Lyophilization of Adjuvanted Vaccines: Methods for Formulation of a Thermostable Freeze-Dried Product

Development of thermostable vaccine adjuvants

INTRODUCTION

The importance of vaccine thermostability has been discussed in the literature. Nevertheless, the challenge of developing thermostable vaccine adjuvants has sometimes not received appropriate emphasis. Adjuvants comprise an expansive range of particulate and molecular compositions, requiring innovative thermostable formulation and process development approaches.

AREAS COVERED

Reports on efforts to develop thermostable adjuvant-containing vaccines have increased in recent years, and substantial progress has been made in enhancing the stability of the major classes of adjuvants. This narrative review summarizes the current status of thermostable vaccine adjuvant development and looks forward to the next potential developments in the field.

EXPERT OPINION

As adjuvant-containing vaccines become more widely used, the unique challenges associated with developing thermostable adjuvant formulations merit increased attention. In particular, more focused efforts are needed to translate promising proof-of-concept technologies and formulations into clinical products.

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

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.

Novel technology for storage and distribution of live vaccines and other biological medicines at ambient temperature

A novel, thin-film platform that preserves live viruses, bacteria, antibodies, and enzymes without refrigeration for extended periods of time is described. Studies with recombinant adenovirus in an optimized formulation that supports recovery of live virus through 16 freeze-thaw cycles revealed that production of an amorphous solid with a glass transition above room temperature and nitrogen-hydrogen bonding between virus and film components are critical determinants of stability. Administration of live influenza virus in the optimized film by the sublingual and buccal routes induced antibody-mediated immune responses as good as or better than those achieved by intramuscular injection. This work introduces the possibility of improving global access to a variety of medicines by offering a technology capable of reducing costs of production, distribution, and supply chain maintenance.

Lyophilized bone marrow cell extract functionally restores irradiation-injured salivary glands

OBJECTIVE

Bone marrow cell extract (BMCE) was previously reported to restore salivary gland hypofunction caused by irradiation injury. Proteins were shown to be the main active factors in BMCE. However, BMCE therapy requires multiple injections and protein denaturation is a concern during BMCE storage. This study aimed to preserve, by lyophilization (freeze-drying), the bioactive factors in BMCE.

METHODS

We developed a method to freeze-dry BMCE and then to analyze its ingredients and functions in vivo. Freeze-dried (FD) BMCE, freshly prepared BMCE (positive control), or saline (vehicle control) was injected into the tail vein of mice that had received irradiation to damage their salivary glands.

RESULTS

Results demonstrated that the presence of angiogenesis-related factors and cytokines in FD-BMCE remained comparable to those found in fresh BMCE. Both fresh and FD-BMCE restored comparably saliva secretion, increased cell proliferation, upregulated regenerative/repair genes, protected salivary acinar cells, parasympathetic nerves, and blood vessels from irradiation-damaged salivary glands.

CONCLUSION

Lyophilization of BMCE maintained its bioactivity and therapeutic effect on irradiation-injured salivary glands. The advantages of freeze-drying BMCE are its storage and transport at ambient temperature.

Development of a thermostable nanoemulsion adjuvanted vaccine against tuberculosis using a design-of-experiments approach

Background

Adjuvants have the potential to increase the efficacy of protein-based vaccines but need to be maintained within specific temperature and storage conditions. Lyophilization can be used to increase the thermostability of protein pharmaceuticals; however, no marketed vaccine that contains an adjuvant is currently lyophilized, and lyophilization of oil-in-water nanoemulsion adjuvants presents a specific challenge. We have previously demonstrated the feasibility of lyophilizing a candidate adjuvanted protein vaccine against Mycobacterium tuberculosis (Mtb), ID93 + GLA-SE, and the subsequent improvement of thermostability; however, further development is required to prevent physicochemical changes and degradation of the TLR4 agonist glucopyranosyl lipid adjuvant formulated in an oil-in-water nanoemulsion (SE).

Materials and methods

In this study, we took a systematic approach to the development of a thermostable product by first identifying compatible solution conditions and stabilizing excipients for both antigen and adjuvant. Next, we applied a design-of-experiments approach to identify stable lyophilized drug product formulations.

Results

We identified specific formulations that contain disaccharide or a combination of disaccharide and mannitol that can achieve substantially improved thermostability and maintain immunogenicity in a mouse model when tested in accelerated and real-time stability studies.

Conclusion

These efforts will aid in the development of a platform formulation for use with other similar vaccines.