ROYALTY STREAM PURCHASE AGREEMENT

Exhibit 10.15

ROYALTY STREAM PURCHASE AGREEMENT

This ROYALTY STREAM PURCHASE AGREEMENT (the “Agreement”) is entered into and effective as of the 7 ^th day of September 2004 (the “Effective Date”), by and between Accentia, Inc., a Florida corporation (“Accentia”) and Pharmaceutical Product Development, Inc., a North Carolina corporation (“PPD”).

WHEREAS, Accentia and Mayo Foundation For Medical Education and Research (“Mayo”), a Minnesota charitable corporation, have entered into that certain Mayo Foundation For Medical Education and Research License Agreement with an effective date of February 10, 2004 (the “Mayo License Agreement”); and

WHEREAS, Accentia and BioDelivery Sciences International, Inc. (“BDSI”), have entered into that certain License Agreement between BioDelivery Sciences International, Inc. and Accentia, dated April 12, 2004 (the “BDSI License Agreement”); and

WHEREAS, Accentia is currently sublicensing pharmacy(s) with regard to selling certain Products and intends to develop and sell certain FDA Products (each, as defined below) pursuant to rights obtained from the Mayo License Agreement and the BDSI License Agreement; and

WHEREAS, PPD desires to purchase a stream of royalty payments that will be based on sales of the Products;

NOW, THEREFORE, in consideration of the foregoing and the representations, warranties, covenants and agreements herein contained, the parties hereto agree as follows.

1. DEFINITIONS. In addition to capitalized terms defined elsewhere in this Agreement, the following capitalized terms shall have the meanings set forth below:

(a) “Affiliate” means with respect to any Person, any Person directly or indirectly controlling, controlled by or under common control with such other Person. For purposes of this definition, a Person shall be deemed to control another entity if it owns or controls, directly or indirectly, at least fifty percent (50%) of the voting securities of another entity (or other comparable ownership interest for an entity other than a corporation) or if it has management control of the other entity.

(b) “Compounded Product” shall mean a Product that contains or comprises an antifungal prepared by a pharmacy that provides prescription fulfillment by extemporaneous compound preparation.

(c) “Enabling Agreements” means the Mayo License Agreement and the BDSI License Agreement.

(d) “FDA Product” means a Product that is approved by the FDA or any other Regulatory Authorities.

( e) “License Quarter” means each quarter that begins on the first day of each January, April, July and October during the Term; provided, however, that the first License Quarter will commence on the Effective Date and end on the day preceding the first day of the next License Quarter.

(f) “Lien” means, with respect to any agreement or other asset, any mortgage, lien, pledge, charge, security interest or encumbrance of any kind in respect of such asset.

(g) “Net Sales” means the amount invoiced by Accentia, or its Affiliates and sublicensees, or any of them, on all sales of Products, less: (i) sales, excise or use taxes shown on the face of the invoice; (ii) credits for defective or returned Products; (iii) regular trade and discount allowances and any amount actually excluded or disallowed by Medicare, Medicaid, third party payer or insurance company. Sales of Products by Accentia or an Affiliate or sublicensee of Accentia to any Affiliate or sublicensee that is a reseller thereof shall be excluded, and only the subsequent sale of such Products by Affiliates or sublicensees of Accentia to unrelated parties shall be deemed Net Sales hereunder. Net Sales shall also include all settlement amounts, payments and damages received by Accentia or its Affiliates and sublicensees, or any of them, which result from litigation or disputes related to or arising from the sale of the Products, including amounts received from enforcement of the Enabling Agreements as described in Paragraph 6(f).

(h) “Person” means an individual, corporation, partnership, limited liability company, association, trust or other entity or organization, but not including a government or political subdivision or any agency or instrumentality of such government or political subdivision.

(i) “Product” means a therapeutic product that (i) is in suitable form for commercial sale and (ii) contains or comprises an antifungal, including but not limited to amphotericin-B, itraconazole or voriconanzole (“Antifungal”), together with any formulation ingredients, regardless of the formulation or mode of administration of such Product, for use in the treatment of chronic sinusitis. For the sake of clarity, the term Product shall include an FDA Product.

(j) “Regulatory Authorities” means any governmental authority in any country responsible for regulatory approvals and post-marketing surveillance of any FDA Product. Regulatory approvals refer to any approvals required for clinical experimentation or commercialization of any FDA Product. Regulatory approvals shall also include receipt of a pricing or reimbursement approval.

(k) “Royalty Stream” means six percent (6%) of Net Sales for all Products that are not FDA Products and seven percent (7%) of Net Sales for all FDA Products. Payments of the Royalty Stream shall be made on a quarterly basis in accordance with Section 6. By way of illustration and example, if an Accentia sublicensee invoices a customer $220 for the sale of a Product (i.e., the sublicensee’s Net Sales is $220), then the Royalty Stream on the transaction, which is payable by Accentia to PPD, would be 6% of $220 or $13.20 regardless of any royalty due Accentia from the sublicensee.

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2. PURCHASE AND SALE OF ROYALTY STREAM

(a) Purchase and Sale. Upon the terms and subject to the conditions of this Agreement: (a) PPD agrees to purchase from Accentia, and Accentia agrees to sell and pay to PPD, upon execution of this Agreement the Royalty Stream for a one-time payment of $2,500,000 in cash (the “Purchase Price”).

(b) Payment. The Purchase Price shall be due and payable not later than thirty (30) days following the Effective Date.

(c) No Assumed Obligations. Notwithstanding any provision in this Agreement or any other writing to the contrary, PPD is acquiring only the Royalty Stream and is not assuming any liability or obligation of Accentia of whatever nature, whether presently in existence or arising or asserted hereafter, whether under any of the Enabling Agreements or otherwise. All such liabilities and obligations shall be retained by and remain obligations and liabilities of Accentia.

3. REPRESENTATIONS AND WARRANTIES OF ACCENTIA

Accentia hereby represents and warrants to PPD as follows.

(a) Corporate Existence and Power. Accentia is a corporation duly incorporated, validly existing and in good standing under the laws of its jurisdiction of incorporation and has all corporate powers and all licenses, authorizations, consents and approvals required to carry on its business as now conducted.

(b) Corporate Authorization. The execution, delivery and performance by Accentia of this Agreement, and the consummation by Accentia of the transactions contemplated hereby are within Accentia’s corporate powers and have been duly authorized by all necessary corporate action on the part of Accentia. This Agreement has been duly executed and delivered and constitutes a valid and binding agreement of Accentia.

(c) Governmental Authorization. The execution, delivery and performance by Accentia of this Agreement does not require any notice to, action or consent by or in respect of, or filing with, any governmental authority, Mayo or BDSI.

(d) Non-Contravention. The execution, delivery and performance by Accentia of this Agreement does not and will not: (i) contravene or conflict with the corporate charter or bylaws of Accentia; (ii) contravene or conflict with or constitute a violation of any provision of any law or regulation binding upon or applicable to Accentia, which contravention, conflict or violation could reasonably be expected to have an adverse effect on Accentia or the Royalty Stream; (iii) contravene or conflict with or constitute a violation of any judgment, injunction, order or decree binding upon or applicable to Accentia, which contravention, conflict or violation could reasonably be expected to have an adverse effect on Accentia or the Royalty Stream; (iv) constitute a default under any agreement or give rise to any right of termination, cancellation or acceleration of any right or obligation of Accentia or to a loss of any benefit relating to the

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Royalty Stream; or (v) result in the creation or imposition of any Lien on the Royalty Stream or other assets of Accentia (except for any Lien in favor of PPD).

(e) [This paragraph is intentionally omitted.]

(f) No Undisclosed Material Liabilities. There are no material liabilities related to the Royalty Stream of any kind whatsoever, whether accrued, contingent, absolute, determined, deteminable or otherwise, and there is no existing condition, situation or set of circumstances that could reasonably be expected to result in such a liability.

(g) Litigation. There is no action, suit, investigation or proceeding (or any basis therefor), of which Accentia has received notice, pending or, to the knowledge of Accentia, threatened, before any governmental authority or arbitrator, which has or could materially affect the Royalty Stream or the business of Accentia. There have been no claims made by any Person with respect to, and no actions, suits or other proceedings relating to Accentia or the conduct of its business, which could reasonably be expected to have an adverse effect thereon.

(h) Compliance with Laws. Accentia is not in violation of, has not violated, and to the knowledge of Accentia, is not under investigation with respect to and has not been threatened to be charged with or given notice of any violation of, any law, rule, ordinance or regulation, or judgment, order or decree entered by any governmental authority, which could reasonably be expected to have a material adverse effect thereon.

(i) Intellectual Property. Exhibit B of the Mayo License Agreement and Exhibit B of the BDSI License Agreement include all intellectual property of Mayo and BDSI, respectively, that directly or indirectly relate to Products. To the best of Accentia’s knowledge, the Products and methods of making or using them do not infringe or misappropriate the intellectual property rights of any third party, and no royalties are owed to any third party with respect to such Products. Neither Accentia, Mayo nor BDSI has received any notice or other communication alleging that a Product infringes or misappropriates the intellectual property rights of a third party.

(j) Enabling Agreements. The Enabling Agreements are in full force and effect and Accentia has all rights under the Enabling Agreements to develop and commercialize the Products and generate the Royalty Stream as contemplated by the Agreement. The copies of the Enabling Agreements as provided by Accentia to PPD are true and correct copies. There have been no amendments or modifications to any of the Enabling Agreements. The Royalty Stream is not subject to any claim of off-set for any other liability or obligation of PPD. Accentia is in compliance with each of the Enabling Agreements and is not in breach of its obligations with respect thereto. Mayo and BDSI are, to the knowledge of Accentia, in compliance with, respectively, the Mayo License Agreement and the BDSI License Agreement, and Accentia has no reason to believe that either Mayo or BDSI does not intend to comply with its obligations pursuant to the Mayo License Agreement and the BDSI License Agreement, respectively. Accentia has not granted any licenses or other rights and has no obligations to grant licenses or other rights with respect to the Products, and, except for the Enabling Agreements, there are no other contracts, arrangements, or understandings relating to the Royalty Stream.

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(k) No Brokers. There is no investment banker, broker, finder or other intermediary which has been retained by or is authorized to act on behalf of Accentia who might be entitled to any fee or commission from PPD or any of its Affiliates upon consummation of the transactions contemplated by this Agreement.

(l) Other Information. This Agreement does not contain any untrue statement of a material fact or omit to state a material fact necessary in order to make the statements contained herein not misleading.

(m) A Compounded Product is being sold by Accentia’s sublicensee as of the Effective Date.

(n) Accentia has disclosed to PPD all material adverse data relating to the Products and their safety in animals and humans and the development and regulatory status known to Accentia as of the Effective Date of this Agreement.

4. REPRESENTATIONS AND WARRANTIES OF BUYER

PPD hereby represents and warrants to Accentia the following.

(a) Organization and Existence. PPD is duly organized, validly existing and in good standing under the laws of its jurisdiction of organization and has all applicable powers and all material governmental licenses, authorizations, consents and approvals required to carry on its business as now conducted.

(b) Corporate Authorization. The execution, delivery and performance by PPD of this Agreement and the consummation by PPD of the transactions contemplated hereby are within the powers of PPD and have been duly authorized by all necessary action on the part of PPD. This Agreement constitutes a valid and binding agreement of PPD.

(c) Governmental Authorization. The execution, delivery and performance by PPD of this Agreement does not require any action by or in respect of, or filing with, any governmental authority.

(d) Finders’ Fees. There is no investment banker, broker, finder or other intermediary that has been retained by or is authorized to act on behalf of PPD who might be entitled to any fee or commission from Accentia or any of its Affiliates upon consummation of the transactions contemplated by this Agreement.

5. COVENANTS

PPD and Accentia agree as follows.

(a) Maintenance of Enabling Agreements. Accentia shall exercise fully all of its rights, and comply fully with all of its obligations, under the Enabling Agreements and shall not,

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without PPD’s prior written approval (not to be unreasonably wit