The cyclosporin PSC 833 increases survival and delays engraftment of human multidrug-resistant leukemia cells in xenotransplanted NOD-SCID mice.

Circumvention of chemoresistance in cancer may involve several modulator drugs with high affinity for the multidrug transporter P-glycoprotein (Pgp), which is expressed in a number of multi-resistant malignancies. Pgp acts as a membrane efflux pump with broad substrate specificity including antineoplastic drugs and endogenous substances such as certain cytokines and sphingolipids. Therefore, the consequence of Pgp blockade could be far more complex than intracellular drug retention. In the present study exposure of the Pgp inhibitor, PSC 833 (1200 ng/ml), to Pgp expressing KG1a/200 human leukemia cells provoked cell cycle arrest and apoptosis in vitro. This finding was put to test in vivo using a xenotransplant model of KG1a/200 human cells intravenously inoculated into non-obese diabetic severe combined immunodeficient (NOD-SCID) mice. The animals were randomly allocated to receive treatment with PSC 833 (n = 32) or placebo (n = 24). PSC 833 (30 mg/kg) was subcutaneously injected six or 12 times separated by 48-96 h. The overall mean whole blood concentration of PSC 833 was 1191 +/- 60 ng/ml (s.e.m.) at 20 h after administration. Tumor engraftment was significantly reduced in the treatment group (P = 0.037), which also had prolonged survival compared to control animals (P = 0.0016). This is the first study that demonstrates antileukemic effects of a Pgp inhibitor as single agent therapy in vivo, and the present data raise the possibility of alternative exploitation of modulators in cancer chemotherapy.

Enhancement of the intestinal absorption of a cyclosporine derivative by milk fat globule membrane.

A cyclosporine derivative, dihydrocyclosporine D, was used for the evaluation of milk fat globule membrane (MFGM) as an emulsifier of lipophilic cyclopeptides. As compared with olive oil formulation, MFGM emulsion significantly enhanced the blood and lymphatic fluid concentrations of the cyclosporine derivative after intraduodenal dosing in rats. Thus, it was suggested that MFGM can be used as an intestinal absorption enhancer of cyclosporines.

Anaemia in children following cardiac transplantation: treatment with low dose human recombinant erythropoietin.

Anaemia is common in children following cardiac transplantation. In a series of 5 children with anaemia beyond the immediate post-operative period one had a hypochromic, microcytic anaemia which corrected with oral iron. The other four had normochromic, normocytic anaemias unresponsive to iron or folate supplementation and associated with inappropriately low levels of erythropoietin. Subcutaneous administration of low dose human recombinant erythropoietin to these four patients resulted in correction of their anaemia. Our findings suggest that erythropoietin deficiency is an important cause of anaemia in transplant recipients and should be sought in cases of anaemia refractory to conventional haematinic therapy. In cases of proven erythropoietin deficiency, treatment with erythropoietin is effective, acceptable to patients and preferable to repeated blood transfusion.

The pharmacokinetics and colonic tissue concentrations of cyclosporine after i.v., oral, and enema administration.

This study compares pharmacokinetic parameters and colonic tissue concentrations of cyclosporine administered by olive-oil or water-retention enemas with conventional intravenous (i.v.) and oral dosing. Five medical students were enrolled in a prospective crossover study. All subjects received a single dose of cyclosporine on four separate occasions, once orally, once as an olive-oil enema, once as a water enema, and once i.v. Cyclosporine concentration was measured in blood and in colonic tissue obtained by flexible sigmoidoscopy. Bioavailability was 18 +/- 7% (mean +/- SD) for the oral dose and was unmeasurable for the oil and water enemas. The concentration of cyclosporine in colon tissue was 32,443 +/- 17,251 ng/g (mean +/- SD) for the i.v. dose, 2797 +/- 1812 ng/g for the oral dose, 21,727 +/- 14,090 ng/g for the oil enema, and 25,318 +/- 30,408 ng/g for the water enema. The authors conclude that the bioavailability of cyclosporine, and thus the systemic absorption after administration by a retention enema, is negligible. The colonic tissue concentration of cyclosporine after i.v. or rectal administration via an enema is tenfold higher than that for oral dosing. These findings suggest that cyclosporine-retention enemas produce high distal colonic tissue concentrations with negligible systemic absorption after a single dose in healthy subjects and should be evaluated as treatment for patients with left-sided colitis. Because cyclosporine administered by the i.v. route provided sharply higher colonic tissue concentrations than those seen with oral therapy, pulse i.v. cyclosporine should be tried for patients with severe ileitis and colitis.

Do calcium channel blockers have any influence on the immunological status of renal graft recipients on ciclosporin therapy?

We have assessed the peripheral distribution of T cells, using the monoclonal antibodies OKT3, OKT4, OKT8 and LEU7 and the proliferative response to phytohaemagglutinin (PHA), in 10 renal transplant recipients. In each patient, the immunological pattern was evaluated twice, both before and after 1 month of calcium antagonist (calcium channel blockers, CaA) treatment. During treatment with CaA, we have observed both a significant decrease in the mitogenic response to PHA and a significant increase in OKT8 cells. Our data support the hypothesis that CaAs per se may have an immunomodulatory effect on T cell distribution independently of changes in ciclosporin (CS) blood levels. These results could also provide a cellular basis for synergism between CS and CaA.

The effect of calcium channel blockers on the cyclosporine dose requirement in renal transplant recipients.

Thirteen patients found to be hypertensive following renal transplantation were treated with either a calcium channel blocker or other antihypertensive therapy for control of blood pressure. Immunosuppression was either with cyclosporine and prednisone alone or with cyclosporine, azathioprine, and prednisone. Patients had weekly or biweekly cyclosporine whole-blood levels measured by radioimmunoassay drawn approximately 12 h after their last dose. Patients treated with cyclosporine and prednisone alone had their cyclosporine dosage adjusted to maintain their cyclosporine level between 400 and 900 ng/mL between 1 and 6 months following transplantation. Patients treated with cyclosporine, azathioprine, and prednisone had their cyclosporine level adjusted to be between 100 and 400 ng/mL during this same time period. Cyclosporine levels were significantly higher in verapamil-treated patients and significantly lower in nifedipine-treated patients as compared to controls. The dose of cyclosporine administered was significantly lower in the verapamil-treated patients and higher in the nifedipine-treated patients than controls. Normalizing the whole-blood cyclosporine level for the dose of cyclosporine, and verapamil-treated patients had a significantly greater, and the nifedipine-treated patients a significantly lower value than control patients. These data suggest the verapamil treatment results in significantly higher levels of cyclosporine whereas nifedipine therapy may actually result in lower cyclosporine levels for a given dose of cyclosporine than seen in patients not exposed to these drugs.

Effects of nitrendipine on blood pressure and blood ciclosporin A level in patients with posttransplant hypertension.

In order to evaluate the antihypertensive effectiveness and interaction with ciclosporin A (CS-A) nitrendipine, a dihydropyridine derivative calcium entry blocking agent, was used in 16 (13 men, 3 women) hypertensive renal posttransplant patients followed by the Nephrology Department of Hacettepe University Hospital. The patients did not receive any antihypertensive drug for a 7-day period. They were then given 20 mg/day nitrendipine for 3 weeks. At the end of this period, mean (+/- SE) supine blood pressure fell from 163/108 +/- 3.6/1.87 to 141/87 +/- 3.8/2.2 mm Hg (p less than 0.01), while the heart rate was unchanged. 14 of 16 patients achieved full control of blood pressure levels with 20 mg/day nitrendipine, and only 2 patients needed a higher dosage of 30 mg/day (20 + 10 mg). After 3 weeks of treatment no significant variations in blood chemistry or renal functional parameters were noticed. There was also no difference between blood CS-A levels before and after treatment with nitrendipine (218.06 +/- 33 vs. 222.68 +/- 26 ng/ml, p greater than 0.05). We conclude that short-term therapy with nitrendipine in renal post-transplant patients does not appear to be harmful and longer term studies are needed to fully evaluate safety and efficacy of this drug. Because it influences neither blood chemistry nor renal functional parameters and blood CS-A level, it may be preferable to other calcium channel blocking agents in this group of patients.

Neurologic complications of liver transplantation.

Nineteen adult patients underwent 21 orthotopic liver transplants at the Cleveland Clinic between November 1984, and August 1986. Eight of 19 (42%) patients developed seizures. One patient suffered a single seizure, and seven patients had multiple, generalized seizures. Two of these seven patients became comatose after several days of seizure activity. Over several weeks, both of these patients regained consciousness--however, they exhibited a cerebellar-type syndrome, manifested as severe ataxia, weakness, and dysarthria. Both patients have improved, but remain neurologically impaired. Laboratory evaluation included serum electrolytes, magnesium, osmolality, and cyclosporine levels. Neurologic testing consisted of cerebrospinal fluid (CSF) analysis, computed tomographic (CT) scanning, and electroencephalography (EEG). Although the CSF protein was mildly elevated in two patients, all cultures remained sterile. None of the CT scans demonstrated any abnormalities. In five patients, the EEG showed generalized slowing consistent with diffuse encephalopathy. Other factors associated with seizures in transplant patients were analyzed, including fluid retention, hypertension, high-dose steroids, hypomagnesemia, graft dysfunction, and demyelinization. Many of our patients had the first three of these factors, since all but one developed their seizures within the first ten postoperative days. Only one patient had mild hypomagnesemia. Trough cyclosporine levels (whole blood, HPLC) were not in the toxic range (greater than 500 ng/mL). The serum osmolality was elevated in all four patients in whom it was measured, ranging from 309 to 341 mOsm/kg. Only three patients exhibited graft dysfunction--two moderate and one severe. The cause of neurologic toxicity following transplantation is unclear. Although many factors have been implicated, no common denominator has emerged. Several reports have linked cyclosporine with seizures and other neurologic problems, such as the cerebellar-type syndrome exhibited in two of our patients. Future studies should include magnetic resonance (MR) imaging of the head and measuring osmolality and cyclosporine levels in the blood and CSF.

Influence of the hepatic drug-metabolizing enzyme-inducer phenobarbitone on cyclosporine nephrotoxicity and hepatotoxicity in renal-allografted rats.

We have investigated the influence of phenobarbitone ([PB]; 40 mg/kg/day), an inducer of hepatic drug metabolism, on high-dose cyclosporine ([CsA] 40 mg/kg/day) nephrotoxicity in normal Lewis (Lew) and renal allografted (DA X Lew F1----Lew) rats of both sexes. In untreated normal animals, CsA nephrotoxicity, assessed biochemically and histologically, in terms of acute and chronic renal structural damage, was consistently greater in male than in female rats. The capacity of PB to induce CsA metabolism was accompanied in normal rats by reductions in nephro- and hepatotoxicity and by prolonged survival of both female and male rats. Similar reductions in CsA-induced renal functional impairment and acute tubular cell injury were achieved in transplanted female (but not male) animals by concomitant PB administration. Continuous PB treatment in transplanted rats was, however, associated with the appearance of hepatic necrosis. While this effect of PB, and its failure to reduce CsA-induced chronic renal damage mitigate against its prospective value in reversing CsA toxicity, PB may nevertheless prove valuable in assessing further the role of drug metabolism in the pathogenesis of CsA nephrotoxicity.

(Nva2)-cyclosporine--less potent than cyclosporine A in rats with lung and heart transplants.

The ability of a new cyclosporine (Cs) derivative, (Nva2)-Cs (CsG), to suppress rejection of lung and heart allografts in rats was determined and compared with that of CsA. Left lungs were transplanted orthotopically; hearts were transplanted heterotopically into the abdomen. (Nva2)-Cs was used in three experimental protocols: (1) single or three (Nva2)-Cs injections given to lung-transplanted rats, (2) daily oral (Nva2)-Cs treatment at different doses compared with similar CsA treatments in heart allografted rats, and (3) An 11-day (Nva2)-Cs treatment starting at increasing intervals after transplantation of hearts. (Nva2)-Cs was found to be immunosuppressive, and effective even when the treatment started as late as four days after transplantation. However, (Nva2)-Cs was less effective than CsA in suppressing rejection of lung and heart allografts at low doses. Because (Nva2)-Cs is possibly not nephrotoxic, it might be a useful drug if used in higher doses than CsA or in combination with other immunosuppressive agents.

A comparison of cyclosporine A and Nva2-cyclosporine (cyclosporine G) in a rat renal allograft model.

We compared CsG and CsA in the DA-to-Lewis rat renal allograft model. At equivalent oral doses, plasma radioimmunoassay (RIA) CsG levels were higher than CsA (P less than 0.02). Neither drug prevented rejection at doses of 5 mg/kg/day. CsG-treated rats had a higher rejection rate at doses of 7.5 mg/kg/day (P less than 0.05). Both drugs were equally effective in preventing rejection at doses of 10 mg/kg/day. Neither drug was nephrotoxic at the doses used in this study. CsG is a potent immunosuppressant, and thus a potential clinical successor to CsA. Since CsG and CsA provide equivalent immunosuppression at therapeutic doses, CsG's clinical significance will ultimately depend on its nephrotoxicity in man.

Absorption of cyclosporine from rabbit small intestine in situ.

The absorption of the immunosuppressive drug, cyclosporine, from intestinal segments in the anesthetized rabbit in situ is reported. The experimental technique allows serial blood sampling with simultaneous sampling of the intestinal perfusate. The method of Loo and Riegelman for estimating the systemically absorbed fraction of the drug was used in conjunction with the in situ method. Taking the length of the rabbit small intestine as 300 cm and using the apparent permeability of cyclosporine determined in polyethylene glycol 400 (PEG 400) at a bulk fluid flow rate of 0.27 mL/min, the anatomical reserve length for cyclosporine was calculated to be -302 cm. The studies demonstrate that a significant portion of the loss of cyclosporine from rabbit small intestine cannot be accounted for as systemically absorbed drug. Furthermore, the apparent permeability coefficient of cyclosporine in these studies is so low that the length of small intestine in the rabbit is not sufficient for complete absorption of the drug from the lumen under the conditions used.

A comparison of the effects of topical cyclosporine and topical steroid on rabbit corneal allograft rejection.

A comparison was made of the effects of topically applied cyclosporine, and topically applied prednisolone acetate, on the prolongation of corneal allograft survival in a recently developed prevascularized rabbit eye model. Animals were treated four times daily for 28 days postgrafting. Both drugs prolonged graft survival when compared with placebo or no treatment but the corticosteroid was significantly more effective than cyclosporine. Furthermore, anterior segment inflammation and graft vascularization were considerably less marked in animals treated with steroid. No cyclosporine could be detected by radioimmunoassay in anterior chamber fluid removed by paracentesis from grafted animals treated with cyclosporine, suggesting poor absorption of the drug across the cornea.