In 2010 to 2014, approximately 44% of global pregnancies were unintended or mistimed [1
]. This percentage is even higher in some developing countries such as South Africa [2
], where unfortunately a high incidence of human immunodeficiency virus infection type-1 (HIV-1) infection is also noted, mostly due to unprotected sexual intercourse [3
]. Given that more than 90% of infections among children are transmitted from their HIV positive mother [4
], consequential severe health burden may be encountered when women at high risk of HIV infection become pregnant. In the duet microbicide trials conducted in Southern Africa, participants including women, men, health professionals, and community stakeholders indicated strong interest in a product that combined prevention of HIV and prevention of pregnancy [5
]. Therefore, it is believed that the design of products that combine HIV prevention agents with contraceptives may lead to enhanced product uptake and effectiveness.
Current existing multipurpose prevention technology (MPT) barrier methods include male and female condoms, diaphragms, and cervical caps. These MPT products provide protection for unintended pregnancy and sexually transmitted infections (STIs) including HIV-1 if they are used correctly and consistently [6
]. However, in practical use, the condom failure rate is much higher than expected, largely due to women’s inability to negotiate their use with their male partners in many cases [11
]. Therefore, women need a new generation of safe and self-initiated MPT products to protect themselves from unintended pregnancy and HIV infection.
A large number of MPTs are currently under development, including intravaginal rings for the delivery of anti-retroviral drugs and contraceptives. A three-month vaginal ring containing dapivirine (DPV) and levonorgestrel (LNG) is under clinical evaluation (MTN-044) for safety and pharmacokinetics (PK) [12
]. The DPV-only vaginal ring has shown effectiveness in HIV prevention in phase III trials, and has exhibited potentially higher levels of protection with higher adherence [13
]. However, a few women who used vaginal rings reported some issues such as ring expulsion [14
] and detection by their male partners [16
]. Ultimately, availability of multiple product options for MPTs would provide women with choices and may increase uptake by women.
The polymeric film as a vaginal dosage form has great potential for development as an MPT product platform. Films have low manufacturing cost, making them affordable for use in women in low-income settings and developing countries. The film is also a portable and discreet dosage form. Their portability is an important consideration for global distribution. Due to these advantages, multiple anti-retroviral drugs including DPV have been successfully formulated into polymeric films as topical microbicides for HIV prevention [18
]. Their user acceptability, safety, pharmacokinetics, (PK) and pharmacodynamics (PD) (ex vivo challenge) have been evaluated in clinical studies [21
]. It was observed that the film platform showed high acceptability, excellent safety profile for vaginal administration, and favorable PK and PD properties. However, to the best of our knowledge, exploration of the polymeric film as an advanced functional vaginal drug delivery platform featuring mucoadhesiveness and controlled release has not yet been explored.
Thiolated polymers were reported to bind to mucin strongly due to covalent bond formation [25
]. Excellent tolerance and safety of thiomer-containing dosage forms has been demonstrated in animals [26
] and clinical trials [28
]. In addition, the features of thiomers such as in situ gelling [29
], controlled release [30
], tissue permeation enhancement [32
], and maximal mucoadhesion around vaginal pH of 3.8–4.5 [33
] makes them highly advantageous for intravaginal drug delivery. In our study, a clinically evaluated polyvinyl alcohol (PVA)-based film was modified through addition of thiomers to improve its tissue residence and extend drug release. These features were incorporated by design to develop a vaginal film product with decreased dosing frequency.
DPV and LNG were selected as the model drugs for designing the MPT film platform. DPV, a non-nucleoside reverse transcriptase inhibitor, has been evaluated in multiple clinical trials in different dosage forms, such as gels, polymeric films, and vaginal rings, for prevention of sexually transmitted HIV [24
]. Hormonal contraceptives have been utilized to decrease the risk of unintended pregnancy since 1969. LNG is a progestin contraceptive drug which is commercially available in oral and intrauterine device formats. Its efficacy and safety has been previously demonstrated [35
]. For this reason, LNG has been evaluated as the hormonal contraceptive component in several MPT products under investigation. When developing an MPT product, it is critical to investigate potential drug–drug interactions and their impact on PK and PD properties [36
]. No diminished effectiveness of contraception was found when oral LNG was used with the DPV vaginal ring in the clinic [37
]. However, the co-delivery of these drugs in a vaginal film has not been evaluated with respect to their local PK. Therefore, it is worthwhile to investigate these properties for this combination in the vaginal polymeric film.
The aim of this proof-of-concept study was to describe the development of an innovative bioadhesive film platform for combined delivery of an antiretroviral drug, DPV, and a progestin, LNG. The MPT film was evaluated in pigtailed macaques, demonstrating that both agents can be delivered in a sustained fashion to provide adequate local (cervicovaginal lavages and tissue) and systemic drug concentrations required for therapeutic efficacy.
MPT products offer the advantage of simultaneously meeting multiple sexual and reproductive health needs, such as contraception and protection against sexually transmitted infections (STIs) including HIV [44
]. The polymeric film is a well-accepted dosage form that has been developed for delivering combinations of antiretroviral drugs [19
]. Clinically advanced vaginal films have been developed for quick drug release as coitally-dependent products. Dosage forms that require less frequent administration are preferred by many users and as such are promising products for enhancing use compliance among these users [46
]. The primary objective of this study was to evaluate the feasibility of MPT bioadhesive films for co-delivering an antiretroviral drug (DPV) and progestin (LNG) as a novel, weekly-administered MPT product.
The polyvinyl alcohol-based quick-dissolving film has been previously evaluated in clinical studies. In these studies it was shown to have a favorable acceptability and safety profile. The feasibility of formulating DPV in this film platform was also confirmed in these studies. Thus, it was reasonable to utilize this film as a platform to explore more advanced applications such as bioadhesion. The DPV-containing bioadhesive film was assessed for physicochemical properties including appearance, weight, and thickness, as well as water content, drug content, puncture strength, and disintegration. Compared to the quick-dissolving film, the incorporation of thiomer significantly increased the puncture strength and disintegration time of the film. The thiolated chitosan synthesized in this study had high molecular weight and low water solubility. Thus, the incorporation of thiolated chitosan could decrease the overall water solubility of the film. In addition to the DPV film, LNG and the combination of LNG/DPV were also formulated in the bioadhesive films. Within the physicochemical assessment, it was found that there was no significant difference between the single entity film and combination film. This was because both DPV and LNG are hydrophobic small molecules, which are unlikely to have significant impact on the film matrix.
Thiomer has been reported as an advanced bioadhesive polymer due to its covalent bond formation with mucin via thiol groups [25
]. This property was confirmed when it was incorporated in our polymeric film matrix using an ex vivo quantitative tensile method. The mucoadhesion of the bioadhesive film increased approximately fivefold after incorporating thiomers. The in vivo film retention in vaginal tissue was also evaluated in a pigtailed macaque model using colposcopy imaging and MRI. This is the first time the in vivo residence time of thiomer-containing formulations was investigated in the vaginal compartment. Two out of five pigtailed macaques showed that the bioadhesive film was retained in the vaginal compartment for at least 7 days. The complete loss of the film for the other three macaques at day 1 or day 3 might have been due to self-grooming, which has been previously observed in some macaques. Thiomer is also a permeation enhancer, as reported in multiple formulations [47
], which necessitates evaluating its distribution in different parts of the female genital tract. However, our MRI results conclusively showed no evidence of contrast for bioadhesive films in the ovaries, upper uterus, or rectum. This suggests that the distribution of bioadhesive film was confined to the vaginal lumen.
In addition to the film persistence observed in vivo, the DPV release from the bioadhesive film was sustained in vivo as compared to the quick-dissolving film. The in vivo release pattern (Table 4
) for DPV from the bioadhesive and quick-dissolving film was consistent with the in vitro data (Figure 4
). The sustained drug release rate can be attributed to the addition of thiomers, which increased the disintegration time of the film significantly (Table 3
). The observed longer disintegration time can be explained by the high content of cross-linked disulfide bonds within the polymeric network [49
]. The increased disintegration time indicated that water took more time to penetrate into the bioadhesive film matrix, which slowed the erosion process, thereby achieving a lower release rate [50
]. In the in vivo study, a 7 day release profile for the DPV bioadhesive film was observed, which demonstrated the potential of this film platform to be developed into a weekly MPT product.
After confirming that this film platform can be used to deliver drug for 1 week, DPV and LNG were co-formulated into the bioadhesive film as a potential MPT product and further evaluated in vivo. The investigation of local and systemic PK of the antiretroviral drug and progestin is regarded as a very important step in the development of MPT product [51
]. The mechanism of action for DPV demands sufficient concentration in the target mucosal tissue, which is the major site for sexually transmitted HIV infection. A study of the LNG intrauterine device not only showed the systemic effectiveness in inhibition of ovulation via binding to the progesterone and estrogen receptors, but also demonstrated local effectiveness via cervical mucus thickening, which inhibits sperm motility [35
]. Thus, for intravaginal delivery of LNG, tissue concentration and systematic circulation are both desirable.
Our data showed sufficient DPV concentration in vaginal fluid, and vaginal and cervical tissues even with co-delivery of LNG. Minimal systemic exposure of DPV was detected at each time point. Slightly higher, but not statistically significant, tissue DPV level was observed for the combination film as compared to the DPV single entity film. This increase may have been due to the lower vaginal mucosal clearance of DPV for the DPV/LNG combination film. A similar result was also reported by Akil A. et al. where the co-delivery of DPV with tenofovir increased the tissue accumulation of DPV in the ex vivo human ectocervical tissue explant model [45
]. These results indicate that co-delivery could have an impact on the local PK of drug. In our study, DPV and LNG showed different PK profiles with co-delivery. LNG displayed lower drug concentration in the vaginal fluid for the combination film as compared to the single entity film, which could result in slightly lower vaginal and cervical tissue concentration observed for the combination film (not statistically significant due to small sample number). However, LNG combination film showed significantly higher drug concentration in the plasma compared to the single entity film. These results indicate that drug–drug interaction may also occur during the co-delivery of anti-retroviral drugs and contraceptives.
One of the possible explanations for the drug–drug interaction during the co-delivery of DPV and LNG is the involvement of cytochrome P-450 (CYP450) enzymes. Multiple studies have shown that CYP3A4 is expressed in vaginal and cervical tissues [52
]. LNG is a substrate of cytochrome P-450 isoenzyme 3A4 (CYP3A4) [55
], and DPV can stimulate the increase of CYP3A4 expression at mRNA levels [52
]. Thus, when co-delivered with DPV, the metabolism of LNG could be increased in the vaginal and cervical tissues. This could result in the decreased vaginal and cervical tissue levels of LNG that were observed in our study. On the other hand, LNG is an inhibitor of CYP2C19 and CYP3A4 [36
], whereas DPV is the substrate of both enzymes that are also expressed in vaginal tissues. Although LNG’s inhibitory activity for these enzymes is weaker than other progestins [56
], the inhibition of CYP3A4 and CYP2C19 could increase DPV levels in vaginal and cervical tissues. Moreover, both DPV and LNG have high protein binding properties, which could play a role in the variable drug exposure observed with combination MPT films. The increased plasma drug level, especially for LNG after co-delivery, could be due to the competitive protein binding; however, this needs to be further studied. Our results indicate potential drug–drug interactions, which require further exploration given that DPV and LNG combination products are also being pursued in a vaginal ring platform.