A phase 2 study with a daily regimen of the oral mTOR inhibitor RAD001 (everolimus) in patients with metastatic clear cell renal cell cancer

New treatment approaches in renal cell carcinoma

Metastatic renal cell carcinoma (RCC) is notoriously chemoresistant; up until recently, immunotherapy (in particular interferon-alpha) has represented the treatment of choice. The understanding of the biology of RCC has resulted in the development of targeted therapies. In particular, multikinase inhibitors (sunitinib, sorafenib, axitinib, pazopanib), antivascular endothelial growth factor agents (bevacizumab), and mammalian target of rapamycin inhibitors (temsirolimus, everolimus) now have a role in the approach to different subsets of RCC. Sunitinib is indicated for the first-line therapy of metastatic RCC as a consequence of a positive phase III trial versus interferon-alpha; sorafenib is now registered for the second-line treatment of RCC, which was earlier treated with cytokine as a consequence of a positive phase III trial versus placebo. Bevacizumab is also indicated in the first-line treatment of metastatic RCC given in combination with interferon-alpha as a consequence of two positive phase III trials. Temsirolimus, unlike the other agents, has also shown activity in poor-prognosis patients, and is now the treatment of choice in previously untreated poor-prognosis RCC as a single agent. Everolimus can be considered as the best therapeutic option in patients with RCC pretreated with targeted agents as a consequence of a positive phase III study versus best supportive care. Markers for appropriate treatment selection, combined use of targeted agents, treatment of special histologies, and adjuvant and neoadjuvant setting represent important special issues to be dealt with in future studies.

Targeting tumorigenesis: development and use of mTOR inhibitors in cancer therapy

The mammalian target of rapamycin (mTOR) is an intracellular serine/threonine protein kinase positioned at a central point in a variety of cellular signaling cascades. The established involvement of mTOR activity in the cellular processes that contribute to the development and progression of cancer has identified mTOR as a major link in tumorigenesis. Consequently, inhibitors of mTOR, including temsirolimus, everolimus, and ridaforolimus (formerly deforolimus) have been developed and assessed for their safety and efficacy in patients with cancer. Temsirolimus is an intravenously administered agent approved by the US Food and Drug Administration (FDA) and the European Medicines Agency (EMEA) for the treatment of advanced renal cell carcinoma (RCC). Everolimus is an oral agent that has recently obtained US FDA and EMEA approval for the treatment of advanced RCC after failure of treatment with sunitinib or sorafenib. Ridaforolimus is not yet approved for any indication. The use of mTOR inhibitors, either alone or in combination with other anticancer agents, has the potential to provide anticancer activity in numerous tumor types. Cancer types in which these agents are under evaluation include neuroendocrine tumors, breast cancer, leukemia, lymphoma, hepatocellular carcinoma, gastric cancer, pancreatic cancer, sarcoma, endometrial cancer, and non-small-cell lung cancer. The results of ongoing clinical trials with mTOR inhibitors, as single agents and in combination regimens, will better define their activity in cancer.

Effective treatment of advanced colorectal cancer by rapamycin and 5-FU/oxaliplatin monitored by TIMP-1

AIM

The mTOR-inhibitor rapamycin has shown antitumor activity in various tumors. Bedside observations have suggested that rapamycin may be effective as a treatment for colorectal carcinomatosis.

METHODS

We established an orthotopic syngenic model by transplanting CT26 peritoneal tumors in Balb/C mice and an orthotopic xenograft model by transplanting SW620 peritoneal tumors in nu/nu mice. Expression levels of tissue inhibitor of matrix-metalloproteinases 1 (TIMP-1) in the tumor and serum was determined by enzyme-linked immunosorbent assay.

RESULTS

Rapamycin significantly suppressed growth of syngenic and xenografted peritoneal tumors. The effect was similar with intraperitoneal or oral rapamycin administration. Tumor suppression was further enhanced when rapamycin was combined with 5-fluorouracil and/or oxaliplatin. The combination treatment showed no acute toxicity. TIMP-1 serum levels correlated well (CC = 0.75; P < 0.01) with rapamycin treatment.

CONCLUSIONS

Rapamycin suppressed advanced stage colorectal cancer, even with oral administration. Combining rapamycin with current chemotherapy regimens significantly increased antitumor efficacy without apparent toxicity. The treatment efficacy correlated with serum TIMP-1 levels, suggesting its potential as a surrogate marker in future clinical trials.

Enhancing mTOR-targeted cancer therapy

BACKGROUND

The mammalian target of rapamycin (mTOR) has emerged as an attractive cancer therapeutic target. Accordingly, several mTOR inhibitors (e.g., rapamycin and its analogs; rapalogs) are currently being tested in many cancer clinical trials. Despite the encouraging results showing that some rapalogs improved overall survival among patients with metastatic renal-cell carcinoma, the single-agent activity of rapalogs in most other tumor-types has been modest, at best.

OBJECTIVE

To review the current understanding of the mTOR axis and discuss potential strategies to enhance mTOR-targeted cancer therapy.

METHODS

Preclinical and clinical data in peer-reviewed reports on the novel biological and therapeutic parts of the mTOR axis are discussed.

CONCLUSION

The mTOR axis involves complex regulatory networks. Inhibition of the mTOR axis with a rapalog induces feedback activation of several survival signaling pathways such as Akt activation, which, in turn, blunt rapalogs' anticancer efficacy. Thus, blockage or prevention of the activation of these survival signaling pathways may enhance mTOR-targeted cancer therapy.