Exhibit 10.22

VIA TELECOPY and FEDERAL EXPRESS

December 30, 2005

Ms. Catharine Newberry

RR#1 Box 1368D Cherry Valley Road

Stroudsburg, PA 18360

Dear Catharine:

It is my pleasure to submit to you this offer of employment with The Medicines Company (the “Company”). Everyone with whom you’ve met is enthusiastic about your joining us and I firmly believe that your background, qualifications, management and leadership credentials will strongly contribute to our business.

On behalf of the Company, I have set forth below the terms of your employment.

1. You will be employed to serve on a full-time basis as Senior Vice President responsible for human strategy, reporting to me. Your anticipated start date is February 1, 2005.

2. Your base salary will be $11,354.17 per pay period (semi-monthly) (annualized rate of $272,500.00).

3. You will be granted options to purchase 100,000 shares of Common Stock of the Company at an exercise price equal to the closing price of the stock on your first day of employment. The options will be subject to a vesting schedule, with 25% of the options vesting one year from your start date, and the

remainder of the options vesting in equal amounts monthly over the then following 3 years.

4. Based on the Company meeting its goals and your meeting your personal performance goals, and at the sole discretion of the Board of Directors, your target bonus shall be 40% of your annual base salary.

Generally this level of bonus would be anticipated if you meet all of the goals set for you and if the Company meets all of its annual business goals. To begin, your individual goals would be set in two steps. First, a set of “90-day objectives” which we will discuss and agree on during the first days of your employment. Second, a set of “2006 annual goals” which we can agree after consideration during the first 90-days of employment. Both sets of goals will take into account the overall Company goals. In subsequent years, we anticipate annual appraisal of the Company’s and of your performance at the end of each calendar year with goal-setting just before the beginning of each calendar year. We believe this should be a collaborative process. At this level of employment, we find that dialogue with the Board of Directors is very useful for performance management.

5. You will be entitled to receive on your start date an agreement from the Company providing severance pay, reimbursement of health care premiums and accelerated stock option vesting in the event that (i) the Company terminates your employment without Cause (as defined in the agreement) or (ii) you terminate your employment for Good Reason (as defined in the agreement). A form of the agreement is enclosed for your review.

6. You will be entitled to participate in any and all benefit programs that the Company establishes and makes available to its employees from time to time, including but not limited to, health insurance, life insurance and disability insurance, to the extent you meet all eligibility requirements for participation.

You have indicated that, in light of the health care benefits that are currently available to you and which you anticipate will remain available, you do not plan to participate in the Company’s health insurance programs. We have agreed that, as long as that is the case, the Company will reimburse you the cost of your existing physical examination program once every two years. We can revise this arrangement if circumstances change.

7. You will be entitled to four weeks weeks of paid vacation per calendar year.

8. You will be required to abide by the rules and regulations of the Company. Your employment with the Company will be “at will;” both the Company and you have the right to terminate the employment at any time for any lawful reason.

9. You will be required to execute two agreements on or before your start date: (i) an Invention and Non-disclosure Agreement, and (ii) a Non-Competition and Non-Solicitation Agreement, forms of both of which are enclosed with this letter.

This offer is contingent upon your successful completion of the Company’s preliminary drug screen and successful completion of all

other facets of the Company’s pre-employment screening process. Also, as a condition of employment you are to present proof of your identity and your eligibility to work in the United States, as required by United States Immigration and Naturalization.

By accepting this offer, you confirm that (i) your work for the Company in the position offered will not violate any non-competition or other agreement with other employers, and (ii) you will not violate any obligation not to use or disclose confidential information obtained from other employers.

This offer letter supersedes and cancels all prior oral and written negotiations, agreements and commitments. This is an offer letter and is not a contract of employment for a particular duration or period.

If this letter sets forth the terms under which you agree to be employed by the Company, please your acceptance and agreement by signing the enclosed copy of this letter in the space provided below.

Very truly yours,

/s/ Clive Meanwell

Clive Meanwell
Chairman and Chief Executive Officer

The foregoing correctly sets forth the terms of my employment by The Medicines Company.

/s/ Catharine Newberry
CATHARINE NEWBERRY