Toward physics-based precision medicine: Exploiting protein dynamics to design new therapeutics and interpret variants.

The goal of precision medicine is to utilize our knowledge of the molecular causes of disease to better diagnose and treat patients. However, there is a substantial mismatch between the small number of food and drug administration (FDA)-approved drugs and annotated coding variants compared to the needs of precision medicine. This review introduces the concept of physics-based precision medicine, a scalable framework that promises to improve our understanding of sequence-function relationships and accelerate drug discovery. We show that accounting for the ensemble of structures a protein adopts in solution with computer simulations overcomes many of the limitations imposed by assuming a single protein structure. We highlight studies of protein dynamics and recent methods for the analysis of structural ensembles. These studies demonstrate that differences in conformational distributions predict functional differences within protein families and between variants. Thanks to new computational tools that are providing unprecedented access to protein structural ensembles, this insight may enable accurate predictions of variant pathogenicity for entire libraries of variants. We further show that explicitly accounting for protein ensembles, with methods like alchemical free energy calculations or docking to Markov state models, can uncover novel lead compounds. To conclude, we demonstrate that cryptic pockets, or cavities absent in experimental structures, provide an avenue to target proteins that are currently considered undruggable. Taken together, our review provides a roadmap for the field of protein science to accelerate precision medicine.

Results from a pilot study of an automated directly observed therapy intervention using artificial intelligence with conditional economic incentives among young adults with HIV.

BACKGROUND: Despite improvements in antiretroviral therapy (ART) availability, suboptimal adherence is common among youth with HIV (YWH) and can increase drug resistance and poor clinical outcomes. Our study examined an innovative mobile app-based intervention that used automated directly observed therapy (aDOT) using artificial intelligence, along with conditional economic incentives (CEIs) to improve ART adherence and enhance viral suppression among YWH. SETTING: We conducted a pilot study of the aDOT-CEI intervention, informed by the operant framework of Key Principles in Contingency Management Implementation, to improve ART adherence among YWH (18-29) in California and Florida who had an unsuppressed HIV viral load. METHODS: We recruited 28 virally unsuppressed YWH from AIDS Healthcare Foundation (AHF) clinics, who used the aDOT platform for 3 months. Study outcomes included feasibility and acceptability, self-reported ART adherence, and HIV viral load. RESULTS: Participants reported high satisfaction with the app (91%), and 82% said that it helped them take their medication. Comfort with the security and privacy of the app was moderate (55%), and 59% indicated the incentives helped improve daily adherence. CONCLUSION: Acceptability and feasibility of the aDOT-CEI intervention were high with potential to improve viral suppression, although some a priori metrics were not met. Pilot results suggest refinements which may improve intervention outcomes, including increased incentive amounts, provision of additional information, and reassurance about app privacy and security. Additional research is recommended to test the efficacy of the aDOT-CEI intervention to improve viral suppression in a larger sample.

PopShift: A Thermodynamically Sound Approach to Estimate Binding Free Energies by Accounting for Ligand-Induced Population Shifts from a Ligand-Free Markov State Model.

Obtaining accurate binding free energies from in silico screens has been a long-standing goal for the computational chemistry community. However, accuracy and computational cost are at odds with one another, limiting the utility of methods that perform this type of calculation. Many methods achieve massive scale by explicitly or implicitly assuming that the target protein adopts a single structure, or undergoes limited fluctuations around that structure, to minimize computational cost. Others simulate each protein-ligand complex of interest, accepting lower throughput in exchange for better predictions of binding affinities. Here, we present the PopShift framework for accounting for the ensemble of structures a protein adopts and their relative probabilities. Protein degrees of freedom are enumerated once, and then arbitrarily many molecules can be screened against this ensemble. Specifically, we use Markov state models (MSMs) as a compressed representation of a protein's thermodynamic ensemble. We start with a ligand-free MSM and then calculate how addition of a ligand shifts the populations of each protein conformational state based on the strength of the interaction between that protein conformation and the ligand. In this work we use docking to estimate the affinity between a given protein structure and ligand, but any estimator of binding affinities could be used in the PopShift framework. We test PopShift on the classic benchmark pocket T4 Lysozyme L99A. We find that PopShift is more accurate than common strategies, such as docking to a single structure and traditional ensemble docking─producing results that compare favorably with alchemical binding free energy calculations in terms of RMSE but not correlation─and may have a more favorable computational cost profile in some applications. In addition to predicting binding free energies and ligand poses, PopShift also provides insight into how the probability of different protein structures is shifted upon addition of various concentrations of ligand, providing a platform for predicting affinities and allosteric effects of ligand binding. Therefore, we expect PopShift will be valuable for hit finding and for providing insight into phenomena like allostery.

Youth Ending the HIV Epidemic (YEHE): Protocol for a pilot of an automated directly observed therapy intervention with conditional economic incentives among young adults with HIV.

BACKGROUND: Young adults have a disproportionately high rate of HIV infection, high rates of attrition at all stages of the HIV care continuum, and an elevated probability of disease progression and transmission. Tracking and monitoring objective measures of antiretroviral therapy (ART) adherence in real time is critical to bolster the accuracy of research data, support adherence, and improve clinical outcomes. However, adherence monitoring often relies on self-reported and retrospective data or requires additional effort from providers to understand individual adherence patterns. In this study, we will monitor medication-taking using a real-time objective measure of adherence that does not rely on self-report or healthcare providers for measurement. METHODS: The Youth Ending the HIV Epidemic (YEHE) study will pilot a novel automated directly observed therapy-conditional economic incentive (aDOT-CEI) intervention to improve ART adherence among youth with HIV (YWH) in California and Florida who have an unsuppressed HIV viral load. The aDOT app uses facial recognition to record adherence each day, and then economic incentives are given based on a participant's confirmed adherence. We will enroll participants in a 3-month pilot study to assess the feasibility and acceptability of the aDOT-CEI intervention using predefined metrics. During and after the trial, a subsample of the pilot participants and staff/providers from participating AIDS Healthcare Foundation (AHF) clinics will participate in individual in-depth interviews to explore intervention and implementation facilitators and barriers. DISCUSSION: YEHE will provide data on the use of an aDOT-CEI intervention to improve adherence among YWH who are not virologically suppressed. The YEHE study will document the feasibility and acceptability and will explore preliminary data to inform a trial to test the efficacy of aDOT-CEI. This intervention has the potential to effectively improve ART adherence and virologic suppression among a key population experiencing health disparities. TRIAL REGISTRATION: The trial registration number is NCT05789875.

iVY: protocol for a randomised clinical trial to test the effect of a technology-based intervention to improve virological suppression among young adults with HIV in the USA.

INTRODUCTION: Young adults with HIV (YWH) experience worse clinical outcomes than adults and have high rates of substance use (SU) and mental illness that impact their engagement in care and adherence to antiretroviral therapy (ART). The intervention for Virologic Suppression in Youth (iVY) aims to address treatment engagement/adherence, mental health (MH) and SU in a tailored manner using a differentiated care approach that is youth friendly. Findings will provide information about the impact of iVY on HIV virological suppression, MH and SU among YWH who are disproportionately impacted by HIV and at elevated risk for poor health outcomes. METHODS AND ANALYSIS: The iVY study will test the effect of a technology-based intervention with differing levels of resource requirements (ie, financial and personnel time) in a randomised clinical trial with an adaptive treatment strategy among 200 YWH (18-29 years old). The primary outcome is HIV virological suppression measured via dried blood spot. This piloted and protocolised intervention combines: (1) brief weekly sessions with a counsellor via a video-chat platform (video-counselling) to discuss MH, SU, HIV care engagement/adherence and other barriers to care; and (2) a mobile health app to address barriers such as ART forgetfulness, and social isolation. iVY has the potential to address important, distinct and changing barriers to HIV care engagement (eg, MH, SU) to increase virological suppression among YWH at elevated risk for poor health outcomes. ETHICS AND DISSEMINATION: This study and its protocols have been approved by the University of California, San Francisco Institutional Review Board. Study staff will work with a Youth Advisory Panel to disseminate results to YWH, participants and the academic community. TRIAL REGISTRATION NUMBER: NCT05877729.

PopShift: A thermodynamically sound approach to estimate binding free energies by accounting for ligand-induced population shifts from a ligand-free MSM.

Obtaining accurate binding free energies from in silico screens has been a longstanding goal for the computational chemistry community. However, accuracy and computational cost are at odds with one another, limiting the utility of methods that perform this type of calculation. Many methods achieve massive scale by explicitly or implicitly assuming that the target protein adopts a single structure, or undergoes limited fluctuations around that structure, to minimize computational cost. Others simulate each protein-ligand complex of interest, accepting lower throughput in exchange for better predictions of binding affinities. Here, we present the PopShift framework for accounting for the ensemble of structures a protein adopts and their relative probabilities. Protein degrees of freedom are enumerated once, and then arbitrarily many molecules can be screened against this ensemble. Specifically, we use Markov state models (MSMs) as a compressed representation of a protein's thermodynamic ensemble. We start with a ligand-free MSM and then calculate how addition of a ligand shifts the populations of each protein conformational state based on the strength of the interaction between that protein conformation and the ligand. In this work we use docking to estimate the affinity between a given protein structure and ligand, but any estimator of binding affinities could be used in the PopShift framework. We test PopShift on the classic benchmark pocket T4 Lysozyme L99A. We find that PopShift is more accurate than common strategies, such as docking to a single structure and traditional ensemble docking-producing results that compare favorably with alchemical binding free energy calculations in terms of RMSE but not correlation - and may have a more favorable computational cost profile in some applications. In addition to predicting binding free energies and ligand poses, PopShift also provides insight into how the probability of different protein structures is shifted upon addition of various concentrations of ligand, providing a platform for predicting affinities and allosteric effects of ligand binding. Therefore, we expect PopShift will be valuable for hit finding and for providing insight into phenomena like allostery.

Apolipoprotein E4 has extensive conformational heterogeneity in lipid-free and lipid-bound forms.

The ε4-allele variant of apolipoprotein E (ApoE4) is the strongest genetic risk factor for Alzheimer's disease, although it only differs from its neutral counterpart ApoE3 by a single amino acid substitution. While ApoE4 influences the formation of plaques and neurofibrillary tangles, the structural determinants of pathogenicity remain undetermined due to limited structural information. Previous studies have led to conflicting models of the C-terminal region positioning with respect to the N-terminal domain across isoforms largely because the data are potentially confounded by the presence of heterogeneous oligomers. Here, we apply a combination of single-molecule spectroscopy and molecular dynamics simulations to construct an atomically detailed model of monomeric ApoE4 and probe the effect of lipid association. Importantly, our approach overcomes previous limitations by allowing us to work at picomolar concentrations where only the monomer is present. Our data reveal that ApoE4 is far more disordered and extended than previously thought and retains significant conformational heterogeneity after binding lipids. Comparing the proximity of the N- and C-terminal domains across the three major isoforms (ApoE4, ApoE3, and ApoE2) suggests that all maintain heterogeneous conformations in their monomeric form, with ApoE2 adopting a slightly more compact ensemble. Overall, these data provide a foundation for understanding how ApoE4 differs from nonpathogenic and protective variants of the protein.

Drug specificity and affinity are encoded in the probability of cryptic pocket opening in myosin motor domains.

The design of compounds that can discriminate between closely related target proteins remains a central challenge in drug discovery. Specific therapeutics targeting the highly conserved myosin motor family are urgently needed as mutations in at least six of its members cause numerous diseases. Allosteric modulators, like the myosin-II inhibitor blebbistatin, are a promising means to achieve specificity. However, it remains unclear why blebbistatin inhibits myosin-II motors with different potencies given that it binds at a highly conserved pocket that is always closed in blebbistatin-free experimental structures. We hypothesized that the probability of pocket opening is an important determinant of the potency of compounds like blebbistatin. To test this hypothesis, we used Markov state models (MSMs) built from over 2 ms of aggregate molecular dynamics simulations with explicit solvent. We find that blebbistatin's binding pocket readily opens in simulations of blebbistatin-sensitive myosin isoforms. Comparing these conformational ensembles reveals that the probability of pocket opening correctly identifies which isoforms are most sensitive to blebbistatin inhibition and that docking against MSMs quantitatively predicts blebbistatin binding affinities (R2=0.82). In a blind prediction for an isoform (Myh7b) whose blebbistatin sensitivity was unknown, we find good agreement between predicted and measured IC50s (0.67 µM vs. 0.36 µM). Therefore, we expect this framework to be useful for the development of novel specific drugs across numerous protein targets.

Chemically Accurate Relative Folding Stability of RNA Hairpins from Molecular Simulations.

To benchmark RNA force fields, we compared the folding stabilities of three 12-nucleotide hairpin stem loops estimated by simulation to stabilities determined by experiment. We used umbrella sampling and a reaction coordinate of end-to-end (5' to 3' hydroxyl oxygen) distance to estimate the free energy change of the transition from the native conformation to a fully extended conformation with no hydrogen bonds between non-neighboring bases. Each simulation was performed four times using the AMBER FF99+bsc0+χOL3 force field, and each window, spaced at 1 Å intervals, was sampled for 1 µs, for a total of 552 µs of simulation. We compared differences in the simulated free energy changes to analogous differences in free energies from optical melting experiments using thermodynamic cycles where the free energy change between stretched and random coil sequences is assumed to be sequence-independent. The differences between experimental and simulated ΔΔ G° are, on average, 0.98 ± 0.66 kcal/mol, which is chemically accurate and suggests that analogous simulations could be used predictively. We also report a novel method to identify where replica free energies diverge along a reaction coordinate, thus indicating where additional sampling would most improve convergence. We conclude by discussing methods to more economically perform these simulations.

Closed-loop superluminal passive cavity.

We demonstrate the operation of a closed-loop fast-light cavity that allows rapid (~10 ms) measurements of the cavity mode frequency and its uncertainty. We vary the scale factor by temperature tuning the atomic density of an intracavity vapor cell. The cavity remains locked even as the system passes through the critical anomalous dispersion where a pole is observed in the scale factor. Positive and negative scale-factor enhancements as large as |S| ≈70 were obtained. To our knowledge, these are the first experiments that demonstrate a scale-factor enhancement in a closed-loop fast-light device by changing the optical path length, laying the groundwork for the improvement of cavity-based metrology instruments such as optical gyroscopes.

Increased HIV-1 transcriptional activity and infectious burden in peripheral blood and gut-associated CD4+ T cells expressing CD30.

HIV-1-infected cells persist indefinitely despite the use of combination antiretroviral therapy (ART), and novel therapeutic strategies to target and purge residual infected cells in individuals on ART are urgently needed. Here, we demonstrate that CD4+ T cell-associated HIV-1 RNA is often highly enriched in cells expressing CD30, and that cells expressing this marker considerably contribute to the total pool of transcriptionally active CD4+ lymphocytes in individuals on suppressive ART. Using in situ RNA hybridization studies, we show co-localization of CD30 with HIV-1 transcriptional activity in gut-associated lymphoid tissues. We also demonstrate that ex vivo treatment with brentuximab vedotin, an antibody-drug conjugate (ADC) that targets CD30, significantly reduces the total amount of HIV-1 DNA in peripheral blood mononuclear cells obtained from infected, ART-suppressed individuals. Finally, we observed that an HIV-1-infected individual, who received repeated brentuximab vedotin infusions for lymphoma, had no detectable virus in peripheral blood mononuclear cells. Overall, CD30 may be a marker of residual, transcriptionally active HIV-1 infected cells in the setting of suppressive ART. Given that CD30 is only expressed on a small number of total mononuclear cells, it is a potential therapeutic target of persistent HIV-1 infection.

Physics-based all-atom modeling of RNA energetics and structure.

The database of RNA sequences is exploding, but knowledge of energetics, structures, and dynamics lags behind. All-atom computational methods, such as molecular dynamics, hold promise for closing this gap. New algorithms and faster computers have accelerated progress in improving the reliability and accuracy of predictions. Currently, the methods can facilitate refinement of experimentally determined nuclear magnetic resonance and x-ray structures, but are 'unreliable' for predictions based only on sequence. Much remains to be discovered, however, about the many molecular interactions driving RNA folding and the best way to approximate them quantitatively. The large number of parameters required means that a wide variety of experimental results will be required to benchmark force fields and different approaches. As computational methods become more reliable and accessible, they will be used by an increasing number of biologists, much as x-ray crystallography has expanded. Thus, many fundamental physical principles underlying the computational methods are described. This review presents a summary of the current state of molecular dynamics as applied to RNA. It is designed to be helpful to students, postdoctoral fellows, and faculty who are considering or starting computational studies of RNA. WIREs RNA 2017, 8:e1422. doi: 10.1002/wrna.1422.

Directed network wiring identifies a key protein interaction in embryonic stem cell differentiation.

Cell signaling depends on dynamic protein-protein interaction (PPI) networks, often assembled through modular domains each interacting with multiple peptide motifs. This complexity raises a conceptual challenge, namely to define whether a particular cellular response requires assembly of the complete PPI network of interest or can be driven by a specific interaction. To address this issue, we designed variants of the Grb2 SH2 domain ("pY-clamps") whose specificity is highly biased toward a single phosphotyrosine (pY) motif among many potential pYXNX Grb2-binding sites. Surprisingly, directing Grb2 predominantly to a single pY site of the Ptpn11/Shp2 phosphatase, but not other sites tested, was sufficient for differentiation of the essential primitive endoderm lineage from embryonic stem cells. Our data suggest that discrete connections within complex PPI networks can underpin regulation of particular biological events. We propose that this directed wiring approach will be of general utility in functionally annotating specific PPIs.

Association of major depression with sexual dysfunction in men.

The effect of type and severity of depression on sexual functioning was examined before treatment in 591 men with Major Depression (MDD) or Atypical Depression, as determined by percentage of subjects meeting Diagnostic and Statistical Manual, 4th Edition (DSM-IV) sexual dysfunction criteria (A and B only), and percentage with Derogatis Inventory of Sexual Function (DISF) scores greater than 1 standard deviation below normal. Sexual dysfunction rates were higher for MDD than for Atypical Depression. Depression affected DISF domains differently: orgasm was most impaired, whereas sexual desire was preserved. More severe depression resulted in greater sexual dysfunction.

Manufacturer evaluations of endograft modifications.

The motivation to modify the design of a vascular device can arise from a number of sources. Clinical experience with the unmodified device could suggest new design modifications to improve device performance or clinical outcomes. Similarly, clinical success with a device often suggests modifications that could broaden the applicability of the device to enable treatment of different or more advanced disease states. As a specific example, both of these scenarios have arisen during the last decade in the evolution of endovascular grafts for the treatment of abdominal aortic aneurysms, with modifications enabling the treatment of patients with shorter infrarenal necks, more angulated anatomy, and smaller access vessels. These modifications have been made by manufacturers and additionally by physicians who create branched and fenestrated devices. The experience to date with the use of fenestrated devices and the development of chimney, snorkel, and periscope techniques suggests that modifications to off-the-shelf devices may provide some clinical benefit. This experience provides additional motivation for manufacturers to develop devices to address the clinical needs not met with their current product lines. For manufacturers, the device development process includes an assessment of the new device design to determine the appropriate evaluation strategy to support the safety and effectiveness of the modified device. This report provides a high-level overview of the process generally followed by device manufacturers to evaluate a proposed device modification before market release, in accordance with local country regulations and recognized international standards such as the International Organization of Standardization (ISO) standards for endovascular grafts (ISO 25539 Part 1).

The effect of gepirone-ER in the treatment of sexual dysfunction in depressed men.

INTRODUCTION: Sexual dysfunction is common in patients with major depressive disorder (MDD). Antidepressant medications especially the selective serotonin reuptake inhibitors (SSRIs) may improve depressive symptoms but further decrease sexual function. Gepirone extended release (gepirone-ER) differs from the SSRIs in only affecting the 5-HT(1A) receptor and has demonstrated efficacy in treatment of depression and sexual dysfunction in depressed women. This report describes the effect of gepirone-ER on sexual function in depressed men. AIM: The aims of this article were to study the effects of gepirone-ER on sexual function in men with MDD and to determine if positive effects are independent of antidepressant or anxiolytic activity. MAIN OUTCOME MEASURES: The main outcome measures of this article were Hamilton depression rating scale (HAMD-17), and changes in sexual functioning questionnaire (CSFQ). METHODS: In an 8-week study, gepirone-ER, placebo, or fluoxetine were administered in a double-blind fashion to 181 depressed men. The CSFQ results were used to determine quality of sexual function. To test for an antidepressant or anxiolytic effect, a 50% reduction in HAMD-17 score separated antidepressant responders from nonresponders, and item 12 of the HAMD scale (psychic anxiety) scores of 0 or 1 separated anxiolytic responders from nonresponders. RESULTS: Gepirone-ER treatment improved total sexual function compared with placebo measured by the CSFQ at weeks 4 (P=0.012) and 8 (P=0.046). At 4 weeks, almost every CSFQ domain is improved. The orgasm domain was especially improved, 67% by week 4. Gepirone-ER antidepressant and anxiolytic nonresponders showed significant improvement in sexual function. Fluoxetine treatment did not produce improvement. In fact, fluoxetine-treated subjects had lower scores on the total CSFQ, less than placebo, and significantly less than gepirone-ER. CONCLUSION: Gepirone-ER improves sexual dysfunction in depressed men. All domains of sexual function improved. Gepirone-ER has a pro-sexual effect independent of antidepressant or anxiolytic activity.

The effect of major depression on sexual function in women.

INTRODUCTION: Eleven hundred eighty-four depressed women were entered into five short-term (8 weeks) studies of gepirone-extended release (ER) vs. placebo for treatment of major depressive disorder (MDD) (134001, 134002, and 134017), or atypical depressive disorder (ADD) (134004 and 134006). The effect of depression on sexual function was examined prior to treatment. AIM: To determine the effect of depression on the prevalence of Diagnostic and Statistical Manual Fourth Edition (DSM-IV) sexual dysfunction diagnoses and the Derogatis Inventory of Sexual Function (DISF) total score and domain scores and to measure the effect of severity of depression. MAIN OUTCOME MEASURES: Hamilton Depression Rating Scale (HAMD-17), DSM-IV diagnoses, and DISF total and domain scores. METHODS: DSM-IV diagnoses--hypoactive sexual desire disorder (HSDD), sexual aversion disorder (SAD), female arousal disorder (FAD), and female orgasmic disorder (FOD)--were made by a trained psychiatrist. The HAMD-17 measured antidepressant efficacy. The DISF or its self-report version measured sexual function. To access the effect of severity of depression, baseline HAMD-17 scores were stratified as mild (<18), moderate (19-22), severe (23-25), or extreme (26-33). All measures were taken at baseline. RESULTS: In this depressed female population, prevalence rates were HSDD 17.7%, SAD 3.4%, FAD 5.8%, and FOD 7.7%. These rates for females are within the reported normal (nondepressed) values. However, DISF scores are one or more standard deviations below population norms for total score. DISF domains are not equally affected: orgasm is most impaired, while sexual desire and sexual arousal are somewhat preserved. Higher HAMD scores result in lower DISF scores (greater sexual dysfunction). CONCLUSIONS: In women, depression affects DISF scores more than DSM-IV diagnoses for sexual dysfunction. With increasing severity of depression (increased HAMD scores), sexual dysfunction becomes greater (lower DISF scores). For equal HAMD scores, DISF scores for MDD and ADD are the same.

Gepirone-ER treatment of low sexual desire associated with depression in women as measured by the DeRogatis Inventory of Sexual Function (DISF) fantasy/cognition (desire) domain--a post hoc analysis.

INTRODUCTION: Gepirone-extended release (ER) is effective in treating hypoactive sexual desire disorder (HSDD), as measured by the percent of females with HSDD that no longer met criteria for HSDD treatment. Another approach is to determine treatment effect on sexual desire using a recognized rating scale for sexual function. Because gepirone-ER has antidepressant and anxiolytic effects, investigation of these effects on sexual desire is appropriate. AIM: The aim of this study was to determine whether gepirone-ER has positive effects on sexual desire as measured by the DeRogatis Inventory of Sexual Function (DISF) in a post hoc analysis of 8- and 24-week studies and if this gepirone effect is independent of its antidepressant or anxiolytic activity. MAIN OUTCOME MEASURES: The main outcome measures used for this study were the Hamilton Depression Rating Scale (HAMD-25), change from baseline (CFB), and DISF CFB. METHODS: Three hundred thirty-four women selected for depressive symptoms, not sexual dysfunction, received gepirone-ER (40-80 mg/day) in a controlled study of atypical depression using the HAMD-25 to measure antidepressant efficacy and a DISF subscale (domain I) to measure sexual cognition/fantasy (desire). After treatment, a 50% reduction from baseline HAMD-25 score identified antidepressant responders. Item 12 of HAMD scale (psychic anxiety) was used to define anxiolytic response scores of 0, 1 as responders, and scores of 2, 3, and 4 as nonresponders. RESULTS: Gepirone-ER had no significant antidepressant or an anxiolytic effect in study 134006; however, DISF results demonstrate that gepirone-ER improves sexual desire in short term (P=0.043) and long term (P=0.006). Both gepirone-ER antidepressant and anxiolytic responders have statistically significant improved sexual desire. Gepirone-ER antidepressant and anxiolytic nonresponders also show statistically significant improvement. CONCLUSIONS: In depressed women, gepirone-ER has three mechanisms of action affecting sexual desire: an antidepressant effect, an anxiolytic effect, and a pro-sexual effect. Gepirone-ER improves sexual desire from the 24th to the 50th percentile according to population norms for the DISF.

Gepirone-ER treatment of hypoactive sexual desire disorder (HSDD) associated with depression in women.

INTRODUCTION: There is currently no Food and Drug Administration (FDA)-approved treatment for hypoactive sexual desire disorder (HSDD). FDA approval of products utilizing testosterone has been delayed due to possible safety concerns. Flibanserin, a 5-HT(1A) agonist, 5-HT(2) antagonist, and gepirone-ER, a 5-HT(1A) agonist, have been shown to have activity in treatment of HSDD. However, more recently, the FDA issued a non-approval letter for flibanserin. AIM: To study the effect of gepirone-ER on HSDD in women with major depressive disorder (MDD). METHODS: At baseline and post-treatment visits, a trained psychiatrist made diagnoses of HSDD based on Diagnostic and Statistical Manual of Mental Disorders Fourth Edition (DSM-IV) criteria. Subjects meeting criteria for HSDD were followed to observe the effect of gepirone-ER (20-80 mg/day), comparator antidepressants (fluoxetine, 20-40 mg/day or paroxetine, 10-40 mg/day), or placebo in reversing DSM-IV diagnosis. A subpopulation of women with Hamilton Depression Rating Scale (HAMD-17) entry scores of 18 or less was evaluated. Adverse events (AEs) of sexual dysfunction were also collected. MAIN OUTCOME MEASURE: Number (%) of patients who no longer met criteria for HSDD (percent resolved). RESULTS: Eight hundred seventy-five women (18-64 years of age, average 38 years old, ∼80% premenopausal) entered three studies; 668 (72.5%) completed. Only 161 (18.4%) met DSM-IV criteria for HSDD. Cumulatively, 63% of gepirone-ER-treated patients reversed their diagnosis of HSDD compared to 40% of placebo-treated patients at end point (8 weeks) (P = 0.007). Selective serotonin reuptake inhibitor-treated patients were not different from placebo. Significant results for gepirone-ER occurred by week 2 (P = 0.0001). Patients who were mildly depressed (HAMD scores of 18 or less) also improved at week 2 (P = 0.01) and week 8 (P = 0.07). Sexual dysfunction AEs were significantly less in gepirone-ER-treated patients than placebo (P = 0.013). CONCLUSIONS: Gepirone-ER may have efficacy in the treatment of HSDD among depressed and possibly nondepressed women. Efficacy occurs by week 2, and does not seem to be purely an antidepressant effect.