Lapatinib in breast cancer - the predictive significance of HER1 (EGFR), HER2, PTEN and PIK3CA genes and lapatinib plasma level assessment

BACKGROUND

Breast cancer treatment trends are currently based on tailored therapies using tumor and patient biomarkers. Lapatinib is the first dual inhibitor of HER1 (EGFR, ErbB1) and HER2 (ErbB2, Neu) tyrosine kinases to be used in clinical practice. However, only HER2 is currently used for therapy indications and new predictors for the treatment with lapatinib are sought.

METHODS AND RESULTS

This minireview focuses on lapatinib and its role in breast cancer treatment. Preclinical and clinical studies as well as pharmacological characteristics are briefly reviewed while the focus is on efficacy assessment including predictive factors for therapy outcome.

CONCLUSION

Lapatinib (Tykerb/Tyverb) was Food and Drug Administration (FDA) approved in 2007 for use in combination with capecitabine for the treatment of HER2-positive advanced or metastatic breast cancer in patients who had received previous treatment (including anthracycline, taxane and trastuzumab containing regimens) and in 2010 for use in combination with letrozole for postmenopausal women with hormonal receptor positive and HER2- positive metastatic breast cancer. In contrast to trastuzumab (Herceptin), lapatinib is orally administered and it targets both HER2 and HER1 receptors. As a synthetic and oral tyrosine kinase inhibitor (TKI), it is convenient, cheaper and easier to produce than monoclonal antibodies. The recommended dosage is not dependent on body weight either. Lapatinib plasma level measurement could be an approach to tailored therapy for further optimizing the dose and prolonging this efficient therapy. New lapatinib response predictors are being evaluated. At this time, only HER2 amplification/overexpression is used to choose lapatinib therapy candidates. Further studies on concurrent HER1 fluorescent in situ hybridization (FISH)/immunohistochemistry (IHC) assessment and/or microarray analyses may produce new data on the predictive role of the HER1 (EGFR) gene/protein. PTEN loss and PIK3CA gene mutations are other markers that may predict lapatinib poor response.

A phase I/II trial of GW572016 (lapatinib) in recurrent glioblastoma multiforme: clinical outcomes, pharmacokinetics and molecular correlation

PURPOSE

We undertook a phase I/II study of the EGFR/erbB2 inhibitor lapatinib in patients with recurrent glioblastoma multiforme (GBM) to determine response rate, pharmacokinetics (PK) and recommended dose in patients taking enzyme-inducing anti-epileptic drugs (EIAEDs) and to explore relationships of molecular genetics to outcome.

METHODS

Recurrent GBM patients taking EIAEDs were enrolled on the phase I portion (starting dose of lapatinib 1,000 mg po bid). In the absence of dose-limiting toxicity (DLT), escalation continued in cohorts of three patients. Patients not on EIAEDs enrolled in the phase II arm (lapatinib 750 mg bid po). Immunohistochemical and quantitative RT PCR studies were performed on tumor to determine PTEN and EGFRvIII status, respectively. Lapatinib PK was analyzed using HPLC with tandem mass spectrometry.

RESULTS

Phase II: Of 17 patients, 4 had stable disease and 13 progressed. Accrual ceased because of no responses. Phase I: Four patients received 1,000 mg bid and three, 1,500 mg bid. No DLT occurred, but escalation stopped because of lack of phase II efficacy. Lapatinib apparent oral clearance in patients taking EIAEDs was 106.9 L h(-1) m(-2) in comparison to 12.1 L h(-1) m(-2) in those not on EIAEDs. In 16 phase II patients, PTEN loss was seen in 6 and EGFRvIII expression in 4. No correlation was seen with outcome and molecular results.

CONCLUSIONS

Lapatinib apparent oral clearance increased by approximately tenfold when given with EIAEDs. In this small sample, EGFRvIII expression and PTEN loss did not predict a favorable subtype. Overall, lapatinib did not show significant activity in GBM patients.

Antiangiogenic strategies in breast cancer management

Angiogenesis is considered one of the key mechanisms of tumour growth and survival. Therefore it represents an ideal pharmaceutical target. Many antiangiogenic agents have been developed so far in several solid tumours and also in breast cancer. Vascular endothelial growth factor (VEFG) is the main target and both monoclonal antibodies and small molecules belonging to the tyrosine kinase inhibitors directed against VEGF(R) have been developed. Some other therapeutic approaches have shown to exert some antiangiogenic activity, such as hormonal agents, metronomic chemotherapy, bisphosphonates and others. In this paper we provide an introduction of the current data supporting the angiogenesis in breast cancer and a review of the most relevant antiagiogenic therapies which have been investigated so far.

Phase II Study to Evaluate the Efficacy and Safety of Neoadjuvant Lapatinib Plus Paclitaxel in Patients With Inflammatory Breast Cancer

Purpose

We conducted a phase II, open-label, multicenter study to evaluate the efficacy, safety, and tolerability of daily lapatinib plus weekly paclitaxel in treatment-naïve patients with inflammatory breast cancer (IBC).

Patients and Methods

The primary end point was pathologic complete response (pCR). Secondary end points included combined clinical response rate (based on Response Evaluation Criteria in Solid Tumors (RECIST) criteria and clinically evaluable skin disease criteria). Patients were assigned to either cohort A (human epidermal growth factor receptor 2 [HER2] 2+ or 3+ by immunohistochemistry [IHC] or fluorescent in situ hybridization [FISH] –amplified ± epidermal growth factor receptor [EGFR] expression) or cohort B (HER2-negative/EGFR-positive). A subpopulation of cohort A considered HER2-positive by the current definition of overexpression (3+ by IHC or FISH-amplified) was also analyzed. Patients received lapatinib at 1,500 mg/d for 14 days, then lapatinib at 1,500 mg/d plus weekly paclitaxel (80 mg/m2) for 12 weeks, followed by surgical resection or additional chemotherapy.

Results

Forty-nine women were enrolled (cohort A, n = 42; cohort B, n = 7). Cohort B was terminated because of slow accrual and lack of efficacy observed in IBC patients with HER2-negative/EGFR-positive tumors enrolled onto the parallel study, EGF103009. pCR occurred in 18.2% (95% CI, 5.2% to 40.3%) of cohort A patients. Combined clinical response rate was 78.6% (95% CI, 63.2% to 89.7%) in all cohort A patients and 78.1% (95% CI, 60.0% to 90.7%) in the HER2-positive subset. Common adverse events included diarrhea, rash, alopecia, and nausea (> 50% of patients in both cohorts). The incidence of grade 3 diarrhea was 55%.

Conclusion

Lapatinib monotherapy for 14 days followed by lapatinib plus paclitaxel for 12 weeks provided clinical benefit in IBC patients with HER2-overexpressing tumors without unexpected toxicity.

Current standards in the treatment of metastatic breast cancer with focus on Lapatinib: a review by a Central European Consensus Panel

In breast cancer, early detection as well as new developments in therapeutic options has resulted in less patients presenting with metastatic disease. However, about one-third of women with early stage breast cancer will eventually develop metastatic disease. Furthermore, approximately 20-30% of patients with breast cancer have tumors that overexpress human epidermal growth factor receptor (HER-2), which is associated with an aggressive tumor phenotype and poor prognosis. The identification of the HER-2 protein led to the development of highly effective therapeutics directed at this receptor. Trastuzumab, a recombinant, humanized, monoclonal antibody that binds to the extracellular domain of the HER-2 protein, has shown significant clinical benefit in metastatic and early-stage HER-2-positive breast cancer. Since the cancer recurs after adjuvant therapy in some women, and metastatic breast cancer eventually develops resistance to trastuzumab, there is a need for alternative treatment modalities to block HER-2 signaling. One of these treatment options is lapatinib, an orally active small molecule that inhibits the tyrosine kinases of HER-2 and the epidermal growth factor receptor type 1 (EGFR). In this consensus statement current treatment options in metastatic and locally advanced disease are discussed with a special focus on lapatinib.

Resistance to HER2 inhibitors: is addition better than substitution? Rationale for the hypothetical concept of drug sedimentation

Twenty years were passed between the discovery of oncogene HER2, the description of its implication in mammary carcinogenesis, and the development of specific targeted therapies. To date, trastuzumab and lapatinib are the two anti-HER2 targeted therapies commonly used, demonstrating therapeutic effects. Although their clinical efficacy seems to be exclusively related to the amplification of the HER2 gene or to the overexpression of the protein, these factors are not sufficient since tumors can develop resistance. Because of a better knowledge in those mechanisms of resistance, novel therapeutic agents could help to bypass them. How should these be used with respect to current anti-HER2 targeted therapies? Recent notions such as oncogene addiction, tumor cell dormancy and residual disease led us to propose a new entity that we named the "sedimentation strategy", in which distinct targeted approaches are summed during the treatment of metastatic breast cancer patients.

Trastuzumab and lapatinib beyond trastuzumab progression for metastatic breast cancer: strategies and pitfalls

The discovery of HER2 gene amplification and protein overexpression in approximately 15-20% of breast cancers and access to the tailored humanized antibody, trastuzumab (Herceptin), have heralded a new era in breast cancer therapy. Trastuzumab combined with chemotherapy has caused marked tumor responses and increased overall survival in patients with metastatic breast cancer, and has also increased survival in the adjuvant setting after radical surgery. However, due to many causes, trastuzumab resistance usually occurs during treatment. In this event, possible options include the replacement of trastuzumab with lapatinib, the continuation of trastuzumab after disease progression with changed chemotherapy and the suspension of the use of targeted agents. New-generation tyrosine kinase inhibitors, which have a broader target, are now considered the key to treatment for breast cancer.

Lapatinib

The human epidermal growth factor receptor (HER) family of growth factor receptor tyrosine kinases (RTKs) plays an important role in the biology of many cancers. In breast cancer, HER2 and its homo- or heterodimerization with HER1 or HER3 are essential for cancer cell growth and survival. Patients overexpressing HER2 have a poor prognosis, which can be substantially improved upon HER2-targeted therapy using the monoclonal antibody trastuzumab. Lapatinib is a novel dual tyrosine kinase inhibitor, blocking HER1 and HER2 tyrosine kinase activity by binding to the ATP-binding site of the receptor's intracellular domain. This results in inhibition of tumor cell growth. The drug is relatively well tolerated in patients, with few and mostly low-grade adverse effects. In particular and unlike to trastuzumab, it has very little, if any, adverse effects on cardiac function. In patients with advanced HER2-positive breast cancer, lapatinib has shown substantial antitumor activity, particularly in combination with capecitabine upon progressive disease following standard therapy with antracyclines, taxanes, and trastuzumab. Ongoing and future studies will explore its role in the adjuvant therapy setting, in drug combinations other than capecitabine, and in the treatment of HER2-positive tumors other than breast cancer.

Lapatinib for treatment of advanced or metastasized breast cancer: systematic review

CONTEXT AND OBJECTIVE

Around 16% to 20% of women with breast cancer have advanced, metastasized breast cancer. At this stage, the disease is treatable, but not curable. The objective here was to assess the effectiveness of lapatinib for treating patients with advanced or metastasized breast cancer.

DESIGN AND SETTING

Systematic review of the literature, developed at Centro Paulista de Economia da Saúde (CPES), Universidade Federal de São Paulo (Unifesp).

METHOD

Systematic review with searches in virtual databases (PubMed, Lilacs [Literatura Latino-Americana e do Caribe em Ciências da Saúde], Cochrane Library, Scirus and Web of Science) and manual search.

RESULTS

Only one clinical trial that met the selection criteria was found. This study showed that lapatinib in association with capecitabine reduced the risk of cancer progression by 51% (95% confidence interval, CI: 0.34-0.71; P < 0.001), compared with capecitabine alone, without any increase in severe adverse effects.

CONCLUSION

The combination of lapatinib plus capecitabine was more effective than capecitabine alone for reducing the risk of cancer progression. Further randomized clinical trials need to be carried out with the aim of assessing the effectiveness of lapatinib as monotherapy or in association for first-line or second-line treatment of advanced breast cancer.

Dynamic contrast-enhanced magnetic resonance imaging pharmacodynamic biomarker study of sorafenib in metastatic renal carcinoma

PURPOSE

Sorafenib is an antiangiogenic agent with activity in renal cancer. We conducted a randomized trial to investigate dynamic contrast magnetic resonance imaging (DCE-MRI) as a pharmacodynamic biomarker.

PATIENTS AND METHODS

Patients were randomly assigned to placebo or 200 or 400 mg twice per day of sorafenib. DCE-MRI was performed at baseline and 4 weeks. DCE-MRI parameters, area under the contrast concentration versus time curve 90 seconds after contrast injection (IAUC(90)), and volume transfer constant of contrast agent (K(trans)) were calculated for a metastatic site selected in a blinded manner. Primary end point was change in K(trans).

RESULTS

Of the 56 assessable patients, 48 underwent two MRIs; 44 MRIs were assessable for study end points. Mean K(trans) log ratios were 0.131 (standard deviation [SD], 0.315), -0.148 (SD, 0.382), -0.271 (SD, 0.499) in placebo, 200- and 400-mg cohorts, respectively (P = .0077 for trend) corresponding to changes of +14%, -14%, and -24%. IAUC(90) log ratios were 0.041 (SD, 0.197), -0.040 (SD, 0.132), -0.356 (SD, 0.411), respectively (P = .0003 for trend), corresponding to changes of +4%, -4%, and -30%. Using a log-rank test, IAUC(90) and K(trans) changes were not associated with progression-free survival (PFS). Patients with high baseline K(trans) had a better PFS (P = .027).

CONCLUSION

IAUC(90) and K(trans) are pharmacodynamic biomarkers for sorafenib, but variability is high and magnitude of effect is less than previously reported. Changes in DCE-MRI parameters after 4 weeks of sorafenib are not predictive of PFS, suggesting that these biomarkers are not surrogate end points. The value of baseline K(trans) as a prognostic or predictive biomarker requires additional study.

New challenges and opportunities in the management of brain metastases in patients with ErbB2-positive metastatic breast cancer

The introduction of trastuzumab for the treatment of tumors that overexpress ErbB2 (also known as HER2) has contributed significantly to recent improvements in systemic therapy for advanced breast cancer. The advances in systemic therapy have highlighted an increasing prevalence of central nervous system involvement in patients with ErbB2-positive breast cancer and a consequent need for new treatment options for brain metastases. Just as ErbB2-targeted systemic therapy has given rise to this challenge, so too could targeted therapy represent an opportunity to meet it. This Review considers the potential for targeted therapy to facilitate effective management of brain metastases in patients with ErbB2-positive breast cancer, and discusses in particular the data currently available in this setting for lapatinib, an orally available small-molecule tyrosine kinase inhibitor of ErbB1 and ErbB2.

Drug Insight: intracellular inhibitors of HER2--clinical development of lapatinib in breast cancer

Targeting the human epidermal growth factor receptor type 2 (HER2) in breast cancer patients whose tumors overexpress HER2 has been clearly demonstrated to be effective in clinical trials with the monoclonal antibody trastuzumab. Not all patients, however, respond to trastuzumab therapy. Lapatinib is an oral receptor tyrosine kinase inhibitor that targets HER2 and the EGFR. Preclinical data reveal that lapatinib has activity in trastuzumab-resistant cell lines as well as synergistic activity with trastuzumab. In a pivotal phase III trial, a combination of lapatinib and capecitabine significantly decreased the risk of disease progression relative to capecitabine alone in women with HER2-positive advanced or metastatic breast cancer previously treated with anthracyclines, taxanes, and trastuzumab. Other trials are evaluating lapatinib in inflammatory breast cancer--for which encouraging data have been reported--in combination with hormone therapy, in combination with trastuzumab, and as an adjunct to adjuvant therapy for early-stage disease. Notably, lapatinib has not been associated with serious or symptomatic cardiotoxicity in clinical trials. It can cross the blood-brain barrier and might therefore have a role in preventing central-nervous-system progression. These features make lapatinib an ideal agent to evaluate more fully in HER2-positive metastatic and early-stage breast cancer.

Development of new targeted therapies for breast cancer

Clinical application of truly targeted therapy relies on identification of a specific molecular feature (the target) that is biologically relevant, reproducibly measurable and definably correlated with clinical benefit. Ideally the target should be crucial to the tumor's malignant phenotype. The target must be easily measurable in readily obtained clinical samples. Interruption, interference or inhibition of the target should yield a clinical response in a significant proportion of patients whose tumors express the target but in few patients whose tumors do not express the target. As such, targeted therapy offers the twin hopes of maximizing efficacy while minimizing toxicity. A critical review of the hallmarks of malignancy provides a framework for considering potential targets and novel therapeutic interventions. The hallmarks of malignancy include uncontrolled proliferation, insensitivity to negative growth regulation, evasion of apoptosis, lack of senescence, invasion and metastasis, angiogenesis, and genomic elasticity. Existing therapies predominantly target proliferation either with cytotoxic agents, ionizing radiation or inhibition of estrogen receptor and HER2 growth factor signaling pathways. Further improvements in therapy must attack the other hallmarks of malignancy and will undoubtedly be accompanied by better means of individual patient selection for such therapies. Indeed, each of these hallmarks presents a therapeutic opportunity. To believe otherwise would be to assume that a feature is both biologically crucial yet therapeutically unimportant, an unlikely paradox.

Efficacy and safety of lapatinib as first-line therapy for ErbB2-amplified locally advanced or metastatic breast cancer

PURPOSE

This study (EGF20009) assessed the efficacy and tolerability of two lapatinib administration schedules as first-line monotherapy in women with ErbB2-amplified locally advanced or metastatic breast cancer.

PATIENTS AND METHODS

Patients with ErbB2-amplified, locally advanced or metastatic breast cancer previously untreated in the metastatic setting were randomly assigned to one of two lapatinib dose cohorts and received either 1,500 mg once daily or 500 mg twice daily. Clinical response was assessed at weeks 8 and 12 and every 12 weeks thereafter.

RESULTS

A total of 138 patients were treated with lapatinib for a median of 17.6 weeks. The overall response rate (complete response [CR] plus partial response [PR]) was 24% in the intent-to-treat population, and 31% of patients derived clinical benefit (CR, PR, or stable disease for >or= 24 weeks). The median time to response was 7.9 weeks, and the progression-free survival rates at 4 and 6 months were 63% and 43%, respectively. The most common lapatinib-related adverse events (AEs) were diarrhea, rash, pruritus, and nausea, and these events were primarily grade 1 or 2. There were no significant differences in clinical activity or the AE profile between the dosing schedules.

CONCLUSION

Lapatinib demonstrated clinical activity and was well tolerated as first-line therapy in ErbB2-amplified locally advanced or metastatic breast cancer. This study supports further evaluation of lapatinib in first-line and early-stage ErbB2-overexpressing breast cancer.

Phase II trial of lapatinib for brain metastases in patients with human epidermal growth factor receptor 2-positive breast cancer

PURPOSE

One third of women with advanced human epidermal growth factor receptor 2 (HER-2)-positive breast cancer develop brain metastases; a subset progress in the CNS despite standard approaches. Medical therapies for refractory brain metastases are neither well-studied nor established. We evaluated the safety and efficacy of lapatinib, an oral inhibitor of epidermal growth factor receptor (EGFR) and HER-2, in patients with HER-2-positive brain metastases.

PATIENTS AND METHODS

Patients had HER-2-positive breast cancer, progressive brain metastases, prior trastuzumab treatment, and at least one measurable metastatic brain lesion. Patients received lapatinib 750 mg orally twice a day. Tumor response was assessed by magnetic resonance imaging every 8 weeks. The primary end point was objective response (complete response [CR] plus partial response [PR]) in the CNS by Response Evaluation Criteria in Solid Tumors (RECIST). Secondary end points included objective response in non-CNS sites, time to progression, overall survival, and toxicity.

RESULTS

Thirty-nine patients were enrolled. All patients had developed brain metastases while receiving trastuzumab; 37 had progressed after prior radiation. One patient achieved a PR in the brain by RECIST (objective response rate 2.6%, 95% conditional CI, 0.21% to 26%). Seven patients (18%) were progression free in both CNS and non-CNS sites at 16 weeks. Exploratory analyses identified additional patients with some degree of volumetric reduction in brain tumor burden. The most common adverse events (AEs) were diarrhea (grade 3, 21%) and fatigue (grade 3, 15%).

CONCLUSION

The study did not meet the predefined criteria for antitumor activity in highly refractory patients with HER-2-positive brain metastases. Because of the volumetric changes observed in our exploratory analysis, further studies are underway utilizing volumetric changes as a primary end point.

Lapatinib: a sword with two edges

Lapatinib is an oral dual tyrosine kinase inhibitor targeting EGFR1 and EGFR2 (HER2). Phase I trials have shown that lapatinib is well tolerated, with mild diarrhea and skin rush as common adverse effects, and low cardiotoxicity. Phase II and III trials provided evidences on clinical effectiveness in advanced or metastatic breast cancer and potential against brain metastases. Lapatinib is active in combination with trastuzumab and in trastuzumab-resistant patients, moreover it has synergistic action with capecitabine. Several clinical trials are in progress to explore the effectiveness of lapatinib in other combinations and against several tumor types.

Phase II Study of Predictive Biomarker Profiles for Response Targeting Human Epidermal Growth Factor Receptor 2 (HER-2) in Advanced Inflammatory Breast Cancer With Lapatinib Monotherapy

Purpose

Inflammatory breast cancer (IBC) is one of the most aggressive forms of breast cancer. Lapatinib, an oral reversible inhibitor of epidermal growth factor receptor (EGFR) and human EGFR 2 (HER-2), demonstrated clinical activity in four of five IBC patients in phase I trials. We conducted a phase II trial to confirm the sensitivity of IBC to lapatinib, to determine whether response is HER-2 or EGFR dependent, and to elucidate a molecular signature predictive of lapatinib sensitivity.

Patients and Methods

Our open-label multicenter phase II trial (EGF103009) assessed clinical activity and safety of lapatinib monotherapy in patients with recurrent or anthracycline-refractory IBC. Patients were assigned to cohorts A (HER-2–overexpressing [HER-2+]) or B(HER-2–/EGFR+) and fresh pretreatment tumor biopsies were collected.

Results

Forty-five patients (30 in cohort A; 15 in cohort B) received lapatinib 1,500 mg once daily continuously. Clinical presentation and biomarker analyses demonstrated a tumor molecular signature consistent with IBC. Lapatinib was generally well tolerated, with primarily grade 1/2 skin and GI toxicities. Fifteen patients (50%) in cohort A had clinical responses to lapatinib in skin and/or measurable disease (according to Response Evaluation Criteria in Solid Tumors) compared with one patient in cohort B. Within cohort A, phosphorylated (p) HER-3 and lack of p53 expression predicted for response to lapatinib (P < .05). Tumors coexpressing pHER-2 and pHER-3 were more likely to respond to lapatinib (nine of 10 v four of 14; P = .0045). Prior trastuzumab therapy and loss of phosphate and tensin homolog 10 (PTEN) did not preclude response to lapatinib.

Conclusion

Lapatinib is well tolerated with clinical activity in heavily pretreated HER-2+, but not EGFR+/HER-2–, IBC. In this study, coexpression of pHER-2 and pHER-3 in tumors seems to predict for a favorable response to lapatinib. These findings warrant further investigation of lapatinib monotherapy or combination therapy in HER-2+ IBC.

Overcoming treatment challenges in advanced breast cancer

OBJECTIVES

To describe new clinical findings, efficacy, and safety regarding the use of targeted agents in the treatment of HER2-positive metastatic breast cancer.

DATA SOURCES

Published research articles, abstracts, and clinical experience.

CONCLUSION

HER2-positive cases of breast cancer tend to be more aggressive and more likely to become resistant to therapy than HER2-negative tumors. The current standard approach to patients with HER2-positive metastatic breast cancer includes the use of trastuzumab. Because cellular mechanisms can arise that can block the efficacy of this approach (and result in clinical resistance), recent research has led to the development of lapatinib, a targeted therapy that can act on HER2 inside the cell to disrupt the signaling pathways thought to be part of tumorigenic mechanisms.

IMPLICATIONS FOR NURSING PRACTICE

Oncology nurses should be aware of the treatment strategies for HER2-positive metastatic breast cancer and its limitations, which is essential for providing optimal nursing care.

Targeting the function of the HER2 oncogene in human cancer therapeutics

The year 2007 marks exactly two decades since human epidermal growth factor receptor-2 (HER2) was functionally implicated in the pathogenesis of human breast cancer (Slamon et al., 1987). This finding established the HER2 oncogene hypothesis for the development of some human cancers. An abundance of experimental evidence compiled over the past two decades now solidly supports the HER2 oncogene hypothesis. A direct consequence of this hypothesis was the promise that inhibitors of oncogenic HER2 would be highly effective treatments for HER2-driven cancers. This treatment hypothesis has led to the development and widespread use of anti-HER2 antibodies (trastuzumab) in clinical management resulting in significantly improved clinical antitumor efficacies that have transformed the clinical practice of oncology. In the shadows of this irrefutable clinical success, scientific studies have not yet been able to mechanistically validate that trastuzumab inhibits oncogenic HER2 function and it remains possible that the current clinical advances are a consequence of the oncogene hypothesis, but not a translation of it. These looming scientific uncertainties suggest that the full promise of the treatment hypothesis may not yet have been realized. The coming decade will see a second generation of HER2-targeting agents brought into clinical testing and a renewed attempt to treat HER2-driven cancers through the inactivation of HER2. Here, I review the development of treatments that target HER2 in the context of the HER2 oncogene hypothesis, and where we stand with regards to the clinical translation of the HER2 oncogene hypothesis.

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.

Issues and controversies in the treatment of HER2 positive metastatic breast cancer

Targeted therapies against the human epidermal growth factor receptor HER2, have led to revolutionary strides in breast cancer research and treatment. Clinical therapeutic decisions in the treatment of patients with HER2 positive metastatic breast cancer are based on appropriate patient selection, the clinical situation, and data related to the available therapeutic agents trastuzumab and lapatinib. Trastuzumab was the first agent tested and approved in 1996 as single agent for patients with chemotherapy-refractory disease, and in combination with paclitaxel as first-line treatment. This intravenous humanized monoclonal antibody is directed against the extracellular domain of the HER2 protein. Lapatinib, an oral small molecule tyrosine kinase inhibitor has more recently become available (in 2007), approved for used in combination with capecitabine for patients with HER2 positive metastatic disease that has progressed on trastuzumab. Important questions and controversies still remain and are reviewed, including patient selection for anti-HER2 treatment of metastatic disease based on HER2 testing, dose scheduling of trastuzumab, duration of therapy, tolerability, role of lapatinib and clinical significance of trastuzumab resistance and efficacy. Ongoing trials designed to maximize the therapeutic ratio of these agents, are also discussed.

Sunitinib: from rational design to clinical efficacy

Sunitinib (SU011248) is an oral small molecular tyrosine kinase inhibitor that exhibits potent antiangiogenic and antitumor activity. Tyrosine kinase inhibitors such as SU6668 and SU5416 (semaxanib) demonstrated poor pharmacologic properties and limited efficacy; therefore, sunitinib was rationally designed and chosen for its high bioavailability and its nanomolar-range potency against the antiangiogenic receptor tyrosine kinases (RTKs)--vascular endothelial growth factor receptor (VEGFR) and platelet-derived growth factor receptor (PDGFR). Sunitinib inhibits other tyrosine kinases including, KIT, FLT3, colony-stimulating factor 1 (CSF-1), and RET, which are involved in a number of malignancies including small-cell lung cancer, GI stromal tumors (GISTs), breast cancer, acute myelogenous leukemia, multiple endocrine neoplasia types 2A and 2B, and familial medullary thyroid carcinoma. Sunitinib demonstrated robust antitumor activity in preclinical studies resulting not only in tumor growth inhibition, but tumor regression in models of colon cancer, non-small-cell lung cancer, melanoma, renal carcinoma, and squamous cell carcinoma, which were associated with inhibition of VEGFR and PDGFR phosphorylation. Clinical activity was demonstrated in neuroendocrine, colon, and breast cancers in phase II studies, whereas definitive efficacy has been demonstrated in advanced renal cell carcinoma and in imatinib-refractory GISTs, leading to US Food and Drug Administration approval of sunitinib for treatment of these two diseases. Studies investigating sunitinib alone in various tumor types and in combination with chemotherapy are ongoing. The clinical benchmarking of this small-molecule inhibitor of members of the split-kinase domain family of RTKs will lead to additional insights regarding the biology, potential biomarkers, and clinical utility of agents that target multiple signaling pathways in tumor, stromal, and endothelial compartments.

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.

Lapatinib: Current Status and Future Directions in Breast Cancer

Lapatinib is an oral receptor tyrosine kinase inhibitor, targeting both the ErbB-1 and ErbB-2 receptors. Pre-clinical in vitro and in vivo models indicate that lapatinib is active as monotherapy, synergistically in combination with trastuzumab, and in trastuzumab-resistant cell lines. Early clinical trials also provide evidence in patients that lapatinib is active against breast cancer. This paper reviews results of phase II and III clinical trials of lapatinib in metastatic breast cancer, evidence for its potential in patients with brain metastases, and current clinical trials as adjuvant treatment in early-stage disease. Our improved understanding of the biology of breast cancer and the use of biomarkers for identification of specific subtypes is allowing us to bring patient-specific novel therapies such as lapatinib to the clinic.

Clinical efforts to combine endocrine agents with targeted therapies against epidermal growth factor receptor/human epidermal growth factor receptor 2 and mammalian target of rapamycin in breast cancer

Enhancing the benefit of endocrine therapy by overcoming de novo or acquired resistance remains an important goal in systemic breast cancer therapy. Progress continues to be made in elucidating the molecular pathways by which estrogen receptor-positive breast cancer cells escape from endocrine therapy. The increasing recognition of the roles of epidermal growth factor receptor (EGFR) and human EGFR2 in cross-talk activation of estrogen receptor signaling has led to studies aimed at identifying whether small-molecule tyrosine kinase inhibitors targeted against these receptors give additive or synergistic effects when combined with endocrine agents. Activation of the phosphatidylinositol-3-OH kinase/Akt pathway has also been associated with resistance to either tamoxifen or estrogen deprivation, and preclinical studies have shown that the mammalian target of rapamycin antagonist temsirolimus can restore endocrine sensitivity in breast cancer cells. Randomized phase II trials of aromatase inhibitors combined with EGFR/human EGFR2 tyrosine kinase inhibitors or mammalian target of rapamycin antagonists have been completed in both the neoadjuvant and advanced breast cancer settings. Larger phase III trials with both approaches are now in progress and have been powered to detect whether either strategy can significantly prolong time to disease progression compared with endocrine therapy alone. The correlation of molecular and clinical results from these ongoing studies will be important to establish appropriate biological variables for selecting those patients who may benefit most from this combined approach.

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.

The era of ErbB-receptor-targeted therapies: advances toward personalized medicine

Central themes in medical practice are the diagnosis, prognosis and treatment of disease. Advances have been made in a number of malignanices including breast cancer, where new therapeutic strategies have significantly improved response rates, the disease-free interval and overall survival. However, complete responses to chemotherapy are achieved in only 10–20% of patients. Recent advances in the understanding of the cellular and molecular biology of cancer have led to the identification of oncogenes and tumor suppressor genes that influence the rate of tumor cell proliferation and cancer progression. These oncogenes represent important therapeutic targets and are currently being incorporated into the design of novel therapeutic approaches. This review emphasizes the role of the ErbB oncogenic receptor family, its effect on tumor biologic behavior and its role as a target for various therapeutic regimens.