** Shares of biotech firm Oragenics OGEN.A fall 53% to $1.80 premarket

** OGEN is raising up to $20 million through a public offering of preferred stock and warrants

** The offering includes up to 800,000 shares of Series H Convertible Preferred Stock and warrants to buy 800,000 more shares

** Each unit of preferred stock and a warrant is priced at $25

** The preferred stock can be converted into common stock at $2.50/share, a 34.6% discount to the stock's last close

** Co has 715,843 outstanding shares with a market cap of $2.73 million - LSEG

** Co says the proceeds will fund concussion clinical trials, repay a $3 million bridge note, and support general corporate needs

** Dawson James Securities is managing the offering

** As of last close, stock down 65.5% YTD

(Reporting by Kamal Choudhury in Bengaluru)

((Kamal.Choudhury@thomsonreuters.com;))