Could a cancer pill ease rare, painful skin diseases?

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: The participant must be at least 18 years of age. The participant must have a clinically and genetically confirmed diagnosis of a keratinopathy (Epidermolytic ichthyosis/EI: KRT 1, 2, or 10 pathogenic variant; Epidermolytic palmoplantar keratoderma/PPK: KRT 9; Pachyonychia congenita/PC form of PPK: KRT 6a, 6b, 6c, 16, 17). A blood or saliva sample will be collected for genetic confirmation if the underlying genetic change has not been confirmed by a CLIA-approved laboratory. The participant must have an investigator scored IGA at screening and baseline of at least 2 (moderate) at affected sites. The participant must abstain from use of any investigational drug or biologic within 4 weeks or 5 half-lives if longer, oral retinoid or oral steroid for at least 4 weeks, and topical medications (prescription or over-the-counter) in the week before the 8-week observation period. Otherwise stable medications (at least a month before the observation period and continued) will be allowed. The participant agrees to use standard of care with respect to bathing and exfoliation/foot care, except in the week before the visits. Moisturizers/ emollients are allowed throughout the treatment period, but use must be consistent and withheld to the designated area of sampling on the arms (EI) or plantar foot (PC/PPK) for 48 hours prior to visits when skin samples are taken. The participant is willing to have blood collected for safety and biopsies for investigation of mechanism. Participant is in good general health and free of any known disease state or physical condition which, in the investigator's opinion, might impair the evaluation of the EI or PC/PPK. Participant is able and willing to follow all study instructions Exclusion Criteria: The participant has EI or PC/PPK lesions on the assessment area that are infected or require therapy to treat the infection within 7 days of enrollment. The participant has had major surgery during the past 4 weeks. Participants have received an investigational drug or biologic within 4 weeks or 5 half-lives, whichever is longer, prior to starting treatment with and during treatment with erlotinib. Participants must be off oral retinoid or oral steroid for at least 4 weeks before drug initiation. Participants who require medications and OTC supplements that inhibit/ induce CYP3A4 activity to control concurrent medical conditions. Participants with known hypersensitivity to any of the ingredients in the study medication formulation. Participants previously treated for invasive cancer within the past 5 years unless the Investigator concludes history of cancer is not confounding to safety. Participants who are pregnant, breastfeeding or planning to become pregnant during the study or within a month after the study ends. Participants of childbearing potential who are unwilling or unable to comply with contraception measures. The participant has any condition or situation which, in the Investigator's opinion, may put the subject at significant risk, could confound the study results, or could interfere significantly with the subject's participation in the study. Participants deemed by the investigator as unwilling or unable to remain compliant with all tests and procedures, adherence to the study drug administration regimen and other protocol-required activities.