Antisecretory Factor, Administered as an Enriched Egg Powder, Salovum®, as Supplementary Therapy for Primary Glioblastoma During Concomitant Radio-chemotherapy.

Glioblastoma (GBM) 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 encompassing antisecretory and anti-inflammatory effect. 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.

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.

In a mouse model of malignant brain tumor, preliminary findings show that intratumoral infusion of AF-16 greatly enhances the effect of simultaneous intratumoral temozolomide treatment (90% and 40% survival, respectively). AF-16 also has preliminarily significant immune modulatory effects on myeloid cells in vitro, but also effects on the secretion of immune modulatory agents from tumor cells. 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.

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.