** Drug developer's U.S.-listed shares up 8.7 pct at $19.61 premarket
** Leerink Swann LLC starts covering stock with "outperform" rating and $25 price target
** "We believe Tekmira's (lipid-nanoparticle nucleic acid) platform represents a best-in-class technology that has been clinically validated," analyst Michael Schmidt writes in note
** Of 3 other analysts covering stock, 1 has "strong buy" rating and 2 have "buy"
** Median price target on stock is $26.25, down from $28.75 two months ago