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Antimicrobial Agents and Chemotherapy, December 2003, p. 3846-3852, Vol. 47, No. 12
0066-4804/03/$08.00+0 DOI: 10.1128/AAC.47.12.3846-3852.2003
Copyright © 2003, American
Society for
Microbiology. All Rights Reserved.
Michael H. Smith,2 Therese Senta-McMillian,2 Inmaculada Soria,3 and Tze-Chiang Meng2*
Department of Dermatology, University of Toronto School of Medicine, Toronto, Ontario, Canada,1 Departments of Clinical Research,2 Pharmacokinetics,3M Pharmaceuticals, Saint Paul, Minnesota3
Received 6 May 2003/ Returned for modification 21 July 2003/ Accepted 18 September 2003
Resiquimod
is a Toll-like receptor 7 (TLR7) and TLR8 agonist that is a potent
inducer of alpha interferon (IFN-
) and other cytokines. The
effects of multiple applications of resiquimod gel were assessed in a
randomized, single-blind, dose-ranging, placebo-controlled study with
41 healthy subjects. Over a 3-week period, 1-g doses of resiquimod or
vehicle gel (3:1 randomization) were applied to a 50-cm2
area of the upper arm according to the following regimens: 0.25%
applied for 8 h two times per week, 0.05% applied for
8 h two times per week, 0.05% applied for 8
h three times per week, and 0.01% applied for 24 h
three times per week. Skin biopsy specimens were obtained prior to the
application of the first dose and after the completion of application
of the last dose. Dosing with 0.01 and 0.05% resiquimod was well
tolerated, but that with 0.25% was not; a dose-response
relationship for local adverse effects was observed. The
level of systemic exposure during multiple topical dosings was
<1% of the applied dose. A significant increase in
responders after completion of application of the last dose was
observed for serum IFN and the interleukin-1 (IL-1) receptor antagonist
(P < 0.01, Fisher's exact test). Increased levels
of mRNA for IL-6, IL-8, IFN-
, and Mx (an
IFN-
-inducible protein) were seen in posttreatment biopsy
specimens from the group receiving 0.25% resiquimod compared to
the levels seen in specimens from the group receiving vehicle only
(P < 0.01, Wilcoxon rank sum test). A
dose-response-related increase in CD3-positive cells consistent with
T-lymphocyte infiltration and a decrease in CD1a-positive
cells, consistent with emigration of Langerhans' cells, were
observed in treated skin. This study suggests that resiquimod is a
potent topically active immune response modifier that significantly
enhances the cutaneous immune
response.
Present
address: Department of Dermatology, Johns Hopkins University School of
Medicine, Baltimore, Md.
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