MC4R and obesity due to melanocortin 4 receptor deficiency: This dual‐cassette vector mimics the body's natural feedback system to achieve autoregulation of the transgene and its efficacy has been examined in genetic models of obesity and diabetes such as db/db mice (Cao et al., 2009) and melanocortin‐4 receptor (MC4R) deficient mice (Siu et al., 2017).