Phase I study of an oral formulation of irinotecan administered daily for 14�days every 3�weeks in patients with advanced solid tumours

Orally delivered solid lipid nanoparticles of irinotecan coupled with chitosan surface modification to treat colon cancer: Preparation, in-vitro and in-vivo evaluations

Irinotecan-loaded solid lipid nanoparticles (IRI-SLNs) was formulated and tested for its potential activity against colon cancer. IRI-SLNs were prepared by applying the principles of DoE. Nanoparticles were further surface modified using chitosan. Characterizations such as size, poly-dispersity, surface charge, morphology, entrapment, drug release pattern, cytotoxicity were conducted. In-vivo studies in male Wistar rats were carried to ascertain distribution pattern of SLNs and their acute toxicity on various vital organs. Lastly, stability of the SLNs were evaluated. Particles had a size, polydispersity and zeta potential of 430.77 ± 8.69 nm, 0.36 ± 0.02 and -40.06 ± 0.61 mV, respectively. Entrapment of IRI was 62.24 ± 2.90% in IRI-SLNs. Sustained drug release was achieved at a colonic pH and long-term stability of NPs was seen. Cytotoxicity assay results showed that SLNs exhibited toxicity on HCT-116 cells. Biodistribution studies confirmed higher concentration of drug in the colon after surface modification. An acute toxicity study conducted for 7 days showed no severe toxic effects on major organs. Thus, we picture that the developed SLNs may benefit in delivering IRI to the tumour cells, therefore decreasing the dose and dose-associated toxicities.

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.

CPT11 with P-glycoprotein/CYP 3A4 dual-function inhibitor by self-nanoemulsifying nanoemulsion combined with gastroretentive technology to enhance the oral bioavailability and therapeutic efficacy against pancreatic adenocarcinomas

Therapeutic efficacies of orally administrated hydrophobic chemodrugs are decreased by poor water solubilities and reduced oral bioavailabilities by P-glycoprotein (P-gp) and CYP450. In this study, CPT11 alone or combined with dual-function inhibitors (baicalein (BA) silymarin (SM), glycyrrhizic acid (GA), and glycyrrhetinic acid (GLA)) of P-gp and CYP450 loaded in a lecithin-based self-nanoemulsifying nanoemulsion preconcentrate (LBSNENP) to improve the solubility and inhibit the elimination by P-gp and CYP450. Results revealed that the LBSNENP composed of Capryol 90, lecithin/Tween 80/Cremophor EL, and propylene glycol at a weight ratio of 18:58:24 (designated PC90C10P0) was optimally selected. Encapsulating CPT11 with PEO-7000K in PC90C10P10/30 further enhanced the resultant hydrogel to be gastro-retainable and to release CPT11 in a sustained manner. Pharmacokinetic study of CPT11-loaded PC90C10P0 administered orally revealed an absolute bioavailability (FAB, vs. intravenous CPT11) of 7.8 ± 1.01% and a relative bioavailability (FRB1, vs. oral solution of CPT11) of 70.7 ± 8.6% with a longer half-life (T_1/2) and mean residence time (MRT). Among the dual-function inhibitors, SM was shown to be the most influential in increasing the oral bioavailability of CPT11. SM also increased the plasma concentration of the SN-38 active metabolite, which formed from the enhanced plasma concentration of CPT11. It is concluded that treatment with CPT11 loaded in PC90C10P0 with or without solubilization with SM could expose tumors to higher plasma concentrations of both CPT11 and SN-38 leading to enhancement of tumor growth inhibition with no signs of adverse effects.

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.

Oral adjuvant therapy for colorectal cancer: recent developments and future targets

Colorectal cancer is considered the third most frequent malignant neoplasm occurring in both men and women worldwide. Most approaches that have been used to fight and treat this type of malignancy are either invasive or nonselective. Noninvasive therapy using oral route can increase patient compliance and reduce treatment costs. Innovative measures such as use of nanotechnology and theranostic systems have been initiated in the oral therapy, which has been proven to be greatly advantageous in decreasing side effects, improving detection and diagnoses. This manuscript investigates recent innovative and novel therapeutic approaches through oral route and potential targets in the treatment of colorectal cancer.

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.

Novel SN38 derivative-based liposome as anticancer prodrug: an in vitro and in vivo study

Background

Many novel drug delivery systems have been extensively studied to exploit the full therapeutic potential of SN38, which is one of the most potent antitumor analogs of camptothecins (CPTs), whose clinical application is seriously hindered by poor water solubility, low plasmatic stability, and severe toxicity, but results are always unsatisfactory.

Methods

In this study, combining the advantages of prodrug and nanotechnology, a lipophilic prodrug of SN38, SN38-PA, was developed by conjugating palmitic acid to SN38 via ester bond at C₁₀ position, and then the lipophilic prodrug was encapsulated into a long-circulating liposomal carrier by film dispersion method.

Results

The SN38-PA liposomes were characterized as follows: an average particle size of 80.13 nm, an average zeta potential of -33.53 mv, and the entrapment efficiency of 99%. Compared with CPT-11, SN38-PA liposome was more stable in close lactone form, more efficient in conversion rate to SN38, and more potent in cytotoxicity against tumor cells. Pharmacokinetic study showed that SN38-PA liposome had significantly enhanced plasma half-life (t_1/2) value of SN38 and increased area under the curve (AUC) of SN38, which was 7.5-fold higher than that of CPT-11. Biodistribution study showed that SN38-PA liposome had more active metabolite SN38 in each tissue. Finally, the pharmacodynamic study showed that SN38-PA liposome had higher antitumor effect with the antitumor inhibition rate of 1.61 times than that of CPT-11.

Conclusion

These encouraging data merit further investigation on this novel SN38-PA liposome.

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

BACKGROUND

Oral drug formulations have several advantages compared to intravenous formulation. Apart from patient convenience and favorable pharmacoeconomics, they offer the possibility of frequent drug administration at home. In this study, we present a new oral irinotecan formulation designed as an enteric coated immediate release tablet which in pre-clinical studies has shown good exposure with low variability.

METHODS

A phase I, dose escalating study to assess safety, tolerability, pharmacokinetics and efficacy of an oral irinotecan formulation and to establish the maximum tolerated dose (MTD). Each treatment cycle was once-daily irinotecan for 14 days followed by 1 week rest.

RESULTS

25 patients were included across four cohorts; 3 patients were included in cohort 1 (20 mg/m²), 7 patients were included in cohort 2 (30 mg/m²), 3 patients were included in cohort 3 (25 mg/m²) and 12 patients were included in cohort 4 (21 mg/m²). Median age was 67 years, 52% were performance status (PS) 0 while 48% were PS 1. Median number of prior therapies was 3 (range 1-6). MTD was established at 21 mg/m². No responses were observed. Nine patients (36%) had stable disease (SD), lasting median 19 weeks (range 7-45 weeks). Among these five patients had previously received irinotecan. No grade 3/4 hematologic toxicities were reported. Totally six patients experienced grade 1/2 anemia, three patients had grade 1/2 leucopenia and 1 patient had grade 1 thrombocytopenia. Most common non-hematological grade 1 and 2 adverse events were nausea, fatigue, diarrhea, vomiting and cholinergic syndrome. Grade 3 toxicities included diarrhea, fatigue, nausea and vomiting, no grade 4 events were reported. PK data showed consistent daily exposures during treatment at days 1 and 14 and no drug accumulation. SN-38 interpatient variability was in the same range as after infusion.

CONCLUSIONS

Oral irinotecan was generally well tolerated; side effects were manageable and similar in type to those observed with intravenous irinotecan. Hematological toxicities were few and only grade 1/2. In this heavily pre-treated patient population, oral irinotecan demonstrated activity even among patients previously treated with irinotecan.

Crystal Structures and Vapor-Induced Crystalline Transformation of 7-Ethyl-10-Hydroxycamptothecin Pseudopolymorphs

Solvent-induced 3 frameworks (the monohydrate, methanol solvate, and dimethyl formamide [DMF] solvate) of an anticancer drug, 7-ethyl-10-hydroxycamptothecin (SN38), were constructed. The crystal structures of the 3 pseudopolymorphs were characterized by single-crystal X-ray diffraction technique for the first time. Crystal structure analysis of all these polymorphs revealed that the monohydrate showed 3D frameworks linked by hydrogen bonds. In the methanol solvate, the 1D molecular chains were linked by the methanol molecules through intermolecular hydrogen bonds to form a 2D sheet. The DMF solvate exhibits the 1D hydrogen bonding-linked chains along b-axis. Vapor-induced transformation has been investigated for the monohydrate, the methanol solvate, and the DMF solvate. The conversion relationships among the 3 solid frameworks are illustrated. Insights regarding transformation mechanisms have been established from consideration of the crystal structures.

Irinotecan-loaded double-reversible thermogel with improved antitumor efficacy without initial burst effect and toxicity for intramuscular administration

Intramuscularly administered, anti-tumour drugs induce severe side effects due to their direct contact with body tissues and initial burst effect. In this study, to solve this problem, a novel double-reversible thermogel system (DRTG) for the intramuscular administration of irinotecan was developed. This irinotecan-loaded DRTG was prepared by dispersing the irinotecan-loaded thermoreversible solid lipid nanoparticles (SLNs) in the thermoreversible hydrogel. In DRTG, the former was solid at 25°C but converted to liquid at 36.5°C; in contrast, the latter existed in a liquid form but transformed to gel state in the body. The DRTG was easily administered intramuscularly. Its particle size and drug content were not noticeably changeable, resulting that it was stable at 40°C for at least 6months. Compared to the irinotecan-loaded solution and conventional hydrogel, the DRTG significantly delayed drug release, leading to a reduced burst effect. Moreover, it showed decreased C_max and maintained the sustained plasma concentrations at a relatively low level for the long period of 60h in rats, resulting in ameliorated side effects of the anti-tumour drug. Furthermore, it gave significantly improved anti-tumour efficacy in tumour-bearing mice compared to the hydrogel but, unlike the conventional hydrogel, induced no body weight loss and local damage to the muscle. Thus, this DRTG with improved antitumor efficacy without initial burst effect and toxicity could provide a potential pharmaceutical system for the intramuscular administration of irinotecan.

STATEMENT OF SIGNIFICANCE

Intramuscularly administered, anti-tumour drugs induce severe side effects due to their direct contact with body tissues and initial burst effect. To solve this problem, we developed a novel double-reversible thermogel system (DRTG) for the intramuscular administration of irinotecan. Unlike the conventional hydrogel, the DRTG is a dispersion of the irinotecan-loaded thermoreversible solid lipid nanoparticles in the thermoreversible hydrogel. In DRTG, the former was solid at 25°C but converted to liquid at 36.5°C; in contrast, the latter existed in a liquid form but transformed to gel state in the body. This DRTG gave significantly improved anti-tumour efficacy in tumour-bearing mice compared to the hydrogel but, unlike the conventional hydrogel, induced no body weight loss and local damage to the muscle.

Advances in oral delivery of anti-cancer prodrugs

INTRODUCTION

Most anticancer drugs have poor aqueous solubility and low permeability across the gastrointestinal tract. Furthermore, extensive efflux by P-glycoproteins (P-gp) in the small intestine also limits the efficient delivery of anticancer drugs via oral route. Area covered: This review explores the prodrug strategy for oral delivery of anticancer drugs. Different categories of oral anticancer prodrugs along with recent clinical studies have been comprehensively reviewed here. Furthermore, novel anticancer prodrugs such as polymer-prodrugs and lipid-prodrugs have been discussed in detail. Finally, various nanocarrier-based approaches employed for oral delivery of anticancer prodrugs have also been discussed. Expert opinion: Premature degradation of anticancer prodrugs in the gastrointestinal tract could lead to variable pharmacokinetics and undesired toxicity. Despite their increased aqueous solubility, the oral bioavailability of several anticancer prodrugs are limited by their poor permeability across the gastrointestinal tract. These limitations can be overcome by the use of functional excipients (polymers, lipids, amino acids/dipeptides), which are specifically absorbed via transporters and receptor-mediated endocytosis. Oral delivery of anticancer prodrugs using nanocarrier-based drug delivery system is a recent development; however it should be justified based on the comparative advantages of encapsulating prodrug in a nanocarrier versus the use of anticancer prodrug molecule itself.

Supramolecular Crafting of Self-Assembling Camptothecin Prodrugs with Enhanced Efficacy against Primary Cancer Cells

Chemical modification of small molecule hydrophobic drugs is a clinically proven strategy to devise prodrugs with enhanced treatment efficacy. While this prodrug strategy improves the parent drug's water solubility and pharmacokinetic profile, it typically compromises the drug's potency against cancer cells due to the retarded drug release rate and reduced cellular uptake efficiency. Here we report on the supramolecular design of self-assembling prodrugs (SAPD) with much improved water solubility while maintaining high potency against cancer cells. We found that camptothecin (CPT) prodrugs created by conjugating two CPT molecules onto a hydrophilic segment can associate into filamentous nanostructures in water. Our results suggest that these SAPD exhibit much greater efficacy against primary brain cancer cells relative to that of irinotecan, a clinically used CPT prodrug. We believe these findings open a new avenue for rational design of supramolecular prodrugs for cancer treatment.

Recent advances in oral anticancer agents for colon cancer

To provide therapeutic alternatives to intravenous colon chemotherapy major recent research is focusing on the development of oral chemotherapeutic agents with the intention to improve the quality of life of patients. Initially 5-fluorouracil was most commonly used for the treatment of colorectal cancer but currently oxaliplatin and irinotecan are also available. The majority of these new drugs are pyrimidines and their analogs. The rationale for using oral anticancer agents is discussed and new drugs, such as farnesyl protein transferase inhibitor S-1, rubitecan, ZD9331, MMI-166, eflornithine, sulindac, and oral camptothecin analogs, among others, are presented with the results of their preclinical and clinical developments. This article focuses on the advancement of clinical development and also discusses the relative merits and demerits of these agents. The accelerated approval of these agents by regulatory authorities is supported by survival benefit, response rate and time to progression.

Cetuximab increases concentrations of irinotecan and of its active metabolite SN-38 in plasma and tumour of human colorectal carcinoma-bearing mice

In a previous study, we showed that cetuximab, a monoclonal antibody directed towards epidermal growth factor receptor, could inhibit P-glycoprotein (P-gp), an efflux protein of ATP-binding cassette family, and lead to an increased P-gp substrate intracellular concentration. Cetuximab is given with irinotecan to patients with metastasis colorectal cancer who did not respond to irinotecan-based therapy. The mechanism of this successful clinical reversion remains unknown. As irinotecan is a P-gp substrate, we tested here whether cetuximab could modify irinotecan concentration in mice. Therefore, concentrations of irinotecan and of its active metabolite SN-38 were measured by HPLC in plasma and tumour of mice bearing a human colorectal carcinoma xenograft when irinotecan is given orally alone or after a pretreatment with cetuximab. Pharmacokinetic analysis showed no significant modification of irinotecan concentrations but a significant increase (1.7-fold) in SN-38 AUCs in plasma and in tumour after a pretreatment with cetuximab. Those results suggest that cetuximab influence irinotecan distribution into tissues probably due to inhibition of P-gp. As SN-38 is 200-fold more potent than irinotecan, cetuximab could reverse irinotecan resistance by an effect on its active metabolite. Inhibiting SN-38 efflux by P-gp drug transporters in biliary system and tumour can lead to pharmacokinetic modification and a higher anticancer efficacy.

Prodrug and nanomedicine approaches for the delivery of the camptothecin analogue SN38

SN38 (7-ethyl-10-hydroxy camptothecin) is a prominent and efficacious anticancer agent. It is poorly soluble in both water and pharmaceutically approved solvents; therefore, the direct formulation of SN38 in solution form is limited. Currently, the water soluble prodrug of SN38, irinotecan (CPT-11), is formulated as a low pH solution and is approved for chemotherapy. However, CPT-11, along with most other water-soluble prodrugs shows unpredictable inter-patient conversion to SN38 in vivo, instability in the physiological environment and variable dose-related toxicities. More recently, macromolecular prodrugs (i.e. EZN-2208, IMMU-130) and nanomedicine formulations (i.e. nanoemulsions, polymeric micelles, lipid nanocapsule/nanoparticle, and liposomes) of SN38 have been investigated for improved delivery to cancer cells and tissues. Specifically, these carriers can take advantage of the EPR effect to direct drug preferentially to tumour tissues, thereby substantially improving efficacy and minimising side effects. Furthermore, oral delivery has been shown to be possible in preclinical results using nanomedicine formulations (i.e. dendrimers, lipid nanocapsules, polymeric micelles). This review summarizes the recent advances for the delivery of SN38 with a focus on macromolecular prodrugs and nanomedicines.

[Metronomic chemotherapy in 2011: update and perspectives]

Angiogenesis is crucial for the growth and metastasis of many cancers. A series of new inhibitors of angiogenesis are now in intensive development. Recent preclinical studies suggest that frequent administration of certain conventional cytotoxic agents at low doses increases their putative antiangiogenic activity. Moreover, many clinical trials confirm efficacy of this metronomic chemotherapy in terms of clinical benefice and survival prolongation. Combining metronomic chemotherapy with hormonotherapy, angiogenesis inhibitors and radiotherapy increases efficacy. Many biomarkers are used to predict optimal drugs and appropriate use of them. This review describes experimental and clinical studies published and discuss its potential uses and limits.

Tyrosine kinase inhibitor enhances the bioavailability of oral irinotecan in pediatric patients with refractory solid tumors

PURPOSE

To assess the maximum-tolerated dosages (MTDs), and dose-limiting toxicities (DLTs) of the epidermal growth factor receptor inhibitor gefitinib and of intravenous (IV) irinotecan when administered together in children with refractory solid tumors. To assess the effect of gefitinib on the pharmacokinetics of IV irinotecan and on the bioavailability of a single oral dose of irinotecan.

PATIENTS AND METHODS

IV irinotecan (15 or 20 mg/m(2)) was given daily for 5 days of 2 consecutive weeks. Oral gefitinib (150 or 112.5 mg/m(2)) was concomitantly given daily for 12 or 21 days. A single oral dose of irinotecan was given on day 9 of course 2 to allow pharmacokinetic analysis.

RESULTS

The study enrolled 29 patients with recurrent solid tumors. The 21-day regimen of oral gefitinib with irinotecan was not tolerated. Diarrhea was the most common DLT. The MTD of the combination regimen was 15 mg/m(2)/d of IV irinotecan for 5 days of 2 consecutive weeks and 112.5 mg/m(2)/d of gefitinib given for 12 days. Gefitinib increased the bioavailability of oral irinotecan by four-fold over that observed in historical controls (median, 0.09 v 0.42; P < .000001), reducing the apparent clearance (an inverse measure of exposure) of irinotecan and SN-38 by 37% and 38%, respectively (P < .0001). A partial response was observed in a patient with refractory Ewing sarcoma.

CONCLUSION

IV irinotecan given with 12 days of oral gefitinib is well tolerated in children. We observed one partial response. Gefitinib significantly enhances the bioavailability of oral irinotecan. This combination warrants further investigation, particularly with orally administered irinotecan.

Phase I trial of oral irinotecan and temozolomide for children with relapsed high-risk neuroblastoma: a new approach to neuroblastoma therapy consortium study

PURPOSE

Irinotecan and temozolomide have single-agent activity and schedule-dependent synergy against neuroblastoma. Because protracted administration of intravenous irinotecan is costly and inconvenient, we sought to determine the maximum-tolerated dose (MTD) of oral irinotecan combined with temozolomide in children with recurrent/resistant high-risk neuroblastoma.

PATIENTS AND METHODS

Patients received oral temozolomide on days 1 through 5 combined with oral irinotecan on days 1 through 5 and 8 through 12 in 3-week courses. Daily oral cefixime was used to reduce irinotecan-associated diarrhea.

RESULTS

Fourteen assessable patients received 75 courses. Because neutropenia and thrombocytopenia were initially dose-limiting, temozolomide was reduced from 100 to 75 mg/m(2)/d for subsequent patients. Irinotecan was then escalated from 30 to 60 mg/m2/d. First-course grade 3 diarrhea was dose-limiting in one of six patients treated at the irinotecan MTD of 60 mg/m2/d. Other toxicities were mild and reversible. The median SN-38 lactone area under the plasma concentration versus time curve at this dose was 72 ng . hr/mL. One patient with bulky soft tissue disease had a complete response through six courses. Six additional patients received a median of seven courses (range, three to 22 courses) before progression.

CONCLUSION

This all-oral regimen was feasible and well tolerated in heavily pretreated children with resistant neuroblastoma, and seven (50%) of 14 assessable patients had response or disease stabilization for three or more courses in this phase I trial. SN-38 lactone exposures were similar to those reported with protracted intravenous irinotecan. The dosages recommended for further study in this patient population are temozolomide 75 mg/m2/d plus irinotecan 60 mg/m2/d when given with cefixime.

Novel Therapeutic Developments Other Than EGFR and VEGF Inhibition in Colorectal Cancer

Developments that may improve existing cytotoxic therapy for colorectal cancer (CRC) include alternatives to 5-fluorouracil (5-FU) such as the liposomal Thymidylate Synthase inhibitor OSI-7904L and the multitargeted antifolate pemetrexed. Studies have explored means of reformulating irinotecan, modulating its pharmacokinetics, and enhancing its activity by maximizing DNA damage through poly(ADP-ribose) polymerase inhibition. Cell cycle inhibitors may offer an alternative to combination with 5-FU. However, as standard regimens become more complex, so do the clinical trials needed to develop new agents, and the path to registration becomes ever more tortuous. It is therefore likely that several drugs with promise in CRC will not be developed for this indication.

Dose-Finding Phase I Clinical and Pharmacokinetic Study of Orally Administered Irinotecan in Patients with Advanced Solid Tumors

PURPOSE

The aim of this study was to determine the daily maximum tolerated dose (MTD) and the dose-limiting toxicity for the following administration schedules: oral irinotecan given over 14 days every 3 weeks (part I) and oral irinotecan administered concomitantly with capecitabine over 14 days every 3 weeks (part II). In total, 42 patients (17 male and 25 female) with solid tumors refractory to standard therapy entered the study.

EXPERIMENTAL DESIGN

Treatment in part I consisted of irinotecan administered orally as semisolid matrix capsules at doses of 25, 30, and 35 mg/m(2) once daily to confirm the MTD of our earlier study. In part II treatment, dose levels for irinotecan combined with capecitabine were 20/1,600, 25/1,600, 30/1,600, and 30/2,000 mg/m(2)/d.

RESULTS

The median number of cycles administered per patient was 2.0 (range, 1-12) in part I and 2.0 (range, 1-13) in study part II. Gastrointestinal toxicities (grade 3 nausea, grades 3 and 4 vomiting, and grades 3 and 4 diarrhea) were dose limiting in both parts of the study. There were no grade 3 or 4 hematologic toxicities. The MTD was 30 mg/m(2)/d for irinotecan single agent and 30/1,600 mg/m(2)/d for the combination with capecitabine. Absorption of irinotecan was rapid, and peak concentrations of irinotecan and metabolite SN-38 were reached within 0 to 3 and 1.5 to 4.0 hours, respectively.

CONCLUSIONS

In conclusion, oral irinotecan and capecitabine is feasible and well tolerated, and the recommended dose for phase II studies is 30/1,600 mg/m(2)/d administered daily for 14 days every 3 weeks.

Cefixime Allows Greater Dose Escalation of Oral Irinotecan: A Phase I Study in Pediatric Patients With Refractory Solid Tumors

Purpose

Irinotecan is active against a variety of malignancies; however, severe diarrhea limits its usefulness. In our phase I study, the intravenous formulation of irinotecan was administered orally daily for 5 days for 2 consecutive weeks (repeated every 21 days) to children with refractory solid tumors. Our objectives were to determine the maximum-tolerated dose (MTD), dose-limiting toxicity, and pharmacokinetics of oral irinotecan and to evaluate whether coadministration of cefixime (8 mg/kg/d beginning 5 days before irinotecan and continuing throughout the course) ameliorates irinotecan-induced diarrhea.

Patients and Methods

In separate cohorts, irinotecan doses were escalated from 15 to 45 mg/m2/d without cefixime and then from 45 to 60 and 75 mg/m2/d with cefixime.

Results

Without cefixime, diarrhea was dose limiting at irinotecan 45 mg/m2/d. Myelotoxicity was not significant at any dose. The MTD was 40 mg/m2/d without cefixime but 60 mg/m2/d with cefixime. Systemic exposure to SN-38 at the MTD was significantly higher with cefixime than without cefixime (mean SN-38 area under the curve: 19.5 ng×h/mL; standard deviation [SD], 6.8 ng × h/mL v 10.4 ng × h/mL; SD, 4.3 ng × h/mL, respectively; P = .030).

Conclusion

Cefixime administered with oral irinotecan is well tolerated in children and allows greater dose escalation of irinotecan. Because diarrhea is a major adverse effect of both intravenous and oral irinotecan, further evaluation of the use of cefixime to ameliorate this adverse effect is warranted.

St. John's Wort modulates the toxicities and pharmacokinetics of CPT-11 (irinotecan) in rats

CPT-11 is a DNA topoisomerase I inhibitor for the therapy of colorectal cancer, whereas St. John's Wort (Hypericum perforatum, SJW) is a widely used herbal anti-depressant. This study aimed to investigate the effects of co-administered SJW on the toxicities and pharmacokinetics of CPT-11 and the underlying mechanisms. The body weight loss, gastrointestinal and hematological toxicities induced by CPT-11, and the pharmacokinetic parameters of CPT-11 were evaluated in rats pretreated with SJW or vehicle. Rats treated with CPT-11 alone experienced rapid decrease in body weight, whereas co-administration of SJW with CPT-11 resulted in lesser body weight loss. The gastrointestinal and hematological toxicities following CPT-11 injection were both alleviated in the presence of SJW. The rat pharmacokinetics of both CPT-11 and its metabolite SN-38 were significantly altered in presence of SJW. In conclusion, co-administered SJW significantly ameliorated the toxicities induced by CPT-11. The protective effect of SJW may be partially due to pharmacokinetic interaction between CPT-11 and SJW.

A randomised phase II multicentre trial of irinotecan (CPT-11) using four different schedules in patients with metastatic colorectal cancer

The purpose of this phase II trial was to compare the efficacy, safety and pharmacokinetics of four irinotecan schedules for the treatment of metastatic colorectal cancer. In total, 174 5-fluorouracil pretreated patients were randomised to: arm A (n=41), 350 mg m(-2) irinotecan as a 90-min i.v. infusion q3 weeks; arm B (n=38), 125 mg m(-2) irinotecan as a 90-min i.v. infusion weekly x 4 weeks q6 weeks; arm C (n=46), 250 mg m(-2) irinotecan as a 90-min i.v. infusion q2 weeks; or arm D (n=49), 10 mg m(-2) day(-1) irinotecan as a 14-day continuous infusion q3 weeks. No significant differences in efficacy across the four arms were observed, although a shorter time to treatment failure was noted for arm D (1.7 months; P=0.02). Overall response rates were in the range 5-11%. Secondary end points included median survival (6.4-9.4 months), and time to progression (2.7-3.8 months) and treatment failure (1.7-3.2 months). Similarly, there were no significant differences in the incidence of grade 3-4 toxicities, although the toxicity profile between arms A, B, and C and D did differ. Generally, significantly less haematologic toxicity, alopecia and cholinergic syndrome were observed in arm D; however, there was a trend for increased gastrointestinal toxicity. Irinotecan is an effective and safe second-line treatment for colorectal cancer. The schedules examined yielded equivalent results, indicating that there is no advantage of the prolonged vs short infusion schedules.