The estimation and translation uncertainties in applying NOAEL to clinical dose escalation.

The systemic exposure at the no-observed-adverse-effect-level (NOAEL) estimated from animals is an important criterion commonly applied to guard the safety of participants in clinical trials of investigational drugs. However, the discrepancy in toxicity profile between species is widely recognized. The objective of the work reported here was to assess, via simulation, the level of uncertainty in the NOAEL estimated from an animal species and the effectiveness of applying its associated exposure value to minimizing the toxicity risk to human. Simulations were conducted for dose escalation of an investigational new chemical entity with hypothetical exposure-response models for the dose-limiting toxicity under a variety of conditions, in terms of between-species relative sensitivity to the toxicity and the between-subject variability in the key parameters determining the sensitivity and pharmacokinetics. Results show a high uncertainty in the NOAEL estimation. Notably, even when the animal species and humans are assumed to have the same sensitivity, which may not be realistic, limiting clinical dose to the exposure at the NOAEL that has been identified in the animals carries a high risk of either causing toxicity or under-dosing, hence undermining the therapeutic potential of the drug candidate. These findings highlight the importance of understanding the mechanism of the toxicity profile and its cross-species translatability, as well as the importance of understanding the dose requirement for achieving adequate pharmacology.

Concordance of Exposure Changes Because of Renal Impairment Between Results of Dedicated Renal Impairment Studies and Population Pharmacokinetic Predictions.

This analysis compared the results from noncompartmental analysis and population pharmacokinetic (PopPK) predictions of exposure changes in patients with renal impairment (RI) for 27 new molecular entities (NMEs) approved between 2000 and 2015. Renal function was identified as a covariate in the final PopPK model for 17 NMEs. The final PopPK model was used to simulate (n = 1000 replicates/individual) the results of a dedicated PK study in subjects with renal impairment. For the majority of NMEs, concordance between observed, and predicted area under the curve (AUC) geometric mean ratio (GMR) was observed (ie, in 17, 11, and 11 NMEs for mild, moderate, and severe renal impairment groups, respectively, the observed and predicted AUC GMR were within the same fold of change). Inclusion of colinear covariates in the PopPK model appeared to be the major driver for the NMEs for which there was discordance. PopPK, when done properly, is a valuable tool for supporting labeling recommendations for subjects with renal impairment.

Molecular Modeling Studies on Cytochrome P450-mediated Drug Metabolism.

Drug metabolism studies play a critical role in the optimization of the therapeutic efficacy of newer drug candidates. Many drug candidates and drugs were withdrawn from the pre-clinical/clinical stage or market due to the poor metabolic profiles. The poor metabolic profiles may make the clinical candidates/drugs inactive or toxic. Therefore, it is necessary to optimize the metabolic profiles at the initial phase of drug discovery and development processes. Recently, molecular modeling approaches were found to be useful in the optimization of metabolic profiles of clinical candidates. The molecular modeling approaches were employed in the identification of various metabolic profiles. In the present study, the current status of the research work on drug metabolism based on molecular modeling methodologies has been reviewed. The basics of drug metabolism and its importance in the physiological process of the human body have been described. Moreover, the involvement of molecular modeling approaches like pharmacophore- based modeling, QSAR, molecular docking, virtual screening, quantum chemical analysis, molecular dynamics, etc., in predicting metabolic profiles of therapeutic agents is analyzed. The present review provides computational insights in the prediction of substrate specificity, metabolic activity, SOM, metabolites, toxicity, etc., on cytochrome P450-mediated drug metabolism. The study may help the researchers to design novel drug candidates for the various classes of therapeutic targets with efficient metabolic profiles.

Molecular structure, NBO analysis of the hydrogen-bonded interactions, spectroscopic (FT-IR, FT-Raman), drug likeness and molecular docking of the novel anti COVID-2 molecule (2E)-N-methyl-2-[(4-oxo-4H-chromen-3-yl)methylidene]-hydrazinecarbothioamide (Dimer) - quantum chemical approach.

Prospective antiviral molecule (2E)-N-methyl-2-[(4-oxo-4H-chromen-3-yl)methylidene]-hydrazinecarbothioamide has been probed using Fourier transform infrared (FTIR), FT-Raman and quantum chemical computations. The geometry equilibrium and natural bond orbital analysis have been carried out with density functional theory employing Becke, 3-parameter, Lee-Yang-Parr method with the 6-311G++(d,p) basis set. The vibrational assignments pertaining to different modes of vibrations have been augmented by normal coordinate analysis, force constant and potential energy distributions. Drug likeness and oral activity have been carried out based on Lipinski's rule of five. The inhibiting potency of 2(2E)-methyl-2-[(4-oxo-4H-chromen-3-yl)methylidene]-hydrazinecarbothioamide has been investigated by docking simulation against SARS-CoV-2 protein. The optimized geometry shows a planar structure between the chromone and the side chain. Differences in the geometries due to the substitution of the electronegative atom and intermolecular contacts due to the chromone and hydrazinecarbothioamide were analyzed. NBO analysis confirms the presence of two strong stable hydrogen bonded NH⋯O intermolecular interactions and two weak hydrogen bonded CH⋯O interactions. The red shift in NH stretching frequency exposed from IR substantiates the formation of NH⋯O intermolecular hydrogen bond and the blue shift in CH stretching frequency substantiates the formation of CH⋯O intermolecular hydrogen bond. Drug likeness, absorption, distribution, metabolism, excretion and toxicity property gives an idea about the pharmacokinetic properties of the title molecule. The binding energy of the nonbonding interaction with Histidine 41 and Cysteine 145, present a clear view that 2(2E)-methyl-2-[(4-oxo-4H-chromen-3-yl)methylidene]-hydrazinecarbothioamide can irreversibly interact with SARS-CoV-2 protease.

Human iPSC-Derived Blood-Brain Barrier Models: Valuable Tools for Preclinical Drug Discovery and Development?

Translating basic biological knowledge into applications remains a key issue for effectively tackling neurodegenerative, neuroinflammatory, or neuroendocrine disorders. Efficient delivery of therapeutics across the neuroprotective blood-brain barrier (BBB) still poses a demanding challenge for drug development targeting central nervous system diseases. Validated in vitro models of the BBB could facilitate effective testing of drug candidates targeting the brain early in the drug discovery process during lead generation. We here review the potential of mono- or (isogenic) co-culture BBB models based on brain capillary endothelial cells (BCECs) derived from human-induced pluripotent stem cells (hiPSCs), and compare them to several available BBB in vitro models from primary human or non-human cells and to rodent in vivo models, as well as to classical and widely used barrier models [Caco-2, parallel artificial membrane permeability assay (PAMPA)]. In particular, we are discussing the features and predictivity of these models and how hiPSC-derived BBB models could impact future discovery and development of novel CNS-targeting therapeutics. © 2020 The Authors.

Placental transfer and safety in pregnancy of medications under investigation to treat coronavirus disease 2019.

Objective: Treatment of coronavirus disease 2019 is mostly symptomatic, but a wide range of medications are under investigation against severe acute respiratory syndrome coronavirus 2. Although pregnant women are excluded from clinical trials, they will inevitably receive therapies whenever they seem effective in nonpregnant patients and even under compassionate use. Methods: We conducted a review of the literature on placental transfer and pregnancy safety data of drugs under current investigation for coronavirus disease 2019. Results: Regarding remdesivir, there are no data in pregnant women. Several other candidates already have safety data in pregnant women, because they are repurposed drugs already used for their established indications. Thus, they may be used in pregnancy, although their safety in the context of coronavirus disease 2019 may differ from conventional use. These include HIV protease inhibitors such as lopinavir/ritonavir that have low placental transfer, interferon that does not cross the placental barrier, and hydroxychloroquine or chloroquine that has high placental transfer. There are also pregnancy safety and placental transfer data for colchicine, steroids, oseltamivir, azithromycin, and some monoclonal antibodies. However, some drugs are strictly prohibited in pregnancy because of known teratogenicity (thalidomide) or fetal toxicities (renin-angiotensin system blockers). Other candidates including tocilizumab, other interleukin 6 inhibitors, umifenovir, and favipiravir have insufficient data on pregnancy outcomes. Conclusion: In life-threatening cases of coronavirus disease 2019, the potential risks of therapy to the fetus may be more than offset by the benefit of curing the mother. Although preclinical and placental transfer studies are required for a number of potential anti-severe acute respiratory syndrome coronavirus 2 drugs, several medications can already be used in pregnant women.

Target-mediated exposure enhancement: a previously unexplored limit of TMDD.

Target-mediated drug disposition (TMDD) is often observed for targeted therapeutics, and manifests as decreases in clearance and volume of distribution with increasing dose as a result of saturable, high affinity target binding. In the present work, we demonstrate that classically defined TMDD is just one of the characteristic features of the system. In fact, for molecules with rapid non-specific elimination relative to target-mediated elimination, binding to target may actually lead to improved exposure at sub-saturating doses. This feature, which we refer to as target-mediated exposure enhancement (TMEE), produces the opposite trend to classical TMDD, i.e., with increasing dose levels, clearance and volume of distribution will also increase. The general model of TMDD was able to well-characterize the pharmacokinetics of two molecules that display TMEE, ALX-0081 and linagliptin. Additional fittings using the commonly reported TMDD model approximations revealed that both the quasi-equilibrium and quasi-steady-state approximations were able to well-describe TMEE; however, the Michaelis-Menten approximation was unable to describe this behavior. With the development of next-generation therapeutics with high affinity for target and rapid non-specific elimination, such as antibody fragments and peptides, this previously unexplored limit of TMDD is anticipated to become increasingly relevant for describing pharmacokinetics of investigational therapeutics.

2020 FDA Drug-drug Interaction Guidance: A Comparison Analysis and Action Plan by Pharmaceutical Industrial Scientists.

BACKGROUND: In January 2020, the US FDA published two final guidelines, one entitled "In vitro Drug Interaction Studies - Cytochrome P450 Enzyme- and Transporter-Mediated Drug Interactions Guidance for Industry" and the other entitled "Clinical Drug Interaction Studies - Cytochrome P450 Enzyme- and Transporter-Mediated Drug Interactions Guidance for Industry". These were updated from the 2017 draft in vitro and clinical DDI guidance. METHODS: This study is aimed to provide an analysis of the updates along with a comparison of the DDI guidelines published by the European Medicines Agency (EMA) and Japanese Pharmaceuticals and Medical Devices Agency (PMDA) along with the current literature. RESULTS: The updates were provided in the final FDA DDI guidelines and explained the rationale of those changes based on the understanding from research and literature. Furthermore, a comparison among the FDA, EMA, and PMDA DDI guidelines are presented in Tables 1, 2 and 3. CONCLUSION: The new 2020 clinical DDI guidance from the FDA now has even higher harmonization with the guidance (or guidelines) from the EMA and PMDA. A comparison of DDI guidance from the FDA 2017, 2020, EMA, and PMDA on CYP and transporter based DDI, mathematical models, PBPK, and clinical evaluation of DDI is presented in this review.

Phase IA/IB study of single-agent tislelizumab, an investigational anti-PD-1 antibody, in solid tumors.

BACKGROUND: The programmed cell death-1/programmed cell death ligand-1 (PD-1/PD-L1) axis plays a central role in suppressing antitumor immunity; axis dysregulation can be used by cancer cells to evade the immune system. Tislelizumab, an investigational monoclonal antibody with high affinity and binding specificity for PD-1, was engineered to minimize binding to FcγR on macrophages to limit antibody-dependent phagocytosis, a potential mechanism of resistance to anti-PD-1 therapy. The aim of this phase IA/IB study was to investigate the safety/tolerability, antitumor effects and optimal dose and schedule of tislelizumab in patients with advanced solid tumors. METHODS: Patients (aged ≥18 years) enrolled in phase IA received intravenous tislelizumab 0.5, 2, 5 or 10 mg/kg every 2 weeks; 2 or 5 mg/kg administered every 2 weeks or every 3 weeks; or 200 mg every 3 weeks; patients in phase IB received 5 mg/kg every 3 weeks. Primary objectives were to assess tislelizumab's safety/tolerability profile by adverse event (AE) monitoring and antitumor activity using RECIST V.1.1. PD-L1 expression was assessed retrospectively with the VENTANA PD-L1 (SP263) Assay. RESULTS: Between May 2015 and October 2017, 451 patients (n=116, IA; n=335, IB) were enrolled. Fatigue (28%), nausea (25%) and decreased appetite (20%) were the most commonly reported AEs. Most AEs were grade 1-2 severity; anemia (4.9%) was the most common grade 3-4 AE. Treatment-related AEs led to discontinuation in 5.3% of patients. Grade 5 AEs were reported in 14 patients; 2 were considered related to tislelizumab. Pneumonitis (2%) and colitis (1%) were the most common serious tislelizumab-related AEs. As of May 2019, 18% of patients achieved a confirmed objective response in phase IA and 12% in phase IB; median follow-up duration was 13.6 and 7.6 months, respectively. Pharmacokinetics, safety and antitumor activity obtained from both phase IA and IB determined the tislelizumab recommended dose; ultimately, tislelizumab 200 mg intravenous every 3 weeks was the dose and schedule recommended to be taken into subsequent clinical trials. CONCLUSIONS: Tislelizumab monotherapy demonstrated an acceptable safety/tolerability profile. Durable responses were observed in heavily pretreated patients with advanced solid tumors, supporting the evaluation of tislelizumab 200 mg every 3 weeks, as monotherapy and in combination therapy, for the treatment of solid tumors and hematological malignancies. TRIAL REGISTRATION NUMBER: NCT02407990.

Tislelizumab in Chinese patients with advanced solid tumors: an open-label, non-comparative, phase 1/2 study.

BACKGROUND: Tislelizumab is an investigational, humanized, IgG4 monoclonal antibody with high affinity and binding specificity for programmed cell death-1 (PD-1) that was engineered to minimize binding to FcγR on macrophages in order to abrogate antibody-dependent phagocytosis, a mechanism of T-cell clearance and potential resistance to anti-PD-1 therapy. METHODS: The purpose of this phase 1/2, open-label, non-comparative study was to examine the safety, tolerability, and antitumor activity of tislelizumab in adult (≥18 years) Chinese patients with histologically or cytologically confirmed advanced solid tumors with measurable disease. The phase 1 portion of the study consisted of a dose-verification study and a pharmacokinetic (PK) substudy; phase 2 was an indication-expansion study including 11 solid tumor cohorts. Patients previously treated with therapies targeting PD-1 or its ligand, programmed cell death ligand-1 were excluded. During dose-verification, dose-limiting toxicities (DLTs) were monitored; safety and tolerability were examined and the previously determined recommended phase 2 dose (RP2D) was verified. The primary endpoint of phase 2 was investigator-assessed objective response rate per Response Evaluation Criteria in Solid Tumors V.1.1. RESULTS: As of December 1, 2018, 300 patients were treated with tislelizumab 200 mg intravenously once every 3 weeks (Q3W). Median duration of follow-up was 8.1 months (range 0.2-21.9). No DLTs were reported during the phase 1 dose-verification study and the RP2D was confirmed to be 200 mg intravenously Q3W. Most treatment-related adverse events (62%) were grade 1 or 2, with the most common being anemia (n=70; 23%) and increased aspartate aminotransferase (n=67; 22%). Of the 251 efficacy evaluable patients, 45 (18%) achieved a confirmed clinical response, including one patient from the PK substudy who achieved a complete response. Median duration of response was not reached for all except the nasopharyngeal carcinoma cohort (8.3 months). Antitumor responses were observed in multiple tumor types. CONCLUSIONS: Tislelizumab was generally well tolerated among Chinese patients. Antitumor activity was observed in patients with multiple solid tumors. TRIAL REGISTRATION NUMBER: CTR20160872.

Investigational drugs to treat hemophilia.

Introduction: Hemophilia A and B are congenital bleeding disorders. The current standard management of patients with severe hemophilia is prophylaxis which is given intravenously two or three times weekly; however, this is associated with a significant burden on the quality of life of the patient. The main attempts to improve the management of hemophilia is hence through the development of a new generation of products with properties facilitating prophylaxis and/or a better control of bleeding.Areas covered: This review describes the preclinical and phase 1/2 studies investigating the innovative products for the management of hemophilia patients with or without coagulation factor inhibitors.Expert opinion: Numerous innovative therapeutics, including factor concentrates and non-clotting factor-based therapies with extended half-life, are under clinical investigation. Among replacement therapies for hemophilia A, the results from phase 1/2 studies indicate that the most interesting products are those bioengineered using XTEN fusion technology. The anti-tissue factor pathway inhibitor antibody concizumab is the most innovative and interesting agent among non-clotting factor products. If the results of ongoing trials confirm the preliminary positive results, these promising agents will provide further improvements in the management and quality of life of patients with hemophilia.

Human-Induced Pluripotent Stem Cell-Derived Hepatocytes and their Culturing Methods to Maintain Liver Functions for Pharmacokinetics and Safety Evaluation of Pharmaceuticals.

Human hepatocytes are essential cell types for pharmacokinetics and the safety evaluation of pharmaceuticals. However, widely used primary hepatocytes with individual variations in liver function lose those functions rapidly in culture. Hepatic cell lines are convenient to use but have low liver functions. Human-Induced Pluripotent Stem (hiPS) cells can be expanded and potentially differentiated into any cell or tissue, including the liver. HiPS cell-derived Hepatocyte-Like Cells (hiPSHeps) are expected to be extensively used as consistent functional human hepatocytes. Many laboratories are investigating methods of using hiPS cells to differentiate hepatocytes, but the derived cells still have immature liver functions. In this paper, we describe the current uses and limitations of conventional hepatic cells, evaluating the suitability of hiPS-Heps to pharmacokinetics and the safety evaluation of pharmaceuticals, and discuss the potential future use of non-conventional non-monolayer culture methods to derive fully functional hiPS-Heps.

GSTZ1 genotypes correlate with dichloroacetate pharmacokinetics and chronic side effects in multiple myeloma patients in a pilot phase 2 clinical trial.

Dichloroacetate (DCA) is an investigational drug targeting the glycolytic hallmark of cancer by inhibiting pyruvate dehydrogenase kinases (PDK). It is metabolized by GSTZ1, which has common polymorphisms altering enzyme or promoter activity. GSTZ1 is also irreversibly inactivated by DCA. In the first clinical trial of DCA in a hematological malignancy, DiCAM (DiChloroAcetate in Myeloma), we have examined the relationship between DCA concentrations, GSTZ1 genotype, side effects, and patient response. DiCAM recruited seven myeloma patients in partial remission. DCA was administered orally for 3 months with a loading dose. Pharmacokinetics were performed on day 1 and 8. Trough and peak concentrations of DCA were measured monthly. GSTZ1 genotypes were correlated with drug concentrations, tolerability, and disease outcomes. One patient responded and two patients showed a partial response after one month of DCA treatment, which included the loading dose. The initial half-life of DCA was shorter in two patients, correlating with heterozygosity for GSTZ1*A genotype, a high enzyme activity variant. Over 3 months, one patient maintained DCA trough concentrations approximately threefold higher than other patients, which correlated with a low activity promoter genotype (-1002A, rs7160195) for GSTZ1. This patient displayed the strongest response, but also the strongest neuropathy. Overall, serum concentrations of DCA were sufficient to inhibit the constitutive target PDK2, but unlikely to inhibit targets induced in cancer. Promoter GSTZ1 polymorphisms may be important determinants of DCA concentrations and neuropathy during chronic treatment. Novel dosing regimens may be necessary to achieve effective DCA concentrations in most cancer patients while avoiding neuropathy.

Retos relacionados con el manejo terapéutico del dolor neuropático / Challenges relating to the therapeutic management of neuropathic pain

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Randomised clinical trial: a placebo-controlled study of subcutaneous or intradermal NEXVAX2, an investigational immunomodulatory peptide therapy for coeliac disease.

BACKGROUND: Nexvax2 contains three gluten-derived peptides, intended to tolerize coeliac disease patients to gluten. Sequences cover six epitopes that trigger immune activation in human leucocyte antigen-DQ2.5-positive patients, most notably after an initial dose. Patients experience gastrointestinal symptoms with increases in serum interleukin-2. Consistent with Nexvax2's induction of non-responsiveness, reactivity disappears after repeated doses, or is avoided with gradual dose escalation. Early clinical trials used intradermal dosing, but pharmacokinetics and rapid onset of effect suggest that subcutaneous delivery may also be effective. AIMS: To document the relative bioavailability of Nevax2 peptides after subcutaneous and intradermal dosing, and the tolerability and ability of subcutaneous dosing to induce non-responsiveness to Nexvax2 peptides. METHODS: A randomised, double-blind, placebo-controlled study was conducted to assess plasma pharmacokinetics after subcutaneous and intradermal Nexvax2 dosing in HLA DQ2.5-positive patients, who had symptoms after an oral gluten challenge. Randomisation was to semi-weekly Nexvax2 (n = 12) or placebo (n = 2) injections, over a 5-week subcutaneous dose escalation and 2-week maintenance period, the latter with four doses of 900 µg, two subcutaneous and two intradermal. Post-dose circulating peptide and interleukin-2 levels were assessed. Investigators recorded adverse events experienced by patients. RESULTS: Subcutaneous dosing resulted in slightly greater exposure. Interleukin-2 responses were seen with the gluten challenge but not after subcutaneous or intradermal dosing of 900 µg. Adverse events were generally mild and self-limited. CONCLUSIONS: Subcutaneous and intradermal dosing of Nexvax2 yield similar bioavailability of constituent peptides; subcutaneous dose escalation avoids an immune response to dominant gluten epitopes.

Population pharmacokinetics of pevonedistat alone or in combination with standard of care in patients with solid tumours or haematological malignancies.

AIMS: A population pharmacokinetic (PK) analysis was conducted to quantify the impact of patient-specific and concurrent medication factors on pevonedistat PK. METHODS: Data were pooled from 6 clinical studies consisting of 335 patients with solid tumours or haematological malignancies administered pevonedistat alone or in combination with azacitidine, docetaxel, carboplatin + paclitaxel, or gemcitabine. Model development and covariate analysis followed standard methods. Parameters and bootstrap 95% confidence intervals were estimated using nonlinear mixed-effects modelling. The final model was evaluated using visual predictive checks and other goodness-of-fit criteria. RESULTS: A linear 2-compartment model best described pevonedistat PK. The final model included the effect of body surface area (BSA) on clearance (CL and Q) and volume of distribution of pevonedistat, effect of concomitantly administered carboplatin + paclitaxel on CL, and effect of albumin on Q. Race, sex, age, tumour type (haematological vs solid), mild or moderate renal impairment (creatinine clearance ≥30 mL/min), or mild hepatic impairment, had no impact on pevonedistat PK. CONCLUSIONS: The clinical PK profile of pevonedistat is comparable in patients with solid tumours or haematological malignancies. All PK parameters exhibited ≥20% change over the observed BSA range (1.38-3 m2 ) with CL ranging from 75.5 to 208% of the reference value, with simulations supporting BSA-based dosing to minimize interindividual variability in drug exposures. Concurrent administration of carboplatin + paclitaxel decreased pevonedistat CL by approximately 44%, while coadministration with azacitidine, gemcitabine or docetaxel did not alter pevonedistat CL. No other factors were identified as influencing pevonedistat PK.

Pharmacokinetics of the Investigational Aurora A Kinase Inhibitor Alisertib in Adult Patients With Advanced Solid Tumors or Relapsed/Refractory Lymphoma With Varying Degrees of Hepatic Dysfunction.

This clinical trial was designed to evaluate the effect of moderate or severe hepatic impairment on the single-dose pharmacokinetics (PK) of the investigational anticancer agent, alisertib, in adult patients with advanced solid tumors or lymphoma. Patients with normal hepatic function (total bilirubin and alanine transaminase [ALT] ≤ upper limit of normal [ULN]), moderate hepatic impairment (1.5 × ULN < total bilirubin ≤ 3 × ULN, with any ALT) or severe hepatic impairment (total bilirubin > 3 × ULN, with any ALT), received a single 50-mg oral dose of alisertib. Blood samples for PK were collected up to 168 hours postdose. Predose samples were also used to assess alisertib plasma protein binding. Patients could continue to receive alisertib for 7 days in 21-day cycles (50, 30, or 10 mg twice daily for normal hepatic function, moderate hepatic impairment, and severe hepatic impairment, respectively). Alisertib was approximately 99% protein bound in all hepatic function groups. Alisertib exposure was similar in moderate and severe hepatic impairment groups, but higher than the normal hepatic function group. The geometric least-squares mean ratios (90% confidence intervals) for unbound alisertib area under the curve extrapolated to infinity for moderate/severe impairment groups versus the normal hepatic function group was 254% (184%, 353%). Patients with moderate or severe hepatic impairment have approximately 150% higher unbound alisertib exposures compared with patients with normal hepatic function. An approximately 60% reduction of the starting dose of alisertib in patients with moderate/severe hepatic impairment is recommended based on pharmacokinetic considerations.