A 42-year-old woman undergoes renal transplantation for end-stage renal disease. She is started on a triple immunosuppressive regimen: prednisolone, azathioprine, and cyclosporine. At 6 weeks post-transplant, she develops tremor, hypertension (BP 158/96 mmHg), and hyperglycemia (fasting glucose 180 mg/dL). Serum creatinine is stable at 1.2 mg/dL. Which of the following is the most likely culprit drug responsible for her current clinical manifestations?