Pharmacokinetic, pharmacodynamic, and pharmacotoxic profiles of recombinant-methionyl human interleukin-2[alanine-125] (r-metHuIL-2[ala-125]) following intravenous and subcutaneous administration in rats.

Comparative pharmacotoxicity studies in rats were performed to evaluate the response to r-metHuIL-2[ala-125] following 2 or 4 weeks of daily intravenous or subcutaneous administration, as well as to evaluate pharmacokinetic and pharmacodynamic responses. Pharmacokinetic analysis indicated that r-metHuIL-2[ala-125] showed high bioavailability and nonlinear concentration profiles. Pharmacodynamic responses to intravenous or subcutaneous dosing with r-metHuIL-2[ala-125], as measured by white blood cell counts, were comparable. Preclinical safety studies (6, 30, and 150 micrograms kg-1 day-1) indicated that r-metHuIL-2[ala-125], whether given intravenously or subcutaneously, was associated with increased circulating and infiltrating levels of lymphocytes and eosinophils. Bone marrow lymphoid hyperplasia and splenic extramedullary hematopoiesis were similarly observed in each study. This pattern of effects was considered an exaggerated pharmacodynamic response to r-metHuIL-2[ala-125]. Of further note was a histopathologic finding described as hepatocyte single cell necrosis which was observed following both intravenous and subcutaneous administration and was considered to be a toxic response to high doses of r-metHuIL-2[ala-125]. The no observable adverse effect level (NOAEL) for r-metHuIL-2[ala-125] via intravenous administration was 6 micrograms kg-1 day-1, while that for subcutaneous administration was 30 micrograms kg-1 day-1. Data herein present a form of rHuIL-2 with pharmacokinetic and pharmacodynamic profiles that are similar when given by these two systemic routes. Pharmacotoxic data, based on NOAELs, suggest that subcutaneous administration may be a preferred clinical route of administration.

Nonlinear pharmacokinetics of recombinant human macrophage colony-stimulating factor (M-CSF) in rats.

The pharmacokinetics and mechanisms of elimination of recombinant human macrophage-colony stimulating factor (M-CSF) were investigated in rats. Intravenous injections of 0.1, 1 or 10 mg/kg M-CSF were administered and plasma samples were measured for M-CSF by bioassay. Systemic clearance decreased and the shape of the concentration-time curve changed with increasing dose, indicating nonlinear pharmacokinetics. At 10 mg/kg, two half-lives were initially observed, but after about 20 hr the plasma M-CSF suddenly declined with a steep slope. The rapidly declining phase suggested a saturable clearance mechanism that was prominent at low plasma concentrations of M-CSF (below 300 ng/ml) and obscured at high plasma concentrations of M-CSF. The rapid decline of plasma M-CSF occurred at earlier times with multiple daily injections of M-CSF, indicating induction of the saturable clearance mechanism. The rapidly declining phase was inhibited by carrageenan, indicating that saturable clearance might be due to metabolism of M-CSF by macrophages. With ligation of either the renal pedicles or ureters, the apparent half-lives of M-CSF increased by a factor of 2- to 3-fold, while the occurrence of the rapidly declining phase was delayed, but not eliminated. Overall, the results are well described by a two-compartment, first-order elimination model with a parallel Michaelis-Menten elimination pathway. First-order elimination is largely performed by the kidneys and the saturable Michaelis-Menten elimination pathway appears to be mediated by cells of the monocyte-macrophage lineage.

Relationship of effective molecular size to systemic clearance in rats of recombinant interleukin-2 chemically modified with water-soluble polymers.

We have examined the effects of a variety of chemical modifications to recombinant human interleukin-2 (rIL-2) on its pharmacokinetic behavior in rats. Unmodified rIL-2 is cleared from plasma with half-lives of 3 and 44 min for the alpha and beta phases. Modification of rIL-2 with monomethoxy polyethylene glycol or polyoxyethylated glycerol increased the half-lives as much as 20-fold, although the volume of distribution remained unchanged at 88 +/- 13 ml/kg. The clearance rates correlated with the effective molecular size of the modified protein determined by size exclusion chromatography. Clearance decreased rapidly as the effective molecular size increased from 19.5 to 70 kDa, whereas above 70 kDa the clearance decreased more slowly. This abrupt change at 70 kDa may be related to the permeability threshold of the kidney glomerular membrane which retains proteins larger than albumin in the plasma. Using the relationship between clearance and effective molecular size, the clearance rates of mixtures of modified rIL-2 could be predicted based on their average effective molecular size. Since the effectiveness of rIL-2 therapy is likely to be related to its pharmacokinetic behavior, the ability to design a molecule with a predictable time course in plasma provides a means to study this relationship.

Another surgical approach for vasculogenic impotence.

Until recently, a defect in the capability of blood to be trapped in the corpus cavernosum so that adequate penile turgidity can be maintained for successful intercourse has not been considered a major etiology for impotence. A diagnostic test called dynamic cavernosography was developed that consists of a cine-taped cavernosogram in conjunction with intracavernous pressure measurements at 3 different cavernous infusion rates. The results of 104 of these tests are presented. More recently, 17 of these patients also have undergone papaverine tests. Of the patients 59 per cent had no or only partial erections at all infusion rates and pressure did not increase to greater than 50 mm. Hg. The papaverine test showed only partial or no tumescence when 60 mg. were injected into the corpora. As a result, 25 patients underwent a penile operation to remove some venous outflow channels. Of the patients who underwent an operation for absent tumescence at any flow rate and who had a large number of venous channels draining the corpora cavernosa on the cavernosogram 59 per cent were potent postoperatively.

Pathogenic significance of P-fimbriated Escherichia coli in urinary tract infections.

The over-all aim of this study was to determine the pathogenic significance, and bacteriological and serological characteristics of P-fimbriated organisms isolated from a general population of patients with bacteriuria. A P-receptor specific particle agglutination test was used to identify P-fimbriated bacteria among 2,010 isolates from male and female patients with bacteriuria (age range infancy to 91 years). Of the 2,010 isolates 206 (10.2 per cent) were positive for P-fimbriae by the P-receptor specific particle agglutination test. Only Escherichia coli was found to be P-fimbriated, with an incidence of 21.5 per cent among 956 Escherichia coli isolates. The critical characteristic of pyelonephritic strains of Escherichia coli was P-fimbriation. In cases of nonobstructive acute pyelonephritis 100 per cent of the infecting bacteria were P-fimbriated. The data indicated clearly that the serotype, biotype, presence of type 1 fimbriae (mannose sensitive), undefined mannose-resistant adhesions, hemolysin production and motility of P-fimbriated Escherichia coli were clinically unimportant differential strain characteristics and not indicative of the virulence of P-fimbriated Escherichia coli within clinical syndromes. Isogenic P-fimbriated Escherichia coli strains were isolated from noncompromised patients in all clinical categories, that is pyelonephritis, asymptomatic bacteriuria and cystitis. A variety of bacterial strains appears to be capable of causing acute pyelonephritis in the presence of obstructive uropathic conditions, regardless of P-fimbriation. Therefore, P-fimbriation becomes a noncritical factor in compromised patients. The P-receptor specific particle agglutination test is a simple and rapid method to determine whether bacteria are P-fimbriated and may be an important screening method to identify those bacteria isolated from individuals at risk for nonobstructive acute pyelonephritis.