Photodegradation and photoyellowing of monoclonal antibody therapeutics.

摘要

Monoclonal antibody (mAb) therapeutics have become increasingly important treatments for many diseases. All monoclonal formulations are susceptible to photodegradation, and are required to be tested for photostability by regulatory agencies. However, the exposure levels specified by the guideline are overstressed conditions for mAb therapeutics, and their behavior under regular manufacture and clinical in-use conditions are seldom studied. In addition, a systematic approach is needed to directly compare the photostability of multiple mAbs considering their high conservativeness in sequences and structures.;Herein, we systematically investigated the photostability of multiple mAb IgG formulations under manufacture-relevant photoexposure conditions using cool white (CW) fluorescent light and found significant photodegradation accompanied by yellow discoloration. Photoyellowing of mAb therapeutics is not uncommon but rarely studied or quantified. We developed a novel colorimetric method to quantify solution yellowing using yellowness index, and discovered the essential roles that UV light and oxygen each played in the photoyellowing of mAb formulations. We demonstrated four practical approaches for mitigating photoyellowing as well as the overall photodegradation resulting from these two factors.;Interestingly, when the UV component in the CW fluorescent light was eliminated by optical filtering, multiple mAb formulations still exhibited illumination-dependent photodegradation and yellowing. We further investigated the mechanisms behind visible light-induced mAb degradation using yellow discoloration as the indicator for photodegradation and tryptophan (Trp) as a model system. Trp solutions did not exhibit any degradation or yellowing when exposed to the same amount of visible light, unless they had previously been photosensitized by Trp derivatives generated with UVA light. These derivatives were detected in multiple mAb formulations before and after further light exposure postpurification, even if the solutions were visually colorless. In summary, our data demonstrate that UV light initiates mAb photodegradation by exciting photolabile residues and generating chromophoric intermediates that function as photosensitizers to propagate further photodegradation when excited by visible light. For the very first time the damaging impact of visible light on protein photostability was investigated and differentiated from that of UV light, and thus limiting light exposure during manufacturing and clinical use is the best approach to reduce mAb photodegradation.