Hear and Now: Ongoing Clinical Trials to Prevent Drug-Induced Hearing Loss

Identification of druggable binding sites and small molecules as modulators of TMC1

Our ability to hear and maintain balance relies on the proper functioning of inner ear sensory hair cells, which translate mechanical stimuli into electrical signals via mechano-electrical transducer (MET) channels, composed of TMC1/2 proteins. However, the therapeutic use of ototoxic drugs, such as aminoglycosides and cisplatin, which can enter hair cells through MET channels, often leads to profound auditory and vestibular dysfunction. To date, our understanding of how small-molecule modulators interact with TMCs remains limited, hampering the discovery of novel drugs. Here, we propose a structure-based drug screening approach, integrating 3D-pharmacophore modeling, molecular dynamics simulations of the TMC1 + CIB2 + TMIE complex, and experimental validation. Our pipeline successfully identified three potential drug-binding sites within the TMC1 pore, phospholipids, and key amino acids involved in the binding of several compounds, as well as FDA-approved drugs that reduced dye uptake in cultured cochlear explants. Our pipeline offers a broad application for discovering modulators for mechanosensitive ion channels.

Rational Design of Inner Ear Drug Delivery Systems

The number of people with hearing loss disorders is enormous, causing great physical and mental stress to patients, as well as a huge social burden. Among these patients, hearing loss caused by inner ear lesions accounts for a large proportion. Therefore, treatment of the inner ear is important. Inner ear drug delivery systems, which can reduce the side effects of systemic drug administration by delivering drugs directly to the inner ear, are important in sensorineural hearing loss. Here, the development of inner ear drug delivery systems is focused, including the complex physiological structure that they face, types of drugs delivered, routes of administration, and forms of drug delivery carrier platforms. Recent studies in this process are presented and it is concluded with a summary and outlook on the problems faced and possible solutions.

A comprehensive review of the impact of natural products in preventing drug-induced ototoxicity

Ototoxicity, the property of certain drugs to cause hearing loss, is a significant concern in medical treatments, particularly with the use of chemotherapeutic agents like cisplatin and aminoglycosides. These drugs can lead to permanent sensorineural hearing loss (SNHL), affecting a substantial proportion of patients. Existing strategies to alleviate these side effects are limited, prompting interest in natural products as potential protective agents. Natural products are being investigated for their ability to counteract these mechanisms through anti-inflammatory and antioxidant properties. The review seeks to highlight the potential of these natural products as complementary therapies to conventional ototoxic medications, emphasizing their protective roles, which are involved in cochlear cellular damage and programmed cell death. Further research is essential to establish standardized protocols for their use and to ensure their integration into clinical practice as effective therapeutic options.

Metabolomic and Cellular Mechanisms of Drug-Induced Ototoxicity and Nephrotoxicity: Therapeutic Implications of Uric Acid Modulation

Certain medications, including cisplatin and neomycin, often cause both hearing loss and renal dysfunction. This study aims to uncover the common mechanisms behind drug-induced ototoxicity and nephrotoxicity to aid early diagnosis and treatment. Metabolomic analyses reveal simultaneous disruptions in endogenous metabolic networks in the kidney, inner ear, and serum after administrating cisplatin or neomycin. Notably, a marked elevation in uric acid (UA), a recognized indicator of renal tubular injury, is identified. Supplementing UA and inhibiting its renal excretion worsen hearing loss and hair cell damage. Single-cell nucleus sequencing and immunohistochemistry reveal major changes in xanthine oxidase and ABCG2, crucial for UA metabolism, primarily in cochlear stria vascularis cells rather than hair cells. Cisplatin triggers a significant release of UA from stria vascularis cells, reaching concentrations sufficient to induce autophagy-dependent ferroptosis in hair cells. In a coculture system, targeted interventions against these two proteins in stria vascularis cells, through either pharmacological inhibition or genetic manipulation, markedly decrease the elevated UA release and the subsequent ferroptosis of hair cells. These findings suggest a metabolic connection between the inner ear and the kidney, highlighting the therapeutic potential of modulating UA to mitigate drug-induced nephrotoxicity and ototoxicity.

Preliminary Analysis of Drug-Induced Ototoxicity in South Korea: Trends From a National Sample Dataset

BACKGROUND AND OBJECTIVES

Certain medications are associated with ototoxicity. This study assesses drug-induced ototoxicity in South Korea by analyzing the Korean national health data.

SUBJECTS AND METHODS

Hospital records of National Health Insurance members from 2009 to 2016 were reviewed. Data were compared between patients with and without hearing loss (HL). Individuals with HL were identified as having a primary diagnosis code for sensorineural HL or another type of HL in at least one outpatient or inpatient record according to the International Classification of Diseases-10.

RESULTS

The members in the HL group increased slightly from 0.8% to 1.0% relative to the total sample, compared with 99.2% to 99.0% among the controls. The proportion of males in the HL group ranged from 45.6% to 47.6%, compared with 48.4% to 48.8% among the controls. The proportion of those aged ≥65 years in the HL group increased from 34.1% to 41.4%, compared with 10.6% to 13.3% among the controls. Hypertension prevalence (24.7%-25.7%) in the HL group was higher than that in the control group (12%-12.6%). Diabetes prevalence in the HL group was 10.6%-12.3%, compared with 4.4%-5.9% among the controls. The use of proton pump inhibitor components increased, particularly esomeprazole magnesium trihydrate and rabeprazole sodium, whereas the usage of pantoprazole sodium sesquihydrate and revaprazan was high initially but declined subsequently. The usage of painkillers such as acetaminophen, loxoprofen sodium, and ibuprofen remained high, and antibiotics such as cephalosporins indicated the highest usage. However, the use of penicillin antibiotics such as amoxicillin decreased significantly. Anticancer agents showed relatively low usage compared with other drug categories, whereas antihistamines showed extremely high usage across all years, with a continual increase.

CONCLUSIONS

These correlations and the underlying mechanisms necessitate further investigation, as several medicines have been linked to an increased risk of HL.

Atomically dispersed copper(I) on tungstosilicic acid for catalytic protection against cisplatin-induced hearing loss

The employment of platinum-based drugs for cancer chemotherapy, which might yield oxidative stress, is regarded as one main factor leading to hearing loss. The exact molecular mechanisms for cisplatin-induced hearing loss require further clarification, thus limiting the development of FDA-approved therapies. Herein, we mimicked the molecular structure of natural antioxidative enzymes to fabricate a four-oxygen-coordinating copper single-atom nanozyme (Cu SAN) exhibiting good superoxide dismutase and catalase activity, to alleviate the oxidative stress induced by platinum-based drugs. Notably, Cu SAN exhibited profound protective effects against cisplatin-induced hair cell damage with only 15 ng mL-1 of Cu species, successfully reversing cisplatin-induced hearing loss via oral administration. Due to its oxidation resistance, pretreatment with Cu SAN significantly improved cell viability and reduced ROS accumulation in cisplatin-triggered hair cell damage in HEI-OC1 cells and cochlear explants. Our results first demonstrated that cisplatin treatment induced cuproptosis in hair cells by modulating copper ion homeostasis. Further investigation revealed that Cu SAN nanozyme effectively alleviated hair cell cuproptosis by regulating FDX1 and reducing aggregated lipoacylated protein. This research underscores the promising potential of four-oxygen-coordinating Cu nanomaterials as a therapeutic approach to combat hearing loss, providing a new strategy for auditory protection.

Roadmap to a Global Template for Implementation of Ototoxicity Management for Cancer Treatment

Ototoxicity is among the adverse events related to cancer treatment that can have far-reaching consequences and negative impacts on quality-of-life for cancer patients and survivors of all ages. Ototoxicity management (OtoM) comprises the prevention, diagnosis, monitoring, and treatment, including rehabilitation and therapeutic intervention, of individuals who experience hearing loss, tinnitus, or balance/vestibular difficulties following exposures to ototoxic agents, including platinum chemotherapy (cisplatin, carboplatin) and cranial radiation. Despite the well-established physical, socioeconomic, and psychological consequences of hearing and balance dysfunction, there are no widely adopted standards for clinical management of cancer treatment-related ototoxicity. Consensus recommendations and a roadmap are needed to guide development of effective and feasible OtoM programs, direct research efforts, address the needs of caregivers and patients at all stages of cancer care and survivorship. Here we review current evidence and propose near-term to longer-term goals to advance OtoM in five strategic areas: (1) beneficiary awareness, empowerment, and engagement, (2) workforce enhancement, (3) program development, (4) policy, funding, and sustainability, and (5) research and evaluation. The goal is to identify needs and establish a roadmap to guide worldwide adoption of standardized OtoM for cancer treatment and improved outcomes for patients and survivors.

Optimized inner ear organoids for efficient hair cell generation and ototoxicity response modeling

Hair cells in the mammalian cochlea are highly vulnerable to damage from drug toxicity, noise exposure, aging, and genetic mutations, with no capacity for regeneration. Progress in hair cell protection research has been limited by the scarcity of cochlear tissue and suitable in vitro models. Here, we present a novel one-step, self-organizing inner ear organoid system optimized with small molecules, which bypasses the need for multi-step expansion and forced differentiation protocols. This approach efficiently generates hair cells and supporting cells that recapitulate the molecular, cellular, and structural characteristics of the inner ear. Single-cell RNA sequencing revealed the diversity and fidelity of cell populations within the organoids. Utilizing this platform, we validated the protective effects of candidate compounds against hair cell damage, highlighting its potential as a powerful tool for drug discovery and mechanistic studies of hair cell protection.

Identification of Druggable Binding Sites and Small Molecules as Modulators of TMC1

Our ability to hear and maintain balance relies on the proper functioning of inner ear sensory hair cells, which translate mechanical stimuli into electrical signals via mechano-electrical transducer (MET) channels, composed of TMC1/2 proteins. However, the therapeutic use of ototoxic drugs, such as aminoglycosides and cisplatin, which can enter hair cells through MET channels, often leads to profound auditory and vestibular dysfunction. Despite extensive research on otoprotective compounds targeting MET channels, our understanding of how small-molecule modulators interact with these channels remains limited, hampering the discovery of novel drugs. Here, we propose a structure-based screening approach, integrating 3D-pharmacophore modeling, molecular dynamics simulations of the TMC1+CIB2+TMIE complex, and experimental validation. Our pipeline successfully identified several novel compounds and FDA-approved drugs that reduced dye uptake in cultured cochlear explants, indicating MET-modulation activity. Simulations, molecular docking and free-energy estimations allowed us to identify three potential drug-binding sites within the channel pore, phospholipids, key amino acids involved in modulator interactions, and TMIE as a flexible component of the MET complex. We also identified shared ligand-binding features between TMC and structurally related TMEM16 proteins, providing novel insights into their distinct inhibition. Our pipeline offers a broad application for discovering modulators for mechanosensitive ion channels.

Pharmacological Approaches to Hearing Loss

Hearing disorders pose significant challenges to individuals experiencing them and their overall quality of life, emphasizing the critical need for advanced pharmacological approaches to address these conditions. Current treatment options often focus on amplification devices, cochlear implants, or other rehabilitative therapies, leaving a substantial gap regarding effective pharmacological interventions. Advancements in our understanding of the molecular and cellular mechanisms involved in hearing disorders induced by noise, aging, and ototoxicity have opened new avenues for drug development, some of which have led to numerous clinical trials, with promising results. The development of optimal drug delivery solutions in animals and humans can also enhance the targeted delivery of medications to the ear. Moreover, large genome studies contributing to a genetic understanding of hearing loss in humans combined with advanced molecular technologies in animal studies have shown a great potential to increase our understanding of the etiologies of hearing loss. The auditory system exhibits circadian rhythms and temporal variations in its physiology, its vulnerability to auditory insults, and its responsiveness to drug treatments. The cochlear clock rhythms are under the control of the glucocorticoid system, and preclinical evidence suggests that the risk/benefit profile of hearing disorder treatments using chronopharmacological approaches would be beneficial. If translatable to the bedside, such approaches may improve the outcome of clinical trials. Ongoing research into the molecular and genetic basis of auditory disorders, coupled with advancements in drug formulation and delivery as well as optimized timing of drug administration, holds great promise of more effective treatments. SIGNIFICANCE STATEMENT: Hearing disorders pose significant challenges to individuals and their overall quality of life, emphasizing the critical need for advanced pharmacological approaches to address these conditions. Ongoing research into the molecular and genetic basis of auditory disorders, coupled with advancements in drug delivery procedures and optimized timing of drug administration, holds the promise of more effective treatments.

Quantum chemistry calculation-aided discovery of potent small-molecule mimics of glutathione peroxidases for the treatment of cisplatin-induced hearing loss

Hearing loss (HL) is a health burden that seriously affects the quality of life of cancer patients receiving platinum-based chemotherapy, and few FDA-approved treatment specifically targets this condition. The main mechanisms that contribute to cisplatin-induced hearing loss are oxidative stress and subsequent cell death, including ferroptosis revealed by us as a new mechanism recently. In this study, we employed the frontier molecular orbital (FMO) theory approach as a convenient prediction method for the glutathione peroxidase (GPx)-like activity of isoselenazolones and discovered new isoselenazolones with great GPx-like activity. Notably, compound 19 exhibited significant protective effects against cisplatin-induced hair cell (HC) damage in vitro and in vivo and effectively reverses cisplatin-induced hearing loss through oral administration. Further investigations revealed that this compound effectively alleviated hair cell oxidative stress, apoptosis and ferroptosis. This research highlights the potential of GPx mimics as a therapeutic strategy against cisplatin-induced hearing loss. The application of quantum chemistry (QC) calculations in the study of GPx mimics sheds light on the development of new, innovative treatments for hearing loss.

Circulating IL-17 reduces the risk of cisplatin-induced hearing loss in children: a bidirectional two-sample Mendelian randomization study

Studies have reported that cytokines and their related signaling pathways play a role in inner ear diseases. In clinical practice, approximately 50% of pediatric cancer patients experience irreversible hearing loss after cisplatin treatment. However, currently, there is a lack of systematic research on the causal relationship between circulating cytokines and cisplatin-induced hearing loss in children. Genetic variant data for 41 circulating cytokines were obtained from a meta-analysis of genome-wide association studies (GWAS) among 8293 individuals of Finnish descent. The GWAS data for Cisplatin-induced hearing loss in children were derived from a multicenter cohort of European pediatric cancer patients and survivors (N = 390), including both cases with hearing loss after cisplatin chemotherapy and controls without hearing loss. Multiple methods were employed for bidirectional Mendelian randomization (MR) estimation. Bonferroni correction was applied to adjust the original P-values, followed by a series of sensitivity analyses. In the directional Mendelian randomization (MR) analysis, it was found that IL-17 was significantly associated with a reduced risk of Cisplatin-induced hearing loss in children (OR: 0.18, CI: 0.06-0.48, P < 0.001, FDR = 0.041). In the reverse MR analysis, there were some nominal causal relationships of Cisplatin-induced hearing loss in children with certain cytokines [M-CSF: (OR: 1.04, CI: 1.01-1.08, P = 0.010, FDR = 0.41); IL-2RA: (OR: 1.03, CI: 1.00-1.05, P = 0.044, FDR = 0.447); MIP-1β: (OR: 1.02, CI: 1.00-1.04, P = 0.041, FDR = 0.447)]. leave-one-out analysis demonstrated that only M-CSF exhibited stability. These findings reveal a causal relationship between IL-17 and cisplatin-induced hearing loss in children. Further research is needed to determine the potential protective mechanisms of IL-17 in cisplatin-induced ototoxicity.