Biomedical subjects

C Arndt

Publications and source records attributed to C Arndt.

At least 37 records · Page 2Linked to original sources

PubMed1998

Phase I trial and pharmacokinetic study of pyrazoloacridine in children and young adults with refractory cancers.

PURPOSE: To define the maximum-tolerated dose (MTD), quantitative and qualitative toxicities, recommended phase II dose, and pharmacokinetics of pyrazoloacridine (PZA) administered as a 1- or 24-hour infusion in children and young adults with refractory cancers. PATIENTS AND METHODS: Twenty-two patients received PZA as a 1-hour infusion at doses of 380 mg/m2 (n = 3), 495 mg/m2 (n = 6), 640 mg/m2 (n = 6), and 835 mg/m2 (n = 7). An additional four patients received PZA as a 24-hour infusion at the MTD (640 mg/m2) for the 1-hour infusion schedule. Plasma samples were obtained for pharmacokinetic analysis in 17 patients. PZA concentration in plasma was measured by reverse-phase high-performance liquid chromatography (HPLC). A two-compartment pharmacokinetic model was fit to the PZA plasma concentration data. RESULTS: On the 1-hour infusion schedule, dose-limiting myelosuppression (neutropenia more than thrombocytopenia) was observed in two of seven patients at the 835-mg/m2 dose level. Myelosuppression did not appear to be ameliorated by prolonging the infusion to 24 hours. Nonhematologic toxicities were minor. Significant neurotoxicity, which was dose-limiting in adults treated with a 1-hour infusion of PZA, was observed in one patient treated at 640 mg/m2, but was not dose-limiting. There was marked interpatient variability in plasma PZA concentrations at all dose levels. The pharmacokinetic profile of PZA was characterized by an initial rapid decline (alpha half-life [t(1/2)alpha], 0.5 hours) followed by a prolonged elimination phase (t(1/2)beta, 30 hours). The volume of distribution at steady-state (Vd(ss)) was 700 L/m2 and the clearance was 300 mL/min/m2. There was no evidence of dose-dependent clearance. The area under the PZA concentration-time curve (AUC) correlated poorly with dose and was more predictive of the degree of myelosuppression than was PZA dose. CONCLUSION: PZA administered as 1- or 24-hour infusion is well tolerated by children and young adults. The dose-limiting toxicity (DLT) is myelosuppression. Neurotoxicity is not prominent in this age group. There was marked interpatient variation in plasma concentrations of PZA. The recommended dose for phase II studies is 640 mg/m2.

Acridines↗

PubMed1998

Additional chemotherapy agents improve treatment outcome for children and adults with advanced B-cell lymphomas.

We report the updated results of an intensive treatment protocol for children (< 18 years) and adults (> or = 18 years) with advanced B-cell lymphomas. The protocol consists of two chemotherapy regimens: A, consisting of cyclophosphamide, doxorubicin, vincristine and high-dose methotrexate (CODOX-M), and B, consisting of ifosfamide, etoposide, and high-dose cytarabine (IVAC). Both cycles included intrathecal chemotherapy (cytarabine or methotrexate). Patients received a total of four cycles in the following sequence: A, B, A, B. Sixty-six previously untreated patients, enrolled before October 1996, were included in the present analysis. Of these, 55 had Burkitt's or Burkitt's-like lymphoma and 11 had diffuse large B-cell lymphoma. There were 53 males ad 13 females; 40 were children and 26 were adults (age range, 3 to 57 years). To date, 61 patients have achieved a complete response to therapy. Two patients subsequently relapsed, but one of these is a long-term survivor after further therapy and a bone marrow transplant. The event-free survival rate is 85% at I year and beyond. The median potential follow-up period is 48 months (range, 12 to 96 months) for patients remaining in complete remission. Neutropenia occurred in 98% of cycles and infection in 46% of A cycles and 50% of B cycles, but the duration was shortened in B cycles by the administration of granulocyte colony-stimulating factor. Positive blood cultures were observed in 21% of A cycles and 28% of B cycles, and there have been three toxic deaths. These results are better than those achieved with an earlier version of CODOX-M, suggesting that the addition of the IVAC regimen is responsible for the improved results. The similarity of the outcome in children and adults, however, confirms our previous observation that, at least in adults younger than 60 years with Burkitt's or Burkitt's-like lymphomas, treatment with regimens similar to those used in children is warranted.

Adolescent↗

PubMed1996

Adults and children with small non-cleaved-cell lymphoma have a similar excellent outcome when treated with the same chemotherapy regimen.

PURPOSE: We have used identical treatment protocols for adults and children with small non-cleaved-cell lymphoma (SNCL) for many years and report here the results of two successive treatment regimens in these age groups. PATIENTS AND METHODS: Seventy-two patients (39 adults and 33 children) were treated with protocol 77-04 between 1977 and 1985. All patients, except those with resected abdominal disease, received 15 cycles of a combination of cyclophosphamide (CTX), doxorubicin (ADR), prednisone (PRED), vincristine (VCR), high-dose methotrexate (MTX), and intrathecal (IT) therapy. Forty-one patients (20 adults and 21 children) were treated with protocol 89-C-41, which has been used since 1989. High-risk patients received four alternating cycles (with a total duration of 12 to 15 weeks) of an intensified version of protocol 77-04 without PRED (CODOX-M), and a new drug combination consisting of ifosfamide, etoposide, high-dose cytarabine (ara-C), and IT MTX (IVAC). Low-risk patients received three cycles of the CODOX-M regimen. High-risk patients were randomized to either receive or not receive granulocyte-macrophage colony-stimulating factor (GM-CSF). RESULTS: Event-free survival (EFS) in protocol 77-04 was 56% at 2 years and beyond. EFS in protocol 89-C-41 was 92% at 2 years and beyond. GM-CSF was associated with increased thrombocytopenia. CONCLUSION: Adults and children with SNCL have a similar prognosis when treated with the same chemotherapy. EFS in high-risk patients has been markedly improved by including IVAC in protocol 89-C-41, and excellent results can be achieved with only four cycles of therapy. In protocol 89-C-41, GM-CSF was not beneficial.

Adolescent↗

PubMed1996

Severe atypical neuropathy associated with administration of hematopoietic colony-stimulating factors and vincristine.

PURPOSE: We have observed a severe atypical neuropathy (SAN) in patients with small non-cleaved-cell (SNCL) and large-cell lymphoma (LCL) treated with intensive chemotherapy and hematopoietic colony-stimulating factors (CSFs). The present analysis was undertaken in an attempt to identify factors associated with the development of this syndrome. PATIENTS AND METHODS: Fifty-four adult and pediatric patients consecutively treated according to the same chemotherapy protocol were included in the analysis. Low-risk patients received three cycles of cyclophosphamide, vincristine, doxorubicin, and high-dose methotrexate (CODOX-M) while in high-risk patients this drug combination was alternated with high-dose cytarabine (ara-C), etoposide, and ifosfamide (IVAC) for a total of four cycles. Twenty-eight patients received a CSF (granulocyte [G]- or granulocyte-macrophage [GM]-CSF), and 26 patients received no CSF. A statistical analysis, which included a logistic regression model, was undertaken to examine the importance of potential contributing factors to the development of SAN. RESULTS: SAN, which consisted of excruciating foot pain, usually associated with marked motor weakness, was observed in 12 patients. There was a highly significant association between the occurrence of this syndrome and the administration of CSFs, and an independent association with the cumulative dose of vincristine given in the first cycle of chemotherapy. Furthermore, the analysis suggested a synergistic effect between administration of the CSFs and vincristine in the genesis of this neuropathy. CONCLUSION: Our results indicate that CSFs can precipitate SAN when given in conjunction with vincristine. The development of SAN was associated most strongly with the cumulative dose of vincristine -- the size of individual doses and the number of doses given in cycle 1 were important to the extent that they influenced the cumulative dose.

Adolescent↗

PubMed1994

Renal function in children and adolescents following 72 g/m2 of ifosfamide.

A detailed analysis of the renal function of 18 children and adolescents aged 7-20 years (median, 16 years) was performed at least 3 months following the completion of a non-platinum-containing chemotherapy regimen with a total dose of 72 g/m2 of ifosfamide. Ifosfamide had been given as a 1-h infusion of 1.8 g/m2 daily for 5 days at 5- to 6-week intervals along with mesna uroprotection. The mean glomerular filtration rate (GFR) as determined by inulin clearance was 100 ml/min/1.73 m2. Although 6 of 18 patients had GFRs below normal, the lowest was only 18% less than the lower limit of normal and would not account for any clinical compromise. The renal plasma flow and filtration fraction were normal. Proximal tubular function evaluation revealed normal fractional excretion (FE) of glucose; normal mean tubular maximum phosphate reabsorption per GFR (TMP)/GFR values; high FE of urate (17%); and mild, generalized aminoaciduria in 6 of the 18 patients. Distal tubular function evaluation showed normal 24-h urinary calcium levels and FE of magnesium as well as normal urinary osmolality after water deprivation. Two patients had mild proteinuria. The findings in this study are encouraging in terms of the lack of clinically significant renal abnormalities observed in patients who had received a cumulative dose of 72 g/m2 of ifosfamide.

Adolescent↗

PubMed1992

Pediatric phase I trial, pharmacokinetic study, and limited sampling strategy for piritrexim administered on a low-dose, intermittent schedule.

Piritrexim, an orally administered, lipid-soluble antifolate, was evaluated in a multi-institutional phase I trial in children. The starting dose was 10 mg/m2/dose administered every 8 h daily for 5 days for 3 consecutive weeks, with dose escalations in increments of 5 mg/m2/dose. Eighteen patients (16 with metastatic sarcoma, 1 with acute lymphoblastic leukemia, and 1 with a brainstem glioma), 3.5-20 years of age, with malignancy refractory to therapy, were entered into the study. The dose-limiting toxicities (DLTs), which were myelosuppression and mucositis, occurred in 4 of 4 patients treated at the 25-mg/m2/dose level but in none of the patients treated at the 15- and 20-mg/m2/dose levels. The recommended dose for phase II trials is 20 mg/m2/dose. Pharmacokinetic monitoring was performed in 15 of the 18 children. The area under the concentration-time curve (AUC) was linearly related to the dose administered. Piritrexim was rapidly absorbed, with the median time to peak level occurring 1.5 h after an oral dose. The terminal half-life of piritrexim ranged from 1.5 to 4.5 h. A limited sampling strategy developed earlier, capable of predicting the AUC based on the plasma concentrations at 3 and 6 h after an oral dose, was prospectively tested in this trial and proved to be highly predictive of the AUC (r = 0.98, P = 0.0001). Pharmacodynamic-pharmacokinetic correlations were obtained after combining data from this and the prior phase I pediatric trial. Trough plasma piritrexim concentration strongly correlated with DLT (P = 0.0016). A trough plasma piritrexim concentration greater than 0.5 microM appeared to be predictive of toxicity. Eleven of 15 patients with trough concentrations exceeding this threshold experienced DLTs. Therapeutic drug monitoring may thus play an important role in adjusting the dose and schedule of piritrexim in future trials.

Adolescent↗

PubMed1990

Chemoattractants stimulate phosphatidylinositol-4-phosphate kinase in human polymorphonuclear leukocytes.

Chemoattractant receptor-mediated hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP2) by phospholipase C is instrumental for leukocyte activation. Previous studies have demonstrated that chemoattractant treatment of intact polymorphonuclear leukocytes (PMN) causes a transient decrease in PIP2 due to phospholipase C activation, followed by an increase in cellular PIP2 levels. The present study determined whether chemoattractants altered the activities of the two enzymes responsible for the synthesis of PIP2, phosphatidylinositol kinase, and phosphatidylinositol-4-phosphate (PIP) kinase. Incubation of intact PMN with the N-formylated peptide chemoattractant formyl-methionyl-leucyl-phenylalanine at 37 degrees C caused a rapid (3 min), 2-fold stimulation of PIP kinase activity isolated from a particulate membrane fraction. The increase in PIP kinase was dose-dependent for a variety of N-formylated chemoattractants as well as leukotriene B4. Lineweaver-Burk analysis showed that the Vmax of PIP kinase was increased 2-fold by formyl-methionyl-leucyl-phenylalanine, without a significant change in the apparent Km of the enzyme for ATP. Phosphatidylinositol kinase was, however, not altered by any chemoattractants tested. Nonchemotactic activators of the oxidative burst in leukocytes such as phorbol myristate acetate and ionophore A23187 did not significantly alter PIP kinase, suggesting a specificity for chemotactic agents. These findings demonstrate direct, chemoattractant-induced stimulation of PMN PIP kinase which may serve to replenish the important phospholipid, PIP2, in the membrane following its hydrolysis by phospholipase C.

1-Phosphatidylinositol 4-Kinase↗

PubMed1988

Characterization of phosphatidylinositol and phosphatidylinositol-4-phosphate kinases in human neutrophils.

Phosphodiesteric cleavage of phosphatidylinositol-4,5-bisphosphate (PtdIns-4,5-P2) is required for transmembrane signaling by chemoattractants in human polymorphonuclear leukocytes (PMN). Considering the importance of PtdIns-4,5-P2 as a reservoir for second messenger substances, we have characterized the enzyme system that synthesizes this phospholipid in human PMN, consisting of kinases for phosphatidylinositol (PtdIns) and phosphatidylinositol-4-phosphate (PtdIns-4-P). The preferred phosphate donor for both enzymes was ATP as compared with GTP. The respective Km for ATP for PtdIns kinase and PtdIns-P kinase were 0.049 +/- 0.013 and 0.062 +/- 0.005 mM and for GTP were 0.242 +/- 0.016 and 0.186 +/- 0.037 mM. PtdIns stimulated the activity of PtdIns kinase to a greater extent than PtdIns-4-P kinase. PtdIns-4-P inhibited the activity of detergent-solubilized PtdIns kinase and stimulated particulate PtdIns-4-P kinase, whereas both enzymes exhibited substrate inhibition to PtdIns-4,5-P2. Mg2+ was the preferred cation for both enzymes, but the apparent Km values (4.1 +/- 0.9 mM for PtdIns kinase and 1.0 +/- 0.7 mM for PtdIns-4-P kinase) were significantly different (p less than 0.005). Mn2+ partially substituted for Mg2+, and both enzymes were inhibited by Ca2+. The polyamine spermine stimulated PtdIns-4-P kinase activity to a greater extent and at lower concentrations than PtdIns kinase. PtdIns kinase was easily solubilized in both Triton X-100 and Nonidet P-40, whereas PtdIns-4-P kinase remained in a detergent-nonextractable membrane fraction. These findings demonstrate that the enzyme system in human PMN that forms PtdIns-4,5-P2 is composed of two distinct enzymes with similar characteristics.

1-Phosphatidylinositol 4-Kinase↗

PubMed1986