Developing ultra-high concentration formulations of human immune globulins for subcutaneous injectables

This work describes the first development of high-concentration suspension formulations of human immune globulin. Colloidal-level dispersions of immune globulin were achieved by suspending a spray dried solid powder of protein in a protein solution made saturated by the addition of pharmaceutical excipients. The spray drying process was used to generate ∼90 % of particles below 20μ. The monomer and aggregates content of immunoglobulin were found to be 93 % and 0.3 %, respectively. The injection forces for the colloidal suspensions were characterized using a dynamic compression test. The concentrations of 300, 380, and 400 mg/mL formulations were injected at 3.8 N, 10 N, and 16.5 N of maximum injection forces, respectively, when a 24-gauge needle was used. The viscosity of a 300 mg/mL suspension was 128 cP. The viscosity of a 380 mg/mL suspension was 284 cP, and the viscosity was higher for the 400 mg/mL formulation; however, injectability was not an issue, which remains rare for non-Newtonian, shear-thickening systems. It is acknowledged that the 400 mg/mL suspension formulation remained relatively challenging as compared to other suspensions for injection because of its very high viscosity, and significant force was required to inject it. We show that where ultra-high-concentration immune globulin is being developed within reasonable constraints of pharmaceutical regulation, with an injectability parameter, formulations might make their way to the clinic when viscosity could say otherwise. However, further work should be conducted to assess chemical stability (using methods such as mass spectrometry) along with forced degradation studies prior any clinical use.