Ryan Morrow

Characterization of the rheological, mucoadhesive, and drug release properties of highly structured gel platforms for intravaginal drug delivery.

This investigation describes the formulation and characterization of rheologically structured vehicles (RSVs) designed for improved drug delivery to the vagina. Interactive, multicomponent, polymeric platforms were manufactured containing hydroxyethylcellulose (HEC, 5% w/w) polyvinylpyrrolidone (PVP, 4% w/w), Pluronic (PL, 0 or 10% w/w), and either polycarbophil (PC, 3% w/w) or poly(methylvinylether-co-maleic anhydride) (Gantrez S97, 3% w/w) as a mucoadhesive agent. The rheological (torsional and dynamic), mechanical (compressional), and mucoadhesive properties were characterized and shown to be dependent upon the mucoadhesive agent used and the inclusion/exclusion of PL. The dynamic rheological properties of the gel platforms were also assessed following dilution with simulated vaginal fluid (to mimic in vivo dilution). RSVs containing PC were more rheologically structured than comparator formulations containing GAN. This trend was also reflected in formulation hardness, compressibility, consistency, and syringeability. Moreover, formulations containing PL (10% w/w) were more rheologically structured than formulations devoid of PL. Dilution with simulated vaginal fluids significantly decreased rheological structure, although RSVs still retained a highly elastic structure (G′ > G′′ and tan δ < 1). Furthermore, RSVs exhibited sustained drug release properties that were shown to be dependent upon their rheological structure. It is considered that these semisolid drug delivery systems may be useful as site-retentive platforms for the sustained delivery of therapeutic agents to the vagina.

Vaginal delivery of the recombinant HIV-1 clade-C trimeric gp140 envelope protein CN54gp140 within novel rheologically structured vehicles elicits specific immune responses.

Rheologically structured vehicle (RSV) gels were developed as delivery systems for vaginal mucosal vaccination with an HIV-1 envelope glycoprotein (CN54gp140). RSVs comprised a mucoadhesive matrix-forming and vaginal fluid absorbing polymer. The mucoadhesive and rheological properties of the RSVs were evaluated in vitro, and the distribution, antigenicity and release of CN54gp140 were analysed by ELISA. CN54gp140 was uniformly distributed within the RSVs and continuously released in vitro in an antigenically intact form over 24 h. Vaginal administration to rabbits induced specific serum IgG, and IgG and IgA in genital tract secretions. The RSVs are a viable delivery modality for vaginal immunization.

Sustained release of proteins from a modified vaginal ring device.

A new vaginal ring technology, the insert vaginal ring (InVR), is presented. The InVR overcomes the current shortfall of conventional vaginal rings (VRs) that are generally ineffectual for the delivery of hydrophilic and/or macromolecular actives, including peptides, proteins and antibodies, due to their poor permeation characteristics in the hydrophobic polymeric elastomers from which VRs are usually fabricated. Release of the model protein BSA from a variety of insert matrices for the InVR is demonstrated, including modified silicone rods, directly compressed tablets and lyophilised gels, which collectively provided controlled release profiles from several hours to beyond 4 weeks. Furthermore, the InVR was shown to deliver over 1 mg of the monoclonal antibody 2F5 from a single device, offering a potential means of protecting women against the transmission of HIV.

Development of liposome gel based formulations for intravaginal delivery of the recombinant HIV-1 envelope protein CN54gp140

Mucosally-administered vaccine strategies are widely investigated as a promising means of preventing HIV infection. This study describes the development of liposomal gel formulations, and novel lyophilised variants, comprising HIV-1 envelope glycoprotein, CN54gp140, encapsulated within neutral, positively charged or negatively charged liposomes. The CN54gp140 liposomes were evaluated for mean vesicle diameter, polydispersity, morphology, zeta potential and antigen encapsulation efficiency before being incorporated into hydroxyethyl cellulose (HEC) aqueous gel and subsequently lyophilised to produce a rod-shaped solid dosage form for practical vaginal application. The lyophilised liposome-HEC rods were evaluated for moisture content and redispersibility in simulated vaginal fluid. Since these rods are designed to revert to gel form following intravaginal application, mucoadhesive, mechanical (compressibility and hardness) and rheological properties of the reformed gels were evaluated. The liposomes exhibited good encapsulation efficiency and the gels demonstrated suitable mucoadhesive strength. The freeze-dried liposome-HEC formulations represent a novel formulation strategy that could offer potential as stable and practical dosage form.

Potential use of vaginal rings for prevention of heterosexual transmission of HIV

It is estimated that >80% of new HIV infections are contracted via heterosexual intercourse. Although a number of preventative strategies have been and are being pursued, the ultimate prevention tool–a safe, inexpensive, and effective vaccine–is nowhere on the horizon despite huge efforts over the past 2 decades. There is growing optimism that a vaginally applied HIV microbicide might be available for women to use within the next 5 years. It is likely that first-generation vaginal microbicides will make use of traditional semi-solid formulations since these are already used for vaginal administration of pharmaceutical substances. However, a number of drawbacks are associated with such formulations that may limit their clinical effectiveness as vaginal microbicide delivery vehicles.In this article, the potential for providing controlled vaginal delivery of HIV microbicides using established vaginal ring technology is considered in detail for the first time. In particular, the article discusses and evaluates the pros and cons associated with prolonged continuous vaginal administration of HIV microbicides, reviews and compares the scientific literature with respect to user acceptability of vaginal semi-solids and rings, and then provides some in vitro data describing the zero-order controlled release of a number of lead candidate non-nucleoside reverse transcriptase inhibitors from silicone elastomer vaginal rings.

Intravaginal immunization using the recombinant HIV-1 clade-C trimeric envelope glycoprotein CN54gp140 formulated within lyophilized solid dosage forms

Vaccine-mediated prevention of primary HIV-1 infection at the heterosexual mucosal portal of entry may be facilitated by highly optimised formulations or drug delivery devices for intravaginal (i.vag) immunization. Previously we described hydroxyethylcellulose (HEC)-based rheologically structured gel vehicles (RSVs) for vaginal immunization of an HIV-1 vaccine candidate, a soluble recombinant trimeric HIV-1 clade-C envelope glycoprotein designated CN54gp140. Here we investigated the efficacy of lyophilized solid dosage formulations (LSDFs) for prolonging antigen stability and as i.vag delivery modalities. LSDFs were designed and developed that upon i.vag administration they would reconstitute with the imbibing of vaginal fluid to mucoadhesive, site-retentive semi-solids. Mice were immunized with lyophilized equivalents of (i) RSVs, (ii) modified versions of the RSVs more suited to lyophilization (sodium carboxymethyl cellulose (NaCMC)-based gels) and (iii) Carbopol® gel, all containing CN54gp140. NaCMC-based LSDFs provided significantly enhanced antigen stability compared to aqueous-based RSVs. Rheological analysis indicated the NaCMC-based LSDFs would offer enhanced vaginal retention in woman compared to more conventional vaginal gel formulations. All LSDFs were well tolerated in the mouse model. Following i.vag administration, all LSDFs boosted systemic CN54gp140-specific antibody responses in sub-cutaneously primed mice. Induction of CN54gp140-specific antibody responses in the female genital tract was evident. Of all the LSDFs the fastest releasing which was lyophilized Carbopol® gel elicited immune responses comparable to buffer instillation of antigen suggesting that rather than slower sustained release, initial high burst release from the LSDFs may suffice. The boosting of specific immune responses upon i.vag administration indicates that LSDFs are viable mucosal vaccine delivery modalities promoting antigen stability and facilitating intimate exposure of CN54gp140 to the mucosal-associated lymphoid tissue of the female genital tract.

P11-12. A novel vaginal ring device for the sustained delivery of recombinant C-clade HIV-1 CN54gp140

BackgroundCervicovaginal (CV) tissue is the primary site for HIV transmission and a major reservoir for viral replication. Therefore, a successful vaccine strategy should induce potent immune responses at this mucosal surface. One potential method for achieving a localised immuneresponse is to administer the antigen directly to the CV tissue (Marx et al., 1993, Wassen et al., 1996). The aim of the study was to evaluate the in vitro release characteristics oflyophilised hydroxypropylmethylcellulose (HPMC) gel inserts containing HIV envelope protein CN54gp140 either as stand-alone formulations or located within a novel rod-insert vaginal ring device (RIVR).MethodsVaginal gel formulations comprising either low or high molecular weight (MW) HPMC and CN54gp140 (0.25% w/w) were prepared. The gels were injected into silicone elastomer tubing, cut to 40 mm lengths, and then lyophilised to produce solid rod inserts. In vitro release testing was performed on rod inserts alone and rod insert vaginal rings (RIVRs) containing two CN54gp140-loaded rod inserts. Release of gp140 was quantified by ELISA.ResultsRelease of CN54gp140 from rods prepared from low MW HPMC was similar for both inserts alone and rings containing inserts (99% cf. 90% over two hr). Release from the high MW inserts was significantly slower and more sustained than the low MW formulations. Also, CN54gp140 release from high MW rod inserts rings (68% of theoretical over 48 hr) was significantly more sustained than high MW inserts alone (86% over 24 hr).ConclusionThe study demonstrates that CN54gp140 (i) maintains its antigenicity during the preparation of HPMC lyophilised rod inserts, and (ii) may be administered in a sustainedmanner when the inserts are placed into an RIVR device. This stable, sustained-release formulation strategy has the potential to induce stronger immune responses andimmune memory upon vaginal administration (Zhao and Leong, 1996; Lofthouse, 2002).