I hope your father is responding well to treatment. My mother is going through this exact same ailment as well and similar treatment, complications and now being prescribed Vidaza. From what I've read and understand, there are two newer treatments showing promise if he does not respond to the Vidaza:
4246 Ruxolitinib (RUX) in Combination with Azacytidine (AZA) in Patients (pts) with Myelodysplastic/Myeloproliferative Neoplasms (MDS/MPNs)
https://ash.confex.com/ash/2016/webp...aper96905.html
(see Conclusion, which states "The benefit seems to be more profound in pts with MDS/MPN-U...")
and
SGI-111
https://cornellleukemia.com/2016/04/...mpn-and-cmmol/
The good thing is that it looks like they can be treated with these above newer treatments (that are in trials still) after being treated by Vidaza (azacitidine).
Wishing your Dad success with his treatment!