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Preliminary Proxy Statement

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Definitive Proxy Statement

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Definitive Additional Materials

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Soliciting Material Pursuant to §240.14a-12

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No fee required.

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Meeting Information

ALDEYRA THERAPEUTICS, INC.

Meeting Type:     Annual Meeting

For holders as of: April 8, 2019

Date: June 4, 2019      Time: 8:00 AM EDT

Location:

Offices of Gunderson Dettmer Stough

Villeneuve Franklin & Hachigian, LLP

One Marina Park Drive, Suite 900

Boston, MA 02210

ALDEYRA THERAPEUTICS, INC.

131 HARTWELL AVE.

LEXINGTON, MA 02421

You are receiving this communication because you hold shares in the company named above.

This is not a ballot. You cannot use this notice to vote these shares. This communication presents only an overview of the more complete proxy materials that are available to you on the Internet. You may view the proxy materials online at www.proxyvote.com or easily request a paper copy (see reverse side).

We encourage you to access and review all of the important information contained in the proxy materials before voting.

See the reverse side of this notice to obtain proxy materials and voting instructions.

— Before You Vote —

How to Access the Proxy Materials

Proxy Materials Available to VIEW or RECEIVE:

NOTICE AND PROXY STATEMENT         FORM 10-K

How to View Online:

Have the information that is printed in the box marked by the arrow (located on the following page) and visit: www.proxyvote.com.

How to Request and Receive a PAPER or E-MAIL Copy:

If you want to receive a paper or e-mail copy of these documents, you must request one. There is NO charge for requesting a copy. Please choose one of the following methods to make your request:

1) BY INTERNET:                 www.proxyvote.com

2) BY TELEPHONE:             1-800-579-1639

3) BY E-MAIL*:                     sendmaterial@proxyvote.com

*If requesting materials by e-mail, please send a blank e-mail with the information that is printed in the box marked by the arrow (located on the following page) in the subject line.

Requests, instructions and other inquiries sent to this e-mail address will NOT be forwarded to your investment advisor. Please make the request as instructed above on or before May 21, 2019 to facilitate timely delivery.

— How To Vote —

Please Choose One of the Following Voting Methods

Vote In Person: Many stockholder meetings have attendance requirements including, but not limited to, the possession of an attendance ticket issued by the entity holding the meeting. Please check the meeting materials for any special requirements for meeting attendance. At the meeting, you will need to request a ballot to vote these shares.

Vote By Internet: To vote now by Internet, go to www.proxyvote.com. Have the information that is printed in the box marked by the arrow (located on the following page) available and follow the instructions.

Vote By Mail: You can vote by mail by requesting a paper copy of the materials, which will include a proxy card.

Voting items

The Board of Directors recommends you vote

FOR the following:

1.  

Election of Three Class II Directors

Nominees

01) Richard H. Douglas, Ph.D.       02) Gary Phillips, M.D.       03) Neal Walker, D.O.

The Board of Directors recommends you vote FOR proposals 2 and 3.

2.  

To ratify the appointment of BDO USA, LLP as Aldeyra Therapeutics, Inc.’s independent registered public accounting firm for the year ending December 31, 2019.

3.  

To approve an amendment to Aldeyra Therapeutics, Inc.’s 2013 Equity Incentive Plan (2013 Plan) to remove the annual limitations on the number of shares subject to awards that may be issued to eligible service providers under the 2013 Plan.

NOTE: Such other business as may properly come before the meeting or any adjournment thereof.