Near-critical fluid micronization of stabilized vaccines, antibiotics and anti-virals

Abstract

Fine powder preparations of vaccines hold promise in resolving many issues encountered in the transport and delivery of vaccines such as loss of potency during transport through the ‘cold chain’ and needle free delivery. We have demonstrated the efficacy of a new powder-generating technique, Carbon dioxide Assisted Nebulization with a Bubble Dryer^® (CAN-BD), for producing dry, active powders of vaccines and small molecule pharmaceuticals. A hepatitis B surface antigen (HBsAg) protein vaccine and a live-attenuated measles vaccine were stabilized in various formulations, then processed into fine powders by nebulizing and drying them at near ambient temperatures (50 °C). Full preservation of HBsAg ELISA activity was achieved for formulations containing sufficient amounts of stabilizing trehalose. The powders were stored for 43 days either at −20 °C or at +66 °C without loss of potency. Commercial live-attenuated virus measles vaccine was further stabilized by adding trehalose or sucrose to retain full potency through CAN-BD drying. Powders had a mass median aerodynamic diameter (MMAD) of 1.9 μm and respirable mass fraction of 94%. A formulation of the anti-viral zanamivir was micronized to give 73% respirable mass fraction and MMAD of 2.4 μm. The antibiotic rifampin was processed by CAN-BD to yield powder with an MMAD of 1.2 μm and 86% respirable mass fraction.

Introduction

Preparation of biopharmaceuticals and vaccines in solid dry formulation is often desirable or necessary to avoid freeze and thermal damage and to meet shelf-life storage stability requirements. In addition, fine powder formulations may be desired for greater storage stability and/or alternatives to the traditional subcutaneous injection delivery route, such as delivery to the lungs. Freeze-drying is the most common process for producing parenteral products as dry formulations. However, there are a large number of vaccines that cannot be lyophilized because they are damaged by the freezing step. These products are vaccines using aluminum hydroxide gel (“alum”) as an adjuvant—the only type of vaccine adjuvant now in commercial use within the United States. It has been shown that alum-conjugated vaccines can undergo serious damage and deactivation when frozen during processing, shipping, or storage [1], [2], [3], [4], [5], [6]. Indeed, it has only recently been recognized that in developing countries, the cold-chain vaccine distribution networks had often been accidentally freezing vaccines [7]. Another drawback of freeze-drying is that further processing (e.g., jet-milling) would be required to transform the freeze-dried cake into a powder for alternative delivery methods such as inhalation.

Carbon dioxide Assisted Nebulization with a Bubble Dryer^® (CAN-BD) is a patented [8], [9], [10], [11], [12], [13], [14], [15], [16] technique for producing fine, dry powders from solutions or suspensions, using either aqueous or non-aqueous solvents [17], [18], [19], [20], [21], [22], [23], [24], [25], [26], [27], [28], [29], [30], [31], [32], [33], [34], [35], [36], [37]. This paper covers the formulation and micronization of four diverse products: recombinant hepatitis B surface antigen protein, live-attenuated measles vaccine virus, an 823 molecular weight antibiotic (rifampin) and a 332 molecular weight anti-viral (zanamivir).