Study patients

Patients were eligible for this study if they were 18–70 years of age and had newly diagnosed glioblastoma, as determined through central pathology review. Other eligibility criteria included Karnofsky Performance Score (KPS) of ≥ 70 [20], adequate bone marrow, liver, and renal function, life expectancy of ≥ 8 weeks, no other prior malignancy within the last 5 years, no active viral infections, and sufficient resected tumor material to produce the autologous vaccine. Patients were excluded if they already had apparent early disease progression/recurrence or pseudo-progression at the baseline visit, similar to the inclusion/exclusion criteria of other recent trials in glioblastoma [4, 21].

Study design and treatments

We conducted this study at over 80 sites in 4 countries: the US, Canada, Germany, and the UK. Patient recruitment was initiated in 2007, and was paused from 2009 to 2011 for economic reasons. The midpoint of enrollment was reached in May of 2014, and the final patient was enrolled in November of 2015. The protocol was approved by the required independent ethics committees and institutional review boards. Written consent was obtained from all patients participating in the trial.

All patients underwent surgical resection and 6 weeks of chemoradiotherapy per SOC, prior to enrollment and randomization in the study.

Randomization was performed centrally and was stratified by clinical site and MGMT (O6-methylguanine-DNA methyltransferase) gene promoter methylation status, which was determined by a central laboratory. Patients were randomized 2:1 to SOC plus autologous DC vaccine (DCVax-L; n = 232) or SOC plus placebo (n = 99). PBMCs were used as placebo control as these cells are visually indistinguishable from DC and are considered immunologically inactive. Patients in both arms continued to receive monthly adjuvant temozolomide (150–200 mg/m2/day × 5 days every 28 days), interspersed with the DC vaccine or placebo treatments administered on Days 0, 10 and 20, then Months 2, 4 and 8, and thereafter at 6-month intervals starting at month 12. Each DCVax-L treatment involved a dose of 2.5 million autologous tumor lysate-pulsed DCs administered intradermally in the upper arm, alternating arms between injection visits.

All patients were allowed to receive DCVax-L following tumor progression/recurrence, as well as other approved treatments per local practice. All parties (investigators, patients and sponsor) remained blinded as to which treatment each patient had received prior to crossover. All patients who chose this option were given the active treatment on a re-start schedule with immunizations at Days 0, 10 and 20, and then months 2, 4 and 8, and every 6 months thereafter beginning with month 12, with Day 0 being the day of the first vaccination post progression. To date, DCVax-L has been shipped for 286 patients (86.4%) in the trial.

Both the study treatment (DCVax-L) and placebo (PBMC) were prepared by Cognate BioServices, Inc. for all patients in the US and Canada, and by Cognate and the Fraunhofer Institute for Cell Therapy together for patients in Europe, during the chemoradiotherapy period before the baseline visit. The production of DCVax-L involved processing the resected tumor tissue into a lysate, and then collection, purification, differentiation, activation and loading of the autologous DCs. In general, approximately 2 g of tumor tissue was needed to produce the full ten doses for the 36-month treatment and follow-up schedule. The vaccine was aliquoted in individual doses and cryopreserved at < 150 °C [22]. The doses were stored centrally, and shipped individually to the clinical trial sites.

Assessments

Baseline assessments included physical examination, neurological examination, vitals, KPS, MRI of brain with and without contrast, hematology (CBC with differential, platelets), and serum chemistries (calcium, magnesium, SGOT, SGPT, alkaline phosphatase, LDH, total bilirubin, BUN, creatinine, electrolytes, glucose). Blood was collected for serum markers of autoimmune disease (anti-DNA) and immune monitoring, at the baseline visit and at treatment visits throughout the trial. MRI brain scans were performed every 2 months, per SOC, after the baseline MRI until radiological tumor progression. All MRI scans were evaluated centrally by 2 blinded independent radiologists, with adjudication by a third such radiologist if needed.

Adverse events were recorded prospectively according to the National Cancer Institute’s Common Terminology Criteria (version 3.0 NCI CTC), until 2 months after the last study treatment. Patients are followed for OS until death.

Statistical analyses

The study’s primary endpoint is PFS, and the secondary endpoint is OS. PFS has not yet been evaluated for this publication and will be the subject of later analyses to allow for central, multi-factorial assessment by an expert panel, using criteria currently emerging as appropriate for immune therapy in this patient population where progression can be complex to determine and pseudo-progression is a known confounding phenomenon. Analysis of the blinded interim data on OS of the ITT population (using SAS version 9.4) was performed 34 months after the midpoint of patient enrollment, and 16 months after the last patient was enrolled and randomized.

General descriptive statistics include the number of observed values, mean, standard deviation, median, and range values for continuous measures. For categorical variables, the number and percentage of subjects with a specific level of the variable are reported. For survival analyses, Kaplan–Meier (KM) curves were generated, yielding estimates of median survival times, along with the two-sided confidence intervals (95% CIs) and estimates of survival at specific time points.