Preclinical development of keliximab, a Primatized anti-CD4 monoclonal antibody, in human CD4 transgenic mice: characterization of the model and safety studies.

The preclinical safety assessment of biopharmaceuticals necessitates that studies be conducted in species in which the products are pharmacologically active. Monoclonal antibodies are a promising class of biopharmaceuticals for many disease indications; however, by design, these agents tend to have limited species cross-reactivity and tend to only be active in primates. Keliximab is a human-cynomolgus monkey chimeric (Primatized) monoclonal antibody with specificity for human and chimpanzee CD4. In order to conduct a comprehensive preclinical safety assessment of this antibody to support chronic treatment of rheumatoid arthritis in patients, a human CD4 transgenic mouse was used for chronic and reproductive toxicity studies and for genotoxic studies. In addition, immunotoxicity studies were conducted in these mice with Candida albicans, Pneumocystis carinii and B16 melanoma cells to assess the effects of keliximab on host resistance to infection and immunosurveillance to neoplasia. The results of these studies found keliximab to be well tolerated with the only effects observed being related to its pharmacologic activity on CD4+ T lymphocytes. The use of transgenic mice expressing human proteins provides a useful alternative to studies in chimpanzees with biopharmaceutical agents having limited species cross-reactivity.

Flow cytometry in the preclinical development of biopharmaceuticals.

Novel biomarkers are often required in the preclinical development of biopharmaceuticals in order to characterize pharmacologic and toxicologic effects and to establish pharmacodynamic and pharmacokinetic relationships. Flow cytometry is uniquely suited for measurement of these biomarkers. Large numbers of single cells in a heterogeneous population can be rapidly identified and characterized with high accuracy and reproducibility. Cells are not damaged by the detection system and can be subsequently sorted for further morphologic or functional analysis. The availability of clinical instruments and a wide range of fluorescent probes have made this technology applicable for use in toxicologic clinical pathology. Flow cytometry has played an integral role in the development of a monoclonal antibody to human CD4 (keliximab, IDEC-CE9.1, SB 210396). Lymphocyte subset analysis and assays for expression, coating, and modulation of human CD4 were used for sequential assessment of the pharmacologic activity of keliximab in transgenic mice expressing human CD4.

The effect of contralateral broad-band noise on acoustic distortion products from the human ear.

In the first part of the study, the effect of ipsilateral stimulus level on contralateral suppression of the 2f2-f2 distortion product by broad-band noise at 60 dB SPL RMS is examined. The levels of the primary stimuli were manipulated independently, giving f1 and f2 growth curves at four different f2 frequencies for four subjects. These typically bell-shaped, growth curves are shifted vertically to lower distortion levels and, in some cases, horizontally to higher primary stimulus levels. These results can be interpreted as an attenuation of both the primary stimuli and the distortion product and could be caused by simple acoustic attenuation produced by middle ear muscle activity, efferent activity or a combination of the two. In the second part of the study, the same contralateral stimulus was used while measuring both 3f1-2f2 and 2f1-f2 distortion products from the ipsilateral ear. The frequency separation of the primary tones was varied. This produced an approximately bandpass shape with the level peaking when the distortion frequency was approximately half an octave below f2, as previously described (Brown and Gaskill, 1990). This shape is thought to be linked with frequency selectivity in the cochlea. Contralateral broadband noise did not affect the tuning or the centre frequency of the bandpass shape or the mean group delay. It did reduce the size of the distortion peak and, in particular, it affected the peak-to-trough height of the 'fine structure' in the amplitude. Vector analysis revealed that the fine structure was due to a signal with substantial delay (probably from the distortion product 'place') which was summed with a larger, less delayed component (probably directly from the f2 'place'). The greater effect of contralateral stimulation on the more delayed component may reflect differences in efferent effect with complex (stimulus place), rather than simple (distortion product place) stimuli.

The effect of aspirin on cochlear mechanical tuning.

The level of cubic distortion measured in the human ear canal reaches a peak when the distortion frequency falls approximately half-an-octave below that of the higher of two stimulus tones. The peak is thought to be indicative of a bandpass filter in the cochlea. The properties of the distortion peak have been measured during the administration of aspirin (3.84 g/day for 2 days) in eight human volunteers. In three of the subjects, there was a downward shift of the center frequency on the distortion peak by as much as 200 Hz during aspirin consumption, but no significant changes in Q3 dB of the peak. In two of these subjects, the shift in distortion peak was not associated with a change in psychophysical threshold. The mean group delay of the emitted distortion was reduced by approximately 0.5 ms in four of the eight subjects. The measurement of stimulus frequency emission (SFE) did not reveal any downward shift of features in the spectrum corresponding to those seen for the distortion peak. It is concluded (1) that aspirin affects the resonance frequency of the bandpass filter revealed by distortion measurement, but not its tuning; and (2) that the bandpass filter is dissociated from the mechanism responsible for the "fine structure" in the SFE spectrum.

Acoustic distortion as a measure of frequency selectivity: relation to psychophysical equivalent rectangular bandwidth.

The magnitude of cubic intermodulation distortion generated when two tones are progressively separated in frequency reaches a broad maximum when the distortion frequency falls just over half an octave below the high-frequency stimulus (f2), when this distortion is measured with a microphone in the ear canal. For the component 2f1-f2, this peak occurs at an f2/f1 ratio of approximately 1.2. The tuning, magnitude, and mean group delay of this distortion peak was measured for a fixed f2 of 4 kHz at 40 dB SPL and a varied f1 at 55 dB SPL in eight human subjects with normal hearing. The distortion peak measures were compared with the frequency selectivity at 4 kHz of the same eight subjects derived using a forward-masking notched-noise paradigm. In the six subjects from whom good, repeatable levels of distortion were measured, a significant negative correlation was found between the tuning of the distortion peak and the psychophysical bandwidth at f2. It is concluded that the tuning of the distortion peak may provide an objective measure of frequency selectivity in the human cochlea.

Compatibility of ceftazidime and aminophylline admixtures for different methods of intravenous infusion.

OBJECTIVE: Aminophylline and ceftazidime are sometimes used concurrently in patients with respiratory disorders. Parenteral aminophylline usually is administered as a constant infusion, and ceftazidime is given intermittently or less commonly as a constant infusion. We evaluated the stability and compatibility of the two drugs when aminophylline is given as a constant intravenous infusion and ceftazidime is administered simultaneously either through a y-site (piggyback method) or as a continuous infusion (constant infusion method). DESIGN: The chemical stability of intravenous aminophylline and ceftazidime in dextrose 5% and NaCl 0.9% for both methods was studied. Three different formulations of ceftazidime from the same manufacturer were studied (minibag using reconstituted ceftazidime, premixed minibag, and ceftazidime arginine). For the piggyback and constant infusion methods, samples were collected at 0, 1, and 2 hours; and 0, 6, and 24 hours, respectively. All experiments were conducted in triplicate. Samples were analyzed in duplicate by a stability-indicating HPLC assay method. OUTCOME MEASURE: Ceftazidime and aminophylline were considered stable if concentrations remained above 90 percent of the original concentrations over the time periods studied. RESULTS: Ceftazidime was determined to be compatible with aminophylline in the piggyback method. In contrast, when aminophylline and ceftazidime were admixed in the same intravenous container (constant infusion method), the two drugs were not stable. CONCLUSIONS: These data indicate that aminophylline and ceftazidime admixtures are incompatible when prepared in the same intravenous container, which may occur if both are given as a constant infusion. The two drugs are compatible when the ceftazidime is piggybacked into a primary intravenous set in which aminophylline is administered as a constant infusion.

Molecular recognition in the minor groove of the DNA helix. Studies on the synthesis of oligonucleotides and polynucleotides containing 3-deaza-2'-deoxyadenosine. Interaction of the oligonucleotides with the restriction endonuclease EcoRV.

An improved procedure for the preparation of 3-deaza-2'-deoxyadenosine (d3CA) is described which is suitable for the synthesis of gram quantities of this analogue. Using phosphoramidite chemistry d3CA has been incorporated into the Eco RV restiction endonuclease recognition sequence (underlined) present in the self-complementary dodecamer d(GACGATATCGTC). The modified oligonucleotides have been thoroughly characterised by nucleoside composition analysis, circular dichroism and thermal melting studies. Studies with Eco RV show that incorporation of d3CA into either the central or outer dA-dT base-pair results in a substantial reduction in the rate of cleavage. The two-step conversion of d3CA to 3-deaza-2'-deoxyadenosine-5'-O-triphosphate (d3CATP) via the 5'-O-tosylate is also described. d3CATP is not a substrate in the poly[d(AT)].poly[d(AT)] primed polymerisation for either E. coli DNA polymerase I or Micrococcus luteus DNA polymerase. In a more detailed kinetic analysis d3CATP was shown to be a competitive inhibitor of E. coli DNA polymerase I with respect to dATP.

Peripheral arterial occlusive disease: P-31 MR spectroscopy of calf muscle.

The effect of a graded exercise protocol on phosphorus-31 magnetic resonance (MR) spectroscopy of calf skeletal muscle in nine healthy (control) subjects and 16 patients with symptomatic peripheral arterial occlusive disease (PAOD) was assessed. Ankle-brachial pressure indexes were obtained in all 16 patients, and 10 patients underwent peripheral arteriography. Temporal profiles of pH and the inorganic phosphorus (Pi) index were calculated from the spectra. A Pi-index recovery rate constant was calculated for each subject. Arteriograms were graded by calculating the runoff resistance in the limb of interest. The pH profiles during exercise did not differ significantly between the PAOD patients and control subjects. The Pi-index recovery rate constant in the PAOD patients was significantly (P less than .01) smaller than in the control subjects. There was no significant correlation between recovery rate and the ankle-brachial pressure indexes, but there was a strong negative correlation between recovery rates and angiographic resistance grades, with smaller recovery rate constants in patients with increased arterial resistance. It is concluded that P-31 MR spectroscopy shows promise as a direct measure of tissue perfusion.

Copper deficiency anemia: altered red blood cell lipids and viscosity in rats.

To investigate membrane lipid abnormalities and their possible role in copper deficiency anemia, we studied lipids, osmotic fragility, and viscosity of red blood cells (RBCs) of rats fed diets containing 1.1 mg Cu/kg (deficient, Cu-) and 6.0 mg Cu/kg (supplemented, Cu+) at age 3 wk for 9 wk. Data show an increase in cholesterol of 43% and in phospholipids of 38% per cell in Cu- compared with Cu+ rats. Thin-layer chromatography of RBC lipids showed an increased amount of phospholipid-malonyldialdehyde adduct in Cu- (0.70 +/- 0.35% [means +/- SD] of total phospholipids) compared with Cu+ (0.29 +/- 0.19%) rats, suggesting increased membrane lipid peroxidation in Cu- RBC. Osmotic fragility of RBCs from Cu- rats was lower. RBC viscosity was significantly higher in Cu- than in Cu+ rats at shear rates of 23, 11.5, and 5.75 shear/s and was similar at shear rates 115 and 46 shear/s. Increased cell viscosity caused by lipid loading and crosslinking of membrane components caused by lipid peroxidation may have a role in the reduced RBC survival and anemia in Cu deficiency.

Hepatic iron accumulation in copper-deficient rats.

Studies of anaemia and tissue iron distribution were carried out in copper-deficient rats and pair-fed control animals given Fe orally or parenterally in varying doses. The anaemia of Cu deficiency was partially but incompletely corrected by oral Fe supplementation of one- to five-fold normal dietary levels or by intramuscular Fe supplementation. Serum Fe increased in Cu-deficient animals as the dose of supplemental Fe was increased. Hepatic Fe accumulation occurred in Cu-deficient rats which were administered with either oral Fe in two- to five-fold excess or low doses of intramuscular Fe. This difference was not seen in animals receiving high doses of intramuscular Fe, but similar relative differences were seen in Cu-deficient and Cu-replete rats which had been given no Fe supplementation. Duodenal Fe was not increased in Cu deficiency. Bone marrow Fe was present in Cu-deficient animals receiving either parenteral or oral Fe supplementation. Present studies suggest that a decrease in caeruloplasmin (EC 1.16.3.1) activity does not wholly explain the anaemia of Cu deficiency. Fe accumulation may be restricted to the liver, suggesting that Cu may be required for normal intracellular Fe metabolism.

Copper deficiency in humans.

Copper is an essential trace element that is required for a number of enzymes which are necessary for normal metabolic function. Metabolic balance studies have demonstrated that daily copper losses are approximately 1.3 mg/day. In order to remain in copper balance, the average adult male must consume a diet which contains at least 2 mg copper/day. It has been assumed that most diets satisfy this requirement because of the ubiquitous presence of copper in most foodstuffs. Recent studies, however, have shown that dietary copper may often fall below the estimated daily needs. Nevertheless, clinically evident copper deficiency has been documented in only a few situations. Of these disorders. Menkes' syndrome has been most intensively studied. This x-linked abnormality is associated with copper deficiency due to impaired gastrointestinal copper absorption. However, the clinical disorder cannot be corrected readily with copper replacement, thus suggesting that Menkes' syndrome may reflect more than simple copper deficiency. Nutritional copper deficiency appears to be well documented in two situations: (1) the newborn, usually premature, undergoing rapid growth on a diet poor in copper, and (2) the patient maintained on total parenteral nutrition for long periods of time without copper supplementation. In both of these situations, anemia and neutropenia are the most striking hematologic abnormalities associated with copper deficiency. Sideroblastic changes as well as nuclear maturation defects observed in erythroid precursors. However, suggest that there is an effect of copper deficiency on the hematopoietic system which cannot be explained solely by defective plasma iron transport.

Effects of copper deficiency on the activity of the selenoenzyme glutathione peroxidase and on excretion and tissue retention of 75SeO3(2-).

Liver and lung activities of the antioxidant enzymes glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD) were determined in control and copper-deficient rats. Decreased activity of SOD was found in liver and decreased activity of the selenoenzyme GSH-Px was found in liver and lung in the copper-deficient animals. The decreased liver activity of GSH-Px could be partially corrected by daily supplementation of the basal diet with sodium selenite. Urinary, fecal and biliary excretion of 75SeO3(2-) were determined in controls and copper-deficient rats in order to assess selenium losses. Urinary excretion of 75Se was not different in the two groups. Fecal loss of 75Se was increased in the copper-deficient animals when compared to controls and biliary excretion was decreased. Tissue retention of 75Se was also determined in both groups. Retention of 75Se in the copper-deficient rats was increased in brain and lung and decreased in liver. This pattern of tissue retention of 75Se is similar to that which occurs in selenium-deficient rats. Copper deficiency in rats results in decreased liver activity of both the copper-containing enzyme SOD and the selenoenzyme GSH-Px. The mechanism of decreased GSH-Px activity is unknown.

Suppression of cryptococcosis and histoplasmosis by ketoconazole in athymic nude mice.

Congenitally athymic nude (nu/nu) mice are more susceptible to disseminated cryptococcosis and histoplasmosis than their heterozygous (nu/ + ) thymus-bearing litter-mates. The therapeutic efficacy of ketoconazole, an orally absorbable antifungal agent, was evaluated in nu/nu and nu/ + mice infected intraperitoneally with Cryptococcus neoformans and Histoplasma capsulatum. Two- to five-week courses of ketoconazole significantly prolonged the survival of nu/nu mice infected with either fungus in dose-dependent fashion, but death eventually followed discontinuance of therapy. More significant protection was seen in nu/ + mice infected with C. neoformans, and markedly lower fungal counts in organs, with some negative cultures, were seen in ketoconazole-treated nu/ + mice infected with H. capsulatum. These studies indicate that ketoconazole is effective against both fungi, although results of treatment are much better in the immunologically intact nu/ + host.

Experimental chemotherapy of histoplasmosis in nude mice.

Nude (nu/nu) mice were infected with Histoplasma capsulatum and treated with varying doses of 3 drug regimens: oral ambruticin, intraperitoneal amphotericin B, and amphotericin B plus oral rifampin. Therapy with amphotericin B alone was the most effective regimen. High-dose ambruticin (50 mg/kg of body weight every 8 hours) led to significantly prolonged survival compared to that of untreated control animals, but no long-term cures. Addition of rifampin produced no benefit and might actually have decreased the efficacy of amphotericin B; this combination may be deleterious in a setting of immunodeficiency.