Description of Securities Registered Under Section 12 of the Securities Exchange Act of 1934

The following information is a summary of the material terms of the common stock of Insmed Incorporated (“we”, “our” and “us,”), which is based upon, and is qualified in its entirety by reference to, our Articles of Incorporation, as amended (the “Articles of Incorporation”), our Amended and Restated Bylaws (the “Bylaws”) and applicable provisions of the Virginia Stock Corporation Act (“VSCA”). This summary may not contain all of the information that is important to you; you can obtain additional information regarding our Articles of Incorporation and Bylaws by referring to such documents, copies of which are included as exhibits to the Annual Report on Form 10-K of which this Exhibit 4.5 is a part.

Under our Articles of Incorporation, we have authority to issue 500,000,000 shares of common stock, par value $0.01 per share. All of our issued and outstanding shares of common stock are fully paid and nonassessable.

Subject to the rights of the holders of any of our preferred stock then outstanding, the holders of our common stock are entitled to receive ratably such dividends, if any, as may be declared from time to time by our board of directors out of legally available funds. As of the date of this Annual Report on Form 10-K, we have not declared or paid any dividends on our shares of common stock, and there were no shares of preferred stock outstanding, although our board of directors is authorized to issue preferred stock with rights senior to those of the common stock without any further vote or action by the holders of our common stock.

In the event we are liquidated, dissolved or our affairs are wound up, after we pay or make adequate provision for all of our known debts and liabilities, each holder of common stock will receive distributions pro rata out of assets that we can legally use to pay distributions, subject to the rights of the holders of any of our preferred stock then outstanding.

Holders of our common stock are entitled to one vote per share and will have the exclusive power to vote on all matters presented to our shareholders, including the election of directors, except as otherwise provided by the VSCA and subject to the rights of the holders of any of our preferred stock then outstanding. An election of directors by our shareholders will be determined by a plurality of the votes cast by the shareholders entitled to vote on the election, although we have a director resignation policy applicable to director nominees in uncontested elections. Our Articles of Incorporation do not provide for cumulative voting. In accordance with our Articles of Incorporation, our board is divided into three classes serving staggered three-year terms, with one class being elected each year at our annual meeting of shareholders.

Subject to certain exceptions set forth in the VSCA, matters other than the election of directors generally will be approved if the votes cast by our shareholders favoring the action exceed the votes cast opposing the action. Subject to the rights of the holders of any of our preferred stock then outstanding, however, the affirmative vote of at least 75% of the voting power of the outstanding shares of our capital stock entitled to vote generally in the election of directors, voting together as a single group, will be required to take the following actions:

•remove a director, which may only be done for cause; and

•alter, amend, repeal, or adopt any provision inconsistent with, the provisions of (1) our Articles of Incorporation that provide for a classified board, director removal only for cause, filling of newly created or vacant directorships, or bylaw amendments or (2) our Bylaws.

Holders of our common stock will have no preference, appraisal or exchange rights, except for any appraisal rights provided by the VSCA. Furthermore, holders of our common stock have no conversion, sinking fund or redemption rights, or preemptive rights to subscribe for any of our securities.

Certain provisions of the VSCA, our Articles of Incorporation and our Bylaws could hamper a third-party’s acquisition of, or discourage a third-party from attempting to acquire control of, us or limit the price that investors might be willing to pay for shares of our common stock. These provisions or arrangements include:

•The ability to issue preferred stock with rights senior to those of our common stock without any further vote or action by the holders of our common stock. The issuance of preferred stock could decrease the amount of earnings and assets available for distribution to the holders of our common stock or could adversely affect the rights and powers, including voting rights, of the holders of our common stock. In certain circumstances, such issuance could have the effect of decreasing the market price of our common stock.

•The existence of a staggered board of directors in which there are three classes of directors serving staggered three-year terms, thus expanding the time required to change the composition of a majority of directors.

•The requirement that shareholders provide advance notice when nominating director candidates to serve on our board of directors.

•The inability of shareholders to convene a shareholders’ meeting without the chairman of the board, the president or a majority of the board of directors first calling the meeting.

•The prohibition against entering into a business combination with the beneficial owner of 10% or more of our

outstanding voting stock for a period of three years after the 10% or greater owner first reached that level of

stock ownership, unless certain criteria are met.