Regorafenib plus Vincristine and Irinotecan in Pediatric Patients with Recurrent/Refractory Solid Tumors: An Innovative Therapy for Children with Cancer Study.

PURPOSE: This phase Ib study defined the safety, MTD, and recommended phase II dose (RP2D) of regorafenib combined with vincristine and irinotecan (VI). Secondary objectives were evaluation of antitumor activity and pharmacokinetics (PK) of regorafenib and irinotecan. PATIENTS AND METHODS: Patients aged 6 months to <18 years with relapsed/refractory solid malignancies [≥50% with rhabdomyosarcoma (RMS)] received regorafenib (starting dose 72 mg/m2/day) concomitantly or sequentially with vincristine 1.5 mg/m2 on days 1 and 8, and irinotecan 50 mg/m2 on days 1-5 (21-day cycle). Adverse events (AE) and tumor response were assessed. PK (regorafenib and irinotecan) were evaluated using a population PK model. RESULTS: We enrolled 21 patients [median age, 10 years; 12, RMS; 5, Ewing sarcoma (EWS)]. The MTD/RP2D of regorafenib in the sequential schedule was 82 mg/m2. The concomitant dosing schedule was discontinued because of dose-limiting toxicities in 2 of 2 patients treated. Most common grade 3/4 (>30% of patients) AEs were neutropenia, anemia, thrombocytopenia, and leukopenia. The overall response rate was 48% and disease control rate [complete response (CR)/partial response/stable disease/non-CR/non-progressive disease] was 86%. Median progression-free survival was 7.0 months [95% confidence interval (CI), 2.9-14.8] and median overall survival was 8.7 months (95% CI, 5.5-16.3). When combined with VI, regorafenib PK was similar to single-agent PK in children and adults (treated with regorafenib 160 mg/day). CONCLUSIONS: Regorafenib can be combined sequentially with standard dose VI in pediatric patients with relapsed/refractory solid tumors with appropriate dose modifications. Clinical activity was observed in patients with RMS and EWS (ClinicalTrials.gov NCT02085148).

Regorafenib plus nivolumab in patients with mismatch repair-proficient/microsatellite stable metastatic colorectal cancer: a single-arm, open-label, multicentre phase 2 study.

Background: Anti-programmed cell death protein 1 antibodies plus multikinase inhibitors have shown encouraging activity in several tumour types, including colorectal cancer. This study assessed regorafenib plus nivolumab in patients with microsatellite stable/mismatch repair-proficient metastatic colorectal cancer. Methods: This single-arm, open-label, multicentre phase 2 study enrolled adults from 13 sites in the USA with previously treated advanced microsatellite stable/mismatch repair-proficient metastatic colorectal cancer. Eligible patients had known extended RAS and BRAF status, progression or intolerance to no more than two (for extended RAS mutant) or three (for extended RAS wild type) lines of systemic chemotherapy and an Eastern Cooperative Oncology Group performance status of 0 or 1. Regorafenib 80 mg/day was administered orally for 3 weeks on/1 week off (increased to 120 mg/day if 80 mg/day was well tolerated) with intravenous nivolumab 480 mg every 4 weeks. Primary endpoint was objective response rate. Secondary endpoints included safety, overall survival, and progression-free survival. Exploratory endpoints included biomarkers associated with antitumour activity. Patients who received at least one dose of study intervention were included in the efficacy and safety analyses. Tumour assessments were carried out every 8 weeks for the first year, and every 12 weeks thereafter until progressive disease/end of the study, and objective response rate was analysed after all patients had met the criteria for primary completion of five post-baseline scans and either 10-months' follow-up or drop out. This trial is registered with ClinicalTrials.gov, number NCT04126733. Findings: Between 14 October 2019 and 14 January 2020, 94 patients were enrolled, 70 received treatment. Five patients had a partial response, yielding an objective response rate of 7% (95% CI 2.4-15.9; p = 0.27). All responders had no liver metastases at baseline. Median overall survival (data immature) and progression-free survival were 11.9 months (95% CI 7.0-not evaluable) and 1.8 months (95% CI 1.8-2.4), respectively. Most patients (97%, 68/70) experienced a treatment-related adverse event; 51% were grade 1 or 2, 40% were grade 3, 3% were grade 4, and 3% were grade 5. The most common (≥20%) events were fatigue (26/70), palmar-plantar erythrodysesthesia syndrome (19/70), maculopapular rash (17/70), increased blood bilirubin (14/70), and decreased appetite (14/70). Higher baseline expression of tumour biomarkers of immune sensitivity correlated with antitumour activity. Interpretation: Further studies are warranted to identify subgroups of patients with clinical characteristics or biomarkers that would benefit most from treatment with regorafenib plus nivolumab. Funding: Bayer/Bristol Myers Squibb.

Assessment of the safe and efficacious dose of the selective progesterone receptor modulator vilaprisan for the treatment of patients with uterine fibroids by exposure-response modelling and simulation.

AIMS: We report population pharmacokinetic (popPK) and exposure-response (E-R) analyses for efficacy (induced amenorrhoea [IA]) and safety (unbound oestradiol [E2] concentrations) of the selective progesterone receptor modulator vilaprisan. Results were used to inform the dose for the Phase 3 programme in patients with uterine fibroids. METHODS: A popPK model was developed using data from Phase 1 and 2 studies (including ASTEROID 1 and 2). The relationship between vilaprisan exposure (steady-state AUC) and IA after oral administration of 0.5, 1, 2 or 4 mg/day over 3 months was analysed in ASTEROID 1 using logistic regression and qualified in ASTEROID 2 by comparing simulated and observed probability for IA after 2 mg/day. The exposure-E2 relationship was analysed visually. RESULTS: Vilaprisan clearance was 22.7% lower in obese vs non-obese patients. The E-R relationship for IA in ASTEROID 1 was steep and consistent with ASTEROID 2, with a maximum probability (Pmax ) of 59% (95% CI: 49-68%). The exposure at which 50% of Pmax is obtained was 36.9 µg*h/L (95% CI: 27.7-48.7 µg*h/L). Simulations showed that 36% of the patients will be below 90% of Pmax for IA after 1 mg/day compared to 2% after 2 mg/day. E2 levels tended to decrease with increasing exposure. While E2 levels remained largely within the physiologic follicular phase range, the clinical relevance of this decrease will be evaluated in long-term studies. CONCLUSIONS: A 2 mg/day dose was selected for Phase 3 as E-R analyses show this dose results in a close to maximum probability for IA, without any safety concerns noted.

Clinical Pharmacokinetics and Pharmacodynamics of the Selective Progesterone Receptor Modulator Vilaprisan: A Comprehensive Overview.

Vilaprisan is a highly potent selective progesterone receptor modulator in development for the treatment of symptomatic uterine fibroids and endometriosis. Its pharmacokinetics are characterized by rapid absorption, almost complete bioavailability, and dose-proportional exposure. The intrinsic factors of age, bodyweight, and race have no clinically relevant effect on the pharmacokinetics and pharmacodynamics of vilaprisan and do not warrant a dose adjustment. Similarly, vilaprisan can be used in patients with mild or moderate renal or hepatic impairment without dose adjustment, but its use is not recommended in patients with severe organ impairment. Vilaprisan has no perpetrator potential on cytochrome P450 (CYP) enzymes or transporters and therefore restrictions in the concomitant use of their substrates are not required. Nonetheless, because it is a sensitive CYP3A4 substrate itself, concomitant use of vilaprisan with strong CYP3A inhibitors or inducers is not recommended. However, there is no risk for QTc prolongation when vilaprisan and a strong CYP3A inhibitor are administered concomitantly, as indicated by a vilaprisan concentration-QTc response analysis across all studies with triplicate electrocardiogram measurements. Furthermore, due to its mode of action, vilaprisan is also not recommended to be used together with progestin-containing oral contraceptives. Vilaprisan shows a steep exposure-response relationship for inducing amenorrhea in patients with uterine fibroids experiencing heavy menstrual bleeding. Based on simulations, a dose of 2 mg/day is expected to induce a maximum bleeding reduction and was thus selected for phase III.

Phase 1 dose-escalation and pharmacokinetic study of regorafenib in paediatric patients with recurrent or refractory solid malignancies.

BACKGROUND: This phase 1 study evaluated safety, pharmacokinetics (PK), maximum tolerated dose (MTD), and antitumour activity of regorafenib in paediatric patients with solid tumours. PATIENTS AND METHODS: Patients (aged 6 months to <18 years) with recurrent/refractory solid tumours received oral regorafenib once daily for 3 weeks on/1 week off. The starting dose (60 mg/m2) was derived from an adult physiology-based PK model and scaled to children; dose escalation was followed by safety expansion of the MTD cohort. Treatment-emergent adverse events (TEAEs) were evaluated using National Cancer Institute Common Terminology Criteria for Adverse Events version 4.0. Regorafenib PK was evaluated using a population PK model. RESULTS: Forty-one patients (median age 13 years) received regorafenib (four cohorts: 60-93 mg/m2). Five of 23 evaluable patients experienced dose-limiting toxicities (Grade 4 thrombocytopenia, Grade 3 maculopapular rash, pyrexia, hypertension, and exfoliative dermatitis [each n = 1]). The MTD was defined as 82 mg/m2. The most common Grade ≥3 drug-related TEAE was thrombocytopenia (10%). The incidence and severity of hypertension, diarrhoea, fatigue, hypothyroidism, and hand-foot skin reaction were lower than reported in adults. Regorafenib exposure increased with dose, with substantial overlap because of moderate-to-high interpatient variability. One patient with rhabdomyosarcoma experienced an unconfirmed partial response; 15 patients had stable disease, five for >16 weeks. CONCLUSIONS: The recommended phase 2 dose of single-agent regorafenib in paediatric patients with solid malignancies is 82 mg/m2. Regorafenib demonstrated acceptable tolerability and preliminary antitumour activity, supporting further investigation in paediatric patients. CLINICAL TRIAL NUMBER: NCT02085148.

NT-proBNP Qualifies as a Surrogate for Clinical End Points in Heart Failure.

N-terminal pro-B-type natriuretic peptide (NT-proBNP) is a well-established biomarker in heart failure (HF) but controversially discussed as a potential surrogate marker in HF trials. We analyzed the NT-proBNP/mortality relationship in real-world data (RWD) of 108,330 HF patients from the IBM Watson Health Explorys database and compared it with the NT-proBNP / clinical event end-point relationship in 20 clinical HF studies. With a hierarchical statistical model, we quantified the functional relationship and interstudy variability. To independently qualify the model, we predicted outcome hazard ratios in five phase III HF studies solely based on NT-proBNP measured early in the respective study. In RWD and clinical studies, the relationship between NT-proBNP and clinical outcome is well described by an Emax model. The NT-proBNP independent baseline risk (R0 , RWD/studies median (interstudy interquartile range): 5.5%/3.0% (1.7-4.9%)) is very low compared with the potential NT-proBNP-associated maximum risk (Rmax : 55.2%/79.4% (61.5-89.0%)). The NT-proBNP concentration associated with the half-maximal risk is comparable in RWD and across clinical studies (EC50 : 3,880/2,414 pg/mL (1,460-4,355 pg/mL)). Model-based predictions of phase III outcomes, relying on short-term NT-proBNP data only, match final trial results with comparable confidence intervals. Our analysis qualifies NT-proBNP as a surrogate for clinical outcome in HF trials. NT-proBNP levels after short treatment durations of less than 10 weeks quantitatively predict hazard ratios with confidence levels comparable to final trial readout. Early NT-proBNP measurement can therefore enable shorter and smaller but still reliable HF trials.

Population pharmacokinetics of regorafenib in solid tumours: Exposure in clinical practice considering enterohepatic circulation and food intake.

AIM: Regorafenib is an oral multikinase inhibitor with clinical efficacy in a range of advanced solid tumours. A population pharmacokinetic (PK) model was developed to evaluate the variability of the PK of regorafenib and its pharmacologically active metabolites M-2 and M-5 in solid tumours. METHODS: The model was initially developed using densely sampled phase 1 data and information on food intake to incorporate enterohepatic circulation (EHC) that was identified to considerably contribute to the PK of regorafenib. This was then applied to sparsely sampled data from four phase 3 studies in patients with advanced solid tumours. The need for exact food intake data to estimate individual drug exposure was evaluated. RESULTS: By incorporating EHC, the model adequately described the PK profiles of regorafenib, M-2 and M-5 after single and multiple doses in patients from phase 1 studies. Individual exposure in phase 3 studies was adequately described based on assumptions on the time and frequency of food intake, although exact food intake data are recommended to improve the estimation. Covariate analysis identified sex and body mass index (BMI) as impacting exposure to regorafenib, and sex as strongly impacting exposure to M-2 and M-5 (also influenced by the BMI effect on parent regorafenib in the joint model developed); however, these factors accounted for a small portion of the overall variability in exposure. CONCLUSIONS: The adequate description of regorafenib PK after multiple dosing requires the incorporation of EHC. Neither single nor combined covariates predicted exposures that would warrant a priori regorafenib dose adjustment.

Population Pharmacokinetic and Exposure-Response Analysis of Finerenone: Insights Based on Phase IIb Data and Simulations to Support Dose Selection for Pivotal Trials in Type 2 Diabetes with Chronic Kidney Disease.

BACKGROUND: Finerenone (BAY 94-8862) is a potent non-steroidal, selective mineralocorticoid receptor antagonist being developed for the treatment of patients with type 2 diabetes and chronic kidney disease. METHODS: We present the population pharmacokinetics and pharmacodynamics (PD) analysis for efficacy and safety markers based on data from two clinical phase IIb studies: ARTS-DN (NCT01874431) and ARTS-DN Japan (NCT01968668). RESULTS: The pharmacokinetics of finerenone were adequately characterized, with estimated glomerular filtration rate (eGFR) and body weight as influencing covariates. The area under the plasma concentration-time curve in Japanese patients did not differ from that in the global population, and the investigated pharmacokinetics were dose- and time-linear. In addition, the pharmacokinetic model provided robust individual exposure estimates to study exposure-response. The concentration-effect relationship over time for the efficacy marker urinary albumin:creatinine ratio (UACR) was well-characterized by a maximum effect model indicating saturation at high exposures. For the safety markers, a log-linear model and a power model were identified for serum potassium concentration and eGFR, respectively, indicating attenuation of effect gains at high exposures. There was no apparent ethnic effect on the investigated pharmacokinetic-pharmacodynamic relationships. The model-predicted times to reach the full (99%) steady-state drug effect on UACR, serum potassium, and eGFR were 138, 20, and 85 days, respectively, while the pharmacokinetic half-life was 2-3 h and steady state was achieved after 2 days, indicating timescale separation. CONCLUSION: Our dose-exposure-response modeling and simulation indicates effects were largely saturated at finerenone 20 mg and doses of both 10 and 20 mg once daily appear safe and efficacious at reducing albuminuria.

Evaluation of Clinically Relevant Drug-Drug Interactions and Population Pharmacokinetics of Darolutamide in Patients with Nonmetastatic Castration-Resistant Prostate Cancer: Results of Pre-Specified and Post Hoc Analyses of the Phase III ARAMIS Trial.

BACKGROUND: Darolutamide, an androgen receptor antagonist with a distinct molecular structure, significantly prolonged metastasis-free survival versus placebo in the phase III ARAMIS study in men with nonmetastatic castration-resistant prostate cancer (nmCRPC). In this population, polypharmacy for age-related comorbidities is common and may increase drug-drug interaction (DDI) risks. Preclinical/phase I study data suggest darolutamide has a low DDI potential-other than breast cancer resistance protein/organic anion transporter protein substrates (e.g., statins), no clinically relevant effect on comedications is expected. OBJECTIVE: Our objective was to evaluate the effect of commonly administered drugs on the pharmacokinetics of darolutamide and the effect of comedications potentially affected by darolutamide on safety in patients with nmCRPC. PATIENTS AND METHODS: Comorbidities and comedication use in the 1509 ARAMIS participants treated with darolutamide 600 mg twice daily or placebo were assessed. A population pharmacokinetic analysis evaluated whether comedications affected the pharmacokinetics of darolutamide in a subset of 388 patients. A subgroup analysis of adverse events (AEs) in statin users versus nonusers was conducted. RESULTS: Most participants (median age 74 years) had at least one comorbidity (98.4% in both arms) and used at least one comedication (98.7% with darolutamide vs. 98.0% with placebo); these were similar across study arms. Despite frequent use of comedications with DDI potential, no significant effects on darolutamide pharmacokinetics were identified. Comedications included lipid-modifying agents (34.5%), ß-blockers (29.7%), antithrombotics (42.8%), and systemic antibiotics (26.9%). AE incidence was similar across study arms in statin users and nonusers. Study limitations include the small sample size for sub-analyses. CONCLUSIONS: These analyses suggest the pharmacokinetic profile of darolutamide is not affected by a number of commonly administered drugs in patients with nmCRPC. Although pharmacokinetic data have indicated that darolutamide has the potential to interact with rosuvastatin, used to assess DDI in these studies, this finding did not seem to translate into increased AEs due to statin use in the ARAMIS trial. Clinicaltrials.gov identifier: NCT02200614.

BACKGROUND: Darolutamide is a medicine used to treat men with prostate cancer that has not spread to other parts of the body (nonmetastatic). Often, these patients are taking other medicines for common age-related illnesses. Taking more than one medicine at the same time increases the chances of what is known as drug­drug interactions. Drug­drug interactions can decrease how well the medicines work or may sometimes increase side effects. STUDY AIM: To test for possible drug­drug interactions in men with prostate cancer who take darolutamide alongside other medicines. STUDY PARTICIPANTS: Men with nonmetastatic prostate cancer who were being treated with a medicine that lowers testosterone, a chemical in the body that causes prostate cancer tumors to grow. Participants took two darolutamide 300 mg tablets, or an inactive placebo, twice a day. WHAT DID THE RESEARCHERS MEASURE?: The researchers documented the number of medicines taken by each participant and the number of other medical conditions that they had. Tests were done to find out whether other medicines affected the way that darolutamide works in the body and whether patients taking darolutamide alongside other medicines experienced more side effects. RESULTS: As would be expected, based on the typical age of patients with prostate cancer, more than 90% of participants in this study used medicines other than darolutamide to manage common age-related illnesses or medical conditions. Taking medicines alongside darolutamide did not impact how darolutamide worked in the body and did not increase the number of side effects experienced by patients. Darolutamide is known to interact with rosuvastatin, a cholesterol-lowering drug. However, in this study, there was no overall increase in side effects among darolutamide-treated patients who took this type of drug compared with in those who did not. CONCLUSION: In this study of patients with nonmetastatic prostate cancer, limited drug­drug interactions were seen when taking darolutamide alongside other medicines given to these patients to manage age-related medical conditions.

Exposure-Response Modeling and Simulation of Progression-Free Survival and Adverse Events of Sorafenib Treatment in Patients With Advanced Thyroid Cancer.

Sorafenib is an oral multikinase inhibitor approved for the treatment of differentiated thyroid carcinoma (DTC), renal cell carcinoma, and hepatocellular carcinoma. In the phase III DECISION trial in patients with DTC, sorafenib exposure and the incidence of some adverse events (AEs) were higher than in previous trials; therefore, we analyzed exposure-response relationships, including progression-free survival (PFS) and selected AEs in patients with DTC. A novel, stratified prediction-corrected visual predictive check (pc-VPC) was developed to show robustness of the exposure-response relationships. Time-to-event simulations confirmed the benefit of the recommended dosing schedule of 800 mg/day: initial doses of 800 mg/day were associated with the highest PFS, whereas lower doses (600 or 400 mg/day) were associated with improved tolerability but reduced PFS. A simulated dose-reduction strategy of 800 mg/day for an initial two cycles followed by dose reductions seemed likely to maintain efficacy while possibly mitigating selected AEs (e.g., diarrhea and hand-foot skin reactions).

CYP3A4-mediated effects of rifampicin on the pharmacokinetics of vilaprisan and its UGT1A1-mediated effects on bilirubin glucuronidation in humans.

AIMS: The primary aim of the present study was to quantify the effects of rifampicin, a strong cytochrome P450 (CYP) 3A4 inducer, on the pharmacokinetics of the new selective progesterone receptor modulator, vilaprisan. In addition, the effects of rifampicin on the glucuronidation of bilirubin, an endogenous UDP-glucuronosyltransferase family 1 member A1 (UGT1A1) substrate, were explored. METHODS: This was an open-label, two-period study in 12 healthy postmenopausal women. Subjects received a single oral dose of vilaprisan 4 mg in each period. In period 2, administration of vilaprisan was preceded and followed by rifampicin 600 mg day-1 . A subtherapeutic dose of midazolam (1 mg) was coadministered with vilaprisan to monitor CYP3A4 induction. Details of the administration and sampling schedule were optimized by means of a physiologically based pharmacokinetic model. Plasma concentrations of vilaprisan, midazolam, and 1'- hydroxy-midazolam were measured and rifampicin-associated changes in the glucuronidation of bilirubin were determined. RESULTS: As predicted by our model, the coadministration of rifampicin was associated with a substantial decrease in exposure to vilaprisan and midazolam - indicated by the following point estimates (90% confidence intervals) for the area under the plasma concentration-time curve from zero to the time of the last quantifiable concentration ratio with or without rifampicin: 0.040 (0.0325, 0.0505) for vilaprisan and 0.144 (0.117, 0.178) for midazolam. Further, it was associated with an increase in bilirubin glucuronidation, indicating that UGT1A1 was induced. CONCLUSIONS: The exposure to vilaprisan was reduced by 96%. Such a reduction is likely to render the drug therapeutically ineffective. Therefore, it is recommended that the use of strong CYP3A4 inducers is avoided when taking vilaprisan.

Exposure-response relationship of regorafenib efficacy in patients with hepatocellular carcinoma.

PURPOSE: To explore the relationship between regorafenib exposure and efficacy in patients with hepatocellular carcinoma (HCC) who had disease progression during sorafenib treatment (RESORCE). METHODS: Exposure-response (ER) analyses for regorafenib were performed using data from a phase 3, randomized, placebo-controlled trial (RESORCE). Patients received 160mg regorafenib or placebo once daily (3weeks on/1week off in a 4-week cycle) with best supportive care until disease progression, death, or unacceptable toxicity. Kaplan-Meier analyses for overall survival (OS) and time-to-progression (TTP) were performed in which regorafenib-treated patients were grouped into four categories according to their estimated average exposure over 4weeks in cycle 1. While this analysis primarily focused on efficacy, a potential correlation between exposure and treatment-emergent adverse events (TEAEs) was also evaluated. If any differences were observed between Kaplan-Meier plots, the ER analysis continued with a multivariate Cox regression analysis to evaluate the correlation between exposure quartile categories and the efficacy and safety parameters while taking into consideration the effect of the predefined clinically relevant demographic and baseline covariates. The functional form of the ER relationship within the regorafenib treatment group was subsequently evaluated. RESULTS: Based on visual assessment of the Kaplan-Meier plots, no meaningful relationship between the exposure categories and TEAEs were observed, although median OS and TTP tended to be longer in the higher exposure categories. Further ER analyses, which considered the effects of predefined covariates and the different shapes of the ER relationship, focused on efficacy. The baseline risk factors Eastern Cooperative Oncology Group (ECOG) performance status ≥1, alpha-fetoprotein levels ≥400ng/ml, and aspartate transaminase or alanine transaminase levels >3×upper limit of normal were significantly associated with OS (P<0.01) and age was associated with TTP. A statistically significant difference was found for OS and TTP between patients receiving regorafenib compared with those receiving placebo in the multivariate ER analysis (P<0.01) in favor of regorafenib. However, within the group of regorafenib-treated patients, the effect of regorafenib exposure on efficacy, either by estimating four effect sizes for each quartile, or by including a continuous linear or nonlinear relationship between individual exposure and efficacy, was not significant (P>0.01) and relatively flat. This suggests that increasing regorafenib exposure would not result in a meaningful increase in OS or TTP. CONCLUSION: After considering the baseline risk factors: ECOG performance status, alpha-fetoprotein levels, and hepatic function for OS and age for TTP, the ER analysis in regorafenib-treated patients showed similar efficacy over the entire predicted exposure range in RESORCE. This supports the selected regorafenib dose of 160mg once daily (3weeks on/1week off in a 4-week cycle) in patients with intermediate or advanced HCC who have experienced disease progression on sorafenib.

Characterization and Prediction of Cardiovascular Effects of Fingolimod and Siponimod Using a Systems Pharmacology Modeling Approach.

Sphingosine 1-phosphate (S1P) receptor agonists are associated with cardiovascular effects in humans. This study aims to develop a systems pharmacology model to identify the site of action (i.e., primary hemodynamic response variable) of S1P receptor agonists, and to predict, in a quantitative manner, the cardiovascular effects of novel S1P receptor agonists in vivo. The cardiovascular effects of once-daily fingolimod (0, 0.1, 0.3, 1, 3, and 10 mg/kg) and siponimod (3 and 15 mg/kg) were continuously recorded in spontaneously hypertensive rats and Wistar-Kyoto rats. The results were analyzed using a recently developed systems cardiovascular pharmacology model, i.e. the CVS model; total peripheral resistance and heart rate were identified as the site of action for fingolimod. Next, the CVS model was interfaced with an S1P agonist pharmacokinetic-pharmacodynamic (PKPD) model. This combined model adequately predicted, in a quantitative manner, the cardiovascular effects of siponimod using in vitro binding assays. In conclusion, the combined CVS and S1P agonist PKPD model adequately describes the hemodynamic effects of S1P receptor agonists in rats and constitutes a basis for the prediction, in a strictly quantitative manner, of the cardiovascular effects of novel S1P receptor agonists.

Model-Based Dose Selection for Intravaginal Ring Formulations Releasing Anastrozole and Levonorgestrel Intended for the Treatment of Endometriosis Symptoms.

Pharmacokinetics (PK) of anastrozole (ATZ) and levonorgestrel (LNG) released from an intravaginal ring (IVR) intended to treat endometriosis symptoms were characterized, and the exposure-response relationship focusing on the development of large ovarian follicle-like structures was investigated by modeling and simulation to support dose selection for further studies. A population PK analysis and simulations were performed for ATZ and LNG based on clinical phase 1 study data from 66 healthy women. A PK/PD model was developed to predict the probability of a maximum follicle size ≥30 mm and the potential contribution of ATZ beside the known LNG effects. Population PK models for ATZ and LNG were established where the interaction of LNG with sex hormone-binding globulin (SHBG) as well as a stimulating effect of estradiol on SHBG were considered. Furthermore, simulations showed that doses of 40 µg/d LNG combined with 300, 600, or 1050 µg/d ATZ reached anticipated exposure levels for both drugs, facilitating selection of ATZ and LNG doses in the phase 2 dose-finding study. The main driver for the effect on maximum follicle size appears to be unbound LNG exposure. A 50% probability of maximum follicle size ≥30 mm was estimated for 40 µg/d LNG based on the exposure-response analysis. ATZ in the dose range investigated does not increase the risk for ovarian cysts as occurs with LNG at a dose that does not inhibit ovulation.

Exploring genetic and non-genetic risk factors for delayed graft function, acute and subclinical rejection in renal transplant recipients.

AIMS: This study aimed at identifying pharmacological factors such as pharmacogenetics and drug exposure as new predictive biomarkers for delayed graft function (DGF), acute rejection (AR) and/or subclinical rejection (SCR). METHODS: Adult renal transplant recipients (n = 361) on cyclosporine-based immunosuppression were followed for the first 6 months after transplantation. The incidence of DGF and AR were documented as well as the prevalence of SCR at 6 months in surveillance biopsies. Demographic, transplant-related factors, pharmacological and pharmacogenetic factors (ABCB1, CYP3A5, CYP3A4, CYP2C8, NR1I2, PPP3CA and PPP3CB) were analysed in a combined approach in relation to the occurrence of DGF, AR and prevalence of SCR at month 6 using a proportional odds model and time to event model. RESULTS: Fourteen per cent of the patients experienced at least one clinical rejection episode and only DGF showed a significant effect on the time to AR. The incidence of DGF correlated with a deceased donor kidney transplant (27% vs. 0.6% of living donors). Pharmacogenetic factors were not associated with risk for DGF, AR or SCR. A deceased donor kidney and acute rejection history were the most important determinants for SCR, resulting in a 52% risk of SCR at 6 months (vs. 11% average). In a sub-analysis of the patients with AR, those treated with rejection treatment including ATG, significantly less frequent SCR was found in the 6-month biopsy (13% vs. 50%). CONCLUSIONS: Transplant-related factors remain the most important determinants of DGF, AR and SCR. Furthermore, rejection treatment with depleting antibodies effectively prevented SCR in 6-month surveillance biopsies.

Modeling and Simulation of In Vivo Drug Effects.

The concept of a pharmacokinetics-pharmacodynamics (PK/PD) assessment of drug development candidates is well established in pharmaceutical research and development, and PK/PD modeling is common practice in all pharmaceutical companies. A recent analysis (Morgan et al., Drug Discov Today 17(9-10):419-424, 2012) revealed however that insufficient certainty in the integrity of the causal chain of fundamental pharmacological steps from drug dosing through systemic exposure, target tissue exposure, and engagement of molecular target to pharmacological response is still the major driver of failure in phase II of clinical drug development. Despite the rise of molecular biomarkers, ethical, scientific, and practical constraints very often still prevent a direct assessment of each necessary step ultimately leading to an intended drug effect or an unintended adverse reaction. Yet, incomplete investigation of the causality of drug responses is a major risk for translational assessments and the prediction of drug responses in different species or other populations. Mechanism-based modeling and simulation (M&S) offers a means to investigate complex physiological and pharmacological processes and to complement experimental data for non-accessible steps in the pharmacological causal chain. With the help of two examples, it is illustrated, what level of physiological detail, state-of-the-art models can represent, how predictive these models are and how mechanism-based approaches can be combined with empirical correlation-based concepts.

Translational pharmacokinetic modeling of fingolimod (FTY720) as a paradigm compound subject to sphingosine kinase-mediated phosphorylation.

A complicating factor in the translational pharmacology of sphingosine 1-phosphate agonists is that they exert their pharmacological effect through their respective phosphate metabolites, which are formed by the enzyme sphingosine kinase (S1PHK). In this investigation, we present a semimechanistic pharmacokinetic model for the interconversion of S1PHK substrates and their respective phosphates in rats and humans with the aim of investigating whether characterization of the rate of phosphorylation in blood platelets constitutes a basis for interspecies scaling using fingolimod as a model compound. Data on the time course of fingolimod and fingolimod-phosphate (fingolimod-P) blood concentrations after intravenous and oral administration of fingolimod and/or fingolimod-P in rats and after oral administration of fingolimod in doses of 0.5, 1.25, and 5 mg once daily in healthy volunteers were analyzed in conjunction with data on the ex vivo interconversion and blood-plasma distribution in rat and human blood, respectively. Integrating the data from the ex vivo and in vivo studies enabled simulation of fingolimod and fingolimod-P concentrations in plasma rather than blood, which are more relevant for characterizing drug effects. Large interspecies differences in the rate of phosphorylation between rats and humans were quantified. In human, phosphorylation of fingolimod in the platelets was four times slower compared with rat, whereas the dephosphorylation rates were comparable in both species. This partly explained the 10-12-fold overprediction of fingolimod-P exposure in human when applying a dose-by-factor approach on the developed rat model. Additionally, differences in presystemic phosphorylation should also be taken into account.

Nonlinear mixed effects modeling of the diurnal blood pressure profile in a multiracial population.

BACKGROUND: Cardiac and cerebrovascular events in hypertensive patients are related to specific features of the 24-hour diurnal blood pressure (BP) profile (i.e., daytime and nighttime BP, nocturnal dip (ND), and morning surge (MS)). This investigation aimed to characterize 24-hour diurnal systolic BP (SBP) with parameters that correlate directly with daytime and nighttime SBP, ND, and MS using nonlinear mixed effects modeling. METHODS: Ambulatory 24-hour SBP measurements (ABPM) of 196 nontreated subjects from three ethnic groups were available. A population model was parameterized in NONMEM to estimate and evaluate the parameters baseline SBP (BSL), nadir (minimum SBP during the night), and change (SBP difference between day and night). Associations were tested between these parameters and patient-related factors to explain interindividual variability. RESULTS: The diurnal SBP profile was adequately described as the sum of 2 cosine functions. The following typical values (interindividual variability) were found: BSL = 139 mm Hg (11%); nadir = 122 mm Hg (14%); change = 25 mm Hg (52%), and residual error = 12 mm Hg. The model parameters correlate well with daytime and nighttime SBP, ND, and MS (R (2) = 0.50-0.92). During covariate analysis, ethnicity was found to be associated with change; change was 40% higher in white Dutch subjects and 26.8% higher in South Asians than in blacks. CONCLUSIONS: The developed population model allows simultaneous estimation of BSL, nadir, and change for all individuals in the investigated population, regardless of individual number of SBP measurements. Ethnicity was associated with change. The model provides a tool to evaluate and optimize the sampling frequency for 24-hour ABPM.

The virtue of translational PKPD modeling in drug discovery: selecting the right clinical candidate while sparing animal lives.

Translational pharmacokinetic-pharmacodynamic (PKPD) modeling has been fully implemented at AstraZeneca's drug discovery unit for central nervous system and pain indications to facilitate timely progression of the right compound to clinical studies, simultaneously assuring essential preclinical efficacy and safety knowledge. This review illustrates the impact of a translational PKPD paradigm with examples from drug discovery programs. Paradoxically, laboratory animal use decreased owing to better understanding of in vitro-in vivo relationships, optimized in vivo study designs, meta-analyses and hypothesis testing using simulations. From an ethical and effectivity perspective, we advocate that translational PKPD approaches should be implemented more broadly in drug discovery.

Pharmacokinetic-pharmacodynamic modeling of the antihypertensive effect of eprosartan in Black and White hypertensive patients.

BACKGROUND AND OBJECTIVE: It is well recognized that many antihypertensive drugs exhibit large interindividual variability in effect and that this wide range of patient response to antihypertensive drugs is a major problem in achieving blood pressure (BP) control. Variability in both drug concentration and drug effect may cause the heterogeneity in antihypertensive drug response. However, for most antihypertensive drugs, no clear relationship between drug concentration and its effect on BP has been reported. This study aimed to describe the relationship between eprosartan exposure and its effect on the systolic blood pressure (SBP) using population pharmacokinetic-pharmacodynamic modeling. Interindividual variability in pharmacokinetics and pharmacodynamics was quantified and the influence of covariates on this relationship was evaluated. PATIENTS AND METHODS: Eprosartan plasma concentrations and SBP measurements were determined in 86 mildly hypertensive patients from the ROTATE study aged 48.1 ± 7.6 years with different ethnic backgrounds (33 White Dutch, 41 Creole Surinamese, 12 Hindustani Surinamese). In 12 of these patients, pharmacokinetics were densely sampled and 24-h ambulatory BP measurements were obtained. Data were analyzed using nonlinear mixed effects modeling. RESULTS: Eprosartan concentration-time profiles were adequately described with a two-compartment pharmacokinetic model with zero-order absorption. A log-linear relationship was used to describe the relationship between concentration and the decrease in SBP. A hypothetical effect compartment was used to describe hysteresis in the drug effect. Approximately 80 % of the maximum decrease in SBP was observed after 24 days. Interindividual variability in drug response was 65 % and decreased to 14 % when ethnicity was added as covariate. Creole Surinamese exhibited no drug response in contrast to White Dutch and Hindustani Surinamese [-2.6 mm Hg per (ng/ml)]. CONCLUSIONS: The developed pharmacokinetic-pharmacodynamic model allows the quantification and explanation of variability in SBP between individuals with ethnicity as a useful determinant of responsiveness to eprosartan.