Updated: 3/9/2019

Cancer Drugs Overview

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Definitions and Concepts
  • Growth fraction 
    • high growth fraction means large percentage of cells are actively dividing
    • cytotoxic drugs are more deadly against
      • high growth fraction tumors
        • leukemias
        • lymphomas
      • normal cells with high growth fraction
        • bone marrow
        • GI
  • Cell-cycle specificity
    • cell-cycle specific drugs
      • act only during certain phases of the cell cycle
      • more effective against high-growth fraction tumors
    • cell-cycle nonspecific drugs
      • used in both high- and low-growth fraction tumors
  • Log-kill hypothesis
    • cytotoxic drugs kill a fixed percentage of tumor cells
      • not a fixed number
Cell Cycle
  • S phase
    • agents binding to DNA
      • alkylating agents
      • anti-tumor antibiotics
      • platinum compounds
    • antimetabolites
      • methotrexate
      • azathioprine
      • 6-MP
      • 5-FU
  • M phase
    • microtubule inhibitors
      • vinca alkaloids
      • paclitaxel
Sites of Action
 
Mechanism of Action
Drugs
 Mechanism
Nucleotide synthesis

Methotrexate

5-FU

↓ thymidine synthesis
6-MP ↓ purine synthesis
DNA

Alkylating agents

Cisplatin

Cross-link DNA

Dactinomycin

Doxorubicin

Intercalate DNA
Etoposide Inhibit topoisomerase II
Cellular division Vinca alkaloids Inhibit MT formation
Paclitaxel Inhibit MT disassembly
 
Important Toxicities

Drugs Toxicities

Bleomycin

Pulmonary fibrosis
Cisplatin and Carboplatin Acoustic nerve damage and nephrotoxicity
Cyclophosphamide Hemorrhagic cystitis
Doxorubicin Cardiotoxicity
Methotrexate, 5-FU, and 6-MP
Myelosuppression
Vincristine Peripheral neuropathy

 

Development of resistance
  • Tumors can develop resistance to anticancer drugs through a variety of mechanisms
    • ↓ sensitivity/affinity
      • etoposide
      • methotrexate
      • vinblastine and vincristine
    • ↓ accumulation
      • methotrexate
      • alkylating agents
      • dactinomycin
    • ↑ drug-inactivating enzymes
      • antimetabolites of purine and pyrimidine
    • ↑ trapping of drug
      • alkylating agents
      • bleomycin
      • cisplatin
      • doxorubicin
    • ↑ DNA repair
      • alkylating agents
      • cisplatin
    • ↓ bioactivation
      • antimetabolites of purine and pyrimidine
  • Combination drug regimens prevent the development of resistance

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