<ARTICLE> 5
<LEGEND>
THIS SCHEDULE CONTAINS SUMMARY FINANCIAL INFORMATION EXTRACTED FROM ONYX
PHARMACEUTICALS, INC.'S UNAUDITED CONDENSED BALANCE SHEET DATED JUNE 30, 1999,
AND UNAUDITED CONDENSED STATEMENT OF OPERATIONS FOR THE SIX MONTHS ENDED JUNE
30, 1999, AND IS QUALIFIED IN ITS ENTIRETY BY REFERENCE TO SUCH FINANCIAL
STATEMENTS.
</LEGEND>
<MULTIPLIER> 1,000

                             
<PERIOD-TYPE>                   6-MOS
<FISCAL-YEAR-END>                          DEC-31-1999
<PERIOD-START>                             JAN-01-1999
<PERIOD-END>                               JUN-30-1999
<CASH>                                          13,398
<SECURITIES>                                     6,564
<RECEIVABLES>                                        0
<ALLOWANCES>                                         0
<INVENTORY>                                          0
<CURRENT-ASSETS>                                20,701
<PP&E>                                          12,038
<DEPRECIATION>                                   8,683
<TOTAL-ASSETS>                                  24,541
<CURRENT-LIABILITIES>                            9,652
<BONDS>                                          3,481
<PREFERRED-MANDATORY>                                0
<PREFERRED>                                          0
<COMMON>                                            12
<OTHER-SE>                                      13,595
<TOTAL-LIABILITY-AND-EQUITY>                    24,541
<SALES>                                              0
<TOTAL-REVENUES>                                 5,027
<CGS>                                                0
<TOTAL-COSTS>                                   13,887
<OTHER-EXPENSES>                                     0
<LOSS-PROVISION>                                     0
<INTEREST-EXPENSE>                                 178
<INCOME-PRETAX>                                (8,357)
<INCOME-TAX>                                         0
<INCOME-CONTINUING>                            (8,357)
<DISCONTINUED>                                       0
<EXTRAORDINARY>                                      0
<CHANGES>                                            0
<NET-INCOME>                                   (8,357)
<EPS-BASIC>                                     (0.73)
<EPS-DILUTED>                                   (0.73)