Preclinical absorption, distribution, metabolism and excretion (ADME) characterization of ICAM1988, an LFA-1/ICAM antagonist, and its prodrug.

Intercellular adhesion molecule (ICAM)-1988 is a small molecule lymphocyte function-associated antigen-1 (LFA-1) antagonist being considered for its anti-inflammatory properties. Following intravenous administration of ICAM1988, clearances in mice, rats, dogs, and monkeys were 17.8, 3.31, 15.4, and 6.85 ml min(-1) kg(-1), respectively. In mass balance studies using [(14)C]-ICAM1988 in rats dosed intravenously, unchanged ICAM1988 contributed to 25.1% of the dose. In rats, the systemic bioavailability of ICAM1988 was improved to 0.28 when the drug was administered orally as its isobutyl ester, ICAM2660. In rats, this was consistent with the complete in vitro conversion of ICAM2660 to ICAM1988 in plasma, and liver and intestinal S9. In dogs and monkeys, ICAM2660 did not improve the bioavailability of ICAM1988. This is consistent with limited in vitro conversion of ICAM2660 to ICAM1988 in plasma and liver S9. In human in vitro studies, ICAM2660 conversion to ICAM1988 in liver was similar to rats while no conversion in plasma and intestinal S9 fractions were observed. Based on the in vitro metabolism similarities of human and rat, it would be anticipated that in human oral administration of ICAM2660 would improve the systemic exposure of ICAM1988.

Pharmacokinetics of insulin-like growth factor I in hypopituitarism: correlation with binding proteins.

We investigated the pharmacokinetics of recombinant human insulin-like growth factor I (rhIGF-I) in growth hormone deficiency (GHD). Nine GHD adults [age 25 +/- 3 (SE) yr] received rhIGF-I (60 microgram/kg sc) twice, 10 h apart, and blood was sampled over 24 h. IGF-I and free IGF-I concentrations increased, whereas IGF binding protein 3 (IGFBP-3) and acid labile subunit (ALS) were unchanged during treatment. There was no correlation between absorption or terminal half-life of IGF-I and IGFBP-3 or ALS, but negative correlations with IGF-I clearance (CL/F) and volume of distribution (V/F). Positive correlations between both IGFBP-3 and ALS and IGF-I maximal concentration (C(max)) and time of C(max) (T(max)) were observed. Compared with normal individuals studied similarly (using 80 microgram/kg), GHD subjects showed a normal absorption half-life, a faster elimination half-life, lower C(max), yet normal T(max) and V/F. In conclusion, GHD is associated with normal absorption and distribution of IGF-I yet faster elimination kinetics. Additionally, IGFBP-3 and ALS concentrations modulate the peak concentrations of IGF-I achieved and correlate reciprocally with its V/F and CL/F, underscoring the critical importance of binding proteins in modulating the bioavailability of IGF-I in vivo in humans.

A single dose of thrombopoietin shortly after myelosuppressive total body irradiation prevents pancytopenia in mice by promoting short-term multilineage spleen-repopulating cells at the transient expense of bone marrow-repopulating cells.

Thrombopoietin (TPO) has been used in preclinical myelosuppression models to evaluate the effect on hematopoietic reconstitution. Here we report the importance of dose and dose scheduling for multilineage reconstitution after myelosuppressive total body irradiation (TBI) in mice. After 6 Gy TBI, a dose of 0.3 microgram TPO/mouse (12 microgram/kg) intraperitoneally (IP), 0 to 4 hours after TBI, prevented the severe thrombopenia observed in control mice, and in addition stimulated red and white blood cell regeneration. Time course studies showed a gradual decline in efficacy after an optimum within the first hours after TBI, accompanied by a replacement of the multilineage effects by lineage dominant thrombopoietic stimulation. Pharmacokinetic data showed that IP injection resulted in maximum plasma levels 2 hours after administration. On the basis of the data, we inferred that a substantial level of TPO was required at a critical time interval after TBI to induce multilineage stimulation of residual bone marrow cells. A more precise estimate of the effect of dose and dose timing was provided by intravenous administration of TPO, which showed an optimum immediately after TBI and a sharp decline in efficacy between a dose of 0.1 microgram/mouse (4 microgram/kg; plasma level 60 ng/mL), which was fully effective, and a dose of 0.03 microgram/mouse (1.2 microgram/kg; plasma level 20 ng/mL), which was largely ineffective. This is consistent with a threshold level of TPO required to overcome initial c-mpl-mediated clearance and to reach sufficient plasma levels for a maximum hematopoietic response. In mice exposed to fractionated TBI (3 x 3 Gy, 24 hours apart), IP administration of 0. 3 microgram TPO 2 hours after each fraction completely prevented the severe thrombopenia and anemia that occurred in control mice. Using short-term transplantation assays, ie, colony-forming unit-spleen (CFU-S) day 13 (CFU-S-13) and the more immature cells with marrow repopulating ability (MRA), it could be shown that TPO promoted CFU-S-13 and transiently depleted MRA. The initial depletion of MRA in response to TPO was replenished during long-term reconstitution followed for a period of 3 months. Apart from demonstrating again that MRA cells and CFU-S-13 are separate functional entities, the data thus showed that TPO promotes short-term multilineage repopulating cells at the expense of more immature ancestral cells, thereby preventing pancytopenia. The short time interval available after TBI to exert these effects shows that TPO is able to intervene in mechanisms that result in functional depletion of its multilineage target cells shortly after TBI and emphasizes the requirement of dose scheduling of TPO in keeping with these mechanisms to obtain optimal clinical efficacy.

Pharmacokinetics of insulin-like growth factor-1 in advanced chronic renal failure.

Information regarding the impact of chronic renal failure (CRF) on IGF-1 serum clearance is limited. Thus we evaluated the pharmacokinetics of insulin-like growth factor-1 (IGF-1) in six normal adults and six adults with advanced CRF (serum creatinine 7 +/- 0.8 mg/dl). All subjects were given 80 micrograms/kg recombinant human IGF-1 s.c. and blood was sampled over 48 hours. Baseline total serum IGF-1 levels were similar in both groups, but peak levels were elevated significantly in CRF; this was apparently related to the reduced distribution volume in CRF subjects. CRF did not affect the metabolic clearance rate (MCR) of total serum IGF-1. Immunoreactive IGF binding protein-3 (IGFBP-3) levels were greater in CRF. Western immunoblots revealed that the apparent increase in IGFBP-3 was largely due to an increase in immunoreactive fragments. IGFBP-3 protease activity was not increased. Thus IGFBP fragment accumulation likely reflects reduced fragment clearance. Western ligand blots revealed elevated 30 and 34 kDa IGFBP levels and IGFBP products in CRF serum. Serum acid labile subunit levels were unchanged in CRF. Peak free IGF-1 levels and the MCR of free IGF-1 did not differ between groups. In both groups the MCR of free IGF-1 exceeded the MCR of total IGF-1 by approximately 30-fold. These data suggest that in CRF patients receiving s.c. IGF-1: (a) total serum IGF-1 levels are increased as a result of elevated circulating IGFBPs that may restrict the distribution of IGF-1 beyond plasma; (b) serum free IGF-1 levels are not altered; and (c) the IGF-1 MCR is unchanged in CRF. Thus, in advanced CRF, apart from a reduction in the total IGF-1 volume of distribution the pharmacokinetics of IGF-1 are largely unaltered.

Kidney as a major clearance organ for recombinant human interleukin-1 receptor antagonist.

This study was designed to provide information on the tissue distribution and elimination of recombinant human interleukin-1 receptor antagonist (rhIL-1ra) in rats. Following intravenous (iv) bolus administration of metabolically labeled [35S]rhIL-1ra alone or together with unlabeled rhIL-1ra, biodistribution of [35S]rhIL-1ra in the early phase as well as at steady state was investigated. The renal elimination of rhIL-1ra at steady state was also studied. In the early phase biodistribution study, 11, 9, 6, and 2% of the dose was distributed to the kidney, liver, gut, and lung, respectively. Additional rhIL-1ra was found in muscle (43%) and plasma (26%). The time profiles of [35S]rhIL-1ra in the kidney and liver were analyzed by integration plots to determine the early-phase distribution clearance of [35S]rhIL-1ra. The distribution clearance of [35]rhIL-1ra per gram of kidney was five times greater than that of the liver. When expressed as clearance per organ, total liver clearance and total renal clearance were comparable, together accounting for approximately 20% of plasma clearance in the early phase. The distribution clearances of [35S]rhIL-1ra in these tissues (liver and kidney) were not affected by coadministration of excess unlabeled rhIL-1ra (5 mg/rat), indicating that clearance occurs via a mechanism having a high capacity for rhIL-1ra. The steady-state biodistribution of rhIL-1ra was also studied to examine the accumulation of rhIL-1ra in the tissues. The tissue-to-plasma concentration ratios at steady state were similar to the corresponding extracellular spaces in the tissues investigated except the kidney, where the ratio was 4.10.(ABSTRACT TRUNCATED AT 250 WORDS)

Reduced muscle protein breakdown in septic rats following treatment with interleukin-1 receptor antagonist.

1. The role of interleukin-1 (IL-1) in sepsis-induced muscle proteolysis was assessed by treating septic rats with recombinant IL-1 receptor antagonist (rIL-1ra). 2. In initial experiments, we tested the effectiveness of IL-1ra in preventing muscle proteolysis induced by administration of IL-1. 3. When normal rats were treated with rIL-1 alpha (three intraperitoneal doses of 100 micrograms/kg body weight each over 16 hr), total and myofibrillar muscle protein breakdown rates, measured as release of tyrosine and 3-methylhistidine, respectively, by incubated extensor digitorum longus muscles, were significantly increased. 4. This metabolic response to IL-1 alpha was completely abolished by rIL-1ra, administered as three intraperitoneal doses of 3 mg/kg body weight each over 16 hr. 5. In subsequent experiments, sepsis was induced in rats by cecal ligation and puncture (CLP); non-septic rats were sham-operated. 6. Treatment of septic rats over 16 hr with a total dose of 25 mg/kg body weight of rIL-1ra reduced, but did not normalize, the increased muscle protein breakdown rates seen during sepsis. 7. When the dose of rIL-1ra was more than doubled and given as a constant infusion at a rate of 4.2 mg/kg body weight/hr for 16 hr, the increased rate of muscle proteolysis in septic rats was normalized. 8. The present study offers the first direct evidence that IL-1 is involved in the regulation of muscle proteolysis during sepsis.

Interleukin-1 receptor antagonist decreases bone loss and bone resorption in ovariectomized rats.

Interleukin-1 (IL-1), a cytokine produced by bone marrow cells and bone cells, has been implicated in the pathogenesis of postmenopausal osteoporosis because of its potent stimulatory effects on bone resorption in vitro and in vivo. To investigate whether IL-1 plays a direct causal role in post ovariectomy bone loss, 6-mo-old ovariectomized rats were treated with subcutaneous infusions of IL-1 receptor antagonist (IL-1ra), a specific competitor of IL-1, for 4 wk, beginning either at the time of surgery or 4 wk after ovariectomy. The bone density of the distal femur was measured non invasively by dual-energy X-ray absorptiometry. Bone turnover was assessed by bone histomorphometry and by measuring serum osteocalcin, a marker of bone formation, and the urinary excretion of pyridinoline cross-links, a marker of bone resorption. Ovariectomy caused a rapid increase in bone turnover and a marked decrease in bone density which were blocked by treatment with 17 beta estradiol. Ovariectomy also increased the production of IL-1 from cultured bone marrow cells. Ovariectomy induced-bone loss was significantly decreased by IL-1ra treatment started at the time of ovariectomy and completely blocked by IL-1ra treatment begun 4 wk after ovariectomy. In both studies IL-1ra also decreased bone resorption in a manner similar to estrogen, while it had no effect on bone formation. In contrast, treatment with IL-1ra had no effect on the bone density and the bone turnover of sham-operated rats, indicating that IL-1ra specifically blocked estrogen-dependent bone loss. In conclusion, these data indicate that IL-1, or mediators induced by IL-1, play an important causal role in the mechanism by which ovariectomy induces bone loss in rats, especially following the immediate post ovariectomy period.

Intraocular diclofenac and flurbiprofen concentrations in human aqueous humor following topical application.

Flurbiprofen Na and diclofenac Na, two ocular antiinflammatory agents, were investigated to determine the aqueous humor concentrations in the human eye following topical application. One hundred sixty-five patients undergoing cataract surgery received a single drop of either diclofenac Na or flurbiprofen Na at selected times prior to the surgical procedure. Aqueous humor samples were aspirated at the beginning of surgery and a sensitive high-performance liquid chromatographic assay was used to determine the concentration of the antiinflammatory agent in the ocular fluid. Samples were obtained between 10 min and 24 hrs after a single instillation of the drug onto the cornea. The highest average concentration of diclofenac was 82 ng/ml at 2.4 hrs after instillation; concentrations remained above 20 ng/ml for over 4 hrs. Thereafter, between 3 and 16 ng/ml diclofenac could be assayed through 24 hrs. The highest average concentration of flurbiprofen, 60 ng/ml, was found at 2.0 hrs. The last detectable flurbiprofen concentration was measured at 7.25 hrs after instillation.

Initial evaluation of human recombinant interleukin-1 receptor antagonist in the treatment of sepsis syndrome: a randomized, open-label, placebo-controlled multicenter trial.

OBJECTIVES: To evaluate the safety, pharmacokinetics, and efficacy of human recombinant interleukin-1 receptor antagonist (IL-1ra) in the treatment of patients with sepsis syndrome. DESIGN: Prospective, open-label, placebo-controlled, phase II, multicenter clinical trial using three different doses of human recombinant IL-1ra. SETTING: Twelve academic medical center intensive care units in the United States. PATIENTS: Ninety-nine patients with sepsis syndrome or septic shock who received standard supportive care and antimicrobial therapy, in addition to infusion with escalating doses of IL-1ra or placebo. INTERVENTIONS: Patients received an intravenous loading dose of either human recombinant IL-1ra (100 mg) or placebo, followed by a 72-hr intravenous infusion of either one of three doses of IL-1ra (17, 67, or 133 mg/hr) or placebo. All patients were evaluated for 28-day, all-cause mortality. MEASUREMENTS AND MAIN RESULTS: A dose-dependent, 28-day survival benefit was associated with IL-1ra treatment (p = .015), as indicated by the following mortality rates: 11 (44%) deaths among 25 placebo patients; eight (32%) deaths among 25 patients receiving IL-1ra 17 mg/hr; six (25%) deaths among 24 patients receiving IL-1ra 67 mg/hr; and four (16%) deaths among 25 patients receiving IL-1ra 133 mg/hr. A dose-related survival benefit was observed with infusion of IL-1ra in patients with septic shock at study entry (n = 65; p = .002) and in patients with Gram-negative infection (n = 45; p = .04). Patients with an increased circulating interleukin-6 (IL-6) concentration of > 100 pg/mL at study entry demonstrated a dose-related survival benefit with IL-1ra treatment (p = .009). In patients with an increased IL-6 concentration at study entry, the magnitude of the decrease in IL-6 concentration 24 hrs after the initiation of therapy was correlated with increasing the IL-1ra treatment dose (p = .052). A significant dose-related reduction in the Acute Physiology and Chronic Health Evaluation (APACHE II) score was achieved by the end of infusion (p = .038). A renal elimination mechanism for IL-1ra was suggested by the positive correlation between IL-1ra plasma clearance and estimated creatinine clearance (p = .001; r2 = .51). Human recombinant IL-1ra was well tolerated. CONCLUSIONS: This initial evaluation suggests that human recombinant IL-1ra is safe and may provide a dose-related survival advantage to patients with sepsis syndrome. A larger, definitive clinical trial is needed to confirm these findings.

Pharmacokinetics, safety and immunomodulatory effects of human recombinant interleukin-1 receptor antagonist in healthy humans.

A phase I study of human recombinant interleukin-1 receptor antagonist (IL-1ra) was conducted in healthy males between the ages of 18 and 30. Twenty-five volunteers received a single, 3 h continuous intravenous infusion of doses ranging between 1 mg/kg and 10 mg/kg IL-1ra. At 3 h into the infusion, plasma IL-1ra levels were 3.1 micrograms/ml and 29 micrograms/ml for the 1 mg/kg and 10 mg/kg doses, respectively. Post-infusion plasma IL-1ra levels declined rapidly, exhibiting an initial half-life of 21 min and a terminal half-life of 108 min. Clinical, hematological, biochemical, endocrinological and immunomodulatory effects were monitored over 72 h and compared to those of four subjects receiving a 3 h infusion of saline. There were no clinically significant differences between the drug and saline groups in symptoms, physical examinations, complete blood counts, mononuclear cell phenotypes, blood chemistry profiles, serum iron and serum cortisol levels. Peripheral blood mononuclear cells (PBMC) obtained after completion of the IL-1ra infusion synthesized significantly less interleukin 6 ex vivo than PBMC from saline-injected controls. These data suggest that transient blockade of interleukin 1 receptors is safe and does not significantly affect homeostasis.

Intravenous recombinant secretory leukoprotease inhibitor augments antineutrophil elastase defense.

Secretory leukoprotease inhibitor (SLPI), a 12-kDa serine antiprotease, normally protects the upper airway epithelial surface from attack by neutrophil elastase (NE). In the context that a variety of inflammatory lung diseases are characterized by large neutrophil burdens with resultant high levels of NE in the lung, recombinant SLPI (rSLPI), a molecule identical to natural SLPI, may be an effective means to augment the anti-NE protective screen of the lung. To determine whether intravenous rSLPI will augment respiratory tract and epithelial surface levels of SLPI and anti-NE capacity, rSLPI was administered intravenously to sheep and SLPI levels were quantified in plasma, lung lymph (as a measure of lung interstitial levels), lung epithelial lining fluid (ELF), and urine. rSLPI (1 g) was administered over 10 min, and after 30 min plasma levels of SLPI were 8 microM and decreased with a half-life of 1.8 h. Lymph SLPI levels paralleled the plasma levels: 4 h after infusion the lymph-to-plasma ratio was 0.8. ELF SLPI levels paralleled the lymph levels: 4 h after infusion the ELF-to-lymph ratio was 0.3. Western analysis demonstrated intact SLPI in lymph and ELF, and functional analysis showed increases in lymph and ELF anti-NE capacity that paralleled the levels of SLPI. As might be expected from a protein with a molecular mass of 12 kDa, urine excretion was high, with 20% of the SLPI excreted over 5 h. However, if the rate of infusion was slowed, SLPI excretion decreased significantly, with a 3-h infusion associated with 9% excretion and a 12-h infusion associated with less than 0.2% excretion.(ABSTRACT TRUNCATED AT 250 WORDS)

Interleukin-1 receptor blockade improves survival and hemodynamic performance in Escherichia coli septic shock, but fails to alter host responses to sublethal endotoxemia.

The present study was undertaken to evaluate the extent to which an endogenous interleukin-1 (IL-1) response contributes to the hemodynamic and metabolic consequences of sublethal endotoxemia or lethal Gram-negative septic shock. Young, healthy baboons received either a sublethal dose of lipopolysaccharide (LPS) or an LD100 of live Escherichia coli bacteria, and one half of the animals in each group were continuously infused with IL-1 receptor antagonist (IL-1ra). Plasma IL-1 beta was not detected in this model of endotoxemia. Administration of IL-1ra had only minimal effects on the modest hemodynamic and metabolic responses to sublethal endotoxemia, and did not attenuate the plasma cytokine response. In contrast, high circulating levels of IL-1 beta (range 300-800 pg/ml) were seen during lethal E. coli septic shock. IL-1ra treatment significantly attenuated the decrease in mean arterial blood pressure (MAP) (from -72 +/- 8 to -43 +/- 6 mm Hg; P less than 0.05) and cardiac output (from -0.81 +/- 0.17 to -0.48 +/- 0.15 liter/min; P less than 0.05), and significantly improved survival from 43 to 100% at 24 h (P less than 0.05). The plasma IL-1 beta and IL-6 responses to lethal E. coli septic shock were also significantly diminished by IL-1ra treatment (P less than 0.05), whereas tumor necrosis factor-alpha (TNF alpha) concentrations were unaffected. We conclude that an exaggerated systemic IL-1 beta response is characteristic of lethal E. coli septic shock, and contributes significantly to the hemodynamic and metabolic consequences of E. coli septic shock. IL-1ra can significantly attenuate the cytokine cascade and improve survival.

Effect of nasolacrimal occlusion on timolol concentrations in the aqueous humor of the human eye.

We studied the effect of manual nasolacrimal occlusion on the concentration of timolol in the aqueous humor of eyes of patients undergoing cataract extraction. Aqueous humor samples were obtained at various times after timolol maleate instillation from patients with or without 5 min of nasolacrimal occlusion; aliquots were assayed by HPLC. In patients receiving occlusion treatment, average timolol concentrations were statistically greater than those in control patients both between 15 and 90 min after instillation and also at 180 min. Pharmacokinetic analysis indicated that occlusion increased the concentration of timolol in the aqueous humor 1.7 times. In both groups, timolol concentrations were highest approximately 1 h after instillation. The decline in aqueous humor timolol concentrations occurred at similar rates in both groups.

Methylprednisolone achieves greater concentrations in the lung than prednisolone. A pharmacokinetic analysis.

Previous studies in humans and rabbits demonstrated that methylprednisolone appears in the lung in greater concentration than prednisolone. To ascertain which pharmacokinetic properties of these drugs explain this difference, we gave methylprednisolone and prednisolone, 5 mg/kg intravenous bolus, to 23 adult rabbits. To measure the plasma concentration versus time curves for methylprednisolone and prednisolone, samples were obtained predose through 480 min postdose. To measure the bronchoalveolar lavage glucocorticoid concentration versus time curves, lavage was performed once per experiment at seven separate time points from 5 to 480 min post-dose (two to four experiments per time point). Bronchoalveolar lavage fluid (BALF) recovery ranged from 50 to 75% and was similar in both groups. Glucocorticoid concentration in plasma and BALF was determined by high performance liquid chromatography. To normalize for the dilutional effects of lavage, epithelial lining fluid (ELF) recovery was quantitated from BALF volume and BALF and plasma urea concentrations. Pharmacokinetic parameters of the two glucocorticoids were calculated both noncompartmentally and by a three-compartment model. The extrapolated plasma glucocorticoid concentrations at time zero of methylprednisolone and prednisolone are similar, but the volume of distribution and plasma half-life of methylprednisolone are significantly greater than those of prednisolone (p less than 0.05). Although the clearance of the two drugs are not significantly different, methylprednisolone appears to have a slower Cl than prednisolone. The mean residence time (the average time drug remained in body) was significantly longer for methylprednisolone than for prednisolone (p less than 0.05), and plasma glucocorticoid concentrations became significantly different in the two groups by 90 min (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

A pharmacokinetic model describing the removal of circulating radiolabeled antibody by extracorporeal immunoadsorption.

Extracorporeal immunoadsorption is a new technique for removal of circulating radiolabeled antibody from the peripheral blood (1) to reduce background activity for improved tumor imaging, and (2) to reduce whole-body and marrow toxicity when high doses of radiolabeled antibodies are used for antitumor therapy. A pharmacokinetic model was developed to describe plasma disappearance of 111In-KC-4G3 prior to, during, and after immunoadsorption in humans. The model is developed based on a two-compartment open model, and during immunoadsorption a third compartment is added for removed radioactivity by the immunoadsorption column. Goodness-of-fit statistics indicate a good fit of the model to the data. The resulting pharmacokinetic parameters for a selected patient are V1 = 2.64 L, VSS = 3.64 L, t 1/2 alpha = 3.77 hr, and t 1/2 beta = 48.5 hr. The immunoadsorption clearance (CLIA = 19.3 ml/min) was 21-fold greater than the patient's plasma clearance (CL10 = 0.899 ml/min), indicating a very effective immunoadsorption process. The model predicts an increase in plasma radioactivity upon termination of immunoadsorption, probably due to redistribution of radioactivity from the extravascular compartment to the plasma in response to the rapid decline in plasma radioactivity during immunoadsorption. Two series of simulations were performed to examine the influence of onset time and duration of immunoadsorption. In series one the onset time was varied and in series two immunoadsorption duration was varied. In series one, the predicted radioactivity amounts adsorbed by the immunoadsorption column ranged from 75% of the injected dose (4-hr onset) to 52% of the injected dose (24-hr onset). In series two, immunoadsorbed radioactivity ranged from 32% (2-hr duration) to 64% of the injected dose (12-hr duration). When instituted as early as 4 hr, the predictions suggest that earlier immunoadsorption onset improves the effectiveness of radioactivity removal, relating to higher early circulation concentrations, and longer immunoadsorption periods remove more radioactivity, but also result in larger predicted radioactivity redistribution form tissue to plasma. To employ the immunoadsorption procedure for tumor imaging and therapy optimally, the data and our predictions indicate that a compromise must be made that will balance immunoadsorption onset and duration against tumor radioactivity uptake and subsequent radioactivity redistribution from tissues back to plasma. Together with biologic considerations providing sufficient antigen-antibody interaction and dependent on the utilized radioisotope, these data support the utility of extracorporeal immunoadsorption during the radioimmunodetection of cancer and for future therapeutic applications.

Improved tumor imaging with radiolabeled monoclonal antibodies by plasma clearance of unbound antibody with anti-antibody column.

Imaging of tumors by using radiolabeled monoclonal antibodies (MoAs) is hindered by the presence of background activity. To reduce this problem, the authors investigated the process of removing labeled MoAs from plasma at selected times by means of extracorporeal immunoadsorption. In seven patients with either lung or breast carcinoma, an indium-111-labeled murine antibody was intravenously administered. Six to 24 hours later, immunoadsorption was performed by passing the patients' plasma through a goat anti-mouse antibody column connected to a plasma separator. Whole-body computer images were obtained before and after the treatment. Blood pool activity in the images was reduced by an average of 59%, while tumor activity dropped by only 10%. Tumor-to-blood activity ratios therefore more than doubled, improving by an average of 121% between the pre- and posttreatment image sets. Eight of 12 areas of known disease and three areas of unknown but later documented disease were detected after the immunoadsorption process, while the three areas of unknown disease and three of the areas of known disease were not detected in the preclearance images. Thus, the feasibility of using extracorporeal immunoadsorption to improve MoA imaging of tumors was demonstrated.

Imaging of non-small cell lung cancers with a monoclonal antibody, KC-4G3, which recognizes a human milk fat globule antigen.

To determine the role of lung cancer tumor imaging with monoclonal antibodies directed against high molecular weight human milk fat globule antigens, we administered i.v. 111In-KC-4G3 to 24 patients with advanced non-small cell lung cancer. One mg of 111In-KC-4G3 was mixed with 0, 9, 49, 99, or 499 mg of unlabeled KC-4G3 and infused i.v. over 1 to 5 h. The mean 111In-KC-4G3 radiochemical purity was greater than 97% and the resultant immunoreactivity averaged 62%. Successful imaging of cancer sites was accomplished in 92% of 24 patients, and 57% of 91 total lesions were visualized. Successful localization of tumor sites related to size (P less than 0.001), with 81% of lesions greater than 3.0 cm in diameter, 50% of lesions 1.5 to 3 cm, and 6% of lesions less than 1.5 cm successfully imaging, and to location (P less than 0.05), with 69% of pulmonary lesions, 80% of soft tissue lesions, and only 32% of bone metastases being visualized. Nonspecific reticulo-endothelial uptake of radioactivity was a major problem. Approximately 35% of 111In was chelated to serum transferrin by 24 and 48 h after infusion. The mean t 1/2 beta for plasma radioisotope and immunoreactive KC-4G3 was 29 and 27 h, respectively. There was no correlation between total infused antibody dose and imaging success or between total dose and effect on 111In and KC-4G3 kinetics. Circulating free KC-4 antigen was measurable in all but one patient before study. Tumor biopsy following infusion could demonstrate antibody presence but not saturable antigen binding. We conclude that (a) 111In-KC-4G3 demonstrates successful tumor localization in non-small cell lung cancers bearing generally high expression of its antigen and (b) further investigations to diminish nonspecific radioactivity for imaging and utilization of high dose radiolabeled antibody for therapeutic intent are warranted.

Pharmacokinetics, biodistribution, and gamma camera imaging of 111In-KC-4G3 murine monoclonal antibody in athymic nude mice with or without human tumor xenografts.

The pharmacokinetics and tissue distribution of the monoclonal antibody radioconjugate 111In-diethylenetriaminepentaacetic acid-KC-4G3, which is directed against a high molecular weight mucin(s) antigen expressed on the human milk fat globule and many epithelial cell membranes, were examined in BALB/c nude mice with and without xenografts of the human tumor lines ZR-75 (mammary adenocarcinoma, KC-4G3 antigen positive) and BALL-1 (B-cell lymphoma, KC-4G3 antigen negative). Plasma of ZR-75 and BALL-1 tumor-bearing nude mice inoculated with 111In-KC-4G3 had a higher initial volume of distribution (V1), steady state volume of distribution (Vss), and plasma clearance and a lower initial half-life (t1/2 alpha) than non-tumor-bearing nude mice. There were no significant differences in biological half-life (t1/2 beta) in tumor- and non-tumor-bearing nude mice. Urinary and fecal excretion of radioactivity by ZR-75 tumor-bearing mice was greater than that of BALL-1 and non-tumor-bearing mice. Localization of 111In-KC-4G3 in mice bearing xenografts of ZR-75 was significantly greater than in mice with BALL-1 tumors. Uptake of 111In-KC-4G3 by ZR-75 tumors averaged 14% of injected dose/g at 72 h after inoculation and was unaffected by antibody dose. Significantly, the radioconjugate concentration in ZR-75 tumors remained relatively constant from 72 to 336 h post-inoculation, while that in normal tissues declined considerably over this period. Nonspecific reticuloendothelial tissue uptake of 111In-KC-4G3 was only moderately affected by pretreatment with a large excess of unlabeled normal mouse immunoglobulin and was not changed by treatment with asialofetuin. Further enhancement of specific localization of 111In-KC-4G3 was obtained by subtraction of the blood pool identified by co-inoculation of 131I-labeled, isotype-identical, normal mouse immunoglobulin. Gamma camera images of 111In-KC-4G3-inoculated ZR-75 tumor-bearing mice showed enhanced tumor localization compared to mice with BALL-1 tumors. The results of this study suggest that 111In-KC-4G3 may prove useful for imaging and possibly therapy of human malignancies expressing the high molecular weight epithelial mucin(s).

Evaluation of eight methods for estimating creatinine clearance in men.

Eight methods for estimating creatinine clearance (CLcr) were compared in 65 men with serum creatinine concentrations (SCr) less than or equal to 1.5 mg/dL (group 1) and 65 men with SCr greater than 1.5 mg/dL (group 2). All patients had SCr values that did not fluctuate by more than +/- 10% for two weeks before and two weeks after measurement of CLcr. For each patient, predictions of CLcr by each of eight currently used formulas were compared with measured CLcr values; both regression analysis and predictive error analysis were used. Group 1 patients ranged in age from 32 to 64 years (mean, 53), weighed from 48 to 105 kg (mean, 73), and were from 63 to 79 inches in height (mean, 69). Group 2 patients ranged from 26 to 63 years of age (mean, 53), weighed from 34 to 141 kg (mean, 80), and were from 63 to 76 inches in height (mean, 70). Measured CLcr values ranged from 29.8 to 197 mL/min in group 1 and from 2.8 to 118 mL/min in group 2. Ranges of SCr values were 0.7-1.5 mg/dL (mean, 1.1) in group 1 and 1.6-7.1 mg/dL (mean, 2.8) in group 2; the formula of Cockcroft and Gault, which uses age, body weight, and SCr, had the highest correlation and the greatest accuracy in group 1, whereas the formula of Jelliffe, which uses body surface area and SCr, had the highest correlation and the greatest accuracy in group 2. Estimation of creatinine clearance can be improved by identification and use of the formula that is best suited to a specific patient population.

Propranolol does not impair exercise oxygen uptake in normal men at high altitude.

Decreased maximal O2 uptake (VO2max) and stimulation of the sympathetic nervous system have been previously shown to occur at high altitude. We hypothesized that tachycardia mediated by beta-adrenergic stimulation acted to defend VO2max at high altitude. Propranolol treatment beginning before high-altitude (4,300 m) ascent reduced heart rate during maximal and submaximal exercise in six healthy men treated with propranolol (80 mg three times daily) compared with five healthy subjects receiving placebo (lactose). Compared with sea-level values, the VO2max fell on day 2 at high altitude, but the magnitude of fall was similar in the placebo and propranolol treatment groups (26 +/- 6 vs. 32 +/- 5%, P = NS) and VO2max remained similar at high altitude in both groups once treatment was discontinued. During 30 min of submaximal (80% of VO2max) exercise, propranolol-treated subjects maintained O2 uptake levels that were as large as those in placebo subjects. The maintenance of maximal or submaximal levels of O2 uptake in propranolol-treated subjects at 4,300 m could not be attributed to increased minute ventilation, arterial O2 saturation, or hemoglobin concentration. Rather, it appeared that propranolol-treated subjects maintained O2 uptake by transporting a greater proportion of the O2 uptake with each heartbeat. Thus, contrary to our hypothesis, beta-adrenergic blockade did not impair maximal or submaximal O2 uptake at high altitude due perhaps to compensatory mechanisms acting to maintain stroke volume and cardiac output.