Leronlimab was studied in combination with Keytruda (pembrolizumab), a known cancer immunotherapy, for the treatment of certain cancers, including metastatic triple-negative breast cancer (mTNBC). Leronlimab is a CCR5 antagonist, while Keytruda is a PD-1 inhibitor. The combination aims to enhance the anti-tumor effect by potentially reversing T-cell exhaustion and inducing an inflamed tumor microenvironment that is more susceptible to immunotherapy.