X0306 4 2019-03-04 0 0001751299 Kaleido Biosciences, Inc. KLDO 0001508051 Flagship Ventures Fund IV General Partner LLC 55 CAMBRIDGE PARKWAY, SUITE 800E CAMBRIDGE MA 02142 1 0 1 0 0001503559 Flagship Ventures Fund IV, L.P. 55 CAMBRIDGE PARKWAY, SUITE 800E CAMBRIDGE MA 02142 0 0 1 0 0001642578 Flagship VentureLabs IV, LLC 55 CAMBRIDGE PARKWAY, SUITE 800E CAMBRIDGE MA 02142 0 0 1 0 0001508053 Flagship Ventures 2007 General Partner LLC 55 CAMBRIDGE PARKWAY, SUITE 800E CAMBRIDGE MA 02142 0 0 1 0 0001508052 Flagship Ventures Fund 2007, L.P. 55 CAMBRIDGE PARKWAY, SUITE 800E CAMBRIDGE MA 02142 0 0 1 0 0001768776 Cadena LLC 55 CAMBRIDGE PARKWAY, SUITE 800E CAMBRIDGE MA 02142 0 0 1 0 0001222012 AFEYAN NOUBAR 55 CAMBRIDGE PARKWAY, SUITE 800E CAMBRIDGE MA 02142 1 0 1 0 0001255927 KANIA EDWIN M JR 55 CAMBRIDGE PARKWAY, SUITE 800E CAMBRIDGE MA 02142 0 0 1 0 Common Stock 42865 I See Footnote Common Stock 42865 I See Footnote Common Stock 1649999 I See Footnote Common Stock 2019-03-04 4 C 0 665908 A 665908 I See Footnote Common Stock 2019-03-04 4 C 0 173586 A 216451 I See Footnote Common Stock 2019-03-04 4 C 0 281203 A 947111 I See Footnote Series A Preferred Stock 2019-03-04 4 C 0 1331816 D Common Stock 665908 0 I See Footnote Series A-1 Preferred Stock 2019-03-04 4 C 0 347173 D Common Stock 173586 0 I See Footnote Series A-1 Preferred Stock 2019-03-04 4 C 0 562407 D Common Stock 281203 0 I See Footnote Shares held by Flagship Ventures Fund 2007, L.P. ("Flagship 2007"). Flagship Ventures 2007 General Partner LLC ("Flagship 2007 GP") is the general partner of Flagship 2007. Noubar B. Afeyan, Ph.D. and Edwin M. Kania, Jr. are the managers of Flagship 2007 LLC. While Mr. Kania is retired from Flagship Pioneering, Inc., he continue to serve as a manager of Flagship 2007 GP. Each of these individuals and entities may be deemed to share voting and investment power with respect to all shares held by Flagship 2007. Each of the reporting persons disclaims beneficial ownership of the shares except to the extent of his or its pecuniary interest therein. Shares held by Flagship VentureLabs IV, LLC ("VentureLabs IV"). Flagship Ventures Fund IV, L.P. ("Flagship Fund IV") is a member of VentureLabs IV and also serves as its manager. Flagship Ventures Fund IV General Partner LLC ("Flagship Fund IV GP") is the general partner of Flagship Fund IV. Noubar B. Afeyan, Ph.D. and Edwin M. Kania, Jr. are the managers of Flagship Fund IV GP. While Mr. Kania is retired from Flagship Pioneering, Inc., he continues to serve as a manager of Flagship Fund IV GP. Each of these individuals and entities may be deemed to share voting and investment power with respect to all shares held by VentureLabs IV. Each of the filing persons disclaims beneficial ownership of the shares except to the extent of his or its pecuniary interest therein Shares held by Cadena LLC ("Cadena"). Noubar B. Afeyan, Ph.D. is the sole manager of Cadena, and may be deemed to possess sole voting and investment power with respect to all shares held by Cadena. Each of the reporting persons disclaims beneficial ownership of the shares except to the extent of his or its pecuniary interest therein. Each share of Series A Preferred Stock converted into shares of the Issuer's common stock, par value $0.001 ("Common Stock"), on a one-for-two basis upon the closing of the Issuer's initial public offering. Shares held by Flagship Ventures Fund IV, L.P. Flagship Fund IV GP is the general partner of Flagship Fund IV. Noubar B. Afeyan, Ph.D. and Edwin M. Kania, Jr. are the managers of Flagship Fund IV GP. While Mr. Kania is retired from Flagship Pioneering, Inc., he continues to serve as a manager of Flagship Fund IV GP. Each of these individuals and entities may be deemed to share voting and investment power with respect to all shares held by Flagship Fund IV. Each of the filing persons disclaims beneficial ownership of the shares except to the extent of his or its pecuniary interest therein. Each share of Series A-1 Preferred Stock converted into shares of the Issuer's Common Stock on a one-for-two basis upon the closing of the Issuer's initial public offering. Due to limitations of the electronic filing system, each of Flagship Ventures Fund V General Partner LLC, Flagship Ventures Fund V, L.P., Flagship VentureLabs V LLC, Flagship VentureLabs V Manager LLC, Flagship Pioneering, Inc., Nutritional Health Disruptive Innovation Fund, L.P., Nutritional Health Side Fund, L.P., Flagship Ventures Opportunities Fund I, L.P., Flagship Ventures Opportunities Fund I General Partner LLC and Noubar B. Afeyan, Ph.D. are filing a separate Form 4 with respect to securities of the Issuer. Flagship Ventures Fund IV General Partner LLC, By: /s/ Noubar B. Afeyan, Name: Noubar B. Afeyan, Ph.D., Title: Manager 2019-03-06 Flagship Ventures Fund IV, L.P., By: Flagship Ventures Fund IV General Partner LLC, its general partner By: /s/ Noubar B. Afeyan, Name: Noubar B. Afeyan, Ph.D., Title: Manager 2019-03-06 Flagship VentureLabs IV LLC, By: Flagship Ventures Fund IV, L.P., its manager, By: Flagship Ventures Fund IV General Partner LLC, its general partner, By: /s/ Noubar B. Afeyan, Name: Noubar B. Afeyan, Ph.D., Title: Manager 2019-03-06 Flagship Ventures 2007 General Partner LLC, By: /s/ Noubar B. Afeyan, Name: Noubar B. Afeyan, Ph.D., Title: Manager 2019-03-06 Flagship Ventures Fund 2007, L.P., By: Flagship Ventures 2007 General Partner LLC, its general partner, By: /s/ Noubar B. Afeyan, Name: Noubar B. Afeyan, Ph.D., Title: Manager 2019-03-06 Cadena LLC, By: /s/ Noubar B. Afeyan, Name: Noubar B. Afeyan, Ph.D., Title: Manager 2019-03-06 Noubar B. Afeyan, Ph.D., By: /s/ Noubar B. Afeyan 2019-03-06 Edwin M. Kania, Jr., By: /s/ Edwin M. Kania, Jr. 2019-03-06