Drugmaker Eli Lilly has issued a warning about “potential safety risks” linked to “knock-off” versions of its weight loss medicine tirzepatide.
Lilly announced in a statement last week that its testing of “compounded tirzepatide” mixed with vitamin B12 revealed “significant levels of an impurity” produced by a chemical reaction between the two ingredients.
Tirzepatide is a glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) drug manufactured by Lilly and sold under the brand name Mounjaro in the UK.
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It said the impurity is “concerning because nothing is known about its short- or long-term effects in humans, the potential impact on the drug’s interaction with the GLP-1 and GIP receptors, toxicity, immune reactions, or how it is absorbed, distributed, metabolized and eliminated”.
“The risks to patients are unknown because tirzepatide has never been studied in combination with B12, and the compounders making these combination drugs are not required to monitor or report adverse events,” it added.
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The company stressed that 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”.
It has notified the US Food and Drug Administration (FDA) about its findings, it added, and recommended that people using the “untested products” speak to their doctor for “advice and discussion on alternative treatment options”.
“Grave concerns”
Lilly said it has “repeatedly expressed grave concerns about the safety of mass-compounded knock-offs” of its tirzepatide medicines.
It added that despite the FDA and a federal court confirming that “mass-compounding of tirzepatide must stop”, the practice continues - with some sellers “claiming to offer ‘personalised’ versions by adding untested additives such as B12” to compounded versions of the drug.
“In reality, these products are not “personalised” at all,” it said. “Most sellers put the same untested additives in all their tirzepatide knockoffs to try to evade FDA regulations.”
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“Our testing results of these so-called ‘personalised’ compounded tirzepatide products show they may pose even greater risks to patients than previously known.”
The company said its discovery of the impurity created when tirzepatide is combined 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”.
It added that vitamin B12 “is just one of the many untested additives used in the mass production of compounded GLP-1s under the guise of ‘personalization’”.
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And it warned that “mass compounders and supposed ‘personalisers’ seeking to circumvent the law” are also mixing tirzepatide with other chemicals, “creating a range of new and untested combination drugs”.
“We also continue to find other critical safety issues in compounded tirzepatide knock-offs, including bacterial contamination, high endotoxin levels and other impurities that are not present in Lilly’s FDA-approved medicines,” it noted.
“Unacceptable risk”
Lilly said the “continued widespread distribution of untested compounded drugs” poses an “unacceptable risk for patients”.
The FDA’s “recent announcement of its intent to take decisive action” against “illegally compounded anti-obesity drugs” is “an important step to enforce the law and protect patients”, it added, and it “urgently” called on “other regulators and law enforcement to do the same”.
The company also urged the FDA to recall all knock-off versions of tirzepatude “combined with untested additives like B12”.
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It comes after Novo Nordisk dismissed its lawsuit against Hims & Hers with the agreement that the digital health platform will sell Novo’s branded weight loss medications and “no longer advertise compounded GLP-1 offerings”.
The Danish drug manufacturer had previously accused Hims & Hers of “unlawfully” mass-compounding “unsafe” and “knock-off” versions of its semaglutide weight loss drugs.
