Pharmacology of Epidermal Growth Factor Inhibitors

Research into the molecular bases of malignant diseases has yielded the development of many novel agents with potential antitumor activity. Evidence for a causative role for the epidermal growth factor receptor (EGFR), which is now regarded as an excellent target for cancer chemotherapy in human cancer, leads to the development of EGFR inhibitors. Two classes of anti-EGFR agents are currently in clinical use: monoclonal antibodies directed at the extracellular domain of the receptor, and the low-molecular-weight receptor tyrosine kinase inhibitors acting intracellularly by competing with adenosine triphosphate for binding to the tyrosine kinase portion of the EGFR. The effect on the receptor interferes with key biological functions including cell cycle arrest, potentiation of apoptosis, inhibition of angiogenesis and cell invasion and metastasis. Cetuximab, a monoclonal antibody, and the receptor tyrosine kinase inhibitors gefitinib and erlotinib are currently approved for the treatment of patients with cancer. New agents with clinical activity are entering the clinic, and new combinatorial approaches are being explored with the aim of improving the potency and pharmacokinetics of EGFR inhibition, to increase the synergistic activity in combination with chemotherapy and overcome resistance to the EGFR inhibitors.

Lapatinib-capecitabine versus capecitabine alone as radiosensitizers in RAS wild-type resectable rectal cancer, an adaptive randomized phase II trial (LaRRC trial): study protocol for a randomized controlled trial

BACKGROUND

Preoperative radiochemotherapy followed by surgical removal of the rectum with total mesorectum excision is the preferred treatment option for stages II and III rectal cancer. However, development of metastatic disease is the main cause of death for these patients with 5-year disease-free survival rates of 56 %. Anti-epidermal growth factor receptor (EGFR) targeted therapy is effective in metastatic rectal cancer, and human epidermal growth factor receptor 2 (HER-2) signaling may mediate resistance to EGFR inhibitors. Moreover, preclinical data support a synergistic effect of EGFR inhibition with radiation therapy.

METHODS/DESIGN

This Bayesian phase II trial with adaptive randomization was designed to assess the efficacy of adding lapatinib, a dual inhibitor of EGFR and HER-2, to standard radiochemotherapy with capecitabine in stages II and III rectal cancer.

DISCUSSION

The results of this trial will provide evidence of the feasibility and efficacy of the combination of lapatinib-capecitabine as radiosensitizers and explore potential predictive biomarkers for response to this novel neoadjuvant approach to resectable rectal cancer.

TRIAL REGISTRATION

EudraCT 2013-001203-36 . Registered on 13 December 2013.

Future of targeted agents in metastatic colorectal cancer

Great strides have been made in improving the outcome of patients with metastatic colorectal cancer and targeted agents are an important part of the treatment arsenal. The approved monoclonal antibodies, bevacizumab, cetuximab and panitumumab, are part of the standard of care, yet only recently have we begun to define which patients benefit from these therapies using predictive tumor biomarkers. More recently, novel agents including aflibercept and regorafenib have had promising results and may become approved therapies. In addition, agents targeting the mTOR pathway and the TNF pathway have demonstrated early evidence of benefit. In the coming years, we may experience an influx of new therapies, possibly leading to further prolongation of patient survival or even, for some, a cure.

Lapatinib side-effect management

Lapatinib is an oral dual tyrosine kinase inhibitor targeting epidermal growth factor receptor and HER2. Diarrhea and dermatologic adverse events are reported commonly by patients treated with lapatinib. Diarrhea can range from mild to severe based on the agents used in combination with lapatinib. The adverse events may diminish quality of life, reduce treatment adherence, and lead to discontinuation of therapy. Consequently, proactive management of diarrhea is crucial, especially in patients receiving lapatinib in combination with other agents that also cause diarrhea. As the utility of lapatinib expands, crucial proactive diarrhea-management and dose-reduction strategies are evolving to decrease the likelihood of grade 3 or 4 toxicity. With regard to dermatologic adverse events, most are mild to moderate in severity, are of limited duration, and frequently do not require treatment intervention. However, in some patients, management of dermatologic adverse events is of great importance. This article reviews data regarding diarrhea and dermatologic adverse events in patients treated with lapatinib and summarizes the key role that oncology nurses play in educating patients about the potential for adverse events and the importance of preventive measures, ongoing surveillance, appropriate treatment, and dose reductions.

Small-molecule inhibitors of the human epidermal receptor family

BACKGROUND

Small molecule inhibitors of human epidermal receptors (HER) have become an integral part of the armamentarium available to the medical oncologist in the treatment of solid tumor malignancies. At present, there are two small-molecule inhibitors (erlotinib and lapatinib) approved by the FDA in the USA, and a third inhibitor, gefitinib, is approved in other countries.

OBJECTIVE

To summarize the current standards of care for these new agents in solid tumors, and to discuss ongoing clinical trials; to review the known mechanisms of action of these inhibitors as well as to discuss both the known predictive markers for response and likely mechanisms of resistance.

METHODS

We reviewed key presentations and recent publications on small-molecule inhibitors targeting the HER family in solid tumors.

CONCLUSIONS

Recent data have highlighted the importance of mutations and amplifications of receptors within the HER family. Amplification of HER2 often translates into responses in anti-HER2 therapy. Mutations either enhance sensitivity or confer resistance to small-molecule inhibitors. Other mechanisms of resistance are being elucidated which should lead to the ability to predict both responses and resistance to HER family inhibitors and should translate into improvements in patient care.

Tumor-specific apoptosis caused by deletion of the ERBB3 pseudo-kinase in mouse intestinal epithelium

Pharmacologic blockade of EGFR or the closely related receptor ERBB2 has modest efficacy against colorectal cancers in the clinic. Although the upregulation of ERBB3, a pseudo-kinase member of the EGFR/ERBB family, is known to contribute to EGFR inhibitor resistance in other cancers, its functions in normal and malignant intestinal epithelium have not been defined. We have shown here that the intestinal epithelium of mice with intestine-specific genetic ablation of Erbb3 exhibits no cytological abnormalities but does exhibit loss of expression of ERBB4 and sensitivity to intestinal damage. By contrast, intestine-specific Erbb3 ablation resulted in almost complete absence of intestinal tumors in the ApcMin mouse model of colon cancer. Unlike nontransformed epithelium lacking ERBB3, intestinal tumors lacking ERBB3 had reduced PI3K/AKT signaling, which led to attenuation of tumorigenesis via a tumor-specific increase in caspase-3-mediated apoptosis. Consistent with the mouse data, which suggest that ERBB3-ERBB4 heterodimers contribute to colon cancer survival, experimentally induced loss of ERBB3 in a KRAS mutant human colon cancer cell line was associated with loss of ERBB4 expression, and siRNA knockdown of either ERBB3 or ERBB4 resulted in elevated levels of apoptosis. These results indicate that the ERBB3 pseudo-kinase has essential roles in supporting intestinal tumorigenesis and suggest that ERBB3 may be a promising target for the treatment of colorectal cancers.

Antitumor activity of the HER2 dimerization inhibitor pertuzumab on human colon cancer cells in vitro and in vivo

PURPOSE

The monoclonal antibody pertuzumab represents the first HER2 dimerization inhibitor with unknown activity in colon cancer treatment. We examined the antitumor activity of pertuzumab as a single agent or in combination with erlotinib or irinotecan in human colon cancer cells in vitro and in vivo.

METHODS

Colon cancer cell lines were tested for HER1/HER2 expression by western blot analysis. The effect of pertuzumab on cell cycle distribution was analyzed by FACS. Nude mice bearing xenograft tumors were treated with pertuzumab alone, or in combination either with irinotecan or with erlotinib. Tumor volume was measured repeatedly. Tumor histology was analyzed for necrosis.

RESULTS

Six of nine cell lines showed high expression of HER1/HER2. Pertuzumab inhibited cell cycle progression in various cell lines. Pertuzumab showed minor antitumor activity in xenograft tumors, but significantly inhibited tumor growth when combined with erlotinib (P < 0.001). Combination of pertuzumab with irinotecan had no additional effect on growth of additional tumors. Pertuzumab treated DLD-1 xenograft tumors did not show enhanced necrosis, which, however, was found in HCT116 derived xenografts.

CONCLUSIONS

Pertuzumab has some antitumor activity on human colon cancer cells in vitro and in vivo, in particular when combined with erlotinib. In vivo, pertuzumab combination treatment was not superior to irinotecan monotherapy. These data warrant further investigation of simultaneous HER1/EGFR TKI inhibition and HER1/HER2 dimerization inhibition for colorectal cancer therapy.

Activity of lapatinib is independent of EGFR expression level in HER2-overexpressing breast cancer cells

Epidermal growth factor receptor (EGFR/ErbB1) and HER2 (ErbB2/neu), members of the ErbB receptor tyrosine kinase family, are frequently overexpressed in breast cancer and are known to drive tumor growth and progression, making them promising targets for cancer therapy. Lapatinib is a selective competitive inhibitor of both the HER2 and EGFR tyrosine kinases. Although lapatinib showed significant activity in patients with HER2-positive breast cancer, the role of EGFR in the response of breast cancer to lapatinib has not been defined. Here, we examined the role of EGFR expression levels in the sensitivity of HER2-overexpressing breast cancer cells to lapatinib. Depletion of EGFR by EGFR small-interfering RNA knockdown did not affect lapatinib sensitivity in these cells, whereas treated HER2 siRNA knockdown cells became more resistant to lapatinib. We conclude that the in vitro activity of lapatinib is not dependent on EGFR expression level in HER2-overexpressing breast cancer cells.

Lapatinib: a tyrosine kinase inhibitor with a clinical role in breast cancer

Lapatinib is a dual (ErbB-1 and ErB-2) receptor tyrosine kinase inhibitor (TKI) that was recently approved by the FDA for the treatment of advanced breast cancer. It shows synergy with trastuzumab, and has demonstrated clinical activity in trastuzumab-resistant tumour. This paper reviews the drug development of lapatinib from preclinical studies to the pivotal Phase III trial and ongoing clinical studies. Areas of interest include the advantages of small molecule TKIs versus antibodies in targeting HER receptors and the efficacy of lapatinib in the treatment of cerebral metastases. The surprisingly high response rate in inflammatory breast cancer raises the possibility of other novel predictive biomarkers. The potential for combination and sequencing with other biological and cytotoxic agents is both exciting and challenging.

EGFR-targeted therapies in colorectal cancer

The management of colorectal cancer relies heavily on the combination of the pyrimidine analog antimetabolite 5-fluorouracil with the platinum-based drug oxaliplatin or the topoisomerase inhibitor irinotecan. Optimization of dosing and scheduling of these agents to improve response and survival continues to evolve. Meanwhile, the rational targeting of molecular signaling pathways that are involved in the etiology of malignancies is currently one of the most promising strategies in novel anticancer drug development. New classes of drugs that target the epidermal growth factor receptor are among the most clinically advanced molecular-targeted therapies and have shown efficacy in colorectal cancer. The current status of epidermal growth factor receptor-targeted therapeutic agents is reviewed, with emphasis on their role in the management of colorectal cancer.

Dual inhibition of ErbB1 (EGFR/HER1) and ErbB2 (HER2/neu)

Targeting of epidermal growth factor receptor (EGFR) and HER2 is a proven anti-cancer strategy. However, heterodimerisation, compensatory 'crosstalk' and redundancy exist in the ErbB network, and there is therefore a sound scientific rationale for dual inhibition of EGFR and HER2. Trials of approved agents in combination, for example trastuzumab and cetuximab, are underway. There is also a new generation of small molecule tyrosine kinase inhibitors (TKIs) and monoclonal antibodies (mABs) that target two or more ErbB receptors. Lapatinib, a TKI of EGFR and HER2, has shown clinical benefit in trastuzumab refractory breast cancer and is poised for FDA approval. Other agents include BIBW-2992 and HKI-272, irreversible TKIs of EGFR and HER2, and pertuzumab, a heterodimerisation inhibitor of EGFR and HER2.

Epidermal growth factor receptor tyrosine kinase inhibitors: present and future role in gastrointestinal cancer treatment: a review

BACKGROUND

Despite advances in conventional and targeted anticancer therapy, the prognosis remains poor for many patients with solid tumors. Ongoing research into the molecular basis of malignant disease, however, has yielded many novel agents with potential activity, including the epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs).

DESIGN

This review summarizes current clinical data for EGFR-TKIs as monotherapy or in combination with 5-fluorouracil/leucovorin, irinotecan, or oxaliplatin, focusing on the rapidly developing area of colorectal, gastroesophageal, and pancreatic cancers.

RESULTS

EGFR-TKIs have limited but valuable activity as monotherapy in non-small cell lung cancer patients who have received prior anticancer treatment. The potential for application as a single agent in colorectal, gastroesophageal, and pancreatic cancers has yet to be demonstrated conclusively and deserves further investigation, especially as second- or third-line therapy. In combination with oxaliplatin-based regimens and 5-fluorouracil/leucovorin-based regimens, TKIs have shown benefits, suggesting that there may be a synergistic effect with chemotherapy. However, combinations with irinotecan-based regimens have been limited by toxicities.

CONCLUSIONS

EGFR-TKIs show benefits when used in combination with chemotherapy, and the favorable toxicity profiles observed suggest that these may be of value in frail or elderly patients.

Small molecule tyrosine kinase inhibitors in the treatment of solid tumors: an update of recent developments

Small molecule tyrosine kinase inhibitors (TKIs) are developed to block intracellular signaling pathways in tumor cells, leading to deregulation of key cell functions such as proliferation and differentiation. Over 25 years ago, tyrosine kinases were found to function as oncogenes in animal carcinogenesis; however, only recently TKIs were introduced as anti cancer drugs in human cancer treatment. Tyrosine kinase inhibitors have numerous good qualities. First, in many tumor types they tend to stabilize tumor progression and may create a chronic disease state which is no longer immediately life threatening. Second, side effects are minimal when compared to conventional chemotherapeutic agents. Third, synergistic effects are seen in vitro when TKIs are combined with radiotherapy and/or conventional chemotherapeutic agents. In this article, we will give an update of the tyrosine kinase inhibitors that are currently registered for use or in an advanced stage of development, and we will discuss the future role of TKIs in the treatment of solid tumors. The following TKIs are reviewed: Imatinib (Gleevec/Glivec), Gefitinib (Iressa), Erlotinib (OSI-774, Tarceva), Lapatinib (GW-572016, Tykerb), Canertinib (CI-1033), Sunitinib (SU 11248, Sutent), Zactima (ZD6474), Vatalanib (PTK787/ZK 222584), Sorafenib (Bay 43-9006, Nexavar), and Leflunomide (SU101, Arava).

Her-2 targeted therapy: beyond breast cancer and trastuzumab

Her-2 is a validated therapeutic target in breast cancer. The two critical questions that remain regarding Her-2 targeting concern 1) the relevance of Her-2 inhibition in other malignancies and 2) the ability of novel agents to achieve greater Her-2 inhibition than trastuzumab. The contribution of cell signaling effects and immunologic mechanisms to the effect of trastuzumab in vivo remains poorly understood. Thus, the preclinical data that support the greater efficacy of novel Her-2 antibodies or small molecule tyrosine kinase inhibitors remain to be validated in clinical trials. In this review, we discuss the evidence from recent trastuzumab clinical trials as a point of departure for consideration of novel Her-2 targeted therapies. Preliminary results from early clinical trials suggest that Her-2 tyrosine kinase inhibitors may extend the population for which this strategy offers therapeutic effect.

Lapatinib: a novel dual tyrosine kinase inhibitor with activity in solid tumors

OBJECTIVE

To review the pharmacology, pharmacokinetics, clinical trials, adverse effects, and drug interactions of lapatinib.

DATA SOURCES

A PubMed search was conducted (1966-August 2005) using the following terms: lapatinib, GW572016, and dual tyrosine kinase inhibitor. Additional information sources included meeting abstracts, clinical trial data, and bibliographies from articles identified through PubMed.

STUDY SELECTION AND DATA EXTRACTION

Preclinical and clinical trials that evaluated lapatinib in cell culture, animal models, and human subjects were selected from the data sources. Pivotal in vitro data and all in vivo data published regarding lapatinib were included.

DATA SYNTHESIS

The development of tyrosine kinase inhibitors has resulted from a search for targeted cancer therapeutics made possible by recent gains in our understanding of tumor cell biology. Lapatinib is a dual tyrosine kinase inhibitor selective for inhibition of epidermal growth factor receptor and human epidermal growth factor receptor-2 autophosphorylation, leading to suppression of proliferation pathways of solid tumors. Lapatinib has shown clinical activity in solid tumors, with the most notable in advanced or metastatic breast cancer, including tumors refractory to trastuzumab. It has a mild adverse effect profile, with the most common adverse events being diarrhea and rash.

CONCLUSIONS

Lapatinib has novel, dual tyrosine kinase inhibitory properties selective for factors overexpressed in some solid tumors. Results from preclinical and Phase I/II trials indicate activity in the treatment of solid tumors, especially advanced or metastatic breast cancer. Application for approval is anticipated pending results of ongoing Phase III trials.