March 7 (Reuters) - Northwest Biotherapeutics Inc on Friday said an independent monitoring board had recommended that a late-stage study of its experimental brain-cancer treatment be continued, based on an interim safety review.

The study involves more than 300 patients newly diagnosed with Glioblastoma multiforme, the most serious form of brain cancer. The main goal of the trial is to determine if the medicine, DCVax-L, can delay progression of the disease when taken on top of standard treatment.

Shares of Northwest Biotherapeutics rose 12 percent in premarket trading, from their closing price on Thursday of $5.96 on the Nasdaq.

It is a so-called immuno-oncology drug, meaning it spurs the body's own immune system to identify and kill cancer cells. Specifically, it harnesses dendritic cells, master cells of the immune system that give instructions to t-cells and b-cells, which make antibodies.

The drug consists of an individual patient's immature dendritic cells, which are drawn from the blood and exposed in a laboratory dish to antigens, or proteins, from brain tumor tissue of the patient obtained in surgery.