(Reuters) -Altimmune Inc said on Tuesday that its obesity drug helped reduce patients' weight by about 10% on average in a mid-stage trial, but concerns over the drug's safety sent the company's shares tumbling nearly 40% in premarket trading.

Nausea and vomiting were the most common adverse events, with one patient experienced a serious case, requiring rehydration, while other cases were of mild and moderate severity, the company said.

In all, 24% of those receiving Altimmune's experimental treatment in the study chose to discontinue the drug, compared with 28.2% of those on a placebo, the company said.

The market for obesity treatments is expected to be a multi-billion dollar one.

Eli Lilly is testing its diabetes drug, Mounjaro, as a potential treatment for obesity, while Novo Nordisk already sells an injectable drug called Wegovy in the United States.

(Reporting by Sriparna Roy and Bhanvi Satija in Bengaluru; Editing by Savio D'Souza)