Fundamental aspects of long-acting tenofovir alafenamide delivery from subdermal implants for HIV prophylaxis.

Global efforts aimed at preventing human immunodeficiency virus type one (HIV-1) infection in vulnerable populations appear to be stalling, limiting our ability to control the epidemic. Long-acting, controlled drug administration from subdermal implants holds significant potential by reducing the compliance burden associated with frequent dosing. We, and others, are exploring the development of complementary subdermal implant technologies delivering the potent prodrug, tenofovir alafenamide (TAF). The current report addresses knowledge gaps in the preclinical pharmacology of long-acting, subdermal TAF delivery using several mouse models. Systemic drug disposition during TAF implant dosing was explained by a multi-compartment pharmacokinetic (PK) model. Imaging mass spectrometry was employed to characterize the spatial distribution of TAF and its principal five metabolites in local tissues surrounding the implant. Humanized mouse studies determined the effective TAF dose for preventing vaginal and rectal HIV-1 acquisition. Our results represent an important step in the development of a safe and effective TAF implant for HIV-1 prevention.

Brief Report: Associations Between Self-Reported Substance Use Behaviors and PrEP Acceptance and Adherence Among Black MSM in the HPTN 073 Study.

BACKGROUND: Pre-exposure prophylaxis (PrEP) is efficacious for HIV prevention. Black men who have sex with men (MSM) accounted for the largest proportion of new HIV diagnoses in the United States relative to other racial/ethnic groups. Black MSM who use substances are at an increased risk for HIV infection and are ideal candidates for PrEP, but barriers to maintaining PrEP adherence remain a concern. We assessed whether substance use behaviors are associated with initiation and adherence to PrEP among a sample of black MSM in the United States. METHODS: Data for this analysis come from the HIV Prevention Trails Network Study 073 (HPTN 073). Substance use behaviors-including alcohol, marijuana, poppers (ie, alkyl nitrites), and stimulants (ie, methamphetamine/cocaine use) including use of these substances before/during condomless anal intercourse (CAI)-were assessed longitudinally through self-report. PrEP adherence was assessed by pharmacological testing in blood. Generalized estimating equations were used to evaluate association between substance use behaviors and PrEP initiation and adherence. RESULTS: Among 226 HIV-negative black MSM, the majority (60%) were 25+ years of age. Most of the substance use behaviors were not significantly associated with PrEP initiation or adherence. However, stimulant use before/during CAI was significantly associated with lower odds of PrEP adherence (adjusted odds ratio = 0.21, 95% confidence interval = 0.07 to 0.61; P = <0.01). CONCLUSIONS: These findings suggest that PrEP adherence is feasible among black MSM who use substances. However, black MSM who engage in stimulant use before/during CAI may present a unique group for additional study and support with enhanced behavioral health and support services.

Rectal Douching Practices Associated with Anal Intercourse: Implications for the Development of a Behaviorally Congruent HIV-Prevention Rectal Microbicide Douche.

Tenofovir administration via rectal douching results in higher rectal-mucosa drug concentration than oral administration. Many who engage in receptive anal intercourse (RAI) use cleansing rectal douches. To inform development of a behaviorally-congruent tenofovir douche, 4751 individuals ≥ 18 years-old, born male, from all US states/territories, who engaged in anal intercourse responded to an online survey. Of those who reported RAI in the prior 3 months, 80% douched beforehand, 82% within 1 h, mean 2.9 consecutive applications; 27% douched afterwards, 83% within 1 h, mean 1.7 consecutive applications. Among multidose users, 78% applied doses within 2 min, and 76% retained liquid < 1 min. Most used tap water (89%) in an enema bottle (50%) or rubber bulb (43%), and douched for cleanliness (97%), to avoid smelling bad (65%), and to enhance pleasure (24%). 98% reported high likelihood of using an HIV-prevention douche. An ideal product will protect within a user's typical number of applications, within 1 h, and be dissolvable in tap water.

Fecal Coliform Bacterial Detection to Assess Enema Adherence in HIV Prevention Clinical Studies.

Evaluating the efficacy of any HIV prevention strategy is dependent on ensuring and objectively monitoring adherence to the intervention. Medicated rectal enemas are a potential method for providing topical, episodic HIV prophylaxis during receptive anal intercourse. Assessing adherence to recommended enema dosing regimens is essential in evaluating the utility of this strategy. We utilized fecal coliform bacteria on used enema tips as a marker for enema use. Enema tip coliforms were tested by repurposing a microtiter plate-based water quality test designed to detect fecal contamination of water. Coliform detection occurred with 100% sensitivity and specificity when tips were assayed on day of use. The assay performed well post-7 day sample storage at room temperature, yielding a sensitivity of 80% and specificity of 93%. All (n = 64) samples collected in a subset of the DREAM-01 rectal microbicide enema clinical trial tested positive, even when tips were evaluated > 7 days post-reported use. The coliform-based enema tip assay allows monitoring of adherence in interventions involving rectal enemas in a sensitive, specific and inexpensive manner. The test performs well in clinical trial settings.

Development of rectal enema as microbicide (DREAM): Preclinical progressive selection of a tenofovir prodrug enema.

HIV pre-exposure prophylaxis (PrEP) strategies have the potential to prevent millions of incident HIV infections each year. However, the efficacy of PrEP strategies has been plagued by issues of non-adherence, likely because of the difficulty in motivating otherwise healthy people to adhere to treatment regimens that require significant behavioral changes and daily discipline. An alternative approach to PrEP is to focus on strategies that fit in to normal, and even desirable, sexual behaviors, such as the use of cleansing enemas by men who have sex with men (MSM) prior to receptive anal intercourse (RAI). Here, we describe preclinical efforts toward optimizing a tenofovir (TFV)-based enema formulation for rectal PrEP. Using a murine model, we compared the plasma and tissue pharmacokinetics of TFV and various TFV prodrugs, including tenofovir disoproxil fumarate (TDF), tenofovir alafenamide (TAF), and hexadecyloxypropyl tenofovir (CMX157), after dosing as enema formulations with varying osmolality and ion content. We observed that the enema vehicle composition played a more important role than the TFV prodrug properties in achieving rapid and therapeutically relevant tenofovir diphosphate (TFV-DP) concentrations in mouse colorectal tissue. Our results support the next steps, which are further preclinical (non-human primate) and clinical development of a hypo-osmolar TFV enema product for rectal PrEP.

MALDI Mass Spectrometry Imaging Reveals Heterogeneous Distribution of Tenofovir and Tenofovir Diphosphate in Colorectal Tissue of Subjects Receiving a Tenofovir-Containing Enema.

Efforts to prevent human immunodeficiency virus (HIV) infection via pre-exposure prophylaxis (PrEP) include the development of anti-HIV drugs as microbicides for topical application to the mucosal sites of infection; however, although understanding the distribution profiles of these drugs in target mucosal tissues is of critical importance to guiding their optimization, data in this regard are largely lacking. With this in mind, we developed a matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI MSI) approach to visualize tenofovir (TFV), an HIV nucleotide analog reverse-transcriptase inhibitor under investigation for use as a topical microbicide, and its active metabolite TFV-diphosphate (TFV-DP) in colorectal biopsies obtained from healthy volunteers who received TFV-containing enemas. Application of MALDI MSI resulted in sufficient spatial resolution to visualize both TFV and TFV-DP and revealed heterogeneity in the distribution profiles of both analytes, including the presence of regions in which TFV and TFV-DP were undetectable, in colorectal tissue at two different time points and concentrations. Cell-specific staining for CD4 T and CD11c dendritic cells, which are important to the establishment of HIV infection, demonstrated that the TFV and TFV-DP distributions were independent of these cell types. MALDI MSI of endogenous lipids demonstrated that the heterogeneity observed for TFV and TFV-DP was not a function of tissue composition or processing. These data provide unique insight into the spatial distribution of TFV and TFV-DP in human colorectal tissue. In addition, this work establishes an approach that can be leveraged to directly detect and visualize these clinically important analytes more broadly in tissue.

Rectal Douching Associated with Receptive Anal Intercourse: A Literature Review.

To inform the development of HIV-prevention rectal douches, we reviewed the scientific literature and online instructional videos on rectal douching associated with receptive anal intercourse (RAI). Up to 88% of men who practice RAI ever have douched, while 43-64% have douched recently. Of them, 87-97% douche before RAI and 13-48% afterwards. Water, occasionally mixed with soap or salt, is used most often, although up to 31% of men use commercial products. Douching is more common among individuals reporting substance use, sexually transmitted infections, or being HIV-infected. Scant literature is available on women's rectal douching practices, but it is apparently less frequent than among men (32 vs. 70%). Videos advise using 2-3 doses of liquid and retaining it for 10-30 s before expelling. These findings can inform the development of a safe and acceptable rectal douche for HIV prevention.

Hypo-osmolar Formulation of Tenofovir (TFV) Enema Promotes Uptake and Metabolism of TFV in Tissues, Leading to Prevention of SHIV/SIV Infection.

Oral preexposure prophylaxis (PrEP) has been approved for prophylaxis of HIV-1 transmission but is associated with high costs and issues of adherence. Protection from anal transmission of HIV using topical microbicides and methods congruent with sexual behavior offers the promise of improved adherence. We compared the pharmacokinetics (PK) and ex vivo efficacy of iso-osmolar (IOsm) and hypo-osmolar (HOsm) rectal enema formulations of tenofovir (TFV) in rhesus macaques. Single-dose PK of IOsm or HOsm high-dose (5.28 mg/ml) and low-dose (1.76 mg/ml) formulations of TFV enemas were evaluated for systemic uptake in blood, colorectal biopsy specimens, and rectal CD4+ T cells. Markedly higher TFV concentrations were observed in plasma and tissues after administration of the HOsm high-dose formulation than with all other formulations tested. TFV and TFV diphosphate (TFV-DP) concentrations in tissue correlated for the HOsm high-dose formulation, demonstrating rapid uptake and transformation of TFV to TFV-DP in tissues. TFV-DP amounts in tissues collected at 1 and 24 h were 7 times and 5 times higher, respectively (P < 0.01), than the ones collected in tissues with the IOsm formulation. The HOsm high-dose formulation prevented infection in ex vivo challenges of rectal tissues collected at 1, 24, and 72 h after the intrarectal dosing, whereas the same TFV dose formulated as an IOsm enema was less effective.

Integrated Delivery of Antiretroviral Treatment and Pre-exposure Prophylaxis to HIV-1-Serodiscordant Couples: A Prospective Implementation Study in Kenya and Uganda.

BACKGROUND: Antiretroviral-based interventions for HIV-1 prevention, including antiretroviral therapy (ART) to reduce the infectiousness of HIV-1 infected persons and pre-exposure prophylaxis (PrEP) to reduce the susceptibility of HIV-1 uninfected persons, showed high efficacy for HIV-1 protection in randomized clinical trials. We conducted a prospective implementation study to understand the feasibility and effectiveness of these interventions in delivery settings. METHODS AND FINDINGS: Between November 5, 2012, and January 5, 2015, we enrolled and followed 1,013 heterosexual HIV-1-serodiscordant couples in Kenya and Uganda in a prospective implementation study. ART and PrEP were offered through a pragmatic strategy, with ART promoted for all couples and PrEP offered until 6 mo after ART initiation by the HIV-1 infected partner, permitting time to achieve virologic suppression. One thousand thirteen couples were enrolled, 78% of partnerships initiated ART, and 97% used PrEP, during a median follow-up of 0.9 years. Objective measures of adherence to both prevention strategies demonstrated high use (≥85%). Given the low HIV-1 incidence observed in the study, an additional analysis was added to compare observed incidence to incidence estimated under a simulated counterfactual model constructed using data from a prior prospective study of HIV-1-serodiscordant couples. Counterfactual simulations predicted 39.7 HIV-1 infections would be expected in the population at an incidence of 5.2 per 100 person-years (95% CI 3.7-6.9). However, only two incident HIV-1 infections were observed, at an incidence of 0.2 per 100 person-years (95% CI 0.0-0.9, p < 0.0001 versus predicted). The use of a non-concurrent comparison of HIV-1 incidence is a potential limitation of this approach; however, it would not have been ethical to enroll a contemporaneous population not provided access to ART and PrEP. CONCLUSIONS: Integrated delivery of time-limited PrEP until sustained ART use in African HIV-1-serodiscordant couples was feasible, demonstrated high uptake and adherence, and resulted in near elimination of HIV-1 transmission, with an observed HIV incidence of <0.5% per year compared to an expected incidence of >5% per year.

Enema ion compositions for enhancing colorectal drug delivery.

Delivering drugs to the colorectum by enema has advantages for treating or preventing both local and systemic diseases. However, the properties of the enema itself are not typically exploited for improving drug delivery. Sodium ions are actively pumped out of the lumen of the colon, which is followed by osmotically-driven water absorption, so we hypothesized that this natural mechanism could be exploited to drive nanoparticles and drugs to the colorectal tissue surface. Here, we report that sodium-based, absorption-inducing (hypotonic) enemas rapidly transport hydrophilic drugs and non-mucoadhesive, mucus penetrating nanoparticles (MPP), deep into the colorectal folds to reach virtually the entire colorectal epithelial surface. In contrast, isotonic and secretion-inducing (hypertonic) vehicles led to non-uniform, poor surface coverage. Sodium-based enemas induced rapid fluid absorption even when moderately hyper-osmolal (~350 mOsm) compared to blood (~300 mOsm), which suggests that active sodium absorption plays a key role in osmosis-driven fluid uptake. We then used tenofovir, an antiretroviral drug in clinical trials for preventing HIV, to test the effects of enema composition on local and systemic drug delivery. We found that strongly hypotonic and hypertonic enemas caused rapid systemic drug uptake, whereas moderately hypotonic enemas with ion compositions similar to feces resulted in high local tissue levels with minimal systemic drug exposure. Similarly, moderately hypotonic enemas provided improved local drug retention in colorectal tissue, whereas hypertonic and isotonic enemas provided markedly reduced drug retention in colorectal tissue. Lastly, we found that moderately hypotonic enema formulations caused little to no detectable epithelial damage, while hypertonic solutions caused significant damage, including epithelial sloughing; the epithelial damage caused increased systemic drug absorption and penetration of MPP into colorectal tissue, a potential advantage in certain drug delivery applications. In summary, we illustrate that enema composition can be adjusted to maximize local versus systemic drug delivery, and that mildly hypotonic, sodium-based vehicles can provide uniform drug and MPP delivery in the colon that maximizes local drug concentrations.

Isoosmolar enemas demonstrate preferential gastrointestinal distribution, safety, and acceptability compared with hyperosmolar and hypoosmolar enemas as a potential delivery vehicle for rectal microbicides.

Rectally applied antiretroviral microbicides for preexposure prophylaxis (PrEP) of HIV infection are currently in development. Since enemas (rectal douches) are commonly used by men who have sex with men prior to receptive anal intercourse, a microbicide enema could enhance PrEP adherence by fitting seamlessly within the usual sexual practices. We assessed the distribution, safety, and acceptability of three enema types-hyperosmolar (Fleet), hypoosmolar (distilled water), and isoosmolar (Normosol-R)-in a crossover design. Nine men received each enema type in random order. Enemas were radiolabeled [(99m)Tc-diethylene triamine pentaacetic acid (DTPA)] to assess enema distribution in the colon using single photon emission computed tomography/computed tomography (SPECT/CT) imaging. Plasma (99m)Tc-DTPA indicated mucosal permeability. Sigmoidoscopic colon tissue biopsies were taken to assess injury as well as tissue penetration of the (99m)Tc-DTPA. Acceptability was assessed after each product use and at the end of the study. SPECT/CT imaging showed that the isoosmolar enema had greater proximal colonic distribution (up to the splenic flexure) and greater luminal and colon tissue concentrations of (99m)Tc-DTPA when compared to the other enemas (p<0.01). Colon biopsies also showed that only the hyperosmolar enema caused sloughing of the colonic epithelium (p<0.05). In permeability testing, the hypoosmolar enema had higher plasma (99m)Tc-DTPA 24-h area under the concentration-time curve and peak concentration compared to the hyperosmolar and isoosmolar enemas, respectively. Acceptability was generally good with no clear preferences among the three enema types. The isoosmolar enema was superior or similar to the other enemas in all categories and is a good candidate for further development as a rectal microbicide vehicle.

Clonidine as an adjunct therapy to opioids for neonatal abstinence syndrome: a randomized, controlled trial.

OBJECTIVE: To determine if oral clonidine would reduce the duration of opioid detoxification for neonatal abstinence syndrome. METHODS: Infants with intrauterine exposure to methadone or heroin and neonatal abstinence syndrome (2 consecutive modified Finnegan scores of > or =9) were enrolled at 2 hospitals during 2002-2005 and followed until final hospital discharge. All enrolled infants (80) received oral diluted tincture of opium according to a standardized algorithm and were randomly assigned to receive oral clonidine (1 microg/kg every 4 hours) (40 infants) or placebo (40 infants). Primary outcome was duration of opioid therapy. Secondary outcomes included the amount of opium required to control symptoms, number of treatment failures, and differences in blood pressure, heart rate, and oxygen saturation. RESULTS: The median length of therapy was 27% shorter in the clonidine group (11 [95% confidence interval: 8-15 days]) than in the placebo group (15 days [95% confidence interval: 12-17 days]). In the clonidine group, 7 infants required restarting opium after initial discontinuation versus none in the placebo group, with the total length of treatment/observation remaining significantly less in the clonidine group. Higher dosages of opium were required by 40% of the infants in the placebo group versus 20% in the clonidine group. Treatment failures occurred in 12.5% of the infants in the placebo group versus none in the clonidine group. Hypertension, hypotension, bradycardia, or desaturations did not occur in either group. Three infants in the clonidine group died as a result of myocarditis, sudden infant death syndrome, and homicide, all after hospital discharge and before 6 months of age. CONCLUSIONS: In this randomized, double-blind trial, adding clonidine to standard opioid therapy for detoxification from in utero exposure to methadone or heroin reduced the duration of pharmacotherapy for neonatal abstinence without causing short-term adverse cardiovascular outcomes. A larger trial is indicated to determine long-term safety.

Pharmacokinetic and metabolic effects of American ginseng (Panax quinquefolius) in healthy volunteers receiving the HIV protease inhibitor indinavir.

BACKGROUND: Complementary and alternative medicine (CAM) use is prevalent among HIV-infected patients to reduce the toxicity of antiretroviral therapy. Ginseng has been used for treatment of hyperglycemia and insulin resistance, a common side effect of some HIV-1 protease inhibitors (PI). However, it is unknown whether American ginseng (AG) can reverse insulin resistance induced by the PI indinavir (IDV), and whether these two agents interact pharmacologically. We evaluated potential pharmacokinetic interactions between IDV and AG, and assessed whether AG improves IDV-induced insulin resistance. METHODS: After baseline assessment of insulin sensitivity using the insulin clamp technique, healthy volunteers received IDV 800 mg q8 h for 3 days and then IDV and AG 1g q8h for 14 days. IDV pharmacokinetics and insulin sensitivity were assessed before and after AG co-administration. RESULTS: There was no difference in the area-under the plasma-concentration-time curve after the co-administration of AG, compared to IDV alone (n = 13). Although insulin-stimulated glucose disposal per unit of insulin (M/I) decreased by an average of 14.8 +/- 5.9% after 3 days of IDV (from 0.113 +/- 0.012 to 0.096 +/- 0.014 mg/kgFFM/min per muU/ml of insulin, p = 0.03, n = 11), M/I remained unchanged after co-administration of IDV and AG. CONCLUSION: IDV decreases insulin sensitivity, which is unaltered by AG co-administration. AG does not significantly affect IDV pharmacokinetics.

Hyperosmolar sexual lubricant causes epithelial damage in the distal colon: potential implication for HIV transmission.

BACKGROUND: Many sexual lubricants are hyperosmolar. Hyperosmolar enemas induce epithelial damage, and enema use has been associated with an increased risk of HIV infection. To inform the development of rectal microbicide formulation, we evaluated the effects of hyperosmolar gels on the rectal mucosa. METHODS: Two commercial lubricants were compounded into iso-osmolar and hyperosmolar mixtures (283 and 3429 mOsm/kg, respectively). Each gel was radiolabeled with 500 micro Ci of (99m)Technetium-diethylene triaminepentaacetic acid, and 10 mL was given rectally to 10 subjects in random sequence. Sigmoidoscopy by an endoscopist blinded to treatment assignment was performed 90 min later to obtain luminal and mucosal samples. Urine radiolabel detection was used to assess mucosal permeability. RESULTS: Epithelial denudation 10 cm from the anus occurred to a greater degree with the hyperosmolar gel than with the iso-osmolar formulation (median toxicity grade, 2.50 vs. 1.17 out of 3, respectively; P=.009). The hyperosmolar gel was also associated with lower isotope luminal concentration at 10 cm, compared with the iso-osmolar gel (median, 8.9% vs. 54.6% of administered concentration, respectively). Mucosal permeability measured through 12 h was reduced with the hyperosmolar gel (P=.037). CONCLUSION: Rectally applied hyperosmolar gels induce greater epithelial denudation and luminal secretion than iso-osmolar gels. Because denudation plausibly increases the risk of HIV transmission, hyperosmolar gels make poor rectal microbicide formulations, and hyperosmolar sexual lubricants may increase susceptibility to HIV infection.