Those four can cause PML,
I'm not sure, but I believe Ocrevus has not shown that yet. The story I recall reading is that one MS patient who was on Ocrevus and
another MS drug which had previously shown to have PML issues -- in short, he was on two
immuno-suppressants -- came down with PML. So they could not pinpoint that on Ocrevus since he was on two drugs. (Someone correct me if I'm wrong about that.)
With that said, it would not surprise if Ocrevus has a PML risk. And we should remember that it's relatively new from its FDA approval so stats are still being collected.
From what I understand -- MS patient, not a doctor -- the risk varies widely if you have the JCV/JC virus in you or not.
The JCV virus is like herpes -- many in the population have the virus in them. JCV normally is not a problem in humans, unless have AIDS or immune problems or you're on the kind of powerful immuno-suppressant drugs that we MS patients are talking about.
If you don't have the JC virus in you, no problem of PML because the theoretical risk is effectively zero.
But if you do have the JC virus in you already (as a significant percentage of the population does), then you run a risk of PML.
FWIW, this neurologist and MS specialist has a video "thought experiment"
where he talks about PML risks. (I'd love to hear others' views on his take on the issue.)