Classification of Anti-Cancer Drugs

Classification of Anticancer Drugs: Types, Mechanism, Examples & Mnemonics

Cancer chemotherapy consists of a diverse group of drugs that destroy cancer cells through different mechanisms. Anticancer drugs are broadly classified into cytotoxic drugs, targeted therapy, and hormonal therapy. Understanding this classification is essential for B.Pharm, M.Pharm, Pharmacy License, Lok Sewa, and other competitive pharmacy examinations.

What are Anticancer Drugs?

Anticancer drugs (antineoplastic drugs) are medications used to prevent, destroy, or inhibit the growth and spread of malignant (cancer) cells. These drugs may act by:

• Damaging DNA
• Inhibiting DNA/RNA synthesis
• Preventing cell division
• Blocking growth factor receptors
• Modulating hormones responsible for tumor growth

Classification of Anticancer Drugs

1. Cytotoxic Drugs

Cytotoxic drugs directly kill rapidly dividing cells by interfering with DNA replication or cell division.

1. Alkylating Agents

These drugs form covalent bonds with DNA, causing cross-linking and inhibition of DNA replication.

Nitrogen Mustards

• Mechlorethamine
• Cyclophosphamide
• Ifosfamide
• Chlorambucil
• Melphalan

Ethylenimine

• Thiotepa

Alkyl Sulfonate

• Busulfan

Nitrosoureas

• Carmustine
• Lomustine

Triazines

• Dacarbazine
• Temozolomide

Methylhydrazine

• Procarbazine

1. Platinum Coordination Complexes

These agents act similarly to alkylating agents by producing DNA cross-links.

Examples:

• Cisplatin
• Carboplatin
• Oxaliplatin

1. Antimetabolites

Antimetabolites inhibit DNA synthesis by mimicking normal cellular metabolites.

Folate Antagonists

• Methotrexate
• Pemetrexed

Purine Antagonists

• 6-Mercaptopurine
• 6-Thioguanine
• Azathioprine
• Fludarabine

Pyrimidine Antagonists

• 5-Fluorouracil (5-FU)
• Capecitabine
• Cytarabine

1. Microtubule-Damaging Agents

These interfere with mitotic spindle formation during cell division.

Vinca Alkaloids

• Vincristine
• Vinblastine
• Vinorelbine

Taxanes

• Paclitaxel
• Docetaxel

Others

• Estramustine

1. Topoisomerase Inhibitors

These inhibit enzymes involved in DNA replication.

Topoisomerase II Inhibitor

• Etoposide

Topoisomerase I Inhibitors

• Topotecan
• Irinotecan

1. Antitumor Antibiotics

These interfere with DNA and RNA synthesis.

Examples:

• Actinomycin D
• Doxorubicin
• Daunorubicin
• Epirubicin
• Mitoxantrone
• Bleomycin
• Mitomycin C

1. Miscellaneous Cytotoxic Drugs

• Hydroxyurea
• L-Asparaginase
• Tretinoin
• Arsenic Trioxide

2. Targeted Therapy

Targeted drugs specifically attack molecular targets present in cancer cells while causing comparatively less damage to normal tissues.

Tyrosine Kinase Inhibitors (TKIs)

Examples:

• Imatinib
• Nilotinib

EGFR Inhibitors

Examples:

• Gefitinib
• Erlotinib
• Cetuximab

Angiogenesis Inhibitors

Prevent formation of new blood vessels supplying tumors.

Examples:

• Sunitinib
• Bevacizumab

Proteasome Inhibitor

Example:

• Bortezomib

Monoclonal Antibody

Example:

• Rituximab

3. Hormonal Therapy

Hormonal drugs are mainly used in hormone-dependent cancers such as breast and prostate cancer.

Glucocorticoids

• Prednisolone

Selective Estrogen Receptor Modulators (SERMs)

• Tamoxifen
• Toremifene

Aromatase Inhibitors

• Letrozole
• Anastrozole
• Exemestane

5α-Reductase Inhibitors

• Finasteride
• Dutasteride

Progestins

• Hydroxyprogesterone acetate

Estrogens

• Ethinyl Estradiol
• Fosfestrol

Selective Estrogen Receptor Down-Regulator (SERD)

• Fulvestrant

Antiandrogens

• Flutamide
• Bicalutamide

GnRH Analogues

• Nafarelin
• Leuprorelin
• Triptorelin

Quick Summary 

Easy Mnemonic

“A PAT TAM H”

• A – Alkylating agents
• P – Platinum compounds
• A – Antimetabolites
• T – Topoisomerase inhibitors
• T – Tubulin (Microtubule) inhibitors
• A – Antitumor antibiotics
• M – Miscellaneous drugs
• H – Hormonal therapy

Important Examination Points

• Cyclophosphamide is the most commonly used alkylating agent.
• Cisplatin is highly effective against testicular and ovarian cancers.
• Methotrexate is a folate antagonist.
• 5-Fluorouracil is a pyrimidine analogue.
• Vincristine causes peripheral neuropathy with minimal myelosuppression.
• Paclitaxel stabilizes microtubules and prevents their depolymerization.
• Doxorubicin is associated with dose-dependent cardiotoxicity.
• Bleomycin primarily causes pulmonary fibrosis.
• Imatinib is the drug of choice for chronic myeloid leukemia (CML).
• Tamoxifen is widely used in estrogen receptor-positive breast cancer.
• Letrozole and Anastrozole are first-line aromatase inhibitors in postmenopausal breast cancer.
• Toxicity of Methotrexate is minimized by Leucovorin (Folinic acid)
• Cyclophosphamide toxicity minimized by MESNA

Anticancer drugs are broadly classified into cytotoxic agents, targeted therapies, and hormonal therapies, each acting through distinct mechanisms to inhibit cancer growth. A clear understanding of their classification, mechanisms, and representative examples is essential for clinical practice and for success in pharmacy examinations such as the Nepal Pharmacy Council License Examination, Lok Sewa, B.Pharm, and M.Pharm entrance examinations. Mastering this classification also provides a strong foundation for studying individual anticancer drugs, their adverse effects, and therapeutic applications.