Treatment of plaque-type psoriasis with oral CF101: data from an exploratory randomized phase 2 clinical trial

New and emerging oral therapies for psoriasis

Psoriasis is a chronic inflammatory skin disease affecting 2-3% of the global population. Traditional systemic treatments, such as methotrexate, cyclosporine, acitretin and fumaric acid esters, have limited efficacy and are associated with significant adverse effects, necessitating regular monitoring and posing risks of long-term toxicity. Recent advancements have introduced biologic drugs that offer improved efficacy and safety profiles. However, their high cost and the inconvenience of parenteral administration limit their accessibility. Consequently, there is a growing interest in developing new, targeted oral therapies. Small molecules, such as phosphodiesterase 4 inhibitors (e.g. apremilast) and TYK2 inhibitor (e.g. deucravacitinib), have shown promising results with favourable safety profiles. Additionally, other novel oral agents targeting specific pathways, including IL-17, IL-23, TNF, S1PR1 and A3AR, are under investigation. These treatments aim to combine the efficacy of biologics with the convenience and accessibility of oral administration, addressing the limitations of current therapies. This narrative review synthesizes the emerging oral therapeutic agents for psoriasis, focusing on their mechanisms of action, stages of development and clinical trial results.

2-Substituted (N)-Methanocarba A3 Adenosine Receptor Agonists: In Silico, In Vitro, and In Vivo Characterization

2-Arylethynyl (N)-methanocarba adenosine 5'-methylamides are selective A3 adenosine receptor (AR) agonists containing a preestablished receptor-preferred pseudoribose conformation. Here, we compare analogues having bulky 2-substitution, either containing or lacking an ethynyl spacer between adenine and a cyclic group. 2-Aryl compounds 9-11, 13, 14, 19, 22, 23, 27, 29, 31, and 34, lacking a spacer, had human (h) A3AR K i values of 2-30 nM, and others displayed lower affinity. Mouse (m) A3AR affinity varied, with 2-arylethynyl having a higher affinity than 2-aryl analogues (7, 8 > 3c, 3d > 3b). However, 2-aryl-4'-truncated derivatives had greatly reduced hA3AR affinity, even containing affinity-enhancing N 6-dopamine-derived substituents. Molecular modeling, including molecular dynamics simulation, predicted stable poses in the canonical A3AR agonist binding site, but 2-aryl (ECL2 interactions) and 2-arylethynyl (TM2 interactions) substituents have different conformations and environments. In a hA3AR miniGαi recruitment assay, 31 (MRS8062) was (slightly) more potent compared to a β-arrestin2 recruitment assay, both in engineered HEK293T cells, and its maximal efficacy (E max) was much higher (165%) than reference agonist NECA's. Thus, in the 2-aryl series, A3AR affinity and selectivity were variable and generally reduced compared to the 2-arylethynyl series, with a greater dependence on the specific aryl group present. Selected compounds were studied in vivo in an ischemic model of peripheral artery disease (PAD). Rigidified 2-arylethynyl analogues 3a-3c were protective in this model of skeletal muscle ischemia-reperfusion injury/claudication, as previously shown only for moderately A3AR-selective ribosides or (N)-methanocarba derivatives. Thus, we have expanded the A3AR agonist SAR for (N)-methanocarba adenosines.

Efficacy and safety of piclidenoson in plaque psoriasis: Results from a randomized phase 3 clinical trial (COMFORT-1)

OBJECTIVE

A3 adenosine receptor (A3AR) is overexpressed in the skin and peripheral blood mononuclear cells of psoriasis patients. We investigated the efficacy/safety of piclidenoson (CF101), an orally bioavailable A3AR agonist that inhibits IL-17 and IL-23 production in keratinocytes, in moderate-to-severe plaque psoriasis.

METHODS

The randomized, placebo- and active-controlled, double-blind phase 3 COMFORT-1 trial randomized patients (3:3:3:2) to piclidenoson 2 mg BID, piclidenoson 3 mg BID, apremilast 30 mg BID or placebo. At Week 16, patients in the placebo arm were re-randomized (1:1:1) to piclidenoson 2 mg BID, piclidenoson 3 mg BID or apremilast 30 mg BID. The primary end point was the proportion of patients achieving ≥75% improvement in Psoriasis Area and Severity Index (PASI) from baseline (PASI-75) at Week 16 versus placebo.

RESULTS

A total of 529 patients were randomized and received ≥1 dose of study medication (safety population). The efficacy analysis population for the primary end point included 426 patients (piclidenoson 2 mg BID, 127; piclidenoson 3 mg BID, 103; apremilast, 118; placebo, 78). Piclidenoson at 2 and 3 mg BID exhibited similar efficacy. The primary end point was met with the 3 mg BID dose: PASI 75 rate of 9.7% versus 2.6% for piclidenoson versus placebo, p = 0.037. The PASI responses with piclidenoson continued to increase throughout the study period in a linear manner. At week 32, analysis in the per-protocol population showed that a greater proportion of patients in the piclidenoson 3 mg BID arm (51/88, 58.0%) achieved improvement from baseline in Psoriasis Disability Index (PDI) compared to apremilast (59/108, 55.1%), and the test for noninferiority trended towards significance (p = 0.072). The safety/tolerability profile of piclidenoson was excellent and superior to apremilast.

CONCLUSIONS

Piclidenoson demonstrated efficacy responses that increased over time alongside a favourable safety profile. These findings support its continued clinical development as a psoriasis treatment (ClinicalTrials.gov identifier: NCT03168256).

Adenosine and Its Receptors in the Pathogenesis and Treatment of Inflammatory Skin Diseases

Inflammatory skin diseases highlight inflammation as a central driver of skin pathologies, involving a multiplicity of mediators and cell types, including immune and non-immune cells. Adenosine, a ubiquitous endogenous immune modulator, generated from adenosine triphosphate (ATP), acts via four G protein-coupled receptors (A1, A2A, A2B, and A3). Given the widespread expression of those receptors and their regulatory effects on multiple immune signaling pathways, targeting adenosine receptors emerges as a compelling strategy for anti-inflammatory intervention. Animal models of psoriasis, contact hypersensitivity (CHS), and other dermatitis have elucidated the involvement of adenosine receptors in the pathogenesis of these conditions. Targeting adenosine receptors is effective in attenuating inflammation and remodeling the epidermal structure, potentially showing synergistic effects with fewer adverse effects when combined with conventional therapies. What is noteworthy are the promising outcomes observed with A2A agonists in animal models and ongoing clinical trials investigating A3 agonists, underscoring a potential therapeutic approach for the management of inflammatory skin disorders.

Small Molecules in the Management of Psoriasis and Psoriatic Arthritis

Psoriasis is a common chronic, immune-mediated inflammatory skin disease associated with various comorbidities. Managing psoriasis is often challenging as the therapy is decided based on the area of the disease, associated comorbidities and impairment in quality of life, besides the patient's preference. Making progress in the development of new molecules that can be used topically or orally, effectively controlling the disease with minimal side effects and providing long-lasting remissions are the needs of the hour. Recent developments in understanding the complexities of the pathogenesis of psoriasis have resulted in the reinforcement of treatment modalities, leading to the evolution of various biologics and small-molecule inhibitors. In comparison with biologics, both patients and treating physicians prefer small molecules for various reasons such as avoiding injections and side effects that are associated with biologics biologics. Moreover small molecules are economical than biologics. Newer small molecules, both topical and oral, are promising additions to the therapeutic arsenal in the management of psoriasis in the future.

Intercellular Signaling Pathways as Therapeutic Targets for Vascular Dementia Repair

Vascular dementia (VaD) is a white matter ischemic disease and the second-leading cause of dementia, with no direct therapy. Within the lesion site, cell-cell interactions dictate the trajectory towards disease progression or repair. To elucidate the underlying intercellular signaling pathways, a VaD mouse model was developed for transcriptomic and functional studies. The mouse VaD transcriptome was integrated with a human VaD snRNA-Seq dataset. A custom-made database encompassing 4053 human and 2032 mouse ligand-receptor (L-R) interactions identified significantly altered pathways shared between human and mouse VaD. Two intercellular L-R systems, Serpine2-Lrp1 and CD39-A3AR, were selected for mechanistic study as both the ligand and receptor were dysregulated in VaD. Decreased Seprine2 expression enhances OPC differentiation in VaD repair. A clinically relevant drug that reverses the loss of CD39-A3AR function promotes tissue and behavioral recovery in the VaD model. This study presents novel intercellular signaling targets and may open new avenues for VaD therapies.

Emerging Oral Therapies for the Treatment of Psoriasis: A Review of Pipeline Agents

The introduction of biologic agents for the treatment of psoriasis has revolutionized the current treatment landscape, targeting cytokines in the interleukin (IL)-23/IL-17 pathway and demonstrating strong efficacy and safety profiles in clinical trials. These agents however are costly, are associated with a risk of immunogenicity, and require administration by intravenous or subcutaneous injection, limiting their use among patients. Oral therapies, specifically small molecule and microbiome therapeutics, have the potential to be more convenient and cost-effective agents for patients and have been a focus of development in recent years, with few targeted oral medications available for the disease. In this manuscript, we review pipeline oral therapies for psoriasis identified through a search of ClinicalTrials.gov (30 June 2022-1 October 2023). Available preclinical and clinical trial data on each therapeutic agent are discussed. Small molecules under development include tumor necrosis factor inhibitors, IL-23 inhibitors, IL-17 inhibitors, phosphodiesterase-4 inhibitors, Janus kinase inhibitors, A3 adenosine receptor agonists, and sphingosine-1-phosphate receptor 1 agonists, several of which are entering phase III trials. Oral microbials have also demonstrated success in early phase studies. As new oral therapies emerge for the treatment of psoriasis, real-world data and comparative trials are needed to better inform their use among patients.

A comprehensive overview of psoriatic research over the past 20 years: machine learning-based bibliometric analysis

Background

The surge in the number of publications on psoriasis has posed significant challenges for researchers in effectively managing the vast amount of information. However, due to the lack of tools to process metadata, no comprehensive bibliometric analysis has been conducted.

Objectives

This study is to evaluate the trends and current hotspots of psoriatic research from a macroscopic perspective through a bibliometric analysis assisted by machine learning based semantic analysis.

Methods

Publications indexed under the Medical Subject Headings (MeSH) term "Psoriasis" from 2003 to 2022 were extracted from PubMed. The generative statistical algorithm latent Dirichlet allocation (LDA) was applied to identify specific topics and trends based on abstracts. The unsupervised Louvain algorithm was used to establish a network identifying relationships between topics.

Results

A total of 28,178 publications were identified. The publications were derived from 176 countries, with United States, China, and Italy being the top three countries. For the term "psoriasis", 9,183 MeSH terms appeared 337,545 times. Among them, MeSH term "Severity of illness index", "Treatment outcome", "Dermatologic agents" occur most frequently. A total of 21,928 publications were included in LDA algorithm, which identified three main areas and 50 branched topics, with "Molecular pathogenesis", "Clinical trials", and "Skin inflammation" being the most increased topics. LDA networks identified "Skin inflammation" was tightly associated with "Molecular pathogenesis" and "Biological agents". "Nail psoriasis" and "Epidemiological study" have presented as new research hotspots, and attention on topics of comorbidities, including "Cardiovascular comorbidities", "Psoriatic arthritis", "Obesity" and "Psychological disorders" have increased gradually.

Conclusions

Research on psoriasis is flourishing, with molecular pathogenesis, skin inflammation, and clinical trials being the current hotspots. The strong association between skin inflammation and biologic agents indicated the effective translation between basic research and clinical application in psoriasis. Besides, nail psoriasis, epidemiological study and comorbidities of psoriasis also draw increased attention.

Curcumin Stereoisomer, Cis-Trans Curcumin, as a Novel Ligand to A1 and A3 Adenosine Receptors

Adenosine receptors (ARs) are being explored to generate non-opioid pain therapeutics. Vanilloid compounds, curcumin, capsaicin, and vanillin possess antinociceptive properties through their interactions with the transient receptor potential channel family. However, their binding with adenosine receptors has not been well studied. The hypothesis in this study was that a vanilloid compound, cis-trans curcumin (CTCUR), binds to each of the two Gi-linked AR subtypes (A₁AR and A₃AR). CTCUR was synthesized from curcumin (CUR) using the cavitand-mediated photoisomerization technique. The cell lines transfected with the specific receptor (A₁AR or A₃AR) were treated with CTCUR or CUR and the binding was analyzed using competitive assays, confocal microscopy, and docking. The binding assays and molecular docking indicated that CTCUR had Ki values of 306 nM (A₁AR) and 400 nM (A₃AR). These values suggest that CTCUR is selective for Gi-linked ARs (A₁AR or A₃AR) over Gs-linked ARs (A_2AAR or A_2BAR), based on our previous published research. In addition, the docking showed that CTCUR binds to the toggle switch domain of ARs. Curcumin (CUR) did not exhibit binding at any of these receptors. In summary, CTCUR and other modifications of CUR can be developed as novel therapeutic ligands for the Gi-linked ARs (A₁AR and A₃AR) involved with pain and cancer.

Topical application of aerial portion of Acalypha indica Linn ameliorates psoriasis in rodents: Evidences from in vivo and in silico studies

ETHANOPHARMACOLOGICAL RELEVANCE

Acalypha indica Linn. is a weed, used traditionally for different skin diseases such as eczema and dermatitis in various parts of India. There are no previous in vivo studies reported on the antipsoriatic potential of this medicinal plant.

AIM

The aim of this study was to investigate antipsoriatic activity of coconut oil dispersion of aerial portion of Acalypha indica Linn. Few lipid-soluble phytoconstituents of this plantwere subjected to molecular docking studies on different targets to determine phytoconstituent responsible for antipsoriatic activity.

METHODS

Virgin coconut oil dispersion of aerial portion of the plant was prepared by mixing three parts of coconut oil and one part of powdered aerial portion. The acute dermal toxicity was determined according to OECD guidelines. Mouse tail model was used to evaluate the antipsoriatic activity. Molecular docking of phytoconstituents was carried out using Biovia Discovery Studio.

RESULTS

In acute dermal toxicity study,the coconut oil dispersion was found to be safe up to the dose of 20000 mg/kg. The dispersion exhibited significant antipsoriatic activity (p < 0.01) at the dose of 250 mg/kg; at 500 mg/kg dose, the activity was similar that of 250 mg/kg dose. In the docking study of the phytoconstituents, 2-methyl anthraquinone was found to be responsible for antipsoriatic activity.

CONCLUSION

This study provides new evidence of Acalypha indica Linn as antipsoriatic plant and justifies its traditional use. Computational studies also endorse the results obtained via acute dermal toxicity study and mouse tail model for evaluation of antipsoriatic potential.

Phenotypic heterogeneity in psoriatic arthritis: towards tissue pathology-based therapy

Psoriatic arthritis (PsA) is a heterogeneous disease involving multiple potential tissue domains. Most outcome measures used so far in randomized clinical trials do not sufficiently reflect this domain heterogeneity. The concept that pathogenetic mechanisms might vary across tissues within a single disease, underpinning such phenotype diversity, could explain tissue-distinct levels of response to different therapies. In this Review, we discuss the tissue, cellular and molecular mechanisms that drive clinical heterogeneity in PsA phenotypes, and detail existing tissue-based research, including data generated using sophisticated interrogative technologies with single-cell precision. Finally, we discuss how these elements support the need for tissue-based therapy in PsA in the context of existing and new therapeutic modes of action, and the implications for future PsA trial outcomes and design.

A Review of the Clinical Trial Landscape in Psoriasis: An Update for Clinicians

As our understanding of the pathogenesis of psoriasis has evolved over the past two decades, so has the number of treatment options. The introduction of biologic agents targeting specific cytokines in the interleukin (IL)-23/IL-17 pathway has proven successful in promoting skin clearance among patients. However, their use is often limited owing to cost, parenteral administration, and possible reduced efficacy over time. Topical therapies have also seen limited advancement, with agents such as corticosteroids and vitamin D derivatives remaining the mainstay of treatment, despite side effects limiting their long-term use. New therapeutic agents are needed to improve disease management for patients. In this review, we summarize pipeline and recently approved therapies undergoing clinical trials for psoriasis during a 12-month search period (30 June 2021 to 30 June 2022) using ClinicalTrials.gov. New-generation biologics and oral small molecules in phase II or III development were included, and pivotal data identified through various search modalities (PubMed, conference presentations, etc.) evaluating each drug candidate will be discussed. Topical therapies will also be discussed in line with recent US Food and Drug Administration approvals. As new therapies continue to enter the treatment landscape, long-term data and comparative trials will be needed to better understand their place among existing therapeutic agents.

Activation of adenosine A3 receptor attenuates progression of osteoarthritis through inhibiting the NLRP3/caspase-1/GSDMD induced signalling

The specific adenosine A3 receptor (A3AR) agonist (CF101) has potential for inflammation and pain in various disease, such as arthritis, cancer and neuropathic pain, while the role of A3AR in post-traumatic OA and the underlying mechanism is largely unknown. CF101 was orally administrated in OA rats induced by anterior cruciate ligament transection (ACLT) surgery, and the rat primary chondrocytes were stimulated by hydrogen peroxide (H₂ O₂ , 300 μM). Histologic grading system was performed for detecting cartilage degeneration and immunohistochemistry for determining pyroptosis. The moleculars associated with cartilage homeostasis and inflammatory cytokines were analysed; moreover, the activation of NLRP3 inflammasome was determined. CF101 treatment significantly attenuated OA cartilage damage, OA-related pain and cartilage pyroptosis. Chondrocytes stimulated by H₂ O₂ evoked ROS release, thereby promoting the activation of NLRP3 inflammasome and facilitating the cleavage of GSDMD, which ultimately resulted in the mass release of pro-inflammatory cytokines including IL-1β and IL-18, and production of matrix hydrolase. The pre-treatment with CF101 powerfully inhibited the above process both in vivo and in vitro. Our findings demonstrated that activation of A3AR attenuates OA progression and relieves pain perception through suppression of cartilage degradation and inhibition of ROS/NLRP3/GSDMD signalling, indicating pyroptosis is a potential candidate for OA treatment.

Drugs Targeting the A3 Adenosine Receptor: Human Clinical Study Data

The A3 adenosine receptor (A3AR) is overexpressed in pathological human cells. Piclidenoson and namodenoson are A3AR agonists with high affinity and selectivity to A3AR. Both induce apoptosis of cancer and inflammatory cells via a molecular mechanism entailing deregulation of the Wnt and the NF-κB signaling pathways. Our company conducted phase I studies showing the safety of these 2 molecules. In the phase II studies in psoriasis patients, piclidenoson was safe and demonstrated efficacy manifested in significant improvements in skin lesions. Namodenoson is currently being developed to treat liver cancer, where prolonged overall survival was observed in patients with advanced liver disease and a Child-Pugh B score of 7. A pivotal phase III study in this patient population has been approved by the FDA and the EMA and is currently underway. Namodenoson is also being developed to treat non-alcoholic steatohepatitis (NASH). A Phase IIa study has been successfully concluded and showed that namodenoson has anti-inflammatory, anti-fibrosis, and anti-steatosis effects. A phase IIb study in NASH is currently enrolling patients. In conclusion, A3AR agonists are promising drug candidates in advanced stages of clinical development and demonstrate safety and efficacy in their targeted indications.

A3 adenosine receptor agonists containing dopamine moieties for enhanced interspecies affinity

Following our study of 4'-truncated (N)-methanocarba-adenosine derivatives that displayed unusually high mouse (m) A₃AR affinity, we incorporated dopamine-related N⁶ substituents in the full agonist 5'-methylamide series. N⁶-(2-(4-Hydroxy-3-methoxy-phenyl)ethyl) derivative MRS7618 11 displayed K_i (nM) 0.563 at hA₃AR (∼20,000-fold selective) and 1.54 at mA₃AR. 2-Alkyl ethers maintained A₃ affinity, but with less selectivity than 2-alkynes. Parallel functional assays of G protein-dependent and β-arrestin 2 (βarr2)-dependent pathways indicate these are full agonists but not biased. Through use of computational modeling, we hypothesized that phenyl OH/OMe groups interact with polar residues, particularly Gln261, on the mA₃AR extracellular loops as the basis for the affinity enhancement. Although the pharmacokinetics indicated facile clearance of parent O-methyl catechol nucleosides 21 and 31, prolonged mA₃AR activation in vivo was observed in a hypothermia model, suggested potential formation of active metabolites through demethylation. Selected analogues induced mouse hypothermia following i.p. injection, indicative of peripheral A₃AR agonism in vivo.

Novel archetype in psoriasis management bridging molecular dynamics in exploring novel therapies

Psoriasis is an autoimmune chronic inflammatory condition of skin affecting 125 million populaces around the globe. It is implicated as a result of multifaceted phenomena involving various cell and subcell activities with the aid of numerous cellular and molecular components including signaling aisle and regulatory proteins owing to the development of such hyperproliferative dermatological conditions. This involves a deeply complex and conflicting pathology owing to genetic and immunological deviations resulting from the unusual presentation of different signaling pathways and regulatory proteins. Explorations of these biomarkers and intervention of molecular and cellular processes in psoriasis are yet to be investigated and could be an exceptional aspect for understanding pathology with successful targeting of disease. In the presented study, we have integrated molecular insights, including signaling molecules, pathways, and proteins implicated in pathogenesis, and we have attempted to link this knowledge to the targeting of these phenomena in order to manage the conditions precisely. Further, therapeutic delivery approaches for targeting distinct layers of skin have also been investigated based on the application of different nanocarriers for successful psoriasis treatment.

Novel Non-Opioid Based Therapeutics for Chronic Neuropathic Pain

Chronic neuropathic pain is currently a major health issue in U.S. complicated by the lack of non-opioid analgesic alternatives. Our investigations led to the discovery of major signaling pathways involved in the transition of acute to chronic neuropathic pain and the identification of several targets for therapeutic intervention. Our translational approach has facilitated the advancement of novel medicines for chronic neuropathic pain that are in advanced clinical development and clinical trials.

Latest Advances for the Treatment of Chronic Plaque Psoriasis with Biologics and Oral Small Molecules

Psoriasis is a common immune-mediated chronic skin disease. Disease severity is influenced by several factors including the extent and localization of skin lesions, severity of pruritus and comorbidities, such as psoriatic arthritis. Moderate to severe psoriasis is defined when cutaneous involvement is diffuse, covering more than 10% of the body surface areas and/or involving the sensitive areas such as face, genitalia, folds or nails or has high impact on patients' quality of life, and it occurs in approximately 15% of cases. In recent years, a growing understanding of psoriasis pathophysiology allowed the development of an increasing number of effective and safe treatments, including biologicals that are indicated for moderate to severe psoriasis. Different classes of biologicals have been already approved, including TNF-α (etanercept, infliximab, adalimumab and certolizumab pegol), IL-12/23 (ustekinumab), IL-17 (secukinumab, ixekizumab, brodalumab) and IL-23 (guselkumab, risankizumab, tildrakizumab) inhibitors. The objective of this narrative review is to revise efficacy and safety data of the latest biologicals, small oral molecules and biosimilar drugs for the treatment of chronic plaque psoriasis at Phase III of clinical development. The latest IL-17 and IL-23 inhibitors include bimekizumab, netakimab and mirikizumab as well as oral small molecules, such as deucravacitinib, a tyrosine kinase 2 selective inhibitor, and piclidenoson, an agonist of the Gi protein-associated A3 adenosine receptor. Additional molecules are in an early phase of development. Highly promising biologicals and small oral molecules are the leading edge of the systemic treatment of psoriasis.

Optical control of adenosine A3 receptor function in psoriasis

Psoriasis is a chronic and relapsing inflammatory skin disease lacking a cure that affects approximately 2% of the population. Defective keratinocyte proliferation and differentiation, and aberrant immune responses are major factors in its pathogenesis. Available treatments for moderate to severe psoriasis are directed to immune system causing systemic immunosuppression over time, and thus concomitant serious side effects (i.e. infections and cancer) may appear. In recent years, the G_i protein-coupled A₃ receptor (A₃R) for adenosine has been suggested as a novel and very promising therapeutic target for psoriasis. Accordingly, selective, and high affinity A₃R agonists are known to induce robust anti-inflammatory effects in animal models of autoimmune inflammatory diseases. Here, we demonstrated the efficacy of a selective A₃R agonist, namely MRS5698, in preventing the psoriatic-like phenotype in the IL-23 mouse model of psoriasis. Subsequently, we photocaged this molecule with a coumarin moiety to yield the first photosensitive A₃R agonist, MRS7344, which in photopharmacological experiments prevented the psoriatic-like phenotype in the IL-23 animal model. Thus, we have demonstrated the feasibility of using a non-invasive, site-specific, light-directed approach to psoriasis treatment.

Treatment of chronic neuropathic pain: purine receptor modulation

Extracellular nucleosides and nucleotides have widespread functions in responding to physiological stress. The "purinome" encompasses 4 G-protein-coupled receptors (GPCRs) for adenosine, 8 GPCRs activated by nucleotides, 7 adenosine 5'-triphosphate-gated P2X ion channels, as well as the associated enzymes and transporters that regulate native agonist levels. Purinergic signaling modulators, such as receptor agonists and antagonists, have potential for treating chronic pain. Adenosine and its analogues potently suppress nociception in preclinical models by activating A1 and/or A3 adenosine receptors (ARs), but safely harnessing this pathway to clinically treat pain has not been achieved. Both A2AAR agonists and antagonists are efficacious in pain models. Highly selective A3AR agonists offer a novel approach to treat chronic pain. We have explored the structure activity relationship of nucleoside derivatives at this subtype using a computational structure-based approach. Novel A3AR agonists for pain control containing a bicyclic ring system (bicyclo [3.1.0] hexane) in place of ribose were designed and screened using an in vivo phenotypic model, which reflected both pharmacokinetic and pharmacodynamic parameters. High specificity (>10,000-fold selective for A3AR) was achieved with the aid of receptor homology models based on related GPCR structures. These A3AR agonists are well tolerated in vivo and highly efficacious in models of chronic neuropathic pain. Furthermore, signaling molecules acting at P2X3, P2X4, P2X7, and P2Y12Rs play critical roles in maladaptive pain neuroplasticity, and their antagonists reduce chronic or inflammatory pain, and, therefore, purine receptor modulation is a promising approach for future pain therapeutics. Structurally novel antagonists for these nucleotide receptors were discovered recently.

P1 Receptor Agonists/Antagonists in Clinical Trials - Potential Drug Candidates of the Future

BACKGROUND

Adenosine mediates various physiological and pathological conditions by acting on its four P1 receptors (A1, A2A, A2B and A3 receptors). Omnipresence of P1 receptors and their activation, exert a wide range of biological activities. Thus, its modulation is implicated in various disorders like Parkinson's disease, asthma, cardiovascular disorders, cancer etc. Hence these receptors have become an interesting target for the researchers to develop potential therapeutic agents. Number of molecules were designed and developed in the past few years and evaluated for their efficacy in various disease conditions.

OBJECTIVE

The main objective is to provide an overview of new chemical entities which have crossed preclinical studies and reached clinical trials stage following their current status and future prospective.

METHODS

In this review we discuss current status of the drug candidates which have undergone clinical trials and their prospects.

RESULTS

Many chemical entities targeting various subtypes of P1 receptors are patented; twenty of them have crossed preclinical studies and reached clinical trials stage. Two of them viz adenosine and regadenoson are approved by the Food and Drug Administration.

CONCLUSION

This review is an attempt to highlight the current status, progress and probable future of P1 receptor ligands which are under clinical trials as promising novel therapeutic agents and the direction in which research should proceed with a view to come out with novel therapeutic agents.

Focusing on Adenosine Receptors as a Potential Targeted Therapy in Human Diseases

Adenosine is involved in a range of physiological and pathological effects through membrane-bound receptors linked to G proteins. There are four subtypes of adenosine receptors, described as A1AR, A2AAR, A2BAR, and A3AR, which are the center of cAMP signal pathway-based drug development. Several types of agonists, partial agonists or antagonists, and allosteric substances have been synthesized from these receptors as new therapeutic drug candidates. Research efforts surrounding A1AR and A2AAR are perhaps the most enticing because of their concentration and affinity; however, as a consequence of distressing conditions, both A2BAR and A3AR levels might accumulate. This review focuses on the biological features of each adenosine receptor as the basis of ligand production and describes clinical studies of adenosine receptor-associated pharmaceuticals in human diseases.

Evidence for the Interaction of A3 Adenosine Receptor Agonists at the Drug-Binding Site(s) of Human P-glycoprotein (ABCB1)

P-glycoprotein (P-gp) is a multidrug transporter that is expressed on the luminal surface of epithelial cells in the kidney, intestine, bile-canalicular membrane in the liver, blood-brain barrier, and adrenal gland. This transporter uses energy of ATP hydrolysis to efflux from cells a variety of structurally dissimilar hydrophobic and amphipathic compounds, including anticancer drugs. In this regard, understanding the interaction with P-gp of drug entities in development is important and highly recommended in current US Food and Drug Administration guidelines. Here we tested the P-gp interaction of some A₃ adenosine receptor agonists that are being developed for the treatment of chronic diseases, including rheumatoid arthritis, psoriasis, chronic pain, and hepatocellular carcinoma. Biochemical assays of the ATPase activity of P-gp and by photolabeling P-gp with its transport substrate [¹²⁵I]-iodoarylazidoprazosin led to the identification of rigidified (N)-methanocarba nucleosides (i.e., compound 3 as a stimulator and compound 8 as a partial inhibitor of P-gp ATPase activity). Compound 8 significantly inhibited boron-dipyrromethene (BODIPY)-verapamil transport mediated by human P-gp (IC₅₀ 2.4 ± 0.6 µM); however, the BODIPY-conjugated derivative of 8 (compound 24) was not transported by P-gp. In silico docking of compounds 3 and 8 was performed using the recently solved atomic structure of paclitaxel (Taxol)-bound human P-gp. Molecular modeling studies revealed that both compounds 3 and 8 bind in the same region of the drug-binding pocket as Taxol. Thus, this study indicates that nucleoside derivatives can exhibit varied modulatory effects on P-gp activity, depending on structural functionalization. SIGNIFICANCE STATEMENT: Certain A₃ adenosine receptor agonists are being developed for the treatment of chronic diseases. The goal of this study was to test the interaction of these agonists with the human multidrug resistance-linked transporter P-glycoprotein (P-gp). ATPase and photolabeling assays demonstrated that compounds with rigidified (N)-methanocarba nucleosides inhibit the activity of P-gp; however, a fluorescent derivative of one of the compounds was not transported by P-gp. Furthermore, molecular docking studies revealed that the binding site for these compounds overlaps with the site for paclitaxel in the drug-binding pocket. These results suggest that nucleoside derivatives, depending on structural functionalization, can modulate the function of P-gp.

Pharmacology of Adenosine Receptors: The State of the Art

Adenosine is a ubiquitous endogenous autacoid whose effects are triggered through the enrollment of four G protein-coupled receptors: A₁, A_2A, A_2B, and A₃. Due to the rapid generation of adenosine from cellular metabolism, and the widespread distribution of its receptor subtypes in almost all organs and tissues, this nucleoside induces a multitude of physiopathological effects, regulating central nervous, cardiovascular, peripheral, and immune systems. It is becoming clear that the expression patterns of adenosine receptors vary among cell types, lending weight to the idea that they may be both markers of pathologies and useful targets for novel drugs. This review offers an overview of current knowledge on adenosine receptors, including their characteristic structural features, molecular interactions and cellular functions, as well as their essential roles in pain, cancer, and neurodegenerative, inflammatory, and autoimmune diseases. Finally, we highlight the latest findings on molecules capable of targeting adenosine receptors and report which stage of drug development they have reached.

Genomic alterations driving psoriasis pathogenesis

Psoriasis is an immune mediated inflammatory skin disease with complex etiology involving interplay between environmental and genetic risk factors as disease initiating event. Enhanced understanding on genetic risk factors, differentially expressed genes, deregulated proteins and pathway-targeted therapeutics have established multiple axis of psoriasis pathogenesis. So far, loci in 424 genes are reported to be associated with psoriasis alongside copy number variations and epigenetic alterations. From clinical perspective, presence of specific genetic trigger(s) in individual psoriasis patient could aid in devising a personalized therapeutic strategy. Therefore, the review presents an updates on reported genomic alterations and their subsequent course of cutaneous inflammations that potentially drive to psoriasis.

The use of biomarkers as a tool for novel psoriatic disease drug discovery

INTRODUCTION

Psoriatic disease is a relatively new term which encompasses psoriatic arthritis, psoriasis, and associated comorbidities. In this heterogeneous condition, the study of biomarkers is necessary to direct best therapy. Resulting in significant disability and socioeconomic burden, recent recommendations stress the need for tight control in psoriatic disease. Areas covered: The authors outline recent advances in the understanding of psoriatic disease pathogenesis which has highlighted multiple biomarkers that have been pursued as drug targets with varying degrees of success. Current drugs targeting biomarkers and therapies in development are evaluated. The methods of biomarker discovery through genomics, transcriptomics, proteomics, metabolomics, and study of the microbiome are also discussed. Expert opinion: Targeting biomarkers for therapeutic benefit appears to a promising field with multiple success stories, notably those associated with signaling through T-helper-17 cells. The use of genomics, transcriptomics, proteomics, and more recently metabolomics will help individualize targeted biomarker therapies, assist in monitoring therapeutic success, and ultimately yield novel therapeutic targets. Advances in the development of novel biologic molecules targeting more than one cytokine may offer additional gains in therapeutic response.

A3 Adenosine Receptors as Modulators of Inflammation: From Medicinal Chemistry to Therapy

The A3 adenosine receptor (A3 AR) subtype is a novel, promising therapeutic target for inflammatory diseases, such as rheumatoid arthritis (RA) and psoriasis, as well as liver cancer. A3 AR is coupled to inhibition of adenylyl cyclase and regulation of mitogen-activated protein kinase (MAPK) pathways, leading to modulation of transcription. Furthermore, A3 AR affects functions of almost all immune cells and the proliferation of cancer cells. Numerous A3 AR agonists, partial agonists, antagonists, and allosteric modulators have been reported, and their structure-activity relationships (SARs) have been studied culminating in the development of potent and selective molecules with drug-like characteristics. The efficacy of nucleoside agonists may be suppressed to produce antagonists, by structural modification of the ribose moiety. Diverse classes of heterocycles have been discovered as selective A3 AR blockers, although with large species differences. Thus, as a result of intense basic research efforts, the outlook for development of A3 AR modulators for human therapeutics is encouraging. Two prototypical selective agonists, N6-(3-Iodobenzyl)adenosine-5'-N-methyluronamide (IB-MECA; CF101) and 2-chloro-N6-(3-iodobenzyl)-adenosine-5'-N-methyluronamide (Cl-IB-MECA; CF102), have progressed to advanced clinical trials. They were found safe and well tolerated in all preclinical and human clinical studies and showed promising results, particularly in psoriasis and RA, where the A3 AR is both a promising therapeutic target and a biologically predictive marker, suggesting a personalized medicine approach. Targeting the A3 AR may pave the way for safe and efficacious treatments for patient populations affected by inflammatory diseases, cancer, and other conditions.

Inhibition of IL-17 and IL-23 in Human Keratinocytes by the A3 Adenosine Receptor Agonist Piclidenoson

Interleukin-17 and interleukin-23 play major roles in the inflammatory process in psoriasis. The Gi protein-associated A₃ adenosine receptor (A₃AR) is known to be overexpressed in inflammatory cells and in peripheral blood mononuclear cells (PBMCs) of patients with autoimmune inflammatory conditions. Piclidenoson, a selective agonist at the A₃AR, induces robust anti-inflammatory effect in psoriasis patients. In this study, we aimed to explore A₃AR expression levels in psoriasis patients and its role in mediating the anti-inflammatory effect of piclidenoson in human keratinocyte cells. A₃AR expression levels were evaluated in skin tissue and PBMCs derived from psoriasis patients and healthy subjects. Proliferation assay and the expression of signaling proteins were used to evaluate piclidenoson effect on human keratinocytes (HaCat). High A₃AR expression levels were found in a skin biopsy and in PBMCs from psoriasis patients in comparison to healthy subjects. Piclidenoson inhibited the proliferation of HaCat cells through deregulation of the NF-κB signaling pathway, leading to a decrease in interleukin-17 and interleukin-23 expression levels. This effect was counteracted by the specific antagonist MRS 1523. A₃AR overexpression in skin and PBMCs of psoriasis patients may be used as a target to inhibit pathological cell proliferation and the production of interleukin-17 and interleukin-23.

Molecular Mechanisms and Management of a Cutaneous Inflammatory Disorder: Psoriasis

Psoriasis is a complex chronic inflammatory cutaneous disorder. To date, robust molecular mechanisms of psoriasis have been reported. Among diverse aberrant immunopathogenetic mechanisms, the current model emphasizes the role of Th1 and the IL-23/Th17 axis, skin-resident immune cells and major signal transduction pathways involved in psoriasis. The multiple genetic risk loci for psoriasis have been rapidly revealed with the advent of a novel technology. Moreover, identifying epigenetic modifications could bridge the gap between genetic and environmental risk factors in psoriasis. This review will provide a better understanding of the pathogenesis of psoriasis by unraveling the complicated interplay among immunological abnormalities, genetic risk foci, epigenetic modification and environmental factors of psoriasis. With advances in molecular biology, diverse new targets are under investigation to manage psoriasis. The recent advances in treatment modalities for psoriasis based on targeted molecules are also discussed.

Small molecule therapy for managing moderate to severe psoriatic arthritis

INTRODUCTION

The majority of psoriatic arthritis (PsA) patients experience a good clinical response to conventional synthetic disease-modifying antirheumatic drugs (csDMARDs) and biologic therapies (bDMARDs). However, treatment failure with these drugs can represent a relevant clinical problem. Moreover, in daily clinical practice, the appropriate identification of patients eligible for these agents can be conditioned by numerous aspects, mainly represented by comorbidities, such as history of malignancies, chronic and recurrent infectious diseases. Areas covered: We searched in the PUBMED database and review published data on the efficacy and safety profile of the small molecules, inhibitor of phosphodiesterase 4, apremilast, and of JAK/STAT pathways, tofacitinib, in PsA. Moreover, we report data on the other JAK inhibitor, baricitinib, and the A(3) adenosine receptors agonist, CF101, emerging by studies conducted in psoriasis patients. Expert opinion: In Psoriatic Arthritis, apremilast appears promising for PsA and recent studies have shown a good efficacy and an acceptable safety profile. Data on tofacitinib in PsA are limited. Studies on the small molecules, baricitinib and CF101 are still incomplete and limited to trials conducted in Rheumatoid Arthritis and in psoriasis. Further studies on small molecules and on their underlining mechanisms are advocated in PsA.

Adenosine A1 and A2A Receptors in the Brain: Current Research and Their Role in Neurodegeneration

The inhibitory adenosine A1 receptor (A1R) and excitatory A2A receptor (A2AR) are predominantly expressed in the brain. Whereas the A2AR has been implicated in normal aging and enhancing neurotoxicity in multiple neurodegenerative diseases, the inhibitory A1R has traditionally been ascribed to have a neuroprotective function in various brain insults. This review provides a summary of the emerging role of prolonged A1R signaling and its potential cross-talk with A2AR in the cellular basis for increased neurotoxicity in neurodegenerative disorders. This A1R signaling enhances A2AR-mediated neurodegeneration, and provides a platform for future development of neuroprotective agents in stroke, Parkinson’s disease and epilepsy.

Adenosine and adenosine receptors in the pathogenesis and treatment of rheumatic diseases

Adenosine, a nucleoside derived primarily from the extracellular hydrolysis of adenine nucleotides, is a potent regulator of inflammation. Adenosine mediates its effects on inflammatory cells by engaging one or more cell-surface receptors. The expression and function of adenosine receptors on different cell types change during the course of rheumatic diseases, such as rheumatoid arthritis (RA). Targeting adenosine receptors directly for the treatment of rheumatic diseases is currently under study; however, indirect targeting of adenosine receptors by enhancing adenosine levels at inflamed sites accounts for most of the anti-inflammatory effects of methotrexate, the anchor drug for the treatment of RA. In this Review, we discuss the regulation of extracellular adenosine levels and the role of adenosine in regulating the inflammatory and immune responses in rheumatic diseases such as RA, psoriasis and other types of inflammatory arthritis. In addition, adenosine and its receptors are involved in promoting fibrous matrix production in the skin and other organs, and the role of adenosine in fibrosis and fibrosing diseases is also discussed.

Novel Oral Therapies for Psoriasis and Psoriatic Arthritis

Several classes of new oral therapy are in use or in development for the treatment of psoriasis. Despite the high efficacy of biologics, new oral therapies remain important as patients generally prefer this mode of administration and they offer an alternative risk-benefit profile. In this review, we discuss the novel modes of action of these drugs, including modulation of cellular pathways involving diverse targets such as Janus kinase, phosphodiesterase 4, sphingosine 1-phosphate, A3 adenosine receptor and rho-associated kinase 2. We review the available evidence around licensed drugs (apremilast) and drugs that are advanced (tofacitinib) or early (ponesimod, baricitinib, peficitinib, INCB039110, CF101, KD025) in the development pipeline. The key limitations of these oral therapies are their modest efficacy profile (apremilast, ponesimod) and the limitations of their safety profile (tofacitinib, ponesimod), while the evidence for the early pipeline drugs are at phase II level only. Potential niches of current unmet needs include apremilast for patients with concomitant psoriatic arthritis, as combination treatments with biologic therapies, and/or for patients in whom multiple biologic therapies have failed due to immunogenicity and secondary inefficacy. The present knowledge gap regarding these novel drugs includes the need for longer clinical trials or observational studies to evaluate safety, and randomised phase III trials for the early pipeline drugs. We conclude that further research and data are necessary to conclusively establish the role of these agents in the current psoriasis treatment paradigm.

Targeting adenosine receptors to prevent inflammatory skin diseases

Adenosine mediates its effects through activation of a family of four G-protein-coupled receptors, named A1 , A2A , A2B and A3 . This nucleoside plays an important role in immunity and inflammation, and the A2A adenosine receptor subtype has a key role in the inhibition of inflammatory processes besides promoting wound healing. In this issue of Experimental Dermatology, Arasa et al. show that the topical application of a selective A2A agonist, CGS 21680, to mouse skin reduced epidermal hyperplasia as well as skin inflammation, similarly to topical corticoids, without side effects like skin atrophy. Rigorously following up this work is important for the development of novel treatment strategies for chronic hyperproliferative inflammatory dermatoses, such as targeting the A2A adenosine receptor family.

Adenosine as a Multi-Signalling Guardian Angel in Human Diseases: When, Where and How Does it Exert its Protective Effects?

The importance of adenosine for human health cannot be overstated. Indeed, this ubiquitous nucleoside is an integral component of ATP, and regulates the function of every tissue and organ in the body. Acting via receptor-dependent and -independent mechanisms [the former mediated via four G-protein-coupled receptors (GPCRs), A1, A2A, A2B, and A3,], it has a significant role in protecting against cell damage in areas of increased tissue metabolism, and combating organ dysfunction in numerous pathological states. Accordingly, raised levels of adenosine have been demonstrated in epilepsy, ischaemia, pain, inflammation, and cancer, in which its behaviour can be likened to that of a guardian angel, even though there are instances in which overproduction of adenosine is pathological. In this review, we condense the current body of knowledge on the issue, highlighting when, where, and how adenosine exerts its protective effects in both the brain and the periphery.

Update on psoriasis immunopathogenesis and targeted immunotherapy

Over recent years, significant progress has been made in characterisation of the underlying pathogenic mechanisms in psoriasis, a common cutaneous disease that is associated with major systemic co-morbidity and reduced life expectancy. Basic science discoveries have informed the design of novel therapeutic approaches, many of which are now under evaluation in late-stage clinical trials. Here we describe the complex interplay between immune cell types and cytokine networks that acts within self-perpetuating feedback loops to drive cutaneous inflammation in psoriasis. Genetic studies have been pivotal in the construction of the disease model and more recently have uncovered a distinct aetiology for rare, pustular variants of psoriasis. The translation of mechanistic insights into potential advancements in clinical care will also be described, including several treatments that target the interleukin-23 (IL-23)/T17 immune axis.

The A3 adenosine receptor: history and perspectives

By general consensus, the omnipresent purine nucleoside adenosine is considered a major regulator of local tissue function, especially when energy supply fails to meet cellular energy demand. Adenosine mediation involves activation of a family of four G protein-coupled adenosine receptors (ARs): A(1), A(2)A, A(2)B, and A(3). The A(3) adenosine receptor (A(3)AR) is the only adenosine subtype to be overexpressed in inflammatory and cancer cells, thus making it a potential target for therapy. Originally isolated as an orphan receptor, A(3)AR presented a twofold nature under different pathophysiologic conditions: it appeared to be protective/harmful under ischemic conditions, pro/anti-inflammatory, and pro/antitumoral depending on the systems investigated. Until recently, the greatest and most intriguing challenge has been to understand whether, and in which cases, selective A(3) agonists or antagonists would be the best choice. Today, the choice has been made and A(3)AR agonists are now under clinical development for some disorders including rheumatoid arthritis, psoriasis, glaucoma, and hepatocellular carcinoma. More specifically, the interest and relevance of these new agents derives from clinical data demonstrating that A(3)AR agonists are both effective and safe. Thus, it will become apparent in the present review that purine scientists do seem to be getting closer to their goal: the incorporation of adenosine ligands into drugs with the ability to save lives and improve human health.

Managing patients with psoriatic disease: the diagnosis and pharmacologic treatment of psoriatic arthritis in patients with psoriasis

Psoriatic arthritis (PsA) is a chronic, systemic inflammatory disease. Up to 40 % of patients with psoriasis will go on to develop PsA, usually within 5-10 years of cutaneous disease onset. Both conditions share common pathogenic mechanisms involving genetic and environmental factors. Because psoriasis is typically present for years before PsA-related joint symptoms emerge, dermatologists are in a unique position to detect PsA earlier in the disease process through regular, routine screening of psoriasis patients. Distinguishing clinical features of PsA include co-occurrence of psoriatic skin lesions and nail dystrophy, as well as dactylitis and enthesitis. Patients with PsA are usually seronegative for rheumatoid factor, and radiographs may reveal unique features such as juxta-articular new bone formation and pencil-in-cup deformity. Early treatment of PsA with disease-modifying anti-rheumatic drugs has the potential to slow disease progression and maintain patient quality of life. Optimally, a single therapeutic agent will control both the skin and joint psoriatic symptoms. A number of traditional treatments used to manage psoriasis, such as methotrexate and cyclosporine, are also effective for PsA, but these agents are often inadequately effective, temporary in benefit and associated with significant safety concerns. Biologic anti-tumour necrosis factor agents, such as etanercept, infliximab and adalimumab, are effective for treating patients who have both psoriasis and PsA. However, a substantial number of patients may lose efficacy, have adverse effects or find intravenous or subcutaneous administration inconvenient. Emerging oral treatments, including phosphodiesterase 4 inhibitors, such as apremilast, and new biologics targeting interleukin-17, such as secukinumab, brodalumab and ixekizumab, have shown encouraging clinical results in the treatment of psoriasis and/or PsA. Active and regular collaboration of dermatologists with rheumatologists in managing patients who have psoriasis and PsA is likely to yield more optimal control of psoriatic dermal and joint symptoms, and improve long-term patient outcomes.

In vivo phenotypic screening for treating chronic neuropathic pain: modification of C2-arylethynyl group of conformationally constrained A3 adenosine receptor agonists

(N)-Methanocarba adenosine 5'-methyluronamides containing 2-arylethynyl groups were synthesized as A3 adenosine receptor (AR) agonists and screened in vivo (po) for reduction of neuropathic pain. A small N(6)-methyl group maintained binding affinity, with human > mouse A3AR and MW < 500 and other favorable physicochemical properties. Emax (maximal efficacy in a mouse chronic constriction injury pain model) of previously characterized A3AR agonist, 2-(3,4-difluorophenylethynyl)-N(6)-(3-chlorobenzyl) derivative 6a, MRS5698, was surpassed. More efficacious analogues (in vivo) contained the following C2-arylethynyl groups: pyrazin-2-yl 23 (binding Ki, hA3AR, nM 1.8), fur-2-yl 27 (0.6), thien-2-yl 32 (0.6) and its 5-chloro 33, MRS5980 (0.7) and 5-bromo 34 (0.4) equivalents, and physiologically unstable ferrocene 36, MRS5979 (2.7). 33 and 36 displayed particularly long in vivo duration (>3 h). Selected analogues were docked to an A3AR homology model to explore the environment of receptor-bound C2 and N(6) groups. Various analogues bound with μM affinity at off-target biogenic amine (M2, 5HT2A, β3, 5HT2B, 5HT2C, and α2C) or other receptors. Thus, we have expanded the structural range of orally active A3AR agonists for chronic pain treatment.

A₃ adenosine receptor allosteric modulator induces an anti-inflammatory effect: in vivo studies and molecular mechanism of action

The A₃ adenosine receptor (A₃AR) is overexpressed in inflammatory cells and in the peripheral blood mononuclear cells of individuals with inflammatory conditions. Agonists to the A₃AR are known to induce specific anti-inflammatory effects upon chronic treatment. LUF6000 is an allosteric compound known to modulate the A₃AR and render the endogenous ligand adenosine to bind to the receptor with higher affinity. The advantage of allosteric modulators is their capability to target specifically areas where adenosine levels are increased such as inflammatory and tumor sites, whereas normal body cells and tissues are refractory to the allosteric modulators due to low adenosine levels. LUF6000 administration induced anti-inflammatory effect in 3 experimental animal models of rat adjuvant induced arthritis, monoiodoacetate induced osteoarthritis, and concanavalin A induced liver inflammation in mice. The molecular mechanism of action points to deregulation of signaling proteins including PI3K, IKK, IκB, Jak-2, and STAT-1, resulting in decreased levels of NF-κB, known to mediate inflammatory effects. Moreover, LUF6000 induced a slight stimulatory effect on the number of normal white blood cells and neutrophils. The anti-inflammatory effect of LUF6000, mechanism of action, and the differential effects on inflammatory and normal cells position this allosteric modulator as an attractive and unique drug candidate.