$4,989.06 Boston, Massachusetts October 18, 1995
FOR VALUE RECEIVED, the undersigned, Scott M. Rocklage (the "Maker"), by this Promissory Note (this
"Note"), absolutely and unconditionally promises to pay to the order of CUBIST PHARMACEUTICALS,
INC., a Delaware corporation (the "Payee"), the aggregate principal amount of Four Thousand Nine Hundred
Eighty Nine Dollars and Six Cents ($5,989.06) on November 28, 1997 (the "Maturity Date"), and to pay interest
on the principal amount outstanding from time to time hereunder, from the date hereof through and including the
date on which such principal amount is paid in full, at a rate of four percent (4%) per annum simple interest.
Interest hereunder shall be due and payable on the first anniversary hereof, the second anniversary hereof and on
the Maturity Date or any accelerated maturity hereof.
The Maker shall have the right to prepay the unpaid principal amount of this Note in full at any time, or in part
from time to time, without premium or prepayment penalty, provided that there is paid with each such principal
prepayment all accrued and unpaid interest to the date of prepayment (calculated on the basis of a 365-day year
for the actual number of days for which the same is due).
All payments of interest and principal hereunder shall be made at the principal residence or business address of
the holder hereof. All payments hereunder shall be applied first to any unpaid accrued interest, second to
payment of all, if any, other amounts except principal due under or in respect of this Note, and third to repayment
This Note is made and delivered by the Maker to the Payee pursuant to that certain letter agreement, dated
October 18, 1995, between the Payee and the Maker.
Anything implied herein to the contrary notwithstanding, in the event that (1) the Maker shall fail to pay when due
all or any portion of the principal of or interest on this Note, (2) the Maker shall make an assignment of the whole
or a substantial