151 AMG 706 first in human, open-label, dose-finding study evaluating the safety and pharmacokinetics (PK) in subjects with advanced solid tumors

Safety, pharmacokinetics, and efficacy of AMG 706, an oral multikinase inhibitor, in patients with advanced solid tumors

PURPOSE

AMG 706 is an investigational, orally bioavailable inhibitor of vascular endothelial growth factor receptors 1, 2, and 3, platelet-derived growth factor receptor, and stem-cell factor receptor. This phase I, dose-finding study evaluated the safety, pharmacokinetics, and pharmacodynamics of AMG 706 in patients with refractory advanced solid tumors.

PATIENTS AND METHODS

AMG 706 was administered at escalating doses of 50 to 175 mg once daily or 25 mg bid for the first 21 days of a 28-day cycle. The 125-mg once-daily dose was also administered continuously. The maximum-tolerated dose (MTD), safety, pharmacokinetics, tumor response, and serum levels of proangiogenic markers were determined.

RESULTS

Seventy-one patients received AMG 706. The MTD was 125 mg once daily administered continuously. The most frequent adverse events were fatigue (55%), diarrhea (51%), nausea (44%), and hypertension (42%). Plasma AMG 706 concentrations increased in a dose-proportional manner with no accumulation after multiple doses. Five patients (7%) had a partial response, 35 patients (49%) had stable disease (at least through day 50), and 31 patients (44%) had progressive disease. Changes in tumor size correlated significantly with an increase in placental growth factor (P = .003) and a decrease in soluble kinase domain receptor (P = .001).

CONCLUSION

In this study of patients with advanced refractory solid tumors, AMG 706 was well tolerated and displayed favorable pharmacokinetics and evidence of antitumor activity. Additional studies of AMG 706 as monotherapy and in combination with various agents are ongoing.

Therapeutic options to target angiogenesis in human malignancies

The critical role of angiogenesis in tumour growth and metastasis is now well established in the literature. Growing tumours stimulate neovascularisation through the secretion of pro-angiogenic growth factors, in particular, basic fibroblast growth factor and VEGF. Several lines of evidence have implicated VEGF in tumourigenesis, and understanding the role of VEGF in tumour angiogenesis has facilitated the development of novel targeting agents that specifically interfere with angiogenesis. Different approaches to disrupting tumour-induced angiogenesis encompass tyrosine kinase inhibitor, monoclonal antibodies, small-molecule inhibitors and transcription inhibitors. However, monoclonal antibody and tyrosine kinase inhibitors are the most advanced drug classes currently being investigated in clinical trials. So far, three anti-VEGF inhibitors, bevacizumab, sunitinib and sorafenib, have been approved for the treatment of solid human malignancies including colorectal cancer, gastrointestinal stromal tumours and renal cell carcinoma. Other antiangiogenic drugs are being investigated in various types of cancer. This review summarises the current literature on the use of these agents to interfere with VEGF, VEGF receptor, the matrix breakdown or other mechanisms involved in angiogenesis.

Emerging antiangiogenic agents in lung cancer

The success of the anti-vascular endothelial growth factor (VEGF) antibody bevacizumab in numerous tumor types including non-small-cell lung cancer (NSCLC) has spurred the development of additional novel antiangiogenic agents with distinct mechanisms of action. These include the small-molecule receptor tyrosine kinase (TK) inhibitors ZD6474, sorafenib, sunitinib malate, and AG-013736, all of which inhibit VEGF receptor TK activity. Because of the structural similarity of the different receptor TKs, these receptor TK inhibitors inhibit multiple receptors in addition to VEGF receptor. Vascular endothelial growth factor Trap, a novel, high-affinity molecule with specificity to the VEGF molecule, was generated as a fusion molecule of the VEGF receptor extracellular domain and the Fc portion of immunoglobulin (Ig) G1. Data from phase I/II trials have indicated the clinical feasibility of these agents, which are currently being investigated in phase II/III trials.

Colorectal cancer and antiangiogenic therapy: What can be expected in clinical practice?

Angiogenesis is a strongly regulated process, which is dependent upon a complex interplay between inhibitory and stimulatory angiogenic factors. It is essential for tumor growth and metastasis: increased angiogenesis is correlated with poor prognosis in cancer patients. Many novel compounds that potently inhibit formation of neoplastic blood vessels have been recently developed. Major categories of angiogenesis antagonists include protease inhibitors, direct inhibitors of endothelial cell proliferation and migration, angiogenic growth factor suppressors, inhibitors of endothelial-specific integrin/survival signalling, copper chelators, and inhibitors with other specific mechanisms. There is increasing interest in developing angio-suppressive agents for colorectal cancer treatment. Some 20 direct and indirect antiangiogenesis drugs are currently being evaluated in clinical trials in colorectal cancer (CRC). Promising results have been reported. These include an increase in overall survival and reduction in the risk of death (Bevacizumab), reversal of cellular resistance (Cetuximab) and activity as second-line therapy in patients who have exhausted other available treatment options (Cetuximab, ABX-EGF, PTK-787, Gefitinib, Erlotinib). This review will outline the mechanisms of action of the principal antiangiogenic drugs, summarize the available data on the use of these new drugs in colorectal cancer, discuss their impact in clinical practice and offer a glimpse into how antiangiogenetic therapy will be integrated into the future care of patients with gastrointestinal cancers.