Targeted and Biological Cancer Therapies
Targeted and biological cancer therapies are anticancer agents that act on defined molecular features of tumour cells or on the host immune response, rather than on the broad mechanism of DNA damage and cell division that characterises classical cytotoxic chemotherapy. They include small-molecule inhibitors of signalling kinases, monoclonal antibodies, immune-checkpoint inhibitors, endocrine (hormone-directed) agents, and inhibitors of tumour blood-vessel formation.
Definition
Targeted and biological cancer therapies are antineoplastic drugs whose action is directed at a specific molecular target (such as a mutated kinase, a cell-surface receptor, an immune-regulatory checkpoint, a hormone receptor, or the angiogenic signalling axis) that the tumour depends on or that modulates antitumour immunity, in contrast to the non-selective cytotoxicity of conventional chemotherapy.
Scope
This area orients the reader to the major pharmacological classes that exploit cancer-specific molecular dependencies or immune mechanisms. It covers the conceptual contrast with cytotoxic chemotherapy, the principal drug classes and their general modes of action, and the role of predictive biomarkers in selecting therapy. The detailed pharmacology of each class is treated in the child topics; this entry is an orienting overview and is not clinical guidance.
Sub-topics
Core questions
- How do targeted and biological agents differ mechanistically from cytotoxic chemotherapy?
- What molecular dependencies (oncogene addiction, receptor overexpression, immune evasion) make a tumour susceptible to a given agent?
- How are predictive biomarkers used to match a therapy to a tumour?
- Why does resistance arise, and how do the major drug classes differ in their resistance patterns?
Key concepts
- Molecular target versus non-selective cytotoxicity
- Small-molecule inhibitors versus biologic (antibody) agents
- Predictive biomarkers and companion diagnostics
- Oncogene addiction
- Acquired and intrinsic resistance
- Endocrine (hormone-directed) therapy
- Tumour angiogenesis
- Immune-checkpoint blockade
Key theories
- Oncogene addiction
- Many tumours become dependent on a single dominant driver oncogene for survival, so that selective inhibition of that driver (for example BCR-ABL by imatinib) can produce disproportionate, sometimes durable, antitumour effects.
- Cancer immune evasion and checkpoint blockade
- Tumours can escape immune destruction by engaging inhibitory immune-checkpoint pathways; releasing these brakes with antibodies can restore antitumour T-cell activity, as first shown clinically with anti-CTLA-4 therapy.
Mechanisms
The agents grouped here share the strategy of acting on a defined molecular feature rather than on bulk proliferation. Small-molecule tyrosine kinase inhibitors occupy the ATP-binding pocket of dysregulated kinases and interrupt growth-signalling cascades. Monoclonal antibodies bind cell-surface antigens or soluble ligands, blocking receptor signalling and recruiting immune effector mechanisms. Immune-checkpoint inhibitors are antibodies that block inhibitory receptors such as CTLA-4 and PD-1, restoring T-cell-mediated antitumour responses. Endocrine therapies deprive hormone-dependent tumours of the receptor signalling that drives their growth. Angiogenesis inhibitors target the vascular signalling, chiefly the VEGF axis, on which growing tumours depend for their blood supply. Across these classes, the production of monoclonal antibodies of defined specificity by hybridoma technology was an enabling technical advance.
Clinical relevance
Targeted and biological therapies are central to contemporary medical oncology and underpin the practice of matching treatment to tumour biology through predictive biomarkers. This entry describes the pharmacological classes at a conceptual level to support understanding of how such therapies are categorised and how they act; it is reference-educational and is not a basis for individual diagnostic or treatment decisions.
Evidence & guidelines
The clinical foundations of this area rest on landmark randomised and single-arm trials, including the demonstration of imatinib activity in chronic myeloid leukaemia, of trastuzumab benefit in HER2-overexpressing breast cancer, of bevacizumab benefit in metastatic colorectal cancer, and of ipilimumab survival benefit in metastatic melanoma. These trials established the principle that molecularly or immunologically directed therapy can change outcomes when matched to the relevant tumour feature.
History
The field grew from two converging advances: the identification of specific oncogenic drivers and the technology to make targeted molecules. Köhler and Milstein's 1975 hybridoma method made monoclonal antibodies of defined specificity possible, seeding the biologics era. In oncology, imatinib's success against BCR-ABL-driven chronic myeloid leukaemia in 2001 became the proof of principle for small-molecule targeted therapy, while trastuzumab validated antibody targeting of an overexpressed receptor. Antiangiogenic therapy and, later, immune-checkpoint blockade extended the strategy to the tumour vasculature and to the host immune response.
Key figures
- Brian Druker
- Dennis Slamon
- Georges Köhler
- César Milstein
- James Allison
Related topics
Seminal works
- druker-2001
- slamon-2001
- hodi-2010
- kohler-milstein-1975
Frequently asked questions
- How do targeted therapies differ from conventional chemotherapy?
- Conventional chemotherapy damages DNA or interferes with cell division in all rapidly dividing cells, whereas targeted and biological therapies act on a specific molecular feature of the tumour or on the immune response, which can give greater selectivity for tumour-relevant biology.
- Why do these therapies often require biomarker testing before use?
- Because a targeted agent works only when its molecular target is present and relevant in the tumour, predictive biomarkers (for example receptor overexpression or a driver mutation) are used to identify the tumours likely to respond.