Right to Purchase up to the Maximum Number of Warrant Shares (as definedbelow) of Common Stock of Accentia Biopharmaceuticals, Inc. (subject to adjustment as provided herein) COMMON STOCK PURCHASE WARRANT

EXHIBIT 10.73

THIS WARRANT AND THE SHARES OF COMMON STOCK ISSUABLE UPON EXERCISE OF THIS WARRANT HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED, OR ANY STATE SECURITIES LAWS. THIS WARRANT AND THE COMMON STOCK ISSUABLE UPON EXERCISE OF THIS WARRANT MAY NOT BE SOLD, OFFERED FOR SALE, PLEDGED OR HYPOTHECATED IN THE ABSENCE OF AN EFFECTIVE REGISTRATION STATEMENT AS TO THIS WARRANT UNDER SAID ACT AND ANY APPLICABLE STATE SECURITIES LAWS OR AN OPINION OF COUNSEL REASONABLY SATISFACTORY TO ACCENTIA BIOPHARMACEUTICALS, INC. THAT SUCH REGISTRATION IS NOT REQUIRED.

Right to Purchase up to the Maximum Number of Warrant Shares (as defined below) of

Common Stock of Accentia Biopharmaceuticals, Inc.

(subject to adjustment as provided herein)

COMMON STOCK PURCHASE WARRANT

ACCENTIA BIOPHARMACEUTICALS, INC., a corporation organized under the laws of the State of Florida (the “Company”), hereby certifies that, for value received, LAURUS MASTER FUND, LTD., or assigns (the “Holder”), is entitled, subject to the terms set forth below, to purchase from the Company (as defined herein) from and after the Effective Date of this Warrant and at any time or from time to time before 5:00 p.m., New York time, through the close of business April 29, 2010 (the “Expiration Date”), up to such number of fully paid and nonassessable shares of Common Stock (as hereinafter defined), $0.001 par value per share (the “Maximum Number of Warrant Shares”) as shall be determined by dividing $4,000,000 by the initial issuance price of shares of Common Stock sold through the initial public offering of the Common Stock (the “Initial Public Offering”), at the applicable Exercise Price per share (as defined below); provided that if by the 270^th day following the date hereof an initial public offering of Common Stock has not taken place, the defined term Maximum Number of Warrant Shares shall mean 1,030,928 shares of Common Stock until such time as an Initial Public Offering shall occur. The number and character of such shares of Common Stock and the applicable Exercise Price per share are subject to adjustment as provided herein.

As used herein the following terms, unless the context otherwise requires, have the following respective meanings:

(a) The term “Company” shall include Accentia Biopharmaceuticals, Inc. and any person or entity that shall succeed, or assume the obligations of, Accentia Biopharmaceuticals, Inc. hereunder.

(b) The term “Common Stock” includes (i) the Company’s Common Stock, par value $0.001 per share; and (ii) any other securities into which or for which any of the securities described in the preceding clause (i) may be converted or exchanged pursuant to a plan of recapitalization, reorganization, merger, sale of assets or otherwise.

(c) The term “Other Securities” refers to any stock (other than Common Stock) and other securities of the Company or any other person (corporate or otherwise) which the holder of the Warrant at any time shall be entitled to receive, or shall have received, on the exercise of the Warrant, in lieu of or in addition to Common Stock, or which at any time shall be issuable or shall have been issued in exchange for or in replacement of Common Stock or Other Securities pursuant to Section 4 or otherwise.

(d) The “Exercise Price” applicable under this Warrant shall be equal to $3.88; provided that, on the date of consummation of the initial public offering of Common Stock, the “Exercise Price” shall be adjusted to an amount equal to the issuance price of the Common Stock issued in connection with such initial public offering (the “IPO Price”).

(e) The “Effective Date” shall mean the earlier of (x) 180 days following the Registration Statement referred to, and defined, in that certain Registration Rights Agreement (as defined in the Securities Purchase Agreement, dated as of the date hereof, by and between the Holder and the Company has become effective, and (y) the in which the entire amount outstanding (including, without limitation, principal, interest and fees) under the Note (as defined in the Securities Purchase Agreement) has either been fully converted into Common Stock and/or been repaid in full in cash; provided that, the Effective Date shall be deemed not occur in the event that an Event of Default (as defined in the Note (as defined in the Securities Purchase Agreement)) has occurred and is continuing beyond any applicable grace period (until such time as such Event of Default has been waived by the Holder).

1. Exercise of Warrant.

1.1 Number of Shares Issuable upon Exercise. From and after the date hereof through and including the Expiration Date, the Holder shall be entitled to receive, upon exercise of this Warrant in whole or in part, by delivery of an original or fax copy of an exercise notice in the form attached hereto as Exhibit A (the “Exercise Notice”), shares of Common Stock of the Company, subject to adjustment pursuant to Section 4.

1.2 Fair Market Value. For purposes hereof, the “Fair Market Value” of a share of Common Stock as of a particular date (the “Determination Date”) shall mean:

(a) If the Company’s Common Stock is traded on the American Stock Exchange or another national exchange or is quoted on the National or SmallCap Market of The Nasdaq Stock Market, Inc. (“Nasdaq”), then the closing or last sale price, respectively, reported for the last business day immediately preceding the Determination Date.

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(b) If the Company’s Common Stock is not traded on the American Stock Exchange or another national exchange or on the Nasdaq but is traded on the NASD Over The Counter Bulletin Board, then the mean of the average of the closing bid and asked prices reported for the last business day immediately preceding the Determination Date.

(c) Except as provided in clause (d) below, if the Company’s Common Stock is not publicly traded, then as the Holder and the Company agree or in the absence of agreement by arbitration in accordance with the rules then in effect of the American Arbitration Association, before a single arbitrator to be chosen from a panel of persons qualified by education and training to pass on the matter to be decided.

(d) If the Determination Date is the date of a liquidation, dissolution or winding up, or any event deemed to be a liquidation, dissolution or winding up pursuant to the Company’s charter, then all amounts to be payable per share to holders of the Common Stock pursuant to the charter in the event of such liquidation, dissolution or winding up, plus all other amounts to be payable per share in respect of the Common Stock in liquidation under the charter, assuming for the purposes of this clause (d) that all of the shares of Common Stock then issuable upon exercise of the Warrant are outstanding at the Determination Date.

1.3 Company Acknowledgment. The Company will, at the time of the exercise of this Warrant, upon the request of the holder hereof acknowledge in writing its continuing obligation to afford to such holder any rights to which such holder shall continue to be entitled after such exercise in accordance with the provisions of this Warrant. If the holder shall fail to make any such request, such failure shall not affect the continuing obligation of the Company to afford to such holder any such rights.

1.4 Trustee for Warrant Holders. In the event that a bank or trust company shall have been appointed as trustee for the holders of this Warrant pursuant to Subsection 3.2, such bank or trust company shall have all the powers and duties of a warrant agent (as hereinafter described) and shall accept, in its own name for the account of the Company or such successor person as may be entitled thereto, all amounts otherwise payable to the Company or such successor, as the case may be, on exercise of this Warrant pursuant to this Section 1.

1.5 Further Exercise Limitation. Notwithstanding anything contained herein to the contrary, the Holder shall not be entitled to exercise this Warrant, in whole or in part, prior to the earlier to occur of (i) two hundred seventy (270) days after the date hereof and (i) one hundred eighty (180) days after the date of the initial public offering of Common Stock. The limitation described in this Section 1.5 shall automatically become null and void without any notice to any Company upon the occurrence and during the continuance of an Event of Default.

2. Procedure for Exercise.

2.1 Delivery of Stock Certificates, Etc., on Exercise. The Company agrees that the shares of Common Stock purchased upon exercise of this Warrant shall be deemed to be issued to the Holder as the record owner of such shares as of the close of business on the date on which this Warrant shall have been surrendered and payment made for such shares in accordance

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herewith. As soon as practicable after the exercise of this Warrant in full or in part, and in any event within three (3) business days thereafter, the Company at its expense (including the payment by it of any applicable issue taxes) will cause to be issued in the name of and delivered to the Holder, or as such Holder (upon payment by such Holder of any applicable transfer taxes) may direct in compliance with applicable securities laws, a certificate or certificates for the number of duly and validly issued, fully paid and nonassessable shares of Common Stock (or Other Securities) to which such Holder shall be entitled on such exercise, plus, in lieu of any fractional share to which such holder would otherwise be entitled, cash equal to such fraction multiplied by the then Fair Market Value of one full share, together with any other stock or other securities and property (including cash, where applicable) to which such Holder is entitled upon such exercise pursuant to Section 1 or otherwise.

2.2 Exercise.

(a) Payment may be made either (i) in cash or by certified or official bank check payable to the order of the Company equal to the applicable aggregate Exercise Price, (ii) by delivery of this Warrant, or shares of Common Stock and/or Common Stock receivable upon exercise of this Warrant in accordance with the formula set forth in subsection (b) below, or (iii) by a combination of any of the foregoing methods, for the number of Common Shares specified in such Exercise Notice (as such exercise number shall be adjusted to reflect any adjustment in the total number of shares of Common Stock issuable to the Holder per the terms of this Warrant) and the Holder shall thereupon be entitled to receive the number of duly authorized, validly issued, fully-paid and non-assessable shares of Common Stock (or Other Securities) determined as provided herein.

(b) Notwithstanding any provisions herein to the contrary, if the Fair Market Value of one share of Common Stock is greater than the Exercise Price (at the date of calculation as set forth below), in lieu of exercising this Warrant for cash, the Holder may elect to receive shares equal to the value (as determined below) of this Warrant (or the portion thereof being exercised) by surrender of this Warrant at the principal office of the Company together with the properly endorsed Exercise Notice in which event the Company shall issue to the Holder a number of shares of Common Stock computed using the following formula:

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3. Effect of Reorganization, Etc.; Adjustment of Exercise Price.

3.1 Reorganization, Consolidation, Merger, Etc. In case at any time or from time to time, the Company shall (a) effect a reorganization, (b) consolidate with or merge into any other person, or (c) transfer all or substantially all of its properties or assets to any other person under any plan or arrangement contemplating the dissolution of the Company, then, in each such case, as a condition to the consummation of such a transaction, proper and adequate provision shall be made by the Company whereby the Holder, on the exercise hereof as provided in Section 1 at any time after the consummation of such reorganization, consolidation or merger or the effective date of such dissolution, as the case may be, shall receive, in lieu of the Common Stock (or Other Securities) issuable on such exercise prior to such consummation or such effective date, the stock and other securities and property (including cash) to which such Holder would have been entitled upon such consummation or in connection with such dissolution, as the case may be, if such Holder had so exercised this Warrant, immediately prior thereto, all subject to further adjustment thereafter as provided in Section 4.

3.2 Dissolution. In the event of any dissolution of the Company following the transfer of all or substantially all of its properties or assets, the Company, concurrently with any distributions made to holders of its Common Stock, shall at its expense deliver or cause to be delivered to the Holder the stock and other securities and property (including cash, where applicable) receivable by the Holder pursuant to Section 3.1, or, if the Holder shall so instruct the Company, to a bank or trust company specified by the Holder and having its principal office in New York, NY as trustee for the Holder.

3.3 Continuation of Terms. Upon any reorganization, consolidation, merger or transfer (and any dissolution following any transfer) referred to in this Section 3, this Warrant shall continue in full force and effect and the terms hereof shall be applicable to the shares of stock and other securities and property receivable on the exercise of this Warrant after the consummation of such reorganization, consolidation or merger or the effective date of dissolution following any such transfer, as the case may be, and shall be binding upon the issuer of any such stock or other securities, including, in the case of any such transfer, the person acquiring all or substantially all of the properties or assets of the Company, whether or not such person shall have expressly assumed the terms of this Warrant as provided in Section 4. In the event this Warrant does not continue in full force and effect after the consummation of the transactions described in this Section 3, then the Company’s securities and property (including cash, where applicable) receivable by the Holder will be delivered to the Holder or the Trustee as contemplated by Section 3.2.

4. Extraordinary Events Regarding Common Stock. In the event that the Company shall (a) issue additional shares of the Common Stock as a dividend or other distribution on outstanding Common Stock or any preferred stock issued by the Company, (b) subdivide its outstanding shares of Common Stock, (c) combine its outstanding shares of the Common Stock into a smaller number of shares of the Common Stock, then, in each such event, the Exercise Price shall, simultaneously with the happening of such event, be adjusted by multiplying the then Exercise Price by a fraction, the numerator of which shall be the number of shares of Common Stock outstanding immediately prior to such event and the denominator of which shall be the number of shares of Common Stock outstanding immediately after such event, and the product

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so obtained shall thereafter be the Exercise Price then in effect. The Exercise Price, as so adjusted, shall be readjusted in the same manner upon the happening of any successive event or events described herein in this Section 4. The number of shares of Common Stock that the holder shall thereafter, on the exercise hereof as provided in Section 1, be entitled to receive shall be adjusted to a number determined by multiplying the number of shares of Common Stock that would otherwise (but for the provisions of this Section 4) be issuable on such exercise by a fraction of which (a) the numerator is the Exercise Price that would otherwise (but for the provisions of this Section 4) be in effect, and (b) the denominator is the Exercise Price in effect on the date of such exercise (taking into account the provisions of this Section 4).

5. Certificate as to Adjustments. In each case of any adjustment or readjustment in the shares of Common Stock (or Other Securities) issuable on the exercise of this Warrant, the Company at its expense will upon the Holder’s request promptly cause its Chief Financial Officer or other appropriate designee to compute such adjustment or readjustment in accordance with the terms of this Warrant and prepare a certificate setting forth such adjustment or readjustment and showing in detail the facts upon which such adjustment or readjustment is based, including a statement of (a) the consideration received or receivable by the Company for any additional shares of Common Stock (or Other Securities) issued or sold or deemed to have been issued or sold, (b) the number of shares of Common Stock (or Other Securities) outstanding or deemed to be outstanding, and (c) the Exercise Price and the number of shares of Common Stock to be received upon exercise of this Warrant, in effect immediately prior to such adjustment or readjustment and as adjusted or readjusted as provided in this Warrant. The Company will forthwith mail a copy of each such certificate to the holder and any Warrant agent of the Company (appointed pursuant to Section 11 hereof).

6. Reservation of Stock, Etc., Issuable on Exercise of Warrant. The Company will at all times reserve and keep available, solely for issuance and delivery on the exercise of this Warrant, shares of Common Stock (or Other Securities) from time to time issuable on the exercise of this Warrant.

7. Assignment; Exchange of Warrant. Subject to compliance with applicable securities laws, this Warrant, and the rights evidenced hereby, may be transferred by any registered holder hereof (a “Transferor”) in whole or in part. On the surrender for exchange of this Warrant, with the Transferor’s endorsement in the form of Exhibit B attached hereto (the “Transferor Endorsement Form”) and together with evidence reasonably satisfactory to the Company demonstrating compliance with applicable securities laws, which shall include, without limitation, a legal opinion from the Transferor’s counsel (at the Company’s expense) that such transfer is exempt from the registration requirements of applicable securities laws, the Company at its expense (but with payment by the Transferor of any applicable transfer taxes) will issue and deliver to or on the order of the Transferor thereof a new Warrant of like tenor, in the name of the Transferor and/or the transferee(s) specified in such Transferor Endorsement Form (each a “Transferee”), calling in the aggregate on the face or faces thereof for the number of shares of Common Stock called for on the face or faces of the Warrant so surrendered by the Transferor.

8. Replacement of Warrant. On receipt of evidence reasonably satisfactory to the Company of the loss, theft, destruction or mutilation of this Warrant and, in the case of any such

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loss, theft or destruction of this Warrant, on delivery of an indemnity agreement or security reasonably satisfactory in form and amount to the Company or, in the case of any such mutilation, on surrender and cancellation of this Warrant, the Company at its expense will execute and deliver, in lieu thereof, a new Warrant of like tenor.

9. Registration Rights. The Holder has been granted certain registration rights by the Company. These registration rights are set forth in a Registration Rights Agreement entered into by the Company and Holder dated as of the date hereof, as the same may be amended, modified and/or supplemented from time to time.

9.1 Maximum Exercise. Notwithstanding anything contained herein to the contrary, the Holder shall not be entitled to exercise this Warrant in connection with that number of shares of Common Stock which would exceed the difference between (i) 4.99% of the issued and outstanding shares of Common Stock and (ii) the number of shares of Common Stock beneficially owned by the Holder. For purposes of the immediately preceding sentence, beneficial ownership shall be determined in accordance with Section 13(d) of the Securities Exchange Act of 1934, as amended, and Regulation 13d-3 thereunder. The limitation described in the first sentence of this Section 10 shall automatically become null and void without any notice to the Company upon the occurrence and during the continuance of an Event of Default (as defined in the Security Agreement dated as of the date hereof among the Holder, the Company and various subsidiaries of the Company, as amended, modified, restated and/or supplemented from time to time), or upon 75 days prior notice to the Company.

10. Warrant Agent. The Company may, by written notice to the each Holder of the Warrant, appoint an agent for the purpose of issuing Common Stock (or Other Securities) on the exercise of this Warrant pursuant to Section 1, exchanging this Warrant pursuant to Section 7, and replacing this Warrant pursuant to Section 8, or any of the foregoing, and thereafter any such issuance, exchange or replacement, as the case may be, shall be made at such office by such agent.

11. Transfer on the Company’s Books. Until this Warrant is transferred on the books of the Company, the Company may treat the registered holder hereof as the absolute owner hereof for all purposes, notwithstanding any notice to the contrary.

12. Notices, Etc. All notices and other communications from the Company to the Holder shall be mailed by first class registered or certified mail, postage prepaid, at such address as may have been furnished to the Company in writing by such Holder or, until any such Holder furnishes to the Company an address, then to, and at the address of, the last Holder who has so furnished an address to the Company.

13. Miscellaneous. This Warrant and any term hereof may be changed, waived, discharged or terminated only by an instrument in writing signed by the party against which enforcement of such change, waiver, discharge or termination is sought. THIS WARRANT SHALL BE GOVERNED BY AND CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK WITHOUT REGARD TO PRINCIPLES OF CONFLICTS OF LAWS. ANY ACTION BROUGHT CONCERNING THE TRANSACTIONS CONTEMPLATED BY THIS WARRANT SHALL BE BROUGHT ONLY IN STATE

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COURTS OF NEW YORK OR IN THE FEDERAL COURTS LOCATED IN THE STATE OF NEW YORK; PROVIDED, HOWEVER, THAT THE HOLDER MAY CHOOSE TO WAIVE THIS PROVISION AND BRING AN ACTION OUTSIDE THE STATE OF NEW YORK. The individuals executing this Warrant on behalf of the Company agree to submit to the jurisdiction of such courts and waive trial by jury. The prevailing party shall be entitled to recover from the other party its reasonable attorneys’ fees and costs. In the event that any provision of this Warrant is invalid or unenforceable under any applicable statute or rule of law, then such provision shall be deemed inoperative to the extent that it may conflict therewith and shall be deemed modified to conform with such statute or rule of law. Any such provision which may prove invalid or unenforceable under any law shall not affect the validity or enforceability of any other provision of this Warrant. The headings in this Warrant are for purposes of reference only, and shall not limit or otherwise affect any of the terms hereof. The invalidity or unenforceability of any provision hereof shall in no way affect the validity or enforceability of any other provision hereof. The Company acknowledges that legal counsel participated in the preparation of this Warrant and, therefore, stipulates that the rule of construction that ambiguities are to be resolved against the drafting party shall not be applied in the interpretation of this Warrant to favor any party against the other party.

14. Further Exercise Limitation. Notwithstanding anything contained herein to the contrary, the Holder shall not be entitled pursuant to the terms of this Warrant to exercise any amounts that would be exercisable prior to the earlier to occur of (i) two hundred seventy (270) days after the date hereof and (i) one hundred eighty (180) days after the date of the initial public offering of Common Stock. The Conversion Shares limitation described in this Section 14 shall automatically become null and void without any notice to any Company upon the occurrence and during the continuance of an Event of Default.

15. Call. If the Company shall have registered the shares of the Common Stock underlying the conversion of the Note (as defined in the Securities Purchase Agreement, the Minimum Borrowing Note (as defined in the Security Agreement) and each Warrant on a registration statement declared effective by the SEC and remaining effective, then, if the average closing price of the Common Stock as reported by Bloomberg, L.P. on the Principal Market for the preceding twenty consecutive (20) trading days for the Company’s Common Stock is equal to or greater than 140% of the IPO Price, the Company may, in the exercise of its discretion, require the exercise of this Warrant in whole or in part, as set forth herein, by delivering a written Notice to Holder (“Notice of Call”). Any warrants not exercised by Holder as required by the Notice of Call within twenty calendar days following the Notice of Call shall automatically terminate and no longer be exercisable.

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IN WITNESS WHEREOF, the Company has executed this Warrant as of the date first written above.

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EXHIBIT A

FORM OF SUBSCRIPTION

(To Be Signed Only On Exercise Of Warrant)

Attention: Chief Financial Officer

The undersigned, pursuant to the provisions set forth in the attached Warrant (No.            ), hereby irrevocably elects to purchase (check applicable box):

The undersigned herewith makes payment of the full Exercise Price for such shares at the price per share provided for in such Warrant, which is $            . Such payment takes the form of (check applicable box or boxes):

The undersigned requests that the certificates for such shares be issued in the name of, and delivered to                                          whose address is                                                                          .

The undersigned represents and warrants that all offers and sales by the undersigned of the securities issuable upon exercise of the within Warrant shall be made pursuant to registration of the Common Stock under the Securities Act of 1933, as amended (the “Securities Act”) or pursuant to an exemption from registration under the Securities Act.

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EXHIBIT B

FORM OF TRANSFEROR ENDORSEMENT

(To Be Signed Only On Transfer Of Warrant)

For value received, the undersigned hereby sells, assigns, and transfers unto the person(s) named below under the heading “Transferees” the right represented by the within Warrant to purchase the percentage and number of shares of Common Stock of Accentia Biopharmaceuticals, Inc. into which the within Warrant relates specified under the headings “Percentage Transferred” and “Number Transferred,” respectively, opposite the name(s) of such person(s) and appoints each such person Attorney to transfer its respective right on the books of Accentia Biopharmaceuticals, Inc. with full power of substitution in the premises.

ACCEPTED AND AGREED:

[TRANSFEREE]

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