Active cellular immunotherapy is an approach that uses live human cells to re-engage the patient's own immune system. The goal of active cellular immunotherapy is to turn the immune system back on to elicit a specific long-lasting response against cancer.
Activated T cells may be the immune system's most potent defense against cancer. Although a variety of immune cells participate in the surveillance and elimination of cancer cells, T cells are uniquely endowed to kill specific tumor cell types. When activated to recognize tumor-associated antigens, T cells proliferate and attack cells bearing those antigens. For this reason, the goal of many investigational active cellular immunotherapies is to stimulate and optimize activation of T cells.
The cellular orchestrators of T cell activation are antigen presenting cells ( APCs ). When encountering tumor-associated antigens in the body, APCs process and display the antigens, and then present them to T cells. When activated by APCs, T cells may recognize and lyse cells bearing those antigens.
Provenge ( Sipuleucel-T ) is the first in a new class of active cellular immunotherapies that are uniquely designed to stimulate a patient's own immune system. Approximately 95% of prostate cancer cells express an antigen called prostatic acid phosphatase, or PAP.
Provenge is designed to help the man's immune cells recognize cells that carry PAP as a foreign antigen and attack those cells.
Dendreon has submitted a Biologics License Application ( BLA ) to the FDA ( Food and Drug Administration ) seeking approval of Provenge for the treatment of asymptomatic, metastatic, androgen-independent ( also known as hormone refractory ) prostate cancer.
On March 29, 2007, the FDA's Office of Cellular, Tissue and Gene Therapies Advisory Committee was asked if the submitted data established that Provenge is reasonably safe and whether there is substantial evidence that the product is efficacious. The Advisory Committee voted 17 to 0 in favor of the safety of Provenge and 13 to 4 in favor of the efficacy of Provenge.
The Biologics License Application was based primarily on a multi-center, randomized, double-blind, placebo-controlled Phase 3 study ( D9901 ) that showed that the group of men with asymptomatic, metastatic, androgen-independent prostate cancer who received Provenge had a median survival time 4.5 months longer than the median survival seen in the group that had been assigned to receive placebo. For the men who received Provenge, there was a 41 percent overall reduction in the risk of death ( p-value = 0.010; HR = 1.7 ). In addition, 34 percent of patients receiving Provenge were alive 36 months after treatment compared to 11 percent of patients randomized to receive placebo.
Treatment with Provenge was generally well tolerated. The majority of side effects were mild, including infusion-related fever and chills that were usually of low grade and typically lasted for one to two days following infusion.
Source: Dendreon, 2007
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