CTLA4 and obesity due to melanocortin 4 receptor deficiency: Although no basic mechanism related to obesity and CTLA4 immunotherapy has been reported, one clinical research report noted that the response rate was significantly higher in patients with BMIs of ≥ 25 kg/m2 who received ipilimumab monotherapy for metastatic malignant melanoma [18], suggesting that the underlying mechanism may be latent and clarified in future research.