I think you make a serious mistake when you conflate cancer drug candidates with cancer drug companies and cancer drug company stocks.
Those of us who bought ARIA under $1.80 don't really have to worry whether Ponatinib will be a commercial success or not. The same is true for Immunogen (TDM-1) or MDVN or SGEN or PCYC or ECYT or a bunch of others. As Peter implies, the task here is to find cancer drug companies that have a good chance of making it to Phase III and beyond with their cancer drug candidates. The Stock Market, not the commercial market, will reward those who manage that task successfully.