Roche dropped as much as 5% in early trading in Zurich on Thursday after releasing results of a small study that showed high rates of nausea and vomiting, as well as other side effects. The company presented the findings late Wednesday to a packed audience at the European Association for the Study of Diabetes meeting in Madrid.

Though Roche’s study only lasted four weeks, investors are tracking it after encouraging early data on the effectiveness of the drug, known as CT-996, sent the company’s shares soaring in July. Roche is pushing its experimental obesity drugs forward quickly in a bid to catch up with Novo Nordisk A/S and Eli Lilly & Co. in the weight-loss market, which is forecast to top $130 billion annually by the end of the decade. 

Roche argued that gradually increasing the dose could mitigate side effects. Five out of six patients who slowly took more reported nausea, while one developed chronic reflux and two had vomiting, the Swiss drugmaker said. Patients who increased their dose more quickly were more likely to have side effects, with six out of seven developing nausea and chronic acid reflux, and five of seven reporting vomiting.

“It’s a long road ahead for Roche,” said Barclays Plc analyst Emily Field. Based on typical timing for patient trials needed for approval, the company may not bring its first weight loss drug to market until 2030, she said.

Novo’s shares climbed as much as 3.8% in early trading in Copenhagen. Lilly’s shares rose 2.2% in New York on Wednesday.

“Roche has the biopharma firepower to potentially compete in this space, but the non-definitive data likely leave investors on the sidelines,” waiting to see how the pill performs in bigger and more definitive studies, BMO Capital Markets’ Evan David Seigerman said in a note. 

The results came a few hours after Novo presented what many investors said was reassuring data on its obesity pill, known by the nickname amycretin. Patients who took the highest dose of Novo’s pill for 12 weeks had a 75% rate of nausea, though with a lower dose, that rate dropped to 31%.

Roche sees its results from the first stage of clinical trials as encouraging and plans larger studies, said Manu Chakravarthy, Roche’s global head of cardiovascular, renal and metabolism product development.

“The whole point of doing a phase one study is to actually push the dose and get to the limits of tolerability so that you understand what the limits of tolerability are,” Chakravarthy said.

In addition to the nausea and vomiting seen in many patients, Roche said one person also had elevated levels of the digestive enzyme lipase. High lipase levels can be a sign of a problem with the pancreas. Patients’ heart rates also tended to increase by about 15 beats a minute, a level that some who asked questions during the presentation said was much higher than is typical for weight loss drugs. 

In addition to the pill, which works similarly to Novo’s Wegovy shot, Roche presented data on an injectable medicine this week that is closer to Lilly’s Zepbound. Side effects on the shot were higher than expected but can be addressed, according to Bloomberg Intelligence. 

Roche’s pill is a simpler molecule than its shot and both Novo’s Wegovy and Lilly’s Zepbound, potentially allowing the challenger to sidestep the supply shortages that have plagued the field’s leaders so far. It still has a way to go, however.

“We really need to see how the drug works in a larger patient population,” said Jared Holz from Mizuho Securities in New York. “We view Novo and Lilly as still the clear leaders in the space.”