[rgejman]

This is just not true. Drug companies will make slight modifications to existing drugs and can get new patents on the new formulations and for new indications. If it works, a drug company can make money off of it even if it's been off-patent for years. See https://en.wikipedia.org/wiki/Lenalidomide vs thalidomide for an example.

For every therapeutic target there are many chemical/biological solutions that can work. If an off-patent compound shows some effect in a pathway, a patentable variant can usually be made.

[danieltillett]

How can you say this is not true then give all example that require a patent? Yes you can mine drugs that are out of patent and find new uses for it that can be patented. Do you know of one new drug that has come to market in recent years without patent protection?

[rgejman]

The difference between (a) an existing, off-patent molecule and a (b) patentable variant of that molecule is somewhat trivial compared to all of the other costs of bringing a drug to market.

But to address your specific question, generics are drugs that come onto the market all of the time without patent protection.