This study is for people with osteosarcoma, a type of bone cancer. Participants have tried other treatments but the cancer has come back (relapsed) or didn't respond (refractory). Researchers are testing two drugs: Tegavivint and Gemcitabine. Tegavivint works by blocking a pathway in cells that helps cancer grow. Gemcitabine is a type of chemotherapy that kills cancer cells.

Key Points:

• The study aims to find the best dose of Tegavivint with Gemcitabine.
• Participants will be checked for side effects, which were mild in earlier tests.
• Eligibility includes having tried other cancer treatments and being healthy enough to participate.

Participants should not have certain other health conditions or be on specific medications. They must agree to birth control if of childbearing potential. This study could help find better treatments for osteosarcoma. If interested, talk to your doctor to see if you qualify.