Barron�s analyst, Andrew Bary believes that there is still considerable upside potential for Sarepta Therapeutics $SRPT. The stock�s value more than doubled last week amid a host of positive developments in the biotech sector, which boosted investors� confidence. Although the drug-maker�s market cap is of $3bn, Bary believes that it not unusual for biotech firms� valuation to be valued at 5-10x more than annual revenue. Its treatment Exondys 51 has the potential of $1bn annual sales.