Treatment of Castration Resistant Prostate Cancer Using Multi-Targeted Recombinant Ad5 PSA/MUC1/Brachyury Based Immunotherapy Vaccines

Background:

- The overall goal of the current project is to expand our immunotherapeutic approach for
the treatment of prostate cancer employing a multi-targeted approach.

- Therapeutic cancer vaccines targeting overexpressed proteins offer a potential method to
activate T cells against tumors.

- A novel adenovirus based vaccines targeting three (3) human tumor associated antigens
(TAA), PSA, MUC1, and brachyury, respectively have demonstrated anti-tumor cytolytic T
cell responses in pre-clinical animal models of cancer.

Objectives:

-To determine the overall safety and recommended phase 2 dose of a combination of three
immunotherapeutic vaccines (ETBX-071, ETBX-061, and ETBX-051) when administered
subcutaneously (SC) to subjects with metastatic castration resistant prostate cancer

Eligibility:

- Subjects age 18 and older with cytologically or histologically confirmed prostate cancer
for which no curative standard approved therapy is available.

- Metastatic Castration Resistant Prostate Cancer (mCRPC) patients with rising PSA or
progressive disease despite castration levels of testosterone.

- Prior treatment with immunotherapy hormonal therapy, radiotherapy, chemotherapy, and/or
other experimental therapy is allowed.

- ECOG performance status less than or equal to 1

- Adequate organ and bone marrow function

- Subjects with a history of autoimmune disease (active or past) and subjects requiring
systemic steroids are not eligible (physiologic doses of steroids for steroid
replacement as well as nasal, topical and inhaled steroids are allowed).
Autoimmune-related thyroid disease, type I diabetes and vitiligo are permitted if the
condition is well controlled.

Design:

- This is a Phase I trial in subjects with mCRPC. A combination of three therapeutic
vaccines (ETBX-071, ETBX-061, and ETBX-051) which use the same modified Adenovirus
vector backbone, separately encoding three well studied TAA,PSA, MUC1, and brachyury,
respectively) will be assessed. The vaccines will be tested at standard dose levels,
with a dose de-escalation (if required) design employed. The dose level of each vaccine
tested will be 5x10 to the eleventh power VP. This dose has been found in a prior phase
1 testing of a similar vaccine Ad5 [E1-, E2b-]-CEA(6D) (ETBX-011) to be well tolerated
(with no DLT s or related SAE s), and be optimal for induction of immune responses.

- Up to six patients will be enrolled at dose level 1. If less than or equal to 1 of 6
patients experience a DLT, an initiation of the dose expansion phase will occur. If more
than or equal to 2 of 6 experience DLT at dose level 1, then dose de-escalation will
occur. Up to six patients will be enrolled at the lower dose level (-1) (1x10 to the
eleventh power VP). If less than or equal to 1 of 6 patients experience a DLT, then the
maximum tolerated (MTD) will be declared at this dose, and initiation of the dose
expansion phase will occur. If more than or equal to 2 of 6 experience DLT at dose level
-1, then a further dose de-escalation will occur. Up to six patients will be enrolled at
the lower dose level (-2) (5x10 to the tenth power VP). If less than or equal to 1 of 6
patients experience a DLT, then the maximum tolerated (MTD) will be declared at this
dose, and initiation of the dose expansion phase will occur. If more than or equal to 2
of 6 experience DLT at dose level -2, then the study will be stopped.

- A dose expansion phase of study will be enrolled after the MTD of the vaccines have been
determined. An additional 12 subjects will be enrolled in the dose expansion component
of the trial, for a total of 18 subjects at the MTD.

- The ETBX-051, ETBX-61 and ETBX-71 vaccines will be administered subcutaneously (SC) at
separate injection sites (proximal limb, preferably the thigh), will be administered SC
every 3 weeks for 3 doses (dose de-escalation cohorts) followed by boosts every 8 weeks
for 1 year (only patients enrolled in dose expansion cohort).

- INCLUSION CRITERIA:

- Age more than or equal to 18 years (male).

- Ability to understand and provide signed informed consent that fulfills Institutional
Review Board (IRB) s guidelines.

- Cytologically or histologically confirmed prostate cancer for which no curative
standard approved therapy is available by either the Laboratory of Pathology at the
NIH Clinical Center or Walter Reed National Military Medical Center at Bethesda prior
to starting this study. If no pathologic specimen is available, patients may enroll
with a pathologist s report showing a histological diagnosis of prostate cancer and a
clinical course consistent with the disease.

- Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 1.

- Subjects who have received prior PSA, MUC1, and/or brachyury-targeted immunotherapy
(e.g. vaccine) are eligible for this trial if this treatment was discontinued at least
3 months prior to enrollment.

- Resolution of all toxic side effects of prior chemotherapy, radiotherapy, or surgical
procedures to NCI CTCAE Grade less than or equal to1.

- Adequate hematologic function at screening, as follows:

- Absolute neutrophil conunt (ANC) greater than or equal to x 10 to the ninth power/L

- Hemoglobin more than or equa to 9 g/dL

- Platelets more than or equal to 75,000/microliter.

- Prothrombin (PT)-international normalized ratio (INR) < 1.5.

- Partial thromboplastin time (PTT) < 1.5 x upper limit of normal (ULN).

- Adequate renal and hepatic function at screening, as follows:

--Serum creatine less than or equal to 1.5x upper limit of normal (ULN) OR creatinine
clearance (CrCl) more than or equal to 40mL/min (if using the Cockcroft-Gault formula
below):

1. Female CrCl = [(140 - age in years) x weight in kg x 0.85] / [72 x serum
creatinine in mg/dL]

2. Male CrCl = [(140 - age in years) x weight in kg x1.00] / [72 x serum creatinine
in mg/dL]

- Total bilirubin less than or equal to 1.5 x ULN OR in subjects with Gilbert s
syndrome, a total bilirubin less than or equal to x ULN

- Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) less than or equal
to 2.5 x ULN, unless liver metastes are present, then values must be less than or
equal to 5 x ULN)

- The effects of ETBX-051, ETBX-061 and ETBX-071 vaccines on the developing human fetus
are unknown. For this reason subjects must agree to use a condom and acceptable
contraceptive method with their partner during the study and for one month after the
last dose of vaccines.

- Ability to attend required study visits and return for adequate follow up, as required
by this protocol.

- Castrate testosterone level (<50ng/dl or 1.7nmol /L)

- Metastatic disease documented by at least one of the following:

- Metastatic bone disease on an imaging study, or

- Soft tissue disease documented by CT/MRI

- Progressive disease at study entry defined as one or more of the following criteria
occurring in the setting of castrate levels of testosterone:

- Radiographic progression defined as any new or enlarging bone lesions or growing lymph
node disease, consistent with prostate cancer

OR

- PSA progression defined by sequence of rising values separated by >1 week (2 separate
increasing values over a minimum of 2ng/ml (PCWG2 PSA eligibility criteria). If
patients had been on flutamide, PSA progression is documented 4 weeks or more after
withdrawal. For patients on bicalutamide or nilutamide disease progression is
documented 6 or more weeks after withdrawal. The requirement for a 4-6 week withdrawal
period following discontinuation of flutamide, nilutamide or bicalutamide only applies
to patients who have been on these drugs for at least the prior 6 months. For all
other patients, they must stop bicalutamide, nilutamide or flutamide the day prior to
enrollment.

- Patients must agree to continue to continuation of androgen deprivation therapy (ADT)
with a gonadotropin-releasing hormone analogue/antagonist or bilateral orchiectomy

- Prior treatment with immunotherapy, hormonal therapy, radium 223, chemotherapy and/or
other experimental therapy is allowed.

EXCLUSION CRITERIA:

- Treatment with an investigational drug study within 28 days of before starting on
study treatment.

- Subjects with concurrent cytotoxic chemotherapy or radiation therapy. There must be at
least 28 days between any other prior chemotherapy (or radiotherapy) and study
treatment. Prior antibody therapy must be discontinued 8 weeks prior to start of study
treatment. Prior hormonal therapy can be discontinued 24 hours prior to start of study
treatment.

- Any prior PSA, MUC1, and/or brachyury-targeted immunotherapy (e.g., vaccine) must have
been discontinued at least 12 weeks before initiation of study treatment. Subjects
must have recovered from all acute toxicities from prior treatment prior to screening
for this study.

- Prior treatment with Adenovirus-Based vectors immunotherapy

- Known active brain or central nervous system metastasis, or seizures requiring
anticonvulsant treatment, cerebrovascular accident, or transient ischemic attack (< 6
months prior to enrollment).

- Subjects with a history of autoimmune disease (active or past), such as but not
restricted to inflammatory bowel disease, systemic lupus erythematosus, ankylosing
spondylitis, scleroderma, or multiple sclerosis. Autoimmune-related thyroid disease,
type I diabetes and vitiligo are permitted if the condition is well controlled.

- Subjects with serious intercurrent chronic or acute illness, such as cardiac or
pulmonary disease, hepatic disease, or other illness considered by the Investigator as
high risk for investigational drug treatment.

- Subjects with a history of heart disease, such as congestive heart failure (class II,
III, or IV defined by the New York Heart Association functional classification),
history of unstable or poorly controlled angina, or history (< 1 year prior to
enrollment) of ventricular arrhythmia.

- Subjects with a medical or psychological impediment that would impair the ability of
the subject to receive therapy per protocol or impact ability to comply with the
protocol or protocol-required visits and procedures.

- Presence of a known active acute or chronic infection, including human
immunodeficiency virus (HIV, as determined by enzyme-linked immunosorbent assay
[ELISA] and confirmed by western blot) and hepatitis B and hepatitis C virus (HBV/HCV,
as determined by HBsAg and hepatitis C serology).

- Subjects on systemic intravenous or oral steroid therapy (or other immunosuppressive,
such as azathioprine or cyclosporin A) are excluded on the basis of potential immune
suppression. Subjects must have had at least 6 weeks of discontinuation of any steroid
therapy (except that used as premedication for chemotherapy or contrast-enhanced
studies) prior to enrollment. Physiologic (replacement) doses of steroids as well as
nasal, topical or inhaled steroids are allowed.

- Subjects with known allergy or hypersensitivity to any component of the
investigational product will be excluded.

- Subjects with acute or chronic skin disorders that will interfere with injection into
the skin of the extremities or subsequent assessment of potential skin reactions will
be excluded.

- Subjects vaccinated with a live (attenuated) vaccine (e.g., FluMist ) or a killed
(inactivated)/subunit vaccine (e.g., PNEUMOVAX , Fluzone ) within 28 days or 14 days,
respectively, of the first planned dose of ETBX vaccine.

- Patients with second malignancy within 3 years of enrollment; Patients curatively
treated non-melanoma skin cancers or carcinoma in situ of the bladder, are not
excluded.

- Use of herbal products that may decrease PSA levels (e.g. saw palmetto)

- Patients who have received radiation therapy, radionuclide therapy or undergone
surgery within certain duration (4 weeks) of enrollment