Incidence of Influenza-related Medical Encounters and the Associated Healthcare Resource Use and Complications Across Adult Age Groups in the United States During the 2015-2020 Influenza Seasons.

BACKGROUND: Research on influenza burden in adults has focused on crude subgroups with cut-points at 65 years, limiting insight into how burden varies with increasing age. This study describes the incidence of influenza-related outpatient visits, emergency room visits, and hospitalizations, along with healthcare resource use and complications in the aging adult population. METHODS: Individuals aged ≥18 years in the United States were evaluated retrospectively in 5 seasonal cohorts (2015-2020 seasons) in strata of age with 5-year increments. Person-level electronic medical records linked to pharmacy and medical claims were used to ascertain patient characteristics and outcomes. Influenza-related medical encounters were identified based on diagnostic codes (International Classification of Diseases, 10th Edition, codes J09*-J11*). RESULTS: Incidence of influenza-related outpatient visits was highest among people aged 18-34 years and declined with increasing age. For emergency room visits, incidence tended to be elevated for people aged 18-34 years, relatively stable from 35 through 60, and increased rapidly after age 60 years. Hospitalization incidence remained relatively stable until about 50 years of age and then increased with age. One in 3 patients was diagnosed with pneumonia after hospitalization, regardless of age. Across seasons, age groups, and clinical settings, on average, 40.8% of individuals were prescribed antivirals and 17.2% antibiotics. CONCLUSIONS: Incidence of influenza-related hospitalizations begins to increase around age 50 years rather than the more common cut-point of 65, whereas incidence of outpatient visits was highest among younger adults. Influenza infections frequently led to antiviral and antibiotic prescriptions, underscoring the role influenza vaccination can play in combating antimicrobial resistance.

Observational safety study of specific outcomes after trivalent cell culture seasonal influenza vaccination (Optaflu® ) among adults in THIN database of electronic UK primary healthcare records.

PURPOSE: To investigate the safety of trivalent seasonal influenza vaccine (TIVc) (Optaflu® ), the first cell culture seasonal trivalent influenza vaccine available in Europe. METHODS: Codes and unstructured text in adult electronic healthcare records (The Health Improvement Network) were searched for a TIVc brand name or batch number and possible outcomes within a 3 month pre- to 6 month post-TIVc exposure study period (2012-2015). The outcomes were severe allergic reactions, Bell's palsy, convulsions, demyelination, paresthesia, noninfectious encephalitis, neuritis (optic and brachial), vasculitis, inflammatory bowel disease, and thrombocytopenia. Risk periods were defined based on biologically plausible time frame postvaccination when an outcome caused by the vaccine might be expected to occur. Possible outcomes were adjudicated against outcome specific case definitions and a date of onset assigned by using electronic and other medical records. Observed (risk period) to expected (outside risk and preexposure periods) rate ratios, postexposure incidence, and plots of time from exposure to outcome were reported. RESULTS: Sixteen of 1011 events from 4578 exposures fulfilled a primary case definition and had a date of onset during the study period. Three were in observed time. The observed-to-expected rate ratios were (3.3, 95% CI 0.3, 31.7) for convulsions and (1.5, 95% CI 0.2, 14.9) for thrombocytopenia with 1 outcome each in observed time. There was 1 incident inflammatory bowel disease in observed, but none in expected, time. CONCLUSION: The small sample size restricts interpretation; however, no hypothesis of an increased risk of a study outcome was generated. Adjudication of events against case definitions to reduce misclassification of onset and outcomes allowed use of precise risk periods. KEY POINTS This observational study did not generate a hypothesis of an association between the first cell-culture seasonal influenza vaccination available in the European Union and any of the study outcomes (severe allergic reactions, Bell's palsy, convulsions, demyelination, paresthesia, noninfectious encephalitis, neuritis [optic and brachial], vasculitis, inflammatory bowel disease [IBD], and thrombocytopenia). The small sample size limits interpretation of the results. The review of each possible outcome identified from electronic healthcare records against case definitions was included to minimize misclassification of time and outcomes and allow the use of precise risk-periods in an observed-to-expected within cohort analysis. Plots of time from exposure to outcome were included to assess the risk windows.

Number of Influenza Risk Factors Informs an Adult's Increased Potential of Severe Influenza Outcomes: A Multiseason Cohort Study From 2015 to 2020.

Background: While studies have evaluated factors influencing the risk of severe influenza outcomes, there is limited evidence on the additive impact of having multiple influenza risk factors and how this varies by age. Methods: Patients ≥18 years of age in the United States were evaluated retrospectively in 5 seasonal cohorts during the 2015-2020 influenza seasons. Patient-level electronic medical records linked to pharmacy and medical claims were used to ascertain covariates and outcomes. Multivariable logistic regression models were fitted for the overall population and by age subgroups to evaluate the association of demographic and clinical characteristics with odds of influenza-related medical encounters (ICD-10 codes J09*-J11*). The logistic regression models included sex, race/ethnicity, geographic region, baseline health care resource use, vaccination status, specific high-risk comorbidities, number of influenza risk factors, body mass index, and smoking status. Odds ratios from each of the 5 seasons were summarized via fixed effect meta-analysis. Results: Season cohort sizes ranged from 887 260 to 3 628 168 adults. Of all patient characteristics evaluated, an individual's cumulative number of high-risk influenza conditions, as defined per the Centers for Disease Control and Prevention, was the most predictive of an increased probability of having an influenza-related medical encounter overall and across age groups. For adults of any age, odds ratios for influenza hospitalization ranged from 1.8 (95% CI, 1.7-2.0) for 1 risk factor to 6.4 (95% CI, 5.8-7.0) for ≥4 risk factors. Conclusions: These results show that a simple measure such as the number of influenza risk factors can be highly informative of an adult's potential for severe influenza outcomes.

Relative vaccine effectiveness of MF59-adjuvanted vs high-dose trivalent inactivated influenza vaccines for prevention of test-confirmed influenza hospitalizations during the 2017-2020 influenza seasons.

OBJECTIVES: This study evaluated relative vaccine effectiveness (rVE) of MF59-adjuvanted trivalent inactivated influenza vaccine (aTIV) vs high-dose trivalent inactivated influenza vaccine (HD-TIV) for prevention of test-confirmed influenza emergency department visits and/or inpatient admissions ("ED/IP") and for IP admissions alone pooled across the 2017-2020 influenza seasons. Exploratory individual season analyses were also performed. METHODS: This retrospective test-negative design study included United States (US) adults age ≥65 years vaccinated with aTIV or HD-TIV who presented to an ED or IP setting with acute respiratory or febrile illness during the 2017-2020 influenza seasons. Test-positive cases and test-negative controls were grouped by vaccine received. The rVE of aTIV vs HD-TIV was evaluated using a combination of inverse probability of treatment weighting and logistic regression to adjust for potential confounders. RESULTS: Pooled analyses over the three seasons found no significant differences in the rVE of aTIV vs HD-TIV for prevention of test-confirmed influenza ED/IP (-2.5% [-19.6, 12.2]) visits and admissions or IP admissions alone (-1.6% [-22.5, 15.7]). The exploratory individual season analyses also showed no significant differences. CONCLUSIONS: Evidence from the 2017-2020 influenza seasons indicates aTIV and HD-TIV are comparable for prevention of test-confirmed influenza ED/IP visits in US adults age ≥65 years.

Relative Effectiveness of the MF59-Adjuvanted Influenza Vaccine Versus High-Dose Influenza Vaccine in Older Adults With Influenza Risk Factors During the 2019-2020 US Influenza Season.

Background: This study estimated the relative vaccine effectiveness (rVE) of the MF59-adjuvanted trivalent influenza vaccine (aTIV) versus high-dose trivalent inactivated influenza vaccine (HD-TIV) for prevention of influenza-related medical encounters (IRMEs) during the 2019-2020 United States (US) influenza season stratified by the cumulative number of influenza risk factors. A secondary objective evaluated outpatient IRMEs and influenza- and pneumonia-related hospitalizations. Methods: This retrospective cohort study included US adults ≥65 years old vaccinated with aTIV or HD-TIV between 1 August 2019 and 31 January 2020. Electronic health records linked to claims were used to ascertain exposure, covariates, risk factors, and outcomes. Multivariable adjusted odds ratios (ORs) were derived using inverse probability of treatment-weighted samples to calculate rVEs independently for individuals with 0, ≥1, 1-2, or ≥3 risk factors. Results: The study included 1 115 725 aTIV and 2 561 718 HD-TIV recipients. For the primary outcome of any IRME, the analysis found comparable effectiveness between aTIV and HD-TIV (rVE, 5.2% [95% confidence interval {CI}, -5.9% to 15.1%]) among those with 0 risk factors, whereas aTIV was more effective than HD-TIV among patients with ≥1, 1-2, or ≥3 risk factors (12.5% [95% CI, 10.0%-15.0%], 18.4% [95% CI, 13.7%-22.9%], and 10.4% [7.4%-13.3%], respectively). The same trends were observed for the secondary outcomes. Conclusions: This study demonstrated comparable effectiveness of aTIV and HD-TIV among individuals with no identified risk factors and higher effectiveness of aTIV compared with HD-TIV in preventing any IRMEs, outpatient IRMEs, and influenza- or pneumonia-related hospitalizations among those with at least 1 or multiple high-risk factors in adults ≥65 years old.

Relative Vaccine Effectiveness of Cell- vs Egg-Based Quadrivalent Influenza Vaccine Against Test-Confirmed Influenza Over 3 Seasons Between 2017 and 2020 in the United States.

Background: Influenza vaccine viruses grown in eggs may acquire egg-adaptive mutations that may reduce antigenic similarity between vaccine and circulating influenza viruses and decrease vaccine effectiveness. We compared cell- and egg-based quadrivalent influenza vaccines (QIVc and QIVe, respectively) for preventing test-confirmed influenza over 3 US influenza seasons (2017-2020). Methods: Using a retrospective test-negative design, we estimated the relative vaccine effectiveness (rVE) of QIVc vs QIVe among individuals aged 4 to 64 years who had an acute respiratory or febrile illness and were tested for influenza in routine outpatient care. Exposure, outcome, and covariate data were obtained from electronic health records linked to pharmacy and medical claims. Season-specific rVE was estimated by comparing the odds of testing positive for influenza among QIVc vs QIVe recipients. Models were adjusted for age, sex, geographic region, influenza test date, and additional unbalanced covariates. A doubly robust approach was used combining inverse probability of treatment weights with multivariable regression. Results: The study included 31 824, 33 388, and 34 398 patients in the 2017-2018, 2018-2019, and 2019-2020 seasons, respectively; ∼10% received QIVc and ∼90% received QIVe. QIVc demonstrated superior effectiveness vs QIVe in prevention of test-confirmed influenza: rVEs were 14.8% (95% CI, 7.0%-22.0%) in 2017-2018, 12.5% (95% CI, 4.7%-19.6%) in 2018-2019, and 10.0% (95% CI, 2.7%-16.7%) in 2019-2020. Conclusions: This study demonstrated consistently superior effectiveness of QIVc vs QIVe in preventing test-confirmed influenza over 3 seasons characterized by different circulating viruses and degrees of egg adaptation.

Relative Effectiveness of the MF59®-Adjuvanted Influenza Vaccine Versus High-Dose and Non-Adjuvanted Influenza Vaccines in Preventing Cardiorespiratory Hospitalizations During the 2019-2020 US Influenza Season.

BACKGROUND: Adults ≥ 65 years of age have suboptimal influenza vaccination responses compared to younger adults due to age-related immunosenescence. Two vaccines were specifically developed to enhance protection: MF59-adjuvanted trivalent influenza vaccine (aIIV3) and high-dose egg-based trivalent influenza vaccine (HD-IIV3e). METHODS: In a retrospective cohort study conducted using US electronic medical records linked to claims data during the 2019-2020 influenza season, we compared the relative vaccine effectiveness (rVE) of aIIV3 with HD-IIV3e and a standard-dose non-adjuvanted egg-based quadrivalent inactivated influenza vaccine (IIV4e) for the prevention of cardiorespiratory hospitalizations, including influenza hospitalizations. We evaluated outcomes in the "any" diagnosis position and the "admitting" position on the claim. A doubly robust methodology using inverse probability of treatment weighting and logistic regression was used to adjust for covariate imbalance. rVE was calculated as 100 * (1 - ORadjusted). RESULTS: The study included 4,299,594 adults ≥ 65 years of age who received aIIV3, HD-IIV3e, or IIV4e. Overall, aIIV3 was associated with lower proportions of cardiorespiratory hospitalizations with diagnoses in any position compared to HD-IIV3e (rVE = 3.9% [95% CI, 2.7-5.0]) or IIV4e (9.0% [95% CI, 7.7-10.4]). Specifically, aIIV3 was more effective compared with HD-IIV3e and IIV4e in preventing influenza hospitalizations (HD-IIV3e: 9.7% [95% CI, 1.9-17.0]; IIV4e: 25.3% [95% CI, 17.7-32.2]). Consistent trends were observed for admitting diagnoses. CONCLUSION: Relative to both HD-IIV3e and IIV4e, aIIV3 provided improved protection from cardiorespiratory or influenza hospitalizations.

The risk of new onset heart failure associated with dopamine agonist use in Parkinson's disease.

The aim of present study was to investigate the risk of heart failure associated with dopamine agonist use in patients with Parkinson's disease. The data sources of this study were four different population-based, healthcare databases in United Kingdom, Italy and Netherlands. A case control study nested within a cohort of Parkinson's disease patients who were new users of either dopamine agonist or levodopa was conducted. Incident cases of heart failure were identified and validated, using Framingham criteria. Controls were matched to cases on age, gender and database. To estimate the risk of newly diagnosed heart failure with ergot and non-ergot derived dopamine agonists, as compared to levodopa, odds ratios and 95% confidence intervals were calculated through conditional logistic regression. In the cohort of 25,459 Parkinson's disease patients (11,151 new users of dopamine agonists, 14,308 new users of levodopa), 518 incident heart failure cases were identified during follow-up. Compared to levodopa, no increased risk of heart failure was found for ergot dopamine agonists (odds ratio: 1.03; 95% confidence interval: 0.69-1.55). Among non-ergot dopamine agonists, only pramipexole was associated with an increased risk of heart failure (odds ratio: 1.61; 95%confidence interval: 1.09-2.38), especially in the first three months of therapy (odds ratio: 3.06; 95% confidence interval: 1.74-5.39) and in patients aged 80 years and older (odds ratio: 3.30; 95% confidence interval: 1.62-7.13). The results of this study indicate that ergot dopamine agonist use in Parkinson's disease patients was not associated with an increased risk of newly diagnosed heart failure. Among non-ergot dopamine agonists, we observed a statistically significant association between pramipexole use and heart failure, especially during the first months of therapy and in very old patients.

Effectiveness of the MF59-adjuvanted trivalent or quadrivalent seasonal influenza vaccine among adults 65 years of age or older, a systematic review and meta-analysis.

BACKGROUND: Standard-dose seasonal influenza vaccines often produce modest immunogenic responses in adults ≥65 years old. MF59 is intended to elicit a greater magnitude and increased breadth of immune response. OBJECTIVE: To determine the effectiveness of seasonal MF59-adjuvanted trivalent/quadrivalent influenza vaccine (aTIV/aQIV) relative to no vaccination or vaccination with standard or high-dose egg-based influenza vaccines among people ≥65 years old. METHODS: Cochrane methodological standards and PRISMA-P guidelines were followed. Real-world evidence from non-interventional studies published in peer-reviewed journals and gray literature from 1997 through to July 15, 2020, including cluster-randomized trials, were eligible. Two reviewers independently extracted data; risk of bias was assessed using the ROBINS-I tool. RESULTS: Twenty-one studies conducted during the 2006/07-2019/20 influenza seasons were included in the qualitative review; 16 in the meta-analyses. Meta-analysis of test-negative studies found that aTIV reduced medical encounters due to lab-confirmed influenza with pooled estimates of 40.7% (95% CI: 21.9, 54.9; I2  = 0%) for non-emergency outpatient visits and 58.5% (40.7, 70.9; I2  = 52.9%) for hospitalized patients. The pooled estimate of VE from case-control studies was 51.3% (39.1, 61.1; I2  = 0%) against influenza- or pneumonia-related hospitalization. The pooled estimates for the relative VE of aTIV for the prevention of influenza-related medical encounters were 13.9% (4.2, 23.5; I2  = 95.9%) compared with TIV, 13.7% (3.1, 24.2; I2  = 98.8%) compared with QIV, and 2.8% (-2.9, 8.5; I2  = 94.5%) compared with HD-TIV. CONCLUSIONS: Among adults ≥65 years, aTIV demonstrated significant absolute VE, improved relative VE compared to non-adjuvanted standard-dose TIV/QIV, and comparable relative VE to high-dose TIV.

Site-specific incorporation of novel backbone structures into proteins.

A number of unnatural amino acids and amino acid analogs with modified backbone structures were substituted for alanine-82 in T4 lysozyme. Replacements included alpha,alpha-disubstituted amino acids, N-alkyl amino acids, and lactic acid, an isoelectronic analog of alanine. The effects of these electronic and structural perturbations on the stability of T4 lysozyme were determined. The relatively broad substrate specificity of the Escherichia coli protein biosynthetic machinery suggests that a wide range of backbone and side-chain substitutions can be introduced, allowing a more precise definition of the factors affecting protein stability.

Characterization of a cofactor that regulates dimerization of a mammalian homeodomain protein.

Dimerization among transcription factors has become a recurrent theme in the regulation of eukaryotic gene expression. Hepatocyte nuclear factor-1 alpha (HNF-1 alpha) is a homeodomain-containing protein that functions as a dimer. A dimerization cofactor of HNF-1 alpha (DCoH) was identified that displayed a restricted tissue distribution and did not bind to DNA, but, rather, selectively stabilized HNF-1 alpha dimers. The formation of a stable tetrameric DCoH-HNF-1 alpha complex, which required the dimerization domain of HNF-1 alpha, did not change the DNA binding characteristics of HNF-1 alpha, but enhanced its transcriptional activity. However, DCoH did not confer transcriptional activation to the GAL4 DNA binding domain. These results indicate that DCoH regulates formation of transcriptionally active tetrameric complexes and may contribute to the developmental specificity of the complex.

Probing protein stability with unnatural amino acids.

Unnatural amino acid mutagenesis, in combination with molecular modeling and simulation techniques, was used to probe the effect of side chain structure on protein stability. Specific replacements at position 133 in T4 lysozyme included (i) leucine (wt), norvaline, ethylglycine, and alanine to measure the cost of stepwise removal of methyl groups from the hydrophobic core, (ii) norvaline and O-methyl serine to evaluate the effects of side chain solvation, and (iii) leucine, S,S-2-amino-4-methylhexanoic acid, and S-2-amino-3-cyclopentylpropanoic acid to measure the influence of packing density and side chain conformational entropy on protein stability. All of these factors (hydrophobicity, packing, conformational entropy, and cavity formation) significantly influence protein stability and must be considered when analyzing any structural change to proteins.

Glimpse into Pathophysiology of Sellar Arachnoid Cysts.

BACKGROUND: Sellar arachnoid cysts are a rare occurrence but may impinge on vital parasellar anatomy and thus are often symptomatic. The etiology of sellar arachnoid cysts is contentious, fueled by heterogeneity in cyst wall structure and contents between cases. The "ball-valve" mechanism is 1 of 2 predominant theories describing their formation, which contends that an aperture in the diaphragm allows cerebrospinal fluid to enter the cyst, propelled by pulsatile flow, but its egress is obscured by the pituitary during the ebb of the pressure wave. CASE DESCRIPTION: Here we present a case of a 51-year-old female with a symptomatic sellar arachnoid cyst. She underwent an endoscopic transsphenoidal fenestration which alleviated her symptoms. CONCLUSIONS: Intraoperative video evidence during arachnoid cyst fenestration supports the "ball-valve" theory of sellar arachnoid cyst development.

Interobserver Reliability of Spinal Adverse Events Severity System - Neuro (SAVES-N): A Prospective Adverse Event Reporting System for Neurosurgical Cases.

BACKGROUND: The reporting of adverse events (AEs) in neurosurgery uses inconsistent definitions and subjective grading systems. A standardized system for recording and describing AEs would allow valid comparisons to be drawn between different institutions, using different technologies, at different times. The Spinal Adverse Events Severity System - Neuro (SAVES-N) system is a modification of the well-validated SAVES-V2 system that encompasses complications from both cranial and spinal surgery. The objective of this study was to assess the interobserver reliability of SAVES-N in spinal and cranial neurosurgery. METHODS: Ten vignettes, including cranial and spinal neurosurgical cases, were assessed by groups of consultant neurosurgeons (n = 5) and neurosurgical registrars (n = 5) using the SAVES-N system. Interobserver reliability for the presence of AEs, the type of AE, and the SAVES severity grade of the AE were calculated using Gwet's AC2 and Fleiss' kappa and were interpreted using the thresholds described by Landis and Koch. RESULTS: Neurosurgeons had almost-perfect agreement (Gwet AC2 = 0.93), whereas registrars had substantial agreement (Gwet's AC2 = 0.74) in determining the presence or absence of AEs. Both neurosurgeons (Fleiss' kappa = 0.78) and registrars (Fleiss' kappa = 0.70) demonstrated substantial agreement within their groups as to the type of AE. Similarly, neurosurgeons (Gwet's AC2 = 0.94) and registrars (Gwet's AC2 = 0.81) both graded the severity of the AE with almost perfect agreement. CONCLUSIONS: The results of this study demonstrate that the scope of the well-validated SAVES-V2 system may be broadened to cranial neurosurgical cases by SAVES-N with substantial to almost-perfect interobserver reliability.

Nonsteroidal anti-inflammatory drugs and the risk of Parkinson disease.

BACKGROUND: Several lines of evidence suggest a role of inflammatory processes in Parkinson disease, although it is still unclear whether inflammation is a cause or rather a consequence of neurodegeneration. METHODS: In a prospective population-based cohort study among 6,512 participants aged >or=55 years, with repeated in-person examination, we evaluated the association between cumulative use of nonsteroidal anti-inflammatory drugs (NSAIDs) and the risk of Parkinson disease. Complete information on filled prescriptions was available from automated pharmacy records. Data were analyzed by means of Cox proportional hazards regression analysis, adjusted for age, sex, smoking habits and coffee consumption. RESULTS: After an average 9.4 years of follow-up, 88 new cases of Parkinson disease were detected. No association was found between use of NSAIDs and the risk of Parkinson disease (adjusted hazard ratio for any NSAID use, 1.50; 95% confidence interval, 0.95-2.37). CONCLUSION: Our findings do not support the hypothesis that NSAIDs might decrease the risk of Parkinson disease.

Obesity in Neurosurgery: A Narrative Review of the Literature.

Obesity is an important consideration in neurosurgical practice. Of Australian adults, 28.3% are obese and it is estimated that more than two thirds of Australia's population will be overweight or obese by 2025. This review of the effects of obesity on neurosurgical procedures shows that, in patients undergoing spinal surgery, an increased body mass index is a significant risk factor for surgical site infection, venous thromboembolism, major medical complications, prolonged length of surgery, and increased financial cost. Although outcome scores and levels of patient satisfaction are generally lower after spinal surgery in obese patients, obesity is not a barrier to deriving benefit from surgery and, when the natural history of conservative management is taken into account, the long-term benefits of surgery may be equivalent or even greater in obese patients than in nonobese patients. In cranial surgery, the impact of obesity on outcome and complication rates is generally lower. Specific exceptions are higher rates of distal catheter migration after shunt surgery and cerebrospinal fluid leak after posterior fossa surgery. Minimally invasive approaches show promise in mitigating some of the adverse effects of obesity in patients undergoing spine surgery but further studies are needed to develop strategies to reduce obesity-related surgical complications.

High levels of HER-2 expression alter the ability of epidermal growth factor receptor (EGFR) family tyrosine kinase inhibitors to inhibit EGFR phosphorylation in vivo.

The epidermal growth factor receptor (EGFR) and HER-2 tyrosine kinases have been implicated in the development, progression, and severity of several human cancers and are attractive targets for therapeutic intervention. SU11925 was developed as a small molecule inhibitor of the tyrosine kinase activity of both EGFR and HER-2. In cellular assays, SU11925 exhibited similar potency against EGFR and HER-2, inhibiting EGF-stimulated EGFR autophosphorylation in A431 (human epidermoid carcinoma) cells with an IC(50) of 30 nM and HER-2 phosphorylation in SK-OV-3TP5 (human ovarian carcinoma) cells with an IC(50) of 38 nM. In contrast to its similar activity against the two targets in cellular assays, approximately 10-fold higher plasma concentrations of SU11925 were required to inhibit HER-2 phosphorylation in HER-2-overexpressing tumors compared with EGFR phosphorylation in EGFR-overexpressing tumors in vivo. Consistent with the proposed mechanism of action of this inhibitor, SU11925 inhibited the s.c. growth of EGFR- and HER-2-dependent tumors in athymic mice at doses that produced substantial inhibition of target receptor phosphorylation in vivo. An unexpected finding from these studies was that higher plasma concentrations of SU11925 were required to inhibit EGFR phosphorylation in vivo in tumors that also express high levels of HER-2 than in tumors that express EGFR alone. This observation, which suggests that it is more difficult to inhibit EGFR phosphorylation in vivo in cells that express high levels of HER-2, was confirmed with ZD1839 (Iressa), a selective EGFR inhibitor that also targets the tyrosine kinase catalytic site. The potential clinical implications of this observation are discussed.

The angiogenesis inhibitor SU5416 has long-lasting effects on vascular endothelial growth factor receptor phosphorylation and function.

SU5416, a selective inhibitor of the tyrosine kinase activity of the vascular endothelial growth factor (VEGF) receptor Flk-1/KDR, is currently in Phase III clinical trials for the treatment of advanced malignancies. In cellular assays, SU5416 inhibits the VEGF-dependent mitogenic/proliferative response of human umbilical vein endothelial cells (HUVECs). In tumor xenograft models, SU5416 inhibits the growth of tumors from a variety of origins by inhibiting tumor angiogenesis. In three different human tumor xenograft models, infrequent (once or twice a week) administration of SU5416 is efficacious despite the fact that it has a short plasma half-life (30 min), which suggests that SU5416 has long-lasting inhibitory activity in vivo. The goal of the present study was to determine the basis for the prolonged activity of SU5416. The results indicate that a short (3 h) exposure to 5 microM SU5416 (to mimic plasma levels of the compound as measured in patients who were receiving SU5416 therapy) produced long-lasting (at least 72 h) inhibition of the VEGF-dependent proliferation of HUVECs in culture, which indicate that SU5416 has long-lasting inhibitory activity in vitro as well as in vivo. SU5416 treatment of HUVECs did not affect surface expression of Flk-1/KDR or the affinity of the receptor for VEGF. Instead, the durability of the in vitro activity of SU5416 was shown to be attributable to its long-lasting ability to specifically inhibit VEGF-dependent phosphorylation of Flk-1/KDR and subsequent downstream signaling, although SU5416 is not an irreversible inhibitor of Flk-1/KDR tyrosine kinase activity. The long-lasting inhibition of cellular responses to VEGF was attributable to the accumulation of SU5416 in cells, as shown using radiolabeled compound, such that inhibitory cellular concentrations of SU5416 are maintained long after the removal of the compound from the medium. The long-lasting inhibitory activity of SU5416 in vitro is consistent with the finding that SU5416 has demonstrated evidence of biological activity in clinical studies when administered twice a week despite a short plasma half-life.

Structure-activity relationship studies of novel carbocyclic influenza neuraminidase inhibitors.

A series of influenza neuraminidase inhibitors with the cyclohexene scaffold containing lipophilic side chains have been synthesized and evaluated for influenza A and B neuraminidase inhibitory activity. The size and geometry of side chains have been modified systematically in order to investigate structure-activity relationships of this class of compounds. The X-ray crystal structures of several analogues complexed with neuraminidase revealed that the lipophilic side chains bound to the hydrophobic pocket consisted of Glu276, Ala246, Arg224, and Ile222 of the enzyme active site. The structure-activity relationship studies of this series have also demonstrated remarkably different inhibitory potency between influenza A and B neuraminidase. This indicated that the lipophilic side chains had quite different hydrophobic interactions with influenza A and B neuraminidase despite their complete homology in the active site. Influenza B neuraminidase appeared to be much more sensitive toward the increased steric bulkiness of inhibitors compared to influenza A neuraminidase. From the extensive structure-activity relationship investigation reported in this article, GS 4071 emerged as one of the most potent influenza neuraminidase inhibitors against both influenza A and B strains.