How would ‘free market’ deal with this thought experiment without regulations

Company A and B release a pill to resolve issue X. Both pills will fix the issue but company A is 20% cheaper but will cause terrible side effects after 20 years which they intentionally do not reveal to the public and there is no regulations forcing them to in any way shape or form.

Of course company A outsells company B and makes huge profits which they take out knowing that eventually the sales will drop after the side effects start showing.

Once these side effects start showing they do anything and everything to minimize and hide these until eventually when it is no longer making profit they liquidate the business and move on with life having taken all the possible money out of the business. There is no regulations around holding anyone responsible or anything else so they wipe their hands clean and move on with life.

If you support regulations around intentionally hiding research then change the situation to the company just not knowing the risks as they hadn’t done long term studies (no regulations forcing them too).