The ASCEND Study: Evaluating TMB-001 in the Treatment of RXLI or ARCI Ichthyosis

Inclusion Criteria

• Subject is male or female, 6 years of age and older at Visit 2 (Baseline).
• Subject has provided written informed consent/assent. A subject under 18 years of age must provide written informed assent and be accompanied by the parent or legal guardian at the time of consent/assent signing. The parent or legal guardian must provide informed consent for the subject. If a subject becomes 18 years of age during the study, the subject must provide written informed consent at that time to continue study participation.
• Females must be postmenopausal (defined as amenorrhea greater than 12 consecutive months in women 50 years of age and older), surgically sterile (hysterectomy, bilateral salpingectomy, or bilateral oophorectomy), or use 2 acceptable forms of birth control. WOCBP must have a negative serum pregnancy test at screening and negative urine pregnancy test (UPT) at Visit 2 (Baseline) (UPTs must have a minimum sensitivity to detect 25 mIU beta human chorionic gonadotropin [β hCG]/mL). Female subjects who become sexually active or begin to have relations with a partner during the study must agree to use 2 forms of birth control for 30 days prior to having relations and to continue such forms of birth control for the duration of the study.
• Subject has clinical diagnosis of CI and has a genetic confirmation of either ARCI (including but not exclusively transglutaminase 1-deficient, ALOX-12B) or RXLI (e.g., deletion of steroid sulfatase gene) subtypes of CI. Other genetically confirmed ARCI-LI mutations can potentially be enrolled as long as the phenotype is consistent with ARCI and the other inclusion criteria are met, as determined by the Investigator.
• The amount of CI affected skin in the Treatment Area at Baseline will be between a minimum of 10% and maximum of 90% of the total BSA (1% BSA is approximately equal to the surface area of the subject's palm and fingers, with the fingers extended yet grouped together, creating a flat oval-like surface area).
• For the Optional Maximal Use arm: The amount of CI affected skin in the Treatment Area at Baseline will be between a minimum of 75% and maximum of 90% of the total BSA.
• Documented history of moderate to severe disease at Screening. Subject's designated VIIS Assessment Areas at Baseline (not applicable for Optional Maximal Use arm):
• Include any of the 4 VIIS Assessment Areas that have some CI disease involving: (a) the upper back from the posterior axillary fold to the other encompassing the T1-T10, (b) the upper arm (excluding elbows), left or right, (c) the shin/lower leg (the portion below the proximal aspect of the kneecap), left or right, and (d) dorsal foot (left or right); AND
• At least 2 of the 4 VIIS Assessment Areas MUST have a scaling score of 3 or more.
• Subject's IGA score in the Treatment Area at Baseline must be 3 or more.
• Subject and parent/guardian (if applicable) are willing and able to apply the study treatment(s) as directed, comply with study instructions, and commit to all follow-up visits for the duration of the study.
• Subject, in the Investigator's opinion, is in good general health and free of any disease state or physical condition that might impair evaluation of the Treatment Areas or exposes the subject to an unacceptable risk by study participation.

Exclusion Criteria

• Subject is pregnant, lactating, or is planning to become pregnant during the study.
• Subject has inflammatory skin diseases that confound the interpretation of results (e.g., atopic dermatitis) unrelated to ichthyosis.
• Subject has genetic abnormality consistent with non-lamellar type or syndromic ichthyoses (including but not exclusively KRT1, KRT10, KRT2, GJB3, GJB4, CDSN)
• Subject, in the Treatment Areas, has used: (a) any topical prescription or over-the-counter (OTC) therapies (except emollients, keratolytics, and topical steroids - see below), that are intended for, or that in the opinion of the Investigator, may impro