A Study to Examine the Effects of the Leptin Receptor (LEPR) Agonist Antibody REGN4461 in Adult Patients With Familial Partial Lipodystrophy (FPLD)

Two cohorts are being studied based on leptin levels. Cohort A is composed of patients with baseline leptin \<8.0 ng/mL and Cohort B is composed of patients with baseline leptin 8.0 to ≤20.0 ng/mL The primary objectives will be evaluated for patients in Cohort A only: * To evaluate the effect of REGN4461 on fasting triglycerides (TG) in patients with elevated baseline fasting TG * To evaluate the effect of REGN4461 on hyperglycemia in patients with elevated baseline Hemoglobin A1c (HbA1c) The following secondary objectives of the study will be evaluated for Cohort B and for the combined set of Cohorts A plus B: * To evaluate the effect of REGN4461 on fasting TG levels in patients with hypertriglyceridemia * To evaluate the effect of REGN4461 on glycemic control in patients with hyperglycemia The following secondary objectives of the study will be evaluated for Cohorts A and B separately, and for the combined set of Cohorts A plus B: * To evaluate the effect of REGN4461 on liver fat in patients with hepatic steatosis * To evaluate the effect of REGN4461 on hunger * To evaluate safety and tolerability of REGN4461 * To characterize the concentration profile of REGN4461 over time * To assess immunogenicity to REGN4461