Inclusion Criteria:  - 1. Subject must be 18 to 65 years of age inclusive, at the time of signing the informed consent.  2. Subject is Fitzpatrick skin type I-VI. 3. A male subject must agree to use contraception during the Treatment Period and for at least 6 months after the last dose of study treatment and refrain from donating sperm during this period.  4. A female subject is eligible to participate if she is not pregnant, not breastfeeding, and at least one of the following conditions applies:  Not a woman of childbearing potential (WOCBP) . OR  A WOCBP who agrees to follow the contraceptive guidance during the Treatment Period and for at least 30 days after the last dose of study treatment.  5. The subject has a clinical diagnosis of PWS located on the face and/or neck. The PWS target lesion on the face and/or neck must have a severity score of Grade ≥3 on the PWS IGA scale at screening and baseline.  6. The longest diameter of the treatment area is ≥3 cm, and the short diameter is ≥2 cm.  7. Subject is capable of giving signed informed consent , which includes compliance with the requirements and restrictions listed in the informed consent form (ICF) and in this protocol.  8. Subject, in the Investigator's opinion, is in good general health and free of any disease state or physical condition that may impair the evaluation of PWS or expose the subject to an unacceptable risk by study participation.  Exclusion Criteria:  1. Subject is pregnant, lactating, or is planning to become pregnant during the study.  2. Subject has plaque/nodular changes and severe hypertrophy within the target PWS area.  3. Subject has Sturge-Weber syndrome or PWS involving ophthalmic nerves. 4. Subject has any skin pathology or condition that, in the Investigator's opinion, could interfere with the evaluation of the study drug or requires use of interfering topical, systemic, or surgical therapy.  5. Subject has evidence of scarring within the target PWS area and/or subject has a history of hypertrophic scarring or keloidal scarring.  6. Subject has PWS lesion located in the eyelid, orbital region, auricle, nasal alar, nasolabial fold, lip region, lips, or oral cavity.  7. Subject is immunosuppressed related to medication use and/or disease . 8. Subject has a hereditary or acquired coagulation disorder or is taking anti coagulants (eg, high and middle dose aspirin) regularly within three weeks of Day 1.  9. Subject has clinically significant ECG abnormalities at Screening 10. Subject has clinically significant laboratory abnormalities as assessed by the Investigator at Screening.  11. Subject has impaired renal (serum creatinine and blood urea nitrogen [BUN] ≥1.5 × upper limit of normal [ULN]) or hepatic (elevated alanine aminotransferase [ALT] or aspartate transaminase [AST] ≥3 × ULN with concurrent elevation in total bilirubin ≥2 × ULN function).  12. Subject has received any therapy on the treatment region that, in the Investigator's opinion, may affect the target PWS area.  13. Subject has a history of cutaneous photosensitization, porphyria, or photodermatosis.  14. Subject has the need or has plans to be exposed to artificial tanning devices or excessive sunlight during the study.  15. Subject has received any therapy, including PDT, to treat PWS in the treatment area within 6 months prior to the initiation of treatment.  16. Subject is currently enrolled in an investigational drug or device study, including clinical studies in dermatology.  17. Subject has used an investigational drug or investigational device treatment within 30 days prior to Day 1.  18. Subject has a history of sensitivity to any of the ingredients in the study drug, including porphyrins, mannitol, and drugs with similar chemical structures.  19. Subject is known or in the opinion of the Investigator likely to be noncompliant with the requirements of the study protocol (eg, due to alcoholism, drug dependency, mental incapacity).  20. Subject has a history of either significant neurological events (such as major stroke) or a mental condition rendering him/her unable to understand the nature, scope, and possible consequences of the study.  21. Subject has an unstable cardiac disease or has any medical condition that in the opinion of the Investigator may worsen from receipt of study treatment or subject participation.  22. Subject is currently taking other photosensitizing medications such as tetracyclines, sulfonamides, phenothiazine, sulfonylurea hypoglycemic agents, thiazide diuretics, quinolones, vitamin A acid, and griseofulvin that may potentially increase the photosensitive reaction in the skin.  23. Subjects currently taking compounds that can eliminate reactive oxygen species or scavenge free radicals such as β-carotene, ethanol, and formate, which may also reduce the activity of Hemoporfin.