Targeted Therapy Concepts

Targeted Therapy Concepts - Precision Strikes

• Principle: Drugs targeting specific molecules (proteins, genes) vital for cancer cell growth & survival.
• Action: Blocks specific cancer signals; distinct from chemotherapy's broad cytotoxicity.
• Key Features:
  • Targets: EGFR, HER2, VEGF, BRAF, ALK, BCR-ABL.
  • Biomarkers: Predictive; guide patient selection (e.g., KRAS for anti-EGFR therapy).
  • Drug Classes:
    • Monoclonal Antibodies (-mab): Target extracellular/surface molecules (e.g., Trastuzumab for HER2+ breast cancer).
    • Small Molecule Inhibitors (-nib): Target intracellular molecules (e.g., Imatinib for CML).
• Benefits: ↑Efficacy in selected patients; often ↓severe side effects than chemo.
• Limitations: Acquired resistance; target heterogeneity.

⭐ KRAS mutation in colorectal cancer predicts resistance to anti-EGFR monoclonal antibodies (e.g., Cetuximab).

Targeted Therapy Concepts - Unlocking Cancer's Code

• Principle: Drugs targeting specific molecules (proteins, genes) crucial for cancer cell growth, progression, and spread. "Lock and key" action against molecular aberrations.
• Action: Interfere with aberrant signaling pathways. Biomarker testing (e.g., EGFR, HER2, BRAF, BRCA) essential to identify susceptible patients.
• Key Classes & Targets:
  • Tyrosine Kinase Inhibitors (TKIs) (small molecules):
    • EGFR: Gefitinib, Erlotinib
    • HER2: Lapatinib
    • BCR-ABL: Imatinib
    • ALK: Crizotinib
    • BRAF: Vemurafenib
  • Monoclonal Antibodies (mAbs) (large molecules):
    • HER2: Trastuzumab
    • EGFR: Cetuximab
    • VEGF (Angiogenesis): Bevacizumab
  • PARP Inhibitors: Olaparib (for BRCA mutations)
  • mTOR Inhibitors: Everolimus
• Advantages: Higher specificity, potentially fewer severe side effects than traditional chemotherapy; improved therapeutic window.
• Challenges: Drug resistance (primary/acquired), unique side-effect profiles (e.g., skin rash, cardiotoxicity).

⭐ Imatinib, a TKI targeting BCR-ABL, revolutionized Chronic Myeloid Leukemia (CML) treatment.

Targeted Therapy Concepts - Surgeon's Smart Bombs

• Precision drugs attacking specific molecules (genes, proteins) vital for cancer cell growth and survival.
• Key Mechanisms:
  • Tyrosine Kinase Inhibitors (TKIs): Intracellularly block aberrant signaling (e.g., Imatinib).
  • Monoclonal Antibodies (mAbs): Extracellularly target cell surface receptors or ligands (e.g., Trastuzumab, Bevacizumab).
• Biomarker testing is crucial for patient selection:
  • HER2 for Trastuzumab.
  • EGFR mutations for Gefitinib/Erlotinib.
  • KRAS wild-type for Cetuximab/Panitumumab.
• Challenges include acquired resistance and unique side-effect profiles (e.g., skin rash with EGFR inhibitors).

Targeted Therapy Concepts - Evolving Battlefront

• Challenges: Drug resistance is a major hurdle.
  • Primary (Intrinsic) Resistance: Cancer cells don't respond from the outset.
    • Pre-existing mutations (e.g., KRAS in EGFR therapy for CRC).
    • Tumor heterogeneity.
  • Acquired (Secondary) Resistance: Develops after initial response.
    • New mutations in the target (e.g., T790M in EGFR for NSCLC).
    • Activation of bypass pathways.
    • Phenotypic switching (e.g., EMT).
• Overcoming Resistance:
  • Combination therapies.
  • Next-generation inhibitors.
  • Intermittent dosing strategies.
• Future Directions:
  • Liquid biopsies (ctDNA) for monitoring resistance & guiding therapy.
  • Novel targets & immunotherapies.
  • AI in drug discovery & personalized medicine.

⭐ Acquired resistance to Imatinib in CML is often due to point mutations in the ABL kinase domain, with T315I being a common culprit conferring broad TKI resistance (except Ponatinib).

High‑Yield Points - ⚡ Biggest Takeaways

• Monoclonal antibodies (mAbs) end in "-mab"; Tyrosine Kinase Inhibitors (TKIs) in "-tinib".
• Trastuzumab targets HER2/neu receptor, crucial in HER2+ breast and gastric cancers.
• Rituximab targets CD20 antigen on B-lymphocytes, used for lymphomas.
• Bevacizumab inhibits VEGF, blocking angiogenesis in colorectal, lung, renal cancers.
• Imatinib targets BCR-ABL tyrosine kinase in CML and c-KIT in GIST.
• EGFR inhibitors (e.g., Cetuximab) require KRAS wild-type status for colorectal cancer treatment.