A phase I pharmacologic and pharmacogenetic trial of sequential 24-hour infusion of irinotecan followed by leucovorin and a 48-hour infusion of fluorouracil in adult patients with solid tumors

Pharmacogenomics Testing in Phase I Oncology Clinical Trials: Constructive Criticism Is Warranted

Simple Summary

Phase I clinical trials are a cornerstone of pharmaceutical development in oncology. Many studies have now attempted to incorporate pharmacogenomics into phase I studies; however, many of these studies have fundamental flaws that that preclude interpretation and application of their findings. Study populations are often small and heterogeneous with multiple disease states, multiple dose levels, and prior therapies. Genetic testing typically includes few variants in candidate genes that do no encapsulate the full range of phenotypic variability in protein function. Moreover, a plurality of these studies do not present scientifically robust clinical or preclinical justification for undertaking pharmacogenomics studies. A significant amount of progress in understanding pharmacogenomic variability has occurred since pharmacogenomics approaches first began appearing in the literature. This progress can be immediately leveraged for the vast majority of Phase I studies. The purpose of this review is to summarize the current literature pertaining to Phase I incorporation of pharmacogenomics studies, analyze potential flaws in study design, and suggest approaches that can improve design of future scientific efforts.

Abstract

While over ten-thousand phase I studies are published in oncology, fewer than 1% of these studies stratify patients based on genetic variants that influence pharmacology. Pharmacogenetics-based patient stratification can improve the success of clinical trials by identifying responsive patients who have less potential to develop toxicity; however, the scientific limits imposed by phase I study designs reduce the potential for these studies to make conclusions. We compiled all phase I studies in oncology with pharmacogenetics endpoints (n = 84), evaluating toxicity (n = 42), response or PFS (n = 32), and pharmacokinetics (n = 40). Most of these studies focus on a limited number of agent classes: Topoisomerase inhibitors, antimetabolites, and anti-angiogenesis agents. Eight genotype-directed phase I studies were identified. Phase I studies consist of homogeneous populations with a variety of comorbidities, prior therapies, racial backgrounds, and other factors that confound statistical analysis of pharmacogenetics. Taken together, phase I studies analyzed herein treated small numbers of patients (median, 95% CI = 28, 24–31), evaluated few variants that are known to change phenotype, and provided little justification of pharmacogenetics hypotheses. Future studies should account for these factors during study design to optimize the success of phase I studies and to answer important scientific questions.

Association between UGT1A1*28 polymorphisms and clinical outcomes of irinotecan-based chemotherapies in colorectal cancer: a meta-analysis in Caucasians

BACKGROUND

Whether UGT1A1*28 genotype is associated with clinical outcomes of irinotecan (IRI)-based chemotherapy in Colorectal cancer (CRC) is an important gap in existing knowledge to inform clinical utility. Published data on the association between UGT1A1*28 gene polymorphisms and clinical outcomes of IRI-based chemotherapy in CRC were inconsistent.

METHODOLOGY/PRINCIPAL FINDINGS

Literature retrieval, trials selection and assessment, data collection, and statistical analysis were performed according to the PRISMA guidelines. Primary outcomes included therapeutic response (TR), progression-free survival (PFS) and overall survival (OS). We calculated odds ratios (OR) and hazard ratios (HR) with 95% confidence intervals (CI). Twelve clinical trials were included. No statistical heterogeneity was detected in analyses of all studies and for each subgroup. Differences in TR, PFS and OS for any genotype comparison, UGT1A1*28/*28 versus (vs) UGT1A1*1/*1 (homozygous model), UGT1A1*1/*28 vs UGT1A1*1/*1 (heterozygous model), and UGT1A1*28/*28 vs all others (recessive model, only for TR) were not statistically significant. IRI dose also did not impact upon TR and PFS differences between UGT1A1 genotype groups. A statistically significant increase in the hazard of death was found in Low IRI subgroup of the homozygous model (HR = 1.48, 95% CI = 1.06-2.07; P = 0.02). The UGT1A1*28 allele was associated with a trend of increase in the hazard of death in two models (homozygous model: HR = 1.22, 95% CI = 0.99-1.51; heterozygous model: HR = 1.13, 95% CI = 0.96-1.32). These latter findings were driven primarily by one single large study (Shulman et al. 2011).

CONCLUSIONS/SIGNIFICANCE

UGT1A1*28 polymorphism cannot be considered as a reliable predictor of TR and PFS in CRC patients treated with IRI-based chemotherapy. The OS relationship with UGT1A1*28 in the patients with lower-dose IRI chemotherapy requires further validation.

Phase I/II study of 24-hour infusion of irinotecan combined with oral UFT for metastatic colorectal cancer

BACKGROUND

To evaluate the efficacy and safety of irinotecan combined with UFT for untreated and pretreated metastatic colorectal cancer.

METHODS

Escalating doses of irinotecan (80-110 mg/m(2)) were administered by 24-hour infusion on day 1. UFT was administered orally at 400 mg/m(2)/day on days 3-7 and 10-14. The treatment cycles were repeated every 2 weeks.

RESULTS

In the phase I study, the maximum tolerated dose of irinotecan was 110 mg/m(2) and the recommended dose for the phase II study was determined to be 100 mg/m(2). Thirty-five patients including 3 patients at the recommended dose in the phase I study were evaluated in the phase II study. The grade 3/4 toxicities observed were leukopenia, neutropenia, thrombocytopenia and anemia. No grade 3 or more severe nonhematological toxicities were noted. The response rate was 62.9% and the median overall survival 16.7 months.

CONCLUSIONS

A 24-hour infusion of irinotecan combined with UFT is feasible and active for metastatic colorectal cancer.

A phase I study of bi-weekly administration of 24-h gemcitabine followed by 24-h irinotecan in patients with solid tumors

PURPOSE

To determine the maximal tolerated doses (MTD) and dose-limiting toxicities (DLT) of combination of 24-h infusions of gemcitabine and irinotecan in patients with advanced solid tumors.

PATIENTS AND METHODS

Twenty-four patients with advanced solid tumors received gemcitabine as a 24-h IV infusion followed by a 24-h infusion of irinotecan every 2 weeks. Pharmacokinetic parameters of both drugs and their metabolites were estimated by using non-compartmental methods.

RESULTS

Twenty-four patients were fully evaluable for toxicity. DLT was observed in two of six patients at irinotecan/gemcitabine 110/150 mg/m(2) (grade 3 diarrhea and grade 3 GI bleeding). No patient developed acute cholinergic symptoms at any dose. Other toxicities were < or =grade 2 nausea, vomiting, and fatigue. Tumor responses were observed in three patients (one CR: cholangiocarcinoma; two PR: SCLC, gastric neuroendocrine tumor). Stable disease >3 months was found in six patients including five patients who had failed short infusions of either drug. Pharmacokinetic analysis showed that C (max) of each drug and active metabolites were dose-dependent. High dose of gemcitabine increased C (max), AUC, and T(1/2) of irinotecan. However, gemcitabine had minimal effects on SN-38.

CONCLUSIONS

The recommended dose for Phase II studies is gemcitabine 125 mg/m(2) given as a 24-h IV infusion on D1 and D15, followed by a 24-h IV infusion of irinotecan 110 mg/m(2) on D2 and D16. Both pretreated patients and chemo-naive patients seem to tolerate higher doses of this combination without significant toxicities. Objective responses among patients with solid tumors, in particular cholangiocarcinoma and small cell lung cancer merits further investigation.