I. INTRODUCTION Breast cancer is a cancer that starts in the cells of the breast in women and men. Worldwide, breast cancer is the second most common type of cancer after lung cancer (10.4% of all cancer incidence, both sexes

Cancer can be described as the uncontrolled growth of abnormal cells. Breast cancer is the second most common type of cancer after lung cancer. Normal breast cells and most breast cancer cells have receptors that attach to circulating estrogen and progesterone. Estrogen and progesterone bind to the receptors and may work with growth factors (e.g., oncogenes and mutated tumor suppressor genes) to cause cancer cell growth and proliferation. Some of the most commonly used breast cancer drugs are Tamoxifen, Raloxifene, Toremifene etc, breast cancer cells need estrogen to grow. These drugs mainly work against the effects of estrogen on these cells. The ProteinLigand interaction plays a significant role in structural based drug designing. In our research work we have taken the Human estrogen receptor and the commercially available drugs against breast cancer. The receptor was docked to the above said drugs and the energy value obtained as follows Tamoxifen (-49.0), Raloxifene (-158.0), Toremifene (-108.0) using the HEX docking software. Depending on the energy values we have chosen the best two drugs they are Raloxifene and Toremifene. We tried to improve the binding efficiency and steric compatibility of the two drugs namely Raloxifene and Toremifene. Several modifications were made to the probable functional groups which were interacting with the receptor molecule. Analogs of this drug molecule were prepared using ACD ChemSketch and docked using HeX docking software. Raloxifene Analog 7 and Toremifene analog 6 were detected with significant energy values and probable lead molecules. The Modified drugs was sketched using Chemsketch were found to be better than the conventional drugs available. Further from this work we can improve the steric compatibility and then ADME/T properties of the Analogs can be analyzed using Inslico ADME/T tools available.