For ET due to CAl-R mutation, I was OK on HU for about 3 years, when it was only one pill per day, but had evil digestive issues during the next year, when it was increased to a second pill some days of the week. I switched last December to a hematologist who is also an MPN specialist. He had me gradually changing over a six month period from HU to Anagrelide, which has meant the end of the messy diarrhea. He told me that HU is the drug of first choice but if people have problems with it, Anagrelide may work better. That's been true for me. I had read about Interferon and Besremi on this site so asked about them. I'm not sure why, but he prefers Anagrelide for me.

No answer, just share the rational. Europe and the USA offer Interferon Alpha 2B as a first line treatment. I live in Canada, there is no way I’ll be getting it. Requested to join a phase three trial. Apparently it was closed, only 100 accepted. I’ve done a cost analysis to purchase as a private citizen. Very expense and would deplete my retirement savings. Another issue would be, who is going to monitor my progress even if I could afford it.
I’m certain cost is the driving factor. It’s funny how the governments of the world fast tracked Covid vaccines. I say ‘best to date’ options should be made available.

For example; why be given hydrea vs the highly researched and effective interferon?

I think they use Hydrea for cost. I’ve heard the newer treatments are very expensive. My mother had PV 24 years ago and it was controlled with Hydrea. I am taking it for ET.

I do not believe that they have received FDA approval for use of ropeinterferon/Bestemi for ET yet. I know there are clinical trials for it.