Akouos IPO Presentation Deck

Proof of Concept Data: AAV-Mediated Delivery of CLRN1 Recovered Hearing in a Knock-Out Mouse Model 35 Preclinical data demonstrated hearing 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 hearing levels near wildtype animals • Early preclinical data show that AAVAnc80 encoding human Clarin-1 can rescue hearing in mature KO-TgAC1 mice Restoration of Hearing Thresholds in CLRN1 KO Mouse Model Click ABR Threshold (dB SPL) 86 dB SPL 81 dB SPL. 76 dB SPL 71 dB SPL 66 dB SPL 61 dB SPL 56 dB SPL 51 dB SPL. 46 dB SPL 41 dB SPL 36 dB SPL 31 dB SPL CONFIDENTIAL 49 60 70 80 90 100 110 117 160 Days Postnatal WT At UTR=untranslated region ABR Waveforms KO-TRAC1 AAV AKOUOS Untreated AAV + UTR Wild-Type Cim1 - TgAC1 KO-TRAC1+Clrn1 + UTR

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