Understanding the mechanisms of action of antiangiogenic agents in metastatic colorectal cancer: a clinician's perspective

The potential of monoclonal antibodies for colorectal cancer therapy

Conventional chemotherapy has significant limitations for colorectal cancer (CRC) treatment, especially those who have developed metastatic recurrence CRC. A growing number of studies have investigated the potential use of monoclonal antibodies (mAbs) for CRC therapy. mAbs showing clinical benefits for CRC, making the treatment more selective with lower side effects without significant immunogenicity. In addition, recent advancements in antibody engineering strategies and the development of bifunctional or even trifunctional drugs have helped to overcome heterogeneity as the main challenge in cancer treatment. The current review discusses advances in applying mAbs for CRC therapy alone, combined, or with small molecules.

Overall Survival and Progression-Free Survival Comparison of Bevacizumab Plus Chemotherapy Combination Regiment versus Chemotherapy Only Regiment in Previously Untreated Metastatic Colorectal Cancer: Systematic Review and Meta-Analysis

BACKGROUND: Colorectal cancer is the third-most common cancer in the world, in which 15%–25% of patients already had metastatic colorectal cancer (mCRC) at the time of diagnosis. The overall survival (OS) of mCRC is poor with the use of chemotherapy. AIM: This systematic review and meta-analysis aim to examine the outcomes of OS and progression-free survival (PFS) of adding bevacizumab to different chemotherapy regiments compared to chemotherapy regiments only in the treatment of untreated mCRC. METHODS: Literature searching was done in databases such as PubMed, EBSCO, SCOPUS, and ScienceDirect. The primary outcome measured in this systematic review and meta-analysis was OS, while the secondary outcome was PFS. Hazard ratio (HR) was used as the main summary measure with 95% confidence interval (CI). Publication bias was measured using a funnel plot. RESULTS: Literature searching resulted in 11 selected studies, 9 selected for meta-analysis. Addition of bevacizumab showed significant better results in OS (HR 0.83, CI 95% 0.74–0.93; p = 0.002; I2 = 29%) and PFS (HR 0.62, 95% CI 0.51–0.75; p < 0.0001, I2 = 78%). CONCLUSION: The addition of bevacizumab to chemotherapy resulted in better OS and PFS in untreated mCRC. Further studies are needed to confirm PFS benefit from the combination of bevacizumab and chemotherapy due to significant heterogeneity.

Safety of Aflibercept in Metastatic Colorectal Cancer: A Literature Review and Expert Perspective on Clinical and Real-World Data

BACKGROUND

Metastatic colorectal cancer (mCRC) represents a substantial health burden globally and an increasing challenge in Asian countries. Treatment options include chemotherapy plus a vascular endothelial growth factor (VEGF) inhibitor (such as bevacizumab, aflibercept or ramucirumab), or anti-epidermal growth factor receptor (EGFR) therapies. Aflibercept, a recombinant fusion protein, has been approved for treatment of mCRC in combination with FOLFIRI for patients whose disease progresses during or after treatment with an oxaliplatin-containing regimen, based on its efficacy and tolerability profile in clinical trials. This report aims to provide an overview of both clinical and real-world evidence and experience on the use of aflibercept in routine clinical practice, with a focus on European, American and Asian populations.

METHODS

A literature search was conducted in PubMed (on 28th February 2019) using the search terms ("aflibercept") and ("Colorectal"OR"CRC") to identify publications containing information on aflibercept-containing regimens.

RESULTS

The adverse events (AE) profile was similar between geographical locations. Across trials, real-world and retrospective studies, grade ≥ 3 hypertension and proteinuria were amongst the most frequently reported AEs.

CONCLUSIONS

The safety profile of aflibercept is generally manageable and comparable across various geographic locations.

Molecular insight of regorafenib treatment for colorectal cancer

Regorafenib is a multi-targeting kinase inhibitor approved for the treatment of metastatic colorectal cancer patients in refractory to standard chemotherapy. Similarly to sorafenib, this agent was originally developed as a RAF1 inhibitor. However, the kinase inhibitory profile is distinct from sorafenib. A broad-spectrum of kinase inhibition induces wide-range drug sensitivity, irrespective of mutation status of major oncogenes. This agent's main therapeutic effects are anti-angiogenesis and the remodeling of tumor microenvironment through several mechanisms of action. The dual blockade of VEGF receptors and TIE2 can lead to both additive anti-angiogenesis effects and the suggestive unique regulation of vessel stability. Additionally, it inhibits molecular escape pathways to VEGF inhibition (e.g., FGF, PIGF, and PDGF signaling), enabling its continuous antiangiogenic effect even in tumors resistant to VEGF inhibitors. Furthermore, regorafenib has the important effect of enhancing anti-tumor immunity via macrophage modulation. Based on this concept, clinical trials have been recently launched for the development of a combination strategy with immune checkpoint inhibitors. Contrary to regorafenib induced clinical benefits and advances in the novel strategy, currently no predictive biomarkers have been identified. In the present review, we revisit and summarize regorafenib's unique mechanisms of action. The review could highlight molecular insights and provide some perspective for the search of predictive biomarkers used in metastatic colorectal cancer patients treated with regorafenib.

Renin-angiotensin system inhibitors for countering proteinuria induced by angiogenesis inhibitors: a retrospective observational analysis

PURPOSE

Occurrence of proteinuria could result in cessation of bevacizumab and ramucirumab treatments. Renin-angiotensin system (RAS) inhibitors exert a renoprotective effect by countering proteinuria. However, the association between renoprotective effect of RAS inhibitors and blood pressure control is unclear. This study assessed the risk factors for proteinuria induced by bevacizumab or ramucirumab and the relationship between renoprotective effect of RAS inhibitors and blood pressure control.

METHODS

A retrospective observational analysis was conducted at Tokyo Women's Medical University, Medical Center East from June 2015 to May 2018. Multivariate logistic regression analysis was used to identify risk factors for proteinuria induced by treatment with bevacizumab and ramucirumab. Renoprotective effect was assessed by analyzing blood pressure data in association with the use of RAS inhibitors.

RESULTS

Out of 208 patients included in this study, proteinuria was observed in 50 (24%) patients. Body mass index ≥ 24 kg/m2 (OR = 2.45, 95% CI 1.21-4.96, p = 0.01), colorectal cancer (OR = 1.95, 95% CI 1.00-3.80, p < 0.05), and use of RAS inhibitors (OR = 0.25 95% CI 0.07-0.92, p = 0.04) were associated with proteinuria induced by treatment with bevacizumab and ramucirumab. A change in systolic blood pressure at second visit was higher in patients with RAS inhibitors compared with those in patients without RAS inhibitors (25 mmHg vs - 5 mmHg, p = 0.04).

CONCLUSION

Although RAS inhibitors protected patients from proteinuria induced by bevacizumab or ramucirumab, RAS inhibitors could not adequately control their blood pressures in patients with proteinuria.

Existing anti-angiogenic therapeutic strategies for patients with metastatic colorectal cancer progressing following first-line bevacizumab-based therapy

Continuous inhibition of angiogenesis beyond progression is an emerging treatment concept in the management of metastatic colorectal cancer patients with prior bevacizumab exposure. Treatment options include the continuation or reintroduction of bevacizumab during the second-line chemotherapy or switching to a different antiangiogenic monoclonal antibody such as aflibercept or ramucirumab. In the selection of treatment, patient-based factors such as performance status, age, tumor burden, and tolerance and sensitivity to the first-line bevacizumab-based therapy, as well as treatment-related factors such as toxicity, efficacy, and cost, should be taken into consideration.

Therapeutic targeting of angiogenesis molecular pathways in angiogenesis-dependent diseases

Angiogenesis is a critical step in the progression of almost all human malignancies and some other life-threatening diseases. Anti-angiogenic therapy is a novel and effective approach for treatment of angiogenesis-dependent diseases such as cancer, diabetic retinopathy, and age-related macular degeneration. In this article, we will review the main strategies developed for anti-angiogenic therapies beside their clinical applications, the major challenges, and the latest advances in the development of anti-angiogenesis-based targeted therapies.

Chemotherapy rechallenge after regorafenib treatment in metastatic colorectal cancer: still hope after the last hope?

INTRODUCTION

The introduction of biological agents in cancer therapy is changing the progression of metastatic colorectal cancer. Currently, resistance to biological agents is an emerging problem; the progression of the disease is caused by the development of resistant clones. According to some authors, these clones can be re-sensitized to traditional and previously utilized chemotherapy agents. The results of the CORRECT study demonstrated the efficacy of regorafenib monotherapy in both KRAS wild type and mutant pretreated patients (pts). Two recent reports showed the potential of reintroduction of chemotherapy, even after treatment with regorafenib.

PATIENTS AND METHODS

We performed a retrospective review of clinical data from patients treated with regorafenib at our institution between March 2012 and March 2013. We analysed patient characteristics, KRAS/NRAS status, response to treatment (evaluated by RECIST v1.1 criteria) and survival.

RESULTS

Regorafenib was administered to 128 patients, and 11 (8.6%) received post-regorafenib therapy (to our knowledge). Seven (63.6%) patients were wild type for KRAS/NRAS. Post-regorafenib therapy represented for all the patients at least the fourth line: all the pts received both oxaliplatin- and irinotecan-based chemotherapy, all of them were treated with bevacizumab, and 7 patients also received cetuximab. Eight patients (72.7%) were treated with standard chemotherapy after regorafenib (irinotecan monotherapy, capecitabine plus oxaliplatin or irinotecan, dacarbazine or raltitrexed), while 3 patients received an experimental therapy (clinical trial). Nine of the 11 (81.8%) patients had PD and 2 patients had SD. The median progression-free survival was 1.6+ months (range 0.5-3.5), the median OS post-regorafenib was 2.1+ months (range 0.5-10.2) and the 6-month OS was 27.3%.

CONCLUSION

Our retrospective analysis showed that after regorafenib therapy, re-introduction of chemotherapy is possible. Unfortunately, we reported a high percentage of disease progression beyond regorafenib, which is likely due to the high percentage of heavily pretreated patients (some received four or five types of therapy before regorafenib). We think that regorafenib could represent a chemotherapy resensitizing agent; however, additional studies are needed in patients who have received less pretreatment.

Genistein suppresses FLT4 and inhibits human colorectal cancer metastasis

Dietary consumption of genistein, found in soy, has been associated with a potentially protective role in colorectal cancer (CRC) development and progression. Herein we demonstrate that genistein will inhibit human CRC cell invasion and migration, that it does so at non-cytotoxic concentrations and we demonstrate this in multiple human CRC cell lines. After orthotopic implantation of human CRC tumors into mice, oral genistein did not inhibit tumor growth, but did inhibit distant metastasis formation, and was non-toxic to mice. Using a qPCR array, we screened for genistein-induced changes in gene expression, followed by Western blot confirmation, demonstrating that genistein downregulated matrix metalloproteinase 2 and Fms-Related Tyrosine Kinase 4 (FLT4; vascular endothelial growth factor receptor 3). After demonstrating that genistein suppressed neo-angiogenesis in mouse tumors, we examined FLT4 expression in primary CRC and adjacent normal colonic tissue from 60 human subjects, demonstrating that increased FLT4 significantly correlates with increased stage and decreased survival. In summary, we demonstrate for the first time that genistein inhibits human CRC metastasis at dietary, non-toxic, doses. FLT4 is identified as a marker of metastatic disease, and as a response marker for small molecule therapeutics that inhibit CRC metastasis.

Metabolic remodeling in human colorectal cancer and surrounding tissues: alterations in regulation of mitochondrial respiration and metabolic fluxes

The aim of the work was to evaluate whether or not there is glycolytic reprogramming in the neighboring cells of colorectal cancer (CRC). Using postoperative material we have compared the functional capacity of oxidative phosphorylation (OXPHOS) in CRC cells, their glycolytic activity and their inclination to aerobic glycolysis, with those of the surrounding and healthy colon tissue cells. Experiments showed that human CRC cannot be considered a hypoxic tumor, since the malignancy itself and cells surrounding it exhibited even higher rates of OXPHOS than healthy large intestine. The absence of acute hypoxia in colorectal carcinomas was also confirmed by their practically equal glucose-phosphorylating capacity as compared with surrounding non-tumorous tissue and by upregulation of VEGF family and their ligands. Studies indicated that human CRC cells in vivo exert a strong distant effect on the energy metabolism of neighboring cells, so that they acquire the bioenergetic parameters specific to the tumor itself. The growth of colorectal carcinomas was associated with potent downregulation of the creatine kinase system. As compared with healthy colon tissue, the tumor surrounding cells display upregulation of OXPHOS and have high values of basal and ADP activated respiration rates. Strong differences between the normal and CRC cells in the affinity of their mitochondria for ADP were revealed; the corresponding K_m values were measured as 93.6±7.7 µM for CRC cells and 84.9±9.9 µM for nearby tissue; both these apparent K_m (ADP) values were considerably (by almost 3 times) lower in comparison with healthy colon tissue cells (256±34 µM).

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Human colorectal cancer is not a pure hypoxic tumor of the Warburg phenotype.

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The total hexokinase activity of CRC cells is close to that in nearby tissues.

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In the tumor there is overexpression of VEGFs (A, B, and C) and their receptors.

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CRC has higher rates of OXPHOS as compared with healthy tissue cells.

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Tumor-surrounding cells cannot fuel via a lactate shunt the growth of CRC cells.

Current phase 1/2 research for neovascular age-related macular degeneration

PURPOSE OF REVIEW

The purpose of this review is to provide an update of phase 1 and 2 clinical trials in neovascular age-related macular degeneration that are either currently underway or recently completed by the end of 2014.

RECENT FINDINGS

Three gene therapy options are currently in early clinical trials, administered via intravitreal (AAV2-sFLT01) or subretinal (AVA-101 and RetinoStat) injection to express angiogenesis inhibitors. Several eye drops are being developed for topical administration for various angiogenic inhibitors, including regorafenib, squalamine lactate, and PAN-90806. Early development of systemic administration options may be intravenous (iSONEP) or oral (X-82). Initial study of local radiation therapy may be via proton beam irradiation or stereotactic radiotherapy. Several intravitreal injections are being studied including human immuno-conjugate molecule (hl-con1), abicipar pegol, PF582, DE-120, ESBA 1008, and REGN2176-3.

SUMMARY

Numerous treatment options of neovascular age-related macular degeneration are in phase 1/2 clinical trials including gene therapy, eye drops, systemic dosing, localized irradiation, and various intravitreal injections. Future phase 3 trial results will be observed closely to determine which of these therapies will be the next novel treatment of neovascular age-related macular degeneration.