Combination of Gemcitabine with Cell-Penetrating Peptides: A Pharmacokinetic Approach Using In Silico Tools

Two Possible Strategies for Drug Modification of Gemcitabine and Future Contributions to Personalized Medicine

Drug repurposing is an emerging strategy, which uses already approved drugs for new medical indications. One such drug is gemcitabine, an anticancer drug that only works at high doses since a portion is deactivated in the serum, which causes toxicity. In this review, two methods were discussed that could improve the anticancer effect of gemcitabine. The first is a chemical modification by conjugation with cell-penetrating peptides, namely penetratin, pVEC, and different kinds of CPP6, which mostly all showed an increased anticancer effect. The other method is combining gemcitabine with repurposed drugs, namely itraconazole, which also showed great cancer cell inhibition growth. Besides these two strategies, physiologically based pharmacokinetic models (PBPK models) are also the key for predicting drug distribution based on physiological data, which is very important for personalized medicine, so that the correct drug and dosage regimen can be administered according to each patient’s physiology. Taking all of this into consideration, it is believed that gemcitabine can be repurposed to have better anticancer effects.

Cell-penetrating peptides improve pharmacokinetics and pharmacodynamics of anticancer drugs

This review concentrates on the research concerning conjugates of anticancer drugs with versatile cell-penetrating peptides (CPPs). For a better insight into the relationship between the components of the constructs, it starts with the characteristic of the peptides and considers its following aspects: mechanisms of cellular internalization, interaction with cancer-modified membranes, selectivity against tumor tissue. Also, CPPs with anticancer activity have been distinguished and summarized with their mechanisms of action. With respect to the conjugates, the preclinical studies (in vitro, in vivo) indicated that they possess several merits in comparison to the parent drugs. They concerned not only better cellular internalization but also other improvements in pharmacokinetics (e.g. access to the brain tissue) and pharmacodynamics (e.g. overcoming drug resistance). The anticancer activity of the conjugates was usually superior to that of the unconjugated drug. Certain anticancer CPPs and conjugates entered clinical trials.

Permeability of Gemcitabine and PBPK Modeling to Assess Oral Administration

Gemcitabine is a nucleoside analog effective against several solid tumors. Standard treatment consists of an intravenous infusion over 30 min. This is an invasive, uncomfortable and often painful method, involving recurring visits to the hospital and costs associated with medical staff and equipment. Gemcitabine’s activity is significantly limited by numerous factors, including metabolic inactivation, rapid systemic clearance of gemcitabine and transporter deficiency-associated resistance. As such, there have been research efforts to improve gemcitabine-based therapy efficacy, as well as strategies to enhance its oral bioavailability. In this work, gemcitabine in vitro and clinical data were analyzed and in silico tools were used to study the pharmacokinetics of gemcitabine after oral administration following different regimens. Several physiologically based pharmacokinetic (PBPK) models were developed using simulation software GastroPlus™, predicting the PK parameters and plasma concentration–time profiles. The integrative biomedical data analyses presented here are promising, with some regimens of oral administration reaching higher AUC in comparison to the traditional IV infusion, supporting this route of administration as a viable alternative to IV infusions. This study further contributes to personalized health care based on potential new formulations for oral administration of gemcitabine, as well nanotechnology-based drug delivery systems.

PBPK Modeling and Simulation of Antibiotics Amikacin, Gentamicin, Tobramycin, and Vancomycin Used in Hospital Practice

The importance of closely observing patients receiving antibiotic therapy, performing therapeutic drug monitoring (TDM), and regularly adjusting dosing regimens has been extensively demonstrated. Additionally, antibiotic resistance is a contemporary concerningly dangerous issue. Optimizing the use of antibiotics is crucial to ensure treatment efficacy and prevent toxicity caused by overdosing, as well as to combat the prevalence and wide spread of resistant strains. Some antibiotics have been selected and reserved for the treatment of severe infections, including amikacin, gentamicin, tobramycin, and vancomycin. Critically ill patients often require long treatments, hospitalization, and require particular attention regarding TDM and dosing adjustments. As these antibiotics are eliminated by the kidneys, critical deterioration of renal function and toxic effects must be prevented. In this work, clinical data from a Portuguese cohort of 82 inpatients was analyzed and physiologically based pharmacokinetic (PBPK) modeling and simulation was used to study the influence of different therapeutic regimens and parameters as biological sex, body weight, and renal function on the biodistribution and pharmacokinetic (PK) profile of these four antibiotics. Renal function demonstrated the greatest impact on plasma concentration of these antibiotics, and vancomycin had the most considerable accumulation in plasma over time, particularly in patients with impaired renal function. Thus, through a PBPK study, it is possible to understand which pharmacokinetic parameters will have the greatest variation in a given population receiving antibiotic administrations in hospital context.

Clinical pharmacokinetic study of latrepirdine via in silico sublingual administration

In recent decades, numerous in silico methodologies have been developed focused on the study of pharmacodynamic, pharmacokinetics and toxicological properties of drugs. The study of the pharmacokinetic behavior of new chemical entities is an essential part of the successful development of a new drug and Gastroplus™ is a simulation software used to predict the pharmacokinetic behavior of chemical entities. Latrepirdine is a drug that has been studied for Alzheimer's disease and Huntington's disease and later abandoned by the pharmaceutical industry already in the clinical trials because it has not demonstrated therapeutic efficacy. During this project, through Gastroplus™ simulations, it was possible to achieve predicted values of C_max coincident with those found in clinical trials, showing its utility in the prediction of pharmacokinetic parameters. Besides, sublingual delivery has the potential to offer improved bioavailability by circumventing first-pass metabolism. This study used GastroPlus™ to simulate sublingual administration of latrepirdine and the results showed improvements in bioavailability and plasma concentrations achieved though this route of administration.

In Silico Pharmacokinetic Study of Vancomycin Using PBPK Modeling and Therapeutic Drug Monitoring

BACKGROUND

Vancomycin has been in clinical use for nearly 50 years and remains the first-line treatment option for Gram-positive infections, including methicillin-resistant Staphylococcus aureus (MRSA). There are multiple strategies to monitor therapy and adjust the dose of this antibiotic. AUC24/MIC ratio has been demonstrated to be the best parameter to predict the effectiveness and safety of vancomycin, and a target ratio of ≥400 is recommended. Still, trough and peak serum levels at steady-state conditions have been used in clinical settings as an accurate and practical method to monitor vancomycin.

METHODS

In this work, we collected and analyzed clinical information of patients being treated in a hospital center in Porto (Portugal) and studied the pharmacokinetics of vancomycin in silico, developing several physiologically based pharmacokinetic (PBPK) models using simulation software GastroPlus™. Different dosages and treatment regimens were studied, and the influence of patients' age, weight and renal function was evaluated; a simulation population was also performed.

RESULTS

A linear effect of dose and a significant influence of weight and renal function in plasmatic levels of vancomycin was observed.

CONCLUSION

The results of this work corroborate the accumulation of vancomycin in plasma and identify some parameters that influence the pharmacokinetics of this antibiotic. The importance of therapeutic monitoring of vancomycin is highlighted, and the usefulness of in silico tools, namely PBPK modeling, is demonstrated.

Synthesis, Biological Activity and In Silico Pharmacokinetic Prediction of a New 2-Thioxo-Imidazoldidin-4-One of Primaquine

The discovery of novel antiparasitic drugs for neglected tropical diseases (NTDs) constitutes a global urgency and requires a range of innovative strategies to ensure a sustainable pipeline of lead compounds. Thus far, primaquine (PQ) is the only transmission-blocking antimalarial that is clinically available, displaying marked activity against gametocytes of all causative species of human malaria (Plasmodium spp.). Chagas disease, caused by Trypanosoma cruzi, is another PQ-sensitive illness besides malaria. One of the major drawbacks of PQ is its metabolism into carboxyprimaquine (CPQ), which is less active than the parent drug. In this study, we developed different synthetic pathways to confer N-protection to PQ through introduction of thioxo-imidazolidin-4-one. The introduction of this group prevents the formation of CPQ, counteracting one major drawback of the parent drug. After that, we evaluated the potential biological activity of the novel 2-thioxo-imidazolidin-4-one derivative of PQ, which showed relevant in vitro activity against Trypanosoma cruzi (IC₅₀ 1.4 μM) compared to PQ (IC₅₀ 1.7 μM) and the reference drug benznidazole (IC₅₀ 1.6 μM). Noting its acceptable pharmacokinetic profile, this PQ conjugate may be a potential scaffold for novel drug exploration against Chagas disease.

Regulation of tumor microenvironment for pancreatic cancer therapy

Pancreatic cancer (PC) is one kind of the most lethal malignancies worldwide, owing to its insidious symptoms, early metastases, and negative responses to current therapies. With an increasing understanding of pathology, the tumor microenvironment (TME) plays a significant role in ineffective treatment and poor prognosis of PC. Thus, a growing number of studies have focused on whether components of the TME could be effective targets for PC therapy. Biomaterials have been widely applied in cancer therapy, and numerous organic or inorganic biomaterials for TME regulation have been developed to inhibit the growth and metastasis of PC, as well as reverse therapeutic resistance. In this review, we discuss various biomaterials utilized to treat PC based on different components of the TME, including, but not limited to, extracellular matrix (ECM), abnormal tumor vascularization, and tumor-associated immune cells, as well as other unconventional therapeutic strategies. Besides, the perspectives on the underlying future of theranostic nanomedicines for PC therapy are also presented.

Gemcitabine Peptide-Based Conjugates and Their Application in Targeted Tumor Therapy

A major obstacle in tumor treatment is associated with the poor penetration of a therapeutic agent into the tumor tissue and with their adverse influence on healthy cells, which limits the dose of drug that can be safely administered to cancer patients. Gemcitabine is an anticancer drug used to treat a wide range of solid tumors and is a first-line treatment for pancreatic cancer. The effect of gemcitabine is significantly weakened by its rapid plasma degradation. In addition, the systemic toxicity and drug resistance significantly reduce its chemotherapeutic efficacy. Up to now, many approaches have been made to improve the therapeutic index of gemcitabine. One of the recently developed approaches to improve conventional chemotherapy is based on the direct targeting of chemotherapeutics to cancer cells using the drug-peptide conjugates. In this work, we summarize recently published gemcitabine peptide-based conjugates and their efficacy in anticancer therapy.