The rationale for mTOR inhibition in epithelial ovarian cancer

The AKT/mTOR signaling pathway is frequently overexpressed in human epithelial ovarian cancer and an attractive target for therapy. In vivo mouse models were confirmative for in vitro findings, where the administration of mTOR inhibitors in ovarian cancer xenografts showed antitumoral as well as antiangiogenic effects. Phase I – II trials are now ongoing with mTOR inhibitors in ovarian cancer patients, some in combination with conventional cytotoxic agents. If further development of mTOR inhibition in ovarian cancer is pursued, studying combinations of mTOR inhibitors with other new targeted therapies would be of interest. mTOR inhibitors in the adjuvant setting could have potential, since, for the moment, there is no standard maintenance therapy in ovarian cancer. A crucial challenge will be to identify strong predictive biomarkers. This review highlights the rationale for the use of mTOR inhibitors in ovarian cancer and summarizes the available preclinical findings.     

Temsirolimus

肾细胞癌占全部肾肿瘤的85%.美国癌症协会估计2007年将有新诊断肾癌患者51190例,其中40%在诊断时已经是晚期或进展期.美国FDA已于2007年5月批准rorisel(Temsirolimus)上市,用于治疗晚期肾细胞癌(RCC).该药是惟一上市的特异性抑制mTOR激酶的药物,是第一个治疗肾癌的靶向治疗药物,也是目前第一剂用于治疗癌症的注射剂.     

Dual EGFR and mTOR targeting in squamous cell carcinoma models, and development of early markers of efficacy

The epidermal growth factor receptor (EGFR) is a validated target in squamous cell carcinoma (SCC) of the head and neck. Most patients, however, do not respond or develop resistance to this agent. Mammalian target of rapamycin (mTOR) is involved in the pathogenesis of SCC of the head and neck (SCCHN). This study aimed to determine if targeting mTOR in combination with EGFR is effective in SCC, and to develop early pharmacodynamic markers of efficacy. Two SCC cell lines, one resistant (HEP2) and one of intermediate susceptibility (Detroit 562) to EGFR inhibitors, were xenografted in vivo and treated with an mTOR inhibitor (temsirolimus), an EGFR inhibitor (erlotinib) or a combination of both. Temsirolimus exerted superior growth arrest in both cell lines than erlotinib. The combined treatment resulted in synergistic antitumor effects in the Detroit 562 cell line. Immunohistochemical assessment of pharmacodynamic effects in fine-needle aspiration (FNA) biopsies early after treatment using phospho MAPK, Phospho-P70 and Ki67 as end points demonstrated pathway abrogation in the Detroit 562 tumours treated with the combination, the only group where regressions were seen. In conclusion, an mTOR inhibitor showed antitumor activity in EGFR-resistant SCC cell lines. Marked antitumor effects were associated with dual pathway inhibition, which were detected by early FNA biopsies.     

Temsirolimus, an mTOR inhibitor, enhances anti-tumour effects of heat shock protein cancer vaccines

Background:

Temsirolimus is a mammalian target of rapamycin (mTOR) inhibitor and rapamycin analogue that is approved for treating advanced renal cell carcinoma (RCC). It is being actively evaluated in clinical trials for melanoma. The mTOR inhibitors are also immunosuppressants and are used clinically to prevent rejection following solid-organ transplant. Novel immunotherapies are being actively developed for immunoresponsive tumours, such as RCC and melanoma.

Methods:

Immune-modulating effects of temsirolimus were characterised when used in combination with cancer vaccines targeting RCC (RENCA) and melanoma (B16). Cancer vaccines were recombinant tumour-specific proteins (CA9 or gp100), and recombinant heat shock protein (HSP; hsp110) served as the immune adjuvant.

Results:

In murine models, temsirolimus enhanced the anti-tumour activity of cancer vaccines used to treat established RENCA and B16 tumours. A tumour prevention model established that the enhanced anti-tumour activity associated with temsirolimus was immune mediated. In mice treated with an HSP-based anti-tumour vaccine, temsirolimus-treated CD8 T cells had greater interferon-γ and cytotoxic T-cell responses when compared with mice treated with vaccine alone. Temsirolimus also enhanced the formation of CD8 memory cells following administration of HSP-based cancer vaccine.

Conclusion:

These results provide a rationale for combining mTOR inhibitor with immunotherapy when treating immunoresponsive tumours.     

A randomised phase II trial of selumetinib vs selumetinib plus temsirolimus for soft-tissue sarcomas

Background:

The MEK inhibitor, selumetinib, suppresses soft-tissue sarcoma (STS) cell proliferation in vitro. Mammalian target of rapamycin inhibitors possess modest activity against STS; however, resistance develops via MAPK pathway feedback activation. The combination of selumetinib and temsirolimus synergistically inhibits STS cell line growth. Therefore, a randomized phase II trial of selumetinib vs selumetinib plus temsirolimus was conducted.

Methods:

Seventy-one adults with advanced STS who received ⩽2 prior chemotherapeutics were randomized to selumetinib 75 mg p.o. bid and allowed to crossover upon progression, or to selumetinib 50 mg p.o. bid plus temsirolimus 20 mg i.v. weekly, with primary endpoint of progression-free survival (PFS).

Results:

There was no difference in PFS between the two arms for the overall cohort (median 1.9 vs 2.1 months); an improved median PFS was observed in the combination arm (N=11) over single agent (N=10) in the prespecified leiomyosarcoma stratum (median 3.7 vs 1.8 months; P=0.01). Four-month PFS rate was 50% (95% confidence interval 0.19–0.81) with the combination vs 0% with selumetinib alone in the leiomyosarcoma cohort. Most common grade 3/4 adverse events with the combination were mucositis (29%), lymphopenia (26%), neutropenia and anaemia (20% each).

Conclusions:

While single-agent selumetinib has no significant activity in STS, the combination may be active for leiomyosarcomas.     

A dual‐specific anti‐IGF‐1/IGF‐2 human monoclonal antibody alone and in combination with temsirolimus for therapy of neuroblastoma

The insulin‐like growth factors (IGFs), IGF‐1 and IGF‐2, have been implicated in the growth, survival and metastasis of a broad range of malignancies including pediatric tumors. They bind to the IGF receptor type 1 (IGF‐1R) and the insulin receptor (IR) which are overexpressed in many types of solid malignancies. Activation of the IR by IGF‐2 results in increased survival of tumor cells. We have previously identified a novel human monoclonal antibody, m708.5, which binds with high (pM) affinity to both human IGF‐1 and IGF‐2, and potently inhibits phosphorylation of the IGF‐1R and the IR in tumor cells. m708.5 exhibited strong antitumor activity as a single agent against most cell lines derived from neuroblastoma, Ewing family of tumor, rhabdomyosarcoma and osteosarcoma. When tested in neuroblastoma cell lines, it showed strong synergy with temsirolimus and synergy with chemotherapeutic agents in vitro. In xenograft models, the combination of m708.5 and temsirolimus significantly inhibited neuroblastoma growth and prolonged mouse survival. Taken together, these results support the clinical development of m708.5 for pediatric solid tumors with potential for synergy with chemotherapy and mTOR inhibitors.     

Inhibitors of the mammalian target of rapamycin

The mammalian target of rapamycin (mTOR) is a downstream protein kinase of the phosphatidylinositol 3′-kinase–Akt signalling pathway. As a result of its position within this pathway and its central role in controlling cellular growth, mTOR is viewed as an important target for anticancer therapeutics development. Currently, the mTOR inhibitor rapamycin (sirolimus, Wyeth) and its derivatives temsirolimus (CCI-779, Wyeth), everolimus (RAD--001, Novartis Pharma AG) and AP-23573 (Ariad Pharmaceuticals) are being evaluated in cancer clinical trials. Preclinical studies suggest that sensitivity to mTOR inhibition may correlate with aberrant activation of the phosphatidylinositol 3′-kinase pathway and/or with aberrant expression of cell-cycle regulatory or antiapoptotic proteins. Clinical trial results show that mTOR inhibitors are generally well tolerated and may induce prolonged stable disease and even tumour regressions in a subset of patients. Questions remain regarding optimal dose, schedule, patient selection and combinationstrategies for this novel class of agents.     

Optimizing treatment for patients with metastatic renal cell carcinoma in the central and Eastern European region

Introduction: Belarus, Bulgaria, Croatia, Czech Republic, Estonia, Hungary, Latvia, Lithuania, Poland, Republic of Moldova, Romania, Russian Federation, Serbia, Slovakia, Slovenia and the Ukraine represent a collection of Central and Eastern European (CEE) countries in which the epidemiology and treatment of cancer varies greatly between and within countries. Current challenges include non-adherence to current treatment guidelines, restrictions in access and reimbursement for new therapies, and a lack of basic oncology programs. Metastatic renal cell carcinoma (mRCC) is a malignancy with historically poor prognosis. In CEE countries, the incidence and mortality rates of mRCC are among the highest in the world. Fortunately, mRCC represents a cancer for which a number of new targeted therapies have recently demonstrated benefit, resulting in new evidence-based treatment guidelines. Incorporating these mRCC treatment recommendations into the routine care of patients with mRCC in CEE countries would represent a major step forward for cancer care in this region.

Areas covered: This review discusses the unique challenges faced by the aforementioned Eastern European countries in the treatment of metastatic renal cell cancer, in an attempt to assist health-care providers in providing the best care possible for their European patients.

Expert opinion: Despite a wealth of clinical trial data supporting the use of targeted therapies for first-line treatment of mRCC, cytokine-based immunotherapy is still used in some of these European countries. With implementation and adherence to existing guidelines, treatment can be clinically and economically optimized in patients with mRCC from this region.