Development and characterization of formulations based on combinatorial potential of antivirals against genital herpes

Abstract

Herpes simplex virus type 2 (HSV-2) treatment faces challenges due to antiviral resistance and systemic side effects of oral therapies. Local delivery of antiviral agents, such as tenofovir (TDF) and zinc acetate dihydrate (ZAD), may offer improved efficacy and reduced systemic toxicity. This study's objective is to develop and evaluate local unit dose formulations of TDF and ZAD combination for local treatment of HSV-2 infection and exploring their individual and combinatory effects in vitro. The study involved the development of immediate-release film and pessary formulations containing TDF and ZAD. These formulations were characterized for physicochemical properties and in vitro drug release profiles. Cytotoxicity and antiviral activity assays were conducted to evaluate the individual and combinatory effects of TDF and ZAD. Film formulations released over 90% of the drugs within 1 h, and pessary formulations within 90 min, ensuring effective local drug delivery. ZAD showed moderate antiviral activity while TDF exhibited significant antiviral activity at non-cytotoxic concentrations. The combination of TDF and ZAD demonstrated synergistic effects in co-infection treatments, reducing the concentration required for 50% inhibition of HSV-2. Developed film and pessary formulations offer consistent and predictable local drug delivery, enhancing antiviral efficacy while minimizing systemic side effects. The combination of TDF and ZAD showed potential synergy against HSV-2, particularly in co-infection treatments. Further preclinical studies on pharmacokinetics, safety, and efficacy are necessary to advance these formulations toward clinical application.

Keywords: Antivirals; Combination therapy; Formulations; Genital herpes; Good health and well-being; Local drug delivery.

Fig. 1

FTIR spectra of TDF, ZAD, placebo film, FE4 (TDF film), FE5 (ZAD film), and FE3 (ZAD + TDF) film

Fig. 2

In vitro drug release studies of film formulation FE3 (Data shown are mean ± SD of n = 6)

Fig. 3

In vitro drug release from pessary formulations (values shown are mean ± SD of n = 6)

Fig. 4

Effect of A zinc acetate dihydrate (ZAD), B tenofovir disoproxil fumarate (TDF), and C ZAD-TDF combination on Vero cells (3 × 10⁵ cells/mL). Each data point represents the mean of OD (optical density) values (n = 3) ± SEM

Fig. 5

HSV-2 plaque reduction profile of zinc acetate dihydrate (A, B, C) and tenofovir disoproxil fumarate (D, E, F) in pre-infection (A, D), co-infection (B, E), and post-infection treatments (C, F). Each bar represents the average number for plaques (n = 3) at different drug concentrations. The results are expressed as mean ± SEM. Asterisks indicate a significant difference (*p < 0.05) in comparison with the virus control group (VC = 100 PFU/mL). Acyclovir was used as a positive control (PC)

Fig. 6

HSV-2 plaque reduction profile of ZAD-TDF combination. A Pre-infection, B co-infection, C post-infection treatments. Each bar represents the average number of plaques (n = 3) at different drug concentrations. The results are expressed as mean ± SEM. Asterisks indicate a significant difference (*p < 0.05) in comparison with the virus control group (VC = 100 PFU/mL). Acyclovir was used as a positive control (PC)