KONCERT A Kaletra ONCE Daily Randomised Trial of the Pharmacokinetics, Safety and Efficacy of Twice-daily Versus Once-daily Lopinavir/Ritonavir Tablets Dosed by Weight as Part of Combination Antiretroviral Therapy in Human Immunodeficiency Virus-1 (HIV-1) Infected Children (PENTA 18) - ICH GCP - Clinical Trials Registry