Safety of G2-S16 Polyanionic Carbosilane Dendrimer as Possible HIV-1 Vaginal Microbicide

The UNAIDS objective for 2020 was 500,000 new HIV-1 infections per year; however, the latest annual reported data confirmed 1.7 million new HIV-1 infections in that year. Those data evidences the need for new prevention strategies and prophylactic treatments. This prevention crisis occurred in spite of the knowledge and availability of efficient prevention strategies. The G2-S16 is a microbicidal polyanionic carbosilane dendrimer currently being tested for topical vaginal application, which has been shown to be efficient in the prevention of HIV-1 infection. However, safety tests were lacked. For this purpose, we injected intravenously G2-S16 dendrimer to CD1 mice, thereby analyzing the hemogram, blood biochemical markers of systemic damage, accumulation in the organs and organ-tissue damage in heart, spleen, kidney, liver and brain. This work shows that even if the G2-S16 dendrimer penetrates the epithelial tissue, it does not cause vaginal irritation or tissue damage. Moreover, the i.v. injection of the G2-S16 dendrimer did not cause a damaging effect on the studied organs and it did not modify the hemogram or the biochemical plasma markers. In conclusion, the G2-S16 dendrimer has a very good safety profile, indicating that this molecule can be a very safe and efficient vaginal microbicide.

Role of G2-S16 Polyanionic Carbosilane Dendrimer in the Prevention of Respiratory Syncytial Virus Infection In Vitro and In Vivo in Mice

The respiratory syncytial virus (RSV) causes respiratory infection and bronchiolitis, requiring hospitalization mainly in infants. The interaction between RSV, envelope glycoproteins G and F, and cell surface heparan sulfate proteoglycans (HSPG) is required for binding and entry into the host cells. A G2-S16 polyanionic carbosilane dendrimer was identified as a possible RSV inhibitor. We speculated that the G2-S16 dendrimer adheres to the host cell-surface HSPG, acts through binding to HS receptors, and prevents further RSV infection. The G2-S16 dendrimer was non-toxic when applied intranasally to Balb/c mice, and interestingly enough, this G2-S16 dendrimer inhibits 85% RSV. Therefore, our G2-S16 dendrimer could be a candidate for developing a new possible therapy against RSV infection.

High Preventive Effect of G2-S16 Anionic Carbosilane Dendrimer against Sexually Transmitted HSV-2 Infection

Anionic carbosilane dendrimers such as G2-S16 are very effective in preventing HSV-2 infection both in vitro and in vivo. We present the main achievements obtained for the G2-S16 dendrimer in vivo, especially related to its efficacy against HSV-2 infection. Moreover, we discuss the mechanisms by which the G2-S16 dendrimer applied vaginally as a topical microbicide has been demonstrated to be safe and harmless for the vaginal microbiome balance, as both conditions present an essential step that has to be overcome during microbicide development. This review points to the marked protective effect of the G2-S16 dendrimer against sexually transmitted HSV-2 infection, supporting its role as a possible microbicide against HSV-2 infection.

Combination of G2-S16 dendrimer/dapivirine antiretroviral as a new HIV-1 microbicide

Aim: To research the synergistic activity of G2-S16 dendrimer and dapivirine (DPV) antiretroviral as microbicide candidate to prevent HIV-1 infection. Materials & methods: We assess the toxicity of DPV on cell lines by MTT assay, the anti-HIV-1 activity of G2-S16 and DPV alone or combined at several fixed ratios. Finally, their ability to inhibit the bacterial growth in vitro was assayed. The analysis of combinatorial effects and the effective concentrations were performed with CalcuSyn software. Conclusion: Our results represent the first proof-of-concept study of G2-S16/DPV combination to develop a safe microbicide.

G2-S16 dendrimer microbicide does not interfere with the vaginal immune system

It is essential that prophylactic drugs do not interfere with the normal function of the immune system. The use of nanoparticles as vaginal microbicides is a promising prevention strategy against sexually transmitted infections. With that aim, our group is working with the G2-S16, a second generation carbosilane dendrimer with sulfonate groups in the periphery, which has been previously shown to be effective against HIV-1 and HSV-2 infection, and it is now on the road to clinical trials. Our objective in this new study is to assess the effects of G2-S16 on the immune barrier of the female reproductive tract. The expression of differentiation, maturation and activation markers was measured in epithelial cells, dendritic cells, M and GM macrophages, and T cells using RT-qPCR and flow cytometry. The results demonstrate that G2-S16 does not alter the natural immunity of the vagina, strongly supporting the biosafety of this dendrimer for clinical use.

G1-S4 or G2-S16 carbosilane dendrimer in combination with Platycodin D as a promising vaginal microbicide candidate with contraceptive activity

Purpose

HIV-1 and herpes simplex virus type-2 (HSV-2) represent two of the most relevant sexually transmitted diseases (STDs) worldwide. Moreover, each year there are >200 million pregnancies worldwide, and more than half are unintended. Continued high rates of unintended pregnancies and spread of HIV-1 and HSV-2 require new approaches to address these problems. G1-S4 and G2-S16 dendrimers emerge as potential candidates for the development of a topical microbicide due to their safety and effectivity against HIV-1 and HSV-2 infection, both in vitro and in vivo. Our goal is to develop a dual topical microbicide to prevent the transmission of STDs and unintended pregnancies. Platycodin D (PD) was selected for its great spermicidal activity, topical application, and biocompatibility.

Materials and methods

Toxicology and inhibitory profile of G1-S4/PD and G2-S16/PD were evaluated in vitro and in vivo. Spermicidal activity was assessed by a computer-assisted sperm analysis system (CASA).

Results

G1-S4/PD and G2-S16/PD presented >95% of HIV-1 inhibition in TZM-bl cells and peripheral blood mononuclear cells. CASA assessment determined that 0.25 mM of PD with therapeutic concentrations of G1-S4 or G2-S16 was able to induce 100% immobilization of the sperm in 30 seconds. To evaluate the toxicity in vivo, a vaginal toxicity assay was performed in BALB/c mice. No significant changes or damage to the vaginal epithelium after 7 consecutive days of application were observed.

Conclusion

Our data indicate that G1-S4/PD and G2-S16/PD combinations are promising candidates to be developed for vaginal microbicides with contraceptive activity.