* FDA issues complete response letter for cariprazine
* Move set to delay launch of antipsychotic drug in U.S.
* Richter shares fall 2.8 percent
BUDAPEST, Nov 21 (Reuters) - U.S. health regulators have declined to approve a new antipsychotic drug from Forest Laboratories and Richter, citing the need for more information, including likely additional clinical trial data.
The Food and Drug Administration (FDA) delivered its verdict on cariprazine for schizophrenia and bipolar disorder in a so-called "complete response letter," the type of letter issued by the agency to convey that it cannot approve a drug application in its current form.
Cariprazine was discovered by Hungarian drugmaker Richter and licensed to Forest in the United States and Canada.
Industry analysts have forecast North American sales of the drug of $250 million in 2017, according to consensus forecasts compiled by Thomson Reuters Pharma.
In its letter the FDA acknowledged that cariprazine demonstrated effectiveness but the two companies said on Thursday it appeared regulators wanted more tests on the optimal dose of the treatment to avoid potential side effects.
"This is likely to cause a delay ... (but) we cannot tell how much; we will be able to tell after consultations with the FDA," said Richter spokeswoman Zsuzsa Beke.
The companies said that the FDA had indicated that its request for more information included the need for additional clinical trial data. But Beke said it was possible this might not turn out to be necessary.
"Whether we need more clinical tests, we can also tell that after the consultations - it is possible that the existing data will be sufficient," she said.
Richter's shares were down 2.8 percent by 1040 GMT.