Lyophilization Strategy Enhances the Thermostability and Field-Based Stability of Conjugated and Comixed Subunit Liposomal Adjuvant-containing Tuberculosis Vaccine Formulation (ID93 + GLA-LSQ).

Abstract

ID93 + GLA-LSQ is an adjuvanted recombinant protein vaccine candidate that has demonstrated robust T-cell immunity and reduced bacterial burden in preclinical studies. Here, we explored the strategy of lyophilization by introducing 10% Trehalose as a bulking agent and cryoprotectant to develop a thermostable single-vial formulation of ID93 + GLA-LSQ. We further examined the stability of lyophilized formulations stored at 4 and 37 °C in the research laboratory and field stability across five study sites. Co-mixed (CoVL) and conjugated (ConjVL) formulations were prepared and assessed for various stability parameters including cake quality, melting point, liposome reformation, particle size, GLA/QS-21 concentration, presence of ID93, and biological activity for three months in the research laboratory and nine months at ambient temperature in five health centers. Stability assessment for both formulations stored in the research laboratory for three months showed that they were physically stable and biologically active. The field-based ambient stability assessment showed that the formulations maintained physical integrity, liposomal structure, and antigen integrity, with limited chemical degradation of GLA and QS-21 adjuvants observed. ConjVL retains GLA slightly better than the CoVL formulation, and a moderate increase in particle size was observed after nine months. These findings showed that the formulations demonstrate a promising stability profile after extended storage at ambient temperature, suggesting the potential for real-world application without strict refrigeration requirements.