Carboplatin was administered i.v. to four groups of three male beagle dogs at doses of 3, 6, 12, and 24 mg/kg (60-580 mg/m2). Plasma samples were obtained at appropriate times and protein-free plasma ultrafiltrates (PU) were generated with Amicon Centrifree micropartition systems. Urine was collected at 24-h intervals for 96 h. PU and urine samples were analyzed for carboplatin by HPLC and for total platinum by atomic absorption spectrophotometry. Carboplatin accounted for about 90% of the free platinum in plasma. The Cmax and AUCinf values for carboplatin and for free platinum increased linearly with dose. The terminal elimination half-life and mean residence times for carboplatin and free platinum were each about 1 h. Total-body clearances for carboplatin (5.6 l/h per m2) and free platinum (5.1 l/h per m2) were constant over the dose range studied, as were the respective volumes of distribution (5.7 and 5.0 l/m2). A mean of 46% of the dose was excreted as carboplatin in 24-h urine; and by 72 h, 70% of the platinum administered was excreted in the urine. Free platinum was cleared by both renal and non-renal processes. These results show that a dose of carboplatin is rapidly excreted in the urine and that carboplatin and plasma-free platinum exhibit linear pharmacokinetics in the beagle dog.

Carboplatin was given as a 30-min infusion to 11 ovarian cancer patients at doses of 170-500 mg/m2. The ages, weights, and creatinine clearances (Clcr) ranged from 44 to 75 years, from 44 to 74 kg, and from 32 to 101 ml/min, respectively. Plasma, plasma ultrafiltrate (PU), and urine samples were obtained at appropriate times for 96 h and were analyzed for platinum. The PU and urine were also analyzed for the parent compound by HPLC. In patients with a Clcr of about 60 ml/min or greater, carboplatin decayed biexponentially with a mean t1/2 alpha of 1.6 h and a t1/2 beta of 3.0 h. The mean (+/- SD) residence time, total body clearance, and apparent volume of distribution were 3.5 +/- 0.4 h, 4.4 +/- 0.85 l/h, and 16 +/- 3 l, respectively. Cmax and AUCinf values increased linearly with dose, and the latter values correlated better with the dose in mg than in mg/m2. No significant quantities of free, ultrafilterable, platinum-containing species other than the parent compound were found in plasma, but platinum from carboplatin became protein-bound and was slowly eliminated with a minimal t1/2 of 5 days. The major route of elimination was excretion via the kidneys. Patients with a Clcr of 60 ml/min or greater excreted 70% of the dose as the parent compound in the urine, with most of this occurring within 12-16 h. All of the platinum in 24-h urine was carboplatin, and only 2%-3% of the dosed platinum was excreted from 48 to 96 h. Patients with a Clcr of less than about 60 ml/min exhibited dose-disproportional increases in AUCinf and MRT values. The latter were inversely related to Clcr (r = -0.98). Over a dose range of 300-500 mg/m2, carboplatin exhibited linear, dose-independent pharmacokinetics in patients with a Clcr of about 60 ml/min or greater, but dose reductions are necessary for patients with mild renal failure.

Regular administration of cyclophosphamide to NZB/NZW female mice effectively protects against the nephritis that is thought to be a model for human SLE nephritis. Reductions in serologic, histologic, and immunofluorescent parameters of the disease are correlated. Intermittent as well as continuous administration of the drug is effective without the development of leukopenia. Possible mechanisms of drug action and a modified approach to therapy of immune complex disease are discussed.Patients with systemic lupus erythematosus (SLE) develop inflammatory disease of many organs. Best understood is the nephritis that is thought to be From the

A B S T R A C T Extractable nuclear antigen (ENA) is composed of at least two components, one a ribonucleoprotein sensitive to ribonuclease or heat and the other a protein. Antibodies to ENA are associated with a relatively benign clinical course in patients with systemic lupus erythematosus (SLE) in which DNA anti-DNA complexes are thought pathogenic. The effect of ENA and anti-ENA on DNA anti-DNA reactions in vitro was studied. ENA effectively inhibited an anti-DNA hemagglutination reaction but no effect was found on binding of radioactive DNA or on the antihemocyanin hemagglutination reaction. The inhibitory effect was not abolished by yeast ribonuclease (RNase), heating, or DNase. Anti-ENA had no effect on anti-DNA hemagglutination. In vivo, ENA altered the NZB/NZW mouse nephritis thought to be a model for human SLE nephritis. These results suggest the possibility of a role for ENA in alteration of diseases due to pathogenic DNA anti-DNA complexes.

Sixteen years earlier a 42-year-old woman with an IgA kappa plasma cell neoplasm presented with bleeding disorder. Her prolonged course was complicated by subsequent development of rheumatoid arthritis, vascular purpura, and an acute membranoproliferative glomerulonephritis (MPGN). The paraprotein and its (Fab')2 fragment showed affinity for a test myeloma IgG2 (lambda ) paraprotein. The patient's serum and the IgA-IgG complex separated by gel filtration did not exhibit cryoprecipitation. The complex also did not dissociate by ultracentrifugation. Electron microscopic and immunofluorescent studies of a renal biopsy sample taken during the episode of nephritis showed subendothelial deposits and a lacy fluorescent pattern strongly positive for IgA and IgG. The same immunoglobulins were eluted from the kidney at postmortem. A low concentration of monoclonal IgA kappa (antibody) and excess unbound polyclonal IgG (antigen) were demonstrated in the patient's serum at the time of MPGN, apparently analogous to the conditions necessary for the induction of experimental immune complex nephritis.