A 52-year-old man from Delhi presents with chest pain on exertion for 3 months. His lipid panel shows total cholesterol 320 mg/dL, LDL 240 mg/dL, HDL 32 mg/dL, and triglycerides 180 mg/dL. He is started on atorvastatin 40 mg daily. After 6 weeks, repeat lipids show total cholesterol 280 mg/dL and LDL 200 mg/dL — a disappointing response. Genetic testing reveals a heterozygous mutation in the LDL receptor gene. Which of the following best explains the limited efficacy of statin therapy in this patient?