Abstract 6519: Dendritic cell vaccine cell numbers and survival in patients with primary glioblastoma
Authors: Dillman Robert O. , Nistor Gabriel I. , Godding Krystal , Robles Rockelle , Keirstead Hans S. 
Published: March 2024

Standard glioblastoma (GBM) treatment is associated with poor survival. A promising novel immunotherapy consists of autologous dendritic cells (DC) pulsed with autologous tumor antigens (ATA) from a lysate of irradiated self-renewing autologous cancer cells. An open-label, phase 2 trial was conducted in 57 patients with primary GBM. Here we report correlations between survival and DC-ATA doses. Two autologous intermediate products were manufactured for each patient: a tumor cell line established from resected GBM, and DC differentiated from cryopreserved peripheral blood monocytes (MC). Patients were enrolled prior to standard radiation therapy (RT) and temozolomide (TMZ) chemotherapy. DC-ATA were manufactured during RT/TMZ, divided into individual doses, then cryopreserved in liquid nitrogen. For each patient-specific vaccine batch, cell numbers were calculated using a hemocytometer; viability was determined before cryopreservation (cryo) using trypan blue and post-cryo using 7ADD per flow cytometry. After RT/TMZ, up to 8 doses were injected s.c. concurrent with TMZ over 6 months. Patients were grouped into tertiles based on DC-ATA cell numbers and survival. Prism 10.03 was used to generate survival curves and calculate correlation coefficients and log-rank and T-Test comparisons. As previously reported, cell line success rate was 71/73, sufficient MC numbers were collected by leukapheresis for 63/65; DC-ATA was successfully manufactured for 60/60; 57 patients were treated; median progression free survival (PFS) and overall survival (OS) were 10.4 and 16.0 months respectively. Correlations were strong between total and viable DC-ATA pre-cryo (0.97, p&lt;0.0001) and post-cryo (0.95, p&lt;0.0001), but weaker between DC-ATA pre- and post-cryo (0.30, p=0.02), and between viable DC-ATA pre- and post-cryo (0.37, p=0.004). When patients were grouped by OS tertiles, medians were 9.8, 18.1, and more than 36 months. There were no differences in the average millions (M) of DC-ATA pre-cryo (10.0, 9.7, 9.6), viable DC-ATA pre-cryo (8.5, 7.8, 7.9), DC-ATA post-cryo (9.0, 10.3, 10.8) or viable DC-ATA post-cryo (6.0, 7.3, 7.4). Similarly, when patients were grouped into tertiles by DC-ATA numbers, there were no differences in OS curves associated with DC-ATA pre-cryo, viable DC-ATA pre-cryo, DC-ATA post-cryo, or viable DC-ATA post-cryo. Pre-cryo viable DC-ATA numbers ranged from 0.27 to 27.0 M. An ineffective dose was not identified; pre-cryo viable DC-ATA doses of less than 2M were associated with OS of 10.4, 13.0, 13.3, and 36.4+ months. Also, there was no OS difference by number of MC used to manufacture DC or by number of DC manufactured. In conclusion, there was no evidence for a dose/response relationship between DC-ATA dose and OS for any of the parameters tested. This data supports that pre-cryo cell counts can be used to establish treatment doses. Pre-cryo viable cell counts of 2M DC-ATA per dose seem sufficient.

Citation Format: Robert O. Dillman, Gabriel I. Nistor, Krystal Godding, Rockelle Robles, Hans S. Keirstead. Dendritic cell vaccine cell numbers and survival in patients with primary glioblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6519.