Vascular Endothelial Growth Factor plus Epidermal Growth Factor Receptor Dual Targeted Therapy in Metastatic Colorectal Cancer: Synergy or Antagonism?

Evidence-based appraisal of the upfront treatment for unresectable metastatic colorectal cancer patients

Colorectal cancer (CRC) is a significant health problem, with around 1 million new cases and 500000 deaths every year worldwide. Over the last two decades, the use of novel therapies and more complex treatment strategies have contributed to progressively increase the median survival of patients with unresectable advanced CRC up to approximately 30 mo. The availability of additional therapeutic options, however, has created new challenges and generated more complicated treatment algorithms. Moreover, several clinically important points are still in debate in first-line, such as the optimal treatment intensity, the most appropriate maintenance strategy, the preferred biologic to be used upfront in patients with KRAS wild-type CRC, and the need for more detailed information on tumor biology. In this moving landscape, this review analyses why the first-line treatment decision is crucial and how the choice may impact on further treatment lines. In addition, it focuses on results of major phase III randomized trials.

A phase II study of capecitabine, oxaliplatin, and cetuximab with or without bevacizumab as frontline therapy for metastatic colorectal cancer. A Fox Chase extramural research study

OBJECTIVES

Dual inhibition of vascular endothelial growth factor (VEGF) and epidermal growth factor receptor (EGFR) demonstrated initial promise in clinical trials. This phase II study tested the efficacy and safety of capecitabine, oxaliplatin, and cetuximab with or without bevacizumab as first-line treatment for metastatic colorectal cancer patients.

METHODS

Patients were randomized to receive capecitabine 850 mg/m2 PO twice daily for 14 days, oxaliplatin 130 mg/ m2 IV day 1, and cetuximab 400 mg/m2 IV loading dose followed by 250 mg/m2 IV days 1, 8, and 15 with (arm A) or without (Arm B) bevacizumab 7.5 mg/kg IV day 1 every 21 days. Tumor samples were collected and retrospectively analyzed for KRAS mutation status. The primary endpoint was response rate, with time to progression (TTP) and overall survival (OS) as secondary objectives.

RESULTS

Twenty-three patients (12 in arm A, 11 in arm B) were enrolled onto the study. Median follow-up was 25.9 months. Both treatments were well tolerated, with expected higher rates of grade 1/2 hypertension and bleeding in arm A. The overall response rate was 54% (36.4% in arm A and 72.7% in arm B). Median time to progression was 8.7 months in arm A and 14.4 months in arm B. The median survival was 18.0 months in arm A and 42.5 months in arm B. The study was prematurely terminated after other studies reported inferior outcomes with dual antibody therapy.

CONCLUSIONS

Although terminated early, the study supports the detrimental effect of combining VEGF and EGFR inhibition in metastatic colorectal cancer.

Panitumumab in combination with cytotoxic chemotherapy for the treatment of metastatic colorectal carcinoma

The fully human anti-epidermal growth factor receptor (EGFR) monoclonal antibody panitumumab has been shown to improve progression-free survival when administered as a monotherapy for patients with chemotherapy-refractory metastatic colorectal cancer (mCRC) and is approved in this setting. Two large randomized clinical trials have investigated panitumumab in combination with 5-fluorouracil, leucovorin, and oxaliplatin (FOLFOX) as a first-line therapy for mCRC and 5-fluorouracil, leucovorin, and irinotecan (FOLFIRI) as a second-line therapy for mCRC. In these studies, the combination of panitumumab with FOLFOX or FOLFIRI resulted in improved progression-free survival compared with FOLFOX or FOLFIRI alone. Improved tumor response was also observed with the addition of panitumumab to FOLFIRI. As in monotherapy trials, the clinical benefits associated with panitumumab treatment were confined to patients with wild-type KRAS tumors, further showing the validity of KRAS mutational status as a predictive biomarker in mCRC. In addition to KRAS mutational status, a number of other potential predictive biomarkers are currently being investigated in mCRC and may eventually help identify patients who are likely to benefit from treatment with anti-EGFR monoclonal antibodies. Toxicities observed during treatment with panitumumab combined with FOLFOX or FOLFIRI were generally manageable and commonly included skin toxicities and gastrointestinal toxicities. Because it can lead to dose delays, dose reductions, and discontinuation, physicians and patients should carefully manage skin toxicity. Overall, the results of these two studies show that panitumumab improves outcomes when added to FOLFOX or FOLFIRI among patients with mCRC with wild-type KRAS.

Angiogenesis in cancer. Basic mechanisms and therapeutic advances

Etiological concepts on cancer development, malignant growth and tumour propagation have undergone a revolutionary development during recent years: Among other aspects, the discovery of angiogenesis - the growth of new blood vessels from pre-existing vasculature - as a key element in the pathogenesis of malignancy has opened an abundance of biologic insights and subsequent therapeutic options, which have led to improved prognosis in many cancers including those originating from colon, lung, breast and kidney. Thereby, targeting the major pro-angiogenic stimulus vascular endothelial growth factor (VEGF) became the focus for therapeutic interventions. However, the use of VEGF-targeting drugs has been shown to be of limited efficacy, which might lie in the fact that tumor angiogenesis is mediated by a variety of different subcellular systems. This review focuses on the basic mechanisms involved in angiogenesis, which potentially represent novel targets for pharmacological agents in the treatment of malignancies.

Safety and pharmacokinetics of motesanib in combination with panitumumab and gemcitabine-Cisplatin in patients with advanced cancer

Purpose. The aim of this study was to assess the safety and tolerability of motesanib (an orally administered small-molecule antagonist of vascular endothelial growth factor receptors 1, 2, and 3, platelet-derived growth factor receptor, and Kit) when administered in combination with panitumumab, gemcitabine, and cisplatin. Methods. This was an open-label, multicenter phase 1b study in patients with advanced solid tumors with an ECOG performance status ≤1 and for whom a gemcitabine/cisplatin regimen was indicated. Patients received motesanib (0 mg [control], 50 mg once daily [QD], 75 mg QD, 100 mg QD, 125 mg QD, or 75 mg twice daily [BID]) with panitumumab (9 mg/kg), gemcitabine (1250 mg/m(2)) and cisplatin (75 mg/m(2)) in 21-day cycles. The primary endpoint was the incidence of dose-limiting toxicities (DLTs). Results. Forty-one patients were enrolled and received treatment (including 8 control patients). One of eight patients in the 50 mg QD cohort and 5/11 patients in the 125 mg QD cohort experienced DLTs. The maximum tolerated dose was established as 100 mg QD. Among patients who received motesanib (n = 33), 29 had motesanib-related adverse events. Fourteen patients had serious motesanib-related events. Ten patients had motesanib-related venous thromboembolic events and three had motesanib-related arterial thromboembolic events, two of which were considered serious. One patient had a complete response and nine had partial responses as their best objective response. Conclusions. The combination of motesanib, panitumumab, and gemcitabine/cisplatin could not be administered consistently and, at the described doses and schedule, may be intolerable. However, encouraging antitumor activity was noted in some cases.

Panitumumab: a review of its use in metastatic colorectal cancer

Panitumumab (Vectibix(R)) is a recombinant, fully human, IgG2 anti-epidermal growth factor receptor (EGFR) monoclonal antibody. This article reviews the clinical efficacy of intravenous panitumumab in combination with chemotherapy in the first- and second-line treatment of metastatic colorectal cancer and as monotherapy in chemotherapy-refractory metastatic colorectal cancer, as well as summarizing its pharmacological properties and tolerability. Panitumumab is indicated for use in patients with wild-type rather than mutant KRAS tumours. The efficacy of intravenous panitumumab 6 mg/kg administered every 2 weeks was examined in randomized, open-label, multicentre, phase III trials in patients with metastatic colorectal cancer. When administered as first- or second-line treatment in combination with chemotherapy, panitumumab plus chemotherapy prolonged progression-free survival to a significantly greater extent than chemotherapy alone in patients with wild-type KRAS tumours; no significant between-group difference in overall survival was seen in the second-line treatment trial. In patients with mutant KRAS tumours, progression-free survival was significantly shorter with panitumumab plus oxaliplatin-based chemotherapy than with oxaliplatin-based chemotherapy alone in the first-line treatment trial, with no significant difference between patients receiving panitumumab plus irinotecan-based chemotherapy (FOLFIRI) and those receiving FOLFIRI alone in the second-line treatment trial. In chemotherapy-refractory patients with metastatic colorectal cancer, panitumumab monotherapy plus best supportive care prolonged progression-free survival to a significantly greater extent than best supportive care alone in both the overall population and in patients with wild-type KRAS tumours, but not in those with mutant KRAS tumours; there was no significant between-group difference in overall survival. Panitumumab has an acceptable tolerability profile when administered as monotherapy or in combination with chemotherapy. It is associated with the skin-related toxicities characteristic of EGFR inhibitors and appears to have a low risk of immunogenicity. In conclusion, in patients with wild-type KRAS tumours, panitumumab is a useful option in combination with chemotherapy for the first- and second-line treatment of metastatic colorectal cancer or as monotherapy for the treatment of chemotherapy-refractory metastatic colorectal cancer.

Panitumumab: a new frontier of target therapy for the treatment of metastatic colorectal cancer

Panitumumab is a fully human monoclonal IgG(2) antibody targeting the EGF receptor (EGFR). This agent represents a new class of drug owing to its fully human nature, and no need for premedication and loading dose. Panitumumab selectively binds to EGFR, blocking the extracellular domain of the receptor, and has not been associated with the formation of any antibodies directed against it. The drug is indicated as monotherapy for the treatment of patients with EGFR-expressing metastatic colorectal carcinoma with non-mutated (wild-type) KRAS after failure of fluoropyrimidine-, oxaliplatin- and irinotecan-containing chemotherapy regimens. The safety profile is favorable and is generally well tolerated; the most common toxicities are skin rashes and diarrhea. Therefore, panitumumab's hypersensitivity reaction rate is lower when compared with a chimeric monoclonal antibody such as cetuximab. Panitumumab increases the clinician's repertoire of agents to treat metastatic colorectal carcinoma. The available clinical data are the most promising for a single-agent anti-EGFR monoclonal antibody in this disease at the present time. These new data open different clinical scenarios in metastatic colorectal carcinoma patients and encourage clinicians and basic researchers to investigate new therapeutic approaches for this patient subset.