Docetaxel and SX-682 in Recurrent/Metastatic Head and Neck Squamous Cell Carcinoma, Salivary Gland Carcinoma, and Advanced Prostate Cancer

Background: Head and neck cancers (HNCs) account for about 5% of all cancers worldwide. They grow in the mouth, throat, nasal cavity, or salivary glands. Prostate cancer is the most common cancer in men in the United States. Survival rates for these cancers are lower than 50% if they spread to other parts of the body or return after treatment. Better treatments are needed. Objective: To test a new drug (SX-682), combined with an approved drug (docetaxel, or DTX), in people with HNCs or prostate cancer. Eligibility People aged 18 years and older with an HNC or prostate cancer that has returned after treatment or has spread. Design: Participants will be screened. They will have blood tests, imaging scans, and a test of their heart function. A tissue sample (biopsy) of the tumor may be taken. Participants will take the study drugs in 3-week cycles. SX-682 is a tablet taken by mouth twice a day from Days 1 to 11 of each cycle. Participants will get a supply of the drug to take home. DTX is given on Day 8 of each cycle through a tube attached to a needle inserted into a vein in the arm. Participants will come to the clinic on Days 1 and 8 of every cycle. They will take both drugs for up to 6 cycles. Participants will have follow-up visits 1 week and 1 month after they finish taking the drugs. Follow-ups will continue every 3 months for 2 years. Then they will have phone or email check-ins twice a year until 5 years have passed.