Novel Isotretinoin Ointment For Congenital Ichthyosis Shows Promise

Patients with recessive X-linked and autosomal recessive lamellar congenital ichthyosis (CI) achieved treatment success with a novel topical isotretinoin ointment known as TMB-001, results from a phase 2b study demonstrated.

“Patients with these deficiencies have generally had very limited treatment options, including lifelong use of emollients and keratolytics, and in severe cases, systemic retinoids,” Christopher G. Bunick, MD, PhD, associate professor of dermatology at Yale University, New Haven, Conn., said at a late-breaking abstract session at the annual meeting of the American Academy of Dermatology. “There is currently no [Food and Drug Administration]-approved drug for CI. So, imagine your patients and their parents, and the frustration they must feel.”

In a study known as CONTROL, he and his colleagues evaluated the effect of TMB-001 on two subtypes of congenital ichthyosis: X-linked recessive ichthyosis (XLRI) and autosomal recessive congenital ichthyosis–lamellar ichthyosis (ARCI-LI). Of the two, the most common is XLRI, which has an estimated incidence of 1:3,000 and is caused by a deficiency of steroid sulfatase, resulting in cholesterol sulfate accumulation in the stratum corneum, retained corneodesmosomes, and reduced corneocyte desquamation, Bunick said.

ARCI-LI is rarer, with a prevalence of 1:100,000, and has been linked to mutations in six genes, most commonly TGM1, resulting in enzyme inactivation and deficient cross-linking of cornified cell envelope proteins.

TMB-001 is a proprietary, novel, topical isotretinoin formulation to treat CI that is being developed by Timber Pharmaceuticals. It uses a patented “IPEG” technology isotretinoin delivery system designed specifically for patients with CI. In a prior phase 2a study, TMB-001 0.1% and 0.2% ointment twice a day demonstrated greater improvement in ≥ 1 and ≥ 2 Investigator Global Assessment (IGA) scores compared with vehicle. Scaling in all patients treated with TMB-001 was considered clear, almost clear, or mild at 8 weeks, and no concerning safety signals were observed.

For the current trial, 33 patients 9 years of age and older with genetically confirmed XLRI/ARCI-LI and ≥ 2 (out of 4) Visual Index for Ichthyosis Severity (VIIS) assessment areas with a ≥ 3 scaling score were randomized 1:1:1 to TMB-001 0.05%, TMB-001 0.1%, or vehicle twice daily for 12 weeks. Primary and secondary efficacy endpoints were reduction of ≥ 50% compared with baseline in VIIS-scaling (VIIS-50) and a ≥ 2-grade reduction in the Investigator Global Assessment (IGA)–scaling score compared with baseline. The patients ranged in age from 23 to 41 years, the majority were White, and their baseline body surface area (BSA) affected ranged from 28% to 38%.

Of the 33 patients, 11 patients received TMB-001 0.05%, 10 received TMB-001 0.1%, and 12 received the vehicle.

Among all patients, 55% had ARCI-LI and 45% had XLRI subtypes, and those with ARCI-LI had greater prior use of corticosteroid, emollient, and oral/topical retinoids. Overall, 100%, 33%, and 75% of patients with XLRI and 50%, 50%, and 17% of patients with ARCI-LI achieved VIIS-50 after receiving TMB-001 0.05%, TMB-001 0.1%, and vehicle, respectively.

An improvement of a ≥ 2-grade IGA score was observed in 80%, 33%, and 25% of patients with XLRI and 50%, 50%, and none of patients with ARCI-LI who received TMB-001 0.05%, TMB-001 0.1%, and vehicle, respectively (P = .018 for TMB-001 0.05% vs. vehicle).

Bunick reported that there were no serious adverse events, no hospitalizations, and no patient deaths. Six patients discontinued treatment, five because of participant withdrawal and one because of physician withdrawal. The four most common treatment-emergent adverse events were erythema (21%), pruritus (21%), pain (15%) and dermatitis (12%).

“These results support ongoing investigation of TMB-001 as a promising alternative to systemic retinoids for participants with CI,” Bunick concluded. He noted that while he is not privy to details of TMB-001’s IPEG delivery system, “the way they have used polyethylene glycol to encapsulate the isotretinoin allows for greater barrier penetration and reduces a lot of the tolerability issues that are seen with other topical retinoids.” In his view, “that is providing this retinoid a greater chance of success. The patented delivery system is not only designed to help the isotretinoin do its job, but also to provide that stability and the ability to compound it, which have been barriers to success in the past.”

Phase 3 trials of the agent are scheduled to begin in June of 2022.

Amy S. Paller, MD, professor and chair of the department of dermatology at Northwestern University, Chicago, who was asked to comment on the study, said that she was impressed that no significant changes from baseline laboratory clinical assessments were observed. “If that’s true, then we don’t have to be monitoring these patients in the same way as with systemic agents,” said Paller, who was involved in the phase 2a proof-of-concept trial of TMB-001. “I think that deserves more investigation. Hopefully that will be looked at in the phase 3 trial.”

Bunick reported having no disclosures related to his presentation. Paller disclosed that she is consultant to and/or an investigator for numerous pharmaceutical companies.

This article originally appeared on MDedge.com, part of the Medscape Professional Network.