Generalized Lipodystrophy

This study is researching a new drug called mibavademab (called "study drug"). The study involves participants with a condition called Generalized Lipodystrophy (GLD). The aim of the study is to see how well mibavademab works and what side effects it has. Researchers will also look at how much mibavademab is in the body at different times. This is a 2-part study: Part A is an efficacy study in pediatric and adult participants, Part B is a safety and pharmacokinetic study in pediatric participants. The study is researching several other questions, including: * How mibavademab affects the amount of sugar in the blood * How mibavademab affects the amount of fat (triglycerides) in the blood * How mibavademab affects the amount of fat that has built up in the liver * Whether the body makes antibodies against the study drug (which could make the drug less effective or could lead to side effects)