** Drug developer Altimmune's ALT.O shares rise ~2% to $8.05 premarket
** Company says its shares will be added to Nasdaq Biotechnology index .NBI before market opens on Dec. 23
** Company currently testing pemvidutide for treatment of obesity and metabolic dysfunction-associated steatohepatitis (MASH)
** Avg rating of brokerages covering Altimmune stock is "buy"; median PT $24 - LSEG
** As of last close, company's shares have fallen 29.8% YTD
(Reporting by Kamal Choudhury in Bengaluru)
((Kamal.Choudhury@thomsonreuters.com))