Alienor Berges

Therapeutic Clearance of Amyloid by Antibodies to Serum Amyloid P Component

BACKGROUND The amyloid fibril deposits that cause systemic amyloidosis always contain the nonfibrillar normal plasma protein, serum amyloid P component (SAP). The drug (R)-1-[6-[(R)-2-carboxy-pyrrolidin-1-yl]-6-oxo-hexanoyl]pyrrolidine-2-carboxylic acid (CPHPC) efficiently depletes SAP from the plasma but leaves some SAP in amyloid deposits that can be specifically targeted by therapeutic IgG anti-SAP antibodies. In murine amyloid A type amyloidosis, the binding of these antibodies to the residual SAP in amyloid deposits activates complement and triggers the rapid clearance of amyloid by macrophage-derived multinucleated giant cells. METHODS We conducted an open-label, single-dose-escalation, phase 1 trial involving 15 patients with systemic amyloidosis. After first using CPHPC to deplete circulating SAP, we infused a fully humanized monoclonal IgG1 anti-SAP antibody. Patients with clinical evidence of cardiac involvement were not included for safety reasons. Organ function, inflammatory markers, and amyloid load were monitored. RESULTS There were no serious adverse events. Infusion reactions occurred in some of the initial recipients of larger doses of antibody; reactions were reduced by slowing the infusion rate for later patients. At 6 weeks, patients who had received a sufficient dose of antibody in relation to their amyloid load had decreased liver stiffness, as measured with the use of transient elastography. These patients also had improvements in liver function in association with a substantial reduction in hepatic amyloid load, as shown by means of SAP scintigraphy and measurement of extracellular volume by magnetic resonance imaging. A reduction in kidney amyloid load and shrinkage of an amyloid-laden lymph node were also observed. CONCLUSIONS Treatment with CPHPC followed by an anti-SAP antibody safely triggered clearance of amyloid deposits from the liver and some other tissues. (Funded by GlaxoSmithKline; ClinicalTrials.gov number, NCT01777243.).

Safety, Pharmacokinetic, and Functional Effects of the Nogo-A Monoclonal Antibody in Amyotrophic Lateral Sclerosis: A Randomized, First-In-Human Clinical Trial

The neurite outgrowth inhibitor, Nogo-A, has been shown to be overexpressed in skeletal muscle in amyotrophic lateral sclerosis (ALS); it is both a potential biomarker and therapeutic target. We performed a double-blind, two-part, dose-escalation study, in subjects with ALS, assessing safety, pharmacokinetics (PK) and functional effects of ozanezumab, a humanized monoclonal antibody against Nogo-A. In Part 1, 40 subjects were randomized (3∶1) to receive single dose intravenous ozanezumab (0.01, 0.1, 1, 5, or 15 mg/kg) or placebo. In Part 2, 36 subjects were randomized (3∶1) to receive two repeat doses of intravenous ozanezumab (0.5, 2.5, or 15 mg/kg) or placebo, approximately 4 weeks apart. The primary endpoints were safety and tolerability (adverse events [AEs], vital signs, electrocardiogram (ECG), and clinical laboratory tests). Secondary endpoints included PK, immunogenicity, functional endpoints (clinical and electrophysiological), and biomarker parameters. Overall, ozanezumab treatment (0.01–15 mg/kg) was well tolerated. The overall incidence of AEs in the repeat dose 2.5 mg/kg and 15 mg/kg ozanezumab groups was higher than in the repeat dose placebo group and repeat dose 0.5 mg/kg ozanezumab group. The majority were considered not related to study drug by the investigators. Six serious AEs were reported in three subjects receiving ozanezumab; none were considered related to study drug. No study drug-related patterns were identified for ECG, laboratory, or vital signs parameters. One subject (repeat dose 15 mg/kg ozanezumab) showed a weak, positive anti-ozanezumab-antibody result. PK results were generally consistent with monoclonal antibody treatments. No apparent treatment effects were observed for functional endpoints or muscle biomarkers. Immunohistochemical staining showed dose-dependent co-localization of ozanezumab with Nogo-A in skeletal muscle. In conclusion, single and repeat dose ozanezumab treatment was well tolerated and demonstrated co-localization at the site of action. These findings support future studies with ozanezumab in ALS. Trial Registration ClinicalTrials.gov NCT00875446 GSK-ClinicalStudyRegister.com GSK ID 111330

Ozanezumab dose selection for amyotrophic lateral sclerosis by pharmacokinetic-pharmacodynamic modelling of immunohistochemistry data from patient muscle biopsies.

Amyotrophic Lateral Sclerosis (ALS) is a rare and fatal neurodegenerative disease with a high unmet medical need. In this context, a potential therapy should be brought to patients in the most expeditious way and early exploration of pharmacology is highly beneficial. Ozanezumab, a humanised IgG monoclonal antibody against Nogo-A protein which is an inhibitor of neurite outgrowth, is currently under development for the treatment of ALS and has been recently assessed in 76 patients in a first-in-human study. Inadequate target engagement has been recognised as a major contributing reason for drug trial failures. In this work, we describe the development of a pharmacokinetic-pharmacodynamic (PKPD) model using immunohistochemistry (IHC) data of co-localization of ozanezumab with Nogo-A in skeletal muscle as a surrogate measure of target engagement. The rich plasma concentration data and the sparse IHC data after one or two intravenous doses of ozanezumab were modelled simultaneously using a non-linear mixed-effect approach. The final PKPD model was a two-compartment PK model combined with an effect compartment PD model that accounted for the delay in ozanezumab concentrations to reach the site of action which is skeletal muscle. Diagnostic plots showed a satisfactory fit of both PK and IHC data. The model was used as a simulation tool to design a dose regimen for sustained drug-target co-localization in a phase II study.

Pharmacokinetics and tolerability of sumatriptan after single-dose administration of a fixed-dose combination tablet of sumatriptan/naproxen sodium 85/500 mg followed two hours later by subcutaneous sumatriptan 4- or 6-mg injection: A randomized, open-label, three-period crossover study in healthy volunteers†

BACKGROUND Rescue medication options that are consistent with the product labeling for sumatriptan/naproxen sodium (S/N) and that have been permitted in >or=1 clinical trial include the use of a second tablet of S/N, sumatriptan tablets (to a total daily dose of 200 mg), and naproxen sodium tablets (within the maximum limits recommended in the labeling). Sumatriptan subcutaneous (SC) injection might be especially useful as rescue medication mostly because of its rapid onset of activity. OBJECTIVE The aim of this study was to assess the pharmacokinetics and tolerability of sumatriptan SC used as rescue medication after the administration of oral S/N for the treatment of migraine. METHODS This randomized, open-label, 3-period crossover study compared the exposure to sumatriptan (Cmax and AUC to 14 hours after the administration of the second dose [AUC(0-14)]) between 3 treatment regimens: an initial dose of S/N 85/500 mg followed 2 hours later by sumatriptan 4 or 6 mg SC (S/N + S4 and S/N + S6, respectively) (test), or sumatriptan 100 mg PO (2 tablets administered 2 hours apart) (S100 + S100) (reference). Healthy adults aged 18 to 55 years were randomly assigned to receive all 3 regimens in a randomized sequence. On day 1 of each treatment period, continuous cardiovascular monitoring (ECG telemetry), serial 12-lead ECG, and serial blood pressure (BP) measurements were conducted 1 hour before to 10 hours after the administration of the first dose. Blood samples for pharmacokinetic assessment were collected up to 14 hours after the administration of the first dose. Adverse events (AEs) were monitored from the time of consent until study completion. Participants returned to the clinic for pharmacokinetic blood sampling (for S/N + S4 and S/N + S6) and for tolerability assessment at 24, 48, and 72 hours after S/N administration. RESULTS A total of 30 healthy adults were randomized. Five withdrew prematurely (3, withdrawn consent; 1, AE; and 1, protocol deviation). Half of the subjects were men, the mean age was 27.8 years, and the mean weight was 79.3 kg (range, 54.6-100.8 kg). With S/N + S4, sumatriptan Cmax and AUC(0-14) did not exceed those with S100 + S100. Sumatriptan Cmax was 1.26-fold higher with S/N + S6 than with S100 + S100. Sumatriptan AUC(0-14) with S/N + S6 was not significantly greater than that with S100 + S100. Differences in serial BP measurements between the SC and S100 + S100 regimens were not statistically significant. The numbers of subjects in whom any AE was reported were 10 (37%) with S/N + S4, 14 (54%) with S/N + S6, and 13 (48%) with S100 + S100. CONCLUSIONS Sumatriptan 4 and 6 mg SC administered 2 hours after an S/N tablet yielded sumatriptan exposure that did not exceed that of S100 + S100. Cmax with the S/N + S6 regimen was 1.26-fold higher than reference values. Both regimens were reasonably well tolerated. Randomized controlled trials are needed to test the efficacy and tolerability of these SC regimens. ClinicalTrials.gov identifier: NCT00875784.

Non linear mixed effects analysis in PET PK-receptor occupancy studies

The characterisation of a pharmacokinetic-receptor occupancy (PK-RO) relationship derived from a PET study is typically modelled in a conventional non-linear least squares (NLLS) framework. In the present work, we explore the application of a non-linear mixed effects approach (NLME) and compare this with NLLS estimation (using both naive pooled data and two-stage approaches) in the context of a direct PK-RO relationship described by an Emax model, using simulated data sets. Target and reference tissue time-activity curves were simulated using a two-tissue compartmental model and an arterial plasma input function for a typical PET study (12 subjects in 3 dose groups with 3 scans each). A range of different PET scenarios was considered to evaluate the impact of between-subject variability and reference region availability. The PET outcome measures derived from the simulations were then used to estimate the parameters of the PK-RO model. The performance of the two approaches was compared in terms of parameters estimates (square mean error SME, root mean square error RMSE) and prediction of the exposure-occupancy relationship. In general, both NLME and NLLS estimation methods provided unbiassed and precise population estimates for the Emax model parameters, although a slight bias was observed for the individual-NLLS method due to a few outliers. The increased value of NLME over NLLS was most notable in the estimation of the between-subject variability (BSV), especially in the case of a more complex PK-RO model when no reference region was available (maximum SME and RMSE values related to BSV of EC₅₀ of 27.6% and 86.5% from NLME versus 264.6% and 689.5% from NLLS). Overall, the NLME approach provided a more robust estimation and produced less-biassed estimates of the population means and variances than either the NLLS approach for the simulations considered.

Comparing probabilistic and descriptive analyses of time-dose-toxicity relationship for determining no-observed-adverse-effect level in drug development.

The no-observed-adverse-effect level (NOAEL) of a drug defined from animal studies is important for inferring a maximal safe dose in human. However, several issues are associated with its concept, determination and application. It is confined to the actual doses used in the study; becomes lower with increasing sample size or dose levels; and reflects the risk level seen in the experiment rather than what may be relevant for human. We explored a pharmacometric approach in an attempt to address these issues. We first used simulation to examine the behaviour of the NOAEL values as determined by current common practice; and then fitted the probability of toxicity as a function of treatment duration and dose to data collected from all applicable toxicology studies of a test compound. Our investigation was in the context of an irreversible toxicity that is detected at the end of the study. Simulations illustrated NOAELs dependency on experimental factors such as dose and sample size, as well as the underlying uncertainty. Modelling the probability as a continuous function of treatment duration and dose simultaneously to data from multiple studies allowed the estimation of the dose, along with its confidence interval, for a maximal risk level that might be deemed as acceptable for human. The model-based data integration also reconciled between-study inconsistency and explicitly provided maximised estimation confidence. Such alternative NOAEL determination method should be explored for its more efficient data use, more quantifiable insight to toxic doses, and the potential for more relevant animal-to-human translation.

Target Mediated Drug Disposition Model of CPHPC in Patients with Systemic Amyloidosis.

The amyloid deposits that cause disease in systemic amyloidosis always contain the normal plasma protein, serum amyloid P (SAP) component. SAP is the target of a novel immunotherapy approach now being developed to eliminate amyloid deposits. The treatment is enabled by, and critically depends on, the use of the drug (R)‐1‐[6‐[(R)‐2‐carboxy‐pyrrolidin‐1‐yl]‐6‐oxo‐hexanoyl]pyrrolidine‐2‐carboxylic acid (CPHPC, GSK2315698, Ro 63‐8695), which depletes circulating SAP almost completely but leaves some SAP in amyloid deposits for specific recognition by subsequently administered therapeutic anti‐SAP antibodies. Herein, we report a mechanistic model that predicts, with clinically acceptable precision, the exposure‐response relationship for CPHPC, both in healthy individuals and in patients with systemic amyloidosis. The model covariates are gender, renal function, total amyloid load, and presence of hepatic amyloid, all of which are known at baseline. The model is being used to predict individualized dosing regimens in an ongoing, first‐in‐human study with anti‐SAP antibodies.

A Phase 2a, Randomized, Crossover Trial of Gabapentin Enacarbil for the Treatment of Postherpetic Neuralgia in Gabapentin Inadequate Responders

OBJECTIVE To compare the efficacy of high-dose (3,600 mg/day) vs low-dose (1,200 mg/day) oral gabapentin enacarbil (GEn) on pain intensity in adults with postherpetic neuralgia (PHN) and a history of inadequate response to ≥1,800 mg/day gabapentin. DESIGN Multicenter, randomized, double-blind, crossover study (NCT00617461). SETTING Thirty-five outpatient centers in Germany and the United States. SUBJECTS Subjects aged ≥18 years with a diagnosis of PHN. METHODS During a 2-week baseline period, subjects received open-label treatment with 1,800 mg/day gabapentin. Subjects who had a mean 24-hour average pain intensity score ≥4 during the last 7 days of the baseline period were randomized to receive GEn (1,200 or 3,600 mg/day) for treatment period 1 (28 days), followed by GEn 2,400 mg/day (4 days), and the alternate GEn dose for treatment period 2 (28 days). RESULTS There was a modest but significant improvement in pain intensity scores with GEn 3,600 mg vs 1,200 mg (adjusted mean [90% confidence interval] treatment difference, -0.29 [-0.48 to -0.10]; P = 0.013). The difference in efficacy between doses was observed primarily in subjects who received the higher dose during treatment period 2; certain aspects of the study design may have contributed to this outcome. Plasma steady-state gabapentin exposure during GEn treatment was as expected and consistent between treatment periods. No new safety signals or adverse event trends relating to GEn exposure were identified. CONCLUSIONS While the overall results demonstrated efficacy in a PHN population, the differences between treatment periods confound the interpretation. These findings could provide insight into future trial designs.

Pharmacokinetics, Safety, and Tolerability Following the Administration of a Single Dose of a Combination Tablet Containing Sumatriptan and Naproxen Sodium in Adolescent Patients With Migraine and in Healthy Adult Volunteers.

Objective: The objective was to compare the pharmacokinetics of sumatriptan and naproxen in adolescent migraineurs and healthy adults after administration of sumatriptan/naproxen sodium combination tablets. Design: The design was an open‐label, randomized, parallel group study. Adolescent migraineurs (12–17 years) and healthy adults received 1 dose of sumatriptan/naproxen: 10 mg/60 mg, 30 mg/180 mg, or 85 mg/500 mg. Pharmacokinetic and safety assessments were conducted. Results: Sumatriptan achieved Cmax rapidly (median tmax: 0.8–1.5 hours for adolescents, 0.5–2.0 hours for adults); elimination was also rapid (geometric mean t½: <2 hours for adolescents, 1.9–2.4 hours for adults). Compared with sumatriptan, naproxen was absorbed and eliminated more slowly (median tmax: 1.0–4.0 hours for adolescents, 1.0–3.0 hours for adults; geometric mean t½: 13.4–16.3 hours for adolescents, 14.3–16.6 hours for adults). Sumatriptan Cmax and AUC were similar for adolescents and adults for the 85 mg/500 mg dose; exposure for the 2 lower doses showed slight differences (not significant). Naproxen Cmax and AUC were comparable between the 2 groups at all doses. Increases in sumatriptan Cmax and AUC were dose proportional; for naproxen, slightly less than proportional. The tablets were generally well tolerated. Conclusion: Sumatriptan and naproxen pharmacokinetics were not dissimilar between adolescent migraineurs and healthy adults.

Time-to-Event Modeling of Left- or Right-Censored Toxicity Data in Nonclinical Drug Toxicology

A time-to-event (TTE) model has been developed to characterize a histopathology toxicity that can only be detected at the time of animal sacrifice. The model of choice was a hazard model with a Weibull distribution and dose was a significant covariate. The diagnostic plots showed a satisfactory fit of the data, despite the high degree of left and right censoring. Comparison to a probabilistic logit model shows similar performance in describing the data with a slight underestimation of survival by the Logit model. However, the TTE model was found to be more predictive in extrapolating toxicity risk beyond the observation range of a truncated dataset. The diagnostic and comparison outcomes would suggest using the TTE approach as a first choice for characterizing short and long-term risk from nonclinical toxicity studies. However, further investigations are needed to explore the domain of application of this kind of approach in drug safety assessment.