Cholangiocarcinoma across England: Temporal changes in incidence, survival and routes to diagnosis by region and level of socioeconomic deprivation.

Background & Aims: While cholangiocarcinoma (CCA) incidence and mortality rates are increasing globally, whether there are regional/temporal variations in these rates for different biliary tract cancer (BTC) subtypes, or whether they differ by sex, socioeconomic status, or route to diagnosis (RtD) remains unknown. In this work, we aimed to perform an in-depth analysis of data on the incidence, mortality, survival and RtD of CCA and other BTCs. Methods: Data on all BTCs diagnosed in England between 2001 and 2018 were extracted from NHS Digital's National Cancer Registration Dataset. Age-standardised incidence rates (ASRs), mortality rates (ASMRs) and net survival rates were calculated, and Kaplan-Meier overall survival estimates and RtD trends were analysed. Analyses were stratified by sex, socioeconomic deprivation, tumour subtype and region. Results: The ASR for CCA rose from 2.9 in 2001-2003 to 4.6 in 2016-2018 and from 1.0 to 1.8 for gallbladder cancers (GBCs). ASMR trends mirror those of incidence, with most deaths due to iCCA. Over 20% of patients with CCA were under 65 years old. The ASRs and ASMRs were consistently higher in the most socioeconomically deprived group for CCA and GBC. The most common RtD was the emergency route (CCA 49.6%, GBC 46.2% and ampulla of Vater cancer 43.0%). The least deprived patients with CCA and ampulla of Vater cancer had better overall survival (p <0.001). Net survival rates rose for all BTCs, with 3-year net survival for CCA increasing from 9.2% in 2001 to 12.6% in 2016-2018. There was notable geographical variation in ASRs, ASMRs and net survival for all BTCs. Conclusions: BTC incidence and mortality rates are increasing, with differences observed between tumour types, socioeconomic deprivation groups, RtDs and geographical regions. This highlights the need for targeted interventions, earlier diagnosis and better awareness of this condition amongst the public and healthcare professionals. Impact and implications: Cholangiocarcinoma (CCA) incidence and mortality rates are rising globally, particularly for intrahepatic CCA. However, it has not previously been reported if, within a single country, there are temporal and regional differences in incidence, mortality and survival rates for different biliary tract subtypes, and whether these differ by sex, socioeconomic status, or route of diagnosis. In this study we show that mortality rates for patients with CCA continue to rise and are almost 40% higher in the most socioeconomically deprived compared to the least; additionally, we observed regional variation within England in incidence, mortality and survival. This study is relevant to researchers and policy makers as it highlights regional variation and inequality, as well as emphasising the need for earlier diagnosis and better awareness of this condition amongst the public and healthcare professionals.

Incidence and survival of soft tissue sarcoma in England between 2013 and 2017, an analysis from the National Cancer Registration and Analysis Service.

There is a paucity of population-based data detailing the incidence and survival of patients with soft tissue sarcoma (STS), in part due to the heterogeneity of disease and changes to classification. Here, the incidence and survival of all STS subtypes registered in England between 2013 and 2017 were analysed using cancer registry data held by the National Cancer Registration and Analysis Service. Age-standardised incidence rates were calculated per 1 000 000 using the 2013 European Standard Population. Net survival was computed using Brenner's alternative method, with the Ederer II estimator. Age-specific overall survival was assessed using Kaplan-Meier. The influence of age, sex, socioeconomic deprivation and diagnostic routes on survival was assessed using Cox proportional hazards modelling. In total, 19 717 patients were diagnosed with STS, an average of 3943 patients per year and representing approximately 0.8% of malignancies. The most common histological diagnoses were Gastrointestinal Stromal Tumours (GIST), leiomyosarcoma and undifferentiated sarcoma, accounting for 20.2%, 13.3% and 12.7% of all sarcomas, respectively. Five-year net survival for all malignant STS was 65.0%; and was lowest for patients with vascular tumours at 39%. Patients from most deprived cohorts had 23% greater chance of dying within 5 years than patients in least deprived areas. This population-based study has allowed us for the first time to define the incidence and survival rates of prevalent STS subtypes in England such as GIST, liposarcoma and leiomyosarcoma, as well as rare entities and groups with inferior outcome. This data is invaluable for service provision, benchmarking and addressing inequality.

Interspecies and in vitro-in vivo scaling for quantitative modeling of whole-body drug pharmacokinetics in patients: Application to the anticancer drug oxaliplatin.

Quantitative systems pharmacology holds the promises of integrating results from laboratory animals or in vitro human systems into the design of human pharmacokinetic/pharmacodynamic (PK/PD) models allowing for precision and personalized medicine. However, reliable and general in vitro-to-in vivo extrapolation and interspecies scaling methods are still lacking. Here, we developed a translational strategy for the anticancer drug oxaliplatin. Using ex vivo PK data in the whole blood of the mouse, rat, and human, a model representing the amount of platinum (Pt) in the plasma and in the red blood cells was designed and could faithfully fit each dataset independently. A "purely physiologically-based (PB)" scaling approach solely based on preclinical data failed to reproduce human observations, which were then included in the calibration. Investigating approaches in which one parameter was set as species-specific, whereas the others were computed by PB scaling laws, we concluded that allowing the Pt binding rate to plasma proteins to be species-specific permitted to closely fit all data, and guaranteed parameter identifiability. Such a strategy presenting the drawback of including all clinical datasets, we further identified a minimal subset of human data ensuring accurate model calibration. Next, a "whole body" model of oxaliplatin human PK was inferred from the ex vivo study. Its three remaining parameters were estimated, using one third of the available patient data. Remarkably, the model achieved a good fit to the training dataset and successfully reproduced the unseen observations. Such validation endorsed the legitimacy of our scaling methodology calling for its testing with other drugs.

Management of Furcation-Involved Molars: Recommendation for Treatment and Regeneration.

Furcation involvement (FI) is one of the most detrimental factors affecting tooth survival rate over time. Several authors have used the severity of FI for assessing the prognosis of the tooth and the complexity of periodontal disease. While many approaches have been shown to improve the prognosis of furcation-involved teeth, clinical guidelines recommending one treatment or another (based on the horizontal and vertical component of the furcation defects) have not yet been proposed. To this aim, the present article introduces recommendations for the treatment of molars with FI and discusses different treatment options with their potential regenerative approaches. Patient-related factors, together with hard and soft-tissue conditions that may affect the outcomes of periodontal regeneration, are discussed.

Optimizing circadian drug infusion schedules towards personalized cancer chronotherapy.

Precision medicine requires accurate technologies for drug administration and proper systems pharmacology approaches for patient data analysis. Here, plasma pharmacokinetics (PK) data of the OPTILIV trial in which cancer patients received oxaliplatin, 5-fluorouracil and irinotecan via chronomodulated schedules delivered by an infusion pump into the hepatic artery were mathematically investigated. A pump-to-patient model was designed in order to accurately represent the drug solution dynamics from the pump to the patient blood. It was connected to semi-mechanistic PK models to analyse inter-patient variability in PK parameters. Large time delays of up to 1h41 between the actual pump start and the time of drug detection in patient blood was predicted by the model and confirmed by PK data. Sudden delivery spike in the patient artery due to glucose rinse after drug administration accounted for up to 10.7% of the total drug dose. New model-guided delivery profiles were designed to precisely lead to the drug exposure intended by clinicians. Next, the complete mathematical framework achieved a very good fit to individual time-concentration PK profiles and concluded that inter-subject differences in PK parameters was the lowest for irinotecan, intermediate for oxaliplatin and the largest for 5-fluorouracil. Clustering patients according to their PK parameter values revealed patient subgroups for each drug in which inter-patient variability was largely decreased compared to that in the total population. This study provides a complete mathematical framework to optimize drug infusion pumps and inform on inter-patient PK variability, a step towards precise and personalized cancer chronotherapy.

Impact of Race and Ethnicity on the Clinical and Angiographic Characteristics, Social Determinants of Health, and 1-Year Outcomes After Everolimus-Eluting Coronary Stent Procedures in Women.

Background The impact of race/ethnicity on coronary stent outcomes in women is unknown. We compared baseline characteristics, social determinants of health, and 1-year outcomes in female African Americans (AA) and Hispanic/Latinas (HL) versus white women after coronary everolimus-eluting stent implantation in all-comer patients. Methods and Results We pooled 1863 women from the PLATINUM Diversity (n=1057 women) and PROMUS ELEMENT PLUS (n=806 women) postapproval studies, with some overlap in study sites. Social determinants of health data were only available for PLATINUM Diversity. The primary end point was 1-year major adverse cardiac events (death, myocardial infarction, or target vessel revascularization). Outcomes were risk adjusted using multivariate Cox regression. The study sample comprised 1417 white (76.1%, reference group), 296 AA (15.9%), and 107 HL (5.7%) women. AA were older, and both AA and HL had more diabetes mellitus and hypertension than white women. AA had larger reference vessel diameters but less lesion calcification, whereas HL had less lesion tortuosity but more calcification. Compared with white women, there was a trend toward higher unadjusted 1-year major adverse cardiac events in AA (12.0% versus 8.0%; P=0.06) but similar rates in HL (11.0% versus 8.0%; P=0.32), and after risk adjustment, there were no differences (AA women: hazard ratio, 1.47; 95% CI, 1.00-2.17; HL women: hazard ratio, 1.33; 95% CI, 0.71-2.44). AA had a 3-fold higher adjusted risk of 1-year myocardial infarction (hazard ratio, 3.45; 95% CI, 1.72-7.14; P=0.01) and increased risk of target vessel revascularization (hazard ratio, 1.82; 95% CI, 1.10-2.94; P=0.02). Independent predictors of major adverse cardiac events included renal disease, prior myocardial infarction, silent ischemia, history of stroke, and multivessel disease. Conclusions Race and ethnicity confer heterogeneity in women undergoing everolimus-eluting stent implantation. Despite more comorbidities and less favorable social determinants of health, AA and HL women have similar 1-year major adverse cardiac events to white women, although AA women seem to have a higher risk of 1-year myocardial infarction. Clinical Trial Registration URL: https://www.clinicaltrials.gov . Unique identifier: NCT02240810.

Associations of Symptomatic Knee Osteoarthritis With Histopathologic Features in Subchondral Bone.

OBJECTIVE: Subchondral bone and the osteochondral junction are thought to contribute to osteoarthritis (OA) knee pain. We undertook this study to identify osteochondral pathologies specifically associated with symptomatic human knee OA. METHODS: Medial tibial plateau samples from 2 groups of subjects (n = 31 per group) were matched for macroscopic chondropathy scores. The symptomatic chondropathy group had undergone total knee replacement for OA knee pain, at which time specimens of the medial tibial plateau were obtained. The asymptomatic chondropathy group included subjects who died of unrelated illness (specimens were obtained at postmortem examination) and who had not previously sought help for knee pain. OA histopathology, immunoreactivity for nerve growth factor (NGF) and CD68 (macrophages), tartrate-resistant acid phosphatase-positive subchondral osteoclasts, and synovitis were compared between groups. RESULTS: Mankin scores, subchondral bone density, and subchondral CD68-immunoreactive macrophage infiltration were similar between the 2 groups. NGF-like immunoreactivity was found in subchondral mononuclear cells and osteoclasts, as well as in chondrocytes. NGF in osteochondral channels and osteoclast densities in subchondral bone were higher in the symptomatic chondropathy group than in the asymptomatic chondropathy group (P < 0.01 and P = 0.02, respectively), as were synovitis scores (P < 0.01). Osteochondral pathology was not significantly associated with synovitis score. The differences in NGF expression and in osteoclast density remained significant after adjustment for age and synovitis score (P = 0.01 and P = 0.04, respectively). Osteochondral NGF and osteoclast densities, together with synovitis scores, explained ~28% of sample allocation to symptomatic or asymptomatic groups. CONCLUSION: Subchondral pathology was associated with symptomatic knee OA, independent of chondropathy and synovitis. Increased NGF expression in osteochondral channels and increased osteoclast density appear to be key features associated with bone pain in knee OA.

Clinical outcomes following implantation of the ION™ paclitaxel-eluting platinum chromium coronary stent in routine clinical practice: Results of the ION U.S. post-approval study.

BACKGROUND: The ION Study assessed clinical outcomes for the thin-strut, ION™ (TAXUS Element) Paclitaxel-Eluting Platinum Chromium Coronary Stent System (Boston Scientific, Marlborough, MA) in unselected patients. METHODS: This prospective, open-label registry enrolled the first 1,120 consenting patients treated with the ION stent without clinical or angiographic inclusion criteria at 40 clinical sites. Follow-up was at discharge, 30 days, 180 days, 1 and 2 years. The primary endpoint, the 1-year rate of cardiac death or MI (CD/MI) in PERSEUS-like patients (i.e., patients similar to those enrolled in PERSEUS, the pivotal approval trial), was tested in patients pooled from the ION study (N = 316), the European TAXUS Element post-approval registry (TE-PROVE; N = 306 PERSEUS-like patients), and the PERSEUS WH/SV populations (N = 1,166); and then compared with a prespecified performance goal. Additional outcomes were examined in the overall ION patient population. RESULTS: A total of 1,111 (out of 1,120) enrolled patients received a study stent. Most patients were male (70%) and mean age was 64 years. At 1 year, the primary endpoint of CD/MI occurred in 2.1% (6/292) of PERSEUS-like patients in ION, and 2.3% (40/1,729) of patients in the combined analysis. The upper one-sided 95% confidence interval for the combined analysis was 2.9%, which was significantly less than the performance goal of 7.6% (P < 0.001). Within patients enrolled in the ION study (N = 1,111), the rate of CD/MI was 4.5% at 1 year and 7.5% at 2 years. Definite/probable stent thrombosis occurred in 2.1% of patients at 1 year and 2.5% at 2 years. CONCLUSIONS: The results of the ION Study confirm the mid-term safety and effectiveness of the ION stent for the treatment of coronary artery disease in everyday clinical practice.

Structural associations of symptomatic knee osteoarthritis.

OBJECTIVE: Structural changes of osteoarthritis (OA) may occur in the absence of pain. In this study, we aimed to identify histopathologic features that are associated with symptomatic knee OA. METHODS: Medial tibial plateaus and synovium samples were obtained at the time of total knee replacement (TKR) surgery for OA (advanced OA group) or were obtained postmortem from subjects who had not sought medical attention for knee pain during the last year of life (non-OA control group). To identify features of OA, we compared the patients with advanced OA with the age-matched non-OA controls (n = 26 per group). To identify OA features associated with symptoms, we compared two additional groups of subjects who were matched for severity of chondropathy (n = 29 per group): patients undergoing TKR for symptomatic OA (symptomatic chondropathy group) and postmortem subjects with similar severity of chondropathy who were asymptomatic during the last year of life (asymptomatic chondropathy group). The histologic features of the samples were graded, and immunoreactivities for macrophages (CD68) and nerve growth factor (NGF) in the synovium were quantified. The cellular localization of synovial NGF was determined by double immunofluorescence analysis. RESULTS: Advanced OA cases displayed more severe changes in the synovium (synovitis, increased synovial NGF, and CD68-immunoreactive macrophages) and cartilage (loss of cartilage surface integrity, loss of proteoglycan, tidemark breaching, and alterations in chondrocyte morphology) than did the non-OA controls. Synovial NGF was localized predominantly to fibroblasts and to some macrophages. The symptomatic chondropathy group displayed greater levels of synovitis, synovial NGF, and loss of cartilage integrity, in addition to alterations in chondrocyte morphology, than did the asymptomatic chondropathy group (P < 0.05 for each comparison). CONCLUSION: Synovitis, increased synovial NGF, alterations in chondrocyte morphology, and loss of cartilage integrity are features of knee OA that may be associated with symptoms.

Increased vascular penetration and nerve growth in the meniscus: a potential source of pain in osteoarthritis.

OBJECTIVES: Meniscal damage is a recognised feature of knee osteoarthritis (OA), although its clinical relevance remains uncertain. This study describes vascular penetration and nerve growth in human menisci, providing a potential mechanism for the genesis of pain in knee OA. METHODS: Menisci obtained post mortem were screened on the basis of high or low macroscopic tibiofemoral chondropathy as a measure of the presence and degree of OA. Forty cases (20 per group) were selected for the study of meniscal vascularity, and 16 (eight per group) for the study of meniscal innervation. Antibodies directed against α-actin and calcitonin gene-related peptide (CGRP) were used to localise blood vessels and nerves by histochemistry. Image analysis was used to compare vascular and nerve densities between groups. Data are presented as median (IQR). RESULTS: Menisci from knees with high chondropathy displayed degeneration of collagen bundles in their outer regions, which were more vascular than the inner regions, with an abrupt decrease in vascularity at the fibrocartilage junction. Vascular densities were increased in menisci from the high compared with low chondropathy group both in the synovium (3.8% (IQR 2.6-5.2), 2.0% (IQR 1.4-2.9), p=0.002) and at the fibrocartilage junction (2.3% (IQR 1.7-3.1), 1.1% (IQR 0.8-1.9), p=0.003), with a greater density of perivascular sensory nerve profiles in the outer region (high chondropathy group, 144 nerve profiles/mm(2) (IQR 134-189); low chondropathy group, 119 nerve profiles/mm(2) (IQR 104-144), p=0.049). CONCLUSION: Tibiofemoral chondropathy is associated with altered matrix structure, increased vascular penetration, and increased sensory nerve densities in the medial meniscus. The authors suggest therefore that angiogenesis and associated sensory nerve growth in menisci may contribute to pain in knee OA.

The synthesis of highly potent, selective, and water-soluble agonists at the human adenosine A3 receptor.

Using a combination of parallel and directed synthesis, the discovery of a highly potent and selective series of adenosine A3 agonists was achieved. High aqueous solubility, required for the intended parenteral route of administration, was achieved by the presence of one or two basic amine functional groups.

The use of a fluorescence-based oxygen uptake assay in the analysis of cytotoxicity.

Cellular oxygen uptake is an informative parameter of cellular function but is not measured routinely in the analysis of cytotoxicity. Here we have evaluated the ability of a fluorescence-based oxygen uptake assay to assess the metabolic activity of common adherent cells including HepG2, LLC-PK1, Hek293T, C2C12, H-4-II-E, and primary rat hepatocytes. The assay employs water-soluble phosphorescent oxygen probes, analysed in standard 96-well plates on a conventional fluorescence plate reader. Using this respirometric method, cellular responses to known toxicants were examined and results compared to those obtained using established cell viability assays such as MTT, LDH and CyQuant. Respirometric analysis successfully detected these cytotoxic insults with responses being influenced by both mode of toxicity and the biochemical characteristics of the individual cell line. Results indicate that the oxygen uptake assay was more sensitive to the impairment of mitochondrial function than the other assays used. In conjunction with assays analysing other biomarkers of cytotoxicity, a more detailed picture of cell response to drug treatment can be obtained.

The photochemistry of N-p-toluenesulfonyl peptides: the peptide bond as an electron donor.

The scope of photobiological processes that involve absorbers within a protein matrix may be limited by the vulnerability of the peptide group to attack by highly reactive redox centers consequent upon electronic excitation. We have explored the nature of this vulnerability by undertaking comprehensive product analyses of aqueous photolysates of 12 N-p-toluenesulfonyl peptides with systematically selected structures. The results indicate that degradation includes a major pathway that is initiated by intramolecular electron transfer in which the peptide bond serves as electron donor, and the data support the likelihood of a relay process in dipeptide derivatives.

Clinical response of azithromycin as an adjunct to non-surgical periodontal therapy in smokers.

BACKGROUND: Antibiotic therapy can be used in very specific periodontal treatment situations such as in refractory cases of periodontal disease found to be more prevalent in smokers. This study was designed to determine the efficacy of azithromycin (AZM) when combined with scaling and root planing (SRP) for the treatment of moderate to severe chronic periodontitis in smokers. METHODS: Thirty-one subjects were enrolled into a 6-month randomized, single-masked trial to evaluate clinical, microbial (using benzoyl- DL-arginine naphthylamine [BANA] assay), and gingival crevicular fluid (GCF) pyridinoline cross-linked carboxyterminal telopeptide of type I collagen (ICTP) levels in response to SRP alone or SRP + AZM. At baseline, patients who smoked > or =1 pack per day of cigarettes who presented with at least five sites with probing depths (PD) of > or =5 mm with bleeding on probing (BOP) were randomized into the test or control groups. At baseline and 3 and 6 months, clinical measurements (probing depth [PD], clinical attachment loss [CAL], and bleeding on probing [BOP]) were performed. GCF bone marker assessment (Ctelopeptide [ICTP] as well as BANA test analyses) were performed at baseline, 14 days, and 3 and 6 months. RESULTS: The results demonstrated that both groups displayed clinical improvements in PD and CAL that were sustained for 6 months. Using a subject-based analysis, patients treated with SRP + AZM showed enhanced reductions in PD and gains in CAL at moderate (4 to 6 mm) and deep sites (>6 mm) (P <0.05). Furthermore, SRP + AZM resulted in greater reductions in BANA levels compared to SRP alone (P <0.05) while rebounds in BANA levels were noted in control group at the 6-month evaluation. No statistically significant differences between groups on mean BOP and ICTP levels during the course of the study were noted. CONCLUSIONS: The utilization of AZM in combination with SRP improves the efficacy of non-surgical periodontal therapy in reducing probing depth and improving attachment levels in smokers with moderate to advanced attachment loss.

Disuse atrophy and exercise rehabilitation in humans profoundly affects the expression of genes associated with the regulation of skeletal muscle mass.

Skeletal muscle atrophy occurs as a consequence of injury, illness, surgery, and muscle disuse, impacting appreciably on health care costs and patient quality of life, particularly in the absence of appropriate rehabilitation. The molecular mechanisms that regulate muscle mass during atrophy and rehabilitation in humans have not been elucidated, despite several robust candidate pathways being identified. Here, we induced skeletal muscle atrophy in healthy volunteers using two weeks of limb immobilization, and then stimulated the restoration of muscle mass with six weeks of supervised exercise rehabilitation. We determined muscle mass and function and performed targeted gene expression analysis at prescribed time points during immobilization and rehabilitation. For the first time, we have identified novel changes in gene expression following immobilization-induced atrophy and during a program of rehabilitative exercise that restored muscle mass and function. Furthermore, we have shown that exercise performed immediately following immobilization induces profound changes in the expression of a number of genes in favor of the restoration of muscle mass, within 24 h. This information will be of considerable importance to our understanding of how immobilization and contraction stimulate muscle atrophy and hypertrophy, respectively, and to the development of novel therapeutic strategies aimed at maintaining or restoring muscle mass.

Competitive electron transfers from a tyrosyl side-chain and peptide bond in the photodegradation of N-tosyl alpha-aminomethylamides: an insight into photosynthesis and photodamage in the biological oxidation of water?

Photo-excited N-tosyl derivatives of phenylalanyl- and, more particularly, O-methyltyrosylmethylamides undergo electron transfer from aryl to tosyl groups whereas the photo-degradation of aliphatic analogues is initiated by electron transfer from the peptide bond, suggesting the latter as one possible reason for the rapid turnover of the D1 protein in biological water oxidation when the essential mediating role of tyrosine 116 in the PSII complex is inhibited.

Enantioselection in peptide bond formation.

Selectivity in abiotic condensations of amino acids remains controversial and stereochemically little explored. We find that competitive activated couplings of N-acyl derivatives of glycine, alanine, valine, proline and phenylalanine with binary, ternary and quaternary mixtures of amides and esters of the same group of amino acids show little selectivity among the reactants, except with respect to configuration, where a consistent and significant preference for heterochiral outcomes, mostly > 80%, is observed. One possible explanation of this selectivity predicts a predisposition to homochiral coupling under conditions that would require the two carboxyl functions to be co-facial in the activated complex.

Novel N6-substituted adenosine 5'-N-methyluronamides with high selectivity for human adenosine A3 receptors reduce ischemic myocardial injury.

We recently reported the identification of a novel human adenosine A3 receptor-selective agonist, (2S,3S,4R,5R)-3-amino-5-[6-[5-chloro-2-(3-methylisoxazol-5-ylmethoxy)benzylamino]purin-9-yl]-4-hydroxytetrahydrofuran-2-carboxylic acid methylamide (CP-608,039), with 1,260-fold selectivity for the human A3 versus human A1 receptor (DeNinno et al., J Med Chem 46: 353-355, 2003). However, because the modest (20-fold) rabbit A3 receptor selectivity of CP-608,039 precludes demonstration of A3-mediated cardioprotection in rabbit models, we identified another member of this class, (2S,3S,4R,5R)-3-amino-5-[6-(2,5-dichlorobenzylamino)purin-9-yl]-4-hydroxytetrahydrofuran-2-carboxylic acid methylamide (CP-532,903), which both retained human A3 receptor selectivity (210-fold; human A3/human A1 Ki: 23/4,800 nM) and had improved rabbit A3 receptor selectivity (90-fold; rabbit A3/rabbit A1 Ki: 23/2,000 nM). Infarct size was measured in Langendorff hearts or in vivo after 30 min of regional ischemia and 120 min of reperfusion. Five-minute perfusion with CP-532,903 before ischemia-reperfusion elicited a concentration-dependent reduction in infarct size in isolated hearts (EC50: 0.97 nM; maximum reduction in infarct size: 77%, P < 0.05 vs. control). Furthermore, administration of CP-532,903 (150 nM) at reperfusion also significantly reduced infarct size by 64% (P < 0.05 vs. control), which was not different (P > or = 0.05) from the cardioprotection provided by the same concentration of drug given before ischemia. The selective rabbit A1 receptor antagonist BWA1433 did not affect CP-532,903-dependent cardioprotection. In vivo, CP-532,903 (1 mg/kg) reduced infarct size by 50% in the absence of significant hemodynamic effects (mean arterial pressure, heart rate, rate-pressure product). CP-532,903 and CP-608,039 represent a novel class of human A3 receptor-selective agonists that may prove suitable for investigation of the clinical cardioprotective efficacy of A3 receptor activation.