First-in-human study of novel SSTR antagonist 177Lu-DOTA-LM3 for peptide receptor radionuclide therapy in patients with metastatic neuroendocrine neoplasms: dosimetry, safety and efficacy

The objective of this study was to assess the safety, dosimetry, and efficacy of the ¹⁷⁷Lu-labeled somatostatin receptor (SSTR) antagonist DOTA-p-Cl-Phe-cyclo (D-Cys-Tyr-D-4-amino-Phe(carbamoyl)-Lys-Thr-Cys)D-Tyr-NH2 (¹⁷⁷Lu-DOTA-LM3) in patients with metastatic neuroendocrine neoplasms (NENs). Methods: Fifty-one patients (age 27-76, mean 51.6±13.9 years) with metastatic NENs underwent peptide receptor radionuclide therapy (PRRT) with ¹⁷⁷Lu-DOTA-LM3 between August 2017 and December 2019. The median administered activity per cycle was 6.1±0.88 GBq (range 2.8-7.4 GBq). ⁶⁸Ga-NODAGA-LM3 PET/CT was used for patient selection and follow-up after ¹⁷⁷Lu-DOTA-LM3 PRRT. Morphologic and molecular responses were evaluated in accordance with RECIST 1.1 and European Organization for Research and Treatment of Cancer (EORTC) criteria. Treatment-related adverse events were graded according to the National Cancer Institute Common Terminology Criteria for Adverse Events, version 5.0. Dosimetry was performed in 11 patients and compared with the SSTR agonist ¹⁷⁷Lu-DOTATOC in 247 patients undergoing PRRT on the same dosimetry protocol. Results: Higher uptake and a longer effective half-life of ¹⁷⁷Lu-DOTA-LM3 was found for whole-body as well as kidneys, spleen, and metastases, resulting in higher mean absorbed organ and tumor doses as compared to the agonist ¹⁷⁷Lu-DOTA-TOC. All patients tolerated therapy without any serious acute adverse effects. Mild nausea without vomiting was observed in 5 (9.8%) patients; no other symptoms were reported. The most severe delayed adverse event was CTC-3 thrombocytopenia in 3 (5.9%) patients. Neither CTC-4 thrombocytopenia nor CTC-3-4 anemia or leukopenia was observed after treatment. No significant decline in renal function was observed, nor was hepatotoxicity. According to RECIST 1.1, disease control could be reached in 40 patients (disease control rate, 85.1%) of 47 patients monitored after ¹⁷⁷Lu-DOTA-LM3 PRRT, with a partial response in 17 (36.2%) and stable disease in 23 (48.9%), whereas 7 (14.9%) patients had progressive disease, and by EORTC criteria, complete remission in 2 (4.3%), partial remission in 21 (44.7%), stable disease in 18 (38.3%), and progressive disease in 6 (12.8%) patients. Conclusion: "Antagonist PRRT" with ¹⁷⁷Lu-DOTA-LM3 could be administered without severe adverse effects and was well tolerated by the majority of patients, with thrombocytopenia occurring only in a few patients. No other severe adverse effects were observed, particularly no nephrotoxicity. The SSTR antagonist ¹⁷⁷Lu-DOTA-LM3 appears to be very promising for PRRT, provides favorable biodistribution and higher tumor radiation doses than SSTR agonists, and was very effective in treating advanced metastatic NENs, especially in patients with low or no SSTR agonist binding, even achieving complete remission in some patients.

Neodymium-140 DOTA-LM3: Evaluation of an In Vivo Generator for PET with a Non-Internalizing Vector

¹⁴⁰Nd (t_1/2 = 3.4 days), owing to its short-lived positron emitting daughter ¹⁴⁰Pr (t_1/2 = 3.4 min), has promise as an in vivo generator for positron emission tomography (PET). However, the electron capture decay of ¹⁴⁰Nd is chemically disruptive to macrocycle-based radiolabeling, meaning that an in vivo redistribution of the daughter ¹⁴⁰Pr is expected before positron emission. The purpose of this study was to determine how the delayed positron from the de-labeled ¹⁴⁰Pr affects preclinical imaging with ¹⁴⁰Nd. To explore the effect, ¹⁴⁰Nd was produced at CERN-ISOLDE, reacted with the somatostatin analogue, DOTA-LM3 (1,4,7,10- tetraazacyclododecane, 1,4,7- tri acetic acid, 10- acetamide N - p-Cl-Phecyclo(d-Cys-Tyr-d-4-amino-Phe(carbamoyl)-Lys-Thr-Cys)d-Tyr-NH2) and injected into H727 xenograft bearing mice. Comparative pre- and post-mortem PET imaging at 16 h postinjection was used to quantify the in vivo redistribution of ¹⁴⁰Pr following ¹⁴⁰Nd decay. The somatostatin receptor-positive pancreas exhibited the highest tissue accumulation of ¹⁴⁰Nd-DOTA-LM3 (13% ID/g at 16 h) coupled with the largest observed redistribution rate, where 56 ± 7% (n = 4, mean ± SD) of the in situ produced ¹⁴⁰Pr washed out of the pancreas before decay. Contrastingly, the liver, spleen, and lungs acted as strong sink organs for free ¹⁴⁰Pr³⁺. Based upon these results, we conclude that ¹⁴⁰Nd imaging with a non-internalizing vector convolutes the biodistribution of the tracer with the accumulation pattern of free ¹⁴⁰Pr. This redistribution phenomenon may show promise as a probe of the cellular interaction with the vector, such as in determining tissue dependent internalization behavior.

A Delphic consensus assessment: imaging and biomarkers in gastroenteropancreatic neuroendocrine tumor disease management

The complexity of the clinical management of neuroendocrine neoplasia (NEN) is exacerbated by limitations in imaging modalities and a paucity of clinically useful biomarkers. Limitations in currently available imaging modalities reflect difficulties in measuring an intrinsically indolent disease, resolution inadequacies and inter-/intra-facility device variability and that RECIST (Response Evaluation Criteria in Solid Tumors) criteria are not optimal for NEN. Limitations of currently used biomarkers are that they are secretory biomarkers (chromogranin A, serotonin, neuron-specific enolase and pancreastatin); monoanalyte measurements; and lack sensitivity, specificity and predictive capacity. None of them meet the NIH metrics for clinical usage. A multinational, multidisciplinary Delphi consensus meeting of NEN experts (n = 33) assessed current imaging strategies and biomarkers in NEN management. Consensus (>75%) was achieved for 78% of the 142 questions. The panel concluded that morphological imaging has a diagnostic value. However, both imaging and current single-analyte biomarkers exhibit substantial limitations in measuring the disease status and predicting the therapeutic efficacy. RECIST remains suboptimal as a metric. A critical unmet need is the development of a clinico-biological tool to provide enhanced information regarding precise disease status and treatment response. The group considered that circulating RNA was better than current general NEN biomarkers and preliminary clinical data were considered promising. It was resolved that circulating multianalyte mRNA (NETest) had clinical utility in both diagnosis and monitoring disease status and therapeutic efficacy. Overall, it was concluded that a combination of tumor spatial and functional imaging with circulating transcripts (mRNA) would represent the future strategy for real-time monitoring of disease progress and therapeutic efficacy.

Preclinical pharmacokinetics, biodistribution, radiation dosimetry and toxicity studies required for regulatory approval of a phase I clinical trial with (111)In-CP04 in medullary thyroid carcinoma patients

Introduction

From a series of radiolabelled cholecystokinin (CCK) and gastrin analogues, ¹¹¹In-CP04 (¹¹¹In-DOTA-(DGlu)₆-Ala-Tyr-Gly-Trp-Met-Asp-Phe-NH₂) was selected for further translation as a diagnostic radiopharmaceutical towards a first-in-man study in patients with medullary thyroid carcinoma (MTC). A freeze-dried kit formulation for multicentre application has been developed. We herein report on biosafety, in vivo stability, biodistribution and dosimetry aspects of ¹¹¹In-CP04 in animal models, essential for the regulatory approval of the clinical trial.

Materials and methods

Acute and extended single dose toxicity of CP04 was tested in rodents, while the in vivo stability of ¹¹¹In-CP04 was assessed by HPLC analysis of mouse blood samples. The biodistribution of ¹¹¹In-CP04 prepared from a freeze-dried kit was studied in SCID mice bearing double A431-CCK2R(±) xenografts at 1, 4 and 24 h pi. Further 4-h animal groups were either additionally treated with the plasma expander gelofusine or injected with ¹¹¹In-CP04 prepared by wet-labelling. Pharmacokinetics in healthy mice included the 30 min, 1, 4, 24, 48 and 72 h time points pi. Dosimetric calculations were based on extrapolation of mice data to humans adopting two scaling models.

Results

CP04 was well-tolerated by both mice and rats, with an LD₅₀ > 178.5 μg/kg body weight for mice and a NOAEL (no-observed-adverse-effect-level) of 89 μg/kg body weight for rats. After labelling, ¹¹¹In-CP04 remained >70% intact in peripheral mouse blood at 5 min pi. The uptake of ¹¹¹In-CP04 prepared from the freeze-dried kit and by wet-labelling were comparable in the A431-CCK2R(+)-xenografts (9.24 ± 1.35%ID/g and 8.49 ± 0.39%ID/g, respectively; P > 0.05). Gelofusine-treated mice exhibited significantly reduced kidneys values (1.69 ± 0.15%ID/g vs. 5.55 ± 0.94%ID/g in controls, P < 0.001). Dosimetry data revealed very comparable effective tumour doses for the two scaling models applied, of 0.045 and 0.044 mSv/MBq.

Conclusion

The present study has provided convincing toxicology, biodistribution and dosimetry data for prompt implementation of the freeze-dried kit formulation without or with gelofusine administration in a multicentre clinical trial in MTC patients.

From preclinical development to clinical application: Kit formulation for radiolabelling the minigastrin analogue CP04 with In-111 for a first-in-human clinical trial

Introduction

A variety of radiolabelled minigastrin analogues targeting the cholecystokinin 2 (CCK2) receptor were developed and compared in a concerted preclinical testing to select the most promising radiotracer for diagnosis and treatment of medullary thyroid carcinoma (MTC). DOTA–DGlu–DGlu–DGlu–DGlu–DGlu–DGlu– Ala–Tyr–Gly–Trp–Met–Asp–Phe–NH₂ (CP04) after labelling with ¹¹¹In displayed excellent characteristics, such as high stability, receptor affinity, specific and persistent tumour uptake and low kidney retention in animal models. Therefore, it was selected for further clinical evaluation within the ERA-NET project GRAN-T-MTC. Here we report on the development of a pharmaceutical freeze-dried formulation of the precursor CP04 for a first multi-centre clinical trial with ¹¹¹In-CP04 in MTC patients.

Materials and methods

The kit formulation was optimised by adjustment of buffer, additives and radiolabelling conditions. Three clinical grade batches of a final kit formulation with two different amounts of peptide (10 or 50 μg) were prepared and radiolabelled with ¹¹¹In. Quality control and stability assays of both the kits and the resulting radiolabelled compound were performed by HPLC analysis.

Results

Use of ascorbic acid buffer (pH 4.5) allowed freeze-drying of the kit formulation with satisfactory pellet-formation. Addition of methionine and gentisic acid as well as careful selection of radiolabelling temperature was required to avoid extensive oxidation of the Met¹¹-residue. Trace metal contamination, in particular Zn, was found to be a major challenge during the pharmaceutical filling process in particular for the 10 μg formulation. The final formulations contained 10 or 50 μg CP04, 25 mg ascorbic acid, 0.5 mg gentisic acid and 5 mg l-methionine. The radiolabelling performed by incubation of 200–250 MBq ¹¹¹InCl₃ at 90 °C for 15 min resulted in reproducible radiochemical purity (RCP) >94%. Kit-stability was proven for >6 months at +5 °C and at +25 °C. The radiolabelled product was stable for >4 h at +25 °C.

Conclusion

A kit formulation to prepare ¹¹¹In-CP04 for clinical application was developed, showing high stability of the kit as well as high RCP of the final product.

90Y-DOTATOC as a Therapeutic Option for Complex Recurrent or Progressive Meningiomas

The standard treatment of meningiomas is surgery or radiotherapy. Complex, especially recurrent or progressive cases, may exhibit tumor growth involving critical neurovascular structures or diffuse growth, resulting in limited efficacy and higher risk of standard treatment. We evaluated whether somatostatin receptor-targeted radionuclide therapy with (90)Y-DOTATOC may be a therapeutic option.

METHODS

Fifteen patients with recurrent or progressive meningiomas after multimodal pretreatment or unfavorable medical risk profile were treated with systemic (90)Y-DOTATOC. Endpoints were progression-free survival and toxicity.

RESULTS

Usually applied doses were 7,400 MBq/m(2) of (90)Y-DOTATOC in 2 fractions. Mean observation time was 49.7 mo (range, 12-137 mo). Overall median progression-free survival was at least 24 mo. Toxicity was moderate, mostly hematologic (n = 8) and transient.

CONCLUSION

(90)Y-DOTATOC therapy is feasible and may represent a promising second- or third-line option for complex meningiomas, which are progressive or otherwise not treatable with a reasonable risk-benefit ratio.

Comparison of 68Ga-DOTANOC and 68Ga-DOTATATE PET/CT within patients with gastroenteropancreatic neuroendocrine tumors

Somatostatin receptor PET tracers such as [(68)Ga-DOTA,1-Nal(3)]-octreotide ((68)Ga-DOTANOC) and [(68)Ga-DOTA,Tyr(3)]-octreotate ((68)Ga-DOTATATE) have shown promising results in patients with neuroendocrine tumors, with a higher lesion detection rate than is achieved with (18)F-fluorodihydroxyphenyl-l-alanine PET, somatostatin receptor SPECT, CT, or MR imaging. (68)Ga-DOTANOC has high affinity for somatostatin receptor subtypes 2, 3, and 5 (sst2,3,5). It has a wider receptor binding profile than (68)Ga-DOTATATE, which is sst2-selective. The wider receptor binding profile might be advantageous for imaging because neuroendocrine tumors express different subtypes of somatostatin receptors. The goal of this study was to prospectively compare (68)Ga-DOTANOC and (68)Ga-DOTATATE PET/CT in the same patients with gastroenteropancreatic neuroendocrine tumors (GEP-NETs) and to evaluate the clinical impact of (68)Ga-DOTANOC PET/CT.

METHODS

Eighteen patients with biopsy-proven GEP-NETs were evaluated with (68)Ga-DOTANOC and (68)Ga-DOTATATE using a randomized crossover design. Labeling of DOTANOC and DOTATATE with (68)Ga was standardized using a fully automated synthesis device. PET/CT findings were compared with 3-phase CT scans and in some patients with MR imaging, (18)F-FDG PET/CT, and histology. Uptake in organs and tumor lesions was quantified and compared by calculation of maximum standardized uptake values (SUVmax) using volume computer-assisted reading.

RESULTS

Histology revealed low-grade GEP-NETs (G1) in 4 patients, intermediate grade (G2) in 7, and high grade (G3) in 7. (68)Ga-DOTANOC and (68)Ga-DOTATATE were false-negative in only 1 of 18 patients. In total, 248 lesions were confirmed by cross-sectional and PET imaging. The lesion-based sensitivity of (68)Ga-DOTANOC PET was 93.5%, compared with 85.5% for (68)Ga-DOTATATE PET (P = 0.005). The better performance of (68)Ga-DOTANOC PET is attributed mainly to the significantly higher detection rate of liver metastases rather than tumor differentiation grade. Multivariate analysis revealed significantly higher SUVmax in G1 tumors than in G3 tumors (P = 0.009). This finding was less pronounced with (68)Ga-DOTANOC (P > 0.001). Altogether, (68)Ga-DOTANOC changed treatment in 3 of 18 patients (17%).

CONCLUSION

The sst2,3,5-specific radiotracer (68)Ga-DOTANOC detected significantly more lesions than the sst2-specific radiotracer (68)Ga-DOTATATE in our patients with GEP-NETs. The clinical relevance of this finding has to be proven in larger studies.

Is there need for radioimmunotherapy? results of a phase I/II study in patients with indolent B-cell lymphomas using lutetium-177-DOTA-rituximab

AIM

The aim of the study was to explore the clinical response to 177Lutetium-DOTA-rituximab (177Lu-D-R) and to determine the maximum tolerated dose (MTD) in the treatment of patients with relapsed follicular, mantle cell or other indolent lymphomas such as marginal zone lymphoma as well as to put these results into context with other therapy options for these patients.

METHODS

Treatment consisted of cold rituximab (250 mg/m2) on day 1 and day 8 and 177Lu-DOTA-Rituximab on day 8. Reassessment was done at week 10. Thirty-one patients (males=17, females=14, median number of pretreatments: 3) were treated in seven cohorts. Escalation of injected activity was carried out in steps of 5 mCi/m². Dosimetry was performed in the first 20 patients.

RESULTS

The MTD was found to be 45 mCi/m2. Thrombocytopenia and leukopenia were the dose-limiting toxicities. Significant anemia only occurred at dose level 7. We observed the nadir of platelets after a median of 36 days from treatment with 177Lu-D-R and a nadir of granulocytes after a median of 50 days from 177Lu-D-R treatment. Non-hematological toxicity was negligible. We observed clinical responses at all dose levels and for all lymphoma entities. Some of the responses were durable; the longest follow up in complete remission is currently over eight years.

CONCLUSION

The MTD of 177Lu-DOTA-Rituximab was found to be 45 mCi/m². Non hematologic toxicity was negligible. Responses were seen in all lymphoma entities and at all dose levels tested. Further testing seems to be most promising mainly in follicular and marginal zone lymphoma in particular as the results compare well to other therapy options for these patients with regard to effectiveness, toxicity and discomfort for the patients.

Glucagon-like peptide-1 receptor imaging for localization of insulinomas

CONTEXT

The surgical removal of insulinomas is hampered by difficulties to localize it using conventional radiological procedures. Recently these tumors were shown to exhibit a very high density of glucagon-like peptide-1 receptors (GLP-1R) in vitro that may be used as specific targets for in vivo receptor radiolabeling.

OBJECTIVE

The objective of the study was to test the 111In-labeled GLP-1R agonist 111In-DOTA-exendin-4 in localizing insulinomas using single photon emission computed tomography in combination with computed tomography images.

DESIGN

This was a prospective open-label investigation.

SETTING

The study was conducted at three tertiary referral centers in Switzerland.

PATIENTS

Patients included six consecutive patients with proven clinical and biochemical endogenous hyperinsulinemic hypoglycemia.

INTERVENTION

(111)In-DOTA-exendin-4 was administered iv at a dose of about 90 MBq (30 microg peptide) over 5 min. Whole-body planar images of the abdomen were performed at 20 min, 4 h, 23 h, 96 h, and up to 168 h after injection. After surgical removal of the insulinomas, GLP-1R expression was assessed in the tumor tissue in vitro by GLP-1R autoradiography.

MAIN OUTCOME MEASURE

The detection rate of insulinomas was measured.

RESULTS

In all six cases, the GLP-1R scans successfully detected the insulinomas identified using conventional methods in four cases. By using a gamma-probe intraoperatively, GLP-1R detection permitted a successful surgical removal of the tumors in all patients, diagnosed histopathologically as five pancreatic and one extrapancreatic insulinomas. In vitro GLP-1R autoradiography showed a high density of GLP-1R in all tested insulinomas.

CONCLUSION

In vivo GLP-1R imaging is an innovative, noninvasive diagnostic approach that successfully localizes small insulinomas pre- and intraoperatively and that may in the future affect the strategy of insulinoma localization.

Role of free fatty acids in regulating gastric emptying and gallbladder contraction

The limited effectiveness of orlistat, an inhibitor of gastrointestinal lipases, in inhibiting fat digestion is not completely understood. Therefore we studied the effect of orally and duodenally administered orlistat on gastric emptying, cholecystokinin (CCK) secretion, and gallbladder contraction. In healthy males, gastric emptying of solids and fat were quantified scintigraphically, gallbladder contraction by ultrasound and CCK release by radioimmunoassay. Three studies were performed: (1) oral and (2) duodenal orlistat with a fat-containing meal, and (3) duodenal orlistat with a fat-free meal. Gastric emptying rates of solids and fat (T50% accelerated by 16 and by 22%, p < 0.05, respectively) were significantly faster after duodenal perfusion of orlistat; gallbladder contraction and CCK release were reduced under these conditions (p < 0.005, respectively). With oral orlistat no significant effect was documented on these parameters. We conclude that fat hydrolysis is essential in the regulation of fat-induced gastric emptying and gallbladder contraction.

Copper complexes of new benzodioxotetraaza macrocycles with potential applications in nuclear medicine

Two novel benzodioxotetraaza macrocycles [2,9-dioxo-1,4,7,10-tetraazabicyclo[10.4.0]1,11-hexadeca-1(11),13,15-triene (H2L1) and 2,10-dioxo-1,4,8,11-tetraazabicyclo[11.4.0]1,12-heptadeca-1(12),14,16-triene (H2L2)] were synthesized by a [1 + 1] crablike cyclization. The protonation constants of both ligands were determined by 1H NMR titration and by potentiometry at 25.0 degrees C in 0.10 M ionic strength in KNO3. The latter method was also used to ascertain the stability constants of their copper(II) complexes. These studies showed that the CuL1 complex has a much lower thermodynamic stability than the CuL2, and the H2L2 displays an excellent affinity for copper(II), due to the good fit of copper(II) into its cavity. The copper complexes of the novel ligands were characterized by electronic spectroscopy in solution and by crystal X-ray diffraction. These studies indicated that the copper center in the CuL1 complex adopts a square-pyramidal geometry with the four nitrogen atoms of the macrocycle forming the equatorial plane and a water molecule at axial position, and the copper in the CuL2 complex is square-planar. Several labeling conditions were tested, and only H2L2 could be labeled with 67Cu efficiently (>98%) in mild conditions (39 degrees C, 15 min) to provide a slightly hydrophilic radioligand (log D = -0.19 +/-0.03 at pH 7.4). The in vitro stability was studied in the presence of different buffers or with an excess of diethylenetriamine-pentaethanoic acid. Very high stability was shown under these conditions for over 5 days. The incubation of the radiocopper complex in human serum showed 6% protein binding.

Biodistribution and elimination characteristics of two 111In-labeled CCK-2/gastrin receptor-specific peptides in rats

BACKGROUND

Due to their high CCK-2/gastrin receptor selectivity, high affinity, and rapid background clearance, radiolabeled minigastrins (MG) are emerging as promising new tools in the diagnosis and therapy of CCK-2/gastrin receptor-positive tumors. In this study, the pharmacokinetic profile, particularly the excretion mode, of two 111In-labeled minigastrins was compared in rats. The first tracer, 111In-MG-0 is based on (D)Glu1-MG, while the second, 111In-MG-11, is its des-(Glu)5-derivative, expected to be less retained in renal tissue.

MATERIALS AND METHODS

The fate of 111In-MG-0 and 111In-MG-11 in the body of rats was investigated during biodistribution and bioelimination experiments, while the respective elimination parameters were determined in perfused rat liver and kidney models.

RESULTS

During biodistribution both compounds were rapidly cleared from the blood and most non-target organs whereas activity levels in the bowel and stomach declined slowly. The overall contribution of hepatobiliary excretion of 111In-MG-0 and 111In-MG-11 was relatively small. In the perfused rat liver their elimination into the bile was negligible. In contrast, renal excretion was the major excretion pathway for both analogs, mainly via glomerular filtration. However, kidney levels were substantially higher and retention was more prolonged in the case of 111In-MG-0 as compared to 111In-MG-11.

CONCLUSION

The presence of the (Glu)5-chain in 111Ln-MG-0 appears to be implicated in the prolonged radioactivity retention in the kidney of rats.

Are radiogallium-labelled DOTA-conjugated somatostatin analogues superior to those labelled with other radiometals?

PURPOSE

Gallium-68 is a metallic positron emitter with a half-life of 68 min that is ideal for the in vivo use of small molecules, such as [68Ga-DOTA,Tyr3]octreotide, in the diagnostic imaging of somatostatin receptor-positive tumours. In preclinical studies it has shown a striking superiority over its 111In-labelled congener. The purpose of this study was to evaluate whether third-generation somatostatin-based, radiogallium-labelled peptides show the same superiority.

METHODS

Peptides were synthesised on solid phase. The receptor affinity was determined by in vitro receptor autoradiography. The internalisation rate was studied in AR4-2J and hsst-HEK-transfected cell lines. The pharmacokinetics was studied in a rat xenograft tumour model, AR4-2J.

RESULTS

All peptides showed high affinities on hsst2, with the highest affinity for the Ga(III)-complexed peptides. On hsst3 the situation was reversed, with a trend towards lower affinity of the Ga(III) peptides. A significantly increased internalisation rate was found in sst2-expressing cells for all 67Ga-labelled peptides. Internalisation into HEK-sst3 was usually faster for the 111In-labelled peptides. No internalisation was found into sst5. Biodistribution studies employing [67Ga-DOTA,1-Nal3]octreotide in comparison to [111In-DOTA,1-Nal3]octreotide and [67Ga-DOTA,Tyr3]octreotide showed a significantly higher and receptor-mediated uptake of the two 67Ga-labelled peptides in the tumour and somatostatin receptor-positive tissues. A patient study illustrated the potential advantage of a broad receptor subtype profile radiopeptide over a high-affinity sst2-selective radiopeptide.

CONCLUSION

This study demonstrates that 67/68Ga-DOTA-octapeptides show distinctly better preclinical, pharmacological performances than the 111In-labelled peptides, especially on sst2-expressing cells and the corresponding animal models. They may be excellent candidates for further development for clinical studies.

Effect of cAMP on porcine ciliary transepithelial short-circuit current, sodium transport, and chloride transport

PURPOSE

To investigate the effects of 8-bromo-cAMP (cAMP) on porcine ciliary transepithelial short-circuit current (Isc) and transport of chloride (Cl-) and sodium (Na+).

METHODS

With Ussing-type chambers, cAMP-induced changes in Isc, electrical resistance (ER), and transepithelial 36Cl- and 22Na+ fluxes were measured. Drugs were applied to the nonpigmented epithelium (NPE) and/or pigmented epithelium (PE) side(s). The effect of IBMX (1, 5, or 10 microM; 3-isobutyl-1-methylxanthine) on Isc-increase induced by 8-bromo-cAMP on the PE side was also tested.

RESULTS

On the NPE side, a single concentration (10 microM, 100 microM, or 1 mM) of 8-bromo-cAMP induced a biphasic (transient peak followed by sustained plateau) Isc increase. On the PE side, 8-bromo-cAMP induced a similar but delayed biphasic Isc increase at 1 mM, a slight plateau-Isc increase at 100 microM, and no Isc increase at 10 microM. In the concentration-response curve, the cAMP-induced peak-Isc increase became significant at a concentration 10,000 times lower on the NPE than on the PE side. At 10 microM, the cumulative cAMP-induced Isc-increase reached its maximum on the NPE side, but was virtually nonexistent on the PE side. IBMX (a phosphodiesterase inhibitor) but not 8-CPT-6-Phe-cAMP (higher permeability than 8-bromo-cAMP) significantly increased the peak-Isc concentration-response curve induced by 8-bromo-cAMP (10 nM-1 mM) on the PE side. On the NPE but not the PE side, 10 microM 8-bromo-cAMP induced a significant but transient increase in net PE-to-NPE 36Cl- flux (1.03 +/- 0.18 microEq/min per square centimeter; P < 0.001). Neither ER nor transepithelial 22Na+ flux was changed after cAMP exposure.

CONCLUSIONS

In porcine ciliary processes, apparently on the NPE side, cAMP triggers a biphasic (transient peak followed by a sustained plateau) Isc increase. Only the peak-Isc increase involves an increase in net PE-to-NPE Cl- transport.

Clinical usefulness of 99mTc-EDDA/HYNIC-TOC scintigraphy in oncological diagnostics: a pilot study

The clinical usefulness of a new 99mTc-labeled somatostatin analogue has been studied from the standpoint of oncological diagnostics. The group of patients studied included 40 individuals with diagnosed malignant neoplasms (32 primary and 8 metastatic). Among the primary tumors were 7 pituitary adenomas (5 hormonally active and 2 inactive), 1 liposarcoma, 2 carcinoids, 1 breast carcinoma, and 21 cases of lung cancer (2 small cell and 19 non-small cell) were represented. The metastatic tumors consisted of: 3 malignant melanomas, 1 pheochromocytoma, 1 prostatic cancer, 1 leiomyosarcoma, 1 pancreatic carcinoma ectopically secreting ACTH, and 1 carcinoid of the thymus. The radiopharmaceutical, 99mTc-EDDA/HYNIC-octreotide, was i.v. administered at the activity of 740-925 MBq. The imaging was comprized of a whole-body scan and single photon emission computed tomography. Positive scintigrams were obtained in 4 of 5 hormonally active pituitary adenomas, in 1 of 2 cases of carcinoid, in liposarcoma, breast cancer, and all cases of small cell (SCLC) and non-small cell lung cancer (NSCLC). The neoplastic metastases were visualized in 2 of 3 cases of melanoma and in patients with pheochromocytoma, pancreatic carcinoma secreting ACTH, and thymic carcinoid. Scintigrams were negative in both hormonally inactive pituitary adenomas, in one case of metastatic malignant melanoma, leiomyosarcoma, and in cases of metastasis from the prostatic carcinomas. The results of this pilot study indicated that 99mTc-EDDA/HYNIC-TOC is a potentially useful radiopharmaceutical for the imaging of a wide range of primary and metastatic tumors. More detailed indications for the clinical usefulness of the new tracer for the imaging of selected tumor types require studies on much larger groups of patients. Special attention should be paid to the successful imaging of all cases of NSCLC.

Targeted radiotherapy for small cell lung cancer using 90Yttrium-DOTATOC, an Yttrium-labelled somatostatin analogue: a pilot trial

BACKGROUND

Some small cell lung carcinomas (SCLC) express neuro-endocrine markers, such as somatostatin receptors. Therefore, somatostatin analogues can be radio-labelled with 111Indium (Octreoscan) for diagnostic scintigraphy, or with 90Y-DOTATOC for therapeutic use. This is the first trial to assess the toxicity and efficacy of treatment with 90Y-DOTATOC in patients with Octreoscan positive SCLC.

METHODS

Patients with SCLC after > or =first line chemotherapy received an Octreoscan scintigraphy and results were compared to CT scans. Patients with strong somatostatin-receptor expression were treated with 60 mCi/m2 90Y-DOTATOC i.v. every 3 weeks, for a total of three cycles. Major inclusion criteria were measurable tumour lesions, disease progression, normal creatinine clearance, PS < or = 2.

RESULTS

Octreoscan scintigraphy identified 70% of all primary tumours, 87% of all mediastinal lesions, but only 26% of all extrathoracic tumour manifestations. Six patients were treated. Median number of 90Y-DOTATOC cycles was 2 (1-3). The only grade 3 toxicity was fatigue (n = 2) and dyspnea (n = 1). There were no severe renal or haematological toxicities. All six patients had tumour progression, median progression free survival (PFS) was 37.5 days (28-52) and median overall (OS) was 103.5 days (28-269).

CONCLUSION

This is the first report of somatostatin-receptor targeted radiotherapy for SCLC in the literature. In contrast to well differentiated neuro-endocrine tumours, 90Y-DOTATOC seems to be inactive in SCLC.

Efficacy of 99mTc-EDDA/HYNIC-TOC Scintigraphy in Differential Diagnosis of Solitary Pulmonary Nodules

Fifty consecutive patients with solitary pulmonary nodules (SPN) on chest radiographs were studied scintigraphically after the administration of a somatostatin analog 99mTc-EDDA/HYNIC-TOC. The activity amounted to 740-925 MBq and a single photon emission computed tomography (SPECT) technique was applied. Verification of the nodule etiology was based on histology or cytology and bacteriology. As additional criterion for nodule benignity, its stable size in a chest radiograph for at least 3 years was accepted. In 31 patients, malignant etiologies of nodules were found. The diagnoses included: 11 adenocarcinomas, 6 squamous-cell carcinomas, 2 large-cell carcinomas, 6 nonsmall-cell lung cancers (NSCLC) of unspecified, more detailed morphology, 2 small-cell lung cancers (SCLC), 2 typical carcinoids, and 2 metastatic tumors: leiomyosarcoma and malignant melanoma. In 19 patients, the following benign tumors were diagnosed: 6 tuberculomas, 2 other granulomas, 4 hamartomas, 2 nonspecific inflammatory infiltrates, 1 abscess, 1 peripheral carcinoid of morphological characteristics of a benign tumor, 1 ectopic lesion of thyroid tissue, and 2 benign tumors of unspecified etiology, with stable size over 3 and 5 years. Positive scintigraphic results were obtained in 28 of 31 patients (90%) with malignant SPNs; among these there were 26 of 27 (96%) cases of primary pulmonary carcinoma. The remaining 2 false-negative cases included metastatic tumors: liposarcoma and melanoma. Among 19 benign lesions, 15 (79%) did not accumulate the radiopharmaceutical. The remaining 4 tumors visible on scintigrams included: 1 tuberculoma, 1 hamartoma, 1 abscess, and 1 case of nonestablished diagnosis (with stable size over 3 years). In conclusion, scintigraphy with 99mTc-EDDA/HYNIC-TOC appears to be an effective procedure for differentiation between malignant and benign SPNs.

Successful targeted radiotherapy with 90Y-DOTATOC in a patient with Merkel cell carcinoma. A Case Report

Merkel cell carcinomas (MCC) belong to the family of neuroendocrine tumors. In addition to other markers, they express somatostatin receptors. They are uncommon, highly malignant skin tumors with an aggressive clinical course. They develop in sun-exposed areas of the skin, mostly in elderly patients. In addition to frequent locoregional recurrences, there is a high incidence of distant metastases. Treatment is stage dependent and consists of operation and chemo- and/or radiotherapy, respectively. The advanced age of patients often impedes adequate therapy. (90)Y-DOTATOC is a novel radiolabeled somatostatin analogue containing the active octapeptide of somatostatin. It is very well tolerated and offers the option of treating somatostatin receptor-positive tumors by targeted radiotherapy. We report the case of an 83-year-old woman with recurrent MCC of the left cheek. The primary tumor and several relapses were treated with surgery and locoregional radiotherapy. After the 3rd relapse, she was treated 4 times with (90)Y-DOTATOC and two complete remissions were achieved. The fourth administration after the 2nd relapse was ineffective and conventional chemotherapy was started. There were no side effects of the (90)Y-DOTATOC. We conclude that due to its good tolerability, (90)Y-DOTATOC therapy should be evaluated further as a new therapy for somatostatin receptor-positive MCC.

Biokinetics and imaging with the somatostatin receptor PET radioligand (68)Ga-DOTATOC: preliminary data

Somatostatin (SMS) scintigraphy is widely used for the detection and staging of neuroendocrine tumours. Because of its superior imaging properties, there is growing interest in the use of positron emission tomography (PET) technology for SMS scintigraphy. This study addressed the production of gallium-68 DOTATOC, its biokinetics and its clinical performance in detecting SMS-positive tumours and metastases. A preparation protocol was developed, yielding 40% overall incorporation of (68)Ga into the peptide (DOTATOC). After column filtration, the radiochemical purity exceeded 98%. Eight patients with histologically verified carcinoid tumours were injected with 80-250 MBq of this tracer. PET acquisition was initiated immediately after administration and carried out until 3 h post injection. Images were quantitated using standardised uptake values and target to non-target ratios. Prior to (68)Ga-DOTATOC PET, all patients underwent indium-111 octreotide planar and single-photon emission tomographic (SPET) imaging. Arterial activity elimination was bi-exponential, with half-lives of 2.0 (+/-0.3) min and 48 (+/-7) min. No radioactive metabolites were detected within 4 h in serum. Maximal tumour activity accumulation was reached 70+/-20 min post injection. Kidney uptake averaged <50% compared with spleen uptake. Of 40 lesions predefined by computed tomography and/or magnetic resonance imaging, (68)Ga-DOTATOC PET identified 100%, whereas (111)In-octreotide planar and SPET imaging identified only 85%. Tumour to non-tumour ratios ranged from >3:1 for liver ((111)In-octreotide: 1.5:1) to 100:1 for CNS ((111)In-octreotide: 10:1). With (68)Ga-DOTATOC >30% additional lesions were detected. It is concluded that PET using (68)Ga-DOTATOC results in high tumour to non-tumour contrast and low kidney accumulation and yields higher detection rates as compared with (111)In-octreotide scintigraphy.

Successful diffusible brachytherapy (dBT) of a progressive low-grade astrocytoma using the locally injected peptidic vector and somatostatin analogue [90Y]-DOTA0-D-Phe1-Tyr3-octreotide (DOTATOC)

We present the therapeutic effect of diffusible brachytherapy (dBT), an innovative approach for the management of symptomatic low grade gliomas [1]. This protocol uses a radiolabelled small diffusible peptidic vector which is a somatostatin analogue to target somatostatin type 2 (sst-2) receptors. The stable radioconjugate [90Y]-DOTA0-D-Phe1-Tyr3-octreotide (DOTATOC) is repeatedly injected via catheters placed into the resection cavity or into tumour nodules. We report on the four year follow-up after initiation of dBT to treat progressive disease in a patient with a complex eleven year history of fibrillary low-grade astrocytoma. The radiopharmakon was not only locally injected into the resection cavity following debulking surgery, but also administered by slow infusion technique to target recurrent and infiltrative tumour zones in the subventricular region around the inferior and posterior horns. In conclusion, peptidic vector based dBT was found to be safe, of mild and transitory toxicity, and effective in long-term tumour control.

Successful diffusible brachytherapy (dBT) of a progressive low-grade astrocytoma using the locally injected peptidic vector and somatostatin analogue [90Y]-DOTA0-D-Phe1-Tyr3-octreotide (DOTATOC)

We present the therapeutic effect of diffusible brachytherapy (dBT), an innovative approach for the management of symptomatic low grade gliomas [1]. This protocol uses a radiolabelled small diffusible peptidic vector which is a somatostatin analogue to target somatostatin type 2 (sst-2) receptors. The stable radioconjugate [90Y]-DOTA0-D-Phe1-Tyr3-octreotide (DOTATOC) is repeatedly injected via catheters placed into the resection cavity or into tumour nodules. We report on the four year follow-up after initiation of dBT to treat progressive disease in a patient with a complex eleven year history of fibrillary low-grade astrocytoma. The radiopharmakon was not only locally injected into the resection cavity following debulking surgery, but also administered by slow infusion technique to target recurrent and infiltrative tumour zones in the subventricular region around the inferior and posterior horns. In conclusion, peptidic vector based dBT was found to be safe, of mild and transitory toxicity, and effective in long-term tumour control.

Tegaserod, a 5-HT4 receptor partial agonist, accelerates gastric emptying and gastrointestinal transit in healthy male subjects

BACKGROUND

Serotonin and its type-4 (5-hydroxytryptamine4) receptor play a major role in the physiology of the gastrointestinal tract. The effect of intravenous and/or oral tegaserod, a 5-hydroxytryptamine4 receptor partial agonist, on gastric emptying, small bowel transit and colonic transit has not been studied in detail in humans.

AIM

To assess the pharmacodynamic effects of repeated oral and intravenous administration of tegaserod on gastric emptying and small intestine and colonic transit.

METHODS

A randomized, placebo-controlled, double-blind, three-way, crossover study of 6 mg oral and 0.6 mg intravenous tegaserod in 12 healthy male subjects was performed. Each treatment arm of the study involved 3 days of twice-daily administration and 1 day of daily administration of the study drugs.

RESULTS

In comparison with placebo, oral and intravenous tegaserod significantly increased the gastric emptying rate (P < 0.01), accelerated colonic filling (P < 0.01) and shortened colonic transit at 48 h (P < 0.05). Tegaserod shortened the small intestine transit time by 30% after oral and by 37% after intravenous administration.

CONCLUSIONS

In healthy subjects, tegaserod markedly accelerated gastric emptying and small intestinal transit, and induced a small but significant acceleration of colonic transit. Tegaserod can act as a promotile agent throughout the gastrointestinal tract.

Gd-DOTA as a gastrointestinal contrast agent for gastric emptying measurements with MRI

Current MR meal markers may interfere with gastric motility and secretion restricting the use of MRI in the measurement of gastric physiology. We therefore evaluated Gd-DOTA as a liquid phase marker, in vitro by determining dissociation, and adherence to the solids, and in vivo by simultaneous MRI (0.35 T scanner, multiple T1-weighted sections of the upper abdomen) and double indicator (perfusion marker PEG 4000, meal marker 99mTc-DTPA) measurements of emptying and secretion, following ingestion of 500 ml 10% glucose. In vitro Gd-DOTA was stable at a pH > 2 with < 2% dissociation at 24 h during incubation with HCl. Dissociation during incubation with HCl was linearly dependent on H+ concentration (0.77 < pH < 2.02). Less Gd-DOTA was absorbed onto the solid phase than 99mTc-DTPA (25% cf 36%). In vivo Gd-DOTA marked gastric contents provided strong positive contrast. Similar emptying curves were observed with both MRI and double-indicator techniques (r = 0.987, P < 0.001). Gd-DOTA has the potential to be a useful liquid phase contrast agent in MR studies on gastric function.

The Diagnostic Value of Mucinous Carcinoma-Associated Antigen (MCA) Tests in Breast Carcinomas

MCA (Mucinous Carcinoma-Associated Antigen) levels of 176 breast carcinoma patients were tested postoperatively by serial determination. One hundred forty-one patients had nonprogressive disease (PD–) while 35 were in the progressive phase (PD +); in the latter the diagnosis was confirmed by means of current diagnostic procedures.

One hundred seventeen of the 141 PD– patients showed MCA levels below cutoff whereas 27 of the 35 PD + cases showed high values. The difference in the incidence of elevated MCA levels between PD–and PD + groups was statistically significant (p < 0.05). The overall diagnostic efficacy of MCA assays showed 77% sensitivity and 82% specificity.

Measurement of gastric emptying by magnetic resonance imaging in humans

A new noninvasive radiation-free method to measure gastric emptying in humans was developed. The upper abdomen was recorded with a magnetic resonance imager after administration of a liquid meal containing Gadolinium tetraazacyclododecane tetraacetic acid as a magnetic resonance image (MRI) marker. Meal volumes, total gastric volumes, and secretory rates were measured. The MRI technique was validated simultaneously by the double indicator method in 5 healthy volunteers and in 5 patients with symptoms of disordered gastric emptying applying gamma camera scintigraphy and MRI in randomized order. Similar gastric meal emptying curves were obtained in volunteers and in patients by MRI and the reference methods as assessed by linear (r greater than 0.90; P less than 0.001) and intraclass correlation analysis (r greater than 0.905) for T1/2, areas under the curve, and percent of gastric meal retained. Furthermore, similar total gastric volumes and gastric secretory rates were measured by MRI and the double indicator technique. The new MRI method correctly reflected gastric emptying disorders in patients. Thus for the first time it is possible to combine these measurements of gastric functions in a single method and to relate them to gastric morphology visualized by the generation of three-dimensional images.