It's a myth that you need a novel molecule to get a patent on a medicine.

A company can develop a formulation of generic, off-patent compounds and get FDA approval for that patented formulation.

Even old off-patent drugs are often brought back in new, on-patent formulations that can't be sold generically until the expiration of the patents on the formulation that was approved.

So even if they used psilocybin, they would get a patent on their formulation and get FDA approval for that formulation.