Role of Antisecretory Factor in Dihydropyrimidine Treatment of Colorectal Cancer

The pyrimidine analogue 5-fluorouracil (5-FU) has a history in oncology for more than 50 years, and is still the backbone in chemotherapy regimens, in particular for gastrointestinal cancer although it is now often substituted with the oral prodrug capecitabine. Since colorectal cancer is the third most common cancer in Europe and the US a great number of patients will be exposed to 5-FU either as part of a curative intent, ie (neo)adjuvant, or with a palliative intention.

One debilitating, and sometimes even life-threatening, toxicity from dihydropyrimidines, e g 5-FU and capecitabine, is gastrointestinal mucositis resulting in, eg severe diarrhoea necessitating in-hospital care including periods of support with iv fluids. The efficacy of current treatment for this adverse effect include iv fluids, loperamide and opioids po and octreotide sc is moderate and new treatment principles or, preferably, ways to prevent such toxicity, are urgently needed. Mucositis is a common adverse effect also from a number of other cancer drugs as well as from radiotherapy.

Cholera induced diarrhoea, as well as other forms of diarrhoea-inducing agents, has been shown to elicit a stimulated, endogenous production of a protein, named "antisecretory factor", ASF. This protein has been chemically characterized in detail. ASF acts by modulating secretion of water and ions but also counteracts inflammatory processes. One of the biologically active peptides of the ASF protein is AF 16, a 16 amino acids long peptide which can easily be synthesized, is chemically very stable, and is therefore used for experimental purposes.

ASF is also produced by hens fed on a diet of fermented grains or a specific diet of sugars and amino acids, leading to an accumulation of the ASF protein in the egg yolk. Spray dried yolk in the form of a powder is commercialized as Salovum registered by the EU authorities as "Food for specific medical purposes", i e is not a drug from a regulatory perspective. Therefore, clinical studies with Salovum (or SPC-flakes, see below) do not need approval from the Medical Products Agency.

Salovum rapidly increase the plasma ASF-concentration. Another way to increase ASF and, thus, to achieve benefit, is to induce its production/conversion by ingestion of oat flakes, specially processed (similar to malting) to contain the proper mix of sugars and amino acids. Such flakes are also commercially available (SPC-flakes) as "Food for specific medical purposes" and has been recommended or considered for a number of secretory pathological conditions, e g for treatment of Mb Meniére.

Salovum has been shown to rapidly, ie within hours to a few days, antagonize diarrhoeal diseases of various etiologies. It has also been used against high fluid passages and inflammation in Crohns disease, Colitis ulcerosa and carcinoids in adults. SPC-flakes have similar effects but need weeks of administration to emerge. Importantly, to raise body ASF, by Salovum or SPC-flakes, for the above indications has not been associated with adverse effects.

Interestingly from an oncological perspective, provision of exogenous ASF and induction of endogenous ASF has been shown to reduce interstitial fluid pressure (IFP) in tumours, increase tumour uptake of cytotoxic drugs and improve survival in animal tumour models.

Thus, to raise body ASF by administration of ASF in the form of Salovum or its endogenous induction by SPC-flakes is seemingly a promising strategy worthwhile to investigate in cancer, both for treatment and counteraction of adverse effects, notably gastrointestinal mucositis, and for improvement of drug cancer treatment. While a clinical trial on administration of ASF as a strategy to improve cancer therapy, notably in glioblastoma, is in a pilot early phase, there is no study ongoing with the aim to counteract chemotherapy induced mucositis.

With this background the present study will investigate if administration of ASF in the form of Salovum combined with induction of endogenous AF by intake of SPC-flakes might be beneficial in colorectal cancer (CRC) patients to prevent dihydropyrimidine based chemotherapy induced gastrointestinal mucositis. Since the study team has also experience from measurements in patients of tumour IFP using 15O-labeled water PET, a pharmacodynamic pilot study for assessement of Salovum/SPC induced changes in tumour IFP will be included as an add on to the main study and open for 10 patients with liver metastatic disease.