Anti-inflammatory potency testing of topical corticosteroids and calcineurin inhibitors in human volunteers sensitized to diphenylcyclopropenone

Abstract

Aims: To quantify the anti-inflammatory potency of topical corticosteroids and topical calcineurin inhibitors by measuring the contact allergic response to a diphenylcyclopropenone (DPCP) challenge in de novo sensitized human volunteers.

Methods: Two randomized, double-blind, vehicle-controlled studies were performed encompassing 76 volunteers: 29 in the first and 47 in the second study. Topical drugs were applied pre- and/or post-treatment in block designs. The compounds were tested simultaneously under occluded patch tests covering DPCP-induced dermatitis. Inhibitory responses were assessed by visual scoring and measurements of the oedema thickness with ultrasound.

Results: When applied both before and after the DPCP challenge, significant anti-inflammatory effects were seen in descending order for tacrolimus 0.1% ointment, clobetasol propionate ointment, betamethasone valerate ointment and hydrocortisone butyrate ointment, while pimecrolimus cream, hydrocortisone ointment and vehicles had no significant effect. Only tacrolimus ointment (P < 0.01) demonstrated a consistent significant pre-treatment inhibitory effect compared with an untreated DPCP control.

Conclusions: This human testing method in which the inflammation of experimentally induced allergic patch test reactions is quantified by objective measurement allows an analysis of the anti-inflammatory potency of not only topical corticosteroids, but also of drugs that have no effect on vasoconstriction. The method allowed comparison of the potencies of four topical corticosteroids and two calcineurin inhibitors.

Keywords: allergic contact dermatitis; anti-inflammatory potency; diphenylcyclopropenone; human test method; topical calcineurin inhibitors; topical corticosteroids.

Figure 1

Automated skin ultrasound measurements of dermal thickness in allergic contact dermatitis (ACD) and control reactions. The red left part of the ultrasound curve shows the intensity of the ultrasound passing through the water chamber in the probe. The high left peak originates from the combined film/epidermal reflection. The red right part of the curve shows the intensity of the ultrasound passing through the subcutaneous layers. The yellow part of the curve indicates the less reflective part of the dermis, while the green part indicates the more reflective part of the dermis. The average thickness of the dermis is calculated based on the super A‐scan. The dermal thickness measurements (in μm) are shown next to the ultrasound images (i.e. C and D) and represent the yellow and green part of the curves. (A) Ultrasound scan of ACD after Dermovate (clobetasol propionate) treatment at 72 h and (B) untreated (positive) diphenylcyclopropenone control scan at 72 h. Data from a participant in Study I are shown

Figure 2

Protocols for sensitization, challenges and topical drug treatment. (A) Flow chart (study I): Volunteers were sensitized on the upper buttock for 48 h. Four weeks later, an initial elicitation challenge (IEC) was performed with a diphenylcyclopropenone (DPCP) dose‐series. After IEC, volunteers were rechallenged with two DPCP doses applied in two separate panels on the upper back followed by post‐treatment with topical drugs. (B) Flow chart (study II): The same setup was used as in study I except that after IEC, test sites were pretreated with four topical products on either side of the upper back (left and right panel). This was followed by rechallenge with a select DPCP dose and finally post‐treatment with topical drugs. (C) Schematic setup of rechallenge and post‐treatment with topical drugs (study I): The two panels each consisted of four small (8‐mm) DPCP patches (shown as vertical hatchings) and a vehicle (acetone) control patch (cross‐hatching). Upon removal of these chambers, three large (12‐mm) chambers loaded with topical drugs (dotted rings), a large vehicle ointment chamber (solid ring), and a large empty (negative control) chamber (dashed ring) were placed on the elicitation areas. (D) Schematic setup of pre‐treatment, rechallenge, and combined pre‐ and post‐treatment with topical drugs (study II): The two pre‐treatment panels each consisted of six test sites comprising four large Finn chambers filled with topical drugs (dotted rings) and two empty chambers (dashed rings). Small (8‐mm) DPCP chambers (vertical hatchings) were placed on the eight pretreated sites and on two untreated sites. The two remaining sites were occluded with empty Finn chambers (cross‐hatchings). The right panel was post‐treated with the same drugs as used for pre‐treatment, again using large Finn chambers (dotted rings)

Figure 3

Anti‐inflammatory effects of topical drugs evaluated by skin ultrasound. (A, B) Post‐treatment at 48 h and 72 h using lower and higher diphenylcyclopropenone (DPCP) doses; (C, D) pre‐treatment at 48 h and 72 h; (E, F) combined pre‐ and post‐treatment for 48 h and 72 h. SEM: standard error of the mean; TCS: topical corticosteroids; TCIs: topical calcineurin inhibitors; Pc: pimecrolimus; Tc: tacrolimus; HC: hydrocortisone; HCB: hydrocortisone butyrate; BV: betamethasone valerate; CP: clobetasol propionate. Asterisks indicate * P < 0.05 and **P < 0.01