Phase Ib Clinical Trial of IGV-001 for Patients with Newly Diagnosed Glioblastoma

PURPOSE

Despite standard of care (SOC) established by Stupp, glioblastoma remains a uniformly poor prognosis. We evaluated IGV-001, which combines autologous glioblastoma tumor cells and an antisense oligonucleotide against IGF type 1 receptor (IMV-001), in newly diagnosed glioblastoma.

PATIENTS AND METHODS

This open-label protocol was approved by the Institutional Review Board at Thomas Jefferson University. Tumor cells collected during resection were treated ex vivo with IMV-001, encapsulated in biodiffusion chambers with additional IMV-001, irradiated, then implanted in abdominal acceptor sites. Patients were randomized to four exposure levels, and SOC was initiated 4-6 weeks later. On the basis of clinical improvements, randomization was halted after patient 23, and subsequent patients received only the highest exposure. Safety and tumor progression were primary and secondary objectives, respectively. Time-to-event outcomes were compared with the SOC arms of published studies.

RESULTS

Thirty-three patients were enrolled, and median follow-up was 3.1 years. Six patients had adverse events (grade ≤3) possibly related to IGV-001. Median progression-free survival (PFS) was 9.8 months in the intent-to-treat population (vs. SOC, 6.5 months; P = 0.0003). In IGV-001-treated patients who met Stupp-eligible criteria, PFS was 11.6 months overall (n = 22; P = 0.001) and 17.1 months at the highest exposure (n = 10; P = 0.0025). The greatest overall survival was observed in Stupp-eligible patients receiving the highest exposure (median, 38.2 months; P = 0.044). Stupp-eligible patients with methylated O⁶-methylguanine-DNA methyltransferase promoter (n = 10) demonstrated median PFS of 38.4 months (P = 0.0008). Evidence of immune activation was noted.

CONCLUSIONS

IGV-001 was well tolerated, PFS compared favorably with SOC, and evidence suggested an immune-mediated mechanism (ClinicalTrials.gov: NCT02507583).

Abstract CT038: Results of a Phase Ib trial of an autologous cell vaccine for newly diagnosed glioblastoma

Background: We evaluated an autologous cell vaccine, a combination of GBM tumor cells and an antisense molecule against insulin-like growth factor type 1 receptor DNA/mRNA (IGF-1R AS ODN), in adults with newly diagnosed GBM (NCT02507583).

Methods: Tumor cells collected during resection were treated ex vivo with IGF-1R AS ODN, encapsulated in biodiffusion chambers with IGF-1R AS ODN, irradiated, then implanted in an abdominal acceptor site on the first post-operative day. Four vaccine exposures were evaluated: lowest (10 chambers implanted for 24 hours); lower (10 / 48 hours); higher (20 / 24 hours); and highest (20 / 48 hours). Standard of care (SOC; ie, radiotherapy and temozolomide) was initiated after 4-6 weeks. Randomization was halted after patient 23 and subsequent patients received the highest exposure. Evaluation of safety and tumor responses were the primary and secondary objectives, respectively. Exploratory objectives included assessment of progression-free survival (PFS) and overall survival (OS). The SOC comparator group was an antecedent cohort of 35 newly diagnosed, GBM patients treated at the same center.

Results: Thirty-three patients were enrolled between September 1, 2015 and March 1, 2018. Six, 5, 5, and 17 patients received the lowest, lower, higher, and highest exposures. Median (range) follow-up was 13 (4-39) months. As of the January 1, 2019 cutoff, no vaccine-related adverse events were observed. Seventeen of 33 (51.5%) remained progression-free, 12 of whom are alive and functioning well. The autologous cell vaccine significantly prolonged PFS and OS vs. SOC (Table). Survival advantages were conferred by the highest exposure to the autologous cell vaccine and good T cell function prior to surgery.

Conclusions: This vaccine was well-tolerated and prolonged PFS and OS when compared with SOC alone.

Table.Survival outcomes in patients receiving vaccine vs. SOC aloneTreatment group2 yr OS estimateMedian OS (mo)p-value v. SOC for OS1 yr PFS estimateMedian PFS estimatep-value v. SOC for PFSVaccine highest dose (N=17)34%21.9.04141%10.4.031Vaccine all (ITT, N=33)31%17.3.01642%9.8.018SOC (n=35)14%12.128%6.9

Citation Format: David W. Andrews, Samantha Garcia, Kevin D. Judy, Larry A. Harshyne, Sanjana Govindarajan, Lawrence Kenyon, Kiran Talekar, Adam Flanders, Kofi-Buaku Atsina, Lyndon Kim, Nina L. Martinez, Wenyin Shi, Maria Werner-Wasik, Mikhail Prosniak, Mark T. Curtis, Rhonda Kean, Emily Bongiorno, Sami Sauma, Kara Pigott, Charles B. Scott, D Craig Hooper. Results of a Phase Ib trial of an autologous cell vaccine for newly diagnosed glioblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr CT038.

Identification of viral genomic elements responsible for rabies virus neuroinvasiveness

Attenuated tissue culture-adapted and natural street rabies virus (RV) strains differ greatly in their neuroinvasiveness. To identify the elements responsible for the ability of an RV to enter the CNS from a peripheral site and to cause lethal neurological disease, we constructed a full-length cDNA clone of silver-haired bat-associated RV (SHBRV) strain 18 and exchanged the genes encoding RV proteins and genomic sequences of this highly neuroinvasive RV strain with those of a highly attenuated nonneuroinvasive RV vaccine strain (SN0). Analysis of the recombinant RV (SB0), which was recovered from SHBRV-18 cDNA, indicated that this RV is phenotypically indistinguishable from WT SHBRV-18. Characterization of the chimeric viruses revealed that in addition to the RV glycoprotein, which plays a predominant role in the ability of an RV to invade the CNS from a peripheral site, viral elements such as the trailer sequence, the RV polymerase, and the pseudogene contribute to RV neuroinvasiveness. Analyses also revealed that neuroinvasiveness of an RV correlates inversely with the time necessary for internalization of RV virions and with the capacity of the virus to grow in neuroblastoma cells.

Development of a cocktail of recombinant-expressed human rabies virus-neutralizing monoclonal antibodies for postexposure prophylaxis of rabies

To provide a cost-effective and safe replacement for human rabies immunoglobulin (HRIG), we used DNA recombinant technology to express 3 human rabies virus-neutralizing human monoclonal antibodies (huMAbs) in a rhabdovirus vector (RhV). Infection of either baby hamster kidney cells or CHO cells, with the resulting RhV-huMAb recombinant viruses, yielded high-level production (< or =40 micro g/mL/48 h) of RhV recombinant-expressed huMAbs (rhuMAbs) that differ in both isotype and epitope-recognition specificity. A cocktail of these rhuMAbs neutralizes several fixed and street wild-type rabies viruses (RVs). Mice and hamsters treated only once with this rhuMAb cocktail after infection with a lethal dose of RV were protected. In the mouse models, the postexposure prophylaxis (PEP) efficacy obtained with the rhuMAb cocktail was comparable to that obtained with HRIG, a finding strongly suggesting that rhuMAbs should be given serious consideration for use in future PEP of humans.

Differential expression of growth factors at the cellular level in virus-infected brain

The contribution of host factors to rabies virus (RV) transcription/replication and axonal/transsynaptic spread is largely unknown. We previously identified several host genes that are up-regulated in the mouse brain during RV infection, including neuroleukin, which is involved in neuronal growth and survival, cell motility, and differentiation, and fibroblast growth factor homologous factor 4 (FHF4), which has been implicated in limb and nervous system development. In this study, we used real-time quantitative RT-PCR to assess the expression of mRNAs specific for neuroleukin, the two isoforms of FHF4 (FHF4-1a and -1b) encoded by the FHF4 gene, and N protein of RV in neurons and astrocytes isolated by laser capture microdissection from mouse brains infected with the laboratory-adapted RV strain CVS-N2c or with a street RV of silver-haired bat origin. Differences in the gene expression patterns suggest that the capacity of RV strains to infect nonneuronal cells and differentially modulate host gene expression may be important in virus replication and spread in the CNS.

Silver-haired bat rabies virus variant does not induce apoptosis in the brain of experimentally infected mice

To examine whether induction of apoptosis plays a role in the pathogenesis of street rabies, we compared the distribution of viral antigens, histopathology, and the induction of apoptosis in the brain of mice infected with a street rabies virus (silver-haired bat rabies virus, SHBRV) and with a mouse-adapted laboratory rabies virus strain (challenge virus standard, CVS-24). Inflammation was identified in the meninges, but not in the parenchyma of the brain of mice infected with either CVS-24 or SHBRV. Necrosis was present in numerous cortical, hippocampal, and Purkinje neurons in CVS-24-infected mice, but only minimal necrosis was identified in mice infected with SHBRV. Likewise, extensive terminal deoxynucleotidyl transferase-mediated dUTP-digoxigenin nick end-labeling (TUNEL) staining was observed in the brain of mice infected with CVS-24 but little or none in the brain of mice infected with SHBRV. Rabies virus antigens were distributed similarly in the CNS infected with either virus. However, the expression of the glycoprotein (G) is more widespread and the staining of G is generally stronger in CVS- than SHBRV-infected mice, whereas the expression of rabies virus nucleoprotein (N) is similar in mice infected with either CVS or SHBRV. The positive TUNEL staining thus correlates with the high level of G expression in CVS-infected mouse brain. Northern blot hybridization revealed that the ratio between the N and G transcripts is similar in brains infected with either virus, indicating that the reduced expression of G protein is not caused by reduced transcription in SHBRV-infected animals. Taken together, these observations suggest that apoptosis is not an essential pathogenic mechanism for the outcome of a street rabies virus infection and that other pathologic processes may contribute to the profound neuronal dysfunction characteristic of street rabies.

Effect of rabies virus infection on gene expression in mouse brain

A variety of molecular genetic approaches were used to study the effect of rabies virus (RV) infection on host gene expression in mouse brain. The down-regulation of gene expression was found to be a major effect of RV infection by using subtraction hybridization. However, a combination of techniques identified approximately 39 genes activated by infection. These included genes involved in regulation of cell metabolism, protein synthesis, synaptic activity, and cell growth and differentiation. Northern blot analysis to monitor temporal activation of several of these genes following infection revealed essentially two patterns of activation: (i) an early response with up-regulation beginning within 3 days after infection and correlating with transcription of RV nuclear protein; and (ii) a late response with enhanced expression occurring at days 6-7 after infection and associated with peak RV replication. The gene activation patterns and the known functions of their products suggest that a number of host genes may be involved in the replication and spread of RV in the brain.

Increased G1 cyclin/cdk activity in cells overexpressing the candidate oncogene, MCT-1

We have recently identified a novel candidate oncogene, MCT-1, in the HUT 78 T-cell line. When overexpressed in NIH3T3 fibroblasts, the MCT-1 gene shortens the G1 phase of the cell cycle and promotes anchorage-independent growth. Progression of cells through a late G1 phase restriction point is regulated by G1 cyclins whose phosphorylation of the retinoblastoma gene product facilitates entry into S phase. Deregulated expression of G1 cyclins and their cognate cdk partners is often found in human tumor cells. In order to address the potential relationship of MCT-1 to cell cycle regulatory molecules, we analyzed the ability of MCT-1 overexpression to modulate cdk4 and cdk6 kinase activity in NIH3T3 fibroblasts constitutively overexpressing MCT-1. We observed an increase in the kinase activity of both cdk4 and cdk6 in asynchronously growing transformed cells compared with the parent cells. This increased kinase activity was accompanied by an elevated level of cyclin D1 protein and increased G1 cyclin/cdk complex formation. We also observed a correlation between increased protein levels of MCT-1 with cyclin D1 expression in a panel of lymphoid cell lines derived from T-cell malignancies. These results demonstrate that constitutive expression of MCT-1 is associated with deregulation of protein kinase-mediated G1 phase checkpoints.

Retinoic acid modulates a bimodal effect on cell cycle progression in human adult T-cell leukemia cells

Retinoids, the analogues of vitamin A, have a broad range of effects on different cell types. One biologically active form of vitamin A is all-trans-retinoic acid (ATRA), which binds to retinoic acid receptors, as does its intracellular metabolite, 9-cis-RA. Earlier studies have documented G1 cell cycle arrest and the induction of apoptosis in human adult T-cell leukemia cells after ATRA treatment. Previous work exploring the growth-inhibitory activity of ATRA in human malignancies has implicated several mechanisms that can arrest cells in the G1 phase of the cell cycle, including activation of p21Waf1 and inhibition of cyclin D1 expression. Therefore, we decided to examine the effects of ATRA exposure on G1 cell cycle components in human adult T-cell leukemia cells. Our data demonstrate a correlation between cyclin/cyclin-dependent kinase activity and subunit complex formation with duration of drug exposure. We also observed an increase in p53 protein levels that were not associated with an increase in p21Waf1 levels. Furthermore, we observed a differential effect on cell cycle progression that was temporally related to length of ATRA exposure. These observations, consistent with a bimodal effect of ATRA on cell cycle progression, may have important implications for the clinical application of ATRA.

A novel candidate oncogene, MCT-1, is involved in cell cycle progression

Using the arbitrarily primed-PCR (AP-PCR) assay to detect genetic abnormalities that occur in a panel of lymphoid cell lines, we identified an amplified stretch of genomic DNA that contained a putative open reading frame. Northern blot analysis with this genomic clone revealed widespread low level expression in normal human tissue. The full cDNA sequence was obtained with no significant homology to any known genes in the genome database. We termed this novel gene with multiple copies in a T-cell malignancy as MCT-1. MCT-1 was localized to the long arm of chromosome Xq22-24 by flourescence in situ hybridization analysis. Although there was no significant homology at the primary sequence level, there was a limited degree of amino acid homology with a domain of cyclin H that appears to specify protein-protein complexes. This relationship between MCT-1 and cyclin H implied a potential role for MCT-1 in cell cycle regulation. Overexpression of MCT-1 increased the proliferative rate of cells by decreasing the length of the G1 phase without a reciprocal increase in the S and G2-M phases. Recent work has established the role of cell cycle regulatory molecules in the development of certain human malignancies. Therefore, we investigated the transforming ability of MCT-1 overexpression using soft agar growth assays and demonstrated that only MCT-1-overexpressing cells were able to establish colonies. Taken together, MCT-1 is a novel candidate oncogene with homology to a protein-protein binding domain of cyclin H.