Treatment of patients with advanced chronic myelogenous leukemia with interferon-alpha-2b and continuous oral cytarabine ocfosfate (YNK01): a pilot study

Interferon therapy in chronic myelogenous leukemia

Interferon (IFN)-alpha, the molecule used in the treatment of chronic myelogenous leukemia and initially prepared from human leucocytes,is now produced essentially by recombinant techniques. Polyethylene glycol (PEG) modifications of proteins could be more effective than the regular molecules; thus, pegylated IFNs more recently have been tested in chronic myelogenous leukemia. PEG modification of proteins reduces sensitivity to proteolysis. Moreover,administration of pegylated IFNs results in less antigenicity and immunogenicity, and prolongation of their plasma half-life has been assessed by pharmacokinetic studies. It is assumed, therefore, that this compound could be more effective and better tolerated. Given the results recently obtained with imatinib, however, whether IFN-alpha will still have a therapeutic role is questionable.

Fulminant bronchiolitis obliterans organizing pneumonia following 2 d of treatment with hydroxyurea, interferon-alpha and oral cytarabine ocfosfate for chronic myelogenous leukemia

A 65-yr-old man developed increasing dyspnea and fulminant respiratory failure 48 h after introduction of hydroxyurea, oral cytarabine ocfosfate (YNK01) and interferon-alpha for treatment of Philadelphia chromosome-positive chronic myelogenous leukemia. The chest radiograph showed bilateral patchy infiltrates while computed tomography revealed multiple bullas, ground glass opacities, and patchy consolidations with possible cavitation. Bronchoscopic examination was normal and microbiological tests performed on all biologic fluids were negative. The patient did not respond to multiple antibiotic treatment and corticosteroid administration and died of progressive respiratory failure 5 d after chemotherapy introduction. The postmortem lung examination was consistent with the diagnosis of bronchiolitis obliterans organizing pneumonia (BOOP).

A phase II study of alpha-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 alpha-interferon (alphaIFN). The use of YNK01 can avoid the daily s.c. injection of conventional AC. To assess the safety and the efficacy of alphaIFN and YNK01, we enrolled 86 consecutive previously untreated chronic phase Ph+ CML patients in a phase II study of alphaIFN (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 alphaIFN 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 alphaIFN and YNK01.

Clinical pharmacokinetics of cytarabine formulations

Cytarabine (cytosine arabinoside, Ara-C) is an effective chemotherapeutic agent for the treatment of acute myelogenous leukaemia and lymphocytic leukaemias. As cytarabine is an S-phase-specific drug, prolonged exposure of cells to cytotoxic concentrations is critical to achieve maximum cytotoxic activity. However, the activity of cytarabine is decreased by its rapid deamination to the biologically inactive metabolite uracil arabinoside. This rapid deamination is the reason for the ongoing search for effective formulations and derivatives of cytarabine that cannot be deaminated and exhibit better pharmacokinetic parameters. Protection of cytarabine from fast degradation and elimination has been investigated by encapsulating the drug into pharmaceutically acceptable carriers. Cytarabine derivatives have shown promise in vitro and in animal models. For example, ancitabine (cyclocytidine), enocitabine and cytarabine ocfosfate have been used clinically in Japan. Cytarabine encapsulated into multivesicular liposomes has been approved in several countries for the intrathecal treatment of lymphomatous meningitis. Although many compounds have been investigated, few cytarabine derivatives are currently available for clinical use. Further research is needed to improve the efficacy of cytarabine against haematological and solid tumours.

Results of a phase II trial of a combination of oral cytarabine ocfosfate (YNK01) and interferon alpha-2b for the treatment of chronic myelogenous leukemia patients in chronic phase

Cytarabine ocfosfate (YNK01) is a prodrug analogue of cytarabine which is resistant to systemic deamination after oral administration. Following initial studies indicating significant anti-tumour activity of YNK01 a phase II trial was initiated in order to assess the tolerability and efficacy of a combination of this agent with interferon alpha-2b (IFN-alpha2b) in recently diagnosed chronic phase CML patients (n = 98). The treatment was subdivided into cycles consisting of 4 weeks of continuous administration of IFN-alpha-2b (3 MU/m(2)/day 1st week and then 5 MU/m(2)/day) and 14 days of oral YNK01 (600 mg/day 1st cycle). At the end of each cycle the dose of YNK01 was adjusted according to the blood count observed during the previous 4 weeks. The median time from diagnosis to inclusion in the trial was 2 months (range 6 days to 7.5 months). At 12 weeks, 62 patients (63%; 95% CI, 54-73) achieved a complete hematological response. At 24 weeks, of 98 patients, two achieved a complete cytogenetic response, 14 a partial response (16% major cytogenetic response rate; 95% CI, 9-24) and 34 a minor response; 19 patients were not evaluable for cytogenetic response. During the trial, 20 patients progressed to accelerated (6) or blastic phases (14). The median time to progression was 15 months (range 2-38 months). At 3 years the overall survival was 79% (95% CI, 70-88). Although the complete hematological response rate compared favorably with the 40% response rate previously obtained with the subcutaneous formulation of Ara-c, the cytogenetic response rate was less than expected. Most of the patients experienced side-effects and all permanently stopped YNK01. Although the combination seems attractive the initial dose of 600 mg per day is probably too high and should be reconsidered in further trials.

Continuous oral cytarabine ocfosfate with interferon-alpha-2b for patients with newly diagnosed chronic myeloid leukaemia: a pilot study

Recombinant(R) interferon alpha (r-IFN-alpha) has been shown to be an effective drug for chronic myeloid leukaemia (CML). However, higher response rates can be achieved using cytarabine along with r-IFN-alpha. YNK01 is a derivative of cytosine arabinoside for oral administration. So far, the only published experience with continuous YNK01 was in advanced CML (10 cases). We have performed a pilot study to evaluate the efficacy and toxicity of the combined therapy r-IFN-alpha and daily oral YNK01 in patients with newly diagnosed Ph+ CML. Ten previously untreated patients were included in the study. Among those patients evaluable for cytogenetic response, 87% (seven out of eight) reached a major cytogenetic response with four reaching complete cytogenetic response (50%). The most significant side-effects were gastrointestinal. Macrocytic anaemia was observed in three patients. In conclusion, continuous oral administration of YNK01 in combination with IFN-alpha is safe and can result in high-cytogenetic response rates.

AraC-based pharmacotherapy of chronic myeloid leukaemia

In interferon-alpha (IFN) treated chronic phase chronic myeloid leukaemia (CML) patients, survival depends on individual risk profile and achievement of a complete haematological response (CHR) and a major cytogenetic response (MCR) (< 35% Philadelphia-chromosome-positive metaphases). The highest cytogenetic response rates have been achieved with the combination of IFN and low-dose sc. AraC (10 mg daily to 10-20 mg/m2 for 10-14 days/month). Whether the higher cytogenetic response rates are also associated with a significant improvement of survival still remains controversial. The different results obtained from large randomised and observational trials may be due to the numbers of patients enrolled, distribution of risk profiles and the treatment schedule, which is influenced greatly by the haematological and gastrointestinal toxicity of AraC. An oral formulation (YNK01), which is lipophilic and resistant to deamination, is currently under investigation. Clinically, it has similar activity, but toxicity leads to discontinuation of treatment in a considerable proportion of patients. The clinical benefits may therefore be outweighed by the dose-limiting toxicity for both application forms. Combinations with other drugs, e.g., STI571 or homoharringtonine, have shown promising early results in vitro and in vivo.