Since the relative expression of fibronectin in the combination vardenafil and nintedanib sample was significantly lower than the estimated ED50 dose of either vardenafil or nintedanib individually, the combination of vardenafil and nintedanib was found to be synergistic for the suppression of ECM fibronectin in human disease IPF fibroblasts. This evidence concerns the gene FN1 and glycogen storage disease VI.