Population pharmacokinetic modeling of sotatercept in healthy participants and patients with pulmonary arterial hypertension.

Sotatercept is a breakthrough, first-in-class biologic, that is FDA-approved for the treatment of pulmonary arterial hypertension (PAH). A population pharmacokinetic (PopPK) model was developed using data from two phase 1 studies in healthy participants, and two phase 2 studies and one phase 3 study in participants with PAH. The pooled sotatercept PK data encompassed single intravenous (IV) or subcutaneous (SC) doses ranging from 0.01 to 3.0 mg/kg, as well as multiple SC doses ranging from 0.03 to 1.0 mg/kg, with PK samples collected up to a maximum of ~150 weeks following Q3W and Q4W dosing regimens. The final PopPK analysis included 350 participants, with 30 and 320 participants receiving sotatercept IV and SC, respectively. A two-compartment model with a first-order absorption rate constant and a linear disposition from central compartment well-described sotatercept PK. The estimated bioavailability is ~66%; bioavailability, clearance (CL), and central volume (VC) have low to moderate inter-individual variability. Time-varying body weight and baseline albumin concentration were statistically significant predictors of PK; CL and VC were predicted to increase with increasing body weight, while CL was predicted to decrease with increasing baseline albumin concentration. However, the magnitude of covariate effects is not predicted to meaningfully alter the disposition of sotatercept. Altogether, the PopPK modeling results demonstrate favorable PK characteristics (low to moderate variability and typical bioavailability), supporting sotatercept as a SC biological agent for the treatment of patients with PAH.

Training the next generation of pharmacometric modelers: a multisector perspective.

The current demand for pharmacometricians outmatches the supply provided by academic institutions and considerable investments are made to develop the competencies of these scientists on-the-job. Even with the observed increase in academic programs related to pharmacometrics, this need is unlikely to change in the foreseeable future, as the demand and scope of pharmacometrics applications keep expanding. Further, the field of pharmacometrics is changing. The field largely started when Lewis Sheiner and Stuart Beal published their seminal papers on population pharmacokinetics in the late 1970's and early 1980's and has continued to grow in impact and use since its inception. Physiological-based pharmacokinetics and systems pharmacology have grown rapidly in scope and impact in the last decade and machine learning is just on the horizon. While all these methodologies are categorized as pharmacometrics, no one person can be an expert in everything. So how do you train future pharmacometricians? Leading experts in academia, industry, contract research organizations, clinical medicine, and regulatory gave their opinions on how to best train future pharmacometricians. Their opinions were collected and synthesized to create some general recommendations.

The Impact of Immunogenicity on the Pharmacokinetics, Efficacy, and Safety of Sotatercept in a Phase III Study of Pulmonary Arterial Hypertension.

Sotatercept, a soluble fusion protein comprising the extracellular domain of activin receptor type IIA linked to the Fc portion of human IgG1, is a first-in-class activin signaling inhibitor under development for the treatment of pulmonary arterial hypertension (PAH). We evaluated antidrug antibody (ADA) development and determined the effects of immunogenicity on the pharmacokinetics (PKs), efficacy, and safety of sotatercept in STELLAR, a multicenter, double-blind phase III trial (NCT04576988) wherein participants with PAH were randomized 1:1 to receive sotatercept (starting dose 0.3; target dose 0.7 mg/kg) or placebo subcutaneously every 3 weeks in combination with background therapies for ≤ 72 weeks. ADA-positive (ADA-POS) participants were identified and characterized for neutralizing antibodies (NAbs). PKs, efficacy, and safety were evaluated by ADA and NAb status. Of 162 evaluable participants, 42 (25.9%) were ADA-POS through week 24, of whom 11 (6.8%) were also NAb-POS. Median onset of ADAs was 3.29 weeks (interquartile range (IQR): 3.14-6.14), and median duration was 6 weeks (IQR: 3.14-17.86). No clinically meaningful differences were found across subgroups that were ADA-NEG, ADA-POS/NAb-NEG, and ADA-POS/NAb-POS, in terms of PKs (sotatercept trough concentration over time, mean postdose trough concentration at the end of treatment, and clearance), efficacy (changes from baseline in 6-minute walk distance, pulmonary vascular resistance, and N-terminal pro-B-type natriuretic peptide levels), and safety (incidence of hypersensitivity, anaphylactic reactions, and administration site reactions). We conclude that ADA incidence from sotatercept treatment was 25.9% and did not meaningfully affect the PKs, efficacy, or safety of sotatercept in participants with PAH.

Challenging the Norm: A Multidisciplinary Perspective on Intravenous to Subcutaneous Bridging Strategies for Biologics.

The transition from intravenous (i.v.) to subcutaneous (s.c.) administration of biologics is a critical strategy in drug development aimed at improving patient convenience, compliance, and therapeutic outcomes. Focusing on the increasing role of model-informed drug development (MIDD) in the acceleration of this transition, an in-depth overview of the essential clinical pharmacology, and regulatory considerations for successful i.v. to s.c. bridging for biologics after the i.v. formulation has been approved are presented. Considerations encompass multiple aspects beginning with adequate pharmacokinetic (PK) and pharmacodynamic (i.e., exposure-response) evaluations which play a vital role in establishing comparability between the i.v. and s.c. routes of administrations. Selected key recommendations and points to consider include: (i) PK characterization of the s.c. formulation, supported by the increasing preclinical understanding of the s.c. absorption, and robust PK study design and analyses in humans; (ii) a thorough characterization of the exposure-response profiles including important metrics of exposure for both efficacy and safety; (iii) comparability studies designed to meet regulatory considerations and support approval of the s.c. formulation, including noninferiority studies with PK and/or efficacy and safety as primary end points; and (iv) comprehensive safety package addressing assessments of immunogenicity and patients' safety profile with the new route of administration. Recommendations for successful bridging strategies are evolving and MIDD approaches have been used successfully to accelerate the transition to s.c. dosing, ultimately leading to improved patient experiences, adherence, and clinical outcomes.

Identification of Novel and Early Biomarkers for Cisplatin-induced Nephrotoxicity and the Nephroprotective Role of Cimetidine using a Pharmacometabolomic-based Approach Coupled with In Vitro Toxicodynamic Modeling and Simulation.

Cisplatin is widely used for the treatment of various types of cancer. However, cisplatin-induced nephrotoxicity (CIN) is frequently observed in patients receiving cisplatin therapy which poses a challenge in its clinical utility. Currently used clinical biomarkers for CIN are not adequate for early detection of nephrotoxicity, hence there is a need to identify potential early biomarkers in predicting CIN. In the current study, a combination of in vitro toxicodynamic (TD) modeling and untargeted global metabolomics approach was used to identify novel potential metabolite biomarkers for early detection of CIN. In addition, we investigated the protective role of cimetidine (CIM), an inhibitor of the organic cation transporter 2 (OCT2), in suppressing CIN. We first characterized the time-course of nephrotoxic effects of cisplatin (CIS) and the protective effects of CIM in a human pseudo-immortalized renal proximal tubule epithelial cell line (RPTEC), SA7K cell line. Secondly, we used a mathematical cell-level, in vitro TD modeling approach to quantitatively characterize the time-course effects of CIS and CIM as single agents and combination in SA7K cells. Based on the experimental and modeling results, we selected relevant concentrations of CIS and CIM for our metabolomics study. With the help of PCA (Principal Component Analysis) and PLS-DA (Projection to Latent Structure - Discriminate Analysis) analyses, we confirmed global metabolome changes for different groups (CIS, CIM, CIS+CIM vs control) in SA7K cells. Based on the criterion of a p-value ≤ 0.05 and a fold change ≥ 2 or ≤ 0.5, we identified 20 top metabolites that were significantly changed during the early phase i.e. within first 12 h of CIS treatment. Finally, pathway analysis was conducted that revealed the key metabolic pathways that were most impacted in CIN.

In vitro to clinical translation of combinatorial effects of doxorubicin and dexrazoxane in breast cancer: a mechanism-based pharmacokinetic/pharmacodynamic modeling approach.

Dexrazoxane (DEX) is the only drug clinically approved to treat Doxorubicin-induced cardiotoxicity (DIC), however its impact on the anticancer efficacy of DOX is not extensively studied. In this manuscript, a proof-of-concept in vitro study is carried out to quantitatively characterize the anticancer effects of DOX and DEX and determine their nature of drug-drug interactions in cancer cells by combining experimental data with modeling approaches. First, we determined the static concentration-response of DOX and DEX in breast cancer cell lines, JIMT-1 and MDA-MB-468. With a three-dimensional (3D) response surface analysis using a competitive interaction model, we characterized their interaction to be modestly synergistic in MDA-MB-468 or modestly antagonistic in JIMT-1 cells. Second, a cellular-level, pharmacodynamic (PD) model was developed to capture the time-course effects of the two drugs which determined additive and antagonistic interactions for DOX and DEX in MDA-MB-468 and JIMT-1, respectively. Finally, we performed in vitro to in vivo translation by utilizing DOX and DEX clinical dosing regimen that was previously identified to be maximally cardioprotective, to drive tumor cell PD models. The resulting simulations showed that a 10:1 DEX:DOX dose ratio over three cycles of Q3W regimen of DOX results in comparable efficacy based on MDA-MB-468 (additive effect) estimates and lower efficacy based on JIMT-1 (antagonistic effect) estimates for DOX + DEX combination as compared to DOX alone. Thus, our developed cell-based PD models can be used to simulate different scenarios and better design preclinical in vivo studies to further optimize DOX and DEX combinations.

International society of Pharmacometrics Mentorship Program (IMP): feedback survey from the first cohort of mentor-mentee pairs.

The International Society of Pharmacometrics (ISoP) Mentorship Program (IMP) aims to help professionals at all career stages to transition into the pharmacometrics field, move to a different role/area within pharmacometrics, or expand their skillsets. The program connects mentees at various stages of their careers with mentors based on established criteria for mentor-mentee matching. Pairing mentees with appropriate mentors ensures strong alignment between mentees' interests and mentors' expertise as this is critical to the success and continuation of the relationship between the mentor and mentee. Once mentors and mentees are connected, they are strongly encouraged to meet at least once per month for an hour. The mentor and mentee have the freedom to tailor their sessions to their liking, including frequency, duration, and topics they choose to focus on. Mentees are encouraged to clearly define their goals to help direct their mentor-mentee relationship and conversations. Mentees and mentors alike are given the opportunity to provide feedback about the program to the ISoP Education Committee through surveys and testimonials. Due to the program's infancy, structured guidelines for mentor-mentee sessions are still being developed and instituted using the program evaluation described in this paper.

Population pharmacokinetic analysis of the P2X3-receptor antagonist gefapixant.

Gefapixant, a P2X3-receptor antagonist, demonstrated objective and subjective efficacy in individuals with refractory or unexplained chronic cough. We report a population pharmacokinetic (PopPK) analysis that characterizes gefapixant pharmacokinetics (PKs), quantifies between- and within-participant variability, and evaluates the impact of intrinsic and extrinsic factors on gefapixant exposure. The PopPK model was initially developed using PK data from six phase I studies. Stepwise covariate method was utilized to identify covariates impacting PK parameters; the model was re-estimated and covariate effects were re-assessed after integrating PK data from three phase II and III studies. Simulations were conducted to evaluate the magnitude of covariate effects on gefapixant exposure. Of 1677 participants included in this data set, 1618 had evaluable PK records. Age, body weight, and sex had statistically significant, but not clinically relevant, effects on exposure. Degree of renal impairment (RI) had statistically significant and clinically relevant effects on exposure; exposure was 17% to 89% higher in those with versus without RI. Simulation results indicated that gefapixant 45 mg administered once daily to patients with severe RI has similar exposure to gefapixant 45 mg administered twice daily to patients with normal renal function. There were no significant effects of proton pump inhibitors or food. Of evaluated intrinsic and extrinsic factors, only RI had a clinically relevant effect on gefapixant exposure. Patients with mild or moderate RI do not require dosage adjustments; however, for patients with severe RI who are not on dialysis, gefapixant 45 mg once daily is recommended.

Pharmacodynamic Modeling Identifies Synergistic Interaction Between Chloroquine and Trastuzumab in Refractory HER2- positive Breast Cancer Cells.

BACKGROUND/AIM: Despite improvements in HER2-positive breast cancer (BC) patients' outcomes with trastuzumab, the occurrence of intrinsic or acquired resistance presents a clinical challenge. Here, we quantitatively assess the combinatorial effects of chloroquine, an autophagy inhibitor, with trastuzumab on JIMT-1 cells, a HER2-positive BC cell-line primarily resistant to trastuzumab. MATERIALS AND METHODS: The temporal changes in JIMT-1 cellular viability were assessed using the CCK-8 kit, where JIMT-1 cells were exposed for 72-h to trastuzumab (0.007-17.19 µM) or chloroquine (5-50 µM) as single-agents, in combination (trastuzumab: 0.007-0.688 µM; chloroquine: 5-15 µM), or control (no drug). Concentration-response relationships were built for each treatment arm to determine drugs' concentrations inducing 50% of cell-killing (IC50). Cellular pharmacodynamic models were built to characterize the time-trajectory of JIMT-1 cellular viability under each treatment arm. The nature of trastuzumab and chloroquine interaction was quantified by estimating the interaction parameter (Ψ). RESULTS: The IC50 were estimated at 19.7 and 24.4 µM for trastuzumab and chloroquine. The maximum killing effect was about thrice higher for chloroquine than trastuzumab (0.0405 vs. 0.0125 h-1), validating chloroquine's superior anti-cancer effect on JIMT-1 cells compared to trastuzumab. The time-delay for chloroquine cell-killing was twice longer than that for trastuzumab (17.7 vs. 7 h), suggesting a chloroquine time-dependent anti-cancer effect. The Ψ was determined at 0.529 (Ψ<1), indicating a synergistic interaction. CONCLUSION: This proof-of-concept study on JIMT-1 cells identified chloroquine and trastuzumab synergistic interaction, warranting further in vivo investigations.

In vitro to clinical translational pharmacokinetic/pharmacodynamic modeling of doxorubicin (DOX) and dexrazoxane (DEX) interactions: Safety assessment and optimization.

Despite high anticancer activity, doxorubicin (DOX)-induced cardiotoxicity (DIC) limits the extensive utility of DOX in a clinical setting. Amongst various strategies explored, dexrazoxane (DEX) remains the only cardioprotective agent to be approved for DIC. In addition, altering the dosing regimen of DOX has also proved to be somewhat beneficial in decreasing the risk of DIC. However, both approaches have limitations and further studies are required to better optimize them for maximal beneficial effects. In the present work, we quantitatively characterized DIC as well as the protective effects of DEX in an in vitro model of human cardiomyocytes, by means of experimental data and mathematical modeling and simulation (M&S) approaches. We developed a cellular-level, mathematical toxicodynamic (TD) model to capture the dynamic in vitro drug-drug interaction, and relevant parameters associated with DIC and DEX cardio-protection were estimated. Subsequently, we executed in vitro-in vivo translation by simulating clinical PK profiles for different dosing regimens of DOX alone and in combinations with DEX and using the simulated PK profiles to drive the cell-based TD models to evaluate the effects of long-term, clinical dosing regimens of these drugs on the relative cell viability of AC16 and to determine optimal drug combinations with minimal cellular toxicity. Here, we identified that the Q3W (once every three weeks) DOX regimen with 10:1 DEX:DOX dose ratio over three cycles (nine weeks) may offer maximal cardio-protection. Overall, the cell-based TD model can be effectively used to better design subsequent preclinical in vivo studies aimed for further optimizing safe and effective DOX and DEX combinations to mitigate DIC.

KIFC1: A Reliable Prognostic Biomarker in Rb-positive Triple-negative Breast Cancer Patients Treated With Doxorubicin in Combination With Abemaciclib.

BACKGROUND/AIM: Triple-negative breast cancer (TNBC) prevalence and risk of relapse are greatest in African American (AA) patients. Doxorubicin (DOX) and abemaciclib (ABE) synergism in Rb-positive TNBC cells (MDA-MB-231), and antagonism in Rb-negative TNBC cells (MDA-MB-468) have been previously shown. Here, we assessed Kinesin-like protein 1 (KIFC1) as an ethnic-specific prognostic biomarker of the DOX+ABE combination for the Rb-status in TNBC. MATERIALS AND METHODS: Literature search for TNBC prognostic biomarkers in the AA population was conducted. MDA-MB-231 and MDA-MB-468 cells were exposed over 72 h to four treatment arms: 1) control (medium without drug), 2) DOX at 50% inhibitory concentration in MDA-MB-231 (0.565 µM) and MDA-MB-468 (0.121 µM), 3) ABE alone (2 µM), and 4) DOX+ABE combination at their corresponding concentrations in each cell-line. KIFC1 protein expression and temporal changes were quantified in MDA-MB-231 cells using western blot. RESULTS: KIFC1, Kaiso, and Annexin A2 are literature-identified AA-specific TNBC prognostic biomarkers. KIFC1 was found to be uncorrelated to other proposed biomarkers, suggesting it may predict risk independently of other TNBC biomarkers. In both cell lines, DOX alone did not significantly change KIFC1 expression relative to control. Conversely, ABE reduced KIFC1 expression in MDA-MB-231 but not in MDA-MB-468 cells. The combination DOX+ABE resulted in a greatest reduction in KIFC1 in MDA-MB-231 cells with a more rapid time-to-full inhibition of KIFC1 compared to ABE alone. CONCLUSION: Change in KIFC1 expression is primarily driven by ABE in Rb-positive TNBC cells. DOX increases ABE speed to achieve a full inhibition of KIFC1 in Rb-positive, yet, without influencing its expression in Rb-negative TNBC cells.

Knowledge dissemination and central indexing of resources in pharmacometrics: an ISOP education working group initiative.

Pharmacometrics is a constantly evolving field that plays a major role in decision making in drug development and clinical monitoring. Scientists in Pharmacometrics, especially in their early phases of career, are often faced with the challenge of identifying adequate resources for self-training and education. Hence, the ISoP Education Committee through its working group dedicated to Central Indexing and knowledge Dissemination has built a database of worldwide educational programs and most common references in Pharmacometrics.

Experimental and computational assessment of the synergistic pharmacodynamic drug-drug interactions of a triple combination therapy in refractory HER2-positive breast cancer cells.

The development of innate and/or acquired resistance to human epidermal growth factor receptor type-2 (HER2)-targeted therapy in HER2-positive breast cancer (HER2 + BC) is a major clinical challenge that needs to be addressed. One of the main mechanisms of resistance includes aberrant activation of the HER2 and phosphatidylinositol 3-kinase/AKT8 virus oncogene cellular homolog/mammalian target of rapamycin (PI3K/Akt/mTOR) pathways. In the present work, we propose to use a triple combination therapy to combat this resistance phenomenon. Our strategy involves evaluation of two targeted small molecule agents, everolimus and dasatinib, with complementary inhibitory circuitries in the PI3K/Akt/mTOR pathway, along with a standard cytotoxic agent, paclitaxel. Everolimus inhibits mTOR, while dasatinib inhibits Src, which is a protein upstream of Akt. An over-activation of these two proteins has been implicated in approximately 50% of HER2 + BC cases. Hence, we hypothesize that their simultaneous inhibition may lead to enhanced cell-growth inhibition. Moreover, the potent apoptotic effects of paclitaxel may help augment the overall cytotoxicity of the proposed triple combination in HER2 + BC cells. To this end, we investigated experimentally and assessed computationally the in vitro pharmacodynamic drug-drug interactions of the various dual and triple combinations to assess their subsequent combinatorial effects (synergistic/additive/antagonistic) in a HER2-therapy resistant BC cell line, JIMT-1. Our proposed triple combination therapy demonstrated synergism in JIMT-1 cells, thus corroborating our hypothesis. This effort may form the basis for further investigation of the triple combination therapy in vivo at a mechanistic level in HER2-therapy resistant BC cells.

Pharmacodynamic Modeling to Evaluate the Impact of Cimetidine, an OCT2 Inhibitor, on the Anticancer Effects of Cisplatin.

Despite potent anticancer activity, the clinical utilization of cisplatin is limited due to nephrotoxicity. As Organic Cation Transporter 2 (OCT2) has been shown to be one of the key transporters involved in the uptake of cisplatin into renal proximal tubules, OCT2 inhibitors such as cimetidine have been explored to suppress cisplatin-induced nephrotoxicity. Nonetheless, the impact of OCT2 inhibition or cimetidine on the anti-cancer effects of cisplatin has not been extensively examined. The main objective of the present study was to quantitatively characterize the anticancer effects of cisplatin and cimetidine and determine their nature of interactions in two cancer cell lines, OCT2-negative hepatocellular carcinoma (HCC) cell line, Huh7, and OCT2-positive breast cancer cell line, MDA-MB-468. First, we determined the static concentration-response curves of cisplatin and cimetidine as single agents. Next, with the help of three-dimensional (3D) response surface analyses and a competitive interaction model, we determined their nature of interactions at static concentrations to be modestly synergistic or additive in Huh7 and antagonistic in MDA-MB-468. These results were consistent with the cell-level pharmacodynamic (PD) modeling analysis which leveraged the time-course effects of drugs as single agents and drug combinations. Our developed PD model can be further used to design future preclinical studies to further investigate the cisplatin and cimetidine combinations in different in vitro and in vivo cancer models.

In vitro to Clinical Translation of Combinatorial Effects of Doxorubicin and Abemaciclib in Rb-Positive Triple Negative Breast Cancer: A Systems-Based Pharmacokinetic/Pharmacodynamic Modeling Approach.

BACKGROUND: Doxorubicin (DOX) and its pegylated liposomal formulation (L_DOX) are the standard of care for triple-negative breast cancer (TNBC). However, resistance to DOX often occurs, motivating the search for alternative treatment approaches. The retinoblastoma protein (Rb) is a potential pharmacological target for TNBC treatment since its expression has been associated with resistance to DOX-based therapy. METHODS: DOX (0.01-20 µM) combination with abemaciclib (ABE, 1-6 µM) was evaluated over 72 hours on Rb-positive (MDA-MB-231) and Rb-negative (MDA-MB-468) TNBC cells. Combination indices (CI) for DOX+ABE were calculated using Compusyn software. The TNBC cell viability time-course and fold-change from the control of phosphorylated-Rb (pRb) protein expression were measured with CCK8-kit and enzyme-linked immunosorbent assay. A cell-based pharmacodynamic (PD) model was developed, where pRb protein dynamics drove cell viability response. Clinical pharmacokinetic (PK) models for DOX, L_DOX, and ABE were developed using data extracted from the literature. After scaling cancer cell growth to clinical TNBC tumor growth, the time-to-tumor progression (TTP) was predicted for human dosing regimens of DOX, ABE, and DOX+ABE. RESULTS: DOX and ABE combinations were synergistic (CI<1) in MDA-MB-231 and antagonistic (CI>1) in MDA-MB-468. The maximum inhibitory effects (Imax) for both drugs were set to one. The drug concentrations producing 50% of Imax for DOX and ABE were 0.565 and 2.31 µM (MDA-MB-231) and 0.121 and 1.61 µM (MDA-MB-468). The first-orders rate constants of abemaciclib absorption (ka) and doxorubicin release from L_DOX (kRel) were estimated at 0.31 and 0.013 h-1. Their linear clearances were 21.7 (ABE) and 32.1 L/h (DOX). The estimated TTP for intravenous DOX (75 mg/m2 every 21 days), intravenous L_DOX (50 mg/m2 every 28 days), and oral ABE (200 mg twice a day) were 125, 31.2, and 8.6 days shorter than drug-free control. The TTP for DOX+ABE and L_DOX+ABE were 312 days and 47.5 days shorter than control, both larger than single-agent DOX, suggesting improved activity with the DOX+ABE combination. CONCLUSION: The developed translational systems-based PK/PD model provides an in vitro-to-clinic modeling platform for DOX+ABE in TNBC. Although model-based simulations suggest improved outcomes with combination over monotherapy, tumor relapse was not prevented with the combination. Hence, DOX+ABE may not be an effective treatment combination for TNBC.

Multiscale and Translational Quantitative Systems Toxicology, Pharmacokinetic-Toxicodynamic Modeling Analysis for Assessment of Doxorubicin-Induced Cardiotoxicity.

Dose-dependent life-threatening doxorubicin-induced cardiotoxicity (DIC) is a major clinical challenge that needs to be addressed. Here, we developed an integrated multiscale and translational quantitative systems toxicology and pharmacokinetic-toxicodynamic (QST-PK/TD) model for optimization of doxorubicin dosing regimens for early monitoring and minimization of DIC. A QST model was established by exposing human cardiomyocytes, AC16 cells, to doxorubicin over a time course, and measuring the dynamics of intracellular signaling proteins, AC16 cell viability and released biomarkers of cardiomyocyte injury such as the B-type natriuretic peptide (BNP). Experiments were scaled up to a three-dimensional and dynamic (3DD) cell culture system to evaluate DIC under various dosing regimens. The PK determinants of doxorubicin influencing DIC were identified in vitro and then translated to the in vivo setting through hybrid physiologically based PK (PBPK)/TD models using preclinical- and clinical-level data extracted from literature. The developed cellular-level QST model captured well the observed dynamics of intracellular proteins, AC16 cell viability and BNP kinetics. In the 3DD setting, dose fractionation of doxorubicin displayed a significant reduction in cardiotoxicity compared to single intravenous doses with equal exposure, implying doxorubicin peak concentrations as the PK determinant for DIC. The in vivo hybrid PBPK/TD models captured well doxorubicin PK and DIC. Peak doxorubicin concentrations correlated well with acute DIC for dose-fractionated regimens, while maximum 48-h moving average concentrations correlated with DIC for dose-fractionated and long-term infusion regimens in vivo. The developed multiscale and translational QST-PK/TD modeling platform may serve as an in silico tool for assessment of early toxicity and/or efficacy of developmental drugs in vitro.

A quantitative systems pharmacological approach identified activation of JNK signaling pathway as a promising treatment strategy for refractory HER2 positive breast cancer.

HER2-positive breast cancer (BC) is a rapidly growing and aggressive BC subtype that predominantly affects younger women. Despite improvements in patient outcomes with anti-HER2 therapy, primary and/or acquired resistance remain a major clinical challenge. Here, we sought to use a quantitative systems pharmacological (QSP) approach to evaluate the efficacy of lapatinib (LAP), abemaciclib (ABE) and 5-fluorouracil (5-FU) mono- and combination therapies in JIMT-1 cells, a HER2+ BC cell line exhibiting intrinsic resistance to trastuzumab. Concentration-response relationships and temporal profiles of cellular viability were assessed upon exposure to single agents and their combinations. To quantify the nature and intensity of drug-drug interactions, pharmacodynamic cellular response models were generated, to characterize single agent and combination time course data. Temporal changes in cell-cycle phase distributions, intracellular protein signaling, and JIMT-1 cellular viability were quantified, and a systems-based protein signaling network model was developed, integrating  protein dynamics to drive the observed changes in cell viability. Global sensitivity analyses for each treatment arm were performed, to identify the most influential parameters governing cellular responses. Our QSP model was able to adequately characterize protein dynamic and cellular viability trends following single and combination drug exposure. Moreover, the model and subsequent sensitivity analyses suggest that the  activation of the stress pathway, through pJNK, has the greatest impact over the observed declines of JIMT-1 cell viability in vitro. These findings suggest that dual HER2 and CDK 4/6 inhibition may be a promising novel treatment strategy for refractory HER2+ BC, however, proof-of-concept in vivo studies are needed to further evaluate the combined use of these therapies.