[Variants of biotechnological drugs in dermatology : Status quo and future]. / Varianten biotechnologischer Arzneistoffe in der Dermatologie : Stand und Ausblick.

Biotechnological drugs, so-called biopharmaceuticals, have complex structures, have special physicochemical characteristics and are subject to special regulatory laws. In addition to recombinant monoclonal antibodies, proteins and fusion proteins, a large number of biotechnological variations have been developed, of which antibody fragments, nanobodies, peptides, and antibody-drug conjugates in particular have found their way into clinical application. In addition to strategies for the treatment of oncological diseases, chronic inflammatory diseases in particular are being addressed, which are also becoming of great importance in dermatology. The advantages of biopharmaceuticals are increasingly being recognised and developed as part of special strategies for topical application. Due to the rapid development of molecular medicine, new targets for biopharmaceuticals are constantly being identified, and pharmacokinetically favourable biotechnological molecules are being created using refined methods. It can be assumed that this development will lead to even more highly innovative therapeutic and diagnostic options.

[Modern topical drugs-new developments in galenics and pharmacology]. / Moderne topische Arzneimittel ­ neue Entwicklungen in Galenik und Pharmakologie.

The importance of topically applied pharmaceuticals, especially for the treatment of dermatological diseases, is still essential. Thanks to detailed knowledge of the organisation and function of the physicochemical barrier of the skin, new galenic concepts have increasingly been developed to market maturity in recent years. Colloidal drug carrier systems in particular, but also targeted physicochemical modifications of matrices are used to optimise the cutaneous bioavailability of topically applied drugs. In addition, new molecules are increasingly becoming available for the development of these preparations or drugs known from systemic therapy are being formulated into topicals. Against this background, dermatopharmacology is also developing more and more into a highly specialised science in this area, which is producing innovative concepts for the therapy of special indications. In addition to the classic small-molecule drugs, biotechnological molecules are increasingly finding their way into application, so that a modern age of dermatopharmacology has dawned, which will open up previously unimagined possibilities for topical therapy now and in the coming years.

Discussion of EMA Draft Guideline on Quality and Equivalence of Topical Products Based on Comparison of Approved Mometasone Furoate Drugs.

INTRODUCTION: Today, the approval for a generic topical product includes the presentation of therapeutic equivalence to the originator based on clinical trials. To facilitate this procedure, in 2018 the European Medicines Agency (EMA) published a draft guideline on quality and equivalence of topical products, which includes request parameters regarding the quality of the newly developed generic product and test protocols for the implementation of equivalence tests regarding efficacy. METHODS: To date, no data are available on the quality and evidence of the proposed test conditions. In this study, we performed an in vitro penetration test (IVPT) following the terms of the EMA draft guideline on two authorized topical products for which therapeutic equivalence was already proven during the approval process. RESULTS: The complex biometric data processing revealed that in vitro equivalence could not be observed for all skin sections for either originator or generic product. Moreover, the necessity of the negative control proposed in the draft guideline is more than questionable. From the results presented, there were indications that a reduced number of skin donors would be sufficient to achieve statistically significant equivalence in the comparison of all applied formulations. Here, n = 7 donors was proposed instead of n ≥ 12 as the EMA draft guideline demands, decreasing the degree of biodiversity simultaneously. Moreover, a higher number of independent replicates (n > 2) was proposed for proper statistics. CONCLUSION: This bioequivalence study shows insufficient parameters, which should be discussed together with the EMA draft guideline.

Progress in Topical and Transdermal Drug Delivery Research-Focus on Nanoformulations.

Skin is the largest organ and a multifunctional interface between the body and its environment. It acts as a barrier against cold, heat, injuries, infections, chemicals, radiations or other exogeneous factors, and it is also known as the mirror of the soul. The skin is involved in body temperature regulation by the storage of fat and water. It is an interesting tissue in regard to the local and transdermal application of active ingredients for prevention or treatment of pathological conditions. Topical and transdermal delivery is an emerging route of drug and cosmetic administration. It is beneficial for avoiding side effects and rapid metabolism. Many pharmaceutical, technological and cosmetic innovations have been described and patented recently in the field. In this review, the main features of skin morphology and physiology are presented and are being followed by the description of classical and novel nanoparticulate dermal and transdermal drug formulations. The biophysical aspects of the penetration of drugs and cosmetics into or across the dermal barrier and their investigation in diffusion chambers, skin-on-a-chip devices, high-throughput measuring systems or with advanced analytical techniques are also shown. The current knowledge about mathematical modeling of skin penetration and the future perspectives are briefly discussed in the end, all also involving nanoparticulated systems.

Efficacy and Safety of Topical Tacrolimus Microemulsion Applied Twice Daily in Patients with Mild to Moderate Scalp Psoriasis.

INTRODUCTION: Involvement of the scalp is common in psoriasis and severely affects the quality of life of those affected. It is difficult to treat and places special demands on the galenics of a drug formulation. Tacrolimus is a calcineurin inhibitor and is approved as an ointment formulation for the treatment of atopic dermatitis. The efficacy and safety of topically applied tacrolimus have also been studied and proven for psoriasis. However, no proprietary pharmaceutical product is currently approved for this indication. METHODS: A multicenter, double-blind, vehicle-controlled phase 3 study was conducted to evaluate the efficacy and safety of 0.1% tacrolimus microemulsion when applied topically twice daily in 128 patients independently of sex with scalp psoriasis. RESULTS: The primary efficacy analysis showed a scalp Investigator Global Assessment (s-IGA) of 0 (absence of disease) or 1 (very mild disease) at 8 weeks in 28.6% of subjects in the tacrolimus group, indicating a significantly better response (p = 0.0476, chi-square test) versus 12.7% of subjects in the placebo group (difference of 15.9%-points). The Dermatology Life Quality Index (DLQI) improved over time and was more pronounced in the group treated with tacrolimus-containing microemulsion than in the placebo group, but showed no statistically significant difference after 8 weeks of use (p = 0.193, ANCOVA). The safety analysis revealed no evidence of cutaneous side effects other than those known. Toxicologically relevant serum levels of tacrolimus could be excluded. CONCLUSION: The study data show that 0.1% tacrolimus microemulsion has good efficacy and safety in the treatment of scalp psoriasis.

Recommendations for risk minimization when using Janus kinase inhibitors for the treatment of chronic inflammatory skin diseases.

In accordance with article 20 of Regulation (EC) No 726/2004, the Pharmacovigilance Risk Assessment Committee (PRAC) of the European Medicines Agency (EMA) has re-evaluated the safety of Janus kinase inhibitors for the treatment of inflammatory diseases and formulated safety information deviating from the previous indications in the respective summary of product characteristics of the products concerned. These refer to the consideration of a possibly increased risk of venous thromboembolic or severe cardiovascular events, an increased infection rate and an increase in the prevalence of skin cancer across drugs and indications. Therefore, in patients with independent risk factors (age 65 years and older, smokers or former smokers, patients with oral contraception or hormone replacement therapy and other risk factors), it is recommended to use Janus kinase inhibitors therapeutically only if there are no suitable treatment alternatives. To facilitate a pragmatic and thorough detection of high-risk patients in everyday clinical practice, an interdisciplinary checklist was developed that is suitable as a working tool from the perspective of the dermatologist.

Efficiency of cutaneous heat diffusion after local hyperthermia for the treatment of itch.

BACKGROUND: Today, itching is understood as an independent sensory perception, which is based on a complex etiology of a disturbed neuronal activity and leads to clinical symptoms. The primary afferents (pruriceptors) have functional overlaps with afferents of thermoregulation (thermoceptors). Thus, an antipruritic effect can be caused by antagonizing heat-sensitive receptors of the skin. The ion channel TRP-subfamily V member 1 (TRPV1) is of particular importance in this context. Repeated heat application can induce irreversible inactivation by unfolding of the protein, causing a persistent functional deficit and thus clinically and therapeutically reducing itch sensation. MATERIAL AND METHODS: To demonstrate relevant heat diffusion after local application of heat (45°C to 52°C for 3 and 5 seconds) by a technical medical device, the temperature profile for the relevant skin layer was recorded synchronously on ex vivo human skin using an infrared microscope. RESULTS: The results showed that the necessary activation temperature for TRPV1 of (≥43°C) in the upper relevant skin layers was safely reached after 3 and 5 seconds of application time. There were no indications of undesirable thermal effects. CONCLUSION: The test results show that the objectified performance of the investigated medical device can be expected to provide the necessary temperature input for the activation of heat-sensitive receptors in the skin. Clinical studies are necessary to prove therapeutic efficacy in the indication pruritus.

Permethrin Steal Effect by Unmasked Corneocytic Keratin in Topical Therapy of Scabies.

INTRODUCTION: The use of epicutaneously applied permethrin in the treatment of common scabies is considered to be the first-line therapy. Due to increasing clinical treatment failure, the development of genetic resistance to permethrin in Sarcoptes scabiei var. hominis has been postulated. In addition, metabolic resistance and pharmacokinetic limitations by parasitic digestion and reactive thickening of stratum corneum are suspected to cause a reduction in cutaneous bioavailability. METHODS: Since lipophilic permethrin is known to form hydrophobic interactions with proteins via van der Waals interactions, a similar interaction was assumed and investigated for permethrin and the protein keratin. Using keratin particles extracted from animal material, a model for hyperkeratotic and parasitic digested scabies skin was developed. Using fluorescence-labeled keratin and ³H-permethrin, their interaction potential was validated by loading and unloading experiments. Additionally, the impact of keratin to permethrin penetration was investigated based on an in vitro model using Franz diffusion cells. RESULTS: For the first time, keratin particles were introduced as a model for dyskeratotic skin, as we were able to show, the keratin particles' interaction potential with permethrin but no penetration behavior into the stratum corneum. Moreover, comparative penetration experiments of a reference formulation with and without added keratin or keratin-adherent permethrin showed that keratin causes a steal effect for permethrin, leading to a relevant reduction in cutaneous bioavailability in the target compartment. CONCLUSION: The results provide further evidence for a relevant pharmacokinetic influencing factor in the epicutaneous application of permethrin and a rationale for the necessity of keratolytic pretreatment in hyperkeratotic skin for the effective use of topical permethrin application in scabies.

Supersaturation as a Galenic Concept for Improving the Cutaneous Bioavailability of Drugs in Topical Therapy.

The essential force that allows an epicutaneously applied drug to penetrate the skin is mediated by diffusion. The physicochemical properties of the skin tissue at the site of application and the concentration gradient of the dissolved drug between the vehicle and the stratum corneum are decisive here. One way to specifically improve these diffusion conditions is to use supersaturation. This uses the physical principle of the difference between the solubility curve and precipitation curve (Ostwald-Miers range). During the conversion of the application vehicle into the segregation vehicle, supersaturation of the dissolved drug substance in a solvent is achieved by evaporation, e.g., of a solubilizer. In principle, the change in solubility can also be achieved by heating and then cooling a solution. This principle has already been realized in a formulation of a fixed combination of calcipotriol and betamethasone dipropionate, two lipophilic drugs susceptible to hydrolysis, and is available on the market as a spray foam.

Pharmakologie der Januskinase-Inhibitoren - Teil 2: Pharmakodynamik: Pharmacology of inhibitors of Janus kinases - Part 2: Pharmacodynamics.

Als niedermolekulare Substanzen haben die Januskinase-Inhibitoren unterschiedliche, dosisabhängige pharmakologische Bindungsselektivitäten, die allerdings keine verlässlichen Aussagen über die klinische Spezifität gewünschter oder unerwünschter Wirkeffekte ermöglichen. Es ist deshalb von besonderer Bedeutung zu erkennen, dass die Pharmakodynamik der einzelnen Januskinase-Inhibitoren in Abhängigkeit der behandelten Indikation wesentlich durch die variablen Regulationsebenen des JAK/STAT-Signalwegs sowie der pharmakokinetischen Bedingungen bestimmt wird. Vor diesem Hintergrund wird deutlich, dass alleinig klinische Studiendaten in definierten Indikationen für die Bewertung der Wirksamkeit und Sicherheit von Januskinase-Inhibitoren geeignet sind. Eine unkritische Extrapolation von Beobachtungen bezüglich Wirksamkeit und Sicherheit aus Studien anderer Indikationen soll deshalb nur mit der gebotenen Zurückhaltung erfolgen.

Pharmacology of inhibitors of Janus kinases - Part 1: Pharmacokinetics.

The use of Janus kinase inhibitors for the treatment of chronic inflammatory diseases is increasingly establishing itself as a treatment option for several indications. In order to make clinical use efficient, pharmacological knowledge of the JAK/STAT signaling pathway and the special features of the pharmacokinetics of the individual drugs is essential. The JAK/STAT signaling pathway is regulated at several levels (receptor, kinase, STAT and SOCS levels), so when Janus kinase inhibitors are used, the clinically relevant pharmacodynamics are highly dependent on the dose regimen, treated indication, comedication and comorbidity. For all practical purposes, it is therefore of great importance to recognize that the factors mentioned above can have a relevant influence on the therapeutic benefit of the use of Janus kinase inhibitors. Against this background, it is particularly important to use the Janus kinase inhibitors in accordance with their approval.

Pharmacology of inhibitors of Janus kinases - Part 2: Pharmacodynamics.

As small molecules, the Janus kinase inhibitors have different, dose-dependent pharmacological binding selectivities, which, however, do not allow reliable statements about the clinical specificity of desired or side effects. It is therefore of particular importance to recognize that the pharmacodynamics of the individual Janus kinase inhibitors as a function of the treated indication is essentially determined by variable levels of regulation of the JAK/STAT signaling pathway and the pharmacokinetic conditions. Against this background, it becomes clear that only clinical trial data in defined indications are suitable for evaluating the efficacy and safety of Janus kinase inhibitors. An uncritical extrapolation of observations regarding efficacy and safety from studies of other indications should therefore only be made with due caution.

[Therapeutic peculiarities in diseases of the nipple skin]. / Therapeutische Besonderheiten bei Erkrankungen der Mamillenhaut.

The nipple region is characterized by special anatomical conditions and from a dermatological perspective can be divided into breast skin, skin of the areola and the skin of the nipple. In a clinical context the nipples are often altered during lactation by mechanical alteration, changes in the environment with maceration by the milk flow and by microbial pathogens. In addition, there is a risk of developing puerperal mastitis. Outside of pregnancy and lactation, eczema diseases are occasionally found on the mammary skin, often with atopic disposition (atopic nipple eczema) or as irritant contact eczema ("joggers nipple"). More rarely, allergic contact eczema is observed from preservatives in topical preparations or metals (piercings). Also, in the context of a scabies infestation involvement of the nipples, especially in women, is regularly observed. Of great clinical importance are rare preinvasive lesions of breast cancer or Paget's disease of the mamilla of the extramammary type. Due to the special anatomical conditions, it is obvious that specific penetration conditions are also derived from the application of topical substances. Experimental studies on human skin ex vivo suggest that depending on the molecular weight and solubility of the drug as well as the vehicle system used, a significant increase in cutaneous bioavailability, especially on the nipple itself through the transpapillary diffusion pathway, may occur. This should be considered in particular in the topical application of drugs with known potential of dose-dependent side effects (e.g. glucocorticoids); however, there is still no clinical evidence for this.

Influence of a Novel Dimeric Ceramide Molecule on the Nanostructure and Thermotropic Phase Behavior of a Stratum Corneum Model Mixture.

The stratum corneum (SC) is the outermost layer of the skin and is composed of a multilayered assembly of mostly ceramids (Cer), free fatty acids, cholesterol (Chol), and cholesterol sulfate (Chol-S). Because of the tight packing of these lipids, the SC features unique barrier properties defending the skin from environmental influences. Under pathological conditions, where the skin barrier function is compromised, topical application of molecules that rigidify the SC may lead to a restored barrier function. To this end, molecules are required that incorporate into the SC and bring back the original rigidity of the skin barrier. Here, we investigated the influence of a novel dimeric ceramide (dim-Cer) molecule designed to feature a long, rigid hydrocarbon chain ideally suited to forming an orthorhombic lipid phase. The influence of this molecules on the thermotropic phase behavior of a SC mixture consisting of Cer[AP18] (55 wt %), cholesterol (Chol, 25 wt %), steric acid (SA, 15 wt %), and cholesterol sulfate (Chol-S, 5 wt %) was studied using a combination of neutron diffraction and 2H NMR spectroscopy. These methods provide detailed insights into the packing properties of the lipids in the SC model mixture. Dim-Cer remains in an all-trans state of the membrane-spanning lipid chain at all investigated temperatures, but the influence on the phase behavior of the other lipids in the mixture is marginal. Biophysical experiments are complemented by permeability measurements in model membranes and human skin. The latter, however, indicates that dim-Cer only partially provides the desired effect on membrane permeability, necessitating further optimization of its structure for medical applications.

Synthesis of specific deuterated derivatives of the long chained stratum corneum lipids [EOS] and [EOP] and characterization using neutron scattering.

The synthesis of specific deuterated derivatives of the long chained ceramides [EOS] and [EOP] is described. The structural differences with respect to the natural compounds are founded in the substitution of the 2 double bonds containing linoleic acid by a palmitic acid branched with a methyl group in 10-position. The specific deuteration is introduced both in the branched and in the terminal methyl group, which was realized by common methods of successive deuteration of carboxylic groups in 3 steps. These modified fatty acids resp. the corresponding ceramides [EOS] and [EOP] were prepared for neutron scattering investigations. First results of these investigations were presented in this manuscript showing that the deuterated compounds could be detected in the stratum corneum lipid model membranes. The deuterated ceramides [EOS] and [EOP] are valuable tools to investigate the influence of these long chained ceramide species on the nanostructure of stratum corneum lipid model membranes.

Synthesis of specifically deuterated ceramide [AP]-C18 and its biophysical characterization using neutron diffraction.

The very heterogeneous group of ceramides is known to be mandatory for proper barrier functions of the outermost layer of mammalian skin, referred to as stratum corneum (SC). The synthesis of a specifically deuterated ceramide [AP]-C18 variant is described. The synthesized ceramide contains the racemic forms of the α hydroxy fatty acid. For the biophysical implementation, the received diastereomeric ceramide was applied in a neutron diffraction experiment. Therefore, a SC lipid model membrane was prepared containing the described ceramide (CER), cholesterol (CHOL), stearic acid (SA), and cholesterol sulfate (ChS) in a ratio of 55/25/15/5wt%. Thus, we were able to localize the deuterated molecule part within the bilayers. In the process, a short-periodicity phase (SPP) was observed with a unit cell scale of about 44Å. For the first time, we were able to confirm former ideas concerning the arrangement of the CER within this quaternary lipid model membrane.

Phase separation in ceramide[NP] containing lipid model membranes: neutron diffraction and solid-state NMR.

The stratum corneum is the outermost layer of the skin and protects the organism against external influences as well as water loss. It consists of corneocytes embedded in a mixture of ceramides, fatty acids, and cholesterol in a molar ratio of roughly 1 : 1 : 1. The unique structural and compositional arrangement of these stratum corneum lipids is responsible for the skin barrier properties. Many studies investigated the organization of these barrier lipids and, in particular, the exact conformation of ceramides. However, so far no consensus has been reached. In this study, we investigate a model system comprised of N-(non-hydroxy-tetracosanoyl)-phytosphingosine/cholesterol/tetracosanoic acid (CER[NP]-C24/CHOL/TA) at a 1 : 1 : 1 molar ratio using neutron diffraction and 2H solid-state NMR spectroscopy at temperatures from 25 °C to 80 °C. Deuterated variants of all three lipid components of the model system were used to enable their separate investigation in the NMR spectra and quantification of the amount of molecules in each phase. Neutron scattering experiments show the coexistence of two lipid phases at low temperatures with repeat spacings of 54.2 Å and 43.0 Å at a physiological skin temperature of 32 °C. They appear to be indistinguishable in the 2H NMR spectra as both phases are crystalline and ceramide molecules do not rotate around their long axis on a microsecond timescale. The evolution of these phases upon heating is followed and with increasing temperature fluid and even isotropically mobile molecules are observed. A model of the organization of the lamellar phases is proposed in which the thicker phase consists of CER[NP]-C24 in a hairpin conformation mixed with CHOL and TA, while the phase with a repeat spacing of 43.0 Å contains CER[NP]-C24 in a V-shape conformation.

Influence of the penetration enhancer isopropyl myristate on stratum corneum lipid model membranes revealed by neutron diffraction and 2H NMR experiments.

The stratum corneum (SC) provides the main barrier properties in native skin. The barrier function is attributed to the intercellular lipids, forming continuous multilamellar membranes. In this study, SC lipid membranes in model ratios were enriched with deuterated lipids in order to investigate structural and dynamical properties by neutron diffraction and 2H solid-state NMR spectroscopy. Further, the effect of the penetration enhancer isopropyl myristate (IPM) on the structure of a well-known SC lipid model membrane containing synthetically derived methyl-branched ceramide [EOS], ceramide [AP], behenic acid and cholesterol (23/10/33/33wt%) was investigated. IPM supported the formation of a single short-periodicity phase (SPP), in which we determined the molecular organization of CER[AP] and CER[EOS]-br for the first time. Furthermore, the thermotropic phase behavior of the lipid system was analyzed by additional neutron diffraction studies as well as by 2H solid-state NMR spectroscopy, covering temperatures of 32°C (physiological skin temperature), 50°C, and 70°C with a subsequent cooldown back to skin temperature. Both techniques revealed a phase transition and a hysteresis effect. During the cooldown, Bragg peaks corresponding to a long-periodicity phase (LPP) appeared. Additionally, 2H NMR revealed that the IPM molecules are isotopic mobile at all temperatures.