Potent analogues of etiprednol dicloacetate, a second generation of soft corticosteroids

Loteprednol etabonate (LE) is the first, highly successful soft corticosteroid (SC) designed using the 'inactive metabolite' approach, starting with ∆¹ -cortienic acid (d-CA). The next generation of SCs based on d-CA was etiprednol dicloacetate (ED). The 17α-dichloroacetyl function serves both as a unique pharmacophore and as the source of the molecule's softness. Highly potent SCs were designed based on a combination of ED and LE, introducing 6, 9 and 16 substituents in the molecule.

The new 6α, 9α, 16α and β 17α-dichloroacetyl 17β-esters were synthesized from the correspondingly substituted ∆¹ -cortienic acids. The anti-inflammatory activity was assessed using LPS-induced TNF α-release under various conditions to determine intrinsic activity vs. systemic biological stability. In vivo anti-inflammatory activity was studied in the widely used ovalbumin-sensitized and ovalbumin-challenged Brown Norway rat model.

The 6α or 9α-fluoro substitution produced highly potent corticosteroids, but the 17α-dichloroacetyl substituent provided 'softness' in all cases. Local application of these steroids will significantly reduce systemic activity, due to the facile hydrolytic deactivation of these molecules.

A 17α-dichloroacetyl derivative of fluticasone (FLU) is highly potent but much safer than the currently used propionate or furoate ester.