Translational pharmacokinetic-pharmacodynamic modeling for an orally available novel inhibitor of anaplastic lymphoma kinase and c-Ros oncogene 1

An integrated quantitative systems pharmacology virtual population approach for calibration with oncology efficacy endpoints

In drug development, quantitative systems pharmacology (QSP) models are becoming an increasingly important mathematical tool for understanding response variability and for generating predictions to inform development decisions. Virtual populations are essential for sampling uncertainty and potential variability in QSP model predictions, but many clinical efficacy endpoints can be difficult to capture with QSP models that typically rely on mechanistic biomarkers. In oncology, challenges are particularly significant when connecting tumor size with time-to-event endpoints like progression-free survival while also accounting for censoring due to consent withdrawal, loss in follow-up, or safety criteria. Here, we expand on our prior work and propose an extended virtual population selection algorithm that can jointly match tumor burden dynamics and progression-free survival times in the presence of censoring. We illustrate the core components of our algorithm through simulation and calibration of a signaling pathway model that was fitted to clinical data for a small molecule targeted inhibitor. This methodology provides an approach that can be tailored to other virtual population simulations aiming to match survival endpoints for solid-tumor clinical datasets.

Lorlatinib as a treatment for ALK-positive lung cancer

Lorlatinib, a third-generation ALK tyrosine kinase inhibitor, has been approved as a treatment for ALK-positive lung cancer. This review provides information regarding the pharmacology and clinical features of lorlatinib, including its efficacy and associated adverse events. Pivotal clinical trials are discussed along with the current status of lorlatinib as a treatment for ALK-positive lung cancer and future therapeutic challenges.

Roadmap on plasticity and epigenetics in cancer

The role of plasticity and epigenetics in shaping cancer evolution and response to therapy has taken center stage with recent technological advances including single cell sequencing. This roadmap article is focused on state-of-the-art mathematical and experimental approaches to interrogate plasticity in cancer, and addresses the following themes and questions: is there a formal overarching framework that encompasses both non-genetic plasticity and mutation-driven somatic evolution? How do we measure and model the role of the microenvironment in influencing/controlling non-genetic plasticity? How can we experimentally study non-genetic plasticity? Which mathematical techniques are required or best suited? What are the clinical and practical applications and implications of these concepts?

Pharmacological and clinical properties of lorlatinib in the treatment of ALK-rearranged advanced non-small cell lung cancer

INTRODUCTION

Approximately 3-7% of advanced non-small cell lung cancers (NSCLC) are driven by an anaplastic lymphoma kinase (ALK) rearrangement. Crizotinib, ceritinib, alectinib, and brigatinib are active ALK inhibitors (ALKi) used to treat this oncogene-driven subset of NSCLC. Resistance occurs with time to ALKi and new therapeutics are being developed. Lorlatinib is an efficacious third-generation ALKi with an ability to overcome resistance mutations that develop with first- or second-generation ALKi.

AREAS COVERED

Herein, the authors review the mechanism of action, pharmacokinetics, pharmacodynamics, clinical efficacy, and safety of lorlatinib and provide their future perspectives on this drug.

EXPERT COMMENTARY

Lorlatinib is a potent ALK and ROS-1 inhibitor that also has activity against many acquired ALK resistance mutations. Clinical trials show the robust systemic and intracranial anti-tumor activity of lorlatinib in ALK rearranged advanced NSCLC. Adverse events of lorlatinib are unique and manageable. These include hypocholesteremia, hypertriglyceridemia, edema, cognitive effects, weight gain, and diarrhea. Loratinib will play an increasing role in the management of ALK-rearranged NSCLC with the optimal sequencing of ALKi undergoing further research.

Preclinical pharmacokinetics, disposition, and translational pharmacokinetic/pharmacodynamic modeling of savolitinib, a novel selective cMet inhibitor

Savolitinib is a novel small-molecule selective cMet inhibitor. This work characterized its pharmacokinetics in preclinical phase, established the preclinical relationships between PK, cMet modulation and anti-tumor efficacy. In vitro and in vivo animal studies were performed for PK characterization. Savolitinib showed good absorption, moderate tissue distribution, low to intermediate clearance, and low accumulation. Hepatic oxidative metabolism followed by urinary and biliary excretions was the major elimination pathway. Based on preclinical PK data, human PK profiles were predicted using empirical methods. Pharmacodynamic studies for evaluating cMet inhibition and anti-tumor efficacy were conducted in nude mice bearing Hs746t xenograft. PK/PD models were built to link the PD measurements to nude mouse PK. The established integrated preclinical PK/PD model contained a two-compartment non-linear PK model, a biomarker link model and a tumor growth transit model. The IC₅₀ of cMet inhibition and the concentration achieving half of the maximal Hs746t tumor reduction by savolitinib were equal to 12.5 and 3.7 nM (free drug), respectively. Based on the predicted human PK data, as well as the established PK/PD model in nude mouse, the human PD (cMet inhibition) profiles were also simulated. This research supported clinical development of savolitinib. Understanding the preclinical PK/PD relationship of savolitinib provides translational insights into the cMet-targeted drug development.

Pharmacokinetic-pharmacodynamic models that incorporate drug-target binding kinetics

Pharmacokinetic/pharmacodynamic (PK/PD) models predict the effect time course resulting from a drug dose. In this review, we summarize the development of mechanistic PK/PD models that explicitly integrate the kinetics of drug-target interactions into predictions of drug activity. Such mechanistic models are expected to have several advantages over approaches in which concentration and effect are linked using variations of the Hill equation, and where preclinical data are often used as a starting point for modeling drug activity. Instead, explicit use of the full kinetic scheme for drug binding enables time-dependent changes in target occupancy to be calculated using the kinetics of drug-target interactions and drug PK, providing a more precise picture of target engagement and drug action in the non-equilibrium environment of the human body. The mechanistic PK/PD models also generate target vulnerability functions that link target occupancy and effect, and inform on the sensitivity of a target to engagement by a drug. Key factors such as the rate of target turnover can also be integrated into the modeling which, together with target vulnerability, provide additional information on the PK profile required to achieve the desired pharmacological effect and on the utility of kinetic selectivity in developing drugs for specific targets.

Pharmacokinetic Study and Tissue Distribution of Lorlatinib in Mouse Serum and Tissue Samples by Liquid Chromatography-Mass Spectrometry

In the present study, we developed and validated a rapid and simple liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the determination of lorlatinib in mouse serum and tissue samples, and such a method was successfully applied to investigate the pharmacokinetic study and tissue distribution of lorlatinib after oral administration. Samples were processed with methanol to precipitate protein and extract drugs, and Afatinib-d6 was used as the internal standard (IS). For LC-MS/MS analysis, compounds were separated on a C18 column by gradient elution (0.1% of formic acid and methanol) at 0.5 mL/min in the positive-ion mode with m/z 407.28 [M + H]⁺ for lorlatinib and m/z 492.10 [M + H]⁺ for IS. Good linearity was observed within the calibration ranges. Selectivity, accuracy (-6.42% to 8.84%), precision (1.69% to 10.98%), recoveries (91.4% to 115.0%), and matrix effect (84.2% to 110.6%) were all within the acceptable ranges. After oral administration, serum concentration of lorlatinib quickly achieved the maximal concentration (2,705.683 ± 539.779 μg/L) at 0.625 ± 0.231 h. The highest concentration was detected in the liver (3,153.93 ng/100 mg), followed by the stomach (2,159.92 ng/100 mg) and the kidney (548.83 ng/100 mg). In conclusion, a simple and rapid detection method was established and validated for determination of lorlatinib in blood and tissue samples of mouse. The pharmacokinetic study and tissue distribution of lorlatinib were successfully investigated using this method.

Bioanalytical liquid chromatography-tandem mass spectrometric assay for the quantification of the ALK inhibitors alectinib, brigatinib and lorlatinib in plasma and mouse tissue homogenates

Several second and third generation ALK inhibitors have been introduced in recent years. A bioanalytical assay for simultaneous quantification of alectinib, brigatinib, and lorlatinib was developed and validated for human plasma. The method was also partially validated for diluted mouse plasma and tissue homogenates of brain, liver, kidney, and spleen. Samples (40 μl) were pretreated in a 96-well plate by protein precipitation with acetonitrile containing the internal standard [²H₈]-alectinib. After chromatographic separation on an ethylene bridged octadecyl silica column by gradient elution at 600 μl/min using 1% (v/v) formic acid (in water) and acetonitrile, compounds were ionized by a turbo electrospray and monitored by selected reaction monitoring on a triple quadrupole mass spectrometer. Validation was performed in a 2-2000 ng/ml concentration range for alectinib and lorlatinib and a 4-4000 ng/ml range for brigatinib. Precisions (within-day and between-day) were in the range 2.2-15.0% and accuracies were in between 87.2 and 110.2% for all matrices and levels. Compounds were sufficiently stable under most investigated conditions. Results of a pilot pharmacokinetic and tissue distribution study for brigatinib in mice are reported. Finally, successful incurred samples reanalysis of tissue homogenate samples containing brigatinib and lorlatinib is presented. Lorlatinib homogenate samples were also successfully reanalyzed using a second independent assay (cross-validation).

Bioanalytical assay for the quantification of the ALK inhibitor lorlatinib in mouse plasma using liquid chromatography-tandem mass spectrometry

A bio-analytical assay for the first third generation ALK inhibitor lorlatinib in mouse plasma was developed and validated. Ten-μl plasma samples were prepared by adding rucaparib as the internal standard and precipitation of the plasma proteins. For LC-MS/MS analysis, compounds were eluted at 0.5 mL/min and separated on a 3-μm particle-size, polar embedded octadecyl silica column by gradient elution using 0.1% of formic acid (in water) and methanol. Compounds were monitored with positive electrospray ionization using a triple quadrupole mass spectrometer in selected reaction monitoring mode. The assay was fully validated in the 2-2000 ng/mL calibration range. Within-day (8.0-11.6%) and between-day (10.0-15.0%) precisions and accuracies (99.0-113.3%) were within acceptable range. Plasma samples were deemed stable for 6 h at ambient temperature, during three freeze-thaw cycles and for 2 months at -30 °C. Finally, the new assay was applied successfully to pilot pharmacokinetic studies in male and female wild-type mice.

Current mathematical models for cancer drug discovery

INTRODUCTION

Pharmacometric models represent the most comprehensive approaches for extracting, summarizing and integrating information obtained in the often sparse, limited, and less-than-optimally designed experiments performed in the early phases of oncology drug discovery. Whilst empirical methodologies may be enough for screening and ranking candidate drugs, modeling approaches are needed for optimizing and making economically viable the learn-confirm cycles within an oncology research program and anticipating the dose regimens to be investigated in the subsequent clinical development. Areas covered: Papers appearing in the literature of approximately the last decade reporting modeling approaches applicable to anticancer drug discovery have been listed and commented. Papers were selected based on the interest in the proposed methodology or in its application. Expert opinion: The number of modeling approaches used in the discovery of anticancer drugs is consistently increasing and new models are developed based on the current directions of research of new candidate drugs. These approaches have contributed to a better understanding of new oncological targets and have allowed for the exploitation of the relatively sparse information generated by preclinical experiments. In addition, they are used in translational approaches for guiding and supporting the choice of dosing regimens in early clinical development.

Translational modeling and simulation approaches for molecularly targeted small molecule anticancer agents from bench to bedside

INTRODUCTION

Recent advances in molecular biology have enabled personalized cancer therapies with molecularly targeted agents (MTAs), which offer a promising future for cancer therapy. Dynamic modeling and simulation (M&S) is a powerful mathematical approach linking drug exposures to pharmacological responses, providing a quantitative assessment of in vivo drug potency. Accordingly, a growing emphasis is being placed upon M&S to quantitatively understand therapeutic exposure-response relationships of MTAs in nonclinical models.

AREAS COVERED

An overview of M&S approaches for MTAs in nonclinical models is presented with discussion about mechanistic extrapolation of antitumor efficacy from bench to bedside. Emphasis is placed upon recent advances in M&S approaches linking drug exposures, biomarker responses (e.g. target modulation) and pharmacological outcomes (e.g. antitumor efficacy).

EXPERT OPINION

For successful personalized cancer therapies with MTAs, it is critical to mechanistically and quantitatively understand their exposure-response relationships in nonclinical models, and to logically and properly apply such knowledge to the clinic. Particularly, M&S approaches to predict pharmacologically active concentrations of MTAs in patients based upon nonclinical data would be highly valuable in guiding the design and execution of clinical trials. Proactive approaches to understand their exposure-response relationships could substantially increase probability of achieving a positive proof-of-concept in the clinic.

The ALK inhibitor PF-06463922 is effective as a single agent in neuroblastoma driven by expression of ALK and MYCN

The first-in-class inhibitor of ALK, c-MET and ROS1, crizotinib (Xalkori), has shown remarkable clinical efficacy in treatment of ALK-positive non-small cell lung cancer. However, in neuroblastoma, activating mutations in the ALK kinase domain are typically refractory to crizotinib treatment, highlighting the need for more potent inhibitors. The next-generation ALK inhibitor PF-06463922 is predicted to exhibit increased affinity for ALK mutants prevalent in neuroblastoma. We examined PF-06463922 activity in ALK-driven neuroblastoma models in vitro and in vivo In vitro kinase assays and cell-based experiments examining ALK mutations of increasing potency show that PF-06463922 is an effective inhibitor of ALK with greater activity towards ALK neuroblastoma mutants. In contrast to crizotinib, single agent administration of PF-06463922 caused dramatic tumor inhibition in both subcutaneous and orthotopic xenografts as well as a mouse model of high-risk neuroblastoma driven by Th-ALK(F1174L)/MYCN Taken together, our results suggest PF-06463922 is a potent inhibitor of crizotinib-resistant ALK mutations, and highlights an important new treatment option for neuroblastoma patients.

New Treatment Options for ALK-Rearranged Non-Small Cell Lung Cancer

OPINION STATEMENT

ALK rearrangements are present in 3-5% of patients with non-small cell lung cancer (NSCLC) and after epidermal growth factor receptor (EGFR) mutations represent the second molecular target in NSCLC to be validated through phase III clinical trials. The PROFILE 1014 international multicentre phase III trial demonstrated the superiority of crizotinib over standard chemotherapy, establishing crizotinib as standard first-line therapy for patients with advanced ALK-positive NSCLC and indicating the requirement for ALK testing to guide selection of optimal first-line therapy for non-squamous NSCLC. Despite impressive and durable responses, progression on treatment reflecting the development of acquired resistance is inevitable. There are several mechanisms of resistance including ALK kinase mutation or copy number gain, activation of bypass pathways and potentially pharmacokinetic failure of therapy (most commonly in CNS). A broad array of newer generation ALK inhibitors are in development that appear effective in the crizotinib-resistant setting including in patients with intracranial progression. These agents, including ceritinib and alectinib, have a higher potency against ALK kinase than crizotinib, activity against mutations that confer resistance to crizotinib and potentially improved CNS penetration. While in selected patients, continued therapy with crizotinib after local ablative treatments of oligo-progressive systemic or CNS disease may be an option, for many patients use of a newer generation compound will be effective. First-line treatment with newer generation ALK inhibitors may have potential advantages over sequential treatment after crizotinib; however, the optimal sequence of therapy with ALK inhibitors has not been determined and is being explored in ongoing phase III studies.

NPM/ALK mutants resistant to ASP3026 display variable sensitivity to alternative ALK inhibitors but succumb to the novel compound PF-06463922

ALK is involved in the onset of several tumors. Crizotinib (Xalkori^TM), a potent ALK inhibitor, represents the current front-line treatment for ALK+ NSCLC and shows great clinical efficacy. However, resistant disease often develops after initial response. ASP3026 is a novel second-generation ALK inhibitor with activity on crizotinib-resistant ALK-L1196M gatekeeper mutant. As resistance is likely to be a relevant hurdle for any drug, we sought to determine the resistance profile of ASP3026 in the context of NPM/ALK+ ALCL. We selected six ASP3026-resistant cell lines by culturing human ALCL cells in the presence of increasing concentrations of drug. The established resistant cell lines carry several point mutations in the ALK kinase domain (G1128S, C1156F, I1171N/T, F1174I, N1178H, E1210K and C1156F/D1203N were the most frequent) that are shown to confer resistance to ASP3026 in the Ba/F3 cell model. All mutants were profiled for cross-resistance against a panel of clinically relevant inhibitors including ceritinib, alectinib, crizotinib, AP26113 and PF-06463922. Finally, a genetically heterogeneous ASP3026-resistant cell line was exposed to second-line treatment simulations with all inhibitors. The population evolved according to relative sensitivity of its mutant subclones to the various drugs. Compound PF-06463922 did not allow the outgrowth of any resistant clone, at non-toxic doses.

Therapeutic targeting of anaplastic lymphoma kinase in lung cancer: a paradigm for precision cancer medicine

The anaplastic lymphoma kinase (ALK) receptor tyrosine kinase was initially discovered as a component of the fusion protein nucleophosmin (NPM)-ALK in anaplastic large-cell lymphoma (ALCL). Genomic alterations in ALK, including rearrangements, point mutations, and genomic amplification, have now been identified in several malignancies, including lymphoma, non-small cell lung cancer (NSCLC), neuroblastoma, inflammatory myofibroblastic tumor, and others. Importantly, ALK serves as a validated therapeutic target in these diseases. Several ALK tyrosine kinase inhibitors (TKI), including crizotinib, ceritinib, and alectinib, have been developed, and some of them have already been approved for clinical use. These ALK inhibitors have all shown remarkable clinical outcomes in ALK-rearranged NSCLC. Unfortunately, as is the case for other kinase inhibitors in clinical use, sensitive tumors inevitably relapse due to acquired resistance. This review focuses on the discovery, function, and therapeutic targeting of ALK, with a particular focus on ALK-rearranged NSCLC.

Biomarker- versus drug-driven tumor growth inhibition models: an equivalence analysis

The mathematical modeling of tumor xenograft experiments following the dosing of antitumor drugs has received much attention in the last decade. Biomarker data can further provide useful insights on the pathological processes and be used for translational purposes in the early clinical development. Therefore, it is of particular interest the development of integrated pharmacokinetic-pharmacodynamic (PK-PD) models encompassing drug, biomarker and tumor-size data. This paper investigates the reciprocal consistency of three types of models: drug-to-tumor, such as established drug-driven tumor growth inhibition (TGI) models, drug-to-biomarker, e.g. indirect response models, and biomarker-to-tumor, e.g. the more recent biomarker-driven TGI models. In particular, this paper derives a mathematical relationship that guarantees the steady-state equivalence of the cascade of drug-to-biomarker and biomarker-to-tumor models with a drug-to-tumor TGI model. Using the Simeoni TGI model as a reference, conditions for steady-state equivalence are worked out and used to derive a new biomarker-driven model. Simulated and real data are used to show that in realistic cases the steady-state equivalence extends also to transient responses. The possibility of predicting the drug-to-tumor potency of a new candidate drug based only on biomarker response is discussed.

PF-06463922, an ALK/ROS1 Inhibitor, Overcomes Resistance to First and Second Generation ALK Inhibitors in Preclinical Models

We report the preclinical evaluation of PF-06463922, a potent and brain-penetrant ALK/ROS1 inhibitor. Compared with other clinically available ALK inhibitors, PF-06463922 displayed superior potency against all known clinically acquired ALK mutations, including the highly resistant G1202R mutant. Furthermore, PF-06463922 treatment led to regression of EML4-ALK-driven brain metastases, leading to prolonged mouse survival, in a superior manner. Finally, PF-06463922 demonstrated high selectivity and safety margins in a variety of preclinical studies. These results suggest that PF-06463922 will be highly effective for the treatment of patients with ALK-driven lung cancers, including those who relapsed on clinically available ALK inhibitors because of secondary ALK kinase domain mutations and/or brain metastases.

Anaplastic lymphoma kinase inhibitors

The anaplastic lymphoma kinase (ALK) gene is a member of the insulin receptor superfamily and it has been associated with more than twenty distinct chimera, including established drivers of several human cancers. Multiple clinical trials have proven that the pharmacological inhibition of ALK signaling leads to remarkable clinical improvement and improves the quality of life of ALK+ cancer patients. Crizotinib was the first ALKi to achieve approval from the Food and Drug Administration, although additional compounds are now moving into diversified clinical trials.

Silencing of Receptor Tyrosine Kinase ROR1 Inhibits Tumor-Cell Proliferation via PI3K/AKT/mTOR Signaling Pathway in Lung Adenocarcinoma

Receptor tyrosine kinase ROR1, an embryonic protein involved in organogenesis, is expressed in certain hematological malignancies and solid tumors, but is generally absent in adult tissues. This makes the protein an ideal drug target for cancer therapy. In order to assess the suitability of ROR1 as a cell surface antigen for targeted therapy of lung adenocarcinoma, we carried out a comprehensive analysis of ROR1 protein expression in human lung adenocarcinoma tissues and cell lines. Our data show that ROR1 protein is selectively expressed on lung adenocarcinoma cells, but do not support the hypothesis that expression levels of ROR1 are associated with aggressive disease. However silencing of ROR1 via siRNA treatment significantly down-regulates the activity of the PI3K/AKT/mTOR signaling pathway. This is associated with significant apoptosis and anti-proliferation of tumor cells. We found ROR1 protein expressed in lung adenocarcinoma but almost absent in tumor-adjacent tissues of the patients. The finding of ROR1-mediated proliferation signals in both tyrosine kinase inhibitor (TKI)-sensitive and -resistant tumor cells provides encouragement to develop ROR1-directed targeted therapy in lung adenocarcinoma, especially those with TKI resistance.

PF-06463922 is a potent and selective next-generation ROS1/ALK inhibitor capable of blocking crizotinib-resistant ROS1 mutations

Oncogenic c-ros oncogene1 (ROS1) fusion kinases have been identified in a variety of human cancers and are attractive targets for cancer therapy. The MET/ALK/ROS1 inhibitor crizotinib (Xalkori, PF-02341066) has demonstrated promising clinical activity in ROS1 fusion-positive non-small cell lung cancer. However, emerging clinical evidence has shown that patients can develop resistance by acquiring secondary point mutations in ROS1 kinase. In this study we characterized the ROS1 activity of PF-06463922, a novel, orally available, CNS-penetrant, ATP-competitive small-molecule inhibitor of ALK/ROS1. In vitro, PF-06463922 exhibited subnanomolar cellular potency against oncogenic ROS1 fusions and inhibited the crizotinib-refractory ROS1(G2032R) mutation and the ROS1(G2026M) gatekeeper mutation. Compared with crizotinib and the second-generation ALK/ROS1 inhibitors ceritinib and alectinib, PF-06463922 showed significantly improved inhibitory activity against ROS1 kinase. A crystal structure of the PF-06463922-ROS1 kinase complex revealed favorable interactions contributing to the high-affinity binding. In vivo, PF-06463922 showed marked antitumor activity in tumor models expressing FIG-ROS1, CD74-ROS1, and the CD74-ROS1(G2032R) mutation. Furthermore, PF-06463922 demonstrated antitumor activity in a genetically engineered mouse model of FIG-ROS1 glioblastoma. Taken together, our results indicate that PF-06463922 has potential for treating ROS1 fusion-positive cancers, including those requiring agents with CNS-penetrating properties, as well as for overcoming crizotinib resistance driven by ROS1 mutation.

Mechanistic understanding of translational pharmacokinetic-pharmacodynamic relationships in nonclinical tumor models: a case study of orally available novel inhibitors of anaplastic lymphoma kinase

The orally available novel small molecules PF06463922 [(10R)-7-amino-12-fluoro-2,10,16-trimethyl-15-oxo-10,15,16,17-tetrahydro-2H-8,4-(metheno)pyrazolo[4,3-h][2,5,11]benzoxadiazacyclotetradecine-3-carbonitrile] and PF06471402 [(10R)-7-amino-12-fluoro-2,10,16-trimethyl-15-oxo-10,15,16,17-tetrahydro-2H-8,4-(azeno)pyrazolo[4,3-h][2,5,11]benzoxadiazacyclo-tetradecine-3-carbonitrile] are second-generation anaplastic lymphoma kinase (ALK) inhibitors targeted to both naïve and resistant patients with non-small cell lung cancer (NSCLC) to the first-generation ALK inhibitor crizotinib. The objectives of the present study were to characterize and compare the pharmacokinetic-pharmacodynamic (PKPD) relationships of PF06463922 and PF06471402 for target modulation in tumor and antitumor efficacy in athymic mice implanted with H3122 NSCLC cells expressing a crizotinib-resistant echinoderm microtubule-associated protein-like 4 (EML4)-ALK mutation, EML4-ALK(L1196M). Furthermore, the PKPD relationships for these ALK inhibitors were evaluated and compared between oral administration and subcutaneous constant infusion (i.e., between different pharmacokinetic [PK] profiles). Oral and subcutaneous PK profiles of these ALK inhibitors were adequately described by a one-compartment PK model. An indirect response model extended with a modulator fit the time courses of PF06463922- and PF06471402-mediated target modulation (i.e., ALK phosphorylation) with an estimated unbound EC50,in vivo of 36 and 20 nM, respectively, for oral administration, and 100 and 69 nM, respectively, for subcutaneous infusion. A drug-disease model based on the turnover concept fit tumor growth curves inhibited by PF06463922 and PF06471402 with estimated unbound tumor stasis concentrations of 51 and 27 nM, respectively, for oral administration, and 116 and 70 nM, respectively, for subcutaneous infusion. Thus, the EC50,in vivo to EC60,in vivo estimates for ALK inhibition corresponded to the concentrations required tumor stasis in all cases, suggesting that the pharmacodynamic relationships of target modulation to antitumor efficacy were consistent among the ALK inhibitors, even when the PK profiles with different administration routes were considerably different.