Dive Brief:

• Eli Lilly’s experimental diabetes injection tirzepatide outperformed Novo Nordisk’s drug Ozempic in a Phase 3 study, showing greater reductions in blood sugar and weight loss, the company reported Thursday. The data could help Lilly’s shot gain acceptance should it win approval.

• Study participants taking tirzepatide reported slightly more frequent gastrointestinal side effects than those on Ozempic, however, and discontinued treatment more often, although rates were low. Doctors may also want to wait for long-term cardiovascular outcomes from a study of tirzepatide that’s due to read out in 2024.

• Lilly and Novo, longtime rivals in diabetes drugmaking, have competing glucose-lowering drugs known as GLP-1 agonists. Lilly’s once-weekly Trulicity has become a blockbuster drug, with $5.1 billion in sales last year, and tirzepatide could upend the market once again if approved.

Dive Insight:

Tirzepatide works by upping production of two hormones that, in turn, help boost insulin production after meals. By increasing levels of the hormone GIP along with GLP-1, Lilly argues, treatment could drive down glucose more than just targeting GLP-1 alone.

That hypothesis appears to have been borne out by the new data from Lilly’s study, dubbed SURPASS-2.

After 40 weeks, three different once-weekly doses of tirzepatide added to metformin lowered blood sugar significantly more than Ozempic and metformin, meeting the study’s primary goal. The 15 milligram tirzepatide dose reduced blood sugar by 2.5 percentage points, from an average baseline of 8.3%, while the 10 milligram dose lowered levels by 2.4 percentage points. Ozempic treatment, by comparison, decreased blood sugar by 1.9 percentage points.

Tirzepatide was also judged by researchers to be superior on secondary endpoints including weight loss and the share of participants who achieved blood sugar levels of 7% or less, a target in diabetes treatment. On the lowest dose tested — 5 milligram — 88% of enrollees reach the 7% blood sugar level, compared with 81% of Ozempic patients.

More study volunteers on tirzepatide reached levels of 5.7% or less, the level seen in non-diabetics, as well.

Ozempic appeared to trigger fewer side effects, however. About 5% of people on low-dose tirzepatide discontinued treatment due to adverse events, rising to nearly 8% of those on the highest dose. By comparison, fewer than 4% of people given Ozempic in the study discontinued the drug.

The most common side effects were nausea, vomiting and diarrhea.

SURPASS-2 is one of several Phase 3 trials comparing tirzepatide against placebo and other drugs such as insulin. One of the most important, however, is a cardiovascular outcomes trial that’s scheduled to produce results by 2024. To be widely adopted, tirzepatide will likely need to prove equivalent to Trulicity in reducing heart complications or death in diabetes with heart disease. Trulicity reduced those risks by 12% versus a placebo.

Until that data reports, doctors may be reluctant to prescribe tirzepatide widely give its new mechanism of action, Mizuho Securities analyst Vamil Divan wrote in a March 4 note to clients. That could give Novo time to build market share for Ozempic and its newer GLP-1, Rybelsus, the first oral drug in this class.

In addition, the Danish pharma has asked the FDA to approve a 2 milligram Ozempic dose, which may improve the drug’s competitive profile versus tirzepatide.

For Lilly, tirzepatide’s success is critical to the long-term strength of its diabetes business. Trulicity is the Indiana-based company’s top-seller, but will lose patent protection in 2027.