    <SEC-DOCUMENT>0001485003-21-000226-index.html : 20211123
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    <ACCEPTANCE-DATETIME>20211123080037
    ACCESSION NUMBER:		0001485003-21-000226
    CONFORMED SUBMISSION TYPE:	8-K
    PUBLIC DOCUMENT COUNT:		16
    CONFORMED PERIOD OF REPORT:	20211122
    ITEM INFORMATION:		Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers: Compensatory Arrangements of Certain Officers
    ITEM INFORMATION:		Financial Statements and Exhibits
    FILED AS OF DATE:		20211123
    DATE AS OF CHANGE:		20211123

    FILER:

    	COMPANY DATA:
    		COMPANY CONFORMED NAME:			Sesen Bio, Inc.
    		CENTRAL INDEX KEY:			0001485003
    		STANDARD INDUSTRIAL CLASSIFICATION:	PHARMACEUTICAL PREPARATIONS [2834]
    		IRS NUMBER:				262025616
    		STATE OF INCORPORATION:			DE
    		FISCAL YEAR END:			1231

    	FILING VALUES:
    		FORM TYPE:		8-K
    		SEC ACT:		1934 Act
    		SEC FILE NUMBER:	001-36296
    		FILM NUMBER:		211434710

    	BUSINESS ADDRESS:
    		STREET 1:		245 FIRST STREET
    		STREET 2:		SUITE 1800
    		CITY:			CAMBRIDGE
    		STATE:			MA
    		ZIP:			02142
    		BUSINESS PHONE:		617-444-8550

    	MAIL ADDRESS:
    		STREET 1:		245 FIRST STREET
    		STREET 2:		SUITE 1800
    		CITY:			CAMBRIDGE
    		STATE:			MA
    		ZIP:			02142

    	FORMER COMPANY:
    		FORMER CONFORMED NAME:	Eleven Biotherapeutics, Inc.
    		DATE OF NAME CHANGE:	20100223
    </SEC-HEADER>
    <DOCUMENT>
    <TYPE>8-K
    <SEQUENCE>1
    <FILENAME>sesn-20211122.htm
    <DESCRIPTION>8-K
    <TEXT>
    Document 1 - file: sesn-20211122.htm

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>EX-99.1
    <SEQUENCE>2
    <FILENAME>jhenderson-departurerele.htm
    <DESCRIPTION>EX-99.1
    <TEXT>
    Document 2 - file: jhenderson-departurerele.htm

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>EX-101.SCH
    <SEQUENCE>3
    <FILENAME>sesn-20211122.xsd
    <DESCRIPTION>XBRL TAXONOMY EXTENSION SCHEMA DOCUMENT
    <TEXT>
    Document 3 - file: sesn-20211122.xsd

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    <DOCUMENT>
    <TYPE>EX-101.LAB
    <SEQUENCE>4
    <FILENAME>sesn-20211122_lab.xml
    <DESCRIPTION>XBRL TAXONOMY EXTENSION LABEL LINKBASE DOCUMENT
    <TEXT>
    Document 4 - file: sesn-20211122_lab.xml

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    <SEQUENCE>5
    <FILENAME>sesn-20211122_pre.xml
    <DESCRIPTION>XBRL TAXONOMY EXTENSION PRESENTATION LINKBASE DOCUMENT
    <TEXT>
    Document 5 - file: sesn-20211122_pre.xml

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    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>6
    <FILENAME>jhenderson-departurerele001.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 6 - file: jhenderson-departurerele001.jpg

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    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>7
    <FILENAME>jhenderson-departurerele002.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 7 - file: jhenderson-departurerele002.jpg

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    <TYPE>GRAPHIC
    <SEQUENCE>8
    <FILENAME>jhenderson-departurerele003.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 8 - file: jhenderson-departurerele003.jpg

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    <DOCUMENT>
    <TYPE>XML
    <SEQUENCE>9
    <FILENAME>sesn-20211122_htm.xml
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 9 - file: sesn-20211122_htm.html

    Document 9 - RAW XML: sesn-20211122_htm.xml

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    <DOCUMENT>
    <TYPE>XML
    <SEQUENCE>10
    <FILENAME>R1.htm
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 10 - file: R1.htm

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    <DOCUMENT>
    <TYPE>EXCEL
    <SEQUENCE>11
    <FILENAME>Financial_Report.xlsx
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 11 - file: Financial_Report.xlsx

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>XML
    <SEQUENCE>12
    <FILENAME>Show.js
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 12 - file: Show.js

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    <DOCUMENT>
    <TYPE>XML
    <SEQUENCE>13
    <FILENAME>report.css
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 13 - file: report.css

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    <DOCUMENT>
    <TYPE>XML
    <SEQUENCE>14
    <FILENAME>FilingSummary.xml
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 14 - file: FilingSummary.html

    Document 14 - RAW XML: FilingSummary.xml

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>JSON
    <SEQUENCE>16
    <FILENAME>MetaLinks.json
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 16 - file: MetaLinks.json

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    <DOCUMENT>
    <TYPE>ZIP
    <SEQUENCE>17
    <FILENAME>0001485003-21-000226-xbrl.zip
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 17 - file: 0001485003-21-000226-xbrl.zip

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