Targeted therapy for cancer: Targeted therapy is a cancer treatment that targets the genetic changes or mutations that turn healthy cells into cancer cells.Tablet ribociclib is a drug under targeted therapy.1 Ribociclib, an oral inhibitor of cyclin-dependent kinases 4 and 6 (CDK 4/6), has been approved for metastatic breast cancer (mBC) treatment of hormone receptor (HR)-positive/human epidermal growth factor receptor 2 (HER2)-negative. The study reported the efficacy of Ribociclib as a new oral drug in a patient with mBC. A 54-year-old female with stage 2 right BC change to stage 4 after about three years later referred to oncology clinic. Due to HRpositivity/HER2-negative, she has been treated with tablet Ribociclib 600 mg (per one day for twenty one days with one-week interval) and with Tablet Letrozole 2.5 mg as a hormonal treatment combination. In new assessment and after 3 months of this oral combination therapy, the chest x-ray of lung showed the complete response. Treatment with Ribociclib plus Letrozole had a complete response in the mBC patient after the targeted therapy.