# Half-life

Source: https://onco.cc/terms/half-life/  
OnCo record `half-life` (Term). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

The time it takes for the amount of a drug in the blood to fall by half. It sets how often a drug must be given: hours to a day for small molecules such as kinase inhibitors, so they are taken daily, and two to four weeks for antibodies, so they are given every three or six weeks.

## Summary

Small molecules are typically cleared by the liver and kidneys within hours to a day, so kinase inhibitors are taken daily; antibodies are protected from breakdown by recycling receptors and persist for two to four weeks, allowing dosing every three or six weeks. Half-life shapes both benefit and harm: a long-lived checkpoint inhibitor keeps working, and keeps causing immune side effects, for months after the last dose, while a radioactive drug's physical half-life (6.6 days for lutetium-177, 10 days for actinium-225) determines how long it irradiates the tumour. Pharmacokinetics is the study of these processes, and matching dose and schedule to them is central to dose optimisation.

## Fields

- Kind: Term
- Last checked: 2026-09-09
- Also known as: half-lives; half life; plasma half-life; elimination half-life; pharmacokinetics; pharmacokinetic; PK; cleared from the body; drug exposure; peak concentration; Cmax; AUC; steady state; steady-state

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/Biological_half-life
- Wikipedia: https://en.wikipedia.org/wiki/Biological_half-life

## Connected records

- terms: [Alpha vs beta emitters](https://onco.cc/terms/alpha-vs-beta/), [Antibody](https://onco.cc/terms/antibody/), [Dose](https://onco.cc/terms/dose/), [Dosimetry](https://onco.cc/terms/dosimetry/), [Fc engineering / effector function](https://onco.cc/terms/fc-effector/), [Prodrug](https://onco.cc/terms/prodrug/)
- technologies: [Monoclonal antibodies](https://onco.cc/technologies/monoclonal-antibody/), [Radioligand therapy (beta emitters)](https://onco.cc/technologies/radioligand-therapy/)

---
JSON: https://onco.cc/api/v1/entities/half-life.json