Personalized medicine is a catch phrase of the 21st century — and with good reason. Advances in genetics and biochemistry promise to tease apart factors that explain why some patients benefit dramatically from a therapy whereas others receive no benefit at all. They also help explain side-effect profiles. To accomplish such lofty goals, drug makers are increasingly partnering with diagnostics companies to develop companion biomarkers. But these companies operate in very different business and regulatory environments, so partnerships can be…