A role for maintenance therapy in managing sarcoma

Despite the use of recommended chemotherapy regimens, patients with metastatic sarcomas have a poor prognosis. To date, the median overall survival for metastatic disease remains less than 18 months. First-line treatment of most metastatic sarcomas consists of chemotherapy with or without surgical excision of residual disease, followed by "watchful waiting" until disease progression or recurrence. According to the current treatment paradigm, recommended by United States and European clinical guidelines, chemotherapy is administered for a fixed number of cycles, and then a watchful waiting approach is taken once a best response is achieved. Single-agent doxorubicin remains the standard for treatment of most soft-tissue sarcomas (STS), as combination and dose-intense regimens have largely failed to improve survival. Combination chemotherapy is the standard treatment approach for osteosarcoma and Ewing's sarcoma, but outcomes are poor for patients with recurrent disease. In order to improve outcomes (in particular, progression-free survival [PFS] and overall survival [OS]), strategies shown to be effective in other solid malignancies, such as maintenance therapy and long-term treatment with targeted therapy, are being investigated in patients with advanced sarcomas. One potential promising approach is the use of mammalian target of rapamycin (mTOR) inhibitors for maintenance therapy. One such mTOR inhibitor, ridaforolimus (AP23573, MK-8669), is currently being evaluated in patients with advanced bone and STS in the ongoing Sarcoma mUlti-Center Clinical Evaluation of the Efficacy of riDaforolimus (SUCCEED) trial.

Strong expression of IGF1R in pediatric gastrointestinal stromal tumors without IGF1R genomic amplification

Wildtype (WT) gastrointestinal stromal tumors (GISTs), lacking mutations in KIT or PDGFRA, represent 85% of GISTs in pediatric patients. Treatment options for pediatric WT GIST are limited. Recently, expression profiling of a limited number of pediatric and adult WT GISTs and more in depth study of a single pediatric WT GIST implicated the insulin-like growth factor 1 receptor (IGF1R) as a potential therapeutic target in pediatric WT GIST. We performed immunoblotting, SNP and FISH studies to determine the extent of expression, biochemical activation and genomic amplification of IGF1R in a larger number of pediatric WT GISTs. Pediatric WT GISTs expressed IGF1R strongly, whereas typical adult KIT mutant GISTs did not. IGF1R gene amplification was not detected in pediatric WT GISTs, and some KIT-mutant GISTs had IGF1R gene deletion due to monosomy 15. Despite the absence of apparent genomic activation mechanisms accounting for overexpression, clinical study of IGF1R-directed therapies in pediatric WT GIST is warranted.

Insulin-like growth factor-I regulation of immune function: a potential therapeutic target in autoimmune diseases?

This topically limited review explores the relationship between the immune system and insulin-like growth factors (IGF-I and IGF-II) and the proteins through which they act, including IGF-I receptor (IGF-IR) and the IGF-I binding proteins. The IGF/IGF-IR pathway plays important and diverse roles in tissue development and function. It regulates cell cycle progression, apoptosis, and the translation of proteins. Many of the consequences ascribed to IGF-IR activation result from its association with several accessory proteins that are either identical or closely related to those involved in insulin receptor signaling. Relatively recent awareness that IGF-I and IGF-IR regulate immune function has cast this pathway in an unexpected light; it may represent an important switch governing the quality and amplitude of immune responses. IGF-I/IGF-IR signaling may also participate in the pathogenesis of autoimmune diseases, although its relationship with these processes seems complex and relatively unexplored. On the one hand, IGF-I seems to protect experimental animals from developing insulin-deficient diabetes mellitus. In contrast, activating antibodies directed at IGF-IR have been detected in patients with Graves' disease, where the receptor is overexpressed by multiple cell types. The frequency of IGF-IR+ B and T cells is substantially increased in patients with that disease. Potential involvement of IGF-I and IGF-IR in the pathogenesis of autoimmune diseases suggests that this pathway might constitute an attractive therapeutic target. IGF-IR has been targeted in efforts directed toward drug development for cancer, employing both small-molecule and monoclonal antibody approaches. These have been generally well-tolerated. Recognizing the broader role of IGF-IR in regulating both normal and pathological immune responses may offer important opportunities for therapeutic intervention in several allied diseases that have proven particularly difficult to treat.

A phase I study of weekly R1507, a human monoclonal antibody insulin-like growth factor-I receptor antagonist, in patients with advanced solid tumors

PURPOSE

A phase I study was conducted to evaluate the pharmacokinetics, pharmacodynamics, safety, and tolerability of R1507-a fully human IgG1 type monoclonal antibody directed against the human insulin-like growth factor-I receptor.

EXPERIMENTAL DESIGN

Patients with advanced solid tumors were assigned to receive i.v. R1507 weekly (qW), starting with 1 mg/kg. Subsequent cohorts were dosed at 3 and then 9 mg/kg. An additional 12 patients received 9 mg/kg R1507 qW. Patients remained on the study until the development of a dose-limiting toxicity or progressive disease.

RESULTS

In total, 37 patients were treated with R1507 qW. No dose-limiting toxicities were identified and the maximum tolerated dose was not reached. The pharmacokinetics of R1507 were characterized by a slow clearance and limited volume of distribution, with an estimated elimination half-life justifying weekly administration. Serum IGF-I ligand levels increased proportionally to dose during the first 72 hours in all cohorts. R1507 was well tolerated. Two patients diagnosed with Ewing's sarcoma had partial responses of 11.5 and >26 months (ongoing at time of submission); 13 patients had stable disease; and 16 had progressive disease as best response by the Response Evaluation Criteria in Solid Tumors.

CONCLUSION

R1507 is well tolerated and shows antitumor activity in patients with solid neoplasms, in particular Ewing's sarcoma. The recommended dose for the weekly schedule is 9 mg/kg qW.

Angiogenesis and vascular targeting in Ewing sarcoma: a review of preclinical and clinical data

Ewing sarcoma is the second most common type of bone cancer in children and young adults. In recent years, the mechanisms by which these tumors develop and maintain their vascular supply have been elucidated. Additional work has demonstrated that inhibition of angiogenic pathways or disruption of established vasculature can attenuate the growth of Ewing sarcoma mouse xenografts. Early clinical data suggest that these results also may extend to patients with Ewing sarcoma who are treated with antiangiogenic or antivascular therapies. For the current review, the authors summarized the available data supporting this approach.

Phase II study of sorafenib in patients with metastatic or recurrent sarcomas

PURPOSE Since activity of sorafenib was observed in sarcoma patients in a phase I study, we performed a multicenter phase II study of daily oral sorafenib in patients with recurrent or metastatic sarcoma. PATIENTS AND METHODS We employed a multiarm study design, each representing a sarcoma subtype with its own Simon optimal two-stage design. In each arm, 12 patients who received 0 to 1 prior lines of therapy were treated (0 to 3 for angiosarcoma and malignant peripheral-nerve sheath tumor). If at least one Response Evaluation Criteria in Solid Tumors (RECIST) was observed, 25 further patients with that sarcoma subtype were accrued. Results Between October 2005 and November 2007, 145 patients were treated; 144 were eligible for toxicity and 122 for response. Median age was 55 years; female-male ratio was 1.8:1. The median number of cycles was 3. Five of 37 patients with angiosarcoma had a partial response (response rate, 14%). This was the only arm to meet the RECIST response rate primary end point. Median progression-free survival was 3.2 months; median overall survival was 14.3 months. Adverse events (typically dermatological) necessitated dose reduction for 61% of patients. Statistical modeling in this limited patient cohort indicated sorafenib toxicity was correlated inversely to patient height. There was no correlation between phosphorylated extracellular signal regulated kinase expression and response in six patients with angiosarcoma with paired pre- and post-therapy biopsies. CONCLUSION As a single agent, sorafenib has activity against angiosarcoma and minimal activity against other sarcomas. Further evaluation of sorafenib in these and possibly other sarcoma subtypes appears warranted, presumably in combination with cytotoxic or kinase-specific agents.

Antitumor activity of GSK1904529A, a small-molecule inhibitor of the insulin-like growth factor-I receptor tyrosine kinase

PURPOSE

Dysregulation of the insulin-like growth factor-I receptor (IGF-IR) signaling pathway has been implicated in the development of many types of tumors, including prostate, colon, breast, pancreatic, ovarian, and sarcomas. Agents that inhibit IGF-IR activity may be useful in treatment of patients with various cancers.

EXPERIMENTAL DESIGN

Kinase assays were used to identify a selective small-molecule inhibitor of IGF-IR activity. The effects of this compound on IGF-IR signaling, cell proliferation, and the cell cycle were determined using a panel of cell lines. Antitumor activity was evaluated in human tumor xenografts growing in athymic mice. Inhibition of IGF-IR and the closely related insulin receptor (IR) was measured in vivo, and the effect on glucose metabolism was evaluated.

RESULTS

GSK1904529A selectively inhibits IGF-IR and IR with IC(50)s of 27 and 25 nmol/L, respectively. GSK1904529A blocks receptor autophosphorylation and downstream signaling, leading to cell cycle arrest. It inhibits the proliferation of cell lines derived from solid and hematologic malignancies, with multiple myeloma and Ewing's sarcoma cell lines being most sensitive. Oral administration of GSK1904529A decreases the growth of human tumor xenografts in mice, consistent with a reduction of IGF-IR phosphorylation in tumors. Despite the potent inhibitory activity of GSK1904529A on IR in vitro and in vivo, minimal effects on blood glucose levels are observed in animals at doses that show significant antitumor activity.

CONCLUSION

GSK1904529A is a promising candidate for therapeutic use in IGF-IR-dependent tumors.

The insulin-like growth factor system and sarcomas

Sarcomas are a diverse group of malignant mesenchymal tumours arising from bone and soft tissues. The identification of critical cellular signalling pathways in sarcomas is an important issue for the development of new targeted therapies. This review highlights the experimental and clinical evidence supporting the role of the insulin-like growth factor (IGF) signalling system in the cellular transformation and progression of several types of sarcoma, including rhabdomyosarcoma, synovial sarcoma, leiomyosarcoma, Ewing's sarcoma and osteosarcoma. Preclinical data suggest that the IGF system could be a promising target for therapy in these sarcomas. Currently, therapies interrupting IGF signalling have been or are being developed. In recent phase 1 clinical studies with humanized monoclonal antibodies directed against IGF receptor type 1 (IGF-1R), objective tumour responses were observed in several patients with Ewing's sarcoma, encouraging further clinical testing in Ewing's sarcoma and other sarcoma (sub)types. Moreover, the occasional occurrence of paraneoplastic hypoglycaemia as a result of the secretion of incompletely processed forms of pro-IGF-II by sarcomas is discussed.

Clinical cancer advances 2008: major research advances in cancer treatment, prevention, and screening--a report from the American Society of Clinical Oncology

A message from ASCO'S president: Nearly 40 years ago, President Richard Nixon signed the National Cancer Act, mobilizing the country's resources to make the "conquest of cancer a national crusade." That declaration led to a major investment in cancer research that has significantly improved cancer prevention, treatment, and survival. As a result, two thirds of people diagnosed with cancer today will live at least 5 years after diagnosis, compared with just half in the 1970s. In addition, there are now more than 12 million cancer survivors in the United States--up from 3 million in 1971. Scientifically, we have never been in a better position to advance cancer treatment. Basic scientific research, fueled in recent years by the tools of molecular biology, has generated unprecedented knowledge of cancer development. We now understand many of the cellular pathways that can lead to cancer. We have learned how to develop drugs that block those pathways; increasingly, we know how to personalize therapy to the unique genetics of the tumor and the patient. Yet in 2008, 1.4 million people in the United States will still be diagnosed with cancer, and more than half a million will die as a result of the disease. Some cancers remain stubbornly resistant to treatment, whereas others cannot be detected until they are in their advanced, less curable stages. Biologically, the cancer cell is notoriously wily; each time we throw an obstacle in its path, it finds an alternate route that must then be blocked. To translate our growing basic science knowledge into better treatments for patients, a new national commitment to cancer research is urgently needed. However, funding for cancer research has stagnated. The budgets of the National Institutes of Health and the National Cancer Institute have failed to keep pace with inflation, declining up to 13% in real terms since 2004. Tighter budgets reduce incentives to support high-risk research that could have the largest payoffs. The most significant clinical research is conducted increasingly overseas. In addition, talented young physicians in the United States, seeing less opportunity in the field of oncology, are choosing other specialties instead. Although greater investment in research is critical, the need for new therapies is only part of the challenge. Far too many people in the United States lack access to the treatments that already exist, leading to unnecessary suffering and death. Uninsured cancer patients are significantly more likely to die than those with insurance, racial disparities in cancer incidence and mortality remain stark, and even insured patients struggle to keep up with the rapidly rising cost of cancer therapies. As this annual American Society of Clinical Oncology report of the major cancer research advances during the last year demonstrates, we are making important progress against cancer. But sound public policies are essential to accelerate that progress. In 2009, we have an opportunity to reinvest in cancer research, and to support policies that will help ensure that every individual in the United States receives potentially life-saving cancer prevention, early detection, and treatment. Sincerely, Richard L. Schilsky, MD President American Society of Clinical Oncology.

The type 1 insulin-like growth factor receptor pathway

Research conducted over the past two decades has shown the importance of the type 1 insulin-like growth factor receptor (IGF1R) in tumorigenesis, metastasis, and resistance to existing forms of cancer therapy. The IGF1R itself has only recently been accepted as a credible treatment target, however, perhaps reflecting the potential problems for drug design posed by normal tissue IGF1R expression, and close homology with the insulin receptor. Currently approximately 12 anti-IGF1R therapeutics are undergoing clinical evaluation, including blocking antibodies and tyrosine kinase inhibitors. This review will summarize the principal signaling pathways activated by IGF1R and the preclinical data that validated this receptor as a treatment target. We will review clinical progress in the testing of IGF1R inhibitory drug candidates, the relative benefits and potential toxicities of coinhibition of the insulin receptor, and the rationale for combining IGF1R blockade with other cancer treatments. An understanding of IGF1R signaling is important because it will guide the incorporation of appropriate molecular markers into clinical trial design. This will be key to the identification of patients most likely to benefit, and so will influence the ability of IGF1R inhibition to make the transition from experimental intervention to clinical therapy.

Insulin and insulin-like growth factor signalling in neoplasia

Insulin and insulin-like growth factors (IGFs) are well known as key regulators of energy metabolism and growth. There is now considerable evidence that these hormones and the signal transduction networks they regulate have important roles in neoplasia. Epidermiological, clinical and laboratory research methods are being used to investigate novel cancer prevention and treatment strategies related to insulin and IGF signalling. Pharmacological strategies under study include the use of novel receptor-specific antibodies, receptor kinase inhibitors and AMP-activated protein kinase activators such as metformin. There is evidence that insulin and IGF signalling may also be relevant to dietary and lifestyle factors that influence cancer risk and cancer prognosis. Recent results are encouraging and have justified the expansion of many translational research programmes.

IGF-1 receptor inhibitors in clinical trials--early lessons

The insulin-like growth factor pathway plays a major role in cancer cell proliferation, survival and resistance to anti-cancer therapies in many human malignancies, including breast cancer. As a key signaling component of IGF system, the IGF-1 receptor is the target of several investigational agents in clinical and pre-clinical development. This review will focus on the rationale for targeting the IGF-1 receptor and other components of the IGF-1 system. In addition, we will examine the role of IGF-1 signaling in resistance to clinically important breast cancer therapies, including cytotoxic chemotherapy, hormonal therapy and erbB targeted agents. We will also review the completed and ongoing clinical investigations with IGF-1 receptors inhibitors to date and the utility of these early data in designing future breast cancer studies with IGF-1 signaling inhibition strategies.

Insulin, insulin-like growth factors and neoplasia

Over the past decade, dozens of epidemiological studies and laboratory experiments have provided evidence for relationships between insulin-like growth factor (IGF) physiology and neoplasia. Population studies provide evidence for a modestly increased risk of a subsequent cancer diagnosis in subjects with IGF-I levels at the high end of the broad normal range, as compared to those at the low end of the normal range. At the cellular level, IGF-I receptor signalling has been shown to play an important role in facilitating the transforming action of a variety of oncogenes. Reducing receptor function with anti-receptor antibodies or specific tyrosine kinase inhibitors reduces the proliferation of many cancers in vitro and in vivo. At present, clinical relevance of the relationship between circulating IGF-I level and cancer risk is limited, but in terms of experimental therapeutics, many clinical trials have been initiated to investigate the possibility that the paradigm of hormonal treatment of cancer may be extended from targeting gonadal steroids to targeting the growth hormone-IGF-I axis.