THU0374 NONSTEROIDAL ANTI-INFLAMMATORY DRUG-SPARING EFFECT OF SECUKINUMAB IN PATIENTS WITH ANKYLOSING SPONDYLITIS: 4-YEAR RESULTS FROM THE MEASURE 2, 3 AND 4 PHASE 3 TRIALS

Background:

Nonsteroidal anti-inflammatory drugs (NSAIDs) are effective in reducing pain and stiffness in ankylosing spondylitis (AS) patients (pts).1However, continuous use of NSAIDs may lead to gastrointestinal, cardiovascular and renal toxicity.2Therefore, reduction in NSAID intake is desirable in AS pts.

Objectives:

To evaluate the long-term effect of secukinumab (SEC) on NSAID intake in AS pts pooled from the 3 SEC trials (MEASURE [M] 2-4).

Methods:

NSAID intake was evaluated prospectively using the Assessment of SpondyloArthritis International Society (ASAS)-NSAID score.3The score was determined by type of NSAID, daily dose, and weights from frequency of intake, as well as % of time use in period. An ASAS-NSAID score of ‘0’ indicates no NSAID intake. Pts with ASAS-NSAID score >0 at baseline (BL) were analysed. SEC dose groups were defined as Any 150 or 300 mg, as defined for pooled safety analyses for SEC. Pts with initial placebo treatment (up to 24 weeks) were included in their respective post-Week 24 SEC dose groups to analyse ASAS-NSAID score at Year (Y) 2 (M2-4), Y3 (M2-3) and Y4 (M2) from BL. From the ASAS-NSAID score at BL, the mean change in ASAS-NSAID score, proportion of pts achieving 50% reduction, and the proportion of pts with score <10 were evaluated for each dose at Y2, 3 and 4. Based on the distribution of ASAS-NSAID scores at BL, 2 subgroups were evaluated: (i) <75 (low user); (ii) ≥75 (high user).

Results:

Overall, 562 pts (SEC: 150 mg, N=467; 300 mg, N=95) were analysed. The mean ASAS-NSAID score decreased with time in both dose groups. Greater improvements were observed in high NSAID users and with longer treatment exposure (Figure). Proportion of pts who achieved 50% reduction in ASAS-NSAID score increased with time in both SEC 150 and 300 mg groups. Proportion of pts with clinically meaningful reduction of ASAS-NSAID score <10 increased with time in both dose groups and in both low and high NSAID users (Table).

TableTime (years)NSAID intakeLow (<0 ASAS-NSAID <75)High (ASAS-NSAID ≥75)OverallSEC 150 mg(N=167)SEC 300 mg#(N=37)SEC 150 mg(N=300)SEC 300 mg#(N=58)SEC 150 mg(N=467)SEC 300 mg#(N=95)Proportion of pts who achieved 50% reduction from BL in ASAS-NSAID score, % (n/m)*225 (38/154)18 (6/33)19 (50/267)14 (7/49)21 (88/421)16 (13/82)323 (13/56)21 (7/33)26 (26/100)17 (8/46)25 (39/156)19 (15/79)429 (7/24)-26 (14/54)-27 (21/78)-Proportion of pts with ASAS-NSAID score <10,% (n/m)*239 (60/154)33 (11/33)12 (33/267)12 (6/49)22 (93/421)21 (17/82)334 (19/56)33 (11/33)17 (17/100)13 (6/46)23 (36/156)22 (17/79)438 (9/24)-20 (11/54)-26 (20/78)-

*Observed data.#MEASURE 3 that evaluated 300 mg was only a 3 year study. N, total number of pts in the group; n, number of pts with response; m, number of evaluable pts

Conclusion:

SEC provided sustained improvement in ASAS-NSAID score in AS pts and was associated with clinically relevant NSAID-sparing effect in AS pts, when used to measure NSAID intake up to 4 years of treatment. Overall, SEC provided long-term NSAID-sparing effects in both high and low NSAID users.

References:

[1]Molto A, et al.Joint Bone Spine. 2017;84:79–82.

[2]Dougados M, et al.Arthritis Res & Ther. 2014;16:481.

[3]Dougados M, et al.Ann Rheum Dis. 2011;70:249–51.

Disclosure of Interests:

Maxime Dougados Grant/research support from: AbbVie, Eli Lilly, Merck, Novartis, Pfizer and UCB Pharma, Consultant of: AbbVie, Eli Lilly, Merck, Novartis, Pfizer and UCB Pharma, Speakers bureau: AbbVie, Eli Lilly, Merck, Novartis, Pfizer and UCB Pharma, Uta Kiltz Grant/research support from: AbbVie, Amgen, Biogen, Novartis, Pfizer, Consultant of: AbbVie, Biocad, Eli Lilly and Company, Grünenthal, Janssen, Novartis, Pfizer, UCB, Speakers bureau: AbbVie, MSD, Novartis, Pfizer, Roche, UCB, Alan Kivitz Shareholder of: AbbVie, Amgen, Gilead, GSK, Pfizer Inc, Sanofi, Consultant of: AbbVie, Boehringer Ingelheim,,Flexion, Genzyme, Gilead, Janssen, Novartis, Pfizer Inc, Regeneron, Sanofi, SUN Pharma Advanced Research, UCB, Paid instructor for: Celgene, Genzyme, Horizon, Merck, Novartis, Pfizer, Regeneron, Sanofi, Speakers bureau: AbbVie, Celgene, Flexion, Genzyme, Horizon, Merck, Novartis, Pfizer Inc, Regeneron, Sanofi, Karel Pavelka Speakers bureau: AbbVie, BMS, MSD, UCB, Medac, Egis, Pfizer, Roche, Biogen, Novartis, Susanne Rohrer Employee of: Novartis, Suzanne McCreddin Shareholder of: Novartis, Employee of: Novartis, Erhard Quebe-Fehling Shareholder of: Novartis, Employee of: Novartis, Brian Porter Shareholder of: Novartis, Employee of: Novartis, Zsolts Talloczy Shareholder of: Novartis, Employee of: Novartis

5-year efficacy and safety of secukinumab in patients with ankylosing spondylitis: end-of-study results from the phase 3 MEASURE 2 trial

BACKGROUND

Secukinumab, a fully human monoclonal antibody that directly inhibits interleukin 17A, has shown significant and sustained improvement in the signs and symptoms of ankylosing spondylitis over 3 years in the MEASURE 2 study. We report the 5-year (end-of-study) results of subcutaneous secukinumab 150 mg in the MEASURE 2 study.

METHODS

MEASURE 2 was a phase 3, double-blind, randomised, placebo-controlled, study done in 13 countries and 53 centres. Patients with ankylosing spondylitis who were 18 years of age or older and fulfilled the modified New York criteria were randomly assigned to receive secukinumab (150 mg or 75 mg) or placebo subcutaneously at baseline and weeks 1, 2, and 3, and then every 4 weeks from week 4. At week 16, patients initially given placebo were randomly assigned again (placebo switchers) to receive secukinumab 150 mg or 75 mg. Efficacy results are reported for patients initially randomised to secukinumab 150 mg and those who switched from placebo to secukinumab 150 mg at week 16. An optional dose escalation from secukinumab 75 mg to 150 mg was initiated beginning week 140. We assessed efficacy endpoints at week 260 (5 years), including Assessment of Spondyloarthritis International Society (ASAS) 20 and ASAS 40, inactive disease according to ankylosing spondylitis disease activity score with C-reactive protein (ASDAS-CRP), Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), BASDAI50, Bath Ankylosing Spondylitis Metrology Index, Bath Ankylosing Spondylitis Functional Index, Short Form-36 Physical Component Summary, and ASAS partial remission. Analyses were stratified by anti-tumour necrosis factor (TNF) status (anti-TNF-naive and anti-TNF inadequate response). The safety analysis included all patients who received one dose or more of secukinumab. We report data as observed without accounting for missing data. The MEASURE 2 study was registered with ClinicalTrials.gov, NCT01649375.

FINDINGS

219 patients were randomly assigned during the trial and 150 (68%) completed 5 years of treatment, including 82 (77%) of 106 patients in the secukinumab 150 mg group and 68 (65%) of 105 in the secukinumab 75 mg group. Efficacy analysis in the secukinumab 150 mg group included 53 patients who completed the study and one additional patient who was assessed in the treatment period weeks 212-260, but did not complete the study. 134 (61%) of 219 patients were anti-TNF-naive and 85 (39%) were anti-TNF inadequate responders. ASAS responses at 5 years with secukinumab 150 mg were 36 (67%) of 54 patients (ASA20) and 27 (50%) patients (ASAS40). Sustained improvement was observed across other efficacy endpoints with secukinumab 150 mg at 5 years. At 5 years, the proportion of patients achieving efficacy endpoints of BASDAI 50 response was 53% (44/83); ASAS 5/6 response was 51% (42/83); ASDAS-CRP inactive disease was 21% (17/81); and ASAS partial remission was 25% (21/83). Exposure-adjusted incidence rates with any secukinumab dose for selected adverse events were 1·0 per 100 patient-years (95% CI 0·4-1·9) for Candida infections, 0·5 (0·1-1·2) for Crohn's disease, 0·4 (0·1-1·1) for ulcerative colitis, 0·6 (0·2-1·4) for major adverse cardiovascular events, 0·5 (0·1-1·2) for uveitis, and 0·6 (0·2-1·4) for malignant or unspecified tumours.

INTERPRETATION

Secukinumab 150 mg provided sustained improvement in the signs, symptoms, and physical function in patients with ankylosing spondylitis after 5 years of treatment. The safety profile of secukinumab remained consistent with previous reports.

FUNDING

Novartis Pharma.

P248 Subcutaneous secukinumab 150 mg provides rapid and sustained relief in total and nocturnal back pain, morning stiffness and fatigue in patients with active AS over 4 years

Background

Ankylosing spondylitis (AS) is a chronic inflammatory condition with pain, stiffness and fatigue reported as the most troubling symptoms. Early and sustained relief of these symptoms is essential for effective management. Secukinumab provided sustained relief from pain and fatigue in AS patients over 2 years in the MEASURE 2 study. We report the effect of subcutaneous secukinumab 150 mg on key clinical symptoms (pain, morning stiffness and fatigue) in AS patients over 208 weeks in MEASURE 2.

Methods

This post-hoc analysis of MEASURE 2 assessed mean change from baseline to Week 208 in total and nocturnal back pain scores (by VAS [0-100]; ASAS outcome component), overall level of spinal pain (neck, back or hip) from BASDAI scores, and morning stiffness (overall level; mean of question 5 and 6 of BASDAI score). Additionally, the SF-36 physical component summary score, overall level of fatigue (BASDAI question 1), FACIT-Fatigue score and patients meeting minimal clinically important difference (MCID) criteria across multiple clinical domains were assessed. Data are shown for patients originally randomised to secukinumab 150 mg and placebo. Data are reported as observed for the overall population and by prior TNF inhibitor (TNFi) therapy status (naive vs inadequate response [IR]).

Results

Baseline characteristics were comparable across secukinumab 150 mg (N = 72) and placebo (N = 74) groups; total mean back pain score was 67.7±17.79, nocturnal back pain score was 64.9±19.58 and morning stiffness was 6.5±2.11. Secukinumab 150 mg-treated patients reported rapid and early reductions in pain scores by Week 4, which were sustained through Week 208 (Table 1). Improvements with secukinumab 150 mg were reported for all key clinical symptoms by Week 4, which were sustained at Week 208. A higher proportion of secukinumab 150 mg-treated patients met MCID criteria at Week 16 vs placebo across multiple clinical domains, which was sustained or further improved through Week 208. Improvements were observed in TNFi-naive and -IR patients, with a greater magnitude of improvement in TNFi-naive patients.

Conclusion

Secukinumab 150 mg was associated with rapid and clinically meaningful improvements in total and nocturnal back pain, morning stiffness and fatigue, with improvements sustained over 4 years of treatment.

Disclosures

H. Marzo-Ortega: Consultancies; AbbVie, Celgene, Janssen, Lilly, Novartis, Pfizer, UCB. Member of speakers’ bureau; AbbVie, Celgene, Janssen, Lilly, Novartis, Pfizer, UCB. Grants/research support; Janssen, Novartis. C. Miceli-Richard: Consultancies; Pfizer, Roche, UCB, Wyeth, Merck. Member of speakers’ bureau; Abbott, Bristol-Myers Squibb, Merck, Pfizer, Roche, Schering-Plough, Wyeth. Grants/research support; AbbVie, Bristol-Myers Squibb, Novartis, Merck, Pfizer, Wyeth. S. Gill: Consultancies; AbbVie, Eli Lilly, Janssen, Novartis, Pfizer, UCB, Amgen, Sanofi-Genzyme. Other; AbbVie, Eli Lilly, Janssen, Novartis, Pfizer, UCB, Amgen, Sanofi-Genzyme. M. Magery: Consultancies; Eli Lilly, Novartis. Grants/research support; AbbVie, UCB, Amgen. P.G.P. Machado: Shareholder/stock ownership; Novartis. Other; Employee of Novartis. A. Shete: Shareholder/stock ownership; Novartis. Other; Employee of Novartis. J. Wang: Other; Employee of Novartis. S. Rohrer: Shareholder/stock ownership; Novartis. Other; Employee of Novartis. A. Deodhar: Consultancies; AbbVie, Amgen, Boehringer Ingelheim, Bristol-Myers Squibb, Eli Lilly, GSK, Galapagos, Janssen, Novartis, Pfizer, UCB. Grants/research support; Eli Lilly, GSK, Novartis, Pfizer, Boehringer Ingelheim, Bristol-Myers Squibb, UCB.

Secukinumab 150/300 mg Provides Sustained Improvements in the Signs and Symptoms of Active Ankylosing Spondylitis: 3-Year Results from the Phase 3 MEASURE 3 Study

Objective

Secukinumab 150 mg has demonstrated significant improvement in signs and symptoms of ankylosing spondylitis (AS), with response rates sustained for up to 5 years. Here, we report end‐of‐study 3‐year efficacy and safety results of secukinumab 150 and 300 mg from the MEASURE 3 study.

Methods

A total of 226 patients was randomized to intravenous secukinumab 10 mg/kg (baseline, weeks 2 and 4) followed by subcutaneous (s.c.) secukinumab 300/150 mg every 4 weeks or a matched placebo. At week 16, placebo patients were re‐randomized to s.c. secukinumab 300/150 mg. Analysis at week 156 included patients initially randomized to secukinumab and those who switched from placebo to secukinumab at week 16 (any secukinumab 300/150 mg). Outcome measures at week 156 included Assessment of Spondyloarthritis International Society (ASAS) 20/40, Bath Ankylosing Spondylitis Disease Activity Index, ASAS partial remission (PR), ASAS 5/6, and Ankylosing Spondylitis Disease Activity Score–C‐reactive protein inactive disease.

Results

The retention rates from weeks 16 to 156 were 80.5% and 80.9% in secukinumab 300 and 150 mg, respectively. ASAS 20/40 response rates at week 156 were 75.0%/56.5% and 68.2%/47.7% for secukinumab 300 and 150 mg, respectively. At week 156, response rates on more stringent clinical end points (eg, ASAS 40, ASAS‐PR) were higher with the 300‐mg dose, particularly in tumor necrosis factor (TNF)–inadequate responder (IR) patients. No new safety findings were observed.

Conclusion

Secukinumab (300 and 150 mg) provided sustained improvements through 3 years in the signs and symptoms of active AS. Improvements with secukinumab 300 mg were numerically higher compared with the 150‐mg dose for some higher hurdle end points and in TNF‐IR patients. The safety profile of secukinumab was consistent with previous reports.

Secukinumab provides sustained improvements in the signs and symptoms of active ankylosing spondylitis with high retention rate: 3-year results from the phase III trial, MEASURE 2

Background

Secukinumab treatment has previously been shown to significantly improve the signs and symptoms of active ankylosing spondylitis (AS), with responses sustained through 2 years. Here, we report the long-term (3 years) efficacy and safety of secukinumab in the MEASURE 2 study.

Methods

MEASURE 2 (NCT01649375) is a 5-year phase III, randomised, double-blind, double-dummy, parallel-group, placebo-controlled study to evaluate the efficacy, safety and tolerability of subcutaneous loading and maintenance dosing of secukinumab in adult subjects with active AS. Subjects were randomised to receive subcutaneous secukinumab 150 mg, 75 mg or placebo at baseline, weeks 1, 2 and 3 and every 4 weeks from week 4. At week 16, placebo-treated subjects were rerandomised to receive secukinumab 150/75 mg.

Results

Retention rates were high during weeks 16–156 and were 86% and 76% for secukinumab 150 and 75 mg, respectively. Secukinumab 150 mg provided sustained improvements in the Assessment of Spondyloarthritis International Society ASAS 20/40 response rates at week 156 (70.1%/60.9%) compared with week 52 (74.2%/57.0%); however, there was a slight decrease for secukinumab 75 mg (54.3%/37.0% vs 62.5%/43.2%, respectively). Sustained improvements were observed in all other end points, including Bath Ankylosing Spondylitis Disease Activity Index, AS Disease Activity Score with C reactive protein inactive disease, ASAS 5/6, Short Form-36 Physical Component Summary and ASAS partial remission. Clinical benefits were observed regardless of prior exposure to anti-tumour necrosis factor agents. The safety profile remained favourable and was consistent with previous reports.

Conclusions

This study showed sustained improvement through 3 years in signs, symptoms and physical function in subjects with AS. Retention rates were high and secukinumab was well tolerated, with a favourable safety profile.

Safety and immunogenicity of a candidate bioconjugate vaccine against Shigella dysenteriae type 1 administered to healthy adults: A single blind, partially randomized Phase I study

BACKGROUND

Shigellae cause severe disease in endemic countries, especially in children. Several efficacy trials have been conducted with candidate vaccines against Shigellae, but the lack of protection, the safety concerns, or manufacturing challenges hindered successful market approval. Conjugated vaccines have been shown to be safe and effective for different pathogens (i.e., Neisseria meningitidis, Shigella pneumonia, Haemophilus influenzae). The bio-conjugation technology, exploited here for the Shigella dysenteriae candidate vaccine, offers a novel and potentially simpler way to develop and produce vaccines against one of the major causes of morbidity and mortality in developing countries.

METHODS

A novel S. dysenteriae bioconjugate vaccine (GVXN SD133) made of the polysaccharide component of the Shigella O1 lipopolysaccharide, conjugated to the exotoxin protein A of Pseudomonas aeruginosa (EPA), was evaluated for immunogenicity and safety in healthy adults in a single blind, partially randomized Phase I study. Forty subjects (10 in each dose group; 2 μg or 10 μg with or without aluminium adjuvant) received two injections 60 days apart and were followed-up for 150 days.

RESULTS

Both doses and formulations were well tolerated; the safety and reactogenicity profiles were consistent with that of other conjugated vaccines, adjuvanted or not, independent of the dose and the number of injections. The GVXN SD133 vaccine elicited statistically significant O1 specific humoral responses at all time points in all vaccination groups. Between-group comparisons did not show statistically significant differences in geometric mean titers of immunoglobulin G and A at any post-vaccination time point.

CONCLUSIONS

This study demonstrated that the GVXN SD133 vaccine has a satisfactory safety profile. It elicited a significant humoral response to Shigella O1 polysaccharides at all doses tested. The protein carrier also elicited functional antibodies, showing the technology's advantages in preserving both sugar and conjugated protein epitopes. This trial is registered at ClinicalTrials.gov (NCT01069471).

[Refeeding syndrome: a review of the literature]

The refeeding syndrome is a dangerous condition, which may even lead to death. The syndrome occurs after re-establishment of adequate nutrition in malnourished and cachectic patients. More specifically its occurrence has been reported during oral, enteral and parenteral feeding. Early diagnosis is crucial for adequate and timely therapy. However, due to a lack of knowledge in the community this is not always achieved. The leading symptom is hypophosphatemia, often accompanied by electrolyte disturbances and vitamin and trace element deficiencies. Due to a concomitant administration of carbohydrates and intravenous fluid volume it may also lead to hypervolemia with cardiac failure. Compromise of other organ functions with a varying degree of severity, even leading to death, have been reported. The most efficient prevention of the refeeding syndrom is recommended by an early identification of patients at risk and the administration of an initially lower caloric nutrition accompanied by a tight and regularly scheduled observation of relevant laboratory parameters.

METHODS

This literature research included the following terms: "refeeding syndrome" and "hypophosphataemia" including the 2006 guidelines from the National Institute for Health and Clinical Excellence (UK).

Initial experience of 3-tesla apparent diffusion coefficient values in characterizing squamous cell carcinomas of the head and neck

BACKGROUND

With the increased clinical use of 3-Tesla (3T) magnets, it becomes important to identify the potential applications of advanced magnetic resonance (MR) imaging techniques such as diffusion-weighted imaging in head and neck pathologies.

PURPOSE

To establish the 3T apparent diffusion coefficient (ADC) values for normal neck structures, and to examine the utility of ADC values in distinguishing head and neck squamous cell carcinomas (HNSCC) from normal neck anatomy.

MATERIAL AND METHODS

3T diffusion-weighted imaging was performed on 10 normal volunteers and 10 patients with known HNSCC. In the volunteers, mean ADC was calculated in the parotid gland, submandibular gland, base of the tongue, pterygoid muscle, masseter muscle, paraspinal muscles, true vocal cord, thyroid gland, thyroid cartilage, cricoid cartilage, and lymph nodes. The mean tumor ADC value was calculated from the 10 patients with HNSCC and compared with the normal ADC values from various neck structures.

RESULTS

The mean ADC value measured in the HNSCC was 1.101 (+/-0.214) x 10(-3) mm(2)/s. This was significantly lower than ADC values of paraspinal muscles, pterygoid muscle, masseter muscle, thyroid gland, and base of the tongue (P=0.0006, 0.0002, 0.0001, 0.001, and 0.002, respectively). The tumor ADC values were not significantly different from ADC values of parotid and submandibular glands (P=0.057 and 0.14, respectively).

CONCLUSION

3T ADC values show potential for distinguishing HNSCC from normal extracranial head and neck structures.

Differentiation of benign and malignant pathology in the head and neck using 3T apparent diffusion coefficient values: early experience

BACKGROUND AND PURPOSE

The purpose of this work was to study differences in apparent diffusion coefficient (ADC) values between benign and malignant head and neck lesions at 3T field strength imaging.

MATERIALS AND METHODS

Our study population in this retrospective study was derived from the patient population who had undergone routine neck 3T MR imaging (for clinical indications) from December 2005 to December 2006. There were 33 patients identified: 17 with benign and 16 with malignant pathologies. In all of the subjects, conventional MR imaging sequences were performed apart from diffusion-weighted sequences. The mean ADC values in the benign and malignant groups were compared using an unpaired t test with unequal variance with a P < 0.05 considered statistically significant.

RESULTS

There was a statistically significant difference (P = .004) between the mean ADC values (in 10(-3) mm(2)/s) in the benign and malignant lesions (1.505 +/- 0.487; 95% confidence interval, 1.305-1.706, and 1.071 +/- 0.293; 95% confidence interval, 0.864-1.277, respectively). There were 2 malignant lesions with ADC values higher than 1.3 x 10(-3) mm(2)/s and 5 benign lesions with ADC values less than 1.3 x 10(-3) mm(2)/s. The lack of overlap of ADC values within 95% confidence limits suggests that a 3T ADC value of 1.3 x 10(-3) mm(2)/s may be the threshold value for differentiation between benign and malignant head and neck lesions.

CONCLUSION

ADC values of benign and malignant neck pathologies are significantly different at 3T imaging, though larger studies are required to establish threshold ADC values that can applied in daily clinical practice.

Application of a bacterial two-hybrid system for the analysis of protein-protein interactions between FemABX family proteins

Protein-protein interactions play an important role in all cellular processes. The development of two-hybrid systems in yeast and bacteria allows for in vivo assessment of such interactions. Using a recently developed bacterial two-hybrid system, the interactions of the Staphylococcus aureus proteins FemA, FemB and FmhB, members of the FemABX protein family, which is involved in peptidoglycan biosynthesis and beta-lactam resistance of numerous Gram-positive bacteria, were analysed. While FmhB is involved in the addition of glycine 1 of the pentaglycine interpeptide of S. aureus peptidoglycan, FemA and FemB are specific for glycines 2/3 and 4/5, respectively. FemA-FemA, FemA-FemB and FemB-FemB interactions were found, while FmhB exists solely as a monomer. Interactions detected by the bacterial two-hybrid system were confirmed using the glutathione S-transferase-pulldown assay and gel filtration.

Factors influencing methicillin resistance in staphylococci

Methicillin resistance in staphylococci is due to an acquired penicillin-binding protein, PBP2' (PBP2a). This additional PBP, encoded by mecA, confers an intrinsic resistance to all beta-lactams and their derivatives. Resistance levels in methicillin-resistant Staphylococcus aureus (MRSA) depend on efficient PBP2' production and are modulated by chromosomal factors. Depending on the genetic background of the strain that acquired mecA, resistance levels range from phenotypically susceptible to highly resistant. Characteristic for most MRSA is the heterogeneous expression of resistance, which is due to the segregation of a more highly resistant subpopulation upon challenge with methicillin. Maximal expression of resistance by PBP2' requires the efficient and correct synthesis of the peptidoglycan precursor. Genes involved in cell-wall precursor formation and turnover, regulation, transport, and signal transduction may determine the level of resistance that is expressed. At this stage, however, there is no information available on the functionality or efficacy of such factors in clinical isolates in relation to methicillin resistance levels.

Improved methods for detection of methicillin-resistant Staphylococcus aureus

In order to assess the performance of two detection methods, a set of 93 recent clinical isolates of Staphylococcus aureus, including a large number of strains that demonstrated low-level methicillin-resistance were evaluated using the MRSA-Screen (Denka Seiken, Japan), a commercial latex agglutination test to detect penicillin-binding protein 2' (PBP2'), and a polymerase chain reaction assay using the LightCycler Instrument (Roche Diagnostics, Switzerland). The results show that the latex agglutination test is highly sensitive if performed after induction by cefoxitin. Inconclusive results can be rapidly confirmed on the same day by real-time polymerase chain reaction used to detect mecA and femA genes.

Nodulisporic acid opens insect glutamate-gated chloride channels: identification of a new high affinity modulator

Nodulisporic acid (NA) is an indole diterpene fungal product with insecticidal activity. NA activates a glutamate-gated chloride channel (GluCl) in grasshopper neurons and potentiates channel opening by glutamate. The endectocide ivermectin (IVM) induces a similar, but larger current than NA. Using Drosophila melanogaster head membranes, a high affinity binding site for NA was identified. Equilibrium binding studies show that an amide analogue, N-(2-hydroxyethyl-2,2-(3)H)nodulisporamide ([(3)H]NAmide), binds to a single population of sites in head membranes with a K(D) of 12 pM and a B(max) of 1.4 pmol/mg of protein. A similar K(D) is determined from the kinetics of ligand binding and dissociation. Four lines of evidence indicate that the binding site is a GluCl. First, NA potentiates opening of a glutamate-gated chloride current in grasshopper neurons. Second, glutamate inhibits the binding of [(3)H]NAmide by increasing the rate of dissociation 3-fold. Third, IVM potently inhibits the binding of [(3)H]NAmide and IVM binds to GluCls. Finally, the binding of [(3)H]IVM is inhibited by NA. The B(max) of [(3)H]IVM is twice that of [(3)H]NAmide, and about half of the [(3)H]IVM binding sites are inhibited by NA with high affinity (K(I) = 25 pM). In contrast, [(3)H]IVM binding to Caenorhabditis elegans membranes is not inhibited by NA at 100 nM, and there are no high affinity binding sites for NA on these membranes. Thus, half of the Drosophila IVM receptors and all of the NA receptors are associated with GluCl. NA distinguishes between nematode and insect GluCls and identifies subpopulations of IVM binding sites.

The essential Staphylococcus aureus gene fmhB is involved in the first step of peptidoglycan pentaglycine interpeptide formation

The factor catalyzing the first step in the synthesis of the characteristic pentaglycine interpeptide in Staphylococcus aureus peptidoglycan was found to be encoded by the essential gene fmhB. We have analyzed murein composition and structure synthesized when fmhB expression is reduced. The endogenous fmhB promoter was substituted with the xylose regulon from Staphylococcus xylosus, which allowed glucose-controlled repression of fmhB transcription. Repression of fmhB reduced growth and triggered a drastic accumulation of uncrosslinked, unmodified muropeptide monomer precursors at the expense of the oligomeric fraction, leading to a substantial decrease in overall peptidoglycan crosslinking. The composition of the predominant muropeptide was confirmed by MS to be N-acetylglucosamine-(beta-1,4)-N-acetylmuramic acid(-L-Ala-D-iGln-L-Lys-D-Ala-D-Ala), proving that FmhB is involved in the attachment of the first glycine to the pentaglycine interpeptide. This interpeptide plays an important role in crosslinking and stability of the S. aureus cell wall, acts as an anchor for cell wall-associated proteins, determinants of pathogenicity, and is essential for the expression of methicillin resistance. Any shortening of the pentaglycine side chain reduces or even abolishes methicillin resistance, as occurred with fmhB repression. Because of its key role FmhB is a potential target for novel antibacterial agents that could control the threat of emerging multiresistant S. aureus.

Identification of three additional femAB-like open reading frames in Staphylococcus aureus

Three new proteins, FmhA, FmhB and FmhC, with significant identities to FemA and FemB were identified in the Staphylococcus aureus (ATCC 55748) genome database. They were mapped to the SmaI-C, SmaI-H and SmaI-A fragments of the S. aureus 8325 chromosome, respectively. Whereas insertional inactivation of fmhA and fmhC had no effects on growth, antibiotic susceptibility, lysostaphin resistance, or peptidoglycan composition of the strains, fmhB could not be inactivated, strongly suggesting that fmhB may be an essential gene. As deduced from the functions of FemA and FemB which are involved in the synthesis of the peptidoglycan pentaglycine interpeptide, FmhB may be a candidate for the postulated FemX thought to add the first glycine to the nascent interpeptide.

Modulation of receptor and receptor subtype affinities using diastereomeric and enantiomeric monosaccharide scaffolds as a means to structural and biological diversity. A new route to ether synthesis

We show that carbohydrates constitute an attractive source of readily available, stereochemically defined scaffolds for the facile attachment of side chains contained in genetically encoded and other amino acids. beta-D- and beta-L-glucose, L-mannose, and the 6-deoxy-6-N-analogue of beta-D-glucose have been employed to synthesize peptidomimetics that bind the SRIF receptors on AtT-20 mouse pituitary cells, five cloned human receptor subtypes (hSSTRs), and the NK-1 receptor. The affinity profile of various sugar-based ligands at the hSSTRs is compared with that of SRIF. Compound 19 bound hSSTR4 with a Ki of 100 nM. Subtle structural changes affect affinities. Evidence is presented that suggests that one compound (8) binds both the AtT-20 cell receptors and the five hSSTRs via a unique mode. The SARs of the glycosides at SRIF receptors differ markedly from those at the NK-1 receptor. For example a 4-benzyl substituent is important for SRIF receptor binding, but the 4-desbenzyl analogue 27 was highly potent (IC50 of 27 nM) at the NK-1 receptor. A new, nonbasic method for the synthesis of base-sensitive ethers from primary and secondary alcohols is also described.

Target size analysis of an avermectin binding site from Drosophila melanogaster

A high-affinity avermectin binding site from Drosophila melanogaster head membranes was subjected to target size analysis by radiation inactivation in order to determine the functional unit size. Using the [3H]ivermectin binding assay to assess ligand binding activity, the target size was determined to be 44.3 +/- 3.9 kDa. This result suggests that the size of the functional unit required for high-affinity ligand binding is a monomer. The membrane-associated acetylcholinesterase present in the Drosophila head membranes was also analyzed by radiation inactivation and served as a control. By monitoring enzymatic activity, the functional unit size of the Drosophila acetylcholinesterase was determined to be 70 +/- 9.7 kDa. This corresponds to the molecular weight of a dimer composed of a 55 kDa subunit and a 16-18 kDa subunit.