[Show abstract][Hide abstract] ABSTRACT: Immunostimulating oligodeoxynucleotides containing CpG motifs (CpG-ODN) have shown promising efficacy in cancer models when injected locally. In a phase I clinical trial, intratumoral infusions of CpG-ODN in glioblastoma (GBM) patients were well tolerated at doses up to 20 mg. This phase II trial was designed to study the efficacy of a local treatment by CpG-ODN in patients with recurrent GBMs. Patients with recurrent GBM occurring at least 3 months after radiotherapy, and previously treated with 1 or 2 regimens of chemotherapy received 20 mg of CpG-ODN (CpG-28) by convection-enhanced delivery. The primary endpoint was the percentage of patients without tumor progression 6 months after inclusion. Secondary endpoints were tolerance, survival, and radiological response. Thirty-four patients were enrolled in two centers between November 2004 and March 2006. Thirty-one patients received CpG-ODN treatment. The progression-free survival (PFS) at 6 months was 19%. One partial response and 3 minor responses were observed. The median overall survival was 28 weeks. Eight patients (24%) were alive 1 year after inclusion and 5 patients (15%) were alive after 2 years. Treatment was usually well tolerated. As reported previously, the most common toxicities were lymphopenia, mild fever, seizures, and transient neurological worsening. Despite a few cases showing a radiological response, CpG-28 showed modest activity on the 6-month PFS in this patient population. The molecular or clinical characteristics of a subgroup of patients that could potentially benefit from such an approach remain to be defined.