**Abstract**

Breast cancer is a major health concern as it is the second leading cause of death from cancer. There are several well-known risk factors that contribute to breast cancer. Despite the various treatment options available, complete cure is still difficult due to heterogenicity of BC subtypes. As a result, identifying BC subtypes is critical for determining the optimal treatment approach. Over the last several years, new drugs targeting particular therapeutic targets have resulted in significant advances in the treatment of breast cancer. Nonetheless, resistance to treatment is the "major" issue, and a significant increase in survival rates has been the main focus for researchers. The purpose of this review article is to provide a broad overview of the molecular basis of drug resistance in breast cancer, as well as a detailed assessment of current treatment options, potential new treatment methods for drug-resistant breast cancer and repurposed drugs used for treatment. The possibility of non-cancer drugs being studied for breast cancer in the future, as well as the obstacles and bottlenecks of drug repurposing, is also highlighted. Finally, we go through present problems and future prospects in drug-resistant breast cancer therapy.

**Keywords:** Breast Cancer, Endocrine Resistance, Oestrogen Receptor Modulation, Drug Repurposing
