It's been a rough day for Panacos Pharmaceuticals (NASDAQ:PANC) investors. The shares opened 37% lower Wednesday morning after lackluster initial results from the phase 2b study of bevirimat tablets. Even though two of the dozen recipients with multiple-drug-resistant HIV responded favorably, the overall antiviral response was disappointing.

The stock bounced off its early lows but was still down about 30% later in the morning. Adding to the drop, RBC Capital downgraded Panacos and marked down its price target on the shares to $5 from $12.

Panacos was recommended two months ago to Rule Breakers newsletter subscribers. As a maturation inhibitor drug designed to treat HIV patients, bevirimat offered hope for the afflicted as well as for the investors. However, clinical trials happen for a reason, and it's usually a bumpy road.

Does this morning's Panacos tumble make you wary of buying into biotechnology? If you're nodding, there's probably an early Amgen (NASDAQ:AMGN) investor laughing at you. If you can stomach the volatility, it may just take a biotech winner or two to offset many more disappointments.

Want an example? Last year, the Fool's Charly Travers singled out Vertex Pharmaceuticals (NASDAQ:VRTX) for Rule Breakers readers. The stock is up 262%. In other words, one Vertex in your portfolio would be enough to offset several tumbles like Panacos'.

It's simple math. Buy into a 10-bagger and you can have nine other investments go to nil while still breaking even. No one is suggesting that Vertex will appreciate tenfold or that Panacos will go to zero, but do consider that growth stock investing is about riding winners and accepting that you will miss along the way.

Later today, the January issue of Rule Breakers will go out to subscribers and to those who go for a 30-day free trial. I don't know if Charly has one of the two picks in the new issue, but I can certainly look forward to two more ultimate growth stocks on the scorecard.

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Longtime Fool contributor Rick Munarriz considers himself one of the few investors to ever lose money by going long on Amgen. He did it in the early 1990s and sold way too soon. He does not own shares in any of the companies in this story. He is also part of the Rule Breakers newsletter research team, seeking out tomorrow's ultimate growth stocks a day early. The Fool has a disclosure policy.