A phase II study of α -interferon and oral arabinosyl cytosine (YNK01) in chronic myeloid leukemia

YNK01 (Starasid) is a prodrug that is adsorbed in the gut and is transformed in the liver in arabinosyl cytosine (AC). Low-dose AC (LDAC) is useful for the treatment of Philadelphia positive (Ph+) chronic myeloid leukemia (CML), especially in combination with α -interferon ( α IFN). The use of YNK01 can avoid the daily s.c. injection of conventional AC. To assess the safety and the efficacy of α IFN and YNK01, we enrolled 86 consecutive previously untreated chronic phase Ph+ CML patients in a phase II study of α IFN (Intron-A) 5 MIU/m 2 daily and YNK01 600 mg daily 14 days a month. The 6-month complete hematologic response and the 12-month major cytogenetic response rates were 78 and 28%, respectively. In a prior study of α IFN and conventional LDAC, they were 62 and 22%, respectively. However, the compliance to the treatment was poor, with 25% of cases discontinuing the treatment within the first year. This was not because of the severity of the side effects but because of the frequency, duration and repetition of the side effects, for an overall frequency of 13.17 adverse events, mostly grade 1 and 2, per patient per year. Therefore, the study of this effective combination is being pursued, testing lower doses of α IFN and YNK01.