Antisecretory Factor During Concomitant and Adjuvant Therapy of Primary Glioblastoma, a Randomised, Prospective and Double Blinded Study

Glioblastoma (GB) is the most common primary brain tumor and also has the worst prognosis with a mean survival time below 1 year and a 5-year survival rate of less than 2%. AF is a 41kilodalton endogenous and essential protein with antisecretory and anti-inflammatory effects. Endogenous AF activity increases after exposure to bacterial toxins and endogenous triggers of inflammation. The active amino-terminal portion of AF has been synthesized as a 16 amino acid peptide (AF-16) and has been used in animal experimental studies. Salovum® is a product based on egg yolk powder B221® and contains high levels of AF. Salovum® is classified as food for special medicinal purposes (FSMP) by the European Union an din other countries.

Many tumors show elevated interstitial fluid pressure (IFP) compared to the surrounding tissue due to vascular leakage, providing a barrier for drug uptake in solid tumors, as well as poor perfusion, resulting in hypoxia and relative resistance to radiochemotherapy.

AF-16 was reported to significantly reduce the IFP in xenotransplanted human glioblastoma by inhibiting an ionic pump, NKCC1, in the tumor tissue. Both Salovum® and AF-inducing specific processed cereals (SPC) prolonged survival in the same models. Systemic temozolomide treatment combined with AF inducing SPC completely blocked tumor growth in GBM xenografts. Likewise, SPC treatment abrogated 90% of pre-established syngeneic tumors in immune competent animals.

Intratumoral delivery of AF-16 potentiated the effect of intratumoral temozolomide in an experimental model of glioblastoma.

Mechanistically, it remains unclear whether AF's effect in tumor models is mediated through decrease of IFP and/or immunomodulation. Also, an effect on the complement system through modulation of circulating complement complexes with proteasome units has been proposed.