(Reuters) - Shares of Synta Pharmaceuticals Corp lost about a third of their value on Thursday after the company reported interim data from a mid-stage study of its experimental lung cancer drug.

The stock, which had risen about 80 percent in the last two months, could be down on profit-taking, Roth Capital analyst Joseph Pantginis said in a note to clients.

The stock, was down 31 percent at $5.00, making it one of the top percentage losers on the Nasdaq. More than 2.5 million shares had changed hands by 1300 ET.

On Wednesday, the biopharmaceutical company reported data that showed a combination of its key drug ganetespib and the standard of care increased progression-free survival in patients with non-small-cell lung cancer.

However, the company said the sample size was small and was not yet enough to prove statistical significance.

There were severe limitations to the interpretation of the data including small patient numbers, BMO Capital Markets analyst Jim Birchenough said in a note.

"We are optimistic that with greater patient numbers statistical significance can be demonstrated," Birchenough said.

(Reporting by Vidya P L Nathan, Prateek Kumar, Adithya Venkatesan in Bangalore; Editing by Roshni Menon)