SAN FRANCISCO ( TheStreet) -- Medivation's ( MDVN) marketing partner Astellas reported Xtandi sales of $14 million for the third quarter and forecast $100 million in sales for the newly launched prostate cancer drug through the end of its fiscal year on March 31, 2013.

Xtandi was developed by Medivation but is being sold by the Japanese drug maker Astellas, which reports sales.

Gauging a consensus for early Xtandi sales has been difficult but $14 million in third-quarter revenue is definitely higher than the Street expected given that Astellas only started selling the drug in the middle of September. Assume that a good chunk of third-quarter sales is wholesaler inventory stocking.

The guidance for $100 million in Xtandi sales through March 31, 2013 -- or six months into the drug's launch -- puts the drug on pace to meet Street expectations for the calendar year 2013.

"Taking into consideration potential sales ramp, Astellas' guidance could imply Oct.-Dec. 2012 sales of $30-35 million and Jan.-March 2013 sales of $51-56 million, favorably positioning Xtandi to at least meet expectations including consensus of approximately $225M, which includes estimates in the mid-$300 millions that we believe are bullish for the first-year of launch for any product," writes Jefferies analyst Biren Amin.

FDA approved Xtandi in August for the post-chemo treatment of men with advanced prostate cancer. In this setting, Xtandi competes mainly with Johnson & Johnson's ( JNJ - Get Report) Zytiga. Both drugs, however, are expected to eventually garner most of their sales in the larger and more lucrative pre-chemo prostate cancer setting, where they also threaten to replace Dendreon's ( DNDN) Provenge.

--Written by Adam Feuerstein in Boston.

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Adam Feuerstein writes regularly for TheStreet. In keeping with company editorial policy, he doesn't own or short individual stocks, although he owns stock in TheStreet. He also doesn't invest in hedge funds or other private investment partnerships. Feuerstein appreciates your feedback; click here to send him an email.