A phase I/II trial of pazopanib in combination with lapatinib in adult patients with relapsed malignant glioma

PURPOSE

Increased mitogenic signaling and angiogenesis, frequently facilitated by somatic activation of EGF receptor (EGFR; ErbB1) and/or loss of PTEN, and VEGF overexpression, respectively, drive malignant glioma growth. We hypothesized that patients with recurrent glioblastoma would exhibit differential antitumor benefit based on tumor PTEN/EGFRvIII status when treated with the antiangiogenic agent pazopanib and the ErbB inhibitor lapatinib.

EXPERIMENTAL DESIGN

A phase II study evaluated the antitumor activity of pazopanib 400 mg/d plus lapatinib 1,000 mg/d in patients with grade 4 malignant glioma and known PTEN/EGFRvIII status not receiving enzyme-inducing anticonvulsants (EIAC). The phase II study used a two-stage Green-Dahlberg design for futility. An independent, parallel phase I component determined the maximum-tolerated regimen (MTR) of pazopanib and lapatinib in patients with grade 3/4 glioma receiving EIACs.

RESULTS

The six-month progression-free survival (PFS) rates in phase II (n = 41) were 0% and 15% in the PTEN/EGFRvIII-positive and PTEN/EGFRvIII-negative cohorts, respectively, leading to early termination. Two patients (5%) had a partial response and 14 patients (34%) had stable disease lasting 8 or more weeks. In phase I (n = 34), the MTR was not reached. On the basis of pharmacokinetic and safety review, a regimen of pazopanib 600 mg plus lapatinib 1,000 mg, each twice daily, was considered safe. Concomitant EIACs reduced exposure to pazopanib and lapatinib.

CONCLUSIONS

The antitumor activity of this combination at the phase II dose tested was limited. Pharmacokinetic data indicated that exposure to lapatinib was subtherapeutic in the phase II evaluation. Evaluation of intratumoral drug delivery and activity may be essential for hypothesis-testing trials with targeted agents in malignant glioma.

Safety and feasibility of targeted agent combinations in solid tumours

The plethora of novel molecular-targeted agents (MTAs) has provided an opportunity to selectively target pathways involved in carcinogenesis and tumour progression. Combination strategies of MTAs are being used to inhibit multiple aberrant pathways in the hope of optimizing antitumour efficacy and to prevent development of resistance. While the selection of specific agents in a given combination has been based on biological considerations (including the role of the putative targets in cancer) and the interactions of the agents used in combination, there has been little exploration of the possible enhanced toxicity of combinations resulting from alterations in multiple signalling pathways in normal cell biology. Owing to the complex networks and crosstalk that govern normal and tumour cell proliferation, inhibiting multiple pathways with MTA combinations can result in unpredictable disturbances in normal physiology. This Review focuses on the main toxicities and the lack of tolerability of some common MTA combinations, particularly where evidence of enhanced toxicity compared to either agent alone is documented or there is development of unexpected toxicity. Toxicities caused by MTA combinations highlight the need to introduce new preclinical testing paradigms early in the drug development process for the assessment of chronic toxicities resulting from such combinations.

Pazopanib: a multikinase inhibitor with activity in advanced renal cell carcinoma

Treatment options for patients with metastatic renal cell carcinoma (RCC) have changed dramatically, and a new paradigm has evolved. IFN-alpha and IL-2 were previously mainstays of therapy, but since December 2005, six new agents have been approved in the USA for the treatment of advanced RCC. Three of these new agents are multitargeted kinase inhibitors, including sunitinib, sorafenib, and recently pazopanib, two target the mTOR (temsirolimus and everolimus), and one is a humanized monoclonal antibody (bevacizumab in combination with IFN-alpha) that targets VEGF. Sunitinib has emerged as the standard of care for treatment-naive RCC patients, with the recently approved bevacizumab and IFN-alpha combination providing an additional option for this population. The recent approval of pazopanib, based on the results from sequential Phase II and III clinical trials demonstrating improved overall response rates and progression-free survival, provides yet another option for front-line therapy. The current article examines the pazopanib preclinical and clinical data, provides an overview of the development of this tyrosine kinase inhibitor, and provides some speculation concerning its role in RCC therapy.

Pazopanib for the treatment of patients with advanced renal cell carcinoma

Dramatic advances in the care of patients with advanced renal cell carcinoma have occurred over the last ten years, including insights into the molecular pathogenesis of this disease, that have now been translated into paradigm-changing therapeutic strategies. Elucidating the importance of signaling cascades related to angiogenesis is notable among these achievements. Pazopanib is a novel small molecule tyrosine kinase inhibitor that targets VEGFR-1, -2, and -3; PDGFR-α, PDGFR-β; and c-kit tyrosine kinases. This agent exhibits a distinct pharmacokinetic profile as well as toxicity profile compared to other agents in the class of VEGF signaling pathway inhibitors. This review will discuss the scientific rationale for the development of pazopanib, as well as preclinical and clinical trials that led to approval of pazopanib for patients with advanced renal cell carcinoma. The most recent information, including data from 2010 national meeting of the American Society of Clinical Oncology, and the design of ongoing Phase III trials, will be discussed. Finally, an algorithm utilizing Level I evidence for the treatment of patients with this disease will be proposed.

An evaluation of the drug interaction potential of pazopanib, an oral vascular endothelial growth factor receptor tyrosine kinase inhibitor, using a modified Cooperstown 5+1 cocktail in patients with advanced solid tumors

Pazopanib, an oral inhibitor of vascular endothelial growth factor receptor, platelet-derived growth factor receptor, and c-kit kinases, inhibits multiple cytochrome P450 (CYP450) enzymes in vitro. This study in patients with advanced cancer evaluated the effect of pazopanib on CYP450 function by comparing the pharmacokinetics of CYP-specific probe drugs in the presence and absence of pazopanib. The probes used included midazolam (CYP3A specific), warfarin (CYP2C9 specific), omeprazole (CYP2C19 specific), caffeine (CYP1A2 specific), and dextromethorphan (CYP2D6 specific). The estimated ratios of the geometric means (90% confidence interval (CI)) for the area under the curve to the last measurable point (AUC(0-t)) for these probe drugs with/without pazopanib were as follows: midazolam, 1.35 (1.18-1.54); omeprazole, 0.81 (0.59-1.12); caffeine, 1.00 (0.77-1.30); and S-warfarin, 0.93 (0.84-1.03). The geometric least-squares (LS) mean ratio of urine dextromethorphan:dextrorphan ranged from 1.33 (0-4-h interval) to 1.64 (4-8-h interval). The data suggest that pazopanib is a weak inhibitor of CYP3A4 and CYP2D6 and has no effect on CYP1A2, CYP2C9, and CYP2C19 in patients with advanced cancer.

Phase II, Open-Label Study of Pazopanib or Lapatinib Monotherapy Compared With Pazopanib Plus Lapatinib Combination Therapy in Patients With Advanced and Recurrent Cervical Cancer

Purpose

Pazopanib and lapatinib are tyrosine kinase inhibitors that target vascular endothelial growth factor receptor, platelet-derived growth factor receptor, and c-Kit or epidermal growth factor receptor (EGFR) and human epidermal growth factor receptor 2 (HER2/neu), respectively. In cervical cancer, EGFR and HER2/neu overexpression and high microvascular density correlate with survival.

Patients and Methods

Patients with measurable stage IVB persistent/recurrent cervical carcinoma not amenable to curative therapy and at least one prior regimen in the metastatic setting were randomly assigned in a ratio of 1:1:1 to pazopanib at 800 mg once daily, lapatinib at 1,500 mg once daily, or lapatinib plus pazopanib combination therapy (lapatinib at 1,000 mg plus pazopanib at 400 mg once daily or lapatinib at 1,500 mg plus pazopanib at 800 mg once daily). Therapy continued until progression or withdrawal because of adverse events (AEs). Primary end point was progression-free survival (PFS), and secondary end points were overall survival (OS), response rate (RR), and safety. The futility boundary was crossed at the planned interim analysis for combination therapy compared with lapatinib therapy, and the combination was discontinued.

Results

Of 230 patients enrolled, 152 were randomly assigned to the monotherapy arms: pazopanib (n = 74) or lapatinib (n = 78). Most patients (62%) had recurrent cancer. Pazopanib improved PFS (hazard ratio [HR], 0.66; 90% CI, 0.48 to 0.91; P = .013) and OS (HR, 0.67; 90% CI, 0.46 to 0.99; P = .045). Median OS was 50.7 weeks and 39.1 weeks and RRs were 9% and 5% for pazopanib and lapatinib, respectively. The only grade 3 AE > 10% was diarrhea (11% pazopanib and 13% lapatinib). Grade 4 AEs were 9% (lapatinib) and 12% (pazopanib).

Conclusion

This study confirms the activity of antiangiogenesis agents in advanced and recurrent cervical cancer and demonstrates the benefit of pazopanib based on the prolonged PFS and favorable toxicity profile.

Pazopanib: an antiangiogenic drug in perspective

Pazopanib, a tyrosine kinase inhibitor targeted to angiogenesis, has been tested in preclinical and clinical trials and has shown promising activity against a variety of solid tumors, such as renal cancer, all of which are related to the angiogenic pathway. It has a safety profile related to this mechanism of action. Diarrhea, hypertension, hair depigmentation and nausea are the most common side effects. Pazopanib is currently under evaluation as monotherapy and in combination with some potentially synergistic agents of proven activity.

Recent advances in systemic therapy: Advances in systemic therapy for HER2-positive metastatic breast cancer

Human epidermal growth factor receptor (HER)2 over-expression is associated with a shortened disease-free interval and poor survival. Although the addition of trastuzumab to chemotherapy in the first-line setting has improved response rates, progression-free survival, and overall survival, response rates declined when trastuzumab was used beyond the first-line setting because of multiple mechanisms of resistance. Studies have demonstrated the clinical utility of continuing trastuzumab beyond progression, and further trials to explore this concept are ongoing. New tyrosine kinase inhibitors, monoclonal antibodies, PTEN (phosphatase and tensin homolog) pathway regulators, HER2 antibody-drug conjugates, and inhibitors of heat shock protein-90 are being evaluated to determine whether they may have a role to play in treating trastuzumab-resistant metastatic breast cancer.

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.