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Exhibit 10.23

AMENDMENT NO. 1
TO THE
VERTEX PHARMACEUTICALS INCORPORATED
2006 STOCK AND OPTION PLAN

Effective February 7, 2008, the Vertex Pharmaceuticals Incorporated 2006 Stock
and Option Plan (the "Plan") hereby is amended as follows:

Section 3 of the Plan is deleted in its entirety and the following is
substituted therefor:

3. SHARES SUBJECT TO THE PLAN

        The number of Shares subject to this Plan as to which Stock Rights may
be granted from time to time shall be (i) 7,350,000 or the equivalent of such
number of Shares after the Administrator, in its sole discretion, has
interpreted the effect of any stock split, stock dividend, combination,
recapitalization or similar transaction in accordance with Section 17 of this
Plan plus (ii) subject to the limitations set forth in this Section 3, 536,625
or the equivalent of such number of Shares after the Administrator, in its sole
discretion, has interpreted the effect of any stock split, stock dividend,
combination, recapitalization or similar transaction in accordance with Section
17 of this Plan. Until the date on which the stockholders of the Company approve
an amendment to the Plan (an "Amendment") approving the increase in the number
of Shares contemplated by Section 3(ii) above, the Shares subject to the Stock
Rights authorized pursuant to Section 3(ii) above (A) shall be segregated from
Shares subject to other Awards issued under the Plan and (B) may only be issued
pursuant to Non-Qualified Stock Options that will not vest prior to stockholder
approval of the Amendment and will terminate if stockholder approval of the
Amendment is not obtained at or before the Company's 2009 Annual Meeting of
Stockholders. The number of Shares subject to this Plan shall be reduced, share
for share, by the number of shares underlying Stock Rights, if any, that are
granted under the Company's 1996 Stock and Option Plan after March 22, 2006.

        If an Option granted hereunder ceases to be outstanding, in whole or in
part (other than by exercise), or if the Company shall reacquire (at no more
than its original issuance price) any Shares issued pursuant to a Stock Grant,
or if any Stock Right expires or is forfeited, cancelled or otherwise terminated
or results in any Shares not being issued, the unissued Shares that were subject
to such Stock Right shall again be available for issuance from time to time
pursuant to this Plan.

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Exhibit 10.23