# ATR

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

## TL;DR

ATR is a DNA-damage alarm kinase. Blocking it makes tumours with broken repair systems collapse under their own replication stress.

## Summary

ATR is a PI3K-like kinase activated by single-stranded DNA at stalled replication forks; it signals through CHK1 to pause the cell cycle and stabilise forks. Tumours with ATM loss, high replication stress or PARP-inhibitor resistance depend on this alarm, so blocking ATR can make them collapse under their own replication stress. ATR inhibitors (ceralasertib, camonsertib, elimusertib) are in phase 2 and 3, notably ceralasertib with durvalumab in NSCLC after immunotherapy (LATIFY) and in ATM-deficient tumours; ATM loss or mutation is found in about 5 to 10 percent of lung adenocarcinomas. No approval has yet been granted, and myelosuppression limits how freely ATR inhibitors can be combined with chemotherapy or PARP inhibitors. Defining a predictive biomarker beyond ATM loss is the key open problem. For a newcomer: ATR is a DNA-damage alarm that broken-repair tumours cannot afford to lose.

## Fields

- Kind: Target
- Last checked: 2026-09-04
- Tags: ddr
- Symbol: ATR
- Class: kinase
- Biology: PI3K-like kinase activated by single-stranded DNA at stalled forks; signals via CHK1.
- Where found: Tumours with ATM loss, replication stress, or PARP-inhibitor resistance

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/Ataxia_telangiectasia_and_Rad3_related
- Wikipedia: https://en.wikipedia.org/wiki/Ataxia_telangiectasia_and_Rad3_related

## Connected records

- cancers: [Non-small-cell lung cancer](https://onco.cc/cancers/nsclc/), [Ovarian cancer](https://onco.cc/cancers/ovarian/), [p53-abnormal endometrial cancer, including uterine serous carcinoma](https://onco.cc/cancers/endometrial-p53-abnormal/), [Platinum-sensitive ovarian cancer](https://onco.cc/cancers/platinum-sensitive-ovarian-cancer/), [Small-cell lung cancer](https://onco.cc/cancers/sclc/), [Triple-negative breast cancer (TNBC)](https://onco.cc/cancers/tnbc/), [Uterine carcinosarcoma](https://onco.cc/cancers/uterine-carcinosarcoma/)
- drugs: [Ceralasertib](https://onco.cc/drugs/ceralasertib/)
- companies: [Aprea Therapeutics](https://onco.cc/companies/aprea-therapeutics/), [Artios Pharma](https://onco.cc/companies/artios-pharma/), [Callio Therapeutics](https://onco.cc/companies/callio-therapeutics/), [Repare Therapeutics](https://onco.cc/companies/repare-therapeutics/)
- pathways: [Base excision repair, PARP & alkylation damage](https://onco.cc/pathways/base-excision-repair-parp/), [DNA damage response & homologous recombination](https://onco.cc/pathways/ddr/), [DNA replication & origin licensing](https://onco.cc/pathways/dna-replication-licensing/), [DNA replication stress](https://onco.cc/pathways/replication-stress/), [Double-strand break repair: HR versus end joining](https://onco.cc/pathways/homologous-recombination-repair/), [p53 / RB / cell-cycle checkpoint](https://onco.cc/pathways/p53-cell-cycle/), [SWI/SNF chromatin remodelling](https://onco.cc/pathways/swi-snf-chromatin/), [Synthetic lethality: paired dependencies](https://onco.cc/pathways/synthetic-lethality-map/), [Telomere maintenance & replicative immortality](https://onco.cc/pathways/telomere-maintenance/), [The p53 network (guardian of the genome)](https://onco.cc/pathways/p53-mdm2-axis/)
- ideas: [Subtype-directed therapy for SCLC (ASCL1 / NEUROD1 / POU2F3 / inflamed)](https://onco.cc/ideas/idea-sclc-subtype-directed/)
- trials: [PHOENIX DDR/Anti-PD-L1](https://onco.cc/trials/phoenix/)
- key papers: [Bao 2006: glioma stem cells resist radiotherapy by activating the DNA damage response](https://onco.cc/key-papers/paper-bao-glioma-stem-cells-radioresistance-nature-2006/), [Genomic characterization of biliary tract cancers identifies driver genes and predisposing mutations](https://onco.cc/key-papers/paper-wardell-biliary-drivers-germline-j-hepatol-2018/)
- technologies: [ATR and CHK1 inhibitors](https://onco.cc/technologies/atr-chk1-inhibitors/), [Radioligand plus DNA-repair inhibitor combinations](https://onco.cc/technologies/radionuclide-parp-combination/), [Synthetic lethality approaches](https://onco.cc/technologies/synthetic-lethality-approaches/)
- people: [Alan D. D'Andrea](https://onco.cc/people/alan-dandrea/)
- terms: [Checkpoint (two meanings)](https://onco.cc/terms/checkpoint/), [Enabling characteristic: genome instability and mutation](https://onco.cc/terms/genome-instability-mutation/)

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