They are not going to get even close to 50% patients. This type of rare disease is different from other disease, patients who are currently on ERT are very unlikely to switch unless there is strong data that support the switch. The monotherapy for US trial included only treatment naive patients or those who had discontinued ERT for at least 6 months. So there is no data on patients who switch from ERT to Amigal. Data from EMA trial compared to ERT/switched to ERT will not be available for two more years.
I am along the line with genisi. At minimum, monotherapy isn't going to be as effective as ERT.