GDANSK, July 10 (Reuters) - Poland's Celon Pharma believes its experimental treatment for acute schizophrenia could eventually achieve annual sales in the billions of dollars, Chief Executive Maciej Wieczorek said on Wednesday.

Last Friday, the company said the drug achieved favourable results in the second phase of clinical studies, showing high efficacy and good tolerance among patients.

"Today, typical anti-psychotics that are still under patent, cost something around $200 to $1,000 per month in therapy. Even with this pricing, I think we can go to the billion (or) billions-dollar product," said Wieczorek, the company's founder who holds a majority stake.

The CEO said that with around six to seven million patients that could be treated, in seven big countries including the United States, the current schizophrenia therapy market was worth an estimated $8 billion.

He added that it is recommended patients take their drug treatments throughout their lives to avoid relapsing.

"Therefore, the market is huge and schizophrenia starts early (in the patient's 20s)," said Wieczorek on a conference call.

Shares in Celon Pharma, whose portfolio includes anti-psychotics medicine Ketrel, anti-tumor drug Aromek and Donepex to treat symptoms of Alzheimer's disease, have surged almost 60% since the Phase II test results, giving the company a market value of roughly $360 million by late trading on Wednesday.

The anti-schizophrenia drug is scheduled to undergo Phase III clinical tests that are typically required by U.S. and European regulators before its possible commercialisation. The tests can take between two to three years, depending on how fast they can be initiated and on support received from agencies. (Reporting by Tymon Miller; Writing by Mateusz Rabiega; Additional reporting by Rafal Wojciech Nowak; Editing by David Holmes and Mark Potter)