Evaluation of the effect of food and ketoconazole on the pharmacokinetics of the smoothened inhibitor PF-04449913 in healthy volunteers

Glasdegib with intensive/nonintensive chemotherapy in Japanese patients with untreated acute myeloid leukemia or high-risk myelodysplastic syndromes

Glasdegib is a potent, selective, oral inhibitor of the hedgehog signaling pathway. In this phase I study, previously untreated Japanese patients with acute myeloid leukemia (AML) or high-risk myelodysplastic syndromes were treated with glasdegib (100 mg once daily) combinations: low-dose cytarabine (20 mg twice daily; cohort 1, n = 6; expansion cohort, n = 15); daunorubicin and cytarabine (60 mg/m2 i.v.; cohort 2, n = 6); or azacitidine (100 mg/m2 i.v.; cohort 3, n = 6). Patients, except cohort 2, were ineligible for intensive chemotherapy. The primary end-point was dose-limiting toxicity in cohorts 1-3 and disease-modifying response in the expansion cohort. Disease-modifying response rate was tested with the null hypothesis of 6.8%, which was set based on the results from the phase II BRIGHT AML 1003 study (NCT01546038). No dose-limiting toxicities were observed in cohorts 1 or 3; one patient in cohort 2 experienced a dose-limiting toxicity of grade 3 erythroderma. The most common grade ≥3 treatment-related adverse events were neutropenia and thrombocytopenia (66.7% each) in cohort 1 and thrombocytopenia (60.0%) in the expansion cohort. In the expansion cohort, the disease-modifying response rate was 46.7% (90% confidence interval, 24.4-70.0; p < 0.0001), with all patients achieving either a complete response or complete response with incomplete blood count recovery. Median overall survival was 13.9 months. In this study, the primary disease-modifying response end-point with glasdegib plus low-dose cytarabine was met. The study confirms the safety and efficacy of glasdegib plus low-dose cytarabine in Japanese patients with AML ineligible for intensive chemotherapy.

Physiologically Based Pharmacokinetic Modeling of the Drug-Drug Interaction Between CYP3A4 Substrate Glasdegib and Moderate CYP3A4 Inducers in Lieu of a Clinical Study

Glasdegib (DAURISMO) is a hedgehog pathway inhibitor approved for the treatment of acute myeloid leukemia (AML). Cytochrome P450 3A4 (CYP3A4) has been identified as a major metabolism and clearance pathway for glasdegib. The role of CYP3A4 in the clearance of glasdegib has been confirmed with clinical drug-drug interaction (DDI) studies following the coadministration of glasdegib with the strong CYP3A4 inhibitor ketoconazole and the strong inducer rifampin. To evaluate potential drug interactions with CYP3A4 modulators, the coadministration of glasdegib with a moderate CYP3A4 inducer, efavirenz, was evaluated using physiologically based pharmacokinetic (PBPK) modeling using the Simcyp simulator. The glasdegib compound file was developed using measured physicochemical properties, data from human intravenous and oral pharmacokinetics, absorption, distribution, metabolism, and excretion studies, and in vitro reaction phenotyping results. The modeling assumptions, model parameters, and assignments of fractional CYP3A4 metabolism were verified using results from clinical pharmacokinetics (PK) and DDI studies with ketoconazole and rifampin. The verified glasdegib and efavirenz compound files, the latter of which was available in the Simcyp simulator, were used to estimate the potential impact of efavirenz on the PK of glasdegib. PBPK modeling predicted a glasdegib area under the concentration-time curve ratio of 0.45 and maximum plasma concentration ratio of 0.75 following coadministration with efavirenz. The PBPK results, in lieu of a formal clinical study, informed the drug label, with the recommendation to double the clinical dose of glasdegib when administered in conjunction with a moderate CYP3A4 inducer, followed by a resumption of the original dose 7 days post-discontinuation.

An Updated Overview of the Role of CYP450 during Xenobiotic Metabolization in Regulating the Acute Myeloid Leukemia Microenvironment

Oxidative stress is associated with several acute and chronic disorders, including hematological malignancies such as acute myeloid leukemia, the most prevalent acute leukemia in adults. Xenobiotics are usually harmless compounds that may be detrimental, such as pharmaceuticals, environmental pollutants, cosmetics, and even food additives. The storage of xenobiotics can serve as a defense mechanism or a means of bioaccumulation, leading to adverse effects. During the absorption, metabolism, and cellular excretion of xenobiotics, three steps may be distinguished: (i) inflow by transporter enzymes, (ii) phases I and II, and (iii) phase III. Phase I enzymes, such as those in the cytochrome P450 superfamily, catalyze the conversion of xenobiotics into more polar compounds, contributing to an elevated acute myeloid leukemia risk. Furthermore, genetic polymorphism influences the variability and susceptibility of related myeloid neoplasms, infant leukemias associated with mixed-lineage leukemia (MLL) gene rearrangements, and a subset of de novo acute myeloid leukemia. Recent research has shown a sustained interest in determining the regulators of cytochrome P450, family 2, subfamily E, member 1 (CYP2E1) expression and activity as an emerging field that requires further investigation in acute myeloid leukemia evolution. Therefore, this review suggests that CYP2E1 and its mutations can be a therapeutic or diagnostic target in acute myeloid leukemia.

Update on glasdegib in acute myeloid leukemia - broadening horizons of Hedgehog pathway inhibitors

Numerous new emerging therapies, including oral targeted chemotherapies, have recently entered the therapeutic arsenal against acute myeloid leukemia (AML). The significant shift toward the use of these novel therapeutics, administered either alone or in combination with intensive or low-intensity chemotherapy, changes the prospects for the control of this disease, especially for elderly patients. Glasdegib, an oral Hedgehog pathway inhibitor, showed satisfactory response rates associated with moderate toxicity and less early mortality than standard induction regimens in this population. It was approved in November 2018 by the FDA and in June 2020 by the EMA for use in combination with low-dose cytarabine as a treatment of newly-diagnosed AML in patients aged ≥ 75 and/or unfit for intensive induction chemotherapy. The current paper proposes an extensive, up-to-date review of the preclinical and clinical development of glasdegib. Elements of its routine clinical use and the landscape of ongoing clinical trials are also stated.

Exploring the Relationship of Drug BCS Classification, Food Effect, and Gastric pH-Dependent Drug Interactions

Food effect (FE) and gastric pH-dependent drug-drug interactions (DDIs) are both absorption-related. Here, we evaluated if Biopharmaceutics Classification System (BCS) classes may be correlated with FE or pH-dependent DDIs. Trends in FE data were investigated for 170 drugs with clinical FE studies from the literature and new drugs approved from 2013 to 2019 by US Food and Drug Administration. A subset of 38 drugs was also evaluated to determine whether FE results can inform the need for a gastric pH-dependent DDI study. The results of FE studies were defined as no effect (AUC ratio 0.80-1.25), increased exposure (AUC ratio ≥1.25), or decreased exposure (AUC ratio ≤0.8). Drugs with significantly increased exposure FE (AUC ratio ≥2.0; N=14) were BCS Class 2 or 4, while drugs with significantly decreased exposure FE (AUC ratio ≤0.5; N=2) were BCS Class 1/3 or 3. The lack of FE was aligned with the lack of a pH-dependent DDI for all 7 BCS Class 1 or 3 drugs as expected. For the 13 BCS Class 2 or 4 weak base drugs with an increased exposure FE, 6 had a pH-dependent DDI (AUC ratio ≤0.8). Among the 16 BCS Class 2 or 4 weak base drugs with no FE, 6 had a pH-dependent DDI (AUC ratio ≤0.8). FE appears to have limited correlation with BCS classes except for BCS Class 1 drugs, confirming that multiple physiological mechanisms can impact FE. Lack of FE does not indicate absence of pH-dependent DDI for BCS Class 2 or 4 drugs. Graphical Abstract.

Pharmacokinetics and Safety of Glasdegib in Participants With Moderate/Severe Hepatic Impairment: A Phase I, Single-Dose, Matched Case-Control Study

This phase I open-label trial (NCT03627754) assessed glasdegib pharmacokinetics and safety in otherwise healthy participants with moderate (Child-Pugh B) or severe (Child-Pugh C) hepatic impairment. Participants with hepatic impairment and age/weight-matched controls with normal hepatic function received a single oral 100-mg glasdegib dose under fasted conditions. The primary end points were area under the plasma concentration-time curve from time zero to infinity (AUCinf ) and maximum plasma concentration (Cmax ). Twenty-four participants (8/cohort) were enrolled. Glasdegib plasma exposures in moderate hepatic impairment were similar to controls, with adjusted geometric mean ratios (GMRs) of 110.8% (90% confidence interval [CI], 78.0-157.3) for AUCinf and 94.8% (69.9-128.4) for Cmax versus controls. In severe hepatic impairment, glasdegib plasma exposures were lower than controls (AUCinf GMR, 75.7%; 90%CI, 51.5-111.0; Cmax GMR, 58.0%; 90%CI, 37.8-89.0). Unbound glasdegib exposures were similar to controls for moderate (AUCinf,u GMR, 118.1%; 90%CI, 88.7-157.2; Cmax,u GMR, 101.1%; 90%CI, 78.4-130.3) and severe hepatic impairment (AUCinf,u GMR, 116.3%; 90%CI 81.8-165.5; Cmax,u GMR, 89.2%, 90%CI, 60.2-132.3). No treatment-related adverse events or clinically significant changes in laboratory values, vital signs, or electrocardiograms were observed. Together with previous findings, this suggests glasdegib dose modifications are not required based on hepatic impairment.

Exposure-response modeling of the effect of glasdegib on cardiac repolarization in patients with cancer

PURPOSE

To characterize the effect of glasdegib on cardiac repolarization (QTc) in patients with advanced cancer.

METHODS

A concentration-QTc model was developed using data from two glasdegib single-agent, dose-escalation trials. Triplicate electrocardiogram was performed at pre-specified timepoints paired with pharmacokinetic blood collections after a single dose and at steady-state. Changes in QTc from baseline were predicted by model-based simulations at the clinical dose (100 mg QD) and in a supratherapeutic setting.

RESULTS

Glasdegib did not affect the heart rate, but had a positive effect on the corrected QT interval, described by a linear mixed-effects model with ΔQTcF (QTc using Fridericia's formula) as the dependent variable with glasdegib plasma concentrations from doses of 5-640 mg QD. The predicted mean QTcF change (upper bound of the 95% CI) was 5.30 (6.24) msec for the therapeutic 100-mg QD dose; at supratherapeutic concentrations (40% and 100% increase over the therapeutic C_max), it was 7.42 (8.74) and 12.09 (14.25) msec, respectively.

CONCLUSIONS

The relationship of glasdegib exposure and QTc was well characterized by the model. The effect of glasdegib on the QTc interval did not cross the threshold of clinical concern for an oncology drug.

TRIAL REGISTRATION

ClinicalTrials.gov ID: NCT01286467 and NCT00953758.

Evaluation of the Relationship of Glasdegib Exposure and Safety End Points in Patients With Refractory Solid Tumors and Hematologic Malignancies

Glasdegib is approved for treating acute myeloid leukemia in elderly patients at 100 mg once daily in combination with low-dose cytarabine. Exposure-efficacy analysis showed that the survival benefit of glasdegib was not glasdegib exposure-dependent. The relationship between glasdegib exposure and adverse event (AE) cluster terms of clinical concern was explored in this analysis. The incidence and severity of dysgeusia, muscle spasms, renal toxicity, and QT interval prolonged was modeled using ordinal logistic regression. AEs were graded using the National Cancer Institute Common Terminology Criteria for Adverse Events (version 4.03). Estimated pharmacokinetic parameters were used to derive glasdegib exposure metrics. Demographic characteristics, disease factors, and other variables of interest as potential moderators of safety signals were evaluated. Clinical trial data from patients who received single-agent glasdegib (N = 70; 5-640 mg once daily); or glasdegib (N = 202, 100-200 mg once daily) with low-dose cytarabine, decitabine, or daunorubicin and cytarabine were analyzed. Glasdegib exposure was statistically significantly associated with the cluster term safety end points dysgeusia, muscle spasms, renal toxicity, and QT interval prolonged. The impact of age on muscle spasms and baseline body weight and creatinine clearance on renal toxicity helped explain the AE grade distribution. At the 100 mg once daily clinical dose, the predicted probabilities of the highest AE grade were 11.3%, 6.7%, 7.7%, and 2.5% for dysgeusia, muscle spasms, renal toxicity, and QT interval prolonged, respectively. Overall, the predicted probability of developing an AE of any severity for these safety end points was low. Therefore, no starting dose adjustments are recommended for glasdegib based on the observed safety profile.

Glasdegib in newly diagnosed acute myeloid leukemia

INTRODUCTION

Acute myeloid leukemia (AML) is an aggressive blood cancer that proves fatal for the majority of affected individuals. Older patients are particularly vulnerable due to more unfavorable disease biology and diminished ability to tolerate intensive induction chemotherapy (ICT). Safer, more efficacious therapies are desperately needed.

AREAS COVERED

We briefly summarize the challenges facing AML treatment and introduce the rapidly expanding therapeutic landscape. Our focus is on the Hedgehog (Hh) pathway and how preclinical evidence has spurred the clinical development of selective inhibitors for oncology indications. Glasdegib is the first Hh pathway inhibitor approved for the treatment of a hematologic malignancy, and we review its pharmacology, safety, efficacy, and potential clinical impact in AML patients.

EXPERT OPINION

Advances in the mechanistic understanding of AML have started to translate into improved therapeutic options for patients with contraindications to ICT. Glasdegib improved overall survival in this population when combined with low-dose cytarabine. While an encouraging development for these difficult to treat patients, alternative combination therapy approaches such as venetoclax plus azacitidine have gained greater clinical traction. Further investigation of glasdegib combination strategies and predictive biomarkers, particularly in regard to overcoming chemoresistance and preventing relapse, is needed to better define its clinical utility.

Evaluation of the impact of renal impairment on the pharmacokinetics of glasdegib in otherwise healthy volunteers

PURPOSE

Glasdegib is being developed for indications in myeloid malignancies. The effect of renal impairment on the pharmacokinetics (PK) of a single, oral, 100-mg glasdegib dose under fasted conditions was assessed.

METHODS

Open-label, parallel-group study (NCT03596567). Participants of good general health were selected and categorized, based on their estimated glomerular filtration rate, into normal (≥ 90 mL/min), moderate (≥ 30 to < 60 mL/min), or severe (< 30 mL/min) renal impairment groups. Blood samples were collected up to 120 h post-dose. PK exposure parameters were calculated using non-compartmental analysis.

RESULTS

All 18 participants completed the study. Respectively, ratios of adjusted geometric means (90% confidence interval) for glasdegib area under the curve from time 0 to infinity and peak plasma concentration versus normal participants were 205% (142-295%) and 137% (97-193%) in the moderate group, and 202% (146-281%) and 120% (77-188%) in the severe group. Glasdegib median time to peak plasma concentration was 2.0 h in both impairment groups and 1.5 h in the normal group. Mean oral clearance was decreased by approximately 50% in both renal impairment groups compared with the normal group. The plasma-free fraction of glasdegib was not altered by renal impairment. Five all-causality adverse events were reported in three participants; two were considered treatment-related.

CONCLUSION

The similar changes in exposure observed for participants with renal impairment, coupled with the known safety data from clinical experience, suggest that a lower starting dose of glasdegib may not be required for moderate or severe renal impairment.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT03596567 (started May 17, 2018).

Glasdegib plus low-dose cytarabine for acute myeloid leukemia: Practical considerations from advanced practitioners and pharmacists

Objective

Acute myeloid leukemia (AML) is primarily a disease of older adults. These patients may not be candidates for intensive treatment, and there has been an ongoing need for treatment options for this group. We review the use of glasdegib, a hedgehog-pathway inhibitor available for use in combination with low-dose cytarabine (LDAC).

Data Sources: PubMed and relevant congress abstracts were searched using the term “glasdegib”. In addition, based on our experience with glasdegib, we considered treatment aspects of particular relevance to pharmacists and advanced practitioners.

Data Summary: In a randomized phase II study, the combination of glasdegib plus LDAC demonstrated superior overall survival versus LDAC alone (hazard ratio 0.51, 80% confidence interval 0.39–0.67, p = 0.0004). The trial reported adverse events (AEs) of special relevance for older patients, such as hematologic events, gastrointestinal toxicity, and fatigue, as well as AEs associated with Hh-pathway inhibitors (alopecia, muscle spasms, dysgeusia). Educating patients about typical AEs can facilitate adherence as well as early AE identification and proactive management. For LDAC, which is a long-established therapy in AML, various stages of delivery need consideration, with attention to individual circumstances. Practical measures such as dispensing a longer supply can reduce the number of return clinic visits, providing a meaningful difference for many patients.

Conclusions

Pharmacists and advanced practitioners play important roles in treatment with glasdegib plus LDAC. Ultimately, framing plans for treatment delivery within the individual circumstances of each patient may enable them to stay on therapy longer, giving them the greatest potential to achieve benefit.

Clinical and Model-Based Evaluation of the Effect of Glasdegib on Cardiac Repolarization From a Randomized Thorough QT Study

Glasdegib is a potent, selective oral inhibitor of the Hedgehog signaling pathway. This phase 1 double‐blind thorough QT study (NCT03162900) evaluated the effects of glasdegib on QTc interval. The study enrolled 36 healthy volunteers to receive a single dose of 150 mg glasdegib (representing a therapeutic dose), 300 mg glasdegib (representing a supratherapeutic dose), 400 mg moxifloxacin (positive control), or placebo under fasted conditions. The study demonstrated that therapeutic and supratherapeutic doses of glasdegib had no significant effect on QTc interval; the upper bound of the 2‐sided 90% confidence intervals (CIs) for all time‐matched least‐squares mean differences in QT interval corrected using Fridericia's formula (QTcF) between glasdegib and placebo was below the prespecified criterion of 20 milliseconds (Food and Drug Administration correspondence reviewed and accepted). Based on an exposure–response analysis, glasdegib was determined not to have a meaningful effect on heart rate (change in RR interval). The mean (90%CI) model‐derived baseline and placebo‐adjusted QTcF at the average maximum observed concentration values corresponding to therapeutic and supratherapeutic glasdegib doses was 7.3 milliseconds (6.5‐8.2 milliseconds) and 13.7 milliseconds (12.0‐15.5 milliseconds), respectively. Together these results demonstrated that following therapeutic and supratherapeutic glasdegib dosing, the change in QTc from baseline was well below the 20‐millisecond threshold of clinical concern in oncology.

Drug-drug interactions of newly approved small molecule inhibitors for acute myeloid leukemia

Several small molecule inhibitors (SMIs) have been recently approved for AML patients. These targeted therapies could be more tolerable than classical antineoplastics, but potential drug-drug interactions (DDI) are relatively frequent. Underestimation or lack of appropriate awareness and management of DDIs with SMIs can jeopardize therapeutic success in AML patients, which often require multiple concomitant medications in the context of prior comorbidities or for the prevention and treatment of infectious and other complications. In this systematic review, we analyze DDIs of glasdegib, venetoclax, midostaurin, quizartinib, gilteritinib, enasidenib, and ivosidenib. CYP3A4 is the main enzyme responsible for SMIs metabolism, and strong CYP3A4 inhibitors, such azoles, could increase drug exposure and toxicity; therefore dose adjustments (venetoclax, quizartinib, and ivosidenib) or alternative therapies or close monitoring (glasdegib, midostaurin, and gilteritinib) are recommended. Besides, coadministration of strong CYP3A4 inducers with SMIs should be avoided due to potential decrease of efficacy. Regarding tolerability, QTc prolongation is frequently observed for most of approved SMIs, and drugs with a potential to prolong the QTc interval and CYP3A4 inhibitors should be avoided and replaced by alternative treatments. In this study, we critically assess the DDIs of SMIs, and we summarize best management options for these new drugs and concomitant medications.

An evaluation of glasdegib for the treatment of acute myelogenous leukemia

Introduction: Despite recent advances in the treatment of adult acute myelogenous leukemia (AML), the overall outcome remains dismal especially in high-risk AML patients, including the elderly and the relapsed/refractory populations. In this setting, various clinical trials have recently explored novel therapeutic agents either used alone or in combination with intensive chemotherapy or low-intensity treatments.Areas covered: The current paper reviews the clinical development of glasdegib, a selective inhibitor of the Hedgehog signaling pathway through binding to its target SMO, for the treatment of AML.Expert opinion: Glasdegib confirmed its efficacy and showed an acceptable tolerability, especially when used in combination either with '3 + 7' chemotherapy or with low-intensity therapies. In 2018, glasdegib was approved by the Food and Drug Administration (FDA) in combination with low-dose cytarabine for the treatment of newly diagnosed AML in patients older than 75 years or presenting with severe comorbidities.

Population Pharmacokinetics of Glasdegib in Patients With Advanced Hematologic Malignancies and Solid Tumors

Glasdegib is an inhibitor of the Hedgehog pathway recently approved in the United States for the treatment of acute myeloid leukemia. A population pharmacokinetic analysis was conducted to characterize the kinetic behavior of glasdegib and its sources of variability (covariates) by utilizing data from 269 patients with cancer treated with oral glasdegib doses ranging from 5 to 640 mg/d. Nonlinear mixed-effects modeling was conducted using NONMEM (v.7.3) and Perl-speaks NONMEM (v.4.2.0). The estimated apparent total clearance, apparent central volume of distribution, and apparent peripheral volume of distribution were 6.27 L/h, 3.32 L, and 279.2 L, respectively. Age, sex, race, and hepatic function were not significant covariates on glasdegib pharmacokinetic parameters. Baseline body weight, percentage bone marrow blasts, creatinine clearance, and use of moderate or strong cytochrome P450 3A inhibitors were statistically significant covariates on apparent total clearance; however, the magnitude of the effects was not considered clinically meaningful.

Glasdegib in the treatment of acute myeloid leukemia

Pharmacologic inhibition of the Hedgehog pathway significantly enhanced the sensitivity of leukemic cells to cytotoxic drugs. Glasdegib (PF-04449913; DAURISMO™) is a potent and selective oral inhibitor of the Hedgehog signaling pathway with clinical activity in patients with acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS), particularly in combination with chemotherapy. The results of Phase Ib/II studies evaluating safety and efficacy of glasdegib combined with chemotherapy in previously untreated patients with AML or high-risk myelodysplastic syndrome have recently been published. In the BRIGHT AML 1003 study, glasdegib in combination with low-dose cytarabine (LDAC) was well tolerated and demonstrated a significant 54% reduction in mortality compared with LDAC for AML patients. In 2018, the US FDA approved glasdegib in combination with LDAC for the treatment of newly diagnosed patients with AML who are 75 years old or older or who have co-morbidities that preclude use of intensive induction chemotherapy.

Safety and Tolerability of Sonic Hedgehog Pathway Inhibitors in Cancer

The hedgehog pathway, for which sonic hedgehog (Shh) is the most prominent ligand, is highly conserved and is tightly associated with embryonic development in a number of species. This pathway is also tightly associated with the development of several types of cancer, including basal cell carcinoma (BCC) and acute promyelocytic leukemia, among many others. Inactivating mutations in Patched-1 (PTCH1), leading to ligand-independent pathway activation, are frequent in several cancer types, but most prominent in BCC. This has led to the development of several compounds targeting this pathway as a cancer therapeutic. These compounds target the inducers of this pathway in Smoothened (SMO) and the GLI transcription factors, although targeting SMO has had the most success. Despite the many attempts at targeting this pathway, only three US FDA-approved drugs for cancers affect the Shh pathway. Two of these compounds, vismodegib and sonidegib, target SMO to suppress signaling from either PTCH1 or SMO mutations that lead to upregulation of the pathway. The other approved compound is arsenic trioxide, which can suppress this pathway at the level of the GLI proteins, although current evidence suggests it also has other targets. This review focuses on the safety and tolerability of these clinically approved drugs targeting the Shh pathway, along with a discussion on other Shh pathway inhibitors being developed.

Absolute Oral Bioavailability of Glasdegib (PF-04449913), a Smoothened Inhibitor, in Randomized Healthy Volunteers

Glasdegib (PF‐04449913) is an oral small‐molecule inhibitor of the Hedgehog signaling pathway under development for treating myeloid malignancies. This was an open‐label phase 1, randomized, 2‐sequence, 2‐treatment, 2‐period, crossover study evaluating the absolute bioavailability of glasdegib in healthy volunteers under fasting condition (NCT03270878). In period 1, 12 eligible subjects received either a single oral dose of glasdegib 100 mg (tablet) or a single intravenous (IV) dose of glasdegib 50 mg. Following ≥6‐day washout, subjects received the treatment that they did not receive in the first period. Blood samples were collected for up to 96 hours after dosing. Drug plasma concentrations were determined by high‐performance liquid chromatography–tandem mass spectrometry. Glasdegib pharmacokinetic parameters were calculated using noncompartmental analysis. The mean terminal half‐life was 14.3 hours for oral tablet treatment vs 13.8 hours for glasdegib IV treatment. The absolute oral bioavailability measured as the ratios (oral/IV) of adjusted geometric mean (90% confidence interval) of dose normalized area under the plasma concentration–time curve was 77.12% (71.83%‐82.81%). Two adverse events (1 mild and 1 moderate in severity) were reported by 2 subjects following oral tablet administration; these were fully resolved by the end of the study.

Evaluation of the effects of formulation, food, or a proton-pump inhibitor on the pharmacokinetics of glasdegib (PF-04449913) in healthy volunteers: a randomized phase I study

PURPOSE

To demonstrate the bioequivalence of the planned maleate salt-based commercial glasdegib tablet formulation [International Council for Harmonization (ICH) glasdegib] to the clinical di-hydrochloride (di-HCl) salt-based glasdegib formulation (di-HCl glasdegib). Additionally, to estimate the effects of a high-fat, high-calorie meal and proton-pump inhibitor (PPI) on the pharmacokinetics of ICH glasdegib.

METHODS

This Phase I open-label study (ClinicalTrials.gov: NCT03130556) enrolled 24 healthy subjects to receive two different tablet formulations of single-dose 100-mg glasdegib under fasted conditions. A subset of healthy volunteers (n = 12) received single-dose 100-mg ICH glasdegib following a high-fat, high-calorie meal or concurrently with a PPI (rabeprazole).

RESULTS

The adjusted geometric mean ratio (ICH glasdegib:di-HCl glasdegib) and 90% confidence intervals (CI) of area under the plasma concentration-time curve from time zero to infinity (AUC_inf) and maximum plasma concentration (C_max) were 104.0% (99.7‒108.5%) and 101.6% (96.1‒107.4%), respectively, within the acceptance range for bioequivalence (80‒125%). The adjusted geometric mean ratio (90% CIs) for AUC_inf and C_max under fed conditions were 84.3% (78.6‒90.6%) and 69.0% (61.8‒77.0%), respectively, relative to fasted conditions. When ICH glasdegib was administered concurrently with the PPI, the adjusted geometric mean ratio (90% CI) of AUC_inf and C_max were 100.6% (93.2‒108.6%) and 80.5% (70.7‒91.6%), respectively, relative to fasted conditions. Glasdegib was generally well tolerated under all conditions studied.

CONCLUSIONS

The ICH glasdegib tablet formulation was bioequivalent to the clinical di-HCl formulation under fasted conditions. A high-fat, high-calorie meal or concurrent PPI treatment had a minimal effect on glasdegib exposure, and was not considered clinically meaningful.

Evaluation of the effect of rifampin on the pharmacokinetics of the Smoothened inhibitor glasdegib in healthy volunteers

AIMS

This study aimed to evaluate the effect of a strong CYP3A inducer, rifampin, on glasdegib pharmacokinetics in healthy volunteers.

METHODS

In an open-label, fixed-sequence, two-period Phase 1 study, subjects received a single 100-mg oral dose of glasdegib alone or following once-daily pre-treatment with 600 mg rifampin. Glasdegib pharmacokinetics were calculated using a noncompartmental analysis.

RESULTS

Twelve healthy male volunteers (3 whites, 5 blacks and 4 others) were enrolled in the study. Mean age, weight, height and body mass index was 37.8 years, 83.0 kg, 177.3 cm and 26.5 kg (m² ) ^-1 , respectively. When dosed alone, glasdegib geometric mean (% coefficient of variation) area under the plasma concentration-time curve from time zero to infinity (AUC_inf ) was 8145 ng × h ml^-1 (23%) and maximum observed concentration (C_max ) was 703.2 ng ml^-1 (19%). With rifampin, glasdegib AUC_inf and C_max decreased, with an adjusted geometric mean ratio (90% confidence interval) 29.66% (26.17-33.62) for AUC_inf and 64.71% (57.21-73.19) for C_max . Mean terminal half-life decreased from 13.39 to 5.11 hours, geometric mean apparent oral clearance increased from 12.27 to 41.38 l h^-1 , whereas median time to C_max remained similar (1.50 vs. 1.25 hours) in the presence of rifampin. All adverse events (n = 29) were mild in severity and resolved by the end of the study.

CONCLUSIONS

Co-administration of rifampin expectedly decreased glasdegib AUC_inf and C_max by ~70% and ~35%, respectively. These results will help to formulate recommendations for dosing strategies in combination with CYP3A inducers in situations where co-administration may be necessary. (clinicaltrials.gov identifier: NCT02430545).

Phase Ib Study of Glasdegib, a Hedgehog Pathway Inhibitor, in Combination with Standard Chemotherapy in Patients with AML or High-Risk MDS

Purpose: This open-label, multicenter, dose-finding, phase Ib study (NCT01546038) evaluated the safety, pharmacokinetics, pharmacodynamics, and clinical activity of the novel Hedgehog pathway Smoothened inhibitor glasdegib (PF-04449913) in patients (N = 52) with acute myeloid leukemia (AML) or high-risk myelodysplastic syndrome (MDS).Experimental Design: Glasdegib 100 or 200 mg was administered orally, once daily in 28-day cycles, in combination with low-dose cytarabine (arm A) or decitabine (arm B) to newly diagnosed patients considered not suitable for standard induction chemotherapy, and in combination with cytarabine/daunorubicin (arm C) to fit patients. The study followed a standard 3+3 dose-escalation design. The primary endpoint was dose-limiting toxicity (DLT). Ten additional patients were enrolled in expansion cohorts of arms A (n = 23) and C (n = 22) to confirm the recommended phase II dose (RP2D).Results: No DLTs were observed in arms A and B; 1 DLT (grade 4 neuropathy) occurred in arm C. The most common treatment-related nonhematologic adverse events were mostly grades 1 and 2 in all arms. Muscle spasms, dysgeusia, and alopecia were generally mild. Overall, 16 patients (31%) achieved a complete remission (CR)/CR with incomplete blood count recovery. Note that 100 mg daily was selected as the RP2D for glasdegib in combination with standard chemotherapies in the absence of an estimated MTD in this setting.Conclusions: Treatment with glasdegib in combination with standard chemotherapy was generally well-tolerated and consistent with prior findings, warranting further evaluation of glasdegib-based combinations in patients with AML or high-risk MDS. Clin Cancer Res; 24(10); 2294-303. ©2018 AACR.

Evaluation of the effect of new formulation, food, or a proton pump inhibitor on the relative bioavailability of the smoothened inhibitor glasdegib (PF-04449913) in healthy volunteers

PURPOSE

This phase I open-label study investigated the oral bioavailability of two novel maleate salt-based glasdegib (PF-04449913) tablet formulations (small- and large-particle size) relative to the current clinical formulation (diHCl salt-based). In addition, the effect of a gastric pH-altering agent (rabeprazole) and food on the pharmacokinetics of the large-particle size formulation of glasdegib were evaluated. The pharmacokinetics of glasdegib oral solution was also assessed.

METHODS

Thirty-four healthy subjects received glasdegib 100 mg as three different formulations in the fasted state (diHCl salt or small- or large-particle size maleate formulation); 13 received the large-particle maleate formulation (fed), and 14 concurrently with rabeprazole (fasted); six subjects received glasdegib 50 mg oral solution (fasted).

RESULTS

For both new tablet formulations of glasdegib, ratios (Test:Reference) of adjusted geometric means (90% confidence interval) of area under the concentration-time curve from 0 to infinity and maximum plasma concentration were within 80-125% compared with the diHCl formulation (fasted). For the large-particle size formulation (fed), these ratios were 86.3% (81.0-92.0%) and 75.7% (65.3-87.7%), respectively, compared with fasted. When the large-particle maleate formulation was administered concurrently with rabeprazole versus alone (fasted), these ratios were 111.9% (102.8-121.9%) and 87.2% (75.9-100.3%), respectively. The pharmacokinetics of oral solution was similar to the tablet.

CONCLUSIONS

The maleate salt-based tablet formulations were bioequivalent to the diHCl tablet formulation. The extent of the observed effect of a high-fat, high-calorie meal or concurrent rabeprazole treatment on glasdegib exposure is not considered clinically meaningful.

Effects of food and grapefruit juice on single-dose pharmacokinetics of blonanserin in healthy Chinese subjects

PURPOSE

The purpose of this study was to investigate the potential effects of a meal and grapefruit juice on the pharmacokinetics of blonanserin and its metabolite N-desethyl blonanserin in healthy Chinese volunteers.

METHODS

This was a single-centre, open-label, fixed-sequence study, where 12 healthy Chinese volunteers received a single dose of 8 mg blonanserin after an overnight fast in period 1 (reference), a high-fat meal during period 2 and with co-administration of 250 mL of grapefruit juice in period 3. The washout period was 7 days. Series of plasma samples were collected after each dose to determine concentrations of blonanserin and its metabolite N-desethyl blonanserin using liquid chromatography-tandem mass spectrometry. Pharmacokinetic parameters were estimated by non-compartmental analysis and compared between periods by standard average bioequivalence ANOVA. Adverse events were monitored throughout the study.

RESULTS

All subjects completed the study. High-fat meals significantly increased blonanserin exposure (AUC_t) 2.58-fold (90% CI 2.21, 3.02), relative to the reference period. Co-administration of blonanserin with grapefruit juice remarkably prolonged elimination half-life of blonanserin (from 9.7 to 21.4 h) and significantly increased exposures to blonanserin and N-desethyl blonanserin by 5.82-fold (90% CI 4.57, 7.42) and 1.81-fold (90% CI 1.65, 1.98), respectively.

CONCLUSIONS

These results suggested that blonanserin was largely metabolised in the intestinal tract before becoming systemically available, and both food and grapefruit juice enhanced exposure to blonanserin and N-desethyl blonanserin. Grapefruit juice increased bioavailability and may have reduced systemic clearance of blonanserin. Further intestinal CYP3A4 and hepatic CYP3A4 might be postulated to explain the delayed elimination of blonanserin. Dose adjustment of blonanserin is needed on the basis of co-intake of known strong CYP3A4 inhibitor. Patients taking high-dose blonanserin also need to be cautious about the ingestion of grapefruit juice.

Phase I study of glasdegib (PF-04449913), an oral smoothened inhibitor, in Japanese patients with select hematologic malignancies

The hedgehog signaling pathway regulates multiple morphogenetic processes during embryogenesis. Aberrant activation of the hedgehog pathway signal transduction in adult tissues is associated with the pathogenesis of hematologic malignancies and solid tumors. We report findings from an open‐label, multicenter phase I trial of the selective, small‐molecule hedgehog signaling inhibitor glasdegib (PF‐04449913) in Japanese patients with select advanced hematologic malignancies. Glasdegib was administered as once‐daily oral doses (25, 50 and 100 mg) in 28‐day cycles after a lead‐in dose on Day −5. The primary objectives were to determine first‐cycle dose‐limiting toxicities, safety, vital signs and laboratory test abnormalities. Secondary objectives included evaluation of pharmacokinetics, pharmacodynamics and preliminary evidence of clinical activity of glasdegib. No dose‐limiting toxicities were noted in the 13 patients in the present study. All patients experienced at least one treatment‐emergent, all‐causality adverse event. The most frequent treatment‐related adverse events (observed in ≥3 patients) were dysgeusia (n = 9), muscle spasms (n = 5), alopecia, decreased appetite (n = 4 each), and increased blood creatinine phosphokinase, constipation and diarrhea (n = 3 each). Two deaths occurred during the study and were deemed not to be treatment‐related due to disease progression. Glasdegib demonstrated dose‐proportional pharmacokinetics, marked downregulation of the glioma‐associated transcriptional regulator GLI1 expression in normal skin, and evidence of preliminary clinical activity, although data are limited. Glasdegib was safe and well tolerated across the dose levels tested. It is confirmed that the 100‐mg dose is safe and tolerable in Japanese patients, and this dose level will be examined in the future clinical trial.