Parameters for successful monthly extended dosing of darbepoetin-alpha in patients undergoing hemodialysis.

AIM: To document the feasibility and report the results of dosing darbepoetin-alpha at extended intervals up to once monthly (QM) in a large dialysis patient population. MATERIAL: 175 adult patients treated, at 23 Swiss hemodialysis centres, with stable doses of any erythropoiesis-stimulating agent who were switched by their physicians to darbepoetin-alpha treatment at prolonged dosing intervals (every 2 weeks [Q2W] or QM). METHOD: Multicentre, prospective, observational study. Patients' hemoglobin (Hb) levels and other data were recorded 1 month before conversion (baseline) to an extended darbepoetin-alpha dosing interval, at the time of conversion, and once monthly thereafter up to the evaluation point (maximum of 12 months or until loss to follow-up). RESULTS: Data for 161 evaluable patients from 23 sites were included in the final analysis. At 1 month prior to conversion, 73% of these patients were receiving darbepoetin-alpha weekly (QW) and 27% of the patients biweekly (Q2W). After a mean follow-up of 9.5 months, 34% received a monthly (QM) dosing regimen, 52% of the patients were receiving darbepoetin-alpha Q2W, and 14% QW. The mean (SD) Hb concentration at baseline was 12.3 +/- 1.2 g/dl, compared to 11.9 +/- 1.2 g/dl at the evaluation point. The corresponding mean weekly darbepoetin-alpha dose was 44.3 +/- 33.4 microg at baseline and 37.7 +/- 30.8 microg at the evaluation point. CONCLUSIONS: Conversion to extended darbepoetin-alpha dosing intervals of up to QM, with maintenance of initial Hb concentrations, was successful for the majority of stable dialysis patients.

Loop-acting diuretics do not bind to Tamm-Horsfall urinary glycoprotein.

1. Binding between the radiolabelled loop-acting diuretics ([14C]frusemide, [14C]ethacrynic acid and [3H]bumetanide) and human Tamm-Horsfall glycoprotein or human serum albumin in vitro was evaluated by equilibrium dialysis. 2. The diuretic action and binding to urinary Tamm-Horsfall glycoprotein of the radiolabelled diuretics in vivo, after intravenous administration, were examined in rabbits. 3. In vitro, all three radiolabelled diuretics bound strongly to human serum albumin, but not to Tamm-Horsfall glycoprotein. 4. Radiolabelled frusemide and bumetanide, but not ethacrynic acid, caused a diuresis in rabbits, but no binding between the drugs and Tamm-Horsfall glycoprotein was seen in vivo. 5. Binding to Tamm-Horsfall glycoprotein does not appear to be an important mechanism in the action of loop diuretics.

A sensitive and specific ELISA using a monoclonal capture antibody for detection of Tamm-Horsfall urinary glycoprotein in serum.

An enzyme-linked immunosorbent assay (ELISA) has been established using Nunc polystyrene immunoplates coated with a monoclonal antibody to human Tamm-Horsfall urinary glycoprotein (THP) to detect and measure THP in human serum. Optimal reaction conditions for both the monoclonal capture antibody and the affinity-purified rabbit anti-human THP second antibody were established to produce standard curves which showed linearity between 20-90 ng/ml with a sensitivity of 2-3 ng/ml. The plate-to-plate standard curve mean coefficient of variation (CV) was 5.9 +/- 2.9% on assays performed on the same day while day to day mean CV was 13.3 +/- 2.4%. The specificity of the ELISA was demonstrated by inhibition of binding after preincubation of both urinary THP standards and serum with monoclonal anti-THP antibody. Sera from 195 blood donors tested by the ELISA had a mean concentration of THP antigenic determinants of 260 +/- 105 ng/ml. Results from three control sera run on all plates used in the survey showed mean CV less than 7.6% while no binding was observed with sera from an anephric patient.

Characterization of monoclonal antibodies specific for human Tamm-Horsfall protein.

Fifteen monoclonal antibodies have been produced to human Tamm-Horsfall protein (THP), identifying at least seven distinct epitopes. The antibodies have been used to isolate from serum an immunoreactive protein which comigrates with urinary THP. In addition, the antibodies may prove useful to set up an immunoenzymoassay for urinary THP as well as for immunoaffinity purification.

[Tumors and kidney transplantation]. / Tumoren und Nierentransplantation.

Incidence and type of de novo tumours were studied retrospectively in 187 consecutive patients who had received kidney transplants between 1967 and 1981 and undergone immunosuppressive therapy for 2 months or longer. Up to the end of June 1983, 18 patients (9.6%) had developed 22 malignancies and 7 of them had died from the tumour. The risk of developing a malignancy appeared to increase with prolonged immunosuppression. No significant difference was noted between patients with and without tumours regarding primary renal disease, duration of pretransplant dialysis, and type or total dose of immunosuppressive drugs. The risk of developing any malignancy appeared to be some 20 times that in the general population. The practical management of patients with de novo tumours is described in the light of our own patient material and the recent literature. Finally, two further oncological problems are discussed: first, the incidental grafting of malignant cells with the transplant, and second, how to proceed in a transplant candidate with a previous malignancy.

Cyclosporine alone or in combination with prednisone in cadaveric renal transplantation.

One hundred recipients of first cadaveric kidney transplants were treated with three different immunosuppressive regimens: (1) conventional immunosuppression, (2) CsA alone, and (3) low-dose CsA in combination with low-dose prednisone, with rapid adjustment to give CsA whole blood trough levels of 300 to 800 ng/mL. One-year graft survival in the aza + pred group was 76%, and in the CsA alone group 75%. Graft survival at two and six months in the CsA-pred group was 94%. The dose of CsA in the CsA-pred group in the first two months posttransplant was only about half that given to the CsA-alone group. Surprisingly, the reduction in the CsA dose also reduced the number of methylprednisolone pulses given for treating rejection by greater than 50%. The incidence of nephrotoxicity and extrarenal side effects also fell considerably. Withdrawal of prednisone in the CsA-pred group after five months led to reversible rejection in two cases. In conclusion, (1) the rapid reduction in the CsA dosage is beneficial and has no drawbacks, and (2) our guidelines for withdrawing prednisone (timing of withdrawal, rate of reduction in dosage) still need further refinement.

Cyclosporin A used alone or in combination with low-dose steroids in cadaveric renal transplantation.

The actual survival rate of 25 primary cadaveric kidney grafts in recipients treated initially with cyclosporin A (CyA) alone was 84%. The survival rate in 37 patients under conventional immunosuppression was 76%. The mean number of dialyses required in the first 4 weeks after transplantation was 1.2 per patient in both groups. At 15-28 months posttransplant, mean serum creatinine levels have remained stable at 175 mumol/l in the CyA group. The mean daily dose of steroids (including methylprednisolone i.v.) in the first two months was 2.07 mg/kg/d in patients under conventional immunosuppression and 0.76 mg/kg/d in the patients receiving CyA (p less than 0.001). The combination of CyA with low-dose steroids enabled the dose of CyA to be rapidly tapered off in once-weekly steps. CyA levels were monitored by determination of whole blood trough concentrations (target level: 300-800 ng/ml). At 60 days posttransplant the average dose of CyA was 6.0 +/- 0.5 mg/kg/d compared with an average daily dose of 11.4 +/- 0.9 as recommended for CyA alone in the protocol for the European multicentre study. This more rapid reduction in the CyA dose reduced nephrotoxicity (serum creatinine levels 174 +/- 14 as compared with 289 +/- 31 mumol/l) (p less than 0.05) and almost halved the number of methylprednisolone pulses given up to the end of the second month. We conclude from these results (1) that previously the dosage of CyA administered at this centre was probably too high, and (2) early adjustment of dose levels on the basis of blood concentrations and with low-dose prednisone cover appears to be safe and effective, but requires further verification.