Transcript Immunologic Targeting - How to Channel a Minimal Response

Immunologic Targeting - How to
Channel a Minimal Response for
Maximal Outcome
Susan Slovin, MD, PhD
Genitourinary Oncology Service
December 1, 2005
Have we succeeded or failed in our
treatments for prostate cancer?
Success
Failure
Docetaxel – standard of care
Not that many approved Ph III drugs
Multiple targeting pathways
Which is the “one” to stop growth
New drugs in the pipeline
Too many approved too fast or
too few reaching approval status
Responses after 1st line CAB
Disease moves too fast
Bone seeking drugs: improved
toxicity profile
No impact on important measures
RATIONALE FOR TARGETED
INTERVENTION
PRO
CON
1. Over-expression and
1. Strictly extracellular, no
undergycosylation of
contact with intracellular
cell surface molecules
pathways. Expression varies.
2. Can target receptor-like 2. Cell can develop “collateral”
molecules which can
signaling/survival pathways.
stimulate intracellular
3. Cell can overcome via
signaling pathways.
multiple mechanisms
3. Can prevent target
rendering tx inadequate.
activation.
TARGETS UNDER EXPLORATION
•
•
•
•
Cell Surface
Mucins, glycolipids,
carbohydrates,
glycoproteins [PSA,
PSMA, KSA]
AR
EGFr
Laminin
•
•
•
•
•
•
Intracellular
Vitamin D (calcitriol)
HSP-90
Proteasome
DNA (HDACs)
BCL-2 [α-sense]
Other – Stroma,
neovasculature
What have we learned from MSKCC
prostate cancer vaccine trials?
1) chemical mimes of known cell surface molecules were shown to be
immunogenic, ie Globo H - first time that a synethetic molecule could
break immunologic tolerance in man
2) role of carriers such as KLH and adjuvants such as QS21 in enhancing
immunogenicity and facilitating the immune response. QS21 still remains
the best adjuvant through all clinical trials.
3) increasing doses of vaccine do not correlate with augmentation of
immunogenicity, ie, lower doses appear to be more immunogenic
(especially seen in the TF trial)
4) immunologic responses were not immediate but took up to 6 or more
months to develop after the last vaccine; no role for boosters unless they
were given either every 4-8 weeks.
5) we learned about the use of PSA slopes - no major impact on pts with high
risk disease destined to progress within two years.
6) No clear cut immunologic endpoint; controversy as to how to design
biologic trials – lead to PSA Working Group Consortium
PSMA
•
•
•
Type II transmembrane glycoprotein
Expression on normal and neoplastic
prostate epithelial cells, neovasculature
Functions as a glutamate-preferring
carboxypeptidase with two enzymatic
activities:
1) Gamma-glutamyl carboxypeptidase (folate
hydrolase
2) N-acetylated alpha-linked l-amino dipeptidase
(NAALADase), an enzyme involved in regulation of
excitation signaling
Prostate Specific Membrane Antigen
COOH
COOH
PSMA:extracellular
form found on
Prostate Specific Membrane
Antigen
cancer
cells
COOH
E
COOH
PSMA:extracellular
form found on
cancer cells
E
COOH
COOH
F
D
E
E
D
C
C
cell
membrane
B
cell
membrane
B
A
A
PSM’: intracellular form
found in normal cells
F
Domain A - aa 1-19
Domain B – aa 20-39
E
D
C
PSM’: intracellular form
found in normal cells
F
Domain A - aa 1-19
Domain B – aa 20-39
COOH
COOH
F
E
D
C
RCC  Bone (10mg)
How to Target PSMA?
Vaccines
• Naked DNA
• rsPSMA
maytansinoid
• Alphavirus vector
Others:
Radionuclide emitter +
MoAb (ext domain)
MoAb +
Neovasculature?
What is the ideal patient population?
What is the appropriate clinical trial endpoint, i.e.,
does a clinical and/or immunologic endpoint exist?
Metastatic population
High titer Abs
No effect on PSA
Continued POD
Rising PSA
High titer Abs
Change in PSA logslope
Disease stabilization
Rationale for targeting signalling
cascades and surface receptors…
a) Most prostate cancers have lost PTEN
b) Tumors that have lost PTEN are insensitive to
EGFr inhibition;
Restoration of PTEN function (mTOR inhibition)
restores sensitivity to EGFR inhibition
c) PTEN negative tumors are sensitive to mTOR
inhibition
The combination of mTOR inhibition and EGFR
inhibition may be a rationale treatment approach.
Plasmid DNA expression vector
used in MSKCC PSMA DNA
vaccines
kana cassette
ori
pCDNA3 polylinker
pING+ HuPSMA
CMV promoter
7213 bp
CAAT
TATA
exon 1
PSMA ORF
Human PSMA
Intron A
T7
Why HLA A02.01?
• HLA-A02.01 allele:
– Peptides that match the HLA-A2.01 binding
consensus are found within the huPSMA and
muPSMA
– Expressed by 40% of the Caucasian population
• To date: 126 patients typed: 65 + (52%)
MSKCC
Cross-over to break tolerance
Cross-over design of clinical trial
Human PSMA
Human
PSMA
Mouse PSMA
Mouse PSMA
Why a DNA Vaccine?
• Relatively inexpensive & simple to purify in large
quantity
• Avoids complex ex vivo expansion and manipulation
of patients’ cells
• Antigen of interest is cloned into a bacterial
expression plasmid with a constitutively active
promoter.
• Bacterial plasmid DNA itself contains immunostimulatory sequences (CpG motifs) that may act as
an immunological adjuvant
• Direct entry of the antigen into the intracellular MHC
class I processing pathway
How to Break Immune
Tolerance to PSMA?
Active
Passive
Vaccines
• Naked DNA
Others:
Radionuclide emitter +
MoAb (ext domain)
MoAb + maytansine
Neovasculature
•
•
•
•
rsPSMA
Alphavirus vector
Cytokine/GM-CSF (transduced cell line)
ACP-fusion protein (cellular product)
CD28/B7 superfamily and the paradigm of professional costimulation
T cell
APC/DC
B7x
BTLA YYY
SHP-1
B7H3
SHP-2
Activation CD28 YYYY
B7.1
Inhibition
B7.2
CTLA-4 YY
B7h
ICOS YY
PD-L1
PD-1 YY
IgC domain
Induced by
Inflammation/
Pathogens
PD-L2
IgV domain
Y Tyrosine
Regulation of T cell activation
TCR
Antigen
MHC
~
CD28
 CTLA-4 : B7 suppression
 Termination of response
B7
TCR
CD28
Antigen
Antigen-specific
T cell Activation
MHC
CTLA-4
~
B7
TCR
 TCR : Antigen MHC
 CD28 : B7 Co-stimulation
CD28
Antigen
Activated T cell
 IL-2 secretion
 Proliferation
 Effector function
 Induction of CTLA-4
MHC
~
B7
CTLA-4
CTLA-4 Blockade Augments Antigen
Specific T-cell Responses
Anti-CTLA-4 mAb
TCR
CD28
Antigen
MHC
TCR
CD28
~
Antigen
B7
MHC
~
B7
CTLA-4
CTLA-4
An activated T cell is
important in destroying
cancer cells or virally
infected cells.
CTLA-4 (in red) is
sequestered in granules
distal to the leading edge of
the immunological synapse.
Image courtesy of the Allison lab,
University of California, Berkeley
CTLA-4
A T-cell interacts with an
antigen presenting cell
(APC) and is activated.
Preformed CTLA-4
granules (in red) migrate to
the synapse. Signals downmodulate T-cell responses
against cancers and other
foreign antigens.
Image courtesy of the Allison lab,
University of California, Berkeley
Anti-Murine CTLA-4 mAb Cures Prostate Cancer
in Mice
300
Source: Kwon et al. PNAS. 1997(94): 8099
Control Ab
Tumor size (mm 2)
Anti-CTLA-4
(100 ug Ab at days 7, 10, & 13)
0
10
30
50
70
Days post tumor injection
90
α-CTLA-4
5000
4500
4000
CA-125
3500
3000
2500
α-CTLA-4
2000
1500
1000
500
0
-120
GVAX
-100
-80
-60
-40
-20
0
20
40
60
80
Days
100
120
140
160
180
200
220
240
260
Pathology of Autoimmune
Breakthrough Events: Dermatitis
B
A
Histopathologic analyses of selected patients experiencing autoimmune events.
(A) Skin rash biopsy from Patient 2 illustrating severe dermatitis with epidermal
spongiosis, significant papillary dermal edema and a prominent inflammatory infiltrate in
both the superficial and deep dermis (10X magnification).
(B) The cellular infiltrate from Patient 2 reveals the predominance of lymphocytes,
monocytes and eosinophils (40X).
Source: Abstract #3424, ASCO 2003
Pathology of Autoimmune Breakthrough Events:
Colitis
D
C
E
CD4
F
CD3
CD8
Histopathologic analyses of
selected patients experiencing
autoimmune events.
(C) Colon biopsy from Patient 9
illustrating severe colitis with
infiltration of the lamina propria
with neutrophils, lymphocytes,
monocytes, plasmacytes and
eosinophils. Neutrophils and
lymphocytes also infiltrate the
crypts; numerous mitotic figures
can be seen in the epithelial cells
lining the crypts (20X).
Immunohistochemistry
evaluating expression of CD3+
(D), CD4+ (E), and CD8+
markers (F) (20X).
Source: Abstract #3424, ASCO 2003