Selective Retinoic Acid Receptor Research Articles

6816 The Estrogen Environment Characteristic of Endometriotic Lesion May Attenuate the Receptor γ-Mediated Antiproliferative Activity of Retinoids

Abstract Disclosure: M. Izawa: None. Y. Azuma: None. F. Taniguchi: None. Background: Endometriosis has been accepted as an estrogen-dependent disease, and the estrogen environment in endometriotic lesions has been proposed as a major background of the pathophysiology. Although the hormonal therapy targeting the reduction of estrogen has been employed to reduce endometriosis-associated symptoms, the limitation of therapy has been well recognized. How to overcome the limitation remains an urgent subject to be explored. [Objective:]We focused on retinoids, which have been known to induce an antiproliferative activity in tumors. Based on the retinoic acid receptor (RAR) expression profile in endometriotic lesions, we evaluated the antiproliferative activity of retinoids using endometriotic cells. Finally, we examined the effect of estrogen on antiproliferative activity. Methods: Endometriotic tissue and cells: Institutional Review Boards approved this project. The chocolate cyst lining in the ovaries of patients with endometriosis was the source of endometriotic tissue. Stromal cells collected from endometriotic tissues were used as endometriotic cells. RAR expression: RNAs were prepared from endometriotic tissues and cells, and single-stranded cDNAs were subjected to RT-PCR. Primers were designed using the UCSF genome browser. Protein expression was examined by Western blotting. Cell proliferation assay: Cells were treated with all-trans retinoic acid (ATRA), selective RAR modulators (sRARMs), BMS753, CD2314 and CD437, RARγ antagonist MM11253 and 17β-estradiol (E2). Viable cells were estimated using WST-8 assay. RNA-seq analysis: Cells were treated with retinoids and E2. RNA samples were used for polyA+ selected library and the strand-specific RNA-seq. Differentially expressed genes with p-values < 0.05 and log2 fold changes > 1 were extracted as responsive genes. Results: RAR expression: Transcripts of wild-type RARα, RARβ, and RARγ were demonstrated in arbitrary 10 regions of patient tissue, and in endometriotic cells. The expression of these RARs was almost at a comparable level. Effect of retinoids and/or estrogen on cell proliferation: Cell proliferation rate was significantly decreased in the presence of ATRA. Among sRARMs tested, only CD437 reduced the cell proliferation. The antiproliferative activity of ATRA was attenuated either in the presence of MM11253 or E2, respectively. ATRA- and/or E2-responsive gene expressions To explore gene expressions in response to retinoids and E2, RNA-seq analysis was performed. The results suggest the diversity of ATRA- and E2-responsive genes in endometriotic lesions.[Conclusion:]Endometriotic cell proliferation was significantly suppressed in response to retinoids through RARγ. The observation that the antiproliferative activity was attenuated in the presence of E2 suggests a suppressive environment against the activity of retinois in endometriotic legions. Presentation: 6/2/2024

Организация профилактики и терапии угревой болезни у подростков на современном этапе.

The organization of prevention and treatment of acne in adolescents, necessary to improve the quality of medical dermatological care, has not been studied enough. The purpose of the study: аnalysis of current and potential opportunities for organizing the prevention and treatment of acne in adolescents. Results. The pathophysiological mechanisms of acne development are being reviewed, considering the characteristics of the puberty period, however, the trends in introducing new approaches to the organization of prevention and treatment of acne in adolescents are not expressed, with the exception of antiandrogen therapy. The official organization of treatment for adolescents with acne considers that any stage of acne development is multifactorial and is based on an inflammatory process. The officially recommended main method of treating acne in adolescents is the combined use of topical agents, especially the combination of benzoyl peroxide and the retinoid adapalene. In complex cases, topical treatment is supplemented with systemic therapy with retinoids (isotretinoin). Prevention of side effects of topical treatment (dry skin, hyperemia or cheilitis) is achieved through the use of moisturizing cosmetics or cream with dexpanthenol, respectively. Officially, in the field of acne prevention and therapy, such methods of influencing acne vulgaris as dermatocosmetics and corneo-or enzyme therapy are not used. The use of local and systemic pre- and probiotics for the treatment of acne has not been introduced. This reveals a connection between the development of acne and the intestinal microbiome. The use of local antiandrogens and insulin-like growth factor 1 inhibitors to control sebum production, as well as selective retinoic acid receptor agonists with a better safety profile compared to retinoid therapy for acne, may be promising for the prevention and treatment of acne in adolescents. Findings. Organization of effective treatment of acne in adolescents should include their clear instructions and correction of dietary habits. Prevention of acne today is practically not organized in the field of medical services.

Study methodology and insights from the palovarotene clinical development program in fibrodysplasia ossificans progressiva

BackgroundThe design of clinical trials in rare diseases is often complicated by a lack of real-world translational knowledge. Fibrodysplasia ossificans progressiva (FOP) is an ultra-rare genetic disorder characterized by skeletal malformations and progressive heterotopic ossification (HO). Palovarotene is a selective retinoic acid receptor gamma agonist. Here, we describe the methodology of three studies in the palovarotene clinical development program in FOP and discuss insights that could inform future research, including endpoint suitability and the impact of trial design.MethodsPVO-1A-001 (NCT02322255) was a prospective, protocol-specified, longitudinal FOP natural history study (NHS). PVO-1A-201 (NCT02190747) was a randomized, double-blind, placebo-controlled phase II trial; PVO-1A-202 (NCT02279095) was its open-label extension. Trial designs, including treatment regimens and imaging assessments, were refined between PVO-1A-201 and PVO-‍1A-202, and within PVO-1A-202, based on emerging data as the studies progressed. Palovarotene doses were administered using a flare-up treatment regimen (higher dose for 2/4 weeks, followed by lower dose for 4/≥8 weeks; from flare-up onset), with or without accompanying chronic (daily) treatment. Flare-up and disease progression outcomes were assessed, including incidence and volume of new HO during flare-ups and/or annually, as well as other clinical, patient-reported, and exploratory outcomes. Safety was monitored throughout all studies.ResultsOverall, 114 and 58 individuals with FOP were enrolled in the NHS and phase II trials, respectively. Results of the NHS and PVO-1A-201 were published in 2022; complete results of PVO-1A-202 will be publicly available in due course. Together the studies yielded important information on endpoint suitability, including that low-dose whole-body computed tomography was the optimum imaging modality for assessing HO progression annually and that long study durations are needed to detect substantial changes in functional and patient-reported outcomes.ConclusionsA flexible clinical development program is necessary for underexplored rare diseases to overcome the many challenges faced. Here, the NHS provided a longitudinal evaluation of FOP progression and interventional trials were based on emerging data. The studies described informed the design and endpoints implemented in the phase III MOVE trial (NCT03312634) and provide a foundation for future clinical trial development.Trial registrationNCT02322255 (registered 23/12/2014); NCT02190747 (registered 15/07/2014); NCT02279095 (registered 30/10/2014).

FRI372 Retinoic Acids Attenuate The Endometriotic Cell Proliferation Through A Cell-specific Receptor Isoform

Abstract Disclosure: M. Izawa: None. Y. Azuma: None. F. Taniguchi: None. [Background] Endometriosis has been accepted as an estrogen-dependent, proliferative and inflammatory disease for over two decades, and the hormonal therapy targeting the reduction of estrogen has been employed as the first choice of treatment to reduce the endometriosis-associated symptoms. However, the limitation of therapy is becoming evident. In the hope of overcoming the limitation, we focused on retinoids, which have been known to elicit antiproliferative activity in breast tumors. Retinoic acid receptor (RAR) expression has been known to correlate with estrogen receptor expression. [Objective] As a first step to test the antiproliferative activity of retinoids in endometriotic lesions, we examined the expression profile of the retinoic acid receptor (RAR) in endometriotic cells. We then examined the antiproliferative activity of retinoids and the effect of estrogen on their activity. [Patients] Institutional Review Boards approved this project. We obtained informed consent from all patients. The chocolate cyst lining in the ovaries of patients with endometriosis was the source of endometriotic tissue. [Methods] Endometriotic cells: Stromal cells were collected from endometriotic tissues and used as endometriotic cells throughout the experiment. RAR gene expression: Single-stranded cDNA was prepared and subjected to PCR. Primer sets were designed using sequences in the UCSF genome browser. At the end of PCR cycles, the reaction mixture was subjected to electrophoresis on agarose gel. As an internal control, β-tubulin mRNA expression was assayed in parallel. Cell proliferation: Endometriotic cells were treated with retinoids in the presence or absence of estradiol (E2). All-trans retinoic acid (ATRA) and selective RAR modulators (SRARMs) were used. The number of viable cells was estimated using WST-8 assay. Ki-67 expression: Ki-67 expression was examined by Western blotting. As an internal control, β-tubulin expression was assayed in parallel. [Results] RAR mRNA expression: Transcripts of wild-type RARα, RARβ, RARγ, and their splice variants were demonstrated. These mRNAs were expressed almost at a comparable level: a truncated form of RARα without a DNA binding domain, a truncated form of RARβ without a transactivation domain at the N-terminal, and a form of RARγ with a distinct transactivation domain at N-terminal region. Effect of Retinoic acids on cell proliferation: The cell proliferation rate and Ki-67 expression were downregulated in the presence of ATRA. Among SRARMs tested, a selective RARγ modulator decreased cell proliferation. The antiproliferative activity of ATRA was attenuated in the presence of E2 in some cells.[Conclusion]We tested the antiproliferative activity of retinoids in endometriotic cells. Although the endometriotic cells responded to retinoids, the present finding suggested the diversity of cell types in endometriotic lesions. Presentation: Friday, June 16, 2023

Strategies for developing retinoic acid receptor alpha-selective antagonists as novel agents for male contraception

Reported here are the synthesis and in vitro evaluation of a series of 26 retinoic acid analogs based on dihydronaphthalene and chromene scaffolds using a transactivation assay. Chromene amide analog 21 was the most potent and selective retinoic acid receptor α antagonist identified from this series. In vitro evaluation indicated that 21 has favorable physicochemical properties and a favorable pharmacokinetic PK profile in vivo with significant oral bioavailability, metabolic stability, and testes exposure. Compound 21 was evaluated for its effects on spermatogenesis and disruption of fertility in a mouse model. Oral administration of compound 21 at low doses showed reproducibly characteristic albeit modest effects on spermatogenesis, but no effects on fertility were observed in mating studies. The inhibition of spermatogenesis could not be enhanced by raising the dose and lengthening the duration of dosing. Thus, 21 may not be a good candidate to pursue further for effects on male fertility.

Discovery of novel RARα agonists using pharmacophore-based virtual screening, molecular docking, and molecular dynamics simulation studies.

Nuclear retinoic acid receptors (RARs) are ligand-dependent transcription factors involved in various biological processes, such as embryogenesis, cell proliferation, differentiation, reproduction, and apoptosis. These receptors are regulated by retinoids, i.e., retinoic acid (RA) and its analogs, as receptor agonists. RAR agonists are promising therapeutic agents for the treatment of serious dermatological disorders, including some malignant conditions. By inducing apoptosis, they are able to inhibit the proliferation of diverse cancer cell lines. Also, RAR agonists have recently been identified as therapeutic options for some neurodegenerative diseases. These features make retinoids very attractive molecules for medical purposes. Synthetic selective RAR agonists have several advantages over endogenous ones, but they suffer poor pharmacokinetic properties. These compounds are normally lipophilic acids with unfavorable drug-like features such as poor oral bioavailability. Recently, highly selective, potent, and less toxic RAR agonists with proper lipophilicity, thus, good oral bioavailability have been developed for some therapeutic applications. In the present study, ligand and structure-based virtual screening technique was exploited to introduce some novel RARα agonists. Pharmacokinetic assessment was also performed in silico to suggest those compounds which have optimized drug-like features. Finally, two compounds with the best in silico pharmacological features are proposed as lead molecules for future development of RARα agonists.

Investigation of selective retinoic acid receptor alpha antagonist ER-50891 and related analogs for male contraception.

Retinoic acid receptor alpha (RARα) antagonist ER-50891 and 15 analogs were prepared and tested in vitro for potency and selectivity at RARα, RARβ, and RARγ using transactivation assays. Minor modifications to the parent molecule such as the introduction of a C4 tolyl group in place of the C4 phenyl group on the quinoline moiety slightly increased the RARα selectivity but larger substituents significantly decreased the potency. Replacement of the pyrrole moiety of ER-50891 with triazole, amides, or a double bond produced inactive compounds. ER-50891 was found to be stable in male mouse liver microsomes and was tested in male mice to assess its effects on spermatogenesis. Characteristic, albeit modest and transient, effects on spermatogenesis were observed.

Reduction of New Heterotopic Ossification (HO) in the Open-Label, Phase 3 MOVE Trial of Palovarotene for Fibrodysplasia Ossificans Progressiva (FOP).

Fibrodysplasia ossificans progressiva (FOP) is an ultra-rare, severely disabling genetic disorder of progressive heterotopic ossification (HO). The single-arm, open-label, phase 3 MOVE trial (NCT03312634) assessed efficacy and safety of palovarotene, a selective retinoic acid receptor gamma agonist, in patients with FOP. Findings were compared with FOP natural history study (NHS; NCT02322255) participants untreated beyond standard of care. Patients aged ≥4 years received palovarotene once daily (chronic: 5mg; flare-up: 20 mg for 4 weeks, then 10 mg for ≥8 weeks; weight-adjusted if skeletally immature). The primary endpoint was annualized change in new HO volume versus NHS participants (by low-dose whole-body computed tomography [WBCT]), analyzed using a Bayesian compound Poisson model (BcPM) with square-root transformation. Twelve-month interim analyses met futility criteria; dosing was paused. An independent Data Monitoring Committee recommended trial continuation. Post hoc 18-month interim analyses utilized BcPM with square-root transformation and HO data collapsed to equalize MOVE and NHS visit schedules, BcPM without transformation, and weighted linear mixed-effects (wLME) models, alongside prespecified analysis. Safety was assessed throughout. Eighteen-month interim analyses included 97 MOVE and 101 NHS individuals with post-baseline WBCT. BcPM analyses without transformation showed 99.4% probability of any reduction in new HO with palovarotene versus NHS participants (with transformation: 65.4%). Mean annualized new HO volume was 60% lower in MOVE versus the NHS. wLME results were similar (54% reduction fitted; nominal p=0.039). All palovarotene-treated patients reported ≥1 adverse event (AE); 97.0% reported ≥1 retinoid-associated AE; 29.3% reported ≥1 serious AE, including premature physeal closure (PPC)/epiphyseal disorder in 21/57 (36.8%) patients aged <14 years. Post hoc computational analyses using WBCT showed decreased vertebral bone mineral density, content, and strength, and increased vertebral fracture risk in palovarotene-treated patients. Thus, post hoc analyses showed evidence for efficacy of palovarotene in reducing new HO in FOP, but high risk of PPC in skeletally immature patients. © 2022 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Palovarotene: First Approval

Palovarotene (Sohonos™) is an orally bioavailable selective retinoic acid receptor (RAR)γ agonist being developed by Ipsen for the reduction of heterotopic ossification (HO) formation in patients with fibrodysplasia ossificans progressiva (FOP). By binding to RARγ, palovarotene inhibits bone morphogenetic protein and SMAD 1/5/8 signalling: interfering with these pathways prevents chondrogenesis and ultimately HO by permitting normal muscle tissue repair or regeneration to occur. Palovarotene received its first approval on 21January 2022 to reduce the formation of HO in adults and children aged 8 years and above for females and 10 years and above for males with FOP in Canada. This article summarizes the milestones in the development of palovarotene leading to this first approval.

Selective Retinoic Acid Receptor γ Antagonist 7C is a Potent Enhancer of BMP-Induced Ectopic Endochondral Bone Formation.

Bone morphogenetic proteins (BMPs) have been clinically applied for induction of bone formation in musculoskeletal disorders such as critical-sized bone defects, nonunions, and spinal fusion surgeries. However, the use of supraphysiological doses of BMP caused adverse events, which were sometimes life-threatening. Therefore, safer treatment strategies for bone regeneration have been sought for decades. Systemic administration of a potent selective antagonist of retinoic acid nuclear receptor gamma (RARγ) (7C) stimulated BMP-induced ectopic bone formation. In this study, we developed 7C-loaded poly lactic nanoparticles (7C-NPs) and examined whether local application of 7C enhances BMP-induced bone regeneration. The collagen sponge discs that absorbed recombinant human (rh) BMP-2 were implanted into the dorsal fascia of young adult mice to induce ectopic bone. The combination of rhBMP-2 and 7C-NP markedly increased the total bone volume and thickness of the bone shell of the ectopic bone in a dose-dependent manner compared to those with rhBMP-2 only. 7C stimulated sulfated proteoglycan production, expression of chondrogenic marker genes, and Sox9 reporter activity in both chondrogenic cells and MSCs. The findings suggest that selective RARγ antagonist 7C or the related compounds potentiate the bone inductive ability of rhBMP-2, as well as support any future research to improve the BMP-2 based bone regeneration procedures in a safe and efficient manner.

Microbial pathogens induce neurodegeneration in Alzheimer\u2019s disease mice: protection by microglial regulation

BackgroundNeurodegeneration is considered the consequence of misfolded proteins’ deposition. Little is known about external environmental effects on the neurodegenerative process. Infectious agent-derived pathogen-associated molecular patterns (PAMPs) activate microglia, key players in neurodegenerative diseases. We hypothesized that systemic microbial pathogens may accelerate neurodegeneration in Alzheimer’s disease (AD) and that microglia play a central role in this process.MethodsWe examined the effect of an infectious environment and of microbial Toll-like receptor (TLR) agonists on cortical neuronal loss and on microglial phenotype in wild type versus 5xFAD transgenic mice, carrying mutated genes associated with familial AD.ResultsWe examined the effect of a naturally bred environment on the neurodegenerative process. Earlier and accelerated cortical neuron loss occurred in 5xFAD mice housed in a natural (“dirty”) environment than in a specific-pathogen-free (SPF) environment, without increasing the burden of Amyloid deposits and microgliosis. Neuronal loss occurred in a microglia-rich cortical region but not in microglia-poor CA regions of the hippocampus. Environmental exposure had no effect on cortical neuron density in wild-type mice. To model the neurodegenerative process caused by the natural infectious environment, we injected systemically the bacterial endotoxin lipopolysaccharide (LPS), a TLR4 agonist PAMP. LPS caused cortical neuronal death in 5xFAD, but not wt mice. We used the selective retinoic acid receptor α agonist Am580 to regulate microglial activation. In primary microglia isolated from 5xFAD mice, Am580 markedly attenuated TLR agonists-induced iNOS expression, without canceling their basic immune response. Intracerebroventricular delivery of Am580 in 5xFAD mice reduced significantly the fraction of (neurotoxic) iNOS + microglia and increased the fraction of (neuroprotective) TREM2 + microglia. Furthermore, intracerebroventricular delivery of Am580 prevented neurodegeneration induced by microbial TLR agonists.ConclusionsExposure to systemic infections causes neurodegeneration in brain regions displaying amyloid pathology and high local microglia density. AD brains exhibit increased susceptibility to microbial PAMPs’ neurotoxicity, which accelerates neuronal death. Microglial modulation protects the brain from microbial TLR agonist PAMP-induced neurodegeneration.

A retinoic acid receptor β2 agonist attenuates transcriptome and metabolome changes underlying nonalcohol-associated fatty liver disease

Nonalcohol-associated fatty liver disease (NAFLD) is characterized by excessive hepatic accumulation of fat that can progress to steatohepatitis, and currently, therapeutic options are limited. Using a high-fat diet (HFD) mouse model of NAFLD, we determined the effects of the synthetic retinoid, AC261066, a selective retinoic acid receptor β2 (RARβ2) agonist, on the global liver transcriptomes and metabolomes of mice with dietary-induced obesity (DIO) using genome-wide RNA-seq and untargeted metabolomics. We found that AC261066 limits mRNA increases in several presumptive NAFLD driver genes, including Pklr, Fasn, Thrsp, and Chchd6. Importantly, AC261066 limits the increases in the transcript and protein levels of KHK, a key enzyme for fructose metabolism, and causes multiple changes in liver metabolites involved in fructose metabolism. In addition, in cultured murine hepatocytes, where exposure to fructose and palmitate results in a profound increase in lipid accumulation, AC261066 limits this lipid accumulation. Importantly, we demonstrate that in a human hepatocyte cell line, RARβ is required for the inhibitory effects of AC261066 on palmitate-induced lipid accumulation. Finally, our data indicate that AC261066 inhibits molecular events underpinning fibrosis and exhibits anti-inflammatory effects. In conclusion, changes in the transcriptome and metabolome indicate that AC261066 affects molecular changes underlying multiple aspects of NAFLD, including steatosis and fibrosis. Therefore, we suggest that AC261066 may have potential as an effective therapy for NAFLD.

A Retinoic Acid Receptor β 2 Agonist Improves Cardiac Function in a Heart Failure Model.

We previously demonstrated that the selective retinoic acid receptor (RAR) β 2 agonist AC261066 reduces oxidative stress in an ex vivo murine model of ischemia/reperfusion. We hypothesized that by decreasing oxidative stress and consequent fibrogenesis, AC261066 could attenuate the development of contractile dysfunction in post-ischemic heart failure (HF). We tested this hypothesis in vivo using an established murine model of myocardial infarction (MI), obtained by permanent occlusion of the left anterior descending coronary artery. Treating mice with AC261066 in drinking water significantly attenuated the post-MI deterioration of echocardiographic indices of cardiac function, diminished remodeling, and reduced oxidative stress, as evidenced by a decrease in malondialdehyde level and p38 mitogen-activated protein kinase expression in cardiomyocytes. The effects of AC261066 were also associated with a decrease in interstitial fibrosis, as shown by a marked reduction in collagen deposition and α-smooth muscle actin expression. In cardiac murine fibroblasts subjected to hypoxia, AC261066 reversed hypoxia-induced decreases in superoxide dismutase 2 and angiopoietin-like 4 transcriptional levels as well as the increase in NADPH oxidase 2 mRNA, demonstrating that the post-MI cardioprotective effects of AC261066 are associated with an action at the fibroblast level. Thus, AC261066 alleviates post-MI cardiac dysfunction by modulating a set of genes involved in the oxidant/antioxidant balance. These AC261066 responsive genes diminish interstitial fibrogenesis and remodeling. Since MI is a recognized major cause of HF, our data identify RARβ 2 as a potential pharmacological target in the treatment of HF. SIGNIFICANCE STATEMENT: A previous report showed that the selective retinoic acid receptor (RAR) β 2 agonist AC261066 reduces oxidative stress in an ex vivo murine model of ischemia/reperfusion. This study shows that AC261066 attenuates the development of contractile dysfunction and maladaptive remodeling in post-ischemic heart failure (HF) by modulating a set of genes involved in oxidant/antioxidant balance. Since myocardial infarction is a recognized major cause of HF, these data identify RARβ 2 as a potential pharmacological target in the treatment of HF.

Administration of a selective retinoic acid receptor-\u03b3 agonist improves neuromuscular strength in a rodent model of volumetric muscle loss

PurposeVolumetric muscle loss is a uniquely challenging pathology that results in irrecoverable functional deficits. Furthermore, a breakthrough drug or bioactive factor has yet to be established that adequately improves repair of these severe skeletal muscle injuries. This study sought to assess the ability of an orally administered selective retinoic acid receptor-γ agonist, palovarotene, to improve recovery of neuromuscular strength in a rat model of volumetric muscle loss.MethodsAn irrecoverable, full thickness defect was created in the tibialis anterior muscle of Lewis rats and animals were survived for 4 weeks. Functional recovery of the tibialis anterior muscle was assessed in vivo via neural stimulation and determination of peak isometric torque. Histological staining was performed to qualitatively assess fibrous scarring of the defect site.ResultsTreatment with the selective retinoic acid receptor-γ agonist, palovarotene, resulted in a 38% improvement of peak isometric torque in volumetric muscle loss affected limbs after 4 weeks of healing compared to untreated controls. Additionally, preliminary histological assessment suggests that oral administration of palovarotene reduced fibrous scarring at the defect site.ConclusionsThese results highlight the potential role of selective retinoic acid receptor-γ agonists in the design of regenerative medicine platforms to maximize skeletal muscle healing. Additional studies are needed to further elucidate cellular responses, optimize therapeutic delivery, and characterize synergistic potential with adjunct therapies.

Trifarotene: First Approval.

Topical trifarotene (Aklief®) is a first-in-class, fourth-generation retinoid [selective retinoic acid receptor (RAR)-γ agonist] being developed by Galderma Research and Development LLC for the treatment of acne vulgaris. In October 2019 trifarotene received its first global approval in the USA for the topical treatment of acne vulgaris in patients 9years of age and older. This article summarizes the milestones in the development of trifarotene leading to its first global approval for acne vulgaris.

Effect of Specific Retinoic Acid Receptor Agonists on Noise-Induced Hearing Loss.

Noise is one of the most common causes of hearing loss in industrial countries. There are many studies about chemical agents to prevent noise-induced hearing loss (NIHL). However, there is no commercially available drug yet. Retinoic acid is an active metabolite of Vitamin A; it has an anti-apoptic role in NIHL. This study aims to verify the differences among selective agonists of retinoic acid receptors (RARs) in NIHL. All-trans retinoic acid (ATRA), AM80 (selective retinoic acid receptor α agonist), AC261066 (Selective retinoic acid receptor β1 agonist), and CD1530 (Selective retinoic acid λ agonist) were injected to 6–7 weeks old CJ5BL/6 mice before noise (110 dB for 3 h) exposure. In the auditory brainstem response test pre-, post 1, 3, and 7 days after noise exposure, not only ATRA but all kinds of selective RAR agonists showed protective effects in hearing threshold and wave I amplitude. Though there was no significant difference in the level of protective effects between agonists, α agonist showed the most prominent effect in preserving hearing function as well as outer hair cells after noise exposure. In conclusion, selective agonists of RAR demonstrate comparable protective effects against NIHL to retinoic acid. Given that these selective RAR agonists have less side effects than retinoic acid, they may be promising potential drugs against NIHL.

A biomarker-directed phase 2 trial of SY-1425, a selective retinoic acid receptor alpha agonist, in adult patients with acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS).

TPS7071 Background: SY-1425 (tamibarotene) is an orally available, synthetic retinoid approved in Japan for the treatment of relapsed/refractory (R/R) APL. SY-1425 is a more potent and selective retinoic acid receptor alpha (RARα) agonist with improved pharmacologic properties compared to all-trans retinoic acid (ATRA) including increased half-life and lack of metabolism by CYP26A1 resulting in extended relative exposures. SY-1425 binding to RARα relieves pathogenic repression of myeloid differentiation. Super-enhancers associated with RARA and upregulation of RARA expression correlate with increased sensitivity to SY-1425 in vitro and predict for response to SY-1425 with induced differentiation and reduced proliferation in RARA-high PDX AML models, but not in RARA-low models. SY-1425 also induces the RARα target gene DHRS3 in RARA-high AML cell lines. This study is designed to demonstrate pharmacodynamic (PD) and clinical effects of SY-1425 in non-APL AML and MDS patients (pts) positive for the RARA super-enhancer associated biomarker or exploratory RARA pathway biomarker, IRF8. Methods: This study is enrolling pts with R/R AML, R/R higher-risk MDS, newly-diagnosed AML ≥60 yrs unlikely to respond to or tolerate standard therapy, and transfusion dependent lower-risk MDS pts without del 5q who are unlikely to respond to or have failed ESAs. Pts must be biomarker positive based on centralized testing of tumor cells from blood. All pts receive SY-1425 at 6 mg/m2/day PO with continuous twice daily dosing. Primary objectives are to characterize the activity of SY-1425 by ORR in AML and higher-risk MDS pts or transfusion independence in lower-risk MDS pts. Secondary objectives include event-free and relapse-free survival, duration of response, overall survival, hematologic improvement and safety. PD evaluation includes induction of DHRS3 and expression of myeloid differentiation markers. Target enrollment is 80 pts. This trial opened in September 2016. Through a protocol amendment, SY-1425 treatment in combination with azacitidine will also be evaluated. ClinicalTrials.gov identifier: NCT02807558.

Identification of potent and selective retinoic acid receptor gamma (RARγ) antagonists for the treatment of osteoarthritis pain using structure based drug design

A series of triaryl pyrazoles were identified as potent pan antagonists for the retinoic acid receptors (RARs) α, β and γ. X-ray crystallography and structure-based drug design were used to improve selectivity for RARγ by targeting residue differences in the ligand binding pockets of these receptors. This resulted in the discovery of novel antagonists which maintained RARγ potency but were greater than 500-fold selective versus RARα and RARβ. The potent and selective RARγ antagonist LY2955303 demonstrated good pharmacokinetic properties and was efficacious in the MIA model of osteoarthritis-like joint pain. This compound demonstrated an improved margin to RARα-mediated adverse effects.

Selective Retinoic Acid Receptor γ Agonists Promote Repair of Injured Skeletal Muscle in Mouse

Retinoic acid signaling regulates several biological events, including myogenesis. We previously found that retinoic acid receptor γ (RARγ) agonist blocks heterotopic ossification, a pathological bone formation that mostly occurs in the skeletal muscle. Interestingly, RARγ agonist also weakened deterioration of muscle architecture adjacent to the heterotopic ossification lesion, suggesting that RARγ agonist may oppose skeletal muscle damage. To test this hypothesis, we generated a critical defect in the tibialis anterior muscle of 7-week-old mice with a cautery, treated them with RARγ agonist or vehicle corn oil, and examined the effects of RARγ agonist on muscle repair. The muscle defects were partially repaired with newly regenerating muscle cells, but also filled with adipose and fibrous scar tissue in both RARγ-treated and control groups. The fibrous or adipose area was smaller in RARγ agonist-treated mice than in the control. In addition, muscle repair was remarkably delayed in RARγ-null mice in both critical defect and cardiotoxin injury models. Furthermore, we found a rapid increase in retinoid signaling in lacerated muscle, as monitored by retinoid signaling reporter mice. Together, our results indicate that endogenous RARγ signaling is involved in muscle repair and that selective RARγ agonists may be beneficial to promote repair in various types of muscle injuries.

Selective RAR gamma antagonist LY2813631 protects against retinoid induced cartilage degradation in preclinical models of arthritis

Purpose: It has been shown that the natural ligand for the Retinoic Acid Receptors (RARs), All Trans Retinoic Acid (ATRA), is deleterious to articular cartilage health and is associated with the breakdown of cartilage in osteoarthritis. Additionally, it has been shown that retinoid levels are increased in the synovial fluid of OA patients. Both natural and synthetic retinoids (RAR agonists) are catabolic to cartilage, block early chondrogenesis and promote chondrocyte hypertrophy via RAR signaling through three RAR subtypes (RAR alpha, beta and gamma). It has been postulated that RAR antagonists may prevent or reverse retinoid-mediated cartilage destruction and a RAR pan antagonist was previously shown to improve clinical scores in the collagen-induced arthritis (CIA) model, albeit with unacceptable adverse effects on testes. We have postulated that the primary beneficial joint effects of RAR antagonists are associated with RARgamma, while the adverse effects on testes are associated with RARalpha. Thus, we have identified a highly selective RARgamma antagonist (LY2813631) to test this hypothesis. Methods: The RAR antagonist LY2813631 demonstrated in vitro selective affinity for RARgamma in a SPA-based binding assay using full length RAR alpha, beta and gamma protein and the synthetic pan agonist 3H-TTNPB. Functional antagonism and selectivity was demonstrated using a GAL4- RAR alpha, beta and gamma and Gal4 response element/Luciferase constructs, co-transfected into HEK 293 cells. Functional activity in chondrocytes was demonstrated using agonist TTNPB and primary bovine chondrocytes, looking at the ability of LY2813631 to regulate OA-relevant genes, such as MMP13, ADAMTS-5 and Type 2 Collagen. In vivo studies utilized Lewis rats to show reversal of RAR gamma agonist induced changes in OA relevant genes in the articular cartilage and reduction in OA-related neoepitopes in the synovial fluid. The collagen induced arthritis (CIA) model was used to determine joint efficacy in rats. Results: In vitro, LY2813631 binds RARgamma (Ki = 0.74 nM) with significantly higher affinity than RARalpha (Ki = 400 nM) and RAR beta (Ki = 25 nM) and shows selective functional antagonism at RAR gamma (Kb = 42 nM) in HEK 293 cells, compared to RARalpha (Kb = 2010 nM) and RAR beta (Kb = 359 nM). Additionally, LY2813631 normalized RAR agonist-induced increases in the catabolic enzyme ADAMTS-5 in primary bovine chondrocytes. In vivo, a selective RARgamma agonist was shown to increase mRNA levels of ADAMTS-5 and decrease mRNA levels of type 2 collagen in the articular cartilage of rats after 3 days of oral dosing. The animals also showed a 5-fold increase in the type 2 collagen neoepitopes 9A4 and CTX-II in synovial fluid. These effects could be blocked by co-dosing RARgamma antagonist LY2813631, demonstrating specific RARgamma-mediated target engagement in the joint space. LY2813631 also improved ankle and knee histopathology scores in the rat CIA model at doses that did not cause testicular degeneration. Conclusions: Our findings support a role for endogenous retinoids in the destruction of articular cartilage in OA and suggest that these effects are primarily mediated through RARgamma signaling. We have also shown that the beneficial effects of RARgamma antagonist LY2813631 can be demonstrated without concomitant adverse effects on the testes, supporting RARgamma as a potentially safe target for disease modification in arthritic diseases.