AB1101 PREVALENCE OF LONG COVID IN RHEUMATIC DISEASE PATIENTS: ANALYSIS OF SAR COVID REGISTRY

Background

Persistent symptoms after acute COVID have been described previously. Main symptoms reported are fatigue, arthralgias, myalgias and mental sickness. Definition and methods vary widely.1

Objectives

To asses prevalence and related factors to long COVID in a retrospective cohort of patients with rheumatic diseases from Argentina.

Methods

A total of 1915 patients were registered from August 18th, 2020 to July 29th, 2021. Patients > 18 years old, with rheumatic disease and confirmed infection by SARS-CoV-2 (antigen or RT-PCR) were included. Those dead, with unknown outcome, wrong date or missing data were excluded. Demographic data, comorbidities, rheumatic disease, and characteristics of SARS-CoV-2 infection were recorded.

Long COVID was defined according to NICE guidelines (persistent symptoms for more than 4 weeks, without alternative diagnosis). Long COVID symptoms were defined by rheumatologist. Severity of infection was classified according to WHO ordinal scale.

We used descriptive statistics, univariate model (Student’s test, chi square test, ANOVA) and multivariate logistic regression analysis.

Results

230 (12%) had long COVID. Median age was 51 (IQR 40-61]) years, 82% were females, 51% were not caucasian. Median of education was 13.3 years (IQR 12 – 16), 79 % had private health insurance and 55 % were employed. Nearly half (n=762, 46%) had comorbidities, the most prevalent was hypertension (n=396, 24%).

The most frequent rheumatic diseases were rheumatoid arthritis (n=719, 42%) and systemic lupus erythematosus (n=280, 16 %). Most were in low activity/remission (79%), used Conventional DMARD (n=773 patients, 45%) and steroids (n=588, 34%) at low dose (n=415, 71%).

Main laboratory findings were abnormal D-dimer (n=94, 28%) and leukopenia (n=93, 26%). Most patients had a WHO ordinal scale < 5 (n=1472, 86%). Median of hospitalization at intensive care unit (ICU) was 8 days [IQR 5, 13]. Treatment for SARS-CoV-2 infection (steroids, anticoagulation, azithromycin, convalescent plasma) was used in 461 (27%) patients.

Most of long COVID (n= 152, 69%) reported 1 symptom, the most frequent was fatigue (n= 55, 22%). Figure 1.

Univariate analysis is presented in Table 1. In multivariate logistic regression analysis non-caucasian ethnicity OR 1.44 (1.07-1.95), years of education OR 1.05 (1-1.09), treatment with cyclophosphamide OR 11.35 (1.56-112.97), symptoms of COVID – 19 OR 13.26 (2.75-242.08), severity scale WHO ≥ 5 OR 2.46 (1.68-3.57), and ICU hospitalization days OR 1.09 (1.05-1.14) were factors associated to long COVID.

Table 1.

Univariate analysis of long COVID syndrome in SAR – COVID registry

VariableAcute COVID n=1486Long COVID n=221P valueAge, years, median [IQR]51 [40, 60]54 [42, 62]0.032Caucasian, n (%)744 (48)132 (53)0.227Female sex, n (%)1242 (80)215 (86)0.066Education, years, median [IQR]12 [10, 17]13 [12, 16]-Private health insurance, n (%)1161 (79)181 (82)0.325Smoking, n (%)381 (25)71 (29)0.224Comorbidities, n (%)650 (45)108 (52)0.066Dyslipidemia, n (%)173 (12)39 (19)0.008Hypertension, n (%)332 (23)60 (29)0.053Low activity/remission disease, n (%)1140 (80)179 (77)1Rheumatoid arthritis, n (%)623 (42)96 (42)1Systemic lupus erythematosus, n (%)243 (16)37 (16)0.996DMARD, n (%)664 (45)109 (47)0.486Cyclophosphamide, n (%)3 (0.2)3 (1)0.035Rituximab, n (%)19 (1)9 (34)0.008Lymphocyte66 (23)19 (30)0.011<1.500 / mm3, n (%)Ferritin > 2000 ng/ml, n (%)32 (11)16 (25)0.011ICU hospitalization, days,7 [4, 10]10 [8, 24]<0.001median [IQR]Treatment for COVID-19, n (%)394 (27)91 (41)<0.001

Conclusion

Prevalence of long COVID was 12%. Non-caucasian ethnicity, higher education, treatment with cyclophosphamide, symptoms of COVID – 19, severe disease and ICU hospitalization days were related to long COVID.

References

[1]Cabrera Martimbianco AL, Pacheco RL, Bagattini ÂM, Riera R. Frequency, signs and symptoms, and criteria adopted for long COVID-19: A systematic review. Int J Clin Pract.

Disclosure of Interests

None declared

POS1238 GLUCOCORTICOIDS, RITUXIMAB AND THE PRESENCE OF INTERSTITIAL LUNG DISEASE ARE ASSOCIATED WITH POOR OUTCOMES OF THE SARS-COV-2 INFECTION IN PATIENTS WITH RHEUMATOID ARTHRITIS: DATA FROM THE NATIONAL REGISTRY SAR-COVID

Background

High disease activity, treatment with glucocorticoids (GC) and rituximab (RTX), have been related to worse outcomes of COVID-19.

Objectives

To assess the clinical characteristics and severity of the SARS-CoV-2 infection in patients with rheumatoid arthritis (RA) included in the SAR-COVID registry and to identify factors associated with poor outcomes.

Methods

SAR-COVID is a national, longitudinal and observational registry. Patients of ≥18 years old, with diagnosis of RA (ACR-EULAR criteria 2010) who had confirmed SARS-CoV-2 infection (RT-PCR or positive serology) were included between 13-8-20 and 31-7-21. Sociodemographic and clinical data, comorbidities, disease activity and treatment at the moment of the SARS-CoV-2 infection were collected. Additionally, infection symptoms, complications, medical interventions and treatments for COVID-19 were registered. Infection severity was assessed using the WHO-ordinal scale (WHO-OS)1. A cut-off value of ≥5 identified patients with severe COVID-19 and those who died.

Statistical analysis: Descriptive statistics. Chi2 or Fischer test, Student T test or Mann-Whitney and Kruskal Wallis or ANOVA, as appropriate. Multiple logistic regression model.

Results

A total of 801 patients were included, with a mean age of 53.1 ± 12.9 years, most of them were female (84.5%) and the median (m) disease duration was 8 years (IQR 4-14). One third were in remission and 46.4% had comorbidities, being the most frequent, hypertension (26.9 %), dyslipidemia (13.5 %), obesity (13.4 %) and diabetes (8.9%). Moreover, 3.2% had interstitial lung disease (ILD) associated with RA. At SARS-CoV-2 diagnosis, 42.5% were receiving glucocorticoids (GC), 73.9% conventional (c) disease modifying antirheumatic drugs (DMARD), 24% biologic (b) DMARD and 9.1% targeted synthetic (ts) DMARD. Among bDMARD, the most frequently used were TNF inhibitors (17%), followed by abatacept (2.8%), IL-6 inhibitors (2.4%) and rituximab (RTX) (2.1%). During the SARS-CoV-2 infection, 95.8% had symptoms, 27% required hospitalization, 7.9% presented complications and 4.4% died due to COVID-19. Severe disease and death (WHO-OS≥5) was present in 7.5% of the patients. They were older (62.9±12.5 vs 52.2±12.7, p<0.001), and they had more frequently ILD (18.5% vs 2%, p<0.001), comorbidities (82.5% vs 43.7%, p<0.001), ≥2 comorbidities (60.3% vs 25.8%, p<0.001), treatment with GC (61% vs 40.7%, p=0.04) and RTX (8.3% vs 1.6%, p=0.007). Conversely, the use of cDMARD and TNF inhibitors was more frequent in patients with WHO-OS<5, nevertheless this difference was not significant. Disease activity was comparable between groups. In multivariable analysis, older age, the presence of diabetes, ILD, the use of GC and RTX were significantly associated with WHO-OS≥5 (Figure 1). Furthermore, older age (65.7±10.8 vs 52.4±12.8, p<0.001), the presence of comorbidities (87.9% vs 44.7%, p<0.001), chronic obstructive pulmonary disease (21.9% vs 5.2%, p=0.002), diabetes (30.3% vs 7.9%, p<0.001), hypertension (57.6% vs 25.6%, p<0.001), cardiovascular disease (15.6% vs 3.2%, p=0.005), cancer (9.1% vs 1.3%, p=0.001), ILD (23.3% vs 2.4%, p<0.001) and the use of GC (61.8% vs 41.4%, p=0.02) were associated with mortality. Older age [OR 1.1 IC95% 1.06-1.13] and the use of GC 5-10 mg/day [OR 4.6 IC95% 1.8-11.6] remained significantly associated with death due to COVID-19.

Figure 1.

Factors associated with severe disease and death due to COVID-19 (WHO-OS≥5) in patients with rheumatoid arthritis. Multivariable analysis. (ref.: reference; PDN: prednisone; OR: odds ratio; CI: confidence interval)

Conclusion

Treatment with RTX and GC, as well as older age, the presence of diabetes and ILD were associated with poor COVID-19 outcomes in this national cohort of patients with RA. Older patients and those taking GC had a higher mortality rate.

References

[1]World Health Organization coronavirus disease (COVID-19) Therapeutic Trial Synopsis Draft 2020.

Disclosure of Interests

None declared

Peptidase neurolysin functions to preserve the brain after ischemic stroke in male mice

Previous studies documented up-regulation of peptidase neurolysin (Nln) after brain ischemia, however, the significance of Nln function in the post-stroke brain remained unknown. The aim of this study was to assess the functional role of Nln in the brain after ischemic stroke. Administration of a specific Nln inhibitor Agaricoglyceride A (AgaA) to mice after stroke in a middle cerebral artery occlusion model, dose-dependently aggravated injury measured by increased infarct and edema volumes, blood-brain barrier disruption, increased levels of interleukin 6 and monocyte chemoattractant protein-1, neurological and motor deficit 24 h after stroke. In this setting, AgaA resulted in inhibition of Nln in the ischemic hemisphere leading to increased levels of Nln substrates bradykinin, neurotensin, and substance P. AgaA lacked effects on several physiological parameters and appeared non-toxic to mice. In a reverse approach, we developed an adeno-associated viral vector (AAV2/5-CAG-Nln) to overexpress Nln in the mouse brain. Applicability of AAV2/5-CAG-Nln to transduce catalytically active Nln was confirmed in primary neurons and in vivo. Over-expression of Nln in the mouse brain was also accompanied by decreased levels of its substrates. Two weeks after in vivo transduction of Nln using the AAV vector, mice were subjected to middle cerebral artery occlusion and the same outcome measures were evaluated 72 h later. These experiments revealed that abundance of Nln in the brain protects animals from stroke. This study is the first to document functional significance of Nln in pathophysiology of stroke and provide evidence that Nln is an endogenous mechanism functioning to preserve the brain from ischemic injury.

Abstract 157: Peptidase Neurolysin Functions to Preserve the Brain After Ischemic Stroke in Mice

The aim of this study was to assess the functional role of peptidase neurolysin (Nln) in the brain after ischemic stroke. Nln is known to inactivate bradykinin, substance P, neurotensin, and angiotensin II, which are cerebrotoxic in the ischemic brain, and to generate angiotensin-(1-7) and Met/Leu-enkephalins, which are cerebroprotective/restorative peptides. To study the functional significance of Nln upregulation in the post-stroke brain we utilized a specific inhibitor of Nln, Agaricoglyceride A (AgaA), in a mouse MCAO model of stroke. Administration of AgaA (10 and 50 mg/kg, i.p.) to mice 1 h after reperfusion (1 h occlusion) aggravated stroke injury measured by increased infarct and edema volume (p < 0.01) and neurological deficit (p < 0.01), in a dose-dependent manner at 24 h after stroke. In this setting, AgaA resulted in a dose-dependent inhibition of Nln in the ischemic but not in the contralateral hemisphere, which, based on preliminary experiments, was also accompanied by increased levels of Nln substrate neuropeptides. In a reverse approach, we developed an adeno-associated virus serotype 2/5 vector encoding mouse Nln driven by cytomegalovirus enhancer/chicken β-actin hybrid (CAG) promoter (AAV2/5-CAG-Nln) to overexpress Nln in the mouse brain prior to stroke. Applicability of AAV2/5-CAG-Nln to transduce catalytically active Nln was confirmed in mouse primary cortical neurons and in mice. In the later experiment, overexpression of Nln in the mouse brain was also accompanied by decreased levels of Nln substrate neuropeptides. Two weeks after in vivo transduction using the AAV5-CAG-Nln, or a control AAV5-CAG-eGFP vector (intrastriatal administration; 1.5 x 10 11 genome copies) mice were subjected to MCAO (1 h occlusion followed by 72 h reperfusion). The results of these experiments revealed that abundance of Nln in the brain protects animals from stroke injury measured by reduced infarct and edema volume (p < 0.01 and 0.05, respectively), and improved neurological deficit (p < 0.05). Based on these observations and the knowledge about endogenous substrates of Nln, we view this peptidase as one of brain’s self-protective mechanisms directed towards preservation and recovery of brain after stroke.

Diarylureas Containing 5-Membered Heterocycles as CB1 Receptor Allosteric Modulators: Design, Synthesis, and Pharmacological Evaluation

Allosteric modulators have attracted significant interest as an alternate strategy to modulate CB₁ receptor signaling for therapeutic benefits that may avoid the adverse effects associated with orthosteric ligands. Here we extended our previous structure-activity relationship studies on the diarylurea-based CB₁ negative allosteric modulators (NAMs) by introducing five-membered heterocycles to replace the 5-pyrrolidinylpyridinyl group in PSNCBAM-1 (1), one of the first generation CB₁ allosteric modulators. Many of these compounds had comparable potency to 1 in blocking the CB₁ agonist CP55,940 stimulated calcium mobilization and [³⁵S]GTP-γ-S binding. Similar to 1, most compounds showed positive cooperativity by increasing [³H]CP55,940 binding, consistent with the positive allosteric modulator (PAM)-antagonist mechanism. Interestingly, these compounds exhibited differences in ability to increase specific binding of [³H]CP55,940 and decrease binding of the antagonist [³H]SR141716. In saturation binding studies, only increases in [³H]CP55,940 B_max, but not K_d, were observed, suggesting that these compounds stabilize low affinity receptors into a high affinity state. Among the series, the 2-pyrrolyl analogue (13) exhibited greater potency than 1 in the [³⁵S]GTP-γ-S binding assay and significantly enhanced the maximum binding level in the [³H]CP5,5940 binding assay, indicating greater CB₁ receptor affinity and/or cooperativity.

des-Formylflustrabromine (dFBr): A Structure-Activity Study on Its Ability To Potentiate the Action of Acetylcholine at α4β2 Nicotinic Acetylcholine Receptors

The naturally occurring indole alkaloid des-formylflustrabromine (dFBr; 1) is one of the first agents shown to act as a selective positive allosteric modulator (PAM) at α4β2 nicotinic acetylcholine receptors (nAChRs). We previously deconstructed this agent to determine which of its structural features contribute to its actions and have identified an agent that might serve as the basis for a " working pharmacophore". Here, we elaborate the dFBr (1; EC₅₀ = 0.2 μM) structure to identify how various structural modifications impact its actions. Electrophysiological studies with Xenopus laevis oocytes identified several compounds with dFBr-like potency and one, the 5-bromo analogue of 1 (i.e., 5-bromo dFBr; 25; EC₅₀ = 0.4 μM), with more than twice the efficacy of 1 as a PAM at α4β2 nAChRs.

Gliotoxin penetrates and impairs the integrity of the human blood-brain barrier in vitro

Cerebral fungal infections represent an important public health concern, where a key element of pathophysiology is the ability of the fungi to cross the blood-brain barrier (BBB). Yet the mechanism used by micro-organisms to cross such a barrier and invade the brain parenchyma remains unclear. This study investigated the effects of gliotoxin (GTX), a mycotoxin secreted by Aspergillus fumigatus, on the BBB using brain microvascular endothelial cells (BMECs) derived from induced pluripotent stem cells (iPSCs). We observed that both acute (2 h) and prolonged (24 h) exposure to GTX at the level of 1 μM or higher compromised BMECs monolayer integrity. Notably, acute exposure was sufficient to disrupt the barrier function in iPSC-derived BMECs, resulting in decreased transendothelial electrical resistance (TEER) and increased fluorescein permeability. Further, our data suggest that such disruption occurred without affecting tight junction complexes, via alteration of cell-matrix interactions, alterations in F-actin distribution, through a protein kinase C-independent signaling. In addition to its effect on the barrier function, we have observed a low permeability of GTX across the BBB. This fact can be partially explained by possible interactions of GTX with membrane proteins. Taken together, this study suggests that GTX may contribute in cerebral invasion processes of Aspergillus fumigatus by altering the blood-brain barrier integrity without disrupting tight junction complexes.

Effect of maternal high-fat diet on key components of the placental and hepatic endocannabinoid system

Maternal obesity in pregnancy has been linked to a spectrum of adverse developmental changes. Involvement of eCBs in obesity is well characterized. However, information regarding eCB physiology in obesity associated with pregnancy is sparse. This study evaluated fetomaternal hepatic, systemic, and placental eCB molecular changes in response to maternal consumption of a HFD. From ≥9 mo before conception, nonpregnant baboons ( Papio spp.) were fed a diet of either 45 (HFD; n = 11) or 12% fat or a control diet (CTR; n = 11), and dietary intervention continued through pregnancy. Maternal and fetal venous plasma samples were evaluated using liquid chromatography-mass spectrometry to quantify AEA and 2-AG. Placental, maternal and fetal hepatic tissues were analyzed using RT-PCR, Western blot, and immunohistochemistry. mRNA and protein expression of endocannabinoid receptors (CB1R and CB2R), FAAH, DAGL, MAGL, and COX-2 were determined. Statistical analyses were performed with the nonparametric Scheirer-Ray-Hare extension of the Kruskal-Wallis test to analyze the effects of diet (HFD vs. CTR), fetal sex (male vs. female), and the diet × sex interaction. Fetal weight was influenced by fetal sex but not by maternal diet. The increase in maternal weight in animals fed the HFD vs. the CTR diet approached significance ( P = 0.055). Maternal circulating 2-AG concentrations increased, and fetal circulating concentrations decreased in the HFD group, independently of fetal sex. CB1R receptor expression was detected in syncytiotrophoblasts (HFD) and the fetal endothelium (CTR and HFD). Placental CB2R protein expression was higher in males and lower in female fetuses in the HFD group. Fetal hepatic CB2R, FAAH, COX-2 (for both fetal sexes), and DAGLα (in male fetuses) protein expression decreased in the HFD group compared with the CTR group. We conclude that consumption of a HFD during pregnancy results in fetal systemic 2-AG and hepatic eCB deficiency.

Novel Diarylurea Based Allosteric Modulators of the Cannabinoid CB1 Receptor: Evaluation of Importance of 6-Pyrrolidinylpyridinyl Substitution

Allosteric modulators of the cannabinoid CB1 receptor have recently been reported as an alternative approach to modulate the CB1 receptor for therapeutic benefits. In this study, we report the design and synthesis of a series of diarylureas derived from PSNCBAM-1 (2). Similar to 2, these diarylureas dose-dependently inhibited CP55,940-induced intracellular calcium mobilization and [³⁵S]GTP-γ-S binding while enhancing [³H]CP55,940 binding to the CB1 receptor. Structure-activity relationship studies revealed that the pyridinyl ring of 2 could be replaced by other aromatic rings and the pyrrolidinyl ring is not required for CB1 allosteric modulation. 34 (RTICBM-74) had similar potencies as 2 in all in vitro assays but showed significantly improved metabolic stability to rat liver microsomes. More importantly, 34 was more effective than 2 in attenuating the reinstatement of extinguished cocaine-seeking behavior in rats, demonstrating the potential of this diarylurea series as promising candidates for the development of relapse treatment of cocaine addiction.

Fetal Syndrome of Endocannabinoid Deficiency (FSECD) In Maternal Obesity

The theory of a fetal origin of adult diseases links many pathological conditions to very early life events and is known as a "developmental programming" phenomenon. The mechanisms of this phenomenon are not quite understood and have been explained by inflammation, stress, etc. In particular the epidemic of obesity, with more than 64% of women being overweight or obese, has been associated with conditions in later life such as mental disorders, diabetes, asthma, and irritable bowel syndrome. Interestingly, these diseases were classified a decade ago as Clinical Syndrome of Endocannabinoid Deficiency (CECD), which was first described by Russo in 2004. Cannabinoids have been used for the treatment of chronic pain for millenniums and act through the mechanism of "kick-starting" the components of the endogenous cannabinoid system (ECS). ECS is a pharmacological target for the treatment of obesity, inflammation, cardiovascular and neuronal damage, and pain. We hypothesize that the deteriorating effect of maternal obesity on offspring health is explained by the mechanism of Fetal Syndrome of Endocannabinoid Deficiency (FSECD), which accompanies maternal obesity. Here we provide support for this hypothesis.

Survival in amoeba--a major selection pressure on the presence of bacterial copper and zinc resistance determinants? Identification of a "copper pathogenicity island"

The presence of metal resistance determinants in bacteria usually is attributed to geological or anthropogenic metal contamination in different environments or associated with the use of antimicrobial metals in human healthcare or in agriculture. While this is certainly true, we hypothesize that protozoan predation and macrophage killing are also responsible for selection of copper/zinc resistance genes in bacteria. In this review, we outline evidence supporting this hypothesis, as well as highlight the correlation between metal resistance and pathogenicity in bacteria. In addition, we introduce and characterize the "copper pathogenicity island" identified in Escherichia coli and Salmonella strains isolated from copper- and zinc-fed Danish pigs.

Structure-activity relationships of substituted 1H-indole-2-carboxamides as CB1 receptor allosteric modulators

A series of substituted 1H-indole-2-carboxamides structurally related to compounds Org27569 (1), Org29647 (2) and Org27759 (3) were synthesized and evaluated for CB1 allosteric modulating activity in calcium mobilization assays. Structure-activity relationship studies showed that the modulation potency of this series at the CB1 receptor was enhanced by the presence of a diethylamino group at the 4-position of the phenyl ring, a chloro or fluoro group at the C5 position and short alkyl groups at the C3 position on the indole ring. The most potent compound (45) had an IC₅₀ value of 79 nM which is ∼2.5 and 10 fold more potent than the parent compounds 3 and 1, respectively. These compounds appeared to be negative allosteric modulators at the CB1 receptor and dose-dependently reduced the Emax of agonist CP55,940. These analogs may provide the basis for further optimization and use of CB1 allosteric modulators.

Diarylureas as allosteric modulators of the cannabinoid CB1 receptor: structure-activity relationship studies on 1-(4-chlorophenyl)-3-{3-[6-(pyrrolidin-1-yl)pyridin-2-yl]phenyl}urea (PSNCBAM-1)

The recent discovery of allosteric modulators of the CB1 receptor including PSNCBAM-1 (4) has generated significant interest in CB1 receptor allosteric modulation. Here in the first SAR study on 4, we have designed and synthesized a series of analogs focusing on modifications at two positions. Pharmacological evaluation in calcium mobilization and binding assays revealed the importance of alkyl substitution at the 2-aminopyridine moiety and electron deficient aromatic groups at the 4-chlorophenyl position for activity at the CB1 receptor, resulting in several analogs with comparable potency to 4. These compounds increased the specific binding of [(3)H]CP55,940, in agreement with previous reports. Importantly, 4 and two analogs dose-dependently reduced the Emax of the agonist curve in the CB1 calcium mobilization assays, confirming their negative allosteric modulator characteristics. Given the side effects associated with CB1 receptor orthosteric antagonists, negative allosteric modulators provide an alternative approach to modulate the pharmacologically important CB1 receptor.

Bacterial killing in macrophages and amoeba: do they all use a brass dagger?

Macrophages are immune cells that are known to engulf pathogens and destroy them by employing several mechanisms, including oxidative burst, induction of Fe(II) and Mn(II) efflux, and through elevation of Cu(I) and Zn(II) concentrations in the phagosome ('brass dagger'). The importance of the latter mechanism is supported by the presence of multiple counteracting efflux systems in bacteria, responsible for the efflux of toxic metals. We hypothesize that similar bacteria-killing mechanisms are found in predatory protozoa/amoeba species. Here, we present a brief summary of soft metal-related mechanisms used by macrophages, and perhaps amoeba, to inactivate and destroy bacteria. Based on this, we think it is likely that copper resistance is also selected for by protozoan grazing in the environment.

Deconstruction of the α4β2 nicotinic acetylcholine receptor positive allosteric modulator desformylflustrabromine

Desformylflustrabromine (dFBr; 1), perhaps the first selective positive allosteric modulator of α4β2 neuronal nicotinic acetylcholine (nACh) receptors, was deconstructed to determine which structural features contribute to its actions on receptors expressed in Xenopus ooycytes using two-electrode voltage clamp techniques. Although the intact structure of 1 was found to be optimal, several deconstructed analogs retained activity. Neither the 6-bromo substituent nor the entire 2-position chain is required for activity. In particular, reduction of the olefinic side chain of 1, as seen with 6, not only resulted in retention of activity/potency but in enhanced selectivity for α4β2 versus α7 nACh receptors. Pharmacophoric features for the allosteric modulation of α4β2 nACh receptors by 1 were identified.

Efficient Synthesis of the 2-amino-6-chloro-4-cyclopropyl-7-fluoro-5-methoxy-pyrido[1,2-c]pyrimidine-1,3-dione core ring system

An optimized total synthesis of the 2-amino-6-chloro-4-cyclopropyl-7-fluoro-5-methoxy-pyrido[1,2-c]pyrimidine-1,3-dione core structure of a new fluoroquinolone-like class of antibacterial agents is described. This synthesis is highlighted by a nearly quantitative ring-closing reaction to form the pyrido[1,2-c]pyrimidine core. This bicyclic ring system serves as a scaffold for a family of biologically active compounds.

Synthesis and evaluation of fluoroquinolone derivatives as substrate-based inhibitors of bacterial efflux pumps

Bacterial efflux pump systems contribute to antimicrobial resistance in pathogenic bacteria. The co-administration of bacterial efflux pump inhibitors with antibiotics is being pursued to overcome efflux-mediated resistance to antibiotics. In this study we investigated a strategy for converting broad-spectrum efflux pump substrates, fluoroquinolone antibacterial agents which are inherently recognized by most efflux transporters, into expanded spectrum efflux pump inhibitors. Employing this strategy against organisms expressing efflux pumps from the MFS, MATE and RND classes of pump systems, we report here the identification of an ofloxacin-based EPI that is a potent inhibitor of MFS (NorA) and MATE (MepA) efflux pumps in Staphylococcus aureus. The methods described here outline a process that we feel will be broadly applicable to the systematic identification of bacterial efflux pump inhibitors.