* Raises FY revenue guidance to 205-215 mln stg from 190-200 mln stg
* Says trading above expectations in six months to end Sept
* Cites strong royalties from prostate cancer drug Zytiga
* Shares up 3.4 percent
LONDON, Oct 3 (Reuters) - BTG raised its full-year revenue guidance on Wednesday, buoyed by summer demand for its snake antivenom and a strong debut for its cancer toxicity drug in the United States.
The British specialist pharmaceutical group said it expected revenue of 205 million to 215 million pounds ($347 million) for the year ending March 31, 2013, up from previous guidance of 190 million to 200 million pounds.
At 0759 GMT, BTG shares were up 3.27 percent at 343 pence, among the top performers on the FTSE 350 and well above the Stoxx European healthcare industry index, down 0.36 percent.
Trading during the first six months had been ahead of expectations, BTG said in an update ahead of its interim results due next month.
It cited high demand for its viper antivenom CroFab during the summer, a strong start for its cancer toxicity drug Voraxaze following its U.S. launch in April, and the continued growth of royalties from Johnson & Johnson's prostate cancer drug Zytiga.
BTG has submitted additional marketing applications for Zytiga in the U.S. and Europe to extend its use to further indications.
First half revenue also included a final royalty payment of $22 million from Pfizer for haemophilia drug BeneFIX and 5.4 million pounds of deferred income following AstraZeneca's decision to terminate the development of CytoFab.
BTG announced in August that CytoFab, an experimental drug for severe sepsis, had failed to help patients in a crucial mid-stage clinical trial.
The company had said it expected to take a charge of approximately 28 million pounds related to the ending of the drug's development.