SIG1459: A novel phytyl-cysteine derived TLR2 modulator with in vitro and clinical anti-acne activity.

Cutibacterium (formerly Propionibacterium acnes) is a major contributor to the pathogenesis of acne. C. acnes initiates an innate immune response in keratinocytes via recognition and activation of toll-like receptor-2 (TLR2), a key step in comedogenesis. Tetramethyl-hexadecenyl-cysteine-formylprolinate (SIG1459), a novel anti-acne isoprenylcysteine (IPC) small molecule, is shown in this study to have direct antibacterial activity and inhibit TLR2 inflammatory signalling. In vitro antibacterial activity of SIG1459 against C. acnes was established demonstrating minimal inhibitory concentration (MIC = 8.5 µmol\L), minimal bactericidal concentration (MBC = 16.1 µmol\L) and minimal biofilm eradication concentration (MBEC = 12.5 µmol\L). To assess SIG1459's anti-inflammatory activity, human keratinocytes were exposed to C. acnes and different TLR2 ligands (peptidoglycan, FSL-1, Pam3CSK4) that induce pro-inflammatory cytokine IL-8 and IL-1α production. Results demonstrate SIG1459 inhibits TLR2-induced IL-8 release from TLR2/TLR2 (IC50  = 0.086 µmol\L), TLR2/6 (IC50  = 0.209 µmol\L) and IL-1α from TLR2/TLR2 (IC50  = 0.050 µmol\L). To assess the safety and in vivo anti-acne activity of SIG1459, a vehicle controlled clinical study was conducted applying 1% SIG1459 topically (n = 35 subjects) in a head-to-head comparison against 3% BPO (n = 15 subjects). Utilizing the Investigator Global Assessment scale for acne as primary endpoint, results demonstrate 1% SIG1459 significantly outperformed 3% BPO over 8 weeks, resulting in 79% improvement as compared to 56% for BPO. Additionally, 1% SIG1459 was well tolerated. Thus, SIG1459 and phytyl IPC compounds represent a novel anti-acne technology that provides a safe dual modulating benefit by killing C. acnes and reducing the inflammation it triggers via TLR2 signalling.

N-Acetylglutaminoyl-S-farnesyl-L-cysteine (SIG-1191): an anti-inflammatory molecule that increases the expression of the aquaglyceroporin, aquaporin-3, in human keratinocytes.

Isoprenylcysteine (IPC) small molecules were discovered as signal transduction modulating compounds ~25 years ago. More recently, IPC molecules have demonstrated antioxidant and anti-inflammatory properties in a variety of dermal cells as well as antimicrobial activity, representing a novel class of compounds to ameliorate skin conditions and disease. Here, we demonstrate a new IPC compound, N-acetylglutaminoyl-S-farnesyl-L-cysteine (SIG-1191), which inhibits UVB-induced inflammation blocking pro-inflammatory cytokine interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-α) production. To investigate further the previously reported hydrating potential of IPC compounds, SIG-1191 was tested for its ability to modulate aquaporin expression. Specifically, aquaporin 3 (AQP3) the most abundant aquaporin found in skin has been reported to play a key role in skin hydration, elasticity and barrier repair. Results show here for the first time that SIG-1191 increases AQP3 expression in both cultured normal human epidermal keratinocytes as well as when applied topically in a three-dimensional (3D) reconstructed human skin equivalent. Additionally, SIG-1191 dose dependently increased AQP3 protein levels, as determined by specific antibody staining, in the epidermis of the 3D skin equivalents. To begin to elucidate which signaling pathways SIG-1191 may be modulating to increase AQP3 levels, we used several pharmacological pathway inhibitors and determined that AQP3 expression is mediated by the Mitogen-activated protein kinase/Extracellular signal-regulated kinase kinase (MEK) pathway. Altogether, these data suggest SIG-1191 represents a new IPC derivative with anti-inflammatory activity that may also promote increased skin hydration based on its ability to increase AQP3 levels.

In vitro and clinical evaluation of SIG1273: a cosmetic functional ingredient with a broad spectrum of anti-aging and antioxidant activities.

BACKGROUND: Isoprenylcysteine (IPC) small molecules were identified as a new class of anti-inflammatory compounds over 20 years ago. Since then, they have been developed as novel cosmetic functional ingredients (CFI) and topical drug candidates. SIG1273 is a second generation CFI that has previously been shown to provide a broad spectrum of benefits for the skin through its anti-inflammatory and antimicrobial properties. OBJECTIVE: To determine whether SIG1273 possesses anti-aging properties in vitro and evaluate the tolerability and activity of SIG1273 when applied topically to human subjects. METHODS: To model photoaging in vitro, human dermal fibroblasts (HDFs) were exposed in culture to UVA to induce collagenase (MMP-1) production. An in vitro wound-healing model was based on the activation of HDF migration into cell-free tissue culture surface. Hydrogen peroxide-induced oxidative stress was performed using HDFs to measure intracellular ROS activity. Radical scavenging capacity was determined using a colorimetric antioxidant assay kit (ABTS method). Lastly, a 4-week, 29-subject study was performed in which SIG1273 was applied topically as a cream to assess its tolerance and activity in reducing the appearance of aging. RESULTS: In vitro studies demonstrate SIG1273 inhibits UVA-induced MMP-1 production, hydrogen peroxide-induced oxidative stress and promotes wound healing. Moreover, SIG1273 was shown to be a radical scavenging antioxidant. Clinical assessment of SIG1273 cream (0.25%) showed it was well tolerated with significant improvement in the appearance of fine lines, coarse wrinkles, radiance/luminosity, pore size, texture/smoothness, hydration and increased firmness. CONCLUSIONS: SIG1273 represents a novel CFI with antioxidant, anti-aging, and anti-inflammatory properties that when applied topically is well tolerated and provides benefits to individuals with aging skin.

SIG1273: a new cosmetic functional ingredient to reduce blemishes and Propionibacterium acnes in acne prone skin.

BACKGROUND: Propionibacterium acnes is a major contributing factor to the inflammatory component of acne. The interaction of P. acnes with keratinocytes leads to an innate immune response via activation of toll-like receptors (TLR2, TLR4) resulting in the production and secretion of pro-inflammatory mediators. SIG1273, an isoprenylcysteine small molecule modulates inflammatory signaling pathways and kills P. acnes. SIG1273 represents a novel cosmetic functional ingredient that provides relief from blemishes in acne prone skin. OBJECTIVE: To assess the keratinocyte response and microbial growth of SIG1273 in vitro and evaluate the tolerability of SIG1273 gel applied topically in acne prone subjects. METHODS: For in vitro studies, human keratinocytes were exposed in culture to live P. acnes and peptidoglycan (PGN) to induce IL-8 production. P. acnes were cultured to determine minimal inhibitory concentration and minimal bactericidal concentration values. A total of 30 subjects were randomized in a double-blind controlled trial receiving 3% SIG1273 gel or vehicle for 6 weeks. Evaluation included inflammatory lesions, noninflammatory lesions, microcomedones, Sebutape scores, and P. acnes counts. RESULTS: In vitro studies demonstrate SIG1273 inhibits P. acnes-induced IL-8 production and inhibits P. acnes growth. SIG1273 gel was well tolerated with no signs of stinging, redness, or itching. Furthermore, improvement in some aspects of acne was observed in subjects applying SIG1273 gel, including inflammatory lesions, microcomedone counts and Sebutape scores. Facial scrubs taken to measure P. acnes colony-forming units showed those applying SIG1273 gel had ~1.0 Log 10 colony reduction over the length of the study, a statistically significantly improvement when compared with vehicle. No significant effects above vehicle were observed for noninflammatory lesions. CONCLUSIONS: SIG1273 represents a novel cosmetic functional ingredient that provides a safe dual modulating benefit to individuals with acne prone skin by reducing P. acnes counts and reducing inflammation.

N-acetyl-S-farnesyl-l-cysteine suppresses chemokine production by human dermal microvascular endothelial cells.

Isoprenylcysteine (IPC) molecules modulate G-protein-coupled receptor signalling. The archetype of this class is N-acetyl-S-farnesyl-l-cysteine (AFC). Topical application of AFC locally inhibits skin inflammation and elicitation of contact hypersensitivity in vivo. However, the mechanism of these anti-inflammatory effects is not well understood. Dermal microvascular endothelial cells (ECs) are involved in inflammation, in part, by secreting cytokines that recruit inflammatory cells. We have previously shown that the sympathetic nerve cotransmitter adenosine-5'-triphosphate (ATP) and adenosine-5'-O-(3-thio) triphosphate (ATPγS), an ATP analogue that is resistant to hydrolysis, increase secretion of the chemokines CXCL8 (interleukin-8), CCL2 (monocyte chemotactic protein-1) and CXCL1 (growth-regulated oncogene α) by dermal microvascular ECs. Production of these chemokines can also be induced by the exposure to the proinflammatory cytokine TNFα. We have now demonstrated that AFC dose-dependently inhibits ATP-, ATPγS- and TNFα-induced production of CXCL1, CXCL8 and CCL2 by a human dermal microvascular EC line (HMEC-1) in vitro under conditions that do not affect cell viability. Inhibition of ATPγS- or TNFα-stimulated release of these chemokines was associated with reduced mRNA levels. N-acetyl-S-geranyl-l-cysteine, an IPC analogue that is inactive in inhibiting G-protein-coupled signalling, had greatly reduced ability to suppress stimulated chemokine production. AFC may exert its anti-inflammatory effects through the inhibition of chemokine production by stimulated ECs.

Topical N-acetyl-S-farnesyl-L-cysteine inhibits mouse skin inflammation, and unlike dexamethasone, its effects are restricted to the application site.

N-acetyl-S-farnesyl-L-cysteine (AFC), a modulator of G protein and G-protein coupled receptor signaling, inhibits neutrophil chemotaxis and other inflammatory responses in cell-based assays. Here, we show topical AFC inhibits in vivo acute inflammation induced by 12-O-tetradecanoyl-phorbol-13-acetate (TPA) and arachidonic acid using the mouse ear model of inflammation. AFC inhibits edema, as measured by ear weight, and also inhibits neutrophil infiltration as assayed by direct counting in histological sections and by measuring myeloperoxidase (MPO) activity as a neutrophil marker. In addition, AFC inhibits in vivo allergic contact dermatitis in a mouse model utilizing sensitization followed by a subsequent challenge with 2,4-dinitrofluorobenzene. Unlike the established anti-inflammatories dexamethasone and indomethacin, AFC's action was restricted to the site of application. In this mouse model, both dexamethasone and indomethacin inhibited TPA-induced edema and MPO activity in the vehicle-treated, contralateral ear. AFC showed no contralateral ear inhibition for either of these end points. A marginally significant decrease due to AFC treatment was seen in TPA-induced epidermal hyperplasia at 24 hours. This was much less than the 90% inhibition of neutrophil infiltration, suggesting that AFC does not act by directly inhibiting protein kinase C.

Metabolic fate and selective utilization of major fatty acids in human sebaceous gland.

The sebaceous gland is an integral part of the pilosebaceous unit of mammalian skin, which produces and secretes a unique mixture of lipids, known as sebum. Wax esters, which account for approximately 25% of human sebaceous lipids, are unique in that they are not synthesized by other cells in the body. To explore the biosynthesis of wax esters, the metabolic fate of exogenously supplied saturated (16:0, 18:0), mono-unsaturated Delta9 (16:1, 18:1), and polyunsaturated (18:2, Delta9,12) fatty acids was followed in biopsy punches from human facial skin rich in sebaceous glands. Acetate was incorporated into all of the cellular and secreted lipids and 16:0 was incorporated into all of the fatty-acid-containing lipids. The 16:0 was elongated to 18:0 and the 16:1 was incorporated primarily into polar lipids, secondarily into triglycerides, but not into other lipids and was elongated to 18:1 (Delta11). As proven by HPTLC analysis, both 18:0 and 18:1 were incorporated into the cellular lipids but at a lower rate into wax esters. Moreover, addition of exogenous 18:1 was not further processed following initial incorporation. Linoleic acid (18:2, Delta9,12) was the only fatty acid tested that appeared to be subjected to beta-oxidation. This was proven to be specific to linoleic acid, as it did not induce the oxidation of other fatty acids. The ability of the sebaceous cells to synthesize wax esters correlated with the beta-oxidation activity in these cells. Thus, the oxidation of linoleic acid is specific for the sebaceous cells and correlates with their function and differentiation. Our results provide evidence that the sebaceous gland selectively utilizes fatty acids as 16:0 is the preferred fatty acid that is incorporated into wax esters and linoleic acid undergoes beta-oxidation.