Competitor GlaxoSmithKline ( GSK) and Prosensa's drisapersen -- also an "exon skipping" drug, like eteplirsen -- seems to work as well, and there's plenty of room for both drugs in this market. I'm staying with my long recommendation, and will take a very close look at Prosensa's initial public offering if the company chooses to pursue that path.

I've had other modest successes on the long side. Although I still feel hesitant about the long-term commercial opportunity in hepatitis C, I recommended buying Gilead Sciences ( GILD) in late July. The stock has risen 37% since that column. Unfortunately, I got a little too cute with my trading and advised waiting for a pullback below $50 per share. Gilead's shares came close but never quite passed that threshold, so I should really only get half credit. Lesson: if you want to own a stock over at least the medium term -- for me, that means six to nine months -- buy a bit right away if the price seems reasonable and worry about building a larger position on pullbacks or weakness over time.

Gilead feels pricey here, for good reason, but the stock probably continues to work into year-end. Even so, investors should consider taking partial profits. Expectations for sofosbuvir (formerly GS-7977) in Hep C are sky-high and Street analyst estimates already reflect a continued successful launch of Stribild in HIV. I worry about whether the stock can continue it's astonishing run through 2013 without another major upside surprise.

Although I correctly predicted Celgene's ( CELG) Abraxane would work in pancreatic cancer, shares remain basically flat, pending announcement of the detailed phase III data at the American Society of Clinical Oncology's (ASCO) Gastrointestinal Cancers Symposium in early 2013. That presentation, which I expect to be positive, should stoke investor excitement. If it doesn't, investors should move on, as it likely indicates that shares are due for an extended pause. (Celgene has had a lot of positive news in recent months.)

If you liked this article you might like

Sarepta Therapeutics Chart Patterns Look Good

Verastem Shares Are Exploding 50% -- Here's Why

Watch the Key Technical Levels

Net Seller, but Itching to Put More Cash to Work