It's tough to notch a double-digit gain on a stock in this market, but I'm thrilled to let you in on a little secret: Our subscribers to TheStreet.com Biotech Select have been guided to three double-digit calls within the last six months, courtesy of Adam Feuerstein, our in-house portfolio manager who runs the Biotech Select service. On Sept. 24, Feuerstein added ImmunoGen ( IMGN) to the model portfolio of Biotech Select when its stock was selling at $4.90 a share. ImmunoGen is now at $7.01 a share, delivering a 43% total return to Biotech Select subscribers. Feuerstein knew that ImmunoGen is developing a second-generation version of the blockbuster breast cancer drug Herceptin in partnership with Roche. Early data on the drug has been very positive, which sparked Roche to accelerate its development. On Oct. 8, Feuerstein added Optimer Pharmaceuticals ( OPTR) to the Biotech Select model portfolio when it was trading at $6.50 a share. Optimer Pharmaceuticals closed recently at $12.90 a share, delivering a 98.5% total return so far to Biotech Select subscribers. Feuerstein added Optimer to the model portfolio because of the company's experimental drug OPT-80, a more effective and convenient antibiotic to target Clostridum difficile. (C. diff is a bacterial super bug that causes severe abdominal pain, bloating and diarrhea and can sometimes be fatal.) Soon after Feuerstein added Optimer to the model portfolio, its shares took off when the company reported positive phase III clinical trial results for OPT-80. On Jan. 20, Feuerstein added CV Therapeutics ( CVTX) to the Biotech Select model portfolio when it was trading at $10.75 a share. Two months later, Feuerstein closed the position when Gilead Sciences ( GILD) announced a $20-per-share buyout of CV Therapeutics. The stock produced an 86% return for Biotech Select subscribers.