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Brain Cancer Vaccine Improves Survival in Mid-Stage Trial

Prophage tested in glioblastoma patients

Positive results have been reported from a single-arm, open-label, phase II study of patients with newly diagnosed glioblastoma multiforme (GBM) who received Prophage autologous cancer vaccine (Agenus Inc.) added to standard-of-care treatment.

In this study, patients lived nearly twice as long as expected after receiving the vaccine. Half of the patients lived for 2 years — an encouraging result for a cancer that often kills patients within 1 year.

Median overall survival (OS) — the trial’s primary endpoint — was 23.8 months and remained durable in patients treated with Prophage and standard of care. For standard of care alone, median OS was 14.6 months. Median progression-free survival was 17.8 months, and nearly 22% of patients were alive without progression at 24 months.

The response to Prophage appeared to be more pronounced in patients with less expression of the checkpoint programmed death ligand-1 (PDL-1) on white blood cells, suggesting that combinations of Prophage with checkpoint modulators, such as programmed death-1 (PD-1) antagonists, might make Prophage more effective in a greater percentage of patients with GBM.

Prophage is an autologous cancer vaccine. Each patient receives vaccine prepared from their own surgically resected tumors. As a result, the vaccine appears to help stimulate the patient’s immune system to attack the cancer based on the spectrum of mutant proteins expressed by their own tumor. Since most cancers result from an accumulation of random mutations, which produce different mutant proteins in each patient, this approach is intended to individually tailor each patient’s vaccine to optimally target the immune attack to that patient’s actual tumor.

The phase II single-arm trial of Prophage in patients with newly diagnosed GBM undergoing gross total resection included 46 patients treated at eight centers in the U.S. The patients were treated with surgical resection, radiation, and temozolomide as the standard of care in addition to Prophage vaccination.

The American Cancer Society estimated that more than 23,000 malignant tumors of the brain or spinal cord would be diagnosed in the U.S. in 2013, and that more than 14,000 people would die from these tumors. GBM is the most common primary malignant brain tumor and accounts for most of the diagnoses. It has been associated with a particularly poor prognosis, with 1- and 5-year survival rates of 34% and 5%, respectively.

The current standard of care for patients with newly diagnosed GBM is surgical resection followed by fractionated external-beam radiotherapy and systemic temozolomide, resulting in median OS of 14.6 months, based on data from a randomized phase III trial. Although this treatment can prolong survival, it is not curative.

Most patients with GBM experience recurrent disease, with a median time to recurrence of 7 months. From the time of recurrence, the median survival is 3 to 9 months. Current treatment options for patients with recurrent GBM include surgery, chemotherapy (i.e., lomustine and temozolomide), bevacizumab, and radiotherapy.

Source: Agenus Inc.; July 1, 2014.

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