There are studies going back into the 1990's showing similar results with hydroxyurea. Most of these studies are from Algeria and Iran, so it may be that specific genotypes found in those countries respond better than with other genotypes. The context in all these studies has to be framed in terms of what they are attempting and that is to find low cost alternatives in countries where proper care for thals is not economically feasible. A poorer quality of life may be had than if the patients transfused, but this is a cost that is much more affordable than the transfusion/chelation regimens.
I feel it is much more useful for intermedia patients than for majors.