Scientists have discovered that popular weight loss drugs such as Ozempic, Wegovy and Mounjaro have been linked to serious side effects, including dental decay, loss of muscle and bone mass, blindness, suicidal ideation, cancer and death.
Regulatory warnings based on premarketing studies and animal studies have linked the drugs to the risk of certain tumors, including thyroid C-cell tumors and pancreatic neoplasms.
The Defender reports: However, observational studies in humans have had mixed results — some have found an increased risk in these cancers and others have not.
Most clinical trials so far often lacked the size or duration to capture long-latency outcomes like cancer, so it is also possible that cancers that will develop in the future haven’t been detected, according to the review.
Some studies have also found that the weight-loss effect of GLP-1 drugs itself lowers the risk of some obesity-related cancers.
The TrialSite News review investigated existing data on thyroid cancer, pancreatic cancer and kidney cancer. It also examined safety signals more generally — warnings of possible cancer risks — identified in databases maintained by the U.S. Food and Drug Administration (FDA) and the European Medicines Administration.
The review concludes that “the story of GLP-1 agonists and cancer is still unfolding,” and it isn’t possible to truly assess cancer outcomes for drugs that are so new. Clinical trials, post-marketing studies and analyses of global adverse event registries will have to be ongoing to determine cancer outcomes.
TrialSite News also concluded that, “The balance of benefits and risks will continue to be scrutinized, but at this point, patients and providers can take cautious confidence in the therapy — embracing its advantages while staying alert, in true TrialSite News spirit, to both data and dissenting signals.”
‘Small risks’ of thyroid cancer can’t be ruled out
The data TrialSite News analyzed on each of the cancers and safety signals were complex. Interpreting results from different studies is not straightforward because there are many complicating factors, according to the review.
For example, GLP-1 drugs contain a black box warning — the highest safety-related warnings that medications can have — regarding the potential risk of thyroid cancers, largely based on animal study findings.
A recent Scandinavian cohort study found no significant rise in thyroid cancer treatments among GLP-1 users compared to other diabetes drug users, and a Swedish study made similar findings.
TrialSite News reanalyzed data from those studies and also found no statistically significant increased risk of thyroid cancers.
However, it did find some evidence of a possible 30% increased risk for the cancer, and that subgroup estimates were imprecise because there were few cancer events.
TrialSite News concluded the study contained real-world data indicating the drugs don’t cause a substantial risk of thyroid cancer, but that small risks can’t be ruled out, and continued surveillance is warranted.
It also noted that data reported to the FDA’s Adverse Event Reporting System (FAERS) found a safety signal for the cancer — contradicting the results from the other studies. The evidence suggests that follow-up studies are needed.
Conflicting evidence for pancreatic, kidney cancers
The evidence for pancreatic cancers was similarly complex. Clinicians have seen red flags, and animal studies show a link, and cohort studies have mixed results.
For kidney cancer, different studies have had conflicting results. A study published in JAMA Oncology found a higher but non-statistically significant rate of cancer among GLP-1 users.
Another study found people taking GLP-1s for diabetes had a lower kidney cancer risk than those taking insulin, but a higher rate than those taking metformin.
Taken as a whole, the review found no clear answer on whether GLP-1s are linked to cancer, or whether they improve some cancer outcomes.
Isolating drug-effects from metabolic changes is challenging, because the drugs work in complex ways and weight loss itself affects the body’s metabolic functioning.
Risks for different cancers associated with the drugs are different, so cancer risk cannot be discussed as a whole, and long-term data at this point is limited.
Additionally, observational studies are also affected by confounding factors that can make it difficult to establish causality and pharmacovigilance data can establish signals, but also don’t contain enough information to determine cause.
TrialSite News concluded that from a clinical perspective, current evidence “does not demand an abrupt change in prescribing practices” for the drugs, but does underscore the need for more research.
Trump announces price cut to GLP-1s
The Trump administration’s deal with Eli Lilly and Novo Nordisk will lower the price of the drugs on Medicare and Medicaid and offer them to consumers at a discount on TrumpRx.gov, a website the Trump administration plans to launch in January.
Eli Lilly makes Mounjoro and Zepbound and is developing an oral GLP-1 drug, orforglipron.
Novo Nordisk makes Ozempic, Wegovy, Rybelsus, Vitoza and Saxenda and has applied to the FDA to seek approval for a high-dose version of Wegovy taken as a pill.
The drugs currently cost between approximately $1,000 to $1,350 per month before insurance, although the companies offer the drugs for between $349 and $499 for people paying out of pocket.
Under the new plan, some medicare patients will pay a co-pay of $50 per month for the drugs.
The lowest doses of the pill form of the drug expected out next year will be $150 per month for people getting them through Medicare, Medicaid or TrumpRx, an administration official told reporters during a Thursday briefing.
Starting doses of existing injections like Novo’s Wegovy and Lilly’s Zepbound will be $350 per month on TrumpRX, but are expected to fall to $245 per month over a two-year period, an administration official said.
The companies also announced they would expand manufacturing capacity in the U.S.