REGISTRATION AND TRADEMARK LICENSE AGREEMENT

EXHIBIT 10.4

REGISTRATION AND TRADEMARK LICENSE AGREEMENT

     This REGISTRATION AND TRADEMARK LICENSE AGREEMENT (this “Agreement”) is made as of November 7, 2007 between Lex Pharmaceuticals, Inc. (“Lex”), a Delaware corporation, and MiddleBrook Pharmaceuticals, Inc., a Delaware corporation (“MiddleBrook”). Lex and MiddleBrook are each referred to individually as a “Party,” and collectively as the “Parties.”

Background Statement

     MiddleBrook and Lex are Parties to an Asset Purchase Agreement, dated as of the date hereof (the “Purchase Agreement”), and the Related Agreements (as defined in the Purchase Agreement). Pursuant to the Purchase Agreement, MiddleBrook has conveyed certain assets to Lex, including the trademarks, trademark applications and domain name set forth on Schedule A (the “Marks”), the approved new drug application numbers 50-405 and 50-406 (including all supplements and amendments thereto, the “Approved Registrations”) and Technical Data and Technical Data Embodiments (as set forth in Section 2.1(a)(i) of the Purchase Agreement). Pursuant to the Purchase Agreement, and subject to conditions set forth therein, Lex may purchase from MiddleBrook investigational new drug application number 73,767 (including any approval thereof and all supplements and amendments thereto, the “IND”) and Technical Data and Technical Data Embodiments (as set forth in Section 2.1(a)(ii) of the Purchase Agreement and, together with the Marks, Approved Registrations and IND, the “Rights”). The Parties desire that MiddleBrook shall have a license to use the Rights and the Parties are entering into this Agreement to set forth the terms and conditions of such license.

Statement of Agreement

     1. Definitions.

     1.1 Terms Defined in Purchase Agreement. Terms defined in the Purchase Agreement and not otherwise defined by this Agreement shall have the meaning given to such terms in the Purchase Agreement.

     1.2 “Adverse Drug Experience” means the definition in the current 21 C.F.R. Section 314.80, as in effect from time to time.

     1.3 “Agreement” has the meaning set forth in the introductory paragraph.

     1.4 “Approved Registrations” has the meaning set forth in the Background Statement.

     1.5 “Consignment Agreement” means the Inventory Consignment Agreement, dated as of the date hereof, between Kef and MiddleBrook.

     1.6 “Governmental Authority” means any nation or government, any state or other political subdivision thereof, any municipal, local, city or county government, any entity exercising executive, legislative, judicial, regulatory or administrative functions of or pertaining to government.

     1.7 “IND” has the meaning set forth in the Background Statement.

     1.8 “Indemnitee” has the meaning set forth in Section 9.3.

     1.9 “Indemnitor” has the meaning set forth in Section 9.3.

     1.10 “Kef” means Kef Pharmaceuticals, Inc., a Delaware corporation.

     1.11 “Kef Stock Purchase Agreement” means that certain Stock Purchase Agreement, dated as of November ___, 2007, between MiddleBrook, the stockholders of Kef and Deerfield Management, L.P., pursuant to which MiddleBrook has a right to purchase all of the capital stock of Kef upon the terms and conditions set forth in such Stock Purchase Agreement.

     1.12 “Kef Stock Purchase Right” means Stock Purchase Right as defined in the Kef Stock Purchase Agreement.

     1.13 “Lex” has the meaning set forth in the introductory paragraph.

     1.14 “Lex Stock Purchase Agreement” means that certain Stock Purchase Agreement, dated as of the date hereof, between MiddleBrook, the stockholders of Lex and Deerfield Management, L.P., pursuant to which MiddleBrook has a right to purchase all of the capital stock of Lex upon the terms and conditions set forth in such Stock Purchase Agreement.

     1.15 “Lex Stock Purchase Right” means Stock Purchase Right as defined in the Lex Stock Purchase Agreement.

     1.16 “License” has the meaning set forth in Section 2.1.

     1.17 “Licensed Patents” has the meaning given to it the Patent Sublicense.

     1.18 “Licensed Product(s)” means all dosage forms, formulations, strengths and package sizes and types of any Cephalexin antibiotic products that may be marketed now or in the future under the Rights.

     1.19 “Marks” has the meaning set forth in the Background Statement.

     1.20 “MiddleBrook” has the meaning set forth in the introductory paragraph.

     1.21 “Minimum Royalty” has the meaning set forth in Section 3.2.

     1.22 “Net Sales” shall mean, with respect to a Licensed Product, the gross amount invoiced by or on behalf of MiddleBrook for that Licensed Product sold to third parties in bona fide, arm’s length transactions, less customary deductions, determined in accordance with MiddleBrook’s standard accounting methods as generally and consistently applied by MiddleBrook, to the extent included in the gross invoiced sales price of any Licensed Product and otherwise directly paid or incurred by MiddleBrook or distributors with respect to the sale of such a Licensed Product, including: (i) applicable sales credits (as described below), (ii) payments or rebates incurred pursuant to federal, state and local government (or agency thereof)

programs, including Medicare and Medicaid rebates, (iii) costs for transit insurance, freight, handling or other transportation billed to customers to the extent included in the invoiced price and (iv) sales, use or excise taxes included in the invoiced price. Applicable sales credits include credits or discounts deducted from the sales price for: (A) customer returns, returned goods allowances, rejected goods and damaged goods not covered by insurance, (B) cash or terms discounts, (C) direct to customer discount or customer rebate programs, including coupons, (D) third party rebates and chargebacks, (E) trade show discounts and stocking allowances, (F) price adjustments on customer inventories following price changes, (G) product recalls, (H) deductions due for discount card programs, (I) amounts credited for uncollectible amounts on previously sold products and (J) agreed by Lex and MiddleBrook in writing, other specifically identifiable amounts included in gross sales of Licensed Products that were or ultimately will be credited and that are substantially similar to those listed above.

     1.23 “Party” means either MiddleBrook or Lex and “Parties” shall mean both MiddleBrook and Lex.

     1.24 “Patent Sublicense” means the Patent Sublicense that may be entered into between Kef and MiddleBrook pursuant to that certain Asset Purchase Agreement, dated as of the date hereof, between MiddleBrook and Kef.

     1.25 “Person” means any corporation, administrator, association, joint venture, partnership, limited liability company, organization, business, individual, trust, government or agency or political subdivision thereof or other legal entity.

     1.26 “Purchase Agreement” has the meaning set forth in the Background Statement.

     1.27 “Regulatory Authority” shall mean any federal, national, multinational, state, provincial or local regulatory agency, department, bureau or other governmental entity with authority over the marketing, pricing and/or sale of a pharmaceutical product in a country, including without limitation FDA in the United States.

     1.28 “Regulatory Obligations” has the meaning set forth in Section 6.1.

     1.29 “Regulatory Responsibilities Agreement” means the Agreement Regarding Regulatory Responsibilities, dated as of the date of this Agreement, between Lex and MiddleBrook.

     1.30 “Related Agreements” has the meaning set forth in the Background Statement.

     1.31 “Rights” has the meaning set forth in the Background Statement.

     1.32 “Royalty” has the meaning set forth in Section 3.

     1.33 “Term” means the period beginning on the date hereof and continuing until the License is terminated pursuant to the terms of this Agreement.

     1.34 “Territory” means the United States of America and Puerto Rico.

     2. Grant of License.

     2.1 Grant. Lex hereby grants to MiddleBrook, upon and subject to the terms and conditions of this Agreement, an exclusive license under the Rights to develop, manufacture, market, distribute and sell, and have manufactured, marketed, distributed and sold, the Licensed Products in the Territory (the “License”).

     2.2 Exclusivity. The License is exclusive as to all Persons, including Lex.

     2.3 No Transfer. MiddleBrook shall not assign the License or grant any sublicense under the License, other than (i) a sublicense to manufacture the Licensed Products solely for sale by or on behalf of MiddleBrook or (ii) such sublicenses as may be necessary to continue the development of, and to obtain marketing approval for, Licensed Products under the Approved Registrations or the IND.

     2.4 Obligation to Develop and Market. MiddleBrook shall at all times during the Term use its commercially reasonable efforts, consistent with usual pharmaceutical industry practice, to develop and commercialize the Licensed Products during the term of this Agreement. MiddleBrook’s obligations under this Section 2.4 may be suspended for so long as there exists any material safety (including toxicity), efficacy, regulatory, medical or intellectual property issue relating to the Licensed Products.

     3. Royalty. In consideration of the grant of the License, MiddleBrook shall pay Lex a royalty (the “Royalty”) as follows:

     3.1 Percent of Net Sales. The Royalty shall be equal to nine percent (9%) of MiddleBrook’s Net Sales of Licensed Products plus such additional amount as may be necessary for MiddleBrook to pay the Minimum Royalty.

     3.2 Minimum Royalty. Regardless of the amount of Net Sales, the minimum Royalty during any calendar quarter shall be Four Hundred Thousand Dollars ($400,000) (the “Minimum Royalty”); provided, that any payments made by MiddleBrook to Kef during any calendar quarter pursuant to the Consignment Agreement shall be included for purposes of determining whether MiddleBrook has paid the Minimum Royalty for such calendar quarter. The Minimum Royalty shall be pro-rated during the first and last calendar quarters of the Term to reflect the portion of such calendar quarters during which the License is in effect.

     3.3 Quarterly Payment. Within forty-five (45) days after the end of each calendar quarter any part of which is during the Term, MiddleBrook shall deliver to Lex (i) a written statement showing all Net Sales during such calendar quarter and (ii) the greater of (A) the Royalty due upon such Net Sales and (B) the Minimum Royalty. All payments shall be made by wire transfer of immediately available funds to an account designated by Lex.

     3.4 Audit. Upon not less than seven (7) days written notice, Lex shall have the right to audit the books and records of MiddleBrook relating to sales of Licensed Products for the purpose of determining the correctness of MiddleBrook’s computation and payment of the Royalty. Such audit may not be conducted more than once in any six-month period and shall be conducted during normal business hours. Lex may engage an accounting firm at its cost to

perform or assist in such audit. MiddleBrook shall provide Lex, its officers, agents and accountants with access to all pertinent books and records and shall reasonably cooperate with Lex’s efforts to conduct such audits.

     4. Ownership of Rights. MiddleBrook acknowledges that, as between the Parties, Lex is the sole and exclusive owner of the Rights, and MiddleBrook shall do nothing inconsistent with such ownership. MiddleBrook shall not challenge Lex’s ownership and rights in or to any of the Rights or assist others in challenging Lex’s ownership thereof. MiddleBrook agrees that nothing in this Agreement shall give MiddleBrook any right, title or interest in the Rights other than the License granted herein. Upon Lex’s request, MiddleBrook shall provide such information and assistance, and execute and deliver such documents, as Lex may reasonably request for purposes of registering, maintaining or enforcing any of the Rights.

     5. No Warranty. The Parties acknowledge that (i) Lex has acquired the Rights from MiddleBrook as of the date hereof on the basis of representations and warranties regarding the Rights made by MiddleBrook for the benefit of Lex and (ii) pursuant to the Regulatory Responsibilities Agreement, MiddleBrook shall be responsible for maintaining and performing all Legal Requirements relating to the Rights. LEX MAKES NO REPRESENTATIONS OR WARRANTIES WHATSOEVER REGARDING THE RIGHTS OR THE LICENSED PRODUCTS, AND MIDDLEBROOK ACKNOWLEDGES THAT IT IS ACCEPTING THE RIGHTS “AS IS” UNDER THE LICENSE.

     6. Regulatory Obligations.

     6.1 Performance by MiddleBrook. During the Term, MiddleBrook shall take all reasonable and appropriate actions, at MiddleBrook’s sole cost and expense, to maintain the Rights and shall oversee, monitor, coordinate and perform all regulatory actions, communications and filings with and submissions, including filings and submissions of supplements and amendments thereto, to each applicable Regulatory Authority or Governmental Authority with respect to each Licensed Product (the “Regulatory Obligations”). Notwithstanding the foregoing, nothing herein shall operate to prevent Lex from taking such actions as Lex, in its sole discretion, deems appropriate to ensure that all Regulatory Obligations are properly and timely performed, subject to prior notice to and consultation with MiddleBrook.

     6.2 Regulatory Meetings and Correspondence. MiddleBrook shall be responsible for interfacing, corresponding and meeting with the applicable Regulatory Authorities with respect to each Licensed Product. Lex shall execute such notices, powers of attorney, acknowledgments, consents and other instruments as MiddleBrook may reasonably request to authorize MiddleBrook to act on Lex’s behalf for all actions before and communications with Regulatory Authorities, the United States Patent and Trademark Office, other Governmental Authorities and with any designated registrars of domain names, as shall be necessary and appropriate to enable MiddleBrook to perform the Regulatory Obligations. Furthermore, as Lex’s agent for such Regulatory Obligations, MiddleBrook shall have complete and sole discretion to take or not take such actions as it deems reasonable and appropriate, provided that MiddleBrook shall comply with all Legal Requirements and shall not cause, and shall use commercially reasonable efforts to prevent, the termination of any of the Rights.

     6.3 Exchange of Information. The Parties shall establish procedures to ensure that the Parties exchange on a timely basis all necessary information to enable MiddleBrook to comply with all Regulatory Obligations, including, without limitation, filing updates, pharmacovigilance filings and investigator notifications. To the extent either Party receives any information regarding Adverse Drug Experiences related to the use of Licensed Products, such Party shall (i) provide the other Party with such information within five (5) days of its receipt, (ii) promptly provide all follow-up information that may reasonably be requested and (iii) otherwise act in accordance with such Adverse Event Reporting Procedures to be agreed upon in writing by the Parties from time to time. Without limiting the foregoing requirement, MiddleBrook shall provide Lex with copies of all communications between MiddleBrook and any Governmental Authorities relating to any of the Licensed Patents, Rights and Licensed Products, in every case within five (5) Business Days of the sending or receipt of such communication by MiddleBrook.

     6.4 Costs and Expenses. MiddleBrook shall bear all costs and expen