Results of phase II studies of pazopanib

GlaxoSmithKline (GSK) has announced results from ongoing Phase II studies of pazopanib in advanced or metastatic renal cell carcinoma (RCC) and ovarian cancer.

These trials were presented at the 43rd Annual Meeting of the American Society of Clinical Oncology (ASCO) in Chicago. The results observed in these trials with pazopanib support further investigations.

Pazopanib is an oral, investigational angiogenesis inhibitor targeting vascular endothelial growth factor receptor (VEGFR), platelet-derived growth factor receptor (PDGFR) and c-kit, important proteins in the angiogenic process. Angiogenesis, which is the growth of new blood vessels in the body, plays a critical role in the growth and spread of tumors.

This ongoing Phase II randomized discontinuation study is evaluating patients with advanced or metastatic RCC who have not received prior systemic therapy or have failed one prior therapy (cytokine or bevacizumab-containing regimen). All patients received 800 mg of pazopanib taken orally, once-daily during a 12 week lead-in period. Based on data available on 60 patients at the time of a planned interim analysis, the Independent Data Monitoring Committee (IDMC) recommended that randomization to placebo for patients with stable disease should be discontinued. The study continued as an open-label, single-arm study with all patients receiving pazopanib.

The preliminary week 12 response rate for all 225 patients was 27%. In addition, stable disease was achieved in 46% of patients for a total disease control rate of 73%. Responses have been observed beyond week 12, and the overall response rate will be reported at study completion. Response was determined according to RECIST (Response Evaluation Criteria In Solid Tumors) which is a set of published rules that defines when cancer patients improve (respond), stay the same (stable), or worsen (progress) during treatments. Almost half of the enrolled patients remain in the study.

"These results with pazopanib are very encouraging," said lead investigator Dr. Thomas Hutson, Baylor Sammons/Texas Oncology PA, Dallas, Texas. "The high response rates seen so far in this study show clear clinical activity in advanced or metastatic renal cell carcinoma, and a number of ongoing studies also demonstrate therapeutic promise in several other tumor types."

The most frequent adverse events (AEs) were diarrhea, fatigue, hair color change, nausea, and hypertension. Pazopanib had a low incidence of hand-foot syndrome (10%), rash (12%), hemorrhage (9%), and mucositis (5%). Please see safety considerations below.

The incidence of RCC is rising throughout the world with 208,000 new cases diagnosed annually. Although patients with early-stage disease can potentially be cured with surgery, many will either experience a recurrence after surgery or have advanced or metastatic disease at the time of initial presentation.

RCC is generally resistant to standard chemotherapy, and immunotherapeutic regimens using recombinant human interleukin-2 (IL-2) and recombinant human interferon 2b (IFN), either alone or in combination, have been widely used in patients with advanced disease. Although high-dose IL-2 has shown promise with durable complete remissions observed in 7% of patients, toxicity has limited its widespread use. Lower dose cytokine therapies have not shown the same magnitude of response and are also limited by their toxicity.8 Recently, several anti-angiogenesis drugs, including sunitinib, sorafenib and bevacizumab have demonstrated clinical activity in patients with advanced or metastatic RCC.8 Although targeted therapies have advanced the treatment of advanced or metastatic RCC, complete and durable responses are not achieved in the majority of patients8 and a need remains for new treatment options.

"These results clearly demonstrate the potential pazopanib offers as a future therapeutic option not only in renal cell cancer, but across many different tumor types," said Debasish Roychowdhury, MD, Vice President, Global Clinical Development, Oncology Medicine Development Centre, GSK. "The broad clinical development program for pazopanib, in various cancers as monotherapy and in combination therapy, including combinations with Tykerb, underscores our continued commitment to delivering effective new treatments for patients with cancer."

This ongoing Phase II open-label, monotherapy study is evaluating pazopanib in patients with cancer of the ovary, fallopian tube or peritoneum, who have failed standard platinum-based therapy. Treatment is continued until disease progression, withdrawal due to AEs, or withdrawal of consent. Biological activity (measured as a decrease in CA-125, a biologic marker of clinical activity) was seen in nine (41%) of 22 evaluable patients with relapsed disease. The most common AEs were diarrhea, nausea, abdominal pain, fatigue, and vomiting. Please see safety considerations below.

Globally, ovarian cancer (204,000 cases and 125,000 deaths) is the sixth most common cancer and the seventh most common cause of death from cancer in women.5 The majority of patients with ovarian cancer will have advanced disease at the time of initial diagnosis. Typically, these patients are managed with surgery followed by combination chemotherapy. Although the majority of patients will respond initially to first-line therapy, recurrent disease remains a considerable problem.