Isabella Iacona

Rituximab (IDEC-C2B8): validation of a sensitive enzyme-linked immunoassay applied to a clinical pharmacokinetic study.

Rituximab is a chimeric monoclonal antibody (MAb) directed against the B-cell CD20 antigen that has been approved for therapy of relapsed and resistant follicular non-Hodgkins lymphoma (NHL). This study describes the development and validation of a highly sensitive, rapid, accurate, precise enzyme-linked immunosorbent assay (ELISA) to measure Rituximab serum concentrations. This study also describes the application of the ELISA method to a pharmacokinetic study in a homogeneous group of patients with follicular lymphoma who received 4 weekly doses of MAb at the standard dose of 375 mg/m2 as consolidation of chemotherapy. In the patients in this study, the median Rituximab serum concentrations increased during therapy, and showed a slow decline during the posttreatment period. The Rituximab elimination half-life of approximately 20 days accounts for the demonstrated accumulation of MAb in serum samples. Because previous pharmacokinetic studies showed a correlation between Rituximab serum levels and tumor response, the ELISA method used in this study, which allows a precise control of serum concentrations, could be useful for predicting the final response to the MAb and for selecting patients able to benefit from higher dosage or repeated drug administration.

A sequence of immuno‐chemotherapy with Rituximab, mobilization of in vivo purged stem cells, high‐dose chemotherapy and autotransplant is an effective and non‐toxic treatment for advanced follicular and mantle cell lymphoma

Summary. Options for relapsed/refractory indolent lymphoma include chemotherapy, immunotherapy and high‐dose therapy with autologous support. The best combination of these approaches, however, is not defined. We treated 10 patients with relapsed/refractory follicular (n = 7) or mantle cell lymphoma (n = 3) using chemotherapy, immunotherapy, high‐dose therapy and autotransplant in a sequence of four phases, each designed to play a specific role in tumour eradication. After the debulking with VACOP‐B (doxorubicin, cyclophosphamide, etoposide, vincristine, prednisone, bleomycin) (phase 1), 9/10 patients responded but none achieved a molecular response. After the immuno‐chemotherapy phase, which combined Rituximab with vincristine and cyclophosphamide, seven patients were in complete response (CR) and three in good partial response (PR), and all those with a molecular marker of disease showed a disappearance of the signal from marrow and blood. Phase 3, which coupled high‐dose cytarabine with Rituximab, was effective in mobilizing an adequate number of progenitor cells that were polymerase chain reaction negative in all informative cases. Phase 4 consisted of high‐dose therapy with autologous support followed by two doses of Rituximab. Autograft was performed in nine patients. The haematopoietic recovery was as expected. This sequence of chemotherapy, immuno‐chemotherapy, stem cell mobilization with in vivo purging and autotransplant, organized in four blocks of treatment, was simple to administer and devoid of toxic effects. It permits rapid attainment of clinical and molecular response and enables the harvest of lymphoma‐free peripheral blood progenitor cells even in heavily pretreated patients with relapsed or refractory disease.

Pharmacokinetic behavior of rituximab: a study of different schedules of administration for heterogeneous clinical settings.

This study was designed to report the pharmacokinetic behavior of Rituximab in patients affected with different diseases and treated with different schedules of administration. A low tumor burden was a common feature of all patients (N = 48) included in our study, whereas the timing of Rituximab administration varied from weekly (groups 1, 2, 3) to monthly (group 4). Group 1 included patients with follicular lymphoma treated with 4 weekly doses of Rituximab after first-line chemotherapy with CHOP. At the start of Rituximab, patients were in partial or complete clinical response but showed persistence of disease at molecular level (bcl-2-positive) in bone marrow and/or peripheral blood. Patients in group 2 had autoimmune disorders and Rituximab was given to act on B-cells, interfering with their production of autoantibodies. In patients with amyloidosis (group 3), Rituximab was given to kill progenitor B-cells of the small clone terminating in amyloid-producing plasma cells. In groups 2 and 3, the target of monoclonal antibody was a population of small B cells, which make an intrinsic feature of the diseases. Group 4 included patients with relapsed or refractory follicular and mantle cell lymphoma who underwent a salvage program of immunochemotherapy, purging in vivo and autotransplant: the first of the six planned doses of Rituximab was administered after a debulking phase with a third-generation regimen, such as VACOP-B. An enzyme-linked immunoassay (ELISA) developed and validated in our laboratory was used for the pharmacokinetic study. Rituximab disposition was characterized by a 2-exponential decay, with a long elimination half-life of approximately 3 weeks (range, 248-859 hours). The total systemic clearance ranged between 3.1 and 11.9 mL/hr/m2. After 4 weekly infusions, Rituximab concentration was ∼2.5 μg/mL, which is approximately 85% of the steady-state level. Steady-state plasma concentrations of Rituximab were reached after 6 to 8 weekly infusions. The adopted pharmacokinetic model (2-compartment open model) seems to provide the best fit of Rituximab disposition both during and after treatment, even when different schedules of drug administration are used. Because several studies reported an association between response and serum Rituximab concentrations, a treatment based on a pharmacokinetic model may be useful for predicting the desired drug concentration.

Clinical Pharmacokinetics of Tretinoin

SummaryRecent reports of the dramatic antitumour effect of tretinoin (all-trans retinoic acid) in patients with acute promyelocytic leukaemia (APL) have generated a great deal of interest in the use of this drug as a chemopreventive and therapeutic agent. However, the biological efficacy of tretinoin is greatly impaired by (presumably) an induced hypercatabolism of the drug leading to reduced tretinoin sensitivity and resistance.Several pharmacokinetic studies have shown that plasma drug exposure [as measured by the plasma area under the concentration-time curve (AUC∞)] declines substantially and rapidly when the drug is administered in a long term daily tretinoin regimen. These observations led to the hypothesis that the rapid development of acquired clinical resistance to tretinoin may have a pharmacological basis and result from an inability to present an effective drug concentration to the leukaemic cells during continuous treatment.The principal mechanisms proposed to explain the increased disappearance of tretinoin from plasma include: (i) decreased intestinal absorption; (ii) enhanced enzymatic catabolism; and (iii) the induction of cytoplasmic retinoic acid binding proteins (CRABP), which leads to increased drug sequestration. The most favoured explanation is that continuous tretinoin treatment acts to induce drug catabolism by cytochrome P450 (CYP) enzymes.Several strategies aimed at preventing or overcoming induced tretinoin resistance have been, and are being, planned. These strategies include intermittent dose administration, administration of pharmacological inhibitors of CYP oxidative enzymes, combination with interferon-α and intravenous administration of liposome-encapsulated tretinoin. As these strategies are now under investigation and the number of patients enrolled is small, further studies are needed to determine the efficacy and toxicity of these new schedules of drug administration.In this article we provide an overview of the relevant aspects of tretinoin physiology and pharmacokinetics, and summarise the current status of knowledge to help in the better optimisation of tretinoin administration.

Efficacy and Pharmacokinetics of Simvastatin in Heart Transplant Recipients

Objective: To evaluate the efficacy and safety of simvastatin administered to a group of heart transplant patients receiving triple-drug immunosuppressive therapy. We also assessed the potential pharmacokinetic interaction between simvastatin and cyclosporine by comparing mean plasma concentrations of simvastatin beta-hydroxy acid, the major metabolite of the drug, in a group of heart transplant patients treated with cyclosporine and in a control group of patients who had not received heart transplants. Both groups received long-term (>6 wk) simvastatin therapy. Design: We monitored hyperlipidemia in 20 hypercholesterolemic heart transplant patients receiving simvastatin 10 mg/d and triple-drug immunosuppressive therapy. Changes in laboratory results before and after 4 months of simvastatin therapy were considered. The same laboratory data were monitored in a control group of 20 nonhypercholesterolemic heart transplant patients who were not treated with simvastatin but were receiving triple-drug immunosuppressive therapy. Plasma concentrations of simvastatin beta-hydroxy acid were measured in 14 hypercholesterolemic patients, 7 of whom had received heart transplants and 7 who had not. Setting: The Division of Cardiology and the First Medical Clinic for the clinical study, as well as the Department of Pharmacology for the pharmacokinetic analysis. Participants: Forty heart transplant patients and 7 hypercholesterolemic nontransplant patients. Main Outcome Measures: Effectiveness of simvastatin was determined by comparing cholesterol and lipoprotein plasma concentrations in 20 patients who underwent heart transplant and were treated with simvastatin for 4 months. The safety of the drug was determined by analyzing changes in laboratory results in the treated group and in the control group, both those who had received heart transplants and those who had received immunosuppressive therapy. Results: After 4 months of simvastatin therapy, total cholesterol decreased by 12.5% and low-density lipoprotein cholesterol decreased by 21.3%. The only statistically significant laboratory change was an increase of 28.7% in the alanine aminotransferase concentrations. Plasma concentrations of simvastatin beta-hydroxy acid were higher in heart transplant patients than in those who had not received heart transplants, the control group. Conclusions: Low-dosage simvastatin treatment seems to be safe and sufficiently effective to decrease cholesterol concentrations. Concomitant treatment with immunosuppressive therapy (primarily cyclosporine) in heart transplant patients appeared to cause a reduced metabolic clearance of simvastatin from the plasma. More extensive studies on the interaction between simvastatin and cyclosporine are needed to understand the marked variability found in the response to simvastatin.

A model of in vivo purging with Rituximab and high-dose AraC in follicular and mantle cell lymphoma

Summary:We studied a model of in vivo purging with Rituximab and high-dose (HD) cytarabine in 14 patients with relapsed/refractory follicular lymphoma and two with refractory mantle cell lymphoma enrolled in a program of HD chemotherapy and autotransplant. After two courses of debulking immunochemotherapy with Rituximab, Vincristine and Cyclophosphamide, we used a combination of Rituximab, HD cytarabine and granulocyte colony-stimulating factor for peripheral blood stem cells (PBSC) mobilization. The median number of CD34+ cells collected was 14.69 × 106/kg (range 5.74–73.2). Monitoring of peripheral CD19+ and CD20+ B cells prior to and throughout the purging period showed that a treatment with Rituximab, Vincristine and Cyclophosphamide results in a profound depletion of B cells in peripheral blood. B-cell depletion persists during mobilization with Rituximab and HD cytarabine allowing a collection of PBSC free of B cells (median CD19+ and CD20+ cells counts 0%). Of nine patients PCR positive for bcl-2 or bcl-1 in blood and marrow at the start of immunochemotherapy, all showed PCR-negative PBSC. In conclusion, in patients with indolent lymphoma, the concurrent administration of Rituximab and HD cytarabine is a safe and efficient method to obtain in vivo purged PBSC. Immunochemotherapy prior to mobilization produces B-cell depletion and seems to be a useful preparative step.

Modulation of all‐trans retinoid acid pharmacokinetics in acute promyelocytic leukaemia by prolonged interferon‐α therapy

Summary. Continuous treatment with all‐trans retinoid acid (ATRA) induces accelerated drag catabolism which is considered responsible for acquired resistance to ATRA. We studied the effect of interferon‐o:2a (IFN) on ATRA pharmacokinetics in two patients with acute promyelocytic leukaemia (APL) in complete remission maintained by alternating 15d of IFN and 15 d of ATRA. Day 15 ATRA levels obtained during IFN + ATRA treatment were significantly higher than those observed in patients maintained on ATRA alone. In one patient IFN was discontinued and day 15 ATRA levels decreased to those observed in patients scheduled for maintenance with ATRA alone. In our two patients IFN substantially reduced the induction of ATRA catabolism, indicating a potential role for IFN in modulating ATRA pharmacokinetics.

All-trans retinoic acid (ATRA) in patients with chronic myeloid leukemia in the chronic phase

Since in vitro observations indicated that all-trans retinoic acid (ATRA), especially in combination with IFNα, can exert significant suppressive effects on Ph+ cells, we investigated the effects and the pharmacokinetic profile of ATRA in a selected cohort of patients with Ph+ chronic myeloid leukemia (CML) in chronic phase. Eighteen patients were treated with ATRA at a dose of 80 mg/m2/day (p.o.), divided into two equal doses after meals, for 7 consecutive days every other week for a maximum of 12 courses (1 course = 1 week on and 1 week off). Pharmacokinetic profiles of ATRA were evaluated during intermittent therapy on days 1 and 7 of course 1; on day 1 of course 2; on day 1 of course 6. Out of the 18 patients treated with ATRA, 11 (61%) went off study before the sixth course of treatment because of progressive hyperleukocytosis (seven cases), or thrombocytosis (one case), or refusal (three cases). Seven (39%) patients completed the first six courses (12 weeks) of treatment with ATRA and two of them (11%) maintained a white blood cell (WBC) <10 × 109/l which was induced by the pretreatment with hydroxyurea. One patient completed the 12th course of ATRA maintaining WBC <10 × 109/l, platelets <500 × 109/l and spleen not palpable. The treatment with ATRA was well tolerated and only one patient discontinued the therapy because of non-hematological side-effects. The area under the concentration-time curve (AUC) decreased significantly (P < 0.001) during the first week of therapy. by adopting an intermittent dosing regimen, 1 week on/ 1 week off (1 course), at the start of courses 2 and 6, we obtained the atra aucs equivalent to the ones achieved on day 1 of course 1. in conclusion, our results showed that atra alone appeared to be unable to control the wbc expansion in the cml patients in chronic phase. moreover, it did not induce any remarkable cytoreductive effects on the platelet count and on the hemoglobin level. the major interest of atra would be in combination with other therapies. if atra was given in combination with ifnα or other agents, dose reduction of these would not be planned. on the basis of the pharmacokinetic profile, atra should be administered intermittently rather than continuously.

Immunochemotherapy with rituximab, vincristine and 5-day cyclophosphamide for heavily pretreated follicular lymphoma.

Purpose: Therapeutic options for relapsed or refractory follicular lymphoma include combination chemotherapy, immunotherapy and, for selected patients, autotransplant. Because of the different mechanisms of action and non-overlapping toxicities, combination of rituximab with chemotherapy is a rational approach. Methods: 30 patients with follicular non-Hodgkin’s lymphoma with advanced-stage disease were treated with four cycles of immunochemotherapy with rituximab 375 mg/m2 on day 1, vincristine 2 mg i.v. on day 2 and cyclophosphamide 400 mg/m2 i.v. from days 2 to 6, repeated at 3-week intervals. All patients had received multiple lines of therapy (median 3); 9 (30%) had relapses (2 after high-dose therapy with autologous transplant), and 21 (70%) were in relapse and refractory to salvage treatment (with an anthracycline-containing regimen in 19). Results: Of 29 patients evaluable for response, 16 (55 %) obtained a complete response (CR) and 3 (10%) a partial response (PR), with an overall response rate of 65% (19/29); 10 patients (35%) achieved less than PR. The median event-free survival was 16.1 months for all patients, being 22.8 months for responders. After a median follow-up of 2 years from the start of therapy (range 6 months to 3.8 years), of 16 patients who achieved CR, 10 remain free of disease. Conclusion: The combination of rituximab with vincristine and 5-day cyclophosphamide is able to produce CR in patients with advanced follicular lymphoma, even in patients resistant to third-generation regimens. The regimen designed on the basis of pharmacokinetics of the chimeric antibody seemed important for the clinical efficacy of the combination.

TIME-DEPENDENT KINETICS OF TRETINOIN IN CHRONIC MYELOGENOUS LEUKAEMIA DURING INTERMITTENT DOSE SCHEDULING: 1 WEEK ON/1 WEEK OFF

AbstractObjective: This study investigated the pharmacokinetics of tretinoin during alternating cycles of 1 week of tretinoin treatment and 1 week drug-free in patients with Ph1+ chronic myelogenous leukaemia (CML) in the chronic phase. Patients: Eighteen patients with CML were treated with tretinoin 80 mg/m2/day (in two divided doses) for 7 consecutive days every other week (one cycle = 1 week on/1 week off). Results: Body systemic exposure to tretinoin as determined by the area under the plasma concentration-time curve (AUC) decreased significantly during the first week of drug administration, from (mean ± SD) 678.3 ± 498.1 to 258.7 ± 272.4 μg/L·h. In about 40% of the patients the decline in plasma concentrations was ≥80%, while 17% of the population did not experience any decline. On day 7 of cycle 1, the mean apparent oral clearance (CL/F) was 2.6 times the corresponding value on day 1. After 1 week without tretinoin, the mean AUC on day 1 of cycle 2 was lower (down 15%) but not statistically different from the corresponding value observed on day 1 of cycle 1; 62% of patients showed an increase in the AUC, which was 40% higher than the corresponding value on day 7 of cycle 1. On day 1 of cycle 6, the AUC and CL/F of tretinoin during a dosage interval were not statistically different from those observed on day 1 of cycle 1 and cycle 2. On all occasions the peak plasma concentration (Cmax) was strongly correlated to the corresponding AUC. No significant change in the time to observed Cmax (tmax) and in the elimination half-life (t½) was observed during the whole study. These results confirmed that the metabolism of tretinoin is rapidly up-regulated in CML patients, with significant declines in plasma drug exposure during the first week of drug administration. After tretinoin was discontinued, a return to the non-induced state followed a mean time-cycle similar to the induction. The strong decrease in the apparent oral drug clearance and the absence of significant variations in the drug half-life demonstrated that the presystemic extraction of tretinoin is the main cause of the marked decline in plasma drug exposure. Conclusion: The favourable pharmacokinetic profile of tretinoin obtained by an intermittent regimen, 1 week on/1 week off therapy (vs continuous administration), suggests that such a therapeutic schedule is the most appropriate for the assessment of clinical efficacy in those pathologies in which its use is suitable.