(1) Dr. Philippe Chambon ("Chambon"), in his capacity as a member of the investment committees 

of DLJCC (as defined below) and of DLJLBO (as defined below), may be deemed to beneficially 

own the shares as to which this Form 4 relates. Dr. Chambon disclaims beneficial ownership 

of such shares except to the extent of his pecuniary interest therein.



Sprout Capital IX, L.P. ("Sprout IX"), Sprout Entrepreneurs Fund, L.P. 

("Sprout Entrepreneurs"), Sprout IX Plan Investors, L.P. ("IX Plan"), Sprout Plan 

Investors, L.P. ("Plan Investors"), Sprout Venture Capital, L.P. ("Sprout Venture") 

and DLJ ESC II, L.P. ("ESC II") are Delaware limited partnerships which make investments 

for long term appreciation. DLJ Capital Corporation ("DLJCC"), a Delaware corporation 

acts as a venture capital partnership management company. DLJCC is also the general partner 

of Sprout Entrepreneurs and Sprout Venture. DLJCC is also the managing general partner of 

Sprout IX and, as such, is responsible for its day-to-day management. DLJCC makes all of 

the investment decisions on behalf of Sprout IX, Sprout Entrepreneurs and Sprout Venture. 

DLJ Associates IX, L.P. ("Associates IX"), a Delaware limited partnership, is a general partner 

of Sprout IX and in accordance with the terms of the relevant partnership agreement, does not 

participate in investment decisions made on behalf of Sprout IX. DLJ Capital Associates IX, 

Inc. ("DLJCA IX"), a Delaware corporation, is the managing general partner of Associates IX. 

Dr. Chambon is a limited partner of Associates IX. DLJ LBO Plans Management Corporation II 

("DLJLBO"), a Delaware corporation, is the general partner of IX Plan and Plan Investors and, 

as such, is responsible for each of their day-to-day management. DLJLBO makes all of the 

investment decisions on behalf of IX Plan and Plan Investors.



(2) Includes (i) 9,375 shares of Common Stock being sold by ESC II, (ii) 2,036 shares 

of Common Stock being sold by DLJCC, (iii) 5,069 shares of Common Stock being sold by 

Plan Investors, (iv) 464 shares of Common Stock being sold by Sprout Entrepreneurs and 

(v) 5,529 shares of Common Stock being disposed of by IX Plan.



(3) Includes (i) 16,782 shares of Common Stock held directly by Plan Investors, (ii) 37,740 

shares of Common Stock held directly by Sprout Venture, (iii) 31,039 shares of Common Stock 

held directly by ESC II, (iv) 993,313 shares of Common Stock held directly by Sprout IX, 

(v) 6,201 shares of Common Stock held directly by Sprout Entrepreneurs, (vi) 73,910 shares 

of Common Stock held directly by IX Plan, (vii) 6,741 shares of Common Stock held directly 

by DLJCC and (x) 54,976 shares of Common Stock held directly by Chambon.