Bench to Bedside Development of [18F]Fluoromethyl-(1,2-2H4)choline ([18F]D4-FCH).

Malignant transformation is characterised by aberrant phospholipid metabolism of cancers, associated with the upregulation of choline kinase alpha (CHKα). Due to the metabolic instability of choline radiotracers and the increasing use of late-imaging protocols, we developed a more stable choline radiotracer, [18F]fluoromethyl-[1,2-2H4]choline ([18F]D4-FCH). [18F]D4-FCH has improved protection against choline oxidase, the key choline catabolic enzyme, via a 1H/2D isotope effect, together with fluorine substitution. Due to the promising mechanistic and safety profiles of [18F]D4-FCH in vitro and preclinically, the radiotracer has transitioned to clinical development. [18F]D4-FCH is a safe positron emission tomography (PET) tracer, with a favourable radiation dosimetry profile for clinical imaging. [18F]D4-FCH PET/CT in lung and prostate cancers has shown highly heterogeneous intratumoral distribution and large lesion variability. Treatment with abiraterone or enzalutamide in metastatic castrate-resistant prostate cancer patients elicited mixed responses on PET at 12-16 weeks despite predominantly stable radiological appearances. The sum of the weighted tumour-to-background ratios (TBRs-wsum) was associated with the duration of survival.

Cognitive Dysfunction in Patients Treated with Androgen Deprivation Therapy: A Multimodality Functional Imaging Study to Evaluate Neuroinflammation.

Background: Androgen deprivation therapy (ADT) for prostate cancer is implicated as a possible cause of cognitive impairment (CI). CI in dementia and Alzheimer's disease is associated with neuroinflammation. In this study, we investigated a potential role of neuroinflammation in ADT-related CI. Methods: Patients with prostate cancer on ADT for ≥3 months were categorized as having ADT-emergent CI or normal cognition (NC) based on self-report at interview. Neuroinflammation was evaluated using positron emission tomography (PET) with the translocator protein (TSPO) radioligand [11C]-PBR28. [11C]-PBR28 uptake in various brain regions was quantified as standardized uptake value (SUVR, normalized to cerebellum) and related to blood oxygen level-dependent functional magnetic resonance imaging (BOLD-fMRI) choice-reaction time task (CRT) activation maps. Results: Eleven patients underwent PET: four with reported CI (rCI), six with reported NC (rNC), and one status unrecorded. PET did not reveal any between-group differences in SUVR regionally or globally. There was no difference between groups on brain activation to the CRT. Regardless of the reported cognitive status, there was strong correlation between PET-TSPO signal and CRT activation in the hippocampus, amygdala, and medial cortex. Conclusions: We found no difference in neuroinflammation measured by PET-TSPO between patients with rCI and rNC. However, we speculate that the strong correlation between TSPO uptake and BOLD-fMRI activation in brain regions involved in memory and known to have high androgen-receptor expression mediating plasticity (hippocampus and amygdala) might reflect inflammatory effects of ADT with compensatory upregulated/increased synaptic functions. Further studies of this imaging readout are warranted to investigate ADT-related CI.

Feasibility of [18F]fluoropivalate hybrid PET/MRI for imaging lower and higher grade glioma: a prospective first-in-patient pilot study.

PURPOSE: MRI and PET are used in neuro-oncology for the detection and characterisation of lesions for malignancy to target surgical biopsy and to plan surgical resections or stereotactic radiosurgery. The critical role of short-chain fatty acids (SCFAs) in brain tumour biology has come to the forefront. The non-metabolised SCFA radiotracer, [18F]fluoropivalate (FPIA), shows low background signal in most tissues except eliminating organs and has appropriate human dosimetry. Tumour uptake of the radiotracer is, however, unknown. We investigated the uptake characteristics of FPIA in this pilot PET/MRI study. METHODS: Ten adult glioma subjects were identified based on radiological features using standard-of-care MRI prior to any surgical intervention, with subsequent histopathological confirmation of glioma subtype and grade (lower-grade - LGG - and higher-grade - HGG - patients). FPIA was injected as an intravenous bolus injection (range 342-368 MBq), and dynamic PET and MRI data were acquired simultaneously over 66 min. RESULTS: All patients tolerated the PET/MRI protocol. Three patients were reclassified following resection and histology. Tumour maximum standardised uptake value (SUVmax,60) increased in the order LGG (WHO grade 2) < HGG (WHO grade 3) < HGG (WHO grade 4). The net irreversible solute transfer, Ki, and influx rate constant, K1, were significantly higher in HGG (p < 0.05). Of the MRI variables studied, DCE-MRI-derived extravascular-and-extracellular volume fraction (ve) was high in tumours of WHO grade 4 compared with other grades (p < 0.05). SLC25A20 protein expression was higher in HGG compared with LGG. CONCLUSION: Tumoural FPIA PET uptake is higher in HGG compared to LGG. This study supports further investigation of FPIA PET/MRI for brain tumour imaging in a larger patient population. CLINICAL TRIAL REGISTRATION: Clinicaltrials.gov, NCT04097535.

Advanced imaging for quantification of abnormalities in the salivary glands of patients with primary Sjögren's syndrome.

OBJECTIVES: To assess non-invasive imaging for detection and quantification of gland structure, inflammation and function in patients with primary Sjogren's syndrome (pSS) using PET-CT with 11C-Methionine (11C-MET; radiolabelled amino acid), and 18F-fluorodeoxyglucose (18F-FDG; glucose uptake marker), to assess protein synthesis and inflammation, respectively; multiparametric MRI evaluated salivary gland structural and physiological changes. METHODS: In this imaging/clinical/histology comparative study (GSK study 203818; NCT02899377) patients with pSS and age- and sex-matched healthy volunteers underwent MRI of the salivary glands and 11C-MET PET-CT. Patients also underwent 18F-FDG PET-CT and labial salivary gland biopsies. Clinical and biomarker assessments were performed. Primary endpoints were semi-quantitative parameters of 11C-MET and 18F-FDG uptake in submandibular and parotid salivary glands and quantitative MRI measures of structure and inflammation. Clinical and minor salivary gland histological parameter correlations were explored. RESULTS: Twelve patients with pSS and 13 healthy volunteers were included. Lower 11C-MET uptake in parotid, submandibular and lacrimal glands, lower submandibular gland volume, higher MRI fat fraction, and lower pure diffusion in parotid and submandibular glands were observed in patients vs healthy volunteer, consistent with reduced synthetic function. Disease duration correlated positively with fat fraction and negatively with 11C-MET and 18F-FDG uptake, consistent with impaired function, inflammation and fatty replacement over time. Lacrimal gland 11C-MET uptake positively correlated with tear flow in patients, and parotid gland 18F-FDG uptake positively correlated with salivary gland CD20+ B-cell infiltration. CONCLUSION: Molecular imaging and MRI may be useful tools to non-invasively assess loss of glandular function, increased glandular inflammation and fat accumulation in pSS.

Specificity of translocator protein-targeted positron emission tomography in inflammatory joint disease.

OBJECTIVE: Expression of the translocator protein (TSPO) on inflammatory cells has facilitated imaging of synovitis with TSPO-targeted positron emission tomography (PET). We aimed to quantitatively assess the specificity of the second-generation TSPO PET radioligand, [11C]PBR28, and to generate simplified PET protocols in patients with inflammatory joint disease (IJD) in this pilot study. METHODS: Three IJD patients (two rheumatoid arthritis and one osteoarthritis) with knee involvement underwent dynamic [11C]PBR28-PET scans before and after administration of 90 mg of oral emapunil (XBD-173), a TSPO ligand the same day. Radial arterial blood sampling was performed throughout the scan, and total radioactivity and radioactive metabolites were obtained. A semi-automated method was used to generate regions of interest. Standardized uptake value (SUV) and SUV ratio corrected for activity in bone and blood between 50 and 70 min (SUVr50-70 bone, SUVr50-70 blood, respectively) and PET volume of distribution (VT) of the radioligand were calculated. RESULTS: A mean [11C]PBR28 radioactivity of 378 (range 362-389) MBq was administered. A significant decrease (p < 0.05) in VT, SUVr50-70 bone and SUVr50-70 blood observed after oral emapunil confirmed the TSPO specificity of [11C]PBR28. A decrease in SUV was not observed in the post-block scan. CONCLUSION: [11C]PBR28 is TSPO-specific radioligand in IJD patients. Simplified PET protocols with static PET acquisition can be used in the management and evaluation of novel therapeutics that target TSPO overexpressing cells.

A positron emission tomography imaging study to confirm target engagement in the lungs of patients with idiopathic pulmonary fibrosis following a single dose of a novel inhaled αvß6 integrin inhibitor.

BACKGROUND: Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive lung disease with poor prognosis and a significant unmet medical need. This study evaluated the safety, pharmacokinetics (PK) and target engagement in the lungs, of GSK3008348, a novel inhaled alpha-v beta-6 (αvß6) integrin inhibitor, in participants with IPF. METHODS: This was a phase 1b, randomised, double-blind (sponsor unblind) study, conducted in the UK (two clinical sites, one imaging unit) between June 2017 and July 2018 (NCT03069989). Participants with a definite or probable diagnosis of IPF received a single nebulised dose of 1000 mcg GSK3008348 or placebo (ratio 5:2) in two dosing periods. In period 1, safety and PK assessments were performed up to 24 h post-dose; in period 2, after a 7-day to 28-day washout, participants underwent a total of three positron emission tomography (PET) scans: baseline, Day 1 (~ 30 min post-dosing) and Day 2 (~ 24 h post-dosing), using a radiolabelled αvß6-specific ligand, [18F]FB-A20FMDV2. The primary endpoint was whole lung volume of distribution (VT), not corrected for air volume, at ~ 30 min post-dose compared with pre-dose. The study success criterion, determined using Bayesian analysis, was a posterior probability (true % reduction in VT > 0%) of ≥80%. RESULTS: Eight participants with IPF were enrolled and seven completed the study. Adjusted posterior median reduction in uncorrected VT at ~ 30 min after GSK3008348 inhalation was 20% (95% CrI: - 9 to 42%). The posterior probability that the true % reduction in VT > 0% was 93%. GSK3008348 was well tolerated with no reports of serious adverse events or clinically significant abnormalities that were attributable to study treatment. PK was successfully characterised showing rapid absorption followed by a multiphasic elimination. CONCLUSIONS: This study demonstrated engagement of the αvß6 integrin target in the lung following nebulised dosing with GSK3008348 to participants with IPF. To the best of our knowledge this is the first time a target-specific PET radioligand has been used to assess target engagement in the lung, not least for an inhaled drug. TRIAL REGISTRATION: clinicaltrials.gov: NCT03069989; date of registration: 3 March 2017.

Integrin αvß6 Positron Emission Tomography Imaging in Lung Cancer Patients Treated With Pulmonary Radiation Therapy.

PURPOSE: Post radiation therapy (RT) lung fibrosis is a major barrier to improved cure rate in lung cancer. Integrin αvß6 plays a key role in fibrogenesis by activating transforming growth factor-ß. Positron emission tomography (PET) studies with a fluorine-18 radiolabelled αvß6 radioligand, [18F]-FBA-A20FMDV2, were performed to assess uptake, and the relationship to RT dose parameters was explored. METHODS AND MATERIALS: Recently treated non-small cell lung cancer patients (<6 months after RT) had [18F]-FBA-A20FMDV2-PET scans, coregistered with the RT planning computed tomography and segmented to RT doses of >40 Gy (excluding tumor), 25 to 40 Gy, 15 to 25 Gy, 8 to 15 Gy, and <8 Gy. PET uptake (standardized uptake value; SUV) corrected for tissue density between 10 and 60 minutes (SUV10-60) was calculated and compared with RT dose, dose per fraction, and biological effective dose (BED). PET uptake was also evaluated in healthy volunteers. RESULTS: Six non-small cell lung cancer (3 male; 3 female) subjects scanned between 6 and 22 weeks after RT and 6 healthy volunteers (3 males; 3 females) were evaluated. Higher mean PET uptake (SUV10-60) was observed in the irradiated lung compared with the healthy lung (2.97 vs 1.99; P < .05). A significant and positive pharmacodynamic relationship was observed between radioligand uptake (SUV10-60) and dose per RT fraction (r2 = 0.63; P < .001) and with BED for fibrosis (r2 = 0.38; P < .001 for α/ß 3 Gy and r2 = 0.33; P < 0.001 for α/ß 5 Gy). CONCLUSIONS: Higher uptake in the irradiated lung and a pharmacodynamic relationship between αvß6 radioligand uptake versus RT dose per fraction and BED for lung fibrosis is consistent with RT induced activation of αvß6 integrin and supports a role for αvß6 in the induction of lung fibrosis after pulmonary RT. αvß6-PET imaging may potentially aid in the assessment and management of radiation-induced pulmonary fibrosis.

Clinical quantification of the integrin αvß6 by [18F]FB-A20FMDV2 positron emission tomography in healthy and fibrotic human lung (PETAL Study).

PURPOSE: The RGD-integrin, αvß6, plays a role in the pathogenesis of pulmonary fibrosis through activation of transforming growth factor beta (TGFß). This study sought to quantify expression of αvß6 in the lungs of healthy humans and subjects with pulmonary fibrosis using the αvß6-selective [18F]FB-A20FMDV2 PET ligand. METHODS: [18F]FB-A20FMDV2 PET/CT scans were performed in healthy subjects and those with fibrotic lung disease. Standard uptake values (SUV) and volume of distribution (VT) were used to quantify αvß6 expression. In subjects with fibrotic lung disease, qualitative assessment of the relationship between αvß6 expression and the distribution of fibrosis on high resolution computed tomography was conducted. RESULTS: A total of 15 participants (6 healthy, 7 with idiopathic pulmonary fibrosis (IPF) and 2 with connective tissue disease (CTD) associated PF) were enrolled. VT and SUV of [18F]FB-A20FMDV2 were increased in the lungs of subjects with pulmonary fibrosis (PF) compared with healthy subjects. Geometric mean VT (95% CI) was 0.88 (0.60, 1.29) mL/cm3 for healthy subjects, and 1.40 (1.22, 1.61) mL/cm3 for subjects with IPF; and SUV was 0.54 (0.36, 0.81) g/mL for healthy subjects and 1.03 (0.86, 1.22) g/mL for subjects with IPF. The IPF/healthy VT ratio (geometric mean, (95% CI of ratio)) was 1.59 (1.09, 2.32) (probability ratio > 1 = 0.988)) and the SUV ratio was 1.91 (1.27, 2.87) (probability ratio > 1 = 0.996). Increased uptake of [18F]FB-A20FMDV2 in PF was predominantly confined to fibrotic areas. [18F]FB-A20FMDV2 measurements were reproducible at an interval of 2 weeks. [18F]FB-A20FMDV2 was safe and well tolerated. CONCLUSIONS: Lung uptake of [18F]FB-A20FMDV2, a measure of expression of the integrin αvß6, was markedly increased in subjects with PF compared with healthy subjects.

Serotonin release measured in the human brain: a PET study with [11C]CIMBI-36 and d-amphetamine challenge.

Positron emission tomography (PET) enables non-invasive estimation of neurotransmitter fluctuations in the living human brain. While these methods have been applied to dopamine and some other transmitters, estimation of 5-hydroxytryptamine (5-HT; Serotonin) release has proved to be challenging. Here we demonstrate the utility of the novel 5-HT2A receptor agonist radioligand, [11C]CIMBI-36, and a d-amphetamine challenge to evaluate synaptic 5-HT changes in the living human brain. Seventeen healthy male volunteers received [11C]CIMBI-36 PET scans before and 3 h after an oral dose of d-amphetamine (0.5 mg/kg). Dynamic PET data were acquired over 90 min, and the total volume of distribution (VT) in the frontal cortex and the cerebellum derived from a kinetic analysis using MA1. The frontal cortex binding potential (BPNDfrontal) was calculated as (VTfrontal/VTcerebellum) - 1. ∆BPNDfrontal = 1 - (BPNDfrontal post-dose/BPNDfrontal baseline) was used as an index of 5-HT release. Statistical inference was tested by means of a paired Students t-test evaluating a reduction in post-amphetamine [11C]CIMBI-36 BPNDfrontal. Following d-amphetamine administration, [11C]CIMBI-36 BPNDfrontal was reduced by 14 ± 13% (p = 0.002). Similar effects were observed in other cortical regions examined in an exploratory analysis. [11C]CIMBI-36 binding is sensitive to synaptic serotonin release in the human brain, and when combined with a d-amphetamine challenge, the evaluation of the human brain serotonin system in neuropsychiatric disorders, such as major depression and Parkinson's disease is enabled.

A study of the focal adhesion kinase inhibitor GSK2256098 in patients with recurrent glioblastoma with evaluation of tumor penetration of [11C]GSK2256098.

Background: GSK2256098 is a novel oral focal adhesion kinase (FAK) inhibitor. Preclinical studies demonstrate growth inhibition in glioblastoma cell lines. However, rodent studies indicate limited blood-brain barrier (BBB) penetration. In this expansion cohort within a phase I study, the safety, tolerability, pharmacokinetics (PK), and clinical activity of GSK2256098 were evaluated in patients with recurrent glioblastoma. Biodistribution and kinetics of [11C]GSK2256098 were assessed in a substudy using positron-emission tomography (PET). Methods: Patients were treated with GSK2256098 until disease progression or withdrawal due to adverse events (AEs). Serial PK samples were collected on day 1. On a single day between days 9 and 20, patients received a microdose of intravenous [11C]GSK2256098 and were scanned with PET over 90 minutes with parallel PK sample collection. Response was assessed by MRI every 6 weeks. Results: Thirteen patients were treated in 3 dose cohorts (1000 mg, 750 mg, 500 mg; all dosed twice daily). The maximum tolerated dose was 1000 mg twice daily. Dose-limiting toxicities were related to cerebral edema. Treatment-related AEs (>25%) were diarrhea, fatigue, and nausea. Eight patients participated in the PET substudy, with [11C]GSK2256098 VT (volume of distribution) estimates of 0.9 in tumor tissue, 0.5 in surrounding T2 enhancing areas, and 0.4 in normal brain. Best response of stable disease was observed in 3 patients, including 1 patient on treatment for 11.3 months. Conclusions: GSK2256098 was tolerable in patients with relapsed glioblastoma. GSK2256098 crossed the BBB at low levels into normal brain, but at markedly higher levels into tumor, consistent with tumor-associated BBB disruption. Additional clinical trials of GSK2256098 are ongoing.

A Microdose PET Study of the Safety, Immunogenicity, Biodistribution, and Radiation Dosimetry of 18F-FB-A20FMDV2 for Imaging the Integrin αvß6.

The αvß6 integrin is involved in the pathogenesis of cancer and fibrosis. A radiolabeled 20-amino-acid αvß6-binding peptide, derived from the foot and mouth virus (NAVPNLRGDLQVLAQKVART [A20FMDV2]), has been developed to image αvß6 levels preclinically. This study was designed to translate these findings into a clinical PET imaging protocol to measure the expression of αvß6 in humans. Methods: Preclinical toxicology was undertaken, and a direct immunoassay was developed for 4-fluorobenzamide (FB)-A20FMDV2. Four healthy human subjects (2 male and 2 female) received a single microdose of 18F-FB-A20FMDV2 followed by a multibed PET scan of the whole body over more than 3 h. Results: There were no findings in the preclinical toxicology assessments, and no anti-A20FMDV2 antibodies were detected before or after dosing with the PET ligand. The mean and SD of the administered mass of 18F-FB-A20FMDV2 was 8.7 ± 4.4 µg (range, 2.7-13.0 µg). The mean administered activity was 124 ± 20 MBq (range, 98-145 MBq). There were no adverse or clinically detectable pharmacologic effects in any of the subjects. No significant changes in vital signs, laboratory study results, or electrocardiography results were observed. Uptake of radioactivity was observed in the thyroid, salivary glands, liver, stomach wall, spleen, kidneys, ureters, and bladder. Time-activity curves indicated that the highest activity was in the bladder content, followed by the kidneys, small intestine, stomach, liver, spleen, thyroid, and gallbladder. The largest component of the residence times was the voided urine, followed by muscle, bladder, and liver. Using the mean residence time over all subjects as input to OLINDA/EXM, the effective dose was determined to be 0.0217 mSv/MBq; using residence times from single subjects gave an SD of 0.0020 mSv/MBq from the mean. The critical organ was the urinary bladder, with an absorbed dose of 0.18 mGy/MBq. Conclusion:18F-FB-A20FMDV2 successfully passed toxicology criteria, showed no adverse effects in this first-in-humans study, and has an effective dose that enables multiple scans in a single subject.

Translocator Protein as an Imaging Marker of Macrophage and Stromal Activation in Rheumatoid Arthritis Pannus.

PET radioligands targeted to translocator protein (TSPO) offer a highly sensitive and specific means of imaging joint inflammation in rheumatoid arthritis (RA). Through high expression of TSPO on activated macrophages, TSPO PET has been widely reported in several studies of RA as a means of imaging synovial macrophages in vivo. However, this premise does not take into account the ubiquitous expression of TSPO. This study aimed to investigate TSPO expression in major cellular constituents of RA pannus-monocytes, macrophages, fibroblastlike synoviocytes (FLS cells), and CD4-positive (CD4+) T lymphocytes (T cells)-to more accurately interpret TSPO PET signal from RA synovium. Methods: Three RA patients and 3 healthy volunteers underwent PET of both knees using the TSPO radioligand 11C-PBR28. Through 3H-PBR28 autoradiography and immunostaining of synovial tissue in 6 RA patients and 6 healthy volunteers, cellular expression of TSPO in synovial tissue was evaluated. TSPO messenger RNA expression and 3H-PBR28 radioligand binding was assessed using in vitro monocytes, macrophages, FLS cells, and CD4+ T cells. Results:11C-PBR28 PET signal was significantly higher in RA joints than in healthy joints (average SUV, 0.82 ± 0.12 vs. 0.03 ± 0.004; P < 0.01). Further, 3H-PBR28-specific binding in synovial tissue was approximately 10-fold higher in RA patients than in healthy controls. Immunofluorescence revealed TSPO expression on macrophages, FLS cells, and CD4+ T cells. The in vitro study demonstrated the highest TSPO messenger RNA expression and 3H-PBR28-specific binding in activated FLS cells, nonactivated M0 macrophages, and activated M2 reparative macrophages, with the least TSPO expression being in activated and nonactivated CD4+ T cells. Conclusion: To our knowledge, this study was the first evaluation of cellular TSPO expression in synovium, with the highest TSPO expression and PBR28 binding being found on activated synovial FLS cells and M2 macrophages. TSPO-targeted PET may therefore have a unique sensitivity in detecting FLS cells and macrophage-predominant inflammation in RA, with potential utility for assessing treatment response in trials using novel FLS-cell-targeted therapies.

Clinical Translation of a Click-Labeled 18F-Octreotate Radioligand for Imaging Neuroendocrine Tumors.

UNLABELLED: We conducted the first-in-human study of (18)F-fluoroethyl triazole [Tyr(3)] octreotate ((18)F-FET-ßAG-TOCA) in patients with neuroendocrine tumors (NETs) to evaluate biodistribution, dosimetry, and safety. Despite advances in clinical imaging, detection and quantification of NET activity remains a challenge, with no universally accepted imaging standard. METHODS: Nine patients were enrolled. Eight patients had sporadic NETs, and 1 had multiple endocrine neoplasia type 1 syndrome. Patients received 137-163 MBq (mean ± SD, 155.7 ± 8 MBq) of (18)F-FET-ßAG-TOCA. Safety data were obtained during and 24 h after radioligand administration. Patients underwent detailed whole-body PET/CT multibed scanning over 4 h with sampling of venous bloods for radioactivity and radioactive metabolite quantification. Regions of interest were defined to derive individual and mean organ residence times; effective dose was calculated with OLINDA 1.1. RESULTS: All patients tolerated (18)F-FET-ßAG-TOCA with no adverse events. Over 60% parent radioligand was present in plasma at 60 min. High tumor (primary and metastases)-to-background contrast images were observed. Physiologic distribution was seen in the pituitary, salivary glands, thyroid, and spleen, with low background distribution in the liver, an organ in which metastases commonly occur. The organs receiving highest absorbed dose were the gallbladder, spleen, stomach, liver, kidneys, and bladder. The calculated effective dose over all subjects (mean ± SD) was 0.029 ± 0.004 mSv/MBq. CONCLUSION: The favorable safety, imaging, and dosimetric profile makes (18)F-FET-ßAG-TOCA a promising candidate radioligand for staging and management of NETs. Clinical studies in an expanded cohort are ongoing to clinically qualify this agent.

18F-FLT PET imaging of cellular proliferation in pancreatic cancer.

Pancreatic ductal adenocarcinoma is known for its poor prognosis. Since the development of computerized tomography, magnetic resonance and endoscopic ultrasound, novel imaging techniques have struggled to get established in the management of patients diagnosed with pancreatic adenocarcinoma for several reasons. Thus, imaging assessment of pancreatic cancer remains a field with scope for further improvement. In contrast to cross-sectional anatomical imaging methods, molecular imaging modalities such as positron emission tomography (PET) can provide information on tumour function. Particularly, tumour proliferation may be assessed by measurement of intracellular thymidine kinase 1 (TK1) activity level using thymidine analogues radiolabelled with a positron emitter for use with PET. This approach, has been widely explored with [(18)F]-fluoro-3'-deoxy-3'-L-fluorothymidine ((18)F-FLT) PET. This manuscript reviews the rationale and physiology behind (18)F-FLT PET imaging, with special focus on pancreatic cancer and other gastrointestinal malignancies. Potential benefit and challenges of this imaging technique for diagnosis, staging and assessment of treatment response in abdominal malignancies are discussed.

A putative biomarker signature for clinically effective AKT inhibition: correlation of in vitro, in vivo and clinical data identifies the importance of modulation of the mTORC1 pathway.

Our identification of dysregulation of the AKT pathway in ovarian cancer as a platinum resistance specific event led to a comprehensive analysis of in vitro, in vivo and clinical behaviour of the AKT inhibitor GSK2141795. Proteomic biomarker signatures correlating with effects of GSK2141795 were developed using in vitro and in vivo models, well characterised for related molecular, phenotypic and imaging endpoints. Signatures were validated in temporally paired biopsies from patients treated with GSK2141795 in a clinical study. GSK2141795 caused growth-arrest as single agent in vitro, enhanced cisplatin-induced apoptosis in vitro and reduced tumour volume in combination with platinum in vivo. GSK2141795 treatment in vitro and in vivo resulted in ~50-90% decrease in phospho-PRAS40 and 20-80% decrease in fluoro-deoxyglucose (FDG) uptake. Proteomic analysis of GSK2141795 in vitro and in vivo identified a signature of pathway inhibition including changes in AKT and p38 phosphorylation and total Bim, IGF1R, AR and YB1 levels. In patient biopsies, prior to treatment with GSK2141795 in a phase 1 clinical trial, this signature was predictive of post-treatment changes in the response marker CA125. Development of this signature represents an opportunity to demonstrate the clinical importance of AKT inhibition for re-sensitisation of platinum resistant ovarian cancer to platinum.

Dose-Finding Quantitative 18F-FDG PET Imaging Study with the Oral Pan-AKT Inhibitor GSK2141795 in Patients with Gynecologic Malignancies.

UNLABELLED: AKT (a serine/threonine-specific protein kinase) regulates many cellular processes contributing to cytotoxic drug resistance. This study's primary objective examined the relationship between GSK2141795, an oral, pan-AKT inhibitor, and (18)F-FDG PET markers of glucose metabolism in tumor tissue to determine whether (18)F-FDG PET could be used to guide personalized dosing of GSK2141795. Biomarker analysis of biopsies was also undertaken. METHODS: Twelve patients were enrolled in 3 cohorts; all underwent dynamic (18)F-FDG PET scans and serial pharmacokinetic sampling at baseline, week 2, and week 4 with tumor biopsies before treatment and at week 4. Response was evaluated by RECIST v1.1 and Gynecologic Cancer Intergroup criteria. Biopsy samples were analyzed for mutations and protein expression. RESULTS: GSK2141795 did not significantly influence blood glucose levels. No dose-response relationship was observed between GSK2141795 pharmacokinetics and (18)F-FDG PET pharmacodynamic measures; however, an exposure-response relationship was seen between maximum drug concentrations and maximal decrease in (18)F-FDG uptake in the best-responding tumor. This relationship also held for pharmacokinetic parameters of exposure and 1,5-anhydroglucitol (a systemic measure of glucose metabolism). Phospho-AKT upregulation at week 4 in biopsies confirmed AKT inhibition by GSK2141795. Single-agent activity was observed with a clinical benefit rate of 27% (3/11) and 30% (3/10) CA125 response in the study's platinum-resistant ovarian patients. AKT pathway activation by PIK3CA/PIK3R1 mutation did not correlate with clinical activity, whereas RAS/RAF pathway mutations did segregate with resistance to AKT inhibition. CONCLUSION: GSK2141795 demonstrated an exposure-response relationship with decreased (18)F-FDG uptake and is active and tolerable. This study's design integrating (18)F-FDG PET, pharmacokinetics, and biomarker analyses demonstrates the potential for clinical development for personalized treatment.

Lapatinib access into normal brain and brain metastases in patients with Her-2 overexpressing breast cancer.

BACKGROUND: Brain metastases are common in human epidermal growth factor receptor (Her)-2-positive breast cancer. Drug access to brain metastases and normal brain is key to management of cranial disease. In this study, positron emission tomography (PET) scanning after administration of radiolabelled lapatinib was used to obtain direct evidence of cranial drug access. METHODS: Patients with Her-2+ metastatic breast cancer either with at least one 1-cm diameter brain metastasis or without brain metastases underwent dynamic carbon-11 radiolabelled lapatinib ([(11)C]lapatinib)-PET. Less than 20 µg of [(11)C]lapatinib was administered before and after 8 days of oral lapatinib (1,500 mg once daily). Radial arterial blood sampling was performed throughout the 90-min scan. The contribution of blood volume activity to the tissue signal was excluded to calculate lapatinib uptake in normal brain and metastases. Partitioning of radioactivity between plasma and tissue (V T) was calculated and the tissue concentration of lapatinib derived. Plasma lapatinib levels were measured and adverse events noted. RESULTS: Six patients (three with brain metastases) were recruited. About 80% plasma radioactivity corresponded to intact [(11)C]lapatinib after 60 min. PET signal in the brain corresponded to circulating radioactivity levels, with no [(11)C]lapatinib uptake observed in normal brain tissue. In contrast, radioactivity uptake in cranial metastases was significantly higher (p = 0.002) than that could be accounted by circulating radioactivity levels, consistent with [(11)C]lapatinib uptake in brain metastases. There was no difference in lapatinib uptake between the baseline and day 8 scans, suggesting no effect of increased drug access by inhibition of the drug efflux proteins by therapeutic doses of lapatinib. CONCLUSIONS: Increased lapatinib uptake was observed in brain metastases but not in normal brain. TRIAL REGISTRATION: ClinicalTrials.gov: NCT01290354.

Why are we failing to implement imaging studies with radiolabelled new molecular entities in early oncology drug development?

In early drug development advanced imaging techniques can help with progressing new molecular entities (NME) to subsequent phases of drug development and thus reduce attrition. However, several organizational, operational, and regulatory hurdles pose a significant barrier, potentially limiting the impact these techniques can have on modern drug development. Positron emission tomography (PET) of radiolabelled NME is arguably the best example of a complex technique with a potential to deliver unique decision-making data in small cohorts of subjects. However, to realise this potential the impediments to timely inclusion of PET into the drug development process must be overcome. In the present paper, we discuss the value of PET imaging with radiolabelled NME during early anticancer drug development, as exemplified with one such NME. We outline the multiple hurdles and propose options on how to streamline the organizational steps for future studies.

Phase II Trial of Cetuximab and Conformal Radiotherapy Only in Locally Advanced Pancreatic Cancer with Concurrent Tissue Sampling Feasibility Study.

BACKGROUND: Preclinical data have indicated the anti-epidermal growth factor receptor (EGFR) agent cetuximab (Erbitux) as a radiosensitizer in pancreatic cancer, but this has not been specifically addressed in a clinical study. We report the results of an original study initiated in 2007, where cetuximab was tested with radiotherapy (RT) alone in locally advanced pancreatic cancer in a phase II trial (PACER). METHODS: Patients (n = 21) received cetuximab loading dose (400 mg/m(2)) and weekly dose (250 mg/m(2)) during RT (50.4 Gy in 28 fractions). Toxicity and disease response end point data were prospectively assessed. A feasibility study of on-trial patient blood and skin sampling was incorporated. RESULTS: Treatment was well tolerated, and toxicity was low; most patients (71%) experienced acute toxicities of grade 2 or less. Six months posttreatment, stable local disease was achieved in 90% of evaluable patients, but only 33% were free from metastatic progression. Median overall survival was 7.5 months, and actuarial survival was 33% at 1 year and 11% at 3 years, reflecting swift metastatic progression in some patients but good long-term control of localized disease in others. High-grade acneiform rash (P = .0027), posttreatment stable disease (P = .0059), and pretreatment cancer antigen 19.9 (CA19.9) level (P = .0042) associated with extended survival. Patient skin and blood samples yielded sufficient RNA and good quality protein, respectively. CONCLUSIONS: The results indicate that cetuximab inhibits EGFR-mediated radioresistance to achieve excellent local control with minimal toxicity but does not sufficiently control metastatic progression in all patients. Translational studies of patient tissue samples may yield molecular information that may enable individual treatment response prediction.