Shionogi's filing triggers a $7 million milestone payment to BioCryst.
Peramivir is an intravenous drug intended to treat the flu in patients who are hospitalized, and too sick to take an oral treatment. The government has authorized use of peramivir as a treatment for the swine flu, but clinical testing is expected to continue until 2011.
In afternoon trading, BioCryst stock rose 79 cents, or 8.5 percent, to $10.10.