Decibel Therapeutics : JPM 2023 Week Presentation

A WORLD OF CONNECTION FOR PEOPLE WITH HEARING AND BALANCE DISORDERSTM

41st Annual Healthcare

Meeting

January 2023

Forward-Looking Statements

This presentation contains forward looking statements that involve substantial risks and uncertainties. All statements, other than statements of historical facts, contained in this presentation, including statements regarding Decibel Therapeutics, Inc.'s (the "Company") strategy, future operations, future financial position, future revenues, projected costs, prospects, plans and objectives of management, the therapeutic potential for the Company's product candidates and preclinical programs, the expected timeline for submitting investigational new drug applications and achieving other anticipated milestones and the sufficiency of Decibel's existing cash resources, are forward looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. The words "anticipate," "believe," "continue," "could," "estimate," "expect," "intend," "may," "might," "plan," "potential," "predict," "project," "should," or "would," or the negative of these terms, or other comparable terminology are intended to identify forward looking statements, although not all forward-looking statements contain these identifying words. The Company may not actually achieve the plans, intentions or expectations disclosed in these forward-looking statements, and you should not place undue reliance on these forward-looking statements. Actual results or events could differ materially from the plans, intentions and expectations disclosed in these forward-looking statements as a result of various important factors, including: uncertainties inherent in the identification and development of product candidates, including the conduct of research activities and the initiation and completion of preclinical studies and clinical trials, the timing of and the Company's ability to submit and obtain approval to initiate clinical development of its product candidates, whether results from preclinical studies will be predictive of the results of later preclinical studies and clinical trials, whether Company's cash resources are sufficient to fund its foreseeable and unforeseeable operating expenses and capital expenditure requirements, uncertainties related to the impact of the COVID-19 pandemic on Company's business and operations, as well as the risks and uncertainties identified in Company's filings with the Securities and Exchange Commission. In addition, the forward-looking statements included in this presentation represent the Company's views as of the date of this presentation. The Company anticipates that subsequent events and developments will cause its views to change. However, while the Company may elect to update these forward-looking statements at some point in the future, it specifically disclaims any

obligation to do so. These forward-looking statements should not be relied upon as representing the Company's views as of any date subsequent to the date of this presentation.

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Hearing & Balance: No Approved Therapies, Rising Awareness of Opportunity

Inner Ear: Optimal Characteristics to Realize Promise of Gene Therapy

Differentiated Platform: Unique Transgene Regulation Capabilities

Maturing Pipeline: Monogenic Hearing Loss, Hair Cell Regeneration

Capitalized to Achieve Milestones: Initial Human Clinical Data, Pipeline Milestones

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Achievements and Anticipated Milestones

DB-OTO in Phase 1/2

• Orphan Drug, Rare Pediatric Disease designations from FDA
• FDA cleared IND to initiate Phase 1/2 clinical trial
• Regeneron commitment through human proof-of-concept

Positive DB-020 IA Data

• Observed ototoxicity rate of 88% in placebo-treated ears
• Protected hearing in 87% of patients who experienced ototoxicity
• Generally well-tolerated

Anticipated Milestones

• Clearance of DB-OTO CTAs
• Global initiation of DB-OTO Phase 1/2 clinical trial
• Milestone payments from Regeneron: DB-OTO, AAV.103
• DB-020data, reg. feedback
• Safety, tolerability, efficacy from initial DB-OTO Phase 1/2 cohort

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Hearing Loss Profoundly Limits Connection to People and Environment

• Potential neurodevelopmental emergency
• Delays in language development
• Risk of impairment in executive function
• Highest relative risk of dementia

Loss of connection often results in limited social interaction, feelings of loneliness and isolation across all ages.

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