Roche and Zealand’s obesity contender clears phase 2, but investors were looking for more

On paper, the study did what it was supposed to do. In the 493-patient ZUPREME-1 trial, petrelintide met its primary endpoint, with all five treatment arms showing statistically significant weight reduction versus placebo at 28 weeks. By week 42, patients achieved up to 10.7% mean weight loss, compared with 1.7% for placebo. The once-weekly injectable was tested in adults living with overweight or obesity on top of a reduced-calorie diet and increased physical activity. 

But obesity is one of the few drug markets where a double-digit weight-loss result can still disappoint. Analysts had hoped petrelintide would do more to separate itself on efficacy, especially given how aggressively Roche has built its obesity pipeline through dealmaking. MarketWatch reported that analysts had been looking for something closer to at least 16% weight loss, helping explain why Zealand’s stock dropped more than 30% after the readout, while Roche also traded lower.

Tolerability is the main selling point

The tougher question is not whether petrelintide works, but what role it can realistically play. Petrelintide belongs to the amylin class, an approach many drugmakers view as promising either as a standalone alternative to GLP-1 drugs or as a combination partner. Zealand and Roche are leaning heavily on the first part of that argument: tolerability. In their release, the companies said petrelintide showed “placebo-like” tolerability, with discontinuation rates due to adverse events of 4.8% in the maximally effective arm versus 4.9% for placebo. They also said there were no vomiting cases and no GI-related discontinuations at that dose.

That safety profile is the main reason the asset still matters. Gastrointestinal side effects remain one of the biggest limitations of current obesity medicines, and Zealand is clearly trying to position petrelintide as a more manageable long-term option for patients who struggle with GLP-1-based treatments. The company also reported that rates of diarrhea and constipation stayed in the single digits, nausea was mostly mild, and no unexpected safety signals emerged, including for alopecia or neuropsychiatric events.

Still, investors appear unconvinced that tolerability alone will be enough. Analysts quoted in industry coverage described the dataset as lacking differentiation, particularly because rival amylin programs are also showing favorable tolerability. Eli Lilly, for example, said in November that its amylin agonist eloralintide delivered up to 20.1% weight loss at 48 weeksin a phase 2 trial and was moving toward phase 3, setting a far higher efficacy bar for the class.

That creates a commercial problem for Roche and Zealand. In obesity, physicians may eventually use a broader menu of therapies tailored to different patient profiles. But when heavyweight competitors such as Lilly and Novo Nordisk are pushing efficacy higher and higher, any new entrant needs a clearer story than “less potent, but easier to tolerate.” Cross-trial comparisons are imperfect, but they are unavoidable in this market, and right now those comparisons are not flattering to petrelintide.

Why the result matters for Roche

The result is especially important for Roche because the Swiss group has spent heavily to buy its way into obesity after arriving later than the first wave of winners. In 2025, Roche signed a deal with Zealand worth up to $5.3 billion for petrelintide, including $1.65 billion upfront. Under that alliance, the companies are co-developing and co-commercializing petrelintide and also plan to combine it with Roche’s dual GLP-1/GIP candidate CT-388.

Petrelintide is only one part of that broader strategy. Roche’s CT-388, obtained through the $2.7bn acquisition of Carmot Therapeutics, posted 22.5% average weight loss at 48 weeks in a phase 2 trial announced in January, though investors were still left debating how competitive the profile really is versus the market leaders. Roche is now trying to build a portfolio rather than bet on a single mechanism, and petrelintide may ultimately matter more as a combination component than as a best-in-class monotherapy. 

That possibility is already shaping the next steps. Roche and Zealand said the ZUPREME-1 data will inform phase 3 design, with phase 3 initiation expected later this year. A second monotherapy study, ZUPREME-2, in overweight or obesity with type 2 diabetes is due to produce topline data in the second half of 2026. The partners also plan to start a phase 2 trial of petrelintide combined with CT-388 later this year, a study that may prove more important strategically than this monotherapy readout.

So the message from the latest data is mixed. Scientifically, Roche and Zealand have a drug that reduced weight, hit its endpoints and appears unusually tolerable. Commercially, however, the bar in obesity has moved so fast that a respectable phase 2 result can still be read as a miss. Unless later datasets show stronger efficacy, petrelintide may find its place not as a category-defining obesity medicine, but as a more niche option for patients prioritizing tolerability or as a building block in combination regimens.