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                                                                    EXHIBIT 10.5

                   AMENDED AND RESTATED CONSULTING AGREEMENT
                   -----------------------------------------

         THIS AMENDED AND RESTATED CONSULTING AGREEMENT ("Agreement") is made as
of this May 16, 2001 by and between Genaera Corporation, a Delaware corporation
(formerly named Magainin Pharmaceuticals Inc.) (the "Company"), and Dr. Michael
Zasloff ("Consultant").

         WHEREAS, the Company and the Consultant are currently parties to a
Consulting Agreement (the "Original Agreement") dated as of September 12, 2000
(the "Effective Date");

         WHEREAS, the parties hereto desire to amend and restate the Original
Agreement upon the terms and conditions hereinafter set forth.

         NOW THEREFORE, in consideration of the covenants and conditions set
forth in this Agreement, the parties, intending to be legally bound, agree as
follows:

                  1.       Resignation as Director. Consultant hereby
                           -----------------------
         voluntarily and irrevocably resigns as a director of the Company
         effective as of the date of the 2001 annual meeting of stockholders of
         the Company. In connection and in furtherance of such resignation,
         Consultant agrees that he shall not be included in the Company's
         nominees for director or otherwise stand for election as a director of
         the Company at such meeting.

                  2.       Consulting Arrangement.  The Company hereby retains
                           ----------------------
         Consultant as a consultant to the Company to perform the consulting
         services in accordance with the terms and conditions hereinafter set
         forth.

         2.1      Term. The period during which consulting services shall be
                  ----
                  provided under this Agreement (the "Consulting Term") began on
                  the Effective Date and shall end on the fifth anniversary
                  thereof, subject to the provisions for earlier termination
                  thereof set forth in Section 5 of this Agreement.

         2.2      Duties and Responsibilities as a Consultant.  During the
                  -------------------------------------------
                  Consulting Term, Consultant shall provide consulting services
                  to the Company as an independent contractor and not as an
                  employee of the Company. Consultant shall at all times during
                  the Consulting Term act as an independent contractor and
                  during such period nothing hereunder shall create or imply a
                  relationship of employer-employee between the Company and
                  Consultant. Consultant shall provide such consulting and
                  advisory services to the Company as may be reasonably
                  requested from time to time by the chief executive officer of
                  the Company. Consultant shall have access to secretarial
                  assistance and a small office for consulting services to be
                  provided at the Company, as appropriate.

         2.3      Extent of Service as a Consultant. During the Consulting Term,
                  ---------------------------------
                  Consultant agrees to devote such time, attention and energy as
                  is necessary to fulfill his duties and responsibilities as a
                  Consultant under Section 2.2 hereof, but in no event shall
                  Consultant be required to spend more than one day in any week
                  or

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                  more than a total of 9 days during the Consulting Term in such
                  consulting activities.

         2.4      Compensation for Consulting Services.
                  ------------------------------------

                  (a)      Within the period of the Consulting Term, Company
                           shall pay Consultant (i) with respect to the period
                           from the Effective Date until the first anniversary
                           thereof, the sum of $271,631.72, and (ii) with
                           respect to the period from the first anniversary of
                           the Effective Date until the fifth anniversary of the
                           Effective Date, the annual sum of $45,000.00 (for a
                           total payment of $180,000.00 for such four-year
                           period commencing on the first anniversary of the
                           Effective Date).  In all cases, the applicable amount
                           shall be payable in prorated amounts upon the dates
                           that the Company regularly pays its senior
                           executives.

                  (b)      Consultant acknowledges that the period within which
                           the Company will make available the purchase of
                           health insurance under COBRA commenced as of the
                           Effective Date. Consultant shall not be entitled to
                           any benefits provided to employees of the Company
                           during the Consulting Term, and, Consultant
                           specifically acknowledges that he is not entitled to
                           participate in any of the Company's benefit plans,
                           including, without limitation, the Company's health
                           and life insurance, disability insurance or 401(k)
                           plans.

                  (c)      Consultant alone, and not the Company, will be solely
                           responsible for payment of all federal, state and
                           local taxes in respect of the payments to be made and
                           benefits to be provided to him under this Agreement.

         2.5      Stock Options.  The Company has previously granted Consultant
                  -------------
                  options to acquire a total of 423,000 shares of the Company's
                  common stock (the "Stock Options") as set forth on Attachment
                  A hereto pursuant to various stock option agreements (the
                  "Option Agreements").  The Company and Consultant hereby
                  acknowledge and agree that (i) the provisions of the Option
                  Agreements will continue to apply to the Company and
                  Consultant during the Consulting Term, (ii) during the
                  Consulting Term, Consultant may exercise the Stock Options as
                  such options have vested, or will vest during the Consulting
                  Term, in accordance with the terms of the Option Agreements,
                  and iii) all provisions of the Option Agreements relating to
                  the period of employment of Consultant by the Company or its
                  subsidiaries shall instead refer to the period of Consultant's
                  services as a consultant to the Company during the Consulting
                  Term.

         2.6      Return of Company Property.  Consultant acknowledges that, in
                  --------------------------
                  accordance with the Original Agreement, he has returned to the
                  Company all lists, books, records, documents, credit cards and
                  other materials or property in his possession, custody or
                  control which are or were owned by the Company or any of its
                  subsidiaries or affiliates, or which are or were used by
                  Consultant or any other officers, employees or agents of the
                  Company or any of its subsidiaries or affiliates in

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                  connection with the conduct of the business of the Company or
                  any of its subsidiaries or affiliates, except those materials
                  and property agreed upon by the Company and Consultant to be
                  necessary for the execution of the Consultant's obligations
                  and responsibilities, which materials and property Consultant
                  shall return at the end of the Consulting Term. Consultant
                  will not deliver to any other person or entity any property of
                  the Company or copies of any property of the Company, or
                  permit any copies thereof to be made by any other person or
                  entity.

                  3.       General Release.  In consideration of the foregoing
                           --------------- including without limitation the
         promises and payments as described in Section 2 above. Consultant
         hereby knowingly, willingly and voluntarily remises, waives, releases
         and forever discharges the Company and its subsidiaries and affiliates,
         the directors, officers, employees, advisors and agents of the Company
         and its subsidiaries and affiliates, and the heirs, executors,
         administrators, successors and assigns of such parties (collectively
         referred to as the "Releasees") of and from any and all manner of
         actions and causes of action, suits, debts, dues, accounts, bonds,
         covenants, contracts, agreements, judgments, claims and demands
         whatsoever in law or equity which Consultant, his heirs, executors,
         administrators or assigns has, had or may hereafter have against the
         Releasees or any of them from or by reason of any cause, matter or
         thing whatsoever from the beginning of his employment with the Company
         to the date of this Agreement, excepting only claims against the
         Company relating to its obligations under this Consulting Agreement and
         including, without in any way limiting the generality of the foregoing,
         any and all matters relating to his employment by the Company and the
         termination thereof and his serving as a director of the Company and
         his resignation thereof, any and all claims under any federal, state or
         local law, any common law claims and all claims for counsel fees and
         costs. Consultant covenants and agrees never to commence, aid in any
         way, prosecute or permit to be commenced against the Releasees any
         action or other proceeding based upon any matters that are the subject
         of or covered by the foregoing. Nothing in this Section 3 shall affect
         or modify in any manner (i) the rights of Consultant and the
         obligations of the Company to indemnify Consultant for acts or matters
         occurring prior to the Effective Date, if and to the extent required
         pursuant to the Company's By-Laws or the Delaware General Corporation
         Law, in each case as in effect on or prior to the Effective Date, and
         (ii) the rights, if any, of Consultant under any directors and officers
         insurance policy purchased by the Company and in effect on or prior to
         the Effective Date.

                  4.       Development and Confidential Information, Etc.
                           ---------------------------------------------

                  (a)      Consultant acknowledges that he is in possession of
                           proprietary and confidential of the Company (the
                           "Confidential Information") received during the
                           period of his employment by the Company. Consultant
                           shall be under a continuing duty, which duty
                           expressly shall survive the termination of this
                           Consulting Agreement, to continue to safeguard and
                           not to disclose any of the Confidential Information,
                           as well as any additional Company Confidential
                           Information that may come into his possession during
                           the term of this Consulting Agreement; except,
                           however, that this duty shall not apply with respect
                           to any information that

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                           is in the public domain or that otherwise is
                           disclosed or enters the public domain through no
                           fault of Consultant.

                  5.       Early Termination of the Consulting Term.  The
                           ----------------------------------------
         Consulting Term shall terminate prior to the expiration of the
         Consulting Term upon the occurrence of any one of the following events:

                  (a)      Death. In the event that Consultant dies during the
                           -----
                           Consulting Term, the Consulting Term shall terminate.

                  (b)      Breach by Consultant. In the event Consultant
                           --------------------
                           violates any of his obligations under this Agreement,
                           the Company may, upon seven (7) days prior notice to
                           Consultant, terminate the Consulting Term; provided,
                           however, that Consultant shall have a reasonable
                           opportunity to cure any breach of his obligations
                           under Section 2.2, 2.3 or 2.6 of this Agreement
                           during such seven (7) days' notice period. In the
                           event of a termination pursuant to this Section 5(b),
                           all payment obligations of the Company set forth in
                           this Agreement shall terminate, and Consultant shall
                           not be entitled to receive any unpaid portion of the
                           cash payments set forth in Section 2.4(a) of this
                           Agreement.

                  6.       Governing Law.  This Agreement shall be governed by
                           -------------
         and interpreted under the laws of the Commonwealth of Pennsylvania,
         without giving effect to the principles of conflicts of law thereof.

                  7.       Notices. All notices and other communications
                           -------
         required or permitted hereunder or necessary or convenient in
         connection herewith shall be in writing and shall be deemed to have
         been given when hand delivered or mailed by registered or certified
         mail, as follows (provided that notice of change of address shall be
         deemed given only when received):

          If to the Company, to:

         Genaera Corporation
         5110 Campus Drive
         Plymouth Meeting, PA 19462
         Attention:  President and Chief Executive Officer

         With a required copy to:

         Morgan, Lewis & Bockius LLP
         1701 Market Street
         Philadelphia, PA 19103-2021

         If to Consultant, to:

         Michael A. Zasloff, M.D., Ph.D.
         274 Linden Lane

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         Merion, PA 19066

         With a required copy to:

         Brett A. Schlossberg, Esquire
         Schlossberg & Associates, P.C.
         340 Highland Lane
         Bryn Mawr, PA 19010-3742

or such other names or addresses as the Company or Consultant, as the case may
be, shall designate by notice to each other person entitled to receive notices
in the manner specified in this Section.

                  8.       Contents of Agreements; Amendment and Assignment.
                           ------------------------------------------------

                  (a)      Except as stated herein, this Agreement supersedes
                           all prior agreements between the parties, including,
                           without limitation, the Employment Agreement between
                           the parties dated February 22, 1988, as amended on
                           June 22, 1992, and sets forth the entire
                           understanding between the parties with respect to the
                           subject matter hereof. This Agreement includes and
                           subsumes the Original Agreement as amended and
                           restated hereby. This Agreement may not be modified
                           except as set forth in writing executed by a duly
                           authorized officer of the Company and by Consultant.

                  (b)      All of the terms and provisions of this Agreement
                           shall be binding upon and inure to the benefit of and
                           be enforceable by the respective heirs, executors,
                           administrators, legal representatives, successors and
                           assigns of the parties hereto, except that the duties
                           and responsibilities of Consultant hereunder are of a
                           personal nature and shall not be assignable or
                           delegable in whole or in part by Consultant and the
                           Company may not transfer or convey its rights
                           hereunder to any third party other than an affiliate
                           of the Company without the prior express written
                           consent of Consultant.

                  9.       Severability.  Should any provision of this
                           ------------
         Agreement, or the application thereof to any person or circumstance, be
         deemed invalid or unenforceable in any jurisdiction then, to the extent
         that no essential purpose of this Agreement is thereby frustrated, the
         remainder of it shall not be affected thereby.

                  10.      Remedies Cumulative; No Waiver. No remedy conferred
                           ------------------------------
         upon the Company by this Agreement is intended to be exclusive of any
         other remedy, and each and every such remedy shall be cumulative and
         shall be in addition to any other remedy given hereunder or now or
         hereafter existing at law or in equity. No delay or omission by the
         Company in exercising any right, remedy or power hereunder or existing
         at law or in equity shall be construed as a waiver thereof, and any
         such right, remedy or power may be exercised by the Company from time
         to time and as often as may be deemed expedient or necessary by the
         Company in its sole discretion.

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                 11.      Miscellaneous.  All section headings are for
                          --------------
         convenience only.  This Agreement may be executed in counterparts, each
         of which is an original. It shall not be necessary in making proof of
         this Agreement or any counterpart hereof to produce or account for any
         of the other counterparts.

                  12.      Consultation with Legal Counsel, Etc. Consultant and
                           -------------------------------------
         Company acknowledge that no promise or inducement for this Agreement
         has been made except as set forth herein. Consultant acknowledges that
         this Agreement is executed without Consultant's reliance upon any
         statement or representation by or on behalf of the Company; that
         Consultant has had an opportunity to discuss this Agreement with his
         attorney; and that Consultant is legally competent to and does
         voluntarily execute this Agreement and accept full responsibility
         therefore.

                  13.      Formation of New Company. In the event Consultant
                           -------------------------
         shall determine in the future to form a company to engage in research,
         development and commercialization efforts relating to isoleucine and/or
         MSI-1436 ("NEWCO"), Consultant and the Company shall discuss in good
         faith a potential relationship between NEWCO and the Company, including
         the licensing of intellectual property by the Company to NEWCO, and the
         participation in NEWCO by the Company as an equity holder.

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         IN WITNESS WHEREOF, the undersigned, intending to be legally bound,
have executed this Agreement as of the date and year first above written.

                                   GENAERA CORPORATION

                                   By:  /s/ Roy Clifford Levitt, M.D.
                                      -------------------------------
                                   Name:  Roy Clifford Levitt, M.D.
                                   Title: President and Chief Executive Officer

                                   CONSULTANT

                                   By: /s/ Michael A. Zasloff, M.D., Ph.D.
                                      ----------------------------------------
                                   Name:  Michael A. Zasloff, M.D., Ph.D.

                                      7<PAGE>

                                                                   EXHIBIT 10.10

Employment Agreement with Michael E. Petrone, M.D.

December 20, 2000

Dr. Michael E. Petrone

Dear Dr. Petrone:

I am pleased to offer you the position of Vice President, Clinical Research with
Magainin Pharmaceuticals Inc., reporting to the Dr. Kenneth Holroyd, Executive
Vice President. Your base salary will be $15,000.00 per month ($180,000/year).
Contingent upon your acceptance of this offer, it is expected that the
Compensation Committee of the Board of Directors will grant to you at its next
meeting options to purchase 50,000 shares of Magainin Common Stock, exercisable
at the fair market value underlying common stock on the date of such meeting.
These options will have a term of 10 years and vest at the rate of 25% per year.
As with all Magainin options, the grant will be subject to execution of a stock
option agreement in the form specified by the Compensation Committee.

If your employment is terminated without cause, you will receive your monthly
base salary, including health benefits through COBRA, for six (6) months
following the date of termination.

Upon the commencement of your employment with the Company, you will be expected
to execute the Company's Drug Free Workplace Policy, Proprietary Information
Agreement, Policy Statement on Securities Trading by Magainin Personnel, and
Corporate Governance - Conflict of Interest Policy, each in the form previously
provided to you. Magainin may have already provided you with certain of its
confidential business or scientific information, which it expects you to keep
confidential, and to use only to further Magainin's legitimate business
interests. Just as Magainin expects you to keep confidential its business or
scientific information, Magainin also expects you to honor your obligations to
your former employers with respect to maintaining the confidentiality of their
business or scientific information.

You will be eligible for twenty (20) days vacation per year. Vacation accrues
proportionate to months employed. Employees are encouraged to take their
vacations yearly. However, up to five (5) days of unused vacation time can be
carried over into next year with supervised approval. In addition, you will be
eligible for the benefits package available to all employees. Enclosed is a
summary of the benefits.
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All the terms and conditions of this Agreement shall be binding upon and inure
to the benefit and be enforceable by the respective heirs, representatives,
successors (including any successor as a result of a merger or similar
reorganization) and assigns of the parties hereto, except that your duties and
responsibilities hereunder are of a personal nature and shall not be assignable
in whole or in part by you.

We look forward to your joining us at Magainin Pharmaceuticals Inc. Please
indicate your acceptance of this offer, which is for at will employment, by your
signature below. This offer of employment will remain in effect until Wednesday,
December 27, 2000. We have agreed that your start date will be Monday, January
8, 2001 at 8:30 A.M., however, this is flexible. Please do not hesitate to speak
with me concerning any questions you may have.

                                          Sincerely,

                                          /s/ Roy C. Levitt, M.D.
                                          -----------------------
                                          Roy C. Levitt, M.D.
                                          President and Chief Executive Officer

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