A Strategy to Model Nonmonotonic Dose-Response Curve and Estimate IC50

Hui Zhang*, Jeanne Holden-Wiltse, Jiong Wang, Hua Liang

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

13 Scopus citations


The half-maximal inhibitory concentration IC50 is an important pharmacodynamic index of drug effectiveness. To estimate this value, the dose response relationship needs to be established, which is generally achieved by fitting monotonic sigmoidal models. However, recent studies on Human Immunodeficiency Virus (HIV) mutants developing resistance to antiviral drugs show that the dose response curve may not be monotonic. Traditional models can fail for nonmonotonic data and ignore observations that may be of biologic significance. Therefore, we propose a nonparametric model to describe the dose response relationship and fit the curve using local polynomial regression. The nonparametric approach is shown to be promising especially for estimating the IC50 of some HIV inhibitory drugs, in which there is a dose-dependent stimulation of response for mutant strains. This model strategy may be applicable to general pharmacologic, toxicologic, or other biomedical data that exhibits a nonmonotonic dose response relationship for which traditional parametric models fail.

Original languageEnglish (US)
Article numbere69301
JournalPloS one
Issue number8
StatePublished - Aug 1 2013

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)
  • Agricultural and Biological Sciences(all)
  • General


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