The detailed results from a mid-stage trial, presented at a meeting of the American Diabetes Association (ADA) in San Diego on Friday, showed a higher efficacy than the 14.9% weight reduction reported by the companies last month in a brief preview of the data.
The treatment regimen starts at a low dosage which is stepped up to reach a maintenance level - the same as with weekly weight-loss shot Wegovy by Novo Nordisk (NOVOb.CO) and Eli Lilly's (LLY.N) Mounjaro, which is expected to win approval for obesity.
The higher efficacy readout on the new drug came from looking at only those trial participants that reached the maximum dosage and from excluding patients who could not keep up with the ramp-up schedule, mainly because of gastrointestinal side effects.
But Germany's family-owned Boehringer and Denmark's Zealand will likely take well over a year to run a pivotal phase III trial on their drug, called BI 456906, and then to argue what they hope will be a better case with regulators.
For one, they aim to better control side effects, which prompted 24.6% of patients to stop taking the drug in the Phase II trial. They plan to give participants more time to ramp up the dosage in the upcoming larger trial.
"The steeper the dose escalation, the more gastrointestinal side effects come up," Paola Casarosa, head of therapeutic areas at Boehringer Ingelheim, told Reuters.
The partners are also eyeing better efficacy by running the planned Phase III trial for longer because weight loss was not yet levelling off at the Phase II study's 46 week cut-off time.
"Additional weight loss could be achieved with longer treatment duration," the companies said in a statement.
As the dose-finding trial was in the second phase of three required for approval, it was relatively small with close to 400 participants.
The readout was based on a group of 77 people who were meant to ramp up to the highest of four experimental drug dosages and 54 of those actually reached that dose.
The design of the Phase III trial is being discussed with regulators, said Boehringer's Casarosa. She would not be drawn on when to expect results.
Rivals already have longer-term data. Eli Lilly said last year that Mounjaro was shown to reduce up to 22.5% in weight after 72 weeks of treatment in a much larger late-stage trial.
Before that, a late-stage trial showed Wegovy helped patients lose about 15%-17% of weight over 68 weeks, depending on patient subgroups in the study.
To entrench its lead in obesity, Novo Nordisk is developing two-drug treatment CagriSema, which was shown last year to reduce body weight by 15.6% after 32 weeks in a Phase II trial on overweight diabetics.
