<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0609</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2026-08-03</periodOfReport>

    <notSubjectToSection16>true</notSubjectToSection16>

    <issuer>
        <issuerCik>0001563577</issuerCik>
        <issuerName>Galera Therapeutics, Inc.</issuerName>
        <issuerTradingSymbol>GRTX</issuerTradingSymbol>
        <issuerForeignTradingSymbol></issuerForeignTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001553053</rptOwnerCik>
            <rptOwnerName>Alleva Lawrence M</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerNonUSAddressFlag>false</rptOwnerNonUSAddressFlag>
            <rptOwnerStreet1>C/O GALERA THERAPEUTICS, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>101 LINDENWOOD DRIVE, SUITE 225</rptOwnerStreet2>
            <rptOwnerCity>MALVERN</rptOwnerCity>
            <rptOwnerState>PA</rptOwnerState>
            <rptOwnerZipCode>19355</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>true</isDirector>
            <isOfficer>false</isOfficer>
            <isTenPercentOwner>false</isTenPercentOwner>
            <isOther>false</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>false</aff10b5One>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2026-08-03</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>D</transactionCode>
                <equitySwapInvolved>false</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>11</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2026-08-03</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>D</transactionCode>
                <equitySwapInvolved>false</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>40</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By the Lawrence M. Alleva Revocable Trust.</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Stock Option (Right to Buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>8.20</value>
                <footnoteId id="F1"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2026-08-03</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>D</transactionCode>
                <equitySwapInvolved>false</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>240</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F2"/>
                    <footnoteId id="F4"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F2"/>
                <footnoteId id="F4"/>
            </exerciseDate>
            <expirationDate>
                <value>2035-02-23</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>240</value>
                    <footnoteId id="F1"/>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">These numbers have been adjusted to reflect the 1-for-200 reverse stock split Galera Therapeutics, Inc. (&quot;Galera&quot;) effected on July 12, 2026.</footnote>
        <footnote id="F2">Pursuant to an Agreement and Plan of Merger, dated as of April 14, 2026 (the &quot;Merger Agreement&quot;), by and among Galera, Obsidian Therapeutics, Inc. (&quot;Obsidian&quot;), Gazelle Parent, Inc. (&quot;Parent&quot;), Onyx MergerSub, Inc., a wholly owned subsidiary of Parent (&quot;Obsidian Merger Sub&quot;), and Gazelle Merger Subsidiary, Inc., a wholly owned subsidiary of Parent (&quot;Galera Merger Sub&quot;), on August 3, 2026, Galera merged with and into Galera Merger Sub, with Galera surviving as a wholly owned subsidiary of Parent (the &quot;Galera Merger&quot;), and Obsidian merged with and into Obsidian Merger Sub, with Obsidian surviving as a wholly owned subsidiary of Parent (together with the Galera Merger, the &quot;Mergers&quot;).</footnote>
        <footnote id="F3">At the effective time of the Galera Merger (the &quot;Galera Effective Time&quot;), each outstanding share of Galera common stock (excluding any shares of Galera common stock held by stockholders who had exercised and perfected appraisal rights for such shares) was converted into the right to receive 0.7019 shares of Parent common stock (the &quot;Galera Exchange Ratio&quot;).</footnote>
        <footnote id="F4">At the Galera Effective Time, each outstanding Galera stock option with an exercise price per share less than $15.62 (each, an &quot;In-the-Money Option&quot;), which was the closing trading price of a share of Galera common stock on the last full trading day on which the Galera common stock was traded prior to the date of the Galera Effective Time, became fully vested and was converted into shares of Parent common stock determined by (i) multiplying the number of shares of Galera common stock underlying the In-the-Money Option by the Galera Exchange Ratio (rounded down to the nearest whole share) then (ii) subtracting the number of shares of Parent common stock with a value equal to the exercise price and withholding taxes each required to be paid with respect to the net exercise of the In-the-Money Option, calculated pursuant to the formula set forth in Section 2.6(i) of the Merger Agreement.</footnote>
    </footnotes>

    <remarks>At the Galera Effective Time, each outstanding Galera stock option that was not an In-the-Money Option (each, a &quot;Non-In-the-Money Option&quot;) was cancelled for no consideration, which cancellation is exempt from Section 16 of the Securities Exchange Act of 1934, as amended, pursuant to Rule 16a-4(d) and Rule 16b-6(d) thereunder. Accordingly, the Reporting Person's Non-In-the-Money Options that were cancelled in connection with the Mergers are not reported herein.</remarks>

    <ownerSignature>
        <signatureName>/s/ J. Mel Sorensen, Attorney-in-Fact for Lawrence M. Alleva</signatureName>
        <signatureDate>2026-08-05</signatureDate>
    </ownerSignature>
</ownershipDocument>
