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T de Witte

Publications and source records attributed to T de Witte.

At least 109 records · Page 6Linked to original sources
PubMed1993

Plasma and cellular pharmacokinetics of m-AMSA related to in vitro toxicity towards normal and leukemic clonogenic bone marrow cells (CFU-GM, CFU-L).

Plasma and cellular pharmacokinetics of m-AMSA were investigated in 5 patients with acute leukemia, using HPLC. The pharmacokinetic data served as a guideline for in vitro toxicity tests on clonogenic bone marrow cells. m-AMSA was administered as a 3-hour intravenous infusion of 100 mg/m2. Median plasma and nucleated blood cell peak concentrations were 1.25 and 6.36 micrograms/ml followed by biphasic elimination with a median T1/2 alpha alpha of 1.6 h and 0.3 h and a median T1/2 beta of 5.0 h and 5.0 h respectively. Median plasma and cellular area under the curve (AUC) for a 24-h period amounted 6.2 micrograms.h/ml and 49.8 micrograms.h/ml respectively. In vitro cellular uptake was maximal at least within 30 minutes. No differential toxicity for CFU-GM and CFU-L was observed in relation to exposure time. Median IC50 for CFU-GM and CFU-L was 2.2, 1.8 and 1.6 micrograms/ml after incubation periods of resp. 0.08, 4 and 24 h. The corresponding m-AMSA concentration x time products to achieve 50% inhibition (IAUC50) were 0.18, 7.2 and 38.4 micrograms.h/ml, respectively. 48-h prestimulation of the clonogenic bone marrow cells with Human Placenta Conditioned Medium increased sensitivity (median 1.7 x) after 4 h incubation with mAMSA. Short exposure provides maximal, concentration-related, cellular uptake, resulting in effective inhibition of growth of clonogenic bone marrow cells.

Acute Disease↗
PubMed1993

Splenic irradiation before bone marrow transplantation for chronic myeloid leukemia: update of a prospective randomized study.

Two hundred and twenty-nine patients with chronic myeloid leukaemia in chronic phase awaiting bone marrow transplantation from an HLA-identical sibling donor were randomized as part of their conditioning, to receive splenic irradiation (SI+, 115 patients), or not (SI-, 114 patients). Both groups were identical in regard to age, sex, donor/recipient sex combination and disease activity. Survival, leukaemia-free survival, incidence of transplant-related mortality, acute and chronic graft versus host disease, incidence of rejection and probability of relapse were not different in either groups at a median follow-up time of 4.5 years (minimum follow-up 2 years). Recovery of peripheral white blood cell counts to 1 x 10(9)/l but not of platelet counts to 50 x 10(9)/l was significantly faster in patients with SI+ (21 vs 24 days). This small benefit does not justify routine splenic irradiation prior to BMT, in CML.

Adolescent↗
PubMed1993

Idarubicin-related side effects in recipients of T-cell-depleted allogeneic bone marrow transplants are schedule dependent.

The influence of three different dosage schedules of anthracycline (idarubicin or daunorubicin)-intensified preparative therapy prior to T-cell-depleted allogeneic bone marrow transplantation (BMT) on (1) the severity and duration of oral toxicity (mucositis), (2) the duration of bone marrow aplasia, and (3) overall survival, relapse, and disease-free survival was studied in 99 BMT patients with standard- or high-risk hematologic malignancies. A further 146 patients who did not receive the anthracycline-intensified conditioning served as (historic) controls. All patients received cyclophosphamide (total dose, 120 mg/kg) on days -6 and -5 and total body irradiation on days -2 and -1 prior to BMT. The 99 patients who received the anthracycline-intensified preparative regimen were given either idarubicin (total dose, 42 mg/m2; n = 88) or daunorubicin (total dose, 156 mg/m2; n = 11) by continuous intravenous infusion between days -7 and -1 prior to BMT in 59 cases (cohort 1), on days -8 and -7 in 17 cases (cohort 2), and on days -12 and -11 in 23 cases (cohort 3). The occurrence of severe oral mucositis and delayed bone marrow recovery was schedule dependent, being substantially lower with earlier administration of the anthracycline-intensified regimen on days -12 and -11 before BMT (cohort 3), in comparison with later administration (cohorts 1 and 2). Plasma drug and metabolite concentrations were measured in 11 patients who received idarubicin. At the time of allogeneic bone marrow infusion (day 0), patients in cohorts 1 and 2 had plasma concentrations of idarubicin and idarubicinol (its active metabolite) in the range of in vitro cytotoxicity. However, in cohort 3, plasma concentrations on day 0 were much lower, which correlated with the lower maximum intensity and shorter duration of mucositis in these patients. In terms of overall survival, relapse rate, and disease-free survival in standard-risk patients, the anthracycline-intensified regimen proved to be very effective. Transplant-related mortality was 25% in the anthracycline group compared with 32% in the controls. The probability of relapse also was significantly less in the anthracycline group in comparison with controls (17% v 46%; P < .001), and the probabilities of long-term overall and disease-free survival were significantly greater (71% v 37% [P < .01] and 63% v 32% [P < .01], respectively). Only three patients in the idarubicin group experienced cardiotoxicity (one in each cohort); the causative relationship with anthracyclines was considered likely in one, possible in one, and doubtful in the third.

Adolescent↗
PubMed1992

Cytotoxicity of CD3-ricin A chain immunotoxins in relation to cellular uptake and degradation kinetics.

The cytotoxicity of WT32 (CD3)-ricin A immunotoxin (IT) to the acute lymphoblastic leukemia T-cell line Jurkat was compared with the rate of internalization and intracellular degradation of WT32 and WT32-ricin A during continuous exposure. Moreover, the influence of NH4Cl and monensin on these processes was studied. Based on protein synthesis inhibition ([3H]leucine incorporation), it appeared that cytotoxicity was not fully expressed directly after exposure to IT due to a delay in either the internalization of membrane-bound IT or the action of intracellular ricin A. Varying the duration of incubation and postponing [3H]leucine addition for up to 24 h after initiation showed that cytotoxicity occurred in two phases, rapid internalization of initially bound IT followed by a continuous but slower uptake, possibly due to reexpression of the CD3 antigen. No differences were found in the rate of internalization and degradation of 125I-labeled WT32 and WT32-ricin A. Internalization started rapidly after binding at 37 degrees C, was fastest during the first 12 h (+/- 360,000 molecules/cell), and continued for at least 24 h (+/- 420,000 molecules/cell). Exocytosis of intracellularly degraded molecules became measurable after 1 to 2 h of incubation at 37 degrees C and increased to approximately 400,000 molecules/cell in 24 h. After 4 h of incubation at 37 degrees C the number of internalized molecules exceeded the amount of WT32 that could maximally bind to the cell membrane (+/- 150,000 molecules/cell), confirming reexpression of antigen. The addition of NH4Cl and monensin enhanced the cytotoxicity of WT32-ricin A, probably due to an increased intracellular amount of IT. These agents appeared to reduce strongly the degradation of internalized WT32, resulting in an accumulation of intracellular molecules. NH4Cl was most effective during the first 12 h of incubation, whereas monensin increased the amount of intracellular WT32 molecules after 2 to 24 h. Our observations suggest that incubation conditions for the optimal cytotoxicity of IT treatment can be predicted by studying the internalization and degradation of the IT or respective monoclonal antibody.

Ammonium Chloride↗
PubMed1992

Treatment of myelodysplastic syndromes (MDS) and high leukaemic risk with low-dose cytosine arabinoside (LD-AraC) plus granulocyte-macrophage colony-stimulating factor (rh GM-CSF). The EORTC Leukaemia Group.

Symptomatic patients with myelodysplastic syndromes (MDS) and 10-30% blasts in the bone marrow were treated with low-dose AraC (2 x 10 mg/m2 subcutaneously (sc) days 1-14) and GM-CSF (fully glycosylated, Sandoz/Schering-Plough, 2 x 150 micrograms protein/day sc) given either subsequently (days 15-21) or simultaneously (days 8-14 and one week rest). Evaluations were carried out after three courses (nine weeks); responding patients could be continued for two further cycles. Eighty-two patients with refractory anaemia and excess of blasts (RAEB), with (RAEBt) or without transformation, were evaluable: 45 RAEB and 37 RAEBt, mean age 64 years (range 17-80 years). A complete remission was achieved in 14 cases (17%), 11 had a good response (13%), and 12 a partial response (15%). Stable disease was found in 21 cases (26%). There were 12 cases of toxic death (15%), progression was noted in eight patients (10%), and death due to disease in three (4%). No difference existed between the two treatment arms with respect to response. Major adverse events during treatment were haemorrhage (25%), infections (23%), and fever with GM-CSF (21%). GM-CSF did not induce leukaemia nor contribute to haemorrhage induced by AraC, but gave rise to an overall response rate of 46% which is high and relatively durable as compared to other treatments in this disease.

Acute Disease↗
PubMed1992

Influence of the conditioning regimen on erythrocyte chimerism, graft-versus-host disease and relapse after allogeneic transplantation with lymphocyte depleted marrow.

Three different conditioning regimens were applied to 144 patients undergoing allogeneic bone marrow transplantation (BMT) with HLA identical sibling marrow, depleted of lymphocytes by counterflow centrifugation. All regimens consisted of cyclophosphamide and fractionated total body irradiation (TBI). In 49 patients treated with regimen A the total TBI dose was 9 Gy. In regimen B the dose rate of TBI was increased and anthracyclines were added (n = 65). Thirty patients received regimen C with a total TBI dose of 12 Gy but no anthracyclines. The different conditioning regimens did not influence the percentage of patients with detectable recipient CFU-GM prior to infusion of donor marrow. The incidences of mixed erythrocyte chimerism at 6 months after BMT were 73, 33 and 20% for regimens A, B and C respectively. The conditioning regimen influenced significantly mixed erythrocyte chimerism from 6 to 24 months after BMT. Both age and the conditioning regimen influenced significantly the incidence of acute graft-versus-host disease (GVHD) (p = 0.017 and 0.0001 respectively). Acute GVHD greater than or equal to I occurred in 15, 29 and 77% of the patients treated with regimens A, B and C respectively. The incidence of acute and chronic GVHD was significantly higher in complete donor chimeras than in mixed chimeras (p less than 0.001 and p less than 0.01). The probability of relapse was 43% in 32 and 18% in 43 good risk patients treated with regimens A and B respectively (p = 0.07). Longer follow-up is needed to draw conclusions about relapse in regimen C.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

No advantage for patients who receive splenic irradiation before bone marrow transplantation for chronic myeloid leukaemia: results of a prospective randomized study.

A total of 239 patients with chronic myeloid leukaemia (CML) in chronic phase awaiting bone marrow transplantation (BMT) from an HLA-identical sibling donor were randomized to receive, as part of their conditioning, splenic irradiation (SI+) or no splenic irradiation (SI-). There was no difference between the SI+ and SI- groups regarding the distribution of age, sex, donor/recipient sex combination and blood counts at diagnosis and at BMT. Survival, leukaemia-free survival (LFS), incidence of transplant-related mortality, incidence of rejection and probability of relapse do not differ between the 117 SI+ and the 118 SI- patients at a median follow-up time of 2.5 years (minimum 0.5 years). LFS at 30 months is 56% (SE 5%) for the SI+ and 51% (SE 6%) for the SI- group (p = 0.65). LFS is better for younger patients (less than 25 years), for patients without T cell depletion and for those with a low white blood cell count at diagnosis (less than 30 x 10(9)/l) (p less than 0.05). It is worst for male recipients of a female marrow (p less than 0.05). The incidence of graft-versus-host disease grade greater than or equal to II was higher in the SI+ group, though not significantly. We conclude that routine splenic irradiation prior to BMT for patients with CML is of no benefit and should not be used as a routine procedure.

Adolescent↗
PubMed1992

Bone marrow transplantation for acute myeloid leukemia: the EBMT experience. A prospective analysis from HLA-typing. The EMBT Leukemia Working Party.

In 1990, 4,234 BMT were performed in Europe; 2,097 autologous BMT (388 AML) and 2,137 allogeneic BMT (494 AML). Although an established therapy with leukemia free survival (LFS) at five years of 41% +/- 5% (EBMT results) its value compared to alternative therapies remains controversial. During the year 1985, the EBMT conducted a prospective evaluation study. In 12 centres 168 patients with AML were registered at the time of HLA-typing. Basic patient data and treatment intention were recorded. 79 patients were HLA-typed at diagnosis. 68 patients in 1st CR and 21 at other stages. Follow-up of these patients was obtained as of January 1, 1991. Three-year LFS is 44% for patients with an HLA-identical donor and 21% for those without (p = 0.02). Of the 68 patients HLA-typed in first CR, 40 had an HLA-identical donor and 28 no donor. Three-year LFS is 42% and 35%. resp. (n.s.). The difference in results between patients typed at diagnosis and first CR patients illustrates the problem of selection. We conclude that patient registration early in the disease can give insight into the process of selection. Allogeneic BMT incorporated prospectively at diagnosis into therapy offers a survival advantage for patients in this age category compared to alternative therapies.

Acute Disease↗
PubMed1990

Clinical and physical aspects of total body irradiation for bone marrow transplantation in Nijmegen.

Eighty-nine patients were transplanted with allogeneic bone marrow after a standard conditioning regimen consisting of cyclophosphamide and fractionated total body irradiation (2 x 4.5 Gy) with average dose rates of 4.1 and 12.3 cGy/min, respectively. The average rectum and lung dose was 9.2 +/- 0.45 and 7.5 +/- 0.78 Gy. In vivo dosimetry was performed in 71 patients irradiated with 18 MV X-rays from left and right lateral. Forty-three patients (48%) died. After increasing the dose rate the incidence of interstitial pneumonitis increased, but the number of relapses decreased.

Adolescent↗