Aldeyra Therapeutics Reports Full-Year 2020 Financial Results and Recent Business Highlights Enrollment Completed in Phase 3 INVIGORATE Trial, with Top-Line Results Expected in the First Half of 2021 Top-Line Results fro

Aldeyra Therapeutics Reports Full-Year 2020 Financial Results and Recent Business Highlights

Enrollment Completed in Phase 3 INVIGORATE Trial, with Top-Line Results Expected in the First

Top-Line Results from Phase 3 TRANQUILITY and TRANQUILITY-2 Trials Expected in the Second Half of 2021

Projected Cash Runway Through

2023, Including Potential New Drug Application Submissions for Dry Eye Disease and Allergic Conjunctivitis

Host Conference Call at 8:00 a.m. ET Today

Lexington, Mass., March 11, 2021

Aldeyra Therapeutics, Inc. (Nasdaq: ALDX) (Aldeyra), a clinical-stage biotechnology company focused on the development of novel therapies with the potential to improve the lives of patients with immune-mediated diseases, today reported

business highlights and financial results for the year ended December 31, 2020.

During the past year, we have worked diligently to advance our

lead investigational compound reproxalap into pivotal Phase 3 clinical trials in dry eye disease and allergic conjunctivitis, two of the largest markets in ophthalmology, stated Todd C. Brady, M.D., Ph.D., President and Chief Executive Officer

of Aldeyra. Based on clinical results to date, we believe reproxalap has the potential to be first-line therapy for the treatment of dry eye disease and an important alternative to corticosteroids for the treatment of allergic conjunctivitis.

We look forward to the potential to further validate the opportunities for reproxalap with the results of the TRANQUILITY, TRANQUILITY-2, and INVIGORATE trials, as we begin 2021 in a strong financial position,

with liquidity expected to fund our current clinical development plans and operations through 2023.

Recent Highlights and Program Updates

Full-Year 2020 Financial Summary

Cash and cash equivalents as of December 31, 2020 were $77.9 million. Based on its current operating plan and including the net proceeds from the

underwritten public offering completed in January 2021, Aldeyra believes that existing cash and cash equivalents will be sufficient to fund currently anticipated operating expenses through the end of 2023, including the completion of the Phase 3

TRANQUILITY and TRANQUILITY-2 trials in dry eye disease; the completion of the Phase 3 INVIGORATE trial in allergic conjunctivitis; the Phase 2 clinical trials of ADX-629 in psoriasis, atopic asthma, and

COVID-19 and the completion of Part 1 of the adaptive Phase 3 GUARD clinical trial in proliferative vitreoretinopathy.

The net loss for full-year 2020

was $37.6 million, or $1.11 per share, compared with a net loss of $60.8 million, or $2.24 per share, for full-year 2019.

Development (R&D) expenses were $24.7 million for full-year 2020 compared with $44.4 million for full-year 2019. The decrease of $19.7 million in R&D expenses primarily reflected a reduction in clinical research and

development expenditures, partially offset by an increase in non-cash compensation costs related to a portion of a contingent acquisition milestone.

Acquired in-process research and development expenses were $1.8 million for full-year 2020 compared with

$6.6 million for full-year 2019. The $4.8 million decrease is related to lower in-process research and development expenses associated with the 2019 acquisition of Helio Vision.

General and administrative (G&A) expenses were $10.0 million for full-year 2020 compared with $12.2 million for full-year 2019. The decrease of

$2.2 million in G&A expenses primarily reflected lower personnel costs, legal costs, public company costs related to continuing compliance with the Sarbanes Oxley Act of 2002, and miscellaneous administrative costs.

Conference Call & Webcast Information

Aldeyra will host a conference call at 8:00 a.m. ET today to discuss its full-year 2020 financial results. The

dial-in numbers are (866) 211-4098 for domestic callers and (647) 689-6613 for international callers. The Conference ID number is

6253616. Due to the expected high demand on our conference provider, please plan to dial in to the call at least 15 minutes prior to the start time.

live webcast of the conference call will also be available on the Investor Relations page of the company s website at https://ir.aldeyra.com. After the live webcast, the event will remain archived on the Aldeyra

Therapeutics website for 90 days.

About Aldeyra Therapeutics

Aldeyra Therapeutics is a clinical-stage biotechnology company focused on the development of novel therapies with the potential to improve the lives of

patients with immune-mediated diseases. Two of the company s lead investigational compounds, reproxalap and ADX-629, target RASP (reactive aldehyde species), which are elevated in ocular and systemic

inflammatory disease and result in cytokine release via activation of a broad array of inflammatory factors, including NF-KB, inflammasomes, and Scavenger Receptor A. 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, a dihydrofolate reductase inhibitor in Phase 3

testing for proliferative vitreoretinopathy, and ADX-1612, a chaperome inhibitor in development for COVID-19 and ovarian cancer. For more information, visit

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: the timing of results from the company s Phase 3 INVIGORATE Trial for the treatment of allergic conjunctivitis; the timing of results from the company s Phase 3 TRANQUILITY and

TRANQUILITY-2 Trials for the treatment of dry eye disease; the timing of results from the company s Phase 2 proof-of-concept

clinical trials of ADX-629; the company s anticipated cash runway; the timing of potential New Drug Application submissions for dry eye disease and allergic conjunctivitis; and the completion of

enrollment of Part 1 of the Phase 3 GUARD Trial of ADX-2191 for the treatment of proliferative vitreoretinopathy. 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; 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 recent COVID-19 outbreak and

subsequent 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, 2019 and

Aldeyra s Quarterly Report on Form 10-Q for the quarter ended September 30, 2020, which are on file with the Securities and Exchange Commission (SEC) and available on the SEC s website at

https://www.sec.gov/. Additional factors may be described in those sections of Aldeyra s Annual Report on Form 10-K for the year ended December 31, 2020, expected to be filed with the SEC in the

first quarter of 2021.

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.

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