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                                                                   Exhibit 10.20

                    AMENDED AND RESTATED EMPLOYMENT AGREEMENT

      THIS AMENDED AND RESTATED EMPLOYMENT AGREEMENT (this "Agreement"), dated
as of February 11, 2005, by and between Alteon Inc., a Delaware corporation (the
"Company"), and Judith S. Hedstrom (the "Employee").

      WHEREAS, the Company wishes to employ the Employee as Chief Operating
Officer; and

      WHEREAS, the Employee wishes to enter into the employ of the Company as
its Chief Operating Officer, having formerly held the role of Senior Vice
President, Corporate Development;

      NOW, THEREFORE, in consideration of the premises and the mutual covenants
contained herein, the parties hereby agree as follows:

      1.    Term of Employment. Subject to the terms and conditions hereof, the
            Company will employ the Employee, and the Employee will serve the
            Company, as Chief Operating Officer, for a period beginning on the
            date hereof and terminating three years thereafter, subject to
            extension by mutual agreement of the Company and the Employee (such
            term, as it may be extended, is hereinafter referred to as the "Term
            of Employment").

      2.    Duties. During the Term of Employment, the Employee will serve as
            Chief Operating Officer, subject to the terms of this Agreement and
            the direction and control of the Board of Directors, and/or the
            Chief Executive Officer of the Company. The Employee will, during
            the Term of Employment, serve the Company faithfully, diligently and
            competently and to the best of Employee's ability, and will,
            consistent with the dignity of the office of Chief Operating Officer
            of the Company, hold, in addition to the office of Chief Operating
            Officer, such other offices in the Company to which Employee may be
            appointed or assigned from time to time by the Board of Directors
            and/or the Chief Executive Officer of the Company and will discharge
            such duties in connection therewith. The Employee shall devote all
            of her business time and attention to the performance of the duties
            hereunder.

      3.    Compensation. During the Term of Employment, the Company will pay to
            the Employee as compensation for the performance of Employee's
            duties and obligations hereunder a base salary at the rate of
            $300,000 per annum ("Salary"), payable in equal semi-monthly
            installments. Such Salary shall be reviewed annually by the Board of
            Directors of the Company in accordance with the Company's
            compensation program. In each of the Company's fiscal years during
            the Term of Employment, the Employee shall be eligible to receive a
            cash bonus of up to $75,000, to be awarded at the sole discretion of
            the Board of Directors of the Company. The Board shall use as a
            basis for determining the extent of such bonus awards the attainment
            of stated goals and objectives for the Employee to be set by the
            Compensation Committee of the Board after consultation with the
            Chief Executive Officer.

      4.    Other Benefits. During the Term of Employment:

            A.    The Employee shall be entitled during the Term of Employment
                  to participate in employee benefit plans and programs of the
                  Company to the extent that Employee's position, tenure,
                  salary, age, health and other qualifications make Employee
                  eligible to participate. The Company does not guarantee the
                  adoption or continuance of any particular employee benefit
                  plan or program during the Term of Employment, and the
                  Employee's participation in any such plan or program shall be
                  subject to the provisions,

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Judith S. Hedstrom

                  rules, regulations and laws applicable thereto; provided,
                  however, that during the Term of Employment, the Employee
                  shall be entitled to health and hospital insurance benefits
                  consistent with the past practices of the Company in effect
                  with respect to Company personnel generally.

            B.    The Employee shall be entitled to 4 weeks vacation per year
                  while employed hereunder. Such vacation may be taken by the
                  Employee at such times as do not unreasonably interfere with
                  the business of the Company. The accumulation of annual
                  vacation time earned, but not taken, will be in accordance
                  with the Company policy guidelines. Additional vacation will
                  be earned in accordance with Company policy.

            C.    The Employee previously has received Options to purchase
                  shares of the Company's common stock (the "Common Stock"), as
                  set forth in Stock Option Grant Agreements dated February 13,
                  2002, December 18, 2002, December 10, 2003 and December 7,
                  2004, which agreements are incorporated herein and shall
                  survive the execution of this Agreement. In addition to these
                  Options, the Company shall grant to the Employee an incentive
                  stock option (or to the extent that such option does not
                  qualify as an incentive stock option, a non-qualified stock
                  option), pursuant to the Company's Amended 1995 Stock Option
                  Plan (the "Plan"), to purchase 300,000 shares of Common Stock
                  with an exercise price equal to the closing price of the
                  Common Stock on the date of the grant of the option. Such
                  option shall be in the form of, and on such terms and
                  conditions as provided in, the Company's standard form of
                  Stock Option Grant Agreement in effect as of the date of this
                  Agreement. Such Stock Option Grant Agreement for such option
                  shall provide, on condition that the Employee is employed by
                  the Company on the relevant vesting dates, that such options
                  shall vest in 36 equal monthly installments on the first day
                  of each calendar month commencing as of January 1, 2005.

      5.    Expenses. During the Term of Employment, the Company will reimburse
            the Employee for all travel and other reasonable business expenses
            incident to the rendering of services by the Employee under this
            Agreement, subject to the submission of appropriate vouchers and
            receipts in accordance with the Company's policy from time to time
            in effect. The Employee will initially be based in or near
            Washington, D.C.; provided, however, that the Company anticipates,
            upon the receipt of favorable data from one or more of its pending
            clinical trials, it may request that Employee relocate to the
            Company's principal offices. If the Company requests that Employee
            relocate, the Company shall reimburse Employee for reasonable agreed
            upon costs associated with such relocation. Prior to such
            relocation, Employee shall be required to maintain her own office,
            either in her home or at some other location of her preference, and
            Employee shall be responsible for costs associated with maintaining
            such office; provided, however, the Company shall reimburse Employee
            for such reasonable costs associated with such office as the Company
            may agree upon.

      6.    Death or Disability.

            A.    This Agreement shall be terminated by the death of the
                  Employee. In addition, this Agreement may be terminated by the
                  Board of Directors of the Company if the Employee shall be
                  rendered incapable by illness or any other disability, from
                  complying with the terms, conditions and provisions on
                  Employee's part to be kept, observed and performed for a
                  period in excess of 180 days (whether or not consecutive) or
                  90 days consecutively, as the case may be, during a 12-month
                  period during the Term of Employment ("Disability"). If this
                  Agreement is terminated by reason of Disability of the
                  Employee, the Company shall give written notice to that effect
                  to the Employee in the manner provided herein. In the event
                  that the Employee receives disability insurance benefits paid
                  for by the Company during any period prior to termination of
                  this Agreement pursuant to this Section 6(A), the Employee's
                  Salary shall be reduced by an amount equal to such disability
                  insurance benefits during such period. The Employee is hereby
                  notified that

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Judith S. Hedstrom

                  she is a Key Employee for the purposes of the Family Medical
                  Leave Act and related laws.

            B.    In addition to and not in substitution for any other benefits
                  which may be payable by the Company with respect to the death
                  or Disability of the Employee in the event of such death or
                  Disability, the Salary payable hereunder shall continue to be
                  paid at the then current rate for three months after the
                  termination of employment, and any bonus to which the Employee
                  would have been entitled for the year in which Employee's
                  death occurs shall be pro rated to the date of Employee's
                  death and paid not later than three months after the
                  termination of employment. In the event of the death of the
                  Employee during the Term of this Agreement, the sums payable
                  hereunder shall be paid to Employee's personal representative.

      7.    Disclosure of Information, Inventions and Discoveries. The Employee
            shall promptly disclose to the Company all processes, trademarks,
            inventions, improvements, discoveries and other information related
            to the business of the Company (collectively, "Developments")
            conceived, developed or acquired by Employee alone or with others
            during the Term of Employment or during any earlier period of
            employment by the Company or any predecessor of the Company, whether
            or not during regular working hours or through the use of materials
            or facilities of the Company. All such Developments shall be the
            sole and exclusive property of the Company, and, upon request, the
            Employee shall promptly deliver to the Company all drawings,
            sketches, models and other data and records relating to such
            Developments. In the event any such Development shall be deemed by
            the Company to be patentable, the Employee shall, at the expense of
            the Company, assist the Company in obtaining a patent or patents
            thereon and execute all documents and do all such other acts and
            things necessary or proper to obtain letters of patents and to
            invest in the Company full right, title and interest in and to such
            Developments. Further, the Employee hereby irrevocably appoints the
            Company and its duly authorized officers and agents as her
            attorneys-in-fact to act for and on her behalf for these purposes
            and instead of her, to execute all documents and papers, including
            any application for patent, copyright or mask work, and to do all
            other lawfully permitted acts reasonably necessary to assign or
            otherwise transfer and perfect her right, title and interest in and
            to the Developments to and in the Company, and to obtain, perfect,
            protect and enforce its rights in the Developments.

      8.    Non-Disclosure. The Employee shall not, at any time during or after
            the Term of Employment, divulge, furnish or make accessible to
            anyone (otherwise than in the regular course of business of the
            Company), or use for Employee's own account or for the account of
            any person, any knowledge or information with respect to
            confidential or secret processes, inventions, discoveries,
            improvements, formulae, plans, materials, devices or ideas or other
            know-how, whether patentable or not, with respect to any
            confidential or secret development or research work or with respect
            to any other confidential or secret aspects of the Company's
            business (including, without limitation, customer lists, supplier
            lists and pricing arrangements with customers or suppliers).

      9.    Non-Competition. The Company and the Employee agree that the
            services rendered by the Employee hereunder are unique and
            irreplaceable. The Employee hereby agrees that, during the Term of
            Employment and for a period of one year thereafter, the Employee
            shall not (i) in any geographical area in the United States or in
            those foreign countries where the Company, during the Term of
            Employment, conducts or proposes to conduct business or initiates
            activities, engage or participate in, directly or indirectly
            (whether as an officer, director, employee, partner, consultant,
            holder of an equity or debt investment, lender or in any other
            manner or capacity), or lend Employee's name (or any part or variant
            thereof) to any business which is, or as a result of the Employee's
            engagement or participation would become, competitive with any
            aspect of the business of the Company, such business being the
            commercialization of the measurement, prevention therapy or reversal
            of glucose-

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Judith S. Hedstrom

            mediated non-enzymatic crosslinking of macro-molecules, and such
            other specific technologies in which the Company has, during the
            Term of Employment, initiated significant plans to develop products,
            (ii) deal, directly or indirectly, in a competitive manner with any
            customers doing business with the Company during the Term of
            Employment (except in connection with the performance of the duties
            and obligations of the Employee during the Term of Employment),
            (iii) solicit any officer, director, employee, consultant or agent
            of the Company to become an officer, director, employee, consultant
            or agent of the Employee, Employee's respective affiliates or anyone
            else, and (iv) engage in or participate in, directly or indirectly,
            any business conducted under any name that shall be the same as or
            similar to the name of the Company or any trade name used by it.
            Ownership, in the aggregate, of less than one percent of the
            outstanding shares of capital stock of any corporation with one or
            more classes of its capital stock listed on a national securities
            exchange or publicly traded in the over-the-counter market shall not
            constitute a violation of the foregoing provision.

      10.   Remedies. The Employee acknowledges that irreparable damage would
            result to the Company if the provisions of Sections 7, 8, 9 or 14
            were not specifically enforced, and agrees that the Company shall be
            entitled to any appropriate legal, equitable or other remedy,
            including injunctive relief, in respect to any failure to comply
            with the provisions of Sections 7, 8, 9 or 14.

      11.   Termination for Cause. In addition to any other remedy available to
            the Company, either at law or in equity, the Employee's employment
            with the Company may be terminated by the Board of Directors for
            Cause, which shall include (i) the Employee's conviction for, or
            plea of nolo contendere, to a felony or a crime involving moral
            turpitude, (ii) the Employee's commission of an act of personal
            dishonesty or a breach of fiduciary duty involving personal profit
            in connection with the Employee's employment by the Company, (iii)
            the Employee's commission of an act which the Board of Directors
            shall reasonably have found to have involved willful misconduct or
            gross negligence on the part of the Employee in the conduct of
            Employee's duties under this Agreement, (iv) habitual absenteeism,
            (v) the Employee's material breach of any material provision of this
            Agreement, (vi) the willful and continued failure by the Employee to
            perform substantially Employee's duties with the Company (other than
            any such failure resulting from Employee's incapacity due to
            physical or mental illness), or (vii) the Employee's failure, at any
            time, to relocate to the Company's principal office within a
            reasonable time following the request of the Company. In the event
            of termination under this Section 11, the Company's obligations
            under this Agreement shall cease and the Employee shall forfeit all
            rights to receive any future compensation under this Agreement.
            Notwithstanding any termination of this Agreement pursuant to this
            Section 11, the Employee, in consideration of Employee's employment
            hereunder to the date of such termination, shall remain bound by the
            provisions of Sections 7, 8, 9 and 14 hereof.

      12.   Termination Without Cause. Each of the Company and Employee may
            terminate this Agreement at any time for any reasons whatsoever,
            without any further liability or obligation of the Company to the
            Employee or of the Employee to the Company from and after the date
            of such termination (other than liabilities or obligations accrued
            but unsatisfied on, or surviving, the date of such termination), by
            sending 30 days' prior written notice to the other party. In the
            event that, without Cause, as that term is defined in Section 11,
            and not as a result of the Employee's death or Disability as set
            forth in Section 6 or a Change in Control as set forth in Section
            15, (a) the Company elects to terminate this Agreement prior to the
            end of the Term of Employment, or (b) the Company gives Employee
            notice of its election not to extend the Term of Employment beyond
            the expiration of the then current Term of Employment, or (c) by the
            date which is four months prior to the end of the then current Term
            of Employment, the Company has not offered to extend the then
            current Term of Employment, the Company shall continue to pay the
            Employee the full Salary (exclusive of bonuses, if any) as such
            Salary would have otherwise accrued for a period of twelve (12)
            months. In the event the Employee elects to terminate prior to the
            end of the Term of

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Judith S. Hedstrom

            Employment, the Company's obligation to pay Salary shall cease as of
            the effective date of termination. Notwithstanding any termination
            of this Agreement pursuant to this Section 12, the Employee, in
            consideration of Employee's employment hereunder to the date of such
            termination, shall remain bound by the provisions of Sections 7, 8,
            9 and 14 hereof. Any termination of this Agreement by the Company as
            provided in this Section 12 shall be in addition to, and not in
            substitution for, any rights with respect to termination of the
            Employee which the Company may have pursuant to Section 11.

      13.   Resignation. In the event that the Employee's services under this
            Agreement are terminated under any of the provisions of this
            Agreement (except by death), the Employee agrees to deliver written
            resignation from all positions held with the Company to the Board of
            Directors, such resignation to become effective immediately;
            provided, however, that nothing herein shall be deemed to affect the
            provisions of Sections 7, 8, 9 and 14 hereof relating to the
            survival thereof following termination of the Employee's services
            hereunder, and provided, further, that except as expressly provided
            in this Agreement, the Employee shall be entitled to no further
            compensation hereunder.

      14.   Data. Upon termination of the Term of Employment or termination
            pursuant to Sections 6, 11 or 12 hereof, the Employee or Employee's
            personal representative shall promptly deliver to the Company all
            books, electronic data, memoranda, plans, records and written data
            of every kind relating to the business and affairs of the Company
            which are then in Employee's possession.

      15.   Change in Control. The Employee is an eligible participant in the
            Alteon Inc. Change in Control Severance Benefits Plan (the
            "Severance Plan"). Upon a Change in Control as defined in the
            Severance Plan, the Employee will be entitled to all of the benefits
            to which she would be entitled under the Severance Plan as in effect
            on June 5, 2003, notwithstanding any amendment or termination of the
            Severance Plan or other action by the Board of Directors of the
            Company as permitted under the Severance Plan which may affect the
            Employee's entitlement to benefits thereunder.

      16.   Insurance. The Company shall have the right, at its own cost and
            expense, to apply for and to secure in its own name or otherwise,
            life, health or accident insurance or any or all of them covering
            the Employee, and the Employee agrees to submit to usual and
            customary medical examinations and otherwise to cooperate with the
            Company in connection with the procurement of any such insurance,
            and any claims thereunder.

      17.   Waiver of Breach. Any waiver of any breach of this Agreement shall
            not be construed to be a continuing waiver or consent to any
            subsequent breach on the part either of the Employee or of the
            Company.

      18.   Assignment. This Agreement shall inure to the benefit of and be
            binding upon the successors and assigns of the Company upon any sale
            of all or substantially all of the Company's assets, or upon any
            merger or consolidation of the Company with or into any other
            entity, all as though such successors and assigns of the Company and
            their respective successors and assigns were the Company. Insofar as
            the Employee is concerned, this Agreement, being personal, may not
            be assigned.

      19.   Severability. To the extent any provision of this Agreement shall be
            invalid or unenforceable, it shall be considered deleted therefrom
            and the remainder of such provision and of this Agreement shall be
            unaffected and shall continue in full force and effect. In
            furtherance and not in limitation of the foregoing, should the
            duration or geographical extent of, or business activities covered
            by, any provision of this Agreement be in excess of that which is
            valid and enforceable under applicable law, then such provision
            shall be construed to cover only that duration, extent or activities
            which may be validly covered and enforceable.

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Judith S. Hedstrom

      20.   Notices. All notices, requests and other communications pursuant to
            this Agreement shall be in writing and shall be deemed to have been
            duly given, if delivered in person or by courier, telegraphed,
            telexed or by facsimile transmission or five business days after
            being sent by registered or certified mail, return receipt
            requested, postage paid, addressed as follows:

            If to the Employee:

                         Judith S. Hedstrom
                         7811 Exeter Road
                         Bethesda, Maryland 20814

            If to the Company:

                         Alteon Inc.
                         6 Campus Drive
                         Parsippany, New Jersey 07054

            with a copy to:

                         William Whelan, Esq.
                         Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, PC
                         One Financial Center
                         Boston, MA 02111

            Any party may, by written notice to the other in accordance with
            this Section 20, change the address to which notices to such party
            are to be delivered or mailed.

      21.   General. Except as otherwise provided herein, the terms and
            provisions of this Agreement and any Stock Option Grant Agreements
            entered into between the Employee and the Company shall constitute
            the entire agreement by the Company and the Employee with respect to
            the subject matter hereof, and shall supersede any and all prior
            agreements or understandings between the Employee and the Company,
            whether written or oral. This Agreement may be amended or modified
            only by a written instrument executed by the Employee and the
            Company. This Agreement may be executed in any number of
            counterparts, all of which, when executed, shall be deemed to be an
            original, and all of which together shall constitute one and the
            same instrument.

      IN WITNESS WHEREOF, the parties have executed this Employment Agreement as
of the day and year first above written.

                                   ALTEON INC.

                                   By: /s/ Kenneth I. Moch
                                       -----------------------------------------
                                       Kenneth I. Moch
                                       President and Chief Executive Officer

                                       /s/ Judith S. Hedstrom
                                       -----------------------------------------
                                       Judith S. Hedstrom