Oral administration of irinotecan in patients with solid tumors: an open-label, phase I, dose escalating study evaluating safety, tolerability and pharmacokinetics

Generation of anti-SN38 antibody for loading efficacy and therapeutic monitoring of SN38-containing therapeutics

SN38, one of the most potent anti-tumor analogues of the camptothecins (CPTs), has limitations in its direct formulation as an anticancer agent due to its super toxicity and poor solubility in water and pharmaceutically approved solvents. However, it has garnered significant scientific interest as a payload in conjugated nanomedicine platforms (e.g., SN-38lip, NK012, SNB-101, and ADCs) to enhance their effectiveness and safety. The development of these platforms necessitates a convenient quantitative determination of SN38 in preclinical and clinical studies, a need that our study directly addresses, offering a practical solution to a pressing problem in cancer research and drug development. This study details the meticulous process of generating poly and monoclonal antibodies (pAb and mAb) against SN38 and their application to measure the SN38 in naked and conjugated forms of SN38-conjugated ADCs. For this purpose, two haptens of SN38 were synthesized by introducing the glycine or 4-amino-4-oxobutanyol(glycine) moiety as a conjugation functional group of the SN38. IR, NMR and mass spectrometric techniques confirmed the chemical modifications of the haptens. The haptens were then conjugated to each bovine serum albumin (BSA) and keyhole limpet hemocyanin (KLH) protein. The SN38-KLH conjugates were meticulously examined for immunization and generation of pAb and mAb. The immunization efficiency, reactivity, binding affinity, specificity, and cross-reactivity of purified pAb and mAb against Irinotecan, a model for the emergence of an SN38 derivative in clinical settings, were evaluated using ELISA and western blotting (WB) techniques. Conjugation efficiency of the SN38 to the KLH was increased using 4-amino-4-oxobutanyol(glycine) moiety, as its immunization efficacy was more to generate pAb. Furthermore, only this hapten could immunized mice to generate mAb recognizing SN38 with nanomolar equilibrium affinity. Our recent findings strongly support the notion that the generated pAb employed in developing an ELISA effectively ascertains the presence of SN38 in SN38-conjugated ADC, with a test midpoint EC50 of 2.5 μg/mL. Our study's unique contribution to the field lies in the development of specific antibodies against SN38 for measuring it on ADC, a feat that has not been achieved before. These immunoassays can be readily applied to detect other SN38-conjugate therapeutic platforms, thereby enhancing their clinical knowledge translation. The affinity of both pAb and mAb also meets the acceptance criteria for quantifying SN38 in fluidic material, as well as in Therapeutic drug monitoring (TDM) studies, a crucial aspect of personalized medicine. The potential applications of the anti-SN38 antibodies extend to reducing SN38-induced systemic toxicity through an inverse targeting strategy, a novel approach that piques further interest in our findings.

Covalent CES2 Inhibitors Protect against Reduced Formation of Intestinal Organoids by the Anticancer Drug Irinotecan

BACKGROUND

Irinotecan is widely used to treat various types of solid and metastatic cancer. It is an ester prodrug and its hydrolytic metabolite (SN-38) exerts potent anticancer activity. Irinotecan is hydrolyzed primarily by carboxylesterase-2 (CES2), a hydrolase abundantly present in the intestine such as the duodenum. We have identified several potent and covalent CES2 inhibi¬tors such as remdesivir and sofosbuvir. Remdesivir is the first small molecule drug approved for COVID-19, whereas sofosbuvir is a paradigm-shift medicine for hepatitis C viral infection. Irinotecan is generally well-tolerated but associated with severe/life-threatening diarrhea due to intestinal accu¬¬mula¬tion of SN-38.

OBJECTIVE

This study was to test the hypothesis that remdesivir and sofosbuvir protect against irinotecan-induced epithelial injury associated with gastrointestinal toxicity.

METHODS

To test this hypothesis, formation of organoids derived from mouse duodenal crypts, a robust cellular model for intestinal regeneration, was induced in the presence or absence of irinotecan +/- pretreatment with a CES2 drug inhibitor.

RESULTS

Irinotecan profoundly inhibited the formation of intestinal organoids and the magnitude of the inhibition was greater with female crypts than their male counterparts. Consistently, crypts from female mice had significantly higher hydrolytic activity toward irinotecan. Critically, remdesivir and sofosbuvir both reduced irinotecan hydrolysis and reversed irinotecan-reduced formation of organoids. Human duodenal samples robustly hydrolyzed irinotecan, stable CES2 transfection induced cytotoxicity and the cytotoxicity was reduced by CES2 drug inhibitor.

CONCLUSION

These findings establish a therapeutic rationale to reduce irinotecan-gastrointestinal injury and serve as a cellular foundation to develop oral formulations of irinotecan with high safety.

The design and discovery of topoisomerase I inhibitors as anticancer therapies

INTRODUCTION

Cancer has been identified as one of the leading causes of death worldwide. The biological target of some anticancer agents is topoisomerase I, an enzyme involved in the relaxation of supercoiled DNA. The synthesis of new compounds with antiproliferative effect and behaving as topoisomerase I inhibitors has become an active field of research. Depending on their mechanism of inhibition, they can be classified as catalytic inhibitors or poisons.

AREAS COVERED

This review article summarizes the state of the art for the development of selective topoisomerase I inhibitors. Collected compounds showed inhibition of the enzyme, highlighting those approved for clinical use, the combination therapies developed, as well as related drawbacks and future focus.

EXPERT OPINION

Research related to topoisomerase I inhibitors in cancer therapy started with camptothecin (CPT). This compound was first selected as a good anticancer agent and then topoisomerase I was identified as its therapeutic target. Derivatives of CPT irinotecan, topotecan, and belotecan are the only clinically approved inhibitors. Currently, their limitations are being addressed by different stretegies. Future studies should focus not only on developing other active molecules but also on improving the bioavailability and pharmacokinetics of potent synthetic derivatives.

Design and synthesis of Aza-boeravinone derivatives as potential novel topoisomerase I inhibitors

Based on the structural skeleton of natural products boeravinones, two types of 6H-chromeno[3,4-b]quinoline derivatives were designed and synthesized by nitrogen atom substitution strategy. Then, their cytotoxic activities were evaluated against six human tumor cell lines including HepG2 (hepatocellular carcinoma), A2780 (ovarian cancer), Hela (cervical cancer), HCT116 (colorectal cancer), SW1990 (pancreatic cancer), and MCF7 (breast cancer). The results showed that compounds ZML-8 and ZML-14 exhibited robust inhibitory activities against HepG2 cells with IC₅₀ values of 0.58 and 1.94 μM, respectively. In addition, ZML-8 and ZML-14 showed higher selectivity against HepG2 and L-02 cells than Topotecan. Mechanistically, ZML-8 and ZML-14 not only induced cell cycle arrest in the G2/M phase and cell apoptosis, but also dose-dependently inhibited topoisomerase I activity and induced DNA damage in HepG2 cells. Molecular docking showed that ZML-8 and ZML-14 could interact with topoisomerase I-DNA complex with a similar binding mode to Topotecan. Inhibitory activities of these two compounds on topoisomerase I were then confirmed in both cell-free systems and in whole-cell lysates. Taken together, compounds ZML-8 and ZML-14 merit further development as a new generation of non-camptothecin topoisomerase I inhibitors for the treatment of cancer.

A Proximal-to-Distal Survey of Healthy Adult Human Small Intestine and Colon Epithelium by Single-Cell Transcriptomics

BACKGROUND & AIMS

Single-cell transcriptomics offer unprecedented resolution of tissue function at the cellular level, yet studies analyzing healthy adult human small intestine and colon are sparse. Here, we present single-cell transcriptomics covering the duodenum, jejunum, ileum, and ascending, transverse, and descending colon from 3 human beings.

METHODS

A total of 12,590 single epithelial cells from 3 independently processed organ donors were evaluated for organ-specific lineage biomarkers, differentially regulated genes, receptors, and drug targets. Analyses focused on intrinsic cell properties and their capacity for response to extrinsic signals along the gut axis across different human beings.

RESULTS

Cells were assigned to 25 epithelial lineage clusters. Multiple accepted intestinal stem cell markers do not specifically mark all human intestinal stem cells. Lysozyme expression is not unique to human Paneth cells, and Paneth cells lack expression of expected niche factors. Bestrophin 4 (BEST4)⁺ cells express Neuropeptide Y (NPY) and show maturational differences between the small intestine and colon. Tuft cells possess a broad ability to interact with the innate and adaptive immune systems through previously unreported receptors. Some classes of mucins, hormones, cell junctions, and nutrient absorption genes show unappreciated regional expression differences across lineages. The differential expression of receptors and drug targets across lineages show biological variation and the potential for variegated responses.

CONCLUSIONS

Our study identifies novel lineage marker genes, covers regional differences, shows important differences between mouse and human gut epithelium, and reveals insight into how the epithelium responds to the environment and drugs. This comprehensive cell atlas of the healthy adult human intestinal epithelium resolves likely functional differences across anatomic regions along the gastrointestinal tract and advances our understanding of human intestinal physiology.

A High-Content Screen for C/EBPα Expression Identifies Novel Therapeutic Agents in Dedifferentiated Liposarcoma

PURPOSE

Dedifferentiated liposarcoma (DDLS), one of the most common and aggressive sarcomas, infrequently responds to chemotherapy. DDLS survival and growth depend on underexpression of C/EBPα, a tumor suppressor and transcriptional regulator controlling adipogenesis. We sought to screen and prioritize candidate drugs that increase C/EBPα expression and may therefore serve as differentiation-based therapies for DDLS.

EXPERIMENTAL DESIGN

We screened known bioactive compounds for the ability to restore C/EBPα expression and inhibit proliferation selectively in two DDLS cell lines but not in normal adipose-derived stem cells (ASC). Selected hits' activity was validated, and the mechanism of the most potent, SN-38, was investigated. The in vivo efficacy of irinotecan, the prodrug of SN-38, was evaluated in DDLS xenograft models.

RESULTS

Of 3,119 compounds, screen criteria were met by 19. Validation experiments confirmed the DDLS selectivity of deguelin, emetine, and SN-38 and showed that they induce apoptosis in DDLS cells. SN-38 had the lowest IC₅₀ (approximately 10 nmol/L), and its pro-apoptotic effects were countered by knockdown of CEBPA but not of TP53. Irinotecan significantly inhibited tumor growth at well-tolerated doses, induced nuclear expression of C/EBPα, and inhibited HIF1α expression in DDLS patient-derived and cancer cell line xenograft models. In contrast, doxorubicin, the most common treatment for nonresectable DDLS, reduced tumor growth by 30% to 50% at a dose that caused weight loss.

CONCLUSIONS

This high-content screen revealed potential treatments for DDLS. These include irinotecan, which induces apoptosis of DDLS cells in a C/EBPα-dependent, p53-independent manner, and should be clinically evaluated in patients with advanced DDLS.

Current Landscape in Organic Nanosized Materials Advances for Improved Management of Colorectal Cancer Patients

Globally, colorectal cancer (CRC) ranks as one of the most prevalent types of cancers at the moment, being the second cause of cancer-related deaths. The CRC chemotherapy backbone is represented by 5-fluorouracil, oxaliplatin, irinotecan, and their combinations, but their administration presents several serious disadvantages, such as poor bioavailability, lack of tumor specificity, and susceptibility to multidrug resistance. To address these limitations, nanomedicine has arisen as a powerful tool to improve current chemotherapy since nanosized carriers hold great promise in improving the stability and solubility of the drug payload and enhancing the active concentration of the drug that reaches the tumor tissue, increasing, therefore, the safety and efficacy of the treatment. In this context, the present review offers an overview of the most recent advances in the development of nanosized drug-delivery systems as smart therapeutic tools in CRC management and highlights the emerging need for improving the existing in vitro cancer models to reduce animal testing and increase the success of nanomedicine in clinical trials.

Possible roles of intestinal P-glycoprotein and cytochrome P450 3A on the limited oral absorption of irinotecan

OBJECTIVES

Irinotecan is a widely intravenously used drug for the treatment of certain types of solid tumours. The oral administration of irinotecan has recently been recognized as being a more effective method for the treatment than intravenous administration. However, the limited oral bioavailability of irinotecan poses a problem for its oral delivery. In this study, we report on an investigation of the mechanism responsible for the limited oral absorption of irinotecan using rats as models.

METHODS

The intestinal absorption of irinotecan in the absence and presence of several compounds was examined using intestinal loop method. The pharmacokinetics of irinotecan was investigated when verapamil, an inhibitor of the P-glycoprotein (P-gp) and cytochrome P450 3A (CYP3A) was pre-administered.

KEY FINDINGS

The intestinal absorption of irinotecan was enhanced in the presence of verapamil, indicating that efflux by intestinal P-gp contributes to its limited oral absorption. Indeed, the oral bioavailability of irinotecan was increased when verapamil was orally pre-administered. This increased oral bioavailability was accompanied by a slight but significant decrease in the formation of a metabolite produced by the action of CYP3A.

CONCLUSION

The findings presented herein suggest that intestinal efflux by P-gp is mainly and intestinal metabolism by CYP3A is partially responsible for the limited oral absorption of irinotecan.

An open label phase 1 study evaluation safety, tolerability, and maximum tolerated dose of oral administration of irinotecan in combination with capecitabine

PURPOSE

Oral administration of chemotherapy offers several advantages in comparison with intravenous administration. Previously, data on a new oral formulation of irinotecan have been published. The aim of the present study was to evaluate the safety, tolerability, and Maximum Tolerated Dose (MTD) of the new oral irinotecan formulation in combination with oral capecitabine.

METHODS

The study was an open label, phase 1, single center, extension part in which oral irinotecan was investigated in combination with capecitabine. The MTD of irinotecan in combination with capecitabine was 17.5 mg/m² once daily for 14 consecutive days in combination with capecitabine 800 mg/m² twice daily. Eligible patients were adults with metastatic or unresectable solid tumors for which no standard curative or palliative therapies existed.

RESULTS

14 patients were included in the extension part. No grade 3 or 4 hematologic toxicities were observed. Non-hematological toxicities included grade 1 and 2 diarrhea, fatigue, cholinergic syndrome, vomiting, and weight loss. Totally, 3 grade 3 toxicities and no grade 4 event were reported. No objective responses were observed. Five patients had stable disease lasting median 14 weeks.

CONCLUSIONS

Capecitabine in combination with oral irinotecan could be a new treatment option offering a more convenient and patient friendly treatment strategy compared to intravenous irinotecan. The combination is fairly tolerated; however, further investigations are needed to assess the efficacy of this regimen.