<TABLE> <S> <C>

<PAGE>
<ARTICLE> 5
<RESTATED>
<MULTIPLIER> 1,000

<S>                             <C>                     <C>                     <C>                     <C>
<C>
<PERIOD-TYPE>                   YEAR                   YEAR                   3-MOS                   6-MOS
9-MOS
<FISCAL-YEAR-END>                          DEC-31-1995             DEC-31-1996             DEC-31-1996             DEC-31-1996
             DEC-31-1996
<PERIOD-END>                               DEC-31-1995             DEC-31-1996             MAR-31-1996             JUN-30-1996
             SEP-30-1996
<CASH>                                           1,427                   2,202                   1,114                     792
                   1,099
<SECURITIES>                                    11,024                  26,394                  23,794                  20,818
                  22,252
<RECEIVABLES>                                      338                     638                     301                     457
                     480
<ALLOWANCES>                                         0                      60                       0                       0
                      60
<INVENTORY>                                         95                      58                     149                     121
                      43
<CURRENT-ASSETS>                                13,039                  29,546                  25,815                  22,722
                  24,268
<PP&E>                                           3,773                   4,160                   3,936                   3,988
                   4,117
<DEPRECIATION>                                   2,350                   3,067                   2,561                   2,761
                   2,958
<TOTAL-ASSETS>                                  14,462                  30,639                  27,370                  24,129
                  25,607
<CURRENT-LIABILITIES>                            5,667                   5,292                   4,245                   3,746
                   1,944
<BONDS>                                              0                       0                       0                       0
                       0
<PREFERRED-MANDATORY>                                0                       0                       0                       0
                       0
<PREFERRED>                                          1                       1                       1                       1
                       1
<COMMON>                                             9                      14                      13                      14
                      15
<OTHER-SE>                                       8,758                  24,332                  23,104                  20,368
                  23,647
<TOTAL-LIABILITY-AND-EQUITY>                    14,462                  30,639                  27,370                  24,129
                  25,607
<SALES>                                            406                     224                      21                      46
                     147
<TOTAL-REVENUES>                                 5,402                   6,265                   2,187                   3,297
                   4,501
<CGS>                                              211                     134                      24                      54
                     129
<TOTAL-COSTS>                                   12,516                  14,216                   3,116                   7,657
                  10,806
<OTHER-EXPENSES>                                     0                       0                       0                       0
                       0
<LOSS-PROVISION>                                     0                       0                       0                       0
                       0
<INTEREST-EXPENSE>                                  11                       6                       2                       4
                       5
<INCOME-PRETAX>                                (6,293)                 (6,709)                   (631)                 (3,761)
                 (5,373)
<INCOME-TAX>                                         0                       0                       0                       0
                       0
<INCOME-CONTINUING>                            (6,293)                 (6,709)                   (631)                 (3,761)
                 (5,373)
<DISCONTINUED>                                       0                       0                       0                       0
                       0
<EXTRAORDINARY>                                      0                       0                       0                       0
                       0
<CHANGES>                                            0                       0                       0                       0
                       0
<NET-INCOME>                                   (6,293)                 (6,709)                   (631)                 (3,761)
                 (5,373)
<EPS-PRIMARY>                                    (.67)                   (.52)                   (.05)                   (.30)
                   (.42)
<EPS-DILUTED>                                    (.67)                   (.52)                   (.05)                   (.30)
                   (.42)


</TABLE>