The fast pace of breakthroughs in cancer immunotherapy, combined with the new paradigm of moving toward high-concentration dosages, is generating new challenges in the formulation of biologics, especially monoclonal antibodies (mAbs). Subcutaneous administration is a desired route for mAbs. However, formulating mAbs for small injection volumes at high concentrations with suitable stability and injectability is a significant challenge. Here, I will present a platform technology that combines the stability of solid forms of antibodies (crystalline or amorphous) with the injectability and tunability of soft hydrogel particles. I will discuss application of this approach to formulate anti-PD-1 antibody pembrolizumab and human immunoglobulin G. In vitro and in vivoperformance of the formulations will be discussed.