<SUBMISSION>
<ACCESSION-NUMBER>0001104659-04-001014
<TYPE>4
<PUBLIC-DOCUMENT-COUNT>1
<PERIOD>20040114
<FILING-DATE>20040115
<REPORTING-OWNER>
<OWNER-DATA>
<CONFORMED-NAME>GILL AJIT
<CIK>0001236921
</OWNER-DATA>
<FILING-VALUES>
<FORM-TYPE>4
<ACT>34
<FILE-NUMBER>000-24006
<FILM-NUMBER>04527763
</FILING-VALUES>
<MAIL-ADDRESS>
<STREET1>C/O NEKTAR THERAPEUTIC
<STREET2>150 INDUSTRIAL ROAD
<CITY>SAN CARLOS
<STATE>CA
<ZIP>94070
</MAIL-ADDRESS>
</REPORTING-OWNER>
<ISSUER>
<COMPANY-DATA>
<CONFORMED-NAME>NEKTAR THERAPEUTICS
<CIK>0000906709
<ASSIGNED-SIC>2834
<IRS-NUMBER>943134940
<STATE-OF-INCORPORATION>DE
<FISCAL-YEAR-END>1231
</COMPANY-DATA>
<BUSINESS-ADDRESS>
<STREET1>150 INDUSTRIAL RD
<CITY>SAN CARLOS
<STATE>CA
<ZIP>94070
<PHONE>6506313100
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>150 INDUSTRIAL ROAD
<CITY>SAN CARLOS
<STATE>CA
<ZIP>94070
</MAIL-ADDRESS>
<FORMER-COMPANY>
<FORMER-CONFORMED-NAME>INHALE THERAPEUTIC SYSTEMS INC
<DATE-CHANGED>19980723
</FORMER-COMPANY>
<FORMER-COMPANY>
<FORMER-CONFORMED-NAME>INHALE THERAPEUTIC SYSTEMS
<DATE-CHANGED>19940303
</FORMER-COMPANY>
</ISSUER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>a4.xml
<DESCRIPTION>4
<TEXT>
<XML>
<?xml version="1.0" encoding="utf-8"?>
<ownershipDocument>
    <schemaVersion>X0201</schemaVersion>

    <documentType>4</documentType>
  <periodOfReport>2004-01-14</periodOfReport>
  <notSubjectToSection16>0</notSubjectToSection16>
    <issuer>
        <issuerCik>0000906709</issuerCik>
        <issuerName>NEKTAR THERAPEUTICS</issuerName>
        <issuerTradingSymbol>NKTR</issuerTradingSymbol>
  </issuer>
  <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001236921</rptOwnerCik>
            <rptOwnerName>GILL AJIT</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>150 INDUSTRIAL ROAD</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>SAN CARLOS</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94070</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
            <reportingOwnerRelationship>
      <isDirector>1</isDirector>
      <isOfficer>1</isOfficer>
      <isTenPercentOwner>0</isTenPercentOwner>
      <isOther>0</isOther>
      <officerTitle>CEO and President</officerTitle>
    </reportingOwnerRelationship>
  </reportingOwner>
  <nonDerivativeTable>
    <nonDerivativeTransaction>
      <securityTitle>
        <value>Common Stock</value>
      </securityTitle>
      <transactionDate>
        <value>2004-01-14</value>
      </transactionDate>
      <transactionCoding>
        <transactionFormType>4</transactionFormType>
        <transactionCode>M</transactionCode>
        <equitySwapInvolved>0</equitySwapInvolved>
      </transactionCoding>
      <transactionTimeliness>
        <value></value>
      </transactionTimeliness>
      <transactionAmounts>
        <transactionShares>
          <value>33956</value>
        </transactionShares>
        <transactionPricePerShare>
          <value>1.3889</value>
        </transactionPricePerShare>
        <transactionAcquiredDisposedCode>
          <value>A</value>
        </transactionAcquiredDisposedCode>
      </transactionAmounts>
      <postTransactionAmounts>
        <sharesOwnedFollowingTransaction>
          <value>105962</value>
        </sharesOwnedFollowingTransaction>
      </postTransactionAmounts>
      <ownershipNature>
        <directOrIndirectOwnership>
          <value>I</value>
        </directOrIndirectOwnership>
        <natureOfOwnership>
          <value>See Footnote</value>
          <footnoteId id="F1"/>
        </natureOfOwnership>
      </ownershipNature>
    </nonDerivativeTransaction>
    <nonDerivativeTransaction>
      <securityTitle>
        <value>Common Stock</value>
      </securityTitle>
      <transactionDate>
        <value>2004-01-14</value>
      </transactionDate>
      <transactionCoding>
        <transactionFormType>4</transactionFormType>
        <transactionCode>M</transactionCode>
        <equitySwapInvolved>0</equitySwapInvolved>
      </transactionCoding>
      <transactionTimeliness>
        <value></value>
      </transactionTimeliness>
      <transactionAmounts>
        <transactionShares>
          <value>32400</value>
        </transactionShares>
        <transactionPricePerShare>
          <value>2.7778</value>
        </transactionPricePerShare>
        <transactionAcquiredDisposedCode>
          <value>A</value>
        </transactionAcquiredDisposedCode>
      </transactionAmounts>
      <postTransactionAmounts>
        <sharesOwnedFollowingTransaction>
          <value>138362</value>
        </sharesOwnedFollowingTransaction>
      </postTransactionAmounts>
      <ownershipNature>
        <directOrIndirectOwnership>
          <value>I</value>
        </directOrIndirectOwnership>
        <natureOfOwnership>
          <value>See Footnote</value>
          <footnoteId id="F1"/>
        </natureOfOwnership>
      </ownershipNature>
    </nonDerivativeTransaction>
    <nonDerivativeTransaction>
      <securityTitle>
        <value>Common Stock</value>
      </securityTitle>
      <transactionDate>
        <value>2004-01-14</value>
      </transactionDate>
      <transactionCoding>
        <transactionFormType>4</transactionFormType>
        <transactionCode>M</transactionCode>
        <equitySwapInvolved>0</equitySwapInvolved>
      </transactionCoding>
      <transactionTimeliness>
        <value></value>
      </transactionTimeliness>
      <transactionAmounts>
        <transactionShares>
          <value>18000</value>
        </transactionShares>
        <transactionPricePerShare>
          <value>3.125</value>
        </transactionPricePerShare>
        <transactionAcquiredDisposedCode>
          <value>A</value>
        </transactionAcquiredDisposedCode>
      </transactionAmounts>
      <postTransactionAmounts>
        <sharesOwnedFollowingTransaction>
          <value>156362</value>
        </sharesOwnedFollowingTransaction>
      </postTransactionAmounts>
      <ownershipNature>
        <directOrIndirectOwnership>
          <value>I</value>
        </directOrIndirectOwnership>
        <natureOfOwnership>
          <value>See Footnote</value>
          <footnoteId id="F1"/>
        </natureOfOwnership>
      </ownershipNature>
    </nonDerivativeTransaction>
  </nonDerivativeTable>
  <derivativeTable>
    <derivativeTransaction>
      <securityTitle>
        <value>Employee Stock Option (right to buy)</value>
      </securityTitle>
      <conversionOrExercisePrice>
        <value>1.3889</value>
      </conversionOrExercisePrice>
      <transactionDate>
        <value>2004-01-14</value>
      </transactionDate>
      <transactionCoding>
        <transactionFormType>4</transactionFormType>
        <transactionCode>M</transactionCode>
        <equitySwapInvolved>0</equitySwapInvolved>
      </transactionCoding>
      <transactionTimeliness>
        <value></value>
      </transactionTimeliness>
      <transactionAmounts>
        <transactionShares>
          <value>33956</value>
        </transactionShares>
        <transactionPricePerShare>
          <value>0.00</value>
        </transactionPricePerShare>
        <transactionAcquiredDisposedCode>
          <value>D</value>
        </transactionAcquiredDisposedCode>
      </transactionAmounts>
      <exerciseDate>
        <value>1994-01-28</value>
        <footnoteId id="F2"/>
      </exerciseDate>
      <expirationDate>
        <value>2004-01-28</value>
      </expirationDate>
      <underlyingSecurity>
        <underlyingSecurityTitle>
          <value>Common Stock</value>
        </underlyingSecurityTitle>
        <underlyingSecurityShares>
          <value>33956</value>
        </underlyingSecurityShares>
      </underlyingSecurity>
      <postTransactionAmounts>
        <sharesOwnedFollowingTransaction>
          <value>0</value>
        </sharesOwnedFollowingTransaction>
      </postTransactionAmounts>
      <ownershipNature>
        <directOrIndirectOwnership>
          <value>I</value>
        </directOrIndirectOwnership>
        <natureOfOwnership>
          <value>See Footnote</value>
          <footnoteId id="F1"/>
        </natureOfOwnership>
      </ownershipNature>
    </derivativeTransaction>
    <derivativeTransaction>
      <securityTitle>
        <value>Employee Stock Option (right to buy)</value>
      </securityTitle>
      <conversionOrExercisePrice>
        <value>2.7778</value>
      </conversionOrExercisePrice>
      <transactionDate>
        <value>2004-01-14</value>
      </transactionDate>
      <transactionCoding>
        <transactionFormType>4</transactionFormType>
        <transactionCode>M</transactionCode>
        <equitySwapInvolved>0</equitySwapInvolved>
      </transactionCoding>
      <transactionTimeliness>
        <value></value>
      </transactionTimeliness>
      <transactionAmounts>
        <transactionShares>
          <value>32400</value>
        </transactionShares>
        <transactionPricePerShare>
          <value>0.00</value>
        </transactionPricePerShare>
        <transactionAcquiredDisposedCode>
          <value>D</value>
        </transactionAcquiredDisposedCode>
      </transactionAmounts>
      <exerciseDate>
        <value>1994-01-31</value>
        <footnoteId id="F2"/>
      </exerciseDate>
      <expirationDate>
        <value>2004-01-31</value>
      </expirationDate>
      <underlyingSecurity>
        <underlyingSecurityTitle>
          <value>Common Stock</value>
        </underlyingSecurityTitle>
        <underlyingSecurityShares>
          <value>32400</value>
        </underlyingSecurityShares>
      </underlyingSecurity>
      <postTransactionAmounts>
        <sharesOwnedFollowingTransaction>
          <value>0</value>
        </sharesOwnedFollowingTransaction>
      </postTransactionAmounts>
      <ownershipNature>
        <directOrIndirectOwnership>
          <value>I</value>
        </directOrIndirectOwnership>
        <natureOfOwnership>
          <value>See Footnote</value>
          <footnoteId id="F1"/>
        </natureOfOwnership>
      </ownershipNature>
    </derivativeTransaction>
    <derivativeTransaction>
      <securityTitle>
        <value>Employee Stock Option (right to buy)</value>
      </securityTitle>
      <conversionOrExercisePrice>
        <value>3.125</value>
      </conversionOrExercisePrice>
      <transactionDate>
        <value>2004-01-14</value>
      </transactionDate>
      <transactionCoding>
        <transactionFormType>4</transactionFormType>
        <transactionCode>M</transactionCode>
        <equitySwapInvolved>0</equitySwapInvolved>
      </transactionCoding>
      <transactionTimeliness>
        <value></value>
      </transactionTimeliness>
      <transactionAmounts>
        <transactionShares>
          <value>18000</value>
        </transactionShares>
        <transactionPricePerShare>
          <value>0.00</value>
        </transactionPricePerShare>
        <transactionAcquiredDisposedCode>
          <value>D</value>
        </transactionAcquiredDisposedCode>
      </transactionAmounts>
      <exerciseDate>
        <value>1994-06-16</value>
        <footnoteId id="F2"/>
      </exerciseDate>
      <expirationDate>
        <value>2004-06-16</value>
      </expirationDate>
      <underlyingSecurity>
        <underlyingSecurityTitle>
          <value>Common Stock</value>
        </underlyingSecurityTitle>
        <underlyingSecurityShares>
          <value>18000</value>
        </underlyingSecurityShares>
      </underlyingSecurity>
      <postTransactionAmounts>
        <sharesOwnedFollowingTransaction>
          <value>0</value>
        </sharesOwnedFollowingTransaction>
      </postTransactionAmounts>
      <ownershipNature>
        <directOrIndirectOwnership>
          <value>I</value>
        </directOrIndirectOwnership>
        <natureOfOwnership>
          <value>See Footnote</value>
          <footnoteId id="F1"/>
        </natureOfOwnership>
      </ownershipNature>
    </derivativeTransaction>
  </derivativeTable>
  <footnotes>
    <footnote id="F1">By The Ajit S &amp; Ann C Gill 1998 Family Trust dtd 10/14/1998</footnote>
    <footnote id="F2">Fully vested</footnote>
  </footnotes>
  <ownerSignature>
    <signatureName>/s/ Paula S. Kasler, by power of attorney</signatureName>
    <signatureDate>2004-01-14</signatureDate>
  </ownerSignature>
</ownershipDocument>

</XML>
</TEXT>
</DOCUMENT>
</SUBMISSION>
