The present disclosure provides, inter alia, methods of treating a solid-tumor by administering an effective amount of a Chemokine Receptor 2 (CCR2) antagonist. Also provided herein are methods of reducing the number of macrophages in a solid tumor microenvironment, said method comprising administering effective amount of a Chemokine Receptor 2 (CCR2) antagonist. In an additional aspect, the current disclosure further provides methods of increasing the number CD8+ T cells in a solid tumor microenvironment, said method comprising administering effective amount of a Chemokine Receptor 2 (CCR2) antagonist. In some embodiments, the CCR2 antagonist has the formula I: