The authors propose a therapy consisting of a constant dosage of reverse transcription inhibitor and protease inhibitor to achieve long-term non-progressor (LTNP) status in human immuno-deficiency virus (HIV) patients. Based on the authors analyses of cytotoxic T lymphocyte precursor (CTLp) concentration at several equilibrium points and the bifurcation of these equilibrium points, they find that administration of drugs with an efficacy lower than a certain level induces a higher CTLp concentration. As a result, drug doses of moderate efficacy result in more patients with LTNP status than doses with high efficacy. In analyses of controllability, they show that a treatment of moderate efficacy is more efficient than one of very high efficacy in terms of controlling the immune system. Using simulations, they demonstrate that their proposed method results in LTNP status in HIV patients.