They will do what is most profitable because it is in the best interest of the company.
Now, because of competition, the cure for cancer would be a very appealing endeavor because that company could make absurd profits in selling that drug. Sure, I can see arguments for failing to find a cure to dispense more treatment drugs, but for the company that finds the cure, the return would be astronomical. An actual conspiracy would be required to do what many of the people that answered Yes are suggesting. A conspiracy and/or collusion would be illegal and would be against the best interest of the company. Accordingly, the only real answer here is no.