Houde D, Berkowitz SA. Conformational comparability of factor IX-Fc fusion protein, factor IX, and purified Fc fragment in the absence and presence of calcium.
J Pharm Sci 2012;
101:1688-700. [PMID:
22271461 DOI:
10.1002/jps.23064]
[Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2011] [Revised: 12/29/2011] [Accepted: 01/05/2012] [Indexed: 01/13/2023]
Abstract
A long lasting recombinant factor IX -Fc fusion protein (rFIX-Fc) is being developed for the treatment of hemophilia B and is currently in late stage clinical investigation. By limiting injection frequency and maintaining efficacy, rFIX-Fc shows promise as a new therapeutic option for hemophilia B patients. However, before gaining regulatory approval, rFIX-Fc must undergo rigorous analytical and biological testing, in addition to clinical trials. Included in this testing is the need to understand this protein's higher-order structure and dynamics. In this study, we investigated and compared the biophysical properties of rFIX-Fc, rFIX, and Fc using hydrogen/deuterium exchange mass spectrometry and differential scanning calorimetry. Within the limits of these techniques, our results show that structural comparability exists between rFIX and the FIX region of rFIX-Fc. In addition, changes in the structure and dynamics of both proteins, in response to calcium binding, a requirement for FIX function, are also highly comparable. In the case of Fc and Fc region of rFIX-Fc, conformational comparability is also established. These biophysical results further support the conclusion that fusing an immunoglobulin gamma 1 Fc to rFIX does not significantly alter the higher-order structure of FIX or Fc, Ca binding to FIX, or Fc functionality.
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