Dive Brief:

• Eli Lilly’s experimental diabetes shot tirzepatide helped obese people who have an underlying medical condition lose more than 15% of their body weight in a late-stage clinical trial. At the highest dose tested, patients receiving the weekly injection lost, on average, 21% of their body weight, Lilly said in a press release Thursday.

• The data suggests tirzepatide could challenge similar drugs marketed by Danish drugmaker Novo Nordisk, which earned about $1.2 billion when prescribed for obesity in 2021. Novo’s weekly weight-loss shot Wegovy helped patients with medical complications lose an average of 15% of their body weight in clinical testing.

• Wall Street analysts forecast swift growth for obesity drugs in coming years as patients, doctors and insurers acknowledge the effectiveness of newer agents like Wegovy and tirzepatide. Wegovy sales alone are expected to reach $5.5 billion in 2026, according to consensus estimates highlighted by Cantor Fitzgerald analyst Louise Chen in January.

Dive Insight:

Drug developers have tried for years to develop and sell an effective obesity treatment. More than a decade ago, three biotechs, Arena Pharmaceuticals, Vivus and Orexigen Therapeutics, were in a tight race to launch new agents. But each were only modestly effective, and none could help patients lose more than 10% of their body weight. All of them struggled commercially.

Vivus and Orexigen ultimately filed for bankruptcy, while Arena jettisoned its weight-loss drug and became a developer of inflammatory disease medicines that Pfizer bought last year for $7 billion.

A group of medicines originally developed for diabetes and known as GLP-1 agonists, though, may succeed where those earlier treatments couldn’t. At a higher dose than the one given to diabetics, the active ingredient in Novo’s shot Victoza helped people on average lose around 7% of their body weight in clinical testing, and more than a third lost over 10%. Novo began selling that treatment under the brand name Saxenda in 2014.

Novo then started targeting obesity and, in 2021, won approval of a higher-dose version of Saxenda known as Wegovy. Despite manufacturing problems that have slowed its launch, sales have already gotten off to a strong start. In her January note, Chen of Cantor Fitzgerald wrote that Wegovy prescriptions exceeded Saxenda’s just five weeks after launching.

Tirzepatide is buliding on that progress. The drug is a GLP-1 agonist, but also contains a second appetite-suppressing hormone called GIP. Lilly has already asked the Food and Drug Administration to approve it as a diabetes treatment, and the data released Thursday suggests an application in obesity could soon follow.

Lilly’s trial, named SURMOUNT-1, tested three different doses of tirzepatide, administered once weekly, in obese patients with a medical complication like high blood pressure or cholesterol. Their weight loss was measured 72 weeks after the trial’s start. When including those who stopped treatment, the average weight loss was 15% in the low-dose group, 20% in those who received the medium dose, and 21% for patients who got the highest dose.

Treatment discontinuations due to side effects were most frequent in the medium-dose group, of which 7% ot patients dropped out. The most common adverse events were gastrointestinal side effects, which are known complications of GLP-1 drugs and now, tirzepatide as well. One third of those taking the medium dose, for example, experienced nausea. Meanwhile, 23% of those on the highest dose had diarrhea and 12% experienced vomiting.

Though comparing drugs across trials can be difficult, those numbers are still lower than what’s been observed with Wegovy. In Novo’s clinical studies, 44% of patients taking Wegovy experienced nausea, 30% suffered diarrhea and 24% reported vomiting.

When it launched Wegovy, Novo priced the drug at $1,297 a month, similar to the cost of Saxenda. Should tirzepatide win FDA approval, Lilly likely will need to keep its price competitive in order to ensure that insurers will cover it.

Novo, meanwhile, is developing a similar type of drug to tirzepatide that is currently in Phase 2 trials.