Sandra P. McCurdy

Absence of the P2X7 receptor alters leukocyte function and attenuates an inflammatory response

When challenged with extracellular ATP, leukocytes respond and activate processes attributed to the P2X7 receptor (P2X7R), an unusual ligand-gated ion channel. To prove P2X7R involvement, blood samples from P2X7R-deficient mice were characterized. Monocytes and lymphocytes associated with wild-type blood responded to ATP and underwent volume/shape changes and shed L-selectin. In contrast, leukocytes from P2X7R-deficient animals demonstrated no change in physical properties or L-selectin expression following ATP challenge. Blood stimulated with LPS or ATP individually generated minimal quantities of the leaderless polypeptide IL-1β, but sequential treatment of wild-type, but not P2X7R-deficient, blood with LPS and ATP yielded large amounts of cell-free cytokine. Based on these differences, wild-type and P2X7R-deficient animals were compared following induction of monoclonal anti-collagen-induced arthritis. Ab-treated wild-type animals subsequently challenged with LPS developed inflamed, swollen paws; their joint cartilage demonstrated lesions, loss of proteoglycan content, and the presence of collagen degradation products. P2X7R-deficient animals subjected to the same challenge were markedly less affected; both the incidence and severity of disease were reduced. These data indicate that ATP does act via the P2X7R to affect leukocyte function and that the P2X7R can serve as an important component of an in vivo inflammatory response.

Discovery of CP-690,550: A Potent and Selective Janus Kinase (JAK) Inhibitor for the Treatment of Autoimmune Diseases and Organ Transplant Rejection

There is a critical need for safer and more convenient treatments for organ transplant rejection and autoimmune disorders such as rheumatoid arthritis. Janus tyrosine kinases (JAK1, JAK3) are expressed in lymphoid cells and are involved in the signaling of multiple cytokines important for various T cell functions. Blockade of the JAK1/JAK3-STAT pathway with a small molecule was anticipated to provide therapeutic immunosuppression/immunomodulation. The Pfizer compound library was screened against the catalytic domain of JAK3 resulting in the identification of a pyrrolopyrimidine-based series of inhibitors represented by CP-352,664 (2a). Synthetic analogues of 2a were screened against the JAK enzymes and evaluated in an IL-2 induced T cell blast proliferation assay. Select compounds were evaluated in rodent efficacy models of allograft rejection and destructive inflammatory arthritis. Optimization within this chemical series led to identification of CP-690,550 1, a potential first-in-class JAK inhibitor for treatment of autoimmune diseases and organ transplant rejection.

The Novel JAK-3 Inhibitor CP-690550 Is a Potent Immunosuppressive Agent in Various Murine Models

JAK‐3 has been shown to play a key role in cytokine signaling via γc, e.g. IL‐2, 4, 7, 9, 15, 21. The current study describes the immunosuppressive effects of CP‐690550, a novel, small molecule inhibitor of JAK‐3, in various murine models. In vitro, CP‐690550 effectively inhibited a murine mixed lymphocyte reaction (MLR) (IC50= 91 nm). Mice chronically dosed with CP‐690550 (1.5–15 mg/kg/day) demonstrated dose‐ and time‐dependent alterations in lymphocyte subsets when examined by flow cytometry. The most dramatic change observed was a 96% reduction in splenic NK1.1 + TCRβ– cell numbers following 21 days of treatment. Delayed‐type hypersensitivity (DTH) responses in sensitized mice were reduced in a dose‐dependent manner following treatment with the JAK‐3 inhibitor (1.87–30 mg/kg, s.c.). Extended survival of neonatal Balb/c hearts implanted into the ear pinna of MHC mismatched C3H/HEN mice was observed with CP‐690550 monotherapy (10–30 mg/kg/day), but improved upon combination with cyclosporin (10 mg/kg/day). These data support the participation of JAK‐3 in various lymphocyte homeostatic functions in mature mice. Furthermore, the ability of CP‐690550 to extend cardiac allograft survival in murine models suggests it may afford a new treatment for prevention of transplant rejection.

Multicity Outbreak of Linezolid-Resistant Staphylococcus epidermidis Associated with Clonal Spread of a cfr-Containing Strain

We report a multicity outbreak of cfr-containing linezolid-resistant Staphylococcus epidermidis in Ohio. Thirty-nine isolates were obtained from 2 hospitals. Two clones with different mechanisms of linezolid resistance were circulating in hospital A. One of these contained the cfr gene, and the other a ribosomal mutation. The clone containing cfr was identical in both hospitals.

Successful Eradication of a Monoclonal Strain of Klebsiella pneumoniae during a K. pneumoniae Carbapenemase- Producing K. pneumoniae Outbreak in a Surgical Intensive Care Unit in Miami, Florida

We describe the investigation and control of a Klebsiella pneumoniae carbapenemase-producing K. pneumoniae outbreak in a 20-bed surgical intensive care unit during the period from January 1, 2009 through January 1, 2010. Nine patients were either colonized or infected with a monoclonal strain of K. pneumoniae. The implementation of a bundle of interventions on July 2009 successfully controlled the further horizontal spread of this organism.

5-(2-Pyrimidinyl)-imidazo[1,2-a]pyridines are antibacterial agents targeting the ATPase domains of DNA gyrase and topoisomerase IV

Dual inhibitors of bacterial gyrB and parE based on a 5-(2-pyrimidinyl)-imidazo[1,2-a]pyridine template exhibited MICs (microg/mL) of 0.06-64 (Sau), 0.25-64 (MRSA), 0.06-64 (Spy), 0.06-64 (Spn), and 0.03-64 (FQR Spn). Selected examples were efficacious in mouse sepsis and lung infection models at <50mg/kg (PO dosing).

Emergence of linezolid-resistant coagulase-negative Staphylococcus in a cancer centre linked to increased linezolid utilization

OBJECTIVES The prevalence of linezolid-resistant coagulase-negative Staphylococcus (CoNS) in the MD Anderson Cancer Center rose from 0.6% in 2007 to 5.5% in 2009. The aim of our study was to analyse the relationship between linezolid use and an outbreak of linezolid-resistant CoNS. PATIENTS AND METHODS We retrospectively identified 27 infection or colonization events. Eleven isolates were available for supplemental investigation; species identification, clonal relatedness and linezolid resistance mutation analysis. The medical records of the affected patients were reviewed and linezolid utilization data were obtained from the pharmacy. RESULTS Available isolates were confirmed as clonally related Staphylococcus epidermidis. Partial 23S rRNA gene sequencing found a G2576T mutation in all of the isolates tested. All patients received linezolid within 3 months prior to an event. Patients without a prior hospitalization had a longer time from admission to event; 29 versus 3.5 days (P = 0.002). The outbreak was preceded by a 51% increase in inpatient linezolid utilization and 64% of affected patients belonged to the leukaemia service, which had a utilization rate 3.1 times that of the other services (95% confidence interval: 2.96-3.23). CONCLUSIONS Increased linezolid utilization preceded the appearance of a linezolid-resistant CoNS clone. Patients probably acquired the clonal strain nosocomially, given the longer time from admission to event among patients with no previous admission to the MD Anderson Cancer Center. Linezolid administration then selected this strain, since all patients received linezolid prior to an event. A linezolid utilization rate of >or=13 defined daily doses/100 patient-days was similar to that reported in two other outbreaks and may be the threshold required to generate an outbreak.

Novel quinoline derivatives as inhibitors of bacterial DNA gyrase and topoisomerase IV.

A structurally novel set of inhibitors of bacterial type II topoisomerases with potent in vitro and in vivo antibacterial activity was developed. Dual-targeting ability, hERG inhibition, and pharmacokinetic properties were also assessed.

Siderophore Receptor-Mediated Uptake of Lactivicin Analogues in Gram-Negative Bacteria

Multidrug-resistant Gram-negative pathogens are an emerging threat to human health, and addressing this challenge will require development of new antibacterial agents. This can be achieved through an improved molecular understanding of drug-target interactions combined with enhanced delivery of these agents to the site of action. Herein we describe the first application of siderophore receptor-mediated drug uptake of lactivicin analogues as a strategy that enables the development of novel antibacterial agents against clinically relevant Gram-negative bacteria. We report the first crystal structures of several sideromimic conjugated compounds bound to penicillin binding proteins PBP3 and PBP1a from Pseudomonas aeruginosa and characterize the reactivity of lactivicin and β-lactam core structures. Results from drug sensitivity studies with β-lactamase enzymes are presented, as well as a structure-based hypothesis to reduce susceptibility to this enzyme class. Finally, mechanistic studies demonstrating that sideromimic modification alters the drug uptake process are discussed.

Pyridone-Conjugated Monobactam Antibiotics with Gram-Negative Activity

Herein we describe the structure-aided design and synthesis of a series of pyridone-conjugated monobactam analogues with in vitro antibacterial activity against clinically relevant Gram-negative species including Pseudomonas aeruginosa , Klebsiella pneumoniae , and Escherichia coli . Rat pharmacokinetic studies with compound 17 demonstrate low clearance and low plasma protein binding. In addition, evidence is provided for a number of analogues suggesting that the siderophore receptors PiuA and PirA play a role in drug uptake in P. aeruginosa strain PAO1.