Light and pH effects on Ipilimumab conformational stability

Monoclonal antibodies (mAbs) are an essential class of proteins with several therapeutic applications. Throughout their production, storage, and administration, these proteins encounter various stressors. Viral inactivation, obtained by low pH exposure, is a key step in their downstream process. It represents a critical stress factor, which can result in protein unfolding, chemical and physical modifications. Additionally, exposure to light during this process can further affect the structural integrity of mAbs. Here, we have studied the nature of the Ipilimumab modifications occurring due to the simultaneous exposure to pH and light. Ipilimumab was first incubated at pH 2 or 3 for 30 min, then neutralized to pH 7 and analyzed by several biophysical techniques. The pH 3 induced denaturation appears reversible, and a moderate aggregation was detected. On the contrary, the pH 2-exposed samples underwent extensive aggregation with formation of insoluble aggregates and fragmentation. These events are particularly critical since they can reduce the availability of the therapeutic protein and increase the occurrence of immune reactions. Moreover, the exposure to light could chemically modify Ipilimumab generating new species distinct from the formulated one amplifying the mentioned effects. Detailed conformational studies on the structural modifications of mAbs may improve the chemical-physical knowledge of these effective drugs and suggest new production strategies for more stable products.