Lapatinib

 Lapatinib is a molecular "cell infiltrator" engineered to fight HER2-positive breast cancer. It penetrates directly inside the cancer cell and simultaneously shuts down two key tumor growth "switches" — the HER2 and EGFR receptors — by blocking their ATP-binding site from within. Where trastuzumab knocks at the door from outside, lapatinib sneaks in through the back. This is precisely why it works even when other targeted therapies have stopped responding. As a bonus, the molecule can cross the blood-brain barrier — a rare trait among cancer drugs that offers hope in cases of brain metastases.