TDT 067 Open Label Multi-Dose Onychomycosis Study

Inclusion Criteria: * Subjects must be between 18 and 65 years of age inclusive, of any race, and of either sex. * Male subjects only: Male subjects must use a reliable form of contraception during their participation in the trial and for 3 months after their last dose of study drug. * Female subjects only: Either of non-childbearing potential (i.e. either surgically sterilized or post menopausal) or must be using adequate contraception, have a negative pregnancy test prior to start of dosing, and must agree to continue to use this method of contraception until 3 months after the last dose. Acceptable contraceptive methods are oral contraceptive, IUD, or diaphragm with spermicide (unless anatomically sterile). * Subjects must be in good general health as confirmed by a medical history and physical examination. * Subjects must have 2 big toes with nails that have the potential to be clipped to provide nail samples. * Subjects must have clinically diagnosed distal subungual onychomycosis of the toenails; at least 5 nails in total must present with onychomycotic signs (onycholysis, subungual hyperkeratosis) including extensive involvement (≥50%) of both large nails and mycological confirmation (positive KOH microscopy) from 1 of the large nails. * Subject must sign a statement of informed consent. * Subjects must be able to understand the requirements of the study, abide by the restriction, and return for all of the required examinations Exclusion Criteria: * Subjects lacking any toes. * Subjects with known hypersensitivity to terbinafine or any of the excipients in the TDT 067. * Subjects with symptomatic tinea pedis requiring treatment. * Subjects with any medical, neurological, or psychiatric conditions that in the opinion of the Investigator would make the subject unsuitable for enrollment onto the study. * Subjects with chronic or active liver disease, as well as subjects with elevated liver function tests above normal for the testing laboratory. * Subjects with renal impairment (creatinine clearance ≤50 mL/min). * Subjects who have received terbinafine tablets within 12 months or topical terbinafine (cream, solution/spray, or gel) within 6 months prior to screening visit; subjects who have received other oral antifungals within 4 months or other topical antifungals within 1 month. * Subjects who have participated within the previous 3 months in a clinical trial for the systemic or topical treatment of onychomycosis. * Subjects being treated with rifampin or cimetidine. * Subjects being treated with an investigational drug within 1 month prior to study start. * Subjects with psoriasis or history of psoriasis. * Subjects with nail dystrophy or other nail abnormalities other than onychomycosis. * Subjects with serious concurrent disease that might prevent completion of the trial. * Subjects who are pregnant (confirmed by pregnancy test) or who plan to become pregnant within the study timeframe or who are nursing. * Subjects who cannot read, understand, or sign the informed consent form or the instructions for applying and removing the study formulations. * Subjects who cannot apply the product to their toenails. * Subjects who do not wish to provide nail clippings. * Subjects who cannot or will not provide adequate blood and urine samples. * Subjects using any nail polish products or other nail cosmetic products on any of the toenails designated for treatment within 7 days prior to the start of treatment and who are unwilling to discontinue use of these products for the duration of this study.