<TABLE> <S> <C>
<PAGE>
<ARTICLE> 5
<LEGEND>
THIS SCHEDULE CONTAINS SUMMARY FINANCIAL INFORMATION EXTRACTED FROM ONYX
PHARMACEUTICALS, INC.'S UNAUDITED CONDENSED BALANCE SHEET DATED
SEPTEMBER 30, 2000, AND UNAUDITED CONDENSED STATEMENT OF OPERATIONS FOR
THE NINE MONTHS ENDED SEPTEMBER 30, 2000, AND IS QUALIFIED IN ITS ENTIRETY
BY REFERENCE TO SUCH FINANCIAL STATEMENTS.
</LEGEND>
<MULTIPLIER> 1,000
<S> <C>
<PERIOD-TYPE> 9-MOS
<FISCAL-YEAR-END> DEC-31-2000
<PERIOD-START> JAN-01-2000
<PERIOD-END> SEP-30-2000
<CASH> 25,897
<SECURITIES> 7,334
<RECEIVABLES> 4,820
<ALLOWANCES> 0
<INVENTORY> 0
<CURRENT-ASSETS> 38,956
<PP&E> 13,418
<DEPRECIATION> 10,204
<TOTAL-ASSETS> 42,548
<CURRENT-LIABILITIES> 9,428
<BONDS> 733
0
0
<COMMON> 14
<OTHER-SE> 32,148
<TOTAL-LIABILITY-AND-EQUITY> 42,548
<SALES> 0
<TOTAL-REVENUES> 19,842
<CGS> 0
<TOTAL-COSTS> 25,503
<OTHER-EXPENSES> 0
<LOSS-PROVISION> 0
<INTEREST-EXPENSE> 120
<INCOME-PRETAX> (4,146)
<INCOME-TAX> 0
<INCOME-CONTINUING> (4,146)
<DISCONTINUED> 0
<EXTRAORDINARY> 0
<CHANGES> 0
<NET-INCOME> (4,146)
<EPS-BASIC> (0.30)
<EPS-DILUTED> (0.30)
</TABLE>