Aldeyra Therapeutics Announces Achievement of Primary Endpoint of Ocular Redness in Randomized, Double- Masked, Vehicle-Controlled Phase 2 Clinical Trial in Dry Eye Disease

Aldeyra Therapeutics Announces Achievement of Primary

Endpoint of Ocular Redness in Randomized, Double- Masked,

Vehicle-Controlled Phase 2 Clinical Trial in Dry Eye Disease

LEXINGTON, Mass., November 2, 2021 Aldeyra

Therapeutics, Inc. (Nasdaq: ALDX) (Aldeyra) today announced achievement of the primary endpoint of ocular redness in a randomized, double-masked,

vehicle-controlled Phase 2 clinical trial in patients with dry eye disease.

The clinical trial enrolled 158 patients: 80 patients were randomized to

receive 0.25% reproxalap ophthalmic solution, and 78 patients were randomized to receive vehicle ophthalmic solution. Patients received four doses one day prior to and two doses during exposure to a 90-minute dry eye chamber with minimal humidity,

high airflow, and forced visual tasking.

Based on final enrollment and data from the run-in cohort of TRANQUILITY, Aldeyra s ongoing Phase 3 trial in

dry eye disease, the Phase 2 trial exceeded 90% power to detect statistical significance in the primary endpoint of ocular redness over all time points in aggregate in the dry eye chamber. Ocular redness scores in the reproxalap group were observed

to be statistically lower than those of vehicle (p = 0.016). Additionally, Schirmer s test scores assessed after the first dose were directionally in favor of reproxalap over vehicle and approached statistical significance (p = 0.068). Mean

visual analog scale ocular dryness and ocular discomfort scores were lower in reproxalap-treated subjects than in vehicle-treated subjects at all of the 18 time points when symptoms were assessed in the dry eye chamber, including the first time

point in the chamber, although differences did not reach statistical significance. Tear RASP level results from the trial are expected to be available later this quarter. Consistent with the clinical experience of reproxalap in more than 1,300

patients, there were no observed safety or tolerability concerns in the trial; the most common adverse event was mild and transient instillation site discomfort lasting less than one minute and similar to many prescribed topical ophthalmic

medications for anterior segment inflammation.

Complementing our rapid and durable symptom control evidenced in three 12- week clinical trials, we

are excited to announce achievement of statistical significance of an objective sign of dry eye disease in a well-controlled clinical trial, stated Todd C. Brady, M.D., Ph.D., President and Chief Executive Officer of Aldeyra. Ocular

redness may be the only dry eye disease sign that is of importance to patients, and the reduction in redness observed in this trial following reproxalap treatment potentially represents a major advance for the chronic treatment of dry eye

Two Phase 3 clinical trials of reproxalap in patients with dry eye disease, TRANQUILITY and TRANQUILITY-2, are ongoing. For each trial, the

planned enrollment is 300 patients, and the primary endpoint is ocular redness. Pending confirmation of statistical powering and other analyses of the Phase 2 clinical trial results announced today, results from the TRANQUILITY trials are expected

to be released by the end of the year.

Reproxalap, an investigational new drug, is a novel small-molecule immune- modulating covalent inhibitor of RASP (reactive aldehyde species), which are

elevated in ocular and systemic inflammatory disease. Reproxalap s mechanism of action has been validated with the demonstration of statistically significant and clinically relevant activity in multiple physiologically distinct late-phase

clinical indications. Reproxalap is currently in Phase 3 clinical development as a 0.25% ophthalmic solution for the treatment of dry eye disease and allergic conjunctivitis, two ocular inflammatory diseases that often occur together.

About Dry Eye Disease

Dry eye disease is a common

inflammatory disease estimated to affect 34 million or more adults in the United States.1 The disease is characterized by insufficient moisture and lubrication in the anterior surface of the

eye, leading to dryness, inflammation, pain, discomfort, irritation, diminished quality of life, and in severe cases, permanent vision impairment. Among many physicians and patients, existing therapy for dry eye disease is generally regarded as

inadequate and often requires weeks or months to demonstrate activity. In patients with dry eye disease, pro-inflammatory RASP may

contribute to ocular inflammation and changes in tear lipid composition. By diminishing RASP levels, Aldeyra s lead RASP inhibitor reproxalap represents a novel and differentiated approach

for the treatment of the symptoms and signs of dry eye disease.

About Aldeyra Therapeutics

Aldeyra Therapeutics is a biotechnology company developing novel immune- modulating therapies to treat ocular and systemic diseases. Two of the company s

lead product candidates, reproxalap and ADX-629, target RASP, which are pre-cytokine, systems-based mediators of inflammation. Reproxalap is being evaluated in Phase 3 clinical trials in patients with dry eye disease and allergic conjunctivitis. The

company s clinical pipeline also includes ADX-2191 (methotrexate for intravitreal injection), a drug candidate in Phase 3 testing for the prevention of proliferative vitreoretinopathy. For more information, visit

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Safe Harbor Statement

This release contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995, including, but not limited to,

statements regarding Aldeyra s development plans and expectations for its product candidates, including plans and expectations relating to current or future clinical development of reproxalap in dry eye disease. Aldeyra intends such

forward-looking statements to be covered by the safe harbor provisions for forward-looking statements contained in Section 21E of the Securities Exchange Act of 1934 and the Private Securities Litigation Reform Act of 1995. In some cases, you

can identify forward-looking statements by terms such as, but not limited to, may, might, will, objective, intend, should, could, can, would,

expect, believe, anticipate, project, on track, scheduled, target, design, estimate, predict, potential,

aim, plan or the negative of these terms, and similar expressions intended to identify forward- looking statements. Such forward-looking statements are based upon current expectations that involve risks, changes in

circumstances, assumptions, and uncertainties. Aldeyra is at an early stage of development and may not ever have any products that generate significant revenue. All of Aldeyra s development timelines may be subject to adjustment depending on

recruitment rate, regulatory review, preclinical and clinical

results, and other factors that could delay the initiation or completion of clinical trials. Important factors that could cause actual results to differ materially from those reflected in

Aldeyra s forward-looking statements include, among others, the timing of enrollment, commencement and completion of Aldeyra s clinical trials, the timing and success of preclinical studies and clinical trials conducted by Aldeyra and its

development partners; updated or refined data based on Aldeyra s continuing review and quality control analysis of clinical data, Aldeyra s ability to design clinical trials with protocols and endpoints acceptable to applicable regulatory

authorities; delay in or failure to obtain regulatory approval of Aldeyra s product candidates; the ability to maintain regulatory approval of Aldeyra s product candidates, and the labeling for any approved products; the risk that prior

results, such as signals of safety, activity or durability of effect, observed from preclinical or clinical trials, will not be replicated or will not continue in ongoing or future studies or clinical trials involving Aldeyra s product

candidates in clinical trials focused on the same or on different indications; the risk that the results from smaller clinical trials or portions of clinical trials may not accurately predict results of larger scale trials or the remainder of a

clinical trial; the scope, progress, expansion, and costs of developing and commercializing Aldeyra s product candidates; uncertainty as to Aldeyra s ability to commercialize (alone or with others) Aldeyra s product candidates

following regulatory approval, if any; the size and growth of the potential markets and pricing for Aldeyra s product candidates and the ability to serve those markets; Aldeyra s expectations regarding Aldeyra s expenses and revenue,

the sufficiency or use of Aldeyra s cash resources and needs for additional financing; political, economic, legal, social and health risks, including the COVID-19 pandemic and related public health measures, that may affect Aldeyra s

business or the global economy; the rate and degree of market acceptance of any of Aldeyra s product candidates; Aldeyra s expectations regarding competition; Aldeyra s anticipated growth strategies; Aldeyra s ability to attract

or retain key personnel; Aldeyra s limited sales and marketing infrastructure; Aldeyra s ability to establish and maintain development partnerships; Aldeyra s ability to successfully integrate acquisitions into its business;

Aldeyra s expectations regarding federal, state and foreign regulatory requirements; regulatory developments in the United States and foreign countries; Aldeyra s ability to obtain and maintain intellectual property protection for its

product candidates; the anticipated trends and challenges in Aldeyra s business and the market in which it operates; and other factors that are described in the Risk Factors and Management s Discussion and Analysis of

Financial Condition and Results of Operations sections of Aldeyra s Annual Report on Form 10-K for the year ended December 31, 2020 and Quarterly Report on Form 10-Q for the quarter ended September 30, 2021, which are on file with the

Securities and Exchange Commission (SEC) and available on the SEC s website at https://www.sec.gov/.

In addition to the risks described above and in Aldeyra s other filings with the SEC, other unknown or

unpredictable factors also could affect Aldeyra s results. No forward-looking statements can be guaranteed and actual results may differ materially from such statements. The information in this release is provided only as of the date of this

release, and Aldeyra undertakes no obligation to update any forward-looking statements contained in this release on account of new information, future events, or otherwise, except as required by law.