Biotech Stock Mailbag: Celsion Short Thesis, Hemispherx

BOSTON ( TheStreet) -- The second-to-last Biotech Stock Mailbag of 2012 begins with an email from Simon K.

" Celsion ( CLSN) has been a great run-up stock lately, but do you think this momentum will last into next year?" he asks.

Celsion is a fantastic and profitable example of the "biotech run-up" strategy espoused by traders, including TheStreet contributor Mark Messier, who runs a subscription trading service built around profiting from biotech stocks that run up in value ahead of catalysts like clinical-trial results and FDA drug-approval decisions.

Messier nailed the trading opportunity in Celsion, with shares up 63% since this Nov. 14 column.

If the surge in Celsion's value is attributable to traders' run-up into the Thermodox phase III trial results in January, remember to heed the rest of Messier's advice: Take profits before the event. If Thermodox blows up, you don't want to kick yourself for not reducing risk exposure and banking easy returns.

Messier on Celsion:

Cautious run-up traders should exit positions before the end of the year to avoid being caught long when the Thermodox results are announced. If you're thinking about holding a position through the results, I recommend taking profits on your initial trade and keeping "free shares" only. Those who like to trade using options can roll run-up profits into calls that expire after data are expected. Because we don't know exactly when in January Celsion will release Thermodox data, it's safest to use your profits to buy calls that expire in February 2013.

Investors get intoxicated on explosive stock runs like we're seeing with Celsion, making it easy to forget the significant risks attached to the Thermodox clinical trial. So let's sober up a bit with a few words from a Celsion short.

I spoke this week with one of my favorite fund managers who focuses almost exclusively on biotech shorts. He is prohibited by his fund's rules from using his name in print. Most recently, he scolded me for being bullish about Clovis Oncology's ( CLVS) pancreatic cancer drug CO-101. He was short and right. He was also very early and right about Elan's Alzheimer's drug bapineuzumab. This guy isn't always right, but he always brings a well-researched perspective to support this bearish views.

Before I get into the reasons he believes the Thermodox phase III study in liver cancer will fail, let's go over some background on the therapy.

Thermodox consists of tiny, heat-sensitive spheres of fat that contain a payload of the chemotherapy drug doxorubicin. When injected into the body, Thermodox accumulates at the site of the tumors. When the tumor site is heated to about 107 degrees using radio waves (radiofrequency thermal ablation, or RFA), the Thermodox spheres melt, bathing the tumor and adjacent tissue in high levels of doxorubicin.

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