Viking Therapeutics' GLP-1 Drug Shows Weight Loss Durability, Stock Responds

Shares of Viking Therapeutics (VKTX) closed 35.7% higher on Tuesday, Sept. 22, after the San Diego-based company released new Phase 1 data for VK2735, its experimental GLP-1/GIP weight-loss drug. The results showed that patients kept most of the weight they had lost even after their doses were spaced out to every other week or once a month. With Tuesday's gain, the stock was up 55.6% for the year.

What the trial showed

The study had two parts. In the first, which measured weight loss, 180 adults with obesity received either VK2735 or a placebo once a week. Those on the drug lost between 16.2% and about 18% of their body weight.

The second part tested whether less frequent dosing could hold those losses in place. Participants who received the drug every other week maintained at least 90% of their mean weight loss, compared with 61% for those who received a placebo. Participants dosed once a month maintained at least 80%.

Viking is testing both an oral version of the drug and one injected under the skin. CEO Brian Lian said in a news release that "flexible dosing approaches will provide both patients and their providers with new options for improving long-term adherence to therapy and sustained weight management."

Why maintenance is the competitive question

The obesity-drug market has been shaped by two products: Novo Nordisk's (NVO) Wegovy and Eli Lilly's (LLY) Zepbound. Their success has drawn dozens of companies into the field, each looking for an edge. Some use amylin rather than GLP-1 to trigger weight loss. Others aim for fewer side effects, such as gastrointestinal discomfort or muscle loss. A third group, which now includes Viking, is focused on helping patients keep weight off.

That last category addresses a practical problem. Weight-loss drugs of this kind are generally taken over long periods, and a regimen that requires fewer doses can be easier for patients to stay on.

The bar remains high. Lilly's portfolio includes Zepbound, a GIP/GLP-1 injection; Foundayo, a GLP-1 pill; and retatrutide, a closely watched drug candidate that targets GLP-1, GIP and glucagon. Whether any new entrant can compete with that lineup is still debated.

How analysts read the data

Cantor analyst Steve Seedhouse took the strongest view. "The fact that this trial delivered precisely as expected reinforces our prevailing thesis that this molecule is superior to [Zepbound] because basically all available data suggest it is," he wrote in a note on Tuesday.

Oppenheimer analyst Jay Olson, writing before the data was released, argued that weight loss itself will not be the main point of difference between Zepbound and VK2735. Instead, he said, "VK2735 should compete effectively on long-term persistence, flexibility, convenience, and continuity of care." The maintenance results speak directly to that case, since they measure how well the drug works when patients take it less often.

Larger trials still to come

These are early-stage results. Phase 1 trials are small and come before the larger studies that regulators require before approving a drug, so the data does not settle how VK2735 would perform against Zepbound in practice.

Points to follow:

• Results from larger, later-stage trials of VK2735, including whether the weight-loss and maintenance figures hold up in more patients.
• Data comparing the oral and injected versions, which Viking is developing in parallel.
• Progress on Lilly's retatrutide and Foundayo, the products against which analysts are measuring Viking's drug.