Re-administration of adeno-associated virus (AAV)-mediated gene therapy remains challenging due to neutralizing antibodies (NAbs) induced by the initial dose. We previously conducted a single-arm trial showing that single-dose administration of AAV-hOTOF gene therapy in individuals with OTOF-related deafness is safe and leads to hearing improvements. Here we initially demonstrate that AAV1-hOTOF re-administration to the contralateral ear in Otof-/- mice with peak serum NAb titers successfully rescued hearing with limited immune activation. After a protocol amendment of our trial, four patients (aged 2.2-3.4 years) with pre-existing NAbs (titers 1:135-1:3,645), who had previously received a single dose of the gene therapy, were enrolled to receive a second dose in the contralateral ear, as part of the ongoing trial, with a follow-up ranging from 26 weeks to 52 weeks. The primary endpoint was the occurrence of dose-limiting toxicities at 6 weeks and secondary endpoints included safety and auditory function. No dose-limiting toxicity occurred within 6 weeks. In the secondary outcomes, the 26-week average auditory brainstem response threshold in the second treated ear improved from >95 dB at baseline to 43 dB, 63 dB, 80 dB and 53 dB in patients 1-4, respectively. Safety assessment showed that all adverse events were grade 1-2, except one grade 3 decreased neutrophil count; no serious adverse events occurred. These data provide preliminary insights on the safety and efficacy of re-administration of AAV1-hOTOF gene therapy in patients with congenital deafness. Longer follow-up and larger cohorts are needed to establish the safety and efficacy of repeated administration of gene therapies. Trial registration no.: ChiCTR2200063181 .

Autosomal recessive deafness 9, caused by OTOF gene mutations, is characterized by severe-to-complete congenital deafness1. Although gene therapy has shown benefits in a small number of patients2-5, its safety and efficacy across broader age ranges and longer follow-up periods, as well as predictors of treatment outcomes, remain unclear. In this single-arm, multicentre trial conducted at eight centres, 42 participants (aged 0.8-32.3 years) received adeno-associated virus (AAV) serotype 1 carrying a human OTOF coding transgene (AAV1-hOTOF) at three vector dose groups, with up to 2.5-year follow-up. The primary end point was dose-limiting toxicity within 6 weeks. The secondary end point assessed efficacy and adverse events. No dose-limiting toxicities were observed. Grade 3 adverse events included decreased neutrophil count. Hearing was recovered in 90% of participants treated with AAV1-hOTOF, with gradual and stable improvement in auditory brainstem response threshold from greater than 97 ± 1 dB normalized hearing level at baseline to 54 ± 3, 51 ± 3, 50 ± 3 and 42 ± 5 dB normalized hearing level at 1, 1.5, 2 and 2.5 years, respectively, and behavioural audiometry improving from greater than 96 ± 3 dB hearing level at baseline to 37 ± 5 dB hearing level at 2.5 years. Participants aged 0.5-18 years showed greater hearing improvement than adults. A higher number of present distortion product otoacoustic emissions at baseline or biallelic non-truncated OTOF variants was associated with better hearing recovery. Participants with hearing recovery demonstrated gradual improvement in speech perception. AAV1-hOTOF is well-tolerated and efficacious across a broader patient population, with sustained therapeutic benefits for up to 2.5 years. Chinese Clinical Trial Registry registration: ChiCTR2200063181 .

Abstract A major challenge in gene therapy for GJB2 -related hearing loss (DFNB1)—the most common form of hereditary deafness—is achieving efficient and precise connexin 26 delivery. Herein, we engineered two cell type-specific promoters (GJB2-1 and WFS1-2274) and developed an AAV capsid, AAV-MAS012, with enhanced transduction efficiency in mature cochlear cells. Our AAV-mediated gene therapy systems restored hearing of low-to-mid-frequencies in newborn Gjb2 cKO mice to wild-type levels and maintained for 45 weeks. Additionally, our therapeutic systems restored low-to-mid-frequencies hearing function to wild-type levels in adult Gjb2 cKO mice. A humanized version of the therapy, AAV-MAS012-WFS1-2274-hGJB2, rescued hearing function in two distinct Gjb2 -deficient mouse models, and demonstrated a favorable safety profile in nonhuman primates. This study represents the first successful hearing restoration in adult Gjb2 -deficient mice. The significant therapeutic efficacy of the humanized gene therapy system shows great potential for clinical translation in DFNB1 patients.

Recent breakthroughs in gene therapy for autosomal recessive deafness 9 (DFNB9) caused by OTOF mutations have transformed treatment paradigms for hereditary hearing loss (HHL). To date, eight clinical trials targeting DFNB9 have been registered in 51 centers across eight countries, demonstrating the rapid progress of gene therapy in auditory medicine. These pioneering studies establish the framework for the clinical translation of gene therapy targeting HHL. This review synthesizes progress in OTOF-related clinical trials, highlighting translational foci such as inner ear drug delivery, trial design, safety assessments, and auditory restoration outcomes. Key challenges in optimizing future therapeutic strategies - including addressing anatomical constraints, refining patient selection criteria, and standardizing outcome measures - are critically examined.

Pathogenic mutations in the OTOF gene cause autosomal recessive hearing loss (DFNB9), one of the most common forms of auditory neuropathy. There is no biological treatment for DFNB9. Here, we designed an OTOF gene therapy agent by dual-adeno-associated virus 1 (AAV1) carrying human OTOF coding sequences with the expression driven by the hair cell-specific promoter Myo15, AAV1-hOTOF. To develop a clinical application of AAV1-hOTOF gene therapy, we evaluated its efficacy and safety in animal models using pharmacodynamics, behavior, and histopathology. AAV1-hOTOF inner ear delivery significantly improved hearing in Otof-/- mice without affecting normal hearing in wild-type mice. AAV1 was predominately distributed to the cochlea, although it was detected in other organs such as the CNS and the liver, and no obvious toxic effects of AAV1-hOTOF were observed in mice. To further evaluate the safety of Myo15 promoter-driven AAV1-transgene, AAV1-GFP was delivered into the inner ear of Macaca fascicularis via the round window membrane. AAV1-GFP transduced 60%-94% of the inner hair cells along the cochlear turns. AAV1-GFP was detected in isolated organs and no significant adverse effects were detected. These results suggest that AAV1-hOTOF is well tolerated and effective in animals, providing critical support for its clinical translation.

BACKGROUND:Gene therapy shows promising potential for patients with autosomal recessive deafness 9 (DFNB9), with ongoing clinical trials (ChiCTR2200063181). A deeper understanding of changes in audiological characteristics is crucial for optimizing the monitoring and evaluation of patients' recovery post-treatment. METHODS:Audiological data were collected from 10 DFNB9 patients who underwent gene therapy, including auditory brain stem response (ABR), auditory steady-state response (ASSR), distortion product otoacoustic emission (DPOAE), and pure-tone audiometry (PTA) tests. FINDINGS:A clear ABR wave V was observed in all participants by 13 weeks. By 52 weeks, distinct ABR waves I and III were visible in some participants. The 1-kHz ABR wave V latency at 85 dB decreased significantly from 9.220 (range 9.015-9.810) ms at 4 weeks to 8.190 (range 7.780-8.530) ms at 52 weeks (p = 0.004), with a trend toward increased wave V amplitude (p = 0.055). Significant correlations were observed between PTA, ABR, and ASSR thresholds at 0.5-4 kHz. The DPOAE signal-to-noise ratio (SNR) at 26 weeks post-treatment showed no significant difference compared with pre-treatment SNR values, nor were there significant correlations between the pre-treatment SNR values and the post-treatment ABR thresholds. CONCLUSIONS:The study demonstrates that ABR and ASSR are reliable objective tools for assessing hearing recovery in DFNB9 patients after gene therapy. ABR reveals positive changes in the auditory pathway over time after gene therapy, enhancing our understanding of the impact of gene therapy on auditory pathway recovery. FUNDING:This work was funded by the National Natural Science Foundation of China.

Pathological mutations in the OTOF gene cause autosomal recessive deafness 9 (DFNB9). Although dual-adeno-associated virus (AAV) gene replacement therapy has been shown to partially rescue the hearing of patients with DFNB9, the therapeutic effects still need further exploration. To investigate the impact of different recombination strategies on the efficacy of OTOF gene therapy, we constructed five dual-AAV1 therapeutic agents using RNA or protein splicing principles. Based on the recombination strategy using RNA splicing, the AAV1-AK system rescued the hearing of Otof-/- mice to 55-70 dB, which outperformed the AAV1-AP and AAV1-TS systems. Based on protein splicing, the AAV1-intein system rescued the hearing of Otof-/- mice to 35-70 dB, which outperformed that of AAV1-AK, and the effects lasted up to 12 months after injection in both newborn and adult mice. The efficacy of otoferlin re-expression and the number and functional restoration of ribbon synapses in the AAV1-intein system were also better than the AAV1-AK system. These results show that protein recombination is more efficient than nucleic acid recombination for gene therapy in DFNB9. Therefore, this work provides not only data for optimization of DFNB9 gene therapy but also a reference for the delivery of other large genes.

Individuals with congenital deafness that have received gene therapy represent a unique group who experience hearing recovery and speech development. However, it is unclear how hearing-related cortex changes because of gene therapy. Here we study neural processing in ten patients using functional near-infrared spectroscopy and electroencephalography during a six-month follow-up period. Patients showed an enhancement of activation in the auditory cortex, particularly in parts of the Sylvian parietotemporal area while listening to music. Activation in the right anterior temporal lobe and left Sylvian parietotemporal area was also enhanced when listening to speech. The electroencephalography data showed that the power of the resting-state electroencephalography beta band at time points T2 and T3 was statistically significantly increased after gene therapy, and mismatch negativity amplitudes at T2 and T3 were statistically significantly higher than those at T0. The mental developmental level of the patients also increased after gene therapy. These preliminary findings illuminate the neural and cognitive effects of gene therapy, supporting its potential effectiveness in auditory and mental development.

Importance:OTOF gene therapy (GT) has been shown to improve hearing and speech. The efficacy of GT remains to be compared against cochlear implantation (CI), the current gold standard for congenital deafness. Objective:To evaluate treatment outcomes in auditory and speech perception between patients with congenital deafness treated with GT, CI, or both. Design, Setting, and Participants:This nonblind cohort study was conducted between December 2022 and November 2024. GT patients received follow-up at 3, 6, and 12 months; CI patients received 1-time evaluation at the corresponding time intervals or longer (3, 6, or 12 months). The study was conducted at a single class A tertiary hospital in China. Participants with congenital severe to complete hearing loss, aged 1 to 18 years, who received GT or CI were enrolled. They were matched on duration of deafness, hearing thresholds, and speech ability at the presurgical baseline. Of 1568 participants screened, 72 participants enrolled. Participants were excluded if they had inner ear malformations or vestibular-cochlear nerve abnormalities. Exposures:GT only vs CI; bimodal (unilateral GT plus contralateral CI) vs bilateral CI; GT (CI turned off [CI-off]) vs unilateral CI. Main Outcomes and Measures:The primary outcomes were auditory and speech perception evaluated by questionnaires, including the Infant-Toddler Meaningful Auditory Integration Scale/Meaningful Auditory Integration Scale (IT-MAIS/MAIS), and tests, including audiometry, speech, and music tests. The main secondary outcome was auditory information processing ability assessed by mismatch negativity (MMN). Results:A total of 11 GT patients (6 male [55%]; mean [SD] age at baseline, 3.7 [2.8] years) and 61 CI patients (34 male [56%]; mean [SD] age at baseline, 1.9 [1.5] years) were enrolled. The mean (SD) auditory brainstem response thresholds were restored from greater than 95.0 (0.0) decibels normalized hearing level (dB nHL) to 54.8 (15.9) dB nHL in 9 GT patients at 12 months. For GT-only vs CI in auditory and speech perception, GT patients performed better in IT-MAIS/MAIS at 6 months (median [IQR] score, 31.0 [30.0-32.0] vs 23.5 [19.0-26.3]; P = .01) and 12 months (median [IQR] score, 32.0 [31.0-32.0] vs 28.0 [24.5-30.5]; P = .007). GT patients showed shorter latencies of MMN at 6 months (median [IQR], 0.20 [0.05-0.21] seconds vs 0.23 [0.22-0.25] seconds; P = .006). For bimodal patients at 12 months, GT (CI-off) patients performed better than unilateral CI patients in speech in a noisy environment (median [IQR] disyllable, -1.0 [-3.0 to 2.4] dB sound pressure level (SPL) vs 5.3 [3.1 to 12.1] dB SPL; P = .03); GT plus CI patients performed better than bilateral CI patients in singing in-tune rates (median [IQR], 66.6% [53.7%-83.9%] vs 37.1% [30.3%-56.3%]; P = .04); GT plus CI patients showed shorter latencies of MMN at 12 months (median [IQR], 0.08 [0.07-0.10] seconds vs 0.21 [0.15-0.23] seconds, P = .01). Conclusions and Relevance:GT patients showed stable hearing recovery and exhibited more rapid improvements in auditory and speech performance than CI patients, while outperforming CI patients in speech in noise performance and music perception. These findings suggest that GT may provide a novel effective treatment alternative for patients with genetically driven congenital deafness.

Aminoglycosides are commonly used for the treatment of life-threatening bacterial infections, however, aminoglycosides may cause irreversible hearing loss with a long-term clinical therapy. The mechanism and prevention of the ototoxicity of aminoglycosides are still limited although amounts of studies explored widely. Specifically, advancements in programmed cell death (PCD) provide more new perspectives. This review summarizes the general signal pathways in programmed cell death, including apoptosis, autophagy, and ferroptosis, as well as the mechanisms of aminoglycoside-induced ototoxicity. Additionally, novel interventions, especially gene therapy strategies, are also investigated for the prevention or treatment of aminoglycoside-induced hearing loss with prospective clinical applications.

Gene therapy has made significant progress in the treatment of hereditary hearing loss. However, most research has focused on deafness-related genes that are primarily expressed in hair cells with less attention given to multisite-expressed deafness genes. MPZL2, the second leading cause of mild-to-moderate hereditary deafness, is widely expressed in different inner ear cells. We generated a mouse model with a deletion in the Mpzl2 gene, which displayed moderate and slowly progressive hearing loss, mimicking the phenotype of individuals with DFNB111. We developed a gene replacement therapy system mediated by AAV-ie for efficient transduction in various types of cochlear cells. AAV-ie-Mpzl2 administration significantly lowered the auditory brainstem response and distortion product otoacoustic emission thresholds of Mpzl2-/- mice for at least seven months. AAV-ie-Mpzl2 delivery restored the structural integrity in both outer hair cells and Deiters cells. This study suggests the potential of gene therapy for MPZL2-related deafness and provides a proof of concept for gene therapy targeting other deafness-related genes that are expressed in different cell populations in the cochlea.

Gene therapy is a promising approach for hereditary deafness. We recently showed that unilateral AAV1-hOTOF gene therapy with dual adeno-associated virus (AAV) serotype 1 carrying human OTOF transgene is safe and associated with functional improvements in patients with autosomal recessive deafness 9 (DFNB9). The protocol was subsequently amended and approved to allow bilateral gene therapy administration. Here we report an interim analysis of the single-arm trial investigating the safety and efficacy of binaural therapy in five pediatric patients with DFNB9. The primary endpoint was dose-limiting toxicity at 6 weeks, and the secondary endpoint included safety (adverse events) and efficacy (auditory function and speech perception). No dose-limiting toxicity or serious adverse event occurred. A total of 36 adverse events occurred. The most common adverse events were increased lymphocyte counts (6 out of 36) and increased cholesterol levels (6 out of 36). All patients had bilateral hearing restoration. The average auditory brainstem response threshold in the right (left) ear was >95 dB (>95 dB) in all patients at baseline, and the average auditory brainstem response threshold in the right (left) ear was restored to 58 dB (58 dB) in patient 1, 75 dB (85 dB) in patient 2, 55 dB (50 dB) in patient 3 at 26 weeks, and 75 dB (78 dB) in patient 4 and 63 dB (63 dB) in patient 5 at 13 weeks. The speech perception and the capability of sound source localization were restored in all five patients. These results provide preliminary insights on the safety and efficacy of binaural AAV gene therapy for hereditary deafness. The trial is ongoing with longer follow-up to confirm the safety and efficacy findings. Chinese Clinical Trial Registry registration: ChiCTR2200063181.

Adeno-associated viral (AAV) vectors are increasingly used as vehicles for gene delivery to treat hearing loss. However, lack of specificity of the transgene expression may lead to overexpression of the transgene in nontarget tissues. In this study, we evaluated the expression efficiency and specificity of transgene delivered by AAV-PHP.eB under the inner ear sensory cell-specific Myo15 promoter. Compared with the ubiquitous CAG promoter, the Myo15 promoter initiates efficient expression of the GFP fluorescence reporter in hair cells, while minimizing non-specific expression in other cell types of the inner ear and CNS. Furthermore, using the Myo15 promoter, we constructed an AAV-mediated therapeutic system with the coding sequence of OTOF gene. After inner ear injection, we observed apparent hearing recovery in Otof-/- mice, highly efficient expression of exogenous otoferlin, and significant improvement in the exocytosis function of inner hair cells. Overall, our results indicate that gene therapy mediated by the hair cell-specific Myo15 promoter has potential clinical application for the treatment of autosomal recessive deafness and yet for other hereditary hearing loss related to dysfunction of hair cells.

A prevalent recessive mutation (c.2485C>T, p.Q829X) within the OTOF gene leads to profound prelingual hearing loss. Here we show that in Otof mice harbouring a mutation (c.2482C>T, p.Q828X) homozygous to human OTOF that faithfully mimics the hearing-loss phenotype, a base editor (consisting of the deaminase ABE7.10max and the Cas9 variant SpCas9-NG) packaged in adeno-associated viruses and injected into the inner ear of the mice via the round-window membrane effectively corrected the pathogenic mutation, with no apparent off-target effects. The treatment restored the levels of the otoferlin protein in 88

Adeno-associated virus (AAV)-mediated gene therapy is widely applied to treat numerous hereditary diseases in animal models and humans. The specific expression of AAV-delivered transgenes driven by cell type-specific promoters should further increase the safety of gene therapy. However, current methods for screening cell type-specific promoters are labor-intensive and time-consuming. Herein, we designed a “multiple vectors in one AAV” strategy for promoter construction in vivo. Through this strategy, we truncated a native promoter for Myo15 expression in hair cells (HCs) in the inner ear, from 1,611 bp down to 1,157 bp, and further down to 956 bp. Under the control of these 2 promoters, green fluorescent protein packaged in AAV-PHP.eB was exclusively expressed in the HCs. The transcription initiation ability of the 2 promoters was further verified by intein-mediated otoferlin recombination in a dual-AAV therapeutic system. Driven by these 2 promoters, human otoferlin was selectively expressed in HCs, resulting in the restoration of hearing in treated Otof −/− mice for at least 52 weeks. In summary, we developed an efficient screening strategy for cell type-specific promoter engineering and created 2 truncated Myo15 promoters that not only restored hereditary deafness in animal models but also show great potential for treating human patients in future.

Background Autosomal recessive deafness 9, caused by mutations of the OTOF gene, is characterised by congenital or prelingual, severe-to-complete, bilateral hearing loss. However, no pharmacological treatment is currently available for congenital deafness. In this Article, we report the safety and efficacy of gene therapy with an adeno-associated virus (AAV) serotype 1 carrying a human OTOF transgene (AAV1-hOTOF) as a treatment for children with autosomal recessive deafness 9. Methods This single -arm, single -centre trial enrolled children (aged 1-18 years) with severe-to-complete hearing loss and confirmed mutations in both alleles of OTOF , and without bilateral cochlear implants. A single injection of AAV1-hOTOF was administered into the cochlea through the round window. The primary endpoint was dose-limiting toxicity at 6 weeks after injection. Auditory function and speech were assessed by appropriate auditory perception evaluation tools. All analyses were done according to the intention-to-treat principle. This trial is registered with Chinese Clinical Trial Registry, ChiCTR2200063181, and is ongoing. Findings Between Oct 19, 2022, and June 9, 2023, we screened 425 participants for eligibility and enrolled six children for AAV1-hOTOF gene therapy (one received a dose of 9 x 10 11 vector genomes [vg] and five received 15 x 10 12 vg). All participants completed follow-up visits up to week 26. No dose-limiting toxicity or serious adverse events occurred. In total, 48 adverse events were observed; 46 (96%) were grade 1-2 and two (4%) were grade 3 (decreased neutrophil count in one participant). Five children had hearing recovery, shown by a 40-57 dB reduction in the average auditory brainstem response (ABR) thresholds at 05-40 kHz. In the participant who received the 9 x 10 11 vg dose, the average ABR threshold was improved from greater than 95 dB at baseline to 68 dB at 4 weeks, 53 dB at 13 weeks, and 45 dB at 26 weeks. In those who received 15 x 10 12 AAV1-hOTOF, the average ABR thresholds changed from greater than 95 dB at baseline to 48 dB, 38 dB, 40 dB, and 55 dB in four children with hearing recovery at 26 weeks. Speech perception was improved in participants who had hearing recovery. Interpretation AAV1-hOTOF gene therapy is safe and efficacious as a novel treatment for children with autosomal recessive deafness 9.

Background To create and develop a delivery approach for clinical inner ear gene therapy, we conducted a study of trans-round window membrane (RWM) microinjection using a pipetting microneedle via transcanal endoscopic ear surgery (TEES). Methods The implementation of the trans-RWM microinjection surgery involved seven cadaveric specimens, and the surgical procedures and the pipetting microneedle were developed and optimized. The TEES procedures included tympanic cavity visualization, RWM exposure, stapes footplate perforation, and trans-RWM microinjection. The feasibility of different pipetting microneedles was evaluated during microinjection. Results Exposure of the RWM microinjection site could be easily achieved in TEES, and the soft-connected pipetting microneedle was most suitable for the trans-RWM microinjection. The fluid outflow from stapes perforation could be visibly observed during the microinjection, which indicated inner ear drug delivery was successful. This inner ear drug delivery approach was successfully applied in the clinical trial. Conclusion The trans-RWM microinjection via the soft-connected pipetting microneedle in TEES was proved to be a feasible delivery approach of the inner ear gene therapy.

Gene therapy focuses on genetic modification to produce therapeutic effects or treat diseases by repairing or reconstructing genetic material, thus being expected to be the most promising therapeutic strategy for genetic disorders. Due to the growing attention to hearing impairment, an increasing amount of research is attempting to utilize gene therapy for hereditary hearing loss (HHL), an important monogenic disease and the most common type of congenital deafness. Several gene therapy clinical trials for HHL have recently been approved, and, additionally, CRISPR-Cas tools have been attempted for HHL treatment. Therefore, in order to further advance the development of inner ear gene therapy and promote its broad application in other forms of genetic disease, it is imperative to review the progress of gene therapy for HHL. Herein, we address three main gene therapy strategies (gene replacement, gene suppression, and gene editing), summarizing the strategy that is most appropriate for particular monogenic diseases based on different pathogenic mechanisms, and then focusing on their successful applications for HHL in preclinical trials. Finally, we elaborate on the challenges and outlooks of gene therapy for HHL.