Phase I clinical and pharmacokinetic/pharmacogenetic study of a triplet regimen of S-1/irinotecan/oxaliplatin in patients with metastatic colorectal or gastric cancer

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.

Anticancer effect of resibufogenin on gastric carcinoma cells through the phosphoinositide 3-kinase/protein kinase B/glycogen synthase kinase 3β signaling pathway

The aim of the present study was to investigate the anticancer effect of resibufogenin in gastric carcinoma cells through the phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT)/glycogen synthase kinase 3β (GSK3β) signaling pathway. MGC-803 cells were treated with 0, 1, 2, 4 and 8 µM resibufogenin for 12, 24 and 48 h. Cell viability and apoptosis were measured using an MTT assay and annexin V staining. Caspase-3 and caspase-8 activity were identified using caspase-3 and caspase-8 activity kits and a variety of protein expression [B cell lymphoma (Bcl)-2, Bcl-2-associated X protein (Bax), cyclin D1, cyclin E, PI3K, phosphorylated AKT, phosphorylated GSK3β and β-catenin] were quantified using western blot analysis. It was revealed that resibufogenin effectively inhibited cell proliferation, and induced apoptosis and caspase-3 and caspase-8 activity in MGC-803 cells. Furthermore, treatment with resibufogenin effectively increased Bax/Bcl-2 expression, and suppressed cyclin D1, cyclin E, PI3K, phosphorylated AKT, phosphorylated GSK3β and β-catenin protein expression in MGC-803 cells. These results suggest that the anticancer effect of resibufogenin induces gastric carcinoma cell death through the PI3K/AKT/GSK3β signaling pathway, offering a novel view of the mechanism by which resibufogenin functions as an agent to treat gastric carcinoma.

Influence of SLCO1B1 in gastric cancer patients treated with EOF chemotherapy

Cytochrome-P450 enzymes, ATP-binding cassette transporters, and solute carriers mediate drug metabolism as metabolic enzymes and membrane transporters, respectively. The present study investigated whether single nucleotide polymorphisms (SNPs) in genes encoding these proteins were predictive or prognostic factors in patients with metastatic gastric cancer (MGC) undergoing chemotherapy. A retrospective study of 108 MGC patients who received epirubicin, oxaliplatin, and 5-fluorouracil (EOF) as first-line treatment was performed. A total of 13 SNPs were genotyped, including SLCO1B1 (rs4149056), SLC2A9 (rs16890979, rs6449213, rs734553), ABCG2 (rs2231142), CYP2C9 (rs1057910, rs1799853), CYP2C19 (rs72552267, rs28399504, rs56337013, rs41291556) and CYP1A2 (rs12720461, rs56107638). The associations between these genotypes and disease-control rate (DCR), progression-free survival (PFS) and overall survival (OS) were analyzed. Patients with SLCO1B1 rs4149056 TT genotype had a significantly shorter OS compared with those with a C allele (CC + CT; 312 vs. 565 days, P=0.039). Multivariate analysis revealed that the rs4149056 TT homozygous genotype was an independent prognostic factor for shorter OS (hazard ratio: 2.565, 95% confidence interval: 1.215–5.415, P=0.014). However, no significant associations between SLCO1B1 rs4149056 and PFS were observed, between the other 12 SNPs and PFS or OS, or between any of the 13 SNPs and DCR. In conclusion, SLCO1B1 rs4149056 TT may be an independent predictor of survival in patients with MCG treated with EOF chemotherapy.

Genotypes Affecting the Pharmacokinetics of Anticancer Drugs

Cancer treatment is becoming more and more individually based as a result of the large inter-individual differences that exist in treatment outcome and toxicity when patients are treated using population-based drug doses. Polymorphisms in genes encoding drug-metabolizing enzymes and transporters can significantly influence uptake, metabolism, and elimination of anticancer drugs. As a result, the altered pharmacokinetics can greatly influence drug efficacy and toxicity. Pharmacogenetic screening and/or drug-specific phenotyping of cancer patients eligible for treatment with chemotherapeutic drugs, prior to the start of anticancer treatment, can identify patients with tumors that are likely to be responsive or resistant to the proposed drugs. Similarly, the identification of patients with an increased risk of developing toxicity would allow either dose adaptation or the application of other targeted therapies. This review focuses on the role of genetic polymorphisms significantly altering the pharmacokinetics of anticancer drugs. Polymorphisms in DPYD, TPMT, and UGT1A1 have been described that have a major impact on the pharmacokinetics of 5-fluorouracil, mercaptopurine, and irinotecan, respectively. For other drugs, however, the association of polymorphisms with pharmacokinetics is less clear. To date, the influence of genetic variations on the pharmacokinetics of the increasingly used monoclonal antibodies has hardly been investigated. Some studies indicate that genes encoding the Fcγ-receptor family are of interest, but more research is needed to establish if screening before the start of therapy is beneficial. Considering the profound impact of polymorphisms in drug transporters and drug-metabolizing enzymes on the pharmacokinetics of chemotherapeutic drugs and hence, their toxicity and efficacy, pharmacogenetic and pharmacokinetic profiling should become the standard of care.

Associations between CYP2A6 polymorphisms and outcomes of adjuvant S-1 chemotherapy in patients with curatively resected gastric cancer

BACKGROUND

Oral fluoropyrimidine S-1 contains tegafur, which is metabolized to 5-fluorouracil by cytochrome P450 2A6 (CYP2A6). We here examined associations between CYP2A6 polymorphisms and treatment outcomes of adjuvant S-1 in gastric cancer patients.

METHODS

Patients received adjuvant S-1 (40 mg/m² twice daily, days 1-28, every 6 weeks for eight cycles) after curative surgery for pathological stage II-III gastric cancer. We analyzed the wild-type allele (W) (CYP2A6*1) and four variant alleles (V) (CYP2A6*4, *7, *9, *10) that abolish or reduce this enzyme activity.

RESULTS

Patients (n = 200) were enrolled between November 2007 and July 2013 with the following clinical characteristics: median age, 57 years (range, 32-83 years); 128 men, 72 women. With a median follow-up of 46.4 months, the 3-year relapse-free survival (RFS) and overall survival (OS) rates were 83.1 % (95 % CI, 77.7-88.5 %) and 94.8 % (95 % CI, 91.6-98.0 %), respectively. Genotype distributions were as follows: W/W (n = 49, 24.5 %), W/V (n = 94, 47.0 %), and V/V (n = 57, 28.5 %). Overall toxicity did not differ according to genotype for any grade (p = 0.612) or grade ≥3 (p = 0.143). However, RFS differed significantly according to CYP2A6 genotype. The 3-year RFS rates were 95.9 % for W/W, 83.1 % for W/V, and 72.5 % for V/V (p = 0.032). Carriers of W/V and V/V genotypes had a poorer RFS with a hazard ratio of 3.41 (95 % CI, 1.01-11.52; p = 0.049) and 4.03 (95 % CI, 1.16-13.93; p = 0.028), respectively, compared with the W/W genotype.

CONCLUSIONS

CYP2A6 polymorphisms are not associated with toxicity of S-1 chemotherapy, but correlate with the efficacy of S-1 in the adjuvant setting for gastric cancer.

A dose-finding study for oxaliplatin, irinotecan, and S-1 (OIS) in patients with metastatic or recurrent gastrointestinal cancer

PURPOSES

To determine the maximum tolerated dose (MTD), recommended dose (RD), and activity of combined oxaliplatin, irinotecan, and S-1 chemotherapy for metastatic or recurrent gastrointestinal (GI) cancer.

METHODS

Oxaliplatin and irinotecan were administered intravenously on day 1, and S-1 was administered orally on days 1-7, every 2 weeks. This phase I study used the following dose levels for oxaliplatin/irinotecan/S-1: level 1, 85/120/60 mg/m²; level 2, 85/120/80 mg/m²; level 3, 85/120/100 mg/m²; level 4, 85/150/100 mg/m²; and level 5, 85/180/100 mg/m². Treatment was repeated for a maximum of 12 cycles, until disease progression, or until unacceptable toxicity.

RESULTS

Twenty-four patients were enrolled between October 2012 and February 2014 (median age 59 years). During the first cycle, one of the six patients in levels 1, 3, and 4 developed a dose-limiting toxicity (grade 3 febrile neutropenia), and none of the three patients in level 5 developed a dose-limiting toxicity. As the planned maximum dose did not reach the MTD, the level 5 dose was defined as the RD. Twenty-one patients were evaluated for response, which included 2 cases of complete response and 8 cases of partial response, with an overall response rate of 47.6 %.

CONCLUSIONS

The combination of oxaliplatin, irinotecan, and S-1 provided an acceptable toxicity profile and modest clinical benefits in patients with advanced GI cancer. The RD was 85 mg/m² of oxaliplatin, 180 mg/m² of irinotecan, and 100 mg/m² of S-1 every 2 weeks.

Trial Watch: Chemotherapy with immunogenic cell death inducers

Accumulating evidence suggests that the clinical efficacy of selected anticancer drugs, including conventional chemotherapeutics as well as targeted anticancer agents, originates (at least in part) from their ability to elicit a novel or reinstate a pre-existing tumor-specific immune response. One of the mechanisms whereby chemotherapy can stimulate the immune system to recognize and destroy malignant cells is commonly known as immunogenic cell death (ICD). Cancer cells succumbing to ICD are de facto converted into an anticancer vaccine and as such elicit an adaptive immune response. Several common chemotherapeutics share the ability of triggering ICD, as demonstrated in vaccination experiments relying on immunocompetent mice and syngeneic cancer cells. A large number of ongoing clinical trials involve such ICD inducers, often (but not always) as they are part of the gold standard therapeutic approach against specific neoplasms. In this Trial Watch, we summarize the latest advances on the use of cyclophosphamide, doxorubicin, epirubicin, oxaliplatin, and mitoxantrone in cancer patients, discussing high-impact studies that have been published during the last 13 months as well as clinical trials that have been initiated in the same period to assess the antineoplastic profile of these immunogenic drugs as off-label therapeutic interventions.