Modification of the hydroxy lactone ring of camptothecin: inhibition of mammalian topoisomerase I and biological activity

Development of an ELISA with acidification treatment for an antibody conjugate incorporating Exatecans

The successful development of Sacituzumab Govitecan and Trastuzumab Deruxtecan has made camptothecin derivatives one of the most popular payloads for antibody-drug conjugates (ADCs). Camptothecin and its derivatives all exist in a pH-dependent equilibrium between the carboxylate and lactone forms. Such transformation may lead to differences in the ratio of the two molecular forms in calibration standards and biological matrix (bio-matrix) samples, thereby leading to inaccurate conjugated antibody results. In this study, we reported an enzyme-linked immunosorbent assay (ELISA) free of the aforementioned influence for the detection of the Exatecans-conjugated antibody (conjugated SM001) in cynomolgus monkey serum. The assay was developed by first acidifying all samples with glacial acetic acid (HAc), then performing neutralization and thereafter capturing conjugated SM001 with anti-Exatecan monoclonal antibody (mAb) and detecting it with biotinylated Nectin4 (hNectin4-Bio) and horseradish peroxidase-labeled streptavidin (SA-HRP). Results showed that all tested performance parameters met the acceptance criteria. The conjugated SM001 concentrations obtained were in parallel to but slightly lower than total antibody (TAb) throughout the pharmacokinetic (PK) study, revealing that the assay strategy implemented for conjugated SM001 measurement worked well for the elimination of interference triggered by the heterogeneous existence of the lactone and carboxylate forms of Exatecan (lactone-Exatecan and carboxylate-Exatecan).

Design, synthesis and biological evaluation of matrine contains benzimidazole derivatives as dual TOPOI and PARP inhibitors for cancer therapy

TOPOI inhibitors have long been a focal point in the research and development of antitumor drugs. PARP-1 plays a crucial role in repairing DNA damage induced by TOPOI inhibitors. Thus, concurrent inhibition of TOPOI and PARP-1 has the potential to augment drug activity. Matrine, characterized by low toxicity and good water solubility, offers advantageous properties. In this investigation, a series of benzimidazole matrine derivatives were designed and synthesized using matrine as the lead compound with the aim of developing dual inhibitors targeting both TOPOI and PARP-1. Among these derivatives, Compound B6 exhibited potent inhibitory effects on PARP-1 and TOPOI, effectively suppressing cancer cell proliferation and migration. Mechanistic assessments revealed that B6 induced DNA damage in HGC-27 cells, leading to G0/G1 cell cycle arrest and significant apoptosis. Molecular docking experiments demonstrated that B6 can effectively enter the active pocket of target proteins, where it forms stable hydrogen bonds with amino acid residues. In vivo, experiments demonstrated that B6 exhibited antitumor activity comparable to that of the positive control drug. The tumor growth inhibition rates (TGIs) for irinotecan, B6 and matrine were 87.0%, 75.4% and 9.7%, respectively. Importantly, B6 demonstrated lower toxicity than the positive control drug. Our findings suggest that TOPOI and PARP-1 may represent potential targets for matrine and B6 emerges as a promising candidate for cancer therapy.

Formulating 10-hydroxycamptothecin into nanoemulsion with functional excipient tributyrin: An innovative strategy for targeted hepatic cancer chemotherapy

This study aimed to develop an innovative dosage form for 10-hydroxycamptothecin (HCPT), a chemotherapeutic agent with limited aqueous solubility and stability, to enhance its parenteral delivery and targeting to hepatic cancer. We formulated HCPT into a nanoemulsion using tributyrin, a dietary component with histone deacetylase inhibitor activity. The resulting HCPT-loaded tributyrin nanoemulsion (Tri-HCPT-E) underwent extensive evaluations. Tri-HCPT-E significantly improved the aqueous solubility, stability, and anti-cancer activities in HepG2 cells. Pharmacokinetic studies confirmed the increased stability and hepatic targeting, with Tri-HCPT-E leading to a 120-fold increase in plasma exposure of intact HCPT and a 10-fold increase in hepatic exposure compared to the commercial free solution. Co-administration of 17α-ethynylestradiol, an up-regulator of low-density lipoprotein (LDL) receptor, further enhanced the distribution and metabolism of HCPT, demonstrating an association between the LDL receptor pathway and hepatic targeting. Most importantly, Tri-HCPT-E exhibited superior in vivo anti-cancer efficacy in a mouse xenograft model compared to the commercial formulation, without causing escalated hepatic or renal toxicity. In conclusion, formulating HCPT into a nanoemulsion with tributyrin has proven to be an innovative and effective strategy for targeted hepatic cancer chemotherapy while tributyrin, a pharmacologically active dietary component, has emerged as a promising functional excipient for drug delivery.

Unleashing the Potential of Camptothecin: Exploring Innovative Strategies for Structural Modification and Therapeutic Advancements

Camptothecin (CPT) is a potent anti-cancer agent targeting topoisomerase I (TOP1). However, CPT has poor pharmacokinetic properties, causes toxicities, and leads to drug resistance, which limit its clinical use. In this paper, to review the current state of CPT research. We first briefly explain CPT's TOP1 inhibition mechanism and the key hurdles in CPT drug development. Then we examine strategies to overcome CPT's limitations through structural modifications and advanced delivery systems. Though modifications alone seem insufficient to fully enhance CPT's therapeutic potential, structure-activity relationship analysis provides insights to guide optimization of CPT analogs. In comparison, advanced delivery systems integrating controlled release, imaging capabilities, and combination therapies via stimulus-responsive linkers and targeting moieties show great promise for improving CPT's pharmacological profile. Looking forward, multifaceted approaches combining selective CPT derivatives with advanced delivery systems, informed by emerging biological insights, hold promise for fully unleashing CPT's anti-cancer potential.

Development and Validation of an ADA-Tolerant Assay for Quantification of an Exatecan-Based ADC in Monkey Plasma

BACKGROUND

The development of an anti-drug antibody (ADA)-tolerant pharmacokinetic (PK) assay is important when the drug exposure is irrelevant to toxicity in the presence of ADA. We aimed to develop and validate an ADA-tolerant assay for an exatecan-based antibody-drug conjugate (ADC) in monkey plasma.

RESULTS

The assay tolerated 5.00 µg/mL of ADA at 12 µg/mL of ADC. Its accuracy and precision results satisfied the acceptance criteria. Furthermore, the assay was free from hook and matrix effects and exhibited good dilutional linearity. Additionally, the ADC in plasma samples was stable under different storage conditions.

METHOD

An ADA-tolerant ADC assay was configured with an anti-payload antibody for capture, and a drug-target protein combined with a horseradish peroxidase (HRP)-labeled antibody against a drug-target-protein tag for detection. Samples were firstly acidified to dissociate drug and ADA complexes, and to convert the carboxylate form to the lactone form of exatecan molecules; then, the ADAs in the samples were removed with a naked antibody-coated microplate. The treated samples were further incubated with coated anti-payload antibody and captured ADC molecules were quantified by the detection reagent. The developed assay was optimized and validated against regulatory guidelines.

CONCLUSIONS

The assay met both methodological and sample-related ADA tolerance requirements, and was applicable to a nonclinical study in cynomolgus monkeys.

Epigenetic modulations in cancer: predictive biomarkers and potential targets for overcoming the resistance to topoisomerase I inhibitors

INTRODUCTION

Altered epigenetic map is frequently observed in cancer and recent investigations have demonstrated a pertinent role of epigenetic modifications in the response to many anticancer drugs including the DNA damaging agents. Topoisomerase I (Top I) is a well-known nuclear enzyme that is critical for DNA function and cell survival and its inhibition causes DNA strand breaks and cell cycle arrest. Inhibitors of human Top I have proven to be a prosperous chemotherapeutic treatment for a vast number of cancer patients. While the treatment is efficacious in many cases, resistance and altered cellular response remain major therapeutic issues.

AREAS COVERED

This review highlights the evidence available till date on the influence of different epigenetic modifications on the response to Top I inhibitors as well as the implications of targeting epigenetic alterations for improving the efficacy and safety of Top I inhibitors.

EXPERT OPINION

The field of epigenetic research is steadily growing. With its assistance, we could gain better understanding on how drug response and resistance work. Epigenetics can evolve as possible biomarkers and predictors of response to many medications including Top I inhibitors, and could have significant clinical implications that necessitate deeper attention.HIGHLIGHTSEpigenetic alterations, including DNA methylation and histone modifications, play a pertinent role in the response to several anticancer treatments, including DNA damaging agents like Top I inhibitors.Although camptothecin derivatives are used clinically as Top I inhibitors for management of cancer, certain types of cancer have inherent and or acquired resistance that limit the curative potential of them.Epigenetic modifications like DNA hypomethylation can either increase or decrease sensitivity to Top I inhibitors by different mechanisms.The combination of Top I inhibitors with the inhibitors of histone modifying enzymes can result in enhanced cytotoxic effects and sensitization of resistant cells to Top I inhibitors.MicroRNAs were found to directly influence the expression of Top I and other proteins in cancer cells resulting in positive or negative alteration of the response to Top I inhibitors.lncRNAs and their genetic polymorphisms have been found to be associated with Top I function and the response to its inhibitors.Clinical trials of epigenetic drugs in combination with Top I inhibitors are plentiful and some of them showed potentially promising outcomes.

The recent developments of camptothecin and its derivatives as potential anti-tumor agents

This review article focuses on the research progress made in the structural modifications of camptothecin (CPT), a potent cytotoxic natural alkaloid. CPT possesses a unique 5-fused ring structure and exhibits various beneficial activities such as anti-proliferative, anti-fungal, insecticidal, and anti-SARS-CoV-2 properties. CPT and its analogs, including Topotecan and Irinotecan, have been successfully developed and marketed as topoisomerase I inhibitors. To enhance the therapeutic potential of CPT, researchers have undertaken structural modifications primarily on the A, B, and E rings of the CPT core structure. These modifications aim to improve the efficacy, selectivity, and pharmacokinetic properties of CPT derivatives. The article reviews the advancements in hybridizing CPT with other bioactive compounds, the synthesis of novel CPT analogs, and their associated biological activities. Moreover, the structure-activity relationship (SAR) of these modified CPT derivatives is summarized to gain insights into their structure-function correlations. In addition to discussing the modifications and biological activities of CPT derivatives, the article also touches upon the mechanism of parent drug release. Many CPT derivatives are prodrugs, meaning they require metabolic activation to generate the active form of the drug. It is a resource for researchers interested in developing novel anti-tumor agents based on CPT, addressing the limitations associated with the parent drug, and exploring various aspects of CPT modifications.

Camptothecin: Solubility, In-Vitro Drug Release, and Effect on Human Red Blood Cells and Sperm Cold Preservation

BACKGROUND: Camptothecin (CPT) is an anticancer drug, and is not employed in the clinic because of its high hydrophobicity and low active form stability. CPT may also have potential for use in cold preservation. OBJECTIVE : To overcome these drawbacks, CPT solubility variations in the presence of cyclodextrins (CDs) and polyethylene glycol (PEG) were evaluated by Higuchi solubility experiments. MATERIALS AND METHODS: CPT was encapsulated in different cyclodextrins and polyethylene glycol using a co-evaporation method. The CPT interactions with CDs and PEG 6000 were investigated by Fourier-transformed infrared spectroscopy (FT-IR), and X-ray powder diffraction (XRPD). Then, CPT complexes were evaluated for in-vitro drug release. To evaluate the potential anticancer efficacy of the CPT complexes system, in-vitro cytotoxicity studies on human red blood cells were carried out using UV assay. The impact of the CPT complex systems on sperm motility protection during cold preservation at 4°C was studied using CASA. RESULTS: The dissolution profile of these preparations shows the improvement of the dissolution of the CPT following a fickien diffusion. The CPT solubility and stability improvement were the cause of the cytotoxicity on the red blood cells test. However, CPT alone, encapsulated, dispersed, and chemically modified protected spermatozoids during cold preservation. CONCLUSION: We confirm the interest in CPT encapsulated and dispersed in anticancer treatments. We also found that CPT encapsulated or dispersed could protect sperm against oxidative damage and improve the membrane integrity of human sperm. Consequently, CPT encapsulated our dispersed could eventually be beneficial for infertility therapy.

Dynamic Interconversions of Single Molecules Probed by Recognition Tunneling at Cucurbit[7]uril-Functionalized Supramolecular Junctions

We introduce a versatile recognition tunneling technique using doubly cucurbit[7]uril‐functionalized electrodes to form supramolecular junctions that capture analytes dynamically by host–guest complexation. This results in characteristic changes in their single‐molecule conductance. For structurally related drug molecules (camptothecin, sanguinarine, chelerythrine, and berberine) and mixtures thereof, we observed distinct current switching signals related to their intrinsic conductance properties as well as pH‐dependent effects which can be traced back to their different states (protonated versus neutral). The conductance variation of a single molecule with pH shows a sigmoidal distribution, allowing us to extract a pK_a value for reversible protonation, which is consistent with the reported macroscopic results. The new electronic method allows the characterization of unmodified drug molecules and showcases the transfer of dynamic supramolecular chemistry principles to single molecules.

Hydroxycamptothecin (HCPT)-loaded PEGlated lipid-polymer hybrid nanoparticles for effective delivery of HCPT: QbD-based development and evaluation

Lipid-polymer hybrid nanoparticles (LPNs) are promising drug delivery systems in various of disease treatment areas, particularly for cancer treatments. Here, a water-insoluble antitumor agent, hydroxycamptothecin (HCPT), was successfully incorporated into LPNs formed from polylactic-co-glycolic acid (PLGA), 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-(methoxy(polyethylene glycol)-2000) (DSPE-PEG2000), and lecithin, by a modified single emulsification-solvent evaporation method. Quality-by-design (QbD) strategy composed of Plackett-Burman and Box-Behnken designs were applied for optimizing HCPT-LPNs with desired properties. The optimized HCPT-loaded lipid-polymer hybrid nanoparticles (HCPT-LPNs) were on the nanoscale, with a final size of 220.9 nm, drug loading of 2.50%. HCPT-LPNs were highly stable in plasma and had pH- and drug loading-related sustained release characteristics. The in vitro cytotoxicity of HCPT-LPNs against MCF-7 and HepG2 cells showed that HCPT-LPNs had higher in vitro cytotoxicity than HCPT solution (HCPT-Sol) with reduced cell viability and IC50 values. In vivo pharmacokinetic assays demonstrated that the AUC of HCPT-LPNs was more than 3 times higher than that of HCPT-Sol after tail vein injection in SD rats. Tumor growth was significantly inhibited compared with HCPT-Sol after a single tail vein injection of HCPT-LPNs in murine LLC-GFP-luc lung cancer bearing mice at a dose of 6 mg/kg, without severe side effects. These results indicate that HCPT-LPNs are the promising drug delivery system for antitumor treatments.

Self-assembly delivery system based on small-molecule camptothecin prodrug for treatment of colorectal carcinoma

The aim of this study was to prepare small-molecule camptothecin (CPT) prodrugs and evaluate their effectiveness in colorectal carcinoma therapy. Prodrug nanoparticles (NPs) were physicochemically characterized and evaluated for their cytotoxicity in human colon cancer (HCT116) cell lines. The antitumor efficacy of the NPs was evaluated in HCT116 tumor-bearing mice. The prepared NPs exhibited high drug loading capacity (32% of CPT w/w) and also kept a high active lactone fraction of CPT (>85%) during circulation. The NPs were internalized into tumor cells efficiently compared with free drug and significantly enhanced the drug's therapeutic efficacy. The developed small-molecule CPT prodrug NPs could be a promising strategy in the clinical therapy of colorectal carcinoma.

Toxicity of Carbon Nanomaterials and Their Potential Application as Drug Delivery Systems: In Vitro Studies in Caco-2 and MCF-7 Cell Lines

Carbon nanomaterials have attracted increasing attention in biomedicine recently to be used as drug nanocarriers suitable for medical treatments, due to their large surface area, high cellular internalization and preferential tumor accumulation, that enable these nanomaterials to transport chemotherapeutic agents preferentially to tumor sites, thereby reducing drug toxic side effects. However, there are widespread concerns on the inherent cytotoxicity of carbon nanomaterials, which remains controversial to this day, with studies demonstrating conflicting results. We investigated here in vitro toxicity of various carbon nanomaterials in human epithelial colorectal adenocarcinoma (Caco-2) cells and human breast adenocarcinoma (MCF-7) cells. Carbon nanohorns (CNH), carbon nanotubes (CNT), carbon nanoplatelets (CNP), graphene oxide (GO), reduced graphene oxide (GO) and nanodiamonds (ND) were systematically compared, using Pluronic F-127 dispersant. Cell viability after carbon nanomaterial treatment followed the order CNP < CNH < RGO < CNT < GO < ND, being the effect more pronounced on the more rapidly dividing Caco-2 cells. CNP produced remarkably high reactive oxygen species (ROS) levels. Furthermore, the potential of these materials as nanocarriers in the field of drug delivery of doxorubicin and camptothecin anticancer drugs was also compared. In all cases the carbon nanomaterial/drug complexes resulted in improved anticancer activity compared to that of the free drug, being the efficiency largely dependent of the carbon nanomaterial hydrophobicity and surface chemistry. These fundamental studies are of paramount importance as screening and risk-to-benefit assessment towards the development of smart carbon nanomaterial-based nanocarriers.

DNA Methylation and Demethylation Are Regulated by Functional DNA Methyltransferases and DnTET Enzymes in Diuraphis noxia

Aphids are economically important insect pests of crops worldwide. Despite resistant varieties being available, resistance is continuously challenged and eventually broken down, posing a threat to food security. In the current study, the epigenome of two related Russian wheat aphid (Diuraphis noxia, Kurdjumov) biotypes (i.e., SA1 and SAM) that differ in virulence was investigated to elucidate its role in virulence in this species. Whole genome bisulfite sequencing covered a total of 6,846,597,083 cytosine bases for SA1 and 7,397,965,699 cytosine bases for SAM, respectively, of which a total of 70,861,462 bases (SA1) and 74, 073,939 bases (SAM) were methylated, representing 1.126 ± 0.321% (SA1) and 1.105 ± 0.295% (SAM) methylation in their genomes. The sequence reads were analyzed for contexts of DNA methylation and the results revealed that RWA has methylation in all contexts (CpG, CHG and CHH), with the majority of methylation within the CpG context (± 5.19%), while the other contexts show much lower levels of methylation (CHG - ± 0.27%; CHH - ± 0.34%). The top strand was slightly (0.02%) more methylated than the bottom strand. Of the 35,493 genes that mapped, we also analyzed the contexts of methylation of each of these and found that the CpG methylation was much higher in genic regions than in intergenic regions. The CHG and CHH levels did not differ between genic and intergenic regions. The exonic regions of genes were more methylated (±0.56%) than the intronic regions. We also measured the 5mC and 5hmC levels between the aphid biotypes, and found little difference in 5mC levels between the biotypes, but much higher levels of 5hmC in the virulent SAM. RWA had two homologs of each of the DNA methyltransferases 1 (DNMT1a and DNMT1b) and DNMT3s (DNMT3a and DNMT3b), but only a single DNMT2, with only the expression of DNMT3 that differed significantly between the two RWA biotypes. RWA has a single ortholog of Ten eleven translocase (DnTET) in the genome. Feeding studies show that the more virulent RWA biotype SAM upregulate DnDNMT3 and DnTET in response to wheat expressing antibiosis and antixenosis.

Helix Self-Assembly Behavior of Amino Acid-Modified Camptothecin Prodrugs and Its Antitumor Effect

For effective antitumor treatment, it is important to increase the water solubility of hydrophobic antitumor drugs and improve their cell absorption efficiency and nuclear transmission capacity. Here, we use endogenous hydrophilic arginine to modify camptothecin (CPT) to increase its water solubility. Surprisingly, the modified CPT can self-assemble into helical nanofibers through intermolecular π-π stacking and hydrophilic-hydrophobic interactions. Prodrug-based nanofibers were better endocytosed into the nucleus than their nonassembled CPT. Moreover, in vivo, such nanofibers had a longer blood circulation time and a better ability to accumulate in the tumor site. Further, we found that the cationic nanofibers can be combined with the anionic cisplatin-polyglutamic acid through electrostatic interaction to achieve a combined antitumor effect. This provides a new idea for achieving more effective cancer chemotherapy effects.

Individualization of Irinotecan Treatment: A Review of Pharmacokinetics, Pharmacodynamics, and Pharmacogenetics

Since its clinical introduction in 1998, the topoisomerase I inhibitor irinotecan has been widely used in the treatment of solid tumors, including colorectal, pancreatic, and lung cancer. Irinotecan therapy is characterized by several dose-limiting toxicities and large interindividual pharmacokinetic variability. Irinotecan has a highly complex metabolism, including hydrolyzation by carboxylesterases to its active metabolite SN-38, which is 100- to 1000-fold more active compared with irinotecan itself. Several phase I and II enzymes, including cytochrome P450 (CYP) 3A4 and uridine diphosphate glucuronosyltransferase (UGT) 1A, are involved in the formation of inactive metabolites, making its metabolism prone to environmental and genetic influences. Genetic variants in the DNA of these enzymes and transporters could predict a part of the drug-related toxicity and efficacy of treatment, which has been shown in retrospective and prospective trials and meta-analyses. Patient characteristics, lifestyle and comedication also influence irinotecan pharmacokinetics. Other factors, including dietary restriction, are currently being studied. Meanwhile, a more tailored approach to prevent excessive toxicity and optimize efficacy is warranted. This review provides an updated overview on today’s literature on irinotecan pharmacokinetics, pharmacodynamics, and pharmacogenetics.

Mechanism of a Novel Camptothecin-Deoxycholic Acid Derivate Induced Apoptosis against Human Liver Cancer HepG2 Cells and Human Colon Cancer HCT116 Cells

BACKGROUND

Camptothecin (CPT) is known as an anticancer drug in traditional Chinese medicine. However, due to the lack of targeting, low solubility, and instability of CPT, its therapeutic applications are hampered. Therefore, we synthesized a series of CPT-bile acid analogues that obtained a national patent to improve their tumour-targeting chemotherapeutic effects on liver or colon cancers. Among these analogues, the compound G2 shows high antitumor activity with enhanced liver targeting and improved oral absorption. It is significant to further investigate the possible anticancer mechanism of G2 for its further clinical research and application.

OBJECTIVE

We aimed to unearth the anticancer mechanism of G2 in HepG2 and HCT116 cells.

METHODS

Cell viability was measured using MTT assay; cell cycle, Mitochondrial Membrane Potential (MMP), and cell apoptosis were detected by flow cytometer; ROS was measured by Fluorescent Microplate Reader; the mRNA and protein levels of cell cycle-related and apoptosis-associated proteins were examined by RT-PCR and western blot, respectively.

RESULTS

We found that G2 inhibited cells proliferation of HepG2 and HCT116 remarkably in a dosedependent manner. Moreover, G2-treatment led to S and G2/M phase arrest in both cells, which could be elucidated by the change of mRNA levels of p21, p27 and Cyclin E and the increased protein level of p21. G2 also induced dramatically ROS accumulated and MMP decreased, which contributed to the apoptosis through activation of both the extrinsic and intrinsic pathways via changing the genes and proteins expression involved in apoptosis pathway in both of HepG2 and HCT116 cells.

CONCLUSION

These findings suggested that the apoptosis in both cell lines induced by G2 was related to the extrinsic and intrinsic pathways.

Pharmacokinetic modeling of the blood-stable camptothecin analog AR-67 in two different formulations

AR-67 is a lipophilic camptothecin analog currently under clinical investigation using a Cremophor EL based formulation. However, as potential toxicity limitations exist in the clinical use of Cremophor, an alternative cyclodextrin (SBE-β-CD) based formulation has been proposed. Pharmacokinetic (PK) studies were conducted in mice and the SBE-β-CD based formulation was compared with the Cremophor EL formulation. PK studies were conducted following intravenous or oral administration of AR-67 in either Cremophor or SBE-β-CD formulation in mice. Noncompartmental analysis was used to determine the plasma and tissue drug distribution. A non-linear mixed effects (population) PK model was developed to fit both the oral and intravenous data and to estimate key PK parameters. The effect of formulation was explored as a covariate in the PK model. AR-67 in the SBE-β-CD formulation had similar plasma PK and biodistribution to that in the Cremophor EL formulation. The proposed two-compartment model described the plasma PK of AR-67 in both formulations adequately. AR-67 in the SBE-β-CD formulation exhibited dose linearity following both oral and intravenous administration. Our studies indicate that SBE-β-CD is a viable alternative to Cremophor EL as a pharmaceutical excipient for formulating AR-67.

Liposomal Irinotecan for Treatment of Colorectal Cancer in a Preclinical Model

Colorectal cancer (CRC) is the most frequently diagnosed cancer and leading cause of cancer-related deaths worldwide. Because of the use of first-line CRC treatments, such as irinotecan (IRI), is hindered by dose-limiting side effects, improved drug delivery systems may have major clinical benefits for CRC treatment. In this study, we generate and characterize liposomal irinotecan (Lipo-IRI), a lipid-based nanoparticle, which shows excellent bioavailability and pharmacokinetics. Additionally, this formulation allows IRI to be maintained in active form and prolongs its half-life in circulation compared to IRI in solution. Compared with IRI statistically, the level of prostaglandin E2 (PGE2) in colonic tissue decreases, and Bifidobacterium spp. (beneficial intestinal microbiota) content increases in the Lipo-IRI-treated group. Moreover, no damage is observed by the hematoxylin and eosin staining of the normal tissue samples from the Lipo-IRI-treated group. In a xenograft mouse model, CRC tumors shrink markedly following Lipo-IRI treatment, and mice receiving a targeted combination of Lipo-IRI and liposomal doxorubicin (Lipo-Dox) extend their survival rate significantly. Overall, our results demonstrate that this formulation of Lipo-IRI shows a great potential for the treatment of colorectal cancer.

Optimal construction and pharmacokinetic study of CZ48-loaded poly (lactic acid) microbubbles for controlled drug delivery

CZ48, a prodrug of camptothecin (CPT) with derivative resistant to lactone hydrolysis, suffers from limited application for cancer treatment due to poor water-solubility, thus causing its low bioavailability and absorption in vivo. To echo this problem, CZ48 was incorporated into poly (lactic acid) (PLA) microbubbles via a double emulsion technique (W/O/W), and the successful loading was confirmed by X-ray diffraction (XRD) patterns and confocal laser scanning microscope (CLSM). The obtained CZ48-loaded microbubbles had a diameter ranging from 0.5 to 6.7 μm, and the encapsulation efficiency and drug-loading content were as high as 85.73 ± 2.41% and 26.07 ± 0.76%, respectively. The in vitro drug release demonstrated that only about 55% of CZ48 was released for CZ48-loaded PLA microbubbles in 48 h. In contrast, over 90% of CZ48 was released for free CZ48 crystals sample in only 5 h. Besides, in vivo pharmacokinetic studies further revealed that the availability of both CZ48 and its metabolite CPT were obviously enhanced after the incorporation of CZ48 into PLA microbubbles. To be noted, the value of AUC_0-∞ of the CZ48-loaded microbubbles was about 5-fold higher than that of free CZ48 suspension, implying a much higher anticancer effect of the CZ48-loaded microbubbles. The half-life time (T_1/2) of both CZ48 and CPT of the CZ48-loaded microbubbles were also significantly longer than that of the free CZ48, indicating a delayed release time for the microbubbles. Hence, this work promotes a promising drug carrier system for the controlled release of CZ48 as well as other drugs with poor water-solubility.

Topoisomerase 1B poisons: Over a half-century of drug leads, clinical candidates, and serendipitous discoveries

Topoisomerases are DNA processing enzymes that relieve supercoiling (torsional strain) in DNA, are necessary for normal cellular division, and act by nicking (and then religating) DNA strands. Type 1B topoisomerase (Top1) is overexpressed in certain tumors, and the enzyme has been extensively investigated as a target for cancer chemotherapy. Various chemical agents can act as "poisons" of the enzyme's religation step, leading to Top1-DNA lesions, DNA breakage, and eventual cellular death. In this review, agents that poison Top1 (and have thus been investigated for their anticancer properties) are surveyed, including natural products (such as camptothecins and indolocarbazoles), semisynthetic camptothecin and luotonin derivatives, and synthetic compounds (such as benzonaphthyridines, aromathecins, and indenoisoquinolines), as well as targeted therapies and conjugates. Top1 has also been investigated as a therapeutic target in certain viral and parasitic infections, as well as autoimmune, inflammatory, and neurological disorders, and a summary of literature describing alternative indications is also provided. This review should provide both a reference for the medicinal chemist and potentially offer clues to aid in the development of new Top1 poisons.

Tetrazine-mediated bioorthogonal prodrug-prodrug activation

The selective and biocompatible activation of prodrugs within complex biological systems remains a key challenge in medical chemistry and chemical biology. Herein we report, for the first time, a dual prodrug activation strategy that fully satisfies the principle of bioorthogonality by the symbiotic formation of two active drugs. This dual and traceless prodrug activation strategy takes advantage of the INVDA chemistry of tetrazines (here a prodrug), generating a pyridazine-based miR21 inhibitor and the anti-cancer drug camptothecin and offers a new concept in prodrug activation.

Structure-Based Drug Design and Identification of H2O-Soluble and Low Toxic Hexacyclic Camptothecin Derivatives with Improved Efficacy in Cancer and Lethal Inflammation Models in Vivo

Camptothecin (CPT) has been shown to block disassembly of the topoisomerase I (Topo I)/DNA cleavable complex. However, the poor aqueous solubility, intrinsic instability, and severe toxicity of CPTs have limited their clinical applications. Herein, we report the design and synthesis of H₂O-soluble and orally bioavailable hexacyclic CPT derivatives. By analysis of a virtual chemical library and cytotoxicity screening in vitro, 9 and 11 were identified as potential prodrugs and chosen for further characterization in vivo. Both compounds exhibited remarkable anticancer and anti-inflammation efficacies in animals and improved drug-like profiles.

Silicon-containing analogs of camptothecin as anticancer agents

The plant pentacyclic alkaloid camptothecin and its structural analogs were extensively studied. These compounds are interesting due to the antitumor activity associated with their ability to inhibit topoisomerase I in tumor cells. During the last decades of the 20th century, a large number of the silicon-containing camptothecins (silatecans) were synthesized. 7-tert-Butyldimethylsilyl-10-hydroxy-camptothecin (DB-67 or AR-67) has enhanced lipophilicity and demonstrates a antitumor activity superior to its carbon analog. To date, certain silatecans are under clinical trials and their ultimate role in cancer therapy appears promising. In this review, we present chemical methodologies for the synthesis of silicon-containing camptothecins, their chemical properties, biological activity, and results of clinical trials.

Synthesis and Biological Evaluation of Paclitaxel and Camptothecin Prodrugs on the Basis of 2-Nitroimidazole

Due to the low esterase activity in human plasma, many ester and carbonate prodrugs tested in humans may be less effective than that in preclinical animals. In this letter, PTX and SN-38 were attached to the N-1 position of 2-nitroimidazole via a carbonate linker. Presumably, 2-aminoimidazole may help promote the intramolecular hydrolysis of the carbonate bond. The prodrugs exhibited a considerable stability in buffers at different pH values as well as in human plasma. Furthermore, a rapid reduction was exhibited in the presence of nitroreductase. An in vitro cytotoxicity assay demonstrated that hypoxic conditions could increase the toxicity of prodrugs. Potentially, the compound species may form a new class of promising antitumor agents.

Design and Synthesis of Chlorinated and Fluorinated 7-Azaindenoisoquinolines as Potent Cytotoxic Anticancer Agents That Inhibit Topoisomerase I

The 7-azaindenoisoquinolines are cytotoxic topoisomerase I (Top1) inhibitors. Previously reported representatives bear a 3-nitro group. The present report documents the replacement of the potentially genotoxic 3-nitro group by 3-chloro and 3-fluoro substituents, resulting in compounds with high Top1 inhibitory activities and potent cytotoxicities in human cancer cell cultures and reduced lethality in an animal model. Some of the new Top1 inhibitors also possess moderate inhibitory activities against tyrosyl-DNA phosphodiesterase 1 (TDP1) and tyrosyl-DNA phosphodiesterase 2 (TDP2), two enzymes that are involved in DNA damage repair resulting from Top1 inhibitors, and they produce significantly more DNA damage in cancer cells than in normal cells. Eighteen of the new compounds had cytotoxicity mean-graph midpoint (MGM) GI50 values in the submicromolar (0.033-0.630 μM) range. Compounds 16b and 17b are the most potent in human cancer cell cultures with MGM GI50 values of 0.063 and 0.033 μM, respectively. Possible binding modes to Top1 and TDP1were investigated by molecular modeling.

Engineering Camptothecin-Derived Norbornene Polymers for Theranostic Application

A multifunctional stimuli-responsive nanotheranostic agent provides huge benefits in nanomedicine by combining both the diagnostic agent and the drug molecule in a single system. This nanosystem is capable of doing multiple tasks, for example, diagnosis, drug delivery, and monitoring the therapeutic response. Hence, theranostic agents are expected to play a significant role in personalized medicine. Herein, a new class of nanotheranostic agents, Pnr-Cbt-Cpt-Pg-Bn, is proposed for the effective delivery of camptothecin. This new class of polymer has been functionalized with a superparamagnetic norbornene cobalt unit for its use in magnetic resonance imaging (MRI). The NMR one-dimensional image confirms the MRI capability of this nanotheranostic agent. This is further modified with the poly(ethylene glycol)-biotin moiety for biocompatibility and site-specificity. The uniqueness of the design is confirmed by an in vitro study where a greater uptake of the nanotheranostic agent is observed when compared with free drugs. Hence, this new class of copolymer shows improved potential as nanotheranostic agents in drug delivery.

10-Hydroxycamptothecin (HCPT) nanosuspensions stabilized by mPEG1000-HCPT conjugate: high stabilizing efficiency and improved antitumor efficacy

In this study, polyethylene glycol (PEG)ylated 10-hydroxycamptothecin (mPEG₁₀₀₀-HCPT) was synthesized and used as a stabilizer to prepare 10-hydroxycamptothecin (HCPT) nanosuspensions for their in vitro and in vivo antitumor investigation. The resultant HCPT nanosuspensions (HCPT-NSps) had a very high drug payload of 94.90% (w/w) and a mean particle size of 92.90±0.20 nm with narrow size distribution (polydispersity index of 0.16±0.01). HCPT-NSps could be lyophilized without the need of the addition of any cryoprotectant and then be reconstituted into nanosuspensions of a similar size by direct resuspension in water. HCPT was in crystalline form in HCPT-NSps. Using mPEG₁₀₀₀-HCPT as stabilizer, insoluble camptothecin and 7-ethyl-10-hydroxycamptothecin could also be easily made into nanosuspensions with similar features such as high drug payload, small particle size, and cryoprotectant-free freeze drying. The 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide assay indicated that the HCPT-NSps had a significantly higher cytotoxicity than HCPT injections, with 3.77 times lower IC₅₀ value against HepG2 cells and 14.1 times lower IC₅₀ value against MCF-7 cells. An in vivo study in H22 tumor-bearing mice after intravenous injection of HCPT-NSps demonstrated that HCPT-NSps significantly improved the antitumor efficacy compared to the commercially available HCPT injections (86.38% vs 34.97%) at the same dose of 5 mg/kg. Even at 1/4 of the dose, HCPT-NSps could also achieve a similar antitumor efficacy to that of HCPT injections. mPEG₁₀₀₀-HCPT may be a highly efficient stabilizer able to provide camptothecin-based drugs, and probably other antitumor agents containing aromatic structure, with unique nanosuspensions or nanocrystals for improved in vivo therapeutic efficacy.

Safe approaches for camptothecin delivery: Structural analogues and nanomedicines

Twenty-(S)-camptothecin is a strongly cytotoxic molecule with excellent antitumor activity over a wide spectrum of human cancers. However, the direct formulation is limited by its poor water solubility, low plasmatic stability and severe toxicity, which currently limits its clinical use. As a consequence, two strategies have been developed in order to achieve safe and efficient delivery of camptothecin to target cells: structural analogues and nanomedicines. In this review, we summarize recent advances in the design, synthesis and development of camptothecin molecular derivatives and supramolecular vehicles, following a systematic classification according to structure-activity relationships (structural analogues) or chemical nature (nanomedicines). A series of organic, inorganic and hybrid materials are presented as nanoplatforms to overcome camptothecin restrictions in administration, biodistribution, pharmacokinetics and toxicity. Nanocarriers which respond to a variety of stimuli endogenously (e.g., pH, redox potential, enzyme activity) or exogenously (e.g., magnetic field, light, temperature, ultrasound) seem the best positioned therapeutic materials for optimal spatial and temporal control over drug release. The main goal of this review is to be used as a source of relevant literature for others interested in the field of camptothecin-based therapeutics. To this end, final remarks on the most important formulations currently under clinical trial are provided.

Do topotecan concentrations in saliva reflect plasma concentrations?

Purpose. There is an increasing interest to use saliva as biological fluid for drug monitoring as it reflects adequately, in some cases, drug concentrations in plasma. A great advantage is that it can be obtained conveniently by a noninvasive method. We describe our experience with respect to the practical use of saliva for pharmacokinetic monitoring of the novel anticancer agent topotecan.

Patients and Methods. Eighty-one saliva sam ples and corresponding plasma samples were ob tained 2 hours after the end of infusion from 15 patients with either ovarian cancer or small cell lung cancer, receiving 1.5 mg/m 2 per day topotecan for 5 consecutive days every 3 weeks. Saliva was obtained by a citric-acid containing dental cotton roll which stimulated the saliva flow.

Results. The plasma topotecan concentrations varied between 3.67 and 24.4 ng/mL, with an intrapa tient (day-to-day) variation of only 9.8%, and an inter patient variation of 27.2%. The saliva concentrations varied between 5.34 and 74.2 ng/mL, with an intrapa tient variation of 25.3%, and an interpatient variation of 53.5%. The mean plasma/saliva topotecan ratio was 0.66 (range 0.21 to 1.58) and was both patient dependent and dependent on the sampling time. The day-to-day variation of the plasma/saliva concentra tion ratio in this daily times five schedule was 27.6%, and the interpatient variation was 45.5%. The saliva concentrations of topotecan were not related to the occurrence of mucositis, which was noted in some patients.

Conclusion. Based on the large variability in the plasma/saliva ratios, we conclude that in our investi gational setting saliva is not a reliable matrix for topotecan analysis and that plasma sampling is to be preferred.

Extravasation of topotecan, a report of two cases

Objective. Extravasations of anticancer agents may give serious complications and specific therapy might be needed. Topotecan is a new cytotoxic drug and is used in many clinical studies. In our clinic two extravasations of topotecan occurred, and the clinical consequences are discussed.

Clinical Features. The extravasations oc curred in two patients who were receiving topo tecan intravenously because of ovarian carcinoma stage III. The patients experienced some discom fort caused by the expansion of soft tissue. How ever, no serious complications were observed.

Case Progress and Outcome. Both patients received all further courses of topotecan without any negative effects.

Conclusion. In conclusion, besides stopping the injection, trying to aspirate the fluid, keeping the arm high, and cooling the swelling, we advise no specific measures to be taken after extravasa tion of topotecan.

Effects of nanoparticle size on antitumor activity of 10-hydroxycamptothecin-conjugated gold nanoparticles: in vitro and in vivo studies

Gold nanoparticles (AuNPs) have emerged as a promising anticancer drug delivery scaffold. However, some controversial points still require further investigation before clinical use. A complete understanding of how animal cells interact with drug-conjugated AuNPs of well-defined sizes remains poorly understood. In this study, we prepared a series of 10-hydroxycamptothecin (HCPT)-AuNP conjugates of different sizes and compared their cytotoxic effect in vitro and antitumor effect in vivo. Transmission electron micrographs showed that the NPs had a round, regular shape with a mean diameter of ~10, 25, and 50 nm. An in vitro drug release study showed that HCPT was continuously released for 120 hours. HCPT-AuNPs showed greater cytotoxic effects on the MDA-MB-231 cell line compared with an equal dose of free HCPT. Notably, HCPT-AuNPs of an average diameter of 50 nm (HCPT-AuNPs-50) had the greatest effect. Furthermore, administration of HCPT-AuNPs-50 showed the most tumor-suppressing activity against MDA-MB-231 tumor in mice among all treatment groups. The results indicate that AuNPs not only act as a carrier but also play an active role in mediating biological effects. This work gives important insights into the design of nanoscale delivery and therapeutic systems.

Biophysical and molecular docking insight into interaction mechanism and thermal stability of human serum albumin isoforms with a semi-synthetic water-soluble camptothecin analog irinotecan hydrochloride

In the present work, we have examined the binding parameters, thermodynamics, and stability of human serum albumin (HSA) isoforms at pH 7.4 and 9.0, using spectroscopic, calorimetric, and molecular docking methods in the presence of water-soluble camptothecin analog irinotecan hydrochloride (CPT-11). We observed that CPT-11 binds to HSA through a static quenching procedure of ground-state complex formation with N-isoform and B-isoform. Hydrogen bond and hydrophobic interactions are the major governing forces that participating in the formation of protein-drug complex. To determine the binding site of CPT-11 within HSA molecules, we also have performed molecular docking experiments. We explored the CPT-11-mediated stability and modulation of HSA by performing dynamic light scattering (DLS) and differential scanning calorimetry (DSC) experiments. DLS and DSC techniques are used to determine the size and the melting point (Tm) of HSA, which was decreased in the presence of CPT-11. Therefore, CPT-11 plays an important role in HSA stability and protein-ligand interactions. The present study provides valuable information in the field of pharmacokinetics, pharmaco-dynamics, and drug discovery.

A novel drug-polyethylene glycol liquid compound method to prepare 10-hydroxycamptothecin loaded human serum albumin nanoparticle

Drug loading strategies and the methods derived for implementing those strategies are crucially important to the preparation of drug loaded human serum albumin nanoparticles (HSA-NPs), because each of them is focused on wrapping up specific types of drugs via certain physical and chemical properties. However, poor adaptability still exists to load drugs like model substance 10-hydroxycamptothecin (HCPT) by conventional methods. Because it typically represents a large class of water-insoluble drugs, who also structurally possess a certain number of hydrophilic groups. So even though they majorly have lipophilicity but they are of low liposolubility. This article presents a new concept of a loading strategy that takes a drug polymer liquid compound as a loading medium. The drug polymer liquid compound was made from low weight polyethylene glycol (l-PEG) and HCPT. Consequently, this strategy has managed to fabricate HCPT-loaded HSA-NPs through an unconventional approach that overcomes drawbacks of current loading means and better results have been obtained, like high entrapment efficiency (over 99%) and less toxicity involvement. Afterward, in vitro and in vivo evaluations and characterizations were performed to help with the in-depth interpretation of the loading mechanism in order to reveal and further investigate the possible far-reaching applications of this method.

Characterization of 9-nitrocamptothecin-in-cyclodextrin-in-liposomes modified with transferrin for the treating of tumor

Encapsulation of hydrophobic drugs in the form of drug-cyclodextrin (CD) complex in liposomes has been applied as a novel strategy to combine the relative advantages of CDs and liposomes into one system, naming drug-in-CD-in-liposome (DCL). In the present study, soluble 9-NC/hydroxypropyl-β-cyclodextrin (HP-β-CD) inclusion complexes were prepared using the freeze-drying technique. Then 9-NC inclusion complexes were further encapsulated into liposomes by ethanol injection method and transferrin (Tf) was conjugated to the surface of 9-NC DCL to obtain Tf modified 9-NC DCL (Tf-9-NC-CL). Compared to PEGylated 9-NC DCL (P-9-NC-CL), the lactone stability and vesicle stability of Tf-9-NC-CL were significantly increased. Both 9-NC and HP-β-CD were found to release from the DCL and Tf modification resulted in reduced release of them. The enhanced targeting efficiency of the Tf-modified liposomes was demonstrated by flow cytometry and confocal microscopy. In vivo pharmacokinetics in rats showed improved lactone stability of 9-NC following intravenous injection of Tf-9-NC-CL. The cytotoxicity of Tf-9-NC-CL against tumor cells and normal cells was investigated in vitro and the antitumor efficacy was evaluated in S180 tumor-bearing mice in vivo. Compared with free 9-NC, 9-NC inclusion complexes and P-9-NC-CL, Tf-9-NC-CL demonstrated the strongest cytotoxicity to tumor cells. And the inhibitory rate of tumor (IRT) values were determined to be 43.08%, 56.92%, 67.69% and 80.00% for 9-NC solution, inclusion complexes, P-9-NC-CL and Tf-9-NC-CL, respectively. In conclusion, Tf modification can be useful in increasing vesicle stability, targeting drug delivery efficiency and antitumor efficacy of DCL containing hydrophobic antitumor drugs, such as 9-NC.

Pharmacodynamics and pharmacokinetics of oral topotecan in patients with advanced solid tumours and impaired renal function

AIMS

The aim of the study was to determine the effect of renal impairment and prior platinum-based chemotherapy on the toxicity and pharmacokinetics of oral topotecan and to identify recommended doses for patients with renal impairment or prior platinum-based (PB) chemotherapy.

METHODS

A multicentre phase I toxicity and pharmacokinetic study of oral topotecan was conducted in patients with advanced solid tumours. Patients were grouped by normal renal function with limited or prior PB chemotherapy or impaired renal function (mild [creatinine clearance (CLcr)  = 50-79 ml min(-1) ], moderate [CLcr  = 30-49 ml min(-1) ], severe [CLcr <30 ml min(-1) ]).

RESULTS

Fifty-nine patients were evaluable. Topotecan lactone and total topotecan area under the concentration-time curve (AUC) was significantly increased in patients with moderate and severe renal impairment (109% and 174%, respectively, topotecan lactone and 148% and 298%, respectively, total topotecan). Asian patients (23 in total) had higher AUCs than non-Asian patients with the same degree of renal impairment. Thirteen dose-limiting toxicities (DLTs) were observed, which were mostly haematological. The maximum tolerated dose (MTD) was 2.3 mg m(-2) day(-1) , given on days 1 to 5 in a 21 day cycle, for patients with prior PB chemotherapy or mild renal impairment, and 1.2 mg m(-2) day(-1) for patients with moderate renal impairment (suggested dose 1.9 mg m(-2) day(-1) for non-Asians). Due to incomplete enrolment of patients with severe renal impairment, the MTD was determined as ≥ 0.6 mg m(-2) day(-1) in this cohort.

CONCLUSIONS

Oral topotecan dose adjustments are not required in patients with prior PB chemotherapy or mildly impaired renal function, but reduced doses are required for patients with moderate or severe renal impairment.

Surface-enhanced Raman spectroscopy of the anti-cancer drug irinotecan in presence of human serum albumin

The development of nanotechnological devices and their clinical application in medicine has become increasingly important, especially in the context of targeted and personalized therapy. This is particularly important in cancer therapy, where antitumor drugs are highly cytotoxic and often exert their therapeutic effect at concentrations close to systemic toxicity. In the last years a growing number of studies has started to report the use of plasmonic nanoprobes in the field of theranostics, broadening the application of vibrational spectroscopies like Raman scattering and surface enhanced Raman scattering (SERS) in biomedicine. The present work aims to identify and characterize the vibrational profiles of a widely used anticancer drug, irinotecan (CPT-11). With a rational approach, SERS experiments have been performed on this analyte employing both Au and Ag colloids, starting from simple aqueous solutions up to albumin mixtures. A major step forward for drug detection in albumin solutions has been taken with the adoption of a simple deproteinization strategy, and a two-in-one-step separation and identification by coupling thin layer chromatography, TLC, with SERS (TLC-SERS). The latter has revealed to be a valid system for protein separation and simultaneous analyte detection, showing a potential to become an innovative, sensitive and low cost method for antineoplastic drug profiling in patients' body fluids.

The self-assembly of anticancer camptothecin-dipeptide nanotubes: a minimalistic and high drug loading approach to increased efficacy

20-(S)-Camptothecin (CPT)-conjugated dipeptides are reported that preassemble into nanotubes with diameters ranging from 80-120 nm. These nanoassemblies maintain a high (∼47 %) drug loading and exhibit greater drug stability (i.e., resistance to lactone hydrolysis), and consequently greater efficacy against several human cancer cells (HT-29, A549, H460, and H23) in vitro compared with the clinically used prodrug irinotecan. A key and defining feature of this system is the use of the CPT-conjugated dipeptide as both the drug and precursor to the nanostructured carrier, which simplifies the overall fabrication process.