18F-BMS-986229 PET to Assess Programmed-Death Ligand 1 Status in Gastroesophageal Cancer

Anti-programmed death 1 (PD-1) inhibitors are the standard of care for advanced gastroesophageal cancer. Although recommendations and approval by regulatory agencies are often based on programmed death ligand 1 (PD-L1) expression, pathologic assessments of PD-L1 status have several limitations. Single-site biopsies do not adequately capture disease heterogeneity within individual tumor lesions or among several lesions within the same patient, the PD-L1 combined positive score is a dynamic biomarker subject to evolution throughout a patient's disease course, and repeated biopsies are invasive and not always feasible. Methods: This was a prospective pilot study of the PD-L1-targeting radiotracer, 18F-BMS-986229, with PET imaging (PD-L1 PET) in patients with gastroesophageal cancer. Patients were administered the 18F-BMS-986229 radiotracer intravenously at a dose of 370 MBq over 1-2 min and underwent whole-body PET/CT imaging 60 min later. The primary objective of this study was to evaluate the safety and feasibility of 18F-BMS-986229. The trial is registered with ClinicalTrials.gov (NCT04161781). Results: Between February 3, 2020, and February 2, 2022, 10 patients with gastroesophageal adenocarcinoma underwent PD-L1 PET. There were no adverse events associated with the 18F-BMS-986229 tracer, and imaging did not result in treatment delays; the primary endpoint was achieved. Radiographic evaluation of PD-L1 expression was concordant with pathologic assessment in 88% of biopsied lesions, and 18F-BMS-986229 uptake on PET imaging correlated with pathologic evaluation by the combined positive score (Spearman rank correlation coefficient, 0.64). Seventy-one percent of patients with 18F-BMS-986229 accumulation on PET imaging also had lesions without 18F-BMS-986229 uptake, highlighting the intrapatient heterogeneity of PD-L1 expression. Patients treated with frontline programmed death 1 inhibitors who had 18F-BMS-986229 accumulation in any lesions on PET imaging had longer progression-free survival than patients without tracer accumulation in any lesions (median progression-free survival, 28.4 vs. 9.9 mo), though the small sample size prevents any definitive conclusions. Conclusion: PD-L1 PET imaging was safe, feasible, and concordant with pathologic evaluation and offers a potential noninvasive tool to assess PD-L1 expression.

First-in-Human Evaluation of Site-Specifically Labeled 89Zr-Pertuzumab in Patients with HER2-Positive Breast Cancer

Radioimmunoconjugates targeting human epidermal growth factor receptor 2 (HER2) have shown potential to noninvasively visualize HER2-positive tumors. However, the stochastic approach that has been traditionally used to radiolabel these antibodies yields poorly defined and heterogeneous products with suboptimal in vivo performance. Here, we describe a first-in-human PET study on patients with HER2-positive breast cancer evaluating the safety, biodistribution, and dosimetry of 89Zr-site-specific (ss)-pertuzumab PET, a site-specifically labeled radioimmunoconjugate designed to circumvent the limitations of random stochastic lysine labeling. Methods: Six patients with HER2-positive metastatic breast cancer were enrolled in a prospective clinical trial. Pertuzumab was site-specifically modified with desferrioxamine (DFO) via a novel chemoenzymatic strategy and subsequently labeled with 89Zr. Patients were administered 74 MBq of 89Zr-ss-pertuzumab in 20 mg of total antibody intravenously and underwent PET/CT at 1 d, 3-4 d, and 5-8 d after injection. PET imaging, whole-body probe counts, and blood draws were performed to assess the pharmacokinetics, biodistribution, and dosimetry. Results: 89Zr-ss-pertuzumab PET/CT was used to assess HER2 status and heterogeneity to guide biopsy and decide the next line of treatment at progression. The radioimmunoconjugate was able to detect known sites of malignancy, suggesting that these tumor lesions were HER2-positive. The optimal imaging time point was 5-8 d after administration, and no toxicities were observed. Dosimetry estimates from OLINDA showed that the organs receiving the highest doses (mean ± SD) were kidney (1.8 ± 0.5 mGy/MBq), liver (1.7 ± 0.3 mGy/MBq), and heart wall (1.2 ± 0.1 mGy/MBq). The average effective dose for 89Zr-ss-pertuzumab was 0.54 ± 0.03 mSv/MBq, which was comparable to both stochastically lysine-labeled 89Zr-DFO-pertuzumab and 89Zr-DFO-trastuzumab. One patient underwent PET/CT with both 89Zr-ss-pertuzumab and 89Zr-DFO-pertuzumab 1 mo apart, with 89Zr-ss-pertuzumab demonstrating improved lesion detection and higher tracer avidity. Conclusion: This study demonstrated the safety, dosimetry, and potential clinical applications of 89Zr-ss-pertuzumab PET/CT. 89Zr-ss-pertuzumab may detect more lesions than 89Zr-DFO-pertuzumab. Potential clinical applications include real-time evaluation of HER2 status to guide biopsy and assist in treatment decisions.

First-in-human imaging with [89Zr]Zr-DFO-SC16.56 anti-DLL3 antibody in patients with high-grade neuroendocrine tumors of the lung and prostate

Background

Delta-like ligand 3 (DLL3) is aberrantly expressed on the cell surface in many neuroendocrine cancers including small cell lung cancer (SCLC) and neuroendocrine prostate cancer (NEPC). Several therapeutic agents targeting DLL3 are in active clinical development. Molecular imaging of DLL3 would enable non-invasive diagnostic assessment to inform the use of DLL3-targeting therapeutics or to assess disease treatment response.

Methods

We conducted a first-in-human immuno-positron emission tomography (immunoPET) imaging study of [89Zr]Zr-DFO-SC16.56, composed of the anti-DLL3 antibody SC16.56 conjugated to desferrioxamine (DFO) and the positron-emitting radionuclide zirconium-89, in 18 patients with neuroendocrine cancers. An initial cohort of three patients received 1-2 mCi of [89Zr]Zr-DFO-SC16.56 at a total mass dose of 2·5 mg and underwent serial PET and computed tomography (CT) imaging over the course of one week. Radiotracer clearance, tumor uptake, and radiation dosimetry were estimated. An expansion cohort of 15 additional patients were imaged using the initial activity and mass dose. Retrospectively collected tumor biopsies were assessed for DLL3 by immunohistochemistry (IHC) (n = 16).

Findings

Imaging of the initial 3 SCLC patients demonstrated strong tumor-specific uptake of [89Zr]Zr-DFO-SC16.56, with similar tumor: background ratios at days 3, 4, and 7 post-injection. Serum clearance was bi-phasic with an estimated terminal clearance half-time of 119 h. The sites of highest background tracer uptake were blood pool and liver. The normal tissue receiving the highest radiation dose was liver; 1·8 mGy/MBq, and the effective dose was 0.49 mSv/MBq. Tumoral uptake varied both between and within patients, and across anatomic sites, with a wide range in SUVmax (from 3·3 to 66·7). Tumor uptake by [89Zr]Zr-DFO-SC16.56 was associated with protein expression in all cases. Two non-avid DLL3 NEPC cases by PET scanning demonstrated the lowest DLL3 expression by tumor immunohistochemistry. Only one patient had a grade 1 allergic reaction, while no grade ≥2 adverse events noted.

Interpretation

DLL3 PET imaging of patients with neuroendocrine cancers is safe and feasible. These results demonstrate the potential utility of [89Zr]Zr-DFO-SC16.56 for non-invasive in vivo detection of DLL3-expressing malignancies.

Funding

Supported by NIH R01CA213448 (JTP), R35 CA263816 (CMR), U24 CA213274 (CMR), R35 CA232130 (JSL), and a Prostate Cancer Foundation TACTICAL Award (JSL), Scannell foundation. The Radiochemistry and Molecular Imaging Probes Core Facility is supported by NIH P30 CA08748.

Methods for the Production of Radiolabeled Bioagents for ImmunoPET

Immunoglobulin-based positron emission tomography (ImmunoPET) is making increasingly significant contributions to the nuclear imaging toolbox. The exquisite specificity of antibodies combined with the high-resolution imaging of PET enables clinicians and researchers to localize diseases, especially cancer, with a high degree of spatial certainty. This review focuses on the radiopharmaceutical preparation necessary to obtain those images-the work behind the scenes, which occurs even before the patient or animal is injected with the radioimmunoconjugate. The focus of this methods review will be the chelation of four radioisotopes to their most common and clinically relevant chelators.

Noninvasive Assessment of Human Epidermal Growth Factor Receptor 2 (HER2) in Esophagogastric Cancer Using 89Zr-Trastuzumab PET: A Pilot Study

Variations in human epidermal growth factor receptor 2 (HER2) expression between the primary tumor and metastases may contribute to drug resistance in HER2-positive (HER2+) metastatic esophagogastric cancer (mEGC). 89Zr-trastuzumab PET (HER2 PET) holds promise for noninvasive assessment of variations in HER2 expression and target engagement. The aim of this study was to describe HER2 PET findings in patients with mEGC. Methods: Patients with HER2+ mEGC were imaged with HER2 PET, 18F-FDG PET, and CT. Lesions were annotated using measurements (on CT) and maximum SUVs (on HER2 PET). Correlation of visualized disease burden among imaging modalities with clinical and pathologic characteristics was performed. Results: Thirty-three patients with HER2+ mEGC were imaged with HER2 PET and CT (12% esophageal, 64% gastroesophageal junction, and 24% gastric adenocarcinoma), 26 of whom were also imaged with 18F-FDG PET. More lesions were identified on 18F-FDG PET (median, 7 [range, 1-14]) than HER2 PET (median, 4 [range, 0-11]). Of the 8 lesions identified on HER2 but not on 18F-FDG PET, 3 (38%) were in bone and 1 was in the brain. Of the 68 lesions identified on 18F-FDG but not on HER2 PET, 4 (6%) were in bone and the remainder were in the lymph nodes (35, 51%) and liver (16, 24%). Of the 33 total patients, 23 (70%) were HER2 imaging-positive (≥50% of tumor load positive). Only 10 patients had 100% of the tumor load positive; 2 had 0% positive. When only patients receiving HER2-directed therapy as first-line treatment were considered (n = 13), median progression-free survival (PFS) therapy was not significantly different between HER2 imaging-positive and -negative patients. Median PFS for patients with at least 1 intense or very intense lesion (SUV ≥ 10) was 16 (95% CI: 11-not reached) mo (n = 7), compared with 12 (95% CI: 6.3-not reached) mo for patients without an intense or very intense lesion (n = 6) (P = 0.35). Conclusion: HER2 PET may identify heterogeneity of HER2 expression and allow assessment of lesions throughout the entire body. A potential application of HER2 PET is noninvasive evaluation of HER2 status including assessment of intrapatient disease heterogeneity not captured by standard imaging or single-site biopsies.

STARLITE 2: Phase 2 study of nivolumab plus 177lutetium-labeled anti–carbonic anhydrase IX (CAIX) monoclonal antibody girentuximab (177Lu-girentuximab) in patients (pts) with advanced clear cell renal cell carcinoma (ccRCC)

TPS752

Background: CAIX is a cell surface glycoprotein expressed in >90% of ccRCC but rarely in normal tissues, providing a target for imaging and therapeutic application. Radiolabeling the anti-CAIX monoclonal antibody girentuximab with 89Zr has shown promise as a novel PET tracer and labeling with 177Lu promise as a therapeutic agent in ccRCC (Muselaers, Eur Urol, 2016). Targeted delivery of radiation to ccRCC cells may prime the immune response by enhancing tumor antigen presentation, providing rationale for combining 177Lu-girentuximab with the anti-PD-1 antibody, nivolumab. This phase 2, open-label, single arm study (NCT05239533) is being conducted to evaluate 177Lu-girentuximab in combination with nivolumab in pts with previously treated ccRCC. Methods: Pts with biopsy-proven ccRCC, progressive disease after prior systemic therapy including ≥1 immunotherapy (IO) agent, adequate organ/marrow function, and ≥1 evaluable lesion by RECIST 1.1 that is also avid on 89Zr-girentuximab PET will be enrolled. There is no limit on number of prior lines of systemic therapy, but pts who stopped IO for immune toxicity are excluded. Treatment consists of 177Lu-girentuximab every 12-14 weeks for a maximum of 3 doses plus nivolumab 240mg every 2 weeks until progressive disease (PD) or unacceptable toxicity. Due to expected cumulative myelosuppression, each subsequent 177Lu-girentuximab dose to the same patient is reduced by 25% (dose 2 = 75% of dose 1; dose 3 = 75% of dose 2). Tumor imaging is performed every 12 weeks. Pts will be evaluated in a safety lead-in phase followed by an expansion phase. In the safety lead-in phase, the MTD of 177Lu-girentuximab in combination with nivolumab will be determined with a 3+3 design using a starting dose of 1804 MBq/m2 (75% of single agent MTD). For cohort 2, dose escalation to 2405 MBq/m2 (single agent MTD) or de-escalation to 1353 MBq/m2 will be based on dose-limiting toxicities. In the expansion phase, a Simon 2-stage optimal design is used to evaluate the primary endpoint of response rate by RECIST 1.1 within 24 weeks. With ≥1 response in the first Simon stage (n=10; includes pts treated at MTD in the safety lead-in phase), a second stage will open (n=19) for a total of 29 pts with ≥3 responses indicating the regimen worthy of further study. Secondary endpoints include PFS, OS, and toxicity including a continuous safety monitoring rule during expansion. Exploratory imaging with 89Zr-girentuximab PET is performed at baseline and before each 177Lu-girentuximab dose with results correlated with RECIST response on conventional imaging. In addition, whole body planar and SPECT imaging are performed after each 177Lu-girentuximab dose to evaluate distribution, lesion uptake and dosimetry of 177Lu-girentuximab. The trial is currently accruing to the safety lead-in phase. Clinical trial information: NCT05239533 .

Practical considerations for navigating the regulatory landscape of non-clinical studies for clinical translation of radiopharmaceuticals

Background

The development of radiopharmaceuticals requires extensive evaluation before they can be applied in a diagnostic or therapeutic setting in Nuclear Medicine. Chemical, radiochemical, and pharmaceutical parameters must be established and verified to ensure the quality of these novel products.

Main body

To provide supportive evidence for the expected human in vivo behaviour, particularly related to safety and efficacy, additional tests, often referred to as “non-clinical” or “preclinical” are mandatory. This document is an outcome of a Technical Meeting of the International Atomic Energy Agency. It summarises the considerations necessary for non-clinical studies to accommodate the regulatory requirements for clinical translation of radiopharmaceuticals. These considerations include non-clinical pharmacology, radiation exposure and effects, toxicological studies, pharmacokinetic modelling, and imaging studies. Additionally, standardisation of different specific clinical applications is discussed.

Conclusion

This document is intended as a guide for radiopharmaceutical scientists, Nuclear Medicine specialists, and regulatory professionals to bring innovative diagnostic and therapeutic radiopharmaceuticals into the clinical evaluation process in a safe and effective way.

DIPG-53. Long-term survival from a Phase 1 dose-escalation trial using convection-enhanced delivery (CED) of radioimmunotherapeutic124I-omburtamab for treatment of diffuse intrinsic pontine glioma (DIPG)

BACKGROUND: Median survival from DIPG is less than one year. In a phase 1 dose escalation study (clinicaltrials.gov NCT01502917) ¹²⁴I-omburtamab targeting B7-H3 was administered intratumorally using CED. METHODS: CED was performed between 4-14 weeks post radiation therapy. Using a 3 + 3 design, ¹²⁴I-omburtamab was escalated from 0.25-10.0 mCi and infusion volumes (Vi) from 250-10,000 µl with serial ¹²⁴I PET/CT performed up to ~1 week post-administration. Toxicities were assessed for 30 days. Dose escalation safety was evaluated. Survival was calculated using Kaplan-Meier statistics. RESULTS: 46 children were treated and evaluable for toxicity and survival;4 patients received partial doses and were evaluable for toxicity only. Three patients experienced dose limiting toxicities. Eleven patients had transient treatment related grade 3 toxicities with no grade 4 or 5 toxicities. Grade 3 nervous system toxicities included: muscular weakness(n=8), dysarthria(n=4), ataxia(n=3), dysphagia(n=3), and gait disturbance(n=1). Lesion absorbed doses ranged from 1,000-1,500cGy/mCi, with lesion-to-whole body radiation absorbed-dose ratios of ~900. A dose of 8mCi and infusion volume of 8,000 µl is safe and may provide a distribution volume up to 20cm³. Median survival was 15.3 months (n =46, 95% CI 12.7, 17.3). Survival rate estimates (95% CI) at 1, 2, 3 and 5 years were 0.67 (0.55;0.82); 0.18 (0.09;0.35); 0.10 (0.04;0.26); and 0.05 (0.01;0.20). Four patients survived >3 years; two remain alive (61+ and 106+ months);two have died (44 and 53 month) with distant CNS disease and one with extra-CNS metastasis. CONCLUSION: Administration of escalating doses and volumes of ¹²⁴I-omburtamab via CED was a viable option for this patient subgroup. The median overall survival was increased 3-4 months compared to historical controls. Anecdotal long-term survival if validated with a planned phase 2 trial would support the concept of whole neuroaxis treatment in combination with CED in a subset of DIPG patients.

STARLITE 2: Phase 2 study of nivolumab plus 177Lutetium-labeled anti-carbonic anhydrase IX (CAIX) monoclonal antibody girentuximab (177Lu-girentuximab) in patients (pts) with advanced clear cell renal cell carcinoma (ccRCC)

TPS4603

Background: CAIX is a cell surface glycoprotein expressed in > 90% of ccRCC but rarely in normal tissues, providing a target for imaging and therapeutic application. Radiolabeling the anti-CAIX monoclonal antibody girentuximab with 89Zr has shown promise as a novel PET tracer and labeling with 177Lu promise as a therapeutic agent in ccRCC (Muselaers, Eur Urol, 2016). Targeted delivery of radiation to ccRCC cells may prime the immune response by enhancing tumor antigen presentation, providing rationale for combining 177Lu-girentuximab with the anti-PD-1 antibody, nivolumab. This phase 2, open-label, single arm study (NCT05239533) is being conducted to evaluate 177Lu-girentuximab in combination with nivolumab in pts with previously treated ccRCC. Methods: Pts with biopsy-proven ccRCC, progressive disease after prior systemic therapy including ≥1 immunotherapy (IO) agent, adequate organ/marrow function, and ≥1 evaluable lesion by RECIST 1.1 that is also avid on 89Zr-girentuximab PET will be enrolled. There is no limit on number of prior lines of systemic therapy, but pts who stopped IO for immune toxicity are excluded. Treatment consists of 177Lu-girentuximab every 12-14 weeks for a maximum of 3 doses plus nivolumab 240mg every 2 weeks until progressive disease (PD) or unacceptable toxicity. Due to expected cumulative myelosuppression, each subsequent 177Lu-girentuximab dose to the same patient is reduced by 25% (dose 2 = 75% of dose 1; dose 3 = 75% of dose 2). Tumor imaging is performed every 12 weeks. Pts will be evaluated in a safety lead-in phase followed by an expansion phase. In the safety lead-in phase, the MTD of 177Lu-girentuximab in combination with nivolumab will be determined with a 3+3 design using a starting dose of 1804 MBq/m2 (75% of single agent MTD). For cohort 2, dose escalation to 2405 MBq/m2 (single agent MTD) or de-escalation to 1353 MBq/m2 will be based on dose-limiting toxicities. In the expansion phase, a Simon 2-stage optimal design is used to evaluate the primary endpoint of response rate by RECIST 1.1 within 24 weeks. With ≥1 response in the first Simon stage (n = 10; includes pts treated at MTD in safety lead-in), a second stage will open (n = 19) for a total of 29 pts with ≥3 responses indicating the regimen worthy of further study. Secondary endpoints include PFS, OS, and toxicity including a continuous safety monitoring rule during expansion. Exploratory imaging with 89Zr-girentuximab PET is performed at baseline and before each 177Lu-girentuximab dose with results correlated with RECIST response on conventional imaging. In addition, whole body planar and SPECT imaging are performed after each 177Lu-girentuximab dose to evaluate distribution, lesion uptake and dosimetry of 177Lu-girentuximab. The trial is currently accruing to the safety lead-in phase. Clinical trial information: NCT05239533.

Phase 1 dose-escalation trial using convection-enhanced delivery of radiolabeled monoclonal antibody for diffuse intrinsic pontine glioma following external radiation therapy

2010

Background: The prognosis of diffuse intrinsic pontine glioma (DIPG) is dire with a median overall survival less than one-year. 124I-omburtamab is a radiolabeled monoclonal antibody that targets B7-H3 epitope. We evaluated the safety of administering escalating doses and volumes of 124I-omburtamab via convection-enhanced delivery (CED) in children with DIPG. Methods: MSKCC 11-011 trial is a standard 3+3 phase 1, open-label, dose escalation study in patients with non-progressive DIPG. CED of 124I-omburtamab was performed between 4-14 weeks post-external radiation therapy. Nine dose levels of a single injection of 124I-omburtamab (Y-mAbs Therapeutics, USA) (range 0.25 to 8.0 mCi; and volume of infusion (Vi) from 250 to 8,000 µl) have been evaluated so far. Patients were assessed weekly for 30 days. Results: 46 children were evaluable for primary and secondary endpoints. The median age at enrolment was 6.5 years (range 2-17). Two patients have experienced AEs CTCAE grade 3 that were categorized as dose limiting toxicities (DLTs), which led to inclusion of three more patients at both the 4 and 6 mCi dose levels. Eight patients have reported transient AEs of grade 3 considered related to 124I-omburtamab. The acute grade 3 AEs were generally indicative of nervous system effects due to volume intolerance or radiation injury, and included hemiparesis (n = 3), dysarthria (n = 3), ataxia (n = 3), dysphagia (n = 2), muscular weakness (n = 2) and gait disturbance (n = 1). There were no related AEs CTCAE grade 4 or 5. Estimations of distribution volumes based on T2-weighted imaging were linearly related to volume with a mean volume of distribution/volume of infusion ratio (Vd/Vi) between 3 and 3.5. The mean ratio of lesion-to-whole body absorbed dose was ̃1000. Median overall survival from diagnosis across all cohorts was 14.8 months (n = 46, 95% CI 11.5, 16.8) and the survival rate estimates (with 95% confidence intervals) at 1, 2, 3 and 5 years were 0.63 (0.46;0.76); 0.13 (0.05;0.26); 0.08 (0.02;0.19); and 0.04 (0.00;0.16), respectively. Four patients have survived > 3 years; two remain alive at 46 and 96 months and two have died at 43 and 53 months, both with CNS disease outside of the treatment field and one with extra-CNS metastases. Conclusions: 124I-omburtamab via CED into the brain stem of children with DIPG and previously irradiated provides a possibility for improved treatment of DIPG. A dose of 8mCi and an infusion volume of 8,000 µl is considered safe and may provide a distribution volume large enough to cover tumor volumes up to 20 cm3. The median overall survival of all patients included in the trial appears to be increased with 3-4 months compared to historical control data from consortia trials. A phase 2 trial aiming at investigating the efficacy of radiolabeled omburtamab administered via CED is being planned. Clinical trial information: NCT01502917.

First-in-Humans Trial of Dasatinib-Derivative Tracer for Tumor Kinase-Targeted PET

We developed a first-of-kind dasatinib-derivative imaging agent, 18F-SKI-249380 (18F-SKI), and validated its use for noninvasive in vivo tyrosine kinase-targeted tumor detection in preclinical models. In this study, we assessed the feasibility of using 18F-SKI for PET imaging in patients with malignancies. Methods: Five patients with a prior diagnosis of breast cancer, renal cell cancer, or leukemia underwent whole-body PET/CT imaging 90 min after injection of 18F-SKI (mean, 241.24 ± 116.36 MBq) as part of a prospective study. In addition, patients underwent either a 30-min dynamic scan of the upper abdomen including, at least partly, cardiac left ventricle, liver, spleen, and kidney (n = 2) or three 10-min whole-body PET/CT scans (n = 3) immediately after injection and blood-based radioactivity measurements to determine the time course of tracer distribution and facilitate radiation dose estimates. A subset of 3 patients had a delayed whole-body PET/CT scan at 180 min. Biodistribution, dosimetry, and tumor uptake were quantified. Absorbed doses were calculated using OLINDA/EXM 1.0. Results: No adverse events occurred after injection of 18F-SKI. In total, 27 tumor lesions were analyzed, with a median SUVpeak of 1.4 (range, 0.7-2.3) and tumor-to-blood ratios of 1.6 (range, 0.8-2.5) at 90 min after injection. The intratumoral drug concentrations calculated for 4 reference lesions ranged from 0.03 to 0.07 nM. In all reference lesions, constant tracer accumulation was observed between 30 and 90 min after injection. A blood radioassay indicated that radiotracer clearance from blood and plasma was initially rapid (blood half-time, 1.31 ± 0.81 min; plasma, 1.07 ± 0.66 min; n = 4), followed variably by either a prolonged terminal phase (blood half-time, 285 ± 148.49 min; plasma, 240 ± 84.85 min; n = 2) or a small rise to a plateau (n = 2). Like dasatinib, 18F-SKI underwent extensive metabolism after administration, as evidenced by metabolite analysis. Radioactivity was predominantly cleared via the hepatobiliary route. The highest absorbed dose estimates (mGy/MBq) in normal tissues were to the right colon (0.167 ± 0.04) and small intestine (0.153 ± 0.03). The effective dose was 0.0258 mSv/MBq (SD, 0.0034 mSv/MBq). Conclusion:18F-SKI demonstrated significant tumor uptake, distinct image contrast despite low injected doses, and rapid clearance from blood.

B7H3-Directed Intraperitoneal Radioimmunotherapy With Radioiodinated Omburtamab for Desmoplastic Small Round Cell Tumor and Other Peritoneal Tumors: Results of a Phase I Study

PURPOSE

Desmoplastic small round cell tumor (DSRCT), a rare sarcoma of adolescents/young adults primarily involving the peritoneum, has a long-term survival of < 20% despite aggressive multimodality treatment. B7H3 is expressed on DSRCT cell surface, providing a target for antibody-based immunotherapy.

PATIENTS AND METHODS

In this phase I study, we evaluated the safety, pharmacokinetics, and biodistribution of intraperitoneal (IP) radioimmunotherapy (RIT) with the anti-B7H3 murine monoclonal antibody ¹³¹I-omburtamab in patients with DSRCT or other B7H3-expressing tumors involving the peritoneum. After thyroid blockade, patients received ¹³¹I-omburtamab as a single IP injection at escalated activities from 1.11 to 3.33/GBq/m². A prior tracer dose of IP 74 MBq¹²⁴I-omburtamab was used for radioimmuno-positron emission tomography imaging. Each injection was followed by IP saline infusion.

RESULTS

Fifty-two patients (48, three, and one with DSRCT, peritoneal rhabdomyosarcoma, and Ewing sarcoma, respectively) received IP ¹³¹I-omburtamab administered on an outpatient basis. Maximum tolerated dose was not reached; there were no dose-limiting toxicities. Major related adverse events were transient: grade 4 neutropenia (n = 2 patients) and thrombocytopenia (n = 1), and grade 1 (10%) and grade 2 (52%) pain lasting < 2 hours related to saline infusion. Hypothyroidism was not observed, and antidrug antibody was elicited in 5%. Mean (± SD) projected peritoneal residence time was 22.4 ± 7.9 hours. Mean projected absorbed doses for ¹³¹I-omburtamab based on ¹²⁴I-omburtamab dosimetry to normal organs were low and well within tolerable limits. More than 80% ¹³¹I remained protein bound in blood 66 hours after RIT. On the basis of peritoneal dose and feasibility for outpatient administration, the recommended phase II activity was established at 2.96 GBq/m². Patients with DSRCT receiving standard whole-abdominal radiotherapy after RIT did not experience unexpected toxicity.

CONCLUSION

IP RIT ¹³¹I-omburtamab was well tolerated with minimal toxicities. Radiation exposure to normal organs was low, making combination therapy with other anticancer therapies feasible.

First-in-Human Trial of Epichaperome-Targeted PET in Patients with Cancer

PURPOSE

124I-PU-H71 is an investigational first-in-class radiologic agent specific for imaging tumor epichaperome formations. The intracellular epichaperome forms under cellular stress and is a clinically validated oncotherapeutic target. We conducted a first-in-human study of microdose 124I-PU-H71 for PET to study in vivo biodistribution, pharmacokinetics, metabolism, and safety; and the feasibility of epichaperome-targeted tumor imaging.

EXPERIMENTAL DESIGN

Adult patients with cancer (n = 30) received 124I-PU-H71 tracer (201±12 MBq, <25 μg) intravenous bolus followed by PET/CT scans and blood radioassays.

RESULTS

124I-PU-H71 PET detected tumors of different cancer types (breast, lymphoma, neuroblastoma, genitourinary, gynecologic, sarcoma, and pancreas). 124I-PU-H71 was retained by tumors for several days while it cleared rapidly from bones, healthy soft tissues, and blood. Radiation dosimetry is favorable and patients suffered no adverse effects.

CONCLUSIONS

Our first-in-human results demonstrate the safety and feasibility of noninvasive in vivo detection of tumor epichaperomes using 124I-PU-H71 PET, supporting clinical development of PU-H71 and other epichaperome-targeted therapeutics.

Preclinical and first-in-human-brain-cancer applications of [18F]poly (ADP-ribose) polymerase inhibitor PET/MR

Background

We report preclinical and first-in-human-brain-cancer data using a targeted poly (ADP-ribose) polymerase 1 (PARP1) binding PET tracer, [¹⁸F]PARPi, as a diagnostic tool to differentiate between brain cancers and treatment-related changes.

Methods

We applied a glioma model in p53-deficient nestin/tv-a mice, which were injected with [¹⁸F]PARPi and then sacrificed 1 h post-injection for brain examination. We also prospectively enrolled patients with brain cancers to undergo dynamic [¹⁸F]PARPi acquisition on a dedicated positron emission tomography/magnetic resonance (PET/MR) scanner. Lesion diagnosis was established by pathology when available or by Response Assessment in Neuro-Oncology (RANO) or RANO-BM response criteria. Resected tissue also underwent PARPi-FL staining and PARP1 immunohistochemistry.

Results

In a preclinical mouse model, we illustrated that [¹⁸F]PARPi crossed the blood–brain barrier and specifically bound to PARP1 overexpressed in cancer cell nuclei. In humans, we demonstrated high [¹⁸F]PARPi uptake on PET/MR in active brain cancers and low uptake in treatment-related changes independent of blood–brain barrier disruption. Immunohistochemistry results confirmed higher PARP1 expression in cancerous than in noncancerous tissue. Specificity was also corroborated by blocking fluorescent tracer uptake with an excess unlabeled PARP inhibitor in patient cancer biospecimen.

Conclusions

Although larger studies are necessary to confirm and further explore this tracer, we describe the promising performance of [¹⁸F]PARPi as a diagnostic tool to evaluate patients with brain cancers and possible treatment-related changes.

Identification of HER2-Positive Metastases in Patients with HER2-Negative Primary Breast Cancer by Using HER2-targeted 89Zr-Pertuzumab PET/CT

Background Human epidermal growth factor receptor 2 (HER2)-targeted therapies are successful in patients with HER2-positive malignancies; however, spatial and temporal heterogeneity of HER2 expression may prevent identification of optimal patients for these therapies. Purpose To determine whether imaging with the HER2-targeted PET tracer zirconium 89 (⁸⁹Zr)-pertuzumab can depict HER2-positive metastases in women with HER2-negative primary breast cancer. Materials and Methods From January to June 2019, women with biopsy-proven HER2-negative primary breast cancer and biopsy-proven metastatic disease were enrolled in a prospective clinical trial (ClinicalTrials.gov NCT02286843) and underwent ⁸⁹Zr-pertuzumab PET/CT for noninvasive whole-biopsy evaluation of potential HER2-positive metastases. ⁸⁹Zr-pertuzumab-avid foci that were suspicious for HER2-positive metastases were tissue sampled and examined by pathologic analysis to document HER2 status. Results Twenty-four women (mean age, 55 years ± 11 [standard deviation]) with HER2-negative primary breast cancer were enrolled. Six women demonstrated foci at ⁸⁹Zr-pertuzumab PET/CT that were suspicious for HER2-positive disease. Of these six women, three had biopsy-proven HER2-positive metastases, two had pathologic findings that demonstrated HER2-negative disease, and one had a fine-needle aspirate with inconclusive results. Conclusion Human epidermal growth factor receptor 2 (HER2)-targeted imaging with zirconium 89-pertuzumab PET/CT was successful in detecting HER2-positive metastases in women with HER2-negative primary breast cancer. This demonstrates the ability of targeted imaging to identify patients for targeted therapies that might not otherwise be considered. © RSNA, 2020 Online supplemental material is available for this article. See the editorial by Mankoff and Pantel in this issue.

Comparison of 68Ga-DOTA-JR11 PET/CT with dosimetric 177Lu-satoreotide tetraxetan (177Lu-DOTA-JR11) SPECT/CT in patients with metastatic neuroendocrine tumors undergoing peptide receptor radionuclide therapy

PURPOSE

Paired imaging/therapy with radiolabeled somatostatin receptor (SSTR) antagonists is a novel approach in neuroendocrine tumors (NETs). The aim of this study was to compare tumor uptake of ⁶⁸Ga-DOTA-JR11 and ¹⁷⁷Lu-satoreotide tetraxetan (¹⁷⁷Lu-DOTA-JR11) in patients with NETs.

METHODS

As part of a prospective clinical trial, 20 patients with metastatic NETs underwent ⁶⁸Ga-DOTA-JR11 PET/CT and serial imaging with ¹⁷⁷Lu-satoreotide tetraxetan. PET/CT and SPECT/CT parameters for lesion uptake and absorbed dose of ¹⁷⁷Lu-satoreotide tetraxetan in lesions were compared using linear regression analysis and Pearson correlation.

RESULTS

A total of 95 lesions were analyzed on ⁶⁸Ga-DOTA-JR11 PET/CT and ¹⁷⁷Lu-satoreotide tetraxetan SPECT/CT. SUVs and tumor-to-normal-tissue ratios on PET/CT and SPECT/CT were significantly correlated (p < 0.01), but the degree of correlation was modest with Pearson correlation coefficients ranging from 0.3 to 0.7. Variation in intrapatient lesional correlation was observed. Nevertheless, in all patients, the lesion SUVpeak uptake ratio for ¹⁷⁷Lu-satoreotide tetraxetan vs. ⁶⁸Ga-DOTA-JR11 was high; even in those with low uptake on ⁶⁸Ga-DOTA-JR11 PET/CT (SUVpeak ≤ 10), a ratio of 8.0 ± 5.2 was noted. Correlation of SUVpeak of ⁶⁸Ga-DOTA-JR11 with projected ¹⁷⁷Lu-satoreotide tetratexan-absorbed dose (n = 42) was modest (r = 0.5, p < 0.01), while excellent correlation of SUVpeak of ¹⁷⁷Lu-satoreotide tetraxetan with projected ¹⁷⁷Lu-satoreotide tetraxetan-absorbed dose was noted (r = 0.9, p < 0.0001).

CONCLUSION

Our study shows that ⁶⁸Ga-DOTA-JR11 PET can be used for patient selection and PRRT and that low tumor uptake on PET should not preclude patients from treatment with ¹⁷⁷Lu-satoreotide tetraxetan. The ability to use single time-point SPECT/CT for absorbed dose calculations could facilitate dosimetry regimens, save costs, and improve patient convenience.

CD38-targeted Immuno-PET of Multiple Myeloma: From Xenograft Models to First-in-Human Imaging

Background Current measurements of multiple myeloma disease burden are suboptimal. Daratumumab is a monoclonal antibody that targets CD38, an antigen expressed on nearly all myeloma cells. Purpose To demonstrate preclinical and first-in-human application of an antibody composed of the native daratumumab labeled with the positron-emitting radionuclide zirconium 89 (⁸⁹Zr) through the chelator deferoxamine (DFO), or ⁸⁹Zr-DFO-daratumumab, for immunologic PET imaging of multiple myeloma. Materials and Methods ⁸⁹Zr-DFO-daratumumab was synthesized by conjugating ⁸⁹Zr to daratumumab with DFO. A murine xenograft model using CD38-positive OPM2 multiple myeloma cells was used to evaluate CD38-specificity of ⁸⁹Zr-DFO-daratumumab. Following successful preclinical imaging, a prospective phase I study of 10 patients with multiple myeloma was performed. Study participants received 74 MBq (2 mCi) of intravenous ⁸⁹Zr-DFO-daratumumab. Each participant underwent four PET/CT scans over the next 8 days, as well as blood chemistry and whole-body counts, to determine safety, tracer biodistribution, pharmacokinetics, and radiation dosimetry. Because ⁸⁹Zr has a half-life of 78 hours, only a single administration of tracer was needed to obtain all four PET/CT scans. Results ⁸⁹Zr-DFO-daratumumab was synthesized with radiochemical purity greater than 99%. In the murine model, substantial bone marrow uptake was seen in OPM2 mice but not in healthy mice, consistent with CD38-targeted imaging of OPM2 multiple myeloma cells. In humans, ⁸⁹Zr-DFO-daratumumab was safe and demonstrated acceptable dosimetry. ⁸⁹Zr-DFO-daratumumab uptake was visualized at PET in sites of osseous myeloma. Conclusion These data demonstrate successful CD38-targeted immunologic PET imaging of multiple myeloma in a murine model and in humans. © RSNA, 2020 Online supplemental material is available for this article.

Safety and Feasibility of PARP1/2 Imaging with 18F-PARPi in Patients with Head and Neck Cancer

PURPOSE

We performed a first-in-human clinical trial. The aim of this study was to determine safety and feasibility of PET imaging with ¹⁸F-PARPi in patients with head and neck cancer.

PATIENTS AND METHODS

Eleven patients with newly diagnosed or recurrent oral and oropharyngeal cancer were injected with ¹⁸F-PARPi (331 ± 42 MBq), and dynamic PET/CT imaging was performed between 0 and 25 minutes postinjection. Static PET/CT scans were obtained at 30, 60, and 120 minutes postinjection. Blood samples for tracer concentration and metabolite analysis were collected. Blood pressure, ECG, oxygen levels, clinical chemistry, and complete blood count were obtained before and after tracer administration.

RESULTS

¹⁸F-PARPi was well-tolerated by all patients without any safety concerns. Of the 11 patients included in the analysis, ¹⁸F-PARPi had focal uptake in all primary lesions (n = 10, SUV_max = 2.8 ± 1.2) and all ¹⁸F-FDG-positive lymph nodes (n = 34). ¹⁸F-PARPi uptake was seen in ¹⁸F-FDG-negative lymph nodes of 3 patients (n = 6). Focal uptake of tracer in primary and metastatic lesions was corroborated by CT alone or in combination with ¹⁸F-FDG. The overall effective dose with ¹⁸F-PARPi PET was 3.9 mSv - 5.2 mSv, contrast was high [SUV_max(lesion)/SUV_max(trapezius muscle) = 4.5] and less variable than ¹⁸F-FDG when compared with the genioglossus muscle (1.3 vs. 6.0, P = 0.001).

CONCLUSIONS

Imaging of head and neck cancer with ¹⁸F-PARPi is feasible and safe. ¹⁸F-PARPi detects primary and metastatic lesions, and retention in tumors is longer than in healthy tissues.

Imaging Patients with Metastatic Castration-Resistant Prostate Cancer Using 89Zr-DFO-MSTP2109A Anti-STEAP1 Antibody

Six-transmembrane epithelial antigen of prostate-1 (STEAP1) is a relatively newly identified target in prostate cancer. We evaluated the ability of PET/CT with 89Zr-DFO-MSTP2109A, an antibody that recognizes STEAP1, to detect lesions in patients with metastatic castration-resistant prostate cancer (mCRPC). Methods: Nineteen mCRPC patients were prospectively imaged using approximately 185 MBq/10 mg of 89Zr-DFO-MSTP2109A. 89Zr-DFO-MSTP2109A PET/CT images obtained 4-7 d after injection were compared with bone and CT scans. Uptake in lesions was measured. Fifteen patients were treated with an antibody-drug conjugate (ADC) based on MSTP2109A; ADC treatment-related data were correlated with tumor uptake by PET imaging. Bone or soft-tissue biopsy samples were evaluated. Results: No significant toxicity occurred. Excellent uptake was observed in bone and soft-tissue disease. Median SUVmax was 20.6 in bone and 16.8 in soft tissue. Sixteen of 17 lesions biopsied were positive on 89Zr-DFO-MSTP2109A, and all sites were histologically positive (1 on repeat biopsy). Bayesian analysis resulted in a best estimate of 86% of histologically positive lesions being true-positive on imaging (95% confidence interval, 75%-100%). There was no correlation between SUVmax tumor uptake and STEAP1 immunohistochemistry, survival after ADC treatment, number of ADC treatment cycles, or change in prostate-specific antigen level. Conclusion:89Zr-DFO-MSTP2109A is well tolerated and shows localization in mCRPC sites in bone and soft tissue. Given the high SUV in tumor and localization of a large number of lesions, this reagent warrants further exploration as a companion diagnostic in patients undergoing STEAP1-directed therapy.

First-in-Humans Imaging with 89Zr-Df-IAB22M2C Anti-CD8 Minibody in Patients with Solid Malignancies: Preliminary Pharmacokinetics, Biodistribution, and Lesion Targeting

Immunotherapy is becoming the mainstay for treatment of a variety of malignancies, but only a subset of patients responds to treatment. Tumor-infiltrating CD8-positive (CD8+) T lymphocytes play a central role in antitumor immune responses. Noninvasive imaging of CD8+ T cells may provide new insights into the mechanisms of immunotherapy and potentially predict treatment response. We are studying the safety and utility of ⁸⁹Zr-IAB22M2C, a radiolabeled minibody against CD8+ T cells, for targeted imaging of CD8+ T cells in patients with cancer. Methods: The initial dose escalation phase of this first-in-humans prospective study included 6 patients (melanoma, 1; lung, 4; hepatocellular carcinoma, 1). Patients received approximately 111 MBq (3 mCi) of ⁸⁹Zr-IAB22M2C (at minibody mass doses of 0.2, 0.5, 1.0, 1.5, 5, or 10 mg) as a single dose, followed by PET/CT scans at approximately 1-2, 6-8, 24, 48, and 96-144 h after injection. Biodistribution in normal organs, lymph nodes, and lesions was evaluated. In addition, serum samples were obtained at approximately 5, 30, and 60 min and later at the times of imaging. Patients were monitored for safety during infusion and up to the last imaging time point. Results: ⁸⁹Zr-IAB22M2C infusion was well tolerated, with no immediate or delayed side effects observed after injection. Serum clearance was typically biexponential and dependent on the mass of minibody administered. Areas under the serum time-activity curve, normalized to administered activity, ranged from 1.3 h/L for 0.2 mg to 8.9 h/L for 10 mg. Biodistribution was dependent on the minibody mass administered. The highest uptake was always in spleen, followed by bone marrow. Liver uptake was more pronounced with higher minibody masses. Kidney uptake was typically low. Prominent uptake was seen in multiple normal lymph nodes as early as 2 h after injection, peaking by 24-48 h after injection. Uptake in tumor lesions was seen on imaging as early as 2 h after injection, with most ⁸⁹Zr-IAB22M2C-positive lesions detectable by 24 h. Lesions were visualized early in patients receiving treatment, with SUV ranging from 5.85 to 22.8 in 6 target lesions. Conclusion: ⁸⁹Zr-IAB22M2C imaging is safe and has favorable kinetics for early imaging. Biodistribution suggests successful targeting of CD8+ T-cell-rich tissues. The observed targeting of tumor lesions suggests this may be informative for CD8+ T-cell accumulation within tumors. Further evaluation is under way.

Retooling a Blood-Based Biomarker: Phase I Assessment of the High-Affinity CA19-9 Antibody HuMab-5B1 for Immuno-PET Imaging of Pancreatic Cancer

PURPOSE

In patients with cancer who have an abnormal biomarker finding, the source of the biomarker in the bloodstream must be located for confirmation of diagnosis, staging, and therapy planning. We evaluated if immuno-PET with the radiolabeled high-affinity antibody HuMab-5B1 (MVT-2163), binding to the cancer antigen CA19-9, can identify the source of elevated biomarkers in patients with pancreatic cancer.

PATIENTS AND METHODS

In this phase I dose-escalating study, 12 patients with CA19-9-positive metastatic malignancies were injected with MVT-2163. Within 7 days, all patients underwent a total of four whole-body PET/CT scans. A diagnostic CT scan was performed prior to injection of MVT-2163 to correlate findings on MVT-2163 PET/CT.

RESULTS

Immuno-PET with MVT-2163 was safe and visualized known primary tumors and metastases with high contrast. In addition, radiotracer uptake was not only observed in metastases known from conventional CT, but also seen in subcentimeter lymph nodes located in typical metastatic sites of pancreatic cancer, which were not abnormal on routine clinical imaging studies. A significant fraction of the patients demonstrated very high and, over time, increased uptake of MVT-2163 in tumor tissue, suggesting that HuMab-5B1 labeled with beta-emitting radioisotopes may have the potential to deliver therapeutic doses of radiation to cancer cells.

CONCLUSIONS

Our study shows that the tumor antigen CA19-9 secreted to the circulation can be used for sensitive detection of primary tumors and metastatic disease by immuno-PET. This significantly broadens the number of molecular targets that can be used for PET imaging and offers new opportunities for noninvasive characterization of tumors in patients.

Phase I Trial of Well-Differentiated Neuroendocrine Tumors (NETs) with Radiolabeled Somatostatin Antagonist 177Lu-Satoreotide Tetraxetan

PURPOSE

Radiolabeled somatostatin receptor 2 (SSTR2) antagonists have shown higher tumor uptake and tumor-to-organ ratios than somatostatin agonists in preclinical models of neuroendocrine tumors (NETs). We performed a phase I study to evaluate the safety and efficacy of SSTR2 antagonist ¹⁷⁷Lu-satoreotide tetraxetan.

PATIENTS AND METHODS

Twenty patients with advanced SSTR2-positive NETs were treated with ¹⁷⁷Lu-satoreotide tetraxetan. Patients first underwent a dosimetry study with ¹⁷⁷Lu-satoreotide tetraxetan to determine the therapeutic activity that could be safely administered. This activity was split into two equal cycles to be delivered 3 months apart. The maximum activity was 7.4 GBq per cycle.

RESULTS

Of 20 patients with NETs (one lung, seven small bowel, nine pancreatic, one gastric, one rectal, one kidney; mean prior treatments: three), six received one cycle of ¹⁷⁷Lu- satoreotide tetraxetan and 14 received two cycles. Hematologic toxicity after cycle 1 was mild-moderate and reversed before cycle 2. However, grade 4 hematologic toxicity occurred in four of seven (57%) patients after cycle 2 of ¹⁷⁷Lu-satoreotide tetraxetan. The study was suspended, and the protocol modified to limit the cumulative absorbed bone marrow dose to 1 Gy and to reduce prescribed activity for cycle 2 by 50%. The best overall response rate was 45% [5% complete response (1/20), 40% partial response (8/20)]; with 40% stable disease (8/20) and 15% progression of disease (3/20). Median progression-free survival (PFS) was 21.0 months (95% CI, 13.6-NR).

CONCLUSIONS

In this trial of heavily treated NETs, preliminary data are promising for the use of ¹⁷⁷Lu-satoreotide tetraxetan. Additional studies are ongoing to determine optimal therapeutic dose/schedule.

Biodistribution and Dosimetry of Intraventricularly Administered 124I-Omburtamab in Patients with Metastatic Leptomeningeal Tumors

Radiation dose estimations are key for optimizing therapies. We studied the role of ¹²⁴I-omburtamab (8H9) given intraventricularly in assessing the distribution and radiation doses before ¹³¹I-omburtamab therapy in patients with metastatic leptomeningeal disease and compared it with the estimates from cerebrospinal fluid (CSF) sampling. Methods: Patients with histologically proven malignancy and metastatic disease to the central nervous system or leptomeninges who met eligibility criteria for ¹³¹I-omburtamab therapy underwent immuno-PET imaging with ¹²⁴I-8H9 followed by ¹³¹I-8H9 antibody therapy. Patients were imaged with approximately 74 MBq of intraventricular ¹²⁴I-omburtamab via an Ommaya reservoir. Whole-body PET images were acquired at approximately 4, 24, and 48 h after administration and analyzed for dosimetry calculations. Peripheral blood and CSF samples were obtained at multiple time points for dosimetry estimation. Results: Forty-two patients with complete dosimetry and therapy data were analyzed. ¹²⁴I-omburtamab PET-based radiation dosimetry estimations revealed mean (±SD) absorbed dose to the CSF for ¹³¹I-8H9 of 0.62 ± 0.40 cGy/MBq, compared with 2.22 ± 2.19 cGy/MBq based on ¹²⁴I-omburtamab CSF samples and 1.53 ± 1.37 cGy/MBq based on ¹³¹I-omburtamab CSF samples. The mean absorbed dose to the blood was 0.051 ± 0.11 cGy/MBq for ¹²⁴I-omburtamab samples and 0.07 ± 0.04 cGy/MBq for ¹³¹I-omburtamab samples. The effective whole-body radiation dose for ¹²⁴I-omburtamab was 0.49 ± 0.27 mSv/MBq. The mean whole-body clearance half-time was 44.98 ± 16.29 h. Conclusion: PET imaging with ¹²⁴I-omburtamab antibody administered intraventricularly allows for noninvasive estimation of dose to CSF and normal organs. High CSF-to-blood absorbed-dose ratios are noted, allowing for an improved therapeutic index to leptomeningeal disease and reduced systemic doses. PET imaging-based estimates were less variable and more reliable than CSF sample-based dosimetry.

Pharmacokinetics and Biodistribution of a [89Zr]Zr-DFO-MSTP2109A Anti-STEAP1 Antibody in Metastatic Castration-Resistant Prostate Cancer Patients

A six-transmembrane epithelial antigen of prostate-1 (STEAP1) is a newly identified target in prostate cancer. The use of radio-labeled STEAP1-targeting antibodies with positron emission tomography (PET) may allow for detection of sites of metastatic prostate cancer and may refine patient selection for antigen-directed therapies. This was a prospective study in seven patients with metastatic castration-resistant prostate cancer who had at least one archival biopsy that was STEAP1-positive by immunohistochemistry. Patients received intravenous injections of ∼185 MBq and 10 mg of [⁸⁹Zr]Zr-DFO-MSTP2109A, a humanized IgG1 monoclonal antibody directed against STEAP1. PET/CT images, blood samples, and whole-body counts were monitored longitudinally in six patients. Here, we report on safety, biodistribution, pharmacokinetics, dose estimates to normal tissues, and initial tumor targeting for this group of patients. There was no significant acute or subacute toxicity. Favorable biodistribution and enhanced lesion uptake (in both bone and soft tissue) were observed on imaging using a mass of 10 mg of DFO-MSTP2109A. The best lesion discrimination was seen at the latest imaging time, a median of 6 days postadministration. Pharmacokinetics showed a median serum T_1/2 β of 198 h, volume of central compartment of 3.54 L (similar to plasma volume), and clearance of 19.7 mL/h. The median biologic T_1/2 for whole-body retention was 469 h. The highest mean absorbed doses to normal organs (mGy/MBq) were 1.18, 1.11, 0.78, 0.73, and 0.71 for liver, heart wall, lung, kidney, and spleen, respectively. Excellent targeting of metastatic prostate sites in both bone and soft tissue was observed, with an optimal imaging time of 6 days postadministration. The liver and heart were the normal organs that experienced the highest absorbed doses. The pharmacokinetics were similar to other antibodies without major cross-reactivity with normal tissues. A more detailed analysis of lesion targeting in a larger patient population with correlation to immunohistology and standard imaging modalities has been reported.

Intraventricular radioimmunotherapy targeting B7H3 for CNS malignancies

e13592

Background: Tumors metastasizing to the central nervous system (CNS) are associated with significant mortality. We tested the toxicity and dosimetry of intraventricular 131I-labeled monoclonal antibody 8H9 targeting surface glycoprotein B7-H3 in patients with primary or metastatic CNS tumors. Methods: Tumor B7-H3 expression was assessed by immunohistochemistry. CSF flow was determined by 111Indium-DTPA cisternography. 131 patients received 2 mCi tracer of intra-Ommaya 124I- or 131I-8H9 for nuclear imaging followed by a therapeutic injection (10-80 mCi, dose levels 1-8 in 10 mCi increments for phase I patients; expanded cohort 50 mCi/injection) 131I-8H9. Pharmacokinetics were studied by serial CSF and blood samplings over 48 hours. Dosimetry was based on pharmacokinetics and region of interest analyses on serial PET. Toxicity was defined by the CTCAE v.3.0. 8H9 dosimetry and therapy injections were repeated after 1 month if no serious adverse events or progressive disease ensued. Tumor response was determined by clinical, radiographic, cytologic criteria; overall survival was noted. Results: 57 patients (ages 2 – 54 years, median age 11.7 years) received 158 injections Primary CNS diagnoses included medulloblastoma (n = 23), ependymoma (N = 8), chordoma (n = 1), rhabdoid tumor (n = 1), choroid plexus carcinoma (n = 3), ETMR (n = 3), glioblastoma multiforme (n = 1) , PXA (n = 1); metastatic tumors included sarcoma (n = 9), melanoma (n = 4), retinoblastoma (n = 2), and ovarian carcinoma (n = 1). Injections were well tolerated and routinely administered in the outpatient setting. Rare self-limited adverse events included grade 1 or 2 fever, headache, vomiting; 3 injections were associated with grade 3 toxicities requiring discontinuation of therapy including chemical meningitis (n = 2),and increasing communicating hydrocephalus (n = 1), Although not a dose limiting toxicity, myelosuppression occurred in patients who had received craniospinal radiation and at dose levels 6 and higher (≥60 mCi). 16 patients remain alive including patients with high-risk malignancies including choroid plexus carcinoma, ETMR, recurrent ependymoma and recurrent medulloblastoma. Conclusions: We conclude that intraventricular 131I-8H9 is safe, has favorable dosimetry to CSF, and may have clinical utility in the treatment of primary and metastatic CNS tumors. Clinical trial information: NCT00089245.

A phase I study of convection-enhanced delivery of 124I-8H9 radio-labeled monoclonal antibody in children with diffuse intrinsic pontine glioma: An update with dose-response assessment

2008

Background: Diffuse intrinsic pontine glioma (DIPG) represents one of the most deadly central nervous system tumors of childhood with a median survival of less than 12 months. Convection-enhanced delivery (CED) has been recently hypothesized as a means for efficiently distributing therapeutic agents within the brain stem. We conducted this study to evaluate CED in children with DIPG. Methods: We performed a standard phase I dose escalation study in patients with non-progressive DIPG 4 to 14 weeks post-completion of radiation therapy. Seven dose levels of a single injection of 124I-8H9 (Omburtamab) (range 0.25 to 4.0 mCi) were studied. Results: 37 children were treated with 34 evaluable for primary and secondary endpoints. The median age at enrollment was 6.8 years old (range 3.2 - 17.9). There was no dose limiting toxicity (DLT). Among adverse events that were at least possibly related to the treatment, there were no grade 4 or 5 events, and only 4 reversible grade 3 events in 4 patients (2 hemiparesis, 1 skin infection and 1 anxiety). Estimations of distribution volumes based on T2-weighted imaging were dose dependent and ranged from 1.5 to 20.8 cm3, and for dose level 7, 10.5 - 19.0 cm3. The mean volume of distribution/volume of infusion ratio (Vd/Vi) was 3.4 ±1.1, and for dose level 7, 3.5 ± 1.0. The mean lesion absorbed dose was 33.3 ± 25.9 Gy, and for dose level 7, 50.1 ± 22.9 Gy. The mean ratio of lesion-to-whole body absorbed dose was 910. The mean volume of distribution/tumor volume ratio on dose level 7 was 82.5%, but the mean tumor overlap was 40.5%. No death occurred as a result of the treatment. Median survival was 15.3 months (n = 29, 95% CI 12.7 - 17.4). Median follow-up time of the 5 surviving patients is 27.2 months (range 11.5 - 72.4). Overall survival rate at 12 months was 64.7% (22/34, 4 alive), and overall survival rate at 24 months 14.7% (5/34, 3 alive). Conclusions: CED in the brain stem of children with DIPG who were previously irradiated is a safe therapeutic strategy. An infusion volume of 4,000 mcl appears to be a reasonable single dose for a target distribution volume but enhanced tumor coverage is likely needed. There seems to be a survival benefit using this therapeutic strategy and outcomes might be dependent on dosimetry and distribution patterns. Clinical trial information: NCT01502917.

Biodistribution and radiation dose estimates for 68Ga-DOTA-JR11 in patients with metastatic neuroendocrine tumors

PURPOSE

Somatostatin 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.

METHODS

Twenty 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.

RESULTS

In 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 SUV_mean 1.4 (range: 0.7-1.8), liver SUV_mean 1.1 (0.7-1.9). A total of 42 tumor lesions were analyzed with median SUV_max 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.

CONCLUSIONS

⁶⁸Ga-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.

Reproducibility and Repeatability of Semiquantitative 18F-Fluorodihydrotestosterone Uptake Metrics in Castration-Resistant Prostate Cancer Metastases: A Prospective Multicenter Study

18F-fluorodihydrotestosterone (18F-FDHT) is a radiolabeled analog of the androgen receptor's primary ligand that is currently being credentialed as a biomarker for prognosis, response, and pharmacodynamic effects of new therapeutics. As part of the biomarker qualification process, we prospectively assessed its reproducibility and repeatability in men with metastatic castration-resistant prostate cancer. Methods: We conducted a prospective multiinstitutional study of metastatic castration-resistant prostate cancer patients undergoing 2 (test/retest) 18F-FDHT PET/CT scans on 2 consecutive days. Two independent readers evaluated all examinations and recorded SUVs, androgen receptor-positive tumor volumes, and total lesion uptake for the most avid lesion detected in each of 32 predefined anatomic regions. The relative absolute difference and reproducibility coefficient (RC) of each metric were calculated between the test and retest scans. Linear regression analyses, intraclass correlation coefficients (ICCs), and Bland-Altman plots were used to evaluate repeatability of 18F-FDHT metrics. The coefficient of variation and ICC were used to assess interobserver reproducibility. Results: Twenty-seven patients with 140 18F-FDHT-avid regions were included. The best repeatability among 18F-FDHT uptake metrics was found for SUV metrics (SUVmax, SUVmean, and SUVpeak), with no significant differences in repeatability among them. Correlations between the test and retest scans were strong for all SUV metrics (R2 ≥ 0.92; ICC ≥ 0.97). The RCs of the SUV metrics ranged from 21.3% (SUVpeak) to 24.6% (SUVmax). The test and retest androgen receptor-positive tumor volumes and TLU, respectively, were highly correlated (R2 and ICC ≥ 0.97), although variability was significantly higher than that for SUV (RCs > 46.4%). The prostate-specific antigen levels, Gleason score, weight, and age did not affect repeatability, nor did total injected activity, uptake measurement time, or differences in uptake time between the 2 scans. Including the most avid lesion per patient, the 5 most avid lesions per patient, only lesions 4.2 mL or more, only lesions with an SUV of 4 g/mL or more, or normalizing of SUV to area under the parent plasma activity concentration-time curve did not significantly affect repeatability. All metrics showed high interobserver reproducibility (ICC > 0.98; coefficient of variation < 0.2%-10.8%). Conclusion: Uptake metrics derived from 18F-FDHT PET/CT show high repeatability and interobserver reproducibility.

Convection-enhanced delivery for diffuse intrinsic pontine glioma: a single-centre, dose-escalation, phase 1 trial

BACKGROUND

Diffuse intrinsic pontine glioma is one of the deadliest central nervous system tumours of childhood, with a median overall survival of less than 12 months. Convection-enhanced delivery has been proposed as a means to efficiently deliver therapeutic agents directly into the brainstem while minimising systemic exposure and associated toxic effects. We did this study to evaluate the safety of convection-enhanced delivery of a radioimmunotherapy agent targeting the glioma-associated B7-H3 antigen in children with diffuse intrinsic pontine glioma.

METHODS

We did a phase 1, single-arm, single-centre, dose-escalation study at the Memorial Sloan Kettering Cancer Center (New York, NY, USA). Eligible patients were aged 3-21 years and had diffuse intrinsic pontine glioma as diagnosed by consensus of a multidisciplinary paediatric neuro-oncology team; a Lansky (patients <16 years of age) or Karnofsky (patients ≥16 years) performance score of at least 50 at study entry; a minimum weight of 8 kg; and had completed external beam radiation therapy (54·0-59·4 Gy at 1·8 Gy per fraction over 30-33 fractions) at least 4 weeks but no more than 14 weeks before enrolment. Seven dose-escalation cohorts were planned based on standard 3 + 3 rules: patients received a single infusion of 9·25, 18·5, 27·75, 37, 92·5, 120·25, or 148 MBq, respectively, at a concentration of about 37 MBq/mL by convection-enhanced delivery of the radiolabelled antibody [¹²⁴I]-8H9. The primary endpoint was identification of the maximum tolerated dose. The analysis of the primary endpoint was done in the per-protocol population (patients who received the full planned dose of treatment), and all patients who received any dose of study treatment were included in the safety analysis. This study is registered with ClinicalTrials.gov, number NCT01502917, and is ongoing with an expanded cohort.

FINDINGS

From April 5, 2012, to Oct 8, 2016, 28 children were enrolled and treated in the trial, of whom 25 were evaluable for the primary endpoint. The maximum tolerated dose was not reached as no dose-limiting toxicities were observed. One (4%) of 28 patients had treatment-related transient grade 3 hemiparesis and one (4%) had grade 3 skin infection. No treatment-related grade 4 adverse events or deaths occurred. Estimated volumes of distribution (Vd) were linearly dependent on volumes of infusion (Vi) and ranged from 1·5 to 20·1 cm³, with a mean Vd/Vi ratio of 3·4 (SD 1·2). The mean lesion absorbed dose was 0·39 Gy/MBq ¹²⁴I (SD 0·20). Systemic exposure was negligible, with an average lesion-to-whole body ratio of radiation absorbed dose higher than 1200.

INTERPRETATION

Convection-enhanced delivery in the brainstem of children with diffuse intrinsic pontine glioma who have previously received radiation therapy seems to be a rational and safe therapeutic strategy. PET-based dosimetry of the radiolabelled antibody [¹²⁴I]-8H9 validated the principle of using convection-enhanced delivery in the brain to achieve high intra-lesional dosing with negligible systemic exposure. This therapeutic strategy warrants further development for children with diffuse intrinsic pontine glioma.

FUNDING

National Institutes of Health, The Dana Foundation, The Cure Starts Now, Solving Kids' Cancer, The Lyla Nsouli Foundation, Cookies for Kids' Cancer, The Cristian Rivera Foundation, Battle for a Cure, Cole Foundation, Meryl & Charles Witmer Charitable Foundation, Tuesdays with Mitch Charitable Foundation, and Memorial Sloan Kettering Cancer Center.

Metabolic Imaging of the Human Brain with Hyperpolarized 13C Pyruvate Demonstrates 13C Lactate Production in Brain Tumor Patients

Hyperpolarized (HP) MRI using [1-13C] pyruvate is a novel method that can characterize energy metabolism in the human brain and brain tumors. Here, we present the first dynamically acquired human brain HP 13C metabolic spectra and spatial metabolite maps in cases of both untreated and recurrent tumors. In vivo production of HP lactate from HP pyruvate by tumors was indicative of altered cancer metabolism, whereas production of HP lactate in the entire brain was likely due to baseline metabolism. We correlated our results with standard clinical brain MRI, MRI DCE perfusion, and in one case FDG PET/CT. Our results suggest that HP 13C pyruvate-to-lactate conversion may be a viable metabolic biomarker for assessing tumor response.Significance: Hyperpolarized pyruvate MRI enables metabolic imaging in the brain and can be a quantitative biomarker for active tumors.Graphical Abstract: http://cancerres.aacrjournals.org/content/canres/78/14/3755/F1.large.jpg Cancer Res; 78(14); 3755-60. ©2018 AACR.

I-124 codrituzumab imaging and biodistribution in patients with hepatocellular carcinoma

Background

I-124 codrituzumab (aka GC33), an antibody directed at Glypican 3, was evaluated in patients with hepatocellular carcinoma (HCC). Fourteen patients with HCC underwent baseline imaging with I-124 codrituzumab (~ 185 MBq, 10 mg). Seven of these patients undergoing sorafenib/immunotherapy with 2.5 or 5 mg/kg of cold codrituzumab had repeat imaging, with co-infusion of I-124 codrituzumab, as part of their immunotherapy treatment. Three patients who progressed while on sorafenib/immunotherapy were re-imaged after a 4-week washout period to assess for the presence of antigen. Serial positron emission tomography (PET) imaging and pharmacokinetics were performed following I-124 codrituzumab. An ELISA assay was used to determine “cold” codrituzumab serum pharmacokinetics and compare it to that of I-124 codrituzumab. Correlation of imaging results was performed with IHC. Short-term safety assessment was also evaluated.

Results

Thirteen patients had tumor localization on baseline I-124 codrituzumab; heterogeneity in tumor uptake was noted. In three patients undergoing repeat imaging while on immunotherapy/sorafenib, evidence of decreased I-124 codrituzumab uptake was noted. All three patients who underwent imaging after progression while on immunotherapy continued to have I-124 codrituzumab tumor uptake. Pharmacokinetics of I-124 codrituzumab was similar to that of other intact IgG. No significant adverse events were observed related to the I-124 codrituzumab.

Conclusions

I-124 codrituzumab detected tumor localization in most patients with HCC. Pharmacokinetics was similar to that of other intact iodinated humanized IgG. No visible cross-reactivity with normal organs was observed.

Electronic supplementary material

The online version of this article (10.1186/s13550-018-0374-8) contains supplementary material, which is available to authorized users.

In Vivo PET Assay of Tumor Glutamine Flux and Metabolism: In-Human Trial of 18F-(2S,4R)-4-Fluoroglutamine

Purpose To assess the clinical safety, pharmacokinetics, and tumor imaging characteristics of fluorine 18-(2S,4R)-4-fluoroglutamine (FGln), a glutamine analog radiologic imaging agent. Materials and Methods This study was approved by the institutional review board and conducted under a U.S. Food and Drug Administration-approved Investigational New Drug application in accordance with the Helsinki Declaration and the Health Insurance Portability and Accountability Act. All patients provided written informed consent. Between January 2013 and October 2016, 25 adult patients with cancer received an intravenous bolus of FGln tracer (mean, 244 MBq ± 118, <100 μg) followed by positron emission tomography (PET) and blood radioassays. Patient data were summarized with descriptive statistics. FGln biodistribution and plasma amino acid levels in nonfasting patients (n = 13) were compared with those from patients who fasted at least 8 hours before injection (n = 12) by using nonparametric one-way analysis of variance with Bonferroni correction. Tumor FGln avidity versus fluorodeoxyglucose (FDG) avidity in patients with paired PET scans (n = 15) was evaluated with the Fisher exact test. P < .05 was considered indicative of a statistically significant difference. Results FGln PET depicted tumors of different cancer types (breast, pancreas, renal, neuroendocrine, lung, colon, lymphoma, bile duct, or glioma) in 17 of the 25 patients, predominantly clinically aggressive tumors with genetic mutations implicated in abnormal glutamine metabolism. Acute fasting had no significant effect on FGln biodistribution and plasma amino acid levels. FGln-avid tumors were uniformly FDG-avid but not vice versa (P = .07). Patients experienced no adverse effects. Conclusion Preliminary human FGln PET trial results provide clinical validation of abnormal glutamine metabolism as a potential tumor biomarker for targeted radiotracer imaging in several different cancer types. ^© RSNA, 2018 Online supplemental material is available for this article. Clinical trial registration no. NCT01697930.

A phase II study of radioimmunotherapy with intraventricular 131 I-3F8 for medulloblastoma

BACKGROUND

High-risk and recurrent medulloblastoma (MB) is associated with significant mortality. The murine monoclonal antibody 3F8 targets the cell-surface disialoganglioside GD2 on MB. We tested the efficacy, toxicity, and dosimetry of compartmental radioimmunotherapy (cRIT) with intraventricular ¹³¹ I-labeled 3F8 in patients with MB on a phase II clinical trial.

METHODS

Patients with histopathologically confirmed high-risk or recurrent MB were eligible for cRIT. After determining adequate cerebrospinal fluid (CSF) flow, patients received 2 mCi (where Ci is Curie) ¹²⁴ I-3F8 or ¹³¹ I-3F8 with nuclear imaging for dosimetry, followed by up to four therapeutic (10 mCi/dose) ¹³¹ I-3F8 injections. Dosimetry estimates were based on serial CSF and blood samplings over 48 hr plus region-of-interest analyses on serial imaging scans. Disease evaluation included pre- and posttherapy brain/spine magnetic resonance imaging approximately every 3 months for the first year after treatment, and every 6-12 months thereafter.

RESULTS

Forty-three patients received a total of 167 injections; 42 patients were evaluable for outcome. No treatment-related deaths occurred. Toxicities related to drug administration included acute bradycardia with somnolence, headache, fatigue, and CSF pleocytosis consistent with chemical meningitis and dystonic reaction. Total CSF absorbed dose was 1,453 cGy (where Gy is Gray; 350.0-2,784). Median overall survival from first dose of cRIT was 24.9 months (95% confidence interval [CI]:16.3-55.8). Patients treated in radiographic and cytologic remission were at a lower risk of death compared to patients with radiographically measurable disease (hazard ratio: 0.40, 95% CI: 0.18-0.88, P = 0.024).

CONCLUSIONS

cRIT with ¹³¹ I-3F8 is safe, has favorable dosimetry to CSF, and when added to salvage therapy using conventional modalities, may have clinical utility in maintaining remission in high-risk or recurrent MB.

First-in-Human Human Epidermal Growth Factor Receptor 2-Targeted Imaging Using 89Zr-Pertuzumab PET/CT: Dosimetry and Clinical Application in Patients with Breast Cancer

In what we believe to be a first-in-human study, we evaluated the safety and dosimetry of ⁸⁹Zr-pertuzumab PET/CT for human epidermal growth factor receptor 2 (HER2)-targeted imaging in patients with HER2-positive breast cancer. Methods: Patients with HER2-positive breast cancer and evidence of distant metastases were enrolled in an institutional review board-approved prospective clinical trial. Pertuzumab was conjugated with deferoxamine and radiolabeled with ⁸⁹Zr. Patients underwent PET/CT with 74 MBq of ⁸⁹Zr-pertuzumab in a total antibody mass of 20-50 mg of pertuzumab. PET/CT, whole-body probe counts, and blood drawing were performed over 8 d to assess pharmacokinetics, biodistribution, and dosimetry. PET/CT images were evaluated for the ability to visualize HER2-positive metastases. Results: Six patients with HER2-positive metastatic breast cancer were enrolled and administered ⁸⁹Zr-pertuzumab. No toxicities occurred. Dosimetry estimates from OLINDA demonstrated that the organs receiving the highest doses (mean ± SD) were the liver (1.75 ± 0.21 mGy/MBq), the kidneys (1.27 ± 0.28 mGy/MBq), and the heart wall (1.22 ± 0.16 mGy/MBq), with an average effective dose of 0.54 ± 0.07 mSv/MBq. PET/CT demonstrated optimal imaging 5-8 d after administration. ⁸⁹Zr-pertuzumab was able to image multiple sites of malignancy and suggested that they were HER2-positive. In 2 patients with both known HER2-positive and HER2-negative primary breast cancers and brain metastases, ⁸⁹Zr-pertuzumab PET/CT suggested that the brain metastases were HER2-positive. In 1 of the 2 patients, subsequent resection of a brain metastasis proved HER2-positive disease, confirming that the ⁸⁹Zr-pertuzumab avidity was a true-positive result for HER2-positive malignancy. Conclusion: This first-in-human study demonstrated safety, dosimetry, biodistribution, and successful HER2-targeted imaging with ⁸⁹Zr-pertuzumab PET/CT. Potential clinical applications include assessment of the HER2 status of lesions that may not be accessible to biopsy and assessment of HER2 heterogeneity.

Pharmacokinetics, Biodistribution, and Radiation Dosimetry for 89Zr-Trastuzumab in Patients with Esophagogastric Cancer

Trastuzumab with chemotherapy improves clinical outcomes in patients with human epidermal growth factor receptor 2 (HER2)-positive esophagogastric adenocarcinoma (EGA). Despite the therapeutic benefit, responses are rarely complete, and most patients develop progression. To our knowledge, this is the first report evaluating ⁸⁹Zr-trastuzumab in HER2-positive EGA; here, we evaluate the safety, pharmacokinetics, biodistribution, and dosimetry ⁸⁹Zr-trastuzumab. Methods: Trastuzumab was conjugated with deferoxamine and radiolabeled with ⁸⁹Zr. A mean activity of 184 MBq was administered to 10 patients with metastatic HER2-positive EGA. PET imaging, whole-body probe counts, and blood draws were performed to assess pharmacokinetics, biodistribution, and dosimetry. Results: No clinically significant toxicities were observed. At the end of infusion, the estimated ⁸⁹Zr-trastuzumab in plasma volume was a median 102% (range, 78%-113%) of the injected dose. The median biologic half-life T_1/2β was 111 h (range, 78-193 h). The median biologic whole-body retention half-life was 370 h (range, 257-578 h). PET images showed optimal tumor visualization at 5-8 d after injection. The maximum tumor SUV ranged from no to minimal uptake in 3 patients to a median of 6.8 (range, 2.9-22.7) for 20 lesions in 7 patients. Dosimetry estimates from OLINDA showed that the organs receiving the highest absorbed doses were the liver and heart wall, with median values of 1.37 and 1.12 mGy/MBq, respectively. Conclusion:⁸⁹Zr-trastuzumab imaging tracer is safe and provides high-quality images in patients with HER2-positive EGA, with an optimal imaging time of 5-8 d after injection.

A curative approach to central nervous system metastases of neuroblastoma

10545

Background: Neuroblastoma metastatic to the central nervous system (CNS NB) is associated with significant mortality (median survival < 6 months, < 10% survival at 36 months). Intraventricular compartmental radioimmunotherapy (cRIT) with radio-iodinated murine IgG1 monoclonal antibody 131I-8H9 targeting tumor cell-surface glycoprotein B7-H3 offers a therapeutic strategy. We analyzed overall survival of patients with CNS NB treated with intraventricular 131I-8H9 cRIT at Memorial Sloan Kettering Cancer Center (MSK) since 2003. Methods: After radiographic and/or pathologic confirmation of CNS NB, and assessment of adequate CSF flow, cRIT eligible patients underwent treatment on an IRB-approved protocol with either temozolomide/irinotecan-based CNS salvage regimen incorporating craniospinal radiation therapy, 131I-8H9 cRIT plus systemic immunotherapy (group 1), or non-regimen therapies with 131I-8H9 cRIT (group 2). cRIT administration involved a 2mCi tracer of 124I- or 131I-8H9 with nuclear imaging and CSF sampling for dosimetry followed by 1 or 2 therapeutic injections up to 70 mCi 131I-8H9. Disease surveillance included serial MR brain/spine, MIBG, CT, and bone marrow evaluation. Data are presented as overall survival after detection of CNS metastasis. Results: 105 patients with CNS NB were evaluated;80 patients (76%) were treated (57 group 1, 23 group 2). Of the 25 patients who were not eligible for cRIT, survival averaged 8.6 months. Of 19 patients with radiographic evidence of disease at the time of cRIT, 7 (36%) demonstrated post cRIT radiographic improvement. At analysis, 45/80 (56%) patients were alive 4.8–152 months (median 58 months) after CNS metastasis, including 36 (45%) at 36 months and 23 (29%) > 60 months. Subgroup analyses of 131I-8H9–treated patients identified age at NB diagnosis (≤18 months), relapse restricted to CNS and group 1 status as factors positively correlated with survival. Conclusions: 76% of patients with CNS NB treated at MSK received 131I-8H9 cRIT, and approximately half completed multimodality CNS salvage regimen with 131I-8H9 cRIT. Despite advanced CNS involvement, over 50% of patients treated with 131I-8H9 cRIT are still alive and nearly 50% have survived at least 36 months. Clinical trial information: NCT00089245.

A phase I study of convection enhanced delivery (CED) of 124I-8H9 radio-labeled monoclonal antibody in children with diffuse intrinsic pontine glioma (DIPG)

2010

Background: Diffuse intrinsic pontine glioma (DIPG) represents one of the most deadly central nervous system tumors of childhood with a median survival of less than 12 months. Convection-enhanced delivery (CED) has been recently hypothesized as a means for augmenting distribution of therapeutic agents within the brain stem. We conducted this study to evaluate CED in children with DIPG. Methods: We performed a standard 3+3 phase I, open-label, dose escalation study in patients with non-progressive DIPG 4 to 14 weeks post-completion or radiation therapy. Seven dose levels of a single injection of 124I-8H9 (range 0.25 to 4.0 mCi, 250 to 4000 mcl) were studied. Results: 25 children were treated. The average age at enrollment 8 years old (range 3-17). There was no dose limiting toxicity (DLT) and adverse events were limited to grade 1 or 2 (CTCAE v4.0). Estimations of distribution volumes were dose dependent and ranged from 1.5 to 20.1 cm3. The mean volume of distribution/volume of infusion (Vd/Vi) was 3.4 (SD 1.2). The mean lesion absorbed dose was 1527 rad/mCi. The mean tumor coverage on dose level 7 was 107%. Conclusions: CED in the brain stem of children with DIPG who were previously irradiated is a safe therapeutic strategy. Up to 4 mCi of 124I-8H9 was well tolerated. An infusion volume of 4000 mcl appears to be a reasonable single dose for good tumor coverage. PET-based dosimetry validates the conceptual basis for direct drug delivery. Based on our finding CED merits further exploration in early phase clinical trials for children with DIPG. Clinical trial information: NCT01502917.

Phase Ib study of codrituzumab in combination with sorafenib in patients with non-curable advanced hepatocellular carcinoma (HCC)

PURPOSE

Codrituzumab, a humanized antibody against glypican-3, is highly expressed in HCC. A phase I study evaluated the combination with sorafenib in HCC.

PATIENTS AND METHODS

In a 3 + 3 design, codrituzumab was given intravenously in various doses with sorafenib 400 mg twice daily to patients with advanced HCC, age ≥18, ECOG 0-1, Child-Pugh A and B7, adequate organ functions, and no prior systemic therapy, with tumor assessment by RECIST 1.0 and safety by CTCAE 3.0. PK and pre, during, and post-therapy ¹²⁴I radiolabeled codrituzumab PET scan imaging were performed.

RESULTS

41 patients were enrolled: 2.5 mg/kg weekly (qw) (12), 5 mg/kg qw (12), 10 mg/kg qw (3), 1600 mg every 2 weeks (q2w) (6), and 1600 mg qw (7). Two drug limiting toxicities occurred: grade 3 hyponatremia at 5 mg/kg and grade 3 hyponatremia and hyperglycemia at 1600 mg q2w. Adverse events occurred in 80% of patients, including at least one ≥grade 3: ten (25%) increased AST, three (7.5%) increased ALT, and ten (25%) increased lipase. There were no responses and nine (25.7%) had stable disease. PK C _max and AUC_t of codrituzumab and sorafenib were comparable to single-agent data. Thirteen out of 14 patients showed ¹²⁴I radiolabeled codrituzumab uptake in tumor. In all three patients who underwent a post-progression PET, glypican-3 remained expressed.

CONCLUSION

Codrituzumab plus sorafenib were tolerated at 1600 mg q2w and 400 mg bid, respectively, with no responses. Codrituzumab exerts selective distribution to HCC cells, and GPC3 does not show any down-regulation post-progression (NCT00976170).

Abstract B44: Optimization and IND enabling investigations of MVT-2163 (89Zr-DFO-5B1) leading to First-in-Human readiness

Rationale: MVT-2163 (89Zr-DFO-5B1) — an anti-CA19.9 human monoclonal antibody formed via conjugation of the chelator desferoxamine (DFO) and radiolabeling with zirconium-89 (89Zr) — was recently reported to have excellent ability to delineate CA19-9 positive malignancies via PET imaging, including pancreatic cancer.(1) Additionally, preclinical studies have shown the antibody has antitumor properties alone(2) and, more recently, in combination with frontline chemotherapies such as nab-Paclitaxel and gemcitabine. Herein, we report the preclinical optimization and characterization of MVT-2163 that led to the recent approval of an IND application for first-in-human trials in patients with metastatic pancreatic cancer.

Methods: The conditions for appending the chelator DFO to MVT-5873 (5B1) were optimized by screening various combinations of reaction pH, stoichiometric ratios of chelate to antibody, buffer type, and incubation times. The optimized conjugation strategy was used to prepare clinical grade DFO-5B1 that was subsequently radiolabeled with 89Zr to yield MVT-2163 for use in human subjects. The biodistribution was determined in healthy female, athymic nude mice at 1, 24, 48, 72, and 120h via gamma counting of resected tissues and comparison to standards. The normal-organ radiation doses were estimated for the 70-kg Standard Adult anatomic model using the time-dependent organ activity concentrations and total-body activities, and the Standard Adult mean organ dose and effective dose were calculated using OLINDA. The stability of MVT-2163 in formulation buffer and in human serum at 37°C was assessed (24, 48, 96, 120, and 168h) via thin layer chromatography and size exclusion chromatography. Additionally, the remaining immunoreactive fraction was determined at the same time points using an in vitro cellular binding assay with BxPC3 cells.

Results: We found that the optimal conjugation strategy was to buffer exchange MVT-5873 into 100mM sodium bicarbonate buffer (pH9) prior to letting the DFO react at 32.5°C for 90m. Unincorporated DFO was removed by buffer exchanging the reaction mixture into 1M ammonium acetate (pH7) buffer. The final MVT-7686 (DFO-5B1) product was stored in long term storage at -80°C. Biodistribution of the MVT-2163 indicated tissue retentions that were within expected norms for a 89Zr-labeled antibody. The highest uptake at 120h in terms of percent injected dose per gram of tissue (%ID/g) was found in the bone, which is common for osteophilic radiometals such as 89Zr. Dosimetry calculations based on the biodistribution results predicted a total absorbed dose of 8.1 rem when accounting for the proposed accompanying low-dose CT scan. The absorbed doses to all organs were within acceptable limits at the proposed human study dose (5 mCi), and the absorbed dose in red marrow — which is often the dose-limiting factor — was within ranges predicted and observed with other 89Zr-radiolabeled antibodies in humans.

The radiochemical purity data indicate that the tracer remains intact in formulation buffer up to 120 hours. Cell binding assays performed with multiple lots of the same material showed that the immunoreactivity remains above 75% when stored up to 120h at room temperature, indicating exemplary stability. The stability and immunoreactivity were slightly lower when incubated in human serum at 37°C. However, the data shows that the immunoreactivity is maintained in human serum for more than up to 168h.

Conclusions: The stability studies in both formulation buffer and human serum indicate that MVT-2163 maintains sufficient radiochemical purity and immunoreactivity. The results of the reported studies support the proposed specifications and the excellent performance has resulted in MVT-2163 being accepted for first in human trials at MSKCC, which are set to begin in Q2 2016.

1. Viola-Villegas NT, et al. J Nucl Med. 2013;54(11):1876-82.

2. Sawada R, et al. Clin Cancer Res. 2011;17(5):1024-32.

Citation Format: Jacob L. Houghton, Serge K. Lyashchenko, Ritsuko Sawada, Pat Zanzonico, Scott Rudge, Wolfgang W. Scholz, Paul Maffuid, Jason S. Lewis.{Authors}. Optimization and IND enabling investigations of MVT-2163 (89Zr-DFO-5B1) leading to First-in-Human readiness. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Advances in Science and Clinical Care; 2016 May 12-15; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2016;76(24 Suppl):Abstract nr B44.

Prospective Clinical Trial of 18F-Fluciclovine PET/CT for Determining the Response to Neoadjuvant Therapy in Invasive Ductal and Invasive Lobular Breast Cancers

¹⁸F-labeled 1-amino-3-fluorocyclobutane-1-carboxylic acid (¹⁸F-fluciclovine) is a leucine analog radiotracer that depicts amino acid transport into cells. ¹⁸F-fluciclovine PET/CT visualizes malignancy, including prostate cancer, invasive ductal breast cancer, and invasive lobular breast cancer. Whether changes in ¹⁸F-fluciclovine avidity reflect changes in tumor burden resulting from treatment has not been shown. In this prospective clinical trial (clinical trials.gov: NCT01864083), changes in ¹⁸F-fluciclovine avidity after neoadjuvant therapy were compared to breast cancer therapy response, as determined by residual tumor burden on pathology, were evaluated. Methods: Twenty-four women with a new diagnosis of locally advanced invasive ductal breast cancer (n = 18) or invasive lobular breast cancer (n = 6) underwent ¹⁸F-fluciclovine PET/CT before and after the completion of neoadjuvant systemic therapy. SUV_max, SUV_mean, metabolic tumor volume, and total lesion avidity were obtained for the primary breast tumor, axillary lymph nodes, and extraaxillary lymph nodes on each examination and corrected for background ¹⁸F-fluciclovine avidity. The relationship between changes in ¹⁸F-fluciclovine avidity and the percentage of reduction of tumor on pathology was assessed with the Spearman rank correlation. Results: The median decrease in the corrected SUV_max of the primary breast lesions was 99% (range, 33%-100%). The median reduction of tumor on pathology was 92% (range, 10%-100%). Changes in ¹⁸F-fluciclovine avidity were strongly correlated with the percentage of reduction of tumor on pathology (Spearman ρ, 0.79; 95% CI, 0.56-0.90; P < 0.001). Conclusion: Changes in ¹⁸F-fluciclovine avidity strongly correlated with the tumor response on pathology in this pilot study.

First-in-Human Imaging with 89Zr-Df-IAB2M Anti-PSMA Minibody in Patients with Metastatic Prostate Cancer: Pharmacokinetics, Biodistribution, Dosimetry, and Lesion Uptake

We conducted a phase I dose-escalation study with ⁸⁹Zr-desferrioxamine-IAB2M (⁸⁹Zr-IAB2M), an anti-prostate-specific membrane antigen minibody, in patients with metastatic prostate cancer.

METHODS

Patients received 185 MBq (5 mCi) of ⁸⁹Zr-IAB2M and Df-IAB2M at total mass doses of 10 (n = 6), 20 (n = 6), and 50 mg (n = 6). Whole-body and serum clearance, normal-organ and lesion uptake, and radiation absorbed dose were estimated, and the effect of mass escalation was analyzed.

RESULTS

Eighteen patients were injected and scanned without side effects. Whole-body clearance was monoexponential, with a median biologic half-life of 215 h, whereas serum clearance showed biexponential kinetics, with a median biologic half-life of 3.7 (12.3%/L) and 33.8 h (17.9%/L). The radiation absorbed dose estimates were 1.67, 1.36, and 0.32 mGy/MBq to liver, kidney, and marrow, respectively, with an effective dose of 0.41 mSv/MBq (1.5 rem/mCi). Both skeletal and nodal lesions were detected with ⁸⁹Zr-IAB2M, most visualized by 48-h imaging.

CONCLUSION

⁸⁹Zr-IAB2M is safe and demonstrates favorable biodistribution and kinetics for targeting metastatic prostate cancer. Imaging with 10 mg of minibody mass provides optimal biodistribution, and imaging at 48 h after injection provides good lesion visualization. Assessment of lesion targeting is being studied in detail in an expansion cohort.

Detection of HER2-Positive Metastases in Patients with HER2-Negative Primary Breast Cancer Using 89Zr-Trastuzumab PET/CT

Our objective was to determine whether imaging with a human epidermal growth factor receptor 2 (HER2)-targeted PET tracer can detect HER2-positive metastases in patients with HER2-negative primary breast cancer.

METHODS

Patients with HER2-negative primary breast cancer and evidence of distant metastases were enrolled in an Institutional Review Board-approved prospective clinical trial. Archived pathologic samples from the patient's primary breast cancer were retested to confirm HER2-negative disease. Patients with confirmed HER2-negative primary breast cancer underwent ⁸⁹Zr-trastuzumab PET/CT to screen for ⁸⁹Zr-trastuzumab metastases. Metastases avid for ⁸⁹Zr-trastuzumab by PET/CT were biopsied and pathologically examined to define HER2 status. Patients with pathologically proven HER2-positive metastases subsequently received off-protocol HER2-targeted therapy to evaluate treatment response.

RESULTS

Nine patients were enrolled, all of whom had pathologic retesting that confirmed HER2-negative primary breast cancer. Five demonstrated suggestive foci on ⁸⁹Zr-trastuzumab PET/CT. Of these 5 patients, 2 had biopsy-proven HER2-positive metastases and went on to benefit from HER2-targeted therapy. In the other 3 patients, biopsy showed no evidence of HER2-positive disease, and their foci on ⁸⁹Zr-trastuzumab PET were considered false-positive.

CONCLUSION

In this proof-of-concept study, we demonstrated that ⁸⁹Zr-trastuzmab PET/CT detects unsuspected HER2-positive metastases in patients with HER2-negative primary breast cancer. Although these are only initial results in a small sample, they are a proof of the concept that HER2-targeted imaging can identify additional candidates for HER2-targeted therapy. More specific HER2-targeted agents will be needed for clinical use.

Initial Results of a Prospective Clinical Trial of 18F-Fluciclovine PET/CT in Newly Diagnosed Invasive Ductal and Invasive Lobular Breast Cancers

(18)F-labeled 1-amino-3-fluorocyclobutane-1-carboxylic acid ((18)F-fluciclovine) is a leucine analog PET/CT radiotracer that depicts amino acid transport into cells. Amino acid transport proteins have been shown to be upregulated in breast malignancies by microarray and immunohistochemical analysis, so we hypothesized that (18)F-fluciclovine may provide a novel method of visualizing breast cancer and now report a prospective clinical trial of (18)F-fluciclovine PET/CT in newly diagnosed advanced local invasive ductal carcinoma (IDC) and invasive lobular carcinoma (ILC).

METHODS

Twenty-seven women with a new diagnosis of locally advanced IDC (n = 19) or ILC (n = 8) underwent PET/CT of the chest after intravenous administration of 370 MBq of (18)F-fluciclovine. The SUVmax, SUVmean, metabolic tumor volume, and total lesion avidity were obtained for the primary breast tumor, axillary lymph nodes, and extraaxillary lymph nodes. Sites of previously unsuspected malignancy were recorded and confirmed by pathology. Results of (18)F-fluciclovine PET/CT were compared with those of (18)F-FDG PET/CT, when available, using the concordance correlation coefficient.

RESULTS

All locally advanced breast cancers were (18)F-fluciclovine-avid. Of 21 patients with pathologically proven axillary nodal metastases, (18)F-fluciclovine-avid axillary nodes were seen in 20. (18)F-fluciclovine detected pathologically proven extraaxillary nodal metastases in 3 patients, including 2 previously unsuspected internal mammary nodes. Fourteen patients underwent (18)F-FDG PET/CT for comparison with (18)F-fluciclovine. Concordance for metabolic tumor volume between (18)F-fluciclovine and (18)F-FDG was strong (concordance correlation coefficient, 0.89; 95% confidence interval, 0.73-0.96), but concordance for SUVmax was weak (concordance correlation coefficient, 0.04; 95% confidence interval, -0.16-0.24). In patients with both modalities available (n = 14), primary ILCs (n = 4) demonstrated (18)F-fluciclovine avidity (median SUVmax, 6.1; range, 4.5-10.9) greater than (18)F-FDG avidity (median SUVmax, 3.7; range, 1.8-6.0). Primary IDCs (n = 10) had a lower (18)F-fluciclovine avidity (median SUVmax, 6.8; range, 3.6-9.9) than (18)F-FDG avidity (median SUVmax, 10; range, 3.3-43.5).

CONCLUSION

(18)F-fluciclovine PET/CT demonstrates potential for imaging of both IDC and ILC, including the detection of unsuspected extraaxillary nodal metastases. The low concordance for SUVmax between (18)F-fluciclovine and (18)F-FDG suggests that these tracers measure different biologic phenomena within the tumor. The apparently higher uptake of (18)F-fluciclovine in ILC requires confirmation in a larger cohort.

A phase I/IIa trial of prostate specific membrane antigen (PSMA) positron emission tomography (PET) imaging with 89Zr-Df-IAB2M in metastatic prostate cancer (PCa)

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Background: There is a pressing need for improved imaging biomarkers to identify disease distribution and response in both localized and advanced prostate cancer patients. PSMA-directed imaging is undergoing analytic and clinical validation for these contexts of use. IAB2M is an anti-PSMA recombinant minibody (Mb) derived from huJ591. We have previously reported on 28 pts imaged with IAB2M(Pandit-Taskar et al, SNM 2015). Here we report the lesion targeting and uptake (SUV) of the Mb and correlation with pathology of biopsied lesions on the full complement of the 38 pts examined in this trial. Methods: 38 pts with progressive metastatic PCa received escalating amounts of the Mb (16 pts at 10mg, 16 pts at 20mg, 6 pts at 50mg) in a phase I/IIa trial. All pts underwent standard imaging (SI) using CT, bone scintigraphy (BS), FDG PET, followed by imaging with 5 mCi of IAB2M. Whole body PET/CT scans were performed and evaluated for lesion targeting and SUVmax. Biopsy (bx) locations were selected by a consensus panel prioritized on the basis of: IAB2M & FDG positivity, IAB2M & FDG mismatch, and CT or BS positivity & any PET mismatch. Results: A total of 556 lesions (410 bone, 146 soft tissue) in 38 pts were detected by SI or IAB2M. In bone, IAB2M detected 344 lesions (83.9%), CT 209 (51%), BS 211 (51.5%), and FDG 109 (26.6%). For soft tissue, IAB2M detected 119 (81.5%), CT 83 (56.8%), and FDG 79 (54.1%). The SUV for bone lesions ranged from 2.1-60.4 for 10mg Mb, 1.7- 33 in 20mg Mb, and 2.3-17.5 in 50mg Mb. For soft tissue lesions, SUV range was 3.1-45.4, 2.1-20, and 1.9-13.8 respectively. 28 bxs (13 bone, 15 soft tissue) were obtained from 27 pts; 27 bxs were evaluable (1 was non-diagnostic). 20/27 (74.1%) bxs were pos for PCa; 20/24 (83.3%) IAB2M pos lesions were path pos and 3/3 (100%) IAB2M neg lesions were neg on path. All imaging and path correlated (true pos + true neg) in 23/27 (85.2%) bxs. Conclusions: PET imaging with IAB2M has demonstrated higher lesion detection when compared with SI. IAB2M’s high concordance with path suggests pos findings represent bx confirmed PCa. Further studies to examine biochemically recurrent prostate cancer are planned. Clinical trial information: NCT01923727.

A Phase I/II Study for Analytic Validation of 89Zr-J591 ImmunoPET as a Molecular Imaging Agent for Metastatic Prostate Cancer

PURPOSE

Standard imaging for assessing osseous metastases in advanced prostate cancer remains focused on altered bone metabolism and is inadequate for diagnostic, prognostic, or predictive purposes. We performed a first-in-human phase I/II study of (89)Zr-DFO-huJ591 ((89)Zr-J591) PET/CT immunoscintigraphy to assess performance characteristics for detecting metastases compared with conventional imaging modalities (CIM) and pathology.

EXPERIMENTAL DESIGN

Fifty patients with progressive metastatic castration-resistant prostate cancers were injected with 5 mCi of (89)Zr-J591. Whole-body PET/CT scans were obtained, and images were analyzed for tumor visualization. Comparison was made to contemporaneously obtained bone scintigraphy and cross-sectional imaging on a lesion-by-lesion basis and with biopsies of metastatic sites.

RESULTS

Median standardized uptake value for (89)Zr-J591-positive bone lesions (n = 491) was 8.9 and for soft-tissue lesions (n = 90), it was 4.8 (P < 0.00003). (89)Zr-J591 detected 491 osseous sites compared with 339 by MDP and 90 soft-tissue lesions compared with 124 by computed tomography (CT). Compared with all CIMs combined, (89)Zr-J591 detected an additional 99 osseous sites. Forty-six lesions (21 bone and 25 soft tissue) were biopsied in 34 patients; 18 of 19 (89)Zr-J591-positive osseous sites and 14 of 16 (89)Zr-J591-positive soft tissue sites were positive for prostate cancer. The overall accuracy of (89)Zr-J591 was 95.2% (20 of 21) for osseous lesions and 60% (15 of 25) for soft-tissue lesions.

CONCLUSIONS

(89)Zr-J591 imaging demonstrated superior targeting of bone lesions relative to CIMs. Targeting soft-tissue lesions was less optimal, although (89)Zr-J591 had similar accuracy as individual CIMs. This study will provide benchmark data for comparing performance of proposed prostate-specific membrane antigen (PSMA) targeting agents for prostate cancer.

Fully-automated synthesis of 16β-(18)F-fluoro-5α-dihydrotestosterone (FDHT) on the ELIXYS radiosynthesizer

Noninvasive in vivo imaging of androgen receptor (AR) levels with positron emission tomography (PET) is becoming the primary tool in prostate cancer detection and staging. Of the potential (18)F-labeled PET tracers, (18)F-FDHT has clinically shown to be of highest diagnostic value. We demonstrate the first automated synthesis of (18)F-FDHT by adapting the conventional manual synthesis onto the fully-automated ELIXYS radiosynthesizer. Clinically-relevant amounts of (18)F-FDHT were synthesized on ELIXYS in 90 min with decay-corrected radiochemical yield of 29±5% (n=7). The specific activity was 4.6 Ci/µmol (170 GBq/µmol) at end of formulation with a starting activity of 1.0 Ci (37 GBq). The formulated (18)F-FDHT yielded sufficient activity for multiple patient doses and passed all quality control tests required for routine clinical use.