In the present study lyophilization of semi-solids was explored with the intention of developing LSDFs for i.vag immunization that were conducive to antigen stability. Desirable attributes of the resulting LSDFs included that they would provide rapid stabilisation of antigen, long-term product stability (avoiding cold-chain storage) and ease of reconstitution upon i.vag administration. Upon administration these formulations were predicted to reconstitute to semi-solids see more by the imbibing of vaginal fluid, permitting intimate contact of the vaccine candidate with the vaginal epithelium. Upon reconstitution the formulations would retain the intended beneficial attributes

of the original semi-solid formulations, including mucoadhesiveness and in the case of the lyophilized RSVs enhanced viscoelasticity, thus enhanced retention compared with more conventional vaginal semi-solid formulations, including

Carbopol®. To enable preparation of the LSDFs, equivalent to their respective semi-solid formulations but with defined dimensions (suitably translational to the human clinic), semi-solids were dispensed into blister packs and subsequently lyophilized. Due to their high viscosity and resistance to deformation the RSVs described previously [12] and [13] were not suitable for dispensing, as they were resistant to settling within wells. The RSV semi-solid formulation (PC3HEC250HHX5PVP4) Akt inhibitor [12] underwent modification to next reduce viscosity thus facilitating lyophilization in blister packs, determined visually through dispensing trials and by rheological flow analysis (manifested as a reduction in viscosity). Modifications trialled included a reduction in the HEC250HHX content from 5% to 1%, omission of the PVP component, and omission of the PVP component plus substitution of the HEC250HHX polymer component with HEC250G, a grade

exhibiting lower Brookfield viscosity (400 mPa s compared to 15,000 mPa s). Rheological flow analysis, used as an aid for the optimisation of processing parameters such as dispensing, in addition to predicting the way in which a material will behave upon storage and end-user application, demonstrated the pseudoplastic nature of all the modified RSVs. Such shear thinning behaviour was a desirable attribute to facilitate expulsion of the semi-solids from the dispensing tubes and to ensure adequate settling into the blister pack wells. Omission of the PVP component had no significant effect on consistency (determined using power law) whereas reduction of the HEC250HHX content resulted in a drop in consistency from 3194 ± 177 Pa sn[12]. Substitution with HEC250G in combination with PVP omission also resulted in a drop in consistency to 399 ± 14 Pa sn. However, dispensing trials demonstrated that the HEC-based semisolids did not exhibit sufficient flow properties to settle uniformly into the blister pack wells. To overcome this, the HEC component of the original RSV formulations was substituted with NaCMC.