After a spectacular 2012, the biotechs as a whole are holding up rather well in the first few weeks of 2013. However, as a bull run matures we inevitably seen leadership narrow and rotations emerge. Two of the larger components of the biotech sector, AMGN and REGN, have flashed some blinking yellow lights over the past few weeks. Note the uptick in selling volume accompanying each recent sell-off. Amgen bulls likely need to hold $83 to avoid confirming a nasty head and shoulders topping pattern, while you can bet Regeneron bears are playing for a breakdown below $164.

Make no mistake, there are other biotechs exuding resiliency here. However, there are indeed two sides to every rotation.

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