Biophysical screening and characterisation in medicinal chemistry

In the last two decades the use of biophysical assays and methods in medicinal chemistry has increased significantly, to meet the demands of the novel targets and modalities that drug discoverers are looking to tackle. The desire to obtain accurate affinities, kinetics, thermodynamics and structural data as early as possible in the drug discovery process has fuelled this innovation. This review introduces the principles underlying the techniques in common use and provides a perspective on the weaknesses and strengths of different methods. Case studies are used to further illustrate some of the applications in medicinal chemistry and a discussion of the emerging biophysical methods on the horizon is presented.

The Wnt Pathway Inhibitor RXC004 Blocks Tumor Growth and Reverses Immune Evasion in Wnt Ligand-dependent Cancer Models

Wnt signaling is implicated in the etiology of gastrointestinal tract cancers. Targeting Wnt signaling is challenging due to on-target toxicity concerns and lack of druggable pathway components. We describe the discovery and characterization of RXC004, a potent and selective inhibitor of the membrane-bound o-acyl transferase Porcupine, essential for Wnt ligand secretion. Absorption, distribution, metabolism, and excretion and safety pharmacology studies were conducted with RXC004 in vitro, and pharmacokinetic exposure assessed in vivo. RXC004 effects on proliferation and tumor metabolism were explored in genetically defined colorectal and pancreatic cancer models in vitro and in vivo. RXC004 effects on immune evasion were assessed in B16F10 immune "cold" and CT26 immune "hot" murine syngeneic models, and in human cell cocultures. RXC004 showed a promising pharmacokinetic profile, inhibited Wnt ligand palmitoylation, secretion, and pathway activation, and demonstrated potent antiproliferative effects in Wnt ligand-dependent (RNF43-mutant or RSPO3-fusion) colorectal and pancreatic cell lines. Reduced tumor growth and increased cancer cell differentiation were observed in SNU-1411 (RSPO3-fusion), AsPC1 and HPAF-II (both RNF43-mutant) xenograft models, with a therapeutic window versus Wnt homeostatic functions. Additional effects of RXC004 on tumor cell metabolism were confirmed in vitro and in vivo by glucose uptake and ¹⁸fluorodeoxyglucose-PET, respectively. RXC004 stimulated host tumor immunity; reducing resident myeloid-derived suppressor cells within B16F10 tumors and synergizing with anti-programmed cell death protein-1 (PD-1) to increase CD8⁺/regulatory T cell ratios within CT26 tumors. Moreover, RXC004 reversed the immunosuppressive effects of HPAF-II cells cocultured with human peripheral blood mononuclear cells, confirming the multiple anticancer mechanisms of this compound, which has progressed into phase II clinical trials.

Significance

Wnt pathway dysregulation drives many gastrointestinal cancers; however, there are no approved therapies that target the pathway. RXC004 has demonstrated the potential to block both tumor growth and tumor immune evasion in a genetically defined, clinically actionable subpopulation of Wnt ligand-dependent gastrointestinal cancers. The clinical utility of RXC004, and other Porcupine inhibitors, in such Wnt ligand-dependent cancers is currently being assessed in patient trials.

Clinical characteristics with inflammation profiling of long COVID and association with 1-year recovery following hospitalisation in the UK: a prospective observational study

BACKGROUND

No effective pharmacological or non-pharmacological interventions exist for patients with long COVID. We aimed to describe recovery 1 year after hospital discharge for COVID-19, identify factors associated with patient-perceived recovery, and identify potential therapeutic targets by describing the underlying inflammatory profiles of the previously described recovery clusters at 5 months after hospital discharge.

METHODS

The Post-hospitalisation COVID-19 study (PHOSP-COVID) is a prospective, longitudinal cohort study recruiting adults (aged ≥18 years) discharged from hospital with COVID-19 across the UK. Recovery was assessed using patient-reported outcome measures, physical performance, and organ function at 5 months and 1 year after hospital discharge, and stratified by both patient-perceived recovery and recovery cluster. Hierarchical logistic regression modelling was performed for patient-perceived recovery at 1 year. Cluster analysis was done using the clustering large applications k-medoids approach using clinical outcomes at 5 months. Inflammatory protein profiling was analysed from plasma at the 5-month visit. This study is registered on the ISRCTN Registry, ISRCTN10980107, and recruitment is ongoing.

FINDINGS

2320 participants discharged from hospital between March 7, 2020, and April 18, 2021, were assessed at 5 months after discharge and 807 (32·7%) participants completed both the 5-month and 1-year visits. 279 (35·6%) of these 807 patients were women and 505 (64·4%) were men, with a mean age of 58·7 (SD 12·5) years, and 224 (27·8%) had received invasive mechanical ventilation (WHO class 7-9). The proportion of patients reporting full recovery was unchanged between 5 months (501 [25·5%] of 1965) and 1 year (232 [28·9%] of 804). Factors associated with being less likely to report full recovery at 1 year were female sex (odds ratio 0·68 [95% CI 0·46-0·99]), obesity (0·50 [0·34-0·74]) and invasive mechanical ventilation (0·42 [0·23-0·76]). Cluster analysis (n=1636) corroborated the previously reported four clusters: very severe, severe, moderate with cognitive impairment, and mild, relating to the severity of physical health, mental health, and cognitive impairment at 5 months. We found increased inflammatory mediators of tissue damage and repair in both the very severe and the moderate with cognitive impairment clusters compared with the mild cluster, including IL-6 concentration, which was increased in both comparisons (n=626 participants). We found a substantial deficit in median EQ-5D-5L utility index from before COVID-19 (retrospective assessment; 0·88 [IQR 0·74-1·00]), at 5 months (0·74 [0·64-0·88]) to 1 year (0·75 [0·62-0·88]), with minimal improvements across all outcome measures at 1 year after discharge in the whole cohort and within each of the four clusters.

INTERPRETATION

The sequelae of a hospital admission with COVID-19 were substantial 1 year after discharge across a range of health domains, with the minority in our cohort feeling fully recovered. Patient-perceived health-related quality of life was reduced at 1 year compared with before hospital admission. Systematic inflammation and obesity are potential treatable traits that warrant further investigation in clinical trials.

FUNDING

UK Research and Innovation and National Institute for Health Research.

Abstract 419: The development of BRPF1 degraders as a potential treatment for acute myeloid leukemia

Acetylation of histones and additional nuclear proteins is a key mechanism in the regulation of gene expression. Aberrant acetylation has been linked to a wide range of diseases including cancer, inflammation, and neurodevelopmental disorders. Histone acetylation is introduced by histone acetyltransferases complexes (HATs), where substrate specificity is dramatically enhanced by scaffolding proteins that activate and target them to specific chromatin sites. A protein of interest with both epigenetic acetyl reader and scaffolding function is the protein Bromodomain and PHD finger-containing protein 1 (BRPF1). The Protein contains domains of two plant homeodomain (PHD) fingers separated by a zinc knuckle (PZP domain), a bromodomain, and a proline-tryptophan-tryptophan-proline (PWWP) Tudor domain. Native BRPF1 complexes can contain either MOZ/MORF or HBO1 as the catalytic MYST-family acetyltransferase subunit and the stable complex with Moz-Tif2 is known to lead to the development of human acute myeloid leukemia (AML). Given this, we chose to pursue the development of BRPF1 degraders to probe cancer disease biology especially in AML, where new therapies are required to overcome several unmet needs such as less-toxic treatments and relapsed/refractory disease paradigms. Here we present the design and synthesis of a range of BRPF1 degraders in highly desirable physicochemical space utilizing in-silico modeling. The prepared degraders which utilize multiple E3 ligases were then screened against cell lines harboring Mixed-lineage leukemia (MLL) translocations specifically the THP-1 cell line. In addition to this, we investigated the ability of the compounds to effectively degrade the target and suitability of our degraders for potential in-vivo exposure through a panel of routine ADMET assays.

Citation Format: Daniel Joseph Glynn, Rosie Crampton, Thomas Pesnot, Andrew Scott, Anne-Chloe Nassoy, Ralph Kirk, Daniele Narducci, Gary Nelson, Lynette Ongiri, Habiba Begum, Vincent Rao, Matilda Bingham, Rhoanne McPherson, Darryl Turner. The development of BRPF1 degraders as a potential treatment for acute myeloid leukemia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 419.

Abstract 3764: Porcupine inhibitor RXC004 enhances immune response in pre-clinical models of cancer

Background: RXC004, a potent and selective porcupine (PORCN) inhibitor, is being investigated in a safety and tolerability study in cancer patients with solid tumours (CT 2017-000720-98). In addition to the tumour targeting role of RXC004 and other Wnt pathway inhibitors, we present pre-clinical data which suggests further potential for RXC004 in modulating the immune system of the tumour microenvironment. Materials and Methods: To evaluate the potential of a novel porcupine inhibitor, RXC004, as an immunomodulatory anti-cancer agent, sub cutaneous B16F10 melanoma (C57BL/6 mice) and CT26 colorectal (BALB/c mice) murine tumour models were utilised. Mice in both models were treated with RXC004 alone or in combination with mouse anti-PD-1 antibody. Flow cytometry analysis was utilised to measure key immune cell populations in the tumour microenvironment. To probe the underlying mechanism of immune modulation in these models and to provide a link to the emerging clinical data suggesting a role for Wnt pathway activation in immune escape, human monocytic cells were isolated from PBMCs and human dendritic cells were derived in vitro. The Wnt pathway was induced in derived Dendritic cells and expression of IDO was measured. Results: In the murine CT26 model, RXC004 treatment reduced tumour size when dosed in combination with anti-PD-1 antibody, causing regression and cures in some animals. Furthermore, flow cytometry showed RXC004 in combination with anti-PD-1 antibody increased the proportion of CD8+ cytotoxic T cells as well as decreasing FoxP3+ regulatory T cells when compared to the monotherapy anti-PD-1 arm. In a syngeneic murine melanoma B16F10 model, RXC004 monotherapy at a dose of 5mg/kg QD orally significantly inhibited tumour growth, as did RXC004 combined with anti-PD-1. RXC004 had no effect on the proliferation of B16F10 cells in vitro, suggesting this was not caused by the compound directly affecting B16 cell proliferation. Flow cytometry analysis of the B16 tumours showed significant immune modulatory effects in the tumour microenvironment. In addition to mouse model data, Wnt pathway activation in human dendritic cells was shown to increase IDO expression. Conclusion: Taken together, data from murine syngeneic mouse models corroborate literature data suggesting that inhibiting the Wnt pathway may promote the immune response against human cancers.

Citation Format: Inder Bhamra, Richard Armer, Matilda Bingham, Catherine Eagle, Alicia Edmenson Cook, Caroline Phillips, Simon Woodcock. Porcupine inhibitor RXC004 enhances immune response in pre-clinical models of cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3764.

Novel porcupine (PORCN) inhibitor RXC004: Evaluation in models of RNF43 loss of function cancers

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Background: Wnt signalling initiates oncogenic pathways involved in tumour initiation, growth, differentiation and metastasis.1 Targeting the Wnt pathway is an attractive approach to cancer treatment. Porcupine (PORCN) is a membrane-bound O-acyltransferase dedicated to the palmitoylation of Wnt ligands, an essential step in the processing of Wnt into active ligands.2 A PORCN inhibitor may benefit patients with cancers in which Wnt signalling is implicated. It has been shown that PORCN inhibition is efficacious in cell lines with upstream mutations in this pathway, eg RNF43 loss of function.3 Methods: Analysis of TCGA data was carried out to identify cancer types harbouring RNF43 mutations.4 Redx PORCN inhibitor RXC004 was evaluated in vitro for Wnt pathway inhibition and anti-proliferative effects using assays previously described for early lead compounds.5Anti-tumour effects of RXC004 were evaluated using a pancreatic CAPAN-2 xenograft in SCID Bg. mice and a gastric PDX model in nu/nu mice. Both models have RNF43 loss of function mutations. Results: TCGA data revealed that both gastric cancer and pancreatic cancer exhibit mutations in the RNF43 gene (18% and 4% respectively),4expected to result in loss of function. RXC004 showed activity in preclinical models of cancers with this genetic background. RXC004 significantly inhibited tumour growth in a CAPAN-2 pancreatic cancer xenograft and in a gastric cancer PDX model when dosed orally once or twice daily. Conclusions: Taken together, these data indicate that RXC004 is a potent inhibitor of tumour growth in RNF43 loss of function preclinical cancer models. RXC004 will be evaluated in a first in human Phase 1 study in 2017. Phase 1a aims are to characterise the safety profile and PK/PD relationship in cancer patients and establish a Phase 1b dose. The efficacy of RXC004 in gastric and pancreatic cancer patients prospectively selected for RNF43 loss of function mutations will be the focus of Phase 1b expansion groups. 1 . Nat. Rev. Cancer, 2013, 13 (1): 11-26.2. J. Biol. Chem., 2012, 287 (27): 23246-23254. 3. PNAS, 2013, 110 (31): 12649-12654 4. Sci. Signal, 2013, 269 (6): 1-34; Cancer Discov., 2012, 2 (5): 401-404 5. AACR Annual Meeting, 2015, 75 (15): abs. 5071.

Abstract 4795: Development of novel, selective, reversible inhibitors equipotent against wild-type and C481S Bruton's tyrosine kinase (BTK)

Redx Oncology has developed novel, differentiated, reversible small molecule inhibitors of BTK, combining current best-in-class potency with improved selectivity profiles, which are suitable for oral, once daily dosing, designed to be equipotent against wild-type and C481S BTK.

BTK is a member of the src-related Tec family of cytoplasmic tyrosine kinases. BTK plays a key role in the BCR signaling pathway, which is required for the development, activation and survival of B-cells. BTK inhibitors have therefore been developed with the aim of treating B-cell malignancies that are dependent on BCR signaling, such as CLL and NHL. Ibrutinib is an irreversible BTK inhibitor that has been approved for the treatment of CLL, MCL and WM.

Irreversible and covalent reversible BTK inhibitors specifically target a cysteine residue C481 within BTK. Following treatment with ibrutinib, cases of secondary resistance have emerged in both CLL and MCL patients. Acquired mutations within BTK such as C481S, C481Y, C481R, C481F have been reported in the literature and clearly interfere with covalent drug binding. It has been predicted that the incidence of observed resistance will increase as clinical use outside clinical trials expands over time. Here, we present our reversible BTK inhibitor series demonstrating subnanomolar binding affinity for WT and C481S forms of BTK, that inhibits formation of pBTK in both WT and C481S BTK expressing cells. In addition, the compound demonstrated significant in vitro potency against a number of lymphoma cell lines including inhibition of BCR signaling and proliferation in OCI-Ly10 cells at nanomolar concentrations. To further investigate the binding nature of these compounds, PBMC wash out studies, measuring CD69 as a marker of B-cell activation, were used to highlight the reversible activity of these compounds.

Some BTK inhibitors also inhibit ITK, which plays a critical role in FcR-stimulated NK cell function that is required for ADCC. ADCC is the mechanism that anti-CD20 antibodies, such as rituximab, are believed to activate, and ibrutinib has been shown to antagonize this mechanism in vitro. As rituximab-combination chemotherapy is today's standard of care in B-cell malignancies, it would be desirable to have a BTK inhibitor with high selectivity for BTK over ITK.

At 1 μM, our lead compound is highly selective when tested against 469 kinase and did not show significant inhibition against other kinases involved in BCR signaling (e.g. Syk, Lyn). Furthermore, the compound has high selectivity versus structurally related cysteine-containing kinases (including EGFR and ITK) both in enzyme and cellular assays.

Our lead compound has a favorable in vitro safety profile and drug-like properties, displaying an improved CYP profile to competitor compounds. In vivo PK demonstrated good oral bioavailability and in vivo efficacy has been demonstrated.

Citation Format: Nicolas E S Guisot, Victoria Walker, Stuart A. Best, Valentina Abet, Rose Chappell, Juliette Emmerich, Kelvin Ho, James R. Kelly, Kristina Lyons, Melanie Müller, Julienne Refuerzo, Louise Sargent, Fatima Talab, Madelene Waldron, Matilda Bingham, Mary-Ann Campbell, Caroline Phillips, Richard Armer. Development of novel, selective, reversible inhibitors equipotent against wild-type and C481S Bruton's tyrosine kinase (BTK). [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4795.

Abstract A199: Development of a series of novel, potent and selective inhibitors of cFMS as a potential treatment for CSF1 expressing cancers via the modulation of the tumor microenvironment and the repolarization of macrophages

Redx Oncology has developed novel small molecule inhibitors of Colony Stimulating Factor 1 Receptor (CSF1R or cFMS) which have proven to be efficacious in an in vivo bone erosion model.

cFMS is a key receptor involved in the survival, modulation and maintenance of cells of the monocyte- macrophage lineage (which include osteoclasts in the bone). In bone, osteoclasts express cFMS whilst osteoblasts express CSF1. The CSF1/cFMS axis is involved, along with RANKL, in the dynamics of bone metabolism. Metastatic tumor cells that express cFMS can be recruited into the bone as part of this dynamic metabolism. Moreover, recent literature has shown that cFMS inhibitors are able to ‘re-educate’ pro-tumurogenic M2 macrophages, which are present in the tumor microenvironment in a CSF positive tumor, into the anti-tumurogenic M1 phenotype.

We present here results of the lead optimization of our novel cFMS inhibitor series.

REDX05182 is a lead compound from the series and is a highly selective cFMS inhibitor which shows potent inhibition of cFMS. It also inhibits the related kinases cKIT, PDGFRA and PDGFRB. Interestingly, however, it exhibits good selectivity over related kinases Flt3 and KDR (VEGFR2). It displays low nanomolar binding affinity for cFMS in a biochemical assay (6nM (5 hours)) and displays slow binding kinetics.

In cellular assays, REDX05182 shows nanomolar inhibition of CSF1 driven cell proliferation of the M-NFS-60 cell line (126nM), CSF1 stimulated phosphorylation of CSF1R in THP-1 cells (182nM) and CSF-1 stimulated differentiation of rat primary macrophages into osteoclasts (102nM).

REDX05182 demonstrates good exposure and bioavailability in vivo and has shown efficacy in a rat model of cancer induced bone resorption using MRMT-1 cancer cells. At 30mg/kg BID a statistically significant improvement in the allodynia score is observed. Also at this dose the osteoclast count in the bone is returned to that of normal bone and the osteolysis is reduced.

Interestingly, REDX05182 has also demonstrated the re-polarization of macrophages from the pro-tumurogenic M2 phenotype to the anti-tumurogenic M1 phenotype in human pBMC's.

In summary, REDX05182 is a potent cFMS inhibitor which has shown activity in vivo and in vitro. Work is continuing on the project to further optimize this lead compound to deliver a clinical candidate.

Citation Format: Sachin G. Mahale, Andrew Belfield, Jamie Wright, Mary-Ann Campbell, Matilda Bingham, Richard Armer. Development of a series of novel, potent and selective inhibitors of cFMS as a potential treatment for CSF1 expressing cancers via the modulation of the tumor microenvironment and the repolarization of macrophages. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr A199.

Medicinal Chemistry Challenges in CNS Drug Discovery

The human brain is a uniquely complex organ, which has evolved a sophisticated protection system to avoid injury from external insults and toxins. Penetrating the blood-brain barrier (BBB) to achieve the drug concentrations required for efficacious target receptor occupancy in the brain region of interest is a unique and significant challenge facing medicinal chemists working on CNS targets. Prospective design of molecules with optimal brain exposure and safety profile requires in-depth understanding of the fundamental relationships between physicochemical properties and in vitro and in vivo outcomes. Following from the now widely accepted “rule of five” guidelines for the design of oral drugs, the physicochemical properties for brain penetration have been extensively studied in an effort to define the characteristics of successful CNS drug candidates. Several key physicochemical properties have been identified that influence the rate of brain permeability and extent of brain penetration, including H-bonding potential, molecular weight, lipophilicity, polar surface area (PSA), ionization state and rotatable bond count. The ability to process this information effectively and engage in multi-parameter prospective design ultimately determines the success in delivering high-quality drug candidates that are suitable robustly to test hypotheses in the clinic and have good probability of reaching the market. This chapter focuses on the medicinal chemistry aspects of drug candidate optimization particular to the CNS therapeutic area, such as crossing the blood-brain barrier (BBB), as well as safety-related issues frequently challenging CNS programs such as hERG selectivity and phospholipidosis.

A HEMOLYTIC SYSTEM ASSOCIATED WITH ENTERITIS IN RABBITS : I. NATURE OF THE CELL CHANGE AND THE SERUM FACTORS CONCERNED

A disease characterized by frequent association of enteritis and polyagglutinable cells often develops in weanling rabbits. The red cell lesion renders the cells susceptible to agglutination and hemolysis in normal rabbit sera. The degree of red cell abnormality varies among different animals and disappears when the animals recover. The abnormality of the red cells responsible for their polyagglutinability and susceptibility to hemolysis was resistant to the action of trypsin or papain and persisted in heated stroma preparations derived from polyagglutinable cells. The factors necessary for agglutination and hemolysis of the polyagglutinable cells are present in normal rabbit sera but are lacking in the sera of affected rabbits. These factors returned to normal levels as the polyagglutinable cell lesion disappeared. The sera of rabbits with polyagglutinable cells contained normal levels of complement and properdin. Whereas the agglutinating factor in normal sera is heat-stable at 56°C for 30 minutes, the hemolytic factor is heat labile. The hemolytic factor is apparently distinct from complement and properdin since it was adsorbed from normal rabbit serum by zymosan or by polyagglutinable cells at 0°C. However, complement was fixed when normal rabbit serum was reacted with stroma from polyagglutinable cells. Hemolysis of polyagglutinable cells by normal rabbit serum at 25°C was inhibited by preliminary incubation of the mixture at 0°C prior to incubation at 25°C. Evidence was obtained which indicated that this inhibition was due to progression of a reaction involving Ca⁺⁺ independent of a reaction involving Mg⁺⁺.

The distribution, abundance and population trends of gentoo, rockhopper and king penguins in the Falkland Islands

The Falkland Islands are a globally important breeding location for seabirds, including penguins. The total breeding populations of three of the four main penguin species present in the Falklands were censused in the austral summer of 1995/96. The results for gentoo and rockhopper penguins suggest declines of about 43 and 90 per cent, respectively, since a similar census in 1932/33. Recent monitoring studies suggest that these declines are still continuing; research to investigate causes (which is likely to reflect changes in the marine, rather than terrestrial environment) is a high priority. In contrast, king penguin populations, currently c. 400 pairs, have increased steadily, by 700 per cent since 1980/81, in line with world-wide trends for this species.

Pharmacology of Glutamate Transport in the CNS: Substrates and Inhibitors of Excitatory Amino Acid Transporters (EAATs) and the Glutamate/Cystine Exchanger System x c −

As the primary excitatory neurotransmitter in the mammalian CNS, l-glutamateparticipates not only in standard fast synaptic communication, but also contributes to higher order signalprocessing, as well as neuropathology. Given this variety of functional roles, interest has been growingas to how the extracellular concentrations of l-glutamate surroundingneurons are regulated by cellular transporter proteins. This review focuses on two prominent systems, eachof which appears capable of influencing both the signaling and pathological actions of l-glutamatewithin the CNS: the sodium-dependent excitatory amino acid transporters (EAATs) and the glutamate/cystineexchanger, system x_c⁻(Sx_c⁻). Whilethe family of EAAT subtypes limit access to glutamate receptors by rapidly and efficiently sequesteringl-glutamate in neurons and glia, Sx_c⁻provides a route for the export of glutamate from cells into the extracellular environment. The primaryintent of this work is to provide an overview of the inhibitors and substrates that have been developedto delineate the pharmacological specificity of these transport systems, as well as be exploited as probeswith which to selectively investigate function. Particular attention is paid to the development of smallmolecule templates that mimic the structural properties of the endogenous substrates, l-glutamate,l-aspartate and l-cystine andhow strategic control of functional group position and/or the introduction of lipophilic R-groups can impactmultiple aspects of the transport process, including: subtype selectivity, inhibitory potency, and substrateactivity.

Ring-Closing Metathesis as a Basis for the Construction of Aromatic Compounds

The use of metathesis, especially in the context of ring-closing metathesis (RCM) to form five- and six-membered rings, is widespread in organic chemistry today. However, there are surprisingly few examples of the reaction being used to form aromatic compounds. The central place of aromatic compounds in both medicinal chemistry and natural products synthesis, coupled with the efficiency and functional group tolerance of RCM catalysts, means that there is now an interesting opportunity to use RCM for the synthesis of arenes. Although the formation of an aromatic compound was viewed in many early examples as an undesirable degradation product, several rationally designed methods towards the preparation of aromatic compounds by RCM have recently been developed.

Use of the site percutaneous breast biopsy device

A new technique is described for image guided percutaneous diagnostic excision biopsy of non-palpable mammographically detected breast lesions. This method involves insertion of a localizing guide wire under stereotactic guidance followed by insertion of the 15 mm diameter biopsy device which is positioned within the breast immediately proximal to the target lesion. A cylindrical cannula is advanced over the lesion which is then separated from the surrounding breast tissue by deploying a garrote wire at the distal end of the cannula. The biopsy device is then removed with the target lesion contained within the cannula. The mammographic lesion is excised without removing any excess adjacent breast tissue, and in one piece, so allowing histological examination of the whole lesion. The experience of the first three cases is described with imaging and histological correlation.

Comparison of the TOX A/B test to a cell culture cytotoxicity assay for the detection of Clostridium difficile in stools

The TOX A/B Test (Techlab, Blacksburg, VA, USA) was compared to cell culture cytotoxicity assay on 1109 consecutive diarrheal stool samples collected from patients with the presumptive diagnosis of Clostridium difficile disease. The TOX A/B Test is an enzyme immunoassay in a microtiter format that detects both toxins A and B. The procedure used for this study takes approximately 1.5 h to perform. Cell culture cytotoxicity was performed by using a fibroblast cell line in a microtiter format read at 4 h, 24 h, and 48 h. One hundred ninety-four of the 1109 samples were positive by the "gold standard" cytotoxicity assay, whereas 189 were positive by EIA. There was a 98.5% agreement between the two assays. When compared to the cytotoxicity assay, the EIA had an initial sensitivity of 94.3% and a specificity of 99.3%. However, after resolution of six discrepants using another ELISA for toxin A detection the sensitivity, specificity, positive and negative predictive values for the TOX A/B test are as follows: 94.5%; 100%; 100%; 98.8%. The corresponding values for the cytotoxicity assay are: 97%; 100%; 100%; and 99.3%. This test seems to have excellent sensitivity and specificity as compared to an in-house cell culture cytotoxicity assay. It is sensitive enough to use as a stand-alone test for the detection of C. difficile toxin in laboratories that do not have cell culture cytotoxicity testing capability.

The nurse practitioners' role in smoking cessation

Most people who smoke want to quit. Smoking is a combination of nicotine addiction, psychologic dependency, and habit. Nurse practitioners are in a unique position to influence clients to stop smoking. The authors discuss individual and group therapy programs and the role of the nurse practitioner. Nurse practitioners are encouraged to start smoking cessation programs in their communities.

Mercy Hospital and Medical Center, Chicago. Marketing physical exams -- a source of new clients

Commitment to care of the medically indigent requires that an institution be financially viable. To ensure this, one health care facility has inaugurated a health appraisal program to attract privately insured patients.

Chronic hemolytic anemia due to cold agglutinins. II. The role of C' in red cell destruction

The sera of four patients with chronic hemolytic anemia due to cold agglutinins deposited C' globulins on normal red cells at 37 degrees C. The circulating cells of the patients were heavily coated with C' complex and were relatively resistant to C' hemolysis by cold agglutinin. Such red cells were removed from the patients' circulation at an exponential rate with (51)Cr t((1/2)) that varied from 7 to 19 days. Normal red cells were removed rapidly by hepatic sequestration during the first hours in the patients' circulation. Thereafter, a slower rate of abnormal destruction occurred which was associated with the accumulation of C' complexes on the red cell and the development of resistance to C' hemolysis by cold agglutinin. Normal red cells coated with sufficient C' complex by action of cold agglutinins in vitro to produce resistance to C' hemolysis by cold agglutinins demonstrated varying degrees of improved survival during the first hours in the circulation of three of the patients. The levels of serum C' were reduced in all four patients with chronic hemolytic anemia due to cold agglutinins. Transfusion of large volumes of normal red cells into two patients further reduced serum C'. (51)Cr-labeled normal red cells survived longer after red cell transfusions than before, because of less rapid destruction during the first hours in the circulation. The reduction in serum C' levels appeared responsible for the improved survival. In subjects without cold agglutinins, the presence of the spleen decreased the survival of red cells from a patient who had previously undergone splenectomy. Splenic removal also predominated in the reduced survival of autologous red cells in one patient. Neither hepatic nor splenic mechanisms predominated in removing autologous C'-coated cells in the other two patients.

Chronic hemolytic anemia due to cold agglutinins: the mechanism of resistance of red cells to C' hemolysis by cold agglutinins

The red cells of patients with chronic hemolytic anemia due to cold agglutinins are agglutinated by antiglobulin serum in a nongamma reaction due to the coating of beta-globulins, C'4 and C'3. The red cells of such patients are abnormally resistant to C' hemolysis by cold agglutinin. Normal red cells can be made equally resistant to C' hemolysis by incubation with cold agglutinin and normal serum at temperatures which allow transient reactions between the red cells and cold agglutinins. The development of resistance to C' hemolysis was related to increasing susceptibility to agglutination in anti-beta(1c)- and anti-beta(1e)-sera and by increasing uptake of (131)I activity from labeled anti-beta-globulin serum containing antibodies for both globulins. There was decrease in the adsorption of (131)I-labeled cold agglutinin during the development of resistance to C' hemolysis and reduced susceptibility to agglutination by cold agglutinins. Since cold agglutinins have been demonstrated to dissociate from the red cell, leaving fractions of C' globulin attached, it is postulated that repeated transient reactions produce the accumulation of incomplete C' complexes. Steric hindrance by the adsorbed C' complexes is probably responsible for the inhibition of the reaction with cold agglutinin. There is evidence that the adsorbed C' complexes also interfere with the hemolytic action of C' even when cold agglutinin has become reattached to the red cells. The accumulation of C' complexes by cold agglutinins appears to be the most important factor in the abnormal resistance to C' hemolysis exhibited by the patient's red cells. Other factors, such as the heterogeneity within a population of normal cells, appear to be of minor significance.