Prosetta, a San Francisco developer of new antiviral therapies, raised $2 million in early financing, VentureWire reports (subscription required). The company termed the funding a “series AAA” round that has the same terms as its earlier $1 million “series A” and $5 million “series AA” financings, but different valuations. Individual investors provided the entire funding, which values the company at over $20 million.

Prosetta, founded by Vishwanath Lingappa, Jaisri Lingappa and other UCSF academics, is working on small-molecule drugs — that is, compounds that can be taken orally — to disrupt the protein coats, or capsids, that viruses form to protect their genes. The company’s first candidate will target hepatitis C.