Population pharmacokinetics and pharmacodynamics of nasal glucagon in patients with type 1 or 2 diabetes.

The objective was to characterize the pharmacokinetics (PK) and pharmacodynamics (PD) of glucagon after injectable or nasal administration and confirm the appropriate therapeutic dose of nasal glucagon (NG) for adult patients. Six clinical studies with PK and five clinical studies with PD (glucose) data were included in the analysis. Doses ranging from 0.5 to 6 mg NG, and 0.5 to 1 mg injectable glucagon were studied. A total of 6284 glucagon and 7130 glucose concentrations from 265 individuals (patients and healthy participants) were available. Population PK/PD modeling was performed using NONMEM. Glucagon exposure and glucose response were simulated for patients administered various doses of NG to confirm the optimal dose. Glucagon PK was well-described with a single compartment disposition with first-order absorption and elimination processes. Bioavailability of NG relative to injectable glucagon was 16%. Exposure-response modeling revealed that lower baseline glucose was associated with higher maximum drug effect. The carry-over effect from prior insulin administration was incorporated into the model through a time-dependent increase in elimination rate of glucose. Simulations showed that more than 99% of hypoglycemic adult patients would experience treatment success, defined as an increase in blood glucose to ≥70 mg/dL or an increase of ≥20 mg/dL from nadir within 30 min after administration of NG 3 mg. The population PK/PD model adequately described the PK and PD profiles of glucagon after nasal administration. Modeling and simulations confirmed that NG 3 mg is the most appropriate dose for rescue treatment during hypoglycemia emergencies.

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.

Once-Weekly Basal Insulin Fc Demonstrated Similar Glycemic Control to Once-Daily Insulin Degludec in Insulin-Naive Patients With Type 2 Diabetes: A Phase 2 Randomized Control Trial.

OBJECTIVE: Basal insulin Fc (BIF) (insulin efsitora alfa; LY3209590), a fusion protein combining a novel single-chain insulin variant with a human IgG Fc domain, is designed for once-weekly basal insulin administration. This phase 2 study assessed the safety and efficacy of BIF versus degludec in insulin-naive patients with type 2 diabetes (T2D) previously treated with oral antihyperglycemic medications. RESEARCH DESIGN AND METHODS: During this randomized, parallel, open-label study, 278 insulin-naive patients with T2D were randomly assigned (1:1) to receive BIF once weekly or degludec once daily over the 26-week treatment period. Both groups were titrated to fasting glucose of 80-100 mg/dL (4.4 to <5.6 mmol/L). The primary end point was HbA1c change from baseline to week 26 (noninferiority margin 0.4%). Secondary end points included fasting blood glucose (FBG), six-point glucose profiles, and rate of hypoglycemia. RESULTS: After 26 weeks of treatment, BIF demonstrated a noninferior HbA1c change from baseline versus degludec, with a treatment difference of 0.06% (90% CI -0.11, 0.24; P = 0.56). Both BIF and degludec treatment led to significant reductions in FBG from baseline. At week 26, the between-treatment difference for BIF versus degludec was 4.7 mg/dL (90% CI 0.1, 9.3; P = 0.09). The rate of level 2 hypoglycemia was low and not significantly different between treatment groups (BIF 0.22 events/patient/year, degludec 0.15 events/patient/year; P = 0.64); there was no severe hypoglycemia. The occurrence of treatment-emergent adverse events was also similar between BIF and degludec. CONCLUSIONS: Once-weekly BIF achieved excellent glycemic control similar to degludec, with no concerning hypoglycemia or other safety findings.

Dose Rationale of Nasal Glucagon in Japanese Pediatric Patients with Diabetes Using Pharmacokinetic/Pharmacodynamic Modeling and Simulation.

BACKGROUND: Nasal glucagon (NG) 3 mg is approved in Japan to treat hypoglycemia in pediatric patients with diabetes, but an NG clinical study has not been performed in Japanese children because of practical and ethical concerns. OBJECTIVE: The aim of this study is to support the dose rationale for NG 3 mg in Japanese pediatric patients with diabetes using modeling and simulation. METHODS: We used a pharmacokinetic/pharmacodynamic bridging approach to extrapolate the available clinical data to Japanese pediatric patients. Population pharmacokinetic/pharmacodynamic modeling was performed using data from seven clinical studies, including five studies in non-Japanese adults, one study in Japanese adults, and one study in non-Japanese pediatric patients. Simulation was then used to estimate glucagon exposure and glucose response after NG 3-mg administration for three age categories of Japanese pediatric patients: 4 to < 8, 8 to < 12, and 12 to < 18 years. Treatment success was defined as an increase in blood glucose to ≥ 70 or ≥ 20 mg/dL from nadir within 30 min after administration of NG 3 mg. Safety was assessed in relation to the predicted maximum glucagon concentration of NG 3 mg using NG clinical trial data and published data on intravenous and intramuscular glucagon. RESULTS: The data showed a rapid and robust glucose response following NG 3 mg in Japanese and non-Japanese adults and non-Japanese pediatric patients, with some differences in glucagon exposure observed across studies. The pharmacokinetic/pharmacodynamic model described the observed clinical data well, and simulations indicated that > 99% of hypoglycemic Japanese pediatric patients in all three age groups would achieve treatment success. Predicted glucose responses to NG 3 mg in Japanese pediatric patients were comparable to those of intramuscular glucagon. Maximum concentration was not associated with the occurrence and severity of common adverse events (nausea, vomiting, and headache) in NG clinical studies. Furthermore, the predicted maximum concentration in Japanese pediatric patients, despite being higher than the observed maximum concentration in NG clinical studies, was substantially lower than the observed maximum concentration of 1 mg of intravenous glucagon, without serious safety issues. CONCLUSIONS: This analysis suggests NG 3 mg has robust efficacy without serious safety concerns in Japanese pediatric patients with diabetes.

Novel Once-Weekly Basal Insulin Fc Achieved Similar Glycemic Control With a Safety Profile Comparable to Insulin Degludec in Patients With Type 1 Diabetes.

OBJECTIVE: Basal Insulin Fc (BIF; insulin efsitora alfa; LY3209590), a fusion protein combining a novel single-chain insulin variant with a human IgG Fc domain, is designed for once-weekly basal insulin administration. This phase 2 study assessed safety and efficacy of BIF versus degludec in 265 patients with type 1 diabetes (T1D) using multiple daily injections. RESEARCH DESIGN AND METHODS: During this randomized, parallel, open-label study, patients with T1D were randomized (1:1) to receive BIF once weekly or degludec once daily over the 26-week treatment period. Both groups were titrated to a fasting glucose level of 80-100 mg/dL. The primary end point was HbA1c change from baseline to week 26 (noninferiority margin, 0.4%). Secondary end points included percent time in range (TIR) (70-180 mg/dL), continuous glucose monitoring (CGM) fasting glucose (FG) level, and rate of hypoglycemia. RESULTS: After 26 weeks, patients receiving BIF had noninferior HbA1c change from baseline versus those receiving degludec, with a statistically significant treatment difference of 0.17% (90% CI 0.01, 0.32; P = 0.07) favoring the comparator. Percent TIR was similar for patients in the BIF (56.1%) and degludec (58.9%; P = 0.112) groups at week 26. FG values were significantly higher for patients receiving BIF (158.8 mg/dL) versus degludec (143.2 mg/dL; P = 0.003). Rates of CGM-derived hypoglycemia were not statistically significantly different for BIF and degludec over 24 h for level 1 (P = 0.960) or level 2 (P = 0.517) hypoglycemia during the treatment period. Occurrence of serious adverse events was similar between the BIF and degludec groups. CONCLUSIONS: Once-weekly BIF demonstrated noninferior glycemic control to once-daily degludec (treatment difference: 0.17% favoring degludec) and no difference in hypoglycemia or other safety findings in patients with T1D.

Safety and efficacy of once-weekly basal insulin Fc in people with type 2 diabetes previously treated with basal insulin: a multicentre, open-label, randomised, phase 2 study.

BACKGROUND: The burden of daily basal insulins often causes hesitancy and delays in the initiation of insulin therapy. Basal insulin Fc (BIF, insulin efsitora alfa), designed for once-weekly administration, is a fusion protein combining a novel single-chain insulin variant with a human immunoglobulin G (IgG) Fc domain. In this study, we explored the safety and efficacy of BIF in people with type 2 diabetes who had been previously treated with basal insulin. METHODS: For this phase 2, 44-site (clinical research centres and hospitals), randomised, open-label, comparator-controlled, 32-week study in the USA, Puerto Rico, and Mexico, we enrolled participants with type 2 diabetes. Eligible participants had to be adults (aged ≥18 years) and to have been treated with basal insulin and up to three oral antidiabetic medicines. Participants were randomly assigned (1:1:1) to subcutaneous administration of BIF (BIF treatment group 1 [BIF-A1] or 2 [BIF-A2]) or insulin degludec. Randomisation was stratified by country, baseline HbA1c values (<8·5% or ≥8·5%; <69·4 or ≥69·4 mmol/mol), use of sulfonylureas (yes or no), and baseline BMI (<30 or ≥30 kg/m2). The randomisation scheme was performed using an interactive web-response system, which ensured balance between treatment groups. Different fasting glucose targets for the BIF-A1 (≤7·8 mmol/L or ≤140 mg/dL; titrated every 2 weeks), BIF-A2 (≤6·7 mmol/L or ≤120 mg/dL; titrated every 4 weeks), and degludec (≤5·6 mmol/L or ≤100 mg/dL) groups were selected. Patients randomly assigned to BIF received a one-time loading dose ranging from 1·5-3 times their calculated weekly dose. The first weekly dose was administered 1 week after the loading dose. We used interstitial fasting glucose measurements from the Dexcom G6 continuous glucose monitoring system to titrate the basal insulin. The primary measure of glycaemic control was change in HbA1c from baseline to week 32 for BIF. BIF was also compared with degludec (with a non-inferiority margin of 0·40%). The efficacy analysis set consisted of data from all randomised study participants who received at least one dose of the study medication and participants were analysed according to the treatment they were assigned. The safety population was the same as the efficacy analysis set. The completed trial is registered at ClinicalTrials.gov (NCT03736785). FINDINGS: Between Nov 15, 2018 and Feb 18, 2020, 399 participants were enrolled and randomised to BIF-A1 (n=135), BIF-A2 (n=132), or degludec (n=132); 202 (51%) were female and 197 (49%) were male. 379 were analysed for the primary outcome (BIF-A1: n=130; BIF-A2: n=125; degludec: n=124). Mean HbA1c change from baseline to week 32, the primary outcome, was -0·6% (SE 0·1%) for BIF-A1 and BIF-A2. Degludec achieved a change from baseline of -0·7% (0·1%). The pooled BIF analysis achieved non-inferiority versus degludec for the treatment difference in HbA1c (0·1% [90% CI -0·1 to 0·3]). The hypoglycaemia (≤3·9 mmol/L or ≤70 mg/dL) event rates (hypoglycaemia events per patient per year) in the BIF groups were 25% lower than those in the degludec group (treatment ratio BIF-A1 vs degludec was 0·75 [0·61-0·93]; and BIF-A2 vs degludec was 0·74 [0·58-0·94]). BIF was well tolerated; treatment-emergent adverse events were similar across groups. INTERPRETATION: Weekly BIF achieved a similar efficacy compared with degludec despite higher fasting glucose targets in the BIF groups. Higher fasting glucose targets and lower glucose variability might have contributed to lower hypoglycaemia rates for BIF compared with degludec. These findings support continued development of BIF as a once-weekly insulin treatment for people with diabetes. FUNDING: Eli Lilly and Company.

PK/PD modeling links accelerated resolution of COVID-19-related clinical symptoms to SARS-CoV-2 viral load reduction in patients following treatment with Bamlanivimab alone or Bamlanivimab and Etesevimab together.

The relationship between severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) viral load reduction and disease symptom resolution remains largely undefined for coronavirus disease 2019 (COVID-19). While the vaccine-derived immunity takes time to develop, neutralizing monoclonal antibodies offer immediate, passive immunity to patients with COVID-19. Bamlanivimab and etesevimab are two potent neutralizing monoclonal antibodies directed to the receptor binding domain of the spike protein of SARS-CoV-2. This study aims to describe the relationship between viral load and resolution of eight common COVID-19-related symptoms in patients following treatment with neutralizing monoclonal antibodies (bamlanivimab alone or bamlanivimab and etesevimab together), in a phase II clinical trial. Corresponding pharmacokinetics (PKs), viral load, and COVID-19-related symptom data were modeled using Nonlinear Mixed Effects Modeling to describe the time-course of eight COVID-19-related symptoms in an ordered categorical manner (none, mild, moderate, and severe), following administration of bamlanivimab or bamlanivimab and etesevimab together to participants with COVID-19. The PK/pharmacodynamic (PD) models characterized the exposure-viral load-symptom time course of the eight preselected COVID-19-related symptoms. Baseline viral load (BVL), change in viral load from baseline, and time since the onset of symptoms, demonstrated statistically significant effects on symptom score probabilities. Higher BVL generally indicated an increased probability of symptom severity. The severity of symptoms decreased over time, partially driven by the decrease in viral load. The effect of increasing time resulting in decreased severity of symptoms was over and above the effect of decreasing viral load. Administration of bamlanivimab alone or together with etesevimab results in a faster time to resolution of COVID-19-related symptoms compared to placebo.

A Quantitative Modeling and Simulation Framework to Support Candidate and Dose Selection of Anti-SARS-CoV-2 Monoclonal Antibodies to Advance Bamlanivimab Into a First-in-Human Clinical Trial.

Neutralizing monoclonal antibodies (mAb), novel therapeutics for the treatment of coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2), have been urgently researched from the start of the pandemic. The selection of the optimal mAb candidate and therapeutic dose were expedited using open-access in silico models. The maximally effective therapeutic mAb dose was determined through two approaches; both expanded on innovative, open-science initiatives. A physiologically-based pharmacokinetic (PBPK) model, incorporating physicochemical properties predictive of mAb clearance and tissue distribution, was used to estimate mAb exposure that maintained concentrations above 90% inhibitory concentration of in vitro neutralization in lung tissue for up to 4 weeks in 90% of patients. To achieve fastest viral clearance following onset of symptoms, a longitudinal SARS-CoV-2 viral dynamic model was applied to estimate viral clearance as a function of drug concentration and dose. The PBPK model-based approach suggested that a clinical dose between 175 and 500 mg of bamlanivimab would maintain target mAb concentrations in the lung tissue over 28 days in 90% of patients. The viral dynamic model suggested a 700 mg dose would achieve maximum viral elimination. Taken together, the first-in-human trial (NCT04411628) conservatively proceeded with a starting therapeutic dose of 700 mg and escalated to higher doses to evaluate the upper limit of safety and tolerability. Availability of open-access codes and application of novel in silico model-based approaches supported the selection of bamlanivimab and identified the lowest dose evaluated in this study that was expected to result in the maximum therapeutic effect before the first-in-human clinical trial.

Population Pharmacokinetics and Pharmacodynamics of the Neutralizing Antibodies Bamlanivimab and Etesevimab in Patients With Mild to Moderate COVID-19 Infection.

Bamlanivimab and etesevimab are neutralizing antibodies indicated for treatment of coronavirus disease 2019 (COVID-19) in patients with early mild or moderate disease. We present the use of pharmacokinetic/pharmacodynamic (PK/PD) modeling that characterizes the timecourse of viral load obtained from 2,970 patients from 2 phase II clinical trials. The model was used for identification of optimal doses that would result in at least 90% of patients achieving serum drug concentrations that result in 90% of maximum drug effect (IC90) for at least 28 days. The serum IC90 (95% confidence interval) was estimated to be 4.2 (3.2-4.3) µg/mL for bamlanivimab and 12.6 (9.7-12.8) µg/mL for etesevimab. Observed clinical trial data confirmed PK and PK/PD model predictions that doses of 700 mg bamlanivimab and 1,400 mg etesevimab would result in maximum reduction in viral load, with no additional effect seen at higher doses. No dose adjustment is recommended as age, sex, race, baseline viral load, and hepatic impairment did not have a significant impact on the PK of the antibodies. Earlier drug administration resulted in greater reductions in viral load, demonstrating the importance of receiving treatment as soon as possible. Relative to placebo, typical reduction in viral load over a 7-day period was estimated to be 80 or 93% (drug administered 4 days or 1 day after the onset of symptoms, respectively), P < 0.0001. PK/PD modeling and simulation was pivotal throughout the drug development and emergency use authorization process.

First-in-Human Study of Bamlanivimab in a Randomized Trial of Hospitalized Patients With COVID-19.

Therapeutics for patients hospitalized with coronavirus disease 2019 (COVID-19) are urgently needed during the pandemic. Bamlanivimab is a potent neutralizing monoclonal antibody that blocks severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) attachment and entry into human cells, which could potentially lead to therapeutic benefit. J2W-MC-PYAA was a randomized, double-blind, sponsor unblinded, placebo-controlled, single ascending dose first-in-human trial (NCT04411628) in hospitalized patients with COVID-19. A total of 24 patients received either placebo or a single dose of bamlanivimab (700 mg, 2,800 mg, or 7,000 mg). The primary objective was assessment of safety and tolerability, including adverse events and serious adverse events, with secondary objectives of pharmacokinetic (PK) and pharmacodynamic analyses. Treatment-emergent adverse event (TEAE) rates were identical in the placebo and pooled bamlanivimab groups (66.7%). There were no apparent dose-related increases in the number or severity of TEAEs. There were no serious adverse events or deaths during the study, and no discontinuations due to adverse events. PKs of bamlanivimab is linear and exposure increased proportionally with dose following single i.v. administration. The half-life was ~ 17 days. These results demonstrate the favorable safety profile of bamlanivimab, and provided the initial critical evaluation of safety, tolerability, and PKs in support of the development of bamlanivimab in several ongoing clinical trials.

Development and Application of a Mechanistic Population Modeling Approach to Describe Abemaciclib Pharmacokinetics.

Abemaciclib is an oral anticancer drug that inhibits cyclin dependent kinases 4 and 6 and is metabolized by cytochrome P450 3A in the intestines and liver to active metabolites. The objectives were (1) to develop a mechanistic model to characterize the pharmacokinetics (PK) of the active moieties and investigate the effect of patient factors and (2) apply the model to dat from two phase III breast cancer trials of abemaciclib in combination with endocrine therapy. To develop the model, data from seven phase I studies and two phase II studies including 421 patients with cancer and 65 healthy individuals were pooled for nonlinear mixed effects modeling. The PK was similar between patients and healthy subjects, and the effects of diarrhea, formulation, race, and patient covariates on exposure were negligible. Application of the model confirmed its predictive performance and that abemaciclib PK did not change when coadministered with endocrine therapy.

Transformation Morphisms and Time-to-Extinction Analysis That Map Therapy Duration From Preclinical Models to Patients With Tuberculosis: Translating From Apples to Oranges.

Background: A major challenge in medicine is translation of preclinical model findings to humans, especially therapy duration. One major example is recent shorter-duration therapy regimen failures in tuberculosis. Methods: We used set theory mapping to develop a computational/modeling framework to map the time it takes to extinguish the Mycobacterium tuberculosis population on chemotherapy from multiple hollow fiber system model of tuberculosis (HFS-TB) experiments to that observed in patients. The predictive accuracy of the derived translation transformations was then tested using data from 108 HFS-TB Rapid Evaluation of Moxifloxacin in Tuberculosis (REMoxTB) units, including 756 colony-forming units (CFU)/mL. Derived transformations, and Latin hypercube sampling-guided simulations were used to predict cure and relapse after 4 and 6 months of therapy. Outcomes were compared to observations, in 1932 patients in the REMoxTB clinical trial. Results: HFS-TB serial bacillary burden and serial sputum data in the derivation dataset formed a structure-preserving map. Bactericidal effect was mapped with a single step transformation, while the sterilizing effect was mapped with a 3-step transformation function. Using the HFS-TB REMoxTB data, we accurately predicted the proportion of patients cured in the 4-month REMoxTB clinical trial. Model-predicted vs clinical trial observations were (i) the ethambutol arm (77.0% [95% confidence interval {CI}, 74.4%-79.6%] vs 77.7% [95% CI, 74.3%-80.9%]) and (ii) the isoniazid arm (76.4% [95% CI, 73.9%-79.0%] vs 79.5% [95% CI, 76.1%-82.5%]). Conclusions: We developed a method to translate duration of therapy outcomes from preclinical models to tuberculosis patients.

Exposure-Response Modeling to Characterize the Relationship Between Ixekizumab Serum Drug Concentrations and Efficacy Responses at Week 12 in Patients With Moderate to Severe Plaque Psoriasis.

Ixekizumab, a high-affinity monoclonal antibody, selectively targets interleukin-17A and has been shown to be efficacious in the treatment of moderate to severe psoriasis. The objective was to describe the relationship between ixekizumab concentrations and efficacy response (static Physician Global Assessment [sPGA] and the Psoriasis Activity and Severity Index [PASI) scores] after 12 weeks of ixekizumab treatment in psoriasis patients from 3 phase 3 studies. Data from 2888 psoriasis patients randomized to receive placebo or 80 mg ixekizumab every 2 weeks or every 4 weeks were analyzed. Separate logistic regression models describing the relationship between ixekizumab concentrations and sPGA or PASI scores at week 12 were used to determine the probability of patients achieving a response and to investigate the impact of various patient factors other than drug concentrations on response rates. Both dosing regimens were efficacious, with higher rates of response achieved with the higher range of observed ixekizumab concentrations after every-2-week dosing. Although higher bodyweight, palmoplantar involvement, lower baseline disease state, or high baseline C-reactive protein were associated with slightly lower response rates, the magnitude of effect of these factors on sPGA(0,1) response was small, with all subgroups able to achieve high levels of response. Other factors tested had no effect including age, sex, and antidrug antibody status. Logistic regression modeling of ixekizumab concentration and efficacy data accurately identified the proportion of responders using sPGA or PASI end points. The higher concentration ranges achieved with 80 mg every 2 weeks versus every 4 weeks were associated with higher response levels.

Population Pharmacokinetic and Exposure-Response Analyses of Prasugrel in Pediatric Patients with Sickle Cell Anemia.

BACKGROUND AND OBJECTIVE: Prasugrel, a P2Y12 adenosine diphosphate (ADP) receptor antagonist, inhibits ADP-mediated platelet activation and aggregation in patients with sickle cell anemia (SCA). We developed a population pharmacokinetic (popPK) model in pediatric patients from 2 to <18 years of age with SCA, and performed exposure-response evaluations to characterize the effects of prasugrel in a subset of these patients who weighed 19 kg or more and experienced at least two episodes of vaso-occlusive crises (VOC) in the past year. METHODS: A three-compartment popPK model adapted from that used in adults with acute coronary syndrome was used to describe the relationship between plasma concentrations of prasugrel's active metabolite (Pras-AM) and time using data from phase II and III clinical studies in children. A VOC event rate model was developed from the phase III study to explore the exposure-response relationship between Pras-AM exposure and VOC, and included evaluation of covariates. RESULTS: The final popPK model for children with SCA provided a reasonable fit to Pras-AM plasma concentrations over time, with estimates of apparent clearance (CL/F) (172 L/h) and apparent volume of distribution (Vd/F) (51.7 L) that were comparable to previous studies in adults. The final model included weight as a covariate on both CL/F and Vd/F, and age as a covariate on CL/F. Analyses of safety (bleeding events requiring medical intervention) and efficacy (VOC event rate) variables showed no apparent relationship to model-predicted Pras-AM exposure quartiles, and no statistically significant effects of intrinsic or extrinsic factors on the VOC event rate were identified in the VOC event rate model. The effect of post hoc exposures on the VOC event rate did not reach statistical significance. CONCLUSIONS: A popPK model was developed that provided reasonable parameter estimates, goodness-of-fit diagnostics, and visual predictive checks when applied to Pras-AM plasma concentrations in pediatric patients with SCA. Post hoc exposures obtained from this model did not correlate with measures of VOC or bleeding events in this population.

Population Pharmacokinetics of Necitumumab in Cancer Patients.

Necitumumab is a second-generation, recombinant, human immunoglobulin G1, epidermal growth factor (EGFR) receptor antibody that specifically blocks the ligand binding site of EGFR. Necitumumab potentially acts by blocking ligand epidermal growth factor (EGF) binding-mediated activation of the EGFR signaling pathway, inhibiting tumor growth, angiogenesis, and anti-apoptotic mechanisms. Necitumumab inhibited the interaction of EGF and EGFR with a concentration that inhibits binding by 50 % of approximately 0.9 nM (0.13 mg/L) and demonstrated antitumor activity during in vivo experiments associated with trough plasma concentrations of approximately 40 mg/L. This work describes the population pharmacokinetics of necitumumab in cancer patients when administered with or without concomitant chemotherapy and evaluates patient characteristics that may guide dosing. Nonlinear mixed-effects modeling of serum concentration data across five clinical studies (phases I-III) indicated that necitumumab exhibited target-mediated drug disposition, commonly observed with monoclonal antibodies, and that pharmacokinetics were expected to be linear in the studied dose ranges when administered as repeated infusions. No age, sex, race, or concomitant medication factors were found influential, while weight was a statistically significant factor for both distribution and elimination. Simulations from the final model indicated that only a limited reduction in patient drug exposure variability would be achieved by weight- or body surface area-based dosing. Necitumumab effective half-life was estimated to approximately 2 weeks, and steady state was achieved within three to four cycles of treatment. The phase III dosing schedule of 800 mg dosed on days 1 and 8 of a 21-day schedule resulted in serum concentrations that exceeded the 40-mg/L threshold indicated by preclinical experiments.

Pharmacokinetics of Isoniazid, Pyrazinamide, and Ethambutol in Newly Diagnosed Pulmonary TB Patients in Tanzania.

Exposure to lower-than-therapeutic levels of anti-tuberculosis drugs is likely to cause selection of resistant strains of Mycobacterium tuberculosis and treatment failure. The first-line anti-tuberculosis (TB) regimen consists of rifampicin, isoniazid, pyrazinamide, and ethambutol, and correct management reduces risk of TB relapse and development of drug resistance. In this study we aimed to investigate the effect of standard of care plus nutritional supplementation versus standard care on the pharmacokinetics of isoniazid, pyrazinamide and ethambutol among sputum smear positive TB patients with and without HIV. In a clinical trial in 100 Tanzanian TB patients, with or without HIV infection, drug concentrations were determined at 1 week and 2 months post initiation of anti-TB medication. Data was analysed using population pharmacokinetic modelling. The effect of body size was described using allometric scaling, and the effects of nutritional supplementation, HIV, age, sex, CD4+ count, weight-adjusted dose, NAT2 genotype, and time on TB treatment were investigated. The kinetics of all drugs was well characterised using first-order elimination and transit compartment absorption, with isoniazid and ethambutol described by two-compartment disposition models, and pyrazinamide by a one-compartment model. Patients with a slow NAT2 genotype had higher isoniazid exposure and a lower estimate of oral clearance (15.5 L/h) than rapid/intermediate NAT2 genotype (26.1 L/h). Pyrazinamide clearance had an estimated typical value of 3.32 L/h, and it was found to increase with time on treatment, with a 16.3% increase after the first 2 months of anti-TB treatment. The typical clearance of ethambutol was estimated to be 40.7 L/h, and was found to decrease with age, at a rate of 1.41% per year. Neither HIV status nor nutritional supplementations were found to affect the pharmacokinetics of these drugs in our cohort of patients.

Impact of nonlinear interactions of pharmacokinetics and MICs on sputum bacillary kill rates as a marker of sterilizing effect in tuberculosis.

The relationships between antituberculosis drug exposure and treatment effects on humans receiving multidrug therapy are complex and nonlinear. In patients on treatment, an analysis of the rate of decline in the sputum bacillary burden reveals two slopes. The first is the α-slope, which is thought to reflect bactericidal effect, followed by a ß-slope, which is thought to reflect sterilizing activity. We sought to characterize the effects of standard first-line treatment on sterilizing activity. Fifty-four patients receiving combination therapy for pulmonary tuberculosis in a clinical trial had drug concentrations measured and Mycobacterium tuberculosis isolates available for MIC identification. Sputum sample cultures were performed at baseline and weekly for 8 weeks. A time-to-event model based on the days to positivity in the liquid cultures was used to estimate the ß-slope. The pharmacokinetic parameters of rifampin, isoniazid, ethambutol, and pyrazinamide were determined for each patient. Multivariate adaptive regression splines analyses, which simultaneously perform linear and nonlinear analyses, were used to identify the relationships between the predictors and the ß-slope. The potential predictors examined included HIV status, lung cavitation, 24-h area under the concentration-time curve (AUC), peak drug concentration (Cmax), AUC/MIC ratio, Cmax/MIC ratio, and the time that that concentration persisted above MIC. A rifampin Cmax of >8.2 mg/liter and a pyrazinamide AUC/MIC of >11.3 were key predictors of the ß-slope and interacted positively to increase the ß-slope. In patients with a rifampin AUC of <35.4 mg · h/liter, an increase in the pyrazinamide AUC/MIC and/or ethambutol Cmax/MIC increased the ß-slope, while increasing isoniazid Cmax decreased it, suggesting isoniazid antagonism. Antibiotic concentrations and MICs interact in a nonlinear fashion as the main drivers of a sterilizing effect. The results suggest that faster speeds of sterilizing effect might be achieved by omitting isoniazid and by increasing rifampin, pyrazinamide, and ethambutol exposures. However, isoniazid and ethambutol exposures may only be of importance when rifampin exposure is low. These findings need confirmation in larger studies. (This study has been registered at controlled-trials.com under registration no. ISRCTN80852505.).

The pyrazinamide susceptibility breakpoint above which combination therapy fails.

OBJECTIVES: To identify the pyrazinamide MIC above which standard combination therapy fails. METHODS: MICs of pyrazinamide were determined for Mycobacterium tuberculosis isolates, cultured from 58 patients in a previous randomized clinical trial in Cape Town, South Africa. The MICs were determined using BACTEC MGIT 960 for isolates that were collected before standard treatment with isoniazid, rifampicin, pyrazinamide and ethambutol commenced. Weekly sputum collections were subsequently made for 8 weeks in order to culture M. tuberculosis in Middlebrook broth medium. Classification and regression tree (CART) analysis was utilized to identify the pyrazinamide MIC predictive of sputum culture results at the end of pyrazinamide therapy. The machine learning-derived susceptibility breakpoints were then confirmed using standard association statistics that took into account confounders of 2 month sputum conversion. RESULTS: The pyrazinamide MIC range was 12.5 to >100 mg/L for the isolates prior to therapy. The epidemiological 95% cut-off value was >100 mg/L. The 2 month sputum conversion rate in liquid cultures was 26% by stringent criteria and 48% by less stringent criteria. CART analysis identified an MIC breakpoint of 50 mg/L, above which patients had poor sputum conversion rates. The relative risk of poor sputum conversion was 1.5 (95% CI: 1.2-1.8) for an MIC >50 mg/L compared with an MIC ≤ 50 mg/L. CONCLUSIONS: We propose a pyrazinamide susceptibility breakpoint of 50 mg/L for clinical decision making and for development of rapid susceptibility assays. This breakpoint is identical to that identified using computer-aided simulations of hollow fibre system output.

Nutritional supplementation increases rifampin exposure among tuberculosis patients coinfected with HIV.

Nutritional supplementation to tuberculosis (TB) patients has been associated with increased weight and reduced mortality, but its effect on the pharmacokinetics of first-line anti-TB drugs is unknown. A cohort of 100 TB patients (58 men; median age, 35 [interquartile range {IQR}, 29 to 40] years, and median body mass index [BMI], 18.8 [17.3 to 19.9] kg/m(2)) were randomized to receive nutritional supplementation during the intensive phase of TB treatment. Rifampin plasma concentrations were determined after 1 week and 2 months of treatment. The effects of nutritional supplementation, HIV, time on treatment, body weight, and SLCO1B1 rs4149032 genotype were examined using a population pharmacokinetic model. The model adjusted for body size via allometric scaling, accounted for clearance autoinduction, and detected an increase in bioavailability (+14%) for the patients in the continuation phase. HIV coinfection in patients not receiving the supplementation was found to decrease bioavailability by 21.8%, with a median maximum concentration of drug in serum (Cmax) and area under the concentration-time curve from 0 to 24 h (AUC0-24) of 5.6 µg/ml and 28.6 µg · h/ml, respectively. HIV-coinfected patients on nutritional supplementation achieved higher Cmax and AUC0-24 values of 6.4 µg/ml and 31.6 µg · h/ml, respectively, and only 13.3% bioavailability reduction. No effect of the SLCO1B1 rs4149032 genotype was observed. In conclusion, nutritional supplementation during the first 2 months of TB treatment reduces the decrease in rifampin exposure observed in HIV-coinfected patients but does not affect exposure in HIV-uninfected patients. If confirmed in other studies, the use of defined nutritional supplementation in HIV-coinfected TB patients should be considered in TB control programs. (This study has the controlled trial registration number ISRCTN 16552219.).

Moxifloxacin population pharmacokinetics and model-based comparison of efficacy between moxifloxacin and ofloxacin in African patients.

Pharmacokinetic exposure and the MIC of fluoroquinolones are important determinants of their efficacy against Mycobacterium tuberculosis. Population modeling was used to describe the steady-state plasma pharmacokinetics of moxifloxacin in 241 tuberculosis (TB) patients in southern Africa. Monte Carlo simulations were applied to obtain the area under the unbound concentration-time curve from 0 to 24 h (fAUC0-24) after daily doses of 400 mg or 800 mg moxifloxacin and 800 mg ofloxacin. The MIC distributions of ofloxacin and moxifloxacin were determined for 197 drug-resistant clinical isolates of Mycobacterium tuberculosis. For a specific MIC, the probability of target attainment (PTA) was determined for target fAUC0-24/MIC ratios of ≥53 and ≥100. The PTAs were combined with the MIC distributions to calculate the cumulative fraction of response (CFR) for multidrug-resistant (MDR) Mycobacterium tuberculosis strains. Even with the less stringent target ratio of ≥53, moxifloxacin at 400 mg and ofloxacin at 800 mg achieved CFRs of only 84% and 58% for multidrug-resistant isolates with resistance to an injectable drug, while the 800-mg moxifloxacin dose achieved a CFR of 98%. Using a target ratio of ≥100 for multidrug-resistant strains (without resistance to injectable agents or fluoroquinolones), the CFR was 88% for moxifloxacin and only 43% for ofloxacin, and the higher dose of 800 mg moxifloxacin was needed to achieve a CFR target of >90%. Our results indicate that moxifloxacin is more efficacious than ofloxacin in the treatment of MDR-TB. Further studies should determine the optimal pharmacodynamic target for moxifloxacin in a multidrug regimen and clarify safety issues when it is administered at higher doses.