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To elucidate D-methionine's (D-met) dose and time rescue parameters from steady-state or impulse noise-induced permanent threshold shift (PTS) and determine D-met rescue's influence on serum and cochlear antioxidant levels. Five D-met doses at 0, 50, 100, or 200 mg/kg/dose administered starting at 1, 24, or 36 hours post steady-state or impulse noise exposure. Auditory brainstem responses at baseline and 21 days post-noise measured PTS. Serum (superoxide dismutase [SOD], catalase [CAT],, glutathione reductaseand glutathione peroxidase [GPx]) and cochlear (Glutathione [GSH] and glutathione disulphide [GSSG]) antioxidant levels measured physiological impact. Chinchillas (10/study group; 6–8/confirmatory groups). D-met significantly reduced PTS for impulse noise (100 mg [2, 6, 14 and 20 kHz]; 200 mg [2, 14 and 20 kHz]) and steady-state noise (all dosing groups, time parameters and tested frequencies). PTS reduction did not significantly vary by rescue time. D-met significantly increased serum SOD (100 and 200 mg for 24 hour rescue) and GPx (50 mg/kg at 24 hour rescue) at 21 days post-noise. Cochlear GSH and GSSG levels were unaffected relative to control. D-met rescues from steady-state and impulse noise-induced PTS even when administered up to 36 hours post-noise and dose-dependently influences serum antioxidant levels even 21 days post-noise. D-met's broad and effective dose/time window renders it a promising antioxidant rescue agent. [ABSTRACT FROM AUTHOR]

Determine if D-methionine (D-met) rescue prevents temporary threshold shift (TTS) from steady-state or impulse noise and determine D-met's impact on serum and cochlear antioxidant levels. D-met at 50, 100 or 200 mg/kg/doses were administered 0, 6 and 18 hours-post noise. ABRs at baseline and 24 hours post-noise measured TTS. Serum (SOD, CAT, GR, GPx) and cochlear (GSH, GSSG) antioxidant levels measured physiological influence. Three control groups, with impulse or steady-state or without noise, were saline-injected. Ten Chinchillas/group. D-met rescue did not significantly reduce TTS or impact serum CAT, SOD, GPx or GR levels vs. noise-exposed control groups, but TTS was greater in all groups relative to no-noise controls. D-met significantly elevated CAT at 50 mg/kg vs. steady-state controls and SOD at 200 mg/kg vs. impulse noise controls. D-met significantly reduced cochlear GSH/GSSG ratios in the 100 mg/kg D-met group vs. impulse noise controls. While D-met rescue has reduced permanent threshold shift in previous studies, it did not reduce TTS in this study. However, D-met rescue did alter selective serum and cochlear oxidative state changes 24 hours post-noise relative to controls. Results demonstrate TTS studies do not always predict PTS protection in otoprotectant experimental designs. [ABSTRACT FROM AUTHOR]

Acquired hearing loss, which can develop after noise insult or ototoxic drug treatment, is a significant clinical, social, and economic issue. A major advance in our understanding came with the discovery that intense metabolic activity in the inner ear drives the formation of free radicals (short-lived, unstable, highly reactive clusters of atoms) in multiple types of cells in the inner ear after both noise and drug insult. Animal studies have now shown that free radicals formed during and after metabolic stress importantly contribute to acquired hearing loss. These new mechanistic insights provided for the first time a rationalefor directly treating the inner ear to prevent hearing impairment. Consequently, use of free radical scavengers, or antioxidants, to prevent acquired hearing loss became a clinically relevant research goal. Many laboratories have now demonstrated that a variety of free radical scavengers reduce the potential for acquired hearing loss in animal subjects. Scientific data, supporting the use of these agents to preventenvironmentally acquired hearing loss, is reviewed. Translational investigations are now essential to confirm the potential utility of these agents in the human inner ear. This article reviews the pharmacological otoprotective agents in or approaching clinical trials to prevent noise-, aminoglycoside-, and cisplatin-induced hearing loss. [ABSTRACT FROM AUTHOR]

Ototoxicity monitoring is particularly critical in patients receiving platinum-based chemotherapy or long-term aminoglycoside antibiotic administration. Furthermore, as new otoprotective agents are developed, audiologists need to not only be able to monitor for ototoxicity but know the various criteria for early detection of ototoxicity and how to grade ototoxic adverse events. The three primary methods for ototoxicity monitoring are conventional audiometry, highfrequency audiometry, and otoacoustic emissions. However, early detection and adverse event criteria depend primarily on conventional and high-frequency audiometry. No consensus exists on determining significant changes in otoacoustic emissions secondary to ototoxic drugs. Also, no consensus exists on how to monitor for tinnitus, although it is a common complication in these patients. Currently, tinnitus surveys can be helpful. A baseline evaluation is critical for accurate interpretation of auditory threshold results. Thus, a team approach is needed to ensure adequate care of these children. For clinical trials and in reading the literature, audiologists need to be aware of the American Speech Language Hearing Association's 1994 criteria for detection of ototoxic change, and the Common Terminology Criteria for Adverse Events, Brock, and the Change scales for classification of adverse events. These methods and scales are reviewed and discussed. [ABSTRACT FROM AUTHOR]

D-methionine (D-met) protects against cisplatin (CDDP) ototoxicity, but the mechanisms are not well understood. This study investigated D-met protection of cochlear oxidative state as measured by superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), glutathione reductase (GR), and malondiadehyde (MDA) levels. The design comprised four groups of five rats each: (1) a saline control group, (2) a CDDP-only-treated group, (3) a CDDP group pretreated with D-met, and (4) a group receiving only D-met. Auditory brainstem response testing (ABR) was performed before and 3 days after injection. CDDP alone caused marked hearing loss; significantly reduced SOD, CAT, and GR levels; and increased MDA levels, but D-met pretreatment protected against these changes. These studies suggest that D-met protects cochlear antioxidant enzyme levels from CDDP-induced decrements. The excellent correlation of enzyme levels with hearing loss and weight loss suggests that antioxidant enzyme level protection may underlie, at least in part, D-met's otoprotective action. [ABSTRACT FROM AUTHOR]

This study describes audiologic methodology and results for evaluating potential ototoxicity in a phase I clinical trial of a new glycopeptide. This study was conducted under good clinical practices, which are regulated by the US Food and Drug Administration (FDA) (21 Code of Federal Regulations), and input from the FDA was sought prior to study implementation. Healthy, normal volunteers underwent extensive medical and audiologic assessments as part of this phase I dose- escalation study of dalbavancin, a new glycopeptide, to assess potential side effects. Audiologic monitoring included air-conduction thresholds in the conventional (0.25-8 kHz) and high-frequency (10-16 kHz) ranges. At baseline, subjects were also tested using word recognition, bone conduction testing if indicated, and tympanometry. Full testing was to be repeated if any subject met the American Speech-Language-Hearing Association (ASHA) 1994 criteria for ototoxic change. However, no subjects demonstrated ototoxic change after receiving dalbavancin, nor were any false-positive results obtained. [ABSTRACT FROM AUTHOR]

Glutathione (GSH) provides an important antioxidant and detoxification pathway. We tested to determine if direct administration of GSH or GSH ester could reduce cisplatin- (CDDP) induced ototoxicity. We tested eight groups of five rats each: a control group, a group receiving 16 mg/kg ip CDDP infused over 30 minutes, and six groups receiving either GSH or GSH ester at 500, 1000, or 1500 mg/kg intraperitoneally 30 minutes prior to 16 mg/kg CDDP. Auditory brainstem response thresholds were measured for click and tone-burst stimuli at baseline and 3 days later. Outer hair cell (OHC) loss was measured for the apical, middle and basal turns. The 500 mg/kg GSH ester reduced hearing loss and OHC loss, but protection decreased as dosage increased, suggesting possible toxicity. GSH was not significantly protective. The best GSH ester protection was less than we have previously reported with D-methionine. [ABSTRACT FROM AUTHOR]

Objectives: D-methionine (D-met) reduces noise induced hearing loss (NIHL) even if administered after noise. This study's purpose was to determine maximum time delay for effective D-met post-noise NIHL rescue measured by auditory brainstem response thresholds. Material and methods: 15 chinchilla groups received steady state or impulse noise. BID D-met or placebo started 7, 9,12,18, 24, 36, or 48 hours after noise and then another 48 hours. BID. ABR threshold shift from baseline was measured at 21 days post-noise exposure. Results:: D-met significantly reduced NIHL ABR threshold shift (p<0.01) for steady state and impulse noise even when administration began up to 36 hours post-noise exposure. Optimal protective dosing delay time occurred up to 24 hours post-noise exposure. Conclusions: D-met rescue is significantly effective with delays to 36 hours post-steady state or -impulse noise exposure. Results may have significant clinical impact for optimal effective D-met protection from NIHL, particularly for unexpected noise exposures. [ABSTRACT FROM AUTHOR]

This study's purpose was to determine if a correlation exists between cochlear antioxidant activity changes and auditory function after induction of aminoglycoside (AG) ototoxicity. Two groups of five 250-350 g albino guinea pigs served as subjects. For 28 days, albino guinea pigs were administered either 200 rog/kg/day amikacin, or saline subcutaneously. Auditory brainstem response testing was performed prior to the first injection and again before sacrifice, 28 days later. Cochleae were harvested and superoxide dismutase, catalase, glutathione peroxidase, glutathione-S-transferase, glutathione reductase activities and malondialdehyde levels were measured. All antioxidant enzymes had significantly lower activity in the amikacin group (p < 0.05) than in the control group. The difference in cochlear antioxidant enzyme activity between groups inversely correlated significantly with the change in ABR thresholds. The greatest correlation was for the high frequencies, which are most affected by aminoglycosides. This study demonstrates that antioxidant enzyme activity and amikacin-induced hearing loss significantly covary. [ABSTRACT FROM AUTHOR]

ELX-02 is an investigational synthetic eukaryotic ribosome-selective glycoside optimized as a translational read-through molecule that induces read through of nonsense mutations, resulting in normally localized full-length functional proteins. ELX-02 is being developed as a therapy for genetic diseases caused by nonsense mutations. Two phase 1a, randomized, double-blind placebo-controlled, single-ascending-dose studies were conducted in healthy human subjects to evaluate the safety and pharmacokinetics of ELX-02. Single subcutaneously injected doses of ELX-02 between 0.3 mg/kg and 7.5 mg/kg showed an acceptable safety profile without severe or serious drug-related adverse events, including a lack of renal and ototoxicity events. Injection of ELX-02 resulted in a rapid time to peak concentration and elimination phase, with complete elimination from the vascular compartment within 10 hours. ELX-02 area under the concentration-time curve to infinity showed dose-exposure linearity (24-fold increase for a 25-fold dose increase), and the maximum concentration showed dose proportionality (17-fold increase for a 25-fold increase). The mean apparent volume of distribution was dose dependent, suggesting an increased distribution and tissue uptake of ELX-02 at higher doses. The primary route of excretion was in the urine, with the majority of the compound excreted unchanged. These results support the evaluation of the safety, pharmacokinetics, and efficacy of repeat dosing in future studies., (© 2019 The Authors. Clinical Pharmacology in Drug Development Published by Wiley Periodicals, Inc. on behalf of American College of Clinical Pharmacology.)

Background: Tobramycin is a critical cystic fibrosis treatment however it causes ototoxicity. This study tested d-methionine protection from tobramycin-induced ototoxicity and potential antimicrobial interference., Methods: Auditory brainstem responses (ABRs) and outer hair cell (OHC) quantifications measured protection in guinea pigs treated with tobramycin and a range of d-methionine doses. In vitro antimicrobial interference studies tested inhibition and post antibiotic effect assays. In vivo antimicrobial interference studies tested normal and neutropenic Escherichia coli murine survival and intraperitoneal lavage bacterial counts., Results: d-Methionine conferred significant ABR threshold shift reductions. OHC protection was less robust but significant at 20kHz in the 420mg/kg/day group. In vitro studies did not detect d-methionine-induced antimicrobial interference. In vivo studies did not detect d-methionine-induced interference in normal or neutropenic mice., Conclusions: d-Methionine protects from tobramycin-induced ototoxicity without antimicrobial interference. The study results suggest d-met as a potential otoprotectant from clinical tobramycin use in cystic fibrosis patients., (Published by Elsevier B.V.)