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The Search for an Alternative to [68Ga]Ga-DOTA-TATE in Neuroendocrine Tumor Theranostics: Current State of 18F-labeled Somatostatin Analog Development.

ABSTRACT: The trend to inform personalized molecular radiotherapy with molecular imaging diagnostics, a concept referred to as theranostics, has transformed the field of nuclear medicine in recent years. The development of theranostic pairs comprising somatostatin receptor (SSTR)-targeting nuclear imaging probes and therapeutic agents for the treatment of patients with neuroendocrine tumors (NETs) has been a driving force behind this development. With the Neuroendocrine Tumor Therapy (NETTER-1) phase 3 trial reporting encouraging results in the treatment of well-differentiated, metastatic midgut NETs, peptide radioligand therapy (RLT) with the 177Lu-labeled somatostatin analog (SSA) [177Lu]Lu-DOTA-TATE is now anticipated to become the standard of care. On the diagnostics side, the field is currently dominated by 68Ga-labeled SSAs for the molecular imaging of NETs with positron emission tomography-computed tomography (PET/CT). PET/CT imaging with SSAs such as [68Ga]Ga-DOTA-TATE, [68Ga]Ga-DOTA-TOC, and [68Ga]Ga-DOTA-NOC allows for NET staging with high accuracy and is used to qualify patients for RLT. Driven by the demand for PET/CT imaging of NETs, a commercial kit for the production of [68Ga]Ga-DOTA-TATE (NETSPOT) was approved by the U.S. Food and Drug Administration (FDA). The synthesis of 68Ga-labeled SSAs from a 68Ge/68Ga-generator is straightforward and allows for a decentralized production, but there are economic and logistic difficulties associated with these approaches that warrant the search for a viable, generator-independent alternative. The clinical introduction of an 18F-labeled SSTR-imaging probe can help mitigate the shortcomings of the generator-based synthesis approach, but despite extensive research efforts, none of the proposed 18F-labeled SSAs has been translated past prospective first-in-humans studies so far. Here, we review the current state of probe-development from a translational viewpoint and make a case for a clinically viable, 18F-labeled alternative to the current standard [68Ga]Ga-DOTA-TATE.

SUBMITTER: Waldmann CM

PROVIDER: S-EPMC6401503 | biostudies-literature | 2019

REPOSITORIES: biostudies-literature

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The Search for an Alternative to [<sup>68</sup>Ga]Ga-DOTA-TATE in Neuroendocrine Tumor Theranostics: Current State of <sup>18</sup>F-labeled Somatostatin Analog Development.

Waldmann Christopher M CM Stuparu Andreea D AD van Dam R Michael RM Slavik Roger R

Theranostics 20190214 5

The trend to inform personalized molecular radiotherapy with molecular imaging diagnostics, a concept referred to as theranostics, has transformed the field of nuclear medicine in recent years. The development of theranostic pairs comprising somatostatin receptor (SSTR)-targeting nuclear imaging probes and therapeutic agents for the treatment of patients with neuroendocrine tumors (NETs) has been a driving force behind this development. With the Neuroendocrine Tumor Therapy (NETTER-1) phase 3 tr ...[more]

PMID: 30867834

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Project description:PurposeIn the characterization of severe lung diseases, early detection of specific inflammatory cells could help to monitor patients' response to therapy and increase chances of survival. Macrophages contribute to regulating the resolution and termination of inflammation and have increasingly been of interest for targeted therapies. [68Ga]Ga-DOTA-TATE is an established clinical radiopharmaceutical targeting somatostatin receptor subtype 2 (SSTR 2). Since activated macrophages (M1) overexpress SSTR 2, the aim of this study was to investigate the applicability of [68Ga]Ga-DOTA-TATE for positron emission tomography (PET) imaging of M1 macrophages in pulmonary inflammation.MethodsInflammation in the pig lungs was induced by warm saline lavage followed by injurious ventilation in farm pigs (n = 7). Healthy pigs (n = 3) were used as control. A 60-min dynamic PET scan over the lungs was performed after [68Ga]Ga-DOTA-TATE injection and [18F]FDG scan was executed afterward for comparison. The uptake of both tracers was assessed as mean standardized uptake values (SUVmean) 30-60-min post-injection. The PET scans were followed by computed tomography (CT) scans, and the Hounsfield units (HU) were quantified of the coronal segments. Basal and apical segments of the lungs were harvested for histology staining. A rat lung inflammation model was also studied for tracer specificity using lipopolysaccharides (LPS) by oropharyngeal aspiration. Organ biodistribution, ex vivo autoradiography (ARG) and histology samples were conducted on LPS treated, octreotide induced blocking and control healthy rats.ResultsThe accumulation of [68Ga]Ga-DOTA-TATE on pig lavage model was prominent in the more severely injured dorsal segments of the lungs (SUVmean = 0.91 ± 0.56), compared with control animals (SUVmean = 0.27 ± 0.16, p < 0.05). The tracer uptake corresponded to the damaged areas assessed by CT and histology and were in line with HU quantification. The [68Ga]Ga-DOTA-TATE uptake in LPS treated rat lungs could be blocked and was significantly higher compared with control group.ConclusionThe feasibility of the noninvasive assessment of tissue macrophages using [68Ga]Ga-DOTA-TATE/PET was demonstrated in both porcine and rat lung inflammation models. [68Ga]Ga-DOTA-TATE has a great potential to be used to study the role and presence of macrophages in humans in fight against severe lung diseases.

Project description:PurposeTo evaluate the safety and efficacy of 177Lu-DOTA-EB-TATE, a radiolabeled somatostatin analog modified by Evans blue, at escalating doses, was used to increase tumor retention in patients with progressive metastatic neuroendocrine tumors (NETs).MethodsThirty-three patients with metastatic NETs were prospectively enrolled into four groups: group A (n = 6, 43 ± 12 years) administered approximately 3.7 GBq (100 mCi) 177Lu-DOTATATE as controls; group B (n = 7, 55 ± 7 years) administered approximately 1.11 GBq (30 mCi) 177Lu-DOTA-EB-TATE; group C (n = 6, 55 ± 10 years) administered approximately 1.85 GBq (50 mCi) 177Lu-DOTA-EB-TATE; group D (n = 14, 50 ± 10 years) administered approximately 3.7 GBq (100 mCi) 177Lu-DOTA-EB-TATE. Treatment-related adverse events were graded according to the CTCAE v.5.0. 68Ga-DOTATATE PET/CT were performed at baseline and 2-3 months after treatment for response evaluation.ResultsAdministration was well tolerated. No CTC 3/4 hematotoxicity, nephrotoxicity, or hepatotoxicity was observed during or after treatment in groups A-C. In group D, CTC-3 hematotoxicity was recorded in 2 patients with multicourse chemotherapy previously. After one-cycle treatment, the SUVmax decreased in group C (Δ% = - 17.4 ± 29.3%) and group D (Δ% = - 15.1 ± 39.1%), but greatly increased in group B (Δ% = 30.0 ± 68.0%) and mildly increased in group A (Δ% = 5.4 ± 45.9%). Referring to EORTC criteria, 16.7% (1/6), 0% (0/7), 50% (3/6), and 50% (7/14) were evaluated as partial response in groups A, B, C, and D, respectively. When selecting lesions with comparable baseline SUVmax ranging from 15 to 40, SUVmax showed no significant decrease in group B (Δ% = - 7.3 ± 24.5%) (P = 0.214), significant decrease in group C (Δ% = - 34.9 ± 12.4%) (P = 0.001), and in group D (Δ% = - 17.9 ± 19.7%) (P = 0.012) as compared with group A with increased SUVmax (Δ% = 8.4 ± 48.8%). SUVmax significantly decreased in the EBTATE groups (groups B-D combined) (Δ% = - 19.0 ± 21.5%) as compared with the TATE group (P = 0.045).Conclusion177Lu-DOTA-EB-TATE is well tolerated and is more effective than 177Lu-DOTATATE. Both 1.85 GBq (50 mCi) and 3.7 GBq (100 mCi) doses appear to be more effective than 1.11 GBq (30 mCi) dose. Further investigation with more cycles of 177Lu-DOTA-EB-TATE treatment and longer follow-up is warranted.Trial registrationTreatment Using 177Lu-DOTA-EB-TATE in Patients with Advanced Neuroendocrine Tumors (NCT03478358). URL: https://register.clinicaltrials.gov/prs/app/action/ViewOrUnrelease?uid=U0001JRW&ts=13&sid=S0007RNX&cx=y3yqv4.

Project description:Radiolabeled somatostatin analog therapy has become an established treatment method for patients with well to moderately differentiated unresectable or metastatic neuroendocrine tumors (NETs). The most frequently used somatostatin analogs in clinical practice are octreotide and octreotate. However, both peptides showed suboptimal retention within tumors. The aim of this first-in-humans study is to explore the safety and dosimetry of a long-acting radiolabeled somatostatin analog, 177Lu-1, 4, 7, 10-tetra-azacyclododecane-1, 4, 7, 10-tetraacetic acid-Evans blue-octreotate (177Lu-DOTA-EB-TATE). Methods: Eight patients (6 men and 2 women; age range, 27-61 y) with advanced metastatic NETs were recruited. Five patients received a single dose, 0.35-0.70 GBq (9.5-18.9 mCi), of 177Lu-DOTA-EB-TATE and underwent serial whole-body planar and SPECT/CT scans at 2, 24, 72, 120, and 168 h after injection. The other 3 patients received intravenous injection of 0.28-0.41 GBq (7.5-11.1 mCi) of 177Lu-DOTATATE for the same imaging acquisition procedures at 1, 3, 4, 24, and 72 h after injection. The dosimetry was calculated using the OLINDA/EXM 1.1 software. Results: Administration of 177Lu-DOTA-EB-TATE was well tolerated, with no adverse symptoms being noticed or reported in any of the patients. Compared with 177Lu-DOTATATE, 177Lu-DOTA-EB-TATE showed extended circulation in the blood and achieved a 7.9-fold increase of tumor dose delivery. The total-body effective doses were 0.205 ± 0.161 mSv/MBq for 177Lu-DOTA-EB-TATE and 0.174 ± 0.072 mSv/MBq for 177Lu-DOTATATE. Significant dose delivery increases to the kidneys and bone marrow were also observed in patients receiving 177Lu-DOTA-EB-TATE compared with those receiving 177Lu-DOTATATE (3.2 and 18.2-fold, respectively). Conclusion: By introducing an albumin-binding moiety, 177Lu-DOTA-EB-TATE showed remarkably higher uptake and retention in NETs as well as significantly increased accumulation in the kidneys and red marrow. It has great potential to be used in peptide receptor radionuclide therapy for NETs with lower dose and less frequency of administration.

Project description:PurposeSomatostatin receptor antagonists have shown promise for imaging neuroendocrine tumors (NETs) in preclinical studies, but clinical data is still very limited. In this study, we assess the feasibility of using the novel somatostatin antagonist 68Ga-DOTA-JR11 for PET imaging of NETs.MethodsTwenty patients with advanced NETs underwent whole-body PET/CT imaging 60 min after injection of 169 MBq (median) 68Ga-DOTA-JR11 as part of a prospective study. Volumes of interest were drawn around up to four 68Ga-DOTA-JR11-avid lesions per patient (with uptake greater than liver) and standardized uptake values were estimated. Additionally, target-to-normal tissue ratios were calculated. A subset of six patients had additional imaging (25-min dynamic scan of the upper abdomen including, at least partly, cardiac left ventricle, liver, spleen, and kidney, and a whole-body PET/CT scan at 30 min post-injection) to determine the time course of tracer distribution and facilitate radiation dose estimates. Absorbed doses were calculated using OLINDA/EXM 1.0.ResultsIn contrast to the known biodistribution of somatostatin receptor agonists, little or no uptake above background was seen in the pituitary gland, spleen, adrenals, and uninvolved liver; e.g., median spleen SUVmean 1.4 (range: 0.7-1.8), liver SUVmean 1.1 (0.7-1.9). A total of 42 tumor lesions were analyzed with median SUVmax 13.0 (range: 2.9-94), TNR blood 9.3 (1.8-87), TNR spleen 4.9 (1.9-48), TNR kidney 2.2 (0.52-28), and TNR liver 10.5 (2.3-107). Tumor uptake reached plateau levels by 20-30 min post-injection. The highest absorbed dose estimates (mGy/MBq) to normal tissues were: urinary bladder wall (0.30; SD 0.06) and kidneys (0.050; SD 0.013). The effective dose (ICRP 103) was 0.022 (SD 0.003) mSv/MBq.Conclusions68Ga-DOTA-JR11 demonstrated rapid tumor uptake, high tumor/background ratios, and rapid clearance from blood. The low liver background is advantageous and may facilitate detection of liver metastases. Dosimetric data compare favorably with published data for 68Ga-DOTATATE and 68Ga-DOTATOC.

Project description:BackgroundSince it was first approved in Europe in 2016, the gallium-68 (68Ga) radiopharmaceutical [68Ga]Ga-DOTA-TOC has been widely used for imaging of somatostatin receptor (SSTR) positive tumours using positron emission tomography-computed tomography (PET/CT). Significant patient benefits have been reported, so its use is rapidly increasing. However, few studies have been published regarding occupational doses to nuclear medicine personnel handling this radiopharmaceutical, despite its manual usage at low distances from the skin and the beta-emission decay scheme, which may result in an increased absorbed dose to their hands. In this context, this study aims to analyse the occupational exposure during the administration of [68Ga]Ga-DOTA-TOC for PET/CT imaging. For this purpose, extremity, eye lens and whole-body dosimetry in terms of Hp(0.07), Hp(3) and Hp(10), respectively, was conducted on six workers with both thermoluminescent dosimeters, and personal electronic dosimeters.ResultsThe non-dominant hand is more exposed to radiation than the dominant hand, with the thumb and the index fingertip being the most exposed sites on this hand. Qualitative analysis showed that when no shielding is used during injection, doses increase significantly more in the dominant than in the non-dominant hand, so the use of shielding is strongly recommended. While wrist dosimeters may significantly underestimate doses to the hands, placing a ring dosimeter at the base of the ring or middle finger of the non-dominant hand may give a valuable estimation of maximum doses to the hands if at least a correction factor of 5 is applied. Personal equivalent doses for the eyes did not result in measurable values (i.e., above the lowest detection limit) for almost all workers. The extrapolated annual dose estimations showed that there is compliance with the annual dose limits during management of [68Ga]Ga-DOTA-TOC for diagnostics with PET in the hospital included in this study.ConclusionsImaging with [68Ga]Ga-DOTA-TOC is a safe process for the workers performing the administration of the radiopharmaceutical, including intravenous injection to the patient and the pre- and post-activity control, as it is highly unlikely that annual dose limits will be exceeded if good working practices and shielding are used.

Dataset Information

The Search for an Alternative to [68Ga]Ga-DOTA-TATE in Neuroendocrine Tumor Theranostics: Current State of 18F-labeled Somatostatin Analog Development.

Publications

The Search for an Alternative to [<sup>68</sup>Ga]Ga-DOTA-TATE in Neuroendocrine Tumor Theranostics: Current State of <sup>18</sup>F-labeled Somatostatin Analog Development.

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