Advanced targeted therapeutic strategies in metastatic breast cancer: from molecular drivers to clinical impact

Abstract

Metastatic breast cancer (MBC) remains a key health problem and still causes most breast cancer deaths around the world, even after big gains in treatment. The varied biology of breast cancer has made clear how limited traditional chemo is and has sped up the move toward specific, tailored treatments. Today, treating MBC depends more than ever on understanding its molecular makeup to find key targets and weak points, such as estrogen receptor (ER) activity, human epidermal growth factor receptor 2 (HER2) levels, mammalian target of rapamycin (mTOR) pathway issues, DNA repair problems, and tumor markers. In recent times, the range of options for MBC has grown quickly with the addition of new types of drugs like selective estrogen receptor degraders (SERDs), cyclin-dependent kinase 4/6 (CDK4/6) inhibitors, and PI3K/AKT/mTOR blockers, which have shown better results in slowing disease and, in certain groups, improving overall survival (OS). The new class of antibody drug conjugates (ADCs) has been especially important, as they let doctors send very strong drugs straight to cancer cells, which has worked well in HER2-positive, low-HER2, and triple-negative types of MBC. Other recent advancements include PARP inhibitors for BRCA-related cancers, tropomyosin receptor kinase (TRK) inhibitors for rare cancer-causing gene fusions, and immune-based methods such as checkpoint drugs, bispecific antibodies, and well-planned drug combos. Even with these gains, controlling the disease for a long time is still hard because of natural and learned resistance, side effects from treatment, how some drugs do not enter the brain well, and the ongoing lack of good choices for aggressive forms like triple-negative breast cancer. This short summary covers how advanced targeted medicines work at the molecular level in MBC, highlights key new findings and ongoing studies from 2023 to 2025, gives a brief view of selected patents, and shares real-world example cases to show the true effect of these advances. Finally, it discusses how resistance is forming and future directions for making treatment even better using molecular data.