**Exhibit 10.10**

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Building75, 3rdAvenueCharlestown Navy YardCharlestown, MA 02129Tel: 617/241-5200Fax: 612/241-8780

November 13, 1991

Richard V. Capasso39 Rocky NookMalden, MA 02148

Dear Rick:

This letter will confirm our offer to youto join BioTransplant, Inc. on the following terms:
| Title:        | Controller                                                                                                                                                                                                                                                                               |
|---------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
|          |                                                                                                                                                                                                                                                                                     |
| Terms:        | This  offer is contingent on your starting on or about December 9, 1991.                                                                                                                                                                                                                 |
|          |                                                                                                                                                                                                                                                                                     |
| Compensation: | $65,000  per year/six month review, no guarantee of salary increase.                                                                                                                                                                                                                     |
|          |                                                                                                                                                                                                                                                                                     |
| Bonus:        | Eligible;  with a guaranteed minimum of $5,000 for 1992.                                                                                                                                                                                                                                 |
|          |                                                                                                                                                                                                                                                                                     |
| Equity:       | 10,000  options; subject to approval by the Board of Directors.                                                                                                                                                                                                                          |
|          |                                                                                                                                                                                                                                                                                     |
| Agreements:   | Your  employment is subject to your signing a Confidentiality, Invention Agreement  and a Non-Compete Agreement with BioTransplant and review of any agreement  you may have with others to insure that your employment with BioTransplant is  not in conflict with any such agreements. |

If these terms are acceptable, pleasesign and return one copy of this agreement.

We look forward to your joining thecompany and sharing in our new challenge.

Best regards,

/s/ Elliot LebowitzElliot Lebowitz, Ph.D.President and C.E.O

AGREED TO:
| By:  | /s/  Richard V. Capasso |   | Date:  | 11/14/91 |
|-----------|-------------------------|--------|--------|----------|
|      |                         |   |   |          |
|      | Richard  V. Capasso     |   |   |     |

 

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Building75, 3rdAvenueCharlestown Navy YardCharlestown, MA 02129Tel: 617/241-5200Fax: 612/241-8780

March31, 1996

Mr. Richard Capasso10 Rolling LaneWayland, MA 01778

Dear Rick:

             Referenceis made to the Letter Agreement dated November 13, 1991, by and betweenBioTransplant Incorporated and you (the “Letter Agreement”).  The Letter Agreement is hereby amended toadd the following additional term:

|   | Severance: | In  the event your employment is terminated without cause, you will receive up to  6 months base salary, payable in 12 equal installments which will be  discontinued upon your securing other employment. |
|--------|------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

             Pleasesign below to acknowledge your agreement with the foregoing.

|   | Very  truly yours,                     |
|--------|----------------------------------------|
|   |                                   |
|   | /s/  Elliot Lebowitz                   |
|   |                                        |
|   | Elliot  Lebowitz, Ph.D.                |
|   | President  and Chief Executive Officer |

AGREED:

| By:    | /s/  Richard V. Capasso |
|--------|-------------------------|
|   |                         |
|   | Richard  V. Capasso     |

Date: April 15, 1996