Mechanism of free and conjugated neocarzinostatin activity: studies on chromophore and protein uptake using a transferrin-neocarzinostatin conjugate.

Targeting studies using the anti-cancer agent neocarzinostatin (NCS), conjugated to anti-bodies have shown relatively poor specificity. From the literature, it is unclear whether NCS mediates its effects either in conjugated or unconjugated form. In the present work we have used a conjugate of NCS with transferrin, a biological ligand with a well defined endocytic route, to probe these mechanisms. NCS was covalently coupled to transferrin using the heterobifunctional reagent sulfo-4-(N-maleimidomethyl)cyclohexane-1-carboxylate (SMCC) and 2-iminothiolane to give a stable thioether-linked conjugate with a ratio of 1.6 mol of NCS per mole of transferrin. The binding activity of transferrin was completely retained. Conjugation of NCS to transferrin resulted in an apparent enhancement of cytotoxicity. However, incubation with excess transferrin had no influence on the observed enhanced toxicity, indicating that endocytosis is not responsible. Further experiments demonstrated that the apparent enhancement was dependent on incubation conditions and not an effect due to endocytosis of ligand. Studies where apo-NCS competed with holo-NCS and transferrin strongly indicated that the cytotoxicity of both NCS and conjugate is mediated by direct entry of the dissociated chromophore into the cell.

A new oral formulation of cyclosporine for early oral immunosuppressive therapy in liver transplant recipients.

CsA-ME is a new oral microemulsion formulation of CsA. Studies in stable liver grafted patients with cholestasis and subsequent poor absorption of the conventional cyclosporine formulation showed a substantial increase in CsA absorption after conversion to CsA-ME. To investigate its use in patients during the early course after liver transplantation we recruited 50 liver transplant recipients in two centers. During the first study phase A CsA-ME was administered to 20 patients in incremental doses after a short initial course of intravenous cyclosporine. During the second study phase B (30 patients) CsA-ME was administered from the time of transplantation. One year actual patient and graft survival of patients included in phase A and B of the trial was between 90% and 93.3%; 50% and 60% of the patients enrolled in phase A and phase B of the trial were free from rejection at month 3, respectively. Chronic rejection was diagnosed in one patient. No increase in the incidence of CsA related side effects was observed. The optimum CsA-ME starting dose was found to be 10 mg/kgbw/day for patients without external biliary diversion and 15 mg/kgbw/day for patients with a T tube in situ. Using these starting doses, 26 consecutive patients with external bile diversion via T tube were treated with CsA-ME from the day of transplantation. Intravenous CsA was necessary only in three patients. When CsA-ME absorption in patients with stable liver function was compared with that in patients with early liver dysfunction, no difference in the pharmacokinetic profiles was observed between the groups. Our results indicate that CsA-ME therapy is effective and well tolerated in liver graft recipients, even in patients with external biliary diversion during the early posttransplant phase. Thus, CsA-ME is a useful alternative to intravenous CsA treatment in these patients.

Conversion to microemulsion cyclosporine in stable renal transplant patients: results after one year.

We switched 302 renal transplant patients from the conventional to a new microemulsion formulation of cyclosporine, to study the latter's safety and efficacy. We used a simple 1:1 conversion of the patient's total daily dose. We measured trough drug levels as well as serum creatinine, liver enzymes, uric acid, and blood pressure values at baseline and at days 4, 8, 15, 29, and months 3, 6 and 12 after drug substitution. Dose adjustments directed at trough levels 80-120 ng/ml were performed, starting at day 8. Within the 12-month observation period, the cyclosporine dose was reduced by 14.7% (204 +/- 60 mg/day baseline vs 174 +/- 51 mg/day after conversion, p < or = 0.001). By day 8, the 1:1 dosage conversion resulted in a modest mean increase in drug trough levels (114 ng/ml baseline vs 120 ng/ml, p < or = 0.01). This increase was accompanied by an increase in serum creatinine concentration, a decrease in calculated creatinine clearance, and an increase in uric acid values (p < or = 0.05). Liver enzymes remained unchanged while systolic and mean arterial blood pressure decreased (p < or = 0.05). After one month, drug trough levels had decreased to baseline (112 ng/ml) and remained there until month 6. They were significantly lower after 12 months (102 +/- 33 ng/ml, p < or = 0.001). Plasma creatinine values decreased to below baseline by month 6 (p < or = 0.001) and month 12 (p < or = 0.001). Twenty-four (8%) biopsy proven rejection episodes and 7 cases of cyclosporine attributed nephrotoxicity occurred in these 302 patients within these 12 months. We conclude, that a 1:1 conversion from conventional to the microemulsion form of cyclosporine is efficacious and safe. However, we advise an initial 10% decrease in dose reduction in those patients whose trough levels are in the high-normal range.

Substitution of conventional cyclosporin with a new microemulsion formulation in renal transplant patients: results after 1 year.

BACKGROUND: A new galenic form of cyclosporin A has been developed, based on microemulsion technology. The bioavailability of the compound is relatively independent of food intake and bile flow. It was the purpose of this prospective clinical trial to study the safety of the microemulsion form of cyclosporin A. METHODS: Three hundred and two renal transplant patients, stratified according to transplant age, were switched from the conventional to the new microemulsion formulation of cyclosporin A. A 1:1 conversion ration was used. Measurements included CsA levels, S-creatinine, liver enzymes, uric acid, and blood pressure. Measurements were performed at baseline and on days 4, 8, 15, 29 and months 3, 6 and 12 after conversion. Dose adjustments were performed to achieve through levels of 80-120 ng/ml. RESULTS: Within the 12-month observation period the cyclosporin dose was reduced by 14.7% (from 204 +/- 60 mg/day at baseline to 174 +/- 51 mg/day after conversion, P < 0.001). Acutely, i.e. by day 8, 1:1 dose conversion resulted in a modest increase of mean drug through levels (from 114 ng/ml at baseline to 120 ng/ml, P < 0.01). This increase was accompanied by an increase in serum creatinine concentration, a decrease in calculated creatinine clearance, and an increase in uric acid values (P < or = 0.05). Liver enzymes remained unchanged while systolic and mean arterial blood pressure decrease (P < 0.05). After 1 month, drug through levels had decreased to baseline (112 ng/ml) and remained there until month 6. They were significantly lower after 12 months (102 +/- 33 ng/ml), P <0.001). Creatinine clearance values increased to above baseline at 6 and 12 months. Within the 1-year period there occurred 24 (= 8%) episodes of biopsy proven rejection and seven episodes of cyclosporin-attributed nephrotoxicity. CONCLUSIONS: The 1:1 conversion from conventional cyclosporin A to the microemulsion formulation s efficacious and safe, but an initial dose reduction of 10% is advised in patients with through levels in the high-normal range.

Influence of bile on cyclosporin absorption from microemulsion formulation in primary liver transplant recipients.

We analysed the absorption, after oral application, of a new galenic form of cyclosporin A (CyA-NOF) in liver-grafted patients (n = 12) during the 1st week (days 2-4) after transplantation. Pharmacokinetic profiling was performed with an open or clamped T tube in situ or with the T tube absent. The pharmacokinetic parameters of CyA-NOF were influenced by T tube clamping and bile diversion. The highest AUC, Cmax and earliest Tmax values were found in patients without a T tube in situ, indicating that absorption of CyA-NOF in patients during the early course after liver transplantation is not bile-independent. CyA-NOF, at a dose of 7.5 mg/kg, was enterally absorbed with appropriate AUC and Cmax levels. Patients receiving a starting dose of 7.5 mg/kg were successfully maintained on CyA-NOF during the subsequent clinical course.

Clinical experience transferring kidney transplant patients from Sandimmun to Sandimmun Neoral--results after 3 months.

The new galenic formulation of cyclosporine prepared as microemulsion (Sandimmun Neoral, SN) shows a significantly improved correlation between both trough level (Cmin) and dose. Moreover, since the bioavailability is increased by 20 to 30% on average, it may lead to a drug overexposure in so far malabsorbing patients. In order to assess safety and to establish an appropriate procedure to switch patients safely from conventional Sandimmun to SN, we initialized an open, stratified (transplant age) clinical trial enrolling 302 patients of our outpatient clinic. We used a simple 1:1 conversion of the patient's total daily dose. Trough drug levels, as well as serum creatinine, liver enzymes, uric acid, and blood pressure values were measured at baseline, at days 4, 8, 15, 29, and at month 3 after drug substitution. Within the three month observation period, the cyclosporine dose was reduced by 14.2% (204 +/- 60 mg/day baseline vs. 175 +/- 54 mg/day after conversion, p < 0.05). By day 8, the 1:1 dosage conversion resulted in a modest mean increase in drug trough levels (114 ng/ml baseline vs. 120 ng/ml, p < 0.05). This increase was accompanied by a slight increase in mean serum creatinine concentration, a decrease in calculated creatinine clearance, and an increase in mean uric acid values (p < 0.05). Liver enzymes remained unchanged while systolic and mean arterial blood pressure decreased (p < 0.05). Parallel to dosage reduction, drug trough levels had decreased after 1 month to baseline (112 ng/ml) and remained there for the remainder of the study.(ABSTRACT TRUNCATED AT 250 WORDS)

Increased serum stability and prolonged biological half-life of neocarzinostatin covalently bound to monoclonal antibodies.

The pharmacokinetics of neocarzinostatin (NCS) have been compared to NCS conjugates with monoclonal antibodies using Balb/c and tumor bearing nude mice. Data on blood and whole body clearance revealed that the high MW conjugate persists in the body far longer and at a higher level than the free drug. Excretion of the free drug occurs with an extremely rapid renal clearance and localization of the remaining drug in the kidney, whereas the NCS immunoconjugate remained in circulation far longer allowing time for tumor localization to occur without renal accumulation of drug. In addition, NCS conjugated to monoclonal antibody was found to retain its activity in human serum better than free drug, in agreement with data obtained for other NCS-derivatives. Half-time of inactivation was greatly extended when measured under relevant conditions in a DNA strand-break assay. The results indicate that two of the most important requirements for the successful targeting of NCS in vivo, decreased clearance rate and increased serum stability are achieved by conjugation to antibody. Both results increase the probability of NCS accumulating in tissue while still in its active form. Coupling of NCS to monoclonal antibody decreases clearance and inactivation rate and increases localization of the active drug in tumor tissue.