Phosphodiesterase 4 in inflammatory diseases: Effects of apremilast in psoriatic blood and in dermal myofibroblasts through the PDE4/CD271 complex

Phosphodiesterase 4 is overexpressed in human keloids and its inhibition reduces fibroblast activation and skin fibrosis

There is a pressing medical need for improved treatments in skin fibrosis including keloids and hypertrophic scars (HTS). This study aimed to characterize the role of phosphodiesterase 4 (PDE4), specifically PDE4B in fibrotic skin remodeling in vitro and in vivo. In vitro, effects of PDE4A-D (Roflumilast) or PDE4B (siRNA) inhibition on TGFβ1-induced myofibroblast differentiation and dedifferentiation were studied in normal (NHDF) and keloid (KF) human dermal fibroblasts. In vivo, the role of PDE4 on HOCl-induced skin fibrosis in mice was addressed in preventive and therapeutic protocols. PDE4B (mRNA, protein) was increased in Keloid > HTS compared to healthy skin and in TGFβ-stimulated NHDF and KF. In Keloid > HTS, collagen Iα1, αSMA, TGFβ1 and NOX4 mRNA were all elevated compared to healthy skin confirming skin fibrosis. In vitro, inhibition of PDE4A-D and PDE4B similarly prevented TGFβ1-induced Smad3 and ERK1/2 phosphorylation and myofibroblast differentiation, elevated NOX4 protein and proliferation in NHDF. PDE4A-D inhibition enabled myofibroblast dedifferentiation and curbed TGFβ1-induced reactive oxygen species and fibroblast senescence. In KF PDE4A-D inhibition restrained TGFβ1-induced Smad3 and ERK1/2 phosphorylation, myofibroblast differentiation and senescence. Mechanistically, PDE4A-D inhibition rescued from TGFβ1-induced loss in PPM1A, a Smad3 phosphatase. In vivo, PDE4 inhibition mitigated HOCl-induced skin fibrosis in mice in preventive and therapeutic protocols. The current study provides novel evidence evolving rationale for PDE4 inhibitors in skin fibrosis (including keloids and HTS) and delivered evidence for a functional role of PDE4B in this fibrotic condition.

[Phosphodiesterase 4 inhibitors in dermatology : Role in the treatment of skin diseases]

BACKGROUND

Chronic inflammatory skin diseases are of great social and medical importance and require effective drug therapy. Phosphodiesterase 4 (PDE4) inhibitors represent a possible therapeutic option by regulating inflammatory processes. PDEs cause the release of proinflammatory cytokines by interfering with signaling pathways. The PDE4 inhibitors apremilast (treatment of psoriasis and Behçet's disease), roflumilast (treatment of chronic obstructive pulmonary disease), and crisaborole (treatment of atopic dermatitis) are currently approved in Europe.

PSORIASIS

Apremilast is used for second-line treatment of plaque psoriasis and psoriatic arthritis and has a favorable side effect profile. Topical PDE4 inhibitors are currently being researched and have not yet been approved by the European Medicines Agency (EMA).

ATOPIC DERMATITIS

The topical PDE4 inhibitor crisaborole was approved by the EMA in 2020 as a topical treatment alternative to glucocorticoids and calcineurin inhibitors. Although the substance has shown good tolerability in studies and also alleviates the accompanying itching, it did not find its way onto the German market. BEHçET'S DISEASE: Apremilast is approved for the treatment of Behçet's disease in adults with refractory, severe oral ulcers.

OUTLOOK

Case studies have also demonstrated the efficacy of systemic PDE4 inhibition in other skin diseases (including blistering autoimmune dermatoses, lichen planus, and acantholytic genodermatoses). The substances are also being researched and used to treat extracutaneous inflammatory diseases.

Topical Therapy for Atopic Dermatitis: What is New and the New Paradigm

Atopic dermatitis (AD) is a chronic inflammatory skin disorder that requires a complex management strategy, which often involves multiple and diverse topicals and systemic treatment regimens. While topical steroids and more recently calcineurin inhibitors have been the mainstay therapy for mild-to-moderate disease, recent advances in the understanding of AD pathogenesis have led to the development of different new targets, rapidly widening our therapeutic armamentarium. This review summarizes their efficacy and safety data. We also review topical optimization strategies, including the recently published topical volume calculator, to maximize long-term disease control, especially when using multiple agents at the same time.

Phosphodiesterase 4 is overexpressed in keloid epidermal scars and its inhibition reduces keratinocyte fibrotic alterations

BACKGROUND

Epidermal remodeling and hypertrophy are hallmarks of skin fibrotic disorders, and keratinocyte to mesenchymal (EMT)-like transformations drive epidermis alteration in skin fibrosis such as keloids and hypertrophic scars (HTS). While phosphodiesterase 4 (PDE4) inhibitors have shown effectiveness in various fibrotic disorders, their role in skin fibrosis is not fully understood. This study aimed to explore the specific role of PDE4B in epidermal remodeling and hypertrophy seen in skin fibrosis.

METHODS

In vitro experiments examined the effects of inhibiting PDE4A-D (with Roflumilast) or PDE4B (with siRNA) on TGFβ1-induced EMT differentiation and dedifferentiation in human 3D epidermis. In vivo studies investigated the impact of PDE4 inhibition on HOCl-induced skin fibrosis and epidermal hypertrophy in mice, employing both preventive and therapeutic approaches.

RESULTS

The study found increased levels of PDE4B (mRNA, protein) in keloids > HTS compared to healthy epidermis, as well as in TGFβ-stimulated 3D epidermis. Keloids and HTS epidermis exhibited elevated levels of collagen Iα1, fibronectin, αSMA, N-cadherin, and NOX4 mRNA, along with decreased levels of E-cadherin and ZO-1, confirming an EMT process. Inhibition of both PDE4A-D and PDE4B prevented TGFβ1-induced Smad3 and ERK1/2 phosphorylation and mesenchymal differentiation in vitro. PDE4A-D inhibition also promoted mesenchymal dedifferentiation and reduced TGFβ1-induced ROS and keratinocyte senescence by rescuing PPM1A, a Smad3 phosphatase. In vivo, PDE4 inhibition mitigated HOCl-induced epidermal hypertrophy in mice in both preventive and therapeutic settings.

CONCLUSIONS

Overall, the study supports the potential of PDE4 inhibitors, particularly PDE4B, in treating skin fibrosis, including keloids and HTS, shedding light on their functional role in this condition.

Next Generation PDE4 Inhibitors that Selectively Target PDE4B/D Subtypes: A Narrative Review

For decades, topical corticosteroids have been the mainstay of treatment for mild-to-moderate inflammatory skin diseases, even though only short-term use is approved for these agents and systemic inflammation is not addressed. Increased understanding of the immunopathogenesis of these conditions, especially for psoriasis and atopic dermatitis, has facilitated the development of antibody-based drugs that neutralize single key cytokines or their associated receptors, such as interleukin (IL)-17A/F, IL-23, and IL-17RA in psoriasis and IL-13 and IL-4Rα in atopic dermatitis. However, oral therapy is still preferred by many patients owing to the ease of use and needle-free administration. Phosphodiesterase 4 (PDE4) inhibitors have been approved for both oral and topical use for inflammatory skin diseases. In this review, we present a summary of an emerging class of selective PDE4B/D inhibitors under clinical development and compare the differences in selectivity of this new generation of PDE4 inhibitors with the less selective currently approved PDE4 inhibitors.

Dysregulated Cyclic Nucleotide Metabolism in Alcohol-Associated Steatohepatitis: Implications for Novel Targeted Therapies

BACKGROUND

Cyclic nucleotides are second messengers, which play significant roles in numerous biological processes. Previous work has shown that cAMP and cGMP signaling regulates various pathways in liver cells, including Kupffer cells, hepatocytes, hepatic stellate cells, and cellular components of hepatic sinusoids. Importantly, it has been shown that cAMP levels and enzymes involved in cAMP homeostasis are affected by alcohol. Although the role of cyclic nucleotide signaling is strongly implicated in several pathological pathways in liver diseases, studies describing the changes in genes regulating cyclic nucleotide metabolism in ALD are lacking.

METHODS

Male C57B/6 mice were used in an intragastric model of alcohol-associated steatohepatitis (ASH). Liver injury, inflammation, and fibrogenesis were evaluated by measuring plasma levels of injury markers, liver tissue cytokines, and gene expression analyses. Liver transcriptome analysis was performed to examine the effects of alcohol on regulators of cyclic AMP and GMP levels and signaling. cAMP and cGMP levels were measured in mouse livers as well as in livers from healthy human donors and patients with alcohol-associated hepatitis (AH).

RESULTS

Our results show significant changes in several phosphodiesterases (PDEs) with specificity to degrade cAMP (Pde4a, Pde4d, and Pde8a) and cGMP (Pde5a, Pde6d, and Pde9a), as well as dual-specificity PDEs (Pde1a and Pde10a) in ASH mouse livers. Adenylyl cyclases (ACs) 7 and 9, which are responsible for cAMP generation, were also affected by alcohol. Importantly, adenosine receptor 1, which has been implicated in the pathogenesis of liver diseases, was significantly increased by alcohol. Adrenoceptors 1 and 3 (Adrb), which couple with stimulatory G protein to regulate cAMP and cGMP signaling, were significantly decreased. Additionally, beta arrestin 2, which interacts with cAMP-specific PDE4D to desensitize G-protein-coupled receptor to generate cAMP, was significantly increased by alcohol. Notably, we observed that cAMP levels are much higher than cGMP levels in the livers of humans and mice; however, alcohol affected them differently. Specifically, cGMP levels were higher in patients with AH and ASH mice livers compared with controls. As expected, these changes in liver cyclic nucleotide signaling were associated with increased inflammation, steatosis, apoptosis, and fibrogenesis.

CONCLUSIONS

These data strongly implicate dysregulated cAMP and cGMP signaling in the pathogenesis of ASH. Future studies to identify changes in these regulators in a cell-specific manner could lead to the development of novel targeted therapies for ASH.

Apremilast loaded lyotropic liquid crystalline nanoparticles embedded hydrogel for improved permeation and skin retention: An effective approach for psoriasis treatment

The present work aimed to prepare and evaluate Apremilast loaded lyotropic liquid crystalline nanoparticles (LCNPs) formulation for skin delivery to enhance the efficacy with reduced adverse effects of the oral therapy in psoriasis treatment. The LCNPs were prepared using the emulsification using a high shear homogenizer for size reduction and optimized with Box Behnken design to achieve desired particle size and entrapment efficiency. The selected LCNPs formulation was evaluated for in-vitro release, in-vitro psoriasis efficacy, skin retention, dermatokinetic, in-vivo skin retention, and skin irritation study. The selected formulation exhibited 173.25 ± 2.192 nm (polydispersity 0.273 ± 0.008) particle size and 75.028 ± 0.235% entrapment efficiency. The in-vitro drug release showed the prolonged-release for 18 h. The ex-vivo studies revealed that LCNPs formulation exhibited drug retention up to 3.2 and 11.9-fold higher, in stratum corneum and viable epidermis compared to conventional gel preparation. In-vitro cell line studies performed on immortal keratinocyte cells (HaCaT cells) demonstrated non-toxicity of selected excipients used in designed LCNPs. The dermatokinetic study revealed the AUC_0-24 of the LCNPs loaded gel was 8.4 fold higher in epidermis and 2.06 fold in dermis, respectively compared to plain gel. Further, in-vivo animal studies showed enhanced skin permeation and retention of Apremilast compared to conventional gel.

The Influence of Apremilast-Induced Macrophage Polarization on Intestinal Wound Healing

There is compelling evidence suggesting a pivotal role played by macrophages in orchestrating intestinal wound healing. Since macrophages display significant plasticity and heterogeneity, exhibiting an either classically activated (M1-like) or alternatively activated (M2-like) phenotype, they can aggravate or attenuate intestinal wound healing. Growing evidence also demonstrates a causal link between impaired mucosal healing in inflammatory bowel disease (IBD) and defects in the polarization of pro-resolving macrophages. By targeting the switch from M1 to M2 macrophages, the phosphodiesterase-4 inhibitor Apremilast has gained recent attention as a potential IBD drug. However, there is a gap in our current knowledge regarding the impact of Apremilast-induced macrophages' polarization on intestinal wound healing. The THP-1 cells were differentiated and polarized into M1 and M2 macrophages, and subsequently treated with Apremilast. Gene expression analysis was performed to characterize macrophage M1 and M2 phenotypes, and to identify possible target genes of Apremilast and the involved pathways. Next, intestinal fibroblast (CCD-18) and epithelial (CaCo-2) cell lines were scratch-wounded and exposed to a conditioned medium of Apremilast-treated macrophages. Apremilast had a clear effect on macrophage polarization, inducing an M1 to M2 phenotype switch, which was associated with NF-κB signaling. In addition, the wound-healing assays revealed an indirect influence of Apremilast on fibroblast migration. Our results support the hypothesis of Apremilast acting through the NF-κB-pathway and provide new insights into the interaction with fibroblast during intestinal wound healing.

Pharmaco-Omics in Psoriasis: Paving the Way towards Personalized Medicine

The emergence of high-throughput approaches has had a profound impact on personalized medicine, evolving the identification of inheritable variation to trajectory analyses of transient states and paving the way for the unveiling of response biomarkers. The utilization of the multi-layered pharmaco-omics data, including genomics, transcriptomics, proteomics, and relevant biological information, has facilitated the identification of key molecular biomarkers that can predict the response to therapy, thereby optimizing treatment regiments and providing the framework for a tailored treatment plan. Despite the availability of multiple therapeutic options for chronic diseases, the highly heterogeneous clinical response hinders the alleviation of disease signals and exacerbates the annual burden and cost of hospitalization and drug regimens. This review aimed to examine the current state of the pharmaco-omic approaches performed in psoriasis, a common inflammatory disease of the skin. We sought to identify central studies that investigate the inter-individual variability and explore the underlying molecular mechanisms of drug response progression via biological profiling in psoriatic patients administered with the extended therapeutic armamentarium of psoriasis, incorporating conventional therapies, small molecules, as well as biological drugs that inhibit central pathogenic cytokines involved in the disease pathogenesis.

Evidence of epistasis in regions of long-range linkage disequilibrium across five complex diseases in the UK Biobank and eMERGE datasets

Leveraging linkage disequilibrium (LD) patterns as representative of population substructure enables the discovery of additive association signals in genome-wide association studies (GWASs). Standard GWASs are well-powered to interrogate additive models; however, new approaches are required for invesigating other modes of inheritance such as dominance and epistasis. Epistasis, or non-additive interaction between genes, exists across the genome but often goes undetected because of a lack of statistical power. Furthermore, the adoption of LD pruning as customary in standard GWASs excludes detection of sites that are in LD but might underlie the genetic architecture of complex traits. We hypothesize that uncovering long-range interactions between loci with strong LD due to epistatic selection can elucidate genetic mechanisms underlying common diseases. To investigate this hypothesis, we tested for associations between 23 common diseases and 5,625,845 epistatic SNP-SNP pairs (determined by Ohta's D statistics) in long-range LD (>0.25 cM). Across five disease phenotypes, we identified one significant and four near-significant associations that replicated in two large genotype-phenotype datasets (UK Biobank and eMERGE). The genes that were most likely involved in the replicated associations were (1) members of highly conserved gene families with complex roles in multiple pathways, (2) essential genes, and/or (3) genes that were associated in the literature with complex traits that display variable expressivity. These results support the highly pleiotropic and conserved nature of variants in long-range LD under epistatic selection. Our work supports the hypothesis that epistatic interactions regulate diverse clinical mechanisms and might especially be driving factors in conditions with a wide range of phenotypic outcomes.

Oral orismilast: Efficacy and safety in moderate-to-severe psoriasis and development of modified release tablets

BACKGROUND

Orismilast is a high-potency phosphodiesterase 4 (PDE4) inhibitor with enhanced selectivity for the PDE4B and PDE4D subtypes.

OBJECTIVES

The objective of this phase 2a trial was to examine the efficacy and safety of orismilast for psoriasis using a first-generation immediate-release (IR) formulation. The objective of the subsequent phase 1 trial was to test new formulations designed to minimize the gastrointestinal (GI)-related adverse events (AEs) observed with the first-generation IR formulation. We examined the following: (1) pharmacokinetic (PK) properties of orismilast modified release (MR) and IR, (2) food effects on PK properties of orismilast MR or IR, (3) safety of orismilast MR compared to placebo.

METHODS

In a phase 2a prospective, randomized, double-blind, placebo-controlled trial, patients with moderate-to-severe psoriasis were randomized to receive 30 mg oral orismilast IR or placebo over 16 weeks. The single-site phase 1 trial consisted of three parts: (1) participants received a single 30 mg dose of orismilast MR and IR (open-label), (2) participants received 30 mg orismilast MR or IR under either fasting condition, following a high-fat meal or low-fat meal (open-label) and (3) participants received up to 60 mg orismilast MR twice-daily or a placebo for 17 days (double-blind).

RESULTS

In the phase 2a trial, treatment with orismilast IR significantly improved the mean Psoriasis Area Severity Index score at week 16 compared to placebo. The phase 1 trial revealed comparable PK properties of the orismilast MR and IR formulations, with participants in the orismilast MR group experiencing fewer GI-related AEs than those receiving orismilast IR (16.7% vs. 33.3%).

CONCLUSION

Orismilast IR displayed higher efficacy compared to placebo in patients with moderate-to-severe psoriasis at week 16. Orismilast MR had similar PK properties and fewer GI disorders compared to the IR formulation in healthy participants. Future development of orismilast will be based on the MR formulation.

MiR-149-5p inhibits cell proliferation, promotes cell apoptosis and retards cell cycle of IL-22-stimulated HaCaT and NHEK keratinocytes via regulating PDE4D

BACKGROUND

Psoriasis is a chronic autoimmune skin disease with unclear pathogenesis. It was found that miR-149-5p was significantly decreased in psoriatic lesion tissues. In this study, we aims to investigate the role and related molecular mechanism of miR-149-5p on psoriasis.

METHOD

IL-22 was used to stimulate HaCaT and NHEK cells to establish psoriasis model in vitro. The miR-149-5p and phosphodiesterase 4D (PDE4D) expression levels were detected by quantitative real-time PCR. HaCaT and NHEK cells proliferation was determined by Cell Couting Kit-8 assay. The cell apoptosis and cell cycle were detected by flow cytometry. The cleaved Caspase-3, Bax and Bcl-2 protein expressions were detected by western blot. The targeting relationship between PDE4D and miR-149-5p was predicted and confirmed by Starbase V2.0 and dual-luciferase reporter assay, respectively.

RESULT

There was a low expression level of miR-149-5p and a high expression of PDE4D in psoriatic lesion tissues. MiR-149-5p could target PDE4D. IL-22 promoted HaCaT and NHEK cells proliferation, while inhibited cell apoptosis and accelerated cell cycle. Moreover, IL-22 decreased the expressions of cleaved Caspase-3 and Bax, and increased the expression of Bcl-2. And the overexpressed miR-149-5p promoted HaCaT and NHEK cells apoptosis, inhibited cell proliferation and retarded cell cycle, meanwhile increased the cleaved Caspase-3 and Bax expressions, decreased the Bcl-2 expression. In addition, PDE4D overexpression has the opposite effect as miR-149-5p.

CONCLUSION

The overexpressed miR-149-5p inhibits IL-22-stimulated HaCaT and NHEK keratinocytes proliferation, promotes cell apoptosis and retards cell cycle by down-regulating the expression of PDE4D, which could be the promising therapeutic target of psoriasis.

Pharmacology of orismilast, a potent and selective PDE4 inhibitor

BACKGROUND

There remains an unmet need for oral medications that are safe and efficacious for long-term management of chronic inflammatory skin diseases (CISD). Inhibition of phosphodiesterase 4 (PDE4) can modulate a broad range of pro-inflammatory cytokines that play a major role in CISD pathogenesis. Orismilast is a second generation PDE4 inhibitor in clinical development for CISD treatment.

OBJECTIVES

The objective of this study was to examine the PDE4 enzymatic activity and anti-inflammatory effects of orismilast in vitro, ex vivo, and in vivo.

METHODS

The PDE1-11 enzymatic activity of orismilast was tested in vitro using a single concentration of 308 nM orismilast. The PDE4 selectivity and inhibitory potency was further examined in a radiometric assay. Orismilast was tested on human whole blood and human peripheral blood mononuclear cells (PBMC) to determine effects on its cytokine secretion and inhibition profile ex vivo. Orismilast was orally administered in a murine model of chronic oxazolone-induced ear skin inflammation. Ear thickness, a marker of inflammation, and inflammatory cytokines were analysed.

RESULTS

Orismilast selectively inhibited PDE4 and demonstrated potent inhibition of PDE4B and PDE4D subtype splice variants in vitro. Orismilast inhibited whole blood and PBMC production of tumour necrosis factor α (TNFα), and the secretion of T-helper (Th)1 (TNFα and IFNγ), Th17 (IL-22 and IL-23), and Th2 (IL-4, IL-5, and IL-13) related cytokines in PBMC. In vivo, 10 and 30 mg/kg doses of orismilast significantly reduced ear thickness and inflammation markers (p < 0.0001, respectively).

CONCLUSION

Orismilast displayed selective and potent PDE4 inhibition and broad-spectrum anti-inflammatory activity in several pre-clinical models. The results of the study support clinical development of oral orismilast as a novel treatment option for CISD including psoriasis, atopic dermatitis, and hidradenitis suppurativa.

Ibudilast ameliorates experimentally induced colitis in rats via down-regulation of proinflammatory cytokines and myeloperoxidase enzyme activity

Objectives: This study was carried out to explore the possible anti-inflammatory effect of ibudilast on acetic acid-induced colitis in rats.

Methods: Fifty adult Wistar rats were separated into 5 groups, including the control group, acetic acid group, acetic acid + vehicle, acetic acid + sulfasalazine (100 mg/kg/day)group, and acetic acid + ibudilast (30 mg/kg/day) group. Colitis was induced in rats by the inter-rectal installation of 2 ml of 4% (v/v) acetic acid. Sulfasalazine and ibudilast were administered orally for ten days after 2 hours of induction.

Results: The treatment with ibudilast significantly reduced disease activity index (DAI), macroscopic colonic scores (MAC), and histopathological changes induced by acetic acid. Also, ibudilast markedly decreased the expression of proinflammatory markers (TNF-α and IL-1β) in colonic tissue. Moreover, ibudilast inhibited myeloperoxidase (MPO) enzyme activity that was increased by acetic acid.

Conclusion: Therefore, ibudilast may have a therapeutic effect in the management of ulcerative colitis.

Effect of Roflumilast Cream (ARQ-151) on Itch and Itch-Related Sleep Loss in Adults with Chronic Plaque Psoriasis: Patient-Reported Itch Outcomes of a Phase 2b Trial

BACKGROUND

Itch is the most bothersome symptom reported by patients with psoriasis. Safe and effective treatments for psoriasis that also address itch are needed.

OBJECTIVES

To report effects of roflumilast cream on itch-related outcomes from a Phase 2b trial.

METHODS

Adults with chronic plaque psoriasis were randomized to roflumilast 0.3%, roflumilast 0.15%, or vehicle once-daily for 12 weeks. Psoriasis severity was assessed via the Investigator Global Assessment (IGA; a 5-point scale assessing plaque thickening, scaling, and erythema ranging from 0 [clear] to 4 [severe]) and ≥ 2 on a modified Psoriasis Area and Severity Index (PASI-HD, which combines severity of lesions and area affected, ranging from 0 [no disease] to 72 [maximal disease], with the actual percentage of the anatomical area involved in those patients with < 10% of anatomical area involved [e.g., 0.1 for 1% to 0.9 for 9%]). Itch was evaluated via Worst Itch Numeric Rating Scale (WI-NRS), Psoriasis Symptom Diary (PSD) Items 1 (severity of itch) and 2 (bother of itch), and itch-related sleep loss NRS scores. Post hoc correlation analyses between WI-NRS and PASI, WI-NRS and itch-related sleep loss, and WI-NRS and DLQI were also performed.

RESULTS

Roflumilast-treated patients had significantly greater improvements than vehicle-treated patients in WI-NRS and PSD Items 1 and 2 beginning at Week 2 and in itch-related sleep loss Weeks 6 through 12. Among patients with baseline WI-NRS ≥ 6, significantly more patients achieved ≥ 4-point improvement with roflumilast than with vehicle as early as Week 2. Itch severity had low correlation with PASI while WI-NRS and IGA were not always aligned.

LIMITATIONS

The first assessment was at 2 weeks, limiting the ability to assess early onset of itch response.

CONCLUSION

Roflumilast cream improved itch and itch-related sleep loss associated with chronic plaque psoriasis.

CLINICALTRIALS

GOV IDENTIFIER

NCT03638258.

Recent developments of phosphodiesterase inhibitors: Clinical trials, emerging indications and novel molecules

The phosphodiesterase (PDE) enzymes, key regulator of the cyclic nucleotide signal transduction system, are long-established as attractive therapeutic targets. During investigation of trends within clinical trials, we have identified a particularly high number of clinical trials involving PDE inhibitors, prompting us to further evaluate the current status of this class of therapeutic agents. In total, we have identified 87 agents with PDE-inhibiting capacity, of which 85 interact with PDE enzymes as primary target. We provide an overview of the clinical drug development with focus on the current clinical uses, novel molecules and indications, highlighting relevant clinical studies. We found that the bulk of current clinical uses for this class of therapeutic agents are chronic obstructive pulmonary disease (COPD), vascular and cardiovascular disorders and inflammatory skin conditions. In COPD, particularly, PDE inhibitors are characterised by the compliance-limiting adverse reactions. We discuss efforts directed to appropriately adjusting the dose regimens and conducting structure-activity relationship studies to determine the effect of structural features on safety profile. The ongoing development predominantly concentrates on central nervous system diseases, such as schizophrenia, Alzheimer's disease, Parkinson's disease and fragile X syndrome; notable advancements are being also made in mycobacterial infections, HIV and Duchenne muscular dystrophy. Our analysis predicts the diversification of PDE inhibitors' will continue to grow thanks to the molecules in preclinical development and the ongoing research involving drugs in clinical development.

Hypericumsampsonii attenuates inflammation in mice with ulcerative colitis via regulation of PDE4/PKA/CREB signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Hypericum sampsonii Hance (Yuanbaocao), a traditional herbal medicine with various pharmacological properties, is traditionally used to treat diarrhea and enteritis in China for hundreds of years. Investigations have uncovered its anti-inflammatory effects and corresponding bioactive constituents in H. sampsonii, however, the mechanisms of action for the treatment of enteritis are still unclear.

AIMS OF THE STUDY

This study aims to investigate the therapeutic effects and molecular mechanisms of H. sampsonii in a dextran sulfate sodium (DSS)-induced ulcerative colitis (UC) mice model.

MATERIALS AND METHODS

The major ingredients of the ethyl acetate extract (HS) in H. sampsonii were analyzed by UPLC-QTOF-MS. The inflammatory state of UC mice was caused by 3% DSS once daily for seven days. During DSS treatment, the mice in the positive drug group and the other three groups were orally administered 5-ASA (positive control) or HS daily. After treatment with HS or 5-ASA for a week, colonic pathological observation and the molecular biological index were performed for therapeutic evaluation, including visual inspection in the length and weight of colons and spleens, pathological morphology by hematoxylin and eosin (HE) staining, determination of oxidative markers, inflammatory cytokines and tumor necrosis factor-alpha (TNF-α) levels in colonic tissues as well as spleen index. Gene expression levels of inflammatory cytokines, antioxidant enzymes and PDE4 were detected using kits and PCR, while the expression of colonic tight junction proteins and relative signals of PKA/CREB signaling pathway were analyzed by Western blot.

RESULTS

The main components in HS were found to be polycyclic polyprenylated acylphloroglucinols (PPAPs). HS distinctly alleviated DSS-stimulated UC-like lesions symptoms as evidenced by a significant recovery from body weight, colon lengths, and histological injuries of colons. HS reduced the accumulation of pro-inflammatory cytokines and improved the mRNA level of IL-10. Simultaneously, the colonic mRNA expression levels of IL-1β, IL-17, iNOS and COX-2 were all significantly suppressed by HS in a dose-dependent manner. Furthermore, HS restored the protein expression of tight junction-associated protein (ZO-1 and occluding). Besides, HS significantly inhibited the protein level of PDE4 and decreased the expressions of PKA and phosphorylated CREB.

CONCLUSION

This is the first work about main composition and anti-UC effect of Hypericum sampsonii Hance. For the first time, this study reveals HS is not toxic in a single dose and exert significantly protective effect in DSS-colitis mice. The underlying mechanisms may involve the improvement to inflammatory status, the protection for intestinal barrier function, the inhibition of PDE4, and the activation of PKA/CREB signaling pathway. This study provided an experimental basis for the traditional application of H. sampsonii Hance in the treatment of diarrhea and dysentery.

What's New in Topicals for Atopic Dermatitis?

Atopic dermatitis (AD) is a chronic inflammatory skin condition that can have tremendous impact on quality of life for affected children and adults. First-line therapy for acute management of AD includes topical therapies such as corticosteroids, calcineurin inhibitors, and, more recently, the phosphodiesterase inhibitor crisaborole. Topical agents have remained the mainstay therapy for decades; however, there has been a longstanding need for topical therapies with high efficacy and low risk of adverse effects with long-term use. Given the ongoing advances in understanding the pathogenesis of AD, there are novel targets for pharmacological intervention. We are now in an unprecedented time with more than 40 topical treatments in the pipeline for AD in addition to many developments and treatments on the horizon. This review summarizes selected therapeutic topical agents in later phases of development that target various aspects in the pathogenesis of AD such as Janus kinase inhibition (ruxolitinib and delgocitinib), phosphodiesterase-4 inhibition (roflumilast and difamilast), aryl hydrocarbon modulation (tapinarof), and modulation of the microbiome. We also review novel targeted therapies that are in early phase clinical trials, including AMTX-100, BEN-2293, and PRN473. Preliminary findings on efficacy and tolerability of most of these agents are promising, but further studies are warranted to evaluate the long-term safety and efficacy of these novel agents against the current standard of care.

Combination Therapy with Apremilast and Biologics for Psoriasis: A Systematic Review

BACKGROUND

The evidence for adding small-molecule drugs to an ongoing biologic treatment is sparse, but combination therapies appear to be advantageous in appropriately selected patients with psoriasis. To our knowledge, efficacy and safety of combination therapy with apremilast and biologics has not previously been reviewed.

MATERIALS AND METHODS

A literature search was performed on Medline (PubMed), Embase, Web of Science, and the Cochrane Library. Inclusion criteria were a diagnosis of psoriasis, age ≥ 18 years, concomitant treatment with apremilast and a specified biologic agent, and available safety and/or efficacy results. All papers written in English and published from database inception to August 2021 were included. No limit was set regarding study size.

RESULTS

The literature search yielded 447 citations. Of these, 19 studies published from 2015 to 2020 were included in the review. All papers referred to retrospective studies, comprising case reports (n = 9), case series (n = 8), or cohort studies (n = 2). A total of 172 patients with psoriasis were identified. Clinical subtypes included plaque psoriasis (n = 164), palmoplantar pustulosis (n = 7), and acute pustular psoriasis (n = 1). The observation period ranged from 3 weeks to 24 months. Geographical origin of studies was North America (n = 11), Europe (n = 4), and Asia (n = 4). In general, apremilast-biologic combination therapy was reported to be safe; across papers, one serious adverse event was registered (hospitalization due to weight loss). Adverse events (AEs) were otherwise mostly mild and gastrointestinal. No differences in AEs were observed in studies comparing apremilast mono- and combination therapy. In several papers, sufficient information about AEs was not reported or could not be extracted. Clinical response to combination treatment was evaluated at various time points, and only few studies used validated scores. In the remaining papers, efficacy data were descriptive and/or in photographic form, or not available. In total, two patients discontinued therapy due to lack of efficacy.

CONCLUSION

Evidence for combined treatment with apremilast and biologics is limited and restricted to retrospective studies of various quality. Based on available data, apremilast may constitute an efficacious and safe add-on treatment to biologic therapy, but properly conducted clinical investigations are needed.

Killing all the birds with one drug - is oral roflumilast a novel treatment option for psoriasis?

Psoriasis is a common, chronic inflammatory skin disease associated with a large number of comorbidities. Though management of moderate-to-severe plaque psoriasis has greatly improved in recent years, patients with refractory disease or contraindications to available treatments still constitute therapeutic challenges. Oral roflumilast, a selective phosphodiesterase-4 (PDE-4) inhibitor, is approved for chronic obstructive pulmonary disease. Experimental studies have shown increased PDE-4 activity in psoriatic skin, and inhibition results in down-regulation of key inflammatory cytokines. Based on mode-of-action and available literature, we hypothesize that oral roflumilast is a future treatment for plaque psoriasis. Contrary to most existing psoriasis therapies, roflumilast has a favorable safety profile and holds the potential to improve not only skin manifestations but also commonly seen comorbidities. If efficacy and safety are confirmed in randomized settings, roflumilast can fill in a large unmet need and may represent a novel, relatively inexpensive, and convenient therapy positioned before biologics.

Development of Apremilast Nanoemulsion-Loaded Chitosan Gels: In Vitro Evaluations and Anti-Inflammatory and Wound Healing Studies on a Rat Model

Apremilast (APL) has profound anti-inflammatory and wound healing activity, alongside other dermal care. This study aims to develop APL-loaded NEs (ANE1-ANE5) using eucalyptus oil (EO) as the oil and Tween-80 and transcutol-HP (THP) as a surfactant and co-surfactant, respectively. The prepared NEs were then evaluated based on mean droplet size (12.63 ± 1.2 nm), PDI (0.269 ± 0.012), ZP (−23.00 ± 5.86), RI (1.315 ± 0.02), and %T (99.89 ± 0.38) and ANE4 was optimized. Further, optimized NEs (ANE4) were incorporated into chitosan gel (2%, w/v). The developed ANE4-loaded chitosan gel was then evaluated for pH, spreadability, in vitro diffusion, and wound healing and anti-inflammatory studies. Moreover, in vivo studies denoted improved anti-inflammatory and wound healing activity and represented a decrease in wound size percentage (99.68 ± 0.345%) for the APNE2 gel test compared to a negative control (86.48 ± 0.87%) and standard control (92.82 ± 0.34%). Thus, the formulation of ANE4-loaded chitosan gels is an efficient topical treatment strategy for inflammatory and wound healing conditions.

An Open-Label, Randomized, Prospective, Comparative, Three-Arm Clinical Trial to Evaluate the Safety and Effectiveness of Apremilast with Three Different Titration Methods in Patients with Chronic Plaque Psoriasis in India

Purpose

To minimize adverse effects (AEs), apremilast is recommended to titrate at the initiation of therapy. But still, many patients experience AEs, resulting in discontinuation of therapy. As a result, many dermatologists have adapted to further titrate apremilast in different ways. The present study was planned to evaluate the safety and effectiveness of apremilast in different dose titration methods as initiation therapy in the treatment of plaque psoriasis.

Patients and Methods

In this open-label, randomized, prospective, comparative, three-arm, single center study, 128 plaque psoriasis patients were included. Patients were randomized into three groups. Group I received standard titration for the first 6 days; Group II received all tablets in a starter pack as once a day (OD) total for 13 days; and Group III received two starter packs as 8 tablets each of apremilast 10 mg and 20 mg as OD and 10 tablets of 30 mg as OD, in total for 26 days. All groups received apremilast 30 mg as twice a day after initial titration. The total duration of apremilast therapy in all groups was 16 weeks.

Results

In safety assessment, AEs were reported in 50%, 41.3% and 25% in Groups I, II and III, respectively (p <0.05) with nausea being the most common AE. In Group I, 10.53% of patients discontinued apremilast whereas 6.52% and 2.27% discontinued in Groups II and III respectively. Maximum number of AEs were seen in Group I in first week only (74.19%) compared with other groups. At week 16, on the Psoriasis Area and Severity Index, PASI 75 was achieved in 31.43%, 42.4% and 33.3% of patients in Groups I, II and III, respectively with no statistical difference between any groups.

Conclusion

It can be concluded that slower titration is a useful strategy for minimizing AEs while at the same time maintaining effectiveness of apremilast.

Clinical Implication of Phosphodiesterase-4-Inhibition

The pleiotropic function of 3′,5′-cyclic adenosine monophosphate (cAMP)-dependent pathways in health and disease led to the development of pharmacological phosphodiesterase inhibitors (PDE-I) to attenuate cAMP degradation. While there are many isotypes of PDE, a predominant role of PDE4 is to regulate fundamental functions, including endothelial and epithelial barrier stability, modulation of inflammatory responses and cognitive and/or mood functions. This makes the use of PDE4-I an interesting tool for various therapeutic approaches. However, due to the presence of PDE4 in many tissues, there is a significant danger for serious side effects. Based on this, the aim of this review is to provide a comprehensive overview of the approaches and effects of PDE4-I for different therapeutic applications. In summary, despite many obstacles to use of PDE4-I for different therapeutic approaches, the current data warrant future research to utilize the therapeutic potential of phosphodiesterase 4 inhibition.

Targeting PDE4 as a promising therapeutic strategy in chronic ulcerative colitis through modulating mucosal homeostasis

Phosphodiesterase-4 (PDE4) functions as a catalyzing enzyme targeting hydrolyzation of intracellular cyclic adenosine monophosphate (cAMP) and inhibition of PDE4 has been proven to be a competitive strategy for dermatological and pulmonary inflammation. However, the pathological role of PDE4 and the therapeutic feasibility of PDE4 inhibitors in chronic ulcerative colitis (UC) are less clearly understood. This study introduced apremilast, a breakthrough in discovery of PDE4 inhibitors, to explore the therapeutic capacity in dextran sulfate sodium (DSS)-induced experimental murine chronic UC. In the inflamed tissues, overexpression of PDE4 isoforms and defective cAMP-mediating pathway were firstly identified in chronic UC patients. Therapeutically, inhibition of PDE4 by apremilast modulated cAMP-predominant protein kinase A (PKA)–cAMP-response element binding protein (CREB) signaling and ameliorated the clinical symptoms of chronic UC, as evidenced by improvements on mucosal ulcerations, tissue fibrosis, and inflammatory infiltrations. Consequently, apremilast maintained a normal intestinal physical and chemical barrier function and rebuilt the mucosal homeostasis by interfering with the cross-talk between human epithelial cells and immune cells. Furthermore, we found that apremilast could remap the landscape of gut microbiota and exert regulatory effects on antimicrobial responses and the function of mucus in the gut microenvironment. Taken together, the present study revealed that intervene of PDE4 provided an infusive therapeutic strategy for patients with chronic and relapsing UC.

Phosphodiesterase-4 Inhibition Reduces Cutaneous Inflammation and IL-1β Expression in a Psoriasiform Mouse Model but Does Not Inhibit Inflammasome Activation

Apremilast (Otezla^®) is an oral small molecule phosphodiesterase 4 (PDE4) inhibitor approved for the treatment of psoriasis, psoriatic arthritis, and oral ulcers associated with Behçet’s disease. While PDE4 inhibition overall is mechanistically understood, the effect of apremilast on the innate immune response, particularly inflammasome activation, remains unknown. Here, we assessed the effect of apremilast in a psoriasis mouse model and primary human cells. Psoriatic lesion development in vivo was studied in K5.Stat3C transgenic mice treated with apremilast for 2 weeks, resulting in a moderate (2 mg/kg/day) to significant (6 mg/kg/day) resolution of inflamed plaques after 2-week treatment. Concomitantly, epidermal thickness dramatically decreased, the cutaneous immune cell infiltrate was reduced, and proinflammatory cytokines were significantly downregulated. Additionally, apremilast significantly inhibited lipopolysaccharide- or anti-CD3-induced expression of proinflammatory cytokines in peripheral mononuclear cells (PBMCs). Notably, inflammasome activation and secretion of IL-1β were not inhibited by apremilast in PBMCs and in human primary keratinocytes. Collectively, apremilast effectively alleviated the psoriatic phenotype of K5.Stat3 transgenic mice, further substantiating PDE4 inhibitor-efficiency in targeting key clinical, histopathological and inflammatory features of psoriasis. Despite lacking direct effect on inflammasome activation, reduced priming of inflammasome components upon apremilast treatment reflected the indirect benefit of PDE4 inhibition in reducing inflammation.

Immunosuppression in Rheumatologic and Auto-immune Disease

Many rheumatologic diseases are thought to originate in dysregulation of the immune system; lupus nephritis, for example, involves humoral immunity, while autoinflammatory diseases such as familial Mediterranean fever are caused by defects in innate immunity. Of note, this dysregulation may involve both upregulation of immune system components and aspects of immunodeficiency. Treatment of rheumatologic diseases thus requires a familiarity with a variety of immunosuppressive medications and their effects on immune system function.In many rheumatologic conditions, due to an incompletely elucidated mechanism of disease, immunosuppression is relatively broad in contrast to agents used, for example, in treatment of transplant rejection. Multiple immunosuppressive drugs may also be used in succession or in combination. As such, an understanding of the mechanisms and targets of immunosuppressive drugs is essential to appreciating their utility and potential adverse effects. Because of the overlap between therapies used in rheumatologic as well as other inflammatory disorders, some of these medications are discussed in other disease processes (e.g., Immunosuppression for inflammatory bowel disease) or in greater detail in other chapters of this textbook (corticosteroids, mTOR inhibitors, antiproliferative agents).

Apremilast effectively inhibits TNFα-induced vascular inflammation in human endothelial cells

BACKGROUND

Patients with chronic inflammatory diseases (e.g. psoriasis and rheumatoid arthritis) are at increased risk for the development of atherosclerosis and cardiovascular diseases (CVD). Previous studies have suggested that phosphodiesterase 4 (PDE4) inhibitors possess anti-inflammatory properties.

OBJECTIVES

Here we examined the effect of the PDE4 inhibitor apremilast, a well-established anti-psoriatic drug, on pro-inflammatory responses in TNFα-activated endothelial cells.

METHODS

Human umbilical vein endothelial cells (HUVEC) were treated with tumour necrosis factor-α (TNFα) in the presence or absence of apremilast. Expression levels of pro-inflammatory cytokines, chemokines and adhesion molecules were assessed by ELISA, western blot and RT-PCR. Effects of apremilast on adhesion and transendothelial migration (TEM) of THP-1 monocytic cells were analysed in transwell assays.

RESULTS

Apremilast suppressed TNFα-induced expression and secretion of important endothelial and monocytic pro-inflammatory factors, including granulocyte-macrophage colony-stimulating factor (GM-CSF), C-X-C motif chemokine ligand 10 (CXCL10), chemokine (C-C motif) ligand 2 (CCL2), vascular cell adhesion molecule 1 (VCAM-1), E-selectin and matrix metalloproteinase-9 (MMP9). Functionally, apremilast reduced adhesion of THP-1 cells to activated HUVECs and TEM in response to TNFα. Mechanistically, apremilast suppressed activation of nuclear factor κB (NFκB) and mitogen-activated protein kinases (MAPK) signalling in activated HUVECs. Furthermore, inhibition of p38, C-Jun-N-terminale Kinase (JNK) and NFκB in activated HUVECs decreased expression of GM-CSF, VCAM-1 and E-selectin. Additionally, apremilast decreased IL-17A-induced secretion of IL-6 and CCL2.

CONCLUSIONS

We demonstrate that apremilast has distinct anti-inflammatory effects in activated HUVECs, indicating that apremilast could have the therapeutic potential to prevent higher risk for CVD in patients with chronic inflammatory diseases.

Identification of phosphodiesterase-4 as the therapeutic target of arctigenin in alleviating psoriatic skin inflammation

Introduction

Arctigenin, derived from Arctium lappa L., has multiple pharmacological activities, including immunoregulatory, anti-diabetic, anti-tumor, and neuroprotective effects. Nevertheless, the potential therapeutic target of arctigenin in modulating inflammation remains undefined.

Objectives

In the present study, we identified that arctigenin was a phosphodiesterase-4 (PDE4) selective inhibitor for the first time. Further investigations were performed to fully uncover the effects and mechanism of arctigenin on experimental murine psoriasis model.

Methods

Crystal structure determination, PDEs enzyme assay, and isothermal titration calorimetry were included to illustrate the binding specialty, inhibitory effects, and selectivity of arctigenin on PDE4D. The anti-inflammatory effects were conducted in LPS-activated human peripheral blood mononuclear cells (PBMCs) and RAW264.7 cells. Imiquimod-induced murine psoriasis was performed to uncover the therapeutic effects and mechanism of arctigenin in vivo.

Results

Arctigenin could bind to the catalytic domain of PDE4D via formation of hydrogen bonds as well as π-π stacking interactions between the dibenzyl butyrolactone of arctigenin and several residues of PDE4D. Accordingly, arctigenin showed prominent anti-inflammation in human PBMCs and murine RAW264.7 cells. PDE4 inhibition by arctigenin resulted in elevation of intracellular cyclic adenosine monophosphate (cAMP) and phosphorylation of cAMP-response element binding protein (CREB), which were largely blocked through intervention of protein kinase A (PKA) activity by H89 treatment or reduction of protein expression by siRNA transfection. Moreover, we first identified that a topical application of arctigenin ameliorated experimental psoriatic manifestations in imiquimod-induced murine psoriasis model by decreasing adhesion and chemotaxis of several inflammatory cells. Further proteomics analysis revealed that arctigenin could rectify the immune dysfunction and hyperactivation of keratinocytes in the inflamed skin microenvironments, which might be largely related to the expression of Keratins.

Conclusion

The research provided credible clew that inhibition of PDE4 by arctigenin might function as the potential therapeutic approach for the treatment of psoriasis.

Apremilast downregulates interleukin-17 production and induces splenic regulatory B cells and regulatory T cells in imiquimod-induced psoriasiform dermatitis

BACKGROUND

Apremilast, a selective inhibitor of the enzyme phosphodiesterase 4, is efficacious for psoriasis. However, detailed in vivo effects of apremilast on psoriasis remain to be elucidated.

OBJECTIVE

To examine the in vivo effects of apremilast on psoriasis.

METHODS

Psoriasiform dermatitis was induced by applying imiquimod (IMQ) on the murine shaved back skin for six days. Mice were treated with apremilast or vehicle intraperitoneally daily.

RESULTS

Apremilast alleviated IMQ-induced psoriasiform dermatitis clinically and pathologically on days 3-6 by reducing infiltration of antigen-presenting cells and interleukin (IL)-17A-positive cells and increasing infiltration of Foxp3-postive cells into the skin on day 6, although a significant increase in IL-10 mRNA level was not observed on day 2. In addition, mRNA expression of IL-17A, IL-17F, and IL-22 was lower in the skin of IMQ-applied mice treated with apremilast than in those without apremilast on day 2, and apremilast inhibited infiltration of IL-17A-producing γδ T cells into the dermis on day 6. Furthermore, apremilast induced regulatory T cells and regulatory B cells in the spleen but not in the draining lymph nodes.

CONCLUSION

Apremilast downregulated IL-17 production and induced splenic regulatory B cells and regulatory T cells in an IMQ-induced psoriasiform dermatitis mouse model.

Apremilast for genital erosive lichen planus in women (the AP-GELP Study): study protocol for a randomised placebo-controlled clinical trial

Background

Genital erosive lichen planus (GELP) is a genital subtype of lichen planus, a chronic autoimmune inflammatory disease of unknown aetiology. In women, GELP is characterised by painful vulvo-vaginal mucosal erosions and scarring, often resulting in poor sexual health and reduced quality of life. Treatment options are limited and often with little effect. Apremilast, a phosphodiesterase 4-inhibitor, has been shown to have a positive effect on psoriasis and other inflammatory skin diseases. We aim to investigate the effect and safety of peroral apremilast in women with GELP in a randomised placebo-controlled double-blinded clinical trial.

Methods

We will recruit 42 adult women with characteristic clinical and/or histological features of moderate-to-severe GELP from a specialised vulva clinic in Oslo, Norway. The patients will be randomised 1:1 to either apremilast 30 mg BID (with an initial dose titration on days 1–6) or a placebo for 24 weeks. The concomitant use of topical corticosteroids will be allowed. The primary end point will be the mean GELP score, a clinical scoring system, at week 24 in the apremilast-treated patients versus the placebo-treated patients. The secondary end points will include the mean GELP score improvement from weeks 0 to 24, patient-reported use of topical steroids, the pain score on a visual analogue scale and the number of patients with GELP score improvements at weeks 16 and 24. The Physician Global Assessment , Patient Global Assessment and selected quality of life and sexual function assessments will be recorded at weeks 0, 16 and 24. The exploratory endpoints include description of immunohistochemical changes before and after apremilast therapy, assessed in vulvar or vaginal biopsies at weeks 0 and 24. Regular follow-ups for possible adverse events will be conducted.

Discussion

The study design is based on experience from studies on apremilast in other inflammatory skin diseases using equivalent apremilast doses for approved indications. The trial may provide evidence for the use of apremilast in women with this burdensome genital dermatosis.

Trial registration

ClinicalTrials.govNCT0365666. Registered on 4 September 2018.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13063-021-05428-w.

Nonclinical genotoxicity and carcinogenicity profile of apremilast, an oral selective inhibitor of PDE4

Apremilast is an oral, selective small molecule inhibitor of phosphodiesterase-4 (PDE4) that has been approved for the treatment of active psoriatic arthritis, moderate to severe plaque psoriasis, and for patients with oral ulcers associated with Behçet's disease. Apremilast modulates the inflammatory cascade in cells by inhibiting PDE4, thus preventing the degradation of cyclic adenosine monophosphate, resulting in the upregulation of interleukin (IL)-10 and the downregulation of proinflammatory cytokines, including IL-23, interferon gamma (IFNγ), and tumor necrosis factor alpha (TNFα). Here, we evaluated the genotoxic and carcinogenic potential of apremilast using Good Laboratory Practice (GLP)-compliant in vitro and in vivo studies. Apremilast was not genotoxic in the genetic toxicology battery, as evaluated for mutagenicity in the Ames test up to concentrations of 5000 μg/plate, clastogenicity in cultured human peripheral blood lymphocytes up to concentrations of 700 ug/mL was in excess of the solubility limit in culture medium and not able to assess; and negative for the induction of micronuclei in the bone marrow micronucleus test in mice up to doses of 2000 mg/kg/day. Furthermore, apremilast did not increase the incidence of tumors in lifetime rat or mouse carcinogenicity studies up to the maximum tolerated dose. In summary, in non-clinical studies, apremilast is not genotoxic and is not carcinogenic.

An evaluation of apremilast for the treatment of adult patients with oral ulcers associated with Behçet's syndrome

INTRODUCTION

Behçet's syndrome is a chronic, multi-system, variable vasculitis of unknown etiology that can result in significant morbidity and mortality. Mucocutaneous lesions such as oral ulcers and genital ulcers are common manifestations that can affect the quality of life of patients significantly. Treatment for mucocutaneous lesions in Behçet's syndrome continues to be critical, and an unmet need remains a significant issue.

AREAS COVERED

This review evaluates the mechanism of action of apremilast, its effect on the number and pain of oral ulcers, other manifestations, such as genital ulcers, disease activity, quality of life and safety profile in Behçet's syndrome patients. Data from clinical trials as well as observational studies were included.

EXPERT OPINION

Two randomized placebo-controlled trials and real-world observational data suggest that apremilast is an effective and well-tolerated treatment modality for oral and genital ulcers in Behçet's syndrome. Observational studies additionally showed beneficial results for skin lesions, arthritis, and intestinal involvement.

Design and dermatokinetic evaluation of Apremilast loaded nanostructured lipid carriers embedded gel for topical delivery: A potential approach for improved permeation and prolong skin deposition

The present study aimed to develop Apremilast loaded nanostructured lipid carriers (NLCs) for topical delivery to overcome the limitations of oral therapy and increase the efficacy. Apremilast loaded NLCs were prepared by hot emulsification technique. The developed formulation was optimized by Box Behnken design and characterized for size, entrapment efficiency, and zeta potential. The selected formulation was investigated for in-vitro release, ex-vivo skin retention, dermatokinetic, psoriasis efficacy, in-vivo skin retention and skin irritation study. The NLCs characterization results showed its spherical shape with the particle size of 157.91 ± 1.267 nm (0.165 ± 0.017 PDI). The entrapment efficiency and zeta potential were found to be 69.144 ± 0.278% and -16.75 ± 1.40 mV, respectively. The in-vitro release study revealed a controlled release of Apremilast from NLCs up to 24 h. The ex-vivo study showed 3-fold enhanced skin retention compared to conventional gel preparation. The formulation depicted improved psoriasis efficacy indicating reduced TNF-α mRNA expression. The cytotoxicity and skin irritation study revealed the prepared formulation has no toxicity or irritation. The study depicts the NLCs loaded Apremilast can be explored for the topical delivery for treatment of psoriasis with improved skin retention and efficacy.

Anti-inflammatory effects of a novel phosphodiesterase-4 inhibitor, AA6216, in mouse dermatitis models

Atopic dermatitis (AD) is a chronic inflammatory skin disease that is commonly treated with corticosteroids. However, these drugs have long-term adverse effects, representing an unmet need for new treatments. AD is associated with dysregulation of phosphodiesterase 4 (PDE4) activity in inflammatory cells and the topical PDE4 inhibitor, crisaborole, is approved by the US FDA for mild-to-moderate AD. In this study, we compared the effects of a novel PDE4 inhibitor, AA6216, with those of crisaborole on skin inflammation. We found that AA6216 is a more potent inhibitor of PDE4 and of cytokine production (TNF-α, IL-12/23p40, IL-4, IL-13, and IFN-γ) by human peripheral blood mononuclear cells (PBMCs) stimulated by phytohemagglutinin (PHA) or anti-CD3 antibodies, with IC₅₀ values ranging from 5.9 to 47 nM. AA6216 also significantly suppressed skin inflammation in three mouse models of dermatitis. In acute and chronic oxazolone-induced dermatitis models, topical AA6216 exhibited stronger inhibitory effects on ear inflammation and cytokine production (TNFα, IL-1β, and IL-4) in skin lesions compared with crisaborole. In a Dermatophagoides farinae-induced dermatitis model, AA6216 significantly reduced the dermatitis score, based on the development of erythema/hemorrhage, scarring/dryness, edema, and excoriation/erosion, compared with a clinically used topical AD drug, tacrolimus. These results suggest the possibility that AA6216 is a novel and effective topical therapeutic agent for the treatment of dermatitis including AD.

The Protective Effects of Apremilast Against Oxygen-Glucose Deprivation/Reperfusion (OGD/R)-Induced Inflammation and Apoptosis in Astroglia Mediated by CREB/BDNF

Oxygen-glucose deprivation and reoxygenation (OGD/R)-induced impairment of astrocytes may lead to neuronal dysfunction in the central nervous system (CNS). Apremilast is a phosphodiesterase 4 (PDE4) inhibitor primarily used for the treatment of psoriasis and psoriatic arthritis that has demonstrated certain neuroprotective properties. PDE4 is an isoenzyme that degrades 3'-5'-cyclic adenosine monophosphate (cAMP), which serves as a neuroprotective agent by promoting neuronal recovery through protein kinase (PKA)-mediated phosphorylation of cAMP response element-binding protein (CREB) and subsequent expression of the neurotrophic factor brain-derived neurotrophic factor (BDNF) and anti-apoptotic B cell lymphoma (Bcl-2). However, the effects of apremilast in astrocytes have not been elucidated. In the present study, we employed an in vitro model of ischemic stroke using oxygen-glucose deprivation and reoxygenation (OGD/R)-challenged astrocytes to investigate the effects of apremilast against apoptosis (the flow cytometry assay), cell death (the lactate dehydrogenase release assay), oxidative stress (2', 7' dichlorofluorescin diacetate staining), and the expression of the key neuroprotective factors CREB and BDNF (Western blot analysis). Our findings show that treatment with apremilast could significantly reduce astrocyte apoptosis and cell death induced by OGD/R as evidenced by reduced release of glial fibrillary acidic protein (GFAP) and improvement of the Bax/Bcl-2 ratio. The results of MTT assay, measurement of lactate dehydrogenase (LDH) release, and flow cytometry confirmed the improvement in cell viability mediated by apremilast. Importantly, we found that CREB phosphorylation was required for the increases in BDNF and Bcl-2 induced by apremilast as well as the decrease in astrocyte apoptosis. These preliminary findings indicate that apremilast may have the potential to prevent astrocyte cell death and promote neuronal healing in cerebral ischemic injury. Further in vivo research will expand our understanding of these promising results.

Ustekinumab therapy changes the transcriptional activity pattern of TGF-β1-3 genes

INTRODUCTION

One of the examples of genes whose expression can be altered by the action of ustekinumab is TGF-β. It is a pleiotropic cytokine whose activity affects psoriatic changes and the state of homeostasis of the whole organism.

AIM

To evaluate the effect of ustekinumab on the transcriptional activity of TGF-β family genes in patients with psoriatic arthritis and to check whether the results obtained can be helpful in monitoring the progress of treatment.

MATERIAL AND METHODS

From total PBMCs obtained from peripheral blood of 14 patients with psoriatic arthritis, total RNA was isolated. The expression level of the TGF-β1, TGF-β2 and TGF-β3 genes was determined by RT-qPCR in real time.

RESULTS

In all the analysed samples, the presence of mRNA of three TGF-β isoforms was quantitated in each week of therapy. TGF-β3 and the smallest TGF-β2 showed the highest expression. Statistically significant correlations were observed in the amount of TGF-β1 and TGF-β3/µg mRNA RNA, TGF-β2 and TGF-β2/µg RNA and TGF-β3 and TGF-β3/µg RNA.

CONCLUSIONS

Ustekinumab influences the transcriptional activity of TGF-β genes, and the changes caused have a bearing on the patient's health.

Apremilast interferes with the TGFβ1-induced transition of human skin fibroblasts into profibrotic myofibroblasts: in vitro study

OBJECTIVES

Fibroblast-to-myofibroblast transition and extracellular matrix overproduction represent progressive events in chronic inflammatory and fibrotic diseases, in which TGFβ1 is one of the key mediators. Phosphodiesterase 4 (PDE4) acts as a proinflammatory enzyme through the degradation of cyclic adenosine monophosphate and it is overexpressed in skin fibroblasts. The study investigated how apremilast (a PDE4 inhibitor) interferes with the intracellular signalling pathways responsible for the TGFβ1-induced fibroblast-to-myofibroblast transition and profibrotic extracellular matrix protein synthesis.

METHODS

Cultured human skin fibroblasts were stimulated with TGFβ1 (10 ng/ml) alone or combined with apremilast (1 and 10 μM) for 4, 16 and 24 h. Other aliquots of the same cells were previously stimulated with TGFβ1 and then treated with apremilast (1 and 10 μM) for 4, 16 and 24 h, always under stimulation with TGFβ1. Gene and protein expression of αSMA, type I collagen (COL1) and fibronectin were evaluated, together with the activation of small mothers against decapentaplegic 2 and 3 (Smad2/3) and extracellular signal-regulated kinase (Erk1/2) proteins.

RESULTS

Apremilast reduced the TGFβ1-induced increase in αSMA, COL1 and fibronectin gene expression at 4 and 16 h, and protein synthesis at 24 h of treatment in cultured fibroblasts, even for cells already differentiated into myofibroblasts by way of a previous stimulation with TGFβ1. Apremilast inhibited the TGFβ1-induced Smad2/3 and Erk1/2 phosphorylation at 15 and 30 min.

CONCLUSION

Apremilast seems to inhibit in vitro the fibroblast-to-myofibroblast transition and the profibrotic activity induced by TGFβ1 in cultured human skin fibroblasts by downregulating Smad2/3 and Erk1/2 intracellular signalling pathways.

Uncovering the mechanism of Jueyin granules in the treatment of psoriasis using network pharmacology

ETHNOPHARMACOLOGICAL RELEVANCE

Our clinical practice demonstrated that Jueyin granules (JYG) benefit patients with mild to moderate psoriasis vulgaris without apparent adverse effects. JYG have been shown to inhibit epidermal proliferation in an imiquimod (IMQ)-induced psoriasis-like mouse model, as well as keratinocyte proliferation. Moreover, JYG causes no acute or chronic toxicity in animal models. However, its related molecular mechanism has still not been elucidated.

AIM OF THE STUDY

To assess the mechanism of JYG against psoriasis.

MATERIALS AND METHODS

This study combined network pharmacology analysis with experiments to investigate the mechanism of JYG against psoriasis. First, the molecular docking technology was used to construct the network of medicinal materials-core active plant ingredients-core targets and identify possible drug targets. Next, high-performance liquid chromatography (HPLC) was used for quality control of JYG. Finally, a mice model of psoriasis was used to further verify the effects of JYG.

RESULTS

(1) Molecular docking analysis of network pharmacology revealed that the therapeutic effects of JYG on psoriasis might be achieved through Vitamin D Receptor (VDR) effects. (2) The concentrations of chlorogenic acid and paeoniflorin were determined using HPLC to establish quality control of JYG. (3) JYG ameliorated pathological characteristics that included in vivo reductions in erythema, scale, and infiltration scores of back and ear lesions in IMQ-induced psoriasis-like mice. Moreover, a reduced number of PCNA-positive and Ki67-positive cells were observed in the epidermis of JYG-treated lesions. JYG also reduced inflammation (interleukin (IL)-17, IL-23) in the peripheral blood of IMQ-induced psoriasis-like mice. As expected, JYG was found to upregulate VDR expression and downregulate p-STAT3 expression in the IMQ group, which may contribute to its mechanism against psoriasis.

CONCLUSION

Overall, this study clarifies the mechanism of JYG against psoriasis and provides evidence to support its clinical use.

Real-World Insight on Apremilast Therapy in Patients with Plaque Psoriasis: Indian Experience

Introduction:

Psoriasis is an immune-mediated inflammatory skin disorder, which follows a chronic course. Apremilast is a novel phosphodiesterase 4 (PDE4) inhibitor, approved by US-FDA for the treatment of moderate to severe plaque psoriasis and psoriatic arthritis. A majority of the data related to the effectivity and safety of apremilast use in psoriasis is extracted from clinical trials. The present study was planned to get an insight into real-world experience with the use of apremilast in patients with moderate-to-severe plaque psoriasis related to its effectiveness and safety in India.

Materials and Methods:

The present study was a retrospective one, wherein a review of the medical records of patients with psoriasis was conducted at one center in Kolkata, who were prescribed apremilast for 16 weeks in a community dermatology practice, from December 2017 to May 2018.

Results:

Out of 39 patients, two patients discontinued treatment due to diarrhea. Only three patients were treatment naïve; the rest had taken some form of systemic therapy before apremilast. At the end of 16 weeks of treatment with apremilast, PASI 100 was achieved in one patient (2.7%), PASI 90 in one (2.7%), PASI 75 in 18 patients (48%), while 14 patients (38%) achieved PASI 50. Eighteen (46%) experienced adverse events, diarrhea being the most common (29.7%).

Conclusion:

The findings of the present study indicate that apremilast is effective in a real-world setting, as compared with clinical trials in achieving certain endpoints like PASI 75, as was found in other real-world studies in other countries, as well.

Apremilast ameliorates ox-LDL-induced endothelial dysfunction mediated by KLF6

Apremilast is a phosphodiesterase 4 (PDE4) inhibitor used in the treatment of psoriasis and several other inflammatory diseases. Interest has been expressed in seeking out therapies that address both psoriasis and atherosclerosis. In the present study, we explored the effects of apremilast in human aortic endothelial cells (HAECs) exposed to oxidized low-density lipoprotein (ox-LDL) to simulate the atherosclerotic microenvironment in vitro. Our findings indicate that apremilast may reduce the expression of lectin-like oxidized-low-density-lipoprotein receptor-1 (LOX-1), the main ox-LDL scavenging receptor. Apremilast also inhibited the expression of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and interleukin-8 (IL-8), which are deeply involved in the chronic inflammatory response associated with atherosclerosis. Interestingly, we found that apremilast inhibited the attachment of U937 monocytes to HAECs by reducing the expression of the chemokine monocyte chemotactic protein 1 (MCP-1) and the cellular adhesion molecule vascular cell adhesion molecule-1 (VCAM-1). This effect was found to be mediated through the rescue of Krüppel like factor 6 (KLF6) expression, which was reduced in response to ox-LDL via increased phosphorylation of c-Jun N-terminal kinase (JNK). These findings suggest a potential role for apremilast in the treatment of atherosclerosis.

Systemic treatment of psoriasis: from methotrexate to biologics

Psoriasis is one of the most frequent chronic inflammatory skin diseases and it has been of interest to many scientists for ages. The review presents data on all systemic treatment options, that are to date officially registered in Russian Federation for moderate-to-severe psoriasis. Aspects of the mechanism of action, efficacy and tolerability of both basic drugs (methotrexate, cyclosporine, acitretin) and biologics (infliximab, adalimumab, etanercept, certolizumab pegol, ustekinumab, guselkumab, secukinumab, ixekizumab, netakimab) and small molecules (tofacitinib, apremilast) are considered in detail. Special emphasis is placed on the important nuances of biological therapy: immunogenicity, drugs' survival and switch due to lack of efficacy. Invention of biologics signified a new era of moderate-to-severe psoriasis treatment. It became possible to achieve complete clinical remission more safely, which significantly improved the quality of life of patients. However, due to the unknown etiology of psoriasis, there is still no universal remedy that would allow to cure every patient, this fact makes scientists from all over the world keep conducting numerous clinical trials to find even more effective and safe therapeutic options.

Commentary: Phosphodiesterase 4 inhibitors as potential adjunct treatment targeting the cytokine storm in COVID-19

The most severe presentation of COVID-19 is characterized by a hyperinflammatory state attributed to the massive pro-inflammatory cytokine release, called "cytokine storm". Several specific anti-inflammatory/immunosuppressive agents are being evaluated by ongoing clinical trials; however, there is currently insufficient evidence for their efficacy and safety in COVID-19 treatment. Given the role of phosphodiesterase 4 (PDE) 4 and cyclic adenosine monophosphate in the inflammatory response, we hypothesize that selective PDE4 inhibition may attenuate the cytokine storm in COVID-19, through the upstream inhibition of pro-inflammatory molecules, particularly TNF-α, and the regulation of the pro-inflammatory/anti-inflammatory balance. Conversely, other anti-cytokine agents lead to the downstream inhibition of specific targets, such as IL-1, IL-6 or TNF-α, and may not be efficient in blocking the cytokine storm, once it has been triggered. Due to their mechanism of action targeting an early stage of the inflammatory response and ameliorating lung inflammation, we believe that selective PDE4 inhibitors may represent a promising treatment option for the early phase of COVID-19 pneumonia before the cytokine storm and severe multiorgan dysfunction take place. Furthermore, PDE4 inhibitors present several advantages including an excellent safety profile; the oral route of administration; the convenient dosing; and beneficial metabolic properties. Interestingly, obesity and diabetes mellitus type 2 have been reported to be risk factors for the severity of COVID-19. Therefore, randomized clinical trials of PDE4 inhibitors are necessary to explore their potential therapeutic effect as an adjunct to supportive measures and other therapeutic regiments.

A Review on Currently Available Potential Therapeutic Options for COVID-19

A series of unexplained pneumonia cases currently were first reported in December 2019 in Wuhan, China. Official names have been announced for the virus responsible, previously known as "2019 novel coronavirus" and the diseases it causes are, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and coronavirus disease (COVID-19), respectively. Despite great efforts worldwide to control SARS-CoV-2, the spread of the virus has reached a pandemic. Infection prevention and control of this virus is the primary concern of public health officials and professionals. Currently, several therapeutic options for COVID-19 are proposed and vaccine development has been initiated for prevention purposes. In this review, we will discuss the most recent evidence about the current potential treatment options including anti-inflammatory drugs, angiotensin-converting enzyme inhibitors/angiotensin receptor blockers, nucleoside analogs, protease inhibitors, monoclonal antibodies, and convalescent plasma therapy. Some other agents such as vitamin D and melatonin, which were recommended as potential adjuvant treatments for COVID-19 infection are also presented. Moreover, the potential use of convalescent plasma for treatment of COVID-19 infection was described. Furthermore, in the next part of the current review, various vaccination approaches against COVID-19 including whole virus vaccines, recombinant subunit vaccine, DNA vaccines, and mRNA vaccines are discussed.

Predictors of Systemic Exposure to Topical Crisaborole: A Nonlinear Regression Analysis

Crisaborole ointment, 2%, is a nonsteroidal phosphodiesterase 4 inhibitor for the treatment of mild to moderate atopic dermatitis. Results from 2 randomized, double-blind, vehicle-controlled phase 3 studies showed that twice-daily crisaborole in children and adults with mild to moderate atopic dermatitis was efficacious and well tolerated. Initial pharmacokinetics (PK) studies of crisaborole indicated absorption with measurable systemic levels of crisaborole. The current analysis was conducted to correlate steady-state systemic exposure parameters with ointment dose and identify covariates impacting PK parameters in healthy participants and patients with atopic dermatitis or psoriasis. A nonlinear regression analysis was conducted using ointment dose and noncompartmental PK parameters at steady state (area under the curve [AUC_ss ] and maximum concentration [C_max,ss ]). PK data were available from 244 participants across 6 clinical studies (AUC_ss , N = 239; C_max,ss , N = 241). Disease condition had the greatest impact on slope in both models, corresponding to 2.5-fold higher AUC_ss and C_max,ss values at a given ointment dose in patients with atopic dermatitis or psoriasis relative to healthy participants. Disease severity, race/ethnicity, and sex had marginal effects on AUC_ss and C_max,ss . Systemic exposures were similar across age groups ≥2 years of age when the same percentage of body surface area (%BSA) was treated. Predictive performance plots for AUC_ss and C_max,ss for different age groups demonstrated that the models adequately describe the observed data. Model predictions indicated that systemic exposure to crisaborole in pediatric patients (2-17 years) is unlikely to exceed systemic exposure in adults (≥18 years), even at the highest possible ointment dose corresponding to a %BSA of 90.

Apremilast Normalizes Gene Expression of Inflammatory Mediators in Human Keratinocytes and Reduces Antigen-Induced Atopic Dermatitis in Mice

Background

Apremilast, an oral phosphodiesterase (PDE) 4 inhibitor, has demonstrated efficacy in psoriasis, while its efficacy in atopic dermatitis (AD) was found to be modest. AD is a chronic inflammatory skin disease associated with activation of T helper (Th) 2 and Th17 immunity and a compromised epidermal barrier.

Objective

The objectives of this study were to examine the expression of PDE4 isoforms in skin from healthy subjects and AD patients, and to determine the effects of apremilast on AD-related inflammatory markers in vitro and in murine models of AD.

Methods

The expression of PDE4 isoforms (A, B, C, and D) in skin biopsies from healthy subjects and AD patients was evaluated using immunohistochemistry and digital image analysis. Using quantitative real-time reverse-transcriptase polymerase chain reaction, we evaluated the effects of apremilast on gene expression in adult human epidermal keratinocytes (HEKa) stimulated by Th2 and Th17 cytokines, and in two mouse models of antigen-induced AD.

Results

Expression of PDE4 isoforms increased up to three-fold in the epidermis of AD patients versus healthy skin. In interleukin (IL)-4 and IL-17-stimulated HEKa cells, apremilast significantly changed the expression of ILs, including IL-12/IL-23p40 and IL-31, and alarmins S100A7, S100A8, and S100A12. In mouse models of AD, apremilast significantly reduced ear swelling and monocyte chemoattractant protein-1 expression.

Conclusion

PDE4 is overexpressed in AD skin compared with normal skin, and inflammatory gene expression by human keratinocytes and mouse dermatitis can be modulated by apremilast.

Apremilast increases IL-10-producing regulatory B cells and decreases proinflammatory T cells and innate cells in psoriatic arthritis and psoriasis

OBJECTIVES

Psoriatic arthritis (PsA) and psoriasis are immune-mediated inflammatory diseases sharing common immunological mechanisms. Regulatory B cells (Breg cells) producing IL-10 (B10 cells), a critical anti-inflammatory B-cell subset, were found to be decreased in both PsA and psoriasis. Apremilast, a phosphodiesterase-4(PDE4) inhibitor, increases IL-10 and therefore, we examined the effect of apremilast on Breg cells.

METHODS

Fifty patients, including 20 with PsA and 30 with psoriasis, were included in the study. The effect of apremilast on Breg cells at 3, 6 and 12 months post-treatment, was examined by flow cytometry in ODN2006 (TLR9)-stimulated peripheral blood mononuclear cells and magnetically-isolated cells. Th1 cells, Th17 cells and NKT were also measured.

RESULTS

Ex vivo stimulated cell analysis identified that post-apremilast (IL-10+CD19+) B10 cells were increased in all PsA and psoriasis patients and correlated with psoriatic skin and joint clinical improvement. Apremilast decreased IFNγ(+) T and NKT cells and IL-17(+)NKT cells. B10 cells also inversely correlated with Th1 cells, and IFNγ(+)NKT cells.

CONCLUSION

These results suggest that Breg cells are a major target of apremilast in PsA and psoriasis and that apremilast-induced increase of Breg cells is associated with a decrease of Th1 cells, IFNγ-producing NKT cells and IL-17-producing NKT cells.