PBTC Phase 2 Study Results for Temozolomide/06-Benzylguanine

An abstract was released ahead of print for a phase 2 Pediatric Brain  Tumor Consortium study on recurrent/progressive high-grade gliomas and brainstem gliomas utilizing the combination of temozolomide and 06-benzylguanine (06 BG).  The study was initially put up on clinicaltrials.gov in January 2006.

O6-Benzylguanine and Temozolomide in Treating Young Patients With Recurrent or Progressive Gliomas or Brain Stem Tumors

http://clinicaltrial.gov/ct2/show/NCT00275002?term=06+temozolomide&rank=10

The thought was that the two agents may work differently to stop tumor growth and that combined chemotherapy might kill more cells.   Temozolomide is an alkylating agent that interferes with DNA replication.  This mechanism of action has seemed dependant on the ability to methylate DNA primarily at the N7 of 0-6 position on guanine.  Some cells were found to be able to repair this DNA damage.  The hope that O6 BG might overcome some of that repair issue.

Of the 41 children evaluated, 16 had brainstem gliomas.  There were no sustained objective responses with any in the brainstem glioma group, however, one patient had long term stable disease of more than 6 courses (28 day course). 

It was concluded that this combination “did not achieve target response rate for pediatric patients with recurrent or progressive high grade glioma or brainstem glioma.”

A phase II study of O6-benzylguanine and temozolomide in pediatric patients with recurrent or progressive high-grade gliomas and brainstem gliomas: a Pediatric Brain Tumor Consortium study   
http://www.ncbi.nlm.nih.gov/pubmed/21968943