Israel-based VBL Therapeutics said a mid-stage study of its experimental brain cancer drug met the main goal of increasing overall survival. 

The drug developer's shares were up 20 percent at $6.70 in premarket trade on Wednesday.

The company said its drug, VBL-111, significantly improved overall survival when used in combination with Roche AG's cancer treatment, Avastin.

The company said it stopped testing the drug as a monotherapy after the disease progressed in nearly half the patients in the study who were given only VBL-111.

VBL is also testing VBL-111 as a treatment for thyroid cancer and ovarian cancer.

The drug is the only one left in the company's clinical pipeline after it stopped development of a second compound, VB-201, as a treatment for psoriasis and ulcerative colitis.

Separately, the company said it expected to begin the only required late-stage study of VBL-111 by mid-2015, according to an agreement with the U.S. Food and Drug Administration.

The FDA lifted a partial clinical hold on the late-stage study in February, six months after asking the company for more data on the drug's potency.

VBL Therapeutics is the name Vascular Biogenics Ltd operates under. Up to Tuesday's close, the stock had fallen nearly 7 percent since the company went public in September.