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.)

For years, biotechs seeking to out-license their drug candidates have had to retain an increasing portion of the development risk.