Pharmacokinetic-pharmacodynamic modeling of methotrexate-induced toxicity in mice

Effects of Mouse Kidney Parvovirus on Pharmacokinetics of Chemotherapeutics and the Adenine Model of Chronic Kidney Disease

Mouse kidney parvovirus (MKPV) causes inclusion body nephropathy in severely immunocompromised mice and renal interstitial inflammation in immunocompetent mice. Here we sought to determine the effects of MKPV on pre-clinical murine models that depend on renal function. To assess the effects of MKPV infection on the pharmacokinetics of 2 renally excreted chemotherapeutic agents, methotrexate and lenalidomide, we measured drug concentrations in the blood and urine of MKPV-infected or uninfected immunodeficient NOD.Cg-PrkdcscidIl2rgtm1Wjl/SzJ (NSG) and immunocompetent C57BL/6NCrl (B6) female mice. No differences in plasma pharmacokinetics were observed for lenalidomide. However, the AUC of methotrexate was 1.5-fold higher in uninfected NSG mice compared with infected NSG mice, 1.9-fold higher in infected B6 mice compared with uninfected B6 mice, and 4.3-fold higher in uninfected NSG mice compared with uninfected B6 mice. MKPV infection did not significantly affect the renal clearance of either drug. To assess effects of MKPV infection on the adenine diet model of chronic kidney disease, MKPV-infected and uninfected B6 female mice were fed a 0.2% adenine diet, and clinical and histopathologic features of disease were assessed over 8 wk. MKPV infection did not significantly alter urine chemistry results, hemogram findings, or serum concentrations of BUN, creatinine, or symmetric dimethylarginine. However, infection did influence histologic outcomes. As compared with uninfected mice, MKPV-infected mice had more interstitial lymphoplasmacytic infiltrates after 4 and 8 wk of diet consumption and less interstitial fibrosis at week 8. Macrophage infiltrates and renal tubular injury were similar between in infected and uninfected mice. These findings indicate that MKPV infection had minimal effects on the renal excretion of 2 chemotherapeutics and on serum biomarkers of renal function. However, infection significantly influenced two histologic features of the adenine diet model of chronic renal disease. MKPV-free mice are critically important in studies evaluating renal histology as an experimental outcome.

CNS penetration of methotrexate and its metabolite 7-hydroxymethotrexate in mice bearing orthotopic Group 3 medulloblastoma tumors and model-based simulations for children

The brain penetration of methotrexate (MTX) and its metabolite 7-hydroxymethotrexate (7OHMTX) was characterized in non-tumor bearing mice and mice bearing orthotopic Group 3 medulloblastoma. Plasma pharmacokinetic studies and cerebral and ventricular microdialysis studies were performed in animals dosed with 200 or 1000 mg/kg MTX by IV bolus. Plasma, brain/tumor extracellular fluid (ECF) and lateral ventricle cerebrospinal fluid (CSF) MTX and 7OHMTX concentration-time data were analyzed by validated LC-MS/MS methods and modeled using a population-based pharmacokinetic approach and a hybrid physiologically-based model structure for the brain compartments. Brain penetration was similar for MTX and 7OHMTX and was not significantly different between non-tumor and tumor bearing mice. Overall, mean (±SD) model-derived unbound plasma to ECF partition coefficient K_p,uu were 0.17 (0.09) and 0.17 (0.12) for MTX and 7OHMTX, respectively. Unbound plasma to CSF K_p,uu were 0.11 (0.06) and 0.18 (0.09) for MTX and 7OHMTX, respectively. The plasma and brain model were scaled to children using allometric principles and pediatric physiological parameters. Model-based simulations were adequately overlaid with digitized plasma and CSF lumbar data collected in children receiving different MTX systemic infusions. This model can be used to further explore and optimize methotrexate dosing regimens in children with brain tumors.

Methotrexate inhibition of SARS-CoV-2 entry, infection and inflammation revealed by bioinformatics approach and a hamster model

Background

Drug repurposing is a fast and effective way to develop drugs for an emerging disease such as COVID-19. The main challenges of effective drug repurposing are the discoveries of the right therapeutic targets and the right drugs for combating the disease.

Methods

Here, we present a systematic repurposing approach, combining Homopharma and hierarchal systems biology networks (HiSBiN), to predict 327 therapeutic targets and 21,233 drug-target interactions of 1,592 FDA drugs for COVID-19. Among these multi-target drugs, eight candidates (along with pimozide and valsartan) were tested and methotrexate was identified to affect 14 therapeutic targets suppressing SARS-CoV-2 entry, viral replication, and COVID-19 pathologies. Through the use of in vitro (EC₅₀ = 0.4 μM) and in vivo models, we show that methotrexate is able to inhibit COVID-19 via multiple mechanisms.

Results

Our in vitro studies illustrate that methotrexate can suppress SARS-CoV-2 entry and replication by targeting furin and DHFR of the host, respectively. Additionally, methotrexate inhibits all four SARS-CoV-2 variants of concern. In a Syrian hamster model for COVID-19, methotrexate reduced virus replication, inflammation in the infected lungs. By analysis of transcriptomic analysis of collected samples from hamster lung, we uncovered that neutrophil infiltration and the pathways of innate immune response, adaptive immune response and thrombosis are modulated in the treated animals.

Conclusions

We demonstrate that this systematic repurposing approach is potentially useful to identify pharmaceutical targets, multi-target drugs and regulated pathways for a complex disease. Our findings indicate that methotrexate is established as a promising drug against SARS-CoV-2 variants and can be used to treat lung damage and inflammation in COVID-19, warranting future evaluation in clinical trials.

Post-Transplantation Cyclophosphamide Uniquely Restrains Alloreactive CD4+ T-Cell Proliferation and Differentiation After Murine MHC-Haploidentical Hematopoietic Cell Transplantation

Post-transplantation cyclophosphamide (PTCy) reduces the incidence and severity of graft-versus-host disease (GVHD), thereby improving the safety and accessibility of allogeneic hematopoietic cell transplantation (HCT). We have shown that PTCy works by inducing functional impairment and suppression of alloreactive T cells. We also have identified that reduced proliferation of alloreactive CD4⁺ T cells at day +7 and preferential recovery of CD4⁺CD25⁺Foxp3⁺ regulatory T cells (T_regs) at day +21 are potential biomarkers associated with optimal PTCy dosing and timing in our B6C3F1→B6D2F1 MHC-haploidentical murine HCT model. To understand whether the effects of PTCy are unique and also to understand better the biology of GVHD prevention by PTCy, here we tested the relative impact of cyclophosphamide compared with five other optimally dosed chemotherapeutics (methotrexate, bendamustine, paclitaxel, vincristine, and cytarabine) that vary in mechanisms of action and drug resistance. Only cyclophosphamide, methotrexate, and cytarabine were effective in preventing fatal GVHD, but cyclophosphamide was superior in ameliorating both clinical and histopathological GVHD. Flow cytometric analyses of blood and spleens revealed that these three chemotherapeutics were distinct in constraining conventional T-cell numerical recovery and facilitating preferential T_reg recovery at day +21. However, cyclophosphamide was unique in consistently reducing proliferation and expression of the activation marker CD25 by alloreactive CD4⁺Foxp3^- conventional T cells at day +7. Furthermore, cyclophosphamide restrained the differentiation of alloreactive CD4⁺Foxp3^- conventional T cells at both days +7 and +21, whereas methotrexate and cytarabine only restrained differentiation at day +7. No chemotherapeutic selectively eliminated alloreactive T cells. These data suggest that constrained alloreactive CD4⁺Foxp3^- conventional T-cell numerical recovery and associated preferential CD4⁺CD25⁺Foxp3⁺ T_reg reconstitution at day +21 may be potential biomarkers of effective GVHD prevention. Additionally, these results reveal that PTCy uniquely restrains alloreactive CD4⁺Foxp3^- conventional T-cell proliferation and differentiation, which may explain the superior effects of PTCy in preventing GVHD. Further study is needed to determine whether these findings also hold true in clinical HCT.

GDF-15 Neutralization Alleviates Platinum-Based Chemotherapy-Induced Emesis, Anorexia, and Weight Loss in Mice and Nonhuman Primates

Platinum-based cancer therapy is restricted by dose-limiting side effects and is associated with elevation of growth differentiation factor 15 (GDF-15). But whether this elevation contributes to such side effects has been unclear. Here, we explored the effects of GDF-15 blockade on platinum-based chemotherapy-induced emesis, anorexia, and weight loss in mice and/or nonhuman primate models. We found that circulating GDF-15 is higher in subjects with cancer receiving platinum-based chemotherapy and is positively associated with weight loss in colorectal cancer (NCT00609622). Further, chemotherapy agents associated with high clinical emetic score induce circulating GDF-15 and weight loss in mice. Platinum-based treatment-induced anorexia and weight loss are attenuated in GDF-15 knockout mice, while GDF-15 neutralization with the monoclonal antibody mAB1 improves survival. In nonhuman primates, mAB1 treatment attenuates anorexia and emesis. These results suggest that GDF-15 neutralization is a potential therapeutic approach to alleviate chemotherapy-induced side effects and improve the quality of life.

Structure-function-guided exploration of the antimicrobial peptide polybia-CP identifies activity determinants and generates synthetic therapeutic candidates

Antimicrobial peptides (AMPs) constitute promising alternatives to classical antibiotics for the treatment of drug-resistant infections, which are a rapidly emerging global health challenge. However, our understanding of the structure-function relationships of AMPs is limited, and we are just beginning to rationally engineer peptides in order to develop them as therapeutics. Here, we leverage a physicochemical-guided peptide design strategy to identify specific functional hotspots in the wasp-derived AMP polybia-CP and turn this toxic peptide into a viable antimicrobial. Helical fraction, hydrophobicity, and hydrophobic moment are identified as key structural and physicochemical determinants of antimicrobial activity, utilized in combination with rational engineering to generate synthetic AMPs with therapeutic activity in a mouse model. We demonstrate that, by tuning these physicochemical parameters, it is possible to design nontoxic synthetic peptides with enhanced sub-micromolar antimicrobial potency in vitro and anti-infective activity in vivo. We present a physicochemical-guided rational design strategy to generate peptide antibiotics.

Methotrexate hepatotoxicity is associated with oxidative stress, and down-regulation of PPARγ and Nrf2: Protective effect of 18β-Glycyrrhetinic acid

18β-glycyrrhetinic acid (18β-GA) is a bioactive component of licorice with promising hepatoprotective activity. However, its protective mechanism on methotrexate (MTX) hepatotoxicity in not well defined. We investigated the hepatoprotective effect of 18β-GA, pointing to the role of peroxisome proliferator activated receptor gamma (PPARγ) and the redox-sensitive nuclear factor erythroid 2-related factor 2 (Nrf2). Wistar rats were orally administered 18β-GA (50 and 100 mg/kg) 7 days either before or after MTX injection. MTX induced significant increase in circulating liver function marker enzymes and bilirubin with concomitant declined albumin levels. Serum pro-inflammatory cytokines, and liver malondialdehyde and nitric oxide were significantly increased in MTX-induced rats. Treatment with 18β-GA significantly reduced serum enzymes of liver function, bilirubin and pro-inflammatory cytokines. 18β-GA attenuated MTX-induced oxidative stress and restored the antioxidant defenses. In addition, 18β-GA improved liver histological structure and decreased the expression of Bax whereas increased Bcl-2 expression. MTX-induced rats showed significant down-regulation of Nrf2, hemoxygenase-1 and PPARγ, an effect that was markedly reversed by 18β-GA supplemented either before or after MTX. In conclusion, 18β-GA protected against MTX-induced liver injury, possibly by activating Nrf2 and PPARγ, and subsequent attenuation of inflammation, oxidative stress and apoptosis. Therefore, 18β-GA can provide protection against MTX-induced hepatotoxicity.

Erlotinib-cisplatin combination inhibits growth and angiogenesis through c-MYC and HIF-1α in EGFR-mutated lung cancer in vitro and in vivo

Combination treatment for non–small cell lung cancer (NSCLC) is becoming more popular due to the anticipation that it may be more effective than single drug treatment. In addition, there are efforts to genetically screen patients for specific mutations in light of attempting to administer specific anticancer agents that are most effective. In this study, we evaluate the anticancer and anti-angiogenic effects of low dose erlotinib-cisplatin combination in NSCLC in vitro and in vivo. In NSCLC cells harboring epidermal growth factor receptor (EGFR) mutations, combination erlotinib-cisplatin treatment led to synergistic cell death, but there was minimal efficacy in NSCLC cells with wild-type EGFR. In xenograft models, combination treatment also demonstrated greater inhibition of tumor growth compared to individual treatment. The anti-tumor effect observed was secondary to the targeting of angiogenesis, evidenced by decreased vascular endothelial growth factor (VEGF) levels and decreased levels of CD31 and microvessel density. Combination treatment targets angiogenesis through down-regulation of the c-MYC/hypoxia inducible factor 1-alpha (HIF-1α) pathway. In fact, cell lines with EGFR exon 19 deletions expressed high basal levels of c-MYC and HIF-1α and correlate with robust responses to combination treatment. These results suggest that low dose erlotinib-cisplatin combination exhibits its anti-tumor activity by targeting angiogenesis through the modulation of the c-MYC/HIF-1α/VEGF pathway in NSCLC with EGFR exon 19 deletions. These findings may have significant clinical implications in patients with tumors harboring EGFR exon 19 deletions as they may be particularly sensitive to this regimen.

Cognitive impact of cytotoxic agents in mice

RATIONALE AND OBJECTIVES

Adjuvant chemotherapy is associated with changes in cognition in a subgroup of cancer patients. Chemotherapy is generally given as a combination of cytotoxic agents, which makes it hard to define the agent responsible for these observed changes. Literature on animal experiments has been difficult to interpret due to variance in experimental setup.

METHODS

We examined the effects of cytotoxic agents administered separately on various cognitive measures in a standardized animal model. Male C57Bl/6 mice received cyclophosphamide, docetaxel, doxorubicin, 5-fluorouracil, methotrexate, or topotecan. These agents represent different compound classes based on their working mechanism and are frequently prescribed in the clinic. A control group received saline. Behavioral testing started 2 or 15 weeks after treatment and included testing general measures of behavior and cognitive task performance: spontaneous behavior in an automated home cage, open field, novel location recognition (NLR), novel object recognition (NOR), Barnes maze, contextual fear conditioning, and a simple choice reaction time task (SCRTT).

RESULTS

Cyclophosphamide, docetaxel, and doxorubicin administration affected spontaneous activity in the automated home cage. All cytotoxic agents affected memory (NLR and/or NOR). Spatial memory measured in the Barnes maze was affected after administration with doxorubicin, 5-fluorouracil, and topotecan. Decreased inhibition in the SCRTT was observed after treatment with cyclophosphamide, docetaxel, and topotecan.

CONCLUSIONS

Our data show that, in mice, a single treatment with a cytotoxic agent causes cognitive impairment. Not all cytotoxic agents affected the same cognitive domains, which might be explained by differences in working mechanisms of the various agents.

Using physiologically-based pharmacokinetic-guided "body-on-a-chip" systems to predict mammalian response to drug and chemical exposure

The continued development of in vitro systems that accurately emulate human response to drugs or chemical agents will impact drug development, our understanding of chemical toxicity, and enhance our ability to respond to threats from chemical or biological agents. A promising technology is to build microscale replicas of humans that capture essential elements of physiology, pharmacology, and/or toxicology (microphysiological systems). Here, we review progress on systems for microscale models of mammalian systems that include two or more integrated cellular components. These systems are described as a "body-on-a-chip", and utilize the concept of physiologically-based pharmacokinetic (PBPK) modeling in the design. These microscale systems can also be used as model systems to predict whole-body responses to drugs as well as study the mechanism of action of drugs using PBPK analysis. In this review, we provide examples of various approaches to construct such systems with a focus on their physiological usefulness and various approaches to measure responses (e.g. chemical, electrical, or mechanical force and cellular viability and morphology). While the goal is to predict human response, other mammalian cell types can be utilized with the same principle to predict animal response. These systems will be evaluated on their potential to be physiologically accurate, to provide effective and efficient platform for analytics with accessibility to a wide range of users, for ease of incorporation of analytics, functional for weeks to months, and the ability to replicate previously observed human responses.

Engineering human T cells for resistance to methotrexate and mycophenolate mofetil as an in vivo cell selection strategy

Gene transfer and drug selection systems that enforce ongoing transgene expression in vitro and in vivo which are compatible with human pharmaceutical drugs are currently underdeveloped. Here, we report on the utility of incorporating human enzyme muteins that confer resistance to the lymphotoxic/immunosuppressive drugs methotrexate (MTX) and mycophenolate mofetil (MMF) in a multicistronic lentiviral vector for in vivo T lymphocyte selection. We found that co-expression of human dihydrofolate reductase (DHFR(FS); L22F, F31S) and inosine monophosphate dehydrogenase II (IMPDH2(IY); T333I, S351Y) conferred T cell resistance to the cytocidal and anti-proliferative effects of these drugs at concentrations that can be achieved clinically (up to 0.1 µM MTX and 1.0 µM MPA). Furthermore, using a immunodeficient mouse model that supports the engraftment of central memory derived human T cells, in vivo selection studies demonstrate that huEGFRt(+)DHFR(FS+)IMPDH2(IY+) T cells could be enriched following adoptive transfer either by systemic administration of MTX alone (4.4 -fold), MMF alone (2.9-fold), or combined MTX and MMF (4.9-fold). These findings demonstrate the utility of both DHFR(FS)/MTX and IMPDH2(IY)/MMF for in vivo selection of lentivirally transduced human T cells. Vectors incorporating these muteins in combination with other therapeutic transgenes may facilitate the selective engraftment of therapeutically active cells in recipients.

Pharmacokinetics, pharmacodynamics and toxicities of methotrexate in healthy and collagen-induced arthritic rats

Methotrexate (MTX) is an anchor drug used to treat rheumatoid arthritis (RA), but responsiveness is variable in effectiveness and toxicity. Methotrexate and its polyglutamate conjugates (MTXPG(n)) in red blood cells (RBC) have been associated with patient response. In the current study, 13 collagen-induced arthritic (CIA) rats and 12 healthy rats were given subcutaneous doses of either saline or 0.3 or 1.5 mg/kg per 2 days of MTX from day 21 to 43 post-induction. Blood samples were obtained at various times to measure MTX in plasma, and MTX and MTXPG(n) in RBC. Effects on disease progression were indicated by body weight and paw size. After multiple-doses, RBC MTX reached steady-state (82.4 nm) within 4 days. The MTXPG(2) and MTXPG(3) in RBC kept increasing until the end of the study, attaining 12.5 and 17.7 nm. Significant weight loss was observed after dosing with 1.5 mg/kg/2 days, whereas moderate effectiveness was observed after dosing with 0.3 mg/kg/2 days. A pharmacokinetic/pharmacodynamic/disease (PK/PD/DIS) model with indirect mechanisms and transduction components incorporating plasma MTX, RBC MTX and RBC MTXPG(n) concentrations, and paw size was developed using naïve data pooling and ADAPT 5. The PK/PD in CIA rats dosed at 0.3 mg/kg/2 days were captured well by our proposed model. Methotrexate showed modest (I(maxd) = 0.16) but sensitive (IC(50d) = 0.712 nm) effectiveness on paw edema. The higher dose produced toxicity. The proposed model offers improved understanding of the effects of methotrexate on rheumatoid arthritis.

Pharmacokinetic application of a bio-analytical LC-MS method developed for 5-fluorouracil and methotrexate in mouse plasma, brain and urine

In the past we have reported significant cognitive deficits in mice receiving 5-fluorouracil in combination with low-dose methotrexate. To explain such interactions, a pharmacokinetic study was designed. A sensitive bio-analytical method was therefore developed and validated for 5-fluorouracil and methotrexate in mouse plasma, brain and urine with liquid chromatography coupled to a single quadrupole mass spectrometer. Chromatographic separation was accomplished by Agilent® Zorbax® SB-C18 column, with isocratic elution (5 mM ammonium acetate and methanol, 70:30, %v/v) at a flow rate of 300 μL/min. The limit of quantitation for both drugs was 15.6 ng/mL (plasma and brain) and 78.1 ng/mL (urine), with interday and intraday precision and accuracy ≤15% and a total run time of 6 min. This bio-analytical method was used for the pharmacokinetic characterization of 5-fluorouracil and methotrexate in mouse plasma, brain and urine over a period of 24 h. This method allowed characterization of the brain concentrations of 5-fluorouracil over a period of 24 h.

Synergistic effect of low-dose cucurbitacin B and low-dose methotrexate for treatment of human osteosarcoma

We investigated the use of cucurbitacin B, a plant-derived tetracyclic triterpenoid, as a single agent or in combination with methotrexate (MTX) for human osteosarcoma (OS) treatment. Cucurbitacin B showed antiproliferative activity against seven human OS cell lines in vitro accompanying G2/M cell cycle arrest, apoptosis, and inhibition of ERK, Akt, and mTOR proteins. Cucurbitacin B in combination with MTX synergistically inhibited OS cell growth in vitro. Low-dose cucurbitacin B (LD-CuB, 0.5 mg/kg body weight) or low-dose MTX (LD-MTX, 150 mg/kg) failed to decrease the size of human OS xenografts in nude mice. However, combined therapy at identical concentrations inhibited tumor growth by 62% vs. LD-CuB and 81% vs. LD-MTX (p<0.001). Strikingly, the effect persisted even when the dose of MTX was decreased by two thirds (VLD-MTX, 50 mg/kg). In conclusion, cucurbitacin B alone or in combination with MTX shows promising antiproliferative activity against human OS.

Induction of pulmonary fibrosis by methotrexate treatment in mice lung in vivo and in vitro

Methotrexate (MTX) has been used as the first-line disease-modifying antirheumatic drug (DMARD) in patients with early progressive rheumatoid arthritis (RA). Several severe side effects such as myelosuppression, hepato-, nephro-, and pulmonary toxicities have been reported. However, the pathogenic mechanism of MTX-induced pulmonary fibrosis is still unknown. Here, we evaluated the morphological and biological changes of the pulmonary fibrosis in mice treated with MTX. Three, four and five weeks after consecutive administration of MTX (3 mg/kg/day), hydroxyproline content in the lung tissues increased significantly to about 2 times higher that of the control level. This result closely reflected to the results of hematoxylin and eosin (HE) and Azan stains. Immunohistochemical analysis revealed that MTX treatment resulted in a decrease of alveolar epithelial cells and an increase of fibroblast cells in the mouse lung tissues. When we examined the effects of MTX on primary mouse alveolar epithelial cell (MAEC) and mouse lung fibroblast (MLF) survival in vitro, the efficiency of MTX-induced cytotoxicity and apoptosis in MAEC was more sensitive than MLF cells. Thus, our results indicate that the administration of MTX by an oral route could induce a fibrotic response with cell dysfunction of the alveolar epithelium by which MTX-induced apoptosis. Our results thus suggest that MTX could induce alveolar epithelial cell injury and resulted in the loss of integrity of the alveolar-capillary barrier basement membranes followed by the recruitment and proliferation of myofibroblasts with the deposition of collagens.

Integration of in silico and in vitro platforms for pharmacokinetic-pharmacodynamic modeling

IMPORTANCE OF THE FIELD

Pharmacokinetic-pharmacodynamic (PK-PD) modeling enables quantitative prediction of the dose-response relationship. Recent advances in microscale technology enabled researchers to create in vitro systems that mimic biological systems more closely. Combination of mathematical modeling and microscale technology offers the possibility of faster, cheaper and more accurate prediction of the drug's effect with a reduced need for animal or human subjects.

AREAS COVERED IN THIS REVIEW

This article discusses combining in vitro microscale systems and PK-PD models for improved prediction of drug's efficacy and toxicity. First, we describe the concept of PK-PD modeling and its applications. Different classes of PK-PD models are described. Microscale technology offers an opportunity for building physical systems that mimic PK-PD models. Recent progress in this approach during the last decade is summarized.

WHAT THE READER WILL GAIN

This article is intended to review how microscale technology combined with cell cultures, also known as 'cells-on-a-chip', can confer a novel aspect to current PK-PD modeling. Readers will gain a comprehensive knowledge of PK-PD modeling and 'cells-on-a-chip' technology, with the prospect of how they may be combined for synergistic effect.

TAKE HOME MESSAGE

The combination of microscale technology and PK-PD modeling should contribute to the development of a novel in vitro/in silico platform for more physiologically-realistic drug screening.

A microfluidic device for a pharmacokinetic-pharmacodynamic (PK-PD) model on a chip

Drug discovery is often impeded by the poor predictability of in vitro assays for drug toxicity. One primary reason for this observation is the inability to reproduce the pharmacokinetics (PK) of drugs in vitro. Mathematical models to predict the pharmacokinetics-pharmacodynamics (PK-PD) of drugs are available, but have several limitations, preventing broader application. A microscale cell culture analog (microCCA) is a microfluidic device based on a PK-PD model, where multiple cell culture chambers are connected with fluidic channels to mimic multi-organ interactions and test drug toxicity in a pharmacokinetic-based manner. One critical issue with microfluidics, including the microCCA, is that specialized techniques are required for assembly and operation, limiting its usability to non-experts. Here, we describe a novel design, with enhanced usability while allowing hydrogel-cell cultures of multiple types. Gravity-induced flow enables pumpless operation and prevents bubble formation. Three cell lines representing the liver, tumor and marrow were cultured in the three-chamber microCCA to test the toxicity of an anticancer drug, 5-fluorouracil. The result was analyzed with a PK-PD model of the device, and compared with the result in static conditions. Each cell type exhibited differential responses to 5-FU, and the responses in the microfluidic environment were different from those in static environment. Combination of a mathematical modeling approach (PK-PD modeling) and an in vitro experimental approach (microCCA) provides a novel platform with improved predictability for testing drug toxicity and can help researchers gain a better insight into the drug's mechanism of action.

Pharmacokinetics of anti-cancer drugs used in breast cancer chemotherapy

Pharmacokinetics of anticancer drugs used in breast cancer therapy are well established. This chapter reviews preclinical and clinical pharmacokinetics of the following drugs: cyclophosphamide, docetaxel, doxorubicin, 5-fluorouracil, methotrexate and tamoxifen. The absorption, distribution, metabolism and elimination of drugs are discussed in the context of breast cancer. The effect of age and menopause status on drug pharmacokinetics is evaluated. The important role of pharmacokinetic-pharmacodynamic modeling in understanding the phenomenon of chemo fog, memory deficit in breast cancer chemotherapy, is explored.

The effects of drug transporter inhibitors on the pharmacokinetics and tissue distribution of methotrexate in normal and tumor-bearing mice: a microdialysis study

PURPOSE

To examine methotrexate (MTX) tumor delivery in a mouse model using an in vivo microdialysis technique and to characterize the impact of prior administration of the known transporter inhibitors probenecid and cyclosporine (CsA), alone and in combination, on plasma and tumor pharmacokinetics of MTX.

METHODS

Different groups of mice were used to evaluate the plasma pharmacokinetics of MTX and the impact of prior administration of probenecid and/or CsA on the plasma pharmacokinetics. Xenografted nude mice were used for microdialysis experiments to measure the subcutaneous (SC), peri- and intratumoral pharmacokinetics of MTX without and with coadministration of probenecid, CsA, and both probenecid and CsA.

RESULTS

The SC dialysates in pre-treated groups demonstrated a delayed disappearance and an enhanced MTX exposure. Similar effects were observed in the tumor peripheral zone. However, this increase was less pronounced. The central tumor findings demonstrated that CsA had a more significant impact on the enhancement of MTX exposure. Probenecid did not increase the exposure of MTX inside the tumor, but caused a longer half-life of central MTX.

CONCLUSIONS

This study revealed significant differences in the relative estimated PK parameters of the plasma, SC, peri-, and intratumoral zones. Additionally, this study demonstrated that the coadministration of MTX with CsA can enhance the intratumoral exposure levels of the drug, whereas coadministration of MTX with probenecid alone, or with a combination of probenecid and CsA, increases intratumoral half-life.

A micro cell culture analog (microCCA) with 3-D hydrogel culture of multiple cell lines to assess metabolism-dependent cytotoxicity of anti-cancer drugs

A microfluidic device with 3-D hydrogel cell cultures has been developed to test the cytotoxicity of anti-cancer drugs while reproducing multi-organ interactions. In this device, a micro cell culture analog (microCCA), cells embedded in 3-D hydrogels are cultured in separate chambers representing the liver, tumor, and marrow, which are connected by channels mimicking blood flow. While the microfluidic network provides a platform for mimicking the pharmacokinetic and pharmacodynamic profiles of a drug in humans, the 3-D hydrogel provides a more physiologically realistic environment to mimic the tissue than monolayer culture. Colon cancer cells (HCT-116) and hepatoma cells (HepG2/C3A) were encapsulated in Matrigel and cultured in the tumor and the liver chamber in a microCCA, respectively. Myeloblasts (Kasumi-1) were encapsulated in alginate in the marrow chamber; a stiffer hydrogel was necessary to prevent cell migration out of the matrix. The cytotoxic effect of Tegafur, an oral prodrug of 5-fluorouracil (5-FU), on each cell line was tested using the microCCA with cell-embedded hydrogel. The comparison of experimental results using a 96-well microtiter plate and a microCCA demonstrated that the microCCA was able to reproduce the metabolism of Tegafur to 5-FU in the liver and consequent death of cells by 5-FU, while the cultures in a 96-well microtiter plate were unable to do so. The microCCA utilizing 3-D hydrogel cell cultures has potential as a platform for pharmacokinetic-based drug screening in a more physiologically realistic environment.

A novel electrophysiological model of chemotherapy-induced cognitive impairments in mice

PURPOSE

Chemotherapeutic agents are known to produce persistent cognitive deficits in cancer patients. However, little progress has been made in developing animal models to explore underlying mechanisms and potential therapeutic interventions. We report an electrophysiological model of chemotherapy-induced cognitive deficits using a sensory gating paradigm, to correspond with performance in two behavioral tasks.

EXPERIMENTAL DESIGN

Mice received four weekly injections of methotrexate and 5-fluorouracil. Whole-brain event-related potentials (ERPs) were recorded throughout using a paired-click paradigm. Mice underwent contextual fear conditioning (CFC) and novel-object recognition testing (NOR).

RESULTS

Chemotherapy-treated animals showed significantly impaired gating 5 weeks after drug treatments began, as measured by the ratio of the first positive peak in the ERP (P1) minus the first negative peak (N1) between first and second auditory stimuli. There was no effect of drug on the amplitude of P1-N1 or latency of P1. The drug-treated animals also showed significantly increased freezing during fear conditioning and increased exploration without memory impairment during novel object recognition.

CONCLUSIONS

Chemotherapy causes decreased ability to gate incoming auditory stimuli, which may underlie associated cognitive impairments. These gating deficits were associated with a hyperactive response to fear conditioning and reduced adaptation to novel objects, suggesting an additional component of emotional dysregulation. However, amplitudes and latencies of ERP components were unaffected, as was NOR performance, highlighting the subtle nature of these deficits.

Effects of chemotherapeutic agents 5-fluorouracil and methotrexate alone and combined in a mouse model of learning and memory

RATIONALE

The concern that adjuvant cancer chemotherapy agents cause cognitive impairment in a significant number of patients has been expressed by patients and healthcare providers, but clinical studies have yielded conflicting results to date.

OBJECTIVE

We directly tested two commonly used chemotherapeutic agents in a mouse model of learning and memory.

MATERIALS AND METHODS

In the present study, mice were conditioned to respond for a liquid reinforcer (Ensure solution) in the presence of an audible tone on day 1 as a measure of acquisition and were then required to perform the same response on day 2 as a measure of retrieval and retention. Methotrexate and 5-fluorouracil were administered prior to the day 1 session.

RESULTS

Methotrexate (1.0-32 mg/kg) alone failed to alter mean latency acquisition, retrieval, or reinforced response rates. Similar to scopolamine, a known amnesic in this assay, 5-fluorouracil (3-75 mg/kg) failed to alter response rates or acquisition latency on day 1 but significantly altered latency to retrieve a previously learned response on day 2. In combination, 3.2 mg/kg methotrexate plus 75 mg/kg 5-fluorouracil significantly increased day 1 and day 2 acquisition and retrieval latencies without altering response rates or motivation to respond as measured by progressive ratio responding.

CONCLUSION

Taken together, these data demonstrate that 5-fluorouracil causes increased latencies for retrieval of previously learned behavioral responses and that combination of chemotherapeutic agents may produce greater delays than either agent alone, including when neither agent alone does so.

Mathematical modeling of topotecan pharmacokinetics and toxicodynamics in mice

The objective of this study was to investigate the pharmacokinetics and toxicodynamics of topotecan (TPT) in mice and to develop an integrated pharmacokinetic/toxicodynamic (PK/TD) model to characterize the relationship between the time course of TPT disposition and the time course of TPT-induced toxicity. TPT was administered to groups of 3-5 mice via i.v. bolus injection, i.p. bolus injection, and by i.p. infusion over 24, 72 and 168 h. Body weight was monitored to assess TPT-induced toxicity, and serial blood samples were collected and analyzed via HPLC to assess TPT pharmacokinetics. We found that TPT-induced toxicity increased dose-dependently for each mode of dosing investigated. The time course of topotecan-induced body weight-loss was delayed relative to the time course of topotecan disposition; nadir body weight was observed as late as 6 days following i.p. bolus dosing, and 3-5 days following termination of i.p. infusion. TPT exhibited non-linear disposition, which was well-characterized through the use of a two-compartment model with saturable elimination from the central compartment. Toxicodynamic data were characterized with an integrated PK/TD model that incorporated an indirect-effect model and four transit compartments to describe transduction events associated with TPT-induced toxicity. This model will be used to support the development of an inverse-targeting strategy that aims to enhance topotecan safety and efficacy.

Determination of methotrexate and its major metabolite 7-hydroxymethotrexate in mouse plasma and brain tissue by liquid chromatography-tandem mass spectrometry

Methotrexate (MTX) is an anticancer agent that is widely used in a variety of human cancers including primary central nervous system lymphoma (PCNSL). Important pharmacological properties that directly bear on the use of MTX in PCNSL, such as mechanisms that govern its uptake into brain tumors, are poorly defined, but are amenable to investigation in mouse models. In order to pursue such preclinical pharmacological studies, a rapid and sensitive liquid chromatography-tandem mass spectrometry (LC/MS/MS) method for the determination of MTX and its metabolite, 7-hydroxymethotrexate (7-OH MTX) in plasma and microdialysate samples from brain tumors and cerebrospinal fluid (CSF) is needed. The plasma assay was based on 10 microl samples and following a protein precipitation procedure enabled direct injection onto a LC/MS/MS system using positive electrospray ionization. A column switching technique was employed for desalting and the clean-up of microdialysate samples from brain tissues. The methods were validated for MTX and 7-OH MTX in both plasma and microdialysate samples from brain tumor and CSF, and produced lower limits of quantification (LLOQ) in plasma of 3.7 ng/ml for MTX and 7.4 ng/ml for 7-OH MTX, and in microdialysate samples of 0.7 ng/ml for both MTX and 7-OH MTX. The utility of the method was demonstrated by estimation of pharmacokinetic (PK) and brain distribution properties of MTX and 7-OH MTX in conscious mice. The method has the advantages of low sample volume, rapid clean-up, and the simultaneous measurement of MTX and 7-OH MTX in plasma and brain tissues allowing detailed PK studies to be completed in individual mice.

Application of Anti-Methotrexate Fab Fragments for the Optimization of Intraperitoneal Methotrexate Therapy in a Murine Model of Peritoneal Cancer

Anti-drug antibodies may be used to impart regio-specific alterations in drug disposition, potentially enhancing the therapeutic selectivity of intracavitary chemotherapy. In the present study, we tested the hypotheses that systemic therapy with anti-methotrexate antibodies would allow increases in the maximum tolerated dose of intraperitoneal methotrexate (MTX) and allow increases in the therapeutic efficacy of intraperitoneal MTX in a murine model of peritoneal cancer. Monoclonal anti-MTX Fab antibody fragments (AMF) were produced, purified, and characterized. AMF pharmacokinetics were determined following i.v. bolus injection (0.4 g/kg) and s.c. bolus injection (0.4, 0.8, 2.2 g/kg). MTX efficacy was investigated in mice bearing peritoneal sarcoma 180 tumors, following administration of MTX via 72 h i.p. infusion at 1.9, 2.8, 3.8 mg/kg, and following combination therapy of 7.5 or 10 mg/kg i.p. MTX (72 h infusion) and 4.2 g/kg s.c. AMF. The mean terminal half-life of AMF was found to be 10.9 +/- 3.3 h and was not dose-dependent, and s.c. bioavailability was 28% +/- 7% at 2.2 g/kg. In mice bearing peritoneal tumors, the maximally tolerated dose of i.p. MTX increased from 1.9 mg/kg (following i.p. MTX alone) to 10 mg/kg (with co-administration of s.c. AMF). Median survival times for saline-treated control animals and animals receiving i.p. MTX (1.9, 2.8, 3.8 mg/kg) were 9, 12, 10, and 7 days, respectively. However, for animals receiving combination therapy with i.p. MTX 7.5 or 10 mg/kg and 4.2 g/kg s.c. AMF, median survival time increased to 17 and 14 days, respectively. As such, the present data suggest that systemic administration of AMF may allow increases in the maximally tolerated dose of i.p. MTX, and allow increases in the therapeutic efficacy of i.p. MTX chemotherapy of peritoneal tumors.

Antibody pharmacokinetics and pharmacodynamics

The U.S. Food and Drug administration (FDA) has approved several polyclonal antibody preparations and at least 18 monoclonal antibody preparations (antibodies, antibody fragments, antibody fusion proteins, etc.). These drugs, which may be considered as a diverse group of therapeutic proteins, are associated with several interesting pharmacokinetic characteristics. Saturable binding with target antigen may influence antibody disposition, potentially leading to nonlinear distribution and elimination. Independent of antigen interaction, concentration-dependent elimination may be expected for IgG antibodies, due to the influence of the Brambell receptor, FcRn, which protects IgG from catabolism. Antibody administration may induce the development of an endogenous antibody response, which may alter the pharmacokinetics of the therapeutic antibody. Additionally, the pharmacodynamics of antibodies are also complex; these drugs may be used for a wide array of therapeutic applications, and effects may be achieved by a variety of mechanisms. This article provides an overview of many of the complexities associated with antibody pharmacokinetics and pharmacodynamics.