PDE4A and serum lipopolysaccharide activity: In our previous studies, we observed that GRMS-55 and the pan-selective PDE4 inhibitor rolipram exhibited anti-inflammatory effects and decreased paw edema in rats with collagen-induced arthritis, at an IC50 of 0.26 and 0.01 mg·L−1, respectively, and suppressed TNF-α production in the rat model of lipopolysaccharide-induced endotoxemia at an IC50 of 1.06 and 0.36 mg·L−1, respectively.