Trial of C134 in Patients With Recurrent GBM

The efficacy of herpes simplex virus (HSV) as a treatment for brain tumors has been
demonstrated experimentally. The earliest studies used an HSV that was genetically engineered
so that the gene for an important enzyme, thymidine kinase (tk) was deleted. This engineered
virus still killed tumor cells but was not toxic. Martuza and colleagues demonstrated that
tumors implanted in mice shrank following treatment with varying doses of this virus.

Additional modified viruses based on the HSV backbone have been developed and tested with
encouraging results.Viruses containing deletions in other important viral genes (e.g., DNA
polymerase and the gene which can make the virus neurotoxic, γ134.5), also retained the
capability of killing cultured human tumors but did not injure mice; in particular, they were
safe for use in the brain. These viruses retained the viral tk gene, and so are susceptible
to the antiviral drug acyclovir which is routinely used to treat HSV Infection, making them
even more safe .

Martuza and colleagues generated G207, a modified HSV that contains (1) deletions of both
copies of γ134.5 and (2) another gene called ribonucleotide reductase, was disabled secondary
to disruption of the U139 gene by insertion of the E. coli LacZ coding region . G207
significantly prolonged survival of nude mice bearing human tumors. In addition, virus
injected into the brains of the HSV sensitive primates (Aotus) did not produce any
deleterious side effects.

G207 and 1716 have both been used in human trials. A dose-escalating phase 1 study of G207
was completed in patients with recurrent, progressive malignant glioma . The trial was
conducted at University of Alabama at Birmingham and Georgetown University Medical Center.
Twenty-one patients were enrolled in a total of seven dose-escalating cohorts, with three
patients per cohort. Patients were stereotactically inoculated with G207 in the enhancing
portions of their tumors. Five separate loci were inoculated in the final cohort; all
previous cohorts were inoculated in a single locus within the enhancing tissue only. No
toxicity definitively related to G207 was observed at doses up to 3 x 109 plaque forming
units (pfu—these are active viral particles). In fact, a toxic dose level was not attained
during this trial. This was due to viral processing techniques, limiting the total dose that
could be administered.

In a Phase IB study, six patients with recurrent, resectable malignant glioma were enrolled
at the University of Alabama at Birmingham, in a trial examining a split dose administration
strategy of G207. Patients underwent inoculation of G207 into their tumors, followed two to
five days later by resection of the tumor and reinoculation of G207 into the tumor cavity. No
dose limiting toxicities were seen in the trial, although one patient suffered a twelve hour
period of mental status changes, weakness, and an elevated temperature when a protocol
deviation resulted in an inadvertent partial dose of virus being administered
intraventricularly, into the cerebrospinal fluid chamber of the brain. The patient fully
recovered quickly and fully. One of the six patients went nearly two years before remote
recurrence of her glioblastoma multiforme resulted in her death. A third study in 9 patients
with recurrent malignant glioma was completed in which G207 was being administered followed
by a single small dose of 5Gy of radiation. Nine patients were followed without any dose
limiting toxicity, and some patients had remarkable responses to treatment. Currently, two
clinical studies of oncolytic HSV are underway that examine G207 in pediatric patients as
well as a novel oncolytic HSV expressing IL- 12, in adult patients. No findings of these two
studies have yet been reported.

C134 was designed to replicate better than 1st gen HSVs. C134 is created by by inserting the
PKR evasion gene, IRS1. from an evolutionary distant herpesvirus HCMV, which allows the virus
to replicate much better but does not produce toxicity.

The described G207 trials clearly demonstrate that increased immune cell infiltrates within
MG are associated with better outcomes. C134 elicits a robust immune response that
contributes greatly to its antitumor effects.

C134 combines advantages of both wild-type and Δγ134.5 HSV and is an improvement over 1st
generation viruses. C134 replicates and lyses tumor cells like a wild-type HSV in the IFN
aberrant tumor environment, but is safe in normal cells. C134 induces immune responses which
exceed those produced by 1st generation viruses. The study is designed to use all the
information from any patients already treated to determine what the best dose for the next
patient should be.

Inclusion Criteria:

- Patients must have histologically or cytologically confirmed recurrent/progressive
glioblastoma multiforme, anaplastic astrocytoma, or gliosarcoma.

- Prior therapy. Patients must have failed external beam radiotherapy 5,000 CGy to the
brain at least 4 weeks prior to enrollment.

- Age 18 years or older, because no dosing or adverse event data are currently available
on the use of IRSl-chimeric HSVl in patients below 18 years of age, children are
excluded from this study but will be eligible for future pediatric phase 1
single-agent trials. Note: 18 is the age of majority in the state of Alabama for
participation in clinical trials.

- Karnofsky Performance Status ≥70%

- Life expectancy of greater than 4 weeks.

- Patients must have normal organ and marrow function as defined below:

- leukocytes ≥3,000/uL

- absolute neutrophil count ≥1,500/uL

- platelets ≥100,000/uL

- total bilirubin within normal institutional limits

- AST(SGOT)/ ALT(SGPT) ≤2.5 X institutional upper limit of normal

- Creatinine within normal institutional limits OR Creatinine clearance ≥60
mL/min/1.73 m2 for patients with creatinine levels

- Residual lesion must be ≥1.0 cm in diameter as determined by MRI.

- The effects of IRS1-chimeric HSV1 on the developing human fetus are unknown. For this
reason, women of child-bearing potential and men must agree to use adequate
contraception prior to study entry and for the first six months after receiving
IRS1-chimeric HSVl. Because it is currently unknown if IRS1-chimeric HSV1 can be
transmitted by sexual contact, a barrier method of birth control should be employed.
Should a woman become pregnant while participating in this study, she should inform
her treating physician immediately.

- Ability to understand and the willingness to sign a written informed consent document
(Informed consent document in Appendix E).

- Females of childbearing potential must not be pregnant; this will be confirmed by a
negative serum pregnancy test within 14 days prior to starting study treatment.

- Steroid use is allowed as long as dose has not increased within 2 weeks of scheduled
C134 administration whenever possible, the patient should be on a steroid dose that is
equivalent to a dexamethasone dose of ≤2mg daily at the time of treatment.

Exclusion Criteria:

- Patients who have had chemotherapy, cytotoxic therapy, immunotherapy or gene therapy
within 6 weeks prior to entering the study, surgical resection within 4 weeks prior to
entering the study, or have received experimental viral therapy at any time (e.g.,
adenovirus, retrovirus or herpesvirus * protocol). Also, those who have not recovered
from adverse events due to therapeutic interventions administered more than 4 weeks
earlier.

- Patients may not be receiving any other investigational agents.

- History of allergic reactions attributed to compound of similar biologic composition
to IRS1-chimeric HSVl.

- Tumor involvement which would require ventricular, brainstem, basal ganglia, or
posterior fossa inoculation or would require access through a ventricle in order to
deliver treatment.

- Prior history of encephalitis, multiple sclerosis, or other CNS infection.

- Required steroid increase within 2 weeks of scheduled IRS1-chimeric HSV1
administration.

- Active oral herpes lesion.

- Concurrent therapy with any drug active against HSV (acyclovir, valaciclovir,
penciclovir, famciclovir, ganciclovir, foscarnet, cidofovir).

- Uncontrolled intercurrent illness including, but not limited to ongoing or active
infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac
arrhythmia, or any other medical condition that precludes surgery . Also, psychiatric
illness/social situations that would limit compliance with study requirements.

- Required steroid increase within 2 weeks of scheduled C134 administration. When
possible, the patient should be on a dexamethasone equivalent dose of ≤2mg daily at
the time of treatment.

- Excluded patient groups

- Pregnant women are excluded from this study because IRS1-chimeric HSV1 is a viral
oncolytic therapy with unknown potential for teratogenic or abortifacient
effects. Because there is an unknown but potential risk for adverse events in
nursing infants secondary to treatment of the mother with IRS1-chimeric HSV1,
breastfeeding should be discontinued if the mother is treated with IRS1-chimeric
HSVl.

- Because patients with immune deficiency will be unable to mount the anticipated
immune response underlying this therapeutic rationale, HIV-seropositive patients
are excluded from this study. Other treatment studies for this disease that are
less dependent on the patients' immune response are more appropriate for
HIV-seropositive patients.