Time-varying brentuximab vedotin pharmacokinetics and weight-based dosing in paediatric patients despite lower exposure in those aged 2 to <6 and 6-11 years.

AIMS: We studied the pharmacokinetics and exposure-response relationships of the brentuximab vedotin (BV) antibody-drug conjugate (ADC) and unconjugated monomethyl auristatin E in haematologic malignancies. METHODS: This population pharmacokinetic analysis included data from five adult and three paediatric studies. Exposures in virtual adult and paediatric populations following BV 1.8 mg/kg (maximum 180 mg) intravenously every 3 weeks were simulated. Clinical endpoints included overall response rate, grade ≥2 peripheral neuropathy (PN) and grade ≥3 neutropenia. RESULTS: BV ADC exhibited linear pharmacokinetics, well-described by a three-compartment model, with body weight being the only significant covariate for exposure. Monomethyl auristatin E exhibited time-varying formation rate. Simulated steady-state BV ADC exposures in patients aged 12 to <18 years were similar to those of adult patients, but 23%-38% lower in patients aged 2 to <12 years. Despite lower exposure, clinical activity was observed with BV 1.8 mg/kg every 3 weeks in those aged 2 to <12 years (overall response rate: 2 to <12 years, 60%; 12 to <18 years, 43%). In adult, but not paediatric patients, increased BV ADC exposures were associated with grade ≥2 PN and grade ≥3 neutropenia occurrence. CONCLUSIONS: BV pharmacokinetics in adult and paediatric patients were consistent. BV ADC exposures were lower in patients aged 2 to <12 years vs. ≥12 years, but no apparent clinically relevant differences in efficacy, grade ≥2 PN or grade ≥3 neutropenia were observed. These data support body weight-based dosing of BV in patients irrespective of age; thus, dose adjustment in those 2 to <12 years does not appear warranted.

Population pharmacokinetic modelling of tremelimumab in patients with advanced solid tumours and the impact of disease status on time-varying clearance.

AIMS: Tremelimumab, a cytotoxic T-lymphocyte-associated protein 4 human monoclonal antibody of the immunoglobulin G2 κ isotype, has been studied in oncology clinical trials as both monotherapy and in combination with durvalumab. This study characterized the pharmacokinetics of tremelimumab as monotherapy and in combination with durvalumab and evaluated the impact of patient covariates on pharmacokinetics. METHODS: A pooled-analysis population pharmacokinetics model was built using NONMEM methodology. Pharmacokinetic data from 5 studies spanning different tumour types and therapy regimens were pooled for model development (956 patients). A dataset pooled from 4 additional studies was used for external validation (554 patients). Demographic and relevant clinical covariates were explored during model development. RESULTS: Tremelimumab exhibited linear pharmacokinetics, well described by a 2-compartment model, with time-varying clearance (0.276 L/day at baseline) associated primarily with therapy regimen and linked with changes in disease status. As monotherapy and combination therapy, tremelimumab clearance over 1 year increased by ~16% and decreased by ~17%, respectively. Pharmacokinetic behaviour was consistent across patient demographics and cancer subtypes. Patients with higher bodyweight and lower albumin levels at baseline had significantly higher clearance; however, no dosage adjustments are warranted. A flat dose (75 mg) was projected to provide comparable exposure to weight-based dosing (1 mg/kg) in adults. CONCLUSION: Tremelimumab exhibited linear pharmacokinetics but consistently opposite trends of time-varying clearance as monotherapy and in combination with durvalumab. Baseline bodyweight and albumin were significant covariates, but conversion from weight-based dosing at 1 mg/kg to flat dosing at 75 mg had no clinically relevant impact.

Phase II randomised trial of type I interferon inhibitor anifrolumab in patients with active lupus nephritis.

OBJECTIVE: To assess the efficacy and safety of the type I interferon receptor antibody, anifrolumab, in patients with active, biopsy-proven, Class III/IV lupus nephritis. METHODS: This phase II double-blinded study randomised 147 patients (1:1:1) to receive monthly intravenous anifrolumab basic regimen (BR, 300 mg), intensified regimen (IR, 900 mg ×3, 300 mg thereafter) or placebo, alongside standard therapy (oral glucocorticoids, mycophenolate mofetil). The primary endpoint was change in baseline 24-hour urine protein-creatinine ratio (UPCR) at week (W) 52 for combined anifrolumab versus placebo groups. The secondary endpoint was complete renal response (CRR) at W52. Exploratory endpoints included more stringent CRR definitions and sustained glucocorticoid reductions (≤7.5 mg/day, W24-52). Safety was analysed descriptively. RESULTS: Patients received anifrolumab BR (n=45), IR (n=51), or placebo (n=49). At W52, 24-hour UPCR improved by 69% and 70% for combined anifrolumab and placebo groups, respectively (geometric mean ratio=1.03; 95% CI 0.62 to 1.71; p=0.905). Serum concentrations were higher with anifrolumab IR versus anifrolumab BR, which provided suboptimal exposure. Numerically more patients treated with anifrolumab IR vs placebo attained CRR (45.5% vs 31.1%), CRR with UPCR ≤0.5 mg/mg (40.9% vs 26.7%), CRR with inactive urinary sediment (40.9% vs 13.3%) and sustained glucocorticoid reductions (55.6% vs 33.3%). Incidence of herpes zoster was higher with combined anifrolumab vs placebo (16.7% vs 8.2%). Incidence of serious adverse events was similar across groups. CONCLUSION: Although the primary endpoint was not met, anifrolumab IR was associated with numerical improvements over placebo across endpoints, including CRR, in patients with active lupus nephritis. TRIAL REGISTRATION NUMBER: NCT02547922.

Relationship of anifrolumab pharmacokinetics with efficacy and safety in patients with systemic lupus erythematosus.

OBJECTIVES: To characterize the relationship of anifrolumab pharmacokinetics with efficacy and safety in patients with moderate to severe SLE despite standard therapy, using pooled data from two phase 3 trials. METHODS: TULIP-1 and TULIP-2 were randomized, placebo-controlled, 52-week trials of intravenous anifrolumab (every 4 weeks for 48 weeks). For the exposure-response analysis, BILAG-based Composite Lupus Assessment (BICLA) or SLE Responder Index [SRI(4)] response rates at week 52 in each quartile/tertile of average anifrolumab serum concentration (Cave) were compared for anifrolumab and placebo in all-comers, patients who completed treatment, and IFN gene signature (IFNGS)-high patients who completed treatment, using average marginal effect logistic regression. Relationships between exposure and key safety events were assessed graphically. RESULTS: Of patients in TULIP-1/TULIP-2 who received anifrolumab (150 mg, n = 91; 300 mg, n = 356) or placebo (n = 366), 574 completed treatment, of whom 470 were IFNGS high. In the exposure-efficacy analyses, BICLA and SRI(4) treatment differences favouring anifrolumab 300 mg vs placebo were observed across Cave subgroups and all analysis populations. Logistic regression identified Cave as a significant covariate for predicted BICLA response, as higher anifrolumab Cave predicted greater efficacy. There was no evidence of exposure-driven incidence of key safety events through week 52 in patients receiving anifrolumab 150 or 300 mg. CONCLUSION: While higher Cave predicted greater efficacy, consistent positive benefit favouring anifrolumab 300 mg vs placebo was observed in BICLA and SRI(4) responses across Cave subgroups in the TULIP trials. There was no evidence of exposure-driven safety events. CLINICALTRIAL.GOV NUMBERS: NCT02446912, NCT02446899.

Exposure-response analysis for selection of optimal dosage regimen of anifrolumab in patients with systemic lupus erythematosus.

OBJECTIVES: The randomized, double-blind, phase 2 b MUSE study evaluated the efficacy and safety of the type I IFN receptor antibody anifrolumab (300 mg or 1000 mg every 4 weeks) compared with placebo for 52 weeks in patients with chronic, moderate to severe SLE. Characterizing the exposure-response relationship of anifrolumab in MUSE will enable selection of its optimal dosage regimen in two phase 3 studies in patients with SLE. METHODS: The exposure-response relationship, pharmacokinetics (PK) and SLE Responder Index (SRI(4)) efficacy data were analysed using a population approach. A dropout hazard function was also incorporated into the SRI(4) model to describe the voluntary patient withdrawals during the 1-year treatment period. RESULTS: The population PK model found that type I IFNGS-high patients, and patients with a higher body weight, had significantly greater clearance of anifrolumab. Stochastic clinical simulations demonstrated that doses <300 mg would lead to a greater-than-proportional reduction in drug exposure owing to type I IFN alpha receptor-mediated drug clearance (antigen-sink effect, more rapid drug clearance at lower concentrations) and suboptimal SRI(4) responses with wider confidence intervals. CONCLUSIONS: Based on PK, efficacy and safety considerations, anifrolumab 300 mg every 4 weeks was recommended as the optimal dosage for pivotal phase 3 studies in patients with SLE.

Population pharmacokinetics, efficacy, and safety of moxetumomab pasudotox in patients with relapsed or refractory hairy cell leukaemia.

AIMS: To characterize the pharmacokinetics (PK) of moxetumomab pasudotox, an anti-CD22 recombinant immunotoxin, in adults with relapsed or refractory hairy cell leukaemia, we examined data from a phase 1 study (Study 1001; n = 49) and from the pivotal clinical study (Study 1053; n = 74). METHODS: Data from both studies were pooled (n = 123) to develop a population PK model. Covariates included demographics, disease state, liver and kidney function, prior treatment, and antidrug antibodies (ADAs). Exposure-response and exposure-safety were analysed separately by study. A 1-compartment model with linear elimination from the central compartment and 2 clearance (CL) rates was developed. RESULTS: Moxetumomab pasudotox was cleared more rapidly after cycle 1, day 1 (CL1 = 24.7 L/h) than subsequently (CL2 = 3.76 L/h), with high interindividual variability (116 and 109%, respectively). In Study 1053, patients with ADA titres >10 240 showed ~4-fold increase in CL. Higher exposures (≥median) were related to higher response rates, capillary leak syndrome and increased creatinine (Study 1053 only), or grade ≥3 adverse events (Study 1001 only). Clinical benefits were still observed in patients with lower exposure or high ADA titres. CONCLUSION: Despite a high incidence of immunogenicity with increased clearance, moxetumomab pasudotox demonstrated efficacy in hairy cell leukaemia.

Two schedules of etirinotecan pegol (NKTR-102) in patients with previously treated metastatic breast cancer: a randomised phase 2 study.

BACKGROUND: New therapeutic options are needed for patients with heavily pretreated breast cancer. Etirinotecan pegol is a long-acting topoisomerase-I inhibitor designed to provide prolonged tumour-cell exposure to SN38, the active metabolite. We aimed to assess the efficacy and safety of two etirinotecan pegol dosing schedules in patients with previously treated metastatic breast cancer to determine an optimum dosing schedule for phase 3 trials. METHODS: In this randomised, two-stage, open-label phase 2 trial, we recruited patients aged 18 years or older who had received taxane therapy and undergone two or fewer previous chemotherapy regimens for metastatic breast cancer, with an Eastern Cooperative Oncology Group performance status of 0 or 1, from 18 sites in three countries. Eligible patients were randomly assigned (1:1) to etirinotecan pegol 145 mg/m(2) every 14 days or every 21 days. The primary endpoint was the proportion of patients with a confirmed objective response as defined by Response Evaluation Criteria in Solid Tumors version 1.0, analysed by intention to treat. Safety was assessed in all patients who received at least one dose of study drug. FINDINGS: 70 patients (35 in each group) were randomly assigned to treatment between Feb 17, 2009 and April 13, 2010. Of the 70 patients, 20 (29%; 95% CI 18·4-40·6) achieved an objective response (two [3%] had a complete response and 18 [26%] had a partial response). Ten patients on the 14-day schedule achieved an objective response (29%; 95% CI 14·6-46·3; eight partial responses, two complete responses) as did ten on the 21-day schedule (29%; 95% CI 14·6-46·3; all partial responses). The most common grade 3 or worse adverse events were delayed diarrhoea (seven [20%] of 35 patients on the 14-day schedule vs eight [23%] of 35 patients on the 21-day schedule), fatigue (five [14%] vs three [9%]), neutropenia (four [11%] vs four [11%]), and dehydration (three [9%] vs four [11%]); 14 [20%] patients discontinued treatment because of drug-related toxicity. There were two possible drug-related deaths (acute renal failure and septic shock) in the 14-day group; other drug-related serious adverse events reported by more than one patient included ten [14%] patients with diarrhoea (six [17%] patients on the 14-day schedule vs four [11%] on the 21-day schedule), six [9%] with dehydration (two [6%] vs four [11%]), two [3%] with nausea (two [6%] vs none), and two [3%] with vomiting (two [6%] vs none). INTERPRETATION: On the basis of the overall clinical data, pharmacokinetics, and tolerability profile, etirinotecan pegol 145 mg/m(2) every 21 days has been selected for a phase 3 trial against treatment of physician's choice in patients with advanced breast cancer.

Exposure-Response and Subgroup Analyses to Support Body Weight-Based Dosing of Brentuximab Vedotin in Children and Young Adults with Newly Diagnosed High-risk Classical Hodgkin Lymphoma.

PURPOSE: The purpose of the study was to evaluate the relationships between brentuximab vedotin (BV) pharmacokinetics, age, and body weight (BW) with efficacy and safety in pediatric and young adult patients with previously untreated, high-risk classical Hodgkin lymphoma in the phase III AHOD1331 study. EXPERIMENTAL DESIGN: Overall, 296 patients (age 2-21 years) in the overall population were randomized to and received BV + chemotherapy; the pharmacokinetic subpopulation comprised 24 patients (age <13 years). Age- and/or BW-based (pharmacokinetic surrogates) subgroup analyses of efficacy and safety were conducted for the overall population. Exposure-response analyses were limited to the pharmacokinetic subpopulation. RESULTS: There were no visible trends in disease characteristics across pediatric age subgroups, whereas BW increased with age. Observed antibody-drug conjugate exposures in patients ages <12 years were lower than those in adults administered BV 1.8 mg/kg every 3 weeks, as exposure increased with BW. Nevertheless, no detrimental impact on event-free survival was seen in younger subgroups: 3-year event-free survival rates were 96.2% (2-<12 years) and 92.0% (12-<18 years), with no events observed in those ages <6 years. Neither early response nor lack of need for radiation therapy was associated with high pharmacokinetic exposure. No evidence of exposure-driven grade ≥2 or ≥3 peripheral neuropathy or grade ≥3 neutropenia was seen in exposure-safety and BW-based subgroup analyses; the incidence of these safety events was comparable across pediatric age subgroups, despite lower exposure in younger children. CONCLUSIONS: No further adjustments based on age or BW are required for the BV dosage (1.8 mg/kg every 3 weeks) approved in children.

Safety, Tolerability, and Pharmacokinetics of Benralizumab: A Phase 1, Randomized, Single-Blind Study of Healthy Chinese Participants.

Purpose: Biological therapies targeting eosinophils have been shown to be effective in treating patients with severe eosinophilic asthma. Benralizumab (Fasenra®, AstraZeneca) is a humanized monoclonal antibody binding to the alpha subunit of the interleukin-5 receptor, which rapidly depletes eosinophils via antibody-dependent cellular cytotoxicity. The aim of this Phase 1 study was to assess the safety, tolerability, and pharmacokinetics of benralizumab in healthy Chinese individuals. Materials and Methods: In this randomized, single-blind study (NCT03928262), healthy Chinese adult participants aged 18 to 45 years, weighing 50 to 100 kg, were randomized 1:1:1 to receive a single subcutaneous (SC) injection of benralizumab 10 mg, 30 mg, or 100 mg in the upper arms on Day 1. Safety was monitored throughout the study (up to Day 85), and blood samples were taken to determine serum benralizumab concentrations and for detection of anti-drug antibody. A non-compartmental analysis was conducted to estimate the pharmacokinetic parameters. Results: Thirty-six healthy participants were enrolled, 12 in each dose group (mean [SD] age 26 [6] years). Following a single SC injection of benralizumab, 13 adverse events were reported by 10 participants (28%), with one mild injection-site reaction assessed as related. The mean serum benralizumab concentrations increased in a dose proportional manner, followed by exponential decreases. The mean terminal half-lives were 15.1 days for the 10 mg dose, 14.4 days for the 30 mg dose, and 15.4 days for the 100 mg dose. All doses resulted in near-complete depletion of eosinophils on Day 2, which was maintained throughout the study to Day 85. Conclusion: A single SC injection of benralizumab was well tolerated by healthy Chinese participants, with no new or unexpected safety findings. The pharmacokinetics of benralizumab in Chinese participants was dose-proportional and consistent with those of non-Chinese participants observed in previous studies. Clinical Trial Registration: NCT03928262 (https://clinicaltrials.gov/ct2/show/NCT03928262).

Relationship Between Anifrolumab Pharmacokinetics, Pharmacodynamics, and Efficacy in Patients With Moderate to Severe Systemic Lupus Erythematosus.

This study aimed to elucidate the pharmacokinetic/pharmacodynamic and pharmacodynamic/efficacy relationships of anifrolumab, a type I interferon receptor antibody, in patients with moderate to severe systemic lupus erythematosus. Data were pooled from the randomized, 52-week, placebo-controlled TULIP-1 and TULIP-2 trials of intravenous anifrolumab (150 mg/300 mg, every 4 weeks for 48 weeks). Pharmacodynamic neutralization was measured with a 21-gene type I interferon gene signature (21-IFNGS) in patients with high IFNGS. The pharmacokinetic/pharmacodynamic relationship was analyzed graphically and modeled with a nonlinear mixed-effects model. British Isles Lupus Assessment Group-based Composite Lupus Assessment (BICLA) response rates were compared across 21-IFNGS neutralization quartiles. Overall, 819 patients received ≥1 dose of anifrolumab or placebo, of whom 676 were IFNGS high. Over 52 weeks, higher average anifrolumab serum concentrations were associated with increased median 21-IFNGS neutralization, which was rapid and sustained with anifrolumab 300 mg (>80%, weeks 12-52), lower and delayed with anifrolumab 150 mg (>50%, week 52), and minimal with placebo. The proportion of patients with week 24 anifrolumab trough concentration exceeding the IC80 (3.88 µg/mL) was greater with anifrolumab 300 mg vs anifrolumab 150 mg (≈83% vs ≈27%), owing to the higher estimated median trough concentration (15.6 vs 0.2 µg/mL). BICLA response rates increased with 21-IFNGS neutralization; more patients had a BICLA response in the highest vs lowest neutralization quartiles at week 52 (58.1% vs 37.6%). In conclusion, anifrolumab 300 mg every 4 weeks rapidly, substantially, and sustainably neutralized the 21-IFNGS and was associated with clinical efficacy, supporting this dosing regimen in patients with systemic lupus erythematosus.

Nonlinear Population Pharmacokinetics of Anifrolumab in Healthy Volunteers and Patients With Systemic Lupus Erythematosus.

We characterized the population pharmacokinetics of anifrolumab, a type I interferon receptor-blocking antibody. Pharmacokinetic data were analyzed from the anifrolumab (intravenous [IV], every 4 weeks) arms from 5 clinical trials in patients with systemic lupus erythematosus (SLE) (n = 664) and healthy volunteers (n = 6). Population pharmacokinetic modeling was performed using a 2-compartment model with parallel linear and nonlinear elimination pathways. The impact of covariates (demographics, interferon gene signature [IFNGS, high/low], disease characteristics, renal/hepatic function, SLE medications, and antidrug antibodies) on pharmacokinetics was evaluated. Time-varying clearance (CL) was characterized using an empirical sigmoidal time-dependent function. Anifrolumab exposure increased more than dose-proportionally from 100 to 1000 mg IV every 4 weeks. Based on population pharmacokinetics modeling, the baseline median linear CL was 0.193 L/day in IFNGS-high patients and 0.153 L/day in IFNGS-low/healthy volunteers. After a year, median anifrolumab linear CL decreased by 8.4% from baseline. Body weight and IFNGS were significant pharmacokinetic covariates, whereas age, sex, race, disease activity, SLE medications, and presence of antidrug antibodies had no significant effect on anifrolumab pharmacokinetics. Anifrolumab at a concentration of 300 mg IV every 4 weeks was predicted to be below the lower limit of quantitation in 95% of patients ≈10 weeks after a single dose and ≈16 weeks after stopping dosing at steady state. To conclude, anifrolumab exhibited nonlinear pharmacokinetics and time-varying linear CL; doses ≥300 mg IV every 4 weeks provided sustained anifrolumab concentrations. This study provides further evidence to support the use of anifrolumab 300 mg IV every 4 weeks in patients with moderate to severe SLE.

Pharmacokinetics, pharmacodynamics, and safety of subcutaneous anifrolumab in patients with systemic lupus erythematosus, active skin disease, and high type I interferon gene signature: a multicentre, randomised, double-blind, placebo-controlled, phase 2 study.

BACKGROUND: 300 mg of intravenous anifrolumab every 4 weeks added to standard-of-care treatment for patients with systemic lupus erythematosus (SLE) reduced disease activity and glucocorticoid requirement in a previous phase 3 trial. Because patients might find subcutaneous administration more convenient than intravenous delivery, we aimed to evaluate the pharmacokinetics, pharmacodynamics, safety, and efficacy of subcutaneous anifrolumab in patients with SLE, active skin disease, and a high type I interferon gene signature. METHODS: This multicentre, randomised, double-blind, placebo-controlled, phase 2 study was done at 12 hospitals and outpatient clinics in Hungary, South Korea, Poland, and the USA. Eligible patients were aged 18-70 years, and had SLE with high type I interferon gene signature and an activity score on the Cutaneous Lupus Erythematosus Disease Area and Severity Index (CLASI) of at least 10. Enrolled participants were randomly assigned (3:1:3:1) by use of a voice-web response system to receive either 150 mg of subcutaneous anifrolumab or corresponding placebo, or 300 mg of subcutaneous anifrolumab or corresponding placebo in addition to stable standard-of-care treatment. The study was double-blinded with respect to intervention but not dose, until 12 weeks. Doses of oral glucocorticoids were tapered after week 12. The primary pharmacokinetic endpoint was the serum concentration of anifrolumab based on the maximum concentration after the first dose and the minimum (trough) concentration before subsequent doses and was measured in all patients who received anifrolumab and had at least one quantifiable serum pharmacokinetics observation following the first dose. The primary pharmacodynamic endpoint was neutralisation of the type I interferon pharmacodynamic signature at week 12 and was assessed in all patients with a high type I interferon pharmacodynamics signature at baseline based on a 21-gene test. Safety was evaluated in the full analysis set, which included all patients who received at least one dose of anifrolumab. This trial is completed and is registered at ClinicalTrials.gov, NCT02962960. FINDINGS: Between March 14, 2017, and Oct 26, 2017, 36 patients were randomly assigned to receive 150 mg of anifrolumab (n=14), 300 mg of anifrolumab (n=13), or placebo (n=9). Two patients in the anifrolumab 150 mg group were excluded from the pharmacodynamic analysis set (n=34). Ten (71%) of 14 patients in the anifrolumab 150 mg group, ten (77%) of 13 patients in the anifrolumab 300 mg group, and nine (100%) of the nine patients in the placebo group completed 52 weeks of treatment. At week 12, pre-dose mean trough serum concentrations of anifrolumab were more than dose proportional between the anifrolumab 150 mg group (19·82 µg/mL [SD 15·01]) and the anifrolumab 300 mg group (60·28 µg/mL [43·66]), and the pharmacokinetics were non-linear. At week 12, the median percentage neutralisation of the type I interferon gene signature was higher with 150 mg (88·0% [median absolute deviation 7·4]) and 300 mg (90·7% [3·3]) of anifrolumab than with placebo (18·5% [8·1]), and more patients in the anifrolumab 150 mg group and the anifrolumab 300 mg group than in the placebo group had neutralisation of 75% or more (eight [67%] of 12 vs ten [77%] of 13 vs one [11%] of nine). At least one adverse event was reported by 23 (85%) of 27 patients in the anifrolumab groups and by seven (78%) of nine patients in the placebo group; most adverse events were of mild-to-moderate severity. Serious adverse events were reported in six (22%) of 27 patients in the anifrolumab groups (four patients in the 150 mg group and two in the 300 mg group). No serious adverse events were reported in the placebo group. Herpes zoster infection was reported by three (11%) of 27 patients in the anifrolumab groups and by one (11%) of nine patients in the placebo group. There were no treatment-related deaths. INTERPRETATION: Anifrolumab, administered subcutaneously every 2 weeks to patients with SLE and moderate-to-severe skin manifestations, had non-linear pharmacokinetics that were more than dose proportional, and neutralised the type I interferon gene signature in a dose-dependent manner. The safety profile was consistent with previous studies of intravenous anifrolumab, supporting the continued development of anifrolumab as a subcutaneously administered therapy for patients with SLE. FUNDING: AstraZeneca.

A therapeutic drug monitoring algorithm for refining the imatinib trough level obtained at different sampling times.

BACKGROUND: Correlation analyses have demonstrated that maintaining an adequate imatinib (IM) trough concentration would be important for clinical response in patients with chronic myeloid leukemia (CML) and Kit-positive gastrointestinal stromal tumors. The objectives of the current work were to use a pharmacokinetic model to refine the trough levels obtained at different sampling times and to propose a therapeutic drug monitoring algorithm and an acceptable sampling time window for imatinib trough sampling. METHODS: The pharmacokinetics of IM in patients (pts) with CML were characterized based on historical data from a Phase III study. In the elimination phase the concentration of IM (C(t)) follows a mono-exponential decline, and the standardized trough concentration (C(min,std) = C(tau)) can be described by a simple algorithm C(min,std) = C(t)* exp(k(e) x Delta t), where Delta t = t - tau, and tau is 24 hours for qd or 12 hours for bid dosing and k(e) is the elimination rate constant. The percent deviation of C(t) from C(min,std) was simulated for different Delta t and k(e) values to define a sampling time window Delta t, within which the percent deviation is <20%. RESULTS: Simulation analysis shows that C(t) is largely dependent on Delta t and k(e). The percent deviation of C(t) at 3 hours before or after tau from C(min,std) will be 7.1%, 13.1%, and 23.4% for pts with low, typical, and high k(e) values, 0.023/hour, 0.041/hour, and 0.070/hour, respectively. However, if a correction is made for C(t) by the algorithm using the typical k(e) value of 0.041 per hour, the percent deviation at 3 hours will be reduced to 5.3%, 0%, and 9.1% for pts with low, typical, and high k(e) values, respectively. Even if the sampling window is extended to +/-6 hours, the corresponding percent deviation will still be reasonable: 10.2%, 0%, and 19.0%, respectively. CONCLUSION: By using the algorithm, the pharmacokinetic sampling window can be extended to a wider window to make the trough sampling easy to implement in the clinical setting, provided that the sampling time and dosing time are accurately recorded.

Population Pharmacokinetic Modeling of Benralizumab in Adult and Adolescent Patients with Asthma.

INTRODUCTION: Benralizumab, an interleukin-5 receptor alpha-directed cytolytic anti-eosinophil monoclonal antibody, was recently approved as add-on maintenance treatment for patients aged 12 years and older with uncontrolled asthma with eosinophilic inflammation. METHODS: Pharmacokinetic (PK) data from nine clinical trials for patients with asthma were pooled and analyzed to further characterize the PK of benralizumab and evaluate demographic covariate effects. RESULTS: Population modeling results demonstrated that the PK of benralizumab were dose-proportional across a wide dosage range and were adequately described by a two-compartment model with first-order absorption from the subcutaneous dosing site and a first-order elimination pathway from the central compartment. Following subcutaneous administration, the absorption half-life of benralizumab was 3.54 days, and the absolute bioavailability was 58.9%. Estimated clearance (CL; 0.291 L/day), central volume of distribution (Vc; 3.13 L), and peripheral volume of distribution (Vp; 2.52 L) were typical for therapeutic immunoglobulins. Elimination half-life was approximately 15.5 days for patients with asthma. Age, sex, race, liver function, renal function, baseline blood eosinophil count, anatomic injection site, and commonly used small-molecule drugs had no clinically relevant impact on benralizumab CL. Only body weight and antidrug antibodies (ADAs) were identified as relevant PK covariates. Power parameters (exponent) of body weight on CL, Vc, and Vp were 0.807, 0.803, and 0.528, respectively, and the presence of ADAs increased benralizumab CL by 124%. CONCLUSIONS: Over 5-20 weeks, the PK of benralizumab were dose-proportional across a dosage range of 0.03-3 mg/kg intravenously and 2-200 mg subcutaneously administered every 4 weeks or every 8 weeks (first three doses every 4 weeks). Body weight and ADA status were identified as relevant PK covariates. Baseline eosinophil count, hepatic and renal functions, anatomical subcutaneous injection site, and commonly used small-molecule drugs had no impact on the PK of benralizumab.

Relationship Between Benralizumab Exposure and Efficacy for Patients With Severe Eosinophilic Asthma.

We evaluated the relationship between benralizumab (30 mg every 4 and 8 weeks (Q4W, Q8W)) pharmacokinetic (PK) exposure and end points of asthma exacerbation rates (AERs) and change from baseline in prebronchodilator forced expiratory volume in 1 second (FEV1 ) for patients with severe, uncontrolled eosinophilic asthma in the SIROCCO/CALIMA phase III trials. In empirical assessment, AER ratios in SIROCCO were similar across PK quartiles. However, the lowest PK quartile in CALIMA had reduced efficacy; low CALIMA placebo AER possibly confounded this result. In population modeling, estimated benralizumab 90% effective concentration for AER reduction was 927 ng/mL, below the Q8W dosage steady-state average PK concentration (1,066 ng/mL). Benralizumab treatment resulted in more rapid FEV1 improvement vs. placebo (estimated half-maximum time: 7.6 vs. 18 days); this response was greater for patients with greater baseline eosinophil counts. These results confirmed 30 mg Q8W is the optimal benralizumab dosage for patients with severe eosinophilic asthma.

Integrated population pharmacokinetics of etirinotecan pegol and its four metabolites in cancer patients with solid tumors.

PURPOSE: Etirinotecan pegol (EP), a long-acting topoisomerase-1 inhibitor, is a polyethylene glycol conjugate of irinotecan, with an intended indication for treatment of breast cancer with brain metastases. The objective of this study was to develop a population pharmacokinetic (popPK) model of EP and four of its metabolites (irinotecan, SN38, SN38-glucuronide, and APC) and determine covariates affecting their pharmacokinetics. METHODS: Data from 83 cancer patients enrolled in phase 1 studies were used. The model was developed in two stages: (1) concentration-time data were analyzed with a 3-analyte model for EP, irinotecan, and SN38; and (2) a 5-analyte model developed based on expansion of 3-analyte model to include concentration-time data for SN38 glucuronide and APC with parameter values from 3-analyte model fixed. Covariate relationships with parameters were selected based on Wald's test within the Wald's Approximation Method approach, first for the 3-analyte model then the 5-analyte model. RESULTS: The final integrated popPK model for the five analytes was a two-compartment per analyte model that followed the metabolic cascade of EP to irinotecan, followed by metabolism of irinotecan to the previously known metabolites, but with altered exposures as compared to administration of irinotecan. With the model developed based on total dose of EP, the population estimates of EP clearance and central volume were 0.237 L/h and 5.5 L, respectively. Patient age, body surface area (BSA), and estimated glomerular filtration rate were found to correlate with EP clearance and BSA with EP central volume. Individuals who were homozygous for UGT1A1*28 genotype had modestly reduced elimination capacity of SN38 compared to heterozygous and wild-type genotypes. Simulations evaluating the clinical importance of significant covariates indicated minimal change in areas under the curve and peak concentrations of EP and SN38. CONCLUSIONS: The pharmacokinetics of EP and four metabolites including the active metabolite SN38 were described by an integrated popPK model. Other than BSA, which was already accounted by a BSA-based dosing scheme, no other covariates were deemed to have clinical implications. No EP starting dose adjustment based on patient demographics and other covariates was deemed necessary.

Simulation-based parameter estimation for complex models: a breast cancer natural history modelling illustration.

Simulation-based parameter estimation offers a powerful means of estimating parameters in complex stochastic models. We illustrate the application of these ideas in the setting of a natural history model for breast cancer. Our model assumes that the tumor growth process follows a geometric Brownian motion; parameters are estimated from the SEER registry. Our discussion focuses on the use of simulation for computing the maximum likelihood estimator for this class of models. The analysis shows that simulation provides a straightforward means of computing such estimators for models of substantial complexity.

The effect of age, race, tumor size, tumor grade, and disease stage on invasive ductal breast cancer survival in the U.S. SEER database.

PURPOSE: To examine the effect of patient and tumor characteristics on breast cancer survival as recorded in the U.S. National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) database from 1973 to 1998. METHODS: A sample of 72,367 female cases from 1973 to 1998 aged 21-90 years with invasive ductal breast cancer were examined with Cox proportional hazards regression to determine the effect of age at diagnosis, race, tumor size, tumor grade, disease stage, and year of diagnosis on disease-specific survival. RESULTS: Larger tumor size and higher tumor grade were found to have large negative effects on survival. Blacks had a 47 % greater risk of death than whites. Year of diagnosis had a positive effect, with a 15 % reduction in risk for each decade in the time period under study. The effects of patient age and disease stage violated the proportional hazards assumption, with distant disease having much poorer short-term survival than one would expect from a proportional hazards model, and younger age groups matching or even falling below the survival rate of the oldest group over time. CONCLUSION: Tumor size, grade, race, and year of diagnosis all have significant constant effects on disease-specific survival in breast cancer, while the effects of age at diagnosis and disease stage have significant effects that vary over time.