Immunotherapies and Targeted Therapies in the Treatment of Metastatic Colorectal Cancer

Colorectal cancer (CRC) is the third leading cause of cancer deaths, and while mortality has largely improved in the developed world, five-year survival for metastatic disease remains dismally low at only 15%. Fortunately, nearly a dozen targeted therapies and immunotherapies have been FDA approved in the past decade for certain patient profiles with metastatic CRC (mCRC), and many others are under development. Checkpoint inhibitors such as pembrolizumab have proven effective at extending survival for mismatch repair (MMR)-deficient and high microsatellite instability (MSI) mCRC patients. In combination with chemotherapy in first- and second-line treatment, antiangiogenic (anti-vascular endothelial growth factor (anti-VGEF)) agent bevacizumab has been shown to increase mCRC survival. Anti-epidermal growth factor receptor (anti-EGFR) agents panitumumab and cetuximab, in combination with chemotherapy, have also prolonged survival among KRAS and all RAS wild-type mCRC patients. Among these patients, anti-EGFR therapy has been found to be more efficacious than bevacizumab. Improved selectivity has allowed small-molecule receptor tyrosine kinase (RTK) inhibitors to target VEGF and EGFR with greater efficacy and tolerability. Combinations of immunotherapies, RTKs, monoclonal antibodies, and cytotoxic drugs are being investigated to provide broad-spectrum protection against relapse by simultaneously targeting many cancer hallmarks. Lastly, human epidermal growth factor receptor 2 (HER2) therapy has shown promise for HER2-positive mCRC patients, though larger clinical trials are required to secure FDA approval.

Retreatment with anti-EGFR monoclonal antibodies in metastatic colorectal cancer: Systematic review of different strategies

BACKGROUND

Despite advances in precision oncology and immunotherapy of tumors, little progress has been made in metastatic colorectal cancer (mCRC) in recent years. Therefore, making the most of available therapies is a necessity. Several studies, based on the pulsatile behavior of RAS clones under EGFR blockade, investigated whether readministration of EGFR-targeted agents is effective beyond second line.

METHODS

A systematic review of studies of retreatment with anti-EGFR monoclonal antibodies has been performed from January 2005 to December 2018 according to PRISMA criteria from PubMed, ESMO and ASCO meetings libraries and Clinicaltrial.gov. Efficacy has been evaluated as objective response rate and survival in available publications. In addition, type and incidence of side effects occurring during on anti-EGFR retreatment have been considered.

RESULTS

26 publications have been retrieved, of which 20 full-text articles and 6 abstracts and categorized as for the retreatment strategy into five groups: rechallenge (n = 10), reintroduction (n = 4), sequence (n = 5), dose escalation (n = 1) and mixed (n = 6). Data of efficacy displayed high heterogeneity across different strategies (objective response rate, ORR = 0.0-53.8%; disease control rate, DCR = 24.0-89.7%), with best results in the setting of rechallenge (ORR = 2.9-53.8%; DCR = 40.0-89.7%).

CONCLUSIONS

Rechallenge with anti-EGFR provides clinical benefit in molecularly selected mCRC patients beyond second line. Further ctDNA-guided studies comparing this option of treatment with current approved advanced line treatments are warranted.

Panitumumab in the treatment of metastatic colorectal cancer, including wild-type RAS, KRAS and NRAS mCRC

The humanized monoclonal antibody panitumumab, targeted against EGFR, plays an important role in patients with metastatic colorectal cancer. This article reviews the body of evidence for panitumumab which demonstrates significant benefits across multiple lines of therapy in those without an extended RAS mutation. The use of panitumumab with RAS mutations is not beneficial and possibly harmful. Panitumumab is well tolerated with manageable toxicities. The role of panitumumab continues to evolve as understanding of sequencing of therapies grows. There is evidence for use as maintenance therapy and conversion therapy for unresectable liver metastases. Future research is likely to focus on biomarkers for improved patient selection and the development of novel therapeutic strategies to overcome resistance.

Optimising the use of cetuximab in the continuum of care for patients with metastatic colorectal cancer

The anti-epidermal growth factor receptor (EGFR) monoclonal antibody cetuximab in combination with chemotherapy is a standard of care in the first-line treatment of RAS wild-type (wt) metastatic colorectal cancer (mCRC) and has demonstrated efficacy in later lines. Progressive disease (PD) occurs when tumours develop resistance to a therapy, although controversy remains about whether PD on a combination of chemotherapy and targeted agents implies resistance to both components. Here, we propose that some patients may gain additional clinical benefit from the reuse of cetuximab after having PD on regimens including cetuximab in an earlier treatment line. We conducted a non-systematic literature search in PubMed and reviewed published and ongoing clinical trials, focusing on later-line cetuximab reuse in patients with mCRC. Evidence from multiple studies suggests that cetuximab can be an efficacious and tolerable treatment when continued or when fit patients with mCRC are retreated with it after a break from anti-EGFR therapy. Furthermore, on the basis of available preclinical and clinical evidence, we propose that longitudinal monitoring of RAS status may identify patients suitable for such a strategy. Patients who experience progression on cetuximab plus chemotherapy but have maintained RAS wt tumour status may benefit from continuation of cetuximab with a chemotherapy backbone switch because they have probably developed resistance to the chemotherapeutic agents rather than the biologic component of the regimen. Conversely, patients whose disease progresses on cetuximab-based therapy due to drug-selected clonal expansion of RAS-mutant tumour cells may regain sensitivity to cetuximab following a defined break from anti-EGFR therapy. Looking to the future, we propose that RAS status determination at disease progression by liquid, needle or excisional biopsy may identify patients eligible for cetuximab continuation and rechallenge. With this approach, treatment benefit can be extended, adding to established continuum-of-care strategies in patients with mCRC.

Overcoming dynamic molecular heterogeneity in metastatic colorectal cancer: Multikinase inhibition with regorafenib and the case of rechallenge with anti-EGFR

In metastatic colorectal cancer (mCRC), fluorouracil-based combination therapy with oxaliplatin or irinotecan is the mainstay of first-line treatment. Patient survival has been significantly improved with the introduction of monoclonal antibodies against VEGF (bevacizumab), VEGFR2 (ramucirumab) or EGFR (cetuximab or panitumumab) in first- and second-line therapies. However, all patients treated with chemotherapy and targeted therapies will eventually relapse, and recently the emergence of alterations in EGFR, RAS, BRAF, ERB-B2, MET and possibly in other genes has been shown to jeopardize response to EGFR blockade. In chemorefractory patients, multikinase inhibition with regorafenib has proved to be effective and rechallenge with chemotherapy or anti-EGFR agents is empirically pursued. This review will critically discuss how the evolving knowledge of mechanisms of resistance driven by intratumoural dynamic molecular heterogeneity can impact on rational choice of treatments in this setting.

A Phase I Trial to Evaluate Antibody-Dependent Cellular Cytotoxicity of Cetuximab and Lenalidomide in Advanced Colorectal and Head and Neck Cancer

mAbs can induce antibody-dependent cellular cytotoxicity (ADCC) via the innate immune system's ability to recognize mAb-coated cancer cells and activate immune effector cells. Lenalidomide is an immunomodulatory agent with the capacity to stimulate immune cell cytokine production and ADCC activity. This phase I trial evaluated the combination of cetuximab with lenalidomide for the treatment of advanced colorectal and head and neck squamous cell cancers (HNSCC). This trial included patients with advanced colorectal cancer or HNSCC. Treatment consisted of cetuximab 500 mg/m(2) i.v. every two weeks with lenalidomide given orally days 1-21 on a 28-day cycle. Three dose levels of lenalidomide were evaluated (15, 20, 25 mg). Correlative studies included measurement of ADCC, FcγRIIIA polymorphism genotyping, measurement of serum cytokine levels, and flow cytometric analysis of immune cell subtypes. Twenty-two patients were enrolled (19 colorectal cancer, 3 HNSCC). Fatigue was the only dose-limiting toxicity. One partial response was observed and 8 patients had stable disease at least 12 weeks. The recommended phase II dose is cetuximab 500 mg/m(2) with lenalidomide 25 mg daily, days 1-21. Correlative studies demonstrated a dose-dependent increase in natural killer cytotoxic activity with increasing doses of lenalidomide. Cetuximab and lenalidomide were well tolerated. There was a lenalidomide dose-dependent increase in ADCC with higher activity in patients enrolled in cohort 3 than those enrolled in cohorts 1/2. Although response was not a primary endpoint, there was evidence of antitumor activity for the combination therapy. Further investigation of lenalidomide as an immunomodulator in solid tumors is warranted. Mol Cancer Ther; 15(9); 2244-50. ©2016 AACR.

Pharmacokinetic and pharmacodynamic evaluation of panitumumab in the treatment of colorectal cancer

INTRODUCTION

Integration of targeted therapy and additional chemotherapy options has improved median overall survival (OS) in patients with unresectable metastatic colorectal cancer (mCRC). Cetuximab and panitumumab are examples of targeted therapies, specifically against the epidermal growth factor receptor (EGFR). This review focuses on Panitumumab, a fully human IgG2 monoclonal antibody, which inhibits key oncogenic downstream cell signalling pathways. Panitumumab and cetuximab have improved tumour response rate, progression-free survival, and OS in mCRC patients in whom the RAS (Rat Sarcoma) gene is of Wild Type (WT) status.

AREAS COVERED

The EGFR signalling pathway and preclinical, Phase I and Phase II clinical studies on the pharmacokinetic, pharmacodynamic and safety evaluation of panitumumab are presented. Phase III studies utilising panitumumab in the first, second and third line setting in mCRC are also described.

EXPERT OPINION

Panitumumab exhibits excellent pharmacokinetics and pharmacodynamics by way of uncomplicated dosing, non-existent drug interactions, minimal infusion reactions and manageable side effects, making it a suitable target for combination treatments. However, innate and acquired resistances are still obstacles. To overcome this, experimented strategies are ongoing, particularly in patients with Her-2 and BRAF gene alterations. Novel biomarkers to improve patient selection and second-generation targeted antibodies are in development.

The use of EGFR inhibitors in colorectal cancer: is it clinically efficacious and cost-effective?

Cetuximab (Erbitux) and panitumumab (Vectibix) are monoclonal antibodies to the EGFR. They are used as monotherapy or in combination with cytotoxic chemotherapy and increase both progression-free survival and overall survival in patients with wild-type RAS metastatic colorectal cancer. The most common side effects of therapy are dermatological, including skin (acneiform) rash, pruritus and hair changes. Despite their clinical activity, cost-effectiveness of the two drugs should be addressed in a discussion of their usage in everyday care. This study provides an up-to-date review of the clinical efficacy and cost-effectiveness of anti-EGFR inhibitors.

Panitumumab safety for treating colorectal cancer

INTRODUCTION

Panitumumab is a human IgG2 mAb against the EGFR, inhibiting tumor cell proliferation, survival and angiogenesis. It has demonstrated clinical efficacy in metastatic colorectal cancer (CRC) in combination with chemotherapy in first- and second-line settings and as monotherapy in third-line setting. Recently, mutations in the RAS genes have been shown to be predictive of lack of efficacy, panitumumab should be restricted to patients with RAS wild-type (wt) tumors.

AREAS COVERED

This review focuses on main efficacy results of panitumumab in metastatic CRC in first-, second- and third-line settings in combination with chemotherapy or as monotherapy. Additionally, we have covered safety aspects of this agent in these indications, especially in K-RAS and all RAS wt patients. These safety aspects refer to the most common toxicities (i.e., acne-like skin rash, diarrhea and hypomagnesaemia).

EXPERT OPINION

Panitumumab adds to the armamentarium of effective agents in the treatment of metastatic CRC. Due to its human origin, panitumumab is a well-tolerated agent with low rates of infusional reactions. Skin toxicity is frequent and should be pre-emptively treated. Other common toxicities related to panitumumab treatment, such as diarrhea and hypomagnesaemia, should be closely monitored to ensure early treatment or substitution.

Options for metastatic colorectal cancer beyond the second line of treatment

Colorectal cancer is the third most common cancer, with recent advances in the management of unresectable metastatic lesions. The aim of this review is to discuss the remaining options for heavily pretreated patients with unresectable metastatic colorectal cancer. Beyond second-line treatment, two epidermal growth factor receptor (EGFR) inhibitors, cetuximab and panitumumab, have a demonstrated clinical interest in patients with KRAS wild-type tumours. However, few data exist in patients pretreated with an anti-EFGR and who are being rechallenged with anti-EGFR drugs. Reintroduction of chemotherapy should be considered. In September 2012, regorafenib, a multi-kinase inhibitor was approved by the US Federal Drug Administration for patients refractory to other standard treatments. In the case of metastases limited to the liver, transarterial chemoembolization, hepatic artery infusion and radioembolization could also be discussed in selected patients. With the multiplication of therapeutic options in first-line, second-line treatment, and beyond, the concept of subsequent lines of chemotherapy should be replaced by a multiline strategy, dependent on the patient and on tumour biology. A better understanding of the tumour biology and predictive factors for the response to these therapies is needed, and further strategic trials are urgently warranted.

Panitumumab in the management of patients with KRAS wild-type metastatic colorectal cancer

The past 15 years has seen a marked increase in available therapeutic options for patients with metastatic colorectal cancer resulting in improvements in median survival from 12 to 24 months. One of these new options is panitumumab, which is a fully humanized monoclonal antibody that binds to the epidermal growth factor receptor of tumor cells and inhibits downstream cell signaling with antitumor effects of inhibition of tumor growth, induction of apoptosis and inhibition of angiogenesis. Large randomized clinical trials have demonstrated significant improvements in tumor response rates and progression-free survival when panitumumab is combined with chemotherapy and as monotherapy in chemorefractory metastatic colorectal cancer. Clinical benefit with panitumumab is limited to patients with nonmutated KRAS tumors. Rash is a common toxicity of panitumumab treatment but can potentially be ameliorated with the use of prophylactic strategies. The role of panitumumab in the overall treatment of metastatic colorectal cancer is evolving and future clinical trials will focus on improved patient selection through use of novel predictive biomarkers, and the optimal timing of treatment.

Single agent panitumumab in KRAS wild-type metastatic colorectal cancer patients following cetuximab-based regimens: Clinical outcome and biomarkers of efficacy

BACKGROUND

Few data are available outlining outcomes of panitumumab in advanced colorectal cancer patients benefiting from prior cetuximab-based regimens.

PATIENTS AND METHODS

Thirty patients with KRAS wild type metastatic colorectal cancer with clinical benefit from prior cetuximab-based regimens between May 2004 and October 2011 were reviewed at nine Italian Institutions. Inclusion key criteria included interruption of cetuximab for reasons other than progressive disease. Patients were classified according to prior regimens (0 or ≥1), prior response or stabilization, surgery of metastases, and Köhne prognostic score. At the time of subsequent progression, patients were treated with single agent panitumumab until progressive disease, unacceptable toxicity, or consent withdrawal.

RESULTS

Panitumumab obtained 67% disease control rate and 30% objective response rate, with median PFS of 4.2 and median OS of 9.6 mo. Patients with BRAF/NRAS/PI3KCA and KRAS (by mutant enriched technique) wild-type tumors had the best chance of response to panitumumab.

CONCLUSIONS

Single agent panitumumab provided significant clinical benefit in heavily pretreated patients without acquired resistance to prior cetuximab-based regimens.

Epidermal growth factor receptor (EGFR) and KRAS mutations during chemotherapy plus anti-EGFR monoclonal antibody treatment in metastatic colorectal cancer

It is now well established that metastatic colorectal cancer patients without KRAS mutation (codon 12) benefit from treatment with an epidermal growth factor receptor monoclonal antibody (anti-EGFR mAb). Recently, EFGR and KRAS mutations have been shown to exist in patients who developed resistance to anti-EGFR mAb. We analyzed KRAS, BRAF V600E and EGFR S492R mutations in 37 post-anti-EGFR mAb tumor samples from 23 patients treated with chemotherapy plus anti-EGFR mAb. No EGFR S492R mutation was detected. A KRAS mutation was found after anti-EGFR mAb in only one tumor. Our results suggest that acquired EGFR S492R and KRAS mutations do not constitute the main mechanism of resistance to anti-EGFR mAb in combination with chemotherapy.

[Optimizing good use and costs of anticancer drugs: A French inter regional study of the Observatory of Cancer]

Optimizing the care management of patients is a major issue for our society. In Brittany-Pays-de-la-Loire (almost 10% of French population), an observatory of cancer has been created in 2003. Its main objective was the follow-up of expensive drugs. The knowledge of the use of these drugs in clinical practice has led to development of a thesaurus of good use. Thus, regular exchanges between clinicians have almost totally reduced not medically justified prescriptions by the thesaurus after and before administration to patient. The thesaurus has given away to national guidelines from 2007. For example, in these two regions, optimization of the use of gemcitabine and bevacizumab has allowed to save respectively 2.5 millions euros between 2005 and 2008 and 3 millions euros between 2009 and 2010 (breast cancer only). Optimizing the use of anticancer drugs has allowed a real health economy without any bad impact on patient management. Respecting medical ethics, the main objective remains to optimize health care. This highly participation of clinicians currently allows to reflect together on the relevance of the last chemotherapy.

Panitumumab following disease progression on cetuximab in patients with metastatic colorectal cancer: A retrospective review

Despite advances in treatment options for metastatic colorectal cancer over the past decade, the number of chemotherapy agents available remains limited. We report here a retrospective review of 11 patients who were treated with panitumumab following documented disease progression on cetuximab. Two patients demonstrated minor radiographic responses, albeit only for a short period of time. We conclude that the use of one epidermal growth factor receptor inhibitor following failure on the other may be of benefit to patients who would otherwise have no other treatment options. However, studies to help identify the subset of patients who might benefit from this strategy are needed.

Cetuximab in metastatic colorectal cancer

Management of metastatic colorectal cancer has evolved in the last 10 years, with the availability of targeted therapies resulting in improvement in quality of life and overall survival. Cetuximab is a chimeric monoclonal antibody that binds to the EGF receptor, and the net effects are inhibition of tumor growth, invasion, angiogenesis and metastasis. Cetuximab binding to the EGF receptor is also known to augment the effects of chemotherapy and radiotherapy. Only tumors expressing wild-type KRAS respond to cetuximab and improvements in progression-free survival and overall survival are seen, whereas patients with mutant KRAS are considered to be resistant. Cetuximab is currently available worldwide for use as monotherapy or in combination with chemotherapy in first-, second- or third-line settings in metastatic colorectal cancer patients with wild-type KRAS.