Exhibit 3.3

BYLAWS

Health Sciences AcquisitionS Corporation

- A Delaware Corporation -

BYLAWS

HEALTH SCIENCES ACQUISITIONS CORPORATION

(the “Corporation”)

ARTICLE I

OFFICES

SECTION 1. Principal Office. The registered office of the Corporation shall be located in such place as may be provided from time to time in the Certificate of Incorporation of the Corporation (the “Certificate of Incorporation”).

SECTION 2. Other Offices. The Corporation may also have offices at such other places both within and without the State of Delaware as the board of directors of the Corporation (the “Board of Directors”) may from time to time determine or as the business of the Corporation may require.

ARTICLE II

STOCKHOLDERS

SECTION 1. Annual Meetings. The annual meeting of the stockholders of the Corporation shall be held wholly or partially by means of remote communication or at such place, within or without the State of Delaware, on such date and at such time as may be determined by the Board of Directors and as shall be designated in the notice of said meeting.

SECTION 2. Special Meetings. Special meetings of the stockholders for any purpose or purposes, unless otherwise prescribed by statute or by the Certificate of Incorporation, may only be held wholly or partially by means of remote communication or at any place, within or without the State of Delaware, and may only be called by resolution of the Board of Directors, or by the Chairman of the Board of Directors (the “Chairman”) or the President.

SECTION 3. Notice and Purpose of Meetings. Written or printed notice of the meeting of the stockholders stating the place, day and hour of the meeting and, in case of a special meeting, stating the purpose or purposes for which the meeting is called, and in case of a meeting held by remote communication stating such means, shall be delivered not less than 10 nor more than 60 days before the date of the meeting, either personally, or by mail, or if prior consent has been received by a stockholder by electronic transmission, by or at the direction of the Chairman or the President, the Secretary, or the persons calling the meeting, to each stockholder of record entitled to vote at such meeting.

SECTION 4. Quorum. The holders of a majority of the shares of capital stock issued and outstanding and entitled to vote, represented in person or by proxy, shall constitute a quorum at all meetings of the stockholders for the transaction of business, except as otherwise provided by statute or by the Certificate of Incorporation. If, however, such quorum shall not be present or represented at any meeting of the stockholders, the stockholders present in person or represented by proxy shall have power to adjourn the meeting from time to time, without notice other than announcement at the meeting, until a quorum shall be present or represented. At such adjourned meeting at which a quorum shall be present or represented any business may be transacted which might have been transacted at the meeting as originally notified.

SECTION 5. Voting Process. If a quorum is present or represented, the affirmative vote of a majority of the shares of stock present or represented at the meeting, by ballot, proxy or electronic ballot, shall be the act of the stockholders unless the vote of a greater number of shares of stock is required by law, by the Certificate of Incorporation or by these bylaws. Each outstanding share of stock having voting power, shall be entitled to one vote on each matter submitted to a vote at a meeting of stockholders. A stockholder may vote either in person, by proxy executed in writing by the stockholder or by his duly authorized attorney-in-fact, or by an electronic ballot from which it can be determined that the ballot was authorized by a stockholder or proxyholder. The term, validity and enforceability of any proxy shall be determined in accordance with the General Corporation Law of the State of Delaware.

SECTION 6. Written Consent of Stockholders Without a Meeting. Whenever the stockholders are required or permitted to take any action by vote, such action may be taken without a meeting, without prior notice and without a vote, if a written consent or electronic transmission, setting forth the action so taken, shall be signed or e-mailed by the holders of outstanding stock having not less than the minimum number of votes that would be necessary to authorize or take such action at a meeting called for such purpose.

ARTICLE III

DIRECTORS

SECTION 1. Powers. The business affairs of the Corporation shall be managed by the Board of Directors, which may exercise all such powers of the Corporation and do all such lawful acts and things as are not by statute or by the Certificate of Incorporation or by these bylaws directed or required to be exercised or done by the stockholders. The Board of Directors may adopt such rules and regulations, not inconsistent with the Certificate of Incorporation or these bylaws or applicable laws, as it may deem proper for the conduct of its meetings and the management of the Corporation.

SECTION 2. Number, Qualifications, Term. The Board of Directors shall consist of one or more members. The number of directors shall be fixed by the Board of Directors and may thereafter be changed from time to time by resolution of the Board of Directors. Directors need not be residents of the State of Delaware nor stockholders of the Corporation.

SECTION 3. Vacancies. Vacancies and newly created directorships resulting from any increase in the number of directors may be filled by a majority of the directors then in office, though less than a quorum, and the directors so chosen shall hold office until the next annual election and until their successors are duly elected and shall qualify. A vacancy created by the removal of a director by the stockholders may be filled by the stockholders.

SECTION 4. Place of Meetings. Meetings of the Board of Directors, regular or special, may be held either within or without the State of Delaware.

SECTION 5. Regular Meetings. Regular meetings of the Board of Directors may be held upon such notice, or without notice, and at such time and at such place as shall from time to time be determined by the Board of Directors.

SECTION 6. Special Meetings. Special meetings of the Board of Directors may be called by the Chairman or the President or by the number of directors who then legally constitute a quorum. Notice of the time and place of all special meetings of the Board of Directors shall be orally or in writing, by telephone, including a voice messaging system or other system or technology designed to record and communicate messages, facsimile, telegraph or telex, or by electronic mail or other electronic means, during normal business hours, at least 24 hours before the date and time of the meeting. If notice is sent by U.S. mail, it shall be sent by first class mail, charges prepaid, at least three days before the date of the meeting.

SECTION 7. Notice; Waiver. Attendance of a director at any meeting shall constitute a waiver of notice of such meeting, except where a director attends for the express purpose of objecting to the transaction of any business because the meeting is not lawfully called or convened. Neither the business to be transacted at, nor the purpose of, any regular or special meeting of the Board of Directors need be specified in the notice or waiver of notice of such meeting.

SECTION 8. Quorum. A majority of the directors then in office shall constitute a quorum for the transaction of business unless a greater number is required by law, by the Certificate of Incorporation or by these bylaws. If a quorum shall not be present at any meeting of directors, the directors present thereat may adjourn the meeting from time to time, without notice other than announcement at the meeting, until a quorum shall be present.

SECTION 10. Action Without A Meeting. Any action required or permitted to be taken at a meeting of the directors may be taken without a meeting if a consent in writing or by electronic transmission, setting forth the action so taken, shall be signed by all of the directors entitled to vote with respect to the subject matter thereof. In addition, meetings of the Board of Directors may be held by means of conference telephone or voice communication as permitted by the General Corporation Law of the State of Delaware.

SECTION 11. Action. Except as otherwise provided by law or in the Certificate of Incorporation or these bylaws, if a quorum is present, the affirmative vote of a majority of the members of the Board of Directors will be required for any action.

SECTION 12. Removal of Directors. Subject to any provisions of applicable law, any or all of the directors may be removed pursuant to the Certificate of Incorporation.

ARTICLE IV

COMMITTEES

SECTION 1. Designation of Committees. The Board of Directors may, by resolution adopted by a majority of the whole Board of Directors, designate one or more committees, each of which shall, except as otherwise prescribed by law, have such authority of the Board of Directors as shall be specified in the resolution of the Board of Directors designating such committee. The Board of Directors shall have the power at any time to change the membership of, to fill all vacancies in and to discharge any such committee, either with or without cause.

SECTION 4. Procedure; Meetings; Quorum. Committee meetings, of which no notice shall be necessary, may be held at such times and places as shall be fixed by resolution adopted by a majority of the members thereof. So far as applicable, the provisions of Article III of these bylaws relating to notice, quorum and voting requirements applicable to meetings of the Board of Directors shall govern meetings of any committee of the Board of Directors. Each committee of the Board of Directors shall keep written minutes of its proceedings and circulate summaries of such written minutes to the Board of Directors before or at the next meeting of the Board of Directors.

ARTICLE V

OFFICERS

SECTION 1. Number. The Board of Directors at its first meeting after each annual meeting of stockholders shall choose a Chief Executive Officer, a Secretary and a Treasurer, none of whom need be a member of the Board of Directors. The Board of Directors may also choose a Chairman from among the directors, one or more Executive Vice Presidents, one or more Vice Presidents, Assistant Secretaries and Assistant Treasurers. The Board of Directors may appoint such other officers and agents as it shall deem necessary, who shall hold their offices for such terms and shall exercise such powers and perform such duties as shall be determined from time to time by the Board of Directors. More than two offices may be held by the same person.

SECTION 2. Compensation. The salaries or other compensation of all officers of the Corporation shall be fixed by the Board of Directors. No officer shall be prevented from receiving a salary or other compensation by reason of the fact that he is also a director.

SECTION 3. Term; Removal; Vacancy. The officers of the Corporation shall hold office until their successors are chosen and qualify. Any officer may be removed at any time, with or without cause, by the affirmative vote of a majority of the whole Board of Directors. Any vacancy occurring in any office of the Corporation shall be filled by the Board of Directors.

SECTION 4. Chairman. The Chairman shall, if one be elected, preside at all meetings of the Board of Directors.

SECTION 5. Chief Executive Officer. The Chief Executive Officer shall be the chief executive officer of the Corporation, shall preside at all meetings of the stockholders and the Board of Directors in the absence of the Chairman, shall have general supervision over the business of the Corporation and shall see that all directions and resolutions of the Board of Directors are carried into effect.

SECTION 6. President. The President shall, in the absence or disability of the Chief Executive Officer, perform the duties and exercise the powers of the Chief Executive Officer and shall perform such other duties and have such other powers as the Board of Directors may from time to time prescribe.

SECTION 7. Vice President. The Executive Vice Presidents shall, in the absence or disability of the President, perform the duties and exercise the powers of the President and shall perform such other duties and have such other powers as the Board of Directors may from time to time prescribe. If there shall be more than one Executive Vice President, the Executive Vice Presidents shall perform such duties and exercise such powers in the absence or disability of the President, in the order determined by the Board of Directors. The Vice Presidents shall, in the absence or disability of the President and of the Executive Vice Presidents, perform the duties and exercise the powers of the President and shall perform such other duties and have such other powers as the Board of Directors may from time to time prescribe. If there shall be more than one vice president, the vice presidents shall perform such duties and exercise such powers in the absence or disability of the President and of the Executive Vice President, in the order determined by the Board of Directors.

SECTION 8. Secretary. The Secretary shall attend all meetings of the Board of Directors and all meetings of the stockholders and record all the proceedings of the meetings of the Corporation and of the Board of Directors in a book to be kept for that purpose. He shall give, or cause to be given, notice of all meetings of the stockholders and special meetings of the Board of Directors, and shall perform such other duties as may be prescribed by the Board of Directors or President, under whose supervision he shall be. He shall have custody of the corporate seal of the corporation and he, or an assistant secretary, shall have the authority to affix the same to an instrument requiring it and when so affixed, it may be attested by his signature or by the signature of such assistant secretary. The Board of Directors may give general authority to any other officer to affix the seal of the Corporation and to attest the affixing by his signature.

SECTION 9. Assistant Secretary. The Assistant Secretary, if there shall be one, or if there shall be more than one, the assistant secretaries in the order determined by the Board of Directors, shall, in the absence or disability of the Secretary, perform the duties and exercise the powers of the Secretary and shall perform such other duties and have such powers as the Board of Directors may from time to time prescribe.

SECTION 10. Treasurer. The Treasurer or Chief Financial Officer shall have the custody of the corporate funds and securities and shall keep full and accurate accounts of receipts and disbursements in books belonging to the Corporation and shall deposit all moneys and other valuable effects in the name and to the credit of the Corporation in such depositories as may be designated by the Board of Directors. He shall disburse the funds of the Corporation as may be ordered by the Board of Directors, taking proper vouchers for such disbursements, and shall render to the Chairman, the President and the Board of Directors, at its regular meetings, or when the Board of Directors so requires, an account of all of his transactions as Treasurer and of the financial condition of the Corporation.

SECTION 11. Assistant Treasurer. The Assistant Treasurer, if there shall be one, or, if there shall be more than one, the Assistant Treasurers in the order determined by the Board of Directors, shall, in the absence or disability of the Treasurer, perform the duties and exercise the powers of the Treasurer and shall perform such other duties and have such other powers as the Board of Directors may from time to time prescribe.

ARTICLE VI

CAPITAL STOCK

SECTION 1. Form. The shares of the capital stock of the Corporation shall be represented by certificates in such form as shall be approved by the Board of Directors and shall be signed by the Chairman, the President, an Executive Vice President or a Vice President, and by the Treasurer or an assistant treasurer or the Secretary or an Assistant Secretary of the Corporation, and may be sealed with the seal of the Corporation or a facsimile thereof.

SECTION 2. Lost and Destroyed Certificates. The Board of Directors may direct a new certificate to be issued in place of any certificate theretofore issued by the Corporation alleged to have been lost or destroyed. When authorizing such issue of a new certificate, the Board of Directors, in its discretion and as a condition precedent to the issuance thereof, may prescribe such terms and conditions as it deems expedient, and may require such indemnities as it deems adequate, to protect the Corporation from any claim that may be made against it with respect to any such certificate alleged to have been lost or destroyed.

SECTION 3. Transfer of Shares. Upon surrender to the Corporation or the transfer agent of the Corporation of a certificate representing shares duly endorsed or accompanied by proper evidence of succession, assignment or authority to transfer, a new certificate shall be issued to the person entitled thereto, and the old certificate cancelled and the transaction recorded upon the books of the Corporation.

ARTICLE VII

INDEMNIFICATION

SECTION 1. (a) The Corporation shall indemnify, subject to the requirements of subsection (d) of this Section, any person who was or is a party or is threatened to be made a party to any threatened, pending or completed action, suit or proceeding, whether civil, criminal, administrative or investigative (other than an action by or in the right of the Corporation), by reason of the fact that he is or was a director, officer, employee or agent of the Corporation, or is or was serving at the request of the Corporation as a director, officer, employee or agent of another corporation, partnership, joint venture, trust or other enterprise, against expenses (including attorneys’ fees), judgments, fines and amounts paid in settlement actually and reasonably incurred by him in connection with such action, suit or proceeding if he acted in good faith and in a manner he reasonably believed to be in or not opposed to the best interests of the Corporation and, with respect to any criminal action or proceeding, had no reasonable cause to believe his conduct was unlawful. The termination of any action, suit or proceeding by judgment, order, settlement, conviction or upon a plea of nolo contendere or its equivalent, shall not, of itself, create a presumption that the person did not act in good faith and in a manner which he reasonably believed to be in or not opposed to the best interests of the Corporation and, with respect to any criminal action or proceeding, had reasonable cause to believe that his conduct was unlawful.

(b) The Corporation shall indemnify, subject to the requirements of subsection (d) of this Section, any person who was or is a party or is threatened to be made a party to any threatened, pending or completed action or suit by or in the right of the Corporation to procure a judgment in its favor by reason of the fact that he is or was a director, officer, employee or agent of the Corporation or is or was serving at the request of the Corporation as a director, officer, employee or agent of another corporation, partnership, joint venture, trust or other enterprise, against expenses (including attorneys’ fees) actually and reasonably incurred by him in connection with the defense or settlement of such action or suit if he acted in good faith and in a manner he reasonably believed to be in or not opposed to the best interests of the corporation and except that no indemnification shall be made in respect of any claim, issue or matter as to which such person shall have been adjudged to be liable to the Corporation unless and only to the extent that the Court of Chancery of the State of Delaware or the court in which such action or suit was brought shall determine upon application that, despite the adjudication of liability but in view of all the circumstances of the case, such person is fairly and reasonably entitled to indemnity for such expenses which the Court of Chancery of the State of Delaware or such other court shall deem proper.

(c) To the extent that a director, officer, employee or agent of the Corporation has been successful on the merits or otherwise in defense of any action, suit or proceeding referred to in subsections (a) and (b) of this Section, or in defense of any claim, issue or matter therein, the Corporation shall indemnify him against expenses (including attorneys’ fees) actually and reasonably incurred by him in connection therewith.

(d) Any indemnification under subsections (a) and (b) of this Section (unless ordered by a court) shall be made by the Corporation only as authorized in the specific case upon a determination that indemnification of the director, officer, employee or agent is proper in the circumstances because he has met the applicable standard of conduct set forth in subsections (a) and (b) of this Section. Such determination shall be made (1) by the Board of Directors by a majority vote of a quorum consisting of directors who were not parties to such action, suit or proceeding, or (2) if such a quorum is not obtainable, or, even if obtainable a quorum of disinterested directors so directs, by independent legal counsel in a written opinion, or (3) by the stockholders.

(e) Expenses incurred by a director, officer, employee or agent in defending a civil or criminal action, suit or proceeding may be paid by the Corporation in advance of the final disposition of such action, suit or proceeding upon receipt of an undertaking by or on behalf of such director or officer to repay such amount if it shall ultimately be determined that he is not entitled to be indemnified by the Corporation as authorized in this Section. Such expenses incurred by other employees and agents may be so paid upon such terms and conditions, if any, as the Board of Directors deems appropriate.

(f) The indemnification and advancement of expenses provided by, or granted pursuant to, the other subsections of this Section shall not limit the Corporation from providing any other indemnification or advancement of expenses permitted by law nor shall they be deemed exclusive of any other rights to which a person seeking indemnification or advancement of expenses may be entitled under any bylaw, agreement, vote of stockholders or disinterested directors or otherwise, both as to action in his official capacity and as to action in another capacity while holding such office.

(g) The Corporation may purchase and maintain insurance on behalf of any person who is or was a director, officer, employee or agent of the Corporation, or is or was serving at the request of the Corporation as a director, officer, employee or agent of another corporation, partnership, joint venture, trust or other enterprise against any liability asserted against him and incurred by him in any such capacity, or arising out of his status as such, whether or not the Corporation would have the power to indemnify him against such liability under the provisions of this Section.

(h) For the purposes of this Section, references to “the Corporation” shall include, in addition to the resulting corporation, any constituent corporation (including any constituent of a constituent) absorbed in a consolidation or merger which, if its separate existence had continued, would have had power and authority to indemnify its directors, officers, employees or agents, so that any person who is or was a director, officer, employee or agent of such constituent corporation, or is or was serving at the request of such constituent corporation as a director, officer, employee or agent of another corporation, partnership, joint venture, trust or other enterprise, shall stand in the same position under the provisions of this Section with respect to the resulting or surviving corporation as he would have with respect to such constituent corporation if its separate existence had continued.

(i) For purposes of this Section, references to “other enterprises” shall include employee benefit plans; references to “fines” shall include any excise taxes assessed on a person with respect to an employee benefit plan; and references to “serving at the request of the Corporation” shall include any service as a director, officer, employee or agent of the Corporation which imposes duties on, or involves services by, such director, officer, employee, or agent with respect to any employee benefit plan, its participants, or beneficiaries; and a person who acted in good faith and in a manner he reasonably believed to be in the interest of the participants and beneficiaries of an employee benefit plan shall be deemed to have acted in a manner “not opposed to the best interests of the Corporation” as referred to in this Section.

(j) The indemnification and advancement of expenses provided by, or granted pursuant to, this Section shall, unless otherwise provided when authorized or ratified by the Board of Directors, continue as to a person who has ceased to be a director, officer, employee or agent of the Corporation and shall inure to the benefit of the heirs executors and administrators of such a person.

(k) The officers and directors of the Corporation, as individuals, shall not be liable until all funds of the Corporation have been distributed, with the exception of the proceeds contained in a trust account, that is subject to the trust agreement to be entered into by the Corporation.

ARTICLE VIII

GENERAL PROVISIONS

SECTION 1. Checks. All checks or demands for money and notes of the Corporation shall be signed by such officer or officers or such other person or persons as the Board of Directors may from time to time designate.

SECTION 2. Fiscal Year. The fiscal year of the Corporation shall be determined, and may be changed, by resolution of the Board of Directors.

SECTION 3. Seal. The corporate seal shall have inscribed thereon the name of the Corporation, the year of its organization and the words “Corporate Seal, Delaware.” The seal may be used by causing it or a facsimile thereof to be impressed or affixed or in any manner reproduced.

SECTION 4. References. Any references in these bylaws to the masculine or feminine gender shall be deemed to include the other unless the context otherwise requires.

ARTICLE IX

AMENDMENTS

SECTION 1. These bylaws may be altered, amended, supplemented or repealed or new bylaws may be adopted (a) at any regular or special meeting of stockholders at which a quorum is present or represented, by the affirmative vote of the holders of a majority of the shares entitled to vote, provided notice of the proposed alteration, amendment or repeal be contained in the notice of such meeting, or (b) by a resolution adopted by a majority of the whole Board of Directors at any regular or special meeting of the Board of Directors. The stockholders shall have authority to change or repeal any bylaws adopted by the directors.