To evaluate the use of HyBryte, a topical photosensitizing agent, to treat patients with patch/plaque phase cutaneous T-cell lymphoma (mycosis fungoides).

The primary objective of this Phase 3 study is to evaluate the ability of an 18-week course of HyBryte and visible light to induce a Treatment Response in patients with patch/plaque phase CTCL compared to patients receiving placebo and visible light.The study will evaluate the efficacy and safety of HyBryte (0.25% hypericin) gel or placebo gel applied twice weekly for 18 weeks. Treated lesions will be covered with opaque material (such as opaque clothing), followed 21 (±3) hours later by the administration of visible light. All of the participant's lesions that are readily available for exposure to the visible light source will be treated and 3 to 5 index lesions in each patient will be prospectively identified and documented for modified Composite Assessment of Index Lesion Severity (mCAILS) evaluation. Participants will be followed every 4 weeks for a total of 12 weeks following their last light session.

Inclusion Criteria:

• Patients must have a clinical diagnosis of cutaneous T-cell lymphoma (CTCL), Stage IA, Stage IB, or Stage IIA.
• Patients with a minimum of three (3) evaluable, discrete lesions.
• Patients willing to follow the clinical protocol and voluntarily give their written informed consent.
• Female patients not pregnant or nursing and willing to undergo a pregnancy test within 30 days prior to treatment initiation.

Exclusion Criteria:

• History of sun hypersensitivity and photosensitive dermatoses including porphyria, systemic lupus erythematosus, Sjögren's syndrome, xeroderma pigmentosum, polymorphous light eruptions, or radiation therapy within 30 days of enrolling.
• History of allergy or hypersensitivity to any of the components of HyBryte.
• A Screening ECG with a QT interval >470 ms (corrected for heart rate using the Fridericia's formula).
• All women of childbearing potential (WOCBP) and males with female partners who are WOCBP not willing to use effective contraception.
• Patients receiving topical steroids or other topical treatments (eg, nitrogen mustard) on treated lesions for CTCL within 2 weeks of enrollment.
• Patients receiving systemic steroids, psoralen UVA radiation therapy (PUVA), narrow band UVB light therapy (NB-UVB) or carmustine (BCNU) or other systemic therapies for CTCL within 4 weeks of enrollment.
• Patients who have received electron beam irradiation within 3 months of enrollment.
• Patients with a history of significant systemic immunosuppression.
• Patients taking other investigational drugs or drugs of abuse within 30 days of entry into this study.
• Patients whose condition is spontaneously improving.
• Patients with tumor stage or erythrodermic CTCL (stages IIB-IV).
• Patients with extensive skin disease (>30% body surface area) who would be, in the judgement of the Principal Investigator, candidates for systemic treatment.
• Patient has any condition that, in the judgment of the PI, is likely to interfere with participation in the study.
• Prior participation in the current study.