Monday, April 28, 2008

Oncology vaccine shows promise in prostate cancer

In the past 30 and 40 years, we've learned much about the components of the immune system and the way the components integrate to cause an anti-tumor effect, but very little of this research has translated into real clinical benefit for patients.

However, at the recent AACR meeting in San Diego, early data suggested a promising synergy when allogeneic granulocyte monocyte colony-stimulating factor (GM-CSF) secreting prostate cancer cell lines (GVAX) and escalating doses of the anti-cytotoxic T-lymphocyte antigen CTLA-4 antibody ipilimumab were combined to treat patients with metastatic hormone-refractory prostate cancer.

Researchers have found a promising synergy of two therapies to treat metastatic prostate cancer that is resistant to hormone therapy. In a phase I study, they evaluated a combination of GVAX immunotherapy with ipilimumab lowered prostate-specific antigen (PSA) levels in some patients. In this trial, the vaccine was administered with escalating doses of anti-CTLA-4 (cytotoxic T-lymphocyte antigen 4) antibody ipilimumab. Researchers believe that the combination of these two immunotherapies may increase immunity to prostate cancer.

Twelve patients were enrolled in this study. All were given the same doses of GVAX (a 500 million cell first dose followed by bi-weekly 300 million-cell doses for 24 weeks), and, in groups of three, different quantities of ipilimumab administered every four weeks (.3mg, 1mg, 3mg, or 5 mg).

Anti-tumor activity was observed in five of the six patients who received the two highest doses of ipilimumab, including PSA-level declines of greater than 50 percent; these PSA declines were maintained in four of these patients for at least six months, and up to 16 months. Among patients with PSA-level declines, complete resolution of multiple lesions on bone scans in two patients was noted, resolution of cancer spread to abdominal lymph nodes in one patient, and improvement in bone pain in one patient.

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