As Of	Filer	Filing¹	For·On·As	Docs:Size	Issuer		Filing Agent

 7/23/18  Flagship Ventures Fd IV Gen’… LLC 4          Dir.,%Own.² 1:43K  Rubius Therapeutics, Inc.         Toppan Merrill/FA        
          Afeyan Noubar
          Flagship V VentureLabs Rx Fund, L.P.
          Flagship VentureLabs IV, LLC
          Flagship Ventures Fund IV, L.P.
          Flagship Ventures Fund IV-Rx, L.P.
          Flagship Ventures Fund V, L.P.
          Flagship Ventures Opportunities Fund I, L.P.
          Kania Edwin M Jr.
 7/23/18  Sohn Catherine A.                 4          Director²   1:4K   Rubius Therapeutics, Inc.         Toppan Merrill/FA        
 7/23/18  Pomerantz Roger                   4          Director²   1:4K   Rubius Therapeutics, Inc.         Toppan Merrill/FA        
 7/23/18  Cuss Francis M                    4          Director²   1:4K   Rubius Therapeutics, Inc.         Toppan Merrill/FA        
 7/23/18  Symonds Jonathan                  4          Director²   1:4K   Rubius Therapeutics, Inc.         Toppan Merrill/FA        

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¹	Filing/Form Type:
	4	Statement of Changes in Beneficial Ownership of Securities by an Insider — Form 4 { The Filer is an Insider² of the Issuer }.
²	Insider:  The Filer is a Director, Officer, 10% Owner and/or Other “insider” of the Issuer.