You have put your finger on a fairly sensitive issue.
It is certain that very powerful interests are not in favour of a universal public system. Clearly, if drug prices were reduced, pharmaceutical companies would have lower profits in Canada. They would only make profits in Europe, where public systems are already in place. That is not always the system we advocate for—a universal public system or a single-payer system, if you will. Those companies will have lower profits.
Insurance companies don't really play a role in a universal public pharmacare system. For instance, when you go to a doctor, you show your health card and that's it. You make no transactions with insurance companies. That's normal. Why would you? It is completely useless.
To establish an analogy with a quote from John Maynard Keynes, which is probably 100 years old now, I would say that insurance companies dig holes and refill them. That is what insurance companies do in the pharmaceutical industry.