Example: Drug Product spectra and information obtained from solid-state CD

This example shows a CD study of a recombinant protective antigen of Bacillis anthracis (rPA). The data provides valuable insights into the conformational stability of rPA in the adsorbed state, i.e. in the final formulation.

Secondary structure of rPA in the free form and adsorbed onto a common adjuvant, alhydrogel, are very similar as can be seen from the far UV CD spectra shown below:

Figure Far UV CD spectra of rPA solution (solid line) and rPA-adjuvant vaccine formulation (dash line).

Near UV CD spectra of the rPA formulation (data not shown), shows sharp bands with the appearance of two new bands in the region of 270- 280 nm. This is due to a more rigid structure of the antigen in the adsorbed state.

Table Estimated secondary structure of rPA Drug Substance (DS) in solution and rPA Drug Product (DP), in the solid-state obtained from the analysis of far UV CD spectra using a commonly used algorithm: CDSSTR.

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