The thermostability of the RTS,S/AS01 malaria vaccine can be increased by co-lyophilizing RTS,S and AS01

Abstract

Background Developing thermostable vaccines is a challenge for pharmaceutical companies due to the inherent instability of biological molecules in aqueous solution. The problem is even more stringent in regions subjected to high temperatures in which protective cold chain is difficult to maintain due to a lack of infrastructure. Here, a simple, cost-effective solution to increase the thermostability of the malaria candidate vaccine RTS,S/AS01 is described. This vaccine currently needs to be stored between 2 and 8 °C due to the sensitivity of liquid AS01 to higher temperatures. The strategy was to increase thermostability by co-lyophilizing the RTS,S antigen and AS01. Methods Co-lyophilization was achieved in a solution containing 5% sucrose, 10 mM potassium phosphate and 0.0312% polysorbate 80 at pH 6.1. The physicho-chemical characteristics and immunogenic properties of the resulting solid product, called CL-vac, fresh or stored at high temperature, were compared to those of the candidate RTS,S/AS01. Results CL-vac proved to be acceptable in terms of visual appearance and physico-chemical characteristics. The structural integrity of both RTS,S and AS01 within CL-vac and its equivalence to the RTS,S/AS01 candidate vaccine were shown. Further, the stability of CL-vac was demonstrated for storage periods including 1 year at 4 °C, 1 year at 30 °C, and up to 6 months at 37 °C. In addition, CL-vac could withstand a heat excursion consisting of 1 month at 45 °C after storage for 1 year at 30 °C. Equivalence and stability were demonstrated by the various analytical tools and the immunogenicity of the samples after storage was also demonstrated in mice. Conclusions In conclusion, the co-lyophilization process appeared as a promising approach to increase RTS/AS01 vaccine thermostability.

Development and Evaluation of a Cryopreserved Whole-Parasite Vaccine in a Rodent Model of Blood-Stage Malaria

“…To facilitate long-term stability, lyophilization (freeze-drying) is used to remove water from the formulation; the addition of a cryoprotectant (e.g., trehalose) helps to stabilize the liposomes during this process ( 35 ). Reconstitution of a lyophilized vaccine just prior to administration would require minimal processing, particularly if the components are colyophilized in a single vial, as has recently been shown for a new thermostable RTS,S/AS01 vaccine formulation ( 36 ). A lyophilized vaccine formulation would have many advantages for deployment, particularly if thermostability is demonstrated.…”

CMC Strategies and Advanced Technologies for Vaccine Development to Boost Acceleration and Pandemic Preparedness

“…Finally, lyophilized vaccines must be reconstituted with a solvent or adjuvant before they can be administered to patients, which requires dosing, compatibility, and in-use stability studies. Interestingly, some promising results were published to increase vaccine thermostability by co-lyophilizing a malaria vaccine with AS01 adjuvant [ 40 ]. With the recent advances in molecular modeling and digital solutions, it is also possible to use in silico models to predict formulation stability by evaluating the interactions between antigens with different buffers (see Section 2.3 for more detail).…”

Reliable particle sizing in vaccine formulations using advanced dynamic light scattering

“…Typical particle diameters of LNPs are in the order of 10s-100s of nanometers, can vary widely, and have even been optimized to target certain organs specifically (Pardeike, et al, 2009;Iyer, et al, 2015;Pardi, et al, 2018;Hou, et al, 2021;Tenchov, et al, 2021). Furthermore, recent studies have evidenced that high antibody titers are generated for an average LNP size of 100 nm in an RNA LNP vaccine in mice (Fortpied, et al, 2020;Hassett, et al, 2021).…”