Stem cells were certainly high-risk, but don't be fooled into thinking that Geron (Nasdaq: GERN) dropping them from its repertoire means the company is suddenly risk-free, because it isn't. You're still going to need a strong stomach to see Geron through to profitability.

Yesterday, the biotech announced the start of a phase 2 trial testing GRN1005 in patients with non-small-cell lung cancer that has spread to the brain. This is the second phase 2 trial for GRN1005; the company started one in breast cancer that had spread to the brain in earlier this month.

The good news is that brain metastases are a highly unmet need. The bad news is that there's a reason for that. It's challenging to get a drug across the blood-brain barrier. Geron thinks it has solved the problem by attaching a known tumor killer -- Bristol-Myers Squibb's (NYSE: BMY) Taxol, which has been around for so long that it already has generic competition -- to a small protein that targets the drug across the blood-brain barrier.

It sounds feasible, but so did stem cells. The phase 1 data for GFN1005 looked promising, but it'll take additional patients in larger phase 2 trials to prove that the concept has merit. Unfortunately, investors will have to wait more than a year, until the second quarter of 2013, before they'll get to see the data.

Geron has a more advanced drug, imetelstat, but it won't finish much earlier. The company is guiding for the four phase 2 trials to be completed by the end of next year.

Waiting a year for a binary event is asking an awful lot of biotech investors. I wouldn't be surprised to see investors abandon the stock during the first half of the year rather than sit on shares without any catalysts. At that point, Foolish investors will have two options: follow suit into companies with catalysts like Aeterna Zentaris (Nasdaq: AEZS) and Keryx Biopharmaceuticals (Nasdaq: KERX) for their perifosine phase 3 data or use the potential dip as an opportunity to buy additional shares of Geron.

Either way, you'll need a strong stomach. But that's something that'll never disappear from biotech investing.

Fool contributor Brian Orelli holds no position in any company mentioned. Check out his holdings and a short bio. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.