Subvisible Particles in IVIg Formulations Activate Complement in Human Serum

When administered intravenously, various particles and nanomedicines activate complement, potentially leading to infusion reactions and other adverse drug reactions. Particles form within formulations of therapeutic proteins due to stresses incurred during shipping, handling, and administration to patients. In this study, IVIg solutions were stored in multiple types of vials and prefilled syringes and exposed to agitation and freeze-thaw stresses to generate particles. The stressed samples were added to human serum to determine whether these particles activated complement. Subvisible IVIg particles ranging in size between 2 and 10 microns activated complement in a fashion that was linearly dependent on the number of particles dosed, whereas little correlation was found between doses of larger particles (>10 microns) and complement activation. Activation of complement by subvisible particles of IVIg followed the alternative pathway, as shown by the release of complement cascade factor Bb and the production of the anaphylatoxins C3a and C5a without generation of C4a. The number and the morphology of subvisible particles formed depended on the applied stress, formulation, and on the container material. But the capacity of the 2- to 10-micron-sized particles to activate complement in human serum appeared to depend only on particle concentration.