Doctors in Victoria fear a possible contaminated batch of counterfeit peptides is behind a cluster of hospitalizations for acute liver toxicity, the ABC reports, with the latest patient falling seriously unwell after taking an unapproved product labeled as retatrutide.

Retatrutide is an experimental weight-loss peptide, and peptides are short chains of amino acids that act as signaling agents, telling the body to carry out processes such as hormone release or tissue repair. Eli Lilly holds the sole patent and is running clinical trials, and the Therapeutic Goods Administration says the retatrutide being sold online is not the same product being tested in those trials.

Jaundice within weeks

Seven Victorian patients have now been hospitalized for acute liver toxicity after using a counterfeit of retatrutide, according to the ABC report. Liver transplant specialist Marie Sinclair said the most recent developed severe liver injury after a second dose of the unregulated product.

The speed is the part worth sitting with. Sinclair said affected patients sustained liver injuries within a few weeks of taking the black-market product: "They may become yellow or jaundiced, which is very frightening for patients, and they can become very unwell."

The batch hypothesis, and its evidence

A contaminated batch circulating in Victoria is one possible explanation, Sinclair said, but she stressed there are no testing results to support it and that it is purely a hypothesis at this stage. She has commissioned testing of counterfeit peptides used by the liver failure patients.

TGA chief medical advisor Robyn Langham told the ABC the localized nature of the cases suggested a batch problem, and that the cluster did not appear to be occurring elsewhere in Australia. Langham was careful to say her comments were not the result of an investigation, and that there are no good batches or safe unapproved peptides, which is the more useful framing: a clean batch of an unapproved injectable is still an unapproved injectable.

94,500 products destroyed

The TGA said more than 94,500 unapproved peptide products had been destroyed this year in collaboration with Australian Border Force. Last week, the TGA and New South Wales Police seized more than $120,000 of illicit peptide and anabolic steroid products from premises allegedly linked to social media influencers.

Canberra Health Services confirmed it had detected liver damage from products sold as retatrutide, but would not give numbers due to the low figures involved. Langham said the TGA was particularly concerned that adolescents were buying and injecting products promoted on social media.

What remains unconfirmed

Victoria's Chief Health Officer Caroline McElnay said unapproved peptide products, particularly injected ones, carry significant safety risks including contamination, infection and local tissue damage, and strongly advised against using any of them. Testing is under way, and until it reports, the batch explanation is a hypothesis with seven hospitalizations behind it and no laboratory result yet.