Seattle Genetics (NASDAQ:SGEN) shares fell around 4% in early trading Wednesday following the announcement of fourth-quarter and annual reports. What happened?

The waiting game
The latest reports didn't reveal any startling developments. But the company's sole approved drug continues a gradual revenue build, and potential growth factors won't hit until next year.

Seattle Genetics has one approved drug: Adcetris for treatment-resistant forms of Hodgkin lymphoma and systemic anaplastic large cell lymphoma. Adcetris received Food and Drug Administration approval in the summer of 2011, but the relatively small patient bases and geographic limitation to the U.S. hindered the drug's earning potential. Net product sales were $35.4 million for the most recent quarter and $138.2 million for the full year.

Adcetris recently received approvals in Europe and Canada. Seattle Genetics expects the new regions to help drive Adcetris' net product sales to the range of $130 to $140 million. That's obviously not a significant step up from last year.

Label expansion would have a greater impact on sales potential. Seattle Genetics has 20 clinical projects under way to evaluate Adcetris' potential for additional indications. Two promising late-stage trials lead the pack.

The first tests Adcetris for patients at risk of residual Hodgkin lymphoma following a stem cell transplant. The second compares Adcetris to methotrexate or bexarotene, but those won't report data until next year.

The financials -- and a potential problem
Seattle Genetics had $364 million in cash and investments at year's end. That should more than maintain a quarterly cash burn that averaged out to about $29 million in 2012. Net loss for the quarter was $10.6 million and $53.8 million for the year, which work out to $0.09 per share and $0.46 per share, respectively.

Overall revenues were $63.9 million for the quarter and $210.8 million for the year. Those numbers include a variety of license payments that the company receives for lending out its anti-body drug conjugate, or ADC, technology. A potential problem could arise for Seattle Genetics in the future if similar technologies take off.

ImmunoGen (NASDAQ:IMGN) already has a similar technology. The company partnered with Roche on T-DM1 -- a promising treatment for a common type of breast cancer. The FDA is set to make a decision early this year, and the drug could go on to blockbuster status.

T-DM1 and Adcetris aren't playing at the same game, but a rapid rise for ImmunoGen could also highlight Seattle Genetics' soft launch.

Foolish bottom line
Seattle Genetics does have other pipeline projects in the works, but they're all in early stages and won't make an impact for quite some time. Adcetris will add sales in the next couple of years, with the level depending on the introduction of new indications. For now, Seattle Genetics sits in limbo as we await the late-stage trial results next year.