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Molecular Weight

The molecular weight, \(MW\), is the molar mass of a drug. In the model, it is used to convert weight-based dose amounts (mg or mg/kg) to a number of molecules dosed. It is also used to convert weight-based drug concentration (ug/mL) to molar concentration (nM).

Molecular Weight in Assess

Drug molecular weight can be calculated based on protein sequence. For antibodies or antibody-like biotherapeutics, typical values can be estimated based on the structure. The typical molecular weight of an antibody is 150 kDa (Janeway et al.).


  • Janeway CA Jr, Travers P, Walport M, et al. Immunobiology: The Immune System in Health and Disease. 5th edition. New York: Garland Science; 2001. The structure of a typical antibody molecule. Available from: