Background and Importance Romiplostim (N-Plate^®) is a Fc-fusion protein in which a TPO agonist peptide is associated with the Fc domain of a human antibody. It contains of two identical subunits each consisting of an Fc domain of human immunoglobulin IgG1 linked to a peptide containing two human TPO receptor binding domains. This drug is indicated in the treatment of immune thrombocytopenic purpura (ITP). As proteinaceous based-medicine, romiplostim is indicated to have low stability, thus the studies on the effects of possible in-use mishandling and in stress conditions are welcomed to get knowledge upon its stability and degradation.

Aim and Objectives To evaluate the impact of in use mishandling and forced degradation on romiplostim chemical structure by evaluation of several Critical Quality Attributes (CQAs).

Material and Methods Vials of romiplostim (N-plate, 0.5 mg/mL) were reconstituted as it is indicated by the manufacturer and submitted to several stress stimuli: exposition at 80 °C (2h), smooth shaking (12h), room light and temperature (excursion aprox. 20-24 °C) exposition (24h), accelerated light exposition (24h) and 1 freeze/thaw cycle. The CQAs evaluated were: (A) primary structure, by peptide mapping-RP/UHPLC-(Orbitrap)MS/MS; (B) tertiary structure by Intrinsic tryptophan fluorescence spectroscopy; (C) aggregation by SE-HPLC/DAD; and functional activity (as the capacity to bind to its therapeutic target) by ELISA.

Results Changes in the primary and tertiary structure and the formation of aggregates were detected after romiplostim samples were submitted to high temperature and to room conditions. These changes detected were accompanied by a loss of functionality. Similar effects were caused when stressed by accelerated light exposition. The smooth shake and freeze/thaw cycle stimuli did not affect the CQAs studied.

Conclusion and Relevance This study proves that romiplostim must be reconstituted and administrated avoiding long-time light exposure and elevated temperatures as they can induce the activation of several degradation pathways which cause loss of functionality and aggregation, and thus, losing the original safety, quality and efficacy of the drug.

References and/or Acknowledgements This study was entirely funded by Project FIS: PI-17/00547 (Instituto Carlos III, Ministerio de Economía y Competitividad, Spain), which means that it was also partially supported by European Regional Development Funds (ERDF).

Conflict of Interest No conflict of interest