DESCRIPTION OF THE REGISTRANT’S SECURITIES REGISTERED PURSUANT TO SECTION 12 OF THE SECURITIES EXCHANGE ACT OF 1934

Exhibit 4.5

DESCRIPTION OF THE REGISTRANT’S SECURITIES

REGISTERED PURSUANT TO SECTION 12 OF THE SECURITIES

EXCHANGE ACT OF 1934

Humanigen, Inc. (“we,” “our,” “us,” or the “Company”) has the following securities described below registered under Section 12 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”). The following summary of the terms of our capital stock is based upon our Amended and Restated Certificate of Incorporation (“Charter”) and our Second Amended and Restated Bylaws (“Bylaws”). This summary does not purport to be complete and is subject to, and is qualified in its entirety by express reference to, the applicable provisions of our Charter and our Bylaws, which are filed as exhibits to our Annual Report on Form 10-K, of which this Exhibit 4.5 is a part, and are incorporated by reference herein. We encourage you to read our Charter, our Bylaws, and the applicable provisions of the Delaware General Corporation Law (the “DGCL”) for more information.

DESCRIPTION OF SECURITIES

Authorized Capital Stock

Our authorized capital stock consists of 250,000,000 shares of which 225,000,000 shares shall be common stock, par value $0.001 per share, and 25,000,000 shares shall be preferred stock, par value of $0.001 per share. As of March 12, 2020 there were 114,304,290 shares of common stock outstanding, held by 44 stockholders of record, although we believe that there may be a significantly larger number of beneficial owners of our common stock. We derived the number of stockholders by reviewing the listing of outstanding common stock recorded by our transfer agent as of March 12, 2020.

Common Stock

Each holder of our common stock is entitled to one vote for each share of common stock held on all matters submitted to a vote of the stockholders. Holders of our common stock are entitled to receive ratably the dividends, if any, as may be declared from time to time by the board of directors out of funds legally available therefor. If there is a liquidation, dissolution or winding up of our company, holders of our common stock would be entitled to share in our assets remaining after the payment of liabilities. Holders of our common stock have no preemptive or conversion rights or other subscription rights, and there are no redemption or sinking fund provisions applicable to the common stock. The outstanding shares of common stock are fully paid and non-assessable. Holders of shares of our common stock are not liable for further calls or to assessments by us. Although our Charter does not currently authorize us to issue preferred stock, if that provision of our charter were amended in the future, the rights, powers, preferences and privileges of holders of common stock would be subordinate to, and may be adversely affected by, the rights of the holders of shares of any series of preferred stock which our board of directors may designate and issue in the future. Certain of our existing holders of common stock have the right to require us to register their shares of common stock under the Securities Act of 1933, as amended, in specified circumstances.

The transfer agent and registrar for our common stock is Computershare Trust Company, N.A. The transfer agent’s address is 250 Royall Street, Canton, Massachusetts 02021 and its telephone number is ###-###-####.

Dividend Policy

We have never declared or paid any cash dividends on our capital stock, and we do not currently intend to pay any cash dividends on our common stock for the foreseeable future. We expect to retain future earnings, if any, to fund the development and growth of our business. Any future determination to pay dividends on our common stock will be at the discretion of our board of directors and will depend upon, among other factors, our financial condition, operating results, current and anticipated cash needs, plans for expansion and other factors that our board of directors may deem relevant.

Anti-Takeover Provisions of Our Charter Documents and Delaware Law

Some provisions of our Charter, our Bylaws and the DGCL could make it more difficult to acquire our company by means of a tender offer, a proxy contest, or otherwise.

Our Bylaws establish advance notice procedures with respect to stockholder proposals and the nomination of candidates for election as directors, other than nominations made by or at the direction of our board of directors or a committee of our board of directors. These procedures provide that notice of stockholder proposals must be timely given in writing to our corporate secretary prior to the meeting at which the action is to be taken. Generally, for a proposal to be timely submitted for consideration at an annual meeting, notice must be delivered to our secretary not less than 90 days nor more than 120 days prior to the first anniversary date of the annual meeting for the preceding year. Our Bylaws specify the requirements as to form and content of all stockholders’ notices. These provisions might preclude our stockholders from bringing matters before our annual meeting of stockholders or from making nominations for directors at our annual meeting of stockholders if the proper procedures are not followed.

Our Charter and Bylaws both provide that vacancies on our board of directors, including newly created directorships, may be filled only by a majority vote of directors then in office, and directors so chosen shall hold office for a term expiring at the next annual meeting of stockholders or until such director’s successor shall have been duly elected and qualified. Accordingly, the board of directors could prevent any stockholder from filling the new directorships with such stockholder’s own nominee.

Our Charter provides that, unless we consent in writing to the selection of an alternative forum, the Delaware Court of Chancery shall be the sole and exclusive forum for (i) any derivative action or proceeding brought on our behalf, (ii) any action asserting a claim of breach of a fiduciary duty owed by any of our current or former directors, officers or other employees to us or our stockholders, (iii) any action asserting a claim arising pursuant to any provision of the DGCL, our Charter or our Bylaws, or (iv) any action asserting a claim against us governed by the internal affairs doctrine; in all cases subject to the court having personal jurisdiction over the indispensable parties named as defendants. This choice of forum provision may limit a stockholder’s ability to bring a claim in a judicial forum that it finds favorable for disputes with us or our directors, officers or other employees, which may discourage such lawsuits against us and our directors, officers and other employees.

Delaware Anti-Takeover Law

We are subject to Section 203 of the DGCL which contains anti-takeover provisions. In general, Section 203 prohibits a publicly held Delaware corporation from engaging in a business combination with an interested stockholder for a period of three years following the date that the person became an interested stockholder, unless the business combination or the transaction in which the person became an interested stockholder is approved in a prescribed manner. Generally, a business combination includes a merger, asset or stock sale or another transaction resulting in a financial benefit to the interested stockholder. An interested stockholder is a person who, together with affiliates and associates, owns 15% or more of the corporation’s voting stock. The existence of this provision may have an anti-takeover effect with respect to transactions that are not approved in advance by our board of directors, including discouraging attempts that might result in a premium over the market price for the shares of common stock held by stockholders.

No Cumulative Voting

Under the DGCL, cumulative voting for the election of directors is not permitted unless a corporation’s certificate of incorporation authorizes cumulative voting. Our Charter does not provide for cumulative voting in the election of directors. Cumulative voting allows a minority stockholder to vote a portion or all of its shares for one or more candidates for seats on our board of directors. Without cumulative voting, a minority stockholder will not be able to gain as many seats on our board of directors based on the number of shares of our stock the stockholder holds as compared to the number of seats the stockholder would be able to gain if cumulative voting were permitted. The absence of cumulative voting makes it more difficult for a minority stockholder to gain a seat on our board of directors to influence our board’s decision regarding a takeover.

Stockholder Action by Written Consent

The DGCL generally provides that the affirmative vote of a majority of the shares entitled to vote on such matter is required to amend a corporation’s certificate of incorporation or bylaws, unless a corporation’s certificate of incorporation or bylaws requires a greater percentage. Our Charter permits our board of directors to amend or repeal most provisions of our Bylaws by majority vote. Generally, our Charter may be amended by holders of a majority of the voting power of the then outstanding shares of our capital stock entitled to vote. The stockholder vote or consent with respect to an amendment of our Charter or Bylaws would be in addition to any separate class vote that might in the future be required under the terms of any series of preferred stock that might be outstanding at the time such a proposed amendment were submitted to stockholders. The DGCL and the provisions of our Bylaws generally permit stockholders owning the requisite percentage of shares of common stock necessary to approve an amendment to our Charter and Bylaws to act by written consent in lieu of a meeting of our stockholders.

Limitation of Liability and Indemnification of Officers and Directors

Our Bylaws provide indemnification, including advancement of expenses, to the fullest extent permitted under applicable law to any person made or threatened to be made a party to any threatened, pending, or completed action, suit, or proceeding, whether civil, criminal, administrative, or investigative by reason of the fact that such person is or was a director or officer of the company, or is or was serving at our request as a director or officer of another corporation, partnership, joint venture, trust, or other enterprise, including service with respect to an employee benefit plan. In addition, our Charter provides that our directors will not be personally liable to us or our stockholders for monetary damages for breaches of their fiduciary duty as directors, unless they violated their duty of loyalty to us or our shareholders, acted in bad faith, knowingly or intentionally violated the law, authorized illegal dividends or redemptions or derived an improper personal benefit from their action as directors. This provision does not limit or eliminate our rights or the rights of any stockholder to seek nonmonetary relief such as an injunction or rescission in the event of a breach of a director’s duty of care. In addition, this provision does not limit the directors’ responsibilities under the DGCL or any other laws, such as the federal securities laws. We have obtained insurance that insures our directors and officers against certain losses and which insures us against our obligations to indemnify the directors and officers. We also have entered into indemnification agreements with our directors and executive officers.