Seattle Genetics (Nasdaq: SGEN) is two for two in recent weeks. After demonstrating its ability to tackle Hodgkin's lymphoma, the development-stage drugmaker announced another positive trial for brentuximab vedotin (SGN-35) yesterday -- this time in anaplastic large cell lymphoma patients.

Brentuximab vedotin elicited a response in 86% of the 58 ALCL patients. We don't know how long the median response rate was because many of the patients are still responding, but it appears it'll be longer than six months because that's where the median follow-up currently stands. That's not bad for patients who failed earlier treatment or couldn't take the medication in the first place.

So if the results were so great and the first trial sent shares up more than 17%, how come shares barely budged yesterday, up just 0.2%? Expectations, my dear Fool, expectations.

Remember the first results came after Seattle Genetics' lintuzumab failed its clinical trial in acute myeloid leukemia. All hopes lay on brentuximab vedotin before the first trial was released, but a positive result on the second trial was somewhat expected.

The first trial was also a confirmation that the company's antibody-drug conjugate technology works. Since Seattle Genetics has licensed the technology to numerous companies -- Bayer, Celldex Therapeutics (Nasdaq: CLDX), Daiichi Sankyo, Genentech, GlaxoSmithKline (NYSE: GSK), AstraZeneca (NYSE: AZN), Takeda, and Progenics Pharmaceuticals (Nasdaq: PGNX) -- proof in a pivotal trial is a good sign that royalties might be coming down the line.

Most importantly, the difference in going from zero to one approved drug is a lot bigger than going from one indication to two. Once the drug is on the market, a drugmaker is only allowed to market it for the approved indication, but doctors can generally prescribe it for anything they want. So-called off-label prescriptions can result in substantial sales, especially in the time between when a drug is shown to work in a clinical trial and when it's approved for the indication.

An approval -- any approval -- is important because Seattle Genetics will almost certainly go after patients earlier in their disease progression. Having brentuximab vedotin already on the market will help it go up directly against drugs such as Roche and Biogen Idec's (Nasdaq: BIIB) Rituxan rather than being used after them.

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