(Reuters) -Viking Therapeutics' experimental tablet reduced weight by as much as 3.3% when tested in volunteers enrolled in a small early-stage trial, meeting Wall Street expectations and sending the company's shares up 15% in premarket trading on Tuesday.

Popular market leaders from Eli Lilly and Novo Nordisk are administered under-the-skin, with companies also testing oral versions that they hope will offer patients a more convenient option.

California-based Viking reported weight loss of 3.3% in seven people given the highest 40-milligram dose of the drug, called VK2735, when adjusted for placebo rates, at 28 days. It helped patients lose weight by 1.1% on average at a half-strength dose.

The Viking drug meets market expectations for weight loss given that Novo Nordisk's pill amycretin showed an efficacy of about 4% at the same time point, and at higher doses, said David Song, an investment partner at ETF-operator Tema ETFs.

Viking said it planned to continue the trial to test higher doses of the drug in healthy or overweight volunteers, given that side effects were mild- and- moderate in severity.

It also expects to initiate a mid-stage study in obese patients later this year.

The data on VK2735 closely follows mid-stage results that showed an injectable version of the drug helped patients lose nearly 15% of their body weight on average.

In a conference call with analysts, the company said patients who have already achieved high weight loss from an injection could transition to oral drugs to help maintain their weight.

On the other hand, "if somebody didn't want to start with an injectable therapy, maybe they could start with an oral for some temporary period of time," said CEO Brian Lian.

When they realize that an injected version "might generate better weight loss, it would probably reduce their resistance to transition to an injectable," he said.