Document:

REGISTRATION
        RIGHTS AGREEMENT

       

      This
        Registration Rights Agreement (this “Agreement”)
        is
        made and entered into as of October __, 2007, by and among Pressure BioSciences
        Inc., a Massachusetts corporation (the “Company”),
        and
        the several purchasers signatory hereto (each such purchaser, a “Purchaser”
and
        collectively, the “Purchasers”).

       

      This
        Agreement is made pursuant to the Securities Purchase Agreement, dated as
        of the
        date hereof, between the Company and each Purchaser (the “Purchase
        Agreement”).

       

      The
        Company and each Purchaser hereby agrees as follows:

       

      1. Definitions.
        Capitalized terms used and not otherwise defined herein that are defined
        in the
        Purchase Agreement shall have the meanings given such terms in the Purchase
        Agreement. As used in this Agreement, the following terms shall have the
        following meanings:

       

      “Advice”
shall
        have the meaning set forth in Section 6(c).

       

      “Effectiveness
        Date”
means
        the date on which the Registration Statement required to be filed hereunder
        is
        declared effective by the Commission.

       

      “Effectiveness
        Period”
shall
        have the meaning set forth in Section 2.

       

      “Filing
        Date”
means
        the date on which the Company initially files the Registration Statement
        with
        the Commission.

       

      “Holder”
or
        “Holders”
means
        the holder or holders, as the case may be, from time to time of Registrable
        Securities.

       

      “Indemnified
        Party”
shall
        have the meaning set forth in Section 5(b).

       

      “Indemnifying
        Party”
shall
        have the meaning set forth in Section 5(b).

       

      “Losses”
shall
        have the meaning set forth in Section 2.

       

      “Plan
        of Distribution”
shall
        have the meaning set forth in Section 2. 

       

      “Prospectus”
means
        the prospectus included in a Registration Statement (including, without
        limitation, a prospectus that includes any information previously omitted
        from a
        prospectus filed as part of an effective registration statement in reliance
        upon
        Rule 430A promulgated under the Securities Act), as amended or supplemented
        by
        any prospectus supplement, with respect to the terms of the offering of any
        portion of the Registrable Securities covered by a Registration Statement,
        and
        all other amendments and supplements to the Prospectus, including post-effective
        amendments, and all material incorporated by reference or deemed to be
        incorporated by reference in such Prospectus.

       

      “Registrable
        Securities”
means
        all of (i) the Shares and (ii) any shares of Common Stock issued or issuable
        upon any stock split, dividend or other distribution, recapitalization or
        similar event with respect to the foregoing. Upon the sale, pursuant to a
        Registration Statement declared
        effective by the SEC or
        an
        exemption from registration under the Securities Act
        (such
        that all transfer restrictions and restrictive legends with respect thereto
        are
        removed upon the consummation of such sale),
        of
        any of
        the securities described in clauses (i) and (ii) of the preceding sentence,
        such
        securities shall no longer be Registrable Securities.

       

      
        
          
          

        

        
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      “Registration
        Statement”
means
        the registration statements required to be filed hereunder, including (in
        each
        case) the Prospectus, amendments and supplements to such registration statement
        or Prospectus, including pre- and post-effective amendments, all exhibits
        thereto, and all material incorporated by reference or deemed to be incorporated
        by reference in such registration statement.

       

      “Rule
        415”
means
        Rule 415 promulgated by the Commission pursuant to the Securities Act, as
        such
        Rule may be amended from time to time, or any similar rule or regulation
        hereafter adopted by the Commission having substantially the same purpose
        and
        effect as such Rule.

       

      “Rule
        424”
means
        Rule 424 promulgated by the Commission pursuant to the Securities Act, as
        such
        Rule may be amended from time to time, or any similar rule or regulation
        hereafter adopted by the Commission having substantially the same purpose
        and
        effect as such Rule.

       

      “Selling
        Stockholder Questionnaire”
shall
        have the meaning set forth in Section 3(a).

       

      “SEC
        Guidance”
means
        (i) any publicly-available written
        guidance, or rule of general applicability of the Commission staff, or (ii)
        written comments, requirements or requests of
        the
        Commission staff to the Company in connection with the review of the
        Registration Statements.

       

      2. Shelf
        Registration. As
        promptly as possible following the Closing Date, the Company shall prepare
        and
        file with the Commission a Registration Statement covering the resale of
        all, or
        such portion as permitted by SEC Guidance (provided that, the Company shall
        use
        commercially reasonable efforts to advocate with the Commission for the
        registration of all or
        the
        maximum number of
        the
        Registrable Securities
        as
        permitted by SEC Guidance),
        of the
        Registrable Securities on the Filing Date that are not then registered on
        an
        effective Registration Statement for an offering to be made on a continuous
        basis pursuant to Rule 415. The Registration Statement shall be on Form S-3
        (except if the Company fails to meet one or more of the Registrant Requirements
        specified in General Instruction I.A. on Form S-3, such registration shall
        be on
        another appropriate form in accordance herewith) and shall contain (unless
        otherwise directed by Holders
        of at
        least
a
        majority of
        the
then
        outstanding Registrable Securities)
        substantially the “Plan of Distribution” attached hereto as Annex A. Subject to
        the terms of this Agreement, the Company shall use commercially reasonable
        efforts to cause the Registration Statement to be declared effective under
        the
        Securities Act as promptly as possible after the filing thereof, but in any
        event on or prior to the applicable Effectiveness Date, and shall use
        commercially reasonable efforts to keep the Registration Statement continuously
        effective under the Securities Act until all Registrable Securities covered
        by
        such Registration Statement have been sold, or may be sold without volume
        restrictions pursuant to Rule 144(k) (or any successor Rule under the Securities
        Act), as determined by the counsel to the Company pursuant to a written opinion
        letter to such effect, addressed and acceptable
        to the Company’s transfer agent and the affected Holders (the “Effectiveness
        Period”).
        Notwithstanding
        any other provision of this Agreement, if any SEC Guidance sets forth a
        limitation of the number of Registrable Securities to be registered on a
        particular Registration Statement (and notwithstanding that the Company used
        commercially reasonable efforts to advocate with the Commission for the
        registration of all or a greater number of Registrable Securities), unless
        otherwise directed in writing by a Holder as to its Registrable Securities,
        the
        number of Registrable Securities to be registered on such Registration Statement
        will be reduced by Registrable Securities represented by Shares (applied,
        in the
        case that some Shares may be registered, to the Holders on a pro rata basis
        based on the total number of unregistered Shares held by such
        Holders).

       

      3. Registration
        Procedures.
        In
        connection with the Company’s registration obligations hereunder, the Company
        shall:

       

      (a) Not
        less
        than five (5) Trading Days prior to the filing of each Registration Statement
        and not less than one (1) Trading Day prior to the filing of any related
        Prospectus or any amendment or supplement thereto, the Company shall, (i)
        furnish to each Holder copies of all such documents proposed to be filed,
        which
        documents (other than those incorporated or deemed to be incorporated by
        reference) will be subject to the review of such Holders, and (ii) cause
        its
        officers and directors, counsel and independent certified public accountants
        to
        respond to such inquiries as shall be necessary, in the reasonable opinion
        of
        respective counsel to each Holder, to conduct a reasonable investigation
        within
        the meaning of the Securities Act. The Company shall not file a Registration
        Statement or any such Prospectus or any amendments or supplements thereto
        to
        which the Holders of a majority of the Registrable Securities shall reasonably
        object in good faith, provided that the Company is notified of such objection
        in
        writing no later than five (5) Trading Days after the Holders have been so
        furnished copies of a Registration Statement or one (1) Trading Day after
        the
        Holders have been so furnished copies of any related Prospectus or amendments
        or
        supplements thereto. Each Holder agrees to furnish to the Company a completed
        questionnaire in the form attached to this Agreement as Annex
        B
        (a
“Selling
        Stockholder Questionnaire”)
        not
        less than two (2) Trading Days prior to the Filing Date or by the end of
        the
        fourth (4th)
        Trading
        Day following the date on which such Holder receives draft materials in
        accordance with this Section. If
        any
        Holder fails to furnish its Selling Stockholder Questionnaire related to
        a
        particular Registration Statement not less than two Trading Days prior to
        the
        Filing Date or by the end of the 4th Trading Day following the date on which
        such Holder receives draft materials in accordance with this Section any
        rights
        of such Holder under this Agreement with regard to such Registration Statement,
        including without limitation, the right to include such Holder’s Registrable
        Securities in such Registration Statement, shall be tolled as to such Holder
        until such information is received by the Company.

       

      
        
          
          

        

        
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      (b) (i)
        Prepare and file with the Commission such amendments, including post-effective
        amendments, to a Registration Statement and the Prospectus used in connection
        therewith as may be necessary to keep a Registration Statement continuously
        effective as to the applicable Registrable Securities for the Effectiveness
        Period and prepare and file with the Commission such additional Registration
        Statements in order to register for resale under the Securities Act all of
        the
        Registrable Securities; (ii) cause the related Prospectus to be amended or
        supplemented by any required Prospectus supplement (subject to the terms
        of this
        Agreement), and as so supplemented or amended to be filed pursuant to Rule
        424;
        (iii) respond as promptly as reasonably possible to any comments received
        from
        the Commission with respect to a Registration Statement or any amendment
        thereto
        and provide as promptly as reasonably possible to the Holders true and complete
        copies of all correspondence from and to the Commission relating to a
        Registration Statement (provided that the Company may excise any information
        contained therein which would constitute material non-public information
        as to
        any Holder which has not executed a confidentiality agreement with the Company);
        and (iv) comply in all material respects with the provisions of the Securities
        Act and the Exchange Act with respect to the disposition of all Registrable
        Securities covered by a Registration Statement during the applicable period
        in
        accordance (subject to the terms of this Agreement) with the intended methods
        of
        disposition by the Holders thereof set forth in such Registration Statement
        as
        so amended or in such Prospectus as so supplemented.

       

      (c) Notify
        the Holders of Registrable Securities to be sold as promptly as reasonably
        possible (i)(A) when a Prospectus or any Prospectus supplement or post-effective
        amendment to a Registration Statement is proposed to be filed; (B) when the
        Commission notifies the Company whether there will be a “review” of such
        Registration Statement and whenever the Commission comments in writing on
        such
        Registration Statement; and (C) with respect to a Registration Statement
        or any
        post-effective amendment, when the same has become effective; (ii) of any
        request by the Commission or any other Federal or state governmental authority
        for amendments or supplements to a Registration Statement or Prospectus or
        for
        additional information; (iii) of the issuance by the Commission or any other
        federal or state governmental authority of any stop order suspending the
        effectiveness of a Registration Statement covering any or all of the Registrable
        Securities or the initiation of any Proceedings for that purpose; (iv) of
        the
        receipt by the Company of any notification with respect to the suspension
        of the
        qualification or exemption from qualification of any of the Registrable
        Securities for sale in any jurisdiction, or the initiation or threatening
        of any
        Proceeding for such purpose; and (v) of the occurrence of any event or passage
        of time that makes the financial statements included in a Registration Statement
        ineligible for inclusion therein or any statement made in a Registration
        Statement or Prospectus or any document incorporated or deemed to be
        incorporated therein by reference untrue in any material respect or that
        requires any revisions to a Registration Statement, Prospectus or other
        documents so that, in the case of a Registration Statement or the Prospectus,
        as
        the case may be, it will not contain any untrue statement of a material fact
        or
        omit to state any material fact required to be stated therein or necessary
        to
        make the statements therein, in light of the circumstances under which they
        were
        made, not misleading.

       

      
        
          
          

        

        
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      (d) Use
        its
        best efforts to avoid the issuance of, or, if issued, obtain the withdrawal
        of
        (i) any order suspending the effectiveness of a Registration Statement, or
        (ii)
        any suspension of the qualification (or exemption from qualification) of
        any of
        the Registrable Securities for sale in any jurisdiction, at the earliest
        practicable moment.

       

      (e) Furnish
        to each Holder, without charge, at least one conformed copy of each such
        Registration Statement and each amendment thereto, including financial
        statements and schedules, all documents incorporated or deemed to be
        incorporated therein by reference to the extent requested by such Person,
        and
        all exhibits to the extent requested by such Person (including those previously
        furnished or incorporated by reference) promptly after the filing of such
        documents with the Commission.

       

      (f) Prior
        to
        any resale of Registrable Securities by a Holder, use its commercially
        reasonable efforts to register or qualify or cooperate with the selling Holders
        in connection with the registration or qualification (or exemption from the
        Registration or qualification) of such Registrable Securities for the resale
        by
        the Holder under the securities or Blue Sky laws of such jurisdictions within
        the United States as any Holder reasonably requests in writing, to keep each
        registration or qualification (or exemption therefrom) effective during the
        Effectiveness Period and to do any and all other acts or things reasonably
        necessary to enable the disposition in such jurisdictions of the Registrable
        Securities covered by each Registration Statement; provided, that the Company
        shall not be required to qualify generally to do business in any jurisdiction
        where it is not then so qualified, subject the Company to any material tax
        in
        any such jurisdiction where it is not then so subject or file a general consent
        to service of process in any such jurisdiction.

       

      (g) Upon
        the
        occurrence of any event contemplated by this Section 3, as promptly as
        reasonably possible under the circumstances taking into account the Company’s
        good faith assessment of any adverse consequences to the Company and its
        stockholders of the premature disclosure of such event, prepare a supplement
        or
        amendment, including a post-effective amendment, to a Registration Statement
        or
        a supplement to the related Prospectus or any document incorporated or deemed
        to
        be incorporated therein by reference, and file any other required document
        so
        that, as thereafter delivered, neither a Registration Statement nor such
        Prospectus will contain an untrue statement of a material fact or omit to
        state
        a material fact required to be stated therein or necessary to make the
        statements therein, in light of the circumstances under which they were made,
        not misleading. If the Company notifies the Holders in accordance with clauses
        (iii) through (v) of Section 3(c) above to suspend the use of any Prospectus
        until the requisite changes to such Prospectus have been made, then the Holders
        shall suspend use of such Prospectus. The Company will use its
        best
        efforts to ensure that the use of the Prospectus may be resumed as promptly
        as
        is practicable. The Company shall be entitled to exercise its right under
        this
        Section 3(g) to suspend the availability of a Registration Statement and
        Prospectus for a period not to exceed 60 calendar days (which need not be
        consecutive days) in any twelve (12) month period.

       

      (h) The
        Company may require each selling Holder to furnish to the Company a certified
        statement as to the number of shares of Common Stock beneficially owned by
        such
        Holder and, if required by the Commission, the natural persons thereof that
        have
        voting and dispositive control over the Shares. During any periods that the
        Company is unable to meet its obligations hereunder with respect to the
        registration of the Registrable Securities solely because any Holder fails
        to
        furnish such information within three Trading Days of the Company’s request,
any
        rights of such Holder under this Agreement, including without limitation,
        the
        right to include such Holder’s Registrable Securities in a Registration
        Statement
        shall be
        tolled and any Event that may otherwise occur solely because of such delay
        shall
        be suspended as to such Holder only, until such information is delivered
        to the
        Company.

       

      
        
          
          

        

        
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      4. Registration
        Expenses.
        All
        fees and expenses incident to the performance of or compliance with this
        Agreement by the Company shall be borne by the Company whether or not any
        Registrable Securities are sold pursuant to a Registration Statement. The
        fees
        and expenses referred to in the foregoing sentence shall include, without
        limitation, (i) all registration and filing fees (including, without limitation,
        fees and expenses) (A) with respect to filings required to be made with any
        Trading Market on which the Common Stock is then listed for trading, and
        (B) in
        compliance with applicable state securities or Blue Sky laws reasonably agreed
        to by the Company in writing (including, without limitation, fees and
        disbursements of counsel for the Company in connection with Blue Sky
        qualifications or exemptions of the Registrable Securities) (ii) printing
        expenses (including, without limitation, expenses of printing certificates
        for
        Registrable Securities, (iii) messenger, telephone and delivery expenses,
        (iv)
        fees and disbursements of counsel for the Company, (v) Securities Act liability
        insurance, if the Company so desires such insurance, and (vi) fees and expenses
        of all other Persons retained by the Company in connection with the consummation
        of the transactions contemplated by this Agreement. In addition, the Company
        shall be responsible for all of its internal expenses incurred in connection
        with the consummation of the transactions contemplated by this Agreement
        (including, without limitation, all salaries and expenses of its officers
        and
        employees performing legal or accounting duties), the expense of any annual
        audit and the fees and expenses incurred in connection with the listing of
        the
        Registrable Securities on any securities exchange as required hereunder.
        In no
        event shall the Company be responsible for any broker or similar commissions
        of
        any Holder or, except to the extent provided for in the Transaction Documents,
        any legal fees or other costs of the Holders.

       

      5. Indemnification.

       

      (a) Indemnification
        by the Company.
        The
        Company shall, notwithstanding any termination of this Agreement, indemnify
        and
        hold harmless each Holder, the officers, directors, members, partners, agents,
        brokers (including brokers who offer and sell Registrable Securities as
        principal as a result of a pledge or any failure to perform under a margin
        call
        of Common Stock), investment advisors, and employees (and any other Persons
        with
        a functionally equivalent role of a Person holding such titles, notwithstanding
        a lack of such title or any other title) of each of them, each Person who
        controls any such Holder (within the meaning of Section 15 of the Securities
        Act
        or Section 20 of the Exchange Act) and the officers, directors, members,
        stockholders, partners, agents and employees (and any other Persons with
        a
        functionally equivalent role of a Person holding such titles, notwithstanding
        a
        lack of such title or any other title) of each such controlling Person, to
        the
        fullest extent permitted by applicable law, from and against any and all
        losses,
        claims, damages, liabilities, costs (including, without limitation, reasonable
        attorneys’ fees) and expenses (collectively, “Losses”),
        as
        incurred, arising out of or relating to (i) any untrue or alleged untrue
        statement of a material fact contained in a Registration Statement, any
        Prospectus or any form of prospectus or in any amendment or supplement thereto
        or in any preliminary prospectus, or arising out of or relating to any omission
        or alleged omission of a material fact required to be stated therein or
        necessary to make the statements therein (in the case of any Prospectus or
        form
        of prospectus or supplement thereto, in light of the circumstances under
        which
        they were made) not misleading, or (ii) any violation or alleged violation
        by
        the Company of the Securities Act, Exchange Act or any state securities law,
        or
        any rule or regulation thereunder, in connection with the performance of
        its
        obligations under this Agreement, except to the extent, but only to the extent,
        that (A) such untrue statements or omissions are based solely upon information
        regarding such Holder furnished in writing to the Company by such Holder
        expressly for use therein, or to the extent that such information relates
        to
        such Holder or such Holder’s proposed method of distribution of Registrable
        Securities and was reviewed and expressly approved in writing by such Holder
        expressly for use in a Registration Statement, such Prospectus or such form
        of
        Prospectus or in any amendment or supplement thereto (it being understood
        that
        each Holder has approved Annex
        A
        hereto
        for this purpose) or (B) in the case of an occurrence of an event of the
        type
        specified in Section 3(c)(iii)-(v), the use by such Holder of an outdated
        or
        defective Prospectus after the Company has notified such Holder in writing
        that
        the Prospectus is outdated or defective and prior to the receipt by such
        Holder
        of the Advice contemplated in Section 6(d). The Company shall notify the
        Holders
        promptly of the institution, threat or assertion of any Proceeding arising
        from
        or in connection with the transactions contemplated by this Agreement of
        which
        the Company is aware.

       

      
        
          
          

        

        
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      (b) Indemnification
        by Holders.
        Each
        Holder shall, severally and not jointly, indemnify and hold harmless the
        Company, its directors, officers, agents, and employees, each Person who
        controls the Company (within the meaning of Section 15 of the Securities
        Act and
        Section 20 of the Exchange Act), and the directors, officers, agents or
        employees of such controlling Persons, to the fullest extent permitted by
        applicable law, from and against all Losses, as incurred, to the extent arising
        out of or based solely upon: (i) such Holder’s failure to comply with the
        prospectus delivery requirements of the Securities Act or (ii) any untrue
        or
        alleged untrue statement of a material fact contained in any Registration
        Statement, any Prospectus, or any form of prospectus, or in any amendment
        or
        supplement thereto or in any preliminary prospectus, or arising out of or
        relating to any omission or alleged omission of a material fact required
        to be
        stated therein or necessary to make the statements therein not misleading
        (A) to
        the extent, but only to the extent, that such untrue statement or omission
        is
        contained in any information so furnished in writing by such Holder to the
        Company specifically for inclusion in such Registration Statement or such
        Prospectus or (B) to the extent that such information relates to such Holder’s
        proposed method of distribution of Registrable Securities and was reviewed
        and
        expressly approved in writing by such Holder expressly for use in a Registration
        Statement (it being understood that each Holder has approved Annex
        A
        hereto
        for this purpose), such Prospectus or such form of Prospectus or in any
        amendment or supplement thereto or (C) in the case of an occurrence of an
        event
        of the type specified in Section 3(c)(iii)-(v), the use by such Holder of
        an
        outdated or defective Prospectus after the Company has notified such Holder
        in
        writing that the Prospectus is outdated or defective and prior to the receipt
        by
        such Holder of the Advice contemplated in Section 6(d). In no event shall
        the
        liability of any selling Holder hereunder be greater in amount than the dollar
        amount of the net proceeds received by such Holder upon the sale of the
        Registrable Securities giving rise to such indemnification
        obligation.

       

      (c) Conduct
        of Indemnification Proceedings.
        If any
        Proceeding shall be brought or asserted against any Person entitled to indemnity
        hereunder (an “Indemnified
        Party”),
        such
        Indemnified Party shall promptly notify the Person from whom indemnity is
        sought
        (the “Indemnifying
        Party”)
        in
        writing, and the Indemnifying Party shall have the right to assume the defense
        thereof, including the employment of counsel reasonably satisfactory to the
        Indemnified Party and the payment of all fees and expenses incurred in
        connection with defense thereof; provided, that the failure of any Indemnified
        Party to give such notice shall not relieve the Indemnifying Party of its
        obligations or liabilities pursuant to this Agreement, except (and only)
        to the
        extent that it shall be finally determined by a court of competent jurisdiction
        (which determination is not subject to appeal or further review) that such
        failure shall have prejudiced the Indemnifying Party.

       

      An
        Indemnified Party shall have the right to employ separate counsel in any
        such
        Proceeding and to participate in the defense thereof, but the fees and expenses
        of such counsel shall be at the expense of such Indemnified Party or Parties
        unless: (i) the Indemnifying Party has agreed in writing to pay such fees
        and
        expenses; (ii) the Indemnifying Party shall have failed promptly to assume
        the
        defense of such Proceeding and to employ counsel reasonably satisfactory
        to such
        Indemnified Party in any such Proceeding; or (iii) the named parties to any
        such
        Proceeding (including any impleaded parties) include both such Indemnified
        Party
        and the Indemnifying Party, and counsel to the Indemnified Party shall
        reasonably believe that a material conflict of interest is likely to exist
        if
        the same counsel were to represent such Indemnified Party and the Indemnifying
        Party (in which case, if such Indemnified Party notifies the Indemnifying
        Party
        in writing that it elects to employ separate counsel at the expense of the
        Indemnifying Party, the Indemnifying Party shall not have the right to assume
        the defense thereof and the reasonable fees and expenses of no more than
        one
        separate counsel shall be at the expense of the Indemnifying Party). The
        Indemnifying Party shall not be liable for any settlement of any such Proceeding
        effected without its written consent, which consent shall not be unreasonably
        withheld or delayed. No Indemnifying Party shall, without the prior written
        consent of the Indemnified Party, effect any settlement of any pending
        Proceeding in respect of which any Indemnified Party is a party, unless such
        settlement includes an unconditional release of such Indemnified Party from
        all
        liability on claims that are the subject matter of such Proceeding.

       

      
        
          
          

        

        
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      Subject
        to the terms of this Agreement, all reasonable fees and expenses of the
        Indemnified Party (including reasonable fees and expenses to the extent incurred
        in connection with investigating or preparing to defend such Proceeding in
        a
        manner not inconsistent with this Section) shall be paid to the Indemnified
        Party, as incurred, within ten Trading Days of written notice thereof to
        the
        Indemnifying Party, provided that the Indemnified Party shall promptly reimburse
        the Indemnifying Party for that portion of such fees and expenses applicable
        to
        such actions for which such Indemnified Party is judicially determined to
        be not
        entitled to indemnification hereunder.

       

      (d) Contribution.
        If the
        indemnification under Section 5(a) or 5(b) is unavailable to an Indemnified
        Party or insufficient to hold an Indemnified Party harmless for any Losses,
        then
        each Indemnifying Party shall contribute to the amount paid or payable by
        such
        Indemnified Party, in such proportion as is appropriate to reflect the relative
        fault of the Indemnifying Party and Indemnified Party in connection with
        the
        actions, statements or omissions that resulted in such Losses as well as
        any
        other relevant equitable considerations. The relative fault of such Indemnifying
        Party and Indemnified Party shall be determined by reference to, among other
        things, whether any action in question, including any untrue or alleged untrue
        statement of a material fact or omission or alleged omission of a material
        fact,
        has been taken or made by, or relates to information supplied by, such
        Indemnifying Party or Indemnified Party, and the parties’ relative intent,
        knowledge, access to information and opportunity to correct or prevent such
        action, statement or omission. The amount paid or payable by a party as a
        result
        of any Losses shall be deemed to include, subject to the limitations set
        forth
        in this Agreement, any reasonable attorneys’ or other fees or expenses incurred
        by such party in connection with any Proceeding to the extent such party
        would
        have been indemnified for such fees or expenses if the indemnification provided
        for in this Section was available to such party in accordance with its
        terms.

       

      The
        parties hereto agree that it would not be just and equitable if contribution
        pursuant to this Section 5(d) were determined by pro rata allocation or by
        any
        other method of allocation that does not take into account the equitable
        considerations referred to in the immediately preceding paragraph.
        Notwithstanding the provisions of this Section 5(d), no Holder shall be required
        to contribute, in the aggregate, any amount in excess of the amount by which
        the
        net proceeds actually received by such Holder from the sale of the Registrable
        Securities subject to the Proceeding exceeds the amount of any damages that
        such
        Holder has otherwise been required to pay by reason of such untrue or alleged
        untrue statement or omission or alleged omission, except in the case of fraud
        by
        such Holder.

       

      The
        indemnity and contribution agreements contained in this Section are in addition
        to any liability that the Indemnifying Parties may have to the Indemnified
        Parties.

       

      
        
          
          

        

        
          -7-

          
            

          

        

        
          
          

        

      

       

      6. Miscellaneous.

       

      (a) Remedies.
        In the
        event of a breach by the Company or by a Holder of any of their respective
        obligations under this Agreement, each Holder or the Company, as the case
        may
        be, in addition to being entitled to exercise all rights granted by law and
        under this Agreement, including recovery of damages, shall be entitled to
        specific performance of its rights under this Agreement. The Company and
        each
        Holder agree that monetary damages would not provide adequate compensation
        for
        any losses incurred by reason of a breach by it of any of the provisions
        of this
        Agreement and hereby further agrees that, in the event of any action for
        specific performance in respect of such breach, it shall not assert or shall
        waive the defense that a remedy at law would be adequate.

       

      (b) No
        Other Registrations.
        The
        Company shall not file any other registration statements (other than on Form
        S-4
        or Form S-8) until the initial
        Registration Statement required hereunder is
        declared
        effective by the Commission, provided that this Section 6(b) shall not prohibit
        the Company from filing amendments to registration statements filed prior
        to the
        date of this Agreement. 

       

      (c) Compliance.
        Each
        Holder covenants and agrees that it will comply with the prospectus delivery
        requirements of the Securities Act as applicable to it in connection with
        sales
        of Registrable Securities pursuant to a Registration Statement.

       

      (d) Discontinued
        Disposition.
        By its
        acquisition of Registrable Securities, each Holder agrees that, upon receipt
        of
        a notice from the Company of the occurrence of any event of the kind described
        in Section 3(c), such Holder will forthwith discontinue disposition of such
        Registrable Securities under a Registration Statement until it is advised
        in
        writing (the “Advice”)
        by the
        Company that the use of the applicable Prospectus (as it may have been
        supplemented or amended) may be resumed. The Company will use its
        best
        efforts to ensure that the use of the Prospectus may be resumed as promptly
        as
        it practicable. The Company may provide appropriate stop orders to enforce
        the
        provisions of this Section 6(d).

       

      (e) Amendments
        and Waivers.
        The
        provisions of this Agreement, including the provisions of this sentence,
        may not
        be amended, modified or supplemented, and waivers or consents to departures
        from
        the provisions hereof may not be given, unless the same shall be in writing
        and
        signed by the Company and the Holders of at
        least
        a majority of
        the
        then outstanding Registrable Securities. If a Registration Statement does
        not
        register all of the Registrable Securities pursuant to a waiver or amendment
        done in compliance with the previous sentence, then the number of Registrable
        Securities to be registered for each Holder shall be reduced pro rata
        among
        all Holders and each Holder shall have the right to designate which of its
        Registrable Securities shall be omitted from such Registration Statement.
        Notwithstanding the foregoing, a waiver or consent to depart from the provisions
        hereof with respect to a matter that relates exclusively to the rights of
        Holders and that does not directly or indirectly affect the rights of other
        Holders may be given by Holders of all of the Registrable Securities to which
        such waiver or consent relates; provided,
        however,
        that
        the provisions of this sentence may not be amended, modified, or supplemented
        except in accordance with the provisions of the immediately preceding
        sentence.

       

      (f) Notices.
        Any and
        all notices or other communications or deliveries required or permitted to
        be
        provided hereunder shall be delivered as set forth in the Purchase
        Agreement.

       

      (g) Successors
        and Assigns.
        This
        Agreement shall inure to the benefit of and be binding upon the successors
        and
        permitted assigns of each of the parties and shall inure to the benefit of
        each
        Holder. The Company may not assign its rights (except by merger) or obligations
        hereunder without the prior written consent of Holders holding at least a
        majority of the then outstanding Registrable Securities. Each Holder may
        assign
        their respective rights hereunder in the manner and to the Persons as permitted
        under the Purchase Agreement.

       

      
        
          
          

        

        
          -8-

          
            

          

        

        
          
          

        

      

       

      (h) Execution
        and Counterparts.
        This
        Agreement may be executed in two or more counterparts, all of which when
        taken
        together shall be considered one and the same agreement and shall become
        effective when counterparts have been signed by each party and delivered
        to the
        other party, it being understood that both parties need not sign the same
        counterpart. In the event that any signature is delivered by facsimile
        transmission or by e-mail delivery of a “.pdf” format data file, such signature
        shall create a valid and binding obligation of the party executing (or on
        whose
        behalf such signature is executed) with the same force and effect as if such
        facsimile or “.pdf” signature page were an original thereof.

       

      (i) Governing
        Law.
        All
        questions concerning the construction, validity, enforcement and interpretation
        of this Agreement shall be determined in accordance with the provisions of
        the
        Purchase Agreement.

       

      (j) Cumulative
        Remedies.
        The
        remedies provided herein are cumulative and not exclusive of any other remedies
        provided by law.

       

      (k) Severability.
        If any
        term, provision, covenant or restriction of this Agreement is held by a court
        of
        competent jurisdiction to be invalid, illegal, void or unenforceable, the
        remainder of the terms, provisions, covenants and restrictions set forth
        herein
        shall remain in full force and effect and shall in no way be affected, impaired
        or invalidated, and the parties hereto shall use their commercially reasonable
        efforts to find and employ an alternative means to achieve the same or
        substantially the same result as that contemplated by such term, provision,
        covenant or restriction. It is hereby stipulated and declared to be the
        intention of the parties that they would have executed the remaining terms,
        provisions, covenants and restrictions without including any of such that
        may be
        hereafter declared invalid, illegal, void or unenforceable.

       

      (l) Headings.
        The
        headings in this Agreement are for convenience only, do not constitute a
        part of
        this Agreement, and shall not be deemed to limit or affect any of the provisions
        hereof.

       

      (m) Independent
        Nature of Holders’ Obligations and Rights.
        The
        obligations of each Holder hereunder are several and not joint with the
        obligations of any other Holder hereunder, and no Holder shall be responsible
        in
        any way for the performance of the obligations of any other Holder hereunder.
        Nothing contained herein or in any other agreement or document delivered
        at any
        closing, and no action taken by any Holder pursuant hereto or thereto, shall
        be
        deemed to constitute the Holders as a partnership, an association, a joint
        venture or any other kind of entity, or create a presumption that the Holders
        are in any way acting in concert with respect to such obligations or the
        transactions contemplated by this Agreement. Each Holder shall be entitled
        to
        protect and enforce its rights, including without limitation the rights arising
        out of this Agreement, and it shall not be necessary for any other Holder
        to be
        joined as an additional party in any proceeding for such
        purpose.

      
 

      [SIGNATURE
        PAGES FOLLOWS]

      

      
        
          
          

        

        
          -9-

          
            

          

        

        
          
          

        

      

      IN
        WITNESS WHEREOF, the parties have executed this Registration Rights Agreement
        as
        of the date first written above.

      
        	 	 	 
	 	
                PRESSURE
                  BIOSCIENCES INC.

              
	 
 	 
 	 
 
	
              	By:  	
              
	 	
                

                Name:
                  Richard T. Schumacher

                Title:
                  President and Chief Executive
                  Officer

              

      

       

       

      [SIGNATURE
        PAGE OF HOLDERS FOLLOWS]

       

      
        
          
          

        

        
          
          

          
            

          

        

        
          
          

        

      

      [SIGNATURE
        PAGE OF HOLDERS TO REGISTRATION RIGHTS AGREEMENT]

      

      

      Name
        of
        Holder: __________________________

       

      Signature
        of Authorized Signatory of Holder:
        __________________________

       

      Name
        of
        Authorized Signatory: _________________________

       

      Title
        of
        Authorized Signatory: __________________________

       

      

      [SIGNATURE
        PAGES CONTINUE]

       

      
        
          
          

        

        
          
          

          
            

          

        

        
          
          

        

      

      ANNEX
        A

       

      Plan
        of Distribution

       

      Each
        selling stockholder (the “Selling
        Stockholders”)
        of the
        Common Stock and any of their pledgees, assignees, and successors-in-interest
        may, from time to time, sell any or all of their shares of common stock on
        any
        stock exchange, market or trading facility on which the shares are traded
        or in
        private transactions. These sales may be at fixed or negotiated prices. A
        Selling Stockholder may use any one or more of the following methods when
        selling shares:

       

      
        	 	
                ·

              	
                ordinary
                  brokerage transactions and transactions in which the broker-dealer
                  solicits purchasers;

              

      

       

      
        	 	
                ·

              	
                block
                  trades in which the broker-dealer will attempt to sell the shares
                  as agent
                  but may position and resell a portion of the block as principal
                  to
                  facilitate the transaction;

              

      

       

      
        	 	
                ·

              	
                purchases
                  by a broker-dealer as principal and resale by the broker-dealer
                  for its
                  account;

              

      

       

      
        	 	
                ·

              	
                an
                  exchange distribution in accordance with the rules of the applicable
                  exchange;

              

      

       

      
        	 	
                ·

              	
                privately
                  negotiated transactions;

              

      

       

      
        	 	
                ·

              	
                settlement
                  of short sales entered into after the effective date of the registration
                  statement of which this prospectus is a
                  part;

              

      

       

      
        	 	
                ·

              	
                broker-dealers
                  may agree with the Selling Stockholders to sell a specified number
                  of such
                  shares at a stipulated price per
                  share;

              

      

       

      
        	 	
                ·

              	
                through
                  the writing or settlement of options or other hedging transactions,
                  whether through an options exchange or otherwise;
                  

              

      

       

      
        	 	
                ·

              	
                a
                  combination of any such methods of sale;
                  or

              

      

       

      
        	 	
                ·

              	
                any
                  other method permitted pursuant to applicable
                  law.

              

      

       

      The
        Selling Stockholders may also sell shares under Rule 144 under the Securities
        Act of 1933, as amended (the “Securities
        Act”),
        if
        available, rather than under this prospectus.

       

      Broker-dealers
        engaged by the Selling Stockholders may arrange for other brokers-dealers
        to
        participate in sales. Broker-dealers may receive commissions or discounts
        from
        the Selling Stockholders (or, if any broker-dealer acts as agent for the
        purchaser of shares, from the purchaser) in amounts to be negotiated, but,
        except as set forth in a supplement to this prospectus, in the case of an
        agency
        transaction not in excess of a customary brokerage commission in compliance
        with
        NASDR Rule 2440; and in the case of a principal transaction a markup or markdown
        in compliance with NASDR IM-2440. 

       

      The
        Selling Stockholders and any broker-dealers or agents that are involved in
        selling the shares may be deemed to be “underwriters” within the meaning of the
        Securities Act in connection with such sales. In such event, any commissions
        received by such broker-dealers or agents and any profit on the resale of
        the
        shares purchased by them may be deemed to be underwriting commissions or
        discounts under the Securities Act. Each Selling Stockholder has informed
        the
        Company that it does not have any written or oral agreement or understanding,
        directly or indirectly, with any person to distribute the Common Stock. In
        no
        event shall any broker-dealer receive fees, commissions and markups which,
        in
        the aggregate, would exceed eight percent (8%).

       

      
        
          
          

        

        
          
          

          
            

          

        

        
          
          

        

      

       

      The
        Company is required to pay certain fees and expenses incurred by the Company
        incident to the registration of the shares. The Company has agreed to indemnify
        the Selling Stockholders against certain losses, claims, damages and
        liabilities, including liabilities under the Securities Act. 

       

      Because
        Selling Stockholders may be deemed to be “underwriters” within the meaning of
        the Securities Act, they will be subject to the prospectus delivery requirements
        of the Securities Act including Rule 172 thereunder. In addition, any securities
        covered by this prospectus which qualify for sale pursuant to Rule 144 under
        the
        Securities Act may be sold under Rule 144 rather than under this prospectus.
        There is no underwriter or coordinating broker acting in connection with
        the
        proposed sale of the resale shares by the Selling Stockholders.

       

      The
        Company has agreed to keep Prospectus effective until the earlier of (i)
        the
        date on which the shares may be resold by the Selling Stockholders without
        registration and without regard to any volume limitations by reason of Rule
        144(k) under the Securities Act or any other rule of similar effect or (ii)
        all
        of the shares have been sold pursuant to this prospectus or Rule 144 under
        the
        Securities Act or any other rule of similar effect. The resale shares will
        be
        sold only through registered or licensed brokers or dealers if required under
        applicable state securities laws. In addition, in certain states, the resale
        shares may not be sold unless they have been registered or qualified for
        sale in
        the applicable state or an exemption from the registration or qualification
        requirement is available and is complied with.

       

      Under
        applicable rules and regulations under the Exchange Act, any person engaged
        in
        the distribution of the resale shares may not simultaneously engage in market
        making activities with respect to the common stock for the applicable restricted
        period, as defined in Regulation M, prior to the commencement of the
        distribution. In addition, the Selling Stockholders will be subject to
        applicable provisions of the Exchange Act and the rules and regulations
        thereunder, including Regulation M, which may limit the timing of purchases
        and
        sales of shares of the common stock by the Selling Stockholders or any other
        person. The Company will make copies of this Prospectus available to the
        Selling
        Stockholders and have informed them of the need to deliver a copy of this
        Prospectus to each purchaser at or prior to the time of the sale (including
        by
        compliance with Rule 172 under the Securities Act).

       

      
        
          
          

        

        
          
          

          
            

          

        

        
          
          

        

      

      Annex
        B

       

      PRESSURE
        BIOSCIENCES INC.

       

      Selling
        Securityholder Notice and Questionnaire

       

      The
        undersigned beneficial owner of common stock (the “Registrable
        Securities”)
        of
        Pressure BioSciences Inc., a Massachusetts corporation (the “Company”),
        understands that the Company has filed or intends to file with the Securities
        and Exchange Commission (the “Commission”)
        a
        registration statement (the “Registration
        Statement”)
        for
        the registration and resale under Rule 415 of the Securities Act of 1933,
        as
        amended (the “Securities
        Act”),
        of
        the Registrable Securities, in accordance with the terms of the Registration
        Rights Agreement (the “Registration
        Rights Agreement”)
        to
        which this document is annexed. A copy of the Registration Rights Agreement
        is
        available from the Company upon request at the address set forth below. All
        capitalized terms not otherwise defined herein shall have the meanings ascribed
        thereto in the Registration Rights Agreement.

       

      Certain
        legal consequences arise from being named as a selling securityholder in
        the
        Registration Statement and the related prospectus. Accordingly, holders and
        beneficial owners of Registrable Securities are advised to consult their
        own
        securities law counsel regarding the consequences of being named or not being
        named as a selling securityholder in the Registration Statement and the related
        prospectus.

       

      NOTICE

       

      The
        undersigned beneficial owner (the “Selling
        Securityholder”)
        of
        Registrable Securities hereby elects to include the Registrable Securities
        owned
        by it in the Registration Statement.

       

      
        
          
          

        

        
          
          

          
            

          

        

        
          
          

        

      

      The
        undersigned hereby provides the following information to the Company and
        represents and warrants that such information is accurate:

       

      QUESTIONNAIRE

       

      
        	1.	
                Name.

              

      

       

      
        	 	
                (a)

              	
                Full
                  Legal Name of Selling
                  Securityholder

              

      

       

        
          

        

         

      

      
        	 	
                (b)

              	
                Full
                  Legal Name of Registered Holder (if not the same as (a) above)
                  through
                  which Registrable Securities are
                  held:

              

      

       

      
        

      

       

      
        	 	
                (c)

              	
                Full
                  Legal Name of Natural Control Person (which means a natural person
                  who
                  directly or indirectly alone or with others has power to vote or
                  dispose
                  of the securities covered by the
                  questionnaire):

              

      

       

      
        

      

       

      
        	2.	
                Address
                  for Notices to Selling
                  Securityholder:

              

      

       

      
        
 

        

      

       

      
        
 

      
        	
                Telephone:
                  ______

              
	
                Fax:
                  ______

              
	
                Contact
                  Person:

              

      

       

      
        	3.	
                Broker-Dealer
                  Status:

              

      

       

      
        	 	
                (a)

              	
                Are
                  you a broker-dealer?

              

      

       

      Yes o
No
o

       

      
        	 	
                (b)

              	
                If
                  “yes” to Section 3(a), did you receive your Registrable Securities as
                  compensation for investment banking services to the
                  Company.

              

      

       

      Yes o
No
o

       

      
        	 	
                Note:

              	
                If
                  no, the Commission’s staff has indicated that you should be identified as
                  an underwriter in the Registration
                  Statement.

              

      

       

      
        
          
          

        

        
          
          

          
            

          

        

        
          
          

        

      

       

      
        	 	
                (c)

              	
                Are
                  you an affiliate of a
                  broker-dealer?

              

      

       

      Yes
o
No
o

       

      
        	 	
                (d)

              	
                If
                  you are an affiliate of a broker-dealer, do you certify that you
                  bought
                  the Registrable Securities in the ordinary course of business,
                  and at the
                  time of the purchase of the Registrable Securities to be resold,
                  you had
                  no agreements or understandings, directly or indirectly, with any
                  person
                  to distribute the Registrable
                  Securities?

              

      

       

      Yes
o
No
o

       

      
        	 	
                Note:

              	
                If
                  no, the Commission’s staff has indicated that you should be identified as
                  an underwriter in the Registration
                  Statement.

              

      

       

      
        	
                4.

              	
                Beneficial
                  Ownership of Other Securities of the Company Owned by the Selling
                  Securityholder.

              

      

       

      Except
        as set forth below in this Item 4, the undersigned is not the beneficial
        or
        registered owner of any securities of the Company other than the securities
        issuable pursuant to the Purchase Agreement.

       

      
        	 	
                (a)

              	
                Type
                  and Amount of other securities beneficially owned by the Selling
                  Securityholder:

              

      

       

      
        

      

       

      
        

      

       

      
        	 	
                (b)

              	
                Shared
                  or sole ownership? If shared, please indicate the name and relationship
                  of
                  the party with whom ownership is
                  shared:

              

      

       

      
        

      

       

      
        

      

       

      
        	5.	
                Relationships
                  with the Company:

              

      

       

      Except
        as set forth below, neither the undersigned nor any of its affiliates, officers,
        directors or principal equity holders (owners of 5% of more of the equity
        securities of the undersigned) has held any position or office or has had
        any
        other material relationship with the Company (or its predecessors or affiliates)
        during the past three years.

       

      State
        any
        exceptions here:

       

      
        

      

       

      
        

      

       

      
        
          
          

        

        
          
          

          
            

          

        

        
          
          

        

      

       

      The
        undersigned agrees to promptly notify the Company of any inaccuracies or
        changes
        in the information provided herein that may occur subsequent to the date
        hereof
        at any time while the Registration Statement remains effective.

       

      By
        signing below, the undersigned consents to the disclosure of the information
        contained herein in its answers to Items 1 through 5 and the inclusion of
        such
        information in the Registration Statement and the related prospectus and
        any
        amendments or supplements thereto. The undersigned understands that such
        information will be relied upon by the Company in connection with the
        preparation or amendment of the Registration Statement and the related
        prospectus.

       

      IN
        WITNESS WHEREOF the undersigned, by authority duly given, has caused this
        Notice
        and Questionnaire to be executed and delivered either in person or by its
        duly
        authorized agent.

      
        	 	 	 	 
	Dated:
                _____________	 	 	Beneficial
                Owner:
                
	
              	 	 	
                
                  

                

              
	 	 	 	By:
	
              	 	 	
                
                  

                

                
                  Name:

                  Title: 

                

              

      

       

      PLEASE
        FAX A COPY OF THE COMPLETED AND EXECUTED NOTICE AND QUESTIONNAIRE, AND RETURN
        THE ORIGINAL BY OVERNIGHT MAIL, TO:

      

      [INSERT
        CONTACT DETAILS]a5571729ex4_3.htm

    Exhibit
      4.3

    
       

      Form
        of
        Investor Warrant Agreement

       

      WARRANT
        AGREEMENT

       

      THIS
        WARRANT AGREEMENT (the “Agreement”) is dated _______ __, 2008, between
        Opexa Therapeutics, Inc., a Delaware corporation (the “Company”) and Continental
        Stock Transfer & Trust Company, acting as warrant agent (the “Warrant
        Agent”).

       

      WHEREAS,
        the Company proposes to issue warrants (collectively with any Additional
        Warrants, the “Series E Warrants”) to acquire up to
[5,625,000] shares, subject to adjustment as provided
        herein, of common stock, $ .50 par value (“Common Stock”), of the Company
        (collectively, the “Warrant Shares”);

       

      WHEREAS,
        each Series E Warrant shall represent the right to purchase from the
        Company, at an initial price of $______ per share [125% of price of
        share of common stock offered to public] (the “Exercise Price”),
        the number of shares specified on the certificates evidencing
        the  Series E Warrants (the “Warrant Certificates”); and

       

      WHEREAS,
        Continental Stock Transfer & Trust Company is willing to serve as the
        Warrant Agent in connection with the issuance of Warrant Certificates and
        the
        other matters as provided herein.

       

      NOW,
        THEREFORE, in consideration of the foregoing and for the purpose of
        defining the terms and provisions of the Series E Warrants and the
        respective rights and obligations thereunder of the Company, the Warrant
        Agent
        and the record holders from time to time of the Series E Warrants (the
“Holders”), the parties hereby agree as follows:

       

      1.  Definitions.  For
        the purposes hereof, the following terms shall have the following
        meanings:

       

      “Business
        Day” means any day except Saturday, Sunday and any day which shall be a federal
        legal holiday in the United States or a day on which banking institutions
        in The
        City of New York are authorized or required by law or other government action
        to
        close.

       

      “Date
        of
        Exercise” means the date on which the Holder shall have delivered to the Company
        (i) a Warrant Certificate, (ii) the Form of Election to Purchase
        attached thereto (with the Warrant Shares Exercise Log attached to it),
        appropriately completed and duly signed, and (iii) in the case of a Cash
        Exercise, payment of the Exercise Price in accordance with Section 9 for
        the
        number of Warrant Shares so indicated by the Holder to be
        purchased.

       

      “Exchange
        Act” means the Securities Exchange Act of 1934, as amended, and the rules and
        regulations of the Securities and Exchange Commission promulgated
        thereunder.

       

      “Expiration
        Date” means the date five years after the Initial Issuance Date.

       

      “Initial
        Issuance Date” means _________ __, 2008.

       

      
        
          
          

        

        
          
          

          
            

          

        

        
          
          

        

      

       

      “Market
        Price” of a share of Common Stock on any date shall mean, (i) if the shares
        of Common Stock are traded on the Nasdaq Global Market or Nasdaq Capital
        Market,
        the last bid price reported on that date; (ii) if the shares of Common
        Stock are no longer quoted on Nasdaq and are listed on any other national
        securities exchange, the last sale price of the Common Stock reported by
        such
        exchange on that date; (iii) if the shares of Common Stock are not quoted
        on a
        any such market or listed on any such exchange and the shares of Common Stock
        are traded in the over-the-counter market, the last price reported on such
        day
        by the OTC Bulletin Board; (iv) if the shares of Common Stock are not
        quoted on a any such market, listed on any such exchange or quoted on the
        OTC
        Bulletin Board, then the last price quoted on such day in the over-the-counter
        market as reported by the National Quotation Bureau Incorporated (or any
        similar
        organization or agency succeeding its functions of reporting prices); or
        (v) if none of clauses (i)-(iv) are applicable, then as determined, in
        good faith, by the Board of Directors of the Company.

       

      “Person”
        means a corporation, association, partnership, limited liability corporation,
        organization, business, individual, government or political subdivision thereof
        or governmental agency.

       

      “Trading
        Day” means (i) a day on which the shares of Common Stock are traded on the
        Nasdaq Global Market, Nasdaq Capital Market, New York Stock Exchange or American
        Stock Exchange on which the shares of Common Stock are then listed or quoted,
        or
        (ii) if the shares of Common Stock are not listed on a any such exchange or
        market, a day on which the shares of Common Stock are traded in the
        over-the-counter market, as reported by the OTC Bulletin Board, or (iii) if
        the shares of Common Stock are not quoted on the OTC Bulletin Board, a day
        on
        which the shares of Common Stock are quoted in the over-the-counter market
        as
        reported by the National Quotation Bureau Incorporated (or any similar
        organization or agency succeeding its functions of reporting prices); provided,
        that in the event that the shares of Common Stock are not listed or quoted
        as
        set forth in clause (i), (ii) or (iii) hereof, then Trading Day shall mean
        a Business Day.

       

      2.  Form
        of
        Warrant Certificates.

       

      (a)  Form.  The
        Warrant Certificates shall be issued in registered form only as definitive
        Warrant Certificates and shall be substantially in the form attached hereto
        as
        Exhibit A, shall be dated the date of issuance thereof (whether upon
        initial issuance, register of transfer, exchange or replacement) and shall
        bear
        such legends and endorsements typed, stamped, printed, lithographed or engraved
        thereon as the Company may deem appropriate and as are not inconsistent with
        the
        provisions of this Agreement. Warrant Certificates evidencing Series E Warrants
        to purchase the number of shares of Common Stock specified on each Warrant
        Certificate shall be signed by, or bear the facsimile signature of, the Chairman
        of the Board, Chief Executive Officer, President, any Vice President, Treasurer
        or Secretary of the Company. In the event the person whose facsimile signature
        has been placed upon any Warrant Certificate shall have ceased to serve in
        the
        capacity in which such person signed the Warrant Certificate before such
        Warrant
        Certificate is issued, it may be issued with the same effect as if he or
        she had
        not ceased to be such at the date of issuance.

       

      
        
          
          

        

        
          2

          
            

          

        

        
          
          

        

      

       

      (b)  Effect
        of Countersignature.  Unless and until countersigned by the
        Warrant Agent pursuant to this Agreement, a Warrant Certificate shall be
        invalid
        and of no effect and may not be exercised by the holder thereof. Such signature
        by the Warrant Agent upon any Warrant Certificate executed by the Company
        shall
        be conclusive evidence that such Warrant Certificate has been duly issued
        under
        the terms of this Agreement.

       

      (c)  Warrant
        Register.  The Warrant Agent shall maintain books (the “Warrant
        Register”), for the registration of original issuance and the registration of
        transfer of Warrant Certificates. Upon the initial issuance of the Warrant
        Certificates, the Warrant Agent shall issue and register the Warrant
        Certificates in the names of the respective holders thereof in such
        denominations and otherwise in accordance with instructions delivered to
        the
        Warrant Agent by the Company. The Company and the Warrant Agent may deem
        and
        treat the registered Holder of each Warrant Certificate as the absolute owner
        of
        the Series E Warrants represented thereby for the purpose of any exercise
        thereof or any distribution to the Holder, and for all other purposes, absent
        actual notice to the contrary.

       

      (d)  Registration
        of Transfers.  The Warrant Agent shall register the transfer of
        any portion of a Warrant Certificate in the Warrant Register, upon surrender
        of
        the Warrant Certificate, with the Form of Assignment attached thereto duly
        completed and signed, to the Company at its address specified herein. Upon
        any
        such registration or transfer, a new Warrant Certificate substantially in
        the
        form attached hereto as Exhibit A (any such new Warrant Certificate, a “New
        Warrant Certificate”), evidencing the portion of the Warrant Certificate so
        transferred shall be issued to the transferee and a New Warrant Certificate
        evidencing the remaining portion of the Warrant Certificate not so transferred,
        if any, shall be issued to the transferring Holder. The delivery of the New
        Warrant Certificate by the Company to the transferee thereof shall be deemed
        to
        constitute acceptance by such transferee of all of the rights and obligations
        of
        a holder of a Warrant Certificate.

       

      3.  Term
        of
        Series E Warrants.  Subject to the terms of Section 4,
        Series E Warrants shall be exercisable by the registered Holder at any time
        and from time to time on or after the Initial Issuance Date to and including
        the
        Expiration Date. At 5:00 p.m., Houston time on the Expiration Date, any
        portion of a Series E Warrant not exercised prior thereto shall be and
        become void and of no value.

       

      4.  Exercise
        of Series E Warrants and Delivery of Warrant Shares.

       

      (a)  If
        an
        effective registration statement is then available for the issuance of the
        Warrant Shares and the exercise is permitted in the state of the residence
        of
        the registered Holder, a registered Holder may only exercise the Series E
        Warrants through a cash exercise (a “Cash Exercise”).  If an effective
        registration statement is not then available for the issuance of the Warrant
        Shares under the Federal securities laws or the state “blue sky” laws of the
        state of the residence of the registered Holder, then a registered Holder
        may
        exercise the Series E Warrants through either (i) through a cashless
        exercise (a “Cashless Exercise”) pursuant to Section 4(b) below or
        (ii) through a Cash Exercise after making customary representations
        requested by the Company regarding investment intent and accredited status
        and
        agreeing to customary transfer restrictions requested by the Company to ensure
        compliance by the Company with applicable securities laws.

       

      
        
          
          

        

        
          3

          
            

          

        

        
          
          

        

      

       

      (b)  The
        Holder
        shall effect a Cashless Exercise by surrendering Warrant Certificates to
        the
        Warrant Agent and noting on the Form of Election to Purchase that the Holder
        wishes to effect a Cashless Exercise, upon which the Company shall issue,
        or
        cause to be issued, to the Holder the number of Warrant Shares determined
        as
        follows:

       

      
        
          	 	
                  X

                	
                  =

                	
                  Y
                    x
                    (A-B)/A

                

        

         

        
          	 	 where:  
	 	
                  X

                	
                  =

                	
                  the
                    number of Warrant Shares to be issued to the Holder;

                
	 	
                  Y

                	
                  =

                	
                  the
                    number of Warrant Shares with respect to which the Warrant Certificates
                    are being exercised;

                
	 	
                  A

                	
                  =

                	
                  the
                    Market Price as of the Date of Exercise; and

                
	 	
                  B

                	
                  =

                	
                  the
                    Exercise Price.

                

        

         

      

      (c)  At
        such
        times, and upon such representations and agreements, if applicable, upon
        surrender of a Warrant Certificate and delivery of the Form of Election to
        Purchase (with the Warrant Shares Exercise Log attached) to the Warrant Agent
        at
        its address for notice set forth in Section 14, and, in the case of a Cash
        Exercise, upon payment of the Exercise Price multiplied by the number of
        Warrant
        Shares that the Holder intends to purchase thereunder (which must be a whole
        number) in accordance with Section 9 (the “Aggregate Exercise Price”), the
        Company shall promptly issue and deliver to the Holder a certificate for
        the
        Warrant Shares issuable upon such exercise. Any Person so designated by the
        Holder to receive Warrant Shares shall be deemed to have become holder of
        record
        of such Warrant Shares as of the Date of Exercise of the relevant Warrant
        Certificate. For so long as there is a then effective registration statement
        covering the issuance of the Warrant Shares or if a Holder effects a Cashless
        Exercise, the Warrant Shares shall be issued free of all restrictive legends,
        and the Company shall, upon request of the Holder, if available, use
        commercially reasonable efforts to deliver Warrant Shares hereunder
        electronically through the Depository Trust Corporation or another established
        clearing corporation performing similar functions. If there is not a then
        effective registration statement covering the issuance of the Warrant Shares
        and
        a Holder effects a Cash Exercise, the Warrant Shares shall be issued in
        certificated form and include customary legends regarding transfer restrictions
        deemed appropriate by the Company. If fewer than all Warrant Shares issuable
        upon exercise of the relevant Warrant Certificate are purchased on such Date
        of
        Exercise, then the Company will execute and deliver to the Holder or its
        assigns
        a New Warrant Certificate (dated the date thereof) evidencing the unexercised
        portion of the relevant Warrant Certificate.

       

      5.  Charges,
        Taxes and Expenses.  Issuance and delivery of certificates for
        Warrant Shares shall be made without charge to the Holder for any issue or
        transfer tax, or transfer agent fee in respect of the issuance of such
        certificates, all of which taxes shall be paid by the Company; provided,
        however, that the Company shall not be obligated to pay any tax which may
        be
        payable in respect of any transfer involved in the registration of any
        certificates for Warrant Shares or Series E Warrants in a name other than
        that of the Holder. The Holder shall be responsible for all other tax
        liabilities that may arise as a result of holding or transferring any Warrant
        Certificate or receiving Warrant Shares upon exercise thereof.

       

      
        
          
          

        

        
          4

          
            

          

        

        
          
          

        

      

       

      6.  Replacement
        of Warrant Certificate.  If any Warrant Certificate is mutilated,
        lost, stolen or destroyed, the Company shall issue or cause to be issued
        in
        exchange and substitution for and upon cancellation thereof, or in lieu of
        and
        substitution for such Warrant Certificate, a New Warrant Certificate, but
        only
        upon receipt of evidence reasonably satisfactory to the Company of such loss,
        theft or destruction and customary and reasonable indemnity, if requested.
        Applicants for a New Warrant Certificate under such circumstances shall also
        comply with such other reasonable regulations and procedures and pay such
        other
        reasonable third-party costs as the Company may prescribe.

       

      7.  Reservation
        of Warrant Shares.  The Company covenants that it will at all
        times reserve and keep available out of its authorized but unissued and
        otherwise unreserved Common Stock, solely for the purpose of enabling it
        to
        issue Warrant Shares upon exercise of all outstanding Series E Warrants as
        herein provided, the number of Warrant Shares which are then issuable and
        deliverable upon the exercise of all outstanding Series E Warrants (taking
        into account the adjustments and restrictions of Section 8). The Company
        covenants that all Warrant Shares so issuable and deliverable shall, upon
        issuance and the payment of the applicable Exercise Price in accordance with
        the
        terms hereof, be duly and validly authorized and issued, and be fully paid
        and
        nonassessable.

       

      8.  Certain
        Adjustments.  The Exercise Price and number of Warrant Shares
        issuable upon exercise of each Series E Warrant then outstanding are
        subject to adjustment from time to time as set forth in this
        Section 8.

       

      (a)  Stock
        Dividends and Splits.  If the Company, (i) pays a stock
        dividend on its Common Stock, (ii) subdivides outstanding shares of Common
        Stock into a greater number of shares, or (iii) combines outstanding shares
        of Common Stock into a lesser number of shares, then in each such case the
        Exercise Price shall be multiplied by a fraction of which the numerator shall
        be
        the number of shares of Common Stock outstanding immediately before such
        event
        and of which the denominator shall be the number of shares of Common Stock
        outstanding immediately after such event. Any adjustment made pursuant to
        clause (i) of this paragraph shall become effective immediately after the
        record date for the determination of shareholders entitled to receive such
        dividend, and any adjustment pursuant to clause (ii) or (iii) of this
        paragraph shall become effective immediately after the effective date of
        such
        subdivision or combination.

       

      (b)  Extraordinary
        Transactions.  If, (i) the Company effects any merger or
        consolidation of the Company with or into another Person, (ii) the Company
        effects any sale of all or substantially all of its assets in one or a series
        of
        related transactions, (iii) any tender offer or exchange offer by the
        Company is completed pursuant to which holders of Common Stock are permitted
        to
        tender or exchange their shares for other securities, cash or property, or
        (iv) the Company effects any reclassification of the Common Stock or any
        compulsory share exchange pursuant to which the Common Stock is effectively
        converted into or exchanged for other securities, cash or property (in any
        such
        case, an “Extraordinary Transaction”), then each Holder’s Series E Warrants will
        become the right thereafter to receive, upon exercise of his or her Series
        E
        Warrants, the same amount and kind of securities, cash or property as such
        Holder would have been entitled to receive upon the occurrence of such
        Extraordinary Transaction if it had been, immediately prior to such
        Extraordinary Transaction, the holder of the number of Warrant Shares then
        issuable upon exercise in full of the relevant Series E Warrant (the “Alternate
        Consideration”) in lieu of Common Stock. The aggregate Exercise Price for each
        Series E Warrant will not be affected by any such Extraordinary
        Transaction, but the Company shall apportion such aggregate Exercise Price
        among
        the Alternate Consideration in a reasonable manner reflecting the relative
        value
        of any different components of the Alternate Consideration. If holders of
        Common
        Stock are given any choice as to the securities, cash or property to be received
        in a Extraordinary Transaction, then each Holder, to the extent practicable,
        shall be given the same choice as to the Alternate Consideration it receives
        upon any exercise of his or her Series E Warrant following such Extraordinary
        Transaction. In addition, at the request of each Holder, upon surrender of
        such
        Holder’s Series E Warrant, any successor to the Company or surviving entity
        in such Extraordinary Transaction shall issue to such Holder a new warrant
        consistent with the foregoing provisions and evidencing the Holder’s right to
        purchase the Alternate Consideration for the aggregate Exercise Price upon
        exercise thereof. Each Series E Warrant (or any such replacement security)
        will
        be similarly adjusted upon any subsequent transaction analogous to a
        Extraordinary Transaction.

       

      
        
          
          

        

        
          5

          
            

          

        

        
          
          

        

      

       

      (c)  Number
        of Warrant Shares.  Simultaneously with any adjustment to the
        Exercise Price pursuant to paragraph (a) of this Section, the number of
        Warrant Shares that may be purchased upon exercise of each Series E Warrant
        shall be increased or decreased proportionately, as the case may be, so that
        after such adjustment the aggregate Exercise Price payable hereunder for
        the
        adjusted number of Warrant Shares shall be the same as the aggregate Exercise
        Price in effect immediately prior to such adjustment.

       

      (d)  Calculations.  All
        calculations under this Section 8 shall be made to the nearest cent or the
        nearest 1/100th of a share, as applicable.

       

      (e)  Notice
        of Adjustments.  Upon the occurrence of each adjustment pursuant
        to this Section 8, the Company at its expense will promptly calculate such
        adjustment in accordance with the terms of this Agreement and prepare a
        certificate setting forth such adjustment, including a statement of the adjusted
        Exercise Price and adjusted number of Warrant Shares or type of Alternate
        Consideration issuable upon exercise of each Series E Warrant (as
        applicable), describing the transactions giving rise to such adjustments
        and
        showing in detail the facts upon which such adjustment is based. The Company
        will promptly deliver to each Holder who makes a request in writing and to
        the
        Warrant Agent, a copy of each such certificate.

       

      (f)  Notice
        of Corporate Events.  If the Company (i) declares a dividend
        or any other distribution of cash, securities or other property in respect
        of
        its Common Stock (other than a dividend payable solely in shares of Common
        Stock) or (ii) authorizes the voluntary dissolution, liquidation or winding
        up of the affairs of the Company, then the Company shall deliver to each
        Holder
        a notice describing the material terms and conditions of such dividend,
        distribution or transaction. Notwithstanding anything to the contrary in
        this
        Section 8(f), the failure to deliver any notice under this
        Section 8(f) or any defect therein shall not affect the validity of the
        corporate action required to be described in such notice. Until the exercise
        of
        its, his or her Series E Warrant or any portion of such Series E
        Warrant, a Holder shall not have nor exercise any rights by virtue of ownership
        of a Series E Warrant as a shareholder of the Company (including without
        limitation the right to notification of shareholder meetings or the right
        to
        receive any notice or other communication concerning the business and affairs
        of
        the Company other than as provided in this Section 8(f)).

       

      
        
          
          

        

        
          6

          
            

          

        

        
          
          

        

      

       

      9.  Payment
        of Exercise Price.  The Holder shall pay the Aggregate Exercise
        Price by paying, in lawful money of the United States, in cash, certified
        check
        or bank draft payable to the order of the Company (or as otherwise agreed
        to by
        the Company) delivered to the Warrant Agent together with the Warrant
        Certificate and Form of Election to Purchase.

       

      10.  Company
        Call Right.  Notwithstanding any other provision contained in this
        Warrant Agreement to the contrary, in the event that the average closing
        bid
        prices per share of Common Stock, as quoted on the Nasdaq Global Market (or
        such
        other exchange or stock market on which the Common Stock may then be listed
        or
        quoted) over a period of 20 consecutive Trading Days, equals or exceeds
        200% of the Exercise Price (appropriately adjusted for any stock split, reverse
        stock split, stock dividend or other reclassification or combination of the
        Common Stock occurring after the date hereof), the Company, upon thirty
        (30) calendar days prior written notice (the “Notice Period”) given to the
        Holder within 10 Business Days of the end of such 20 consecutive Trading
        Day period, may call the Series E Warrants, in whole and not in part, at a
        redemption price equal to $0.01 per share of Common Stock then purchasable
        pursuant to the Series E Warrants called for redemption. The Holder shall
        have the right to exercise the Series E Warrants prior to the end of the
        Notice Period. As of the last day of the Notice Period, any Series E
        Warrants timely and validly called for redemption by the Company shall terminate
        and permanently cease to be exercisable and the Holders shall then be entitled
        only to receive the redemption price.

       

      Notwithstanding
        the ability of the
        Company to call the Series E Warrants for redemption, the Company agrees
        that the Series E Warrants underlying any warrant agreement issued to the
        underwriters and their designees and transferees in connection with the public
        offering in which the Series E Warrants were issued will not be subject to
        the call right and redemption set forth herein.

       

      11.  Holder
        not Deemed a Stockholder.  Except as otherwise specifically
        provided herein, the Holder, solely in such Person’s capacity as a Holder, shall
        not be entitled to vote or receive dividends or be deemed the holder of share
        capital of the Company for any purpose, nor shall anything contained in the
        Series E Warrants be construed to confer upon the Holder, solely in such
        Person’s capacity as a Holder, any of the rights of a stockholder of the Company
        or any right to vote, give or withhold consent to any corporate action (whether
        any reorganization, issue of stock, reclassification of stock, consolidation,
        merger, conveyance or otherwise), receive notice of meetings, receive dividends
        or subscription rights, or otherwise, prior to the issuance to the Holder
        of the
        Warrant Shares to which Person is then entitled to receive upon the due exercise
        of the Series E Warrants.

       

      
        
          
          

        

        
          7

          
            

          

        

        
          
          

        

      

       

      12.  No
        Fractional Shares.  No fractional shares will be issued in
        connection with any exercise of a Series E Warrant. In lieu of any
        fractional shares which would otherwise be issuable, the Company shall pay
        cash
        equal to the product of such fraction multiplied by the Market Price on the
        Date
        of Exercise.

       

      13.  Exchange
        Act Filings.  The Holder agrees and acknowledges that it shall
        have sole responsibility for making any applicable filings with the U.S.
        Securities and Exchange Commission pursuant to Sections 13 and 16 of the
        Exchange Act as a result of its acquisition of any Series E Warrant and the
        Warrant Shares and any future retention or transfer thereof.

       

      14.  Notices.  Any
        and all notices or other communications or deliveries hereunder (including
        without limitation any Exercise Notice) shall be in writing and shall be
        deemed
        given and effective on the earliest of (i) the date of transmission, if
        such notice or communication is delivered via facsimile at the facsimile
        number
        specified in this Section prior to 5:00 p.m. (Houston time) on a Trading
        Day, (ii) the next Trading Day after the date of transmission, if such
        notice or communication is delivered via facsimile at the facsimile number
        specified in this Section on a day that is not a Trading Day or later than
        5:00 p.m. (Houston time) on any Trading Day, (iii) the Trading Day
        following the date of mailing, if sent by nationally recognized overnight
        courier service, or (iv) upon actual receipt by the party to whom such
        notice is required to be given. The addresses for such communications shall
        be:

       

      if
        to the
        Company:

      

      Opexa
        Therapeutics, Inc.

      2635
        North Crescent Ridge
        Drive

      The
        Woodlands, Texas 77381

      Attn:
        Chief Financial
        Officer

      Facsimile
        No.: (281)
        872-8585

      

      if
        to the
        Warrant Agent:

      Continental
        Stock Transfer & Trust
        Company

      17
        Battery Place, 8th
        Floor

      New
        York, New York 10004

      Attention:
        Office of General
        Counsel

      

      if
        to the
        Holder:

      

      to
        the
        address or facsimile number appearing on the Warrant Register or such other
        address or facsimile number as the Holder may provide to the Company in
        accordance with this Section 14.

      

      
        
          
          

        

        
          8

          
            

          

        

        
          
          

        

      

       

      15.  Warrant
        Agent.

       

      (a)  The
        Company and the Warrant Agent hereby agree that the Warrant Agent will serve
        as
        an agent of the Company as set forth in this Agreement.

       

      (b)  The
        Warrant Agent shall not by any act hereunder be deemed to make any
        representation as to validity or authorization of the Series E Warrants or
        the Warrant Certificates (except as to its countersignature thereon) or of
        any
        securities or other property delivered upon exercise of any Series E
        Warrant, or as to the number or kind or amount of securities or other property
        deliverable upon exercise of any Series E Warrant or the correctness of the
        representations of the Company made in such certificates that the Warrant
        Agent
        receives.

       

      (c)  The
        Warrant Agent shall not have any duty to calculate or determine any required
        adjustments with respect to the Exercise Price or the kind and amount of
        securities or other property receivable by Holders upon the exercise of
        Series E Warrants, nor to determine the accuracy or correctness of any such
        calculation.

       

      (d)  The
        Warrant Agent shall not (i) be liable for any recital or statement of fact
        contained herein or in the Warrant Certificates or for any action taken,
        suffered or omitted by it in good faith in the belief that any Warrant
        Certificate or any other document or any signature is genuine or properly
        authorized, (ii) be responsible for any failure by the Company to comply
        with any of its obligations contained in this Agreement or in the Warrant
        Certificates, (iii) be liable for any act or omission in connection with
        this Agreement except for its own gross negligence or willful misconduct
        or
        (iv) have any responsibility to determine whether a transfer of a
        Series E Warrant complies with applicable securities laws.

       

      (e)  The
        Warrant Agent is hereby authorized to accept instructions with respect to
        the
        performance of its duties hereunder from the Chief Executive Officer, the
        President, any Vice President, the Treasurer, or the Secretary or any Assistant
        Secretary of the Company and to apply to any such officer for written
        instructions (which will then be promptly given) and the Warrant Agent shall
        not
        be liable for any action taken or suffered to be taken by it in good faith
        in
        accordance with the instructions of any such officer, except for its own
        gross
        negligence or willful misconduct, but in its discretion the Warrant Agent
        may in
        lieu thereof accept other evidence of such or may require such further or
        additional evidence as it may deem reasonable.

       

      (f)  The
        Warrant Agent may exercise any of the rights and powers hereby vested in
        it or
        perform any duty hereunder either itself or by or through its attorneys,
        agents
        or employees, provided reasonable care has been exercised in the selection
        and
        in the continued employment of any persons. The Warrant Agent shall not be
        under
        any obligation or duty to institute, appear in or defend any action, suit
        or
        legal proceeding in respect hereof, unless first indemnified to its
        satisfaction. The Warrant Agent shall promptly notify the Company in writing
        of
        any claim made or action, suit or proceeding instituted against or arising
        out
        of or in connection with this Agreement.

       

      
        
          
          

        

        
          9

          
            

          

        

        
          
          

        

      

       

      (g)  The
        Company will take such action as may reasonably be required by the Warrant
        Agent
        in order to enable it to carry out or perform its duties under this
        Agreement.

       

      (h)  The
        Warrant Agent shall act solely as agent of the Company hereunder. The Warrant
        Agent shall only be liable for the failure to perform such duties as are
        specifically set forth herein.

       

      (i)  The
        Warrant Agent may consult with legal counsel satisfactory to it (who may
        be
        legal counsel for the Company), and the Warrant Agent shall incur no liability
        or responsibility to the Company or to any Holder for any action taken, suffered
        or omitted by it in good faith in accordance with the opinion or advice of
        such
        counsel.

       

      (j)  The
        Company agrees to pay to the Warrant Agent compensation for all services
        rendered by the Warrant Agent hereunder as the Company and the Warrant Agent
        may
        agree from time to time, and to reimburse the Warrant Agent for reasonable
        expenses incurred in connection with the execution and administration of
        this
        Agreement (including the reasonable compensation and expenses of its counsel),
        and further agrees to indemnify the Warrant Agent for, and hold it harmless
        against, any loss, liability or expense incurred without gross negligence,
        bad
        faith or willful misconduct on its part, arising out of or in connection
        with
        the acceptance and administration of this Agreement.

       

      (k)  The
        Warrant Agent, and any shareholder, director, officer or employee of the
        Warrant
        Agent, may buy, sell or deal in any of the Series E Warrants or other
        securities of the Company or its Affiliates or become pecuniarily interested
        in
        transactions in which the Company or its Affiliates may be interested, or
        contract with or lend money to the Company or its Affiliates or otherwise
        act as
        fully and freely as though it were not the Warrant Agent under this Agreement.
        Nothing herein shall preclude the Warrant Agent from acting in any other
        capacity for the Company or for any other Person.

       

      (l)  No
        resignation or removal of the Warrant Agent and no appointment of a successor
        warrant agent shall become effective until the acceptance of appointment
        by the
        successor warrant agent as provided herein. The Warrant Agent may resign
        its
        duties and be discharged from all further duties and liability hereunder
        (except
        liability arising as a result of the Warrant Agent’s own gross negligence or
        willful misconduct) after giving written notice to the Company. The Company
        may
        remove the Warrant Agent upon written notice, and the Warrant Agent shall
        thereupon in like manner be discharged from all further duties and liabilities
        hereunder, except as aforesaid. The Warrant Agent shall, at the Company’s
        expense, cause to be mailed (by first class mail, postage prepaid) to each
        Holder of a Series E Warrant at such Holder’s last address as shown on the
        register of the Company maintained by the Warrant Agent a copy of said notice
        of
        resignation or notice of removal, as the case may be. Upon such resignation
        or
        removal, the Company shall appoint in writing a new warrant agent. If the
        Company fails to do so within a period of 30 days after it has been
        notified in writing of such resignation by the resigning Warrant Agent or
        after
        such removal, then the resigning Warrant Agent or the Holder of any
        Series E Warrant may apply to any court of competent jurisdiction for the
        appointment of a new warrant agent. After acceptance in writing of such
        appointment by the new warrant agent, it shall be vested with the same powers,
        rights, duties and responsibilities as if it had been originally named herein
        as
        the Warrant Agent. Not later than the effective date of any such appointment,
        the Company shall give notice thereof to the resigning or removed Warrant
        Agent.
        Failure to give any notice provided for in this Section 15(l), however, or
        any
        defect therein, shall not affect the legality or validity of the resignation
        of
        the Warrant Agent or the appointment of a new warrant agent, as the case
        may
        be.

       

      
        
          
          

        

        
          10

          
            

          

        

        
          
          

        

      

       

      (m)  Any
        corporation into which the Warrant Agent or any new warrant agent may be
        merged
        or any corporation resulting from any consolidation to which the Warrant
        Agent
        or any new warrant agent shall be a party or any corporation to which the
        Warrant Agent transfers substantially all of its corporate trust business
        shall
        be a successor Warrant Agent under this Agreement without any further act,
        provided that such corporation (i) would be eligible for appointment as
        successor to the Warrant Agent under the provisions of Section 15(l) or
        (ii) is a wholly owned subsidiary of the Warrant Agent. Any such successor
        Warrant Agent shall promptly cause notice of its succession as Warrant Agent
        to
        be mailed (by first class mail, postage prepaid) to each Holder in accordance
        with Section 14.

       

      16.  Miscellaneous.

       

      (a)  Successors
        and Assigns.  This Agreement shall be binding on and inure to the
        benefit of the Company, the Warrant Agent and the Holders, and their respective
        successors and assigns. Subject to the preceding sentence, nothing in this
        Agreement shall be construed to give to any Person other than the Company,
        the
        Warrant Agent and the Holders any legal or equitable right, remedy or cause
        of
        action under this Agreement.

       

      (b)  Amendments
        and Waivers.  The Company may, without the consent of the
        Holders, by supplemental agreement or otherwise, (i) make any changes or
        corrections in this Agreement that are required to cure any ambiguity or
        to
        correct or supplement any provision herein which may be defective or
        inconsistent with any other provision herein or (ii) add to the covenants
        and agreements of the Company for the benefit of the Holders, or surrender
        any
        rights or power reserved to or conferred upon the Company in this Agreement;
        provided that, in the case of (i) or (ii), such changes or corrections shall
        not
        adversely affect the interests of Holders of then outstanding Series E Warrants
        in any material respect. The Company may, with the consent, in writing or
        at a
        meeting, of the Holders of outstanding Series E Warrants exercisable for
        two-thirds of the Warrant Shares, amend in any way, by supplemental agreement
        or
        otherwise, this Agreement and/or all of the outstanding Warrant Certificates;
        provided, however, that no such amendment shall adversely affect any
        Series E Warrant differently than it affects all other Series E
        Warrants, unless the Holder thereof consents thereto. The Warrant Agent shall
        at
        the request of the Company, and without need of independent inquiry as to
        whether such supplemental agreement is permitted by the terms of this
        Section 16(b), join with the Company in the execution and delivery of any
        such supplemental agreements, but shall not be required to join in such
        execution and delivery for such supplemental agreement to become
        effective.

       

      
        
          
          

        

        
          11

          
            

          

        

        
          
          

        

      

       

      (c)  Choice
        of Law, etc.  All questions concerning the construction,
        validity, enforcement and interpretation of this Agreement shall be governed
        by
        and construed and enforced in accordance with the internal laws of the State
        of
        New York, without regard to the principles of conflicts of law thereof. Each
        party hereto hereby irrevocably waives, to the fullest extent permitted by
        applicable law, any and all right to trial by jury in any legal proceeding
        arising out of or relating to this Agreement or the transactions contemplated
        hereby. If either party shall commence an action or proceeding to enforce
        any
        provisions of this Agreement, then the prevailing party in such action or
        proceeding shall be reimbursed by the other party for its attorneys’ fees and
        other costs and expenses incurred with the investigation, preparation and
        prosecution of such action or proceeding.

       

      (d)  Interpretation.  The
        headings herein are for convenience only, do not constitute a part of this
        Agreement and shall not be deemed to limit or affect any of the provisions
        hereof.

       

      (e)  Severability.  In
        case any one or more of the provisions of this Agreement shall be invalid
        or
        unenforceable in any respect, the validity and enforceability of the remaining
        terms and provisions of this Agreement shall not in any way be affected or
        impaired thereby and the parties will attempt in good faith to agree upon
        a
        valid and enforceable provision which shall be a commercially reasonable
        substitute therefor, and upon so agreeing, shall incorporate such substitute
        provision in this Agreement.

       

      (f)  Additional
        Series E Warrants. The Company may from time to time issue additional
        warrants (the “Additional Warrants”) under this Warrant Agreement, without
        requiring the consent of any Holder, with the same terms as the warrants
        initially issued hereunder.

       

      [The
        remainder of this page has been left intentionally blank.]

       

      
        
          
          

        

        
          12

          
            

          

        

        
          
          

        

      

       

      IN
        WITNESS WHEREOF, the parties has caused this Agreement to be duly
        executed by its authorized officer as of the date first indicated
        above.

       

      
        

        
          	 	
                  OPEXA
                    THERAPEUTICS, INC.

                	 
	 	 	 	 
	 	 	 	 
	 	
                  By:

                	 	 
	 	
                  Name:

                	
                  David
                    B. McWilliams

                	 
	 	
                  Title:

                	
                  President

                	 

        

        

        

        

        

        

        
          	 	
                  CONTINENTAL
                    STOCK TRANSFER & TRUST COMPANY

                	 
	 	 	 	 
	 	 	 	 
	 	
                  By:

                	 	 
	 	
                  Name:

                	 	 
	 	
                  Title:

                	 	 

        

         

        
          
            
            

          

          
            
              Signature
                page to Warrant Agreement

            

            
              

            

          

          
            
            

          

        

      

       

      Exhibit
        A

       

      EXERCISABLE
        ON OR AFTER ________ __, 2008

      AND
        ON OR
        BEFORE _______ __, 2013

       

      
        
          	
                  No.
                    ____________

                	 	
                  Series E
                    Warrant to Purchase ___________
                    Shares

                

        

      

       

      Series E
        Warrant Certificate

       

      WARRANTS
        TO ACQUIRE COMMON STOCK OF OPEXA THERAPEUTICS, INC.

       

      This
        Series E Warrant Certificate certifies that,
        _________________________________, or registered assigns, is the registered
        holder of a Series E Warrant (the “Warrant”) to acquire from Opexa
        Therapeutics, Inc., a Delaware corporation (the “Company”), the number of fully
        paid and non-assessable shares of Common Stock, $.50 par value, of the Company
        (the “Common Stock”) specified above for consideration equal to $ _____________
        (the “Exercise Price”) per share of Common Stock. The Series E Warrant
        evidenced by this Series E Warrant Certificate shall not be exercisable
        after and shall terminate and become void as of 5:00 P.M., Houston time,
        on
        ________ ___, 2013 (the “Expiration Date”).

       

      The
        Series E Warrant evidenced by this Series E Warrant Certificate is
        part of a duly authorized issue of warrants expiring on the Expiration Date
        entitling the Holder hereof to receive shares of Common Stock, and is issued
        or
        to be issued pursuant to a Warrant Agreement dated _______ _____, 2008 (the
“Warrant Agreement”), duly executed and delivered by the Company to Continental
        Stock Transfer & Trust Company, as warrant agent (the “Warrant Agent”,
        which term includes any successor Warrant Agent under the Warrant Agreement),
        which Warrant Agreement is hereby incorporated by reference in and made a
        part
        of this instrument and is hereby referred to for a description of the rights,
        limitation of rights, obligations, duties and immunities thereunder of the
        Warrant Agent, the Company and the Holders (“Holders” meaning, from time to
        time, the registered holders of the warrant issued thereunder). To the extent
        any provisions of this Series E Warrant Certificate conflicts with any
        provision of the Warrant Agreement, the provisions of the Warrant Agreement
        shall apply. A copy of the Warrant Agreement may be obtained by the Holder
        hereof upon written request to the Company at 2635 North Crescent Ridge
        Drive, The Woodlands, Texas 77381 Attention: Investor Relations. Capitalized
        terms not defined herein have the meanings ascribed thereto in the Warrant
        Agreement.

       

      This
        Series E Warrant may be exercised, in whole or in part, at any time on or
        after _______ __, 2008 and on or before the Expiration Date, subject to the
        terms of the Warrant Agreement, by surrendering this Warrant Certificate,
        with
        the Form of Election to Purchase set forth hereon properly completed and
        executed, together with payment of the Aggregate Exercise Price in accordance
        with Section 9 of the Warrant Agreement in the case of a Cash Exercise.
        Each exercise must be for a whole number of Warrant Shares. In the event
        that
        upon any exercise of the Series E Warrant evidenced hereby the number of
        shares of Common Stock acquired shall be less than the total number of shares
        of
        Common Stock which may be purchased pursuant to this Series E Warrant,
        there shall be issued to the Holder hereof or such Holder’s assignee a new
        Series E Warrant Certificate evidencing the unexercised portion of this
        Series E Warrant.

       

      
        
          
          

        

        
          Exhibit
            A - Page 1

          
            

          

        

        
          
          

        

      

       

      The
        Warrant Agreement provides that upon the occurrence of certain events the
        Exercise Price set forth on this Series E Warrant Certificate may, subject
        to certain conditions, be adjusted, and that upon the occurrence of certain
        events the number of shares of Common Stock and/or the type of securities
        or
        other property issuable upon the exercise of this Series E Warrant shall be
        adjusted. No fractions of a share of Common Stock will be issued upon the
        exercise of this Series E Warrant, but the Company will pay the cash value
        thereof determined as provided in the Warrant Agreement.

       

      The
        Warrant Agreement provides in certain circumstances for a call right on the
        part
        of the Company, pursuant to which this Series E Warrant may be
        terminated.

       

      Series E
        Warrant Certificates, when surrendered at the office of the Warrant Agent
        by the
        registered Holder thereof in person or by such Holder’s legal representative or
        attorney duly appointed and authorized in writing, may be exchanged, in the
        manner and subject to the limitations provided in the Warrant Agreement,
        but
        without payment of any service charge, for another Series E Warrant
        Certificate or Series E Warrant Certificates of like tenor evidencing in
        the aggregate the right to purchase a like number of Warrant
        Shares.

       

      Each
        taker
        and holder of this Series E Warrant Certificate, by taking or holding the
        same, consents and agrees that the holder of this Series E Warrant
        Certificate when duly endorsed in blank may be treated by the Company, the
        Warrant Agent and all other persons dealing with this Series E Warrant
        Certificate as the absolute owner hereof for any purpose and as the person
        entitled to exercise the rights represented hereby or the person entitled
        to the
        transfer hereof on the register of the Company maintained by the Warrant
        Agent,
        any notice to the contrary notwithstanding, provided that until such transfer
        on
        such register, the Company and the Warrant Agent may treat the registered
        Holder
        hereof as the owner for all purposes.

       

      This
        Series E Warrant does not entitle any Holder to any of the rights of a
        shareholder of the Company.

       

      This
        Series E Warrant Certificate and the Warrant Agreement are subject to
        amendment as provided in the Warrant Agreement.

       

      This
        Series E Warrant Certificate shall not be valid or obligatory for any
        purpose until it shall have been countersigned by the Warrant
        Agent.

       

      [The
        remainder of this page has been left intentionally blank.]

       

      
        
          
          

        

        
          Exhibit
            A - Page 2

          
            

          

        

        
          
          

        

      

       

      IN
        WITNESS WHEREOF, the undersigned have caused this Series E Warrant
        Certificate to be executed as of the date set forth below.

       

      
        	 	OPEXA
                THERAPEUTICS, INC.	 
	 	 	 	 
	
                 

              	
                By:
                  

              	 	 
	 	 Name	 David
                B. McWilliams	 
	 	 Title 	President	 
	 	 	 	 

      

       

       

      
        	
                 

              	
                By:
                  

              	/s/ 	 
	 	 Name	 	 
	 	 Title	 	 
	 	 	 	 
	 	 DATED:
                ______________________________, 2008 	 

      

       

      
         

        
          	 	 Countersigned:	 
	 	 	 
	 	
                  CONTINENTAL
                    STOCK TRANSFER & TRUST COMPANY,

                  as
                    Warrant Agent

                	 
	 	 	 	 
	
                   

                	
                  By:
                    

                	 	 
	 	 Name	 	 
	 	 Title 	 	 
	 	 	 	 

        

         

        
          
            
            

          

          
            Exhibit
              A - Page 3

            
              

            

          

          
            
            

          

        

      

      

      FORM
        OF
        ELECTION TO PURCHASE

       

      

      To
        Opexa
        Therapeutics, Inc.:

      

      In
        accordance with the Series E Warrant Certificate enclosed with this Form of
        Election to Purchase, the undersigned hereby irrevocably elects to exercise
        the
        Series E Warrant with respect to Warrant Shares in accordance with the
        terms of the Warrant Agreement.

       

      1.           Form
        of Exercise Price.  The Holder intends that payment of the
        Exercise Price shall be made as:

       

      a
        Cash Exercise;

       

      a
        Cashless Exercise; or

       

      The
        Holder
        understands that any Cashless Exercise is subject to compliance with all
        the
        terms of the Warrant Agreement.

      

      2.           Payment
        of Exercise Price.  If the Holder has elected a Cash Exercise with
        respect to some or all of the Warrant Shares to be issued pursuant hereto,
        the
        Holder shall send via wire transfer to the account of the Company the sum
        of $
        ______________ in immediately available funds, which sum represents the
        Aggregate Exercise Price (as defined in the Warrant Agreement) for the number
        of
        shares of Common Stock to which this Form of Election to Purchase relates,
        together with any applicable taxes payable by the undersigned pursuant to
        the
        Series E Warrant.

       

      The
        undersigned requests that certificates for the shares of Common Stock issuable
        upon this exercise be issued in the name of

       

      
        
          	 	
                  Name:

                	 	 
	 	 	 	 
	 	
                  Address:

                	 	 
	 	 	 	 
	 	 	 	 
	 	 	 	 
	 	 	 	 
	 	 	 	 
	 	
                  Social
                    Security or Tax I.D. No.:
                    _________________________

                

        

      

       

      
        
          
          

        

        
          
            Form
              of Election to Purchase

          

          
            

          

        

        
          
          

        

      

       

      WARRANT
        SHARES EXERCISE LOG

       

      
        
          	
                  
                    Date

                  

                	 	
                  
                    Number
                      of Warrant Shares Available to be Exercised

                  

                	 	
                  
                    Number
                      of Warrant Shares Exercised

                  

                	 	
                  
                    Number
                      of Warrant Shares Remaining to be
                      Exercised

                  

                
	 	 	 	 	 	 	 
	 	 	 	 	 	 	 

        

      

       

      
        
          
          

        

        
          
            Warrant
              Shares Exercise Log

          

          
            

          

        

        
          
          

        

      

       

      FORM
        OF
        ASSIGNMENT

       

      [To
        be
        completed and signed only upon transfer of Warrant]

       

      

      FOR
        VALUE
        RECEIVED, the undersigned hereby sells, assigns and transfers
        unto                      the
        right represented by the within Series E Warrant Certificate to purchase
        ________________ shares of Common Stock of Opexa Therapeutics, Inc. to which
        the
        within Series E Warrant Certificate relates and appoints
        ________________________________ attorney to transfer said right on the books
        of
        Opexa Therapeutics, Inc. with full power of substitution in the
        premises.

       

      Dated:  __________________,
        20_____

       

      
        
          	 	 
	 	
                  (Signature
                    must conform in all respects to name of holder as specified on
                    the front
                    page of the Series E Warrant Certificate)

                
	
                   

                	 
	 	
                  Address
                    of Transferee:

                
	 	 
	 	 
	 	 
	 	 
	 	
                   

                  In
                    the presence of:

                
	 	 

        

      

       

       

      
        Form
          of Assignment

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