The ribosome quality control factor Asc1 determines the fate of HSP70 mRNA on and off the ribosome.

Cells survive harsh environmental conditions by potently upregulating molecular chaperones such as heat shock proteins (HSPs), particularly the inducible members of the HSP70 family. The life cycle of HSP70 mRNA in the cytoplasm is unique-it is translated during stress when most cellular mRNA translation is repressed and rapidly degraded upon recovery. Contrary to its 5' untranslated region's role in maximizing translation, we discovered that the HSP70 coding sequence (CDS) suppresses its translation via the ribosome quality control (RQC) mechanism. The CDS of the most inducible Saccharomyces cerevisiae HSP70 gene, SSA4, is uniquely enriched with low-frequency codons that promote ribosome stalling during heat stress. Stalled ribosomes are recognized by the RQC components Asc1p and Hel2p and two novel RQC components, the ribosomal proteins Rps28Ap and Rps19Bp. Surprisingly, RQC does not signal SSA4 mRNA degradation via No-Go-Decay. Instead, Asc1p destabilizes SSA4 mRNA during recovery from heat stress by a mechanism independent of ribosome binding and SSA4 codon optimality. Therefore, Asc1p operates in two pathways that converge to regulate the SSA4 mRNA life cycle during stress and recovery. Our research identifies Asc1p as a critical regulator of the stress response and RQC as the mechanism tuning HSP70 synthesis.

Inhibition of capsaicin-induced increase in dermal blood flow by the oral CGRP receptor antagonist, telcagepant (MK-0974).

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT: * Calcitonin gene-related peptide (CGRP) was first described as a potent vasodilator. * CGRP is also increasingly recognized as a key player in the pathophysiology of migraine, and CGRP receptor antagonists potentially offer a new approach for treating migraine. * A novel pharmacodynamic assay to measure CGRP receptor antagonist activity non-invasively in humans has been developed, which involves measuring the increase in dermal blood flow induced by topical application of capsaicin on the forearm. WHAT THIS STUDY ADDS: * This study shows that the novel oral CGRP receptor antagonist, telcagepant, inhibits the increases in dermal blood flow induced by the topical application of capsaicin on the human forearm. * This experimental medicine model may have utility to assist in dose selection for the development of CGRP receptor antagonists. AIMS: To evaluate inhibition of capsaicin-induced increase in dermal blood flow (DBF) following telcagepant (MK-0974), a potent and selective orally bioavailable calcitonin gene-related peptide (CGRP) receptor antagonist being developed for the acute treatment of migraine. METHODS: A three-period crossover study in 12 healthy adult men. Each subject received a single oral dose of telcagepant 300 mg, telcagepant 800 mg or placebo at 0 h, followed 0.5 and 3.5 h later by two topical doses of 300 and 1000 microg capsaicin per 20 microl water-ethanol mixture. Capsaicin was applied at two sites on the volar surface of the subjects' left and right forearms. DBF was assessed by laser Doppler perfusion imaging immediately before ('baseline'), and 0.5 h after each capsaicin application at 1 and 4 h. Plasma samples to determine telcagepant concentrations were collected immediately after laser Doppler perfusion imaging. A pharmacodynamic model was developed to explore the relationship between plasma concentration and inhibition of capsaicin-induced increase in DBF. RESULTS: Geometric mean plasma concentrations after dosing with 300 mg and 800 mg telcagepant were 720 and 1146 nm, respectively, at 1 h, vs. 582 and 2548 nm, respectively, at 4 h. The pharmacodynamic model suggested that the EC(90) for telcagepant inhibition of capsaicin-induced increases in DBF was 909 nm. CONCLUSIONS: Telcagepant inhibits the increases in DBF induced by the topical application of capsaicin on the human forearm. This experimental medicine model may have utility to assist in dose selection for the development of CGRP receptor antagonists.

Ceftolozane/tazobactam dose regimens in severely/morbidly obese patients with complicated intra-abdominal infection or complicated urinary tract infection.

Ceftolozane/tazobactam is approved for treatment of complicated intra-abdominal infection (cIAI) and complicated urinary tract infection (cUTI) with renal function-based dose adjustment. Given that creatinine clearance, body weight and sex are highly correlated in severely/morbidly obese patients, this study investigated whether approved dosing regimens for ceftolozane/tazobactam are appropriate in severely/morbidly obese patients based on simulated pharmacokinetic/pharmacodynamic target attainment, with confirmation from observed clinical outcomes data from the phase 3 clinical development programme. Using a previously published population pharmacokinetic model, 1000 patients were randomly sampled from an internal pooled database of 201 severely/morbidly obese patients (BMI ≥ 35 kg/m2) and were used for Monte Carlo simulation to test whether the labelled dose regimens can achieve ≥90% probability of a target of 32.2% (1-log kill) time above free ceftolozane concentration against pathogens at an MIC up to 8 mg/L. Clinical outcomes data for severely/morbidly obese patients with cIAI or cUTI from pivotal phase 3 studies were summarised to calculate clinical and composite cure rates as a complimentary support. With the approved renal function-based dosing regimens, >90% target attainment of bactericidal activity was achieved at MICs up to 8 mg/L in the simulated severely/morbidly obese patients with cIAI or cUTI, similar to target attainment in non-obese patients and further confirmed by phase 3 outcomes where cure rates in severely/morbidly obese patients and non-obese patients are similar. Approved dosing regimens of ceftolozane/tazobactam, adjusted according to renal function, can achieve adequate target attainment and high clinical cure rates in severely/morbidly obese patients with cIAI or cUTI.

Safety, Tolerability, and Pharmacokinetics of 3 g of Ceftolozane/Tazobactam in Healthy Adults: A Randomized, Placebo-Controlled, Multiple-Dose Study.

Ceftolozane/tazobactam is an antibacterial approved at 1.5 g (1g/0.5 g) every 8 hours (q8h); higher doses may provide additional benefits in difficult-to-treat infections. We conducted a phase I trial in healthy adults evaluating safety, tolerability, and pharmacokinetics of 3 g (2 g/1 g) ceftolozane/tazobactam administered q8h for 10 days. Sixteen participants were randomized (2:1:1) to 3 g ceftolozane/tazobactam, 1.5 g ceftolozane/tazobactam, or placebo. Participants underwent regular safety and plasma drug level assessments, with a follow-up safety visit 7 days after completion. No adverse events (AEs) were reported with placebo; 75% of participants in the 1.5-g and 50% in the 3-g arm experienced AEs. AE types were similar between the ceftolozane/tazobactam groups; all AEs were mild. No participants experienced clinically meaningful laboratory assessment or electrocardiogram abnormalities. Both ceftolozane and tazobactam exhibited dose-proportional pharmacokinetics without accumulation and without substantial differences in clearance and volume of distribution between groups. In the 3-g group, mean ceftolozane parameters were: peak concentration 104 µg/mL (day 1), 112 µg/mL (day 10); half-life 3 hours (day 10); area under the concentration-time curve (AUC(0-t) ) 272 µg·h/mL (day 1), 300µg·h/mL (day 10). Mean tazobactam parameters were: peak concentration 28 µg/mL (day 1), 26 µg/mL (day 10); half-life 1 hour (day 10); AUC(0-t) 47µg·h/mL (day 1), 41µg·h/mL (day 10). Administration of 3 g ceftolozane/tazobactam q8h for 10 days was safe and well tolerated in healthy volunteers.

PK/PD Target Attainment With Ceftolozane/Tazobactam Using Monte Carlo Simulation in Patients With Various Degrees of Renal Function, Including Augmented Renal Clearance and End-Stage Renal Disease.

INTRODUCTION: Ceftolozane/tazobactam is an antibacterial agent with potent in vitro activity against Gram-negative pathogens, including many extended-spectrum ß-lactamase-producing Enterobacteriaceae and drug-resistant Pseudomonas aeruginosa. Because ceftolozane/tazobactam is primarily excreted renally, appropriate dose adjustments are needed for patients with renal impairment. Monte Carlo simulations were used to determine the probability of pharmacokinetic/pharmacodynamic target attainment for patients with varying degrees of renal function, including augmented renal clearance (ARC) and end-stage renal disease (ESRD) with hemodialysis. METHODS: Monte Carlo simulations were conducted for 1000 patients with ARC and normal renal function, mild renal impairment, moderate renal impairment, or severe renal impairment, and for 5000 patients with ESRD. Simulated dosing regimens were based on approved doses for each renal function category. Attainment targets for ceftolozane were 24.8% (bacteriostasis), 32.2% (1-log kill; bactericidal), and 40% (2-log kill) fT > minimum inhibitory concentration (MIC). The target for tazobactam was to achieve a 20% fT > minimum effective concentration (MEC) at an MEC of 1 mg/L, which was derived from a neutropenic mouse thigh infection model and was confirmed by efficacy data from clinical studies for complicated intraabdominal infections and complicated urinary tract infections. RESULTS: In patients with ARC or normal renal function, ≥91% achieved bactericidal activity (32.2% fT > MIC) up to an MIC of 4 mg/L with a 1000-mg ceftolozane dose. In patients with renal impairment (mild, moderate, severe, ESRD), ≥93% achieved bactericidal activity up to an MIC of 8 mg/L. In patients of all renal function categories, the approved dosing regimens of tazobactam achieved ≥91% target attainment against a target of 20% fT > MEC. CONCLUSIONS: At the approved dosing regimens for ceftolozane/tazobactam, ≥91% of patients in all renal function categories, including ARC (up to 200 mL/min) and ESRD, reached target attainment for bactericidal activity at MICs that correspond to susceptibility breakpoints for Enterobacteriaceae and P. aeruginosa.

Ceftolozane/tazobactam pharmacokinetic/pharmacodynamic-derived dose justification for phase 3 studies in patients with nosocomial pneumonia.

Ceftolozane/tazobactam is an antipseudomonal antibacterial approved for the treatment of complicated urinary tract infections (cUTIs) and complicated intra-abdominal infections (cIAIs) and in phase 3 clinical development for treatment of nosocomial pneumonia. A population pharmacokinetic (PK) model with the plasma-to-epithelial lining fluid (ELF) kinetics of ceftolozane/tazobactam was used to justify dosing regimens for patients with nosocomial pneumonia in phase 3 studies. Monte Carlo simulations were performed to determine ceftolozane/tazobactam dosing regimens with a > 90% probability of target attainment (PTA) for a range of pharmacokinetic/pharmacodynamic targets at relevant minimum inhibitory concentrations (MICs) for key pathogens in nosocomial pneumonia. With a plasma-to-ELF penetration ratio of approximately 50%, as observed from an ELF PK study, a doubling of the current dose regimens for different renal functions that are approved for cUTIs and cIAIs is needed to achieve > 90% PTA for nosocomial pneumonia. For example, a 3-g dose of ceftolozane/tazobactam for nosocomial pneumonia patients with normal renal function is needed to achieve a > 90% PTA (actual 98%) for the 1-log kill target against pathogens with an MIC of ≤ 8 mg/L in ELF, compared with the 1.5-g dose approved for cIAIs and cUTIs.

Pharmacokinetics, safety, and tolerability of ceftolozane/tazobactam in healthy Japanese, Chinese, and white subjects.

Ceftolozane/tazobactam, a novel antibacterial with potent activity against Gram-negative pathogens, was developed for treatment of complicated urinary tract infections, including pyelonephritis, and intra-abdominal infections. A phase 1 pharmacokinetic (PK) study of ceftolozane/tazobactam in healthy Japanese, Chinese, and white volunteers was conducted to assess the potential effect of ethnicity on PK. The PK of ceftolozane, tazobactam, and tazobactam metabolite M1 was compared after single 1.5- and 3-g intravenous doses of ceftolozane/tazobactam. Ten Japanese, nine Chinese, and ten white subjects were enrolled, and 27 completed all doses of study medication. Dose-normalized PK parameters for ceftolozane and tazobactam were similar among Japanese, Chinese, and white subjects (at 1.5-g and 3-g doses, ceftolozane area under the plasma concentration-time curve from zero to infinity [AUC0-∞ ] = 166.3, 165.9, and 185.5 h µg/mL, respectively, and 157.7, 158.5, and 181.2 h µg/mL, respectively; tazobactam AUC0-∞ = 48.5, 43.2, and 50.1 h µg/mL, respectively, and 47.3, 43.7, and 50.0 h µg/mL, respectively. The 90% CIs of their ratio estimates were within the range 0.80 to 1.25 with the exception of AUC0-∞ for ceftolozane after the 3-g dose (0.79). The cumulative amount of ceftolozane and tazobactam excreted in urine was similar among ethnic groups. For all groups, treatment-emergent adverse events (AEs) were mild; no deaths or serious AEs were reported. The PK of ceftolozane/tazobactam was approximately dose proportional (i.e. doubling the dose approximately doubles the exposure) and similar among the groups. No dosage adjustment is needed for ceftolozane/tazobactam in Japanese and Chinese patients.

Population pharmacokinetics of ceftolozane/tazobactam in healthy volunteers, subjects with varying degrees of renal function and patients with bacterial infections.

Ceftolozane/tazobactam is a novel antipseudomonal cephalosporin and ß-lactamase inhibitor in clinical development for treatment of complicated urinary tract (cUTI) and intra-abdominal (cIAI) infections and nosocomial pneumonia. The population pharmacokinetics of ceftolozane/tazobactam were characterized in healthy volunteers, subjects with varying degrees of renal function, and patients with cIAI or cUTI. Serum concentration data from 376 adults who received ceftolozane/tazobactam in doses ranging from 500 to 3000 mg were analyzed to identify factors contributing to the pharmacokinetic variability. Ceftolozane/tazobactam pharmacokinetics were well described by a linear two-compartment model with first-order elimination and moderate between-subject variability in both clearance and volume of distribution (Vc). For both ceftolozane and tazobactam, clearance was highly correlated with renal function with creatinine clearance influencing exposure, and infection influencing Vc. Body weight was an additional covariate affecting the Vc of ceftolozane. Other covariates tested, such as age, body weight, sex, ethnicity, and presence of infection, had no clinically relevant effects on exposure. The final pharmacokinetic models adequately described the plasma concentrations of ceftolozane and tazobactam and form the basis for further modeling and simulation including evaluation of probability of target attainment in a diverse population with varying demographics, degrees of renal function, and infection status.

Dose-dependent binding of AZD3783 to brain 5-HT1B receptors in non-human primates and human subjects: a positron emission tomography study with [11C]AZ10419369.

RATIONALE: The serotonin 5-HT(1B) receptor is a potential target for the pharmacologic treatment of depression. Positron emission tomography (PET) determination of 5-HT(1B) receptor occupancy with drug candidates targeting this receptor in non-human primate and human subjects may facilitate translation of research from animal models and guide dose selection for clinical studies. AZD3783 is a recently developed, orally bioavailable 5-HT(1B) receptor antagonist with potential antidepressant properties. OBJECTIVES: To determine the relationship between plasma concentration of AZD3783 and occupancy at primate brain 5-HT(1B) receptors using PET and the radioligand [(11)C]AZ10419369. METHODS: PET studies with [(11)C]AZ10419369 were performed in three non-human primates at baseline and after intravenous injection of AZD3783. Subsequently, PET measurements were undertaken in six human subjects at baseline and after administration of different single oral doses of AZD3783 (1-40 mg). RESULTS: After administration in non-human primates and human subjects, AZD3783 reduced regional [(11)C]AZ10419369 binding in a dose-dependent and saturable manner. The AZD3783 plasma concentration required for 50% receptor occupancy (K (i,plasma)) for monkeys was 25 and 27 nmol/L in occipital cortex and striatum, respectively. Corresponding estimates for human occipital cortex and ventral striatum were 24 and 18 nmol/L, respectively. CONCLUSIONS: The potential antidepressant AZD3783 binds in a saturable manner to brain 5-HT(1B) receptors with a similar in vivo affinity for human and monkey receptors. [(11)C]AZ10419369 can be successfully used to determine occupancy at brain 5-HT(1B) receptors in vivo and constitutes a useful tool for dose selection in clinical studies with 5-HT(1B) receptor compounds.

Single- and multiple-dose pharmacokinetics and tolerability of telcagepant, an oral calcitonin gene-related peptide receptor antagonist, in adults.

Telcagepant is a novel, orally active, and selective calcitonin gene-related peptide receptor antagonist being developed for acute treatment of migraine with and without aura. Three separate clinical studies were conducted to evaluate the pharmacokinetics and tolerability of telcagepant following single oral doses in healthy young and elderly men and women and multiple oral doses in men. Telcagepant was rapidly absorbed with a time to maximum concentration of approximately 1.5 hours. The terminal half-life was approximately 6 hours. A greater than dose-proportional increase was observed in the area under the plasma concentration versus time curve from zero to infinity. Following twice-daily dosing, with each dose separated by 2 hours, steady state was achieved in approximately 3 to 4 days with an accumulation ratio of approximately 2. There were no clinically meaningful pharmacokinetic differences when compared across age and gender. Telcagepant was generally well tolerated up to single doses of 1200 mg and multiple doses of 400 mg twice daily.