Viking Therapeutics' hot stock is slipping following the results of its latest obesity drug trial

Shares of Viking Therapeutics (VKTX) fell on Monday, giving up early gains, as analysts questioned the path forward for its weight-loss drug in development, even after positive results were reported in clinical trials.

The company's weight-loss drug, which is being tested in oral and injectable forms, resulted in a placebo-adjusted average weight loss of up to 6.8% of a patient's body weight in a recent study with the oral version, Viking said Monday at a Survey industry conference. JPMorgan analysts previously identified the conference as a likely catalyst for Viking shares, as production and sales of the treatment are likely to be in several clinical trials and years away.

Viking shares, which had risen premarket, recently fell about 11% – even as they are up more than 250% so far this year.

Analysts at Deutsche Bank wrote on Monday that they believe it will be “very costly” for Viking to build the capacity to produce both oral and injectable versions of the drug in various dosage sizes. That cost and schedule, they wrote, meant current weight-loss giants Eli Lilly (LLY) and Novo Nordisk (NVO) had “built moats” that would make it difficult for Viking and others to compete.

Previous trials of Viking's drugs have sent the company's shares sharply higher several times this year – and sent shares of Eli Lilly and Novo Nordisk lower at times amid fears that their dominance in weight loss would be challenged could.