Eli Lilly Raises Alarm Over Impurities in Compounded Tirzepatide

Eli Lilly & Co. has issued a public warning about potential health risks associated with compounded versions of its weight-loss and diabetes drug, tirzepatide, marketed under the brand names Mounjaro and Zepbound. The company’s testing revealed significant levels of an impurity formed when tirzepatide is mixed with vitamin B12, a combination often sold by telehealth companies, pharmacies, and medical spas. Lilly cautioned that the effects of this impurity on human health are unknown, including its potential toxicity and impact on the drug's interaction with GLP-1 and GIP receptors.

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Compounding refers to the practice of creating custom formulations of medications to meet individual patient needs. This practice gained traction during the tirzepatide shortage, which the FDA declared over in late 2024. Following this, many compounders have continued to market "personalized" versions of tirzepatide, often incorporating additives like vitamin B12, glycine, and niacinamide. Lilly argues that these formulations are not genuinely personalized but rather mass-produced products that circumvent regulatory scrutiny.

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In an open letter, Lilly emphasized the risks associated with untested compounded drugs, stating, “The continued widespread distribution of untested compounded drugs is an unacceptable risk for patients.” The company has urged the FDA to recall all compounded tirzepatide products containing untested additives. Lilly's Chief Medical Officer, David Hyman, noted, “Nothing is known about its short- or long-term effects in humans,” highlighting the lack of clinical studies on the combination of tirzepatide and B12.

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Scott Brunner, CEO of the Alliance for Pharmacy Compounding (APC), responded to Lilly's warning by questioning the validity of the findings. He stated, “B12 is a well-studied and remarkably benign drug,” and pointed out that compounding of tirzepatide with B12 has been ongoing for about four years without a significant trend of adverse events. Brunner called for more transparency from Lilly regarding the source and handling of the samples tested.

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While Lilly's findings indicate serious safety concerns, the APC argues that the lack of adverse events reported over several years suggests that the compounded products may not pose the risks Lilly claims. The debate continues over the legitimacy of compounded drugs and whether they fulfill a necessary role in patient care or simply exploit regulatory loopholes.

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As the FDA increases its scrutiny of compounded drugs, Lilly's legal actions against compounding pharmacies and telehealth companies are likely to intensify. The company has already filed lawsuits against several entities for marketing unapproved versions of its drugs. Meanwhile, the FDA has issued warning letters to multiple telehealth companies for misleading claims about compounded GLP-1 drugs, signaling a potential shift towards stricter regulations in the compounding industry.

FiercePharma

• “People receiving tirzepatide-B12 products from compounders, telehealth companies, medspas, or anyone else should be aware that they may be using a potentially dangerous product with unknown risks.” — Eli Lilly

Medpage Today

• “Our discovery of this new impurity created when tirzepatide is compounded with B12 highlights the risks to patients of haphazardly mixing untested additives with complex molecules like tirzepatide without rigorous testing, clinical trials and FDA approval,” — Eli Lilly

FiercePharma

• “for anyone outside the company to evaluate the claim.” — Scott Brunner, CEO of APC

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Eli Lilly's warning underscores the complexities and risks associated with compounded medications, particularly in a rapidly evolving market for obesity and diabetes treatments.

Eli Lilly Warns of Vitamin B12 Impurity in Compounded Tirzepatide