A 19-year-old male presents with a 3-year history of severe acne unresponsive to topical retinoids, benzoyl peroxide, and two courses of oral doxycycline. On examination, the structure marked **A** — multiple confluent deep inflammatory nodules 8–15 mm in diameter on the cheeks and jawline that are erythematous, tender, and indurated — is noted alongside post-inflammatory hyperpigmentation and ice-pick scarring. Global Acne Severity Scale score is Grade 4. Baseline liver function tests and lipid profile are normal. Which of the following is the most appropriate next step in management?