O6-Benzylguanine (O6-BG) is a synthetic derivative of guanine. It is an antineoplastic agent. It exerts its effect by acting as a suicide inhibitor of the enzyme O6-alkylguanine-DNA alkyltransferase which leads to interruption of DNA repair. O6-BG was used clinically in combination with the alkylating agent temozolomide for glioblastoma, however the combination was found to be overly toxic without adding significant benefit.[1][2][3]

IUPAC name
Other names
6-(Benzyloxy)guanine; 6-O-Benzylguanine; O(6)-bGua; O6-BG
3D model (JSmol)
ECHA InfoCard 100.161.788
Molar mass 241.254 g·mol−1
Density 1.432 g/mL
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

O6-BG is also used as a biochemical tool in the study of DNA repair mechanisms.


  1. ^ Quinn, JA; Desjardins, A; Weingart, J; Brem, H; Dolan, ME; Delaney, SM; Vredenburgh, J; Rich, J; et al. (2005). "Phase I trial of temozolomide plus O6-benzylguanine for patients with recurrent or progressive malignant glioma". Journal of Clinical Oncology. 23 (28): 7178–87. doi:10.1200/JCO.2005.06.502. PMID 16192602.
  2. ^ Quinn, J. A.; Jiang, S. X.; Reardon, D. A.; Desjardins, A.; Vredenburgh, J. J.; Rich, J. N.; Gururangan, S.; Friedman, A. H.; et al. (2009). "Phase II Trial of Temozolomide Plus O6-Benzylguanine in Adults with Recurrent, Temozolomide-Resistant Malignant Glioma". Journal of Clinical Oncology. 27 (8): 1262–7. doi:10.1200/JCO.2008.18.8417. PMC 2667825. PMID 19204199.
  3. ^ Blumenthal, Deborah T. (2015). "A phase III study of radiation therapy (RT) and O6-benzylguanine, (O6-BG) plus BCNU versus RT and BCNU alone and methylation status in newly-diagnosed glioblastoma (GBM) and gliosarcoma: Southwest Oncology Group (SWOG) Study S0001". International Journal of Clinical Oncology. 20: 650–8. doi:10.1007/s10147-014-0769-0. PMC 4465052. PMID 25407559.

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