Safety, Tolerability, and Pharmacokinetics of Zagotenemab in Participants with Symptomatic Alzheimer's Disease: A Phase I Clinical Trial

Background

Zagotenemab (LY3303560), a monoclonal antibody, preferentially binds to extracellular, misfolded, aggregated tau that has been implicated in Alzheimer's disease (AD).

Objective

The goal of this study was to assess the safety and pharmacokinetics of multiple doses of zagotenemab in participants with AD.

Methods

This was a Phase Ib, multi-site, participant- and investigator-blind, placebo-controlled, parallel-group study in participants with mild cognitive impairment due to AD or mild to moderate AD. After screening, participants were randomized to zagotenemab 70 mg, 210 mg, or placebo every 4 weeks for up to 49 weeks and were followed up for 16 weeks.

Results

A total of 13 males and 9 females, aged 59 to 84 years, were dosed. No deaths occurred during this study. A total of 4 serious adverse events occurred in 2 participants who then discontinued the study. The most commonly reported (3 or more participants) treatment-emergent adverse events were sinus bradycardia, headache, fall, and bronchitis. The pharmacokinetics profile showed generally linear exposures across the dose range studied with a clearance of ~8 mL/h. The half-life of zagotenemab in serum was ~20 days. A dose-dependent increase in plasma tau was observed. No other significant pharmacodynamic differences were observed due to low dose levels and limited treatment duration.

Conclusions

No dose-limiting adverse events were observed with zagotenemab treatment. Pharmacokinetics of zagotenemab were typical for a monoclonal antibody. Meaningful pharmacodynamic differences were not observed.Clinicaltrials.gov: NCT03019536.

Donanemab exposure and efficacy relationship using modeling in Alzheimer's disease

INTRODUCTION

Donanemab is an amyloid-targeting therapy that specifically targets brain amyloid plaques. The objective of these analyses was to characterize the relationship of donanemab exposure with plasma biomarkers and clinical efficacy through modeling.

METHODS

Data for the analyses were from participants with Alzheimer's disease from the phase 1 and TRAILBLAZER-ALZ studies. Indirect-response models were used to fit plasma phosphorylated tau 217 (p-tau217) and plasma glial fibrillated acidic protein (GFAP) data over time. Disease-progression models were developed using pharmacokinetic/pharmacodynamic modeling.

RESULTS

The plasma p-tau217 and plasma GFAP models adequately predicted the change over time, with donanemab resulting in decreased plasma p-tau217 and plasma GFAP concentrations. The disease-progression models confirmed that donanemab significantly reduced the rate of clinical decline. Simulations revealed that donanemab slowed disease progression irrespective of baseline tau positron emission tomography (PET) level within the evaluated population.

DISCUSSION

The disease-progression models show a clear treatment effect of donanemab on clinical efficacy regardless of baseline disease severity.

Donanemab Population Pharmacokinetics, Amyloid Plaque Reduction, and Safety in Participants with Alzheimer's Disease

Donanemab is an amyloid-targeting therapy that resulted in robust amyloid plaque reduction and slowed Alzheimer's disease (AD) progression compared with placebo in the phase II TRAILBLAZER-ALZ study (NCT03367403). The objectives of the current analyses are to characterize (i) the population pharmacokinetics of donanemab, (ii) the relationship between donanemab exposure and amyloid plaque reduction (response), and (iii) the relationship between donanemab exposure and amyloid-related imaging abnormalities with edema or effusions (ARIA-E). Model development included data from participants with mild cognitive impairment or mild to moderate dementia due to AD from the phase Ib study on donanemab (NCT02624778) and participants with early symptomatic AD from the TRAILBLAZER-ALZ study. The analysis showed donanemab has a terminal elimination half-life of 11.8 days. Body weight and antidrug antibody titer impact donanemab exposure but not the pharmacodynamic response. Maintaining a donanemab serum concentration above 4.43 μg/mL (95% confidence interval: 0.956, 10.4) is associated with amyloid plaque reduction. The time to achieve amyloid plaque clearance (amyloid plaque level < 24.1 Centiloids) varied depending on the baseline amyloid level, where higher baseline levels were associated with fewer participants achieving amyloid clearance. The majority of participants achieved amyloid clearance by 52 weeks on treatment. Apolipoprotein ε4 carriers, irrespective of donanemab serum exposure, were 4 times more likely than noncarriers to have an ARIA-E event by 24 weeks.

Association of Amyloid Reduction After Donanemab Treatment With Tau Pathology and Clinical Outcomes: The TRAILBLAZER-ALZ Randomized Clinical Trial

Question

Is donanemab-induced amyloid reduction associated with slowing of tau pathology and clinical decline in individuals with Alzheimer disease?

Findings

In early symptomatic Alzheimer disease, donanemab induced a robust decrease in amyloid plaque levels by 24 weeks, with baseline plaque directly associated with magnitude of amyloid reduction and inversely associated with probability of complete clearance. In individuals with amyloid clearance, post hoc modeling suggests that amyloid levels would remain below the positivity threshold for almost 4 years without treatment; in treated patients, greater plaque clearance was associated with slower progression of tau positron emission tomography and slower clinical decline (in apolipoprotein E ε4 carriers only).

Meaning

Exploratory post hoc analyses of the Study of LY3002813 in Participants With Early Symptomatic Alzheimer’s Disease (TRAILBLAZER-ALZ) identified potential associations between amyloid lowering, tau pathology, and clinical outcomes.

Importance

β-amyloid plaques and neurofibrillary tau deposits biologically define Alzheimer disease.

Objective

To perform post hoc analyses of amyloid reduction after donanemab treatment and assess its association with tau pathology and clinical measures.

Design, Setting, and Participants

The Study of LY3002813 in Participants With Early Symptomatic Alzheimer’s Disease (TRAILBLAZER-ALZ) was a phase 2, placebo-controlled, randomized clinical trial conducted from December 18, 2017, to December 4, 2020, with a double-blind period of up to 76 weeks and a 48-week follow-up period. The study was conducted at 56 centers in the US and Canada. Enrolled were participants from 60 to 85 years of age with gradual and progressive change in memory function for 6 months or more, early symptomatic Alzheimer disease, elevated amyloid, and intermediate tau levels.

Interventions

Donanemab (an antibody specific for the N-terminal pyroglutamate β-amyloid epitope) dosing was every 4 weeks: 700 mg for the first 3 doses, then 1400 mg for up to 72 weeks. Blinded dose-reduction evaluations occurred at 24 and 52 weeks based on amyloid clearance.

Main Outcomes and Measures

Change in amyloid, tau, and clinical decline after donanemab treatment.

Results

The primary study randomized 272 participants (mean [SD] age, 75.2 [5.5] years; 145 female participants [53.3%]). The trial excluded 1683 of 1955 individuals screened. The rate of donanemab-induced amyloid reduction at 24 weeks was moderately correlated with the amount of baseline amyloid (Spearman correlation coefficient r, −0.54; 95% CI, −0.66 to −0.39; P < .001). Modeling provides a hypothesis that amyloid would not reaccumulate to the 24.1-centiloid threshold for 3.9 years (95% prediction interval, 1.9-8.3 years) after discontinuing donanemab treatment. Donanemab slowed tau accumulation in a region-dependent manner as measured using neocortical and regional standardized uptake value ratios with cerebellar gray reference region. A disease-progression model found a significant association between percentage amyloid reduction and change on the integrated Alzheimer Disease Rating Scale only in apolipoprotein E (APOE) ε4 carriers (95% CI, 24%-59%; P < .001).

Conclusions and Relevance

Results of post hoc analyses for donanemab-treated participants suggest that baseline amyloid levels were directly associated with the magnitude of amyloid reduction and inversely associated with the probability of achieving complete amyloid clearance. The donanemab-induced slowing of tau was more pronounced in those with complete amyloid clearance and in brain regions identified later in the pathologic sequence. Data from other trials will be important to confirm aforementioned observations, particularly treatment response by APOE ε4 status.

Trial Registration

ClinicalTrials.gov Identifier: NCT03367403

Robust Pharmacodynamic Effect of LY3202626, a Central Nervous System Penetrant, Low Dose BACE1 Inhibitor, in Humans and Nonclinical Species

Background: The development of beta-site amyloid-beta precursor protein cleaving enzyme (BACE) 1 inhibitors for the treatment of Alzheimer’s disease requires optimization of inhibitor potency, selectivity, and brain penetration. Moreover, there is a need for low-dose compounds since liver toxicity was found with some BACE inhibitors. Objective: To determine whether the high in vitro potency and robust pharmacodynamic effect of the BACE inhibitor LY3202626 observed in nonclinical species translated to humans. Methods: The effect of LY3202626 versus vehicle on amyloid-β (Aβ) levels was evaluated in a series of in vitro assays, as well as in in vivo and multi-part clinical pharmacology studies. Aβ levels were measured using analytical biochemistry assays in brain, plasma, and cerebrospinal fluid (CSF) of mice, dogs and humans. Nonclinical data were analyzed using an ANOVA followed by Tukey’s post hoc test and clinical data used summary statistics. Results: LY3202626 exhibited significant human BACE1 inhibition, with an IC50 of 0.615±0.101 nM in a fluorescence resonance energy transfer assay and an EC50 of 0.275±0.176 nM for lowering Aβ1–40 and 0.228±0.244 nM for Aβ1–42 in PDAPP neuronal cultures. In dogs, CSF Aβ1hboxx concentrations were significantly reduced by ∼80% at 9 hours following a 1.5 mg/kg dose. In humans, CSF Aβ1–42 was reduced by 73.1±7.96 % following administration of 6 mg QD. LY3202626 was found to freely cross the blood-brain barrier in dogs and humans. Conclusion: LY3202626 is a potent BACE1 inhibitor with high blood-brain barrier permeability. The favorable safety and pharmacokinetic/pharmacodynamic profile of LY3202626 supports further clinical development.

Donanemab (LY3002813) Phase 1b Study in Alzheimer's Disease: Rapid and Sustained Reduction of Brain Amyloid Measured by Florbetapir F18 Imaging

BACKGROUND

Donanemab (LY3002813) is an IgG1 antibody directed at an N‑terminal pyroglutamate of amyloid beta epitope that is present only in brain amyloid plaques.

OBJECTIVES

To assess effects of donanemab on brain amyloid plaque load after single and multiple intravenous doses, as well as pharmacokinetics, safety/tolerability, and immunogenicity.

DESIGN

Phase 1b, investigator- and patient-blind, randomized, placebo-controlled study.

SETTING

Patients recruited at clinical research sites in the United States and Japan.

PARTICIPANTS

61 amyloid plaque-positive patients with mild cognitive impairment due to Alzheimer's disease and mild-to-moderate Alzheimer's disease dementia.

INTERVENTION

Six cohorts were dosed with donanemab: single dose 10-, 20- or 40- mg/kg (N = 18), multiple doses of 10-mg/kg every 2 weeks for 24 weeks (N = 10), and 10- or 20-mg/kg every 4 weeks for 72 weeks (N=18) or placebo (N = 15).

MEASUREMENTS

Brain amyloid plaque load, using florbetapir positron emission tomography, was assessed up to 72 weeks. Safety was evaluated by occurrence of adverse events, magnetic resonance imaging, electrocardiogram, vital signs, laboratory testing, neurological monitoring, and immunogenicity.

RESULTS

Treatment with donanemab resulted in rapid reduction of amyloid, even after a single dose. By 24 weeks, amyloid positron emission tomography mean changes from baseline for single donanemab doses in Centiloids were: -16.5 (standard error 11.22) 10-mg/kg intravenous; 40.0 (standard error 11.23) 20 mg/kg intravenous; and -49.6 (standard error 15.10) 40-mg/kg intravenous. Mean reduction of amyloid plaque in multiple dose cohorts by 24 weeks in Centiloids were: 55.8 (standard error 9.51) 10-mg/kg every 2 weeks; -50.2 (standard error 10.54) 10-mg/kg every 4 weeks; and -58.4 (standard error 9.66) 20-mg/kg every 4 weeks. Amyloid on average remained below baseline levels up to 72 weeks after a single dose of donanemab. Repeated dosing resulted in continued florbetapir positron emission tomography reductions over time compared to single dosing with 6 out of 28 patients attaining complete amyloid clearance within 24 weeks. Within these, 5 out of 10 patients in the 20 mg/kg every 4 weeks cohort attained complete amyloid clearance within 36 weeks. When dosing with donanemab was stopped after 24 weeks of repeat dosing in the 10 mg every 2 weeks cohort, florbetapir positron emission tomography reductions were sustained up to 72 weeks. For the single dose cohorts on day 1, dose proportional increases in donanemab pharmacokinetics were observed from 10 to 40 mg/kg. Dose proportional increases in pharmacokinetics were also observed at steady state with the multiple dose cohorts. Donanemab clearance was comparable across the dose levels. Mean donanemab elimination-half-life following 20 mg/kg single dose was 9.3 days with range of 5.6 to 16.2 days. Greater than 90% of patients had positive treatment-emergent antidrug antibodies with donanemab. However, overall, the treatment-emergent antidrug antibodies did not have a significant impact on pharmacokinetics. Donanemab was generally well tolerated. Amongst the 46 participants treated with donanemab, the following amyloid-related imaging abnormalities, common to the drug class, were observed: 12 vasogenic cerebral edema events (12 [19.7%] patients), 10 cerebral microhemorrhage events (6 [13.0%] patients), and 2 superficial siderosis events (2 [4.3%] patients).

CONCLUSIONS

Single and multiple doses of donanemab demonstrated a rapid, robust, and sustained reduction up to 72 weeks in brain amyloid plaque despite treatment-emergent antidrug antibodies detected in most patients. Amyloid-related imaging abnormalities were the most common treatment-emergent event.

Discovery and Early Clinical Development of LY3202626, a Low-Dose, CNS-Penetrant BACE Inhibitor

The beta-site APP cleaving enzyme 1, known as BACE1, has been a widely pursued Alzheimer's disease drug target owing to its critical role in the production of amyloid-beta. We have previously reported the clinical development of LY2811376 and LY2886721. LY2811376 advanced to Phase I before development was terminated due to nonclinical retinal toxicity. LY2886721 advanced to Phase II, but development was halted due to abnormally elevated liver enzymes. Herein, we report the discovery and clinical development of LY3202626, a highly potent, CNS-penetrant, and low-dose BACE inhibitor, which successfully addressed these key development challenges.

Phase II (NAVIGATE-AD study) Results of LY3202626 Effects on Patients with Mild Alzheimer's Disease Dementia

Background:

LY3202626 is a small molecule inhibitor of β-site amyloid precursor protein cleaving enzyme (BACE)1 shown to reduce amyloid-β (Aβ)_1–40 and Aβ_1–42 concentrations in plasma and cerebrospinal fluid developed for the treatment of Alzheimer’s disease (AD).

Objective:

To assess the change from baseline in flortaucipir positron emission tomography (PET) after treatment with LY3202626 compared with placebo in patients with mild AD dementia.

Methods:

Patients received daily 3 mg or 12 mg doses of LY3202626 or placebo for 52 weeks. The primary outcome was assessment of cerebral neurofibrillary tangle load by flortaucipir PET. The study was terminated early following an interim analysis due to a low probability of identifying a statistically significant slowing of cognitive and/or functional decline.

Results:

A total of 316 patients were randomized and 47 completed the study. There was no statistically significant difference between placebo and either dose of LY3202626 from baseline to 52 weeks, or in annualized change for flortaucipir PET. There was no clinically meaningful difference between placebo and LY3202626 doses on efficacy measures of cognition and function. No deaths or serious adverse events considered related to LY3202626 were reported. A statistically significant increase in treatment-emergent adverse events in the psychiatric disorders system organ class was reported for both LY3202626 doses compared to placebo.

Conclusion:

LY3202626 tested at doses generating 70–90% BACE inhibition was generally well tolerated in this study. LY3202626 treatment did not result in a clinically significant change in cerebral tau burden as measured by flortaucipir nor in change of functional or cognitive decline compared to placebo.

Donanemab (LY3002813) dose-escalation study in Alzheimer's disease

INTRODUCTION

This study explored the safety and tolerability features of donanemab (LY3002813) in patients with mild cognitive impairment due to Alzheimer's disease (AD) or mild to moderate AD dementia.

METHODS

Patients with AD were enrolled into the single-ascending dose phase and were administered a single, intravenous (IV) dose of donanemab (five dosing cohorts from 0.1 to 10 mg/kg) or placebo followed by a 12-week follow-up period for each dose level. After the follow-up period, the same patients proceeded into the multiple-ascending dose (MAD) phase (five cohorts) and were administered IV doses of donanemab (0.3 to 10 mg/kg) or placebo approximately once per month for up to four doses depending on the initial doses (only cohort 1 went from 0.1 mg/kg to a higher dose of 0.3 mg/kg during the MAD phase). This phase concluded with a 12-week follow-up period. The relative exposure assessment of an unblinded, single, subcutaneous 3-mg/kg dose of donanemab in patients with AD was also performed, followed by a 12-week follow-up period. One cohort of healthy subjects received an unblinded, single, IV 1-mg/kg dose of donanemab. These two cohorts did not continue to the MAD phase.

RESULTS

Donanemab was generally well tolerated up to 10 mg/kg. After single-dose administration from 0.1 to 3.0 mg/kg, the mean terminal elimination half-life was ≈4 days, increasing to ≈10 days at 10 mg/kg. Only the 10-mg/kg dose showed changes in amyloid positron emission tomography. Amyloid reduction of 40% to 50% was achieved. Approximately 90% of subjects developed anti-drug antibodies at 3 months after a single intravenous dose.

DISCUSSION

Intravenous donanemab 10 mg/kg can reduce amyloid deposits in AD despite having a shorter than expected half-life.

Efficacy and Safety of Lanabecestat for Treatment of Early and Mild Alzheimer Disease: The AMARANTH and DAYBREAK-ALZ Randomized Clinical Trials

Importance

Alzheimer disease (AD) is a neurodegenerative disorder characterized by cognitive deterioration and impaired activities of daily living. Current treatments provide only minor symptomatic improvements with limited benefit duration. Lanabecestat, a brain-permeable inhibitor of human beta-site amyloid precursor protein-cleaving enzyme 1 (BACE1/β-secretase), was developed to modify the clinical course of AD by slowing disease progression.

Objective

To assess whether lanabecestat slows the progression of AD compared with placebo in patients with early AD (mild cognitive impairment) and mild AD dementia.

Design, Setting, and Participants

AMARANTH (first patient visit on September 30, 2014; last patient visit on October 4, 2018) and DAYBREAK-ALZ (first patient visit on July 1, 2016; last patient visit on September 28, 2018) were randomized, placebo-controlled, phase 2/3 and phase 3 clinical trials lasting 104 weeks and 78 weeks, respectively. AMARANTH and DAYBREAK-ALZ were multicenter, global, double-blind studies conducted at 257 and 251 centers, respectively, located in 15 and 18 countries or territories, respectively. A population-based sample of men and women aged 55 to 85 years who met National Institute on Aging-Alzheimer's Association criteria for early AD or mild AD dementia was screened using cognitive assessments, and the presence of amyloid was confirmed. Patients were excluded for unstable medical conditions or medication use, significant cerebrovascular pathologic findings, or a history of vitiligo and/or current evidence of postinflammatory hypopigmentation. AMARANTH screened 6871 patients; 2218 (32.3%) were randomized, and 539 patients completed the study. DAYBREAK-ALZ screened 5706 patients; 1722 (30.2%) were randomized, and 76 patients completed the study.

Interventions

Patients were randomized (1:1:1) to once-daily oral doses of lanabecestat (20 mg), lanabecestat (50 mg), or placebo.

Main Outcomes and Measures

The primary outcome measure was change from baseline on the 13-item Alzheimer Disease Assessment Scale-cognitive subscale. Secondary outcomes included Alzheimer's Disease Cooperative Study-Instrumental Activities of Daily Living Inventory, Clinical Dementia Rating, Functional Activities Questionnaire, Mini-Mental State Examination, and Neuropsychiatric Inventory. Efficacy analyses were conducted on the intent-to-treat population.

Results

Among 2218 AMARANTH patients, the mean (SD) age was 71.3 (7.1) years, and 1177 of 2218 (53.1%) were women. Among 1722 DAYBREAK-ALZ patients, the mean (SD) age was 72.3 (7.0) years, and 1023 of 1722 (59.4%) were women. Both studies were terminated early after futility analysis. There were no consistent, reproducible dose-related findings on primary or secondary efficacy measures. Psychiatric adverse events, weight loss, and hair color changes were reported in a higher percentage of patients receiving lanabecestat than placebo.

Conclusions and Relevance

Treatment with lanabecestat was well tolerated and did not slow cognitive or functional decline.

Trial Registration

ClinicalTrials.gov identifiers: NCT02245737 and NCT02783573.

An integrated PK-PD model for cortisol and the 17-hydroxyprogesterone and androstenedione biomarkers in children with congenital adrenal hyperplasia

Aims

The aim of this study was to characterize the pharmacokinetic/pharmacodynamic relationships of cortisol and the adrenal biomarkers 17‐hydroxyprogesterone and androstenedione in children with congenital adrenal hyperplasia (CAH).

Methods

A nonlinear mixed‐effect modelling approach was used to analyse cortisol, 17‐hydroxyprogesterone and androstenedione concentrations obtained over 6 hours from children with CAH (n = 50). A circadian rhythm was evident and the model leveraged literature information on circadian rhythm in untreated children with CAH. Indirect response models were applied in which cortisol inhibited the production rate of all three compounds using an I_max model.

Results

Cortisol was characterized by a one‐compartment model with apparent clearance and volume of distribution estimated at 22.9 L/h/70 kg and 41.1 L/70 kg, respectively. The IC₅₀ values of cortisol concentrations for cortisol, 17‐hydroxyprogesterone and androstenedione were estimated to be 1.36, 0.45 and 0.75 μg/dL, respectively. The inhibitory effect was found to be more potent on 17OHP than D4A, and the IC₅₀ values were higher in salt‐wasting subjects than simple virilizers. Production rates of cortisol, 17‐hydroxyprogesterone and androstenedione were higher in simple‐virilizer subjects. Half‐lives of cortisol, 17‐hydroxyprogesterone and androstenedione were 60, 47 and 77 minutes, respectively.

Conclusion

Rapidly changing biomarker responses to cortisol concentrations highlight that single measurements provide volatile information about a child's disease control. Our model closely captured observed cortisol, 17‐hydroxyprogesterone and androstenedione concentrations. It can be used to predict concentrations over 24 hours and allows many novel exposure metrics to be calculated, e.g., AUC, AUC‐above‐threshold, time‐within‐range, etc. Our long‐range goal is to uncover dose–exposure–outcome relationships that clinicians can use in adjusting hydrocortisone dose and timing.

Pharmacokinetics and Pharmacodynamics of LY2599666, a PEG-Linked Antigen Binding Fragment that Targets Soluble Monomer Amyloid-β

LY2599666 is a humanized, affinity-optimized monoclonal antibody antigen-binding fragment linked to a PEG molecule and targets soluble amyloid-β (Aβ) monomers. This first-in-human dose ascending study assessed pharmacokinetics (PK) (measured as serum free LY2599666 concentration) and pharmacodynamic (PD) effects (measured as plasma total soluble Aβ40 and Aβ42) after a single subcutaneous (SC) dose of 10, 25, 100, and 200 mg LY2599666 in healthy subjects. As LY2599666 binds to multiple soluble Aβ monomers, a two-target mediated drug disposition model (TMDD) was developed to simultaneously fit serum LY2599666 concentration and Aβ monomer levels. Four Alzheimer's disease patients completed 25 mg once-weekly dosing of LY2599666 for 12 weeks. In addition, single cerebrospinal fluid samples were collected to assess penetration capability across the blood-brain barrier. PK and PD data collected from the multiple dose cohort aligned with model predictions, suggesting the established TMDD model predicted suppression of soluble Aβ40 and Aβ42 in plasma after SC dosing of LY2599666.

Clinically Negligible Pharmacokinetic and Pharmacodynamic Interactions Between Lanabecestat and Dabigatran Etexilate, a Prototypical P-gp Substrate

Lanabecestat, a novel β-site amyloid precursor protein-cleaving enzyme 1 inhibitor evaluated for Alzheimer treatment, inhibits P-glycoprotein (P-gp) activity in vitro. After oral 50-mg lanabecestat administration, gastric fluid lanabecestat concentrations exceed half-maximal inhibitory concentration (IC₅₀ ), suggesting P-gp inhibition at the intestinal wall. Plasma drug concentrations following 50 mg lanabecestat administered once daily are <10% of IC₅₀ , suggesting minimal systemic P-gp interaction. Dabigatran etexilate (DE) is the prodrug of dabigatran, a thrombin inhibitor and P-gp substrate, making dabigatran exposure an intestinal P-gp activity indicator. This study (NCT02568397) was conducted in 60 healthy subjects receiving a single dose of 150 mg DE alone or during a lanabecestat treatment regimen. On day 16, lanabecestat and DE were coadministered; on day 20, DE was dosed 4 hours after lanabecestat. Safety was assessed using clinical labs, electrocardiogram, vital signs, Columbia Suicide Severity Rating Scale scores, adverse events, and eye and skin examinations. Pharmacokinetic/pharmacodynamic samples were collected up to 36 hours postdose. Geometric mean plasma dabigatran area under the curve from time 0 to infinity (AUC_0-∞ ) and the maximum plasma drug concentration (C_max ) increased by 15% and 17%, respectively, when coadministered with lanabecestat. When DE was dosed 4 hours after lanabecestat, there was no effect on plasma dabigatran AUC_0-∞ , C_max , or thrombin time. DE had no effect on lanabecestat's AUC_0-∞ and C_max at steady state (day 16) versus lanabecestat alone (day 15). No clinically relevant safety concerns were observed. Lanabecestat has no clinically meaningful effect on dabigatran exposure or on P-gp activity at the intestinal wall.

Assessment of Transporter Polymorphisms as a Factor in a BCRP Drug Interaction Study With Lanabecestat

Lanabecestat is a human β-site amyloid precursor protein-cleaving enzyme 1 inhibitor in development to slow disease progression in patients with early Alzheimer's disease. The study evaluated the breast cancer resistance protein (BCRP) inhibition potential of lanabecestat on the pharmacokinetics (PK) of rosuvastatin, a probe for BCRP activity, in healthy white subjects who were not carriers of SLCO1B1 (c.521T>C), not homozygotes for ABCG2 (c.421C>A or c.34G>A), and not heterozygotes of ABCG2 (c.421C>A and c.34G>A). The safety of lanabecestat + rosuvastatin, the effects of rosuvastatin on the PK of lanabecestat, and the effects of multiple genetic polymorphisms on rosuvastatin exposure were assessed. Geometric mean ratios of the maximum observed rosuvastatin concentration (C_max ), area under the rosuvastatin concentration-versus-time curve (AUC) from time 0 to infinity, and time of maximum observed drug concentration (t_max ) when rosuvastatin was administered alone and with lanabecestat were contained within 0.8-1.25, as were lanabecestat AUC at steady state and t_max at steady state when lanabecestat was administered alone or with rosuvastatin. Lanabecestat C_max at steady state increased 8% in the presence of rosuvastatin. Except for an approximately 80% increase of rosuvastatin AUC (P < .05) in the heterozygotes of ABCG2 c.421C>A relative to the CC genotype, there were no statistically significant associations between rosuvastatin exposure and polymorphisms assessed. Lanabecestat + rosuvastatin was associated with few treatment-emergent adverse events, all of which resolved and were mild. Lanabecestat does not meaningfully impact BCRP activity; therefore, restriction of concomitant administration with BCRP substrates, such as rosuvastatin, may be unnecessary.

Development Review of the BACE1 Inhibitor Lanabecestat (AZD3293/LY3314814)

Several ongoing clinical development programs are investigating potential disease-modifying treatments for Alzheimer's disease (AD), including lanabecestat (AZD3293/LY3314814). Lanabecestat is a brain-permeable oral inhibitor of human beta-site amyloid (Aβ) precursor protein-cleaving enzyme 1 (BACE1) that reduces Aβ production. As a potent BACE1 inhibitor, lanabecestat significantly reduced soluble Aβ species and soluble amyloid precursor proteins (sAPPβ) in mouse, guinea pig, and dog in a time- and dose-dependent manner. Significant reductions in plasma and cerebrospinal fluid (CSF) Aβ1-40 and Aβ1-42 were observed in Phase 1 studies of healthy subjects and AD patients treated with lanabecestat. Three lanabecestat trials are ongoing and intended to support registration in Early AD: (1) Phase 2/3 study in patients with mild cognitive impairment (MCI) due to AD and mild AD dementia (AMARANTH, NCT02245737); (2) Delayed-start extension study (AMARANTH-EXTENSION, NCT02972658) for patients who have completed treatment in the AMARANTH Study; and (3) Phase 3 study in mild AD dementia (DAYBREAK-ALZ, NCT02783573). This review will discuss the development of lanabecestat, results from the completed nonclinical and clinical studies, as well as describe the ongoing Phase 3 clinical trials.

Validation and Clinical Utility of ELISA Methods for Quantification of Amyloid-β of Peptides in Cerebrospinal Fluid Specimens from Alzheimer’s Disease Studies

The aim of this study was to validate assays for measurement of amyloid-β (Aβ) peptides in cerebrospinal fluid (CSF)specimens according to regulatory guidance and demonstrate their utility with measurements in specimens from Alzheimer’s disease (AD) studies. Methods based on INNOTEST(®)β-AMYLOID(1-42) and prototype INNOTEST(®)β-AMYLOID(1-40) ELISAkits were developed involving pre-analytical sample treatment with Tween-20 for reliable analyte recovery.Validation parameters were evaluated by repeated testing of CSF pools collected and stored in the same manner as clinical specimens. Intra- and interassay coefficients of variation were ≤11% and relative accuracy was within ± 10% for both analytes. Dilutional linearity was demonstrated for both analytes from a spiked CSF pool, but not from a non-spiked native CSF pool. Recovery of standard Aβ peptide spikes standard ranged from 77% to 93%. No interference was observed from the investigational drugs LY2811376, LY2886721, LY3002813, or semagacestat. Aβ(1-40) and Aβ(1-42) were stable in CSF for up to 8 hours at room temperature and during 5 f reeze-thaw cycles from ≤−20◦C and ≤−70◦C. In frozen native CSF specimens, Aβ(1-40) was mostly stable up to 3 years at ≤−70◦C, whereas stability of Aβ(1-42) was limited to 221 days. Dose-dependent changes in measured CSF Aβ were observed in healthy volunteers up to 36 hours after treatment with the-site cleavage enzyme inhibitor LY2886721. In conclusion, rigorous validation tests have successfully demonstrated the strengths and operational limitations of these INNOTEST(®)-based assays.They have proved to be robust and reliable tools for pharmacodynamic evaluations of investigational AD therapeutics in clinical trials.

Semagacestat pharmacokinetics are not significantly affected by formulation, food, or time of dosing in healthy participants

Semagacestat, a γ-secretase inhibitor, reduces formation of amyloid beta peptide. Two single-dose (140 mg), open-label, randomized, 3-period, crossover studies evaluated the effect of formulation, food, and time of dosing on the pharmacokinetics and pharmacodynamics of semagacestat in healthy participants. The first study (n = 14) compared tablet to capsules. For all formulations, the median time to maximum plasma concentration (t(max)) was generally 1.0 hour. Plasma elimination was rapid, with a half-life of approximately 2.5 hours. Tablet form II bioavailability (F) relative to capsule was approximately 100% (F = 1.03 [90% confidence interval (CI), 0.96-1.10]). In the second study, participants (n = 27) received semagacestat either fed or fasting in the morning or fasting in the evening. No significant change in exposure (AUC(0-∞) [area under the concentration-time curve from 0 to infinity] ratio = 1.02, [90% CI, 0.990-1.05]) occurred with food, whereas maximum plasma concentration (C(max)) declined approximately 15%, and median t(max) was delayed to 1.5 hours. Time of dosing made no significant difference in AUC(0-∞), C(max), or t(max) (AUC(0-∞) ratio 1.01, [90% CI, 0.975-1.04]). No clinically significant safety concerns occurred in either study. Accordingly, semagacestat may be dosed without regard to formulation, food, or time of administration.

Cortisol response to individualised graded insulin infusions: a reproducible biomarker for CNS compounds inhibiting HPA activation

AIM

To determine the potential of cortisol secretion, in response to a physiological stressor, as a biomarker for centrally active compounds targeting the hypothalamic-pituitary-adrenocortical (HPA) axis.

METHODS

Cortisol response to hypoglycaemia was measured in 26 healthy males in two stages: firstly to derive an algorithm for individualized, graded insulin infusion rates to achieve defined hypoglycaemic targets over 3 h and secondly to determine the inter- and intra-subject variability of cortisol response to hypoglycaemia over two identical periods by measuring the maximum (t(max) ), time to maximum (C(max) ) response and cortisol area under the response curve (AUC).

RESULTS

Hypoglycaemia induced a consistent cortisol response starting at approximately 1 h, corresponding to blood glucose concentrations of approximately 3.3 mmol l⁻¹, and peaking approximately 3 h after the start of infusion. The inter- and intra-subject coefficients of variation (CVs) of cortisol response were approximately 19 and 19% (AUC), 15 and 19 % (C(max) ) and 10 and 14% (t(max) ), respectively. The intra-subject CVs for the ratio of maximum cortisol response to baseline concentration and rate of initial cortisol response between study days were more variable (32.8% and 59.0%, respectively). The blood glucose-cortisol response model derived from the study was predictive of the individual observed cortisol responses, and estimated a blood glucose EC(50) associated with onset of the cortisol response of 3.3 mmol l⁻¹.

CONCLUSIONS

Gradual hypoglycaemia is an effective, reproducible and well-tolerated method of stimulating a cortisol response and may therefore be useful in assessing the neuroendocrine response to HPA axis inhibitors, such as corticotropin-releasing hormone-1 (CRH-1) antagonists.

Endobronchial cuff pressures

In 20 adult patients (18 male) who presented for thoracotomy, the trachea was intubated using Mallinckrodt disposable double-lumen tubes (18 large and two medium). The endobronchial cuff was inflated by a trained operating department assistant using an air-filled syringe. The volume of air and the initial endobronchial cuff pressure were measured. The minimum cuff pressure required to prevent respiratory gas leakage from the isolated lung was measured also and maintained using the Cardiff Cuff Controller. Mean initial cuff pressure was 69.3 (SEM 6.0) mm Hg, whereas the mean minimum cuff pressure was 29.5 (4.0) mm Hg (P < 0.0001). The results suggest that the method described of inflating the endobronchial cuff may lead to overinflation and subsequent excessive pressure on the endobronchial wall.

The Riyadh Intensive Care Program applied to a mortality analysis of a teaching hospital intensive care unit

A computerised system of prediction of death using the Riyadh Intensive Care Program was applied retrospectively over a 17-month period to data collected prospectively on 1155 patients admitted to our intensive care unit. Variables which enable organ failure scores to be generated were recorded daily to make these predictions. Consultant medical opinion predicted that outcome was hopeless in 55% (115/209) of the patients who died. The predictive power of the computer demonstrated a sensitivity of 14.8% and a specificity of 99.8%. It is possible that the occurrence of three false predictions of death in the latter part of the series may have been related to a change in our antibiotic policy. We would be unhappy to recommend the general use of a computerised program for prediction of death without careful explanation of its significance and dangers.

Resuscitation in late pregnancy

This paper considers cardiopulmonary resuscitation in obstetric patients at term and the influence of aortocaval compression on the outcome. The maximum chest compression force produced by eight physicians was measured as a function of angle of inclination using an inclined plane. The compression force at an angle of 27 degrees is 80% of that in the supine position and the Cardiff resuscitation wedge, designed to prevent aortocaval compression, is described with this inclination. Midwives' expertise in basic life support 6 months after instruction was assessed using a manikin simulator. The majority had acquired errors in external chest compression and mouth to mouth ventilation. These were corrected by additional tuition. Resuscitation of the manikin on the Cardiff wedge was found to be as efficient as in the supine position.

Tracheal tube cuff pressure. Clinical use of the Cardiff Cuff Controller

Seventy-one adult patients (31 male, 40 female) who presented for surgery underwent orotracheal intubation with Portex Blue Line standard cuff disposable tubes (9-mm for males, 8-mm for females). The tracheal tube cuff was inflated by a trained assistant using a syringe and the initial cuff pressure measured; the minimum cuff pressure required to prevent respiratory gas leakage was also measured and the cuff pressure maintained above this pressure throughout the operation by means of the Cardiff Cuff Controller. Initial cuff pressure values averaged 11.9 kPa for males and 13.5 kPa for females compared with minimum cuff pressure values of 5.2 and 1.2 kPa, respectively. The differences between initial and minimum pressures were statistically highly significant (p much less than 0.001). It is concluded that the present method of inflation may lead to gross overinflation of tracheal tube cuffs and that cuff pressure monitoring may be performed simply by means of an electropneumatic controller. The difference in minimum cuff pressure between males and females suggests that the difference in tracheal size between the sexes is greater than the 9-mm to 8-mm difference in tracheal tube size.

Blood-gas tension measurement in anaesthesia by bubble equilibration and mass spectrometry

If a small bubble gas is equilibrated with a volume of blood the partial pressures of the components of the bubble after equilibration approximate to the original tensions in the blood. A method is described in which the bubble is analysed by a respiratory mass spectrometer connected to a mini-computer. The normal respiratory monitoring function of the mass spectrometer need be interrupted for only 20 s for each sample and the complete equilibration and analysis procedure takes only 3 min. Theoretical studies, experimental tests and records of experimental usage show that, in a subject anaesthetized with halothane in nitrous and oxygen, tension can be measured with an overall SD of 5% for carbon dioxide and halothane and, certain reservations, an SD of about 3% for nitrous oxide.

Entonox analgesia in labour. A pilot study to reduce the delay between demand and supply

In a pilot study in six mothers using 50% nitrous oxide and 50% oxygen (Entonox) as an intermittent self-administered analgesic during labour, a significant reduction in the mean times to attain specified end-tidal nitrous oxide concentrations was obtained by a continuous nasal supplement of Entonox. The method proved acceptable in this small number of patients and there were no demonstrable effects upon fetal heart rate.

The reduction of pollution. A simple approach to the reduction of pollution in the dental operating theatre

This paper describes the construction and evaluation of a simple anti-pollution device for use with the McKesson nasal mask for dental anaesthesia. The device is attached to the expiratory valve of the mask and spilled halothane vapour is adsorbed onto activated charcoal. In theatre use, comparing similar dental anaesthesia sessions, it resulted in a reduction of approximately 78% in the mean halothane concentration (vol./vol.) at a point equidistant from the expiratory valve as the faces of surgeon and anaesthetist. This percentage reduction was consistent with the weight gained by the activated charcoal container (Cardiff 'Aldasorber') compared with the weight of halothane vapourised.

Interaction of extrinsic fluorescent probes with E. coli glutamine synthetase

Binding of 2-p-toluidinylnaphthalene-6-sulfonate (TNS) to adenylylated (E--11) glutamine synthetase is cooperative and time-dependent, with 3 dye sites per subunit. In fluorescence polarization experiments TNS and pyrene butyrate give normalized Perrin plots that indicate a symmetrical arrangement of dye excited state dipoles, relative to the rotational axis of the oblate ellipsoid of the dodecameric native enzyme.

Entonox analgesia--a method of reducing the delay between demand and supply

Mothers in labour using a self-administered 50% N2O and 50% O2 (Entonox) demand system, experience a time lag between making a demand at the onset of a contraction and pain relief. A practical method is described of reducing this time lag by supplementing the intermittent supply from the demand valve system with a continuous nasal flow of N2O and O2. Consequently a basal arterial N2O tension is maintained and when a demand is made, a higher level of N2O is attained in any time interval compared with that using the demand system alone. In six trained volunteers under laboratory conditions, the N2O levels measured at the mouth on a breath-by-breath basis using a mass spectrometer, showed a substantial and statistically significant reduction in the time taken to attain end-tidal N2O concentrations in the range 10-25%. This method seems worthy of a clinical trial.

The Cardiff Aldavac anaesthetic-scavenging system

The Cardiff Aldavac system consists of a reservoir, adsorption canister, flow restrictor and the necessary pipe connections. It enables theatre pollution control without structural alteration or special installation. It utilizes the hospital piped medical vacuum system but protects the system from excessive flows or contamination by volatile anaesthetics and still allows the vacuum to be used for other purposes.

Adiposity and the pharmacokinetics of halothane. The effect of adiposity on the maintenance of and recovery from halothane anaesthesia

Thirty fit patients (15-70 years, 46-98 kg) undergoing body-surface operations were selected to include a wide range of adiposity (12-45% of total body weight estimated from measurements of skinfold thickness). They were anaesthetized with halothane and 70% N2O in O2. From measurements of total ventilation (ml min-1 kg-1) and of halothane concentrations in inspired (F1) end-tidal (FE') and 'mixed-spill' (FS) gases, the following parameters were calculated for 5-min intervals from 20 to 40 min after induction; the rate of uptake of halothane per percent inspired concentration (Vha1 ml min-1%-1) and the degree of equilibrium achieved with the inspired concentration, calculated as FE'/F1 expressed as a percentage. Multiple-regression analysis of the results for 19 patients, taking account of the effects of body fat, ventilation, age, and the blood-gas partition coefficient lambda of halothane for the individual patient, showed that Vha1 increased with adiposity (b=0-375, P=0-0019), and with ventilation (b=0-054, P=0-09) but decreased with increasing age (b=-0-258, P=0-006). The time intervals between the end of the anaesthetic and the achievement of four defined levels of recovery (response to painful stimulus obedience to a simple command, response to a question, orientation in time and space), were recorded. Multiple-regression analysis showed that recovery time increased with addiposity, duration of administration and end-tidal concentration at the end of the administration, and decreased with increasing age. All four effects were statistically non-significant at the first levels of recovery but all increased at the later levels and all eventually became significant.

Halothane solubility in human blood

In a study of the influence of nutritional state on halothane anaesthesia, results were obtained which showed how the blood/gas partition coefficient for halothane varied with blood chemistry in 20 patients undergoing elective surgery. For each patient the partition coefficient lambda was measured by equilibration at 37 degrees C of a blood sample with a 1% halothane in 5% carbon dioxide in air mixture, followed by chemical extraction and estimation of the halothane content by gas chromatography. The haematocrit and haemoglobin, serum albumin, total protein, triglyceride and cholesterol concentrations were measured by routine laboratory methods. Regressions were sought of lambda on each of these, and on the globulin concentration and the ratios of albumin: globulin and albumin: total protein, deduced from these determinations. The only statistically significant regression (P = 0.0004) was that of lambda on the serum triglyceride concentration (T) (mmol/litre): lambda = 1.83 + 0.424T. The dependence of lambda on haemoglobin concentration was not statistically significant, but the slope of the regression was consistent with those of previous investigators. The regressions of lambda, corrected to the mean triglyceride concentration, on the ratios of albumin: globulin and albumin: total protein were not statistically significant but were not significantly different from an earlier reported result.

Rebreathing in a T-piece: volunteer and theoretical studies of the Jackson-Rees modification of Ayre's T-piece during spontaneous respiration

The Jackson-Rees modification of Ayre's T-piece was examined experimentally and theoretically to see what effects the theoretical restrictions of Onchi, Hayashi and Ueyama (1957) (1:1 I:E ratio, zero deadspace volume) and the square-wave approximation of Mapleson (1958) may have had on the calculated critical fresh-gas flow rate necessary to prevent rebreathing of exhaled alveolar gases. In the experimental examination six conscious alert volunteers breathed through the system as the fresh-gas flow rate was varied in steps, and their ventilation was recorded at each value. Assuming that under rebreathing conditions a normal arterial PCO2 is maintained by hyperventilation, this experimental situation is identical with one of the two considered theoretically by assuming sine-wave inspiratory and expiratory waveforms, zero longitudinal mixing in deadspace volumes and perfect mixing in the alveoli. Agreement between experimental and theoretical results justifies the assumptions made in the theoretical analysis and the results indicate that a fresh-gas flow rate of about twice the normal ventilation is necessary to eliminate rebreathing completely from the Jackson-Rees modification of Ayre's T-piece. The exact requirement depends on the deadspace/tidal volume (VD/VT) and I:E ratios. The onset of hyperventilation at lower fresh-gas flow rates is gradual and, in spontaneous breathing with VD/VT approximately equal to 40% and I:E ratio = 1:1.2, is only 10-20% at a fresh-gas flow rate of 1.5 times the normal ventilation.