Eli Lilly’s launch of type 2 diabetes drug Mounjaro has been an historic success, with the drug on track for both blockbuster sales and an expansion into obesity in 2023. 

However, class-wide coverage limits could keep Eli Lilly’s wonder drug out of the hands of many of those who could benefit most.

Approved last year, Mounjaro is off to a hot start. The shot posted first-quarter sales of $569 million, handily beating Wall Street consensus. It’s expected to generate sales of $3.7 billion for the full year, according to a recent investor note from J.P. Morgan.

The Food and Drug Administration is slated to approve the medicine, whose active compound is tirzepatide, for obesity later this year. That follows data from a Phase 3 trial in obese diabetics, dubbed SURMOUNT-2, showing roughly 16% weight loss. 

Additionally, enrollees in the SURMOUNT-1 trial, which didn’t include those with diabetes, lost 22.5% of their body mass. That’s on par with the results seen with bariatric surgery, an older treatment option.

By contrast, Novo Nordisk’s Ozempic and its sibling drug Wegovy, both of which contain the active ingredient semaglutide, resulted in weight loss of 17% in studies. Those two drugs spurred sales of nearly $10 billion last year and are growing quickly as well. 

All three drugs are part of the glucagon-like peptide 1 (GLP-1) receptor agonist class. However, Mounjaro’s unprecedented level of efficacy could make it one of the highest-grossing drugs of all time, bringing yearly revenue exceeding $25 billion to Lilly. The drugmaker is in the process of completing a rolling submission for weight loss in the coming weeks, with a FDA decision expected in late 2023.

Notwithstanding federal regulatory activity, patients have already been using the drug unapproved for that purpose, with some telemedicine obesity care providers marketing it as such. Once an obesity indication is secured, Mounjaro is likely to ride its leading efficacy to a market-leading position among GLP-1s. 

“Lilly’s blockbuster therapy to tackle the global obesity pandemic will undoubtedly gain widespread adoption by patients and providers,” predicted Akash Patel, a pharma analyst at GlobalData, in a recent note predicting its dominance. 

That could be a boon for the 42% of U.S. adults and 20% of children and adolescents who, according to the latest estimates from the Centers for Disease Control and Prevention, have obesity. Even moreso for those populations disproportionately affected. 

As compared to non-Hispanic Asian and non-Hispanic white adults, obesity rates tend to be higher in non-Hispanic Black and Hispanic adults. Rates skew higher among people with lower income and education versus those in higher income and education brackets. The disparities appear among people covered by Medicaid versus people who are commercially insured, too.

As is the case in other situations facing the broader healthcare system, not everyone who could benefit will be able to access these drugs. The medications are still significantly underused. As of 2016, just 1% of office-based visits for patients with obesity received a prescription for an anti-obesity medication. 

That’s likely because many physicians still favor a weight-loss treatment approach focused mainly on restricting calories and increasing physical activity. Doctors may neglect to take into account contravening factors like food insecurity and the effects of other social determinants of health. 

Insurers are also in that philosophical camp. Neither Medicare nor private insurers typically reimburse for antiobesity therapies, including the GLP-1s. That situation can be traced back to a decision Congress made in 2006 to prohibit Medicare from covering these treatments as part of the Medicare Prescription Drug, Improvement, and Modernization Act. Private payers often follow the lead of their public counterparts.

Medicaid agencies, too, have perpetuated this access gap by refraining from defining obesity as a medical condition, even though it was declared a complex chronic disease by the American Medical Association in 2013. Four years later, only six state Medicaid agencies covered obesity treatments. 

In this week’s New England Journal of Medicine, a pair of physicians from the University of Massachusetts Chan Medical School called for state Medicaid agencies to expand coverage.

They wrote that the drugs’ exclusion from the 80-million strong Medicaid program “undermines opportunities for addressing inequities associated with obesity and obesity-related morbidity for the Medicaid-covered population, particularly for members of marginalized racial and ethnic groups that are disproportionately affected by obesity and related health conditions and have high rates of Medicaid coverage.”

The newer weight-loss therapies, then, are gaining ground first and foremost as options for those who can afford to pay out of pocket. That status quo is a holdover from a time when obesity was thought of as a “lifestyle choice,” rather than a serious health concern, and associated treatments were considered merely cosmetic.

Since then, the literature has also demonstrated not only the many factors that contribute to obesity, but the condition’s linkage to many other costly chronic diseases. 

Obesity was associated with an estimated $260.6 billion in direct medical costs in the U.S. in 2016. Inpatient costs are 46% higher and spending on prescription medications is 80% higher among people with obesity than among those without overweight or obesity.

As understanding of obesity has evolved, “approaches to managing obesity as well as insurance coverage of these approaches must also shift, particularly in the Medicaid program.” 

Unless and until that happens, the tirzepatide tap won’t widen for all.