Eli Lilly and Novo Nordisk have been locked in a fierce battle to corner the weight-loss market, and while it is effectively a duopoly now, emerging competitors could soon challenge their lead.

Seizing on the explosive popularity of products like Wegovy and Zepbound, smaller players have pitched weight-loss candidates of their own. Shares of Viking Therapeutics, a mid-cap biopharmaceutical company, surged on Tuesday following positive trial results.

Viking has been developing its own candidate for obesity and type 2 diabetes. The drug, VK2735, is a dual agonist that targets two distinct hormone receptors simultaneously: glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP). By utilizing the same mechanism of action as Lilly's tirzepatide, the drug stands as a direct competitor to Zepbound and Mounjaro.

In the latest study, nearly all patients achieved some degree of weight loss. Trial participants lost between 16% and 19% of their body weight after 21 weeks, compared to 0% in the placebo group, Viking said. Crucially, weight loss showed no signs of plateauing by week 21, and an exploratory group reached 22% weight loss by week 33 with continued dosing.

Shares of Viking Therapeutics surged 35% to $40.68 on Tuesday, pacing toward their largest single-day percentage gain since February 2024.

Like Lilly and Novo's popular injectables, VK2735 is delivered under the skin once a week. Viking is developing an oral formulation of the drug as well.

It isn't the only one looking to snap up market share. Swiss healthcare giant Roche announced positive trial results for its own obesity drug candidate on Tuesday. The once-weekly injection, enicepatide, was acquired through Roche's $2.7 billion purchase of Carmot Therapeutics in 2023.

In a mid-stage trial, enicepatide-another dual agonist-delivered up to 15.5% weight loss over 48 weeks in patients with type 2 diabetes who were overweight or obese, with no plateau in weight reduction. At the highest dose, the drug also produced a mean blood-sugar reduction of 2.65% after 48 weeks.

Vontobel analyst Stefan Schneider noted that overweight or obese patients with Type 2 diabetes are an inherently difficult-to-treat population. However, he believes enicepatide is shaping up to be a strong competitor, given that a significant proportion of patients restored normal glucose levels while achieving sustained weight loss.

Citi's Graham Parry went a step further by singling out potential rivals. While the drugs weren't tested side-by-side under identical conditions, Parry highlighted that enicepatide "compares well to approved Mounjaro" as well as drugs in development like Novo's CagriSema.

Both Lilly and Novo's U.S.-listed shares were trading lower on Tuesday, falling 1.2% and 0.9% in the premarket session, respectively. Roche's U.S.-listed shares, which trade over the counter, weren't yet active.

The clinical updates came on the heels of Novo's capital markets day, where management laid out an ambitious plan for growth that included the launch of five "multi-blockbusters" by 2030. Shares closed lower on Monday as skepticism swirled around the company's commentary around leaning on dealmaking, possibly through large acquisitions.