Glucocorticoid receptor binding: a biphasic dependence on molecular size as revealed by the bilinear LinBiExp model

The clinical efficacy of fluticasone propionate combined with ACEI/ARB in the treatment of immunoglobulin A nephropathy

BACKGROUND

Immunoglobulin A nephropathy (IgAN) is the most common primary glomerulopathy worldwide, and lacks the effective treatment. The study was aimed to investigate the clinical efficacy of fluticasone propionate aerosol combined with angiotensin converting enzyme inhibitor / angiotensin receptor blocker (ACEI/ARB) in the treatment of IgAN.

METHODS

142 patients with biopsy-proven IgAN at Shenzhen People?s hospital from June 2018 to June 2020 were enrolled. The patients were randomly divided into the supportive care plus fluticasone group and the supportive care group. The patients of the supportive care plus fluticasone group were treated with fluticasone propionate aerosol (250 ?g Bid) combined with ACEI/ARB, while the supportive care group was merely treated with ACEI/ARB. The patients were followed up at 3, 6 and 9 months after enrollment. Primary outcomes include changes in proteinuria and estimated glomerular filtration rate (eGFR).

RESULTS

The level of proteinuria in the supportive care plus fluticasone group was significantly lower compared with the supportive care group at 0, 3, 6 and 9 months. Meanwhile, during the follow-up period, no serious adverse events were recorded during the study in either group. However, fluticasone treatment did not alleviate the decline in eGFR.

CONCLUSION

Fluticasone propionate aerosol combined with ACEI/ARB can reduce the level of proteinuria in thetreatment of IgAN, and has no significant effects on renal function.

Understanding the correlation between structure and dynamics of clocortolone pivalate by solid state NMR measurement

Structural characteristics of clocortolone pivalate are unique in the topical corticosteroid field having high penetration power through the stratum corneum of skin as well as low corticosteroid-related adverse effects.

A Receptor Model With Binding Affinity, Activation Efficacy, and Signal Amplification Parameters for Complex Fractional Response Versus Occupancy Data

In quantitative pharmacology, multi-parameter receptor models are needed to account for the complex nonlinear relationship between fractional occupancy and response that can occur due to the intermixing of the effects of partial receptor activation and post-receptor signal amplification. Here, a general two-state receptor model and corresponding quantitative forms are proposed that unify three distinct processes, each characterized with its own parameter: 1) receptor binding, characterized by K_d, the equilibrium dissociation constant used for binding affinity; 2) receptor activation, characterized by an (intrinsic) efficacy parameter ε; and 3) post-activation signal transduction (amplification), characterized by a gain parameter γ. Constitutive activity is accommodated via an additional ε_R0 parameter quantifying the activation of the ligand-free receptor. Receptors can be active or inactive in both their ligand-free and ligand-bound states (two-state receptor theory), but ligand binding alters the likelihood of activation (induced fit). Because structural data now confirm that for most receptors in their active conformation, the small-molecule ligand-binding site is buried inside, straightforward binding to the active form (direct conformational selection) is unlikely. The proposed general equation has parameters that are more intuitive and better suited for optimization by nonlinear regression than those of the operational (Black and Leff) or del Castillo–Katz model. The model provides a unified framework for fitting complex data including a) fractional responses that do not match independently measured fractional occupancies, b) responses measured after partial irreversible inactivation of the “receptor reserve” (Furchgott method), c) fractional responses that are different along distinct downstream pathways (biased agonism), and d) responses with constitutive receptor activity. Furthermore, unlike previous models, the present one can be reduced back for special cases of its parameters to consecutively nested simplified forms that can be used on their own when adequate (e.g., ε_R0 = 0, no constitutive activity; γ = 1: E_max model for partial agonism; ε = 1: Clark equation).

Risks and benefits of corticosteroids in arthritic diseases in the clinic

Glucocorticoids (GCs) constitute a first line treatment for many autoimmune and inflammatory diseases. Due to their potent anti-inflammatory and immunosuppressive actions, GCs are added frequently to disease modifying antirheumatic drugs (DMARDs) in various arthritic diseases, such as rheumatoid arthritis. However, their prolonged administration or administration at high doses is associated with adverse effects that may be (quality of) life-threatening, including osteoporosis, metabolic, gastrointestinal and cardiovascular side effects. In this review, we summarize the clinical and pharmacological effects of GCs in different arthritic diseases, while documenting the current research efforts towards the identification of novel and more efficient GCs with reduced side effects.

Toward Small-Molecule Inhibition of Protein-Protein Interactions: General Aspects and Recent Progress in Targeting Costimulatory and Coinhibitory (Immune Checkpoint) Interactions

Protein-Protein Interactions (PPIs) that are part of the costimulatory and coinhibitory (immune checkpoint) signaling are critical for adequate T cell response and are important therapeutic targets for immunomodulation. Biologics targeting them have already achieved considerable clinical success in the treatment of autoimmune diseases or transplant recipients (e.g., abatacept, belatacept, and belimumab) as well as cancer (e.g., ipilimumab, nivolumab, pembrolizumab, atezolizumab, durvalumab, and avelumab). In view of such progress, there have been only relatively limited efforts toward developing small-molecule PPI inhibitors (SMPPIIs) targeting these cosignaling interactions, possibly because they, as all other PPIs, are difficult to target by small molecules and were not considered druggable. Nevertheless, substantial progress has been achieved during the last decade. SMPPIIs proving the feasibility of such approaches have been identified through various strategies for a number of cosignaling interactions including CD40-CD40L, OX40-OX40L, BAFFR-BAFF, CD80-CD28, and PD-1-PD-L1s. Here, after an overview of the general aspects and challenges of SMPPII-focused drug discovery, we review them briefly together with relevant structural, immune-signaling, physicochemical, and medicinal chemistry aspects. While so far only a few of these SMPPIIs have shown activity in animal models (DRI-C21045 for CD40-D40L, KR33426 for BAFFR-BAFF) or reached clinical development (RhuDex for CD80-CD28, CA-170 for PD-1-PD-L1), there is proof-of-principle evidence for the feasibility of such approaches in immunomodulation. They can result in products that are easier to develop/ manufacture and are less likely to be immunogenic or encounter postmarket safety events than corresponding biologics, and, contrary to them, can even become orally bioavailable.

Small-Molecule Inhibitors of the CD40-CD40L Costimulatory Protein-Protein Interaction

Costimulatory interactions are required for T cell activation and development of an effective immune response; hence, they are valuable therapeutic targets for immunomodulation. However, they, as all other protein-protein interactions, are difficult to target by small molecules. Here, we report the identification of novel small-molecule inhibitors of the CD40-CD40L interaction designed starting from the chemical space of organic dyes. For the most promising compounds such as DRI-C21045, activity (IC50) in the low micromolar range has been confirmed in cell assays including inhibition of CD40L-induced activation in NF-κB sensor cells, THP-1 myeloid cells, and primary human B cells as well as in murine allogeneic skin transplant and alloantigen-induced T cell expansion in draining lymph node experiments. Specificity versus other TNF-superfamily interactions (TNF-R1-TNF-α) and lack of cytotoxicity have also been confirmed at these concentrations. These novel compounds provide proof-of-principle evidence for the possibility of small-molecule inhibition of costimulatory protein-protein interactions, establish the structural requirements needed for efficient CD40-CD40L inhibition, and serve to guide the search for such immune therapeutics.

Chiral Alkyl Halides: Underexplored Motifs in Medicine

While alkyl halides are valuable intermediates in synthetic organic chemistry, their use as bioactive motifs in drug discovery and medicinal chemistry is rare in comparison. This is likely attributable to the common misconception that these compounds are merely non-specific alkylators in biological systems. A number of chlorinated compounds in the pharmaceutical and food industries, as well as a growing number of halogenated marine natural products showing unique bioactivity, illustrate the role that chiral alkyl halides can play in drug discovery. Through a series of case studies, we demonstrate in this review that these motifs can indeed be stable under physiological conditions, and that halogenation can enhance bioactivity through both steric and electronic effects. Our hope is that, by placing such compounds in the minds of the chemical community, they may gain more traction in drug discovery and inspire more synthetic chemists to develop methods for selective halogenation.

TNF superfamily protein-protein interactions: feasibility of small- molecule modulation

The tumor necrosis factor (TNF) superfamily (TNFSF) contains about thirty structurally related receptors (TNFSFRs) and about twenty protein ligands that bind to one or more of these receptors. Almost all of these cell surface protein-protein interactions (PPIs) represent high-value therapeutic targets for inflammatory or immune modulation in autoimmune diseases, transplant recipients, or cancers, and there are several biologics including antibodies and fusion proteins targeting them that are in various phases of clinical development. Small-molecule inhibitors or activators could represent possible alternatives if the difficulties related to the targeting of protein-protein interactions by small molecules can be addressed. Compounds proving the feasibility of such approaches have been identified through different drug discovery approaches for a number of these TNFSFR-TNFSF type PPIs including CD40-CD40L, BAFFR-BAFF, TRAIL-DR5, and OX40-OX40L. Corresponding structural, signaling, and medicinal chemistry aspects are briefly reviewed here. While none of these small-molecule modulators identified so far seems promising enough to be pursued for clinical development, they provide proof-of-principle evidence that these interactions are susceptible to small-molecule modulation and can serve as starting points toward the identification of more potent and selective candidates.

Activity-limiting role of molecular size: size-dependency of maximum activity for P450 inhibition as revealed by qHTS data

Analysis of a large number of data on cytochrome P450 (P450) inhibition obtained from quantitative high-throughput screening assays from the PubChem BioAssay Database clearly indicates that molecular size has an important activity-limiting role for datasets focused on drug-like compounds (PubChem BioAssay Identifier [AID] 1851) as well as for datasets also incorporating a wider range of environmental chemicals (AIDs 410, 899, 883, 891, and 884). Maximum inhibitory activity increases with size for small enough structures then plateaus and begins to show a decreasing trend for larger structures. Log-scaled maximum median inhibitory concentration (pIC50) as a function of molecular size could be fitted well with a bilinear model (LinBiExp), and the shape of the curve is quite similar across five P450 isozymes (CYP1A2, 2C9, 2C19, 2D6, and 3A4) with a turning-point of maximum inhibition around 300-500 Da. While the present size-based approach cannot account for the variability of activity in general, using data for a very large number of compounds, it still provides an intuitive interpretation of the maximum P450-inhibitory activity obtainable for a given molecular size and highlights the presence of an "optimum" size range.

Effects of representative glucocorticoids on TNFα- and CD40L-induced NF-κB activation in sensor cells

Glucocorticoids are an important class of anti-inflammatory/immunosuppressive drugs. A crucial part of their anti-inflammatory action results from their ability to repress proinflammatory transcription factors such as nuclear factor-κB (NF-κB) and activator protein-1 (AP-1) upon binding to the glucocorticoid receptor (GR). Accordingly, sensor cells quantifying their effect on inflammatory signal-induced NF-κB activation can provide useful information regarding their potencies as well as their transrepression abilities. Here, we report results obtained on their effect in suppressing both the TNFα- and the CD40L-induced activation of NF-κB in sensor cells that contain an NF-κB-inducible SEAP construct. In these cells, we confirmed concentration-dependent NF-κB activation for both TNFα and CD40L at low nanomolar concentrations (EC50). Glucocorticoids tested included hydrocortisone, prednisolone, dexamethasone, loteprednol etabonate, triamcinolone acetonide, beclomethasone dipropionate, and clobetasol propionate. They all caused significant, but only partial inhibition of these activations in concentration-dependent manners that could be well described by sigmoid response-functions. Despite the limitations of only partial maximum inhibitions, this cell-based assay could be used to quantitate the suppressing ability of glucocorticoids (transrepression potency) on the expression of proinflammatory transcription factors caused by two different cytokines in parallel both in a detailed, full dose-response format as well as in a simpler single-dose format. Whereas inhibitory potencies obtained in the TNF assay correlated well with consensus glucocorticoid potencies (receptor-binding affinities, Kd, RBA, at the GR) for all compounds, the non-halogenated steroids (hydrocortisone, prednisolone, and loteprednol etabonate) were about an order of magnitude more potent than expected in the CD40 assay in this system.

Interference of boswellic acids with the ligand binding domain of the glucocorticoid receptor

Boswellic acids (BAs) possess anti-inflammatory properties in various biological models with similar features to those of glucocorticoids (GCs), such as suppression of the release of pro-inflammatory cytokines. Hence, the molecular mechanism of BAs responsible for their anti-inflammatory features might be attributable to interference with the human glucocorticoid receptor (GR). Due to obvious structural similarities with GCs, we conducted pharmacophore studies as well as molecular docking simulations of BAs as putative ligands at the ligand binding site (LBS) of the GR in distinct functional states. In order to verify receptor binding and functional activation of the GR by BAs, radiometric binding assays as well as GR response element-dependent luciferase reporter assay were performed with dexamethasone (DEX) as a functional positive control. With respect to the observed position of GCs in GR crystal complexes in the active antagonist state, BAs docked in a flipped orientation with estimated binding constants reflecting nanomolar affinities. For validation, DEX and other steroids were successfully redocked into their crystal poses in similar ranges as reported in the literature. In line with the pharmacophore and docking models, the BAs were strong GR binders (radiometric binding assay), albeit none of the BAs activated the GR in the reporter gene assay, when compared to the GC agonist DEX. The flipped scaffolds of all BAs dislodge the known C-11 function from its receiving amino acid (Asn564), which may explain the silencing effects of receptor-bound BAs in the reporter gene assay. Together, our results constitute a compelling example of rigid keys acting in an adaptable lock qualifying as a reversed induced fit mechanism, thereby extending the hitherto published knowledge about molecular target interactions of BAs.

Small-molecule protein-protein interaction inhibitors: therapeutic potential in light of molecular size, chemical space, and ligand binding efficiency considerations

As the ultimate function of proteins depends to a great extent on their binding partners, protein-protein interactions (PPIs) represent a treasure trove of possible new therapeutic targets. Unfortunately, interfaces involved in PPIs are not well-suited for effective small molecule binding. Nevertheless, successful examples of small-molecule PPI inhibitors (PPIIs) are beginning to accumulate, and the sheer number of PPIs that form the human interactome implies that, despite the relative unsuitability of PPIs to serve as "druggable" targets, small-molecule PPIIs can still provide novel pharmacological tools and new innovative drugs in at least some areas. Here, after some illustrative examples, accumulating information on the binding efficiency, molecular size, and chemical space requirements will be briefly reviewed. Therapeutic success can only be achieved if these considerations are incorporated into the search process and if careful medicinal chemistry approaches are used to address the absorption, distribution, metabolism, and excretion requirements of larger molecules that are often needed for this target class due to the lower efficiency of binding.

Pharmacokinetic features of difluprednate ophthalmic emulsion in rabbits as determined by glucocorticoid receptor-binding bioassay

PURPOSE

Difluprednate (6α,9-difluoro-11β,17,21-trihydroxy-1,4-pregnadiene-3,20-dione 21-acetate 17-butyrate, DFBA) has long been used as an anti-inflammatory dermatological agent. The main objectives of the current study were to evaluate the pharmacokinetic and pharmacodynamic features of DFBA when used as an ophthalmic agent, and to compare these features with those of other common ophthalmic agents, to determine which has the highest activity.

METHODS

A glucocorticoid (GC) receptor-binding test was performed to evaluate GC receptor-binding activity (GCRBA, the index of pharmacological effect). Using this information, we calculated dose-response curves, IC(50) values, and K(d) values to evaluate each drug's K(i) value. Finally, we performed studies in live rabbits to compare the activity of 4 formulations [0.002%, 0.01%, or 0.05% DFBA, or an ophthalmic solution of 0.1% betamethasone sodium phosphate (BMP)] at 4 time points (0.5, 1, 2, 4  h). At each time point, blood and eye samples were taken so that C(max) (the maximum equivalent concentration of the active DFBA metabolite, DFB), T(max) (the time at which C(max) was measured), and the area under the concentration-time curve could be compared across the 4 formulations.

RESULTS

BMP had the highest K(i) value (8.4 × 10(-8) nmol/L), whereas DFB had the lowest (6.1 × 10(-11) nmol/L). The GCRBA of DFBA was intermediate to these 2 values (7.8 × 10(-10) nmol/L). Instillation of the DFBA ophthalmic emulsion in the eyes of rabbits led to dose-dependent increases in GCRBA, which was mostly attributable to the activity of DFB. The 0.05% DFBA ophthalmic emulsion elicited the greatest response in both aqueous humor and iris/ciliary body tissues, though there were no significant dose-dependent differences in GCRBA in plasma samples.

CONCLUSIONS

The 0.05% DFBA ophthalmic emulsion appears to be an effective and safe anti-inflammatory treatment in ocular tissues. It is comparable, and possibly even superior, to the 0.1% BMP solution, and may be particularly useful in cases of severe disease where treatment with BMP solution alone is insufficient.

Effective and specific inhibition of the CD40-CD154 costimulatory interaction by a naphthalenesulphonic acid derivative

Costimulatory interactions are important regulators of T-cell activation and, hence, promising therapeutic targets in autoimmune diseases as well as in transplant recipients. Following our recent identification of the first small-molecule inhibitors of the CD40-CD154 costimulatory protein-protein interaction (J Mol Med 87, 2009, 1133), we continued our search within the chemical space of organic dyes, and we now report the identification of the naphthalenesulphonic acid derivative mordant brown 1 as a more active, more effective, and more specific inhibitor. Flow cytometry experiments confirmed its ability to concentration-dependently inhibit the CD154(CD40L)-induced cellular responses in human THP-1 cells at concentrations well below cytotoxic levels. Binding experiments showed that it not only inhibits the CD40-CD154 interaction with sub-micromolar activity, but it also has considerably more than 100-fold selectivity toward this interaction even when compared to other members of the tumor necrosis factor superfamily pairs such as TNF-R1-TNF-α, BAFF-R(CD268)-BAFF(CD257/BLys), OX40(CD134)-OX40L(CD252), RANK(CD265)-RANKL(CD254/TRANCE), or 4-1BB(CD137)-4-1BBL. There is now sufficient structure-activity relationship information to serve as the basis of a drug discovery initiative targeting this important costimulatory interaction.

Organic dyes as small molecule protein-protein interaction inhibitors for the CD40-CD154 costimulatory interaction

It is becoming increasingly clear that small molecules can often act as effective protein-protein interaction (PPI) inhibitors, an area of increasing interest for its many possible therapeutic applications. We have identified several organic dyes and related small molecules that (i) concentration-dependently inhibit the important CD40-CD154 costimulatory interaction with activities in the low micromolar (microM) range, (ii) show selectivity toward this particular PPI, (iii) seem to bind on the surface of CD154, and (iv) concentration-dependently inhibit the CD154-induced B cell proliferation. They were identified through an iterative activity screening/structural similarity search procedure starting with suramin as lead, and the best smaller compounds, the main focus of the present work, achieved an almost 3-fold increase in ligand efficiency (DeltaG(0)/nonhydrogen atom = 0.8 kJ/N(nHa)) approaching the average of known promising small-molecule PPI inhibitors (approximately 1.0 kJ/N(nHa)). Since CD154 is a member of the tumor necrosis factor (TNF) superfamily of cell surface interaction molecules, inhibitory activities on the TNF-R1-TNF-alpha interactions were also determined to test for specificity, and the compounds selected here all showed more than 30-fold selectivity toward the CD40-CD154 interaction. Because of their easy availability in various structural scaffolds and because of their good protein-binding ability, often explored for tissue-specific staining and other purposes, such organic dyes can provide a valuable addition to the chemical space searched to identify small molecule PPI inhibitors in general.

Structure-transfection activity relationships with glucocorticoid-polyethyl-enimine conjugate nuclear gene delivery systems

Efficient nuclear gene delivery is essential for successful gene therapy. It was previously reported that the transport of DNA into nucleus may be facilitated by glucocorticoid (GC). In this study, five glucocorticoids with different structures and potencies were conjugated with low molecular weight PEI 1800, and the degree of substitution of glucocorticoids was controlled to be close to each other. The glucocorticoid-polyethylenimine (GC-PEI)/pDNA complexes were prepared and their physico-chemical properties and transfection efficiency were investigated. The results showed that the complexes had similar physico-chemical properties, but their transfection activities were different statistically. In order to explore the reason of this difference, the affinity of GC-PEI polymer with GC receptor was analyzed by the application of molecular docking, and the correlation between transfection activity and the potency of five GC was investigated. The result showed that receptor binding of five GC was different and transgene expression enhanced linearly with the increasing GC potency, but logP. In addition, confocal microscopy examination confirmed that GC-PEI/DNA complexes were more effectively translocated in the nucleus than PEI 25K or PEI 1800 complexes and the cytotoxicities of the GC-PEI polymers were lower than that of PEI 25K. These results demonstrated that transfection activity of GC-PEI polymer correlated with its GC potency, and this regularity might be useful for the development of more efficient GC substituted polymer as promising nuclear-targeting carrier.

Modeling corticosteroid effects in a rat model of rheumatoid arthritis I: mechanistic disease progression model for the time course of collagen-induced arthritis in Lewis rats

A mechanism-based model was developed to describe the time course of arthritis progression in the rat. Arthritis was induced in male Lewis rats with type II porcine collagen into the base of the tail. Disease progression was monitored by paw swelling, bone mineral density (BMD), body weights, plasma corticosterone (CST) concentrations, and tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta, IL-6, and glucocorticoid receptor (GR) mRNA expression in paw tissue. Bone mineral density was determined by PIXImus II dual energy X-ray densitometry. Plasma CST was assayed by high-performance liquid chromatography. Cytokine and GR mRNA were determined by quantitative real-time polymerase chain reaction. Disease progression models were constructed from transduction and indirect response models and applied using S-ADAPT software. A delay in the onset of increased paw TNF-alpha and IL-6 mRNA concentrations was successfully characterized by simple transduction. This rise was closely followed by an up-regulation of GR mRNA and CST concentrations. Paw swelling and body weight responses peaked approximately 21 days after induction, whereas bone mineral density changes were greatest at 23 days after induction. After peak response, the time course in IL-1beta, IL-6 mRNA, and paw edema slowly declined toward a disease steady state. Model parameters indicate TNF-alpha and IL-1beta mRNA most significantly induce paw edema, whereas IL-6 mRNA exerted the most influence on BMD. The model for bone mineral density captures rates of turnover of cancellous and cortical bone and the fraction of each in the different regions analyzed. This small systems model integrates and quantitates multiple factors contributing to arthritis in rats.

Modeling corticosteroid effects in a rat model of rheumatoid arthritis II: mechanistic pharmacodynamic model for dexamethasone effects in Lewis rats with collagen-induced arthritis

A mechanism-based model for pharmacodynamic effects of dexamethasone (DEX) was incorporated into our model for arthritis disease progression in the rat to aid in identification of the primary factors responsible for edema and bone loss. Collagen-induced arthritis was produced in male Lewis rats after injection of type II porcine collagen. DEX was given subcutaneously in single doses of 0.225 or 2.25 mg/kg or 7-day multiple doses of 0.045 or 0.225 mg/kg at 21 days postdisease induction. Effects on disease progression were measured by paw swelling, bone mineral density (BMD), body weights, plasma corticosterone (CST), and tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta, IL-6, and glucocorticoid receptor (GR) mRNA expression in paw tissue. Lumbar and femur BMD was determined by PIXImus II dual-energy X-ray absorptiometry. Plasma CST was assayed by high-performance liquid chromatography. Cytokine and GR mRNA were assayed by quantitative real-time polymerase chain reaction. Indirect response models, drug interaction models, transduction processes, and the fifth-generation model of corticosteroid dynamics were integrated and applied using S-ADAPT software to describe how dexamethasone binding to GR can regulate diverse processes. Cytokine mRNA, GR mRNA, plasma CST, and paw edema were suppressed after DEX administration. TNF-alpha mRNA expression and BMD seemed to increase immediately after dosing but were ultimately reduced. Model parameters indicated that IL-6 and IL-1beta were most sensitive to inhibition by DEX. TNF-alpha seemed to primarily influence edema, whereas IL-6 contributed the most to bone loss. Lower doses of corticosteroids may be sufficient to suppress the cytokines most relevant to bone erosion.

Retrometabolic drug design: Principles and recent developments

Retrometabolic drug design incorporates two major systematic approaches: the design of soft drugs (SDs) and of chemical delivery systems (CDSs). Both aim to design new, safe drugs with an improved therapeutic index by integrating structure-activity and -metabolism relationships; however, they achieve it by different means: whereas SDs are new, active therapeutic agents that undergo predictable metabolism to inactive metabolites after exerting their desired therapeutic effect, CDSs are biologically inert molecules that provide enhanced and targeted delivery of an active drug to a particular organ or site through a designed sequential metabolism that involves several steps. General principles and recent developments are briefly reviewed with various illustrative examples from different therapeutic areas with special focus on soft corticosteroids and on brain targeting.