Purpose: G protein-coupled receptor agonists are being used as radiolabeled vectors for in vivo l... more Purpose: G protein-coupled receptor agonists are being used as radiolabeled vectors for in vivo localization and therapy of tumors. Recently, somatostatin-based antagonists were shown to be superior to agonists. Here, we compare the new [ 111 In/ 68 Ga]labeled bombesin-based antagonist RM1 with the agonist [ 111 In]-AMBA for targeting the gastrin-releasing peptide receptor (GRPR). Experimental Design: IC 50 , K d values, and antagonist potency were determined using PC-3 and HEK-GRPR cells. Biodistribution and imaging studies were done in nude mice transplanted with the PC-3 tumor. The antagonist potency was assessed by evaluating the effects on calcium release and on receptor internalization monitored by immunofluorescence microscopy. Results: The IC 50 value of [ nat In]-RM1 was 14 ± 3.4 nmol/L. [ nat/111 In]-RM1 was found to bind to the GRPR with a K d of 8.5 ± 2.7 nmol/L compared with a K d of 0.6 ± 0.3 nmol/L of [ 111 In]-AMBA. A higher maximum number of binding site value was observed for [ 111 In]-RM1 (2.4 ± 0.2 nmol/L) compared with [ 111 In]-AMBA (0.7 ± 0.1 nmol/L). [ nat Lu]-AMBA is a potent agonist in the immunofluorescence-based internalization assay, whereas [ nat In]-RM1 is inactive alone but efficiently antagonizes the bombesin effect. These data are confirmed by the calcium release assay. The pharmacokinetics showed a superiority of the radioantagonist with regard to the high tumor uptake (13.4 ± 0.8% IA/g versus 3.69 ± 0.75% IA/g at 4 hours after injection. as well as to all tumor-to-normal tissue ratios. Conclusion: Despite their relatively low GRPR affinity, the antagonists [ 111 In/ 68 Ga]-RM1 showed superior targeting properties compared with [ 111 In]-AMBA. As found for somatostatin receptor-targeting radiopeptides, GRP-based radioantagonists seem to be superior to radioagonists for in vivo imaging and potentially also for targeted radiotherapy of GRPR-positive tumors. (Clin Cancer Res 2009;15(16):5240-9
European Journal of Nuclear Medicine and Molecular Imaging, May 29, 2008
Purpose Diethylenetriamine-pentaacetic acid (DTPA)-coupled minigastrins are unsuitable for therap... more Purpose Diethylenetriamine-pentaacetic acid (DTPA)-coupled minigastrins are unsuitable for therapeutic application with the available β-emitting radiometals due to low complex stability. Low tumour-to-kidney ratio of the known radiopharmaceuticals is further limiting their potency. We used macrocyclic chelators for coupling to increase complex stability, modified the peptide sequence to enhance radiolytic stability and studied tumour-to-kidney ratio and metabolic stability using 111 In-labelled derivatives. Methods Gastrin derivatives with decreasing numbers of glutamic acids were synthesised using 111 In as surrogate for therapeutic radiometals for in vitro and in vivo studies. Gastrin receptor affinities of the nat In-metallated compounds were determined by receptor autoradiography using 125 I-CCK as radioligand. Internalisation was evaluated in AR4-2J cells. Enzymatic stability was determined by incubating the 111 In-labelled peptides in human serum. Biodistribution was performed in AR4-2J-bearing Lewis rats. Results IC 50 values of the nat In-metallated gastrin derivatives vary between 1.2 and 4.8 nmol/L for all methioninecontaining derivatives. Replacement of methionine by norleucine, isoleucine, methionine-sulfoxide and methioninesulfone resulted in significant decrease of receptor affinity (IC 50 between 9.9 and 1,195 nmol/L). All cholecystokinin receptor affinities were >100 nmol/L. All 111 In-labelled radiopeptides showed receptor-specific internalisation. Serum mean-life times varied between 2.0 and 72.6 h, positively correlating with the number of Glu residues. All 111 In-labelled macrocyclic chelator conjugates showed higher tumour-to-kidney ratios after 24 h (0.37-0.99) compared to 111 In-DTPA-minigastrin 0 (0.05). Tumour wash out between 4 and 24 h was low. Imaging studies confirmed receptor-specific blocking of the tumour uptake. Conclusions Reducing the number of glutamates increased tumour-to-kidney ratio but resulted in lower metabolic stability. The properties of the macrocyclic chelator-bearing derivatives make them potentially suitable for clinical purposes.
PET (positron emission tomography) is a powerful diagnostic and imaging technique which requires ... more PET (positron emission tomography) is a powerful diagnostic and imaging technique which requires short-lived positron emitting isotopes. The most commonly used are accelerator-produced 11 C and 18 F. An alternative is the use of metallic positron emitters. Among them 68Ga deserves special attention because of its availability from long-lived 68Ge/68Ga generator systems which render 68 Ga radiopharmacy independent of an onsite cyclotron. The coordination chemistry of Ga 3+ is dominated by its hard acid character. A variety of mono-and bifunctional chelators have been developed which allow the formation of stable 68 Ga 3+ complexes and convenient coupling to biomolecules. 68 Ga coupling to small biomolecules is potentially an alternative to 18 F-and 11 Cbased radiopharmacy. In particular, peptides targeting G-protein coupled receptors overexpressed on human tumour cells have shown preclinically and clinically high and specific tumour uptake. Kit-formulated precursors along with the generator may be provided, similar to the 99 Mo/ 99m Tc-based radiopharmacy, still the mainstay of nuclear medicine.
Die vorliegende Handlungsempfehlung dient als Grundlage zur Qualitätssicherung der Somatostatinre... more Die vorliegende Handlungsempfehlung dient als Grundlage zur Qualitätssicherung der Somatostatinrezeptor (SSTR-) PET/CT bei onkologischen Patienten. Die Leitlinie wurde interdisziplinär erarbeitet und enthält neben der Definition und Zielsetzung einen Konsens hinsichtlich der erforderlichen klinischen Hintergrundinformationen, Indikationsstellung, Durchführung, Auswertung, Dokumentation und Befunderstellung. Dabei werden die beiden gebräuchlichsten Radiotracer der SSTR-PET/CT (68Ga-DOTATOC und 68Ga-DOTATATE) vertieft dargestellt. Die SSTR-PET/CT erfordert eine enge Interaktion zwischen den zuweisenden und ausführenden Fachdisziplinen unter Berücksichtigung bereits vorhandener Leitlinien und Handlungsempfehlungen europäischer und deutscher Fachgesellschaften, namentlich der European Association of Nuclear Medicine (EANM), der Deutschen Gesellschaft für Endokrinologie (DGE), Deutschen Gesellschaft für Nuklearmedizin (DGN) und Deutschen Röntgengesellschaft (DRG).
Fatigue has been recognized as one of the most frequent complaints in IBS. The aims of the presen... more Fatigue has been recognized as one of the most frequent complaints in IBS. The aims of the present study are to examine: 1) the different dimensions of fatigue in IBS controlling for neuroticism, somatization and job stress; 2) the
Opioid peptides recently attracted much attention as low molecular weight compounds, which can ta... more Opioid peptides recently attracted much attention as low molecular weight compounds, which can target malignant cells expressing opioid receptors on their cell surface. Therefore opioid peptides have a potential to be introduced as radiopharmaceuticals. In this paper, we describe the method of conjugation of two bifunctional chelating agents (BFCAs), hydrazinopyridine-3-carboxylic acid (HYNIC) and 1,4,7,10-tetraazacyclo-dodecane-1,4,7,10-tetraacetic acid (DOTA), to the N-terminal amino group of morphiceptin, endomorphin-2, and two of their analogs modified in position 3. GABA was used as a spacer molecule. μ-Opioid binding affinities ofthe peptides were compared with the binding affinities ofBFCA-GABA-peptide conjugates. It was shown that the introduction of HYNIC to μ-opioid ligands causes only a slight decrease of μ-opioid receptor affinity, while DOTA-conjugates loose their affinity for μ-receptors completely.
The chelator somatostatin analogue dota-o-phe~-tyr3-octreotide (DOTATOC), which is stably labeled... more The chelator somatostatin analogue dota-o-phe~-tyr3-octreotide (DOTATOC), which is stably labeled with the ~-emitting radioisotope yttrium 90 (90y), is used as internal radiotherapy for the treatment of patients with advanced neuroendocrine tumors. We report 5 patients who developed chronic renal failure, caused in 3 patients by biopsy-proven thrombotic microangiopathy (TMA). Twenty-nine patients (14 men, 15 women) with normal renal function before therapy were treated with divided intravenous doses Of 9°Y-DOTATOC approximately 8 weeks apart (mean normalized cumulative dose, 165.4-+ 36.4 mCi/m2). Twenty-two of 29 patients were administered a normalized cumulative dose of 200 mCi/m 2 withoutside effects. Among the 7 patients (6 women, 1 man) administered a normalized cumulative dose greater than 200 mCi/m 2, 5 patients (4 women, 1 man) developed renal failure. Increasing serum creatinine levels were observed within 3 months after the last 9°y-DOTATOC injection. The evolution was rapidly progressive in 3 patients, resulting in end-stage renal failure within 6 months. The remaining 2 patients developed chronic renal insufficiency (mean serum creatinine levet, 300/~mol/L an average 16 months after the end of treatment). Renal biopsies performed in 3 patients showed typical signs of TMA involving g!omeruli, arterioles, and small arteries. Patients treated with high-dose s0y-DOTATOC internal radiotherapy (cumulative dose > 200 mCi/m 2) are at high risk to develop severe renal failure caused by TMA lesions. The histopathologic lesions are identical to those found after external radiotherapy, which suggests a causal relationship between s°Y-DOTATOC and renal TMA.
Die Liganden (I), deren Co(II)‐Chelate reversibler Sauerstoffaufnahme unterliegen, wurden durch Z... more Die Liganden (I), deren Co(II)‐Chelate reversibler Sauerstoffaufnahme unterliegen, wurden durch Zugabe der Pyridin‐2‐aldehyde zu den entsprechenden Polyaminen in EtOH dargestellt, katalytisch (Pd/C) hydriert und als Hydronitrate isoliert.
Current concepts for the treatment of somatostatin receptor positive tumours have not been very m... more Current concepts for the treatment of somatostatin receptor positive tumours have not been very motivating up to now. A promising alternative could be the new peptidic vector DOTA-D-Phe1-Tyr3-Octreotide (DOTATOC) recently developed in Basel. It may be labelled with the β-emitter yttrium-90 (90Y) for internal radiotherapy after systemic application. Pilot therapy studies have shown convincing results with this new radiopharmaceutical. These studies are presented with regard to efficacy and possible toxicity. In summary, the new receptor-mediated 90Y-DOTATOC therapy led to tumour response in the majority of patients, and only in some receiving high cumulative doses of >200 mCi per m2 body surface renal and hematological toxicity due to irradiation occured. For the reduction of renal accretion, concepts with concomitant amino acid infusions containing L-lysine in a higher concentration are currently under way.
Purpose: G protein-coupled receptor agonists are being used as radiolabeled vectors for in vivo l... more Purpose: G protein-coupled receptor agonists are being used as radiolabeled vectors for in vivo localization and therapy of tumors. Recently, somatostatin-based antagonists were shown to be superior to agonists. Here, we compare the new [ 111 In/ 68 Ga]labeled bombesin-based antagonist RM1 with the agonist [ 111 In]-AMBA for targeting the gastrin-releasing peptide receptor (GRPR). Experimental Design: IC 50 , K d values, and antagonist potency were determined using PC-3 and HEK-GRPR cells. Biodistribution and imaging studies were done in nude mice transplanted with the PC-3 tumor. The antagonist potency was assessed by evaluating the effects on calcium release and on receptor internalization monitored by immunofluorescence microscopy. Results: The IC 50 value of [ nat In]-RM1 was 14 ± 3.4 nmol/L. [ nat/111 In]-RM1 was found to bind to the GRPR with a K d of 8.5 ± 2.7 nmol/L compared with a K d of 0.6 ± 0.3 nmol/L of [ 111 In]-AMBA. A higher maximum number of binding site value was observed for [ 111 In]-RM1 (2.4 ± 0.2 nmol/L) compared with [ 111 In]-AMBA (0.7 ± 0.1 nmol/L). [ nat Lu]-AMBA is a potent agonist in the immunofluorescence-based internalization assay, whereas [ nat In]-RM1 is inactive alone but efficiently antagonizes the bombesin effect. These data are confirmed by the calcium release assay. The pharmacokinetics showed a superiority of the radioantagonist with regard to the high tumor uptake (13.4 ± 0.8% IA/g versus 3.69 ± 0.75% IA/g at 4 hours after injection. as well as to all tumor-to-normal tissue ratios. Conclusion: Despite their relatively low GRPR affinity, the antagonists [ 111 In/ 68 Ga]-RM1 showed superior targeting properties compared with [ 111 In]-AMBA. As found for somatostatin receptor-targeting radiopeptides, GRP-based radioantagonists seem to be superior to radioagonists for in vivo imaging and potentially also for targeted radiotherapy of GRPR-positive tumors. (Clin Cancer Res 2009;15(16):5240-9
European Journal of Nuclear Medicine and Molecular Imaging, May 29, 2008
Purpose Diethylenetriamine-pentaacetic acid (DTPA)-coupled minigastrins are unsuitable for therap... more Purpose Diethylenetriamine-pentaacetic acid (DTPA)-coupled minigastrins are unsuitable for therapeutic application with the available β-emitting radiometals due to low complex stability. Low tumour-to-kidney ratio of the known radiopharmaceuticals is further limiting their potency. We used macrocyclic chelators for coupling to increase complex stability, modified the peptide sequence to enhance radiolytic stability and studied tumour-to-kidney ratio and metabolic stability using 111 In-labelled derivatives. Methods Gastrin derivatives with decreasing numbers of glutamic acids were synthesised using 111 In as surrogate for therapeutic radiometals for in vitro and in vivo studies. Gastrin receptor affinities of the nat In-metallated compounds were determined by receptor autoradiography using 125 I-CCK as radioligand. Internalisation was evaluated in AR4-2J cells. Enzymatic stability was determined by incubating the 111 In-labelled peptides in human serum. Biodistribution was performed in AR4-2J-bearing Lewis rats. Results IC 50 values of the nat In-metallated gastrin derivatives vary between 1.2 and 4.8 nmol/L for all methioninecontaining derivatives. Replacement of methionine by norleucine, isoleucine, methionine-sulfoxide and methioninesulfone resulted in significant decrease of receptor affinity (IC 50 between 9.9 and 1,195 nmol/L). All cholecystokinin receptor affinities were >100 nmol/L. All 111 In-labelled radiopeptides showed receptor-specific internalisation. Serum mean-life times varied between 2.0 and 72.6 h, positively correlating with the number of Glu residues. All 111 In-labelled macrocyclic chelator conjugates showed higher tumour-to-kidney ratios after 24 h (0.37-0.99) compared to 111 In-DTPA-minigastrin 0 (0.05). Tumour wash out between 4 and 24 h was low. Imaging studies confirmed receptor-specific blocking of the tumour uptake. Conclusions Reducing the number of glutamates increased tumour-to-kidney ratio but resulted in lower metabolic stability. The properties of the macrocyclic chelator-bearing derivatives make them potentially suitable for clinical purposes.
PET (positron emission tomography) is a powerful diagnostic and imaging technique which requires ... more PET (positron emission tomography) is a powerful diagnostic and imaging technique which requires short-lived positron emitting isotopes. The most commonly used are accelerator-produced 11 C and 18 F. An alternative is the use of metallic positron emitters. Among them 68Ga deserves special attention because of its availability from long-lived 68Ge/68Ga generator systems which render 68 Ga radiopharmacy independent of an onsite cyclotron. The coordination chemistry of Ga 3+ is dominated by its hard acid character. A variety of mono-and bifunctional chelators have been developed which allow the formation of stable 68 Ga 3+ complexes and convenient coupling to biomolecules. 68 Ga coupling to small biomolecules is potentially an alternative to 18 F-and 11 Cbased radiopharmacy. In particular, peptides targeting G-protein coupled receptors overexpressed on human tumour cells have shown preclinically and clinically high and specific tumour uptake. Kit-formulated precursors along with the generator may be provided, similar to the 99 Mo/ 99m Tc-based radiopharmacy, still the mainstay of nuclear medicine.
Die vorliegende Handlungsempfehlung dient als Grundlage zur Qualitätssicherung der Somatostatinre... more Die vorliegende Handlungsempfehlung dient als Grundlage zur Qualitätssicherung der Somatostatinrezeptor (SSTR-) PET/CT bei onkologischen Patienten. Die Leitlinie wurde interdisziplinär erarbeitet und enthält neben der Definition und Zielsetzung einen Konsens hinsichtlich der erforderlichen klinischen Hintergrundinformationen, Indikationsstellung, Durchführung, Auswertung, Dokumentation und Befunderstellung. Dabei werden die beiden gebräuchlichsten Radiotracer der SSTR-PET/CT (68Ga-DOTATOC und 68Ga-DOTATATE) vertieft dargestellt. Die SSTR-PET/CT erfordert eine enge Interaktion zwischen den zuweisenden und ausführenden Fachdisziplinen unter Berücksichtigung bereits vorhandener Leitlinien und Handlungsempfehlungen europäischer und deutscher Fachgesellschaften, namentlich der European Association of Nuclear Medicine (EANM), der Deutschen Gesellschaft für Endokrinologie (DGE), Deutschen Gesellschaft für Nuklearmedizin (DGN) und Deutschen Röntgengesellschaft (DRG).
Fatigue has been recognized as one of the most frequent complaints in IBS. The aims of the presen... more Fatigue has been recognized as one of the most frequent complaints in IBS. The aims of the present study are to examine: 1) the different dimensions of fatigue in IBS controlling for neuroticism, somatization and job stress; 2) the
Opioid peptides recently attracted much attention as low molecular weight compounds, which can ta... more Opioid peptides recently attracted much attention as low molecular weight compounds, which can target malignant cells expressing opioid receptors on their cell surface. Therefore opioid peptides have a potential to be introduced as radiopharmaceuticals. In this paper, we describe the method of conjugation of two bifunctional chelating agents (BFCAs), hydrazinopyridine-3-carboxylic acid (HYNIC) and 1,4,7,10-tetraazacyclo-dodecane-1,4,7,10-tetraacetic acid (DOTA), to the N-terminal amino group of morphiceptin, endomorphin-2, and two of their analogs modified in position 3. GABA was used as a spacer molecule. μ-Opioid binding affinities ofthe peptides were compared with the binding affinities ofBFCA-GABA-peptide conjugates. It was shown that the introduction of HYNIC to μ-opioid ligands causes only a slight decrease of μ-opioid receptor affinity, while DOTA-conjugates loose their affinity for μ-receptors completely.
The chelator somatostatin analogue dota-o-phe~-tyr3-octreotide (DOTATOC), which is stably labeled... more The chelator somatostatin analogue dota-o-phe~-tyr3-octreotide (DOTATOC), which is stably labeled with the ~-emitting radioisotope yttrium 90 (90y), is used as internal radiotherapy for the treatment of patients with advanced neuroendocrine tumors. We report 5 patients who developed chronic renal failure, caused in 3 patients by biopsy-proven thrombotic microangiopathy (TMA). Twenty-nine patients (14 men, 15 women) with normal renal function before therapy were treated with divided intravenous doses Of 9°Y-DOTATOC approximately 8 weeks apart (mean normalized cumulative dose, 165.4-+ 36.4 mCi/m2). Twenty-two of 29 patients were administered a normalized cumulative dose of 200 mCi/m 2 withoutside effects. Among the 7 patients (6 women, 1 man) administered a normalized cumulative dose greater than 200 mCi/m 2, 5 patients (4 women, 1 man) developed renal failure. Increasing serum creatinine levels were observed within 3 months after the last 9°y-DOTATOC injection. The evolution was rapidly progressive in 3 patients, resulting in end-stage renal failure within 6 months. The remaining 2 patients developed chronic renal insufficiency (mean serum creatinine levet, 300/~mol/L an average 16 months after the end of treatment). Renal biopsies performed in 3 patients showed typical signs of TMA involving g!omeruli, arterioles, and small arteries. Patients treated with high-dose s0y-DOTATOC internal radiotherapy (cumulative dose > 200 mCi/m 2) are at high risk to develop severe renal failure caused by TMA lesions. The histopathologic lesions are identical to those found after external radiotherapy, which suggests a causal relationship between s°Y-DOTATOC and renal TMA.
Die Liganden (I), deren Co(II)‐Chelate reversibler Sauerstoffaufnahme unterliegen, wurden durch Z... more Die Liganden (I), deren Co(II)‐Chelate reversibler Sauerstoffaufnahme unterliegen, wurden durch Zugabe der Pyridin‐2‐aldehyde zu den entsprechenden Polyaminen in EtOH dargestellt, katalytisch (Pd/C) hydriert und als Hydronitrate isoliert.
Current concepts for the treatment of somatostatin receptor positive tumours have not been very m... more Current concepts for the treatment of somatostatin receptor positive tumours have not been very motivating up to now. A promising alternative could be the new peptidic vector DOTA-D-Phe1-Tyr3-Octreotide (DOTATOC) recently developed in Basel. It may be labelled with the β-emitter yttrium-90 (90Y) for internal radiotherapy after systemic application. Pilot therapy studies have shown convincing results with this new radiopharmaceutical. These studies are presented with regard to efficacy and possible toxicity. In summary, the new receptor-mediated 90Y-DOTATOC therapy led to tumour response in the majority of patients, and only in some receiving high cumulative doses of >200 mCi per m2 body surface renal and hematological toxicity due to irradiation occured. For the reduction of renal accretion, concepts with concomitant amino acid infusions containing L-lysine in a higher concentration are currently under way.
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Papers by Helmut Maecke