The Development and Testing of a Patient Decision Aid for Individuals with Homologous Recombinant Proficient Ovarian Cancer Who Are Considering Niraparib Maintenance Therapy.

New treatments for ovarian cancer are available that require trade-offs between progression-free survival and quality of life. The aim of this study was to develop a decision aid for patients with homologous recombinant proficient (HRP) tumors, as the benefit-harm ratio of niraparib needs consideration. This decision aid was created with a systematic and iterative development process based on the Ottawa Decision Support Framework. The decision aid was user-tested for acceptability, usability, and comprehensibility using a survey completed by a sample of patients with ovarian cancer and oncologists. This decision aid follows the International Patient Decision Aids Standards (IPDAS) criteria in its development. User-test respondents (n = 13 patients; 13 physicians) reported that the decision aid used language that was easy to follow (69% patients; 85% physicians), was an appropriate length (69% patients; 62% physicians) and provided the right amount of information (54% patients; 54% physicians). Most respondents (92% patients; 62% physicians) would recommend this decision aid for HRP patients considering niraparib. This is the first decision aid for patients with HRP ovarian cancers who are considering niraparib maintenance therapy. It is available on-line and is being further evaluated in a pragmatic clinical trial in Saskatchewan.

The development of peptide-boron difluoride formazanate conjugates as fluorescence imaging agents.

Two new fluorescence imaging probes have been synthesized by incorporating a versatile alkyne-substituted boron difluoride formazanate precursor with peptides through copper-catalyzed alkyne-azide cycloaddition. The formazanate dye was appended to a C-terminal amino acid of ghrelin for imaging the growth hormone secretagogue receptor (GHSR-1a). To demonstrate versatile bioconjugation chemistry, the formazanate dye was added to the N-terminus of bombesin for targeting the gastrin releasing peptide receptor (GRPR). These are the first examples of using this emerging class of dyes, boron difluoride formazanates, for the labelling of biomolecules.

A study of 99mTc/Re-tricarbonyl complexes of 4-amino-1,8-naphthalimides.

Three 4-amino-1,8-naphthalimide analogues were synthesized, consisting of the tridentate chelators di-2-picolylamine, (pyridin-2-ylmethyl)glycinate, and iminodiacetate conjugated to the naphthalimide scaffold. Coordination with fac-99mTc/Re(CO)3 resulted in metal complexes with overall charges of -1, 0, or +1. Upon coordination of Re(i), the initial naphthalimide-based fluorescence is largely maintained for both negative and neutral complexes compared to their free ligand forms, while an increase in fluorescence quantum yield was observed for the positively charged complex. OVCAR-8 ovarian cancer cells were stained with each of the complexes, demonstrating that the positive complex is more lipophilic and cell membrane permeable than the neutral and negative complexes. Each of the three technetium-99m labelled naphthalimide complexes were successfully produced from fac-[99mTc(CO)3(H2O)3]+ in 15 minutes at 70 °C and isolated in radiochemical yields ranging from 60-95% with radiochemical purities greater than 95%. These fluorescent metal complexes of various charges can be used to tune pharmacokinetic and cellular uptake properties of 99mTc/Re-naphthalimide-bioconjugates, while still maintaining desirable fluorescence properties.

Single Amino Acid Replacement in G-7039 Leads to a 70-fold Increase in Binding toward GHS-R1a.

The growth hormone secretagogue receptor type 1a (GHS-R1a) is a class A rhodopsin-like G protein coupled receptor (GPCR) that is expressed in a variety of human tissues and is differentially expressed in benign and malignant prostate cancer. Previously, the peptidomimetic [1-Nal4 ,Lys5 (4-fluorobenzoyl)]G-7039 was designed as a molecular imaging tool for positron emission tomography (PET). However, this candidate was a poor binder (IC50 =69 nm), required a lengthy four-step radiosynthesis, and had a cLogP above 8. To address these challenges, we now report on changes targeted at the 4th position of G-7039. A 2-fluoropropionic acid (2-FPA) group was added on to Lys5 to determine the potential binding affinity of the [18 F]-2-FP radiolabeled analogue, which could be prepared by simplified radiochemistry. Lead candidate [Tyr4 ,Lys5 (2-fluoropropionyl)]G-7039 exhibited an IC50 of 0.28 nm and low picomolar activity toward GHS-R1a. Molecular docking revealed a molecular basis for this picomolar affinity.

High Affinity Fluorescent Probe for Proteinase-Activated Receptor 2 (PAR2).

PAR2 is a proteolytically activated G protein-coupled receptor (GPCR) that is implicated in various cancers and inflammatory diseases. Ligands with low nanomolar affinity for PAR2 have been developed, but there is a paucity of research on the development of PAR2-targeting imaging probes. Here, we report the development of seven novel PAR2-targeting compounds. Four of these compounds are highly potent and selective PAR2-targeting peptides (EC50 = 10 to 23 nM) that have a primary amine handle available for facile conjugation to various imaging components. We describe a peptide of the sequence Isox-Cha-Chg-ARK(Sulfo-Cy5)-NH2 as the most potent and highest affinity PAR2-selective fluorescent probe reported to date (EC50 = 16 nM, K D = 38 nM). This compound has a greater than 10-fold increase in potency and binding affinity for PAR2 compared to the leading previously reported probe and is conjugated to a red-shifted fluorophore, enabling in vitro and in vivo studies.

A dual modality 99mTc/Re(i)-labelled T140 analogue for imaging of CXCR4 expression.

The C-X-C chemokine receptor 4 (CXCR4) has been shown to be overexpressed in at least 23 types of cancer, including prostate cancer which has been shown to have a significant distinction of expression rates between cancerous compared to healthy or benign tissue. In an attempt to exploit the difference in expression, we have synthesized a derivative of T140, a peptide antagonist for CXCR4, containing a fluorescent 4-amino-1,8-naphthalimide appended with a di-(2-picolyl)amine binding unit to chelate rhenium or technetium-99m for fluorescence or SPECT imaging. The rhenium-coordinated variant was shown to have similar binding affinity for the receptor as T140 and showed specific uptake by fluorescence microscopy in CXCR4 expressing cells. The peptide was radiolabelled with technetium-99m in decay corrected radiochemical yields ranging from 60-85%, radiochemical purities >95%, and molar activities of 36-44 GBq µmol-1. The technetium-99m labelled peptide showed two-fold higher uptake in U87 cells expressing CXCR4 compared to non-transfected cells. Ex vivo biodistribution studies were performed using the technetium-99m labelled peptide in NOD/SCID mice bearing tumors derived from U87 cells with CXCR4. Tumor uptake of 0.51 ± 0.09% ID g-1 was observed two-hours post-injection. Our novel T140 derivative is suitable for imaging of CXCR4 expression by confocal microscopy. Further structural modifications to the peptide or metal complex may result in improved biodistribution for use in SPECT imaging of CXCR4 expressing tumors.

A truncated RHAMM protein for discovering novel therapeutic peptides.

The receptor for hyaluronan mediated motility (RHAMM, gene name HMMR) belongs to a group of proteins that bind to hyaluronan (HA), a high-molecular weight anionic polysaccharide that has pro-angiogenic and inflammatory properties when fragmented. We propose to use a chemically synthesized, truncated version of the protein (706-767), 7 kDa RHAMM, as a target receptor in the screening of novel peptide-based therapeutic agents. Chemical synthesis by Fmoc-based solid-phase peptide synthesis, and optimization using pseudoprolines, results in RHAMM protein of higher purity and yield than synthesis by recombinant protein production. 7 kDa RHAMM was evaluated for its secondary structure, ability to bind the native ligand, HA, and its bioactivity. This 62-amino acid polypeptide replicates the HA binding properties of both native and recombinant RHAMM protein. Furthermore, tubulin-derived HA peptide analogues that bind to recombinant RHAMM and were previously reported to compete with HA for interactions with RHAMM, bind with a similar affinity and specificity to the 7 kDa RHAMM. Therefore, in terms of its key binding properties, the 7 kDa RHAMM mini-protein is a suitable replacement for the full-length recombinant protein.

Introduction of Peripheral Carboxylates to Decrease the Charge on Tm(3+) DOTAM-Alkyl Complexes: Implications for Detection Sensitivity and in Vivo Toxicity of PARACEST MRI Contrast Agents.

A series of structurally modified Tm(3+) DOTAM-alkyl complexes as potential PARACEST MRI contrast agents has been synthesized with the aim to decrease the overall positive charge associated with these molecules and increase their biocompatibility. Two types of structural modification have been performed, an introduction of terminal carboxylate arms to the alkyl side chains and a conjugation of one of the alkyl side chains with aspartic acid. Detailed evaluation of the magnetic resonance imaging chemical exchange contrast associated with the structurally modified contrast agents has been performed. In contrast to the acutely toxic Tm(3+) DOTAM-alkyl complexes, the structurally modified compounds were found to be tolerated well during in vivo MRI studies in mice; however, only the aspartic acid modified chelates produced an amide proton-based PARACEST signal.

Nuclear spin hyperpolarization of the solvent using signal amplification by reversible exchange (SABRE).

Here we report the polarization of the solvent OH protons by SABRE using standard iridium-based catalysts under slightly acidic conditions. Solvent polarization was observed in the presence of a variety of structurally similar N-donor substrates while no solvent enhancement was observed in the absence of substrate or para-hydrogen (p-H2). Solvent polarization was sensitive to the polarizing field and catalyst:substrate ratio in a manner similar to that of substrate protons. SABRE experiments with pyridine-d5 suggest a mechanism where hyperpolarization is transferred from the free substrate to the solvent by chemical exchange while measured hyperpolarization decay times suggest a complimentary mechanism which occurs by direct coordination of the solvent to the catalytic complex. We found the solvent hyperpolarization to decay nearly 3 times more slowly than its characteristic spin-lattice relaxation time suggesting that the hyperpolarized state of the solvent may be sufficiently long lived (∼20s) to hyperpolarize biomolecules having exchangeable protons. This route may offer future opportunities for SABRE to impact metabolic imaging.

Maximizing T2-exchange in Dy(3+)DOTA-(amide)X chelates: fine-tuning the water molecule exchange rate for enhanced T2 contrast in MRI.

PURPOSE: The water molecule exchange rates in a series of DyDOTA-(amide)X chelates were fine-tuned to maximize the effects of T2-exchange line broadening and improve T2 contrast. METHODS: Four DyDOTA-(amide)X chelates having a variable number of glycinate side-arms were prepared and characterized as T2-exchange agents. The nonexchanging DyTETA chelate was also used to measure the bulk water T2 reduction due solely to T2*. The total transverse relaxivity (r2tot) at 22, 37, and 52°C for each chelate was measured in vitro at 9.4 Tesla (400 MHz) by fitting plots of total T2 (-1) versus concentration. The water molecule exchange rates for each complex were measured by fitting (17)O line-width versus temperature data taken at 9.4 Tesla (54.3 MHz). RESULTS: The measured transverse relaxivities due to water molecule exchange (r2ex) and bound water lifetimes (τM) were in excellent agreement with Swift-Connick theory, with DyDOTA-(gly)3 giving the largest r2ex = 11.8 s(-1) mM(-1) at 37°C. CONCLUSION: By fine-tuning the water molecule exchange rate at 37°C, the transverse relaxivity has been increased by 2 to 30 times compared with previously studied Dy(3+)-based chelates. Polymerization or dendrimerization of the optimal chelate could yield a highly sensitive, molecule-sized T2 contrast agent for improved molecular imaging applications.

A DOTAM-based paraCEST agent favoring TSAP geometry for enhanced amide proton chemical shift dispersion and temperature sensitivity.

The Tm(3+) chelate of DOTAM [1,4,7,10-tetrakis(carbamoylmethyl)-1,4,7,10-tetraazacyclododecane] possessing sterically demanding t-butyl amide substitution favors TSAP geometry. This chelate displayed a paraCEST signal associated with the highly shifted amide proton signal at approximately -100 ppm that was beyond the frequency of macromolecule magnetization transfer. This signal also displayed high temperature dependence (0.57 ppm °C(-1)) in the range of 35-42 °C and at neutral pH.

Water-soluble gold nanoparticles (AuNP) functionalized with a gadolinium(iii) chelate via Michael addition for use as a MRI contrast agent.

A contrast agent suitable for magnetic resonance imaging based on small, water soluble gold nanoparticles (AuNP) conjugated to over 50 Gd3+ chelators has been prepared by using an interfacial Michael addition in aqueous media. The resultant chelator-AuNP conjugates have been successfully characterised by 1H NMR spectroscopy, IR spectroscopy, ICP-OES, ζ-potential analysis, TEM and MRI. T1-weighted in vivo images of mouse kidney were obtained using the agent at 9.4 T. A preliminary in vivo experiment produced no ill effects and the clearance profile of the agent suggests it is suitable for animal testing at clinically relevant concentrations.

DOTAM-type ligands possessing arginine pendant groups for use in PARACEST MRI.

A synthetic methodology was developed for the preparation of metal-chelating ligands that possess arginine pendant groups relying on the alkylation of 1,4,7,10-tetraazacyclododecane (cyclen) with arginine-containing electrophiles. Conditions for the selective trialkylation or peralkylation of cyclen are described, the outcome being dependent on the nature of the arginine-derived electrophile and the solvent used for the reaction. Lanthanide metal complexes of the ligands prepared by the described route were evaluated for their suitability as PARACEST contrast agents for use in magnetic resonance imaging. The Dy(3+) and Tm(3+) complexes display CEST effects that are associated with the amide protons proximate to the metal center. These signals exhibit pH dependence in the range of 6.0-8.0 and thus may have the potential for pH measurement in physiological range.

ParaCEST MRI contrast agents capable of derivatization via"click" chemistry.

A comprehensive series of lanthanide chelates has been prepared with a tetrapropargyl DOTAM type ligand. The complexes have been characterized by a combination of (1)H NMR, single-crystal X-ray crystallography, CEST and relaxation studies and have also been evaluated for potential use as paramagnetic chemical exchange saturation transfer (ParaCEST) contrast agents in magnetic resonance imaging (MRI). We demonstrate the functionalization of several chelates by means of alkyne-azide "click" chemistry in which a glucosyl azide is used to produce a tetra-substituted carbohydrate-decorated lanthanide complex. The carbohydrate periphery of the chelates has a potent influence on the CEST properties as described herein.

Contrast agents possessing high temperature sensitivity.

Contrast agents based on lanthanide tetra-propargyl DOTAM complexes suitable for temperature mapping by magnetic resonance spectroscopy (MRS) are reported. Sensitivity values from 1.05 ppm/°C to 1.76 ppm/°C were determined which represents an improvement of 2-3 times over currently available lanthanide temperature-responsive contrast agents.

Synthesis and characterization of new ferrocene peptide conjugates.

Three classes of diamine linked ferrocene (Fc)-conjugates were prepared and their properties were investigates in solution and the solid state: (a) acyclic diamine-linked 1,n'-Fc conjugates, (b) acyclic diamine-linked 1,n'-Fc peptide conjugates, and (c) cyclic 1,n'-Fc-peptide diamine conjugates. In all cases, the synthetic procedure started from 1,1'-ferrocenecarboxylic acid methyl ester or 1,1'-ferrocene dicarboxylic acid or their amino acid conjugates followed by coupling with diaminoalkanes. The resulting conjugates exhibit H-bonding as is evident by temperature and, in some cases, concentration-dependent NMR shifts and in the solid-state structure of one of the conjugates. Our studies show that the structural properties of Fc-diamine-linked systems are different from those of the related cystamine conjugates, presumably due to the enhanced flexibility of the conjugates.