Immunogenicity of avelumab in patients with metastatic Merkel cell carcinoma or advanced urothelial carcinoma

Like other monoclonal antibodies, immune checkpoint inhibitors may be immunogenic in some patients, potentially affecting pharmacokinetics (PKs) and clinical outcomes. In post hoc analyses, we characterized antidrug antibody (ADA) development with avelumab monotherapy in patients with metastatic Merkel cell carcinoma (mMCC) from the JAVELIN Merkel 200 trial (first-line [1L; N = 116] and second-line or later [≥2L; N = 88] cohorts) or with advanced urothelial carcinoma (aUC) from the JAVELIN Bladder 100 (1L maintenance [N = 350]) and JAVELIN Solid Tumor (≥2L [N = 249]) trials. Treatment-emergent ADAs developed in a numerically higher proportion of patients with aUC (1L maintenance, 19.1%; ≥2L, 18.1%) versus mMCC (1L, 8.2%; ≥2L, 8.9%); incidences within tumor types were similar by line of therapy. In PK analyses, numerically lower avelumab trough concentration and higher baseline clearance were observed in treatment-emergent ADA+ versus ADA- subgroups; however, differences were not clinically relevant. Numerical differences in overall survival, progression-free survival, or objective response rate by ADA status were observed; however, no clinically meaningful trends were identified. Proportions of patients with treatment-emergent adverse events (TEAEs; any grade or grade 3/4), serious TEAEs, TEAEs leading to treatment discontinuation, or infusion-related reactions were similar, with overlapping 80% confidence intervals between ADA subgroups. Efficacy and safety observations were similar in subgroups defined by early development of ADA+ status during treatment. In conclusion, no meaningful differences in PKs, efficacy, and safety were observed between subgroups of avelumab-treated patients with different ADA status. Overall, these data suggest that ADAs are not relevant for treatment decisions with avelumab.

Tumor growth inhibition modeling in patients with second line biliary tract cancer and first line non-small cell lung cancer based on bintrafusp alfa trials

This analysis aimed to quantify tumor dynamics in patients receiving either bintrafusp alfa (BA) or pembrolizumab, by population pharmacokinetic (PK)-pharmacodynamic modeling, and investigate clinical and molecular covariates describing the variability in tumor dynamics by pharmacometric and machine-learning (ML) approaches. Data originated from two clinical trials in patients with biliary tract cancer (BTC; NCT03833661) receiving BA and non-small cell lung cancer (NSCLC; NCT03631706) receiving BA or pembrolizumab. Individual drug exposure was estimated from previously developed population PK models. Population tumor dynamics models were developed for each drug-indication combination, and covariate evaluations performed using nonlinear mixed-effects modeling (NLME) and ML (elastic net and random forest models) approaches. The three tumor dynamics' model structures all included linear tumor growth components and exponential tumor shrinkage. The final BTC model included the effect of drug exposure (area under the curve) and several covariates (demographics, disease-related, and genetic mutations). Drug exposure was not significant in either of the NSCLC models, which included two, disease-related, covariates in the BA arm, and none in the pembrolizumab arm. The covariates identified by univariable NLME and ML highly overlapped in BTC but showed less agreement in NSCLC analyses. Hyperprogression could be identified by higher tumor growth and lower tumor kill rates and could not be related to BA exposure. Tumor size over time was quantitatively characterized in two tumor types and under two treatments. Factors potentially related to tumor dynamics were assessed using NLME and ML approaches; however, their net impact on tumor size was considered as not clinically relevant.

Semi-mechanistic population pharmacokinetic/pharmacodynamic modeling of a Plasmodium elongation factor 2 inhibitor cabamiquine for prevention and cure of malaria

Cabamiquine is a novel antimalarial agent that demonstrates the potential for chemoprevention and treatment of malaria. In this article, the dose-exposure-response relationship of cabamiquine was characterized using a population pharmacokinetic (PK)/pharmacodynamic (PD) model, incorporating the effects of cabamiquine on parasite dynamics at the liver and blood stages of malaria infection. Modeling was performed sequentially. First, a three-compartmental population PK model was developed, comprising linear elimination, a transit absorption model in combination with first-order absorption, and a recirculation model. Second, this model was expanded into a PK/PD model using parasitemia data from an induced blood stage malaria (IBSM) human challenge model. To describe the parasite growth and killing in the blood, a turnover model was used. Finally, the liver stage parasite dynamics were characterized using data from a sporozoite challenge model (SpzCh), and system parameters were fixed based on biological plausibility. Cabamiquine concentration in the central compartment was used to drive parasite killing at the blood and liver stages. Blood stage minimum inhibitory concentrations (MICb) were estimated at 7.12 ng/mL [95% confidence interval (CI95%): 6.26-7.88 ng/mL] and 1.28 ng/mL (CI95%: 1.12-1.43 ng/mL) for IBSM and SpzCh populations, respectively, while liver stage MICl was lower (0.61 ng/mL; CI95%: 0.24-0.96 ng/mL). In conclusion, a population PK/PD model was developed by incorporating parasite dynamics and drug activity at the blood and liver stages based on clinical data and biological knowledge. This model can potentially facilitate antimalarial agent development by supporting the efficient selection of the optimal dosing regimen.

A multistate modeling and simulation framework to learn dose-response of oncology drugs: Application to bintrafusp alfa in non-small cell lung cancer

The dose/exposure-efficacy analyses are often conducted separately for oncology end points like best overall response, progression-free survival (PFS) and overall survival (OS). Multistate models offer to bridge these dose-end point relationships by describing transitions and transition times from enrollment to response, progression, and death, and evaluating transition-specific dose effects. This study aims to apply the multistate pharmacometric modeling and simulation framework in a dose optimization setting of bintrafusp alfa, a fusion protein targeting TGF-β and PD-L1. A multistate model with six states (stable disease [SD], response, progression, unknown, dropout, and death) was developed to describe the totality of endpoints data (time to response, PFS, and OS) of 80 patients with non-small cell lung cancer receiving 500 or 1200 mg of bintrafusp alfa. Besides dose, evaluated predictor of transitions include time, demographics, premedication, disease factors, individual clearance derived from a pharmacokinetic model, and tumor dynamic metrics observed or derived from tumor size model. We found that probabilities of progression and death upon progression decreased over time since enrollment. Patients with metastasis at baseline had a higher probability to progress than patients without metastasis had. Despite dose failed to be statistically significant for any individual transition, the combined effect quantified through a model with dose-specific transition estimates was still informative. Simulations predicted a 69.2% probability of at least 1 month longer, and, 55.6% probability of at least 2-months longer median OS from the 1200 mg compared to the 500 mg dose, supporting the selection of 1200 mg for future studies.

ARTIFICIAL INTELLIGENCE: CREATING NEW PARADIGMS IN THE MANAGEMENT OF NON-COMMUNICABLE DISEASES

The role of Artificial Intelligence (AI) in medical science is growing immensely. Since AI contains features that can address both preventive and therapeutic aspects of non-communicable diseases (NCDs), it can potentially lessen the massive burden of morbidity and mortality associated with NCDs. AI can help in various ways in NCDs including predicting disease occurrence, monitoring, ensuring treatment and follow-up of patients. Low- and middle-income countries can harness the benefit of AI for the management of chronic diseases and effectively address challenges like manpower shortage, accessibility to health care, etc. However, AI needs to be used responsibly and rationally in NCDs for its maximum benefit.

Causal chemoprophylactic activity of cabamiquine against Plasmodium falciparum in a controlled human malaria infection: a randomised, double-blind, placebo-controlled study in the Netherlands

BACKGROUND

Cabamiquine is a novel antimalarial that inhibits Plasmodium falciparum translation elongation factor 2. We investigated the causal chemoprophylactic activity and dose-exposure-response relationship of single oral doses of cabamiquine following the direct venous inoculation (DVI) of P falciparum sporozoites in malaria-naive, healthy volunteers.

METHODS

This was a phase 1b, randomised, double-blind, placebo-controlled, adaptive, dose-finding, single-centre study performed in Leiden, Netherlands. Malaria-naive, healthy adults aged 18-45 years were divided into five cohorts and randomly assigned (3:1) to receive cabamiquine or placebo. Randomisation was done by an independent statistician using codes in a permuted block schedule with a block size of four. Participants, investigators, and study personnel were masked to treatment allocation. A single, oral dose regimen of cabamiquine (200, 100, 80, 60, or 30 mg) or matching placebo was administered either at 2 h (early liver-stage) or 96 h (late liver-stage) after DVI. The primary endpoints based on a per-protocol analysis set were the number of participants who developed parasitaemia within 28 days of DVI, time to parasitaemia, number of participants with documented parasite blood-stage growth, clinical symptoms of malaria, and exposure-efficacy modelling. The impact of cabamiquine on liver stages was evaluated indirectly by the appearance of parasitaemia in the blood. The Clopper-Pearson CI (nominal 95%) was used to express the protection rate. The secondary outcomes were safety and tolerability, assessed in those who had received DVI and were administered one dose of the study intervention. The trial was prospectively registered on ClinicalTrials.gov (NCT04250363).

FINDINGS

Between Feb 17, 2020 and April 29, 2021, 39 healthy participants were enrolled (early liver-stage: 30 mg [n=3], 60 mg [n=6], 80 mg [n=6], 100 mg [n=3], 200 mg [n=3], pooled placebo [n=6]; late liver-stage: 60 mg [n=3], 100 mg [n=3], 200 mg [n=3], pooled placebo [n=3]). A dose-dependent causal chemoprophylactic effect was observed, with four (67%) of six participants in the 60 mg, five (83%) of six participants in the 80 mg, and all three participants in the 100 and 200 mg cabamiquine dose groups protected from parasitaemia up to study day 28, whereas all participants in the pooled placebo and 30 mg cabamiquine dose group developed parasitaemia. A single, oral dose of 100 mg cabamiquine or higher provided 100% protection against parasitaemia when administered during early or late liver-stage malaria. The median time to parasitaemia in those with early liver-stage malaria was prolonged to 15, 22, and 24 days for the 30, 60, and 80 mg dose of cabamiquine, respectively, compared with 10 days for the pooled placebo. All participants with positive parasitaemia showed documented blood-stage parasite growth, apart from one participant in the pooled placebo group and one participant in the 30 mg cabamiquine group. Most participants did not exhibit any malaria symptoms in both the early and late liver-stage groups, and those reported were mild in severity. A positive dose-exposure-efficacy relationship was established across exposure metrics. The median maximum concentration time was 1-6 h, with a secondary peak observed between 6 h and 12 h in all cabamiquine dose groups (early liver-stage). All cabamiquine doses were safe and well tolerated. Overall, 26 (96%) of 27 participants in the early liver-stage group and ten (83·3%) of 12 participants in the late liver-stage group reported at least one treatment-emergent adverse event (TEAE) with cabamiquine or placebo. Most TEAEs were of mild severity, transient, and resolved without sequelae. The most frequently reported cabamiquine-related TEAE was headache. No dose-related trends were observed in the incidence, severity, or causality of TEAEs.

INTERPRETATION

The results from this study show that cabamiquine has a dose-dependent causal chemoprophylactic activity. Together with previously demonstrated activity against the blood stages combined with a half-life of more than 150 h, these results indicate that cabamiquine could be developed as a single-dose monthly regimen for malaria prevention.

FUNDING

The healthcare business of Merck KGaA, Darmstadt, Germany.

Nontubercular bacterial and fungal infections in patients of chronic obstructive pulmonary disease

Introduction

Acute exacerbation of chronic obstructive pulmonary disease (COPD), frequently due to respiratory tract infection is the major cause of morbidity and mortality, and estimate suggests that it is currently the third leading cause of death worldwide.

Aims and Objectives

This study aims to study the prevalence of nontubercular bacterial and fungal infections in patients of COPD.

Materials and Methods

It is an observational study done for 1-year period from August 2017 to July 2018. A total of 100 COPD patients who fulfilled the inclusion and exclusion criteria were analyzed in the present study. These cases were classified according to the Global Initiative for Chronic Obstructive Lung Disease (GOLD) combined assessment criteria and subjected to sputum or in some cases Bronchoalveolar lavage (BAL) fluid examination for nontubercular bacterial and fungal pathogens. Serum galactomannan assay, bronchoscopy, and computed tomography chest were done in selected cases.

Results

The age of the study population ranged from 40 to 85 years and the mean age was 60.01 ± 9.85 years. Majority of the patients were male (81.0%) and most (78.0%) of them were smokers. Most of the patients belonged to GOLD Grades 2 and 3. Forty-six percent of the patients did show pathogenic organisms in sputum examination. Out of these, 80.4% were bacterial, mainly Gram-negative organisms (Acinetobacter, Pseudomonas, Escherichia coli, Enterobacter, Proteus, and Citrobacter) and 19.6% of cases were having fungal infections (Candida and Aspergillus).

Conclusions

Increasing patient age, smoking habit, and severity of COPD were related to an increasing frequency of bacterial and fungal infections. Early detection and proper treatment could help in preventing the morbidity and mortality related to COPD.

Variable or variate? A conundrum in pharmacometrics exposure-response models

Key elements of scientific writing-consistency and clarity-can be compromised in case of inaccurate use of methodological terms, especially in complex and multidisciplinary scientific fields. Such is the case in reports of pharmacometrics exposure-response analyses with the use of the terms univariate/multivariate and univariable/multivariable. This perspective outlines the issues in the use of these terms, clarifies their definitions, provides examples, and makes recommendations for authors, reviewers, and journals in the fields of clinical pharmacology and pharmacometrics.

Model-informed approach for risk management of bleeding toxicities for bintrafusp alfa, a bifunctional fusion protein targeting TGF-β and PD-L1

PURPOSE

Bintrafusp alfa (BA) is a bifunctional fusion protein composed of the extracellular domain of the transforming growth factor-β (TGF-β) receptor II fused to a human immunoglobulin G1 antibody blocking programmed death ligand 1 (PD-L1). The recommended phase 2 dose (RP2D) was selected based on phase 1 efficacy, safety, and pharmacokinetic (PK)-pharmacodynamic data, assuming continuous inhibition of PD-L1 and TGF-β is required. Here, we describe a model-informed dose modification approach for risk management of BA-associated bleeding adverse events (AEs).

METHODS

The PK and AE data from studies NCT02517398, NCT02699515, NCT03840915, and NCT04246489 (n = 936) were used. Logistic regression analyses were conducted to evaluate potential relationships between bleeding AEs and BA time-averaged concentration (C_avg), derived using a population PK model. The percentage of patients with trough concentrations associated with PD-L1 or TGF-β inhibition across various dosing regimens was derived.

RESULTS

The probability of bleeding AEs increased with increasing C_avg; 50% dose reduction was chosen based on the integration of modeling and clinical considerations. The resulting AE management guidance to investigators regarding temporary or permanent treatment discontinuation was further refined with recommendations on restarting at RP2D or at 50% dose, depending on the grade and type of bleeding (tumoral versus nontumoral) and investigator assessment of risk of additional bleeding.

CONCLUSION

A pragmatic model-informed approach for management of bleeding AEs was implemented in ongoing clinical trials of BA. This approach is expected to improve benefit-risk profile; however, its effectiveness will need to be evaluated based on safety data generated after implementation.

Translation of liver stage activity of M5717, a Plasmodium elongation factor 2 inhibitor: from bench to bedside

Background

Targeting the asymptomatic liver stage of Plasmodium infection through chemoprevention could become a key intervention to reduce malaria-associated incidence and mortality.

Methods

M5717, a Plasmodium elongation factor 2 inhibitor, was assessed in vitro and in vivo with readily accessible Plasmodium berghei parasites. In an animal refinement, reduction, replacement approach, the in vitro IC₉₉ value was used to feed a Population Pharmacokinetics modelling and simulation approach to determine meaningful effective doses for a subsequent Plasmodium sporozoite-induced volunteer infection study.

Results

Doses of 100 and 200 mg would provide exposures exceeding IC₉₉ in 96 and 100% of the simulated population, respectively.

Conclusions

This approach has the potential to accelerate the search for new anti-malarials, to reduce the number of healthy volunteers needed in a clinical study and decrease and refine the animal use in the preclinical phase.

Graphical Abstract

Avelumab Dose Selection for Clinical Studies in Pediatric Patients with Solid Tumors

Background and Objective

A phase I/II trial evaluated the safety, antitumor activity, and pharmacokinetics of avelumab (anti-PD-L1 antibody) in pediatric patients with refractory/relapsed solid tumors (NCT03451825). This study aimed to inform avelumab dose selection in pediatric populations using population pharmacokinetic modeling and simulations.

Methods

Patients aged < 18 years with refractory/relapsed solid tumors enrolled in phase I received avelumab 10 or 20 mg/kg intravenously every 2 weeks. A pediatric population pharmacokinetic model was developed via the frequentist prior approach.

Results

Pharmacokinetic parameters from 21 patients who received avelumab 10 mg/kg (n = 6) or 20 mg/kg (n = 15) were analyzed. Patients had a wide range of weights and ages (medians, 37.3 kg and 12 years). Exposures with 10-mg/kg dosing were lower vs adult dosing, particularly in patients weighing < 40 kg, whereas 20-mg/kg dosing achieved or exceeded adult exposures, irrespective of body weight. A two-compartment linear model with time-varying clearance using body weight as a covariate, with the frequentist prior approach, best described pediatric data. In this model, optimal overlap in exposure with adult data was achieved with 800 mg every 2 weeks for patients aged ≥ 12 years and weighing ≥ 40 kg, and 15 mg/kg every 2 weeks for patients aged < 12 years or weighing < 40 kg.

Conclusions

Based on exposure matching, the recommended doses for further avelumab studies, including combination studies, are 15 mg/kg every 2 weeks for pediatric patients aged < 12 years or weighing < 40 kg and the adult flat dose of 800 mg every 2 weeks for pediatric patients aged ≥ 12 years and weighing ≥ 40 kg.

Clinical Trial Registration

ClinicalTrials.gov NCT03451825.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40262-022-01111-8.

Applying Modeling and Simulations for Rational Dose Selection of Novel Toll-Like Receptor 7/8 Inhibitor Enpatoran for Indications of High Medical Need

Dual toll‐like receptor (TLR) 7 and TLR8 inhibitor enpatoran is under investigation as a treatment for lupus and coronavirus disease 2019 (COVID‐19) pneumonia. Population pharmacokinetic/pharmacodynamic (PopPK/PD) model‐based simulations, using PK and PD (inhibition of ex vivo‐stimulated interleukin‐6 (IL‐6) and interferon‐α (IFN‐α) secretion) data from a phase I study of enpatoran in healthy participants, were leveraged to inform dose selection for lupus and repurposed for accelerated development in COVID‐19. A two‐compartment PK model was linked to sigmoidal maximum effect (E_max) models with proportional decrease from baseline characterizing the PD responses across the investigated single and multiple doses, up to 200 mg daily for 14 days (n = 72). Concentrations that maintain 50/60/90% inhibition (IC_50/60/90) of cytokine secretion (IL‐6/IFN‐α) over 24 hours were estimated and stochastic simulations performed to assess target coverage under different dosing regimens. Simulations suggested investigating 25, 50, and 100 mg enpatoran twice daily (b.i.d.) to explore the anticipated therapeutic dose range for lupus. With 25 mg b.i.d., > 50% of subjects are expected to achieve 60% inhibition of IL‐6. With 100 mg b.i.d., most subjects are expected to maintain almost complete target coverage for 24 hours (> 80% subjects IC_90,IL‐6 = 15.5 ng/mL; > 60% subjects IC_90,IFN‐α = 22.1 ng/mL). For COVID‐19, 50 and 100 mg enpatoran b.i.d. were recommended; 50 mg b.i.d. provides shorter IFN‐α inhibition (median time above IC₉₀ = 13 hours/day), which may be beneficial to avoid interference with the antiviral immune response. Utilization of PopPK/PD models initially developed for lupus enabled informed dose selection for the accelerated development of enpatoran in COVID‐19.

Model-informed drug development supporting the approval of the avelumab flat-dose regimen in patients with advanced renal cell carcinoma

Avelumab is an anti–PD‐L1 monoclonal antibody approved as monotherapy for Merkel cell carcinoma (MCC) and urothelial carcinoma (UC), and in combination with axitinib for advanced renal cell carcinoma (aRCC). Although initially approved with weight‐based dosing (10 mg/kg intravenously [IV] every 2 weeks [Q2W]), avelumab was subsequently approved for flat dosing (800 mg IV Q2W) based on population pharmacokinetic (PopPK), exposure‐efficacy, and exposure‐safety modeling in MCC and UC. Here, through modeling and simulation, we provide justification for a flat‐dose regimen of avelumab plus axitinib in aRCC. Simulated exposure metrics from the previous monotherapy PopPK model (1827 patients) for both weight‐based and flat‐dose regimens were compared with exposure metrics from treatment‐naive patients with aRCC who received avelumab plus axitinib (488 patients). The aRCC population exposures were derived from a fit‐for‐purpose PopPK model developed using data from monotherapy and combination studies and the existing base structural PopPK model. Exposure‐response relationships for safety were analyzed, including grade ≥3 treatment‐emergent adverse events (TEAEs), any‐grade infusion‐related reactions, and TEAE any‐grade immune‐related adverse events (irAEs). Weight‐based dosing of avelumab in the aRCC population yielded similar PK exposures to the flat‐dose regimen reference exposures in the monotherapy population. Increased avelumab exposure was not associated with increased probabilities of grade ≥3 TEAEs or any‐grade IRRs, although there was a weak association with an increased probability of any‐grade irAEs. Overall, models in aRCC suggest that the avelumab 800‐mg Q2W flat‐dose regimen would provide similar benefits compared with weight‐based dosing with no meaningful change in the probability of AEs.

Model-Based Characterization of the Bidirectional Interaction Between Pharmacokinetics and Tumor Growth Dynamics in Patients with Metastatic Merkel Cell Carcinoma Treated with Avelumab

PURPOSE

Empirical time-varying clearance models have been reported for several immune checkpoint inhibitors, including avelumab (anti-programmed death ligand 1). To investigate the exposure-response relationship for avelumab, we explored semimechanistic pharmacokinetic (PK)-tumor growth dynamics (TGD) models.

PATIENTS AND METHODS

Plasma PK data were pooled from three phase I and II trials (JAVELIN Merkel 200, JAVELIN Solid Tumor, and JAVELIN Solid Tumor JPN); tumor size (TS) data were collected from patients with metastatic Merkel cell carcinoma (mMCC) enrolled in JAVELIN Merkel 200. A PK model was developed first, followed by TGD modeling to investigate interactions between avelumab exposure and TGD. A PK-TGD feedback loop was evaluated with simultaneous fitting of the PK and TGD models.

RESULTS

In total, 1,835 PK observations and 338 TS observations were collected from 147 patients. In the final PK-TGD model, which included the bidirectional relationship between PK and TGD, avelumab PK was described by a two-compartment model with a positive association between clearance and longitudinal TS, with no additional empirical time-varying clearance identified. TGD was described by first-order tumor growth/shrinkage rates, with the tumor shrinkage rate decreasing exponentially over time; the exponential time-decay constant decreased with increasing drug concentration, representing the treatment effect through tumor shrinkage inhibition.

CONCLUSIONS

We developed a TGD model that mechanistically captures the prevention of loss of antitumor immunity (i.e., T-cell suppression in the tumor microenvironment) by avelumab, and a bidirectional interaction between PK and TGD in patients with mMCC treated with avelumab, thus mechanistically describing previously reported time variance of avelumab elimination.

Pharmacometric modeling and machine learning analyses of prognostic and predictive factors in the JAVELIN Gastric 100 phase III trial of avelumab

Avelumab (anti–PD‐L1) is an approved anticancer treatment for several indications. The JAVELIN Gastric 100 phase III trial did not meet its primary objective of demonstrating superior overall survival (OS) with avelumab maintenance versus continued chemotherapy in patients with advanced gastric cancer/gastroesophageal junction cancer; however, the OS rate was numerically higher with avelumab at timepoints after 12 months. Machine learning (random forests, SIDEScreen, and variable‐importance assessments) was used to build models to identify prognostic/predictive factors associated with long‐term OS and tumor growth dynamics (TGDs). Baseline, re‐baseline, and longitudinal variables were evaluated as covariates in a parametric time‐to‐event model for OS and Gompertzian population model for TGD. The final OS model incorporated a treatment effect on the log‐logistic shape parameter but did not identify a treatment effect on OS or TGD. Variables identified as prognostic for longer OS included older age; higher gamma‐glutamyl transferase (GGT) or albumin; absence of peritoneal carcinomatosis; lower neutrophil‐lymphocyte ratio, lactate dehydrogenase, or C‐reactive protein (CRP); response to induction chemotherapy; and Eastern Cooperative Oncology Group performance status of 0. Among baseline and time‐varying covariates, the largest effects were found for GGT and CRP, respectively. Liver metastasis at re‐baseline predicted higher tumor growth. Tumor size after induction chemotherapy was associated with number of metastatic sites and stable disease (vs. response). Asian region did not impact OS or TGD. Overall, an innovative workflow supporting pharmacometric modeling of OS and TGD was established. Consistent with the primary trial analysis, no treatment effect was identified. However, potential prognostic factors were identified.

COVID-19 infection in patients with haematological disease - A tertiary centre experience from north India

This retrospective study was aimed to understand the clinical, laboratory, radiological parameters and the outcome of COVID-19 patients with underlying haematological disease. All patients with known haematological disease admitted with COVID-19-positive status from April to August 2020 in the COVID-19 facility of a tertiary care centre in north India, were included. Their medical records were analyzed for outcome and mortality risk factors. Fifty four patients, 37 males, were included in the study. Of these, 36 patients had haematological malignancy and 18 had benign disorder. Fever (95.5%), cough (59.2%) and dyspnoea (31.4%) were the most common symptoms. Nine patients had severe disease at diagnosis, mostly malignant disorders. Overall mortality rate was 37.0 per cent, with high mortality seen in patients with aplastic anaemia (50.0%), acute myeloid (46.7%) and lymphoblastic leukaemia (40.0%). On univariate analysis, Eastern Cooperative Oncology Group performance status >2 [odd ratio (OR) 11.6], COVID-19 severity (OR 8.2), dyspnoea (OR 5.7) and blood product transfusion (OR 6.4) were the predictors of mortality. However, the presence of moderate or severe COVID-19 (OR 16.6, confidence interval 3.8-72.8) was found significant on multivariate analysis. The results showed that patients with haematological malignancies and aplastic anaemia might be at increased risk of getting severe COVID-19 infection and mortality as compared to the general population.

518. Model-informed Dose Selection of Dual Toll-like Receptor 7/8 Inhibitor Enpatoran (M5049) for the Treatment of COVID-19 Pneumonia

Background

Enpatoran, formerly known as M5049, is a potential first-in-class small molecule antagonist of toll-like receptors (TLR) 7 and 8, which may prevent viral-associated hyperinflammatory response and progression to ‘cytokine storm’ in coronavirus disease 2019 (COVID-19) patients. The objective of this study was to leverage existing population pharmacokinetic/pharmacodynamic (popPK/PD) models for enpatoran to inform dose selection for an accelerated Phase II study in COVID-19 patients with pneumonia.

Methods

The popPK/PD models were based on plasma PK and PD biomarker (ex vivo-stimulated interleukin [IL]6 and interferon α [IFNα] secretion) data from the enpatoran first-in-human Phase I study in healthy participants (Port A, et al. Lupus Sci Med 2020;7(Suppl. 1): Abstract P135). A two-compartment model describing PK used a sigmoidal E_max model with proportional decrease from baseline characterizing the PD response across the investigated single and multiple daily dose range of 1–200 mg (N=72). Concentrations that inhibited 50% and 90% (IC₅₀/IC₉₀) of cytokine secretion were estimated and stochastic simulations were performed to assess target coverage under different dosing regimens.

Results

Simulations suggested that, to achieve maximal inhibition of IL-6 over time, enpatoran PK concentrations would be maintained above the IC₉₀ throughout the dosing interval with doses of 100 mg and 50 mg twice daily in 90% and 30% of participants, respectively. In comparison, IFNα inhibition was predicted to be lower, with IC₉₀ coverage in 60% and 8% of participants with twice daily doses of 100 mg and 50 mg enpatoran, respectively.

Conclusion

Utilization of existing popPK/PD models allowed for the accelerated development of enpatoran in COVID-19 to address an unprecedented global pandemic. Rational model-informed dose selection was supported by data from a Phase I study in which there were no safety concerns.

Disclosures

Lena Klopp-Schulze, PhD, Merck KGaA, Darmstadt, Germany (Employee) Jamie Shaw, BS, EMD Serono Research & Development Institute, Inc., Billerica, MA, USA (an affiliate of Merck KGaA, Darmstadt, Germany) (Employee) Jennifer Dong, PhD, EMD Serono Research & Development Institute, Inc., Billerica, MA, USA (an affiliate of Merck KGaA, Darmstadt, Germany) (Employee) Akash Khandelwal, PhD, Merck KGaA, Darmstadt, Germany (Employee, Shareholder) Elizabeth Adams, MD, BioNTech SE, Germany (Employee)EMD Serono Research & Development Institute, Inc., Billerica, MA, USA (an affiliate of Merck KGaA, Darmstadt, Germany)(employer at the time of study) (Employee) Dongzi Yu, MD, EMD Serono Research & Development Institute, Inc., Billerica, MA, USA (an affiliate of Merck KGaA, Darmstadt, Germany) (Employee) Kosalaram Goteti, PhD, EMD Serono Research & Development Institute, Inc., Billerica, MA, USA (an affiliate of Merck KGaA, Darmstadt, Germany) (Employee)Pfizer (Shareholder)

Safety, pharmacokinetics, and antimalarial activity of the novel plasmodium eukaryotic translation elongation factor 2 inhibitor M5717: a first-in-human, randomised, placebo-controlled, double-blind, single ascending dose study and volunteer infection study

BACKGROUND

M5717 is the first plasmodium translation elongation factor 2 inhibitor to reach clinical development as an antimalarial. We aimed to characterise the safety, pharmacokinetics, and antimalarial activity of M5717 in healthy volunteers.

METHODS

This first-in-human study was a two-part, single-centre clinical trial done in Brisbane, QLD, Australia. Part one was a double-blind, randomised, placebo-controlled, single ascending dose study in which participants were enrolled into one of nine dose cohorts (50, 100, 200, 400, 600, 1000, 1250, 1800, or 2100 mg) and randomly assigned (3:1) to M5717 or placebo. A sentinel dosing strategy was used for each dose cohort whereby two participants (one assigned to M5717 and one assigned to placebo) were initially randomised and dosed. Randomisation schedules were generated electronically by independent, unblinded statisticians. Part two was an open-label, non-randomised volunteer infection study using the Plasmodium falciparum induced blood-stage malaria model in which participants were enrolled into three dose cohorts. Healthy men and women of non-childbearing potential aged 18-55 years were eligible for inclusion; individuals in the volunteer infection study were required to be malaria naive. Safety and tolerability (primary outcome of the single ascending dose study and secondary outcome of the volunteer infection study) were assessed by frequency and severity of adverse events. The pharmacokinetic profile of M5717 was also characterised (primary outcome of the volunteer infection study and secondary outcome of the single ascending dose study). Parasite clearance kinetics (primary outcome of the volunteer infection study) were assessed by the parasite reduction ratio and the corresponding parasite clearance half-life; the incidence of recrudescence up to day 28 was determined (secondary outcome of the volunteer infection study). Recrudescent parasites were tested for genetic mutations (exploratory outcome). The trial is registered with ClinicalTrials.gov (NCT03261401).

FINDINGS

Between Aug 28, 2017, and June 14, 2019, 221 individuals were assessed for eligibility, of whom 66 men were enrolled in the single ascending dose study (eight per cohort for 50-1800 mg cohorts, randomised three M5717 to one placebo, and two in the 2100 mg cohort, randomised one M5717 to one placebo) and 22 men were enrolled in the volunteer infection study (six in the 150 mg cohort and eight each in the 400 mg and 800 mg cohorts). No adverse event was serious; all M5717-related adverse events were mild or moderate in severity and transient, with increased frequency observed at doses above 1250 mg. In the single ascending dose study, treatment-related adverse events occurred in three of 17 individuals in the placebo group; no individual in the 50 mg, 100 mg, or 200 mg groups; one of six individuals in each of the 400 mg, 1000 mg, and 1250 mg groups; two of six individuals in the 600 mg group; and in all individuals in the 1800 mg and 2100 mg groups. In the volunteer infection study, M5717-related adverse events occurred in no participants in the 150 mg or 800 mg groups and in one of eight participants in the 400 mg group. Transient oral hypoesthesia (in three participants) and blurred vision (in four participants) were observed in the 1800 mg or 2100 mg groups and constituted an unknown risk; thus, further dosing was suspended after dosing of the two sentinel individuals in the 2100 mg cohort. Maximum blood concentrations occurred 1-7 h after dosing, and a long half-life was observed (146-193 h at doses ≥200 mg). Parasite clearance occurred in all participants and was biphasic, characterised by initial slow clearance lasting 35-55 h (half-life 231·1 h [95% CI 40·9 to not reached] for 150 mg, 60·4 h [38·6 to 138·6] for 400 mg, and 24·7 h [20·4 to 31·3] for 800 mg), followed by rapid clearance (half-life 3·5 h [3·1 to 4·0] for 150 mg, 3·9 h [3·3 to 4·8] for 400 mg, and 5·5 h [4·8 to 6·4] for 800 mg). Recrudescence occurred in three (50%) of six individuals dosed with 150 mg and two (25%) of eight individuals dosed with 400 mg. Genetic mutations associated with resistance were detected in four cases of parasite recrudescence (two individuals dosed with 150 mg and two dosed with 400 mg).

INTERPRETATION

The safety, pharmacokinetics, and antimalarial activity of M5717 support its development as a component of a single-dose antimalarial combination therapy or for malaria prophylaxis.

FUNDING

Wellcome Trust and the healthcare business of Merck KGaA, Darmstadt, Germany.

Abstract 1361: Population pharmacokinetic modeling of avelumab to support flat dosing in patients with locally advanced or metastatic urothelial carcinoma

BACKGROUND Avelumab is a human IgG1 monoclonal antibody targeting PD-L1 that is approved in the US for second-line locally advanced or metastatic urothelial carcinoma (UC) and first-line maintenance (1LM) treatment of patients with UC that has not progressed with first-line platinum-containing chemotherapy. The current analysis aimed to evaluate the pharmacokinetics (PK) of avelumab and justify an 800-mg every-2-week (Q2W) flat-dosing regimen for 1LM-UC patients.

METHODS: PK data from avelumab-treated patients with solid tumors in 4 clinical studies were included. Patients received weight-based doses of avelumab ranging from 1 to 20 mg/kg, while all 1LM-UC patients received doses of 10 mg/kg. Blood samples from 1LM-UC patients were collected predose and immediately before the end of infusion from cycles 1 through 13 for evaluation of PK and immunogenicity. Avelumab population pharmacokinetics (popPK) were characterized using the structural component of a pre-established time-varying popPK model. Baseline clearance and percent change in clearance from baseline were explored through summary statistics to assess the potential effects of immunogenicity and PD-L1 status on avelumab PK. The distribution of single-dose and steady-state exposure metrics predicted in the 1LM-UC population were compared to simulated exposure distributions following 10-mg/kg Q2W and 800-mg Q2W avelumab monotherapy treatment to support the 800-mg Q2W flat-dosing regimen. PopPK analyses were performed with NONMEM version 7.4.3, and data manipulation and postprocessing were performed with R version 3.5.0.

RESULTS: A 2-compartment popPK model with body weight as a covariate on clearance and volume satisfactorily characterized avelumab PK using 15,392 PK records from 2,171 patients, which included 4,566 PK records from 344 1LM-UC patients. Avelumab PK parameters in 1LM-UC patients were consistent with parameters in other patients with solid tumors. Average baseline clearance and percent change from baseline clearance in 1LM-UC patients grouped by immunogenicity (antidrug antibody ever positive vs never positive) or PD-L1 status (positive vs negative vs missing PD-L1 immune cell expression by SP263) ranged from 0.0257 to 0.0295 L/h and from −2.3% to 6.9%, respectively. The distributions of post hoc predicted single-dose and steady-state avelumab exposures overlapped with simulated exposures of patients with solid tumors receiving avelumab 800 mg Q2W.

CONCLUSIONS: The popPK analysis found that avelumab PK in the 1LM-UC patient population is consistent with the previously described disposition. Neither immunogenicity nor PD-L1 status had clinically meaningful impacts on avelumab clearance, and no clinically meaningful change in avelumab clearance over time was detected. Overall, the popPK analysis supports the 800-mg Q2W flat-dosing regimen for 1LM-UC patients.

Citation Format: Jerry Li, Carlo Bello, Akash Khandelwal, Yulia Vugmeyster, Dana Nickens, Ana Ruiz-Garcia, Swan Lin. Population pharmacokinetic modeling of avelumab to support flat dosing in patients with locally advanced or metastatic urothelial carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1361.

Abstract 1362: Exposure-response (E-R) analysis of efficacy for avelumab as first-line maintenance therapy for urothelial carcinoma in the JAVELIN Bladder 100 study

BACKGROUND: Avelumab, a monoclonal antibody targeting PD-L1, was recently approved in the United States for first-line maintenance (1LM) treatment of patients with locally advanced or metastatic urothelial carcinoma (UC) that has not progressed with first-line platinum-containing chemotherapy. This analysis assessed the potential relationship between covariates, including avelumab exposure, and overall survival (OS) in patients with UC.

METHODS: This analysis included all patients (N=350) who received avelumab 10 mg/kg every 2 weeks (Q2W) + best supportive care (BSC; arm A) in the JAVELIN Bladder 100 study (intention-to-treat population). Exposure metrics were derived based on a separate population pharmacokinetic model. The exposure-response analyses were conducted using parametric time-to-event (TTE) methodology, and the distribution of survival vs time was tested using exponential, Weibull, log-normal, and log-logistic distributions. A stepwise covariate search was conducted to determine the full and final models (forward addition α=0.05; backward elimination α=0.01). Model adequacy and predictability were evaluated using TTE-visual predictive checks and the likelihood ratio test.

RESULTS: The best fit to the hazard distribution was the log-normal distribution. Avelumab exposure (cycle 1 day 15 trough concentration) was associated with a higher probability of longer OS in both univariate and multivariate regression models. Nonvisceral metastatic disease at the time of initiating first-line chemotherapy was associated with higher probability of longer OS compared with visceral metastasis; this was a study stratification factor and a known predictor of OS in this population. Hemoglobin was also identified as a predictor of OS, consistent with previous reports. However, several factors may have confounded the interpretation of the exposure-OS modeling results, including an imbalance of baseline health status across the exposure quartiles, eg, Eastern Cooperative Oncology Group performance status (ECOG PS) and body weight, and that the data were from a single-dose regimen. Covariates that were not identified as predictors of OS were antidrug antibody status, Asian race, age, sex, smoking history, baseline ECOG PS, best response to first-line chemotherapy, and first-line chemotherapy regimen (α=0.01).

CONCLUSION: The E-R analyses were considered exploratory and no definite conclusions could be made on the impact of exposure on OS, as other variables confounded the relationship. Overall, the exposure from avelumab 10 mg/kg IV Q2W + BSC was associated with a manageable safety and tolerability profile and demonstrated superior efficacy compared with BSC alone in terms of OS as 1LM in patients with UC.

Citation Format: Jennifer Hibma, Jerry Li, Carlo Bello, Akash Khandelwal, Yulia Vugmeyster, Dana Nickens, Swan Li. Exposure-response (E-R) analysis of efficacy for avelumab as first-line maintenance therapy for urothelial carcinoma in the JAVELIN Bladder 100 study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1362.

Abstract 1360: Exposure-response safety analysis of avelumab in patients with locally advanced or metastatic urothelial carcinoma

BACKGROUND: Avelumab is a human IgG1 monoclonal antibody targeting PD-L1 that is approved in the US for second-line locally advanced or metastatic urothelial carcinoma (UC) and first-line maintenance (1LM) treatment of patients with UC that has not progressed with first-line platinum-containing chemotherapy. The current analysis was conducted to evaluate the relationships between avelumab exposure and the probability of experiencing adverse events in 1LM-UC patients.

METHODS: Avelumab exposures following 10-mg/kg every-2-weeks (Q2W) dosing in 1LM-UC patients were derived from post hoc parameter estimates from a population pharmacokinetic model. Safety endpoints included grade ≥3 treatment-emergent adverse events (TEAEs), any-grade infusion-related reactions (IRRs), and any-grade immune-related adverse events (irAEs). For each safety endpoint, avelumab exposures were assessed by univariate screen followed by a full model including influence of all potential covariates and a final model that retained statistically significant covariates (α=0.01) after backwards elimination. Safety analyses were performed with R version 3.5.0 by binomial logistic regression.

RESULTS: A total of 344 1LM-UC patients treated with avelumab were included in the analyses. Of these patients, 163 (47%), 101 (29%), and 74 (21.5%) experienced grade ≥3 TEAE, any-grade IRR, and any-grade irAE, respectively. Avelumab exposure did not demonstrate statistically significant relationships with grade ≥3 TEAE or any-grade irAE. Any-grade IRR demonstrated a potentially confounded inverse relationship with avelumab exposure (p=0.009), a trend also seen in patients with advanced renal cell carcinoma. In all models, immunogenicity and PD-L1 status were tested as covariates but were not predictors for any safety endpoint.

CONCLUSIONS: The exposure range associated with avelumab 10-mg/kg Q2W dosing demonstrated no clinically meaningful relationships with any of the safety endpoints. Given the similarity in avelumab exposures between the flat 800-mg Q2W and weight-based 10-mg/kg dosing, the findings of this analysis support the use of the flat-dosing regimen for 1LM-UC patients.

Citation Format: Jerry Li, Carlo Bello, Akash Khandelwal, Yulia Vugmeyster, Dana Nickens, Swan Lin. Exposure-response safety analysis of avelumab in patients with locally advanced or metastatic urothelial carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1360.

Rabies encephalitis

Rabies is an almost always fatal disease that physicians and patients dread due to its dismal prognosis and limited treatment options. Transmission of this disease occurs through the bite of dogs and wild animals (like jackal in our case). Other rare forms of transmission may be through inhalation in bat-infested caves and human-to-human transmission by infected corneal transplants, solid organ and tissue transplantation, and sometimes in laboratory settings. Its diagnosis is usually clinical in the absence of availability of special laboratory investigations at the point-of-care facility. Few people have described the role of imaging in diagnosis. We hereby report a patient with rabies encephalitis, having a history of jackal bite and classical MRI findings that we can use for early diagnosis in the absence of typical clinical features and specialised diagnostic testing.

Tele-Medicine Services in Hematological Practice During Covid Pandemic: Its Feasibility and Difficulties

In COVID 19 pandemic, delivery and access of health care services have become challenging. Telemedicine services can be considered for management of patients with hematological diseases. This study included all patients who enrolled for telemedicine facility for hematology from May 15 to July 15, 2020. Patient’s demographic and disease related parameters were recorded during the teleconsultation call. Overall satisfaction of attending doctor and patients were also recorded. A total of 1187 teleconsultation appointments were taken, of which 944 (79.6%) were successfully attended. Median age of patients was 38 years (range- 0.5–78 years), with 38% females. 55% of successful calls were from patients suffering a malignant hematological disorder. 24% had an active complaint pertaining to their disease or treatment. Of these, 162 (17%) were asked for a physical consultation. A significant association was found between the requirement of physical consultation and diagnosis (p < 0.001), absence of active complaint (< 0.0001) and education level of responder (p = 0.008). Patients understand that teleconsultation is helpful in preventing COVID-19 infection (71.4%) and avoids outpatient department rush (14.5%) associated with physical appointments; and around 80% patients were satisfied with the teleconsult. With the emergence of COVID 19, many localities under partial lockdown with constant fear of contacting virus amongst patients and health care providers, we can clearly see the advantages as well as feasibility of telemedicine services for our patients. The acute surge in telemedicine could be harnessed in the future to provide comprehensive and integrated care to patients of hematological disorders.

Semimechanistic Clearance Models of Oncology Biotherapeutics and Impact of Study Design: Cetuximab as a Case Study

This study aimed to explore the currently competing and new semimechanistic clearance models for monoclonal antibodies and the impact of clearance model misspecification on exposure metrics under different study designs exemplified for cetuximab. Six clearance models were investigated under four different study designs (sampling density and single/multiple‐dose levels) using a rich data set from two cetuximab clinical trials (226 patients with metastatic colorectal cancer) and using the nonlinear mixed‐effects modeling approach. A two‐compartment model with parallel Michaelis–Menten and time‐decreasing linear clearance adequately described the data, the latter being related to post‐treatment response. With respect to bias in exposure metrics, the simplified time‐varying linear clearance (CL) model was the best alternative. Time‐variance of the linear CL component should be considered for biotherapeutics if response impacts pharmacokinetics. Rich sampling at steady‐state was crucial for unbiased estimation of Michaelis–Menten elimination in case of the reference (parallel Michaelis–Menten and time‐varying linear CL) model.

Selection of the Recommended Phase 2 Dose for Bintrafusp Alfa, a Bifunctional Fusion Protein Targeting TGF-β and PD-L1

Bintrafusp alfa, a first‐in‐class bifunctional fusion protein composed of the extracellular domain of the TGF‐βRII receptor (TGF‐β “trap”) fused to a human IgG1‐blocking PD‐L1, showed a manageable safety profile and clinical activity in phase I studies in patients with heavily pretreated advanced solid tumors. The recommended phase 2 dose (RP2D) was selected based on integration of modeling, simulations, and all available data. A 1,200‐mg every 2 weeks (q2w) dose was predicted to maintain serum trough concentration (C_trough) that inhibits all targets of bintrafusp alfa in circulation in > 95% of patients, and a 2,400‐mg every 3 weeks (q3w) dose was predicted to have similar C_trough. A trend toward an association between exposure and efficacy variables and a relatively stronger inverse association between clearance and efficacy variables were observed. Exposure was either weakly or not correlated with probability of adverse events. The selected intravenous RP2D of bintrafusp alfa is 1,200 mg q2w or 2,400 mg q3w.

Avelumab flat dose regimen: Justification for use in advanced renal cell carcinoma (aRCC)

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Background: Avelumab, an anti–PD-L1 monoclonal antibody, was recently approved for the treatment of aRCC in combination with axitinib and was previously indicated for the treatment of metastatic Merkel cell carcinoma (MCC) and platinum-treated advanced/metastatic urothelial carcinoma (UC). Although avelumab was approved with weight-based dosing (10 mg/kg intravenously [IV] every 2 weeks [Q2W]), it was subsequently approved for flat dosing (800 mg IV Q2W) based on population pharmacokinetic (popPK), exposure-efficacy and exposure-safety modeling and simulations in MCC and UC (Novakovic AM, et al. Clin Pharmacol Ther. 2019). The justification for the recommended flat-dose regimen for avelumab as combination therapy with axitinib in aRCC is presented. Methods: Simulated exposure metrics (eg, area under the curve) from the previous popPK model (data from 1,827 patients with solid tumors across 3 clinical trials) for both weight-based and flat-dose regimens were compared with the exposure metrics obtained from treatment-naive patients with aRCC enrolled in 2 clinical studies (N = 488 from NCT02493751 and NCT02684006) who received avelumab (10 mg/kg Q2W) + axitinib (5 mg orally twice daily). Avelumab exposure-response relationships for safety and efficacy were also analyzed. Endpoints included grade ≥3 treatment-emergent adverse events (TEAEs), any-grade infusion-related reactions (IRRs) and immune-related (ir)AEs, and progression-free survival (PFS) by independent review. Results: The administration of weight-based dosing of avelumab in the aRCC population yielded similar PK exposures to simulated reference exposures of the flat-dose regimen in the solid tumor population. Avelumab exposure was not associated with increased probabilities of grade ≥3 TEAEs or IRRs, although there was a weak association with an increased probability of any-grade irAEs. Conclusions: The similar exposures observed for both avelumab dosing regimens in aRCC, and in prior studies in the MCC and UC populations, suggest that the 800 mg Q2W flat-dose regimen will maintain the benefit-risk ratio for avelumab + axitinib for treatment-naive patients with aRCC. Clinical trial information: NCT02493751 . Clinical trial information: NCT02684006.

Changing Body Weight-Based Dosing to a Flat Dose for Avelumab in Metastatic Merkel Cell and Advanced Urothelial Carcinoma

Avelumab, an anti–programmed death‐ligand 1 monoclonal antibody approved for the treatment of metastatic Merkel cell carcinoma and platinum‐treated urothelial carcinoma, was initially approved with a 10 mg/kg weight‐based dose. We report pharmacokinetic (PK)/pharmacodynamic analyses for avelumab comparing weight‐based dosing and a flat 800 mg dose, developed using data from 1,827 patients enrolled in 3 clinical trials (NCT01772004, NCT01943461, and NCT02155647). PK metrics were simulated for weight‐based and flat‐dosing regimens and summarized by quartiles of weight. Derived exposure metrics were used in simulations of exposure‐safety (various tumors) and exposure‐efficacy (objective responses; Merkel cell or urothelial carcinoma). Flat dosing was predicted to provide similar exposure to weight‐based dosing, with slightly lower variability. Exposure‐safety and exposure‐efficacy simulations suggested similar benefit:risk profiles for the two dosing regimens. These pharmacometric analyses provided the basis for the US Food and Drug Administration approval of a flat dose of avelumab 800 mg every 2 weeks in approved indications.

Population pharmacokinetic modeling to facilitate dose selection of tapentadol in the pediatric population

OBJECTIVE

The main aim of this analysis was to characterize the pharmacokinetics (PK) of the strong analgesic tapentadol in 2-year-old to <18-year-old patients with acute pain and to inform the optimal dosing strategy for a confirmatory efficacy trial in this patient population.

METHODS

The analysis dataset included tapentadol concentrations obtained from 92 pediatric patients receiving a single tapentadol oral solution (OS) dose of 1.0 mg/kg bodyweight in two single-dose PK clinical trials. Population PK analysis was performed using nonlinear mixed effects modeling. Simulations were performed to identify tapentadol OS doses in pediatric subjects (2 to <18 years) that would produce exposures similar to those in adults receiving safe and efficacious doses of tapentadol IR (50-100 mg every 4 hrs).

RESULTS

Tapentadol PK in children aged from 2 to <18 years was best described by a one-compartment model. Mean population apparent clearance and apparent volume of distribution for a typical subject weighing 45 kg were 170 L/h and 685 L, respectively. Clearance, expressed in bodyweight units as L/h/kg, decreased with increasing age whereas total clearance (L/h) increased with increasing age. Model-based simulations suggested that a tapentadol OS dose of 1.25 mg/kg to children and adolescents aged 2 to <18 years would result in efficacious tapentadol exposures similar to those in adults receiving tapentadol immediate release 50-100 mg every 4 hrs. The proposed tapentadol OS dose was subsequently applied in a confirmatory efficacy trial in 2 to <18-year-old patients suffering from acute postsurgical pain.

CONCLUSION

This analysis provides an example of a model-based approach for a dose recommendation to be used in an efficacy trial in the pediatric population. Uniform dosing based on bodyweight was proposed for the treatment of acute pain in children aged from 2 to <18 years.

Time-Varying Clearance and Impact of Disease State on the Pharmacokinetics of Avelumab in Merkel Cell Carcinoma and Urothelial Carcinoma

Avelumab, a human anti-programmed death ligand 1 immunoglobulin G1 antibody, has shown efficacy and manageable safety in multiple tumors. A two-compartment population pharmacokinetic model for avelumab incorporating intrinsic and extrinsic covariates and time-varying clearance (CL) was identified based on data from 1,827 patients across three clinical studies. Of 14 tumor types, a decrease in CL over time was more notable in metastatic Merkel cell carcinoma and squamous cell carcinoma of the head and neck, which had maximum decreases of 32.1% and 24.7%, respectively. The magnitude of reduction in CL was higher in responders than in nonresponders. Significant covariate effects of baseline weight, baseline albumin, and sex were identified on both CL and central distribution volume. Significant covariate effects of black/African American race, C-reactive protein, and immunogenicity were found on CL. None of the covariate or time-dependent effects were clinically important or warranted dose adjustment.

Blunt Cerebrovascular Injuries: Advances in Screening, Imaging, and Management Trends

Blunt cerebrovascular injury is a relatively uncommon but sometimes life-threatening injury, particularly in patients presenting with ischemic symptoms in that vascular territory. The decision to pursue vascular imaging (generally CT angiography) is based on clinical and imaging findings. Several grading scales or screening criteria have been developed to guide the decision to pursue vascular imaging, as well as to recommend different treatment options for various injuries. The data supporting many of these guidelines and options are limited however. The purpose of this article is to review and compare these scales and criteria and the data supporting clinical efficacy and to make recommendations for future research in this area.

Patterns of metastasis and recurrence in thymic epithelial tumours: longitudinal imaging review in correlation with histological subtypes

AIM

To determine the patterns of metastasis and recurrence in thymic epithelial tumours based on longitudinal imaging studies, and to correlate the patterns with World Health Organization (WHO) histological classifications.

MATERIALS AND METHODS

Seventy-seven patients with histopathologically confirmed thymomas (n=62) and thymic carcinomas (n=15) who were followed with cross-sectional follow-up imaging after surgery were retrospectively studied. All cross-sectional imaging studies during the disease course were reviewed to identify metastasis or recurrence. The sites of involvement and the time of involvement measured from surgery were recorded.

RESULTS

Metastasis or recurrence was noted in 24 (31%) of the 77 patients. Patients with metastasis or recurrence were significantly younger than those without (median age: 46 versus 60, respectively; p=0.0005), and more commonly had thymic carcinomas than thymomas (p=0.002). The most common site of involvement was the pleura (17/24), followed by the lung (9/24), and thoracic nodes (9/24). Abdominopelvic involvement was noted in 12 patients, most frequently in the liver (n=8). Lung metastasis was more common in thymic carcinomas than thymomas (p=0.0005). Time from surgery to the development of metastasis or recurrence was shortest in thymic carcinoma, followed by high-risk thymomas, and was longest in low-risk thymoma (median time in months: 25.1, 68.8, and not reached, respectively; p=0.0015).

CONCLUSIONS

The patterns of metastasis and recurrence of thymic epithelial tumours differ significantly across histological subgroups, with thymic carcinomas more commonly having metastasis with shorter length of time after surgery. The knowledge of different patterns of tumour spread may contribute to further understanding of the biological and clinical behaviours of these tumours.

Radiologist's perspective for the Meckel's diverticulum and its complications

The Meckel's diverticulum is the commonest congenital anomaly of the gastrointestinal tract, often presenting with complications such as gastrointestinal bleeding, intussusception, bowel obstruction and diverticulitis, which are often misdiagnosed. Imaging plays an important role in the early diagnosis and characterization of these conditions and is very helpful in decision making. The Meckel's diverticulum and its complications have myriad presentations and appearances on various imaging modalities. Thus, sound knowledge of the anatomy, embryology, clinical presentation, imaging characteristics and complications is crucial to the practice of abdominal imaging. We present a review of the literature and current radiological practices in the diagnosis and management of the Meckel's diverticulum and its various complications with special emphasis on the imaging of various complications, mimickers and pathological correlation.

Ruptured Aortic Aneurysm Secondary to Psoas abscess after Intravesical Bacilli Calmette-Guérin

Bacillus Calmette-Guérin (BCG) is a live attenuated strain of Mycobacterium bovis that has been used as effective treatment for early-stage transitional carcinoma of the urinary bladder. We present a case of a 68 year old man who had an abdominal aortic aneurysm following BCG therapy for bladder cancer. Contrast enhanced computerized tomogram (CECT) of abdomen and pelvis revealed bilateral hypodense lesions suggestive of psoas abscesses. In addition, a saccular abdominal aortic aneurysm measuring 4x3.6 cm involving infrarenal aorta with surrounding hematoma was seen. At surgery, he was found to have a psoas abscess and hemorrhage. He underwent ligation of the aorta and an axillary-bifemoral bypass. He was given one year of anti-tubercular therapy to which he responded clinically.

Cellular quantitative structure-activity relationship (Cell-QSAR): conceptual dissection of receptor binding and intracellular disposition in antifilarial activities of Selwood antimycins

We present the cellular quantitative structure–activity relationship (cell-QSAR) concept that adapts ligand-based and receptor-based 3D-QSAR methods for use with cell-level activities. The unknown intracellular drug disposition is accounted for by the disposition function (DF), a model-based, nonlinear function of a drug’s lipophilicity, acidity, and other properties. We conceptually combined the DF with our multispecies, multimode version of the frequently used ligand-based comparative molecular field analysis (CoMFA) method, forming a single correlation function for fitting the cell-level activities. The resulting cell-QSAR model was applied to the Selwood data on filaricidal activities of antimycin analogues. Their molecules are flexible, ionize under physiologic conditions, form different intramolecular H-bonds for neutral and ionized species, and cross several membranes to reach unknown receptors. The calibrated cell-QSAR model is significantly more predictive than other models lacking the disposition part and provides valuable structure optimization clues by factorizing the cell-level activity of each compound into the contributions of the receptor binding and disposition.

A fast method for testing covariates in population PK/PD Models

The development of covariate models within the population modeling program like NONMEM is generally a time-consuming and non-trivial task. In this study, a fast procedure to approximate the change in objective function values of covariate-parameter models is presented and evaluated. The proposed method is a first-order conditional estimation (FOCE)-based linear approximation of the influence of covariates on the model predictions. Simulated and real datasets were used to compare this method with the conventional nonlinear mixed effect model using both first-order (FO) and FOCE approximations. The methods were mainly assessed in terms of difference in objective function values (ΔOFV) between base and covariate models. The FOCE linearization was superior to the FO linearization and showed a high degree of concordance with corresponding nonlinear models in ΔOFV. The linear and nonlinear FOCE models provided similar coefficient estimates and identified the same covariate-parameter relations as statistically significant or non-significant for the real and simulated datasets. The time required to fit tesaglitazar and docetaxel datasets with 4 and 15 parameter-covariate relations using the linearization method was 5.1 and 0.5 min compared with 152 and 34 h, respectively, with the nonlinear models. The FOCE linearization method allows for a fast estimation of covariate-parameter relations models with good concordance with the nonlinear models. This allows a more efficient model building and may allow the utilization of model building techniques that would otherwise be too time-consuming.

Rigorous treatment of multispecies multimode ligand-receptor interactions in 3D-QSAR: CoMFA analysis of thyroxine analogs binding to transthyretin

For a rigorous analysis of the receptor-ligand binding, speciation of the ligands caused by ionization, tautomerism, covalent hydration, and dynamic stereoisomerism needs to be considered. Each species may bind in several orientations or conformations (modes), especially for flexible ligands and receptors. A thermodynamic description of the multispecies (MS), multimode (MM) binding events shows that the overall association constant is equal to the weighted sum of the sums of microscopic association constants of individual modes for each species, with the weights given by the unbound fractions of individual species. This expression is a prerequisite for a precise quantitative characterization of the ligand-receptor interactions in both structure-based and ligand-based structure-activity analyses. We have implemented the MS-MM correlation expression into the comparative molecular field analysis (CoMFA), which deduces a map of the binding site from structures and binding affinities of a ligand set, in the absence of experimental structural information on the receptor. The MS-MM CoMFA approach was applied to published data for binding to transthyretin of 28 thyroxine analogs, each forming up to four ionization species under physiological conditions. The published X-ray structures of several analogs, exhibiting multiple binding modes, served as templates for the MS-MM superposition of thyroxine analogs. Additional modes were generated for compounds with flexible alkyl substituents, to identify bound conformations. The results demonstrate that the MS-MM modification improved predictive abilities of the CoMFA models, even for the standard procedure with MS-MM selected species and modes. The predicted prevalences of individual modes and the generated receptor site model are in reasonable agreement with the available X-ray data. The calibrated model can help in the design of inhibitors of transthyretin amyloid fibril formation.

Hydrogen adsorption in several types of carbon nanotubes

In this work, we aim to study the hydrogen adsorption in several kinds of carbon nanotubes grown under different process conditions and to correlate the findings with the morphological microstructure and physical properties of these materials. The growth conditions and the behaviour with respect to hydrogen interaction of various carbon nanotubes are discussed, to establish microstructure-process-property relationships. In particular, we have analyzed several types of carbon nanotubes, namely one single-walled and five multi-walled having different tube diameter (due to different deposition techniques and conditions), different defectiveness and submitted to different surface treatments. To better understand the differences among the various samples, they have been investigated using field emission scanning electron microscopy and high resolution transmission electron microscopy for the morphological and structural characteristics, thermo-gravimetric analysis for the sample purity and Brunauer-Emmett-Teller analysis for the surface area. The experimental measurements on the ability of the different types of carbon nanotubes to adsorb and/or releasing hydrogen have been performed at 77 K with a volumetric Sievert analytical tool. Our findings clearly demonstrate a direct correlation between the exposed surface area and adsorbed hydrogen capacity, which confirms their linear relationship observed previously. For instance, single-walled nanotubes with surface area density of approximately 800 m2/g have showed hydrogen storage of approximately 1.7 wt% at a pressure of 35 atm. Adsorption process seems to be perfectly reversible. The adsorption values have been compared with a simple model, in order to evaluate the potentialities for carbon-based nanomaterials in future hydrogen storage applications.