Updated IMPACT Results Confirm that Provenge® Improves Overall Survival in Patients with Metastatic Castrate-Resistant Prostate Cancer (CRPC)

Data from the pivotal Phase 3 IMPACT (IMmunotherapy for Prostate AdenoCarcinoma Treatment) study, a 512-patient, multi-center, randomized, double-blind, placebo-controlled study evaluating men with asymptomatic or minimally symptomatic, metastatic, castrate-resistant (hormone-refractory) prostate cancer (CRPC) with overall survival as the primary endpoint, demonstrates that sipuleucel-T (Provenge®, Dendreon Corporation) does extends overall survival in men with CRPC. The data will be presented at the American Society of Clinical Oncology 2010 Genitourinary Cancers Symposium (ASCO-GU) in San Francisco on Friday, March 5 at 1:45 pm PT.

Active Cellular Immunotherapies

Sipuleucel-T is an investigational product candidate for men with advanced prostate cancer and may represent the first in a new class of Active Cellular Immunotherapies (ACIs) specifically designed to engage the patient's own immune system against cancer. The drug candidate and other ACIs are uniquely designed to use live human cells to engage the patient's own immune system with the goal of eliciting a specific long-lasting response against cancer. In contrast to Passive Cellular Immunotherapy, where effector cells are infused into the patient but not induced or expanded within the patient, ACI involves inducing an effective response to tumor cells within patients whose immune systems have failed to do so on their own. These methods generally involve introducing tumor antigens to the host effector cells.

Results

A sensitivity analysis performed with longer-term follow-up (36.5 months) and additional events (349 deaths) collected at the time of study closure demonstrated that sipuleucel-T increased three-year survival by 40 percent compared to placebo (32.1% vs 23.0%), the median survival difference of sipuleucel-T compared to placebo was maintained at 4.1 months, with a 24.1% reduction in the risk of death [HR=0.759] and a p-value of 0.017.

As previously reported in a primary analysis (34.1 months median follow-up; 331 deaths), the IMPACT study met its pre-specified primary endpoint of significantly improving overall survival compared to placebo, demonstrating that sipuleucel-T increased three-year survival by 38 percent compared to placebo (31.7% vs 23.0%), extending median survival by 4.1 months compared to placebo (25.8 months vs. 21.7 months), with a 22.5 percent reduction in the risk of death [HR=0.775] and a p-value of 0.032.

In addition, new analyses demonstrated that the median predicted survival of the two treatment arms using the Halabi model were well balanced (20.3 months for sipuleucel-T vs 21.2 months for placebo). Furthermore, in an analysis in which patients were censored at the time of docetaxel use, the sipuleucel-T treatment effect remained strong [HR=0.649].

As previously reported, the most common adverse reactions were chills, fever, headache, aches, influenza-like illness and sweating.

"The results from the IMPACT study corroborate earlier studies with sipuleucel-T in demonstrating an improvement in overall survival for men with metastatic castration resistant prostate cancer. This is the first therapeutic vaccine to demonstrate a survival benefit in cancer," said Philip Kantoff, M.D., Director of the Lank Center for Genitourinary Oncology, Chief of the Division of Solid Tumor Oncology, and Chief Clinical Research Officer at Dana-Farber Cancer Institute, Professor of Medicine at Harvard Medical School, and principal investigator of the IMPACT study. "Furthermore, the results of this study validate cancer immunotherapy as an entirely new treatment paradigm that can provide patients with a clinically meaningful survival benefit coupled with a well-tolerated safety profile."

License Application

Dendreon Corporation is seeking licensure for sipuleucel-T for men with metastatic CRPC and submitted an amended Biologics License Application for which the U.S. Food and Drug Administration assigned a Prescription Drug User Fee Act date of May 1, 2010.

A New Treatment for Advanced Kidney Cancer

The U.S. Food and Drug Administration earlier this week approved pazopanib (Votrient®, GW786034; GlaxoSmithKline), the sixth drug to be approved for kidney cancer since 2005.

Pazopanib, is an oral medication that selectively inhibits vascular endothelial growth factor receptors (VEGFR)-1, -2 and -3, c-kit and platelet derived growth factor receptor (PDGF-R), which may result in inhibition of angiogenesis, or growth of new blood vessels, in tumors in which these receptors are upregulated. All solid tumors need blood vessels to survive, and by stopping or slowing this process, Pazopanib and similar drugs medicines in this category, may halt the progression of tumor growth

Pazopanib is intended for people with advanced renal cell carcinoma (RCC), a type of kidney cancer in which the cancerous cells are found in the lining of very small tubes (tubules) in the kidney. This form of cancer is common type of kidney cancer and accounts for approximately nine out of ten cases. In 2009, approximately 49,000 people were diagnosed with renal cell carcinoma and 11,000 people died from the disease.

“The last five years have seen dramatic improvements in treatment options for patients with kidney cancer. Before 2005, the options available offered only limited effectiveness,” said Richard Pazdur, M.D., director, Office of Oncology Drug Products in the FDA’s Center for Drug Evaluation and Research. The five other drugs approved for kidney cancer and their approval dates include sorafenib (December 2005), sunitinib (January 2006), temsirolimus (May 2007), everolimus (March 2009), and bevacizumab (July 2009).

The safety and effectiveness of pazopanib was evaluated in a 435-patient phase III study that examined a patient’s progression-free survival (PFS) – the length of time, following enrollment in the study, before the tumor began growing again or before the patient died. Progression-free survival averaged 9.2 months for patients receiving pazopanib compared to 4.2 months for patients who did not receive the drug.

Patients were randomly assigned on a 2-to-1 basis to receive either pazopanib or placebo. Pazopanib reduced the risk of disease progression or death by 54% (hazard ratio = 0.46 with 95% confidence interval 0.34 to 0.62; P<0.0000001). The overall response rate in the pazopanib arm for the overall study population was 30% with duration of response of 59 weeks. When specific patient groups were evaluated, those with no prior drug treatment experienced 11.1 months of median PFS with pazopanib versus 2.8 months with placebo.

Patients who had previously received cytokine-based treatment showed 7.4 months of median PFS with pazopanib versus 4.2 months with placebo. These results were featured in an oral presentation at the annual American Society for Clinical Oncology (ASCO) meeting in Orlando, Florida. Adverse reactions included diarrhea (incidence ≥20%) , high blood pressure, hair color changes, nausea, loss of appetite, vomiting, fatigue, weakness, abdominal pain and headache.

Pazopanib can also cause severe and fatal liver toxicity. Health care professionals should order blood tests to monitor liver function before and during treatment with the drug. Since pazopanib can harm a fetus, it should not be used during pregnancy.

“The study shows that pazopanib significantly improved PFS for patients regardless of whether or not they had prior therapy. While there have been many treatment advances for patients with advanced kidney cancer, there is still a need for medicines that are effective and well-tolerated,”said Dr. Cora N. Sternberg, Department of Medical Oncology, San Camillo and ForlaniniHospitals, Rome, Italy.
“Additionally, patients did not experience a significant decline in health-related quality of life with no significant differences between pazopanib and placebo.”

The drug has also been associated with heart rhythm irregularities. Patients receiving pazopanib should be monitored with periodic electrocardiograms, which measure heart rhythm, and blood tests to monitor electrolytes since an electrolyte imbalance can lead to an irregular heart rhythm.

Pazopanib has a broad clinical program across multiple tumor types. Study details are available at www.clinicaltrials.gov. Programs currently underway in advanced RCC include a head-to-head comparison trial with sunitinib in patients with no prior drug treatment. More than 2,000 patients have been treated to date in clinical trials.

Commenting on the approval of pazopanib in RCC, Paolo Paoletti, Senior Vice President, R&D Oncology Unit noted: “We’re extremely pleased to see the progress in developing pazopanib for advanced kidney cancer, but this represents just one type of cancer in need of new treatments. Our global studies using pazopanib are designed to find new ways to use a proven mechanism to fight a diverse group of cancers. This further demonstrates our efforts to discover new medicines that provide tangible clinical benefits for patients."

For more information

• Sternberg CN, Szczylik C, Lee E, Salman PV, et al. A Randomized, Double-blind Phase III Study of Pazopanib in Treatment-naive and Cytokine-pretreated Patients with Advanced Renal Cell Carcinoma (RCC). Abstract #5021 Presented at the 2009 American Society of Clinical Oncology annual meeting.
• Hutson TE, Figlin RA. Novel therapeutics for metastatic renal cell carcinoma. Cancer. 2009 May 15;115(10 Suppl):2361-7. Review.
• Hutson TE, Figlin RA, et al Targeted Therapies for Metastatic Renal Cell Carcinoma: An Overview of Toxicity and Dosing Strategies. The Oncologist. 2008; 13: 1084-1096.
• Sonpavde G, Hutson TE, Sternberg CN. Pazopanib, a potent orally administered small-molecule multitargeted tyrosine kinase inhibitor for renal cell carcinoma. Expert Opin Investig Drugs. 2008 Feb;17(2):253-61. Review.
• Sonpavde G and Hutson T. Pazopanib: A Novel Multitargeted Tyrosine Kinase Inhibitor. Curr Oncol Rep. 2007;Mar9(2):115-9.
• Parkin M, Bray F et al. Global Cancer Statistics, 2002. CA Cancer J Clin. 2005 Mar-Apr;55(2):74-108.

Illustration courtesy of the American Society of Clinical Oncology.