PDGFRβ and GSK3 may regulate body weight, as PDGFRβ and GSK3 deficiencies reduce high-fat diet-induced obesity in mice.45,46 Fidaxomicin is minimally absorbed into the circulation, so it is speculated that its inhibition of intestinal PDGFRβ and GSK3β may regulate body weight indirectly. The gene discussed is GSK3B; the disease is obesity due to melanocortin 4 receptor deficiency.