The purpose of this study is to determine how beta-glucan affects the immune system in subjects with melanoma.

This is a clinical pilot study using oral beta-glucan on patients with advanced stage III-IV melanoma without evidence of disease receiving adjuvant Pembrolizumab. The aim is to see whether beta-glucan treatment in combination with Pembrolizumab may provide augmented immunologic phenotypes such as decreased peripheral MDSCs, enhanced T effector cell function, or enhanced cytokine production in the peripheral blood or plasm of enrolled subjects. Secondary outcome measures will include clinical endpoints such as recurrence, progression free survival and overall survival.

Inclusion Criteria:

• Any patients with suspected (clinical) or definitive (tissue) diagnosis of Stage III-IV melanoma starting or continuing adjuvant Pembrolizumab without active evidence of disease (NED).
• Must be treatment naïve or have had treatment no less than 6 months prior to enrollment
• 18 years or older
• Must be able to take pills
• ECOG performance status of 0-3
• Ability to understand and willingness to sign a written informed consent
• Members of all racial and ethnic groups are eligible for this study

Exclusion Criteria:

• History of hypersensitivity reactions attributed to beta-glucan
• Patients receiving continuous or other ongoing immunosuppressive therapy
• Uncontrolled intercurrent illness including, but not limited to, autoimmune diseases, ongoing or active infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia, or psychiatric illness/social situations that would limit compliance with study requirements
• Any patients who have serious autoimmune toxicity during the study period, or those who have disease recurrence during the 6-week study period should be excluded and analyzed separately
• Patients with mucosal melanoma
• Patients with concurrent malignancy or recent history thereof