It's been a tough few years for RNAi. Last fall, Roche AG discontinued its preclinical RNAi work, and Novartis AG declined to expand an RNAi partnership with Alnylam Pharmaceuticals Inc. Pfizer Inc. followed suit earlier this year, closing its oligonucleotide therapeutics unit.

In a time when it's difficult to raise capital through the public markets, licensing deals are necessary to fund programs, and M&A has developed into the go-to exit strategy for private biotechs.

The decision of when to raise capital sometimes becomes more of a macroeconomic issue than one based solely on the status of an individual company. Yet the macro picture remains hazy – some analysts think things will get better, while others think they will get worse.

As the biotech industry matured – and drug makers both big and small faced capital constraints – spinning off assets into separate companies developed into a popular mechanism to increase shareholder value.

The annual meeting of the American Association for the Study of Liver Diseases kicks off this week, but biotechs with hepatitis C drugs may be busier talking with potential partners than with hepatologists during the event.

ChemoCentryx Inc. and Cempra Holdings LLC just filed S-1s within a week of each other, joining the limited number of biotechs looking to test the initial public offering (IPO) waters. (See BioWorld Today, Oct. 14, 2011, and Oct. 18, 2011.)