X0306 4 2019-09-06 0 0001341235 Aldeyra Therapeutics, Inc. ALDX 0001662693 Clark David J C/O ALDEYRA THERAPEUTICS, INC. 131 HARTWELL AVENUE LEXINGTON MA 02421 0 1 0 0 Chief Medical Officer Common Stock 2019-09-06 4 P 0 5000 5.0622 A 17878 D The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $5.03 to $5.07, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the Securities Exchange Commission, upon request, full information regarding the number of shares purchased at each separate price within the ranges set forth in this footnote (1) to this Form 4. Includes 1,366 shares of common stock acquired under the Issuer's Employee Stock Purchase Plan (ESPP) in 2019. /s/ David Clark 2019-09-10