Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of development stage biotechnology company Isis Pharmaceuticals (NASDAQ:IONS)  jumped as much as 17% following the approval of Kynamro by the Food and Drug Administration.

So what: Kynamro, which was developed with Sanofi (NASDAQ:SNY), is designed to treat homozygous familial hypercholesterolemia, or HoFH, a disease that makes it difficult to remove bad-LDL cholesterol from the body and can lead to cardiovascular disease. It shouldn't come as a surprise, though, that the drug was approved with a warning label that it can cause liver toxicity -- this was a repeated concern raised throughout its trials and by the FDA panel. Sanofi is expected to begin marketing the drug immediately at a price of between $125,000 and $200,000, according to BMO Capital Markets analyst Jim Birchenough.

Now what: Now we get to watch what unfolds when a rare disease suddenly gets two newly approved competing drugs all within a matter of weeks. Aegerion Pharmaceuticals' (NASDAQ: AEGR) Juxtapid was actually approved earlier than its PDUFA date by the FDA, albeit with the same liver toxicity warning. Isis will be relying on Sanofi's marketing expertise to unlike Kynamro's full potential which some analysts have pegged around $400 million in peak sales. Isis itself will get somewhere around 30% to 50% of the profits, depending on total sales of the drug. Aegerion, on the other hand, only partnered its drug, Juxtapid, with Catalent three weeks ago. Nothing against Catalent, but I'm giving Isis the upper hand with Sanofi in its corner. It should, nonetheless, be an interesting battle to watch!

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