X0306 4 2019-02-28 0 0001751299 Kaleido Biosciences, Inc. KLDO 0001219016 BONNEY MICHAEL W C/O KALEIDO BIOSCIENCES, INC. 65 HAYDEN AVENUE LEXINGTON MA 02421 1 1 0 0 Executive Chair Common Stock 2019-02-28 4 P 0 68965 13.95 A 1005968 D Common Stock 2019-02-28 4 P 0 2555 14.65 A 1008523 D Common Stock 2019-03-04 4 C 0 417673 A 1426196 D Common Stock 2019-03-04 4 C 0 225000 A 225000 I See Foonote Series B Preferred Stock 2019-03-04 4 C 0 835347 D Common Stock 417673 0 D Series B Preferred Stock 2019-03-04 4 C 0 450000 D Common Stock 225000 0 I See Footnote Each share of Series B 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. The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $13.50 to $14.35, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares purchased at each separate price within the range. The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $14.52 to $14.72, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares purchased at each separate price within the range. Shares held in the Michael and Alison Bonney 2016 Irrevocable Trust, which has an independent trustee. /s/ Joshua T. Brumm, as Attorney in Fact 2019-03-04