Evinacumab: Mechanism of action, clinical, and translational science.

Homozygous familial hypercholesterolemia (HoFH) is a rare and serious genetic condition characterized by premature cardiovascular disease due to severely elevated low-density lipoprotein cholesterol (LDL-C). HoFH primarily results from loss-of-function (LOF) mutations in the LDL receptor (LDLR), reducing LDL-C clearance such that patients experience severe hypercholesterolemia, exacerbating the risk of developing cardiovascular events. Treatment options such as statins, lomitapide, ezetimibe, proprotein convertase subtilisin/kexin type 9 inhibitors, and apheresis help lower LDL-C; however, many patients with HoFH still fail to reach their target LDL-C levels and many of these lipid-lowering therapies are not indicated for pediatric use. Angiopoietin-like protein 3 (ANGPTL3) has been identified as a target to treat elevated LDL-C by acting as a natural inhibitor of lipoprotein lipase (LPL) and endothelial lipase (EL), enzymes involved in the hydrolysis of the triglyceride and phospholipid content of very low-density lipoproteins. Persons heterozygous for LOF mutations in ANGPTL3 were reported to have lower LDL-C than non-carriers and lower risk of coronary artery disease. Evinacumab is a first-in-class human monoclonal antibody that specifically binds to ANGPTL3 to prevent its inhibition of LPL and EL. In clinical trials, a 15 mg/kg intravenous dose every 4 weeks has shown a mean percent change from baseline in LDL-C of ~50% in adult, adolescent, and pediatric patients with HoFH. This mini review article describes the mechanism of action of evinacumab, evinacumab population PK and PD modeling, and clinical development history of evinacumab for the treatment of HoFH.

Evinacumab for Pediatric Patients With Homozygous Familial Hypercholesterolemia.

BACKGROUND: Homozygous familial hypercholesterolemia (HoFH) is a rare genetic disorder characterized by severely elevated low-density lipoprotein cholesterol (LDL-C) levels due to profoundly defective LDL receptor (LDLR) function. Given that severely elevated LDL-C starts in utero, atherosclerosis often presents during childhood or adolescence, creating a largely unmet need for aggressive LDLR-independent lipid-lowering therapies in young patients with HoFH. Here we present the first evaluation of the efficacy and safety of evinacumab, a novel LDLR-independent lipid-lowering therapy, in pediatric patients with HoFH from parts A and B of a 3-part study. METHODS: The phase 3, part B, open-label study treated 14 patients 5 to 11 years of age with genetically proven HoFH (true homozygotes and compound heterozygotes) with LDL-C >130 mg/dL, despite optimized lipid-lowering therapy (including LDLR-independent apheresis and lomitapide), with intravenous evinacumab 15 mg/kg every 4 weeks. RESULTS: Evinacumab treatment rapidly and durably (through week 24) decreased LDL-C with profound reduction in the first week, with a mean (SE) LDL-C reduction of -48.3% (10.4%) from baseline to week 24. ApoB (mean [SE], -41.3% [9.0%]), non-high-density lipoprotein cholesterol (-48.9% [9.8%]), and total cholesterol (-49.1% [8.1%]) were similarly decreased. Treatment-emergent adverse events were reported in 10 (71.4%) patients; however, only 2 (14.3%) reported events that were considered to be treatment-related (nausea and abdominal pain). One serious treatment-emergent adverse event of tonsillitis occurred (n=1), but this was not considered treatment-related. CONCLUSIONS: Evinacumab constitutes a new treatment for pediatric patients with HoFH and inadequately controlled LDL-C despite optimized lipid-lowering therapy, lowering LDL-C levels by nearly half in these extremely high-risk and difficult-to-treat individuals. REGISTRATION: URL: https://www.clinicaltrials.gov; Unique identifier: NCT04233918.

Population Pharmacokinetic Analysis of Quizartinib in Healthy Volunteers and Patients With Relapsed/Refractory Acute Myeloid Leukemia.

Quizartinib is an FMS-like tyrosine kinase 3 (FLT3) inhibitor that has shown robust clinical activity in patients with FLT3-internal tandem duplication-mutated relapsed/refractory acute myeloid leukemia (AML). This analysis evaluated the population pharmacokinetics (PK) of quizartinib and its active metabolite, AC886, in a pooled analysis of data from 649 healthy volunteers or patients with AML from 8 clinical trials including the phase 3 QuANTUM-R study. Quizartinib was given as a single dose or multiple once-daily doses of 20, 30, 60, or 90 mg. Nonlinear mixed-effects modeling was performed using observed concentrations of quizartinib and AC886. Strong CYP3A inhibitor use resulted in an 82% increase in the area under the curve (AUC) and a 72% increase in the maximum concentration (Cmax ) of quizartinib. Albumin level, age, and body surface area were statistically significant covariates on quizartinib PK. However, their individual effects on quizartinib AUC and Cmax were <20%. For AC886, strong CYP3A inhibitor use, body surface area and black/African American race were significant covariates. Except for strong CYP3A inhibitor use, the effects on the overall exposure (AUC of quizartinib + AC886) were <20%. The population PK model provided an adequate description of the observed concentrations of quizartinib and AC886 in both healthy volunteers and patients with AML. Only concomitant use of strong CYP3A inhibitors had a clinically meaningful effect on quizartinib PK exposure.

Effect of Food on the Pharmacokinetics of Quizartinib.

Quizartinib is an oral, highly potent, and selective type II FMS-like tyrosine kinase 3 inhibitor in development for acute myeloid leukemia. This parallel-group study evaluated potential food effects on quizartinib absorption in healthy subjects who received a single 30-mg dose after overnight fasting (n = 34) or a high-fat, high-calorie meal (n = 30). Blood samples were collected through 504 hours after dosing, and pharmacokinetic parameters calculated were maximum observed concentration (Cmax ) and area under plasma concentration-time curve from time 0 to last quantifiable concentration (AUClast ) and from time 0 to infinity (AUCinf ). Mean quizartinib pharmacokinetic profiles were similar under fasted and fed conditions. The geometric least squares means ratios (%) for fed/fasted and associated 90% confidence intervals (CIs) for Cmax , AUClast , and AUCinf were 91.58 (82.15-102.08), 105.39 (90.79-122.35), and 108.39 (91.54-128.34), respectively. The 90%CI for the ratio fell within the 80% to 125% limits for Cmax and AUClast , with 90%CI for AUCinf slightly outside the limits (ie, 128%). Food delayed quizartinib time to Cmax by 2 hours. All adverse events were either mild or moderate; no discontinuations due to adverse events occurred. Based on these results, quizartinib can be administered without regard to food.

A drug-drug interaction study to assess the potential effect of acid-reducing agent, lansoprazole, on quizartinib pharmacokinetics.

PURPOSE: Quizartinib, a potent, selective FMS-like tyrosine kinase 3 (FLT3) inhibitor, is currently in phase 3 development for patients with FLT3-internal tandem duplication-mutated acute myeloid leukemia (AML). Acid-reducing agents (ARAs; e.g., proton pump inhibitors) are frequently used during AML treatment. Since quizartinib demonstrates pH-dependent solubility, the effect of lansoprazole coadministration on pharmacokinetics (PK) of quizartinib tablet formulation was assessed. METHODS: An open-label, parallel-group study randomized 64 healthy adults to single-dose quizartinib 30 mg alone (reference) or lansoprazole (60 mg once daily, days 1-5) + single-dose quizartinib 30 mg (day 5) (test). Plasma concentrations of quizartinib and its active metabolite, AC886, were measured to 504 h postdose; the effect of lansoprazole on quizartinib PK was assessed by analysis of variance. RESULTS: Quizartinib geometric mean ratios (test/reference) and 90% confidence intervals for maximum observed plasma concentration (Cmax), area under the concentration-time curve to last measurable drug concentration (AUClast), and AUC to infinity were 86.11% (78.4%, 94.6%), 93.96% (79.6%, 110.9%), and 95.30% (80.2%, 113.3%), respectively. Comparisons showed a modest decrease in quizartinib absorption when co-administered with lansoprazole, with lower limits for Cmax and AUClast just below 80-125% limits. Treatment-emergent adverse events were mild or moderate; the most frequent in either treatment group were headache [quizartinib alone: (n = 3) 10%], upper respiratory tract infection [quizartinib alone: (n = 2) 6.7%; lansoprazole + quizartinib: (n = 3) 9.1%], and muscle tightness [quizartinib alone: (n = 2) 6.7%]. CONCLUSIONS: Concomitant lansoprazole had minimal effect on quizartinib PK as a formulated tablet, indicating that quizartinib can be administered with ARAs.

Pharmacokinetics, Metabolism, and Excretion of [14C]Esaxerenone, a Novel Mineralocorticoid Receptor Blocker in Humans.

Esaxerenone (CS-3150) is a novel, nonsteroidal, selective mineralocorticoid receptor blocker. The absorption, metabolism, distribution, and excretion of esaxerenone were assessed in in vitro studies and in a clinical study, where [14C]esaxerenone (150 µCi/20 mg) was administered orally to six healthy male subjects. The plasma concentrations of esaxerenone and its metabolites (M4, M11, and M1) were measured using liquid chromatography-tandem mass spectrometry. The recovery of radioactivity was 92.5%, with 38.5% and 54.0% excreted in the urine and feces, respectively. The half-life of radioactivity in blood and plasma was approximately 30 hours, similar to that of the unchanged form in plasma. The blood-to-plasma ratio was 0.628, demonstrating low partitioning to blood components. In plasma, esaxerenone was the most abundant moiety (40.8%), followed by O-glucuronide (21.4%; M4), acyl-glucuronide of amide-bond hydrolysate (8.0%; M11), and the deshydroxyethyl form (1.7%; M1). In vitro studies showed that esaxerenone was a substrate of CYP3A and multiple UDP-glucuronosyltransferase isoforms. Oxidation contributed approximately 30% to its clearance, as indicated by the excretion ratio of oxidized metabolites into urine and feces. Caco-2 studies showed that esaxerenone was a substrate of P-glycoprotein and breast cancer resistance protein; however, the excretion ratios of the unchanged form in the feces and urine were 18.7% and 1.6%, respectively, indicating that these transporters were not important for the absorption and elimination of esaxerenone. Low urinary excretion of esaxerenone suggested that the plasma exposure of esaxerenone was not affected by renal dysfunction. Multiple elimination pathways including oxidation, glucuronidation, and hydrolysis, and the low contribution of transporters, indicated limited drug-drug interaction potential.

Patritumab with Cetuximab plus Platinum-Containing Therapy in Recurrent or Metastatic Squamous Cell Carcinoma of the Head and Neck: An Open-Label, Phase Ib Study.

PURPOSE: Patritumab plus cetuximab with platinum as first-line therapy for patients with recurrent and/or metastatic (R/M) squamous cell carcinoma of the head and neck (SCCHN) was evaluated for safety and to determine the recommended phase II combination dose. PATIENTS AND METHODS: Patients aged ≥18 years with confirmed R/M SCCHN received intravenous patritumab (18 mg/kg loading dose; 9 mg/kg maintenance dose every 3 weeks) + cetuximab (400 mg/m2 loading dose; 250 mg/m2 maintenance dose weekly) + cisplatin (100 mg/m2 every 3 weeks) or carboplatin (AUC of 5) for six cycles or until toxicity, disease progression, or withdrawal. Primary endpoints were dose-limiting toxicities [DLT; grade ≥3 (21-day observation period)] and treatment-emergent adverse events (TEAE). Pharmacokinetics, human antihuman antibodies (HAHA), tumor response, progression-free survival (PFS), and overall survival (OS) were assessed. RESULTS: Fifteen patients completed a median (range) of 8.7 (2.0-20.7) patritumab cycles. No DLTs were reported. Serious adverse events were reported in 9 patients (patritumab-related n = 4). TEAEs (N = 15 patients) led to patritumab interruption in 7 patients. Patritumab-related dose reductions were reported in 1 patient. Patritumab (18 mg/kg) pharmacokinetics (N = 15) showed mean (SD) AUC0-21d of 2,619 (560) µg/day/mL and maximum concentration of 499.9 (90.4) µg/mL. All patients were HAHA-negative at study end (single, transient low titer in 1 patient). Tumor response rate (complete plus partial response; N = 15) was 47%. Median (95% confidence interval) PFS and OS (N = 15) were 7.9 (3.7-9.7) and 13.5 (6.6-17.5) months, respectively. CONCLUSIONS: Patritumab (18 mg/kg loading dose, 9 mg/kg maintenance dose) plus cetuximab/platinum was tolerable, active in SCCHN, and selected as the phase II dose regimen.

Population pharmacokinetic analysis of patritumab, a HER3 inhibitor, in subjects with advanced non-small cell lung cancer (NSCLC) or solid tumors.

PURPOSE: The purpose of this analysis was to develop a population pharmacokinetic (PK) model for patritumab, a fully human monoclonal antibody that targets human epidermal growth factor receptor 3. METHODS: A total of 833 serum concentrations were included in this analysis; serum concentrations were obtained from 145 subjects (136 with non-small cell lung cancer, nine with solid tumors) treated with patritumab [9 or 18 mg/kg intravenously every 3 weeks (q3w)] in one phase 1 and one phase 1b/2 study. Data were analyzed by nonlinear mixed-effect modeling. RESULTS: Patritumab PKs were best described through a two-compartment model with first-order elimination and interindividual variability on clearance (CL), volume of the central compartment (V c), distributional clearance, and volume of the peripheral compartment. In the final model, CL and V c were estimated as 0.0238 L/h and 3.62 L, respectively. Body weight (BW) and baseline albumin were found to be covariates for CL and BW was a covariate for V c. Covariates associated with hepatic and renal impairment were not significant on CL. Simulations showed that BW-based dosing reduced interindividual variability in patritumab exposure compared with fixed dosing. CONCLUSIONS: The PK of patritumab was linear at the doses studied and well described by the two-compartment model. Hepatic and renal impairment did not appear to affect PK. Our results support BW-based dosing of patritumab on a q3w schedule.

Phase 1 Evaluation of [(64)Cu]DOTA-Patritumab to Assess Dosimetry, Apparent Receptor Occupancy, and Safety in Subjects with Advanced Solid Tumors.

PURPOSE: The purpose of this study was to evaluate the safety, dosimetry, and apparent receptor occupancy (RO) of [(64)Cu]DOTA-patritumab, a radiolabeled monoclonal antibody directed against HER3/ERBB3 in subjects with advanced solid tumors. PROCEDURES: Dosimetry subjects (n = 5) received [(64)Cu]DOTA-patritumab and underwent positron emission tomography (PET)/X-ray computed tomography (CT) at 3, 24, and 48 h. Evaluable RO subjects (n = 3 out of 6) received [(64)Cu]DOTA-patritumab at day 1 and day 8 (after 9.0 mg/kg patritumab) followed by PET/CT at 24 h post-injection. Endpoints included safety, tumor uptake, and efficacy. RESULTS: The tumor SUVmax (± SD) was 5.6 ± 4.5, 3.3 ± 1.7, and 3.0 ± 1.1 at 3, 24, and 48 h in dosimetry subjects. The effective dose and critical organ dose (liver) averaged 0.044 ± 0.008 mSv/MBq and 0.46 ± 0.086 mGy/MBq, respectively. In RO subjects, tumor-to-blood ratio decreased from 1.00 ± 0.32 at baseline to 0.57 ± 0.17 after stable patritumab, corresponding to a RO of 42.1 ± 3. CONCLUSIONS: [(64)Cu]DOTA-patritumab was safe. These limited results suggest that this PET-based method can be used to determine tumor-apparent RO.

Clinical Translation and Validation of a Predictive Biomarker for Patritumab, an Anti-human Epidermal Growth Factor Receptor 3 (HER3) Monoclonal Antibody, in Patients With Advanced Non-small Cell Lung Cancer.

BACKGROUND: During early clinical development, prospective identification of a predictive biomarker and validation of an assay method may not always be feasible. Dichotomizing a continuous biomarker measure to classify responders also leads to challenges. We present a case study of a prospective-retrospective approach for a continuous biomarker identified after patient enrollment but defined prospectively before the unblinding of data. An analysis of the strengths and weaknesses of this approach and the challenges encountered in its practical application are also provided. METHODS: HERALD (NCT02134015) was a double-blind, phase 2 study in patients with non-small cell lung cancer (NSCLC) randomized to erlotinib with placebo or with high or low doses of patritumab, a monoclonal antibody targeted against human epidermal growth factor receptor 3 (HER3). While the primary objective was to assess safety and progression-free survival (PFS), a secondary objective was to determine a single predictive biomarker hypothesis to identify subjects most likely to benefit from the addition of patritumab. Although not identified as the primary biomarker in the study protocol, on the basis of preclinical results from 2 independent laboratories, expression levels of the HER3 ligand heregulin (HRG) were prospectively declared the predictive biomarker before data unblinding but after subject enrollment. An assay to measure HRG mRNA was developed and validated. Other biomarkers, such as epidermal growth factor receptor (EGFR) mutation status, were also evaluated in an exploratory fashion. The cutoff value for high vs. low HRG mRNA levels was set at the median delta threshold cycle. A maximum likelihood analysis was performed to evaluate the provisional cutoff. The relationship of HRG values to PFS hazard ratios (HRs) was assessed as a measure of internal validation. Additional NSCLC samples were analyzed to characterize HRG mRNA distribution. RESULTS: The subgroup of patients with high HRG mRNA levels ("HRG-high") demonstrated clinical benefit from patritumab treatment with HRs of 0.37 (P = 0.0283) and 0.29 (P = 0.0027) in the high- and low-dose patritumab arms, respectively. However, only 102 of the 215 randomized patients (47.4%) had sufficient tumor samples for HRG mRNA measurement. Maximum likelihood analysis showed that the provisional cutoff was within the optimal range. In the placebo arm, the HRG-high subgroup demonstrated worse prognosis compared with HRG-low. A continuous relationship was observed between increased HRG mRNA levels and lower HR. Additional NSCLC samples (N = 300) demonstrated a similar unimodal distribution to that observed in this study, suggesting that the defined cutoff may be applicable to future NSCLC studies. CONCLUSIONS: The prospective-retrospective approach was successful in clinically validating a probable predictive biomarker. Post hoc in vitro studies and statistical analyses permitted further testing of the underlying assumptions. However, limitations of this analysis include the incomplete collection of adequate tumor tissue and a lack of stratification. In a phase 3 study, findings are being confirmed, and the HRG cutoff value is being further refined. CLINICALTRIALSGOV NUMBER: NCT02134015.

The P-glycoprotein transport system and cardiovascular drugs.

Permeability glycoprotein (P-gp) mediates the export of drugs from cells located in the small intestine, blood-brain barrier, hepatocytes, and kidney proximal tubule, serving a protective function for the body against foreign substances. Intestinal absorption, biliary excretion, and urinary excretion of P-gp substrates can therefore be altered by either the inhibition or induction of P-gp. A wide spectrum of drugs, such as anticancer agents and steroids, are known P-gp substrates and/or inhibitors, and many cardiovascular drugs have recently been observed to have clinically relevant interactions as well. We review the interactions among commonly prescribed cardiovascular drugs that are P-gp substrates and observe interactions involving P-gp that may be relevant to clinical practice. Cardiovascular drugs with narrow therapeutic indexes (e.g., antiarrhythmic agents, anticoagulant agents) have demonstrated large increases in concentrations when coadministered with potent P-gp inhibitors, thus increasing the risk for drug toxicity. Therefore, dose adjustment or use of alternative agents should be considered when strong P-gp-mediated drug-drug interactions are present. Finally, interactions between novel drugs and known P-gp inhibitors are now being systematically evaluated during drug development, and recommended guidelines for the administration of P-gp substrate drugs will be expanded.

Characterisation of exposure versus response of edoxaban in patients undergoing total hip replacement surgery.

Edoxaban is an oral direct factor Xa inhibitor approved for the prevention of venous thromboembolism (VTE) in Japan. The objectives of this analysis were to characterise the population pharmacokinetics (PK) of edoxaban and the relationships between edoxaban exposure and clinical outcomes in a phase IIb study of surgical patients following total hip replacement (THR). A total of 1,795 subjects from a phase IIb study, 10 phase I studies, and three phase IIa studies were included in the PK analysis. The exposure-response analysis included data from surgical patients assigned to edoxaban in the phase IIb study. Edoxaban disposition in healthy and post-surgical patients was well-described with a linear, two-compartment model. Creatinine clearance was significantly correlated with edoxaban clearance and the rate of oral absorption was affected by surgery. The probability of a post-operative VTE was significantly correlated with steady-state metrics of edoxaban exposure estimated for each subject by Bayesian post-hoc methods with age and gender being the significant and expected covariates. The incidence of bleeding was low in these studies and hence no exposure-response relationship could be identified. These analyses suggest that edoxaban has a predictable anticoagulant effect in this patient population leading to dose-proportional reduction in incidence of VTE with low incidence of bleeding.