Have you ever used Google Scholar (https://scholar.google.com/) to find medical research information? What's nice about it is the sort by year function for the search results to get the latest research information on treatments being used. I did a search for EGPA and it came up with a good sized list:
https://scholar.google.com/scholar?as_vis=1&q=egpa+treatment&hl=en&as_sdt=1,24&as_ylo=2020