This clinical trial is focused on studying treatments for patients with advanced HER2-expressing solid tumors. These are types of cancer that have a protein called HER2 on their surface, which can make the cancer grow more quickly. The study is testing a new treatment called BDC-1001, both on its own and in combination with another medication called nivolumab, which is also known by its code names BMS936558 and ABP 206. Nivolumab is a type of drug that helps the immune system fight cancer.

The purpose of the study is to find out how safe and tolerable BDC-1001 is when used alone and when combined with nivolumab. The study will also look at how well these treatments work against the cancer. The study is divided into different parts. In the first part, patients will receive BDC-1001 alone to see how their bodies react to it. In the second part, patients will receive both BDC-1001 and nivolumab to see if the combination is safe and effective. Later parts of the study will focus on how well the treatments work in shrinking the tumors or stopping them from growing.

Participants in the study will receive the treatments through an infusion, which means the medication is given directly into the bloodstream through a vein. The study will monitor patients closely to check for any side effects and to see how the cancer responds to the treatment. The goal is to find the best dose of BDC-1001 that can be used safely and effectively, both on its own and with nivolumab, for treating advanced HER2-expressing solid tumors.