Phase Ib study of eprenetapopt (APR-246) in combination with pembrolizumab in patients with advanced or metastatic solid tumors

Background

We conducted a phase I, multicenter, open-label, dose-finding, and expansion study to determine the safety and preliminary efficacy of eprenetapopt (APR-246) combined with pembrolizumab in patients with advanced/metastatic solid tumors (ClinicalTrials.gov NCT04383938).

Patients and methods

For dose-finding, requirements were non-central nervous system primary solid tumor, intolerant to/progressed after ≥1 line of treatment, and eligible for pembrolizumab; for expansion: (i) gastric/gastroesophageal junction tumor, intolerant to/progressed after first-line treatment, and no prior anti-programmed cell death receptor-1 (PD-1)/programmed death-ligand 1 (PD-L1) therapy; (ii) bladder/urothelial tumor, intolerant to/progressed after first-line cisplatin-based chemotherapy, and no prior anti-PD-1/PD-L1 therapy; (iii) non-small-cell lung cancer (NSCLC) with previous anti-PD-1/PD-L1 therapy. Patients received eprenetapopt 4.5 g/day intravenously (IV) on days 1-4 with pembrolizumab 200 mg IV on day 3 in each 21-day cycle. Primary endpoints were dose-limiting toxicity (DLT), adverse events (AEs), and recommended phase II dose (RP2D) of eprenetapopt.

Results

Forty patients were enrolled (median age 66 years; range 27-85) and 37 received eprenetapopt plus pembrolizumab. No DLTs were reported and the RP2D for eprenetapopt in combination was 4.5 g/day IV on days 1-4. The most common eprenetapopt-related AEs were dizziness (35.1%), nausea (32.4%), and vomiting (29.7%). AEs leading to eprenetapopt discontinuation occurred in 2/37 patients (5.4%). In efficacy-assessable patients (n = 29), one achieved complete response (urothelial cancer), two achieved partial responses (NSCLC, urothelial cancer), and six patients had stable disease.

Conclusions

The eprenetapopt plus pembrolizumab combination was well tolerated with an acceptable safety profile and showed clinical activity in patients with solid tumors.

•

Eprenetapopt in combination with pembrolizumab was well tolerated with an acceptable safety profile.

•

Eprenetapopt plus pembrolizumab demonstrated clinical activity in heavily pre-treated patients with solid tumors.

•

This is the first clinical trial evaluating the combination of a p53 reactivator with immuno-oncology therapy.

•

This work informs the development of treatment combining immunotherapy with agents targeting specific pathways such as p53.

Structure-activity relationship around PI-2620 highlights the importance of the nitrogen atom position in the tricyclic core

Tau aggregates represent a critical pathology in Alzheimer's disease (AD) and other forms of dementia. The extent of Tau neurofibrillary tangles across defined brain regions corresponds well to the observed level of cognitive decline in AD. Compound 1 (PI-2620) was recently identified as a promising Tau positron emission tomography tracer for AD and non-AD tauopathies. To evaluate the impact of the N-atom position with respect to Tau- and off-target binding, tricyclic core analogs of PI-2620 with nitrogen atoms at different positions were prepared. Affinity to aggregated Tau was evaluated using human AD brain homogenates, and their off-target binding was evaluated in a monoamine oxidase A (MAO-A) competition assay. The novel tricyclic core derivatives all displayed inferior Tau binding or MAO-A off-target selectivity, indicating PI-2620 to be the optimal design for high affinity binding to Tau and high MAO-A selectivity.

Lead Optimization Highlights the Importance of Off-Target Assays to Develop a PET Tracer for the Detection of Pathological Aggregated Tau in Alzheimer's Disease and Other Tauopathies

The first candidate PI-2014 was tested in healthy controls and subjects with Alzheimer's disease (AD). As PI-2014 displayed off-target binding to monoamine oxidase A (MAO-A), a new lead with improved binding to Tau and decreased MAO-A binding was required. For compound optimization, Tau binding assays based on both human AD brain homogenate and Tau-paired helical filaments were employed. Furthermore, two MAO-A screening assays based on (1) human-recombinant MAO-A and (2) displacement of 2-fluoro-ethyl-harmine from mouse brain homogenate were employed. Removing the N-methyl group from the tricyclic core resulted in compounds displaying improved Tau binding. For the final round of optimization, the cyclic amine substituents were replaced by pyridine derivatives. PI-2620 (2-(2-fluoropyridin-4-yl)-9H-pyrrolo[2,3-b:4,5-c']dipyridine) emerged as a best candidate displaying high Tau binding, low MAO-A binding, high brain uptake, and fast and complete brain washout. Furthermore, PI-2620 showed Tau binding on brain sections from corticobasal degeneration, progressive supranuclear palsy, and Pick's disease.

Discovery of 2-(4-(2-fluoroethoxy)piperidin-1-yl)-9-methyl-9H-pyrrolo[2,3-b:4,5-c']dipyridine ([18F]PI-2014) as PET tracer for the detection of pathological aggregated tau in Alzheimer's disease and other tauopathies

The compound screening was initiated with a direct staining assay to identify compounds binding to Tau aggregates and not Abeta plaques using human brain sections derived from late stage Alzheimer's disease donors. The binding of Tau aggregate selective compounds was then quantitatively assessed with human brain derived paired helical filaments utilizing the label-free Back Scattering Interferometry assay. In vivo biodistribution experiments of selected fluorine-18 labeled compounds were performed in mice to assess brain uptake, brain washout, and defluorination. Compound 11 emerged as the most promising candidate, displaying high in vitro binding affinity and selectivity to neurofibrillary tangles. Fluorine-18 labeled compound 11 showed high brain uptake and rapid washout from the mouse brain with no observed bone uptake. Furthermore, compound 11 was able to detect Tau aggregates in tauopathy brain sections from corticobasal degeneration, progressive supranuclear palsy, and Pick's disease donors. Thus, 2-(4-(2-fluoroethoxy)piperidin-1-yl)-9-methyl-9H-pyrrolo[2,3-b:4,5-c']dipyridine (PI-2014, compound 11) was selected for characterization in a first-in-human study.

Building a Community - Academic Partnership to Enhance Hepatitis C Virus Screening

BACKGROUND

An estimated 3.5 million Americans are chronically infected with hepatitis C virus (HCV). However, the majority are unaware of their HCV diagnosis and few are treated. New models are required to diagnose and link HCV infected patients to HCV care. This paper describes an innovative partnership between Sisters Together and Reaching (STAR), Inc., a community organization, and Johns Hopkins University (JHU), an academic institution, for the identification of HCV cases.

METHODS

STAR and JHU identified a mutual interest in increasing hepatitis C screening efforts and launched an HCV screening program which was designed to enhance STAR's existing HIV efforts. STAR and JHU used the Bergen Model of Collaborative Functioning as theoretical framework for the partnership. We used descriptive statistics to characterize the study population and correlates of HCV antibody positivity were reported in univariable/multivariable logistic regression.

RESULTS

From July 2014 to June 2015, 325 rapid HCV antibody tests were performed in community settings with 49 (15%) positive HCV antibody tests. 33 of the 49 HCV antibody positive individuals answered questions about their HCV testing history and 42% reported a prior positive result but were not engaged in care and 58% reported that they were unaware of their HCV status. In multivariable analysis, factors that were significantly associated with screening HCV antibody positive were increasing age (AOR: 1.06, 95% CI 1.02-1.10), male sex (AOR: 5.56, 95% CI 1.92-14.29), and history of injection drug use (AOR: 39.3, 95% CI 15.20-101.49).

CONCLUSIONS

The community-academic partnership was successful in identifying individuals with hepatitis C infection through a synergistic collaboration. The program data suggests that community screening may improve the hepatitis C care continuum by identifying individuals unaware of their HCV status or aware of their HCV status but not engaged in care and linking them to care.

Abstract P6-12-08: Healthcare barrier profiles in patients navigated for cancer screening and treatment and the impact of the affordable care act

Background: The underserved community experiences barriers to cancer screening that result in overall greater mortality rates across all cancers. Insurance coverage brought forth by the Affordable Care Act has the potential to significantly impact these barriers through reducing the burden of health care cost on the patient. In this study the authors observe the impact of the Affordable Care Act on the barrier profiles presented by the patients navigated for cancer screening and treatment.

Methods: Patient navigation encounters were recorded for a total of 1146 patients navigated for cancer screening and treatment at the Cleveland Clinic Foundation from the years 2012 through 2015. A total of 3259 encounters were classified into barrier types. Health care billed encounters were retrieved from EPIC for this group of patients from the time they entered patient navigation and classified in terms of insurance coverage. Patients were categorized according to their barrier profile. Appropriate generalized linear regression models were used to test for association of these profiles to number and types of navigation and health care encounters and cost, and to test for change in types of encounters and patient barrier profiles through time.

Results: The insurance barrier is present in 23% of all navigation encounters. Patients presenting with an insurance barrier had a greater mean number of navigation (p<0.001) and health care encounters (p<0.006), had a greater proportion of self-paid health care encounters (p<0.001) and a lower total cost billed for health care encounters after controlling for number of encounters (p<0.001) . The access barrier is present in 53% of navigation encounters while patients that present with only the access barrier account for 42% of the entire sample. Patients that present with only the access barrier have doubled every year (OR 2.2 per year, 95% CI [1.8 2.6]) from 2012 to 2015, while the proportion of self-paid health care encounters (OR 0.26 per year, 95% CI [0.25 0.28]) and the presence of the insurance barrier (OR 0.55 per year, 95% CI [ 0.49 0.62]) have more than halved during this time period.

Conclusion: Although the Affordable Care Act has clearly had an impact by lowering the number of insurance barrier navigation encounters through time, it has uncovered access as the predominant remaining barrier. Understanding and targeting the access barrier will be the most effective way to potentiate the effects of the ACA on patients being navigated for cancer screening and treatment.

Citation Format: Raska P, Ott MA, Steele A, Bailey A, Hickman D, Allen D, Urbanek D, Glass K, Bailey J, Bell K, Montero A, Abraham J. Healthcare barrier profiles in patients navigated for cancer screening and treatment and the impact of the affordable care act. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P6-12-08.

A calibration phantom for direct, in vivo measurement of 241Am in the axillary lymph nodes

A calibration phantom was developed at the University of Cincinnati (UC) to determine detection efficiency and estimate the quantity of activity deposited in the axillary lymph nodes of a worker who had unknowingly sustained a wound contaminated with 241Am at some distant time in the past. This paper describes how the Livermore Torso Phantom was modified for calibrating direct, in vivo measurements of 241Am deposited in the axillary lymph nodes. Modifications involved milling a pair of parallel, flat bottom, cylindrical holes into the left and right shoulders (below the humeral head) of the Livermore Torso Phantom in which solid, 1.40-cm-diameter cylindrical rods were inserted. Each rod was fabricated using a muscle tissue substitute. One end of each rod contained a precisely known quantity of Am sealed in a 1-cm-diameter, 2.54-cm-deep well to simulate the axillary lymph nodes when inserted into the modified Livermore Torso Phantom. The fixed locations for the axillary lymph nodes in the phantom were determined according to the position of the Level I and the combined Level II + III axillary lymph nodes reported in the literature. Discrete calibration measurements for 241Am in the simulated axillary lymph nodes located in the right and left sides of the thorax were performed using pairs of high-resolution germanium detectors at UC and Lawrence Livermore National Laboratory. The percent efficiency for measuring the 59.5 keV photon from Am deposited in the right and left axillary lymph nodes using a pair of 3,000 mm2 detectors is 2.60 +/- 0.03 counts gamma-1 and 5.45 +/- 0.07 counts gamma-1, respectively. Activity deposited in the right and left axillary lymph nodes was found to contribute 12.5% and 19.7%, respectively, to a lung measurement and 1.2% and 0.2%, respectively, to a liver measurement. Thus, radioactive material mobilized from a wound in a finger or hand and deposited in the axillary lymph nodes has been shown to confound results of a direct, in vivo measurement of the lungs.

Pandemic influenza: preventing the emergence of novel strains and countermeasures to ameliorate its effects

Influenza is a seasonal disease that peaks every year in the winter months. Antigenic drift of the viral surface proteins, particularly the hemagglutinin (HA), is responsible for the virus's ability to evading the host's immune system, and for the severity of the disease. Pandemic influenza arises when an influenza virus carrying a novel HA gene enters into the naive human population, resulting in excess morbidity and mortality. Three major influenza pandemics were experienced in the last century and the emergence of a new pandemic strain is considered a matter of time. Our current understanding suggests that pandemic influenza strains arise from influenza viruses circulating in the natural reservoir, although the presence of intermediate hosts is considered essential in this process. Pigs and land-based birds have been shown to play a major role in the ecology of influenza viruses by providing an environment in which influenza viruses can change their phenotype, expand their host range, and eventually transmit to humans. In recent years, a great detail of attention has been placed on understanding the epidemiological and molecular factors that can lead to interspecies transmission of influenza viruses. In this review we will discuss the ecological and molecular aspects that lead to pandemic influenza as well as the intervention strategies at our disposal that can reduce the emergence of pandemic influenza strains and/or minimize their effects.

Techniques for reducing anesthetic injection pain

BACKGROUND

The authors conducted a study that considered family physicians' and dentists' knowledge and application of techniques to reduce the pain associated with anesthetic injections. They also assessed practitioners' discomfort with patients' injection pain and needle anxiety/phobia.

METHODS

The authors designed a questionnaire about awareness and use of 10 techniques for reducing pain of anesthetic injection and mailed it to 2,000 randomly selected family physicians and general dentists. They analyzed the data to examine differences between disciplines regarding awareness and use of techniques, reasons for not using techniques, number of injections given per week, and predictive value of certain demographic variables on reported use of individual techniques and on practitioner reactions to patients' pain and anxiety.

RESULTS

The response rate was 35 percent. The authors used the chi2 test for differences between disciplines' awareness of and use or nonuse of techniques, Wilcoxon testing to assess differences between disciplines' median values of number of weekly injections and logistic regression to study demographic variables' predictive values (P = .01). General dentists give more injections than do family physicians. Differences existed between disciplines' awareness and use of eight of 10 techniques. Disciplines reported cost and time issues as reasons for not using some techniques. Number of years in practice and age were associated with use of six techniques. Dentists reported feeling greater personal effects of patients' pain and needle anxiety/phobia than did family physicians.

CONCLUSIONS

Those not using pain-lessening techniques inaccurately identified time and cost as problems, suggesting that respondents may be less familiar with these techniques than otherwise reported. Further study is recommended.

CLINICAL IMPLICATIONS

Pain reduction techniques for anesthetic injection cost little to implement, are not time liabilities, and can lessen avoidable pain and reduce the incidence of needle phobia.

A whole body counting facility in a remote Enewetak Island setting

The U.S. Department of Energy (DOE) has recently implemented a series of strategic initiatives to address long-term radiological surveillance needs at former U.S. test sites in the Marshall Islands. The plan is to engage local atoll communities in developing shared responsibilities for implementing radiation protection programs for resettled and resettling populations. As part of this new initiative, DOE agreed to design and construct a radiological laboratory on Enewetak Island, and help develop the necessary local resources to maintain and operate the facility. This cooperative effort was formalized in August 2000 between the DOE, the Republic of the Marshall Islands (RMI), and the Enewetak/Ujelang Local Atoll Government (EULGOV). The laboratory facility was completed in May 2001. The laboratory incorporates both a permanent whole body counting system to assess internal exposures to 137Cs, and clean living space for people providing 24-h void urine samples. DOE continues to provide on-going technical assistance, training, and data quality review while EULGOV provides manpower and infrastructure development to sustain facility operations on a full-time basis. This paper will detail the special construction, transportation and installation issues in establishing a whole body counting facility in an isolated, harsh environmental setting.

Analysis of two matrix metalloproteinase inhibitors and their metabolites for induction of phospholipidosis in rat and human hepatocytes(1)

ABT-770 [(S)-N-[1-[[4'-trifluoromethoxy-[1,1'-biphenyl]-4-yl]oxy]methyl-2-(4,4-dimethyl-2,5-dioxo-1-imidazolidinyl)ethyl]-N-hydroxyformamide], a matrix metalloproteinase inhibitor (MMPI), produced generalized phospholipidosis in rats. Phospholipid accumulation was accompanied by retention of drug-related material and was associated with increased mortality. Generation of a successful drug candidate depended upon understanding the cause of the phospholipidosis and redesigning the chemical structure accordingly. ABT-770 and other MMPIs, plus several metabolites of each, were assayed for their ability to induce phospholipidosis in primary cultured rat and human hepatocytes. Phospholipid accumulation was detected by following the incorporation of a fluorescent phospholipid analogue into intracytoplasmic inclusion bodies characteristic of phospholipid storage disorders. At 24 and 48 hr, none of the parent compounds induced phospholipidosis in vitro in rat or human hepatocytes. Phospholipidosis was associated primarily with an amine metabolite of ABT-770. The amine metabolite of another MMPI, ABT-518 ([S-(R*,R*)]-N-[1-(2,2-dimethyl-1,3-dioxol-4-yl)-2-[[4-[4-(trifluoromethoxy)-phenoxy]phenyl]sulfonyl]ethyl]-N-hydroxyformamide), produced little phospholipidosis in rat and human hepatocytes even at concentrations up to 100 microM. The presence or absence of phospholipidosis in the in vitro assay correlated well with ultrastructural findings and drug accumulation in rat tissues. ABT-770, which produced phospholipidosis associated with its amine metabolite in vitro and in vivo, also generated a higher tissue to plasma distribution of metabolites particularly in tissues where phospholipidosis was observed. ABT-518 and its amine metabolite, however, produced low tissue to plasma ratios and induced little to no phospholipidosis in vitro or in vivo. These results demonstrate that the phospholipidosis observed for ABT-770 could be attributed to a cationic metabolite, and that altering the properties of such a metabolite, by modification of the parent compound, alleviated the disorder.

Isinglass/collagen: denaturation and functionality

Isinglass is widely used commercially to clarify alcoholic beverages by aggregation of the yeast and other insoluble particles. It is derived from swim bladders of tropical fish by solubilisation in organic acids and consists predominantly of the protein collagen. The low content of intermolecular cross-links allows ready dissolution of swim bladder compared to bovine hide which is cross-linked by a high proportion of stable bonds and requires enzymic digestion to solubilise. Isinglass is no longer effective as a clarifying agent if thermally denatured hence the collagenous triple helical structure must be maintained. Thermal denaturation of isinglass occurs at 29 degrees C, compared to 40-41 degrees C for mammalian collagens, primarily due to the lower hydroxyproline content. The hydroxyproline is essential for the formation of H-bonded water-bridges through the hydroxyl group and the peptide chain thereby stabilising the triple helix. Based on the lower enthalpy determined by differential scanning calorimetry we have calculated that the thermally labile domain of the isinglass molecule was 41 residues compared to 66 for mammalian collagen. The fining efficiency was unaffected by pH, chelating agents, detergents and removal of surface proteins from yeast cells. Studies on the mechanism of action of isinglass have shown that higher molecular weight aggregates that increase the length of the collagen molecules (trimers, tetramers, etc.) increase efficiency and that their surface charge are important in the clarification process. By chemical modification, we have shown that blocking positively charged groups had no effect on the fining process, whilst negative charges are clearly essential and that increasing the negative charge by succinylation increases its efficacy. Solutions of bovine hide collagen were shown to be equally effective in refining beers and standard yeast preparations. The higher thermal denaturation temperature, ready availability and reproducibility of bovine collagen preparations gives it considerable advantages over isinglass.

Potent inhibition of the cytochrome P-450 3A-mediated human liver microsomal metabolism of a novel HIV protease inhibitor by ritonavir: A positive drug-drug interaction

ABT-378 is a potent in vitro inhibitor of the HIV protease and is currently being developed for coadministration with another HIV protease inhibitor, ritonavir, as an oral therapeutic treatment for HIV infection. In the present study, the effect of ritonavir, a potent inhibitor of cytochrome P-450 (CYP) 3A, on the in vitro metabolism of ABT-378 was examined. Furthermore, the effect of ABT-378-ritonavir combinations on several CYP-dependent monooxygenase activities in human liver microsomes was also examined. ABT-378 was found to undergo NADPH- and CYP3A4/5-dependent metabolism to three major metabolites, M-1 (4-oxo) and M-3/M-4 (4-hydroxy epimers), as well as several minor oxidative metabolites in human liver microsomes. The mean apparent K(m) and V(max) values for the metabolism of ABT-378 by human liver microsomes were 6.8 +/- 3.6 microM and 9.4 +/- 5.5 nmol of ABT-378 metabolized/mg protein/min, respectively. Ritonavir inhibited human liver microsomal metabolism of ABT-378 potently (K(i) = 0.013 microM). The combination of ABT-378 and ritonavir was much weaker in inhibiting CYP-mediated biotransformations than ritonavir alone, and the inhibitory effect appears to be primarily due to the ritonavir component of the combination. The ABT-378-ritonavir combinations (at 3:1 and 29:1 ratios) inhibited CYP3A (IC(50) = 1.1 and 4.6 microM), albeit less potently than ritonavir (IC(50) = 0.14 microM). Metabolic reactions mediated by CYP1A2, CYP2A6, and CYP2E1 were not affected by the ABT-378-ritonavir combinations. The inhibitory effects of ABT-378-ritonavir combinations on CYP2B6 (IC(50) = >30 microM), CYP2C9 (IC(50) = 13.7 and 23.0 microM), CYP2C19 (IC(50) = 28.7 and 38.0 microM), and CYP2D6 (IC(50) = 13.5 and 29.0 microM) were marginal and are not likely to produce clinically significant drug-drug interactions.

Expression of arylamine N-acetyltransferase in human intestine

BACKGROUND

Arylamine N-acetyltransferases in humans (NAT1 and NAT2) catalyse the acetylation of arylamines including food derived heterocyclic arylamine carcinogens. Other substrates include the sulphonamide 5-aminosalicylic acid (5-ASA), which is an NAT1 specific substrate; N-acetylation of 5-ASA is a major route of metabolism. NAT1 and NAT2 are both polymorphic.

AIMS

To investigate NAT expression in apparently healthy human intestines in order to understand the possible role of NAT in colorectal cancer and in the therapeutic response to 5-ASA.

METHODS

The intestines of four organ donors were divided into eight sections. DNA was prepared for genotyping NAT1 and NAT2 and enzymic activities of NAT1 and NAT2 were determined in cytosols prepared from each section. Tissue was fixed for immunohistochemistry with specific NAT antibodies. Western blotting was carried out on all samples of cytosol and on homogenates of separated muscle and villi after microdissection.

RESULTS

NAT1 activity of all cytosols was greater than NAT2 activity. NAT1 and NAT2 activities correlated with the genotypes of NAT1 and NAT2 and with the levels of NAT1 staining determined by western blotting. The ratio of NAT1:NAT2 activities showed interindividual variations from 2 to 70. NAT1 antigenic activity was greater in villi than in muscle. NAT1 was detected along the length of the villi in the small intestine. In colon samples there was less NAT1 at the base of the crypts with intense staining at the tips.

CONCLUSIONS

The interindividual variation in NAT1 and NAT2 in the colon could affect how individuals respond to exposure to specific NAT substrates including carcinogens and 5-ASA.

Evaluation of the selectivity of In vitro probes and suitability of organic solvents for the measurement of human cytochrome P450 monooxygenase activities

There is a need for methodology to predict clinically significant drug-drug interactions so that clinical studies can be directed toward interactions which are likely to be clinically relevant. To this end, we evaluated selective assays for the seven drug-metabolizing cytochrome P450 (P450) isozymes 1A2 (caffeine N3-demethylation), 2A6 (coumarin 7-hydroxylation), 2C9 (tolbutamide hydroxylation), 2C19 (S-mephenytoin 4-hydroxylation), 2D6 (dextromethorphan O-demethylation), 2E1 (chlorzoxazone 6-hydroxylation), and 3A4/5 (dextromethorphan N-demethylation). Using initial rate conditions, we determined the Km and Vmax values of each reaction in human liver microsomes from three individuals. Because organic solvents (usually methanol) are frequently used as solubilization aids for drugs/inhibitors, we also screened several solvents for inhibitory activity. Methanol was the least inhibitory toward P450s 2A6, 2D6, and 3A4, dimethylformamide was the least inhibitory toward P450s 1A2 and 2C9, and acetonitrile was the least inhibitory toward P450s 2C19 and 2E1. Using substrate concentrations close to the determined Km and an appropriate solvent (where necessary), we used the selective inhibitors furafylline (1A2), 8-methoxypsoralen (2A6), sulfaphenazole (2C9), S-mephenytoin (2C19), quinidine (2D6), diethyldithiocarbamate (2E1), and troleandomycin (3A4) to assess the limitations of each probe assay as an indicator of the P450 isoform in question. Our results were consistent with these inhibitors and probes, being selective tools for studying P450 drug metabolism.

Immunochemical detection of arylamine N-acetyltransferase in normal and neoplastic bladder

The N-acetyltransferase (NAT) phenotype is an important determinant of individual susceptibility to occupational bladder cancer. N-Acetyltransferases arc known to metabolize aromatic amine bladder carcinogens, but the functional significance of NAT expression in the target organ is unclear. To resolve this issue, polygonal antisera against purified recombinant enzymes and C-terminal peptides of human NAT Type 1 (NAT1) and Type 2 (NAT2) were generated. Western blot analysis of exfoliated cells from human urine, pig bladder homogenate, and human bladder tumor-derived cell lines showed that NAT1 was expressed in all three systems, whereas NAT2 did not appear to be expressed in the bladder. Immunohistochemical analysis of human bladder tumor sections indicated that well-differentiated tumor cells expressed NAT1, with the highest level of expression being found in the umbrella cells that line the bladder lumen. Poorly differentiated tumor regions appeared to express NAT1 at lower levels than did well-differentiated areas. These findings support the hypothesis that aromatic amines are metabolized in the bladder epithelium by NAT1.

Enzyme kinetic properties of human recombinant arylamine N-acetyltransferase 2 allotypic variants expressed in Escherichia coli

Arylamine N-acetyltransferase (NAT2) catalyses the N-acetylation of primary arylamine and hydrazine drugs and chemicals. N-Acetylation is subject to polymorphism, and humans can be categorized as either fast or slow acetylators according to their ability to N-acetylate certain arylamine substrates in vivo. Genetic variants at the polymorphic NAT2 locus have been described. We expressed five of the most common NAT2 variants (NAT2 4, NAT2 5A, NAT2 5B, NAT2 6A and NAT2 7B) in Escherichia coli as a convenient source of the human variants. The apparent Km values (at 100 microM acetyl CoA as co-substrate) of the different NAT2 variants for sulphamethazine, dapsone, p-anisidine, 2-aminofluorene, procainamide and isoniazid were determined. Data show that the apparent Km of the slow variant NAT2 7B for the arylamine sulphamethazine was 10-fold lower than all the other allotypes. The apparent Km for the structurally related sulphone antibiotic dapsone was 5-fold lower for the slow variant NAT2 7B when compared with the wild-type NAT2 4. These results indicate that the NAT2 7B specific amino acid substitution, Gly286-Glu, is important in promoting the binding of sulphamethazine and dapsone to the active site.

Dapsone acetylation by human liver arylamine N-acetyltransferases and interaction with antiopportunistic infection drugs

Dapsone is used in the treatment of Pneumocystis carinii pneumonia, an opportunistic infection that afflicts acquired immunodeficiency syndrome (AIDS) patients. Inhibition of N-acetyltransferase (NAT)-dependent acetylation of dapsone could increase peak plasma concentrations of dapsone and shift the biotransformation pathway to the P450-mediated formation of a toxic metabolite of dapsone, the hydroxylamine. Therefore, we have determined using human liver cytosol and bacterially expressed NATs, the NAT isoform responsible for acetylating dapsone and the potential for antiopportunistic infection drugs to inhibit this metabolic pathway. Formation of monoacetyldiaminodiphenylsulfone (MADDS) was quantitated by HPLC/UV detection at 270 nm after incubation of dapsone with 100 microM acetyl coenzyme A regenerating system and human liver cytosol. The mean +/- SD apparent KM for the formation of MADDS in three different human livers predicted to be fast acetylators based on genotyping was 98 +/- 17.6 microM, and the Vmax was 190 +/- 20 pmol/min/mg cytosol protein. Eadie-Hofstee transformation of the substrate velocity data was linear, indicating acetylation by a kinetically single enzyme. Sulfamethazine (250 microM) inhibited dapsone acetylation by 100% and 80%, respectively, at dapsone concentrations of 3 and 100 microM, in both fast- and slow-acetylating liver cytosol preparations, whereas para-amino-benzoic acid (100 microM) did not inhibit MADDS formation at either of these dapsone concentrations. Lineweaver-Burk plots of dapsone acetylation in the presence of 0, 25, and 50 microM sulfamethazine showed an increase in the apparent KM, with increase in sulfamethazine concentration with no change in the Vmax, indicating competitive inhibition of dapsone acetylation by sulfamethazine. The apparent KM of dapsone acetylation by bacterially expressed NAT1 and NAT2 enzymes was 687 and 136 microM, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Measurement of the attenuation coefficient for Livermore Thoracic Phantom lungs fabricated using contemporary materials

The University of Cincinnati has reproduced the original formulation for the Livermore Thoracic Phantom lungs using contemporary materials and has adopted the linear attenuation coefficient as the primary quality assurance parameter for evaluating the performance capabilities of these new lung phantoms. The Livermore Thoracic Phantom was originally fabricated in 1978 to intercalibrate detector systems used to measure plutonium and other low-energy, photon emitting radionuclides deposited in the respiratory tract. The linear attenuation coefficient is a critical performance indicator for these phantom lungs since the presence of any material with a high effective atomic number (where Z > or = 20) will make a significant change in the photoelectric cross section, the predominant mode of interaction for plutonium x rays. A set of test lungs was fabricated with KCl to introduce a known quantity of 40K in the phantom and to determine, by measurement and calculations, what change would be made to the attenuation coefficient at photon energies below 100 keV as a result of the modified formulation. The KCl increased the linear attenuation coefficient below 60 keV by more than a factor of two, which would produce a substantial systematic error in any subsequent calibration measurements performed with these modified phantom lungs. These results support use of the attenuation coefficient as an important performance indicator for the Livermore Thoracic Phantom lungs and also suggest that KCl not be added to the lung tissue substitute formulation as a means to incorporate 40K in the phantom for low energy calibrations.

Diarrheal morbidity during the first 2 years of life among HIV-infected infants

OBJECTIVE

To determine the incidence, cause, and patterns of diarrhea during the first 2 years of life among infants infected perinatally with the human immunodeficiency virus (HIV).

DESIGN

A cohort study in which infants were enrolled shortly after birth and followed up longitudinally using biweekly surveillance for the occurrence of diarrhea. Stool specimens collected at the onset of diarrhea were evaluated for enteropathogens. Infants who were infected with HIV were compared with uninfected infants.

SUBJECTS

Infants born to HIV-infected women at the University of Maryland Hospital, Baltimore, were recruited at 0 to 3 months of age. This analysis included 58 infants enrolled in the cohort and followed up at least 15 months (unless death intervened) whose HIV status was established (18 HIV-infected infants and 40 HIV-uninfected infants).

MEASUREMENTS AND RESULTS

The overall incidence of diarrhea in HIV-infected infants was 3.2 episodes per 12 child-months compared with 1.5 episodes per 12 child-months among HIV-uninfected infants (incidence density ratio, 2.2; P < .05). An enteropathogen was identified in stool specimens collected during 20% of diarrheal episodes occurring in HIV-infected infants and during 25% of diarrheal episodes occurring in HIV-uninfected infants. Episodes that persisted for 14 days or longer were significantly more common among HIV-infected infants. The peak incidence of diarrhea occurred at 0 to 5 months of age for HIV-infected infants compared with 6 to 11 months for HIV-uninfected infants. Early onset of diarrhea (< 6 months old) in HIV-infected infants was associated with the later development of persistent episodes of diarrhea, and those with persistent episodes had more severe HIV infection, characterized by a significantly higher frequency of opportunistic infections and lower CD4+ T-lymphocyte counts by 1 year of age.

CONCLUSION

Both acute and persistent episodes of diarrhea are major sources of morbidity in HIV-infected infants. Moreover, persistent diarrhea is a marker for rapid progression of HIV disease.

Polonium metabolism in adult female baboons

The biokinetics of polonium in nonhuman primates (Papio anubis) has been studied after intravenous injection of 210Po citrate. The urinary excretion of polonium in the baboon could be described by a single exponential function with a half-time of 15.6 days. Excretion fractions of polonium were found to be markedly different from those reported for other species, including humans. Polonium-210 was found to be distributed throughout the soft tissues of the baboon with 29% of the injected polonium being deposited in liver, 7% in kidneys and 0.6% in spleen. Retention of polonium in all tissues exhibited single exponential functions; however, the biological half-times were variable, ranging from 15 to 50 days.

Chromosomal localization of human genes for arylamine N-acetyltransferase

Arylamine N-acetyltransferase is encoded at two loci, AAC-1 and AAC-2, on human chromosome 8. The products of the two loci are able to catalyse N-acetylation of arylamine carcinogens, such as benzidine and other xenobiotics. AAC-2 is polymorphic and individuals carrying the slow-acetylator phenotype are more susceptible to benzidine-induced bladder cancer. We have identified yeast artificial chromosome clones encoding AAC-1 and AAC-2 and have used the cloned DNAs as fluorescent probes for in situ hybridization. The hybridization patterns allow assignment of AAC-1 and AAC-2 to chromosome 8p21.3-23.1, a region in which deletions have been associated with bladder cancer [Knowles, Shaw and Proctor (1993) Oncogene 8, 1357-1364].

Genotyping human polymorphic arylamine N-acetyltransferase: identification of new slow allotypic variants

Arylamine N-acetyltransferase catalyses the N-acetylation of primary arylamine and hydrazine drugs and chemicals. N-acetylation is subject to a polymorphism and humans can be categorized as either fast or slow acetylators according to their ability to N-acetylate polymorphic substrates in vivo. Previously, slow acetylation has been linked to four distinct polymorphic N-acetyltransferase (pnat) alleles each of which contains one or more point mutations within the coding region of the pnat gene. One new rare slow variant of pnat has been identified by cloning and sequencing the pnat DNA from an individual whose NAT phenotype was determined by in vivo acetylation of the polymorphic substrate sulphamethazine. This allele, designated S1c, differs from the wild type fast allele at nucleotide positions 341 and 803. A second new rare slow allotypic variant, designated S3, has been identified by resistance of the pnat specific DNA to digestion with the restriction enzymes Fok I and Bam HI. A method of genotyping individuals for the arylamine N-acetyltransferase (NAT) polymorphism is presented which correctly predicts the phenotype of greater than 95% (21 of 22) of individuals as measured by the extent of acetylation of sulphamethazine in urine. This refined genotyping method was applied to a clinical population of 48 Caucasians with classical or definite rheumatoid arthritis each receiving daily between 150 and 500 mg of the anti-rheumatic drug, D-penicillamine. There is no difference in the N-acetyltransferase phenotype of the individuals who developed proteinuria and the control group with no adverse effects.

Arylamine N-acetyltransferase in human red blood cells

N-Acetyltransferase activities associated with erythrocytes from 20 individuals have been determined with p-aminobenzoic acid as substrate. A three-fold variation in Vmax is found. The N-acetyltransferase genotype of the individuals has been determined and there is no correlation between the extent of acetylation measured in the individuals' erythrocytes and the inheritance of alleles at the polymorphic NAT locus. Folate is confirmed to be an inhibitor of arylamine N-acetyltransferase activity measured in erythrocytes. The content of folate in erythrocytes of individuals also varies. The individual with the maximum folate content has the minimum N-acetyltransferase activity. The monomorphic N-acetyltransferase gene from individuals spanning the range of N-acetyltransferase activity have been amplified, using the polymerase chain reaction. The pattern of restriction enzyme digestion of the monomorphic N-acetyltransferase gene with a series of eight restriction enzymes is the same for individuals spanning the activity range of arylamine N-acetyltransferase in their erythrocytes.

Characterization of the P1-purinoceptors mediating contraction of the rat colon muscularis mucosae

1. Previous studies had shown that adenosine and adenine nucleotides including adenosine 5'-triphosphate (ATP) caused contraction of the rat colon muscularis mucosae via P1 and P2Y-purinoceptors respectively, and that the stable ATP analogue adenylyl 5'-(beta,gama- methylene)diphosphonate (AMPPCP) had an unexpected direct action on the P1-purinoceptors. The P1-purinoceptors have now therefore been further characterized by use of the adenosine analogues 5'-N-ethylcarboxamidoadenosine (NECA) and N6-cyclopropyladenosine (CPA) and the antagonist 1,3-dipropyl-8-cyclopentylxanthine (DPCPX), which is selective for the A1 subtype. The P2-purinoceptor antagonist suramin was also used, to investigate the selectivity of the P2 agonists. 2. The order of potency of P1 agonists for contraction was CPA greater than NECA greater than AMPPCP greater than or equal to adenosine, and DPCPX (1 nM) caused greater than two fold shifts to the right of the log concentration-response curves for each of these agonists, although the shifts were not always parallel and Schild analysis of the inhibition of the effect of adenosine resulted in a plot with a slope greater than unity. These results indicate that the P1-purinoceptor mediating contraction is of the A1 subtype, as has been found in other tissues in which adenosine causes contraction. 3. The P2-purinoceptor antagonist suramin (300 microM) had no effect on the responses to adenosine or to AMPPCP, but abolished contractions induced by the related stable ATP analogue adenosine 5'-(alpha,beta-methylene)triphosphonate (AMPCPP). Contractions induced by ATP, which were not affected by DPCPX (10nM) alone, were only partially inhibited by suramin (300microM), revealing an A1 component to its action which could be blocked by DPCPX (10 nM).4. In conclusion, these results show that the rat colon muscularis mucosae possesses contractile A, receptors in addition to the previously characterized P2y receptors, and confirms our finding that the stable ATP analogue, AMPPCP, has an unexpected direct action on these Al receptors.

N-acetyltransferase polymorphism. Comparison of phenotype and genotype in humans

N-Acetyltransferase (NAT) isoenzymes are encoded at two loci. One locus encodes an NAT which is expressed widely in tissues, does not vary amongst human individuals and is termed monomorphic NAT (mNAT). The second locus encodes an NAT which is termed polymorphic NAT (pNAT), has a distinct tissue distribution and is responsible for the difference in ability between individuals in acetylating certain arylamine (e.g. sulphamethazine) and hydrazine (e.g. isoniazid) drugs which are polymorphic substrates. We describe a simple DNA based method for genotyping individuals for pNAT. The 'fast' NAT allele (F1) and the three 'slow' alleles (S1, S2 and S3) can be distinguished by using PCR with oligonucleotide primers specific for pNAT followed by restriction enzyme digestion of the amplified product. Heterozygotes are easily identified. The genotype of individual Caucasians compares well with the extent of acetylation of sulphamethazine. The allele distribution of the Caucasian population described here differs from that reported after Southern blot analysis of a Japanese population (Deguchi et al., J Biol Chem 265: 12757-12760, 1990). The most frequent allele at the polymorphic nat locus in Caucasians, S1, is absent in the Japanese population. This difference between the two populations is likely to be the basis of the known interethnic variation in acetylator phenotype frequencies.

Incorporation of imaging into a temporal coherence sensor

An image-processing technique based on temporal coherence differences in a scene is described. Resultant processed images are presented that demonstrate an increase in the signal-to-clutter ratio of the order of 10(2) for a He-Ne laser in a white-light background (FWHM 200 nm). Problems of processing speed, dynamic range, and image misalignment are addressed. Modifications in both the optical design and electronic signal processing are proposed. Comparison with nonimaging experiments indicates that signal-to-clutter gains approaching 10(8) are feasible.

Computerized versus standard administration of the Jenkins Activity Survey (Form T)

Using 60 male university students as subjects, this investigation compared the psychometric properties of computerized and paper-and-pencil versions of the student version (Form T) of the Jenkins Activity Survey. Data indicated that these different versions of the JAS demonstrated similar norms, reliabilities, and validities. The comparability of the JAS across administration modes suggested that computerizing the test does not significantly alter its characteristics. Implications of these findings and suggestions for future research are discussed.

Toxicity of hemorrhagic ascitic fluid associated with hemorrhagic pancreatitis

Hemorrhagic pancreatitis was induced in dogs by a retrograde infusion of the pancreatic duct with a mixture of taurocholate sodium and trypsin. Seven of the 13 dogs were pretreated with antibiotics. The hemorrhagic ascitic fluid (HAF) recovered from the dogs' abdomens was injected intraperitoneally into mice in volumes of 2.5, 5, 10, 15, and 20 mL. The mice were divided into two groups depending on whether the HAF received was from dogs given antibiotics. The mortality among the mice was proportional to the volume of HAF injected. The mortality among mice receiving the sterile HAF was 79.4% at 20 mL, 55.8% at 15 mL, 29.4% at 10 mL, 26% at 5 mL, and 17% at 2.5 mL. There were no deaths among mice receiving 25 mL and saline solution and the mortality was 15% among mice receiving 20 mL of dog plasma.