The purpose of this study is to determine the safety of photodynamic therapy (PDT) with lemuteporfin topical solution (LTS) in healthy subjects and subjects with mild acne.

This is a sequentially staged (Stage 1-4), proof of concept study assessing the safety of photodynamic therapy (PDT) and lemuteporfin topical solution (LTS) in healthy subjects and subjects with mild acne. Approximately 12 subjects will be enrolled in Stage 1 in order to determine a maximum tolerated light dose following LTS application. Up to 90 subjects with mild acne will be enrolled in Stage 2 in order to assess the safety of PDT following a single LTS application. Up to 50 subjects will be enrolled in Stage 3 in order to assess the safety of PDT following repeat LTS applications. Up to 40 subjects will be enrolled into Stage 4 to assess multiple treatments of LTS-PDT.

Inclusion Criteria:

• Stage 1 only: healthy subjects
• Stage 1-4: male or female subjects age 18 years or older
• Stage 2: subjects with sebum excretion rate of 4 or higher on forehead
• Stage 2-4: subjects with at least 2 inflammatory acne lesions on the forehead
• Stage 3-4: subjects with sebum excretion rate of 5 or higher on forehead

Exclusion Criteria:

• Poor skin condition on back (Stage 1) or face (Stage 2 & 3)
• Severe facial acne, acne fluminans/conglobata, or nodulocystic acne
• Stage 2-4: previous use of Diane-35 within 6 months of Day 0, systemic acne treatment or systemic antibiotic treatment within 28 days of Day 0, topical acne treatment to the face within 14days of Day 0 or PDT to the face within 3 months of Day 0
• Stage 2-4: previous treatment of isotretinoin or other oral retinoids