A 52-year-old man from Delhi presents with a 3-month history of progressive muscle pain and weakness in his legs. He was started on atorvastatin 40 mg daily 6 weeks ago for hypercholesterolaemia (total cholesterol 320 mg/dL, LDL 240 mg/dL). On examination, he has proximal muscle tenderness and mild elevation of creatine kinase (CK 850 U/L, normal <200). His lipid panel shows total cholesterol 180 mg/dL and LDL 95 mg/dL. Renal function and liver enzymes are normal. Which of the following best explains the biochemical mechanism underlying his current clinical presentation?