Somatostatin receptor
agonists and antagonists
Melpomeni Fani
Clinic of Radiology and Nuclear Medicine
University of Basel Hospital, Switzerland
Somatostatin and somatostatin receptors
Human Somatostatin (SS-14)
 peptide hormone (SS-14 and SS-28)
regulates the release of many hormones
and inhibits the secretion of peptides and
neuroregulators from a variety of
Ala—Gly—Cys—Lys—Asn—Phe—Phe
Trp
S
S
Lys
neuroendocrine tumors, and in some cases
reduces tumor growth
Cys—Ser—Thr—Phe—Thr
 5 G-protein coupled receptor subtypes (sstr1, sstr2, sstr3, sstr4 and sstr5)
 not useful to be developed into targeting (radio)ligands because of metabolic
instability (T1/2 ≈ 2-3 min)
From the natural somatostatin to stabilized analogs
Octreotide (Sandostatin®)
Human Somatostatin (SS-14)
Novartis
Ala—Gly—Cys—Lys—Asn—Phe—Phe
Trp
S
S
Cys—Ser—Thr—Phe—Thr
Lys
DPhe—Cys— Phe
S
S
Thr(ol)—Cys— Thr
D
Trp
Lys
First radiolabelled somatostatin analogs
123I-TOC
123I
DPhe—Cys— Tyr
S
S
D
Trp
Lys
Thr(ol)—Cys— Thr
111In-DTPA-Octreotide
(Octreoscan®)
111In
—DTPA— DPhe—Cys— Phe
S
S
D
Trp
Lys
Thr(ol)—Cys— Thr
FDA approval: June 2, 1994
Radiolabelled somatostatin analogs routinely applied
into the clinic
111In-DTPA-Octreotide
(Octreoscan®)
111In
DOTA-TOC
—DTPA— DPhe—Cys— Phe
D
Trp
S
State-of-the-art
—DOTA—DPhe—Cys— Tyr
D
Trp
S
S
Lys
S
Lys
Thr(ol)—Cys— Thr
Thr(ol)—Cys— Thr
DOTA-NOC
DOTA-TATE
—DOTA—DPhe—Cys—1-Nal
S
S
Thr(ol)—Cys— Thr
D
Trp
Lys
—DOTA— DPhe—Cys— Tyr
S
S
Thr—Cys— Thr
D
Trp
Lys
Affinity profile (IC50, nM)
Compound
sstr1
sstr2
sstr3
sstr4
sstr5
111In-DTPA-octreotidea
> 10’000
22 ± 3.6
182 ± 13
> 1’000
237 ± 52
68Ga-DOTA-TOCa
> 10’000
2.5 ± 0.5
613 ± 140 > 1’000
68Ga-DOTA-TATEa
> 10’000
0.2 ± 0.04 > 1’000
68Ga-DOTA-NOCb
> 10’000
1.9 ± 0.4
300 ± 140
40.0 ± 5.8 260 ± 74
73 ± 21
377 ± 18
7.2 ± 1.6
All values are IC50±SEM in nM
aReubi
JC et al., Eur J Nucl Med 2000;27:273–282
bAntunes
P et al., Eur J Nucl Med Mol Imaging 2007;34:982-993
Somatostatin receptor imaging in NETs
Ex. G2 NET of the Ileum
FDA approved
(registered)
investigation
time: > 24 h
Octreoscan®
68Ga-DOTA-TOC
scintigraphy 24 h p.i.
PET 1 h p.i.
not approved
investigation
time: 90 min
radiation
exposure: 9 mSv
radiation
exposure: 3 mSv
sensitivity: ~ 70%
sensitivity: ~ 85%
Courtesy of G. Nicolas, University of Basel Hospital, Switzerland
68Ga-DOTA-TATE
vs 111In-DTPA-OC
Octreoscan®
68Ga-DOTA-TATE
scintigraphy 4 h p.i.
PET 1 h p.i.
Courtesy of D. Wild, University Hospital Freiburg, Germany
68Ga-DOTA-TATE
vs 68Ga-DOTA-NOC
68Ga-DOTA-TATE
PET 1h p.i.
sst2 receptor
Sensitivity ~ 85%
68Ga-DOTA-NOC
PET 1h p.i.
sst2,3,5 receptor
Sensitivity ~ 95%
D. Wild et al., J Nucl Med 2013;54:364
discrepant results: Kabasakal L, et al., Eur J Nucl Med Mol Imaging 2012;39:1271
The reason of success: The target
Immunohistochemical Detection of sstr2
 incidence
 density
JC Reubi, Endocrine Rev 2003;24:389-427
Ligands targeting G-Protein Coupled Receptors
Agonists
G-Protein Coupled Receptors
(adjusted)
In vitro internalization
Control
SS-14
In-DOTA-NOC
Agonist-induced internalization
Confocal microscopy images after 30’
incubation in HEK-sstr3 cells
Time course of agonist-induced sst2 internalization
in vivo
Agonist (TATE) in AR42J (sstr2-positive cells)
A
B
C
D
E
F
0 min
10 min
20 min
1h
6h
24 h
Agonist (TATE) in Pancreas (sstr2-positive tissue)
G
H
I
J
K
L
0 min
10 min
20 min
1h
24 h
1h
Antag
Waser B, et al., J Nucl Med 2009;50:936
Internalization rate and tumor/pancreas uptake
Storch D., et al., J Nucl Med 2005;46:1561
Internalization and tumor retention/washout
The pansomatostatin ligand 111In-KE88 targets both sstr2 and sstr3 tumors
but is only internalizes in sstr3
(the non-internalizing ligand shows fast washout)
sstr2
sstr3
No internalization
internalization
kidneys
15 min
30 min
60 min
120 min
240 min
Ginj M., et al., Clin Cancer Res 2008;14:2019
Further developments in the field…
The importance of the vector
Antagonists instead of Agonists
Agonist
Antagonist
Stimulate receptor function
Do not stimulate activity
e.g. receptor internalization or
Ca2+-release
Block agonist induced
activity
The pioneers of radiolabelled somatostatin
receptor antagonists
Jean E. Rivier
(peptide analogs)
Jean Claude Reubi
(affinity, antagonism)
Helmut R. Maecke
(radiolabelled analogs)
In vitro internalization ?
TOC (agonist)
Ga-NODAGA-LM3 (antagonist)
Antagonist does not induce internalization
Confocal microscopy images after 30’ incubation in HEK-sstr2 cells
Fani M, et al., J Nucl Med 2011;52:1110
In vivo internalization ?
Agonist (TATE) in AR42J tumors
A
0 min
1h
6h
24 h
Antagonist (DOTA-BASS) in AR42J tumors
Waser B, et al., J Nucl Med 2009;50:936
Are radiolabelled receptor antagonists superior to agonists?
TATE: D-Phe-cyclo(Cys-Tyr-D-Trp-Lys-Thr-Cys)Thr
%IA/g
BASS: p-NO2-Phe-cyclo(D-Cys-Tyr-D-Trp-Lys-Thr-Cys)D-Tyr-NH2
Antagonists have more
binding sites than agonists !!
111
111
In-DOTA-sst3-ODN8
In-DOTA-sst -ODN-8
3
111
0,30
0,30
bound/free
bound/free
tu
m
or
hs
st
2-
e
Antagonists showed much higher tumor uptake !!
111
In-DOTA-NOC
In-DOTA-NOC
0,35
0,35
M
us
cl
re
as
Pa
nc
ey
K
id
n
Li
ve
r
0,40
0,40
0,25
0,25
75-fold
0,010
0,010
0,20
0,20
0,15
0,15
higher
0,005
0,005
0,10
0,10
Bmax
0,05
0,05
0,000
0,000
0
0
20 40
40
20
60
60
0,00
0,00
0
0
1000
1000
2000
2000
3000
3000
4000
4000
5000
5000
bound
bound (pM)
(pM)
Ginj M, et al., PNAS 2006;103:16436–41
111In-Octreoscan®
0.68 %IA
Agonist
111In-DOTA-BASS
1.3 %IA
Antagonist
111In-DOTA-JR11
3.6 %IA
Antagonist
Scintigraphy 24 h p.i.
111In-Octreoscan®
0.68 %IA
Agonist
111In-DOTA-BASS
1.3 %IA
Antagonist
111In-DOTA-JR11
3.6 %IA
Antagonist
Scintigraphy 24 h p.i.
The importance of the chelator
Selected chelators for radiometals
almost all radiometals
68Ga, 64Cu, 111In (18F)
(111In, 68Ga, 90Y, 177Lu, 213Bi, 46/47Sc,…)
O
HO
N
N
O
N
OH
HO
O
O
DOTA
NOTA (NODAGA)
OH
68Ga-DOTA-LM3
& 68Ga-NODAGA-LM3
LM3: p-Cl-Phe-cyclo(D-Cys-Tyr-D-Aph(Cbm)-Lys-Thr-Cys)-D-Tyr-NH2
D-Aph(Cbm): D-4-amino-carbamoyl-phenylalanine
Code
DOTA-LM3
Introduction of a
chelate
68Ga-DOTA-LM3
Exchange of the
chelator
68Ga-NODAGA-LM3
sstr2 (IC50; nM)
0.39 ± 0.05
12.5 ± 4.3
1.3 ± 0.3
Reference agonist
68Ga-DOTA-TATE
0.2 ± 0.04
Fani M, et al., J Nucl Med 2011;52:1110
Significantly higher tumor uptake can be achieved
with the antagonists, compared to agonists and for
the same antagonist it depends on the chelator
50
68
Ga-DOTA-TATE
68
Ga-DOTA-LM3
68
Ga-NODAGA-LM3
40
**
30
37.3 ± 5.5
28.7 ± 5.6
17.8 ± 2.2
20
10
Sp r
le
en
Lu
ng
K
id
n
St ey
om
a
In ch
te
st
in
e
A
dr
e
Pa nal
nc
re
as
M
us
cl
e
B
on
e
Tu
m
or
ve
Li
rt
ea
H
lo
od
0
B
%IA/g
*
Organs
*P < 0.05 and **P < 0.01 statistically significant
Image contrast of sstr2-specific antagonists vs agonist
68Ga-DOTA-TATE
68Ga-DOTA-LM3
68Ga-NODAGA-LM3
Coronal
% IA/g
0
15
MIP
Fani M, et al., J Nucl Med 2011;52:1110
The importance of the
radionuclide
The (radio)metal determines receptor affinity !
JR11: Cpa-cyclo[D-Cys-Aph(Hor)-D-Aph(Cbm)-Lys-Thr-Cys]-D-Tyr-NH2
Cpa = 4-Cl-phenylalanine; Aph(Hor) = 4-amino-L-hydroorotyl-phenylalanine; D-Aph(Cbm) = D-4-amino-carbamoyl-phenylalanine
DOTA-JR11
(Radio)metal
IC50 (nmol/L)
-
0.72 ± 0.12
Ga(III)
29 ± 2.7
Cu(II)
16 ± 1.2
In(III)
3.8 ± 0.7
Lu(III)
0.7 ± 0.15
Y(III)
0.47 ± 0.05
Loss of
affinity in
the 68GaPET probe
Excellent
affinity for
the
therapeutic
probe
Fani M, et al., J Nucl Med 2012;53:1481
68Ga-DOTA-JR11
& 68Ga-NODAGA-JR11 vs 68Ga-DOTA-TATE
Compound
IC50 (nmol/L)
68Ga-DOTA-JR11
29.0 ± 2.7
68Ga-NODAGA-JR11
1.2 ± 0.2
68Ga-DOTA-TATE
0.2 ± 0.05
68Ga-DOTA-TATE
18%
68Ga-DOTA-JR11
24%
150-fold
68Ga-NODAGA-JR11
31%
Fani M, et al., J Nucl Med 2012;53:1481
Clinical translation
Comparison of 68Ga-DOTA-TOC and 68Ga-NODAGA-JR11 PET/CT
(ClinicalTrials.gov NCT02162446)
68Ga-DOTA-TOC
5 metastases
68Ga-NODAGA-JR11 (68Ga-OPS202)
10
metastases
PET 1h p.i.
68Ga-NODAGA-JR11 (68Ga-OPS202)
vs 68Ga-DOTA-TOC shows
increased tumour detection rate due to an improved Tumour-toBackground Uptake Ratio (Phase I/II, 12 pts)
(ClinicalTrials.gov NCT02162446)
Tumour-to-Background Ratio
(median Tumour (SUVmax) / median
Background (SUVmax))
Ga-68-DOTATOC
6,0
Ga-68-OPS202-15µg (A)
68Ga-DOTA-TOC
68Ga-OPS202
4,0
2,0
0,0
T:Liver
T:Pancreas T:Intestine T:Spleen
15 µg
Comparison of 177Lu-DOTA-JR11 and 177Lu-DOTA-TATE
dosimetry
177Lu-DOTA-TATE
(Agonist)
Isodose curves based on
3D voxel dosimetry analysis
177Lu-DOTA-JR11
(Antagonist)
Isodose curves based on
3D voxel dosimetry analysis
Gy/GBq
Gy/GBq
mean dose: 1.4 Gy/GBq
mean dose: 5.7 Gy/GBq
Tumor-to-kidney
Tumor-to-kidney
dose ratio: 1.1
dose ratio: 2.5
Wild D, et al., J Nucl Med 2014; 24;55:1248
Status of radiolabelled somatostatin receptor antagonists
DOTA-JR11: OPS201
Clinical Trials

NODAGA-JR11: OPS202
68Ga-NODAGA-JR11 (68Ga-OPS202)
vs 68Ga-DOTA-TOC
University of Basel Hospital, Switzerland
(ClinicalTrials.gov NCT02162446)
 The “theranostic pair” 68Ga-DOTA-JR11 and 177Lu-DOTAJR11 (68Ga-/177Lu-OPS201)
Memorial Sloan Kettering Cancer Center, New York, US
(ClinicalTrials.gov NCT02609737)
 Larger-scale multicenter clinical trials are planned for 68GaNODAGA-JR11 (68Ga-OPS202) and 177Lu-DOTA-JR11
(177Lu-OPS201)
OctreoPharm/IPSEN
Radiolabelled somatostatin receptor
antagonists
 represent the recent most favorable
innovation in molecular imaging and
PRRT of NETs
 may well be the future of imaging and
treatment of sstr-positive tumors
Prof. Helmut Maecke
Dr. Rosalba Mansi
Dr. Andreas Bauman
Luigi Del Pozzo, MSc
Prof. Damian Wild
Dr. Guillaume Nicolas
Dr. Felix Kaul