Use of an anti-vascular endothelial growth factor antibody in a pharmacokinetic strategy to increase the efficacy of intraperitoneal chemotherapy

Integrated PK/PD Modeling Relates Smoothened Inhibitor Biomarkers to The Heterogeneous Intratumor Disposition of Cetuximab in Pancreatic Cancer Tumor Models

Therapeutic antibodies have shown little efficacy in the treatment of pancreatic ductal adenocarcinomas (PDAC). Tumor desmoplasia, hypovascularity, and poor perfusion result in insufficient tumor cell exposure, contributing to treatment failure. Smoothened inhibitors of hedgehog signaling (sHHi) increase PDAC tumor permeability, perfusion, and drug delivery, and provide a tool to develop a quantitative, mechanistic understanding as to how the temporal dynamics of tumor priming can impact intratumor distribution of monoclonal antibodies (mAb). A linked pharmacokinetic (PK)/pharmacodynamic (PD) model was developed to integrate the plasma and tumor PK of a sHHi priming agent with its effects upon downstream stromal biomarkers Gli1, hyaluronic acid, and interstitial fluid pressure in PDAC patient-derived xenograft (PDX) tumors. In parallel, in situ tumor concentrations of cetuximab (CTX: anti-epidermal growth factor receptor; EGFR) were quantified as a marker for tumor delivery of mAb or antibody-drug conjugates. A minimal, physiologically-based pharmacokinetic (mPBPK) model was constructed to link sHHi effects upon mechanistic effectors of tumor barrier compromise with the intratumor distribution of CTX, and CTX occupancy of EGFR in tumors. Integration of the mPBPK model of mAb deposition and intratumor distribution with the PK/PD model of tumor responses to priming not only identified physiological parameters that are critical for tumor antibody distribution, but also provides insight into dosing regimens that could achieve maximal tumor disposition of therapeutic antibodies under conditions of transient PDAC tumor permeability barrier compromise that mechanistically-diverse tumor priming strategies may achieve.

Mathematical Models to Characterize the Absorption, Distribution, Metabolism, and Excretion of Protein Therapeutics

Therapeutic proteins (TPs) have ranked among the most important and fastest-growing classes of drugs in the clinic, yet the development of successful TPs is often limited by unsatisfactory efficacy. Understanding pharmacokinetic (PK) characteristics of TPs is key to achieving sufficient and prolonged exposure at the site of action, which is a prerequisite for eliciting desired pharmacological effects. PK modeling represents a powerful tool to investigate factors governing in vivo disposition of TPs. In this mini-review, we discuss many state-of-the-art models that recapitulate critical processes in each of the absorption, distribution, metabolism/catabolism, and excretion pathways of TPs, which can be integrated into the physiologically-based pharmacokinetic framework. Additionally, we provide our perspectives on current opportunities and challenges for evolving the PK models to accelerate the discovery and development of safe and efficacious TPs. SIGNIFICANCE STATEMENT: This minireview provides an overview of mechanistic pharmacokinetic (PK) models developed to characterize absorption, distribution, metabolism, and elimination (ADME) properties of therapeutic proteins (TPs), which can support model-informed discovery and development of TPs. As the next-generation of TPs with diverse physicochemical properties and mechanism-of-action are being developed rapidly, there is an urgent need to better understand the determinants for the ADME of TPs and evolve existing platform PK models to facilitate successful bench-to-bedside translation of these promising drug molecules.

Clinically translatable cytokine delivery platform for eradication of intraperitoneal tumors

Proinflammatory cytokines have been approved by the Food and Drug Administration for the treatment of metastatic melanoma and renal carcinoma. However, effective cytokine therapy requires high-dose infusions that can result in antidrug antibodies and/or systemic side effects that limit long-term benefits. To overcome these limitations, we developed a clinically translatable cytokine delivery platform composed of polymer-encapsulated human ARPE-19 (RPE) cells that produce natural cytokines. Tumor-adjacent administration of these capsules demonstrated predictable dose modulation with spatial and temporal control and enabled peritoneal cancer immunotherapy without systemic toxicities. Interleukin-2 (IL2)-producing cytokine factory treatment eradicated peritoneal tumors in ovarian and colorectal mouse models. Furthermore, computational pharmacokinetic modeling predicts clinical translatability to humans. Notably, this platform elicited T cell responses in NHPs, consistent with reported biomarkers of treatment efficacy without toxicity. Combined, our findings demonstrate the safety and efficacy of IL2 cytokine factories in preclinical animal models and provide rationale for future clinical testing in humans.

Development and Evaluation of Competitive Inhibitors of Trastuzumab-HER2 Binding to Bypass the Binding-Site Barrier

Our group has developed and experimentally validated a strategy to increase antibody penetration in solid tumors through transient inhibition of antibody-antigen binding. In prior work, we demonstrated that 1HE, an anti-trastuzumab single domain antibody that transiently inhibits trastuzumab binding to HER2, increased the penetration of trastuzumab and increased the efficacy of ado-trastuzumab emtansine (T-DM1) in HER2+ xenograft bearing mice. In the present work, 1HE variants were developed using random mutagenesis and phage display to enable optimization of tumor penetration and efficacy of trastuzumab-based therapeutics. To guide the rational selection of a particular 1HE mutant for a specific trastuzumab-therapy, we developed a mechanistic pharmacokinetic (PK) model to predict within-tumor exposure of trastuzumab/T-DM1. A pharmacodynamic (PD) component was added to the model to predict the relationship between intratumor exposure to T-DM1 and the corresponding therapeutic effect in HER2+ xenografts. To demonstrate the utility of the competitive inhibition approach for immunotoxins, PK parameters specific for a recombinant immunotoxin were incorporated into the model structure. Dissociation half-lives for variants ranged from 1.1 h (for variant LG11) to 107.9 h (for variant HE10). Simulations predicted that 1HE co-administration can increase the tumor penetration of T-DM1, with inhibitors with longer trastuzumab binding half-lives relative to 1HE (15.5 h) further increasing T-DM1 penetration at the expense of total tumor uptake of T-DM1. The PK/PD model accurately predicted the response of NCI-N87 xenografts to treatment with T-DM1 or T-DM1 co-administered with 1HE. Model predictions indicate that the 1HE mutant HF9, with a trastuzumab binding half-life of 51.1 h, would be the optimal inhibitor for increasing T-DM1 efficacy with a modest extension in the median survival time relative to T-DM1 with 1HE. Model simulations predict that LG11 co-administration will dramatically increase immunotoxin penetration within all tumor regions. We expect that the mechanistic model structure and the wide range of inhibitors developed in this work will enable optimization of trastuzumab-cytotoxin penetration and efficacy in solid tumors.

Convection enhanced delivery of anti-angiogenic and cytotoxic agents in combination therapy against brain tumour

Convection enhanced delivery is an effective alternative to routine delivery methods to overcome the blood brain barrier. However, its treatment efficacy remains disappointing in clinic owing to the rapid drug elimination in tumour tissue. In this study, multiphysics modelling is employed to investigate the combination delivery of anti-angiogenic and cytotoxic drugs from the perspective of intratumoural transport. Simulations are based on a 3-D realistic brain tumour model that is reconstructed from patient magnetic resonance images. The tumour microvasculature is targeted by bevacizumab, and six cytotoxic drugs are included, as doxorubicin, carmustine, cisplatin, fluorouracil, methotrexate and paclitaxel. The treatment efficacy is evaluated in terms of the distribution volume where the drug concentration is above the corresponding LD90. Results demonstrate that the infusion of bevacizumab can slightly improve interstitial fluid flow, but is significantly efficient in reducing the fluid loss from the blood circulatory system to inhibit the concentration dilution. As the transport of bevacizumab is dominated by convection, its spatial distribution and anti-angiogenic effectiveness present high sensitivity to the directional interstitial fluid flow. Infusing bevacizumab could enhance the delivery outcomes of all the six drugs, however, the degree of enhancement differs. The delivery of doxorubicin can be improved most, whereas, the impacts on methotrexate and paclitaxel are limited. Fluorouracil could cover the comparable distribution volume as paclitaxel in the combination therapy for effective cell killing. Results obtain in this study could be a guide for the design of this co-delivery treatment.

A 3D CFD model of the interstitial fluid pressure and drug distribution in heterogeneous tumor nodules during intraperitoneal chemotherapy

Although intraperitoneal chemotherapy (IPC) has evolved into an established treatment modality for patients with peritoneal metastasis (PM), drug penetration into tumor nodules remains limited. Drug transport during IPC is a complex process that depends on a large number of different parameters (e.g. drug, dose, tumor size, tumor pressure, tumor vascularization). Mathematical modeling allows for a better understanding of the processes that underlie drug transport and the relative importance of the parameters influencing it. In this work, we expanded our previously developed 3D Computational Fluid Dynamics (CFD) model of the drug mass transport in idealized tumor nodules during IP chemotherapy to include realistic tumor geometries and spatially varying vascular properties. DCE-MRI imaging made it possible to distinguish between tumorous tissues, healthy surrounding tissues and necrotic zones based on differences in the vascular properties. We found that the resulting interstitial pressure profiles within tumors were highly dependent on the irregular geometries and different zones. The tumor-specific cisplatin penetration depths ranged from 0.32 mm to 0.50 mm. In this work, we found that the positive relationship between tumor size and IFP does not longer hold in the presence of zones with different vascular properties, while we did observe a positive relationship between the percentage of viable tumor tissue and the maximal IFP. Our findings highlight the importance of incorporating both the irregular tumor geometries and different vascular zones in CFD models of IPC.

Physiologically-based modeling of monoclonal antibody pharmacokinetics in drug discovery and development

Over the past few decades, monoclonal antibodies (mAbs) have become one of the most important and fastest growing classes of therapeutic molecules, with applications in a wide variety of disease areas. As such, understanding of the determinants of mAb pharmacokinetic (PK) processes (absorption, distribution, metabolism, and elimination) is crucial in developing safe and efficacious therapeutics. In the present review, we discuss the use of physiologically-based pharmacokinetic (PBPK) models as an approach to characterize the in vivo behavior of mAbs, in the context of the key PK processes that should be considered in these models. Additionally, we discuss current and potential future applications of PBPK in the drug discovery and development timeline for mAbs, spanning from identification of potential target molecules to prediction of potential drug-drug interactions. Finally, we conclude with a discussion of currently available PBPK models for mAbs that could be implemented in the drug development process.

Magnetically assisted intraperitoneal drug delivery for cancer chemotherapy

Intraperitoneal (IP) chemotherapy has revived hopes during the past few years for the management of peritoneal disseminations of digestive and gynecological cancers. Nevertheless, a poor drug penetration is one key drawback of IP chemotherapy since peritoneal neoplasms are notoriously resistant to drug penetration. Recent preclinical studies have focused on targeting the aberrant tumor microenvironment to improve intratumoral drug transport. However, tumor stroma targeting therapies have limited therapeutic windows and show variable outcomes across different cohort of patients. Therefore, the development of new strategies for improving the efficacy of IP chemotherapy is a certain need. In this work, we propose a new magnetically assisted strategy to elevate drug penetration into peritoneal tumor nodules and improve IP chemotherapy. A computational model was developed to assess the feasibility and predictability of the proposed active drug delivery method. The key tumor pathophysiology, including a spatially heterogeneous construct of leaky vasculature, nonfunctional lymphatics, and dense extracellular matrix (ECM), was reconstructed in silico. The transport of intraperitoneally injected magnetic nanoparticles (MNPs) inside tumors was simulated and compared with the transport of free cytotoxic agents. Our results on magnetically assisted delivery showed an order of magnitude increase in the final intratumoral concentration of drug-coated MNPs with respect to free cytotoxic agents. The intermediate MNPs with the radius range of 200-300 nm yield optimal magnetic drug targeting (MDT) performance in 5-10 mm tumors while the MDT performance remains essentially the same over a large particle radius range of 100-500 nm for a 1 mm radius small tumor. The success of MDT in larger tumors (5-10 mm in radius) was found to be markedly dependent on the choice of magnet strength and tumor-magnet distance while these two parameters were less of a concern in small tumors. We also validated in silico results against experimental results related to tumor interstitial hypertension, conventional IP chemoperfusion, and magnetically actuated movement of MNPs in excised tissue.

Computational modelling of drug delivery to solid tumour: Understanding the interplay between chemotherapeutics and biological system for optimised delivery systems

Drug delivery to solid tumour involves multiple physiological, biochemical and biophysical processes taking place across a wide range of length and time scales. The therapeutic efficacy of anticancer drugs is influenced by the complex interplays among the intrinsic properties of tumours, biophysical aspects of drug transport and cellular uptake. Mathematical and computational modelling allows for a well-controlled study on the individual and combined effects of a wide range of parameters on drug transport and therapeutic efficacy, which would not be possible or economically viable through experimental means. A wide spectrum of mathematical models has been developed for the simulation of drug transport and delivery in solid tumours, including PK/PD-based compartmental models, microscopic and macroscopic transport models, and molecular dynamics drug loading and release models. These models have been used as a tool to identify the limiting factors and for optimal design of efficient drug delivery systems. This article gives an overview of the currently available computational models for drug transport in solid tumours, together with their applications to novel drug delivery systems, such as nanoparticle-mediated drug delivery and convection-enhanced delivery.

Convection enhanced delivery of chemotherapeutic drugs into brain tumour

Convection enhanced delivery (CED) of chemotherapeutic drugs can successfully bypass the blood-brain barrier (BBB). However, the treatment efficacy is significantly variable in clinic owing to the absence of proper drugs and the lack of understanding on the local drug transport. In this study, mathematical modelling is employed to investigate the suitability of six chemotherapeutic drugs from the perspective of intratumoural transport, including fluorouracil, carmustine, cisplatin, methotrexate, doxorubicin and paclitaxel. The convection/diffusion/reaction model coupled with Darcy's law is applied to a 3-D realistic brain tumour model that is extracted from magnetic resonance (MR) images. The modelling demonstrates the advantages of CED in enhancing the convective flow of interstitial fluid and reducing the drug concentration dilution caused by the fluid loss from blood stream in the tumour region around the infusion site. The delivery outcomes of the drug in CED treatments are strongly dependent on its physicochemical properties. Convection is more effective in determining the transport of paclitaxel and methotrexate in brain tumour. Paclitaxel exhibits its superiority in drug penetration and accumulation, resulting in the largest effective delivery volume as compared to the other studied drugs. Nanocarrier and diagnostic ultrasound are able to enhance the drug penetration for achieving improved delivery outcomes. Results obtained in this study can serve as a guide for optimising CED treatment regimens.

Mathematical modeling of intraperitoneal drug delivery: simulation of drug distribution in a single tumor nodule

The intraperitoneal (IP) administration of chemotherapy is an alternative treatment for peritoneal carcinomatosis, allowing for higher intratumor concentrations of the cytotoxic agent compared to intravenous administration. Nevertheless, drug penetration depths are still limited to a few millimeters. It is thus necessary to better understand the limiting factors behind this poor penetration in order to improve IP chemotherapy delivery. By developing a three-dimensional computational fluid dynamics (CFD) model for drug penetration in a tumor nodule, we investigated the impact of a number of key parameters on the drug transport and penetration depth during IP chemotherapy. Overall, smaller tumors showed better penetration than larger ones, which could be attributed to the lower IFP in smaller tumors. Furthermore, the model demonstrated large improvements in penetration depth by subjecting the tumor nodules to vascular normalization therapy, and illustrated the importance of the drug that is used for therapy. Explicitly modeling the necrotic core had a limited effect on the simulated penetration. Similarly, the penetration depth remained virtually constant when the Darcy permeability of the tissue changed. Our findings illustrate that the developed parametrical CFD model is a powerful tool providing more insight in the drug transport and penetration during IP chemotherapy.

Interactions Between Therapeutic Proteins and Small Molecules: The Shared Role of Perpetrators and Victims

Therapeutic proteins (TPs) are becoming increasingly important as therapeutic agents. A consequence of expanding their clinical indications is coadministration with well-established small-molecule drugs (sMDs), which could lead to unpredictable effects. According to the existing regulatory guidance, the development of an sMD includes the evaluation of potential drug-drug interactions (DDIs). For TPs, only a few drug interaction studies have been published. Limited clinically relevant models, long half-lives, and complex elimination pathways are among the associated difficulties.

Modelling drug transport during intraperitoneal chemotherapy

Despite a strong rationale for intraperitoneal (IP) chemotherapy, the actual use of the procedure is limited by the poor penetration depth of the drug into the tissue. Drug penetration into solid tumours is a complex mass transport process that involves multiple parameters not only related to the used cytotoxic agent but also to the tumour tissue properties and even the therapeutic setup. Mathematical modelling can provide unique insights into the different transport barriers that occur during IP chemotherapy as well as offer the possibility to test different protocols or drugs without the need for in vivo experiments. In this work, a distinction is made between three different types of model: the lumped parameter model, the distributed model and the cell-based model. For each model, we discuss which steps of the transport process are included and where assumptions are made. Finally, we focus on the advantages and main limitations of each category and discuss some future perspectives for the modelling of IP chemotherapy.

Mathematical modeling of intraperitoneal drug delivery: simulation of drug distribution in a single tumor nodule

The intraperitoneal (IP) administration of chemotherapy is an alternative treatment for peritoneal carcinomatosis, allowing for higher intratumor concentrations of the cytotoxic agent compared to intravenous administration. Nevertheless, drug penetration depths are still limited to a few millimeters. It is thus necessary to better understand the limiting factors behind this poor penetration in order to improve IP chemotherapy delivery. By developing a three-dimensional computational fluid dynamics (CFD) model for drug penetration in a tumor nodule, we investigated the impact of a number of key parameters on the drug transport and penetration depth during IP chemotherapy. Overall, smaller tumors showed better penetration than larger ones, which could be attributed to the lower IFP in smaller tumors. Furthermore, the model demonstrated large improvements in penetration depth by subjecting the tumor nodules to vascular normalization therapy, and illustrated the importance of the drug that is used for therapy. Explicitly modeling the necrotic core had a limited effect on the simulated penetration. Similarly, the penetration depth remained virtually constant when the Darcy permeability of the tissue changed. Our findings illustrate that the developed parametrical CFD model is a powerful tool providing more insight in the drug transport and penetration during IP chemotherapy.

Sorafenib Decreases Tumor Exposure to an Anti-carcinoembryonic Antigen Monoclonal Antibody in a Mouse Model of Colorectal Cancer

In this investigation, we test the hypothesis that treatment with sorafenib, an anti-angiogenic agent, decreases tumor vascularization and, consequently, hinders the delivery of monoclonal antibodies (mAb) to xenograft tumors. Severe combined immunodeficiency mice bearing carcinoembryonic antigen (CEA) expressing tumor xenografts were divided into control and sorafenib-treated groups. Sorafenib was administered to the latter group at 50 mg/kg IP every 48 h, starting 4 days post-tumor implantation. When tumors attained a size of 200-300 mm(3), mice were evaluated for (a) tumor microvessel density (using immunohistochemical analysis), (b) tumor macromolecular extravasation (using Evans Blue Dye (EBD)), (c) pharmacokinetics of an anti-CEA mAb, T84.66, following an intravenous dose of 10 mg/kg, and (d) intra-tumoral spatial distribution of T84.66 (using autoradiography). Sorafenib treatment resulted in a substantial reduction in tumor growth rate, a visible reduction in tumor microvessel density, and in a 46.4% decrease in EBD extravasation in tumor tissue (p < 0.0455). For control and treated mice, no significant difference was found for the area under the mAb plasma concentration-time curve (AUC(0-7d): 1.67 × 10(3) ± 1.28 × 10(2) vs. 1.76 × 10(3) ± 1.75 × 10(2) nM × day, p = 0.51). However, tumor AUC(0-7d) was reduced by 40.8% in sorafenib-treated mice relative to that observed in control mice (5.61 × 10(2) ± 4.27 × 10(1) vs. 9.48 × 10(2) ± 5.61 × 10(1) nM × day, p < 0.001). Sorafenib therapy was also found to markedly alter mAb tumor spatial distribution. The results collectively suggest that sorafenib treatment causes a significant reduction in mAb delivery to, and distribution within, solid tumors.

Angiogenesis-Related Markers and Prognosis After Cytoreductive Surgery and Hyperthermic Intraperitoneal Chemotherapy for Metastatic Colorectal Cancer

BACKGROUND

Patients presenting with peritoneal metastases (PM) of colorectal cancer (CRC) can be curatively treated with cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC). Angiogenesis is under control of multiple molecules of which HIF1a, SDF1, CXCR4, and VEGF are key players. We investigated these angiogenesis-related markers and their prognostic value in patients with PM arising from CRC treated with CRS and HIPEC.

PATIENTS AND METHODS

Clinicopathological data and tissue specimens were collected in 2 tertiary referral centers from 52 patients who underwent treatment for isolated PM of CRC. Whole tissue specimens were subsequently analyzed for protein expression of HIF1a, SDF1, CXCR4, and VEGF by immunohistochemistry. Microvessel density (MVD) was analyzed by CD31 immunohistochemistry. The relationship between overall survival (OS) and protein expression as well as other clinicopathological characteristics was analyzed.

RESULTS

Univariate analysis showed that high peritoneal cancer index (PCI), resection with residual disease and high expression of VEGF were negatively correlated with OS after treatment with CRS and HIPEC (P < 0.01, P < 0.01, and P = 0.02, respectively). However, no association was found between the other markers and OS (P > 0.05). Multivariate analysis showed an independent association between OS and PCI, resection outcome and VEGF expression (multivariate HR: 6.1, 7.8 and 3.8, respectively, P ≤ 0.05).

CONCLUSIONS

An independent association was found between high VEGF expression levels and worse OS after CRS and HIPEC. The addition of VEGF expression to the routine clinicopathological workup could help to identify patients at risk for early treatment failure. Furthermore, VEGF may be a potential target for adjuvant treatment in these patients.

Multiscale tumor spatiokinetic model for intraperitoneal therapy

This study established a multiscale computational model for intraperitoneal (IP) chemotherapy, to depict the time-dependent and spatial-dependent drug concentrations in peritoneal tumors as functions of drug properties (size, binding, diffusivity, permeability), transport mechanisms (diffusion, convection), spatial-dependent tumor heterogeneities (vessel density, cell density, pressure gradient), and physiological properties (peritoneal pressure, peritoneal fluid volume). Equations linked drug transport and clearance on three scales (tumor, IP cavity, whole organism). Paclitaxel was the test compound. The required model parameters (tumor diffusivity, tumor hydraulic conductivity, vessel permeability and surface area, microvascular hydrostatic pressure, drug association with cells) were obtained from literature reports, calculation, and/or experimental measurements. Drug concentration-time profiles in peritoneal fluid and plasma were the boundary conditions for tumor domain and blood vessels, respectively. The finite element method was used to numerically solve the nonlinear partial differential equations for fluid and solute transport. The resulting multiscale model accounted for intratumoral spatial heterogeneity, depicted diffusive and convective drug transport in tumor interstitium and across blood vessels, and provided drug flux and concentration as a function of time and spatial position in the tumor. Comparison of model-predicted tumor spatiokinetics with experimental results (autoradiographic data of 3H-paclitaxel in IP ovarian tumors in mice, 6 h posttreatment) showed good agreement (1% deviation for area under curve and 23% deviations for individual data points, which were several-fold lower compared to the experimental intertumor variations). The computational multiscale model provides a tool to quantify the effects of drug-, tumor-, and host-dependent variables on the concentrations and residence time of IP therapeutics in tumors.

PK/TD modeling for prediction of the effects of 8C2, an anti-topotecan mAb, on topotecan-induced toxicity in mice

To facilitate the development of an inverse targeting strategy, where anti-topotecan antibodies are administered to prevent systemic toxicity following intraperitoneal topotecan, a pharmacokinetic/toxicodynamic (PK/TD) model was developed and evaluated. The pharmacokinetics of 8C2, a monoclonal anti-topotecan antibody, were assessed following IV and SC administration, and the data were characterized using a two compartmental model with nonlinear absorption and elimination. A hybrid PK model was constructed by combining a PBPK model for topotecan with the two-compartment model for 8C2, and the model was employed to predict the disposition of topotecan, 8C2, and the topotecan-8C2 complex. The model was linked to a toxicodynamic model for topotecan-induced weight-loss, and simulations were conducted to predict the effects of 8C2 on the toxicity of topotecan in mice. Increasing the molar dose ratio of 8C2 to topotecan resulted in a dose-dependent decrease in the unbound (i.e., not bound to 8C2) topotecan exposure in plasma (AUCf) and a decrease in the extent of topotecan-induced weight-loss. Consistent with model predictions, toxicodynamic experiments showed substantial reduction in the percent nadir weight loss observed with 30 mg/kg IP topotecan after co-administration of 8C2 (20 ± 8% vs. 10 ± 8%). The investigation supports the use of anti-topotecan mAb to reduce the systemic toxicity of IP topotecan chemotherapy.

Effects of Intraperitoneal Bevacizumab Administration on Colonic Anastomosis and Early Postoperative Adhesion Formation

Aim. The purpose of this study is to investigate the effect of intraperitoneal (IP) bevacizumab on colonic anastomosis and evaluate the effects on early postoperative adhesion formation. Materials and Methods. A total of 24 mature female Sprague-Dawley rats were used for this study. Rats were randomly assigned to a control group that received saline (n = 8) or to experimental groups (n = 8 each) that received bevacizumab at a dose of 2.5 mg/kg (group 1) or 5 mg/kg (group 2). Animals were killed humanely on the seventh day after operation, and measurements of anastomotic strength and biochemical variables were performed. Results. The mean adhesion grade was 2.63 ± 0.92, and 1 ± 0.93 and 0.75 ± 0.71 for the control and test groups, respectively. Bevacizumab significantly reduced adhesion formation in both low-dose and high-dose IP applications ( P < .05). When all groups were compared, it was found that VEGF levels decreased significantly only in the tissue ( P = .001), whereas there was no significant difference in the blood and the IP fluid ( P = .73 and .08, respectively). We evaluated hydroxyproline levels, anastomosis bursting pressure, and histopathological healing scores. When each of these parameters were examined, there was statistical difference between groups ( P = .01, .004, and .01, respectively). It was found that these parameters significantly decreased depending on increasing drug dose. Conclusion. IP administration of bevacizumab effectively reduced the formation of adhesions and caused significant impairment of anastomotic wound healing when standard doses were administered (5 mg/kg), but the 2.5-mg/kg dosage did not affect the anastomotic wound healing and also effectively reduced the formation of adhesions.

Application of PBPK modeling to predict monoclonal antibody disposition in plasma and tissues in mouse models of human colorectal cancer

This investigation evaluated the utility of a physiologically based pharmacokinetic (PBPK) model, which incorporates model parameters representing key determinants of monoclonal antibody (mAb) target-mediated disposition, to predict, a priori, mAb disposition in plasma and in tissues, including tumors that express target antigens. Monte Carlo simulation techniques were employed to predict the disposition of two mAbs, 8C2 (as a non-binding control mouse IgG1 mAb) and T84.66 (a high-affinity murine IgG1 anti-carcinoembryonic antigen mAb), in mice bearing no tumors, or bearing colorectal HT29 or LS174T xenografts. Model parameters were obtained or derived from the literature. (125)I-T84.66 and (125)I-8C2 were administered to groups of SCID mice, and plasma and tissue concentrations were determined via gamma counting. The PBPK model well-predicted the experimental data. Comparisons of the population predicted versus observed areas under the plasma concentration versus time curve (AUC) for T84.66 were 95.4 ± 67.8 versus 84.0 ± 3.0, 1,859 ± 682 versus 2,370 ± 154, and 5,930 ± 1,375 versus 5,960 ± 317 (nM × day) at 1, 10, and 25 mg/kg in LS174T xenograft-bearing SCID mice; and 215 ± 72 versus 233 ± 30, 3,070 ± 346 versus 3,120 ± 180, and 7,884 ± 714 versus 7,440 ± 626 in HT29 xenograft-bearing mice. Model predicted versus observed 8C2 plasma AUCs were 312.4 ± 30 versus 182 ± 7.6 and 7,619 ± 738 versus 7,840 ± 24.3 (nM × day) at 1 and 25 mg/kg. High correlations were observed between the predicted median plasma concentrations and observed median plasma concentrations (r (2) = 0.927, for all combinations of treatment, dose, and tumor model), highlighting the utility of the PBPK model for the a priori prediction of in vivo data.

Pharmacokinetics of pegylated liposomal doxorubicin administered by intraoperative hyperthermic intraperitoneal chemotherapy to patients with advanced ovarian cancer and peritoneal carcinomatosis

The pharmacokinetics of pegylated liposomal doxorubicin (PLD) were investigated in 17 women undergoing intraoperative hyperthermic intraperitoneal chemotherapy (HIPEC) for advanced ovarian cancer and peritoneal carcinomatosis. HIPEC was performed immediately after completing debulking surgery, which included a number of peritonectomy procedures. PLD was injected and allowed to equilibrate in peritoneal cavity filled with 4 liters of physiological solution and stabilized at 42°C; next, the outflow line was opened and perfusion proceeded for 1 h. PLD was stable in peritoneal perfusate and plasma. During HIPEC, PLD peritoneal perfusate/plasma gradients averaged ∼600 or ≥1000 for peak concentration or area under the curve. After HIPEC, PLD plasma levels remained stable or decreased. Biopsy samples of residual normal peritoneum or ovarian carcinomatosis were collected at the end of HIPEC and were shown to contain free doxorubicin. Correlating PLD decrements in peritoneal perfusate with plasma exposure to PLD or peritoneal deposition of free doxorubicin showed that the former occurred during preperfusional equilibration of PLD in peritoneal cavity, whereas the latter occurred during 1 h of perfusion. Plasma exposure to PLD correlated negatively with the number of peritonectomy procedures performed during surgery, whereas peritoneal deposition of free doxorubicin correlated positively. Taken together, these results show that PLD administered by intraoperative HIPEC undergoes limited systemic diffusion and releases active free doxorubicin in peritoneum exposed to ovarian carcinomatosis. PLD pharmacokinetics seem to be influenced by peritonectomy procedures.

Intraperitoneal bevacizumab combined with cytoreductive surgery: a pre-clinical study of tolerance and pharmacokinetics in an animal model

INTRODUCTION

Cytoreductive Surgery (CRS) combined with Hyperthermic Intraperitoneal Chemotherapy (HIPEC) is currently the only potentially curative treatment for peritoneal carcinomatosis (PC). Systemic administration of bevacizumab improves survival in patients with metastatic colorectal or ovarian cancer. Intraperitoneal administration of bevacizumab has been shown to be safe and effective in treating malignant ascites. The combination of CRS with intraperitoneal (IP) bevacizumab could maximize local control and survival from PC, but the associated morbidity from this is unknown. The aim of this study was to evaluate the safety of the combination of CRS with IP bevacizumab and to determine the pharmacokinetics of the drug in a rabbit model.

METHODS

Twenty healthy rabbits underwent a standardized procedure of debulking surgery, including peritonectomy and gastrointestinal anastomosis and were randomized to receive IP bevacizumab (25 mg/kg) or placebo. Another group of three rabbits underwent an instillation of IP bevacizumab (25 mg/kg) without surgery.

RESULTS

One rabbit that received IP bevacizumab died with no complication associated with the use of bevacizumab at autopsy. There was no significant difference between IP bevacizumab and placebo in weight loss, length of surgery or morbidity. The plasma concentration of bevacizumab increased to a peak at 24 h post IP administration. Bevacizumab was not detected in the plasma of animals without surgery.

CONCLUSION

This study suggests that IP bevacizumab does not increase morbidity and mortality of debulking surgery in an animal model. When surgery is performed, the pharmacokinetics of IP bevacizumab are modified in plasma.

Pharmacokinetic mAb-mAb interaction: anti-VEGF mAb decreases the distribution of anti-CEA mAb into colorectal tumor xenografts

To date, there has been little investigation of the risk for drug-drug interactions involving monoclonal antibodies. The present work examined the effects of an anti-vascular endothelial growth factor (anti-VEGF) antibody on the plasma, tissue, and tumor disposition of T84.66, an anti-carcinoembryonic antigen (CEA) antibody, in mice. SCID mice bearing CEA-expressing human colorectal cancer (LS174T) xenografts were divided into control and anti-VEGF-treated groups. When tumors reached 200-300 mm(3) in size, (125)I-T84.66 was administered intravenously at 10 mg/kg (400 μCi/kg). Radioactivity in plasma and tissue samples was counted, and T84.66 concentrations were determined. Areas under the concentration vs. time curves (AUC) were calculated. In separate groups of mice, Evans Blue Dye was administered to evaluate the effect of anti-VEGF on tumor vascular permeability. The investigations did not demonstrate significant effects of anti-VEGF therapy on T84.66 pharmacokinetics in plasma or in non-tumor tissues. T84.66 plasma AUC((0-10 days)) values were 2.37 × 10(3) ± 1.54 × 10(2) and 2.56 × 10(3) ± 1.01 × 10(2) nM × day, for the control and treated groups (p = 0.148). Conversely, anti-VEGF treatment significantly reduced tumor vascular permeability to Evans Blue Dye by 45.0 % (p = 0.0012), and anti-VEGF therapy decreased T84.66 tumor AUC((0-10 days)) by more than 60 % (7.27 × 10(2) ± 51.4 vs. 1.98 × 10(3) ± 90.1 nM × day, p < 0.0001). Our findings suggest that anti-VEGF therapies may lead to a substantial reduction in the delivery of monoclonal antibodies to tumor tissues. It is interesting and important to note that this pharmacokinetic interaction occurs at the target site, and that no alterations in T84.66 disposition were visible based on assessment of plasma pharmacokinetics alone.

Systemic administration of bevacizumab prolongs survival in an in vivo model of platinum pre-treated ovarian cancer

Ovarian cancer patients often suffer from malignant ascites and pleural effusion. Apart from worsening the outcome, this condition frequently impairs the quality of life in patients who are already distressed by ovarian cancer. This study investigated whether single intraperitoneal administration of the anti-VEGF antibody bevacizumab is capable of reducing the ascites-related body surface and prolonging survival. The study was performed in an orthotopic murine model of peritoneal disseminated platin-resistant ovarian cancer. Mice were treated with bevacizumab and/or paclitaxel or buffer (control). Reduction of body surface and increased survival rates were assessed as therapeutic success. Survival of mice in all treatment groups was significantly enhanced when compared to the non-treatment control group. The combination of paclitaxel plus bevacizumab significantly improved body surface as well as overall survival in comparison to a treatment with only one of the drugs. Treatment of malignant effusion with a single dose of bevacizumab as an intraperitoneal application, with or without cytostatic co-medication, may be a powerful alternative to systemic treatment.

Enhanced antitumor activity of low-dose continuous administration schedules of topotecan in prostate cancer

PURPOSE

The objective of this study was to determine the antitumor effects of alternate dosing schedules of topotecan in prostate cancer.

RESULTS

A concentration-dependent increase in cytotoxicity was observed in PC-3 and LNCaP cells after topotecan treatment using conventional and metronomic protocols. A significant increase in potency (2.4-18 fold, after 72 hr) was observed following metronomic dosing compared to conventional dosing administration in both cell lines. Metronomic dosing also increased the percentage of PC-3 cells in the G2/M, compared to control, but did not alter LNCaP cell cycle distribution. Metronomic dosing increased p21 protein expression in LNCaP and PC-3 cells compared to conventional dosing. The observed in vitro activity was confirmed using an in vivo model of human prostate cancer. Metronomic dosing and continuous infusion decreased tumor volume significantly (p < 0.05) compared to control and conventional topotecan treatment, but had no effect on tumor vascular staining.

METHODS

The cytotoxicity of topotecan after conventional or metronomic dosing was determined by examining cellular morphology, mitochondrial enzymatic activity (MTT), total cellular protein (SRB), annexin V and propidium iodine (PI) staining, cell cycle and western blot analysis in human prostate cancer cell lines (PC-3 and LNCaP) and the effects metronomic or continuous infusion on tumor growth in an in vivo tumor xenograft model.

CONCLUSIONS

These data support the hypothesis that low-dose continuous administration of topotecan increases potency compared to conventional dosing in prostate cancer. These data also suggest the novel finding that the enhanced antitumor activity of topotecan following low-dose exposure correlates to alterations in cell cycle and increased p21 expression.

Evaluation of combined bevacizumab and intraperitoneal carboplatin or paclitaxel therapy in a mouse model of ovarian cancer

PURPOSE

To evaluate the pharmacokinetics of bevacizumab following IP and IV administration, and to investigate combined bevacizumab therapy (IP or IV) with IP paclitaxel or carboplatin in a mouse model of ovarian cancer.

METHODS

Bevacizumab pharmacokinetics were investigated following IV or IP dosing, and mice bearing peritoneal A2780 xenografts were treated with vehicle, IV or IP bevacizumab, IP paclitaxel, IP paclitaxel with co-administration of IV or IP bevacizumab, IP carboplatin, and IP carboplatin with co-administration of IV or IP bevacizumab. Survival time was defined as the time to death or the time to reach 120% of baseline body weight.

RESULTS

Following IP administration, bevacizumab was rapidly absorbed and bioavailability was 92.8%. Median survival time, which was 33 days for control mice, was increased by 24% with IP paclitaxel. IP carboplatin failed to increase survival time when administered alone. IV and IP bevacizumab increased survival time by 42 and 33%. Combined bevacizumab and IP paclitaxel was superior to paclitaxel alone (P = 0.01 for IV and P = 0.04 for IP bevacizumab), and combined bevacizumab and IP carboplatin was superior to carboplatin alone (P = 0.002 for IV and P = 0.02 for IP bevacizumab). There were no significant differences in survival between groups receiving bevacizumab IV or IP, either alone (P = 0.586), in combination with paclitaxel (P = 0.467), or in combination with carboplatin (P = 0.149).

CONCLUSIONS

Following IP administration to mice, bevacizumab demonstrates rapid and near complete absorption. Bevacizumab therapy, initiated prior to IP carboplatin or paclitaxel administration, increased survival time significantly in mice, and results were not dependent on the route of bevacizumab administration (IV vs. IP).

The pharmacokinetic/pharmacodynamic pipeline: translating anticancer drug pharmacology to the clinic

Progress in an understanding of the genetic basis of cancer coupled to molecular pharmacology of potential new anticancer drugs calls for new approaches that are able to address key issues in the drug development process, including pharmacokinetic (PK) and pharmacodynamic (PD) relationships. The incorporation of predictive preclinical PK/PD models into rationally designed early-stage clinical trials offers a promising way to relieve a significant bottleneck in the drug discovery pipeline. The aim of the current review is to discuss some considerations for how quantitative PK and PD analyses for anticancer drugs may be conducted and integrated into a global translational effort, and the importance of examining drug disposition and dynamics in target tissues to support the development of preclinical PK/PD models that can be subsequently extrapolated to predict pharmacologic characteristics in patients. In this article, we describe three different physiologically based (PB) PK modeling approaches, i.e., the whole-body PBPK model, the hybrid PBPK model, and the two-pore model for macromolecules, as well as their applications. General conclusions are that greater effort should be made to generate more clinical data that could validate scaled preclinical PB-PK/PD tumor-based models and, thus, stimulate a framework for preclinical to clinical translation. Finally, given the innovative techniques to measure tissue drug concentrations and associated biomarkers of drug responses, development of predictive PK/PD models will become a standard approach for drug discovery and development.

Pharmacokinetics and pharmacodynamics of monoclonal antibodies: concepts and lessons for drug development

Monoclonal antibodies (mAbs) have complex pharmacology; pharmacokinetics and pharmacodynamics depend on mAb structure and target antigen. mAbs targeting soluble antigens often exhibit linear pharmacokinetic behavior, whereas mAbs targeting cell surface antigens frequently exhibit nonlinear behavior due to receptor-mediated clearance. Where nonlinear kinetics exist, clearance can change due to receptor loss following repeated dosing and/or disease severity. mAb pharmacodynamics are often indirect, with delayed clinically relevant outcomes. This behavior provides challenges during clinical development; studies must be carefully planned to account for complexities specific to each agent. Selection of a starting dose for human studies can be difficult. Species differences in pharmacology need to be considered. Various metrics are available for scaling from animals to humans. Optimal dose selection should ensure uniform mAb exposure across all individuals. Traditional approaches such as flat dosing and variable dosing based upon body surface area or weight should be supported by pharmacokinetic and pharmacodynamic behavior, including target antigen and concurrent disease states. The use of loading doses or dose adjustments to improve clinical response is also a consideration. The evaluation of drug interactions requires innovative designs. Due to the pharmacokinetic properties of mAbs, interacting drugs may need to be administered for protracted periods. Consequently, population pharmacokinetic and pharmacodynamic model-based approaches are often implemented to evaluate mAb drug interactions.