Afamelanotide (SCENESSE) is a synthetic α-melanocyte stimulating hormone analog and first-in-class melanocortin-1 receptor agonist that is approved in the EU for the prevention of phototoxicity in adults with erythropoietic protoporphyria. Afamelanotide differs from endogenous α-melanocyte stimulating hormone at the fourth and seventh amino acid residues, increasing its resistance to immediate degradation and increasing its binding time to melanocortin-1 receptor. Afamelanotide is mimic the pharmacological activity of α-melanocyte stimulating hormone by binding to the melanocortin-1 receptor on melanocytes and activating the synthesis of eumelanin. Eumelanin provides photoprotection through mechanisms including, but not limited to, the absorption and scattering of visible and UV light and antioxidant activity. Afamelanotide increases eumelanin density in healthy volunteers and patients with erythropoietic protoporphyria. In healthy, fair-skinned volunteers, a significant increase in melanin density and skin darkening in both sun-exposed and non-sun-exposed sites was seen with subcutaneous injections of afamelanotide. The most common afamelanotide adverse events included headache and nausea. Common adverse effects include back pain, upper respiratory tract infections, decreased appetite, migraine, and dizziness.

Trifarotene is a novel first-in-class fourth-generation topical retinoid. It is a potent and selective RAR gamma-agonist. In multiple mouse models, trifarotene exhibited superior comedolytic, anti-inflammatory and depigmenting activity compared with other topical retinoids. In this 52-week study, trifarotene was safe, well-tolerated and effective in moderate facial and truncal acne. Trifarotene is in phase II clinical trial for the treatment of ichthyosis.

Crisaborole is a topically administered, boron-containing, anti-inflammatory compound that inhibits the phosphodiesterase-4 (PDE4) activity and thereby suppresses the cytokine release of TNFalpha, IL-12, IL-23 and other cytokines. PDE4 is an an enzyme that converts the intracellular second messenger 3'5'-cyclic adenosine monophosphate (cAMP) into the active metabolite adenosine monophosphate (AMP). By inhibiting PDE4 and thus increasing levels of cAMP, crisaborole controls inflammation. The use of boron chemistry enabled synthesis of a low-molecular-weight compound (251 daltons), thereby facilitating effective penetration of crisaborole through human skin. Crisaborole is in clinical development for the topical treatment of psoriasis and being pursued for the topical treatment of atopic dermatitis. Preliminary studies in children and adults demonstrated favorable efficacy and safety profiles. Crisaborole may represent an anti-inflammatory option that safely minimizes the symptoms and severity of AD and that can be used for both acute and long-term management.

Efinaconazole is triazole used as a 10% topical solution for the treatment of onychomycosis, a fungal infection of the nails. It was approved for use in Canada and the USA in 2014 and is marketed by Valeant Pharmaceuticals North America LLC under the name Jublia. Like other antifungal triazoles, efinaconazole inhibits the fungal cytochrome P450 enzyme lanosterol 14α demethylase (CYP51), thereby disrupting ergosterol synthesis and, consequently, membrane integrity and growth in fungi. CYP51 is evolutionarily conserved and, in mammals, mediates conversion of lanosterol to meiosis-activating sterols (MAS); MAS are intermediates in the biosynthesis of cholesterol and may have a signaling role in initiating meiosis and oocyte maturation. Azoles have higher affinity for fungal CYP51 compared to the mammalian enzyme and such selectivity contributes to the safety of this therapeutic class. Azoles have been reported to produce reproductive and developmental toxicity in both humans and laboratory animals. The mechanism is unknown but inhibition of mammalian CYP51 as well as other CYPs, e.g. CYP17, CYP19 and CYP26, have been postulated to play a role.

Tavaborole is a boron-based pharmaceutical agent indicated for the topical treatment of toenail onychomycosis, a fungal infection of the nail and nail bed due to Trichophyton rubrum or Trichophyton mentagrophytes infection. Tavaborole acts by inhibiting an aminoacyl-transfer ribonucleic acid (tRNA) synthetase (AARS) - Leucyl-tRNA synthetase. Leucyl-tRNA synthetase is an essential fungal enzyme required for protein synthesis and for the catalysis of ATP-dependent ligation of L-leucine to tRNA(Leu). Tavaborole’s low molecular weight (approximately half of most antifungals, such as terbinafine and efinaconazole) permits optimal nail plate penetration, superior to that of existing topical antifungal medications.

Luliconazole (trade names Luzu, Lulicon) is an imidazole antifungal drug. As a 1% topical cream, It is indicated for the treatment of athlete's foot, jock itch, and ringworm caused by dermatophytes such as Trichophyton rubrum, Microsporum gypseum and Epidermophyton floccosum. Luliconazole is an antifungal that belongs to the azole class. Although the exact mechanism of action against dermatophytes is unknown, luliconazole appears to inhibit ergosterol synthesis by inhibiting the enzyme lanosterol demethylase. Inhibition of this enzyme’s activity by azoles results in decreased amounts of ergosterol, a constituent of fungal cell membranes, and a corresponding accumulation of lanosterol. Pharmacokinetic and safety results from phase 1 studies in patients with onychomycosis have demonstrated high concentrations of luliconazole within the nail plates of the great toe and have shown that this agent is well tolerated when administered as a 10% solution.

Difluprednate is a corticosteroid used as an anti-inflammatory steroidal drug used primarily in ocular surgery. It is thought to act by the induction of phospholipase A2 inhibitory proteins (lipocortins). It is postulated that these proteins control the biosynthesis of potent mediators of infammation such as prostaglandins and leukotrienes by inhibiting the release of their common precursor arachidonic acid. Arachidonic acid is released from membrane phospholipids by phospholipase A2. It is marketed by Alcon under the tradename Durezol.

Rifaximin is a structural analog of rifampin and a non-systemic, gastrointestinal site-specific antibiotic. Rifaximin acts by inhibiting bacterial ribonucleic acid (RNA) synthesis and contributes to restore intestinal microflora imbalance. It is FDA approved for the treatment of travelers’ diarrhea, reduction in risk of overt hepatic encephalopathy (HE) recurrence and treatment of irritable bowel syndrome with diarrhea. More common side effects are: black, tarry stools; dizziness or lightheadedness; muscle spasm; rapid breathing; shortness of breath; trouble sleeping. Co-administration of cyclosporine, with XIFAXAN resulted in 83-fold and 124-fold increases in rifaximin mean Cmax in healthy subjects.

Sertaconazole is a azole antifungal that is FDA approved for the treatment of interdigital tinea pedis in immunocompetent patients 12 years of age and older, caused by: Trichophyton rubrum, Trichophyton mentagrophytes, and Epidermophyton floccosum. Sertaconazole interacts with 14-α demethylase, a cytochrome P-450 enzyme necessary to convert lanosterol to ergosterol. As ergosterol is an essential component of the fungal cell membrane, inhibition of its synthesis results in increased cellular permeability causing leakage of cellular contents. Common adverse reactions include contact dermatitis, dry skin, burning skin and application site skin tenderness.

Pimecrolimus, an ascomycin macrolactam derivative, is an inhibitor of T-cell and mast-cell activation, developed and launched by Novartis for the potential treatment of psoriasis and allergic, irritant and atopic dermatitis. The topical formulation had been launched in the US by February 2002 for mild-to-moderate atopic dermatitis in patients aged two years and older. Pimecrolimus is an immunomodulating agent. The mechanism of action of pimecrolimus in atopic dermatitis is not known. While the following have been observed, the clinical significance of these observations in atopic dermatitis is not known. It has been demonstrated that pimecrolimus binds with high affinity to macrophilin-12 (FKBP-12) and inhibits the calcium dependent phosphatase, calcineurin. Therefore, it inhibits T cell activation by blocking the transcription of early cytokines. In particular, pimecrolimus inhibits at nanomolar concentrations Interleukin-2 and interferon gamma (Th1-type) and Interleukin-4 and Interleukin-10 (Th2-type) cytokine synthesis in human T-cells. In addition, pimecrolimus prevents the release of inflammatory cytokines and mediators from mast cells in vitro after stimulation by antigen/IgE. Following the administration of a single oral radiolabeled dose of pimecrolimus numerous circulating O-demethylation metabolites were seen. Studies with human liver microsomes indicate that pimecrolimus is metabolized in vitro by the CYP3A sub-family of metabolizing enzymes. No evidence of skin mediated drug metabolism was identified in vivo using the minipig or in vitro using stripped human skin.