On the Cellular Pharmacokinetics of 6-Thioguanine in Acute Myelogenous Leukemia

The pharmacokinetics of 6-thioguanine were studied in 10 patients with acute myelogenous leukemia treated with 25-100 mg/m(2) orally. The concentration of 6-thioguanine in plasma was determined with reversed phase high performance liquid chromatography (HPLC). After isolation of leukemic cells and erythrocytes by density centrifugation, HClO4 extraction of nucleotides and isolation of thiol containing substances on mercurial cellulose, the intracellular concentration of phosphorylated 6-thioguanine metabolites was measured by anion exchange HPLC. The plasma peak concentration of 6-thioguanine was significantly correlated (r(2) = 0.60) to the dose administered. In the leukemic cells, the 5'-mono-(TGMP) and 5'-triphosphates (TGTP) of 6-thioguanosine could be detected in nine of the patients. In one patient only TGMP was seen. The diphosphate could be detected in low concentrations in 6 patients. In all patients, the concentration of TGMP was higher than that of TGTP which was higher than the diphosphate. The interindividual variation in cellular TGMP and TGTP concentration was > 100-fold and independent of dose, while the variation in plasma 6-TG was < 15-fold. There was no correlation between dose or plasma area under the concentration versus time curve (AUC) of 6-TG and the cellular AUC of TGMP or TGTP. However, the AUC of TGMP and TGTP correlated significantly (r(2) = 0.64). The t1/2 of the intracellular metabolites and of 6-thioguanine in plasma were in the same order (4.4, 5.2 and 5.0 h for plasma 6-thioguanine, the intracellular mono- and triphosphate respectively). Phosphorylated metabolites of 6-thioguanine were detectable in erythrocytes from 8 patients. The kinetic pattern of the metabolites in erythrocytes was different from that in leukemic cells. While shortly after administration being eliminated according to first order kinetics in the leukemic cells, the concentration of intracellular metabolites in the erythrocytes was raising during the first 24 h after the treatment. The concentration of the metabolites were, however, much (100-fold) lower in erythrocytes compared to leukemic cells. Furthermore, the triphosphate was the predominant metabolite in the erythrocytes and considerable amounts of the diphosphate was seen while the concentration in the monophosphate was low. We conclude that there is a considerable interindividual variation in the cellular pharmacokinetics of TGMP and TGTP. The concentration of the phosphorylated metabolites in the leukemic cells cannot be predicted by determination of plasma 6-thioguanine concentration, nor by the concentration of the same metabolites in the erythrocytes.

Granulocyte-macrophage colony-stimulating factor to increase efficacy of mitoxantrone, etoposide and cytarabine in previously untreated elderly patients with acute myeloid leukaemia: a Swedish multicentre randomized trial

A total of 110 patients, aged 64 years or over, with de novo acute myeloid leukaemia (AML) and white blood cell counts <50 x 109/l were treated with 3 d of cytarabine 1 g/m2 twice daily, mitoxantrone 12 mg/m2 and etoposide 200 mg/m2, randomized with or without the addition of granulocyte-macrophage colony-stimulating factor (GM-CSF) 200 microg/m2. The primary aim was to evaluate the effect of GM-CSF on the remission rate. Secondary aims included comparison of duration of remission, survival and infectious complications and the impact of maintenance therapy with thioguanine. Complete remission (CR) was achieved by 64% of patients without GM-CSF, and by 65% of patients who received GM-CSF, the median remission duration was 13 vs. 6 months, the median overall survival (OS) was 14 vs. 9 months, the mean time to neutrophil recovery was 25 vs. 17 d (P = 0.03) and the number of positive blood cultures was 46 vs. 39 (P = 0.05) respectively. The impact of thioguanine remains unanswered since only 30 patients remained in CR after consolidation therapy. We conclude that induction therapy is feasible with acceptable toxicity in elderly patients with AML, albeit with a high relapse rate and short OS. GM-CSF prior to, and in combination with, induction treatment reduced the time to neutrophil recovery and the number of neutropenic septicaemia cases but did not improve the OS of AML in the elderly.

Oral etoposide in patients with hematological malignancies: a clinical and pharmacokinetic study

Tumor responses after daily oral administration of low-dose etoposide have been demonstrated in both hematological and solid tumors. The aim of the present phase II trial was to determine tumor response, and toxicity and to delineate the pharmacokinetics of oral low-dose etoposide in patients with hematological malignancies in a palliative treatment setting. Thirty-two patients with non-Hodgkin's lymphoma (NHL), acute myeloblastic (AML) and lymphoblastic leukemia, multiple myeloma, and myelodysplastic syndrome (MDS) were included. Patients were given oral etoposide, 100 mg once daily for 14 d in a 21-d cycle. Serum etoposide concentrations were determined on d 1, 7, and 14 of every cycle before etoposide administration and, in addition, 1, 2, 3, 4, and 24 h after drug intake on d 1. The median age of patients was 68 yr (range: 50-89 yr). The median time from diagnosis to inclusion in the study was 21 mo (range: 0.5-144 mo) and most patients had advanced disease and were heavily pretreated. Eleven patients completed three or more cycles. Eight of 11 patients with acute leukemia and 1 of 2 with MDS received only 1 course because of toxicity (n = 5) or progression (n = 4). One patient with AML, a Jehovah's Witness, was treated up-front and achieved a complete remission and two patients with low-grade NHL gained a complete and a partial remission, respectively. Twenty-one of 32 patients were evaluable for toxicity during the first cycle. In 67%, the white blood cell count nadir was < 2.0 x 109/L and in 38% < 1.0 x 10(9)/L. Platelet count nadir was less than 25 x 10(9)/L in 24% of evaluable patients. During all cycles (n = 79), eight patients developed febrile neutropenia, four of whom with a fatal outcome. The correlation between the area under the curve (AUC) of the free fraction of etoposide and leukopenia was statistically significant at a log analysis (n = 12; p < 0.05). There was also a statistically significant correlation between the AUC and the 24-h concentration (n = 15; p < 0.005) and between the concentrations at 24 h and d 7 (n = 11; p < 0.005) of the free fractions of etoposide. In conclusion, etoposide had a moderate clinical effect in this group of heavily pretreated patients. Moreover, toxicity was substantial, in particular leukopenia, which correlated to the free-etoposide AUC.

Long-term follow-up of patients >or=60 yr old with acute myeloid leukaemia treated with intensive chemotherapy

It is still controversial how to treat elderly patients with acute myeloid leukaemia (AML), and results have been poor with most regimens. We report the long-term results of a randomised study performed by the Leukaemia Group of Middle Sweden during 1984-88 comparing two intensive chemotherapeutic drug combinations. Ninety patients >or=60-yr old with untreated AML were randomly allocated to treatment with daunorubicin, cytosine arabinoside (ara-C), and thioguanine (TAD) (43 patients) or a combination in which aclarubicin was substituted for daunorubicin (TAA) (47 patients). Forty-four patients (49%) entered complete remission (CR), 22/43 (51%) in the TAD group and 22/47 (47%) in the TAA group (ns). The CR rate in patients <or=70 yr of age was 30/42 (71%) and in patients >70 yr 14/48 (29%) (P<0.0001). Early death within 30 d after treatment initiation was more often seen in patients >70 yr than in patients <or=70 yr of age, 40% and 12%, respectively (P<0.005). The median cause-specific survival time was 178 d in the total patient group, and the 2-, 5-, and 10-yr survivals were 22%, 11%, and 8%, respectively. The cause-specific survival was not significantly different between the two treatment arms. At long-term follow-up >or=10 yr after inclusion of the last patient, 5/90 patients (one in the TAD group and four in the TAA group, respectively) were still alive, four in continuous complete remission and one in second complete remission. Thus, both treatment regimens appear to have similar efficacy, with a relatively high complete remission rate, and a reasonable survival as compared to other studies including some long-term survivors. However, early deaths are still numerous, particularly in patients above 70 yr of age, and the relapse rate is substantial.

In vitro topo II--DNA complex accumulation and cytotoxicity of etoposide in leukaemic cells from patients with acute myelogenous and chronic lymphocytic leukaemia

Topoisomerase II (topo II) is the target enzyme of etoposide, and DNA--topo II complex accumulation is considered crucial for the cytotoxic effect. We used a SDS--KCl precipitation assay to determine the complex accumulation induced by etoposide in leukaemic cells isolated from 58 patients, 31 with acute myelogenous leukaemia (AML), and 27 with chronic lymphocytic leukaemia (CLL). To investigate whether the sensitivity towards etoposide was dependent on the complex accumulation in the cells, we investigated the drug-induced DNA damage using a DNA unwinding assay and the in vitro cytotoxicity of etoposide using the MTT assay. AML cells had higher complex accumulation (P=0.006) and more DNA damage (P=0.029) compared with CLL cells. The data support a relationship between etoposide-induced complex accumulation and DNA damage in leukaemic cells from AML and CLL patients. However, the induced DNA damage did not translate to in vitro cytotoxicity, suggesting that other factors, such as DNA repair and apoptosis functions, also play important roles to determine the etoposide sensitivity.

P-Glycoprotein inhibitor valspodar (PSC 833) increases the intracellular concentrations of daunorubicin in vivo in patients with P-glycoprotein-positive acute myeloid leukemia

PURPOSE

The aim of the present study was to evaluate the effect of the cyclosporine derivative valspodar (PSC 833; Amdray, Novartis Pharma, Basel, Switzerland) on the concentration of daunorubicin (dnr) in leukemic blast cells in vivo during treatment.

PATIENTS AND METHODS

Ten patients with acute myeloid leukemia (AML) were included. Leukemic cells from seven of the patients were P-glycoprotein (Pgp)-positive. dnr 100 mg/m(2) was given as a continuous infusion over 72 hours. After 24 hours, a loading dose of valspodar was given, followed by a 36-hour infusion of 10 mg/kg per 24 hours. Blood samples were drawn at regular intervals, and concentrations of dnr and its main metabolite, daunorubicinol, in plasma and isolated leukemic cells were determined by high-pressure liquid chromatography.

RESULTS

The mean dnr concentrations in leukemic cells 24 hours after the start of infusion (before valspodar) were 18.8 micromol/L in Pgp-negative samples and 13.5 micromol/L in Pgp-positive samples. After 8 hours of valspodar infusion, these values were 25.8 and 24.0 micromol/L, respectively. The effect of valspodar was evaluated from the ratio of the area under the curve (AUC) for dnr concentration versus time in leukemic cells to the AUC for dnr concentration against time in the plasma. For the seven patients with Pgp-positive leukemia, the mean ratio increased by 52%, from 545 on day 1 to 830 on day 2 (P<.05) when valspodar was given. In the three patients with Pgp-negative leukemia, no significant difference was observed.

CONCLUSION

These results strongly suggest that valspodar, by interacting with Pgp, can increase the cellular uptake of dnr in leukemic blasts in vivo.

Distribution of 2-chloro-2'-deoxyadenosine, 2-chloro-2'-arabino-fluoro-2'-deoxyadenosine, fludarabine and cytarabine in mice: a whole-body autoradiography study

The distribution characteristics of tritiated nucleoside analogs, 2-chloro-2'-deoxyadeonosine (CdA), 2-chloro-2'-arabino-fluoro-2'-deoxyadenosine (CAFdA), 2-fluoroarabinosyladenine (F-ara-A) and cytosine arabinoside (ara-C) were compared in mice using whole-body autoradiography. CdA, CAFdA and F-ara-A have quite similar molecular structures, but they differ substantially in clinical activity as well as the side effects. Eight mice were injected intravenously in couples. One mouse from each pair was killed 20 min postinjection and the other mouse from each pair 4 h after the injection. The distribution of the label was then analyzed by whole-body autoradiography. The distribution of the nucleoside analogs was rapid and uniform. High concentrations were found in highly perfused organs. After 4 h the overall concentration had decreased but relatively high activities were found in the skin for CdA and CAFdA, in the thymus for ara-C and the bone marrow for CdA. Both CdA and CAFdA were found in the brain, but the concentration was surprisingly lower after 4 h for CAFdA, a lipophilic and more stable analog as compared to CdA. There was an uptake of CdA, F-ara-A and CAFdA in the skin. There were signs of retention of ara-C in parts of the thymus. The present investigations indicate that the nucleoside analog transport to the brain in mice is not primarily dependent upon passive diffusion over a lipophilic barrier, but suggestive of a specific transport mechanism.

Biochemical pharmacology and resistance to 2-chloro-2'-arabino-fluoro-2'-deoxyadenosine, a novel analogue of cladribine in human leukemic cells

The objective of the present study was to investigate the biochemical pharmacology of 2-chloro-2'-arabino-fluoro-2'-deoxyadenosine (CAFdA)--a fluorinated analogue of cladribine [2-chloro-2'-deoxyadenosine, Leustatin (CdA)] with improved acid and metabolic stability--in human leukemic cell lines and in mononuclear cells isolated from patients with chronic lymphocytic leukemia (CLL) and acute myelocytic leukemia (AML). We have also made and characterized two cell lines that are not sensitive to the growth inhibitory and cytotoxic effects of CAFdA. Incubation of cells isolated from the blood of CLL and AML patients with various concentrations of CdA or of CAFdA accumulated CdA and CAFdA nucleotides in a dose-dependent manner. A significantly higher rate of phosphorylation to monophosphates was observed for CAFdA than for CdA in cells from CLL patients (n = 14; P = 0.04). The differences in the phosphorylation were even more pronounced for the respective triphosphates in both CLL (n = 14; P = 0.001) and AML (n = 4; P = 0.04) cells. Retention of CAFdA 5'-triphosphate (CAFdATP) was also longer than that for CdA 5'-triphosphate (CdATP) in cells from leukemic patients. The relative efficacy of CAFdA as a substrate for purified recombinant deoxycytidine kinase (dCK), the key enzyme in the activation of nucleoside analogues, was very high and exceeded that of CdA as well as the natural substrate, deoxycytidine, by a factor of 2 and 8, respectively. The Km for CAFdA with dCK was also lower than that for CdA, as measured in crude extracts from the human acute lymphoblastic leukemia cell line CCRF-CEM and the promyelocytic leukemia cell line HL60. Acquired resistance to CAFdA in HL60 and in CCRF-CEM cell lines was directly correlated to the decreased activity of the nucleoside phosphorylating enzyme, dCK. Resistant cells also showed a considerable degree of cross-resistance to analogues that were activated by dCK. These observations demonstrated that dCK phosphorylates CAFdA more efficiently than CdA. Furthermore, CAFdATP is apparently more stable than CdATP and the mechanisms of resistance to CAFdA are similar to those leading to CdA resistance. These results encourage studies on the clinical effect of CAFdA in lymphoproliferative diseases.

Etoposide-induced DNA strand breaks in relation to p-glycoprotein and topoisomerase II protein expression in leukaemic cells from patients with AML and CLL

Elevated expression of the membrane transporter p-glycoprotein (pgp) and impaired expression of the nuclear enzyme topoisomerase II (topo II) are well-known mechanisms for in vitro acquired drug resistance. The clinical relevance of topo II remains unclear, whereas a relationship between pgp levels and treatment results has been shown in acute myelogenous leukaemia (AML). We have investigated the relationships between the levels of topo II and pgp, and in vitro sensitivity to etoposide in mononuclear blood cells from 24 patients with AML, 16 with chronic lymphocytic leukaemia (CLL) and five healthy blood donors. Following incubation with etoposide, AML cells showed more DNA damage, determined by a DNA unwinding technique, than CLL cells (P = 0.001), whereas there was no difference in cellular etoposide accumulation. Pgp and topo IIbeta levels, determined by Western blot, showed a pronounced variation between patients, but no correlation with induced DNA damage, whereas topo IIalpha protein was undetectable. In the AML group, topo IIbeta expression correlated with pgp expression (rho = 0.7, P = 0.001, n = 24). The topo IIbeta expression was 147.4(+/-74.6)% in the pgp+ AML cells (n = 10), compared to 33.4(+/-27.8)% in pgp- AML cells (n = 14) (P = 0.0001). Our results show a previously unknown coexpression of topo IIbeta and pgp in AML, thereby suggesting that topo IIbeta is a potentially interesting resistance factor in AML.

Addition of etoposide to CHOP chemotherapy in untreated patients with high-grade non-Hodgkin's lymphoma

BACKGROUND

Second- and third-generation chemotherapy protocols for the treatment of aggressive non-Hodgkin's lymphomas (NHL) have considerable, and age-related, toxic effects. In addition, they do not seem to prolong overall survival in comparison to standard CHOP chemotherapy. In this phase II study we investigated the feasibility and efficacy of the addition of etoposide to the conventional CHOP regimen.

PATIENTS AND METHODS

Toxicity and clinical efficacy were determined in 132 patients with previously untreated high-grade NHL. There were 51 patients in clinical stage I and II and 81 patients in stage III and IV, with a median age of 54 years (range 17-85). Patients received standard-dose CHOP plus etoposide 100 mg/m2 i.v. on day 1 and 200 mg/m2 p.o. on days 2-3.

RESULTS

The overall response rate was 84%, with 70% complete and 14% partial responses. The predicted three- and five-year survivals for the group as a whole were 60% and 53%, respectively, and the corresponding disease-free survivals for patients achieving complete remissions were 65% and 56%, respectively. Outcome was not different from that of CHOP-treated patients in a recently completed Nordic study performed during the same time period. Myelosuppression (WHO grade 3-4), observed in 87% of patients and infectious complications (WHO grade 3-4) in 33%, dominated the toxicity profile of this regimen. Fifty-seven of 92 complete responders (62%) received 6-8 CHOP-E cycles with no reductions in planned dose intensity. LDH level higher than normal, extranodal sites = 2, stage III-IV at diagnosis were all indicators of a poor survival.

CONCLUSIONS

We conclude that CHOP-E treatment is effective in high-grade NHL. However, mainly due to severe myelosuppression frequent schedule modifications were required and the results are not obviously superior to those of conventional CHOP.

Cladribine for untreated or early low-grade non-Hodgkin's lymphoma

PATIENTS AND METHODS

Forty-four patients, with low-grade non-Hodgkin's lymphoma (LG-NHL) were included in a phase II study between June 1993 and May 1995 and treated with cladribine (CdA) 0.12 mg/kg as a 2 h i.v. infusion daily x 5, repeated after 28 days for up to 6 courses. Thirty-four patients were previously untreated and 10 had progressive disease after initial response to limited chlorambucil treatment. Five patients had also received involved field radiotherapy. Eight patients had mantle cell lymphomas, 22 follicle centre lymphomas, 5 lymphoplasmacytoid lymphomas, 4 small cell lymphocytic lymphomas, 4 marginal zone B-cell lymphomas and I had unclassified low-grade NHL. The response rate was 64%, with 11 (25%) CR and 17 (39%) PR while 5 (11%) patients progressed during treatment. The response rate was similar in previously treated and untreated patients. The median number of CdA courses delivered was 3 (1-6) in non-responding patients and 6 (2-6) in responders. Median survival from inclusion was not reached with a median follow-up of 40 months. The median time to progression was 7 mo for all patients, 25+ mo for CR and 16 mo for PR patients. Toxicity was sometimes severe with 2 treatment related deaths, one infectious related and one due to a mucocutaneous syndrome and pulmonary microembolism. In addition, 5 grade 3 or 4 infectious episodes were seen. Seven patients experienced grade 3 or 4 thrombocytopenia and 20 had grade 3 or 4 neutropenia. We conclude that the majority of patients with low-grade non-Hodgkin's lymphoma respond to CdA but that the adverse effects may be severe.

Multidrug resistance phenotype in leukaemic cells from patients with acute myelocytic leukaemia can be detected with 99Tc(m)-MIBI

The aim of the study was to investigate whether 99Tc(m)-MIBI (Cardiolite), recently shown to be a substrate for P-glycoprotein, has the potential to be used as a marker for mdr1 gene expression and whether cyclosporin A (CyA) can modify its accumulation in vivo. Leukaemic cells from ten patients with acute myelocytic leukaemia (AML) were used, five with undetectable mdr1 gene expression and five with mdr1 mRNA levels ranging from 1.0 to 3.8 mdr1 mRNA transcripts per cell. Cells were incubated with 99Tc(m)-MIBI, or with daunorubicin (Dnr), with and without 3 microM CyA. The median 99Tc(m)-MIBI accumulation (% of added radioactivity) in mdr1-negative cells was 0.89% and in the mdr1-positive cells 0.34%, P = 0.01. In mdr1-negative cells, the median increase in 99Tc(m)-MIBI accumulation with CyA was 30% compared with the mdr1-positive cells with a median increase of 242%, P = 0.009. CyA had no significant effect on Dnr accumulation in four of the mdr1-negative samples. The median increase of Dnr accumulation in the mdr1-positive cells was 40%. The results show that 99Tc(m)-MIBI with a high sensitivity can detect rather low levels of mdr1 gene expression in clinical samples. Consequently, 99T(c)m-MIBI scintigraphy has the potential to be used for monitoring the effect of resistance modifiers on the accumulation and retention of cytostatic drugs in human tumours in vivo.

Gain of chromosome 7 marks the progression from indolent to aggressive follicle centre lymphoma and is a common finding in patients with diffuse large B-cell lymphoma: a study by FISH

Gain of chromosome 7 represents one of the most frequent cytogenetic findings in B-cell lymphomas with a follicular growth pattern. We used fluorescence in situ hybridization (FISH) and a probe specifying chromosome 7 on lymph node imprints and/or bone marrow (BM) and peripheral blood (PB) smears from six consecutive patients with follicle centre lymphomas (FCLs) grade I or II (low-grade lymphomas), four patients with FCLs grade III and 11 patients with diffuse large B-cell lymphomas (DLBCLs) (high-grade lymphomas). We found gains of chromosome 7 in 14/18 successfully analysed cases (i.e. 2/6 FCLs grade I-II, 3/3 FLCs grade III and in 9/9 DLBCLs) using lymph node imprints. Moreover, the FISH technique demonstrated gains of chromosome 7 in 1/4 BM and 0/4 PB samples from FCLs grade I-II, in 2/4 BM and 2/4 PB specimens from FCLs grade III and in 4/9 BM and 2/9 PB samples from the DLBCLs. In contrast, morphologically recognizable lymphoma cells were seen in only 1/4 BM and 0/4 PB samples from the FCLs grade III and in 1/11 BM and 1/11 PB samples from the DLBCLs. We conclude that: (i) gain of chromosome 7 marks the progression from indolent to aggressive FCL and would appear to be a common finding in patients with FCLs grade III and in DLBCLs, (ii) clonal lymphoid cells occur frequently in BM and PB in high-grade lymphomas, making traditional staging by cytomorphology uncertain, and (iii) using gains of chromosome 7 as a marker of lymphoma cells, FISH is a useful method to detect minimal residual disease in FCLs grade III and DLBCLs.

Relationship between cladribine (CdA) plasma, intracellular CdA-5'-triphosphate (CdATP) concentration, deoxycytidine kinase (dCK), and chemotherapeutic activity in chronic lymphocytic leukemia (CLL)

Seventeen patients with CLL were treated with oral 2-chloro-2'-deoxyadenosine (cladribine, CdA, 10 mg/m2) on 3 consecutive days and the pharmacokinetic parameters of CdA in patient plasma and its intracellular nucleotides (CdAMP, CdATP) in circulating leukemic cells were studied after the last dose intake and up to 72 h thereafter. The median terminal half life (t1/2) of CdA in plasma was 21.1 h and the area under the curve (AUC) was median 1.2 microMh. The median t1/2 was 14.6 h for CdAMP and 9.7 h for CdATP. The AUC of CdATP in leukemic cells is lower than the AUC of CdAMP (median ratio 0.60). There was no correlation between cellular CdATP and plasma CdA concentrations or dCK activity. The clinical response was related to higher Cmax values for plasma CdA (p = 0.05) and higher products of dCK activity and CdA Cmax of plasma (p = 0.02). The activity of dCK alone was not related to the clinical outcome in this patient group. The results suggest that further steps in the mechanism of action of CdA beyond its bioactivation may be more important, e.g. the extent of DNA fragmentation or the ability of the leukemic cell to go into apoptosis, than the concentration of CdA nucleotides alone.

Pharmacokinetics of cladribine in plasma and its 5'-monophosphate and 5'-triphosphate in leukemic cells of patients with chronic lymphocytic leukemia

The pharmacokinetic parameters of cladribine (CdA) in patient plasma and its intracellular nucleotides CdA 5'-monophosphate (CdAMP) and CdA 5'-triphosphate (CdATP) were delineated in circulating leukemia cells in 17 patients with chronic lymphocytic leukemia, after the last dose intake and up to 72 h thereafter. Patients were treated with 10 mg/m2 CdA p.o. on 3 consecutive days. A novel and specific ion-pair liquid chromatographic method, which separates the intracellular CdA nucleotides, was used. The area under the concentration versus time curve (AUC) of CdAMP in leukemia cells was generally higher (median, 47 micromol/liter x h) than the AUC of CdATP (median, 22 micromol/liter x h); however, in some patients (3 of 17), the reverse relationship was seen. The median ratio between the AUC values for CdATP and CdAMP was 0.60 (95% confidence interval, 0.4-1.0). The median half-life (t(1/2)) of CdAMP was 15 h, and that of CdATP was 10 h. The median terminal t(1/2) of CdA in plasma was 21 h. A significant correlation was found between the maximum plasma CdA and cellular CdAMP concentrations (r = 0.56, P = 0.02). There was no correlation between the AUC values of cellular CdAMP and CdATP (r = 0.224, P = 0.55). No correlation was found between deoxycytidine kinase activity and intracellular pharmacokinetic parameters of CdAMP or CdATP. The response to treatment was not significantly related to intracellular concentration of CdAMP or active metabolite CdATP. There is great heterogeneity among patients in terms of AUC and t(1/2) of CdAMP and CdATP. Furthermore, the results emphasize the differences between the pharmacokinetics of plasma CdA and those of the metabolites in circulating leukemic cells.

Stability and analysis of 2-chloro-2'-deoxyadenosine, 2-chloro-2'-arabino-fluoro-2'-deoxyadenosine and 2-chloroadenine in human blood plasma

Cladribine (2-chloro-2'-deoxyadenosine, CdA) is a purine nucleoside analog with activity against lymphoproliferative and autoimmune disorders. 2-Chloro-2'-arabino-fluoro-2'-deoxyadenosine (CAFdA), a derivative of CdA with better acid stability, shows a similar in vitro spectrum of activity as CdA. 2-Chloroadenine (CAde) is the major catabolite of both CdA and CAFdA. We have developed a high performance liquid chromatography method to measure CdA, CAFdA and their metabolite CAde in plasma. This method employees an internal standard, chloroadenosine (CAdo), and a C8 solid-phase extraction to isolate and concentrate the substances. Chromatographic separation was achieved using a C8 reverse-phase column, with UV detection at 265 nm, which gives a limit of detection of 1 nmol/l for all substances. The method was reproducible with intra- and inter-assay coefficients of variations below 6% at 50 nmol/l and at 5 nmol/l below 23%. The average recoveries of CdA, CAde, CAFdA and the internal standard were higher than 70%. Stability studies of authentic patient samples show that samples containing CdA should be kept in a refrigerator or on ice to prevent degradation. Plasma containing CAde should not be kept at -20 degrees C for longer than 10 weeks before analysis. CdA and CAFdA remain almost stable during storage at -20 degrees C for 12 weeks.

Intermittent infusion of cladribine (CdA) in previously treated patients with low-grade non-Hodgkin's lymphoma

Thirty-six patients with previously treated low-grade non-Hodgkin's lymphoma (LG-NHL) were included in a phase II study between August 1990 and February 1994 and treated with 0.12 mg/kg CdA as a 2 h.i.v. infusion daily x V, q 28 days up to 6 courses. Twenty-three were refractory to previous chemotherapy while 13 were relapsed. Four patients had mantle cell lymphoma, 17 follicle centre cell derived lymphoma, 7 lymphoplasmacytoid lymphomas and, 8 had small lymphocytic lymphoma. The response rate was 42%, with 5 (14%) CR and 10 (28%) PR while 6 (16%) patients progressed during treatment. The median number of delivered CdA courses was 3 (1-6) in non-responding cases and 6 (2-6) in responders. The median time to progression was 9 mo for all patients, 23 mo for CR and 16 mo for PR patients. Toxicity was sometimes severe with 3 infectious deaths (1 pneumocystis carinii pneumonia, 1 gram negative septicemia, and 1 fungal pneumonia), and 6 grade 3 or 4 infectious episodes. We conclude that responses to CdA in this group of heavily pre-treated patients is impressive. However, toxicity is considerable and the rate of opportunistic infections is worrisome.

The clinical pharmacokinetics of cladribine

Cladribine is a new purine nucleoside analogue with promising activity in low-grade lymphoproliferative disorders, childhood acute myelogenous leukaemia and multiple sclerosis. Reversed phase high performance liquid chromatography and radioimmunoassay have been used for the analysis of the plasma pharmacokinetics of cladribine. The major (inactive) metabolite in plasma, chloroadenine, can only be detected by liquid chromatography. The oral bioavailability of cladribine is 37 to 51%, and that of subcutaneous administration is 100%. The terminal half-life varies from 5.7 to 19.7 hours and the apparent volume of distribution from 54 to 357 L/m2. The concentration in the cerebrospinal fluid is 25% of that in plasma in patients without central nervous system disease; in patients with meningeal disease, the cladribine concentration in the cerebrospinal fluid exceeds that in plasma. Cladribine is a prodrug and needs intracellular phosphorylation to active nucelotides. The intracellular concentration of these metabolites is several hundred-fold higher than that of cladribine in plasma and they are retained in leukaemia cells with half-lives between 9 and > 30 hours depending on diagnosis and sampling schedule. There is no correlation between the plasma concentration of cladribine and that of the intracellular metabolites. The renal clearance of cladribine is 51% of total clearance and 21 to 35% of an intravenously administered dose is excreted unchanged in the urine. Pretreatment with cladribine increases the intracellular accumulation of the active metabolite of cytarabine, cytosine arabinoside 5'-triphosphate, by 36 to 40%.

Dose escalation of high-dose cyclophosphamide and etoposide with high-dose doxorubicin (CDE) and filgrastim for poor-risk non-Hodgkin's lymphoma

PURPOSE

To identify the highest possible dose of cyclophosphamide (C) and etoposide (E) to be given with high-dose doxorubicin (D) and filgrastim (G-CSF) but without stem cell support in high-risk non-Hodgkin's lymphoma.

PATIENTS AND METHODS

High-dose CDE was given to 18 evaluable patients, 5 had previous chemotherapy. All patients received D 90 mg/sqm and G-CSF 20 micrograms/kg/day. The first cohort had C 1800 mg/sqm and E 450 mg/sqm. Chemotherapy was given in equally divided doses over three days. Dose escalation was performed thrice up to C 3900 mg/sqm and E 975 mg/sqm. One to four courses were given.

RESULTS

The median number of days (quartile values) with neutrophils < 0.5 x 10(9)/l was 9 days (7-10), untransfused platelets < 20 x 10(9)/l 6 days (3-7), fever > or = 38 degrees C 5 days (3-8), intravenous antibiotics 10 days (9-12), with packed red cell transfusion 1 day (0-2), and with platelet transfusion 2 days (1-3). Six patients had complete remission and 11 partial remission from first course. There was no difference in toxicity according to dose level. A second course was given to 15 patients, resulting in fewer days with neutropenia (mean 7.2), and intravenous antibiotics (mean 6.3). Mucositis was the main non-hematologic toxicity.

CONCLUSIONS

Very high-dose CDE with G-CSF but without stem cell support is feasible as primary therapy. The toxicity was similar to that of standard autologous stem cell transplantation programs.

A limited sampling strategy for estimation of the cladribine plasma area under the concentration versus time curve after intermittent i.v. infusion, s.c. injection, and oral administration

Cladribine is a newly developed antimetabolite with promising activity in lymphoproliferative disorders. Recent pharmacokinetics investigations have suggested that there is a relationship between its plasma area under the concentration versus time curve (AUC) and the degree of neutropenia posttreatment as well as the therapeutic outcome in hairy-cell leukemia. To enable a simple estimation of the plasma AUC, a limited sampling strategy was developed. Stepwise linear regression was used to determine which were the most important data points for estimation of the plasma AUC after 2-h i.v. infusion, s.c. injection (5 mg/m2), and oral administration (10 mg/m2) in 27 patients. The most important data points after i.v. infusion in 12 patients were 1, 4, and 24 h, in order of importance. The AUC could be estimated as 2.9081 x C1h + 5.1851 x C4h + 20.3265 x C24h. The accuracy and precision (mean value +/- SD for the determined/estimated AUC was 0.99 +/- 0.053) of the model could not be increased by the addition of more data points. A somewhat lower accuracy and precision (0.96 +/- 0.089) was seen with the 2-, 4-, and 24-h data points. These were used to test the regression technique prospectively for the estimation of the AUC after i.v. administration in another set of 10 patients. The accuracy and precision of the estimation of the AUC was similar in this group (1.01 +/- 0.109). In all, 11 patients were treated orally (10 mg/m2) and 10 patients were treated by s.c. injection (5 mg/m2). The most important data points for estimation of the AUC were 2.5, 24, and 0.5 h after oral administration (AUC = 0.8630 x C0.5h + 4.2337 x C2.5h + 45.4364 x C24h) and 9, 1, and 16 h after s.c. injection (AUC = 1.8821 x C1h + 16.4256 x C9h + 25.4518 x C16h). The accuracy and precision were 1.01 +/- 0.064 after oral dosing and 0.99 +/- 0.11 after s.c. injection. The derived mathematical models are reliable for estimation of the plasma AUC of cladribine after 2-h i.v. infusion, oral administration, and s.c. injection.

Ultrafiltration and subsequent high performance liquid chromatography for in vivo determinations of the protein binding of etoposide

Etoposide is extensively (approximately 94%) bound to plasma proteins and the free non-protein-bound levels have been shown to correlate more closely to toxicity than total drug concentrations. A rapid and easily performed method, compared to the time consuming equilibrium dialysis, to obtain the free fraction is needed. The aim of this study was to evaluate ultrafiltration and subsequent high performance liquid chromatography (HPLC) for the determination of protein binding of etoposide. Spiked plasma from healthy, drug-free volunteers was used to compare ultrafiltration, using Amicon Centrifree filters, with equilibrium dialysis at 37 degrees C. The variability (CV) of the ultrafiltration method was 6.1 and 13.5% (n = 6) at 37 degrees C and room temperature (RT), respectively. The relative size of the free fraction obtained by ultrafiltration at 37 degrees C and RT was 1.22 (P = 0.0005) and 0.37 (P = 0.0001), respectively, compared with equilibrium dialysis at 37 degrees C. The chromatographic separation of metabolites from the mother compound when free etoposide is analyzed is crucial. It is shown that a hydroxy-acid metabolite of etoposide is quite dominant in a protein-free plasma fraction. The free concentrations were determined throughout a dose interval of 24 h in a patient receiving etoposide 100 mg/m2 daily. Ultrafiltration and subsequent HPLC is considered convenient and suitable for in vivo pharmacokinetic investigations.

Higher in vivo protein binding of etoposide in children compared with adult cancer patients

Etoposide is bound to plasma albumin (94%). Previous studies have revealed altered protein binding of etoposide in cancer patients. This has clinical implications since only the free fraction is considered pharmacologically active. We have studied the etoposide protein binding in 11 children (eight acute lymphocytic leukemia, two malignant histiocytosis, and one oligodendroglioma; age 1-17 years) and 46 adult patients (28 acute myelocytic leukemia, eight lymphoma, one multiple myeloma, and nine small cell lung cancer; age 38-81 years). All patients were treated with etoposide 50-200 mg/m2 i.v. or orally. Plasma from ten healthy volunteers, 26-50 years of age, was spiked with etoposide, 10 micrograms/ml, and the protein binding was compared with that in patient samples. The free etoposide concentration was determined by high performance liquid chromatography (HPLC) after ultrafiltration at room temperature. The free etoposide fraction was lower, 2.5 +/- 0.6% (mean +/- SD), in the children compared with 5.0 +/- 3.6% in adult cancer patients. In plasma from healthy adults it was 3.2 +/- 0.3%. It is concluded that children have significantly lower levels of free etoposide compared with adult patients (P = 0.03) as well as with healthy subjects (P = 0.001), which is likely to affect metabolism and renal clearance as well as cellular uptake of the drug.

Oral cladribine as primary therapy for patients with B-cell chronic lymphocytic leukemia

PURPOSE

Purine analogs have wide potential indications in the treatment of hematologic malignancies, but intravenous administration has been required. We previously established that the oral bioavailability of cladribine is 50%. Our aim was to evaluate the efficacy and toxicity of oral cladribine to previously untreated patients with chronic lymphocytic leukemia (CLL).

PATIENTS AND METHODS

Sixty-three patients with symptomatic but previously untreated CLL received cladribine solution 10 mg/m2/d orally for 5 consecutive days in monthly courses.

RESULTS

Complete remission (CR) was achieved in 24 patients (38%), and 23 patients (37%) had a partial response (PR). Most patients, including those in whom there was no remission (NR) achieved normal blood lymphocyte counts. Failure to meet response criteria was mostly due to thrombocytopenia. The median response duration was not reached at 2 years. The median survival time among 13 deceased patients was 322 days, whereas the median observation time of surviving patients is 760 days. The overall survival rate at 2 years is 82%. Response rate was associated with clinical stage. Grade III to IV infectious toxicity occurred in one third of patients.

CONCLUSION

Orally administered cladribine is an effective and feasible therapy for CLL, and produces durable remissions in three quarters of the patients. However, significant toxicity may occur and further studies are required to assess long-term effects and quality-of-life aspects.

Determination of 2-chloro-2'-deoxyadenosine nucleotides in leukemic cells by ion-pair high-performance liquid chromatography

A specific isocratic ion-pair HPLC method for the quantitation of mono-, di- and triphosphates of 2-chloro-2'-deoxyadenosine (CdA) in leukemic cells from patients is described. The method is based on an extraction of nucleotides from cells with a solution of perchloric acid containing triethylammonium phosphate followed by an isocratic separation on an Ultrasphere ODS column (250 x 4.6 mm, 5 microns) with a mixture of 89% triethylammonium phosphate buffer (0.08 M, pH 6.1) and 11% methanol as the eluent. UV absorbance at 265 nm was used. The limit of detection was 65 nM. Standard curves for the CdA triphosphate (CdATP) were linear within the concentration range of 200 nM to 12 microM. The mean overall recovery of CdATP was 90% within a concentration range of standard curves. The within-day and day-to-day coefficients of variation at concentrations of 1.44 microM and 6.25 microM CdATP were < 10%. The applicability of the method was demonstrated by in vitro studies of the accumulation of CdA mono-, di- and triphosphates in CCRF-CEM cells and by determination of the cellular pharmacokinetics of CdA nucleotides in leukemic cells from a patient treated with CdA.

Long-term survival following cladribine (2-chlorodeoxyadenosine) therapy in previously treated patients with chronic lymphocytic leukemia

PURPOSE

To assess long-term survival following cladribine salvage treatment for previously treated patients with chronic lymphocytic leukemia.

PATIENTS AND METHODS

Fifty-two patients aged 39-84 years with previously treated CLL received cladribine 0.12 mg/kg/day in 2-hour infusions for 5 days in monthly courses. Two-thirds were refractory to previous therapy, and 8 had prior fludarabine.

RESULTS

Sixteen (31%) patients achieved complete response (CR) and 14 (27%) partial remission (PR) according to consensus criteria. Response correlated with clinical stage, number of previous treatment regimes, blood lymphocyte count, and lymphocyte halflife following the first cladribine course. Toxicity included pneumonia (n = 9), herpes zoster (n = 7), and septicemia (n = 2). Four patients in CR underwent high-dose chemotherapy with autologous blood stem cell support, and 2 remain in CR 48 and 60 months from start of cladribine, and 2 had relapse at 42 and 48 months, respectively. Median progression-free survival (Kaplan-Meier analysis) for CR patients was 23 months from start of cladribine treatment, and for PR patients 16 months. The projected overall survival was 80% at 3 years for CR patients, and the median survival 28 months for PR patients and 4 months for non-responding patients.

CONCLUSIONS

Our previous finding of durable CRs from cladribine in advanced CLL is thus confirmed in a larger patient material, and follow-up indicate that long-term survival may be achieved.

Prognostic significance of proliferative and apoptotic fractions in low grade follicle center cell-derived non-Hodgkin's lymphomas

BACKGROUND

The biologic parameters, DNA ploidy and proliferative activity, have been suggested as prognostic factors in non-Hodgkin's lymphoma (NHL). However, reports on the prognostic importance of these factors in follicle center cell-derived (FCC) centroblastic/centrocytic (CB/CC) NHL patients with long follow-up are scarce.

METHODS

Apoptotic fractions were quantified in 60 patients with CB/CC NHL by in situ labeling of DNA strand breaks in nuclei [TdT-mediated dUTP/dATP in situ 3'OH--end labeling (TUNEL)]. The findings were related to S-phase and MIB-1 counts, DNA ploidy, and clinical outcome.

RESULTS

In CB/CC NHL, the percentages of proliferating and apoptotic cells were lower than in reactive germinal centers (GC; P < 0.05; mean, 0.188 vs 3.263% and 19.05 vs. 69.4% for TUNEL and MIB-1 positive cells in CB/CC and GC, respectively). Significantly higher percentages of MIB-1 and TUNEL positive cells were observed in patients with complete remission when compared with the partial remission / no response group (P < 0.01). The size of proliferative and apoptotic fractions did not correlate with the overall survival of the patients. However, follicular and diffuse growth pattern, elevated serum lactic dehydrogenase, advanced stage, and age indicated a lower probability of 5- and 10-year survival.

CONCLUSIONS

The investigation of proliferative and apoptotic fractions in FCC lymphomas may help to define groups of patients to who would benefit from aggressive, high dose therapy protocols and patients to whom less aggressive strategies can be applied safely.

Pharmacokinetics of mitoxantrone, etoposide and cytosine arabinoside in leukemic cells during treatment of acute myelogenous leukemia--relationship to treatment outcome and bone marrow toxicity

Twenty-seven patients with acute myelogenous leukemia (AML) were given remission induction treatment with mitoxantrone, etoposide and cytosine arabinoside (ara-C). The pharmacokinetics in leukemic blood cells of mitoxantrone, etoposide and the active metabolite of ara-C, ara-CTP, were determined during the first day of treatment. There was a large interpatient variability of the area under the time versus concentration curve (AUC) for all three drugs. On the individual level, there was no correlation between the AUCs of the different drugs. Neither did the AUC of any individual drug nor the calculated total intracellular drug exposure have any association with the outcome of treatment or hematological toxicity, measured as duration of leukopenia/thrombocytopenia. In conclusion, when combination chemotherapy with mitoxantrone, etoposide and ara-C is given to patients with AML, intracellular drug concentrations, achieved after the first dose of each drug, do not seem to be predictive for treatment response or hematological toxicity.

Disease-related hypocholesterolemia in patients with hairy cell leukemia. Positive correlation with spleen size but not with tumor cell burden or low density lipoprotein receptor activity

BACKGROUND

Hypocholesterolemia is common in patients with various malignant diseases, and may be a risk factor for the development or a consequence of the tumor, by different possible mechanisms.

METHODS

Serum lipids were analyzed in 66 patients with symptomatic hairy cell leukemia (HCL) before and repeatedly after treatment with cladribine. Low density lipoprotein (LDL) receptor activity of hairy cells from 12 patients was analyzed.

RESULTS

The median pretreatment serum cholesterol was 4.78 mmol/l. Total cholesterol, LDL cholesterol, and triglycerides were inversely correlated with the spleen size, but not with other markers of tumor burden. High density lipoprotein (HDL) cholesterol correlated to serum beta 2-microglobulin. Anemia and hypocholesterolemia developed synchronously before diagnosis in one patient. After cladribine therapy, there was a highly significant increase in all serum lipids. Low density lipoprotein receptor activity of HCL cells was elevated in only one of 12 patients; this patient had high serum cholesterol. Hypocholesterolemia predicted posttreatment neutropenic fever.

CONCLUSION

Hypocholesterolemia is a common disease-related finding in HCL, which is not caused by an increased LDL receptor activity of leukemia cells, but related to spleen size, predicts posttreatment fever, and is completely reverted after successful treatment of leukemia.

Evaluation of the cytotoxic activity of gemcitabine in primary cultures of tumor cells from patients with hematologic or solid tumors

Gemcitabine (2'-deoxy-2',2'-difluorocytidine; dFdC) is a novel nucleoside analog that has shown clinical activity against solid tumors. The semiautomated fluorometric microculture cytotoxicity assay (FMCA) was used for evaluation of the cytotoxicity of gemcitabine in vitro in primary cultures of human cells from patients with hematologic or solid tumors. The activity pattern of cytarabine (ara-C), 2-chlorodeoxyadenosine (CdA), etoposide (VP-16), doxorubicin, and cisplatin were included for comparison. One hundred forty samples were tested using continuous drug exposure. Gemcitabine showed high activity against hematologic samples, whereas little or no activity was observed in the solid tumor groups. A similar pattern of activity also was observed for ara-C and CdA, whereas etoposide, cisplatin, and doxorubicin were relatively more active in solid tumors. Cross-resistance analysis between gemcitabine and the standard drugs revealed the following rank order of correlation coefficients: ara-C > doxorubicin > CdA > cisplatin > VP-16. The results indicate that gemcitabine is differentially active against hematologic tumors and that the activity pattern of gemcitabine resembles that of ara-C. However, these results also indicate that gemcitabine may be more active against some solid tumor groups in comparison to ara-C and CdA.

High-performance liquid chromatography with fluorometric detection for monitoring of etoposide and its cis-isomer in plasma and leukaemic cells

The podophyllotoxin derivative etoposide, extensively used in anticancer therapy, is highly protein-bound (95%) in plasma. It is a chiral drug and only the trans-isomer is pharmacologically active. Isomerisation to the inactive cis-lactone occurs in plasma. The cis-lactone is often present in ultrafiltrates of plasma from patients treated with etoposide, therefore it is important to separate the isomers when free etoposide concentrations are assayed. There is reason to believe that free and cellular concentrations are more important for the effect of etoposide therapy than total plasma concentrations. A high-performance liquid chromatographic (HPLC) method for quantification of etoposide and its cis-isomer in plasma, total and non-protein-bound concentrations, and in leukaemic cells is described. After addition of teniposide as internal standard the drugs were extracted with chloroform. Etoposide, its cis-isomer, teniposide and endogenous substances were separated isocratically on a Spherisorb phenyl reversed-phase column. Detection was performed fluorometrically, lambda ex/em = 230/330 nm. Non-protein-bound concentrations were determined after ultrafiltration. The detection limit for etoposide was 10 ng/ml plasma, 25 ng/ml ultrafiltrate and 10 ng/50 x 10(6) cells. The sensitivity of the assay for the cis-lactone was twice as high due to higher fluorescence. The protein binding of the cis-lactone in plasma from ten healthy blood donors was 54.5 +/- 4.8% (mean +/- S.D.). Thus, the free fraction was about ten-fold higher than that of the mother compound. The assay is convenient and sensitive enough for the determination of free and cellular fractions of etoposide.

Studies of the organ distribution in mice of teniposide liposomes designed for treatment of diseases in the mononuclear phagocytic system

Liposomes can be used for the delivery of drugs in cancer chemotherapy. After i.v. injection liposomes are to a large extent taken up by the mononuclear phagocytic system (MPS). When treating diseases in the MPS, such as the histiocytic syndromes, this property is of potential value for drug targeting and may lead to a more efficient therapy with less systemic toxicity. Teniposide (VM-26) is a potent anti-tumor drug. Its lipophilicity makes it suitable for liposomal formulation. Teniposide liposomes were prepared by dissolving egg phosphatidylcholine and dioleoyl phosphatidic acid (19:1 molar ratio) in methylene chloride together with teniposide. After solvent evaporation, the dry lipid film was dispersed in a glucose solution (50 mg/mL), and size calibration was obtained by filtration through polycarbonate filters. The amount of teniposide incorporated was 2.5 mol%. To investigate the organ distribution, teniposide liposomes containing radiolabeled teniposide or phospholipid were given i.v. to mice. By increasing the size of the vesicles, the MPS uptake could be modulated. When vesicles of 200 nm and 1 and 3 microns were injected, the drug levels in the spleen were increased 2.6-, 6.8-, and 21-fold 40 min after injection, compared with levels after injection of the commercial teniposide formulation. It was concluded that organ distribution of teniposide in mice could be modified by administering the drug in liposomal form with the potential of improved treatment of diseases engaging the MPS.

Mitoxantrone, etoposide and ara-C vs doxorubicin-DNA, ara-C, thioguanine, vincristine and prednisolone in the treatment of patients with acute myelocytic leukaemia. A randomized comparison

Complex-binding of anthracyclines to DNA may increase their therapeutic efficacy. In a previous randomized trial patients with acute myelocytic leukaemia (AML) receiving combination chemotherapy including a DNA-bound doxorubicin preparation had a longer duration of first complete remission (CR) and survival than patients receiving free doxorubicin. In a parallel phase I/II study a combination of mitoxantrone, activity. In this randomized study of AML patients (15-60 years) induction treatment with MEA was compared to a combination of doxorubicin/DNA conjugate ara-C, thioguanine, vincristine and prednisolone (POCAL-DNA). The study was closed after an interim analysis of 86 patients. Thirty-five/42 (83%) and 20/44 (45%) patients entered CR in the MEA and POCAL-DNA groups, respectively (p < 0.001). With rescue therapy the corresponding figures were 88 and 64% (p < 0.02). Median survival was 27.8 and 13.1 months for MEA and POCAL-DNA patients, respectively (p < 0.03). In conclusion, the MEA regimen has a very high antileukaemic activity in good accordance with our previous experience. Since we could not reproduce our earlier clinical results using DNA-bound anthracyclines, the source and preparation of DNA seem to be of major importance.

Kinetics and metabolism of 2-chloro-2'-deoxyadenosine and 2-chloro-2'-arabino-fluoro-2'-deoxyadenosine in the isolated perfused rat liver

2-Chloro-2'-deoxyadenosine (CdA), a newly developed anticancer drug, has been tested in phase II trials in the treatment of lymphoproliferative disorders. 2-Chloro-2'-arabino-fluoro-2'-deoxyadenosine (CAFdA), an acid stable derivative of CdA with promising anti-lymphoproliferative activity, has been suggested as a potentially effective oral drug. In the present study, we investigated the metabolism of CdA and CAFdA in isolated perfused rat liver. The liver was recycled with a perfusate containing CdA or CAFdA (2-200 micrograms/ml) for 3.5 h. The elimination half-lives were concentration-dependent for both CdA and CAFdA. The elimination rate of CAFdA was slower than that of CdA, suggesting that CAFdA is more stable than CdA against deglycosylation by hepatic enzymes. The amount of 2-chloroadenine (CAde), the major metabolite of CdA and CAFdA, increased proportionally with time and dose. The first passage effect was approximately 50% both for CdA and CAFdA. Less than 1% of CdA and CAFdA were recovered as intact drug in the bile during the experiment and less than 1% of CdA and 0.1% of CAFdA were found as CAde in the bile, respectively. The structural identity of metabolites present in the perfusates was verified utilizing electrospray ionization mass spectrometry.

Targeting of teniposide to the mononuclear phagocytic system (MPS) by incorporation in liposomes and submicron lipid particles; an autoradiographic study in mice

Liposomes are concentrated in the mononuclear phagocytic system in vivo and may therefore be of value as carriers of drugs when treating diseases involving phagocytic cells. Teniposide (VM-26) is a potent and lipophilic cytotoxic drug. Teniposide was incorporated in large unilamellar liposomes (LUVs) consisting of egg phosphatidylcholine and dioleoyl phosphatidic acid and into the novel submicron lipid particles containing cholesteryl oleate, cholesteryl palmitate and soybean lecithin, in order to evaluate the drug targeting effect. Radiolabelled teniposide and lipids were used and the organ distribution in mice was studied with whole-body autoradiography 20 and 90 min post i.v. injection. When the commercial formulation of teniposide (Vumon) was administered, teniposide accumulated in the liver where the drug is metabolized. Biliary excretion was rapid and considerable already after 20 min. The liposomal formulation enhanced liver uptake of teniposide slightly. The distribution of radiolabelled phosphatidyl choline differed from that of teniposide indicating instability of the liposomes in circulation. Despite this, the splenic uptake of the drug was significantly enhanced by administration in liposomes. In the red pulp of the spleen the teniposide level was 23 times higher 90 min post injection, using the liposomal formulation as compared to free drug. The submicron lipid particles were mainly accumulated in the liver and to a lesser extent in the spleen. The study shows that liposomes and lipid particles enhance splenic and liver uptake and can be used to target teniposide to the MPS.

Neutropenic fever following cladribine therapy for symptomatic hairy-cell leukemia: predictive factors and effects of granulocyte-macrophage colony-stimulating factor

BACKGROUND

Neutropenic fever is the commonest complication of cladribine therapy for hairy-cell leukemia (HCL), leading to a 3% mortality rate. Our aim was to identify predictive factors and evaluate the effects of concomitant granulocyte-macrophage colony-stimulating factor (GM-CSF).

PATIENTS AND METHODS

We studied 102 patients with active HCL given cladribine for 7 days. Pretreatment parameters predicting neutropenic fever were analysed. Twelve patients at high risk for febrile complications also received 400 micrograms GM-CSF per day on days 1 through 21.

RESULTS

Pretreatment anemia, hypocholesterolemia, bone marrow differential with a high percentage of hairy cells and a low percentage of myelopoietic cells, low albumin, and high C-reactive protein predicted neutropenic fever. The addition of GM-CSF did not improve the kinetics of recovery for neutrophils, hemoglobin or platelets, as compared to matched control patients. However, GM-CSF significantly reduced cladribine-induced lymphopenia, but not the incidence of neutropenic fever.

CONCLUSION

Factors predicting febrile neutropenia were identified. GM-CSF protected from cladribine lymphotoxicity but did not improve neutropenia or febrile episodes.

Bioavailability and bacterial degradation of rectally administered 2-chloro-2'-deoxyadenosine

2-Chloro-2'-deoxyadenosine (CdA) is a new drug for the treatment of hairy cell leukemia and other lymphoproliferative diseases. It is generally administered as a continuous intravenous infusion during 5-7 days. The oral bioavailability is only 50%. The bioavailability after rectal administration was investigated in two patients with chronic lymphocytic leukemia. Five milligrams per square metre was given i.v. as a 2-h infusion and 24 h later the same dose was administered rectally in a gel formulation. The mean bioavailability was only 21% due to deglycosylation of CdA to 2-chloroadenine (CAde). To further elucidate the factors which are important for the rectal availability of CdA, the in vitro stability of CdA in bacterial cultures was tested. Clostridium perfringens and Escherichia coli as well as whole feces rapidly deglycosylated CdA to CAde while Bacteroides fragilis, Enterococcus faecalis as well as saliva only degraded CdA slowly or not at all. It is concluded that, due to bacterial degradation, rectal administration of CdA has no advantage over oral administration.

Low-dose cladribine for symptomatic hairy cell leukaemia

Cladribine is an effective therapy for hairy cell leukaemia (HCL), but the standard regime is frequently complicated by neutropenic fever and prolonged T-cell depression. We studied 102 patients with active HCL following treatment with various doses of cladribine given for 7 d. Two patients received 1 mg cladribine/m2/d without toxicity or effect. Eight subsequent patients received 2 mg cladribine/m2/d, and normalized cytopenia as quickly as 94 control patients receiving a standard dose (3.4 mg/m2 or 0.085 mg/kg), with significantly less lymphopenia and a similar complete remission rate.

Expression of deoxycytidine kinase and phosphorylation of 2-chlorodeoxyadenosine in human normal and tumour cells and tissues

Deoxycytidine kinase (dCK) activates several clinically important drugs, including the recently developed antileukaemic compound 2-chlorodeoxyadenosine (CdA). The distribution of dCK in cells and tissues has previously been determined by activity measurements, which may be unreliable because of the presence of other enzymes with overlapping substrate specificities. Therefore we have measured dCK polypeptide levels in extracts of normal and malignant human peripheral blood mononuclear cells, gastrointestinal tissues and sarcomas, using a specific immunoblotting technique, as well as the phosphorylation of CdA in the same extracts. High levels of dCK were found in all major subpopulations of normal mononuclear leucocytes (120 +/- 19 ng dCK/mg protein) and in B-cell chronic lymphocytic leukaemia (81 +/- 30 ng/mg, n = 23). Hairy-cell leukaemia contained lower levels (28 +/- 23 ng/mg, n = 7), as did three samples of T-cell chronic lymphocytic leukaemia (18 +/- 14 ng/mg). Phytohaemagglutinin stimulation of normal lymphocytes did not lead to any substantial increase in either dCK activity or protein expression (less than 2.5-fold). The human CEM wt T-lymphoblastoid cell line contained 56 +/- 1 ng/dCK/mg protein, while in the CEM ddC50 and AraC8D mutants that lack dCK activity, no dCK polypeptide could be detected. In colon adenocarcinomas, the dCK content was significantly higher (20 +/- 9 ng/mg, n = 20) than in normal colon mucosa (8 +/- 3.5 ng/mg, n = 19, P < 0.05). A similar pattern of dCK expression was found in gastric adenocarcinomas (21 +/- 13 ng/mg, n = 5) and normal stomach mucosa (6 +/- 5 ng/mg, n = 5, P < 0.15). One leiomyosarcoma and one extra-skeletal osteosarcoma showed dCK levels comparable with those found in normal lymphocytes (84 +/- 6 and 109 +/- 4 ng/mg, respectively), while other sarcoma samples contained lower levels, comparable to the gastrointestinal adenocarcinomas (20 +/- 7 ng/mg, n = 12). Thus, dCK is expressed constitutively and predominantly in lymphoid cells, but it is also found in solid non-lymphoid tissues, with increased levels in malignant cells. The phosphorylation of CdA in crude extracts showed a close correlation to the dCK polypeptide level.

Interspecies differences in the kinetic properties of deoxycytidine kinase elucidate the poor utility of a phase I pharmacologically directed dose-escalation concept for 2-chloro-2'-deoxyadenosine

2-Chloro-2'-deoxyadenosine (CdA, Cladribine), is a purine antimetabolite currently under investigation in phase II clinical trials for the treatment of lymphoid malignancies. Significant differences in CdA toxicity between mice and humans were observed during phase I clinical evaluation. For the elucidation of interspecies differences in drug toxicity the pharmacokinetics of CdA after subcutaneous injection and the kinetic properties of the CdA-phosphorylating enzyme, deoxycytidine kinase (dCK), were compared in mice and humans. The ratio of the dose lethal to 10% of mice (LD10) to the maximum tolerated dose (MTD) in humans was 50 and the ratio of the area under the curve obtained at approximately one-half the LD10 (AUCapprox. one-half the LD10)/AUC(MTD) was 49. A significant interspecies difference was observed in the kinetic properties of dCK, the main CdA-activating enzyme. With CdA as a substrate, the Michaelis constant (Km) of dCK in crude extracts of mouse thymus was 10 times higher than that in human thymus. An approximately 9-fold interspecies difference in maximum velocity (Vmax)/Km indicated a higher efficiency of dCK for CdA in humans than in mice. The peak plasma concentration was 210 times higher and exceeded the Km in mice. Initial and terminal half-lives were approximately 7 times shorter in mice and trough levels were similar in mice and humans. Thus, the differences in AUCs at equitoxic doses are largely explained by differences in the target enzyme properties and the pharmacokinetic pattern. The observed lower tolerance for CdA in humans as compared with mice confirms the view that antimetabolites may not be good candidates for pharmacokinetically guided dose-escalation schemes unless detailed information on interspecies variability in drug bioactivation is available.

Interactions between cladribine (2-chlorodeoxyadenosine) and standard antileukemic drugs in primary cultures of human tumor cells from patients with acute myelocytic leukemia

The semiautomated fluorometric microculture cytotoxicity assay (FMCA), based on the measurement of fluorescence generated from cellular hydrolysis of fluorescein diacetate (FDA) to fluorescein in microtiter plates, was used for in vitro evaluation of Cladribine (2-chlorodeoxyadenosine, CdA) interactions with five standard antileukemic drugs: amsacrine (Am), etoposide (VP16), daunorubicin (Dnr), cytosine arabinoside (AraC), and mitoxantrone (Mit). Samples from 31 patients with acute myelocytic leukemia (AML) were tested with continuous drug exposure. A large heterogeneity with respect to cell kill was observed for all combinations tested. An additive model provided a significantly better fit of the data compared to the effect of the most active single agent of the combination (Dmax) only for CdA+AraC. When the frequency of additive and synergistic interactions were calculated according to the multiplicative concept for drug interactions, the highest frequencies were observed for CdA+AraC and CdA+Dnr. This interaction pattern was confirmed by isobologram analysis. Cross-resistance analysis revealed high correlations between CdA and AraC whereas the correlations were weaker between CdA and the other drugs. The highest frequency of synergistic interactions was obtained for AraC+CdA, despite their cross-resistance. Of the non-cross-resistant drugs tested, Dnr appears to be the most effective adjunct to CdA in terms of interactions at the cellular level.

Analysis of 2-chloro-2'-deoxyadenosine in human blood plasma and urine by high-performance liquid chromatography using solid-phase extraction

A reversed-phase high-performance liquid chromatographic (HPLC) method for the simultaneous determination of a new and promising anticancer drug, 2-chloro-2'-deoxyadenosine (CdA), and its metabolite, 2-chloroadenine (CAde), in plasma and urine was developed. A solid-phase extraction procedure with guaneran as internal standard (IS) was used. Plasma (1 ml) or diluted urine (1/100) mixed with 1 ml of phosphate buffer (10 mM, pH 6.5) was applied on a C8 isolute cartridge, which was prewashed with acetonitrile and phosphate buffer. The cartridge was further washed with 2.5 ml of 1% acetonitrile/phosphate buffer and 2.5 ml of hexane/dichloromethane (50/50). The compounds were eluted from the cartridge with 2.5 ml 5% MeOH in ethyl acetate. Chromatographic separation was achieved on C18 column eluted isocratically with phosphate buffer (10 mM, pH 3.0) containing 11% MeOH and 7% acetonitrile, and ultraviolet (UV) detection at 265 nm. Recoveries of CdA and CAde at 100 nmol/L were 90.6 +/- 4.9 and 98.7 +/- 7.8%, respectively. Recovery of IS was 96.1 +/- 6.1% at 250 nmol/l. The inter- and intraday coefficients of variation (CV) were < 10% at different concentrations within the range 1-500 nmol/L for both substances. In plasma, limits of detection of CdA and CAde were 1 and 2 nmol/L, respectively. In urine, the limit of detection was 100 nmol/L for both compounds. Standard curves were linear up to 50 and 500 nmol/L for urine and plasma, respectively. The present method will be a useful tool for further investigations of the pharmacokinetics of CdA in patients treated with different routes of administration.

Phosphorylation of 2-chlorodeoxyadenosine (CdA) in extracts of peripheral blood mononuclear cells of leukaemic patients

2-Chlorodeoxyadenosine (CdA) is an antileukaemic agent used in treatment of hairy cell leukaemia (HCL) and chronic lymphocytic leukaemia of B- and T-cell type (B-CLL and T-CLL). The aim of this study was to elucidate the interpatient variability of CdA phosphorylation and its relation to response to CdA treatment. In extracts of peripheral blood mononuclear cells of patients with B-CLL (n = 39), CdA phosphorylation was significantly higher than in HCL (n = 19) when calculated per protein (391 +/- 155 pmol CdA phosphorylated/mg protein/min versus 288 +/- 166 pmol/mg/min, P < 0.001), but was the same when calculated per cell (12 +/- 5.9 pmol/10(6) cells/min versus 14 +/- 5.9 pmol/10(6) cells/min) due to a larger cell volume in HCL. In T-CLL (n = 6), CdA phosphorylation was significantly lower than in B-CLL, both when calculated per protein (128 +/- 68 pmol/mg/min, P < 0.001) or per cell (5.7 +/- 2.7 pmol/10(6) cells/min, P < 0.05). This low CdA phosphorylation in T-CLL was unexpected because normal B- and T-lymphocytes contain equal amounts of CdA phosphorylation. With B-CLL, 21 patients who responded (complete and partial response) to CdA treatment showed a significantly higher CdA phosphorylation than 13 patients not responding to CdA treatment (456 +/- 170 pmol/mg/min versus 309 +/- 97 pmol/mg/min, P < 0.01). We conclude that the level of CdA phosphorylation is correlated with the response of leukaemias to CdA treatment.