Study Helps to Explain IG Distribution in the Body

CSL Behring has developed a pharmacokinetic (PK) model that shows how the body absorbs, distributes, metabolizes and eliminates immunoglobulin (IG) following subcutaneous (SC) administration. The PK model provides a new means of simulating the mechanism by which SCIG is transported after it is injected into the subcutaneous tissue, which could affect the volume and frequency of IG dosing for primary immunodeficiency (PI) patients.

Currently, little is understood about the clinical implications of SC versus intravenous (IV) dosing of IG in PI patients, or about where SCIG travels within the body after it is administered and how long it remains there. This new model, which describes a complex system of continuous interactions between extravascular (tissue) and intravascular (blood) compartments that help determine the location and level of SCIG in different parts of the body after injection, shows that fluctuations in serum IgG after IVIG dosing were lower in the first half of the 30-day dosing cycle and higher in the second half of the cycle than would be anticipated. This, then, supports the theory that IgG distribution from the intravascular to the extravascular compartment occurs early in the dosing cycle, with the reverse occurring later in the dosing cycle.

“Clearly, a need exists to better understand the highly complex pharmacokinetic interactions that take place after an infusion of IgG, especially SCIG, in areas of the body that are not traditionally monitored by clinicians,” said Stephen Jolles, MD, University Hospital of Wales, Cardiff, U.K. “This new PK model represents a major step toward filling this need, especially for clinicians who measure serum IgG as a means of determining overall levels of IgG, and provides valuable insight into movement of IgG around the body with implications for improving PI patient dosing and treatment.”