Updated: 2/13/2018

Cancer Drugs Overview

Review Topic
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
Nucleotide synthesis



↓ thymidine synthesis
6-MP ↓ purine synthesis

Alkylating agents


Cross-link DNA



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

Drugs Toxicities


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