Insulin-like growth factor 1: role in the auditory system and therapeutic potential in otology

Teprotumumab-Related Hearing Loss: A Large-Scale Analysis and Review of Voluntarily Reported Patient Complaints to the Food and Drug Administration (FDA)

PURPOSE

Accumulating case reports and series have suggested that teprotumumab may significantly increase the risk of hearing impairment that, in some cases, does not resolve. This study investigates the association between hearing impairment and teprotumumab use.

METHODS

A disproportionality analysis was conducted using the United States Food and Drug Administration Adverse Event Reporting System, a publicly accessible database used for postmarketing surveillance and research. All adverse event reports containing the terms "teprotumumab" or "Tepezza" and a similar comparison group from all patients with the same indications for teprotumumab use (e.g., autoimmune thyroiditis, endocrine ophthalmopathy, and hyperthyroidism) but who had not received the drug were selected. Hearing impairment events were identified using the hearing impairment Standardized MedDRA Query.

RESULTS

A total of 940 teprotumumab-associated adverse events were identified, including 84 hearing-related adverse events, with the first reported to the Food and Drug Administration in April 2020. A comparison group of 32,794 nonteprotumumab adverse events was identified with 127 hearing-related adverse events reported. Use of teprotumumab in patients with thyroid conditions was associated with a nearly 24-fold (proportional reporting ratio [PRR] 23.6, 95% confidence interval [CI]: 18.1-30.8) increased likelihood of any hearing disorder ( p value <0.0001). The association was specifically elevated for a variety of deafness conditions (e.g., bilateral deafness [PRR: 41.9; 95% CI: 12.8-136.9]), Eustachian tube disorders (PRR: 34.9; 95% CI: 4.9-247.4), hypoacusis (PRR: 10.1; 95% CI: 7.6-13.3), and tinnitus (PRR: 8.7; 95% CI: 6.2-12.1).

CONCLUSIONS

Patients treated with teprotumumab should receive warnings regarding the increased risk of hearing-related impairments and receive audiometry before, during, and after treatment.

The Role of Molecular and Cellular Aging Pathways on Age-Related Hearing Loss

Aging, a complex process marked by molecular and cellular changes, inevitably influences tissue and organ homeostasis and leads to an increased onset or progression of many chronic diseases and conditions, one of which is age-related hearing loss (ARHL). ARHL, known as presbycusis, is characterized by the gradual and irreversible decline in auditory sensitivity, accompanied by the loss of auditory sensory cells and neurons, and the decline in auditory processing abilities associated with aging. The extended human lifespan achieved by modern medicine simultaneously exposes a rising prevalence of age-related conditions, with ARHL being one of the most significant. While our understanding of the molecular basis for aging has increased over the past three decades, a further understanding of the interrelationship between the key pathways controlling the aging process and the development of ARHL is needed to identify novel targets for the treatment of AHRL. The dysregulation of molecular pathways (AMPK, mTOR, insulin/IGF-1, and sirtuins) and cellular pathways (senescence, autophagy, and oxidative stress) have been shown to contribute to ARHL. However, the mechanistic basis for these pathways in the initiation and progression of ARHL needs to be clarified. Therefore, understanding how longevity pathways are associated with ARHL will directly influence the development of therapeutic strategies to treat or prevent ARHL. This review explores our current understanding of the molecular and cellular mechanisms of aging and hearing loss and their potential to provide new approaches for early diagnosis, prevention, and treatment of ARHL.

A Biologic With Otologic Consequences: Analysis of Hearing Loss and Teprotumumab Using the FDA Adverse Event Reporting System

OBJECTIVES

To evaluate otologic adverse reactions (OARs), including hearing loss (OARs-HL) among patients taking teprotumumab, a new biologic approved for the treatment of active thyroid eye disease, using publicly available pharmacovigilance reporting data.

STUDY DESIGN

Retrospective database review.

METHODS

The Food and Drug Administration Adverse Events Reporting System (FAERS) was queried for cases involving teprotumumab from 2020Q1 to 2023Q1. Patient demographics and adverse reactions (OAR and OAR-HL) were evaluated. Logistic regression was used to predict OAR and OAR-HL, and disproportionality analysis was performed using OpenVigil.

RESULTS

A total of 2,109 teprotumumab-AR cases were reported, of which 296 (14.05%; mean age 55.46 yr) were OARs. Of these, 149 (7.06%) reported OAR-HL and 194 (9.20%) reported other OAR (e.g., tinnitus, ear discomfort, vertigo), with 47 (2.23%) reporting both. Disproportionality analysis showed a reported odds ratio (ROR) for OARs-HL of 44.33 (95% confidence interval [CI], 37.40-52.55; p < 0.001). Age was associated with RORs of 1.02 (95% CI, 1.01-1.04) and 1.04 (95% CI, 1.02-1.07) for developing OARs and specifically OARs-HL, respectively (p < 0.01). Age 50 and 65 years and older were associated with RORs of 2.54 (95% CI, 1.16-6.38) and 3.36 (95% CI, 1.75-6.53), respectively, for OARs-HL (p < 0.05).

CONCLUSION

This study using FAERS data suggests an increased risk of OARs, specifically hearing loss, associated with teprotumumab. Increasing age was a significant predictor of OARs. Audiometric counseling and evaluation should be considered with teprotumumab therapy in Graves' orbitopathy patients, especially in older patients.

Reduction of Teprotumumab-Induced Hearing Loss With Comparable Efficacy Using Half-Dose Therapy

Teprotumumab has been shown to be effective in the treatment of thyroid eye disease, a potentially vision-threatening condition. Adverse events, including sensorineural hearing loss, have been associated with teprotumumab. The authors present the case of a 64-year-old female who discontinued teprotumumab due to significant sensorineural hearing loss after 4 infusions, along with other adverse events. The patient was unresponsive to a subsequent course of intravenous methylprednisolone and orbital radiation, during which she experienced worsening thyroid eye disease symptoms. Teprotumumab was restarted 1 year later, at a half dose of 10 mg/kg for 8 infusions. Three months post-treatment, she retains resolution of double vision and orbital inflammatory signs, and significant improvement in proptosis. She tolerated all infusions with an overall reduction in the severity of her adverse events and without return of significant sensorineural hearing loss. The authors conclude that a lower dose of teprotumumab can be effective for patients with active moderate-severe thyroid eye disease who experience significant or intolerable adverse events.

Potential Ototoxicity of Insulin-like Growth Factor 1 Receptor Signaling Inhibitors: An In Silico Drug Repurposing Study of the Regenerating Cochlear Neuron Transcriptome

Spiral ganglion neurons (SGNs) connect cochlear hair cells with higher auditory pathways and their degeneration due to drug toxicity (ototoxicity) contributes to hearing loss. This study aimed to identify drug classes that are negatively correlated with the transcriptome of regenerating SGNs. Human orthologs of differentially expressed genes within the regenerating neonatal mouse SGN transcriptome were entered into CMap and the LINCS unified environment and perturbation-driven gene expression was analyzed. The CMap connectivity scores ranged from 100 (positive correlation) to -100 (negative correlation). Insulin-like growth factor 1/receptor (IGF-1/R) inhibitors were highly negatively correlated with the regenerating SGN transcriptome (connectivity score: -98.87). A systematic literature review of clinical trials and observational studies reporting otologic adverse events (AEs) with IGF-1/R inhibitors identified 108 reports (6141 treated patients). Overall, 16.9% of the treated patients experienced any otologic AE; the rate was highest for teprotumumab (42.9%). In a meta-analysis of two randomized placebo-controlled trials of teprotumumab, there was a significantly higher risk of hearing-related (pooled Peto OR [95% CI]: 7.95 [1.57, 40.17]) and of any otologic AEs (3.56 [1.35, 9.43]) with teprotumumab vs. a placebo, whether or not dizziness/vertigo AEs were included. These results call for close audiological monitoring during IGF-1-targeted treatment, with prompt referral to an otolaryngologist should otologic AEs develop.

Teprotumumab-Related Hyperglycemia

CONTEXT

Graves orbitopathy (GO) or thyroid eye disease is a potentially sight-threatening and disfiguring autoimmune disease. Teprotumumab is a monoclonal antibody against the insulin-like growth factor-I receptor that was recently approved for GO treatment. Hyperglycemia is a recognized adverse event of teprotumumab, occurring in 10% of patients in 2 recent randomized controlled trials.

OBJECTIVE

Our study aimed to report the incidence, severity, management, and longitudinal glycemic changes in patients treated with teprotumumab in an academic practice cohort.

METHODS

This longitudinal, observational study included all consecutive patients treated with teprotumumab between March 2020 and May 2022 at 1 institution. Hemoglobin A1c (HbA1c) was measured every 3 months.

RESULTS

Forty-two patients with baseline normoglycemia (n = 22), prediabetes (n = 10), and diabetes (n = 10) were followed for a mean of 47.5 weeks. Overall, HbA1c increased by 0.5% at 3 months. Least-squares mean changes in HbA1c at 3 months were 1.3 (P < .001), 0.7 (P = .01), and 0.1 (P = .41) in patients with diabetes, prediabetes, and normoglycemia, respectively. Twenty-two patients (52%) had hyperglycemia, which was graded as mild, moderate, and life-threatening in 55% (12/22), 41% (9/22), and 5% (1/22) of cases, respectively. Age, pre-existing diabetes, and Hispanic and Asian race/ethnicity were significant risk factors for hyperglycemia. Among patients with hyperglycemia, 36.4% (8/22) returned to baseline glycemic status at last follow-up.

CONCLUSION

While effective, teprotumumab carries a significant risk of hyperglycemia, especially in patients with diabetes. Hyperglycemia may persist after stopping teprotumumab. These findings underscore the importance of guidelines for screening and management of teprotumumab-related hyperglycemia.

Prospective Assessment of Otologic Adverse Events due to Teprotumumab: Preliminary Results

OBJECTIVE

To assess a series of patients receiving teprotumumab therapy and objectively quantify the rates of otologic adverse events.

STUDY DESIGN

A prospective cohort study of adult patients receiving teprotumumab between May 2020 and January 2022.

SETTING

Tertiary referral center.

METHODS

Prior to treatment initiation, an ototoxicity-specific audiometric battery was completed, which included conventional audiometry (frequencies 250-8000 Hz), ultrahigh-frequency audiometry (9000-20,000 Hz), tympanometry, speech discrimination scores, and distortion product otoacoustic emissions (DPOAEs). Testing was then repeated after treatment completion.

RESULTS

In total, 35 patients were recruited, with a median (range) age of 48.5 years (21-74), and 8 (22.8%) were male. The most common subjective symptom reported was a hearing decline (25.7%), followed by aural fullness (17.1%) and tinnitus (14.3%). Fourteen patients had both pre- and posttreatment audiometric data. Among them, 3 patients (21.4%) were found to have changes in standard frequency audiometry, and 10 (71.4%) had changes in high-frequency audiometry, with 2 patients having changes in both. Less than half (n = 5) of the 11 patients with changes in standard or high-frequency pure tone hearing noted subjective hearing decline. Changes in DPOAE were noted in 4 patients out of 13 (30.7%). Two patients discontinued treatment due to hearing decline. Finally, 3 patients (8.6%) were diagnosed with patulous eustachian tube (PET) by an otolaryngologist, and another 3 patients are suspected to have PET based on symptom description during ophthalmologic follow-up.

CONCLUSION

In our cohort, a high incidence of otologic symptoms was found to be associated with teprotumumab usage. Subjective hearing decline, changes in ultrahigh-frequency hearing as well as eustachian tube dysfunction may be encountered and suggest the potential ototoxicity of teprotumumab.

Future Projections in Thyroid Eye Disease

BACKGROUND AND AIMS

This review aims to summarize current and emerging therapies for treatment of thyroid eye disease (TED), in the light of novel understanding of pathogenetic mechanisms, leading to new treatment options and clinical trials.

METHODS

We reviewed and analyzed peer-reviewed literature reporting recent translational studies and clinical trials in the treatment of TED. Searches were made at www.pubmed.gov with keywords "thyroid eye disease," "Graves' ophthalmopathy," "thyroid orbitopathy," and "Graves' orbitopathy."

RESULTS

Surgery is reserved for rehabilitation in chronic TED or for emergent compressive optic neuropathy. Oral and intravenous glucocorticoid therapy has been used for decades with variable efficacy in acute TED, but results may be temporary and side effects significant. Nonsteroidal oral immunosuppressive agents offer modest benefit in TED. Several immunomodulatory monoclonal antibodies, including rituximab and tocilizumab, have shown efficacy for inactivating TED. Recently, teprotumumab, an insulin-like growth factor 1 receptor (IGF-1R) inhibitor, has demonstrated significant improvement in proptosis, clinical activity score, diplopia, and quality of life in patients with active TED, with good tolerability. Newly proposed TED therapies, currently in preclinical and clinical trial phases, include thyroid-stimulating hormone (TSH) receptor inhibitory drugs, RVT-1401, local anti-vascular endothelial growth factor therapy, IGF-1R drugs delivered subcutaneously and orally, and desensitization to the TSH receptor with modified TSH receptor peptides.

CONCLUSION

New, albeit incomplete, understanding of the molecular mechanisms of TED has led to new promising therapies and offered improved outcomes in TED patients. Their full role and their relationship to classical immune suppression should be clarified over the next few years.

Hearing Dysfunction After Treatment With Teprotumumab for Thyroid Eye Disease

PURPOSE

To characterize the frequency, severity, and resolution of hearing dysfunction in patients treated with teprotumumab for thyroid eye disease (TED).

DESIGN

Prospective observational case series.

METHODS

Ophthalmic examination and adverse event assessment, including otologic symptoms, were performed at baseline, after infusions 2, 4, and 8, and at 6-month follow-up in consecutive patients who received at least 4 teprotumumab infusions. Laboratory test results were collected at baseline and during treatment. Audiometry, patulous eustachian tube (PET) testing, and otolaryngology evaluation were obtained for patients with new or worsening otologic symptoms, with a subset obtaining baseline and posttreatment testing.

RESULTS

Twenty-seven patients were analyzed (24 females, 3 males, average 56.3 years old). Twenty-two patients (81.5%) developed new subjective otologic symptoms, after a mean of 3.8 infusions (SD 1.8). At 39.2-week average follow-up after the last infusion, most patients with tinnitus (100%), ear plugging/fullness (90.9%), and autophony (83.3%) experienced symptom resolution, whereas only 45.5% (5 of 11) of patients with subjective hearing loss/decreased word comprehension experienced resolution. Six patients underwent baseline and posttreatment audiometry, 5 of whom developed teprotumumab-related sensorineural hearing loss (SNHL) and 1 patient also developed PET. Three of the 5 patients with teprotumumab-related SNHL had persistent subjective hearing loss at last follow-up. A prior history of hearing loss was discovered as a risk factor for teprotumumab-related SNHL (P = .008).

CONCLUSIONS

Hearing loss is a concerning adverse event of teprotumumab, and its mechanism and reversibility should be further studied. Until risk factors for hearing loss are better understood, we recommend baseline audiometry with PET testing and repeat testing if new otologic symptoms develop. Screening, monitoring, and prevention guidelines are needed.

Efficacy and Safety of Teprotumumab in Thyroid Eye Disease

Thyroid eye disease (TED; also known as thyroid-associated ophthalmopathy) is an autoimmune condition with disabling and disfiguring consequences. Teprotumumab is the first and only medication approved by the United States Food and Drug Administration for the treatment of TED. We review the efficacy and safety of teprotumumab in TED, highlighting results from the 2 randomized, double-masked, placebo-controlled trials. Post-approval case reports of teprotumumab use in patients with compressive optic neuropathy (CON) and inactive TED were similarly favorable to those from the trials. The preliminarily results of teprotumumab for CON and inactive TED should be investigated in formal clinical trials. Teprotumumab should be avoided in pregnancy. Evidence also suggests that teprotumumab may exacerbate pre-existing inflammatory bowel disease, worsen hyperglycemia, and be associated with hearing impairment. Patients at risk for these adverse events need to be closely monitored with baseline and periodic assessments.

Insulin-like Growth Factor 1 Signaling in Mammalian Hearing

Insulin-like growth factor 1 (IGF-1) is a peptide hormone belonging to the insulin family of proteins. Almost all of the biological effects of IGF-1 are mediated through binding to its high-affinity tyrosine kinase receptor (IGF1R), a transmembrane receptor belonging to the insulin receptor family. Factors, receptors and IGF-binding proteins form the IGF system, which has multiple roles in mammalian development, adult tissue homeostasis, and aging. Consequently, mutations in genes of the IGF system, including downstream intracellular targets, underlie multiple common pathologies and are associated with multiple rare human diseases. Here we review the contribution of the IGF system to our understanding of the molecular and genetic basis of human hearing loss by describing, (i) the expression patterns of the IGF system in the mammalian inner ear; (ii) downstream signaling of IGF-1 in the hearing organ; (iii) mouse mutations in the IGF system, including upstream regulators and downstream targets of IGF-1 that inform cochlear pathophysiology; and (iv) human mutations in these genes causing hearing loss.

Teprotumumab: Interpreting the Clinical Trials in the Context of Thyroid Eye Disease Pathogenesis and Current Therapies

Teprotumumab, a monoclonal antibody targeted against the insulin-like growth factor 1 (IGF-1) receptor, was recently approved by the United States Food and Drug Administration for the treatment of thyroid eye disease (TED). Phase 1 studies of teprotumumab for the treatment of malignancies demonstrated an acceptable safety profile but limited effectiveness. Basic research implicating the IGF-1 receptor on the CD-34+ orbital fibrocyte in the pathogenesis of TED renewed interest in the drug. Two multicenter, randomized, double-masked, clinical trials (phase 2 and 3) evaluated the efficacy of 8 infusions of teprotumumab every 3 weeks versus placebo in 170 patients with recent-onset active TED, as defined by a clinical activity score (CAS) of at least 4. Teprotumumab was superior to placebo for the primary efficacy end points in both studies: overall responder rate as defined by a reduction of 2 or more CAS points and a reduction of 2 mm or more in proptosis (69% vs. 20%; P < 0.001; phase 2 study) and proptosis responder rate as defined by a reduction of 2 mm or more in proptosis (83% vs. 10%; P < 0.001; phase 3 study). In both studies, treatment with teprotumumab compared with placebo achieved a significant mean reduction of proptosis (-3.0 mm vs. -0.3 mm, phase 2 study; -3.32 mm vs. -0.53 mm, phase 3 study) and CAS (-4.0 vs. -2.5, phase 2 study; -3.7 vs. -2.0, phase 3 study). Teprotumumab also resulted in a greater proportion of patients with a final CAS of 0 or 1, higher diplopia responder rate, and a larger improvement in the Graves' Ophthalmopathy Quality of Life overall score. More than half of patients (62%, phase 2 trial; 56%, phase 3 trial) who were primary end point responders maintained this response at 51 weeks after the last dose of therapy. The most common adverse events reported with teprotumumab included muscle spasms (25%), nausea (17%), alopecia (13%), diarrhea (13%), fatigue (10%), hearing impairment (10%), and hyperglycemia (8%). Teprotumumab is contraindicated for those with inflammatory bowel disease and who are pregnant. Although the current dosing regimen has proven effective for TED, dose-ranging studies including variable concentrations, infusion frequencies, and durations of teprotumumab therapy in the setting of TED have not been performed.