May 11, 2021

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This presentation contains “forward-looking statements” and information within the meaning of the Private Securities Litigation Reform Act of 1995, including, but not limited to: our expectation about timing and execution of anticipated milestones, including our planned investigational new drug submissions for AK-OTOF and AK-antiVEGF, initiation of clinical trials, and additional product candidate and targetselections; our expectations regarding our internal manufacturing capabilities and external manufacturing supply; our expectations regarding our regulatory strategy; and the geographic expansion of the Resonate™ program. These forward-looking statements may be accompanied by such words as “aim,” “anticipate,” “believe,” “continue,” “could,” “estimate,” “expect,” “forecast,” “goal,” “intend,” “may,” “might,” “plan,” “potential,” “possible,” “target,” “will,” “would,” and other words and terms of similar meaning. Akouos 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 factors, including: our limited operating history; uncertainties inherent in the development of product candidates, including the initiation and completion of nonclinical studies and clinical trials; the timing of and our ability to submit and obtain regulatory approval; whether results from nonclinical studies will be predictive of results or success of clinical trials; our ability to obtain sufficient cash resources to fund our foreseeable and unforeseeable operating expenses and capital expenditure requirements; our ability to obtain, maintain, and enforce our intellectual property; the impact of the COVID-19 pandemic on our business, results of operations, and financial condition; the potential that our internal manufacturing capabilities and/or external manufacturing supply may experience delays; risks related to competitive programs; and the other risks and uncertainties that are described in the Risk Factors section included in the Company’s most recent Annual Report on Form 10-K, which is on file with the Securities and Exchange Commission, and in other filings that Akouos may make with the Securities and Exchange Commission in the future. Any forward-looking statements contained in this presentation represent Akouos’s views only as of the date made and should not be relied upon as representing its views as of any subsequent date. Except as required by law, Akouos explicitly disclaims any obligation to update any forward-looking statements.

Forward Looking Statements

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Genetic Medicine Platform Focused on Inner Ear Conditions

High Unmet Need and Opportunity to Create Value

~466mm people worldwide with disabling hearing loss, including ~34mm children. Over 8,000 children are born with genetic sensorineural hearing loss every year in the US and Europe. No pharmacologic options are available

Multimodal Precision Genetic Medicine Platform

Building a platform of proprietary AAVAnc vectors, a novel delivery approach that is designed to be familiar to surgeons, and multimodal tools such as gene transfer, knockdown, and editing

Potential for Rapid Advancement ofLead Program, AK-OTOF

AK-OTOF generated promising nonclinical data and has potential for rapid clinical readout using an objective, clinically accepted efficacy endpoint. Targeting IND submission to FDA in 1H 2022

Disciplined Execution to Support Build of Pipeline with Potential for

Broad Applicability

AK-antiVEGF, a potential gene therapy for vestibular schwannoma, targeting IND submission to FDA in 2022. AK-CLRN1 product candidate selected. GJB2 product candidate selection and two additional target announcements expected in 2021

Manufacturing to Support Near- and Long-Term Growth

Established internal infrastructure to manufacture vector for GLP toxicology studies. Partnered with well-established CDMOs to advance cGMP campaigns, for both the AK-OTOF and AK-antiVEGF IND submissions. Developing internal cGMP manufacturing infrastructure and capabilities in 2021

World-Class Management Team with Unique Combination of Expertise

Purposefully assembled team of experts in auditory anatomy and physiology, otopathology, human genetics, inner ear drug delivery, gene therapy, and rare disease drug development and commercialization

Abbreviations: AAV = adeno-associated viral; CDMO = contract development and manufacturing organization; cGMP = current good manufacturing practice; FDA = U.S. Food and Drug Administration; IND = investigational new drug application.

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2020 in Review and Key Milestones

2020 Highlights Key Recent and Upcoming Milestones

• Expanded team and board of directors

• Continued progress towards IND filing to support planned AK-OTOF Phase 1/2 clinical trial

• General alignment with FDA on path to IND submission for AK-antiVEGF

• AK-CLRN1 product candidate selection; next milestone is pre-IND meeting

• Initiated build of internal manufacturing capabilities to support research and future clinical activities

• Raised approximately $349 million in gross proceeds, which is expected to fund operations for at least two years

• Announced Resonate™ program providing genetic testing for eligible individuals with auditory neuropathy

• Presented data at ARO and ASGCT conferences

• AK-OTOF received ODD and RPDD from FDA

• Targeting IND submission for AK-OTOF in 1H 2022

• Continuing progress towards IND submission for AK-antiVEGF targeted in 2022

• Demonstrating broad applicability of platform with GJB2 candidate selection and hair cell regeneration and autosomal dominant hearing loss target announcements expected in 2021

• Establishing infrastructure and capabilities for internal cGMP manufacturing in 2021

Abbreviations: ARO = Association for Research in Otolaryngology; ASGCT = American Society of Gene and Cell Therapy; cGMP = current good manufacturing practice; FDA = U.S. Food and Drug Administration; IND = investigational new drug application.; ODD = Orphan Drug Designation; RPDD = Rare Pediatric Disease Designation.

Experienced Management Team with Otology, Genetic Medicine, and Rare Disease Drug Development Expertise

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Michael McKenna, M.D.Founder, Chief Medical Officer

Kathy Reape, M.D.Chief Development Officer

Karoline Shair, Ph.D., J.D.Chief Legal Officer

John ConnellySVP, Portfolio Strategy, R&D Operations

Emmanuel Simons, Ph.D., M.B.A.Founder, Chief Executive Officer

Jennifer WellmanChief Operating Officer

Sachiyo MinegishiChief Financial Officer

Gregory Robinson, Ph.D.Chief Scientific Officer

Deep Pipeline Highlights Breadth of Platform

Product Candidate orDevelopment Program(Indication)

EstimatedPrevalence(US and EU)

Stage of DevelopmentNext Planned

MilestoneDiscovery Preclinical Phase 1/2 Pivotal

Hair Cells

AK-OTOF

(OTOF-mediated Hearing Loss)20,000 ▪ IND Submission

AK-CLRN1

(Usher Syndrome Type 3A)2,000 ▪ Pre-IND Meeting

Autosomal Dominant

Hearing LossPending Target

Selection▪ Target

Announcement

Supporting Cells

GJB2(GJB2-mediated Hearing Loss) 200,000

▪ Candidate Selection

Hair Cell Regeneration Pending Target Selection

▪ Target Announcement

Secreted Proteins

AK-antiVEGF

(Vestibular Schwannoma) 200,000 ▪ IND Submission

Gene Transfer Gene Transfer + Knockdown Therapeutic Protein ExpressionAAV-Enabled Modalities:5

Abbreviation: IND = investigational new drug application.

How We Hear

Ear Drum

Round Window Membrane

(RWM)

Spiral Ganglion Cells

AuditoryNerve

Oval Window

• Sound enters the ear through the external auditory canal of the outer ear, where it vibrates the ear drum

• The sound vibrations are then relayed through the middle ear where they articulate with the cochlea at the oval window

• The cochlea contains a long, coiled, ribbon-like epithelial membrane that is suspended between two cochlear fluid compartments

• Sensory cells, called hair cells, sense the movement of fluid and convert the fluid waves into nerve impulses that are sent along the auditory nerve to the brain

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2

3

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Illustration ©Chris Gralapp6

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Overview of Genetically-Driven Hearing Loss

Autosomal Recessive

Autosomal Dominant

Nonsyndromic Syndromic

>75 genes >30 genes

>48 >10

1 of 500 newborns has disabling hearing loss

Genetic Causes (60-80%)

Syndromic (25-20%)

Nonsyndromic(75-80%)

Recessive(~80%)

Dominant (~19%)

Mitochondrial & X-Linked (~1%)

Complex Etiology (20-40%)

• Tens of millions of children with monogenic hearing loss worldwide

• Congenital hearing loss recognized as a potential neurodevelopmental emergency by the American Academy of Pediatrics

• Some of the most common forms of monogenic deafness affect an estimated 200,000 individuals in the U.S. and Europe

• No drugs currently approved for the treatment of sensorineural hearing loss

Note: Syndromic hearing loss means, in addition to hearing loss, the individual has other symptoms of medical importance.

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The Anatomy and Biology of the Inner Ear Are Ideal for One-Time Genetic Medicines

While the unique anatomical challenges of delivering to the inner ear have hindered genetic medicine development for hearing loss and other inner ear conditions, we believe Akouos is uniquely positioned to overcome these

delivery challenges

Opportunity to Leverage Learnings from Development of Genetic Medicines for the Eye and Brain

Unique Advantages of the Inner Ear

• Enclosed compartments → opportunity for local, targeted delivery

• Reduced immune surveillance → lower impact of neutralizing antibodies

• Non-dividing target cells → potential for one-time delivery to provide life-long benefit

• Fewer target cells and smaller delivery volume → less vector required for meaningful transgene expression

• Anatomy is fully developed at birth → more favorable benefit-risk profile in pediatric populations

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The Akouos Precision Genetic Medicine Platform

Novel Delivery Approach

Proprietary AAV Vector Library

Multimodal Capabilities

Gene transfer targeting loss-of-function mutations

Gene knockdown or editing targeting toxic gain-of-function or dominant negative mutations

Therapeutic protein expression (e.g., monoclonal antibody) targeting disease pathways responsible for non-monogenic hearing loss

Abbreviation: AAV = adeno-associated viral.

Akouos’s novel delivery approach is designed to allow for the safe and effective delivery of product candidates through the round window membrane (RWM)

• The surgical approach (transcanal tympanotomy) and venting (stapedotomy) are minimally invasive and routine in standard otologic practice

• Akouos's delivery device is designed to deliver product candidates in a fixed volume at a controlled flow rate and to be familiar to otologic surgeons

• Direct intracochlear administration through the RWM, with venting of the stapes footplate, allows for distribution of product candidates across the full length of the cochlea

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Novel Delivery Approach Designed to Enable Efficient Access to Target Cells and Controlled Distribution of Product Candidates Throughout the Cochlea

Vent in Stapes / Oval Window

Injected Fluid PathAkouos Delivery Device

in Round Window

Uncoiled Cochlea

Illustrations ©Chris Gralapp.

Administered fluid path

Abbreviation: kHZ = kilohertz.

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AAVAnc80 Exhibits High Transduction Efficiency Compared to Other AAV Capsids in Nonclinical Studies

Capsid AAV1 AAV2 AAV8 AAVAnc80Dose 21x 3.5x 7x 1x

Multiple independent investigations have shown increased hair cell transduction efficiency of AAVAnc80 relative to other AAV capsids in mouse and non-human primate models

0

20

40

60

80

100

%G

FP+

OH

Cs

0

20

40

60

80

100%

GFP

+IH

Cs

Apex

Base

AAVAnc80 Transduces Cochlear Hair Cells More Efficiently than Other AAV Capsids

Abbreviations: AAV = adeno-associated viral; IHCs = inner hair cells; GFP = green fluorescent protein; OHCs = outer hair cells.

Landegger et al. (2017), Nature Biotechnology 35, 280-284

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Multi-Dose Tropism Study in Cynomolgus Macaque Showed Efficient Inner Hair Cell Transduction at Three Weeks

75 to 100% of inner hair cells (IHCs) express transgene at 6E10 vg per cochlea in the cynomolgus macaque

Inn

er

Ha

ir C

ell

Tra

ns

du

cti

on

(%

) 100

80

60

40

20

00.06 0.5 4 32

2.4E11 vg6.0E10 vg1.5E10 vg

Dose

AAVAnc80-eGFP

Cochlear Frequency

Position (kHz)

Percentage of Inner Hair Cells Expressing GFP Three WeeksFollowing Administration of an AAVAnc80 Vector Encoding GFP

AAVAnc80-GFP Expression in Cynomolgus Macaque Cochlea Across Frequencies and Doses (in Vector Genomes (vg) per Cochlea)

Abbreviations: AAV = adeno-associated viral; GFP = green fluorescent protein; IHC = inner hair cells; kHz = kilohertz; OHC = outer hair cells; SC = supporting cells.

% Inner

Hair C

ells

Expre

ssin

g G

FP

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The High Transduction Efficiency of AAVAnc80 Coupled with Local Delivery to the Inner Ear Compartment Allows for a Dual Vector Approach for Larger Transgenes

Ability to deliver transgenes that are larger than 5 kilobases in size creates the potential for broader treatment of inner ear conditions

Percentage of Inner Hair Cells Expressing Transgene Three Weeks Following Administration of Dual AAVAnc80 Vectors

Cochlear Frequency Position (kHz)

% IH

Cs

Exp

ress

ing

GFP

Full-length protein

5’ GFP cDNA 3’ GFP cDNA

5’ GFP cDNA

3’ GFP cDNA

GFP mRNA

Abbreviations: AAV = adeno-associated viral; ABR = auditory brainstem response; cDNA = complementary DNA; GFP = green fluorescent protein; h = human; dB = decibels;IHCs = inner hair cells; ITR = inverted terminal repeats; kHz = kilohertz; mRNA = messenger RNA; polyA = polyadenylation tail; SA = splice acceptor; SD = splice donor; vg = vector genome.

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AAVAnc80 Efficiently Transduces Multiple Cell Types in the Inner Ear

• Conducted nonclinical studies across three different non-human primate models using GFP as a reporter gene delivered by AAVAnc80

• AAVAnc80 can efficiently transduce multiple target cell populations throughout the cochlea in the primate inner ear

• Pre-existing neutralizing antibodies, even at relatively high levels in serum, did not inhibit cochlear cell transduction following intracochlear delivery

AA

VA

nc80

-GF

P

Negative

Contr

ol

Abbreviations: AAV = adeno-associated viral; GFP = green fluorescent protein.

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Novel Delivery Approach Is Designed to Allow for the Safe and Effective Delivery of Product Candidates

Key Attributesof Delivery Approach

Akouos’s Novel Delivery ApproachPlanned for Clinical Use

A minimally invasive surgical approach

✓ Transcanal Tympanotomy(A standard surgical approach that provides access through the external auditory canal and

does not require drilling through mastoid)

Distribution of product candidate along full length of cochlea

✓ Fenestration of stapes footplate to serve as a vent(Achieved by a standard surgical technique called a stapedotomy)

Direct intracochlear administration through round window membrane

✓ Akouos Delivery Device

Delivery of product candidate at fixed volume and fixed rate

✓ Akouos Delivery Device

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Three weeks following intracochlear administration of AAVAnc80-eGFP, average

transduction per dose group and by cochlear frequency position. Seven NHPs with

venting of the stapes footplate (6 unilateral and 1 bilateral, for a total of 8 ears).

Three weeks following intracochlear administration of AAVAnc80-eGFP at a dose of

4.5E10 vg per cochlea, average transduction by cochlear frequency position. One NHP

with venting and two NHPs without venting of the stapes footplate (all bilateral, 6 ears).

Venting Supports Distribution of AAVAnc80 Across Length of Cochlea Following Intracochlear Administration

AAVAnc80-eGFP Efficiently Transduces Inner Hair Cells in Non-human Primates with Venting of Stapes Footplate

Without Venting, AAVAnc80-eGFP Transduction of Inner Hair Cells is Sporadic and Biased to Base of Cochlea in Non-human Primates

There may be potential to overcome this barrier, e.g., through increased dose, larger volume, and/or slower infusion, but these strategies may not be ideal for clinical development

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Dose (vg per cochlea):

% IH

Cs e

xpre

ssin

g e

GF

P

Cochlear Frequency Position (kHz)

% IH

Cs e

xpre

ssin

g e

GF

P

Cochlear Frequency Position (kHz)

Dose (vg per cochlea):

Abbreviations: AAV = adeno-associated viral; eGFP = enhanced green fluorescent protein; IHCs = inner hair cells; kHz = kilohertz; NHP = non-human primate; vg = vector genome.

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Multimodal Capabilities Create Potential to Address a Broad Range of Monogenic and Non-Monogenic Inner Ear Conditions

Gene Transfer

Single Vector

Dual Vector

Gene Knockdown

RNA-interference

Therapeutic Protein

Expression

Gene Editing

Nuclease-based

Non-nuclease-

based

CLRN1 OTOF Undisclosed autosomal dominant indications

GJB2

Hair Cell Regeneration

Vestibular Schwannoma

Akouos Precision Genetic Medicine Platform

Modality

Hair Cells

Secreted Proteins

Supporting Cells

Target

Initial pipeline spans multiple vector-mediated modalities and cochlear targets to potentially address inner ear conditions affecting hundreds of thousands of individuals in the U.S. and Europe

AK-OTOF Overview

• AK-OTOF encodes otoferlin, a protein that enables the sensory cells of the ear to release neurotransmitter vesicles, activating auditory neurons

• AK-OTOF

• Use AAVAnc80 as a delivery vehicle for the OTOF gene

• Administer product candidate directly into the inner ear• Delivery Method

• Progress and Status

• Promising nonclinical data generated in translationally relevant mouse models

• Pre-IND meeting with FDA; executing on agreed IND-enabling nonclinical studies

• Designing a Phase 1/2 trial for AK-OTOF and targeting an IND submission in 1H 2022

• FDA granted ODD and RPDD for AK-OTOF

• Indication• Treatment of OTOF-mediated hearing loss, a form of sensorineural hearing loss caused by

mutations in the OTOF gene

• Mutations in the OTOF gene are a major cause of genetic non-syndromic hearing loss

• Encodes otoferlin to enable release of neurotransmitter vesicles to activate auditory neurons in response to sound

• Auditory neurons then carry electronically encoded acoustic information to the brain allowing us to hear

• Mechanism of Action

• Estimated 20,000 cases of OTOF-mediated hearing loss in the US and EU• Prevalence

18Abbreviations: AAV = adeno-associated viral; FDA = U.S. Food and Drug Administration; IND = investigational new drug application;

ODD = Orphan Drug Designation; OTOF = otoferlin; RPDD = Rare Pediatric Disease Designation.

Dual Vector Delivery of AK-OTOF Led to Restoration of ABR Thresholds and Durable Auditory Function in Mice

AK-OTOF utilizes a dual vector approach to restore durable auditory function in knock-out mouse models –one AAVAnc80 vector carries the 5’ fragment of OTOF gene and the other AAVAnc80 vector carries the 3’ fragment of the OTOF gene

Weeks Post-Injection

Clic

k A

BR

th

resh

old

(d

B S

PL)

1 4 10 15 25 30

90

80

70

60

50

40

30

20

100

Otof-/- (n=6)

Otof-/- (5’ alone; n=3)

Otof-/- (5’ + 3’; n=8)

Wild-type (n=8)

Restoration of ABR Thresholds in Otof Knock-out MiceReceiving a Dual AAV Vector Expressing OTOF

Intracochlear Delivery of AK-OTOF Resulted in Significant, Long-term Hearing Restoration in Otof Knock-out Mice

Clic

k A

BR

th

resh

old

(d

B S

PL) 100

80

60

40

20

0

Approximate Age at ABR Test(Administration at 1 week old)

1 mo 3 mo 7 mo 10 mo

Otof-/- + AAVAnc80-hOTOF (n=3 per group)

Wild-Type (n=6 at 1 mo; n=3 at 10 mo)

Untreated Otof-/- (n=5)

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Akil et al., PNAS (2019)

Abbreviations: AAV = adeno-associated viral; ABR = auditory brainstem response; dB SPL = decibel sound pressure level; mo = month; OTOF = otoferlin.

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A Single Dose of AK-OTOF Restored Auditory Function in Otoferlin Knockout (Otof -/-) Mice with Mature Cochleae

Time re Click Onset (msec) Time re Click Onset (msec) Time re Click Onset (msec)

Wild-Type Vehicle Control Otoferlin KO + Vehicle Control Otoferlin KO + AAVAnc80-hOTOF

In a nonclinical study, a single dose of AK-OTOF restored auditory function in mice lacking otoferlin

Abbreviations: dB SPL = decibel sound pressure level; KO = knockout; msec = millisecond.

Planned AK-OTOF Phase 1/2 Clinical Trial

Part A Dose Escalation

Assess: Safety, tolerability, and bioactivity

Part BCohort Expansion

Assess: Safety and effectiveness

Up to 5-year clinical follow-up

(1) Based on pre-IND meeting with FDA in September 2019.

Key Eligibility• Individuals with otoferlin gene (OTOF)-mediated hearing loss • Amenable to surgical delivery and potential for benefit• May enroll children as young as one year old in the expansion phase (1)

Administration • Administered to trial participants through a single unilateral intracochlear injection

Efficacy Endpoints • Objective and clinically relevant ABR testing and age-appropriate behavioral assessment

Timing• Target IND submission in 1H 2022• Intend to file the delivery device along with the investigational product as a combination product (1)

21 Abbreviations: ABR = auditory brainstem response; FDA = U.S. Food and Drug Administration; IND = investigational new drug application.

AK-antiVEGF Overview

• AK-antiVEGF encodes a secreted inhibitor of vascular endothelial growth factor (VEGF) to treat vestibular schwannoma

• AK-antiVEGF

• Progress and Status

• Computational modelling supports the potential for diffusion of anti-VEGF protein, at or above reported biologically active levels, to site of tumor

• An initial NHP study long-term, local expression of anti-VEGF protein is robust and well tolerated

• Pre-IND meeting feedback supports IND submission targeted in 2022

• Indication• Treatment of vestibular schwannoma, a common intracranial tumor

• Current interventional standard of care consists of surgical resection / removal and/or radiation, both of which typically result in hearing loss and can be associated with significant morbidity

• Systemic anti-VEGF has been shown to reduce tumor volume and improve hearing in some patients with vestibular schwannoma

• Local delivery may avoid the systemic side effects of high dose intravenous VEGF inhibitor infusion and could remove or reduce the need for other interventions

• Mechanism of Action

• Estimated to affect approximately 200,000 individuals in the US and EU• Prevalence

• Uses AAVAnc80 as a delivery vehicle to achieve local, sustained anti-VEGF protein at tumor site

• Administer product candidate directly into the inner ear• Delivery Method

22 Abbreviations: AAV = adeno-associated viral; IND = investigational new drug application; NHP = non-human primate; VEGF = vascular endothelial growth factor.

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AK-antiVEGF for the Treatment of Vestibular Schwannoma

Human Data Demonstrate Ability of Systemic VEGF Inhibitor to Improve Hearing and Reduce Tumor Volume in Some Patients with

Vestibular Schwannoma

Nonclinical Data in NHPs Demonstrate Delivery of AK-antiVEGF is Well-Tolerated and Results in Potentially Therapeutic Protein Expression

AAV-mediated anti-VEGF protein secretion in perilymph

Computational Modeling Supports Feasibility of Diffusion to Tumor Site

Shifts in ABR thresholds(relative to baseline ABRs in the same

ear prior to intracochlear administration are shown at 1, 2, 3,

and 6 months post-intracochlear administration of an AAVAnc80

vector encoding anti-VEGF. Group means (±SD) at each timepoint

reflect bilateral measurements in each NHP on study.

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1. Range of location of early VS from MRI data (Koen 2020 Otolaryngol Head Neck Surg)

Abbreviations: AAV = adeno-associated viral; ABR = auditory brainstem response; dB = decibel; IAC = internal auditory canal; kHz = kilohertz; mm = millimeter; NHP = non-human primate; SD = standard deviation; VEGF = vascular endothelial growth factor.

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AK-CLRN1 Overview

• AK-CLRN1 encodes clarin-1, a protein believed to modulate cochlear hair cell mechanotransduction and synaptic function, for patients with Usher syndrome type 3A

• AK-CLRN1

• Progress and Status

• Published data demonstrate ability of AAV-mediated delivery of mouse CLRN1 to rescue auditory function in mouse model of Usher syndrome type 3A

• Additional nonclinical data with AAVAnc80-mediated delivery of human CLRN1 demonstrate auditory function rescue in mice with mature cochleae

• Product candidate selected

• Indication

• Treatment of sensorineural hearing loss due to mutations in the CLRN1 gene

• Mutations of CLRN1 gene cause syndromic genetic hearing / vision loss, characterized by progressive sensorineural hearing impairment and progressive vision loss

• Mutations in CLRN1 gene reduce the production and localization of CLRN-1 protein to hair cell membranes

• AK-CLRN1 is intended to treat hearing loss in patients with Usher syndrome type 3A by delivery of a healthy copy of CLRN1 to cochlear hair cells

• Mechanism of Action

• Estimated 2,000 cases in the US and EU• Prevalence

• Uses AAVAnc80 as a delivery vehicle for the CLRN1 gene

• Administer product candidate directly into the inner ear• Delivery Method

Abbreviation: AAV = adeno-associated viral.

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Proof of Concept Data: AAV-mediated Delivery of CLRN1Recovered Auditory Function in a Knock-out Mouse Model

•Nonclinical data demonstrated auditory function preservation in the KO-TgAC1 mouse model, which recapitulates the auditory phenotype observed in human USH3A patients

•AAV delivery of mouse Clrn1 with its endogenous UTR preserves auditory function at levels near wildtype animals

•Early nonclinical data show that AAVAnc80 encoding human clarin-1 can rescue auditory function in KO-TgAC1 mice with mature cochleae

WT KO-TgAC1 KO-TgAC1 + Clrn1 + UTR

Restoration of Auditory Function in CLRN1 KO Mice Injected at P2-3

ABR Waveforms

Abbreviations: AAV = adeno-associated viral; ABR = auditory brainstem response; db SPL = decibel sound pressure level; KO = knockout; UTR = untranslated region; WT = wild type.

Geng et al., Scientific Reports (2017)

• Today, few individuals with auditory neuropathy receive a genetic diagnosis. A key barrier is the availability and accessibility of genetic testing.

• A genetic diagnosis for auditory neuropathy:

▪ Can empower individuals to make informed choices, foster connections with others living with disabling hearing loss, and may provide valuable insight into medical management

▪ Could help individuals and their healthcare providers determine potential eligibility for future clinical trials

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The Resonate™ Program Seeks to Improve Access to Genetic Testing for Eligible Individuals with Auditory Neuropathy

Akouos is partnering with Blueprint Genetics to provide access to a potential genetic diagnosis at no cost to eligible individuals, their insurance, or their healthcare providers

• To be eligible for the program, individuals:

▪ Can be any age;

▪Must have a current or prior clinical diagnosis of bilateral auditory neuropathy, or a medical history consistent with bilateral auditory neuropathy; and

▪Must not have a syndromic medical history

• Participants in the program have access to the Blueprint Genetics Comprehensive Hearing Loss and Deafness Panel that includes more than 230 genes associated with genetic forms of hearing loss

The program is available in the United States and plans to expand to additional geographic regions throughout 2021

TM

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Key Advantages to Our Manufacturing Process

Low dose requirements given small size and compartmentalized nature of the inner ear

Targeted delivery and high transduction efficiency alleviate the need for large scale production

Exclusive access to AAVAnc vectors for inner ear provides opportunity to optimize production process and secure additional competitive advantage

Potential to expand beyond Phase 1/2

Well characterized HEK293 cell suspension and 250 L bioreactor system

Clinical-scale and intended commercial-scale manufacturing process for Akouos’s product candidates, including AK-OTOF, has resulted in multiple successful at-scale batches of

AAVAnc80 vectors

Abbreviations: AAV = adeno-associated viral; HEK293 = human embryonic kidney 293; L = liter.

• Existing agreement with Lonza, which performed manufacturing for pivotal IND-enabling nonclinical studies for the AK-OTOF program

• Working with multiple third-party manufacturers to advance cGMP campaigns for both the AK-OTOF and AK-antiVEGF IND submissions

Manufacturing to Support Near- and Long-Term Growth

Expertise in Gene Therapy and Gene Editing

• Expertise covers development from vector design through drug product manufacture

• Developing scalable manufacturing capabilities, which may allow for significant control over process development timelines and cost

• Developing internal capabilities to support manufacturing activities through Phase 1/2 clinical trials

• Leveraging single use, disposable, closed system operations aligned to genetic medicine platform to promote both flexibility and cost-effectiveness

• Internal analytical and process development

• 250-liter single-use bioreactor system using suspension HEK293 cells

• Completed manufacturing of AK-antiVEGF for IND-enabling GLP toxicology study

Building In-House Research and cGMP

Manufacturing Capabilities

Agreements with Well-Established CDMOs

28 Abbreviations: AAV = adeno-associated viral; CDMO = contract development and manufacturing organization; cGMP = current good manufacturing practice; GLP = good laboratory practice; HEK293 = human embryonic kidney 293; IND = investigational new drug application.

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2020 in Review and Key Milestones

2020 Highlights Key Recent and Upcoming Milestones

• Expanded team and board of directors

• Continued progress towards IND filing to support planned AK-OTOF Phase 1/2 clinical trial

• General alignment with FDA on path to IND submission for AK-antiVEGF

• AK-CLRN1 product candidate selection; next milestone is pre-IND meeting

• Initiated build of internal manufacturing capabilities to support research and future clinical activities

• Raised approximately $349 million in gross proceeds, which is expected to fund operations for at least two years

• Announced Resonate™ program providing genetic testing for eligible individuals with auditory neuropathy

• Presented data at ARO and ASGCT conferences

• AK-OTOF received ODD and RPDD from FDA

• Targeting IND submission for AK-OTOF in 1H 2022

• Continuing progress towards IND submission for AK-antiVEGF targeted in 2022

• Demonstrating broad applicability of platform with GJB2 candidate selection and hair cell regeneration and autosomal dominant hearing loss target announcements expected in 2021

• Establishing infrastructure and capabilities for internal cGMP manufacturing in 2021

Abbreviations: ARO = Association for Research in Otolaryngology; ASGCT = American Society of Gene and Cell Therapy; cGMP = current good manufacturing practice; FDA = U.S. Food and Drug Administration; IND = investigational new drug application.; ODD = Orphan Drug Designation; RPDD = Rare Pediatric Disease Designation.