Phase I/II study of everolimus combined with mFOLFOX-6 and bevacizumab for first-line treatment of metastatic colorectal cancer

Background This phase I/II trial evaluated toxicity and antitumor activity of everolimus plus mFOLFOX6 + bevacizumab for first-line treatment of metastatic colorectal cancer (mCRC). Methods A phase I, modified 3 + 3 Fibonacci schema determined the maximum tolerated dose (MTD) of everolimus, followed by phase II dose expansion. The phase II primary objective was progression-free survival at 6 months (PFS-6 m). Results The everolimus MTD was 10 mg daily with mFOLFOX6 + bevacizumab based on safety from phase I (n = 22). Twenty-five patients were treated in the phase II at 10 mg everolimus daily. Frequent grade 3-4 adverse events were neutropenia (64%), leukopenia (28%) and hypokalemia (26%). Grade 2 stomatitis was observed in 62% of patients. Two dose-limiting toxicities were observed with one attributed to everolimus 10 mg daily (grade 3 diarrhea, hypokalemia, and anorexia) and grade 3 coronary vasospasm attributed to fluorouracil. The objective response rate was 53% and was higher (86%) in those with PTEN deficiency. PFS-6 m was 96% (95% CI 89-99.9%) at the MTD (n = 35). The everolimus recommended phase II dose of this regimen is 7.5 mg daily due to frequent stomatitis and dose reductions. Conclusions Everolimus plus mFOLFOX-6 + bevacizumab is tolerable and demonstrated preliminary efficacy for first-line mCRC. Further studies are warranted in PTEN deficiency.

The role of the PI3K pathway in colorectal cancer

In the last decade treatment for colorectal cancer (CRC) has evolved with the addition of contemporary chemotherapy drugs and targeted therapies. Despite this progress, our drug armamentarium is by no means complete and modern molecular biology techniques have led to the identification of a number of 'druggable' targets. One of the most important current drug targets is the phosphatidyl-inositol 3-kinase (PI3K) pathway, which is frequently deregulated in patients with CRC. In vitro and in vivo data strongly support the clinical development of compounds affecting signal transduction via the PI3K pathway. In this review we outline the role of PI3K in the development and progression of CRC and discuss data from current and ongoing clinical trials targeting this pathway. In addition we make suggestions toward the optimization of future research in order to derive the maximum benefit for patients with CRC.

Everolimus in colorectal cancer

INTRODUCTION

There has been a strong preclinical rationale for studying mammalian target of rapamycin (mTOR) inhibitors as single agents or in combination, in multiple malignancies and colorectal cancer in particular.

AREAS COVERED

The authors summarize the complete clinical experience to date of all trials, both published and in abstract form, of everolimus in colorectal cancer. While initial Phase I trials showed promise, further studies have confirmed that single agent everolimus is not active in advanced metastatic colorectal carcinoma with trials showing single agent tolerability, but without significant hints of efficacy in terms of either objective tumor responses or prolonged stable disease. Combination regimens, including combinations with cytotoxic chemotherapy, and inhibitors of VEGF, EGFR and HDAC have been tested specifically in the colorectal setting in Phase I and Phase II clinical trials. The authors discuss the potential reasons for mixed results and suggest future directions for the development of everolimus in colorectal malignancies.

EXPERT OPINION

Studies demonstrate limited clinical activity of everolimus for the treatment of advanced colorectal cancer and have been complicated by increases in toxicity. However, the central role of the PI3K/mTOR pathway in cancer biology suggests that other drug combinations with mTOR inhibition may still merit evaluation.

Novel antineoplastics targeting genetic changes in colorectal cancer

Cytotoxic chemotherapy remains the mainstay of the medical -management of colorectal cancer (CRC). Research over the last two decades has led to a molecular understanding of the oncogenic mechanisms involved in CRC and has contributed to the rational development of antineoplastics that target these mechanisms. During carcinogenesis, genetic changes often occur in molecules that play key functional roles in cancer such as cell proliferation, angiogenesis, apoptosis, cell death and immune-mediated destruction of cancer cells. Here, we review novel antineoplastics that are approved or in development for CRC that target molecules associated with genetic aberrations in CRC. Some of these targeted antineoplastics have proven effective against other solid tumors and hold promise in treating CRC whereas others are now routinely used in combination with cytotoxic agents. This article reviews antineoplastics that target genetic changes in CRC, their antitumor mechanisms, and their stage of development.