FGF21 and obesity due to melanocortin 4 receptor deficiency: Moreover, several FGF21 analogs, such as Pegbelfermin (Bristol-Myers Squibb), LY2405319 (Eli Lilly), and PF05231023 (Pfizer), have passed Phase I/II trials and were reported to be generally well tolerated and effective in treating obesity or diabetes [15–17].