I didn't look to see how many options/warrants they have seems they through in some warrants with each financing so maybe stock isn't a cheap as it looks?
The good news is they don't seem to do really large dilutive offerings when they do a raise. The last raise was on 12/7/12 where they raised about $4M through 1.8M units where each unit consisted of one share of common stock and one warrant to purchase 0.50 of a share of common stock with warrants having a 5-year term and exercisable at $2.20 per share (http://www.arrowheadresearch.com/press-releases/arrowhead-announces-pricing-public-offering-common-stock-and-warrants ).
Of course, given that each raise is small, they have to do these more frequently than one would normally expect. If this frequency is any indication, presumably we can expect more dilution around March or April of 2013.