Perspectives on long-acting formulations of pre-exposure prophylaxis (PrEP) among men who have sex with men who are non-adherent to daily oral PrEP in the United States

INTRODUCTION

Pre-exposure prophylaxis (PrEP) persistence among men who have sex with men (MSM) in real world clinical settings for HIV prevention is suboptimal. New longer-acting formulations of PrEP are becoming available, including injectables, subdermal implants, and other oral medications. These longer-acting formulations have the potential to improve retention among those who have challenges remaining adherent to daily oral PrEP.

METHODS

We interviewed 49 MSM who had initiated but discontinued oral PrEP at three diverse clinics across the United States. We examined participants' perspectives about long-acting PrEP formulations and how long-acting options could affect PrEP use using thematic analysis.

RESULTS

Participants were not very knowledgeable about long-acting formulations of PrEP but were open to learning about them and considering use. Participants were concerned about safety and efficacy of products given that they were still newer and/or in development. Finally, participants had clear preferences for oral pills, injectables, and then subdermal implants and were most interested in options that reduced the number of visits to the clinic.

CONCLUSION

Long-acting formulations of PrEP are acceptable to MSM with suboptimal PrEP persistence and have the potential to improve PrEP persistence. However, many felt they needed more information on safety, efficacy, and use to consider these options. As these long-acting formulations are implemented, public health campaigns and clinical interventions to encourage may maximize uptake particularly among those who are not currently adherent to daily oral PrEP.

Facilitators for retaining men who have sex with men in pre-exposure prophylaxis care in real world clinic settings within the United States

BACKGROUND

Pre-exposure prophylaxis (PrEP) can significantly reduce HIV acquisition especially among communities with high HIV prevalence, including men who have sex with men (MSM). Much research has been finding suboptimal PrEP persistence; however, few studies examine factors that enhance PrEP persistence in real-world settings.

METHODS

We interviewed 33 patients who identified as MSM at three different PrEP clinics in three regions of the U.S. (Northeast, South, Midwest). Participants were eligible if they took PrEP and had been retained in care for a minimum of 6 months. Interviews explored social, structural, clinic-level and behavioral factors that influencing PrEP persistence.

RESULTS

Through thematic analysis we identified the following factors as promoting PrEP persistence: (1) navigation to reduce out-of-pocket costs of PrEP (structural), (2) social norms that support PrEP use (social), (3) access to LGBTQ + affirming medical providers (clinical), (4) medication as part of a daily routine (behavioral), and (5) facilitation of sexual health agency (belief).

DISCUSSION

In this sample, persistence in PrEP care was associated with structural and social supports as well as a high level of perceived internal control over protecting their health by taking PrEP. Patients might benefit from increased access, LGBTQ + affirming medical providers, and communications that emphasize PrEP can promote sexual health.

Mechanism of the enhancement of electrical conductivity of nanocrystalline silicon due to hydrogen plasma treatment

The mechanism of electrical charge transport in hydrogenated nanocrystalline silicon (nc-Si:H) and the enhancement in electrical conductivity by hydrogen plasma exposure has been studied. Nanoscale electrical conduction measurements (laterally on the surface) suggested that the dominant charge transport in nc-Si:H occurs through the crystalline grain interiors while grain boundaries are highly resistive. Room temperature low-power/short-duration (10 W, 10 s) surface hydrogen plasma treatment enhanced the local surface and bulk electrical conductivity of nc-Si:H films which was attributed to improved passivation of surface and bulk dangling bonds, increase in crystalline fraction and decrease in grain boundary (GB) fraction. However, the improvement in electrical conductivity due to high-power/long-duration (50 W, 10 min) hydrogen plasma exposure was not as pronounced as low-power/short-duration exposure. Temperature-dependent dark conductivity measurements showed dual activation-energy behavior; increase in activation energy in the high-temperature regime (400-585 K) was attributed to the temperature dependence of tunneling probability of carriers and explained using a heteroquantum dots model. A decrease in activation energy with plasma exposure was observed which was explained using the framework of a three-phase model of nc-Si:H where GB width and barrier potential played a critical role in determining the relative contribution of tunneling and thermally activated carrier transport.

Chronic thromboxane synthase inhibition prevents fructose-induced hypertension

To investigate the role of thromboxane A(2) in the development of hypertension in the fructose-fed rat, we treated male fructose-fed rats with dazmegrel (a thromboxane synthase inhibitor) and monitored blood pressure, fasting plasma parameters, and insulin sensitivity for 7 weeks. Systolic blood pressure was measured each week using tail plethysmography, and an oral glucose tolerance test was performed at the end of the study to assess insulin sensitivity. Treatment with a 60% fructose diet and dazmegrel (100 mg. kg(-1). d(-1) via oral gavage) was initiated on the same day. Plasma triglyceride levels increased 2-fold in both fructose- and fructose/dazmegrel-treated groups, and plasma insulin levels tended to be higher in these groups, although not significantly. Systolic blood pressure increased significantly throughout the study in the fructose-fed group only (132+/-3 versus 112+/-4 mm Hg in control rats, 118+/-2 mm Hg in control-treated rats, 116+/-2 mm Hg in fructose-treated rats). Both fructose groups demonstrated a higher peak insulin response to oral glucose challenge and had 40% to 60% lower insulin sensitivity index values. The results of this study show that treatment with a thromboxane synthase inhibitor, dazmegrel, can prevent the development of hypertension but does not improve insulin sensitivity or other fructose-induced metabolic impairments. Based on these data, we conclude that the potent vasoconstrictor thromboxane is involved in the link between hyperinsulinemia/insulin resistance and hypertension.

NO/PGI2-independent vasorelaxation and the cytochrome P450 pathway in rabbit carotid artery

1. The nature and cellular mechanisms that are responsible for endothelium-dependent relaxations resistant to indomethacin and NG-nitro-L-arginine methyl ester (L-NAME) were investigated in phenylephrine (PE) precontracted isolated carotid arteries from the rabbit. 2. In the presence of the cyclo-oxygenase inhibitor, indomethacin (10 microM), acetylcholine (ACh) induced a concentration- and endothelium-dependent relaxation of PE-induced tone which was more potent than the calcium ionophore A23187 with pD2 values of 7.03 +/- 0.12 (n = 8) and 6.37 +/- 0.12 (n = 6), respectively. The ACh-induced response was abolished by removal of the endothelium, but was not altered when indomethacin was omitted (pD2 value 7.00 +/- 0.10 and maximal relaxation 99 +/- 3%, n = 6). Bradykinin and histamine (0.01-100 microM) had no effect either upon resting or PE-induced tone (n = 5). 3. In the presence of indomethacin plus the NO synthase inhibitor, L-NAME (30 microM), the response to A23187 was abolished. However, the response to ACh was not abolished, although it was significantly inhibited with the pD2 value and the maximal relaxation decreasing to 6.48 +/- 0.10 and 67 +/- 3%, respectively (for both P < 0.01, n = 8). The L-NAME/indomethacin insensitive vasorelaxation to ACh was completely abolished by preconstriction of the tissues with potassium chloride (40 mM, n = 8). 4. The Ca(2+)-activated K+ (KCa) channel blockers, tetrabutylammonium (TBA, 1 mM, n = 5) and charybdotoxin (CTX, 0.1 microM, n = 5), completely inhibited the nitric oxide (NO) and prostacyclin (PGI2)-independent relaxation response to ACh. However, iberiotoxin (ITX, 0.1 microM, n = 8) or apamin (1-3 microM, n = 6) only partially inhibited the relaxation. 5. Inhibitors of the cytochrome P450 mono-oxygenase, SKF-525A (1-10 microM, n = 6), clotrimazole (1 microM, n = 5) and 17-octadecynoic acid (17-ODYA, 3 microM, n = 7) also reduced the NO/PGI2-independent relaxation response to ACh. 6. In endothelium-denuded rings of rabbit carotid arteries, the relaxation response to exogenous NO was not altered by either KCa channel blockade with apamin (1 microM, n = 5) or CTX (0.1 microM, n = 5), or by the cytochrome P450 mono-oxygenase blockers SKF-525A (10 microM, n = 4) and clotrimazole (10 microM, n = 5). However, the NO-induced response was shifted to the right by LY83583 (10 microM, n = 4), a guanylyl cyclase inhibitor, with the pD2 value decreasing from 6.95 +/- 0.14 to 6.04 +/- 0.09 (P < 0.01). 7. ACh (0.01-100 microM) induced a concentration-dependent relaxation of PE-induced tone in endothelium-denuded arterial segments sandwiched with endothelium-intact donor segments. This relaxation to ACh was largely unaffected by indomathacin (10 microM) plus L-NAME (30 microM), but abolished by the combination of indomethacin, L-NAME and TBA (1 mM, n = 5). 8. These data suggest that in the rabbit carotid artery: (a) ACh can induce the release of both NO and EDHF, whereas A23187 only evokes the release of NO from the endothelium, (b) the diffusible EDHF released by ACh may be a cytochrome P450-derived arachidonic acid metabolite, and (c) EDHF-induced relaxation involves the opening of at least two types of KCa channels, whereas NO mediates vasorelaxation via a guanosine 3': 5'-cyclic monophosphate (cyclic GMP)-mediated pathway, in which a cytochrome P450 pathway and KCa channels do not seem to be involved.