Emma Bateman

Background: The value of cancer therapies lies in enhancing anti‐tumor efficacy while minimizing toxicity. However, these aspects are rarely studied together, often due to the challenges of modelling both within the same framework. In preclinical settings, rat models like the Dark Agouti Mammary Adenocarcinoma (DAMA) model are used to evaluate both efficacy and toxicity concurrently but are limited in duration, relying on a single dose to evaluate efficacy and toxicity outcomes. Aim: This study aimed to develop a cyclical chemotherapy model using the DAMA model to better mimic multi‐cycle clinical scenarios. Methods: Methotrexate (MTX) was administered in various dosing schedules to assess tumor control and animal welfare. Results: A dose of 2 mg/kg administered once weekly provided sufficient tumor control and the longest survival (14.25 ± 2.87 days), while maintaining animal welfare and yielding an acceptable efficacy‐to‐toxicity ratio. Dosing frequency, rather than cumulative dose, had a greater impact on welfare, as 2 mg/kg MTX once weekly substantially affected animal welfare, whereas the total cumulative dose of 4 mg/kg MTX did not. Conclusion: These findings will be utilized in future studies testing interventions designed for preventing chemotherapy toxicity whilst maintaining tumor efficacy.

Purpose: Neratinib is a pan-human epidermal growth factor receptor (HER) tyrosine kinase inhibitor (TKI) used in the treatment of HER2+ breast cancer. Diarrhea is the most commonly reported toxicity, with the majority experiencing at least some grade of diarrhea. The mechanisms behind neratinib-induced diarrhea are yet to be fully defined, but have been linked to gut microbiome changes, specifically decreased levels of the genera Blautia . This study aimed to investigate the efficacy of Blautia luti (B.luti) administered as a daily probiotic on neratinib-induced diarrhea, and its effects on the gut microbiome in a well-established rat model. Methods: Female albino Wistar (AW) rats ( n = 40) were randomly allocated to groups including; vehicle control (VC), neratinib alone, B.luti alone and neratinib + B.luti in different schedules (Pre, Pre & Post or Post). Daily oral gavage administration of B.luti (10 ⁷ CFU/ml) was given according to corresponding schedules, alongside a 28-day cycle of neratinib (50 mg/kg). Diarrhea was graded daily, and faecal samples collected for gut microbiome analysis at study end. Ileum and colon samples were collected for intestinal analysis. 16S rRNA gene sequencing was performed on faecal samples and H&E performed on intestinal tissue for injury evaluation. Results: Grade 3 diarrhea was reduced in the Post group when compared to the neratinib alone group ( p = 0.0122). No significant differences were seen in the tissue injury scores of the ileum or colon. There was no significant change in microbial composition with B.luti administration. Conclusion: This study demonstrated that administration of B.luti supplementation, was effective in reducing neratinib-induced diarrhea severity when consumed concurrently. This administration schedule may have a protective role in the intestines through immunomodulation.

Cytotoxicity (i.e. cell death) is the core mechanism by which chemotherapy induces its anti-cancer effects. Unfortunately, this same mechanism underpins the collateral damage it causes to healthy tissues. The gastrointestinal tract is highly susceptible to chemotherapy’s cytotoxicity, resulting in ulcerative lesions (termed gastrointestinal mucositis, GI-M) that impair the functional capacity of the gut leading to diarrhea, anorexia, malnutrition and weight loss, which negatively impact physical/psychological wellbeing and treatment adherence. Preventing these side effects has proven challenging given the overlapping mechanisms that dictate chemotherapy efficacy and toxicity. Here, we report on a novel dietary intervention that, due to its localized gastrointestinal effects, is able to protect the intestinal mucosal from unwanted toxicity without impairing the anti-tumor effects of chemotherapy. The test diet (containing extensively hydrolyzed whey protein and medium chain triglycerides (MCTs)), was investigated in both tumor-naïve and tumor-bearing models to evaluate its effect on GI-M and chemo-efficacy, respectively. In both models, methotrexate was used as the representative chemotherapeutic agent and the diet was provided ad libitum for 14 days prior to treatment. GI-M was measured using the validated biomarker plasma citrulline, and chemo-efficacy defined by tumor burden (cm³/g body weight). The test diet significantly attenuated GI-M (P = 0.03), with associated reductions in diarrhea (P < 0.0001), weight loss (P < 0.05), daily activity (P < 0.02) and maintenance of body composition (P < 0.02). Moreover, the test diet showed significant impact on gut microbiota by increasing diversity and resilience, whilst also altering microbial composition and function (indicated by cecal short and brained chain fatty acids). The test diet did not impair the efficacy of methotrexate against mammary adenocarcinoma (tumor) cells. In line with the first model, the test diet minimized intestinal injury (P = 0.001) and diarrhea (P < 0.0001). These data support translational initiatives to determine the clinical feasibility, utility and efficacy of this diet to improve chemotherapy treatment outcomes.

Lapatinib is an orally administered, dual ErbB1/ErbB2 tyrosine kinase inhibitor (TKI). It is effective in ErbB2 + ve breast cancer treatment. However, lapatinib is associated with diarrhoea with an incidence of 47–75%. The mechanism of ErbB1 TKI-induced diarrhoea remains unclear. ErbB1 or epidermal growth factor receptor (EGFR) is expressed in gastrointestinal mucosa whereby the primary site for drug absorption is intestine. Thus, administration of ErbB1 oral TKI may disrupt gut homeostasis, leading to diarrhoea. Nevertheless, further investigations are required. We observed that lapatinib inhibited 50% Walker 256 breast tumour cells and IEC-6 small intestinal cell growth. Higher percentage of necrosis was observed in lapatinib-treated Walker 256. Lapatinib-treated IEC-6 showed higher percentage of late apoptosis. Only ErbB2 mRNA was detected in Walker 256 but both ErbB1 and ErbB2 mRNAs were detected in IEC-6, yet both protein staining were detected in both cells. Lapatinib exhibited cytotoxic properties on ErbB1/ErbB2 expressing cell lines, with intestinal cells being more sensitive to lapatinib compared to tumour cells. Lapatinib induced necrosis in tumour cells, while inducing late apoptosis in intestinal cells may explain lapatinib-induced diarrhoea in patients administered with the drug which could be due to apoptosis of intestinal epithelial cells leading to barrier disruption and consequently diarrhoea.

Radiotherapy-induced gut toxicity (RIGT) is associated with diarrhoea, pain and rectal bleeding and can occur as an acute or chronic toxicity. The microvasculature has been shown to be altered in the development of RIGT; however, the features are not yet characterized. We hypothesized that apoptosis of microvascular cells would occur early in the gastrointestinal tract following fractionated irradiation, followed by late microvascular changes, including sclerosis and telangiectasis.

Oral chemotherapy with SN38 is restricted by its poor solubility in gastrointestinal (GI) fluids and low permeability. Here we report the oral delivery of SN38 by a combined lipophilic prodrug and lipid-based formulation strategy. A lead lipophilic prodrug of SN38, SN38-undecanoate (SN38-unde20), was incorporated into a self-microemulsifying drug delivery system (SMEDDS) for improved in vitro and in vivo performance. The formulation was purposefully designed and optimized with long chain lipids and lipid-based nonionic surfactants to maximize drug solubilization in GI conditions, facilitate trans-membrane permeation, and hence improve oral absorption. SN38-unde20-SMEDDS significantly increased (>7 fold) drug solubilization in the aqueous phase compared to unformulated drug during in vitro lipolysis and drug solubilization studies. In an orally dosed in vivo pharmacokinetics study in a Dark Agouti rat model, the SN38-unde20-SMEDDS formulation confirmed oral absorption of SN38-unde20 and subsequent reconversion to SN38. Importantly, the overall plasma exposure of SN38 (AUC_0→∞) was equivalent for orally dosed SN38-unde20-SMEDDS in comparison with a parenteral dose of SN38-unde20-SMEDDS and SN38 at an identical dose (10 mg/kg). The combination of lipophilic prodrug along with an optimal delivery carrier is demonstrated to enable effective oral delivery of challenging chemotherapeutic compounds that are conventionally dosed by injection.

Irinotecan chemotherapy toxicities can be severe, and may result in treatment delay, morbidity and in some rare cases death. This systematic review of systematic reviews synthesises all meta-analyses on biomarkers for irinotecan toxicity across all genetic models for Asians, Caucasians, low dose, medium/high dose and regimens with and without fluorouracil. False-positive findings are a problem in pharmacogenetics, increasing the importance of systematic reviews. Four systematic reviews that investigated the effect of the polymorphisms UGT1A1*6 and/or*28 on neutropenia or diarrhoea toxicity were included. Both UGT1A1*6 and *28 were reliably demonstrated to be risk factors for irinotecan-induced neutropenia, with tests for both polymorphisms potentially being particularly useful in Asian cancer patients. UGT1A1*6 and *28 were also related to diarrhoea toxicity; however, at low doses of irinotecan there was evidence that UGT1A1*28 was not. In synthesising the best available evidence, this umbrella systematic review provides a novel reference for clinicians applying personalised medicine and identifies important research gaps.

Methotrexate chemotherapy is associated with various toxicities which can result in the interruption or discontinuation of treatment and a subsequently raised risk of relapse. This umbrella systematic review was conducted to synthesize the results of all existing systematic reviews that investigate the pharmacogenetics of methotrexate-induced toxicity, with the aim of developing a comprehensive reference for personalized medicine. Databases searched were PubMed, Embase, JBI Database of Systematic Reviews and Implementation Reports, DARE, and ProQuest. Papers were critically appraised by two reviewers, and data were extracted using a standardized tool. Three systematic reviews on methotrexate-induced toxicity were included in the review. Meta-analyses were reported across Asian, Caucasian, pediatric and adult patients for the MTHFR C677T and A1298C polymorphisms. Toxicity outcomes included different forms of hematologic, ectodermal and hepatic toxicities. Results varied considerably depending on the patient groups and subgroups investigated in the different systematic reviews, as well as the genetic models utilized. However, significant associations were found between the MTHFR C677T allele and; hepatic toxicity, myelosuppression, oral mucositis, gastrointestinal toxicity, and skin toxicity. Additionally, limited evidence suggests that the MTHFR A1298C polymorphism may be associated with decreased risk of skin toxicity and leukopenia. This umbrella systematic review has synthesized the best available evidence on the pharmacogenetics of methotrexate toxicity. The next step in making personalized medicine for methotrexate therapy a clinical reality is research on the effectiveness and cost-effectiveness of MTHFR genotype testing to enable the close monitoring of at-risk patients for the timely initiation of rescue therapies.

Purpose To review the literature surrounding the involvement of the endothelium and matrix metalloproteinases (MMP) in radiotherapy-induced gut toxicity (RIGT) and further elucidate its complex pathobiology. Results RIGT involves damage to the gastrointestinal mucosa and is associated with diarrhoea, pain, and rectal bleeding depending on the area of exposure. The mechanisms underpinning RIGT are complex and have not yet been elucidated. Members of the MMP family, particularly MMP-2 and -9, have recently been identified as being key markers in RIGT and chemotherapy-induced gut toxicity (CIGT). Furthermore, the microvasculature has long been implicated in the development of toxicities following both chemotherapy and radiotherapy, however, the mechanisms behind this are yet to be explored. Conclusions It is proposed that matrix metalloproteinases are key regulators of endothelial mediators, and may play a key role in inducing damage to intestinal microvasculature following radiotherapy.