Clinical studies published in peer-reviewed journals report hearing loss rates of 23-65% among Tepezza patients, far exceeding the 10% rate disclosed in the original prescribing information. A 2021 study in Endocrine Practice documented sensorineural hearing loss in 65% of patients, with many cases being permanent. Teprotumumab inhibits IGF-1R signaling, which is critical for cochlear hair cell maintenance. Plaintiffs allege Horizon knew of the elevated ototoxicity risk from clinical trials but minimized warnings to protect the drug's commercial success ($2B+ annual revenue).

Defendants

Entity	Role	Note
Horizon Therapeutics	Original Manufacturer	Developed and launched Tepezza — acquired by Amgen in October 2023
Amgen Inc.	Current Manufacturer (Acquirer)	Acquired Horizon Therapeutics for $27.8B — assumed Tepezza liabilities

Litigation Timeline

Jan 2020

FDA approves Tepezza for thyroid eye disease (first and only approved treatment)

2021

Endocrine Practice study reports 65% hearing loss rate in Tepezza patients

Jul 2023

FDA updates Tepezza label to include hearing impairment warning

Oct 2023

Amgen completes $27.8B acquisition of Horizon Therapeutics

2024

First wave of Tepezza hearing loss lawsuits filed

2025-2026

~200 cases filed. JPML MDL petition expected

Intelligence Signals

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Key Facts

Status: active

Geographic Exposure

·N.D. Ill. (JPML consolidation venue — expected)

·Illinois state courts (Horizon HQ in Deerfield, IL)

·California, New York, Texas (high filing states)

·Nationwide filing — cases in multiple federal districts

Eligibility Criteria

✓Received Tepezza (teprotumumab) infusion treatment
✓Diagnosed with hearing loss, tinnitus, or other auditory injury
✓Hearing symptoms developed during or after Tepezza treatment
✓Hearing loss confirmed by audiometric testing

Sources

FDA Tepezza Label Amgen SEC Filings Endocrine Practice Ototoxicity Study FDA FAERS Dashboard