Adsorption of irinotecan onto oral adsorbent AST-120 (Kremezin) for preventing delayed diarrhea

Mechanisms and emerging strategies for irinotecan-induced diarrhea

Irinotecan (also known as CPT-11) is a topoisomerase I inhibitor first approved for clinical use as an anticancer agent in 1996. Over the past more than two decades, it has been widely used for combination regimens to treat various malignancies, especially in gastrointestinal and lung cancers. However, severe dose-limiting toxicities, especially gastrointestinal toxicity such as late-onset diarrhea, were frequently observed in irinotecan-based therapy, thus largely limiting the clinical application of this agent. Current knowledge regarding the pathogenesis of irinotecan-induced diarrhea is characterized by the complicated metabolism of irinotecan to its active metabolite SN-38 and inactive metabolite SN-38G. A series of enzymes and transporters were involved in these metabolic processes, including UGT1A1 and CYP3A4. Genetic polymorphisms of these metabolizing enzymes were significantly associated with the occurrence of irinotecan-induced diarrhea. Recent discoveries and progress made on the detailed mechanisms enable the identification of potential biomarkers for predicting diarrhea and as such guiding the proper patient selection with a better range of tolerant dosages. In this review, we introduce the metabolic process of irinotecan and describe the pathogenic mechanisms underlying irinotecan-induced diarrhea. Based on the mechanisms, we further outline the potential biomarkers for predicting the severity of diarrhea. Finally, based on the current experimental evidence in preclinical and clinical studies, we discuss and prospect the current and emerging strategies for the prevention of irinotecan-induced diarrhea.

Tight-Binding Small-Molecule Carboxylesterase 2 Inhibitors Reduce Intracellular Irinotecan Activation

As the primary enzyme responsible for the activatable conversion of Irinotecan (CPT-11) to SN-38, carboxylesterase 2 (CES2) is a significant predictive biomarker toward CPT-11-based treatments for pancreatic ductal adenocarcinoma (PDAC). High SN-38 levels from high CES2 activity lead to harmful effects, including life-threatening diarrhea. While alternate strategies have been explored, CES2 inhibition presents an effective strategy to directly alter the pharmacokinetics of CPT-11 conversion, ultimately controlling the amount of SN-38 produced. To address this, we conducted a high-throughput screening to discover 18 small-molecule CES2 inhibitors. The inhibitors are validated by dose-response and counter-screening and 16 of these inhibitors demonstrate selectivity for CES2. These 16 inhibitors inhibit CES2 in cells, indicating cell permeability, and they show inhibition of CPT-11 conversion with the purified enzyme. The top five inhibitors prohibited cell death mediated by CPT-11 when preincubated in PDAC cells. Three of these inhibitors displayed a tight-binding mechanism of action with a strong binding affinity.

Is there a role for charcoal in palliative diarrhea management?

OBJECTIVE

Symptomatic therapy is an intervention centered entirely on symptom management and pain relief. The utilization of charcoal in diarrhea management is a pertinent example of this type of medical care. Diarrhea is an ailment defined as an escalation in the frequency of bowel movements, unformed stool, abdominal discomfort, and pain. These symptoms can be extremely debilitating for patients, and effectuate frustration as well as severely dampening mood and overall well-being. This narrative review aims to explore the use of charcoal in diarrhea management and its possible benefits in alleviating discomfort associated with these symptoms.

METHODS

The authors used PubMed, MEDLINE, and Google Scholar searches on recent literature available on the role of activated charcoal in diarrhea management.

RESULTS

It was found that the main precursors of diarrhea include drugs and bacterial infection. Activated charcoal has a firm history in its ability to attract and expel ingested toxins from the gastrointestinal tract. It acts to prevent system absorption of these adverse entities, adsorbing them on the surface of its particles, making it a suitable diarrheal treatment.

CONCLUSIONS

Diarrhea can present itself alongside a multitude of treatments and conditions, such as chemotherapy, primary malignancy, intestinal, colorectal and pancreatic cancer, bacterial infection, and irritable bowel syndrome, making activated charcoal a potential therapy in these conditions. In comparison, with other common anti-diarrheal treatments, activated charcoal has exceptionally few side-effects. Overall, further research is necessary in order to wholly determine the effectiveness of charcoal in the management of diarrhea.

Therapeutic targeting of CPT-11 induced diarrhea: a case for prophylaxis

CPT-11 (irinotecan), a DNA topoisomerase I inhibitor is one of the main treatments for colorectal cancer. The main dose limiting toxicities are neutropenia and late onset diarrhea. Though neutropenia is manageable, CPT-11 induced diarrhea is frequently severe, resulting in hospitalizations, dose reductions or omissions leading to ineffective treatment administration. Many potential agents have been tested in preclinical and clinical studies to prevent or ameliorate CPT-11 induced late onset diarrhea. It is predicted that prophylaxis of CPT-11 induced diarrhea will reduce sub-therapeutic dosing as well as hospitalizations and will eventually lead to dose escalations resulting in better response rates. This article reviews various experimental agents and strategies employed to prevent this debilitating toxicity. Covered topics include schedule/dose modification, intestinal alkalization, structural/chemical modification, genetic testing, anti-diarrheal therapies, transporter (ABCB1, ABCC2, BCRP2) inhibitors, enzyme (β-glucuronidase, UGT1A1, CYP3A4, carboxylesterase, COX-2) inducers and inhibitors, probiotics, antibiotics, adsorbing agents, cytokine and growth factor activators and inhibitors and other miscellaneous agents.

Rapid deconjugation of SN-38 glucuronide and adsorption of released free SN-38 by intestinal microorganisms in rat

One of the dose-limiting toxicities of irinotecan hydrochloride (CPT-11) is delayed-onset diarrhea. CPT-11 is converted to its active metabolite, SN-38, which is conjugated to SN-38 glucuronide (SN-38G). SN-38G excreted in the intestinal lumen is extensively deconjugated by bacterial β-glucuronidase, resulting in the regeneration of SN-38, which causes diarrhea. However, the deconjugation of SN-38G by the intestinal microflora remains to be clarified. This study aimed to investigate the microbial transformation of SN-38G by an anaerobic mixed culture of rat cecal microorganisms. Concentrations of SN-38G and SN-38 were then determined using high-performance liquid chromatography. Complete deconjugation of SN-38G to SN-38 in the mixed cultures was observed within 1 h of incubation, with 62.7% of the added SN-38G being found in the supernatant. Approximately 80.4% of the SN-38 in the supernatant was bound to protein, and the remaining 19.6% was detected as active free SN-38. In total, only 12.3% (19.6 × 62.7%) of the SN-38G added to the test tube was found in the supernatant in the ultrafiltrable free form, indicating that approximately 90% of the SN-38G added to the growth medium either remained adsorbed onto the pelleted fraction or occurred in a protein-bound form in the supernatant. The remaining 10% of the SN-38G added to the growth medium existed in the unbound form, the form capable of causing damage to the intestinal membrane. In conclusion, these results indicated that the greater part of the SN-38 produced from SN-38G by the action of bacterial β-glucuronidase is rapidly adsorbed onto intestinal bacterial cell walls or dietary fibers in pelleted fraction, and only 10% remains in the ultrafiltrable unbound form in the intestinal luminal fluid.

Chemotherapy-induced diarrhoea

PURPOSE OF REVIEW

Diarrhoea is a major manifestation of chemotherapy-induced mucositis that until recently has received very little attention. To date, there is no detailed understanding of the underlying mechanisms of the condition. The purpose of this review is to examine the plethora of recent studies, both in the laboratory and in the clinic, which have attempted to elucidate effective treatment options.

RECENT FINDINGS

Over recent years, there have been many new treatment options trialled for ameliorating chemotherapy-induced diarrhoea. Some of these have shown great promise in small clinical studies and now need to be investigated in larger trials. Furthermore, there have been developments in the understanding of the underlying mechanisms of chemotherapy-induced diarrhoea. These developments may also lead to effective treatment options.

SUMMARY

Here, we describe the current thinking behind the mechanisms of chemotherapy-induced diarrhoea and present current and new treatment options. This opinion article highlights the shift towards more effective research into diarrhoea caused by chemotherapy.

Activated charcoal to prevent irinotecan-induced diarrhea in children

BACKGROUND

We performed a prospective study to evaluate the efficacy of activated charcoal (AC) to prevent irinotecan-induced diarrhea (IID).

PROCEDURE

We designed a prospective trial including all patients receiving irinotecan as part of their chemotherapy treatment. Patients were divided into two groups. The experimental group received AC at a dose of 250 mg three times daily during irinotecan administration. The number and severity of events were graded according to the gastrointestinal toxicity criteria of the NCI Common Toxicity Criteria. We used descriptive statistics, Mann-Whitney U test, and Fisher's exact test to evaluate our results.

RESULTS

Twenty-two evaluable patients were included for a total of 66 irinotecan chemotherapy cycles. Ten patients received AC and 12 did not. There were 45 cycles in the experimental group and 21 in the control group. A total of 28 events of diarrhea were registered, 13 in 45 cycles (28.88%) in the experimental group and 15 in 21 cycles (71.42%) in the control group (P = 0.002). Grade 3 and 4 diarrhea was present in 4.4% of patients receiving AC against 52.3% in the controls (P = 0.010). Chemotherapy was discontinued in 6.6% in the experimental group and 52.3% in the control group.

CONCLUSIONS

The use of AC decreased the frequency and severity of IID improving compliance with treatment. We consider AC and effective and safe prophylactic treatment to prevent IID.

[In-vitro study of the drug interactions between Miglitol, an alpha-glucosidase inhibitor, and adsorbents]

The interactions between miglitol, an alpha-glucosidase inhibitor, and six adsorbents (carbon spheres, cholestyramine, colestimide, sevelamer hydrochloride, calcium polystyrene sulfonate, and sodium polystyrene sulfonate) were investigated in vitro. Miglitol corresponding to the minimum dose and adsorbents corresponding to the maximum dose were incubated at 37 degrees C for 180 min in solutions of pH 1.2 (gastric pH condition) and pH 6.8 (enteric pH condition), with and without the presence of carbohydrates, which were added to observe the effects on food adsorption. The adsorption ratio of miglitol to carbon spheres was 13.6% and 0% in pH 1.2 solution and 86.4% and 5.0% in pH 6.8 solution without and with the presence of carbohydrates, respectively. Thus, the adsorption ratio was higher in pH 6.8 solution. Adsorption of miglitol to calcium polystyrene sulfonate was nearly the same, 15.0-21.9%, at both pH. The adsorption ratio of miglitol to sodium polystyrene sulfonate was 43.4% and 45.5%, respectively, in pH 1.2 solution without and with carbohydrates. In the pH 6.8 solutions, however, the respective adsorption ratios were low (5.2% and 11.3%). Miglitol did not adsorb to cholestyramine, sevelamer hydrochloride or colestimide under any pH condition examined. The above results suggest that miglitol adsorbs to carbon spheres and polystyrene sulfonic acid cation exchange resins. However, considering that miglitol is taken just before eating and thus exists in gastointestinal fluids together with food, and that the site of its effect is the upper small intestine, the interactions between miglitol and these adsorbents will most likely not be a problem.