The use of oncolytic viruses in cancer therapy has the same appeal as immunotherapy, and accumulating evidence is now showing that much of the therapeutic effect of oncolytic viral therapy is mediated through the resulting immune response. The following oncolytic viral therapies have reported clinical results in brain tumor patients.
The intra-tumoral infusion of a genetically-engineered poliovirus, called PVS-RIPO, as a therapy for brain cancer was pioneered by Matthias Gromeier at Duke University, during more than 10 years of research. The modified virus is currently the subject of a phase I trial for recurrent glioblastoma at the Preston Robert Tisch Brain Tumor Center at Duke.
PVS-RIPO is an engineered form of poliovirus which has no disease causing ability due to the splicing of DNA from a cold-causing rhinovirus into the poliovirus genome. As the poliovirus receptor is present on most tumour cells, the virus selectively enters and kills tumour cells, while sparing normal tissue. No nerve cell killing or evidence of poliomyelitis has been observed. Infection of tumour cells by the virus is expected to arouse a tumour-specific immune response, in addition to the direct killing of tumour cells by the virus.
In the phase I trial at Duke, adult patients with recurrent supratentorial glioblastoma, 1-5 cm in diameter, with a KPS over 70 may be eligible. PVS-RIPO is infused directly into the brain by a convection enhanced delivery system. Some preliminary trial data will be presented at the upcoming 2014 annual meeting of ASCO. The already published abstract reveals that 10 patients have been treated to date, at dose levels 1-5. The prolonged steroid use in five of seven patients at dose levels 3-5 indicate that dose level 2 is likely the optimal dose. Eight of ten patients are still alive – the two patients that died had previous disease progression on Avastin (bevacizumab), known to be a precarious situation, with few therapies having effect post-Avastin failure. At the time of the abstract publication, the first two treated patients were still alive at 20 and 19 months post-PVS-RIPO treatment.
The first patient in this trial, Stephanie Lipscomb, was featured in the May 5, 2014 issue of People magazine, in an article titled “Killing Cancer with Polio”. Diagnosed at the age of 20 with glioblastoma, she underwent conventional treatments, including radiation and chemotherapy, and had disease progression months later, a not unusual course of events. Given six months to live without further effective treatments, her doctors then presented her with another option: the chance to join the newly opened PVS-RIPO trial. She immediately said yes, and underwent the viral infusion in May 2012. Two years later, she is symptom-free and in “excellent health”.
The second patient treated in this trial, Fritz Andersen, wrote a short memoir of his experiences with GBM for the Washington Post newspaper. This was published in September 2013, over a year since his treatment in the PVS-RIPO trial. He was still without tumour regrowth at that time.
A phase II/III trial for recurrent glioblastoma is already being planned, in addition to plans for trials for pediatric brain tumours and trials for other tumour types. How quickly these proceed likely depends on the outcome of the current phase I trial, with an estimated primary completion date of January 2015. This form of virotherapy could represent a new highly effective option which is much needed by this patient population.
A 60 minutes television special aired on March 29, 2015 provides the most up-to-date information on how the PVS-RIPO trial is going and introduces us to several of the patients treated on the trial. 22 patients have been treated on this trial as of March 2015, with six different viral dosings having been tried. 11 patients are still alive and being followed-up. Seven patients have survived at least a year beyond the viral infusion, with three of these patients still alive at 21, 33 and 34 months. Most remarkable are the complete and durable remissions as seen in Stephanie Lipscomb (patient #1, 34 months from infusion) and Fritz Andersen (patient #2, 33 months from infusion), leading several of the Duke researchers to make statements to the effect that this is the most promising therapy they’ve seen during their long careers.
May 25, 2015 interview with Darrel Bigner about the progress of the trial.
DNX-2401 is a replicating oncolytic virus specially designed to treat glioblastoma by DNAtrix, a biotech company with offices in Houston, Texas, and San Diego, California. DNX-2401 is directly injected into the tumour, where it selectively invades and kills tumour cells, which rupture and stimulate an additional immune response.
There are currently four DNX-2401 trials underway or completed. The first (NCT00805376) is a completed phase I trial for recurrent malignant glioma, conducted at MD Anderson Cancer Center in Texas. The second (NCT01956734), a phase I trial for recurrent glioblastoma, has been completed in Spain. The third (NCT02197169) is a phase I trial of DNX-2401 active, but no longer recruiting in Florida, Ohio and Texas. The fourth trial for recurrent glioblastoma is combining DNX-2401 with the PD-1 antibody pembrolizumab (Keytruda), and is recruiting in Arkansas, New York, Ohio, Utah, and Toronto Canada (NCT02798406).
Preliminary outcome data from the ongoing DNX-2401 trial at MD Anderson was presented at the 20th International Conference on Brain Tumor Research and Therapy, held in Lake Tahoe, California, in July 2014. Surgical specimens from 12 patients in the biological endpoint group demonstrated that DNX-2401 is capable of infecting, replicating in, and killing human glioma cells in situ. Of the 25 patients in the clinical assessment group, 3 (12%) had a complete response (tumour disappearance), which the abstract described as “remarkable”. These 3 patients are still alive and progression-free at 3.2, 2, and 1.75 years after treatment. MRI imaging revealed increased enhancement prior to tumour regression, interpreted as an inflammatory response. One tumour was resected during this time of increased MRI-enhancement, primarily revealing immune cells (macrophages and CD8 T-cells), and rare glioma cells. Notably, the 3 complete responders had 10- to 10,000-fold increased levels of interleukin-12p70, a Th1 cytokine, in their serum compared with all the other patients in the study. This implies that the 3 complete responders benefitted from a vigorous immune response in addition to the direct oncolytic activities of the DNX-2401 virus.
November 15, 2014. SNO conference, Miami Florida
The three patients with complete response are still alive at 42 months (3.5 years), 32 months (2.7 years) , and 29 months (2.4 years) from DNX-2401 treatment.
May 8, 2015
A news story on the FOX 26 Houston news website (link no longer works) reported that Phil Bauman, one of the complete responders, is still alive and progression-free at 3 and a half years from viral treatment, while the two other complete responders have since had recurrences. The article also states that 50% of patients in the trial were partial responders.
As of early 2016, Phil was in his 54th month after receiving diagnosis on September 1, 2011.
Newcastle Disease Virus
Newcastle Disease virus (NDV) is a poultry virus which is non-pathogenic in humans. It has a tropism, or preference, for cancer cells, which have no viral defense. In the cancer cell, the virus replicates and quickly causes its demise (1).
There are two general strategies which use NDV. The virus itself may be injected into the patient. Alternatively, an ex vivo preparation called an oncolysate containing fragments of NDV infected cancer cells may be used.
Therapy with intravenous infusions of Newcastle Disease Virus does not necessarily require the addition of dendritic cell therapy for success. A retrospective study of NDV therapy (the MTH-68/H strain) for malignant glioma was published in 2004 (2). Since 1996, this group treated 14 cases of progressive high-grade glioma, all refractory to chemotherapy. Of these 14, five continued to have progressive disease, without response to the NDV infusions. Two others died of causes unrelated to tumour progression. Three had promising response to NDV treatment but follow-up at the time of publication was only 4-18 months. The remaining four cases all had long-term survival and clinical improvement with four to seven years of NDV therapy. These cases are described individually in the study. Three were pediatric (ages 12, 12 and 1.5) and one was a 44-year old woman.
Case 1 was a 12 year old boy, diagnosed with a left fronto-temporal GBM in September 1994. He underwent surgery, radiation, and later initiated tamoxifen treatment. A local recurrence was discovered in November 1995 and the boy was treated with two different regimens of chemotherapy, neither one able to stop continuous tumour growth. By March 1996 the boy was wheel-chair bound, had seizures and a low KPS of 40. NDV was initiated in April 1996. Over the next 7 months there was neurological and functional improvement (the last seizure occured in July 1996), though borderline tumour growth was still observed. Between November 1996 and September 1998, the tumour shrank by 95%. In January 1997, dexamethasone, anti-seizure medication, and tamoxifen were all discontinued. After seven years of NDV therapy, the young man was attending college, achieving above average grades.
Case 2 was a 12 year old girl, diagnosed in July 1995 with a grade III-IV left frontal glioma. A subtotal resection was followed by 60 Gy radiation and chemotherapy. In September 1996 the tumour recurred and was fully resected. In November there was another small recurrence. By July 1997, the girl was bed-ridden with hemiplegia and facial palsy and also had difficulty speaking. NDV therapy commenced at that time. Over the next 2-3 years her situation improved, and by March 2000 an MRI showed almost complete tumour disappearance. The facial palsy and hemiparesis improved, speech returned to normal and her KPS was 90. In February 2003, nearly six years after NDV initiation, the young woman was still alive and well.
Cases 3 and 4 were one pediatric (1.5 year old boy) and one adult, both diagnosed with glioblastoma. These two were still alive and functional after 5.5 years and 4 years of NDV therapy following the failure of conventional therapies.
The therapeutic effects of NDV are mediated by the immune system
Evidence from a human trial of DNX-2401 (described further down the page) points to the critical involvement of the immune system in mediating the therapeutic efficacy of oncolytic virotherapy. Importantly, a complete response was observed only in patients who had a dramatic elevation in type-1 cytokines of the immune system. This human evidence is corroborated by a recent study (3) performed on mice. Researchers found that the injection of Newcastle Disease Virus into orthotopically implanted brain tumours led to a special form of cell death, called immunogenic cell death, which elicited an anti-tumour immune response and tumour eradication in about half of the mice.
The GL261 cell line, a high-fidelity model of GBM, was implanted into the brains of immunocompetent mice. Seven days later, mice received a single injection of NDV (Hitchner B1 strain) into the tumour. The gain in survival for the treated mice was dramatic: median survival was more than doubled (from 28 to 64 days) and half of the treated mice were still alive at 100 days, while none of the control mice survived to day 50. While the mice had shown developing tumours on an MRI scan 7 days after treatment, the surviving mice showed completely healthy brains at day 100 (except for the needle tracts from cell injection).
To assess the involvement of the immune system in this dramatic tumour regression following NDV therapy, the hallmarks of immunogenic cell death were searched for in NDV-infected GL261 cells in vitro. Surface-exposed calreticulin (ecto-CTR) is the most important determinant of immunogenic cell death, according to the authors. Calreticulin appeared on the surface of NDV-infected GL261 cells as early as 24 hours after infection, reaching a maximum at 72-96 hours. Immunogenic danger signaling molecules were released and the expression of cancer-antigen PMEL17 was increased on the infected cells.
Next, signs of immunogenic cell death were investigated in vivo. Three weeks after treatment, mononuclear cells (ie lymphocytes and monocytes/macrophages) were isolated from the tumour-bearing mouse brains. Interferon-gamma expressing CD8+ (cytotoxic T lymphocytes) and CD4+ T cells were significantly elevated in the treated mice versus the control mice. Also, the tumour-infiltrating lymphocyte population was enriched in CD4+ T cells and lower in immunosuppressive myeloid-derived suppressor cells in NDV-treated compared with untreated mice.
Remarkably, when genetically-modified mice lacking functional T- and B-cells were given the same treatment, the therapeutic effect of NDV was almost completely wiped out. Over half of the immune-competent mice were again still alive at 100 days, while all the immunodeficient mice were dead by about day 20. NDV-treatment made surprisingly little difference in the survival of mice without functional immune systems. The same effect was observed in wild-type mice after depletion of their CD8+ T-cell population: NDV-treatment made very little difference to the survival of mice without CD8+ T-cells.
Newcastle Disease Virus efficacy depends on the immune system and has little effect in Rag-2 knockout mice lacking mature T- and B-cells or in mice depleted of CD8+ T-cells
Futhermore, when three long-term surviving mice were re-challenged with GL261 glioma cells, the mice were all completely resistant to tumour growth without any further treatment. However, when four other long-term surviving mice were challenged with Lewis lung carcinoma cells, they all developed tumours. These experiments show that the long-term surviving mice had aquired an anti-tumor memory immunity that was specific to the GL261 glioma cells.
In summary, this study, the first to describe the immune responses following oncolytic virotherapy in an orthotopic, syngeneic glioma model, shows that NDV injected into the tumour results in immunogenic glioma cell death, which causes the immune system to mount a strong anti-tumour response specific to the exposed tumour antigens leading to complete tumour eradication in about half of the mice, followed by anti-tumour memory immunity and resistance to further challenges with the same strain of glioma cell.
Thus, in this model, the therapeutic effect of NDV-treatment was almost completely mediated by the immune system, showing that oncolytic virotherapy in this case should be considered a form of immunotherapy.
Immunotherapy with Dendritic Cells and Newcastle Disease Virus in Glioblastoma Multiforme. Nesselhut et al. 2011.
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MTH-68/H oncolytic viral treatment in human high-grade gliomas. Csatary et al. 2004.
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Newcastle disease virotherapy induces long-term survival and tumor-specific immune memory in orthotopic glioma through the induction of immunogenic cell death. Koks et al. 2014.
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