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Exhibit 10.42 FIRST AMENDMENT TODEVELOPMENT AND COMMERCIALIZATION AGREEMENT This Amendment to Development and Commercialization Agreement (this Amendment) is made and
entered into this Fourteenth day of December, 2004 (the Effective Date), by and between Advancis
Pharmaceutical Corporation, a Delaware corporation (Advancis), and Par Pharmaceutical, Inc., a
Delaware corporation (Par). WHEREAS, Advancis and Par are parties to that certain Development and Commercialization
Agreement dated May 28, 2004 (the Development and Commercialization Agreement); and WHEREAS, Advancis and Par wish to modify the Development and Commercialization Agreement so
that the development and commercialization of an amoxicillin-only product for the pediatric
population targeting acute otitis media will be replaced by the development and commercialization
of an amoxicillin clavulanic acid product for such indication, in accordance with the terms of this
Amendment. NOW, THEREFORE, in consideration of the mutual covenants and promises contained in this
Amendment and other good and valuable consideration, the receipt and sufficiency of which are
hereby acknowledged, Advancis and Par agree as follows: 1. Definitions; Format. All capitalized terms not otherwise defined in this Amendment
shall have the definitions ascribed to such terms in the Development and Commercialization
Agreement. Where a textual passage is amended in part only, new
language will be shown
double underlined, deleted language will be shown
in strikeout, and language that is unmodified will
be shown as an ellipsis (...). Double underlining, deleted language and ellipses are for
convenience only and are not part of the Development and
Commercialization Agreement, as amended. 2. Development Plan. Pursuant to Section 4.1 of the Development and Commercialization
Agreement, the Development Plan had been agreed to by the Parties by letter dated June 2, 2004.
The Parties agree to work together in good faith to mutually agree in writing upon an amended and
restated Development Plan within one week of the Effective Date of this Amendment which will
reflect the modifications to the Development Program set forth in this Amendment (the Amended and
Restated Development Plan). The Amended and Restated Development Plan will be substantially
similar to the most recent development plan materials circulated by Advancis to Par as of the date
of this Amendment. 3. Modification of Definition of Compound. Section 1.20, the definition of Compound
is amended to read as follows: Compound
means, individually and collectively, as applicable,
the Amox-Only Compound and the Amox-Clav Compound. 
the compound
amoxicillin, including all racemates, chelates, complexes,
enantiomers, diastereoisomers, salts, bases, esters, hydrates,
solvates, polymorphs, crystal forms, crystal habits, -1-




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prodrugs, isotopic or radiolabeled equivalents, metabolites, or the
like, thereof and all mixtures of any of the foregoing. 4. Addition of New Definition of Amox-Only Compound. A new Section 1.20.1, the
definition of Amox-Only Compound is inserted to read as follows: Amox-Only Compound means the compound amoxicillin, including
all racemates, chelates, complexes, enantiomers, diastereoisomers,
salts, bases, esters, hydrates, solvates, polymorphs, crystal forms,
crystal habits, prodrugs, isotopic or radiolabeled equivalents,
metabolites, or the like, thereof and all mixtures of any of the
foregoing. 5. Addition of New Definition of Amox-Clav Compound. A new Section 1.20.2, the definition
of Amox-Clav Compound is inserted to read as follows: Amox-Clav Compound means the compounds amoxicillin and
clavulanic acid, including all racemates, chelates, complexes,
enantiomers, diastereoisomers, salts, bases, esters, hydrates,
solvates, polymorphs, crystal forms, crystal habits, prodrugs,
isotopic or radiolabeled equivalents, metabolites, or the like,
thereof and all mixtures of any of the foregoing. 6. Modification of Definition of Adult Product. Section 1.1, the definition of Adult
Product is amended to read as follows: Adult Product means a pharmaceutical presentation of the
Amox-Only Compound (a) that utilizes or incorporates
PULSYSÔ,
and (b) that contains no active
pharmaceutical ingredient (including any active pharmaceutical
ingredient that acts as an [***]) other than the
Amox-Only Compound, and (c) that is used or is being developed for the
Adult Product Indication.,and (c) that is used or is being
developed for the Adult Product Indication, other than formulations
of Exhibit A. 7. Modification of Definition of Pediatric Product. Section 1.59, the definition of
Pediatric Product is amended to read as follows: Pediatric Product means,
as the case may be, (a) a
pharmaceutical presentation of the
Amox-Only Compound
(a)(i) that utilizes or incorporates PULSYSÔ,
(b)(ii) that contains no active pharmaceutical ingredient
(including any active pharmaceutical ingredient that acts as a
[***]) other than the
Amox-Only Compound, and
(c)
(iii) that is used or is being developed for the
Pediatric Product Indications,
[***]; and/or
(b) the pharmaceutical presentation of the Amox-Clav Compound (i)
that utilizes or incorporates PULSYSÔ, [***] INDICATES MATERIAL THAT HAS BEEN OMITTED AND FOR WHICH CONFIDENTIAL TREATMENT HAS BEEN
REQUESTED. ALL SUCH OMITTED MATERIAL HAS BEEN FILED WITH THE SECURITIES AND EXCHANGE COMMISSION
PURSUANT TO RULE 24b-2 UNDER THE SECURITIES AND EXCHANGE ACT OF 1934, AS AMENDED. -2-




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that contains no active pharmaceutical ingredient other than the
Amox-Clav Compound, and (iii) that is used or is being developed for
the Pediatric Product Indication [***] other than
formulations of Exhibit A. 8. Modification of Definition of Adult Product Indication. Section 1.2, the
definition of Adult Product Indication is amended to read as follows: Adult
Product Indication means [***] in adolescents/adults
in accordance with the protocols set forth in
the Amended and Restated Development Plan, [***] and any other indication agreed to by the
Parties. 9. Modification of Definition of Pediatric Product Indications. Section 1.60, the
definition of Pediatric Product Indications is amended to read as follows: Pediatric Product Indications means (i) 
[***]; (ii)  [***]
, both in accordance with
the protocols set forth in the Amended and Restated Development
Plan,; and (c) any other indications agreed to by the Parties. 10. Deletion of Exhibit A. Exhibit A is deleted from the Development and
Commercialization Agreement. In addition, the last sentence of Section 14.2 (No Conflicts), which
refers to Exhibit A, is deleted. 11. Modification of Section 2.3 Non-Competition. Section 2.3, Non-Competition is
amended to read as follows: Non-Competition.During the Term, and except as through
the Collaboration pursuant to this Agreement neither pParty
for the Territory shall develop, market, sell or distribute any
pharmaceutical product that [***], wherein (a)the sole
active pharmaceutical ingredient in such product is the Amox-Only
Compound; or (b) with respect to indications for acute otitis
media in the pediatric population, the only active pharmaceutical
ingredients in such product are the Amox-Clav Compound.
Notwithstanding the foregoing, it is expressly agreed that this
Section 2.3 does not apply to any formulations of Exhibit A. 12. Section 4.2.2.2. The Parties hereby understand and agree that Section 4.2.2.2 of the
Development and Commercialization Agreement shall apply with the following clarifications: (a)
[***], and (b) [***]. 13. No Other Changes; Execution. Except as explicitly set forth in this Amendment, no
amendment or modification to the Development and Commercialization Agreement is hereby made. This
Amendment may be executed in counterparts and delivered by facsimile. [***] INDICATES MATERIAL THAT HAS BEEN OMITTED AND FOR WHICH CONFIDENTIAL TREATMENT HAS BEEN
REQUESTED. ALL SUCH OMITTED MATERIAL HAS BEEN FILED WITH THE SECURITIES AND EXCHANGE COMMISSION
PURSUANT TO RULE 24b-2 UNDER THE SECURITIES AND EXCHANGE ACT OF 1934, AS AMENDED. -3-




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IN WITNESS WHEREOF, the Parties hereto have caused this Amendment to be executed as a sealed
instrument in their names by their properly and duly authorized officers or representatives as of
the date first above written. ADVANCIS PHARMACEUTICAL CORPORATION By: /s/ Edward M. Rudnic Print Name: Edward M. Rudnic Title: Chairman, President and CEO  PAR PHARMACEUTICAL, INC. By: /s/ Scott Tarriff Print Name: Scott Tarriff Title: President and CEO -4-