Exhibit 10.1

SEPARATION AGREEMENT AND GENERAL RELEASE

This Agreement dated as of May 16, 2001 is by and between Genzyme
Transgenics Corporation ("GTC"), its predecessors, subsidiaries, successors,
related and affiliated companies, assigns, officers, directors, stockholders,
agents, and executives (hereinafter referred to collectively with GTC as the
"Company") and Sandra Nusinoff Lehrman, M.D., her executors, heirs,
administrators, and assigns (hereinafter referred to as "Executive"). In
consideration of the mutual covenants contained herein, the parties agree as
follows:

1. RESIGNATION. Executive hereby resigns as President and Chief Executive
Officer, and as a director, of GTC, effective as of the date of this Agreement.
Executive's employment with the Company shall terminate at the close of business
on May 25, 2001 (the "Termination Date"). Effective immediately, Executive will
not take any action on behalf of the Company except at the specific request of
the Board. Executive shall not be required to report for work prior to the
Termination Date but shall make herself reasonably available to the Board for
consultation. Effective immediately, Executive hereby resigns from all offices
she holds in any corporations or other entities affiliated with or related to
GTC.

2. SEVERANCE PAYMENT. For purposes of calculating the severance payment,
Executive's resignation shall be treated as a termination without cause under
Section 4.1(b) of Executive's Employment Agreement. Executive will receive a
total severance equal to $820,383.56 paid in substantially equal installments in
accordance with the Company's standard payroll practices over the twenty-four
month period beginning after the Termination Date (the "Severance Period"). This
payment includes twenty-four (24) months of Executive's base salary at the time
of termination ($380,000 on an annualized basis) plus a bonus equal to
$60,383.56 ($152,000 prorated for the portion of 2001 that Executive is employed
by the Company through the Termination Date). Executive acknowledges and agrees
that this payment fully satisfies any severance obligation contained in her
employment contract dated as of July 1, 1998, as amended to date.

3. ADDITIONAL CONSIDERATION. Within fourteen days after the Company receives a
copy of this Agreement signed by Executive, the Company will deliver to
Executive an option to purchase 100,000 shares of GTC common stock at an
exercise price of $6.70 per share. This option shall be fully vested upon grant
and shall be subject to the same terms and conditions as the Company's other
nonstatutory stock options except that this option shall be exercisable for
three years from the date of the grant notwithstanding termination of
Executive's employment with the Company.

4. INSURANCE AND OTHER BENEFITS

a. HEALTH AND DENTAL INSURANCE. Subject to any restrictions in the
applicable policy, the Company shall continue at its sole expense, Executive's
family health and dental benefits during the Severance Period on the same basis
as for active employees unless notified in writing that coverage is no longer
necessary. If Executive cannot continue as part of the group plan, the Company
will obtain substantially equivalent coverage.

b. LIFE INSURANCE COVERAGE. The Company shall continue to provide
Executive with the existing group life insurance coverage during the Severance
Period. If the Company cannot continue the existing group coverage, the Company
will secure comparable coverage.

c. RETIREMENT PLANS. Executive shall continue to participate in GTC's
retirement plans during the Severance Period. If such continuation is not
permitted under the relevant plan, the Company will provide Executive with a
lump sum payment equal to the amount of the Company's contribution on the same
basis as during her active employment.

d. OUTPLACEMENT SERVICES. In order to assist Executive with her
departure from GTC, GTC will pay for the services of a professional outplacement
firm that is mutually satisfactory to the parties during the Severance Period to
assist her in securing new employment.

e. VACATION PAY. Executive will receive payment for 118.3 accrued
vacation hours.

f. CESSATION OF BENEFITS. Unless otherwise provided for expressly in
this Agreement, all other benefits will cease as of the Termination Date,
including without limitation, the accrual of vacation time.

STOCK OPTIONS. As of the Termination Date all further vesting under
Executive's currently outstanding stock options set forth below will cease and
such options will be exercisable in accordance with their terms for a period of
90 days after the Termination Date:

OPTION GRANT DATE EXERCISE PRICE TOTAL SHARES VESTED SHARES
- --------------------------------------------------------------------------------------------

July 1, 1998 $7.75 150,000 90,000
- --------------------------------------------------------------------------------------------
May 25, 1999 $4.5625 85,000 51,000
- --------------------------------------------------------------------------------------------
May 24, 2000 $17.3125 85,000 34,000
- --------------------------------------------------------------------------------------------
March 14, 2001 $5.0312 150,000 30,000
- --------------------------------------------------------------------------------------------

- --------------------------------------------------------------------------------------------

Executive has until 90 days after the Termination Date to exercise any
of the foregoing options that are exercisable as of the Termination Date.

5. RETURN OF PROPERTY. Executive immediately shall cease to use and shall return
all papers, files, documents, computers, reference guides, equipment, keys,
identification, credit cards, software, computer access codes, disks and
institutional manuals, and any other property belonging to the Company on or
before the Termination Date. Executive shall not retain any copies, duplicates,
reproductions or excerpts thereof.

6. NONDISCLOSURE OF CONFIDENTIAL INFORMATION. Executive acknowledges that during
the course of her employment with the Company she has become acquainted with
and/or developed confidential information belonging to the Company and its
customers. Executive agrees not to use to her own advantage or to disclose to
any person or entity any confidential information of the Company or of any past
or present customer of the Company, including but not limited to

financial data or projections, customer lists, projects, economic information,
systems, plans, methods, procedures, operations, techniques, know-how, trade
secrets or merchandising or marketing strategies. In addition, Executive shall
continue to be bound by the provision of her agreement pertaining to
confidential information.

7. MUTUAL GENERAL RELEASE. In consideration of the payment of Severance Pay and
other benefits set forth in this Agreement, Executive for herself, executors,
heirs, administrators, assigns, and anyone else claiming by, through or under
her, and the Company irrevocably and unconditionally, release, and forever
discharge each other with respect to any and all debts, demands, actions, causes
of action, suits, covenants, contracts, wages, bonuses, damages and any and all
claims, demands, liabilities, and expenses (including attorneys' fees and costs)
whatsoever of any name or nature both in law and in equity ("Claim") which
either now has, ever had or may in the future have against the other by reason
of any matter, cause or thing which has happened, developed or occurred before
the signing of this Agreement, including, but not limited to, any and all suits
in tort or contract, and any Claims or suits relating to salary, wages, bonuses
and commissions, the breach of an oral or written contract, misrepresentation,
defamation, and interference with prospective economic advantage, interference
with contract, intentional and negligent infliction of emotional distress,
negligence, breach of the covenant of good faith and fair dealing, and Claims
arising out of, based on, or connected with her employment by the Company and
the termination of that employment as set forth in this Agreement, including any
causes of action or Claims for unlawful employment discrimination of any kind,
arising under or based on Title VII of the Civil Rights Act of 1964, as amended;
the Age Discrimination in Employment Act, as amended; the Equal Pay Act of 1963;
the Massachusetts Fair Employment Practices Act M.G.L. c.151B et seq.; the
Massachusetts Civil Rights Act; the Massachusetts Equal Rights Law and any other
state or federal equal employment opportunity or anti-discrimination law,
policy, order or regulation affecting or relating to Claims or rights of
Executive, which Executive ever had, now has, or claims to have against the
Company. Subject to the provisions of Section 12, Executive and the Company
further agree not to institute any charge, complaint, or lawsuit to challenge
the validity of this Agreement or the circumstances surrounding its execution.
Executive waives any right or claim to reinstatement or re-employment by the
Company. Nothing in this Agreement shall preclude any action by the Executive or
the Company to enforce their respective rights under this Agreement.

8. NONADMISSIONS CLAUSE. It is understood and agreed that this Agreement does
not constitute any admission by the Company that any action taken with respect
to Executive was unlawful or wrongful, or that such action constituted a breach
of contract or violated any federal or state law, policy, rule or regulation.

9. NONDISCLOSURE OF THIS AGREEMENT. Executive expressly agrees, and hereby
instructs her attorney, accountant, or tax advisor and immediate family, if any,
that the nature and terms of this Agreement are confidential, and expressly
agrees not to discuss or disclose them, or the facts and contentions contained
therein, without the prior written consent of the Company, with or to any
person, except to the Internal Revenue Service, state tax authorities, her
accountant or tax advisor, her attorneys, her immediate family, or as required
by law. Executive may share with future employers information concerning her
obligations with respect to confidential and proprietary information.

10. NON-DISPARAGEMENT. Executive agrees that she will not disparage or make
negative statements about the Company or any of its officers, directors, agents,
executives, successors and assigns, programs or products. The Company agrees to
instruct its officers and directors not to make any statement that disparages
Executive.

11. RECOMMENDATION. The Company will, in good faith, use all reasonable efforts
to direct all requests for information about Executive received from prospective
employers to a single officer of the Company, who shall initially be John B.
Green. The Company agrees to develop and review with Executive a verbal
reference to be provided by the designated officer of the Company in response to
any such requests.

12. BREACH. In the event that either party institutes legal proceedings to
enforce this Agreement, each agrees that the sole remedy available shall be
enforcement of the terms of this Agreement and/or a claim for damages resulting
from the breach of this Agreement, including reasonable attorney's fees incurred
in such proceedings but that under no circumstances shall either be entitled to
receive or collect any damages for claims that has been released under this
Agreement in accordance with the General Release contained in Section 7 of this
Agreement.

13. REPRESENTATIONS. Executive acknowledges that in exchange for entering into
this Agreement she has received good and valuable consideration in excess of
that to which she would otherwise have been entitled in the absence of this
Agreement. This consideration includes, but is not limited to, the Additional
Consideration described in Section 3. Executive further acknowledges the
sufficiency of that consideration.

14. TIME TO CONSIDER AGREEMENT. Executive acknowledges that she has been advised
in writing to consult with an attorney and has had ample opportunity to consult
with and review this Agreement with an attorney of her choice and has been given
a period of at least twenty-one (21) days within which to consider whether to
sign this Agreement. Executive may sign this Agreement prior to the end of this
twenty-one (21) day period.

15. REVOCATION. It is agreed and understood that for a period of seven (7) days
following the execution of this Agreement, which period shall end at 5:00 p.m.
on the seventh day following the date of execution, Executive may revoke this
Agreement. This Agreement will not become effective or enforceable until this
revocation period has expired.

16. SEVERABILITY. If any of the terms of this Agreement shall be held to be
invalid and unenforceable, the remaining terms of this Agreement are severable
and shall not be affected thereby.

17. ENTIRE AGREEMENT. This Agreement and its Exhibits constitutes the entire
agreement between the parties about or relating to Executive's termination of
employment from the Company, or the Company's obligations to her with respect to
her termination and fully supersedes any and all prior agreements or
understanding between the parties except for the obligations with respect to
inventions, intellectual property, proprietary information and non-solicitation,
which remains in full force and effect. The terms of this Agreement are
contractual in nature and not a mere recital, and they shall take effect as a
sealed document. This Agreement shall be governed by the laws of the
Commonwealth of Massachusetts, and may not be changed

orally, but only by agreement in writing signed by both parties. The parties
attest that no other representations were made regarding this Agreement other
than those contained herein.

18. COUNTERPARTS. This Agreement may be executed in any number of counterparts,
each of which when executed and delivered constitutes an original of this
Agreement, but all the Counterparts shall together constitute one and the same
agreement. No counterpart shall be effective until each party has executed at
least one counterpart.

GENZYME TRANSGENICS CORPORATION

By: /s/ Francis J. Bullock
---------------------------
Name: Francis J. Bullock
Title: Director and Chairman,
Compensation Committee

EXECUTIVE:

/s/ Sandra Nusinoff Lehrman
-------------------------------
Sandra Nusinoff Lehrman, M.D.