Evaluating Dermal Pharmacokinetics and Pharmacodymanic Effect of Soft Topical PDE4 Inhibitors: Open Flow Microperfusion and Skin Biopsies.

PURPOSE: To investigate the difference in clinical efficacy in AD patients between two topical PDE4 inhibitors using dermal open flow microperfusion and cAMP as a pharmacodynamic read-out in fresh human skin explants. METHODS: Clinical formulations were applied to intact or barrier disrupted human skin explants and both skin biopsy samples and dermal interstitial fluid was sampled for measuring drug concentration. Furthermore, cAMP levels were determined in the skin biopsies as a measure of target engagement. RESULTS: Elevated cAMP levels were observed with LEO 29102 while no evidence of target engagement was obtained with LEO 39652. In barrier impaired skin the dISF concentration of LEO 29102 was 2100 nM while only 33 nM for LEO 39652. For both compounds the concentrations measured in skin punch biopsies were 7-33-fold higher than the dISF concentrations. CONCLUSIONS: Low unbound drug concentration in dISF in combination with minimal target engagement of LEO 39652 in barrier impaired human skin explants supports that lack of clinical efficacy of LEO 39652 in AD patients is likely due to insufficient drug availability at the target. We conclude that dOFM together with a pharmacodynamic target engagement biomarker are strong techniques for establishing skin PK/PD relations and that skin biopsies should be used with caution.

Discovery and early clinical development of 2-{6-[2-(3,5-dichloro-4-pyridyl)acetyl]-2,3-dimethoxyphenoxy}-N-propylacetamide (LEO 29102), a soft-drug inhibitor of phosphodiesterase 4 for topical treatment of atopic dermatitis.

Development of orally available phosphodiesterase 4 (PDE4) inhibitors as anti-inflammatory drugs has been going on for decades. However, only roflumilast has received FDA approval. One key challenge has been the low therapeutic window observed in the clinic for PDE4 inhibitors, primarily due to PDE4 mediated side effects. Here we describe our approach to circumvent this issue by applying a soft-drug concept in the design of a topically acting PDE4 inhibitor for treatment of dermatological diseases. We used a fast follower approach, starting from piclamilast. In particular, simultaneous introduction of 2'-alkoxy substituents and changing an amide to a keto linker proved to be beneficial when designing potential soft-drug candidates. This effort culminated in identification of LEO 29102 (20), a potent, selective, and soft-drug PDE4 inhibitor with properties suitable for patient-friendly formulations giving efficient drug delivery to the skin. Compound 20 has reached phase 2 and demonstrated clinically relevant efficacy in the treatment of atopic dermatitis.

Antimalarial and antiplasmodial activities of norneolignans. Syntheses and SAR.

A systematic change of the substituents and side chain of the norneolignan hinokiresinol afforded a 10 fold improvement of the IC(50) value toward inhibition of the growth of Plasmodium falciparum. The more potent compounds controlled the parasitemia in mice infected with Plasmodium berghei.

Structure and absolute configuration of nyasol and hinokiresinol via synthesis and vibrational circular dichroism spectroscopy.

The absolute configuration of the norlignan (+)-nyasol was determined to be S by comparison of the experimental vibrational circular dichroism data with first-principle calculations taking into account the eight lowest energy conformations. The established absolute configuration of (+)-nyasol enables establishment of the absolute configuration of (-)-hinokiresinol, which is concluded to be S. A total synthesis and resolution of hinokiresinol has been performed to resolve the conflicting reports of the coupling constant of the vinylic protons of the disubstituted double bond in this molecule. Racemic hinokiresinol was resolved. Both enantiomers possess the same antiplasmodial activity.

Conformationally restricted anti-plasmodial chalcones.

Chalcones can exist as Z- or E-isomers and it is generally anticipated that both isomers are equipotent. In order to determine the active isomer of anti-plasmodial chalcones a series of analogues locked in the Z- or the E-form were prepared and evaluated for their anti-plasmodial activity. It was shown that the Z-locked analogue was nearly inactive, whereas the E-locked analogues were equipotent to the parent chalcones, indicating that the E-isomer is the active conformation.

Synthesis of prenylated benzaldehydes and their use in the synthesis of analogues of licochalcone A.

In this paper, a general applicable synthesis of prenylated aromatic compounds exemplified by prenylated benzaldehydes starting from readily available acetophenones is described. The synthesized benzaldehydes are used to prepare a number of novel analogues of Licochalcone A, a known antibacterial compound, and for the exploration of the pharmacophoric elements that are essential for the antibacterial activity. It is shown that the hydroxyl group in the A ring is essential for the activity and that the hydroxyl group in the B ring has no influence on the antibacterial effect of Licochalcone A. Furthermore, it is shown that the prenyl group at the position 5 of the B ring also has a dominating influence on the activity. This aliphatic group can be replaced by other lipophilic long chained substituents in order to maintain the activity.

Antibacterial chalcones--bioisosteric replacement of the 4'-hydroxy group.

Hydroxy chalcones, for example, Licochalcone A, has for several years been known to be antibacterial. The low aqueous solubility and the medium antibacterial potency have limited the usefulness of the compounds. We describe the bioisosteric replacement of the essential 4'-hydroxy group in the hydroxy chalcones with bioisosters of varied degrees of acidity resulting in both more potent and more soluble compounds. The more acidic 4'-hydroxy analogues (e.g., 3'-fluoro- or 3',5'-difluoro-) gave almost inactive compounds whereas exchanging the hydroxy group with a carboxy group resulted in a potent compound with a high aqueous solubility. Further optimisation and SAR-analysis resulted in soluble and potent carboxy chalcones [e.g., 3,5-dibromo- and 3,5-di(trifluoromethyl)-].