Major shareholders.
 
                                                             PERCENTAGE OWNED (1)                                                        ------------------------                                                          BEFORE        AFTER NAME AND ADDRESS OF BENEFICIAL OWNERS     SHARES (1)    OFFERING     OFFERING -----------------------------------------------------  -----------  ----------- Warburg, Pincus Ventures, L.P. (2)........  3,661,638        44.9   466 Lexington Avenue   New York, NY 10017 LF SL Holding LLC (3).....................    555,555         6.9   30 Rockefeller Plaza, 62(nd) Floor   New York, NY 10020 Sheryle J. Bolton (4).....................    349,999         4.2 Dr. Michael M. Merzenich (5)..............    670,574         8.3 Dr. Paula A. Tallal (6)...................    803,843        10.0 Frank M. Mattson (7)......................     73,999           * Dr. William M. Jenkins....................    565,022         7.0 Diane H. Church (8).......................     35,666           * James A. Mills (9)........................     20,332           * Carleton A. Holstrom (10).................    194,449         2.4 Rodman W. Moorhead, III (2)(11)...........  3,661,638        44.9 Dr. Leonard S. Schleifer..................     52,941           * James E. Thomas (2)(11)...................  3,661,638        44.9 David A. Tanner (12)......................    555,555         6.9 All directors and executive    officers as a group (12 persons) (13)...  6,984,068        80.7 
 
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