Population Pharmacokinetics of Oral Topotecan in Infants and Very Young Children with Brain Tumors Demonstrates a Role of ABCG2 rs4148157 on the Absorption Rate Constant

Current Status of Pharmacokinetic Research in Children: A Systematic Review of Clinical Trial Records

BACKGROUND

Many medications have different pharmacokinetics in children than in adults. Knowledge about the safety and efficacy of medications in children requires research into the pharmacokinetic profiles of children's medicines. By analysing registered clinical trial records, this study determined how frequently pharmacokinetic data is gathered in paediatric drug trials.

METHODS

We searched for the pharmacokinetic data from clinical trial records for preterm infants and children up to the age of 16 from January 2011 to April 2022. The records of trials involving one or more drugs in preterm infants and children up to the age of 16 were examined for evidence that pharmacokinetic data would be collected.

RESULTS

In a total of 1483 records of interventional clinical trials, 136 (9.17%) pharmacokinetic data involved adults. Of those 136 records, 60 (44.1%) records were pharmacokinetics trials involving one or more medicines in children up to the age of 16. 20 (33.3 %) in America, followed by 19 (31.6 %) in Europe. Most trials researched medicines in the field of infection or parasitic diseases 20 (33.3%). 27 (48.2%) and 26 (46.4%) trials investigated medicines that were indicated as essential medicine.

CONCLUSION

The pharmacokinetic characteristics of children's drugs need to be better understood. The current state of pharmacokinetic research appears to address the knowledge gap in this area adequately. Despite slow progress, paediatric clinical trials have experienced a renaissance as the significance of paediatric trials has gained international attention. The outcome of paediatric trials will have an impact on children's health in the future. In recent years, the need for greater availability and access to safe child-size pharmaceuticals has received a lot of attention.

The Impact of Pharmacogenetics on Pharmacokinetics and Pharmacodynamics in Neonates and Infants: A Systematic Review

In neonates, pharmacogenetics has an additional layer of complexity. This is because in addition to genetic variability in genes that code for proteins relevant to clinical pharmacology, there are rapidly maturational changes in these proteins. Consequently, pharmacotherapy in neonates has unique challenges. To provide a contemporary overview on pharmacogenetics in neonates, we conducted a systematic review to identify, describe and quantify the impact of pharmacogenetics on pharmacokinetics and -dynamics in neonates and infants (PROSPERO, CRD42022302029). The search was performed in Medline, Embase, Web of Science and Cochrane, and was extended by a PubMed search on the ‘top 100 Medicines’ (medicine + newborn/infant + pharmacogen*) prescribed to neonates. Following study selection (including data in infants, PGx related) and quality assessment (Newcastle–Ottawa scale, Joanna Briggs Institute tool), 55/789 records were retained. Retained records relate to metabolizing enzymes involved in phase I [cytochrome P450 (CYP1A2, CYP2A6, CYP2B6, CYP2C8/C9/C18, CYP2C19, CYP2D6, CYP3A5, CYP2E1)], phase II [glutathione-S-transferases, N-acetyl transferases, UDP-glucuronosyl-transferase], transporters [ATP-binding cassette transporters, organic cation transporters], or receptor/post-receptor mechanisms [opioid related receptor and post-receptor mechanisms, tumor necrosis factor, mitogen-activated protein kinase 8, vitamin binding protein diplotypes, corticotrophin-releasing hormone receptor-1, nuclear receptor subfamily-1, vitamin K epoxide reductase complex-1, and angiotensin converting enzyme variants]. Based on the available overview, we conclude that the majority of reported pharmacogenetic studies explore and extrapolate observations already described in older populations. Researchers commonly try to quantify the impact of these polymorphisms in small datasets of neonates or infants. In a next step, pharmacogenetic studies in neonatal life should go beyond confirmation of these associations and explore the impact of pharmacogenetics as a covariate limited to maturation of neonatal life (ie, fetal malformations, breastfeeding or clinical syndromes). The challenge is to identify the specific factors, genetic and non-genetic, that contribute to the best benefit/risk balance.

Clinical pharmacology of cytotoxic drugs in neonates and infants: Providing evidence-based dosing guidance

Cancer in neonates and infants is a rare but challenging entity. Treatment is complicated by marked physiological changes during the first year of life, excess rates of toxicity, mortality, and late effects. Dose optimisation of chemotherapeutics may be an important step to improving outcomes. Body size–based dosing is used for most anticancer drugs used in infants. However, dose regimens are generally not evidence based, and dosing strategies are frequently inconsistent between tumour types and treatment protocols. In this review, we collate available pharmacological evidence supporting dosing regimens in infants for a wide range of cytotoxic drugs. A systematic review was conducted, and available data ranked by a level of evidence (1–5) and a grade of recommendation (A–D) provided on a consensus basis, with recommended dosing approaches indicated as appropriate. For 9 of 29 drugs (busulfan, carboplatin, cyclophosphamide, daunorubicin, etoposide, fludarabine, isotretinoin, melphalan and vincristine), grade A was scored, indicating sufficient pharmacological evidence to recommend a dosing algorithm for infants. For busulfan and carboplatin, sufficient data were available to recommend therapeutic drug monitoring in infants. For eight drugs (actinomycin D, blinatumomab, dinutuximab, doxorubicin, mercaptopurine, pegaspargase, thioguanine and topotecan), some pharmacological evidence was available to guide dosing (graded as B). For the remaining drugs, including commonly used agents such as cisplatin, cytarabine, ifosfamide, and methotrexate, pharmacological evidence for dosing in infants was limited or non-existent: grades C and D were scored for 10 and 2 drugs, respectively. The review provides clinically relevant evidence-based dosing guidance for cytotoxic drugs in neonates and infants.

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Treating cancer in neonates and infants is challenging.

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Dose optimisation of cytotoxic drugs is an important step to improving outcomes.

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Clinical pharmacological evidence supporting dosing regimens in infants was collated.

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All available pharmacological evidence was ranked by a level of evidence.

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A grade of recommendation was derived and a recommended dose per agent provided.

Personalized medicine of non-gene-specific chemotherapies for non-small cell lung cancer

Non-small cell lung cancer is recognized as the deadliest cancer across the globe. In some areas, it is more common in women than even breast and cervical cancer. Its rise, vaulted by smoking habits and increasing air pollution, has garnered much attention and resource in the medical field. The first lung cancer treatments were developed more than half a century ago. Unfortunately, many of the earlier chemotherapies often did more harm than good, especially when they were used to treat genetically unsuitable patients. With the introduction of personalized medicine, physicians are increasingly aware of when, how, and in whom, to use certain anti-cancer agents. Drugs such as tyrosine kinase inhibitors, anaplastic lymphoma kinase inhibitors, and monoclonal antibodies possess limited utility because they target specific oncogenic mutations, but other drugs that target mechanisms universal to all cancers do not. In this review, we discuss many of these non-oncogene-targeting anti-cancer agents including DNA replication inhibitors (i.e., alkylating agents and topoisomerase inhibitors) and cytoskeletal function inhibitors to highlight their application in the setting of personalized medicine as well as their limitations and resistance factors.

Pharmacogenetics in Neuroblastoma: What Can Already Be Clinically Implemented and What Is Coming Next?

Pharmacogenetics is one of the cornerstones of Personalized Precision Medicine that needs to be implemented in the routine of our patients' clinical management in order to tailor their therapies as much as possible, with the aim of maximizing efficacy and minimizing toxicity. This is of great importance, especially in pediatric cancer and even more in complex malignancies such as neuroblastoma, where the rates of therapeutic success are still below those of many other types of tumors. The studies are mainly focused on germline genetic variants and in the present review, state of the art is presented: which are the variants that have a level of evidence high enough to be implemented in the clinic, and how to distinguish them from the ones that still need validation to confirm their utility. Further aspects as relevant characteristics regarding ontogeny and future directions in the research will also be discussed.

Medically Important Alterations in Transport Function and Trafficking of ABCG2

Several polymorphisms and mutations in the human ABCG2 multidrug transporter result in reduced plasma membrane expression and/or diminished transport function. Since ABCG2 plays a pivotal role in uric acid clearance, its malfunction may lead to hyperuricemia and gout. On the other hand, ABCG2 residing in various barrier tissues is involved in the innate defense mechanisms of the body; thus, genetic alterations in ABCG2 may modify the absorption, distribution, excretion of potentially toxic endo- and exogenous substances. In turn, this can lead either to altered therapy responses or to drug-related toxic reactions. This paper reviews the various types of mutations and polymorphisms in ABCG2, as well as the ways how altered cellular processing, trafficking, and transport activity of the protein can contribute to phenotypic manifestations. In addition, the various methods used for the identification of the impairments in ABCG2 variants and the different approaches to correct these defects are overviewed.

A pharmacogenetics study of platinum-based chemotherapy in lung cancer: ABCG2 polymorphism and its genetic interaction with SLC31A1 are associated with response and survival

Objective: The expression and function of platinum transporters affect drug tissue concentration and therapeutic effects. We had previously characterized functional variant of platinum intake transporter SLC31A1 gene. We aimed to investigate the association of platinum efflux transporter gene ABCG2 polymorphism and combined ABCG2 and SLC31A1 polymorphisms with clinical outcomes of NSCLC patients receiving platinum-based chemotherapy. Methods: We genotyped thirteen tagging and functional SNPs of ABCG2 in 1004 patients, and assessed their association with response, toxicity and survival using unconditional logistic regression and Cox proportional hazards regression analyses respectively. Results: Nonsynonymous rs2231142 (odds ratio [OR] 2.07; 95 % confidence interval [CI] 1.26-3.63), rs1871744 (OR 0.60; 95 % CI 0.42-0.87) and their haplotype and diplotype were associated with objective response. Rs4148157 was associated with shorter overall survival (Log-rank P = 0.002; hazard ratio [HR] 1.22; 95 % CI 1.05-1.42). Furthermore, the combined SLC31A1 rs2233914 and ABCG2 rs1871744 genotype was significantly associated with poor response (OR 0.31; 95 % CI 0.17-0.56; P _interaction = 0.003). And the combined genotypes of the functional rs10759637 of SLC31A1 and the nonsynonymous rs2231142 (Log-rank P = 5.20×10^-5; HR 1.47; 95 % CI 1.19-1.81; P _interaction = 0.007) or linked rs4148157 of ABCG2 were significantly associated with poor survival. Conclusion: This study reveals divergent association of ABCG2 polymorphism with response and survival of NSCLC patients receiving platinum-based chemotherapy, demonstrates the combined effects of functional variants of ABCG2 and SLC31A1 on clinical outcomes, and highlights pharmacogenetic relevance of platinum transporter genes interaction.

Pharmacokinetics and population pharmacokinetics in pediatric oncology

Pharmacokinetic research has become increasingly important in pediatric oncology as it can have direct clinical implications and is a crucial component in individualized medicine. Population pharmacokinetics has become a popular method especially in children, due to the potential for sparse sampling, flexible sampling times, computing of heterogeneous data, and identification of variability sources. However, population pharmacokinetic reports can be complex and difficult to interpret. The aim of this article is to provide a basic explanation of population pharmacokinetics, using clinical examples from the field of pediatric oncology, to facilitate the translation of pharmacokinetic research into the daily clinic.

Pheophorbide A: Fluorescent Bcrp Substrate to Measure Oral Drug-Drug Interactions in Real-Time In Vivo

We investigated whether pheophorbide A (PhA) could serve as a selective breast cancer resistance protein (BCRP) substrate (victim) to screen in vivo using fluorescent live animal imaging for transporter-mediated interactions with orally administered inhibitors (perpetrators), and whether that could be coupled with serum sampling to measure the systemic concentration of PhA with a fast-throughput in vitro fluorescent assay. PhA is a breakdown product of chlorophyll and is highly fluorescent in the near-infrared (NIR) spectrum. Whole-body NIR fluorescence was greater in the Bcrp KO compared with wild-type (WT) mice fed a regular diet containing chlorophyll and PhA, with fluorescence in WT mice confined to the intestine. PhA intestinal enterocyte fluorescence, after removing lumen contents, was greater in Bcrp knockout (KO) mice versus WT mice due to PhA enterocyte absorption and lack of PhA efflux by Bcrp. This difference was eliminated by maintaining the mice on an alfalfa (chlorophyll/PhA)-free diet. The area under the fluorescence ratio-time curve up to 6 hours (AUC_{FL 0-6 h}) of orally administrated PhA was 3.5 times greater in the Bcrp KO mice compared with WT mice, and the PhA serum concentration was 50-fold higher in KO mice. Pretreatment with known BCRP inhibitors lapatinib, curcumin, elacridar, pantoprazole, and sorafenib, at clinically relevant doses, significantly increased PhA AUC_{FL 0-6 h} by 2.4-, 2.3-, 2.2-, 1.5-, and 1.4-fold, respectively, whereas the area under PhA serum concentration-time curve calculated up to 6 hours (AUC_{Serum 0-6 h}) increased by 13.8-, 7.8-, 5.2-, 2.02-, and 1.45-fold, respectively, and corresponded to their hierarchy as in vitro BCRP inhibitors. Our results demonstrate that live animal imaging using PhA can be used to identify BCRP inhibitors and to assess the potential for BCRP-mediated clinical drug-drug interactions.

Challenges and Opportunities for Increasing the Knowledge Base Related to Drug Biotransformation and Pharmacokinetics during Growth and Development

It is generally acknowledged that there is a need and role for informative pharmacokinetic models to improve predictions and simulation as well as individualization of drug therapy in pediatric populations of different ages and developmental stages. This special issue contains more than 20 papers responding to the challenge of providing new information on scaling factors, ontogeny functions for drug metabolizing enzymes and transporters, the mechanisms underlying the observed developmental trajectories for these gene products, age-dependent changes in physiologic processes affecting drug disposition in children, as well as in vitro and in vivo studies describing the relative contribution of ontogeny and genetic factors as sources of variability in drug disposition in children. Considered together, these contributions serve to illustrate some of the current limitations regarding sample availability, number, and quality, but also provide a framework that allows for the potential value of the results of a given study to be interpreted within the context of these limitations. Among the challenges for the future are improving our understanding of the mechanisms regulating age-dependent changes in factors influencing drug disposition and response, thereby facilitating generalization to systems lacking detailed data, better integrating age-dependent changes in pharmacokinetics with age-dependent changes in pharmacodynamics, and allowing better predictability and individualization of drug disposition and response across the pediatric age spectrum.

Novel bivalent securinine mimetics as topoisomerase I inhibitors

A series of novel bivalent securinine mimetics incorporating different linkers between C-15 and C-15' were synthesized and their topoisomerase I (Topo I) inhibitory activities evaluated. It was thus revealed that mimetic R2 incorporating a rigid m-substituted benzene linker exhibits Topo I inhibitory activity three times that of parent securinine. Comprehensive structure-activity relationship analyses in combination with docking studies were used to rationalize the potent activity of these bivalent mimetics. Mechanistic studies served to confirm the deductions arising from docking studies that the active bivalent mimetics not only inhibited complexation between Topo I and DNA but also stabilized the Topo I-DNA complex itself.

HNRNPA2B1 regulates the epithelial-mesenchymal transition in pancreatic cancer cells through the ERK/snail signalling pathway

Background

Heterogeneous nuclear ribonucleoprotein A2B1 (HNRNPA2B1) is closely related to tumour occurrence and development, oncogene expression, apoptosis inhibition and invasion and metastasis capacities. However, its function in the epithelial–mesenchymal transition (EMT) of pancreatic cancer is not fully understood.

Methods

By comparing various wild-type pancreatic cancer cell lines, we determined which have a higher expression level of HNRNPA2B1 accompanied by the higher expression of N-cadherin and vimentin and lower expression of E-cadherin. Therefore, to elucidate the role of HNRNPA2B1 in EMT, we generated models of HNRNPA2B1 knockdown and overexpression in different types of pancreatic cancer cell lines (MIA Paca-2, PANC-1 and Patu-8988) and examined changes in expression of EMT-related factors, including CDH1, CDH2, vimentin and snail.

Results

The results show that HNRNPA2B1 promotes EMT development by down-regulating E-cadherin and up-regulating N-cadherin and vimentin, and also stimulates the invasion capacity and inhibits viability in human pancreatic cancer cell lines, the similar results in vivo experiments. Moreover, we found that HNRNPA2B1 likely regulates EMT progression in pancreatic carcinoma via the ERK/snail signalling pathway.

Conclusions

The results of this work suggest that HNRNPA2B1 inhibition has potential antitumour effects, which warrants in-depth investigation.

Schedule-Dependent Antiangiogenic and Cytotoxic Effects of Chemotherapy on Vascular Endothelial and Retinoblastoma Cells

Current treatment of retinoblastoma involves using the maximum dose of chemotherapy that induces tumor control and is tolerated by patients. The impact of dose and schedule on the cytotoxicity of chemotherapy has not been studied. Our aim was to gain insight into the cytotoxic and antiangiogenic effect of the treatment scheme of chemotherapy used in retinoblastoma by means of different in vitro models and to evaluate potential effects on multi-drug resistance proteins. Two commercial and two patient-derived retinoblastoma cell types and two human vascular endothelial cell types were exposed to increasing concentrations of melphalan or topotecan in a conventional (single exposure) or metronomic (7-day continuous exposure) treatment scheme. The concentration of chemotherapy causing a 50% decrease in cell proliferation (IC50) was determined by MTT and induction of apoptosis was evaluated by flow cytometry. Expression of ABCB1, ABCG2 and ABCC1 after conventional or metronomic treatments was assessed by RT-qPCR. We also evaluated the in vivo response to conventional (0.6 mg/kg once a week for 2 weeks) and metronomic (5 days a week for 2 weeks) topotecan in a retinoblastoma xenograft model. Melphalan and topotecan were cytotoxic to both retinoblastoma and endothelial cells after conventional and metronomic treatments. A significant decrease in the IC50 (median, 13-fold; range: 3–23) was observed following metronomic chemotherapy treatment in retinoblastoma and endothelial cell types compared to conventional treatment (p<0.05). Metronomic topotecan or melphalan significantly inhibited in vitro tube formation in HUVEC and EPC compared to vehicle-treated cells (p<0.05). Both treatment schemes induced apoptosis and/or necrosis in all cell models. No significant difference was observed in the expression of ABCB1, ABCC1 or ABCG2 when comparing cells treated with melphalan or topotecan between treatment schedules at the IC50 or with control cells (p>0.05). In mice, continuous topotecan lead to significantly lower tumor volumes compared to conventional treatment after 14 days of treatment (p<0.05). Continuous exposure to melphalan or topotecan increased the chemosensitivity of retinoblastoma and endothelial cells to both chemotherapy agents with lower IC50 values compared to short-term treatment. These findings were validated in an in vivo model. None of the dosing modalities induced multidrug resistance mechanisms while apoptosis was the mechanism of cell death after both treatment schedules. Metronomic chemotherapy may be a valid option for retinoblastoma treatment allowing reductions of the daily dose.