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Supplementary Figure S1 from Targeted Imaging of Colonic Tumors in Smad3−/− Mice Discriminates Cancer and Inflammation

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BACKGROUND: The PET tracer (4S)-4-(3-[(18)F]fluoropropyl)-l-glutamate ((18)F-FSPG) targets the system x(C)(–) cotransporter, which is overexpressed in various tumors. PURPOSE: To assess the role of (18)F-FSPG PET/CT in intracranial malignancies. MATERIALS AND METHODS: Twenty-six patients (mean age, 54 years ± 12; 17 men; 48 total lesions) with primary brain tumors (n = 17) or brain metastases (n = 9) were enrolled in this prospective, single-center study (ClinicalTrials.gov identifier: NCT02370563) between November 2014 and March 2016. A 30-minute dynamic brain (18)F-FSPG PET/CT scan and a static whole-body (WB) (18)F-FSPG PET/CT scan at 60–75 minutes were acquired. Moreover, all participants underwent MRI, and four participants underwent fluorine 18 ((18)F) fluorodeoxyglucose (FDG) PET imaging. PET parameters and their relative changes were obtained for all lesions. Kinetic modeling was used to estimate the (18)F-FSPG tumor rate constants using the dynamic and dynamic plus WB PET data. Imaging parameters were correlated to lesion outcomes, as determined with follow-up MRI and/or pathologic examination. The Mann-Whitney U test or Student t test was used for group mean comparisons. Receiver operating characteristic curve analysis was used for performance comparison of different decision measures. RESULTS: (18)F-FSPG PET/CT helped identify all 48 brain lesions. The mean tumor-to-background ratio (TBR) on the whole-brain PET images at the WB time point was 26.6 ± 24.9 (range: 2.6–150.3). When (18)F-FDG PET was performed, (18)F-FSPG permitted visualization of non-(18)F-FDG–avid lesions or allowed better lesion differentiation from surrounding tissues. In participants with primary brain tumors, the predictive accuracy of the relative changes in influx rate constant K(i) and maximum standardized uptake value to discriminate between poor and good lesion outcomes were 89% and 81%, respectively. There were significant differences in the (18)F-FSPG uptake curves of lesions with good versus poor outcomes in the primary brain tumor group (P < .05) but not in the brain metastases group. CONCLUSION: PET/CT imaging with (4S)-4-(3-[(18)F]fluoropropyl)-l-glutamate ((18)F-FSPG) helped detect primary brain tumors and brain metastases with a high tumor-to-background ratio. Relative changes in (18)F-FSPG uptake with multi-time-point PET appear to be helpful in predicting lesion outcomes. Clinical trial registration no. NCT02370563 © RSNA, 2022 Online supplemental material is available for this article.

Supplementary Data from Inhibition of Mammalian Target of Rapamycin Is Required for Optimal Antitumor Effect of HER2 Inhibitors against HER2-Overexpressing Cancer Cells

[18F]V-1008 localization observed in Ptf1a-Cre;LSL-KrasG12D/+;Tgfbr2+/- (KTC) pancreatic lesions

PDF file - 90KB, Scheme 1. 19FFB-VAD-FMK (3) (A) and 127IIZ-VAD-FMK (5) (B) synthetic schemes.

Purpose: To evaluate noninvasive imaging methods as predictive biomarkers of response to trastuzumab in mouse models of HER2-overexpressing breast cancer. The correlation between tumor regression and molecular imaging of apoptosis, glucose metabolism, and cellular proliferation was evaluated longitudinally in responding and nonresponding tumor-bearing cohorts.Experimental Design: Mammary tumors from MMTV/HER2 transgenic female mice were transplanted into syngeneic female mice. BT474 human breast carcinoma cell line xenografts were grown in athymic nude mice. Tumor cell apoptosis (NIR700-Annexin V accumulation), glucose metabolism [2-deoxy-2-[18F]fluoro-d-glucose positron emission tomography ([18F]FDG-PET)], and proliferation [3′-[18F]fluoro-3′-deoxythymidine-PET ([18F]FLT-PET)] were evaluated throughout a biweekly trastuzumab regimen. Imaging metrics were validated by direct measurement of tumor size and immunohistochemical analysis of cleaved caspase-3, phosphorylated AKT, and Ki67.Results: NIR700-Annexin V accumulated significantly in trastuzumab-treated MMTV/HER2 and BT474 tumors that ultimately regressed but not in nonresponding or vehicle-treated tumors. Uptake of [18F]FDG was not affected by trastuzumab treatment in MMTV/HER2 or BT474 tumors. [18F]FLT-PET imaging predicted trastuzumab response in BT474 tumors but not in MMTV/HER2 tumors, which exhibited modest uptake of [18F]FLT. Close agreement was observed between imaging metrics and immunohistochemical analysis.Conclusions: Molecular imaging of apoptosis accurately predicts trastuzumab-induced regression of HER2+ tumors and may warrant clinical exploration to predict early response to neoadjuvant trastuzumab. Trastuzumab does not seem to alter glucose metabolism substantially enough to afford [18F]FDG-PET significant predictive value in this setting. Although promising in one preclinical model, further studies are required to determine the overall value of [18F]FLT-PET as a biomarker of response to trastuzumab in HER2+ breast cancer.

Supplementary Data from Imaging Biomarkers Predict Response to Anti-HER2 (ErbB2) Therapy in Preclinical Models of Breast Cancer

Supplementary Figures S1-S2; Supplementary Table S1.

Purpose: To evaluate noninvasive molecular imaging methods as correlative biomarkers of therapeutic efficacy of cetuximab in human colorectal cancer cell line xenografts grown in athymic nude mice. The correlation between molecular imaging and immunohistochemical analysis to quantify epidermal growth factor (EGF) binding, apoptosis, and proliferation was evaluated in treated and untreated tumor-bearing cohorts.Experimental Design: Optical imaging probes targeting EGF receptor (EGFR) expression (NIR800-EGF) and apoptosis (NIR700-Annexin V) were synthesized and evaluated in vitro and in vivo. Proliferation was assessed by 3′-[18F]fluoro-3′-deoxythymidine ([18F]FLT) positron emission tomography. Assessment of inhibition of EGFR signaling by cetuximab was accomplished by concomitant imaging of NIR800-EGF, NIR700-Annexin V, and [18F]FLT in cetuximab-sensitive (DiFi) and insensitive (HCT-116) human colorectal cancer cell line xenografts. Imaging results were validated by measurement of tumor size and immunohistochemical analysis of total and phosphorylated EGFR, caspase-3, and Ki-67 immediately following in vivo imaging.Results: NIR800-EGF accumulation in tumors reflected relative EGFR expression and EGFR occupancy by cetuximab. NIR700-Annexin V accumulation correlated with cetuximab-induced apoptosis as assessed by immunohistochemical staining of caspase-3. No significant difference in tumor proliferation was noted between treated and untreated animals by [18F]FLT positron emission tomography or Ki-67 immunohistochemistry.Conclusions: Molecular imaging can accurately assess EGF binding, proliferation, and apoptosis in human colorectal cancer xenografts. These imaging approaches may prove useful for serial, noninvasive monitoring of the biological effects of EGFR inhibition in preclinical studies. It is anticipated that these assays can be adapted for clinical use.

Purpose: Apoptosis, or programmed cell death, can be leveraged as a surrogate measure of response to therapeutic interventions in medicine. Cysteine aspartic acid–specific proteases, or caspases, are essential determinants of apoptosis signaling cascades and represent promising targets for molecular imaging. Here, we report development and in vivo validation of [18F]4-fluorobenzylcarbonyl–Val–Ala–Asp(OMe)–fluoromethylketone ([18F]FB-VAD-FMK), a novel peptide-based molecular probe suitable for quantification of caspase activity in vivo using positron emission tomography (PET).Experimental Design: Supported by molecular modeling studies and subsequent in vitro assays suggesting probe feasibility, the labeled pan-caspase inhibitory peptide, [18F]FB-VAD-FMK, was produced in high radiochemical yield and purity using a simple two-step, radiofluorination. The biodistribution of [18F]FB-VAD-FMK in normal tissue and its efficacy to predict response to molecularly targeted therapy in tumors was evaluated using microPET imaging of mouse models of human colorectal cancer.Results: Accumulation of [18F]FB-VAD-FMK was found to agree with elevated caspase-3 activity in response to Aurora B kinase inhibition as well as a multidrug regimen that combined an inhibitor of mutant BRAF and a dual PI3K/mTOR inhibitor in V600EBRAF colon cancer. In the latter setting, [18F]FB-VAD-FMK PET was also elevated in the tumors of cohorts that exhibited reduction in size.Conclusions: These studies illuminate [18F]FB-VAD-FMK as a promising PET imaging probe to detect apoptosis in tumors and as a novel, potentially translatable biomarker for predicting response to personalized medicine. Clin Cancer Res; 20(8); 2126–35. ©2014 AACR.

Purpose: To evaluate 2-deoxy-2-[18F]fluoro-d-glucose positron emission tomography imaging (18FDG-PET) as a predictive, noninvasive, pharmacodynamic (PD) biomarker of response following administration of a small-molecule insulin-like growth factor-1 receptor and insulin receptor (IGF-1R/IR) inhibitor, OSI-906.Experimental Design:In vitro uptake studies of 3H-2-deoxy glucose following OSI-906 exposure were conducted evaluating correlation of dose with inhibition of IGF-1R/IR as well as markers of downstream pathways and glucose metabolism. Similarly, in vivo PD effects were evaluated in human tumor cell line xenografts propagated in athymic nude mice by 18FDG-PET at 2, 4, and 24 hours following a single treatment of OSI-906 for the correlation of inhibition of receptor targets and downstream markers.Results: Uptake of 3H-2-deoxy glucose and 18FDG was significantly diminished following OSI-906 exposure in sensitive tumor cells and subcutaneous xenografts (NCI-H292) but not in an insensitive model lacking IGF-1R expression (NCI-H441). Diminished PD 18FDG-PET, collected immediately following the initial treatment agreed with inhibition of pIGF-1R/pIR, reduced PI3K (phosphoinositide 3-kinase) and MAPK (mitogen activated protein kinase) pathway activity, and predicted tumor growth arrest as measured by high-resolution ultrasound imaging.Conclusion:18FDG-PET seems to serve as a rapid, noninvasive PD marker of IGF-1R/IR inhibition following a single dose of OSI-906 and should be explored clinically as a predictive clinical biomarker in patients undergoing IGF-1R/IR–directed cancer therapy. Clin Cancer Res; 17(10); 3332–40. ©2011 AACR.

PDF file - 79KB, 19FFB-VAD-FMK and parent peptide enzyme selectivity. Biochemistry, fluorescence measured IC50 values, collected as duplicates, of the parent peptide, VAD-FMK, and 19FFB-VAD-FMK against caspases-3/6/7/8.

PDF file - 165KB, Supplemental Materials and Methods, Figure Legends.

Purpose:Pancreatic cancer is among the most aggressive malignancies and is rarely discovered early. However, pancreatic “incidentalomas,” particularly cysts, are frequently identified in asymptomatic patients through anatomic imaging for unrelated causes. Accurate determination of the malignant potential of cystic lesions could lead to life-saving surgery or spare patients with indolent disease undue risk. Current risk assessment of pancreatic cysts requires invasive sampling, with attendant morbidity and sampling errors. Here, we sought to identify imaging biomarkers of high-risk pancreatic cancer precursor lesions.Experimental Design:Translocator protein (TSPO) expression, which is associated with cholesterol metabolism, was evaluated in premalignant and pancreatic cancer lesions from human and genetically engineered mouse (GEM) tissues. In vivo imaging was performed with [18F]V-1008, a TSPO-targeted PET agent, in two GEM models. For image-guided surgery (IGS), V-1520, a TSPO ligand for near-IR optical imaging based upon the V-1008 pharmacophore, was developed and evaluated.Results:TSPO was highly expressed in human and murine pancreatic cancer. Notably, TSPO expression was associated with high-grade, premalignant intraductal papillary mucinous neoplasms (IPMNs) and pancreatic intraepithelial neoplasia (PanIN) lesions. In GEM models, [18F]V-1008 exhibited robust uptake in early pancreatic cancer, detectable by PET. Furthermore, V-1520 localized to premalignant pancreatic lesions and advanced tumors enabling real-time IGS.Conclusions:We anticipate that combined TSPO PET/IGS represents a translational approach for precision pancreatic cancer care through discrimination of high-risk indeterminate lesions and actionable surgery.

PDF file - 137KB, IHC semi-quantification. Semi-quantitative analysis of cleaved caspase-3 histological samples of DLD-1 and SW620 xenograft tumors treated with vehicle or AZD-1152 (A). Evaluation of multiple low field (2.5x) micrographs revealed a statistical significant difference between vehicle- and drug-treated SW620 (p < 0.0001) tumors but not for analogously treated DLD-1 tumors (p = 0.524). Similar analysis of cleaved caspase-3 histological samples of COLO-205 and LIM-2405 treatment cohorts revealed a statistical significant difference between vehicle-treated and combination-treated COLO-205 (p = 0.025) tumors but not for analogously treated LIM-2405 tumors (p = 0.325) (B).

PDF file - 93KB, Scheme 2. 18FSFB (9) (A) and 18FFB-VAD-FMK (11) (B) synthetic schemes. Compound (9) radiosynthesis was performed systematically using an automated radiochemistry module.

PDF file - 43KB, Docking scores are reported as ranked by the Crash (steric repulsion) score from the protein flexibility (PF-score) scoring function of the Tripos SYBYL-X v2.0 software suite that also features (among other scoring parameters) comparison with SurflexDock Total_Score (statistical estimate of binding affinity, -log Kd), Polar (measure of polar contacts), Strain (measure of internal ligand energetic strain) and Similarity (index of shape-based morphological similarity to reference covalent inhibitor compound) term score parameters. Proposed N-terminal modifications to the VAD-FMK peptide scaffold all scored comparably using these criteria indicating minimal predicted perturbation to interactions with the caspase-3 protein target.

Purpose: A significant fraction of HER2-overexpressing breast cancers exhibit resistance to the HER2 antibody trastuzumab. Hyperactivity of the phosphatidylinositol 3-kinase (PI3K)/AKT pathway confers trastuzumab resistance, and mammalian target of rapamycin (mTOR) is a major downstream effector of PI3K/AKT. Therefore, we examined whether mTOR inhibitors synergize with trastuzumab.Experimental Design: Immunocompetent mice bearing HER2+ mammary tumors were treated with trastuzumab, the mTOR inhibitor rapamycin, or the combination. Mice were imaged for tumor cell death using an optical Annexin-V probe and with [18F]FDG positron emission tomography. The signaling and growth effects of the mTOR inhibitor RAD001 on HER2+ cells treated with trastuzumab or lapatinib were evaluated.Results: Treatment of mice with trastuzumab plus rapamycin was more effective than single-agent treatments, inducing complete regression of 26 of 26 tumors. The combination induced tumor cell death (Annexin-V binding) and inhibited FDG uptake. Rapamycin inhibited mTOR and tumor cell proliferation as determined by phosphorylated S6 and Ki-67 immunohistochemistry, respectively. In culture, the combination of RAD001 plus trastuzumab inhibited cell growth more effectively than either drug alone. Trastuzumab partially decreased PI3K but not mTOR activity. Knockdown of TSC2 resulted in HER2-independent activation of mTOR and dampened the response to trastuzumab and lapatinib. Treatment with the HER2 inhibitor lapatinib decreased phosphorylated S6 and growth in TSC2-expressing cells but not in TSC2-knockdown cells.Conclusions: Inhibition of PI3K and mTOR are required for the growth-inhibitory effect of HER2 antagonists. These findings collectively support the combined use of trastuzumab and mTOR inhibitors for the treatment of HER2+ breast cancer. (Clin Cancer Res 2009;15(23):7266–76)

Supplementary Figures S1-S4 from Molecular Imaging of Therapeutic Response to Epidermal Growth Factor Receptor Blockade in Colorectal Cancer

Supplementary Information including Supplementary Tables S1, S2 and S3 and Legends for Supplementary Movies S1 and S2

Real-time image-guided surgery of Ptf1a-Cre;LSL-KrasG12D/+;Smad4fl/fl (KSC) mouse using V-1520

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Supplementary Methods, Figure Legends 1-13, Table 1 from A Kinome-Wide Screen Identifies the Insulin/IGF-I Receptor Pathway as a Mechanism of Escape from Hormone Dependence in Breast Cancer

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Estrogen receptor α (ER)–positive breast cancers adapt to hormone deprivation and become resistant to antiestrogens. In this study, we sought to identify kinases essential for growth of ER+ breast cancer cells resistant to long-term estrogen deprivation (LTED). A kinome-wide siRNA screen showed that the insulin receptor (InsR) is required for growth of MCF-7/LTED cells. Knockdown of InsR and/or insulin-like growth factor-I receptor (IGF-IR) inhibited growth of 3 of 4 LTED cell lines. Inhibition of InsR and IGF-IR with the dual tyrosine kinase inhibitor OSI-906 prevented the emergence of hormone-independent cells and tumors in vivo, inhibited parental and LTED cell growth and PI3K/AKT signaling, and suppressed growth of established MCF-7 xenografts in ovariectomized mice, whereas treatment with the neutralizing IGF-IR monoclonal antibody MAB391 was ineffective. Combined treatment with OSI-906 and the ER downregulator fulvestrant more effectively suppressed hormone-independent tumor growth than either drug alone. Finally, an insulin/IGF-I gene expression signature predicted recurrence-free survival in patients with ER+ breast cancer treated with the antiestrogen tamoxifen. We conclude that therapeutic targeting of both InsR and IGF-IR should be more effective than targeting IGF-IR alone in abrogating resistance to endocrine therapy in breast cancer. Cancer Res; 71(21); 6773–84. ©2011 AACR.

PDF file - 198K, Breast cancer cell lines and receptor expression (S1); Correlations among optical metabolic measurements (S2).

Abnormal cellular metabolism is a hallmark of cancer, yet there is an absence of quantitative methods to dynamically image this powerful cellular function. Optical metabolic imaging (OMI) is a noninvasive, high-resolution, quantitative tool for monitoring cellular metabolism. OMI probes the fluorescence intensities and lifetimes of the autofluorescent metabolic coenzymes reduced NADH and flavin adenine dinucleotide. We confirm that OMI correlates with cellular glycolytic levels across a panel of human breast cell lines using standard assays of cellular rates of glucose uptake and lactate secretion (P < 0.05, r = 0.89). In addition, OMI resolves differences in the basal metabolic activity of untransformed from malignant breast cells (P < 0.05) and between breast cancer subtypes (P < 0.05), defined by estrogen receptor and/or HER2 expression or absence. In vivo OMI is sensitive to metabolic changes induced by inhibition of HER2 with the antibody trastuzumab (herceptin) in HER2-overexpressing human breast cancer xenografts in mice. This response was confirmed with tumor growth curves and stains for Ki67 and cleaved caspase-3. OMI resolved trastuzumab-induced changes in cellular metabolism in vivo as early as 48 hours posttreatment (P < 0.05), whereas fluorodeoxyglucose-positron emission tomography did not resolve any changes with trastuzumab up to 12 days posttreatment (P > 0.05). In addition, OMI resolved cellular subpopulations of differing response in vivo that are critical for investigating drug resistance mechanisms. Importantly, OMI endpoints remained unchanged with trastuzumab treatment in trastuzumab-resistant xenografts (P > 0.05). OMI has significant implications for rapid cellular-level assessment of metabolic response to molecular expression and drug action, which would greatly accelerate drug development studies. Cancer Res; 73(20); 6164–74. ©2013 AACR.

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PDF file - 783K, Cyanide addition to MCF10A cells changes NADH and FAD fluorescence lifetime components (S1); The optical redox ratio increases with ER and HER2 expression (S2); NADH and FAD fluorescence lifetime components for breast cancer cells (S3); Optical metabolic endpoints allow graphical separation of breast cancer subtypes (S4); Effects of trastuzumab on the NADH and FAD fluorescence lifetime components of responsive and resistant cells (S5); Distribution density modeling of inter-cellular populations with trastuzumab treatment in vitro (S6); NADH and FAD fluorescence lifetime components from in vivo BT474 mouse xenografts with trastuzumab treatment (S7); NADH and FAD fluorescence lifetime components from in vivo HR6 mouse xenografts with trastuzumab treatment (S8); NADH and FAD fluorescence lifetime components from in vivo MDA-MB-361 mouse xenografts with trastuzumab treatment (S9).

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Cancer cells characteristically consume glucose through Warburg metabolism1, a process that forms the basis of tumour imaging by positron emission tomography (PET). Tumour-infiltrating immune cells also rely on glucose, and impaired immune cell metabolism in the tumour microenvironment (TME) contributes to immune evasion by tumour cells2–4. However, whether the metabolism of immune cells is dysregulated in the TME by cell-intrinsic programs or by competition with cancer cells for limited nutrients remains unclear. Here we used PET tracers to measure the access to and uptake of glucose and glutamine by specific cell subsets in the TME. Notably, myeloid cells had the greatest capacity to take up intratumoral glucose, followed by T cells and cancer cells, across a range of cancer models. By contrast, cancer cells showed the highest uptake of glutamine. This distinct nutrient partitioning was programmed in a cell-intrinsic manner through mTORC1 signalling and the expression of genes related to the metabolism of glucose and glutamine. Inhibiting glutamine uptake enhanced glucose uptake across tumour-resident cell types, showing that glutamine metabolism suppresses glucose uptake without glucose being a limiting factor in the TME. Thus, cell-intrinsic programs drive the preferential acquisition of glucose and glutamine by immune and cancer cells, respectively. Cell-selective partitioning of these nutrients could be exploited to develop therapies and imaging strategies to enhance or monitor the metabolic programs and activities of specific cell populations in the TME. Positron emission tomography measurements of nutrient uptake in cells of the tumour microenvironment reveal cell-intrinsic partitioning in which glucose uptake is higher in myeloid cells, whereas glutamine is preferentially acquired by cancer cells.

Exosomes are small, 40–130 nm secreted extracellular vesicles that recently have become the subject of intense focus as agents of intercellular communication, disease biomarkers and potential vehicles for drug delivery. It is currently unknown whether a cell produces different populations of exosomes with distinct cargo and separable functions. To address this question, high-resolution methods are needed. Using a commercial flow cytometer and directly labelled fluorescent antibodies, we show the feasibility of using fluorescence-activated vesicle sorting ( FAVS) to analyse and sort individual exosomes isolated by sequential ultracentrifugation from the conditioned medium of DiFi cells, a human colorectal cancer cell line. EGFR and the exosomal marker, CD9, were detected on individual DiFi exosomes by FAVS; moreover, both markers were identified by high-resolution stochastic optical reconstruction microscopy on individual, approximately 100 nm vesicles from flow-sorted EGFR/CD9 double-positive exosomes. We present evidence that the activation state of EGFR can be assessed in DiFi-derived exosomes using a monoclonal antibody (mAb) that recognizes “conformationally active” EGFR (mAb 806). Using human antigen-specific antibodies, FAVS was able to detect human EGFR and CD9 on exosomes isolated from the plasma of athymic nude mice bearing DiFi tumour xenografts. Multicolour FAVS was used to simultaneously identify CD9, EGFR and an EGFR ligand, amphiregulin (AREG), on human plasma-derived exosomes from 3 normal individuals. These studies demonstrate the feasibility of FAVS to both analyse and sort individual exosomes based on specific cell-surface markers. We propose that FAVS may be a useful tool to monitor EGFR and AREG in circulating exosomes from individuals with colorectal cancer and possibly other solid tumours. Keywords: exosomes; extracellular vesicles; flow cytometry; EGFR; amphiregulin; xenograft models; colorectal cancer; cetuximab; mAb 806 (Published: 24 June 2016) Citation: Journal of Extracellular Vesicles 2016, 5: 29254 - http://dx.doi.org/10.3402/jev.v5.29254

Current PET radiotracer production models result in facility and operational costs that scale prohibitively with the number of tracers synthesized, particularly those made as a single dose-on-demand. Short of a paradigm shift in the technology and economics of radiotracer production, the impact of PET on precision medicine will be limited. Inexpensive, microfluidic radiochemistry platforms have the potential to significantly reduce costs associated with dose-on-demand production and expand the breadth of PET tracers accessible for molecular imaging. To produce a miniaturized dose-on-demand device for [68Ga]Ga-PSMA-11 production, a microfluidic chip was assembled in polydimethylsiloxane (PDMS), combining all components of tracer production in an integrated, compact, and easily utilized platform. On-chip radionuclide concentration, as well as radionuclide and precursor starting material mixing and reaction were incorporated. The radionuclide was sourced from a standard, commercially available 68Ge/68Ga generator. Optimal reaction conditions were determined, which included precursor concentration (5 μg/mL), temperature (95 °C), and reaction time (1 min). The total trapping efficiency of combined on-chip SCX and SAX columns was greater than 70 % and could be accomplished in ~ 12 min. Under optimized conditions, [68Ga]Ga-PSMA-11 could be reliably synthesized starting from a complete generator elution (1100 MBq [29.7 mCi]) in ~ 12 min, with an average radiochemical yield of 70 %, radiochemical purity > 99 %, and specific activity > 740 MBq/μg (20 mCi/μg). Quality control testing demonstrated that tracer produced using this platform met or exceeded all typical FDA requirements for human use. A simple, low-cost, dose-on-demand radiosynthesis strategy, such as the chip presented here, represents an opportunity to reduce the financial barriers associated with PET imaging. While this study focused on a device for [68Ga]Ga-PSMA-11, the technology is also applicable to a wide range of other tracers where low-cost, automated, dose-on-demand production is highly desirable.

The current utilization of positron emission tomography (PET) imaging is limited due to the high costs associated with production facility start-up and operations; subsequently, there has been a movement towards microfluidic synthesis of radiolabeled imaging pharmaceuticals (tracers). In this review, we summarize the current status of microfluidic radiosynthesis units for producing fluorine-18 labeled PET imaging tracers, including a discussion of the relative strengths and weaknesses of such devices. In addition, we provide a brief overview of the radiotracers that have been produced using microfluidic devices to date. Finally, we discuss the prospects for the future of this field, including the potential of newly envisioned devices developed that may allow operators to easily synthesize specialized tracers for individual patient doses.