Background and purpose:Apremilast is an orally administered phosphodiesterase-4 inhibitor, currently in phase 2 clinical studies of psoriasis and other chronic inflammatory diseases. The inhibitory effects of apremilast on pro-inflammatory responses of human primary peripheral blood mononuclear cells (PBMC), polymorphonuclear cells, natural killer (NK) cells and epidermal keratinocytes were explored in vitro, and in a preclinical model of psoriasis.Experimental approach: Apremilast was tested in vitro against endotoxin-and superantigen-stimulated PBMC, bacterial peptide and zymosan-stimulated polymorphonuclear cells, immunonoglobulin and cytokine-stimulated NK cells, and ultraviolet B light-activated keratinocytes. Apremilast was orally administered to beige-severe combined immunodeficient mice, xenotransplanted with normal human skin and triggered with human psoriatic NK cells. Epidermal skin thickness, proliferation index and inflammation markers were analysed. Key results: Apremilast inhibited PBMC production of the chemokines CXCL9 and CXCL10, cytokines interferon-g and tumour necrosis factor (TNF)-a, and interleukins (IL)-2, IL-12 and IL-23. Production of TNF-a by NK cells and keratinocytes was also inhibited. In vivo, apremilast significantly reduced epidermal thickness and proliferation, decreased the general histopathological appearance of psoriasiform features and reduced expression of TNF-a, human leukocyte antigen-DR and intercellular adhesion molecule-1 in the lesioned skin. Conclusions and implications: Apremilast displayed a broad pattern of anti-inflammatory activity in a variety of cell types and decreased the incidence and severity of a psoriasiform response in vivo. Inhibition of TNF-a, IL-12 and IL-23 production, as well as NK and keratinocyte responses by this phosphodiesterase-4 inhibitor suggests a novel approach to the treatment of psoriasis.

Apremilast, an oral small molecule inhibitor of phosphodiesterase 4 (PDE4), is in development for chronic inflammatory disorders, and has shown efficacy in psoriasis, psoriatic arthropathies, and Behçet's syndrome. In March 2014, the US Food and Drug Administration approved apremilast for the treatment of adult patients with active psoriatic arthritis. The properties of apremilast were evaluated to determine its specificity, effects on intracellular signaling, gene and protein expression, and in vivo pharmacology using models of innate and adaptive immunity. Apremilast inhibited PDE4 isoforms from all four sub-families (A1A, B1, B2, C1, and D2), with IC50 values in the range of 10 to 100 nM. Apremilast did not significantly inhibit other PDEs, kinases, enzymes, or receptors. While both apremilast and thalidomide share a phthalimide ring structure, apremilast lacks the glutarimide ring and thus fails to bind to cereblon, the target of thalidomide action. In monocytes and T cells, apremilast elevated intracellular cAMP and induced phosphorylation of the protein kinase A substrates CREB and activating transcription factor-1 while inhibiting NF-κB transcriptional activity, resulting in both up- and down-regulation of several genes induced via TLR4. Apremilast reduced interferon-α production by plasmacytoid dendritic cells and inhibited T-cell cytokine production, but had little effect on B-cell immunoglobulin secretion. In a transgenic T-cell and B-cell transfer murine model, apremilast (5mg/kg/day p.o.) did not affect clonal expansion of either T or B cells and had little or no effect on their expression of activation markers. The effect of apremilast on innate immunity was tested in the ferret lung neutrophilia model, which allows monitoring of the known PDE4 inhibitor gastrointestinal side effects (nausea and vomiting). Apremilast significantly inhibited lung neutrophilia at 1mg/kg, but did not induce significant emetic reflexes at doses <30 mg/kg. Overall, the pharmacological effects of apremilast are consistent with those of a targeted PDE4 inhibitor, with selective effects on innate immune responses and a wide therapeutic index compared to its gastrointestinal side effects.

PurposeTo investigate the pharmacokinetics and disposition of [14C]pomalidomide following a single oral dose to healthy male subjects.MethodsEight subjects were administered a single 2 mg oral suspension of [14C]pomalidomide. Blood (plasma), urine and feces were collected. Mass balance of radioactivity and the pharmacokinetics of radioactivity, pomalidomide and metabolites were determined. Metabolite profiling and characterization was performed. The enzymes involved in pomalidomide metabolism and the potential pharmacological activity of metabolites were evaluated in vitro.ResultsMean recovery was 88 %, with 73 and 15 % of the radioactive dose excreted in urine and feces, respectively, indicating good oral absorption. Mean Cmax, AUC0−∞ and tmax values for pomalidomide in plasma were 13 ng/mL, 189 ng*h/mL and 3.0 h. Radioactivity and pomalidomide were rapidly cleared from circulation, with terminal half-lives of 8.9 and 11.2 h. Pomalidomide accounted for 70 % of the circulating radioactivity, and no circulating metabolite was present at >10 % of parent compound. Pomalidomide was extensively metabolized prior to excretion, with excreted metabolites being similar to those observed in circulation. Clearance pathways included cytochrome P450-mediated hydroxylation with subsequent glucuronidation (43 % of the dose), glutarimide ring hydrolysis (25 %) and excretion of unchanged drug (10 %). 5-Hydroxy pomalidomide, the notable oxidative metabolite, was formed primarily via CYP1A2 and CYP3A4. The hydroxy metabolites and hydrolysis products were at least 26-fold less pharmacologically active than pomalidomide in vitro.ConclusionsFollowing oral administration, pomalidomide was well absorbed, with parent compound being the predominant circulating component. Pomalidomide was extensively metabolized prior to excretion, and metabolites were eliminated primarily in urine.

To determine the effect of dexamethasone on the antimyeloma effects of lenalidomide, we tested in vitro proliferation, tumor suppressor gene expression, caspase activity, cell cycling, and apoptosis levels in a series of multiple myeloma (MM) and plasma cell leukemia cell lines treated with lenalidomide and dexamethasone, alone or in combination. The effect of dexamethasone on the immunomodulatory activities of lenalidomide such as T cell and natural killer (NK) cell activation was measured via interleukin [IL]-2 production, and interferon-gamma and granzyme B production respectively. Lenalidomide inhibited proliferation in most cell lines tested, and this effect was enhanced by dexamethasone. This effect was observed in MM cells containing the high-risk cytogenetic abnormalities t(4;14), t(14;16), del17p, del13, and hypodiploidy. Mechanistically, lenalidomide plus dexamethasone synergistically induced expression of the tumor suppressor genes Egr1, Egr2, Egr3, p15, p21, and p27 in MM cell lines and MM patient cells. The combination activated caspases 3, 8, and 9; and induced cell cycle arrest and apoptosis. Lenalidomide alone increased T cell production of IL-2, and NK cell production of interferon-gamma and granzyme B. Notably, dexamethasone antagonized these immunostimulatory effects of lenalidomide in a dose-dependent manner. These data further elucidate the mechanism of action of lenalidomide and dexamethasone in MM, and suggest that use of low-dose dexamethasone with lenalidomide may retain the antiproliferative effect of lenalidomide while permitting greater immunomodulatory effects of this combination regimen.

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