A 14-year-old boy with genetically confirmed familial Mediterranean fever (FMF) continues to experience 4-5 attacks per month despite escalation to the maximum tolerated dose of colchicine. His attacks involve severe abdominal pain, fever to 39.5°C (103.1°F), and arthritis. Laboratory evaluation during attacks shows markedly elevated serum amyloid A. Which biologic agent has the strongest evidence from randomized controlled trials for efficacy in colchicine-resistant FMF?