Topical Use of Isotretinoin Shows Promise as Treatment For Congenital Ichthyosis

In a Phase 3 ASCEND Study, topical use of isotretinoin and its major metabolites to treat congenital ichthyosis (CI) showed minimal absorption when applied to 75-90% of the body surface. Interim results of the study will be presented at Society for Pediatric Dermatology’s Annual Meeting July 13-16.¹

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The topical formulation, developed by Timber Pharmaceuticals, Inc., is being evaluated in an ongoing double-blind, vehicle-controlled randomized 12-week study. This will be followed by 12 weeks of open label treatment for patients aged 6 and over with moderate to severe X-linked recessive CI (XLRI) or autosomal recessive CI (ARCI).

“The dry, thickened, and scaling skin that people living with these rare genetic keratinization disorders must deal with can be seriously debilitating, especially in the most severe cases of XLRI and ARCI,” said Joyce M.C. Teng, M.D., Ph.D., professor and director of pediatric dermatology, Stanford University, in a press release. “If we can overcome toxicity challenges of oral treatment with a novel topical formulation of isotretinoin, we may be able to provide better care for our patients.”

Participants self-applied the study drug with the lotion and reported results in an eDiary. They also checked in through virtual and in-person visits to assess results.

A subset of individuals is participating in a 12-week open label Maximal Use Study (MuST). The first 9 participants who finished the first 15 days of the MuST study indicated minimal absorption of isotretinoinin pharmacokinetic (PK) analyses when TMB-001 0.05% was applied to 75-90% of the body surface.

The 9 individuals, aged 12-62, demonstrated mean plasma concentrations (ng/mL) of isotretinoin at Day 14 of 4.83 (range: 1.46-16.59), 4-oxo-isotretinoin of 13.71 (6.52-47.86), tretinoin of 0.08 (0-0.66) and 4-oxo-tretinoin of 0.

“We are advancing innovative clinical research evaluating TMB-001, a topical isotretinoin formulated using our proprietary IPEG™ delivery system that enables targeted delivery to the epidermis and dermis with the potential to minimize systemic drug absorption, which we hope will translate into better safety and lower systemic toxicity while still maintaining high degrees of efficacy,” said Alan Mendelsohn, M.D., chief medical officer of Timber, in a press release.

Researchers are encouraged by the results of the interim PK data. When results are compared to plasma isotretinoin concentrations that that are commonly seen on the labels of oral therapies, which are as high as 862ng/mL with a single dose of 80mg of isotretinoin, the levels with topical use are promising. 

Reference

1. Timber Pharmaceuticals to Present Interim Analyses From Phase 3 ASCEND Study of TMB-001 in Congenital Ichthyosis. News Release. Globe Newswire. June 20, 2023. Accessed June 21, 2023. https://www.globenewswire.com/news-release/2023/06/20/2691018/0/en/Timber-Pharmaceuticals-to-Present-Interim-Analyses-From-Phase-3-ASCEND-Study-of-TMB-001-in-Congenital-Ichthyosis.html