effect of deterring hostile takeovers or delaying changes in our control or management. These provisions are intended to enhance the likelihood of continued stability in the composition of our board of directors and its policies and to discourage certain types of transactions that may involve an actual or threatened change in control. These provisions are designed to reduce our vulnerability to an unsolicited acquisition proposal. The provisions also are intended to discourage certain tactics that may be used in proxy fights. However, such provisions could have the effect of discouraging others from making tender offers for our shares and, as a consequence, they also may inhibit fluctuations in the market price of our shares that could result from actual or rumored takeover attempts. Such provisions also may have the effect of preventing changes in our management.

Section 203 of the Delaware General Corporation Law

We are subject to Section 203 of the DGCL, which prohibits a Delaware corporation from engaging in a business combination with any interested stockholder for a period of three years following the date the person became an interested stockholder, with the following exceptions:

In general, Section 203 of the DGCL defines business combination to include the following:

Section 203 of the DGCL defines an “interested stockholder” as an entity or person who, together with the entity’s or person’s affiliates and associates, beneficially owns, or is an affiliate of the corporation and within three years prior to the

time of determination of interested stockholder status did own, 15% or more of the outstanding voting stock of the corporation. A Delaware corporation may “opt out” of these provisions with an express provision in its certificate of incorporation. We have not opted out of these provisions, which may as a result, discourage or prevent mergers or other takeover or change of control attempts of us.