The data obtained from patients with LPL-deficiency who received a single treatment with multiple injections of alipogene tiparvovec, support the initial expectation that the protein product is minimally immunogenic, if at all: neither treatment-emergent antibody responses against LPL nor T-cells responses against LPL were found. The gene discussed is LPL; the disease is hyperinsulinemic hypoglycemia, familial, 4.