In the complex race of cancer treatment, the evolution of breast cancer therapy resembles a dynamic battle of "as high as the mountain, the magic rises higher." Every technological breakthrough not only advances patient survival rates but also reveals deeper biological challenges.

The history of breast cancer treatment is an ongoing process of combating resistance and searching for new therapies. HER2, a receptor that is abnormally overexpressed in certain malignancies, including breast cancer, has emerged as a key player. It is overexpressed in approximately 20-30% of breast cancer tumors and is considered a driving oncogene in HER2-amplified cancers.

In HER2-positive breast cancer, HER2 stimulates downstream signaling pathways such as RAS-RAF-ERK and PI3K-PTEN-AKT, promoting cancer cell proliferation. As a result, HER2 has become a crucial biomarker for cancer diagnosis and a major therapeutic target in treatments such as antibody-drug conjugates (ADCs).

Also, take hormone receptor-positive (HR+) breast cancer as an example. Endocrine therapy was once the primary treatment, but as tumors evaded drug inhibition by activating the CDK4/6 signaling pathway, resistance issues gradually emerged. The advent of CDK4/6 inhibitors brought new hope to patients and supported a multibillion-dollar market.

However, over time, it also gradually exposed the dilemma of resistance, with the activation of the PI3K-AKT-mTOR signaling pathway becoming a new challenge. In recent years, research into this pathway has deepened, with AKT, the core node of the PI3K-AKT-mTOR pathway, attracting considerable attention for its critical role in tumor cell proliferation, immune evasion, and angiogenesis.

Although the PI3K and mTOR targets have long been hotspots for research, they each have issues of safety and insufficient efficacy. mTOR inhibitors have shown poor effectiveness, with an objective response rate (ORR) of only 9.5%, while PI3K inhibitors, though effective, have serious side effects, such as high blood sugar, with severe adverse events (grade 3 or higher) occurring in up to 76% of patients. Therefore, AKT inhibitors, as a key target in the PI3K-AKT-mTOR signaling pathway, are highly anticipated in both research and application. In recent years, the potential of AKT inhibitors in breast cancer treatment has gradually emerged with continued research.

At the same time, the development of bispecific HER2-targeted ADCs (antibody-drug conjugates) has been attracting increasing attention. These innovative therapies combine the precise targeting ability of anti-HER2 monoclonal antibodies with the powerful cytotoxic effect of ADCs, while the bispecific design addresses the issue of tumor heterogeneity, offering new hope for hard-to-treat breast cancer patients.

ADCs like DS8201 are transforming the treatment landscape for HER2-positive breast cancer patients. The rapid development of bispecific HER2-targeted ADCs promises to overcome the limitations of current therapies and provide precise treatments for HER2-low expression or even HER2-negative patient groups.

In HR+ breast cancer, the iteration of CDK4/6 inhibitors and the development of new first-line combination therapies have provided patients with more treatment options. In triple-negative breast cancer, ADCs targeting TROP2 and other markers have become research hotspots, bringing new hope to patients. Furthermore, recent breakthroughs in breast cancer immunotherapy have also provided patients with new treatment options. For example, the increasing use of PD-1/PD-L1 inhibitors and other immunotherapies in breast cancer is offering patients more treatment possibilities.

The innovative trajectory of breast cancer treatment clearly demonstrates the rise of "dark horse" drugs: starting with solving resistance issues, breakthroughs are being sought through an in-depth analysis of signaling pathways. Whether it is the much-discussed AKT inhibitors or the rapid development of bispecific HER2-targeted ADCs, these new therapies herald a more dynamic future for breast cancer treatment. In this patient-centered race, scientists and pharmaceutical companies are injecting more possibilities into the extension of life through continuous iterative innovations.