International Journal of Clinical Case Reports 2024, Vol.14, No.2, 79-86 http://medscipublisher.com/index.php/ijccr 82 Tyrosine kinase inhibitors (TKIs) are a class of targeted drugs that block the growth signals of cancer cells by inhibiting the activity of receptor tyrosine kinases (Claudiani et al., 2021). They are commonly used in the treatment of solid tumors and hematologic malignancies. For example, Imatinib is used for chronic myeloid leukemia, and Gefitinib and Erlotinib are used for non-small cell lung cancer. Antibody therapy involves the use of monoclonal antibodies to recognize and bind to specific antigens on the surface of tumor cells, thereby triggering the immune system's attack or directly blocking the growth signals of cancer cells. For example, Trastuzumab is used for the treatment of breast cancer, and Cetuximab is used for colon cancer. Poly (ADP-ribose) polymerase (PARP) inhibitors are used to treat cancer patients with mutations in DNA repair genes such as BRCA1/2. These drugs work by inhibiting the activity of PARP enzymes, disrupting the DNA repair mechanism in cancer cells and causing cell death. Olaparib and Niraparib are common PARP inhibitors. The classification of targeted drugs depends on their mechanisms of action and targets. The selection and application of these drugs will be determined based on the specific disease and molecular characteristics of the patient. This personalized treatment approach holds the promise of improving treatment outcomes and survival rates for cancer patients. 2.2 Mechanisms of targeted therapy Targeted therapy is a treatment strategy used for cancer and other diseases. Its mechanism is based on intervening in specific biomolecules or signaling pathways related to the disease, aiming to inhibit or block the growth and spread of diseased cells. Doctors and researchers need to identify specific targets in cancer cells, which are often molecules or signaling pathways closely associated with the development and growth of cancer. This can be achieved through molecular biology, genomics, proteomics, and cell biology techniques. Once the targets are identified, scientists can design and develop specific drugs that interact with these targets in different ways. These drugs are typically prepared through molecular engineering or synthetic organic chemistry methods. Targeted therapy drugs can interact with targets through different mechanisms, depending on the nature of the target. Some targeted therapy drugs not only treat cancer by inhibiting growth signals but also induce apoptosis (cell self-destruction) in cancer cells. This can be achieved by affecting DNA repair, metabolism, or the cell cycle of the cells. Immune checkpoint inhibitors are a class of targeted therapy drugs that enhance the immune system's attack on cancer cells by relieving the suppression of T cells. This treatment activates the patient's own immune system, helping it identify and destroy cancer cells (Pan and Xiong, 2022). The mechanism of targeted therapy involves the precise identification of targets, drug design and development, and specific interactions between drugs and targets. These drugs attack disease-related biomolecules or signaling pathways in a more precise manner, offering more effective treatment methods and reducing damage to normal cells. This approach holds the promise of improving the treatment outcomes of cancer and other diseases. 2.3 Treatment tolerance and resistance Treatment tolerance and resistance refer to the phenomenon where disease cells, especially in the context of cancer, gradually weaken or no longer respond as expected to treatment during the course of therapy. This may lead to disease deterioration or further spread. Treatment tolerance and resistance are common challenges in the clinical medical field, as they limit the effectiveness of treatment. Treatment tolerance refers to the gradual weakening or loss of sensitivity to treatment in disease cells that initially responded to therapy. This may be due to mutations or changes in biological mechanisms within the cells, enabling them to resist the effects of treatment. Treatment tolerance can lead to disease recurrence or accelerated progression. Treatment resistance refers to disease cells exhibiting resistance to treatment either before receiving
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