Item 1(a).
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Name of Issuer:
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Rubius Therapeutics, Inc. (the Issuer)
Item 1(b).
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Address of Issuers Principal Executive Offices:
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399 Binney Street, Suite 300, Cambridge, MA 02139
Item 2(a).
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Names of Persons Filing:
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The names of the persons filing this report (collectively, the Reporting Persons) are:
Flagship VentureLabs IV LLC (VentureLabs IV)
Flagship Ventures Fund IV, L.P. (Flagship IV Fund)
Flagship Ventures Fund IV-Rx, LP (Flagship IV-Rx Fund)
Flagship Ventures Fund IV General Partner LLC (Flagship IV GP)
Flagship V VentureLabs Rx Fund, L.P. (VentureLabs Rx V)
Flagship Ventures Fund V, L.P. (Flagship V Fund)
Flagship Ventures Fund V General Partner LLC (Flagship V GP)
Flagship Ventures Opportunities Fund I, L.P. (Flagship Opportunities I)
Flagship Ventures Opportunities Fund I General Partner LLC (Flagship Opportunities GP)
Noubar B. Afeyan, Ph.D. (Dr. Afeyan)
Item 2(b).
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Address of Principal Business Office or, if None, Residence:
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The address of the principal business office of each of the Reporting Persons is:
c/o Flagship Pioneering Inc.
55 Cambridge Parkway, Suite 800E
Cambridge, Massachusetts 02142
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VentureLabs IV
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Delaware
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Flagship IV Fund
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Delaware
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Flagship IV-Rx Fund
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Delaware
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Flagship IV GP
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Delaware
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VentureLabs Rx V
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Delaware
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Flagship V Fund
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Delaware
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Flagship V GP
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Delaware
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Flagship Opportunities I
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Delaware
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Flagship Opportunities GP
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Delaware
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Dr. Afeyan
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United States of America
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Item 2(d).
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Title of Class of Securities:
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Common Stock, $0.001 par value per share (Common Stock).