**Exhibit 10.12**

Effective as of May 15, 2001

Mr. Walter Ogier433 Main StreetWinchester, MA  01890

Dear Walter:

I am writing to confirm our offer to youfor a position as President and Chief Operating Officer, reporting to ElliotLebowitz, Ph.D., Chief Executive Officer. We are pleased to offer you a starting salary of $20,130.00 per month(equivalent to $241,560.00 per year), to be paid semi-monthly and reviewedannually.  The monthly salary includesan allowance to help offset contributions to certain benefits should you electthem.  You are also eligible for anannual cash bonus of 35% of base salary and to participate in our annualmerit-based stock option program, provided that any award of options will besubject to the approval of our Board of Directors**.**You are also entitled toreceive shares of BTI common stock in accordance with the terms and conditionsof the Eligix, Inc. Management Equity Incentive Plan. In addition, you willreceive medical and dental insurance, 15% of the cost of which is contributedby the employee.  Term life insurance,equivalent to one times your annual salary, and parking will be provided by thecompany without employee contribution. Long-term disability insurance isprovided, 100% of the cost is contributed by the employee (your annual premiumwould be approximately $1,416.00).  Youwill also be entitled to three weeks paid vacation accrued on an annual basisand 11 paid holidays per year.  In theevent your employment is terminated by Biotransplant without cause, you would receiveup to 12 months double base salary, payable in 24 equal semi-monthlyinstallments, which would be discontinued upon your securing other employment.

Your employment is subject to yoursigning an Invention, Non-Disclosure and Non-Compete Agreement withBioTransplant, in the form previously provided to you, and review of anyagreement you may have with others to insure that your employment withBioTransplant is not in conflict with any such agreements.

Also, this offer is contingent upon yourability to provide proof of your legal right to work in the United States, asdefined by Federal regulations.

By signing this letter below, youacknowledge that the foregoing offered terms of your employment withBioTransplant do not constitute (i) a significant diminution of your duties,responsibilities, power, title or office in effect at Eligix, Inc. immediatelyprior to your acceptance of this offer or (ii) a material reduction in yourcompensation (including without limitation, salary, bonuses, options and benefits)or material change in your manner of compensation (including withoutlimitation, the timing of any salary or bonus payments) in effect for you atEligix, Inc. immediately prior to your acceptance of this offer.

If you agree to the terms outlined above,please sign both copies of this letter and return one copy using the enclosed,stamped envelope.

We look forward to your joiningBioTransplant. We are confident that you will make a significant contributionto BioTransplant's future success.

Sincerely,

/s/ Elliot LebowitzElliot Lebowitz, Ph.D.President and CEO

Accepted and Agreed to:

| /s/  Walter C. Ogier        |   |                     |
|-----------------------------|--------|--------------------------|
|                             |   |                     |
| Name:  Walter C. Ogier |   | Date:  May 15, 2001 |