Oncology is the largest and fastest growing therapy area in the drug industry, with a market estimated to reach $190 billion by 2022. But cancer is a devilishly complex disease, and investors trying to profit from the effort to develop successful therapies are faced with a bewildering array of companies working on competing approaches to attack it.For investors looking for a small biotech stock for the riskier potion of their portfolios, one company taking on simpler problems with a single drug is easy to understand and stands to win big if successful.