Overcoming barriers in Menkes disease: A standardized high quality and stable injectable copper histidinate

Copper histidinate injection, utilized for Menkes disease treatment, suffers from chemical instability and the absence of validated quality control methods. This study aims to develop an optimized stability formulation of copper histidinate and to evaluate its chemical stability using validated methods, supported by microbiological and elemental impurity risk assessment. The original formulation was modified by altering the stoichiometric ratio of histidine to copper from 1:2 to 1:3 (Cu-Hi_inj 1:3). The results indicated a significantly enhanced stability for Cu-Hi_inj 1:3, maintaining copper integrity under all tested conditions, unlike Cu-Hi_inj 1:2, which exhibited notable copper degradation at temperatures above 8°C. The new formulation displayed no degradation except at 60°C, rendering the calculation of validity period (t₉₀) unfeasible. This significantly enhanced stability is attributed to the increased histidine content in Cu-Hi_inj 1:3, which augments the chelating capacity of the copper-histidine complex. Additionally, two validated analytical methods, namely flame atomic absorption spectrometry and redox titration (the latter being an accessible analytical method for compounding pharmacies), demonstrated precision and accuracy for copper quantification, with negligible matrix effects. Sterility tests confirmed the absence of microbial growth, validating the aseptic manufacturing process. This study extends and optimizes the manufacturing procedure by incorporating active principles as salts or neutral substances and accommodating a broader pH range. The Cu-Hi_inj 1:3 formulation not only offers enhanced stability but also shows potential for industrial production, thus improving access to Menkes disease treatment while ensuring safety and efficacy.