Figure 1.

Biophysical characterization of rituximab at 37°C (native, black) and thermally-stressed conditions, after incubation of the rituximab formulation at 45°C for 4 h (red), 55°C for 4 h (blue), and 65°C for 4 h (green). Techniques used in structural characterization were (a) tryptophan fluorescence spectroscopy, (b) far-UV circular dichroism spectroscopy, and (c) dynamic light scattering. The essentially identical overlap of the spectra of the native and 45°C and 55°C heat-stressed samples indicates that these techniques do not detect any structural changes to rituximab after preheating to these temperatures. Upon heating at 65°C, however, structural changes and aggregation occur.