The role of clinical imaging in oncology drug development: progress and new challenges

In 2008, the role of clinical imaging in oncology drug development was reviewed. The review outlined where imaging was being applied and considered the diverse demands across the phases of drug development. A limited set of imaging techniques was being used, largely based on structural measures of disease evaluated using established response criteria such as response evaluation criteria in solid tumours. Beyond structure, functional tissue imaging such as dynamic contrast-enhanced MRI and metabolic measures using [18F]flourodeoxyglucose positron emission tomography were being increasingly incorporated. Specific challenges related to the implementation of imaging were outlined including standardisation of scanning across study centres and consistency of analysis and reporting. More than a decade on the needs of modern drug development are reviewed, how imaging has evolved to support new drug development demands, the potential to translate state-of-the-art methods into routine tools and what is needed to enable the effective use of this broadening clinical trial toolset. In this review, we challenge the clinical and scientific imaging community to help refine existing clinical trial methods and innovate to deliver the next generation of techniques. Strong industry-academic partnerships and pre-competitive opportunities to co-ordinate efforts will ensure imaging technologies maintain a crucial role delivering innovative medicines to treat cancer.

Brain exposure of osimertinib in patients with epidermal growth factor receptor mutation non-small cell lung cancer and brain metastases: A positron emission tomography and magnetic resonance imaging study

Brain metastases (BMs) are associated with poor prognosis in epidermal growth factor receptor mutation-positive (EGFRm) non-small cell lung cancer (NSCLC). Osimertinib is a third-generation, irreversible, EGFR-tyrosine kinase inhibitor that potently and selectively inhibits EGFR-sensitizing and T790M resistance mutations with efficacy in EGFRm NSCLC including central nervous system (CNS) metastases. The open-label phase I positron emission tomography (PET) and magnetic resonance imaging (MRI) study (ODIN-BM) assessed [¹¹ C]osimertinib brain exposure and distribution in patients with EGFRm NSCLC and BMs. Three dynamic 90-min [¹¹ C]osimertinib PET examinations were acquired together with metabolite-corrected arterial plasma input functions at: baseline, after first oral osimertinib 80 mg dose, and after greater than or equal to 21 days of osimertinib 80 mg q.d. treatment. Contrast-enhanced MRI was performed at screening and after 25-35 days of osimertinib 80 mg q.d.; treatment effect was assessed per CNS Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 and per volumetric changes in total BM using a novel analysis approach. Four patients (aged 51-77 years) completed the study. At baseline, ~1.5% injected radioactivity reached the brain (ID_max[brain] ) 22 min (median, T_max[brain] ) after injection. Total volume of distribution (V_T ) in whole brain was numerically higher compared with the BM regions. After a single oral osimertinib 80 mg dose, there was no consistent decrease in V_T in whole brain or BMs. After greater than or equal to 21 days' daily treatment, V_T in whole brain and BMs were numerically higher versus baseline. MRI revealed 56%-95% reduction in total BMs volume after 25-35 days of osimertinib 80 mg q.d. treatment. The [¹¹ C]osimertinib crossed the blood-brain and brain-tumor barriers and had a high, homogeneous brain distribution in patients with EGFRm NSCLC and BMs.

Abstract 6217: TP53 loss with whole genome doubling mediates heterogeneous intra-patient therapy response in EGFR-driven lung adenocarcinoma: A TRACERx study

Introduction: Mutations in the epidermal growth factor receptor (EGFR) are often found in never-smokers who develop lung adenocarcinoma (LUAD) and resistance to receptor-targeted tyrosine kinase inhibitors (TKIs) generally occurs within five years of treatment. Mixed responses, where individual tumor lesions within the same patient respond differently to treatment, contribute to early treatment failure and indicate the involvement of multiple genomic alterations. TP53 loss of function has been associated with both tolerance to chromosomal instability (CIN) and with shortened progression free survival in EGFR-driven tumors. The aim of this study was to investigate the hypothesis that CIN, together with loss of p53 function, may lead to diverse genotypes that underlie the mixed responses observed in EGFR-driven LUAD.

Experimental Procedures: We used genetically engineered mouse models (GEMMs), driven by EGFR with or without concomitant Trp53 loss and human isogenic cell lines to investigate cellular evolution and the effect of whole genome doubling on targeted therapy responses and mechanisms of resistance. Next generation sequencing and shallow whole genome single cell analyses, together with longitudinal imaging analysis from the Aura clinical trials (AURA2, AURA3 and the AURA extension cohort, Identifiers: NCT02094261, NCT02151981 and NCT01802632) was used to investigate the effect of p53 loss on tumor evolution.

Results: EGFR mutant tumors with clonal Trp53 loss or TP53 pathway disruption displayed increased Weighted Genome Integrity Index (wGII) and higher cell to cell variation in both the mouse and TRACERx data sets. We found that TP53 loss of function increased the incidence of mixed responses and resistance to targeted therapy in both mouse and human tumors leading to early treatment failure and reduced survival. Whole-exome sequencing (median depth of 92x, range: 58-169x) of nine erlotinib-resistant EGFR mouse tumors identified four EGFR bypassing mutations (oncogenic KRAS mutations; Q61H, Q61R, and two G12D mutations) and one likely driver mutation in FGFR2 (C286R). We could only identify one known resistance associated mutation, EGFRT790M, in EGFR mutant tumors with concomitant loss of Trp53. In depth analysis revealed no major copy number differences in treatment naÏve vs resistant EGFR mutant tumors. In contrast, 70% of all tumors with concomitant Trp53 loss had amplified a region of mouse chromosome 7, harboring MET and BRAF. Investigating an isogenic EGFR/TP53 mutant cell model system revealed whole genome doubling as advantageous in overcoming the selection pressure induced by targeted therapy.

Conclusion: We find that loss of TP53 in the context of mutated EGFR leads to an altered and plastic genomic landscape, with multiple copy number changes, which in turn facilitates therapy resistance.

Citation Format: Sebastijan Hobor, Maise Al Bakir, Marcin Skrzypski, Alexander M. Frankell, Bjorn Bakker, Thomas B. Watkins, Aleksandra Markovets, Jonathan R. Dry, Andrew P. Brown, Jasper van der Aart, Dahmane Oukrif, Marco Novelli, Matthew J. Renshaw, William Hill, Hilda van den Bos, Diana C. Spierings, Juliann Chmielecki, Carl Barrett, Kevin Litchfield, Elza de Bruin, Floris Foijer, Karen H. Vousden, TRACERx consortium, Robert E. Hynds, Crispin T. Hiley, Nnennaya Kanu, Simone Zaccaria, Eva C. Gronroos, Charles Swanton. TP53 loss with whole genome doubling mediates heterogeneous intra-patient therapy response in EGFR-driven lung adenocarcinoma: A TRACERx study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 6217.

Safety, pharmacokinetics, and pharmacodynamics of Gln-1062, a prodrug of galantamine

Introduction

Gln-1062 (MEMOGAIN) is an intranasally administered lipophilic prodrug of galantamine. Based on high brain-to-blood concentrations observed in pre-clinical studies, Gln-1062 is expected to have superior cognitive efficacy compared to oral galantamine.

Methods

Forty-eight healthy elderly subjects were randomized 12:4 to Gln-1062 (5.5, 11, or 22 mg, b.i.d., for 7 days) or placebo. Safety, tolerability, pharmacokinetics, and pharmacodynamics were assessed repeatedly. Pharmacokinetics were compared with 16 mg oral galantamine.

Results

Gln-1062 up to 22 mg, b.i.d., was well tolerated. Gln-1062 plasma concentrations increased immediately following dosing (median T_max of 0.5 hour [range 0.5-1.0]). C_max and AUC_0-last increased in a dose-linear manner over all three dose levels. Gln-1062 was rapidly cleaved into galantamine. Gln-1062 significantly improved adaptive tracking (sustained attention) with 1.95% (95% confidence interval [CI] 0.630-3.279, P = 0.0055) compared to placebo after correction for individual baseline performance.

Discussion

Gln-1062 was considered to be safe and caused fewer gastrointestinal side effects than oral galantamine. Gln-1062 behaved pharmacokinetically as expected and improved performance on cognitive tests.

Characterisation of the pharmacodynamic effects of the P2X7 receptor antagonist JNJ-54175446 using an oral dexamphetamine challenge model in healthy males in a randomised, double-blind, placebo-controlled, multiple ascending dose trial

BACKGROUND

This is the first report of the pharmacodynamic (PD) effects of the selective, potent and brain-penetrant P2X7 receptor (P2X7R) antagonist JNJ-54175446. Activation of the P2X7R, an adenosine triphosphate-gated ion channel, leads to the production of pro-inflammatory cytokines, which have been linked to neuroinflammation and play a role in the pathogenesis of mood disorders. Previous clinical studies with JNJ-54175446 demonstrated peripheral target engagement of JNJ-54175446 by assessing ex vivo lipopolysaccharide (LPS)-stimulated cytokine production. Blood-brain barrier penetration and a clear dose-receptor occupancy relationship was demonstrated using positron emission tomography.

AIMS

The objectives of this double-blind, placebo-controlled, translational study were to assess the safety and tolerability of administering multiple doses of JNJ-54175446 and to explore its PD effects using a dexamphetamine challenge.

METHODS

Subjects (N = 64) were randomised to either JNJ-54175446 (50-450 mg; n = 48) or placebo (n = 16) and underwent a baseline oral 20 mg dexamphetamine challenge followed by 11 consecutive days q.d. dosing with JNJ-54175446/placebo and a randomised crossover dexamphetamine/placebo challenge.

RESULTS

At all doses tested, JNJ-54175446 was well tolerated and suppressed the ex vivo LPS-induced release of cytokines. At doses ⩾100 mg, JNJ-54175446 attenuated dexamphetamine-induced increases in locomotion and enhanced the mood-elevating effects of dexamphetamine, suggesting that a dose that is approximately twice as high is needed to obtain a central PD response compared to the dose needed for maximum peripheral occupancy.

CONCLUSION

Overall, the observed pharmacological profile of JNJ-54175446 in the dexamphetamine challenge paradigm is compatible with a potential mood-modulating effect.

Evaluation of the Novel PET Tracer [11C]HACH242 for Imaging the GluN2B NMDA Receptor in Non-Human Primates

PURPOSE

There are currently no positron emission tomography (PET) radiotracers for the GluN2B (NR2B) binding sites of brain N-methyl-D-aspartate (NMDA) receptors. In rats, the GluN2B antagonist Ro25-6981 reduced the binding of N-((5-(4-fluoro-2-[¹¹C]methoxyphenyl)pyridin-3-yl)methyl)cyclopentanamin ([¹¹C]HACH242). This paper reports the evaluation of [¹¹C]HACH242 PET in non-human primates at baseline and following administration of the GluN2B negative allosteric modulator radiprodil.

PROCEDURES

Eight 90-min dynamic [¹¹C]HACH242 PET scans were acquired in three male anaesthetised rhesus monkeys, including a retest session of subject 1, at baseline and 10 min after intravenous 10 mg/kg radiprodil. Standardised uptake values (SUV) were calculated for 9 brain regions. Arterial blood samples were taken at six timepoints to characterise pharmacokinetics in blood and plasma. Reliable input functions for kinetic modelling could not be generated due to variability in the whole-blood radioactivity measurements.

RESULTS

[¹¹C]HACH242 entered the brain and displayed fairly uniform uptake. The mean (± standard deviation, SD) T_max was 17 ± 7 min in baseline scans and 24 ± 15 min in radiprodil scans. The rate of radioligand metabolism in plasma (primarily to polar metabolites) was high, with mean parent fractions of 26 ± 10 % at 20 min and 8 ± 5 % at 85 min. Radiprodil increased [¹¹C]HACH242 whole-brain SUV in the last PET frame by 25 %, 1 %, 3 and 17 % for subjects 1, 2, 3 and retest of subject 1, respectively. The mean brain to plasma ratio was 5.4 ± 2.6, and increased by 39 to 110 % in the radiprodil condition, partly due to lower parent plasma radioactivity of -11 to -56 %.

CONCLUSIONS

The present results show that [¹¹C]HACH242 has a suitable kinetic profile in the brain and low accumulation of lipophilic radiometabolites. Radiprodil did not consistently change [¹¹C]HACH242 brain uptake. These findings may be explained by variations in cerebral blood flow, a low fraction of specifically bound tracer, or interactions with endogenous NMDA receptor ligands at the binding site. Further experiments of ligand interactions are necessary to facilitate the development of radiotracers for in vivo imaging of the ionotropic NMDA receptor.

Quantification of human brain PDE4 occupancy by GSK356278: A [11C](R)-rolipram PET study

We characterized the relationship between the plasma concentration of the phospodiesterase (PDE)-4 inhibitor GSK356278 and occupancy of the PDE4 enzyme in the brain of healthy volunteers, using the positron emission tomography (PET) tracer [¹¹C](R)-rolipram. To this end, PET scans were acquired in eight male volunteers before and at 3 and 8 h after a single 14 mg oral dose of GSK356278. A metabolite-corrected arterial input function was used in conjunction with the dynamic PET emission data to estimate volumes of distribution (V_T) from a two-tissue compartment model. The administration of GSK356278 reduced [¹¹C](R)-rolipram whole brain V_T by 17% at 3 h post-dose (p = 0.01) and by 4% at 8 h post-dose. The mean plasma C_max was 42.3 ng/ml, leading to a PDE4 occupancy of 48% at T_max. The in vivo affinity of GSK356278 was estimated as EC₅₀ = 46 ± 3.6 ng/ml. We present the first report of a direct estimation of PDE4 blockade in the living human brain. In vivo affinity of GSK356278 for the PDE4, estimated in this early phase study, was combined with GSK356278 safety and tolerability data to decide on a therapeutic dose for future clinical development.

First in human evaluation of [18F]PK-209, a PET ligand for the ion channel binding site of NMDA receptors

Background

Efforts to develop suitable positron emission tomography (PET) tracers for the ion channel site of human N-methyl-d-aspartate (NMDA) receptors have had limited success. [¹⁸F]PK-209 is a GMOM derivative that binds to the intrachannel phencyclidine site with high affinity and selectivity. Primate PET studies have shown that the volume of distribution in the brain was reduced by administration of the NMDA receptor antagonist MK-801, consistent with substantial specific binding. The purpose of the present study was to evaluate [¹⁸F]PK-209 in 10 healthy humans by assessing test–retest reproducibility and binding specificity following intravenous S-ketamine administration (0.5 mg ∙ kg⁻¹). Five healthy subjects underwent a test–retest protocol, and five others a baseline-ketamine protocol. In all cases dynamic, 120-min PET scans were acquired together with metabolite-corrected arterial plasma input functions. Additional input functions were tested based on within-subject and population-average parent fractions.

Results

Best fits of the brain time-activity curves were obtained using an irreversible two-tissue compartment model with additional blood volume parameter. Mean test–retest variability of the net rate of influx K_i varied between 7 and 24% depending on the input function. There were no consistent changes in [¹⁸F]PK-209 PET parameters following ketamine administration, which may be a consequence of the complex endogenous ligand processes that affect channel gating.

Conclusions

The molecular interaction between [¹⁸F]PK-209 and the binding site within the NMDA receptor ion channel is insufficiently reproducible and specific to be a reliable imaging agent for its quantification.

Trial registration

EudraCT 2014-001735-36. Registered 28 April 2014

Human Dosimetry of the N-Methyl-d-Aspartate Receptor Ligand 11C-GMOM

The methylguanidine derivative ¹¹C-GMOM (¹¹C-labeled N-(2-chloro-3-thiomethylphenyl)-N'-(3-methoxyphenyl)-N'-methylguanidine) has been used successfully to quantify N-methyl-d-aspartate (NMDA) receptor binding in humans. The purpose of the present study was to estimate the ¹¹C-GMOM radiation dose in healthy humans. Methods: After ¹¹C-GMOM injection, 3 female and 2 male subjects underwent 10 consecutive whole-body PET scans in approximately 77 min. Seven source organs were defined manually, scaled to a sex-specific reference, and residence times were calculated for input into OLINDA/EXM software. Accepted tissue-weighting factors were used to calculate the effective dose. Results: The mean absorbed radiation doses in source organs ranged from 7.7 μGy·MBq^-1 in the brain to 12.7 μGy·MBq^-1 in the spleen. The effective dose (±SD) was 4.5 ± 0.5 μSv·MBq^-1Conclusion: The effective dose of ¹¹C-GMOM is at the lower end of the range seen for other ¹¹C-labeled ligands, allowing for serial PET scanning in a single subject.

Testing the effects of Δ9-THC and D-cycloserine on extinction of conditioned fear in humans

Preclinical evidence implicates several neurotransmitter systems in the extinction of conditioned fear. These results are of great interest, because the reduction of acquired fear associations is critical in therapies for anxiety disorders. We tested whether findings with respect to the N-methyl-D-aspartate (NMDA) and cannabinoid receptor (CB) systems in animals carry over to healthy human subjects. To that end, we administered selected doses of D-cycloserine (partial NMDA receptor agonist, 250 mg), delta-9-tetrahydrocannabinol (THC, CB(1) receptor agonist, 10 mg), or placebo prior to the extinction session of a 3-day conditioning protocol. D-cycloserine did not affect within-session extinction, or the retention of extinction in healthy human participants, in contrast with patient data but in line with previous reports in healthy volunteers. During extinction training, Δ9-THC reduced conditioned skin conductance responses, but not fear-potentiated startle. This effect was not retained at the retention test 2 days later, suggesting it was dependent on acute effects of the drug. Our findings implicate that facilitation of the CB(1) or NMDA system with the substances used in this study does not affect conditioned fear extinction lastingly in healthy humans. The apparent discrepancy between these findings and the results from (pre-)clinical trials is discussed in terms of room for improvement in these systems in healthy volunteers, and the lack of specificity of THC as a CB(1) agonist.

Within-subject comparison of [(11)C]-(+)-PHNO and [(11)C]raclopride sensitivity to acute amphetamine challenge in healthy humans

[(11)C]PHNO is a D(2)/D(3) agonist positron emission tomography radiotracer, with higher in vivo affinity for D(3) than for D(2) receptors. As [(11)C]-(+)-PHNO is an agonist, its in vivo binding is expected to be more affected by acute fluctuations in synaptic dopamine than that of antagonist radiotracers such as [(11)C]raclopride. In this study, the authors compared the effects of an oral dose of the dopamine releaser amphetamine (0.3 mg/kg) on in vivo binding of [(11)C]-(+)-PHNO and [(11)C]raclopride in healthy subjects, using a within-subjects, counterbalanced, open-label design. In the dorsal striatum, where the density of D(3) receptors is negligible and both tracers predominantly bind to D(2) receptors, the reduction of [(11)C]-(+)-PHNO binding potential (BP(ND)) was 1.5 times larger than that of [(11)C]raclopride. The gain in sensitivity associated with the agonist [(11)C]-(+)-PHNO implies that ∼65% of D(2) receptors are in the high-affinity state in vivo. In extrastriatal regions, where [(11)C]-(+)-PHNO predominantly binds to D(3) receptors, the amphetamine effect on [(11)C]-(+)-PHNO BP(ND) was even larger, consistent with the higher affinity of dopamine for D(3). This study indicates that [(11)C]-(+)-PHNO is superior to [(11)C]raclopride for studying acute fluctuations in synaptic dopamine in the human striatum. [(11)C]-(+)-PHNO also enables measurement of synaptic dopamine in D(3) regions.