Examination of Diazaspiro Cores as Piperazine Bioisosteres in the Olaparib Framework Shows Reduced DNA Damage and Cytotoxicity

Development of poly­(ADP-ribose) polymerase inhibitors (PARPi’s) continues to be an attractive area of research due to synthetic lethality in DNA repair deficient cancers; however, PARPi’s also have potential as therapeutics to prevent harmful inflammation. We investigated the pharmacological impact of incorporating spirodiamine motifs into the phthalazine architecture of FDA approved PARPi olaparib. Synthesized analogues were screened for PARP-1 affinity, enzyme specificity, catalytic inhibition, DNA damage, and cytotoxicity. This work led to the identification of <b>10e</b> (12.6 ± 1.1 nM), which did not induce DNA damage at similar drug concentrations as olaparib. Interestingly, several worst in class compounds with low PARP-1 affinity, including <b>15b</b> (4397 ± 1.1 nM), induced DNA damage at micromolar concentrations, which can explain the cytotoxicity observed in vitro. This work provides further evidence that high affinity PARPi’s can be developed without DNA damaging properties offering potential new drugs for treating inflammatory related diseases

Brain Imaging of Vesicular Monoamine Transporter Type 2 in Healthy Aging Subjects by ¹⁸F-FP-(+)-DTBZ PET

<div><p></p><p>¹⁸F-FP-(+)-DTBZ is a novel PET radiotracer targeting vesicular monoamine transporter type 2 (VMAT2). The goal was to explore the image features in normal human brains with ¹⁸F-FP-(+)-DTBZ as a reference of molecular landmark for clinical diagnosis in Parkinson's disease (PD) and related disorders.</p><p>Materials and Methods</p><p>A total of 22 healthy subjects (59.3±6.0 years old) including 7 men and 15 women were recruited for MRI and ¹⁸F-FP-(+)-DTBZ PET scans. A total number of 55 brain VOIs were selected for quantitation analysis. The regional specific uptake ratio (SUR) was calculated with occipital as reference from MRI-based spatially normalized ¹⁸F-FP-(+)-DTBZ images. Regional percentage SUR to that of anterior putamen was calculated. Average SUR images were displayed in 2D and 3D space to illustrate the image patterns. The correlation between age and regional VMAT2 uptake was also examined.</p><p>Results</p><p>Visual assessment showed symmetric uptake of ¹⁸F-FP-(+)-DTBZ and obviously highest in striatum, followed by nucleus accumbens, hypothalamus, substantia nigra, and raphe nuclei. Quantification analysis revealed striatal VMAT2 density of anterior putamen>posterior putamen>caudate nucleus. Other subcortical regions were with moderate VMAT2 distribution (6∼51% SUR of anterior putamen), while slightly lower VMAT2 was observed in cerebellum (10.60% SUR) and much lower in neocortex (<5% SUR). No significant correlation of SUR to age was found in subcortical regions.</p><p>Conclusion</p><p>Using ¹⁸F-FP-(+)-DTBZ PET, we showed the 2D and 3D imaging features of the VMAT2 distribution <i>in vivo</i> in healthy aging brains. The <i>in vivo</i> imaging characteristics of VMAT2 is consistent with the expression of VMAT2 in a recent autopsy study. Therefore, 3D visualization and higher image quality of ¹⁸F-FP-(+)-DTBZ PET imaging might potentially be a powerful biomarker in detecting VMAT2 distribution of subcortical regions, and for Parkinson's disease and related neuropsychiatric disorders involving related monoaminergic systems.</p></div

The mean regional SUR value and percentage SUR normalized to that of anterior putamen.

<p>Two dash lines indicated levels of 0% (lower) and 5% (upper) SUR to the anterior putamen, respectively. This clearly illustrated the distribution spectrum of VMAT2 density in the regions of subcortex, cerebellum, cingulate and neocortex. Ct: Caudate, APt: Anterior Putamen, PPt: Posterior Putamen, SN: Substantia nigra, NAc: Nucleus accumbens, Rap: Raphe, Hy: Hypothalamus, Th: Thalamus, Hip: Hippocampus, Am: Amygdala, LC: Locus coeruleus, BS: Brain stem, Vem: Vermis, Cb: cerebellum cortex, SF: Superior Frontal, MiF: Middle Frontal, IF: Inferior Frontal, MeF: Medial Frontal, MA: Motor Area, Olf: Olfactory, SP: Superior Parietal, IP: Inferior Parietal, ST: Superior Temporal, MiT: Middle Temporal, IT: Inferior Temporal, SO: Superior Occipital, MO: Middle Occipital, AC: Anterior Cingulate, MC: Middle Cingulate, PC: Posterior Cingulate.</p

2D and 3D views of the average VMAT2 distribution in normal aging brain using ¹⁸F-FP(+)-DTBZ.

<p>The sagittal view of the VMAT2 distribution in the section of right substantia nigra was displayed in (A) with the three lines indicating three different 2D transverse views as illustrated in (B), (C) and (D) at the level of striatum, NAc, and brain stem, respectively. The 3D visualizations of subcortical VMAT2 binding were illustrated in (E) and also at the views of (F) posterior, (G) right lateral, and (H) anterior with corresponding VOI.</p

Alpha Synuclein Fibrils Contain Multiple Binding Sites for Small Molecules

The fibrillary aggregation of the protein alpha synuclein (Asyn) is a hallmark of Parkinson’s disease, and the identification of small molecule binding sites on fibrils is essential to the development of diagnostic imaging probes. A series of molecular modeling, photoaffinity labeling, mass spectrometry, and radioligand binding studies were conducted on Asyn fibrils. The results of these studies revealed the presence of three different binding sites within fibrillar Asyn capable of binding small molecules with moderate to high affinity. A knowledge of the amino acid residues in these binding sites will be important in the design of high affinity probes capable of imaging fibrillary species of Asyn

Regional Amyloid Deposition in Amnestic Mild Cognitive Impairment and Alzheimer's Disease Evaluated by [¹⁸F]AV-45 Positron Emission Tomography in Chinese Population

<div><p>Background</p><p>To compare the neocortical amyloid loads among cognitively normal (CN), amnestic mild cognitive impairment (aMCI), and Alzheimer's disease (AD) subjects with [¹⁸F]AV-45 positron emission tomography (PET).</p> <p>Materials and Methods</p><p>[¹⁸F]AV-45 PET was performed in 11 CN, 13 aMCI, and 12 AD subjects to compare the cerebral cortex-to-whole cerebellum standard uptake value ratios (SUVRs) of global and individual volumes of interest (VOIs) cerebral cortex. The correlation between global cortical [¹⁸F]AV-45 SUVRs and Mini-Mental State Examination (MMSE) scores was analyzed.</p> <p>Results</p><p>The global cortical [¹⁸F]AV-45 SUVRs were significantly different among the CN (1.08±0.08), aMCI (1.27±0.06), and AD groups (1.34±0.13) (p = 0.0003) with amyloidosis positivity rates of 9%, 62%, and 92% in the three groups respectively. Compared to CN subjects, AD subjects had higher SUVRs in the global cortical, precuneus, frontal, parietal, occipital, temporal, and posterior cingulate areas; while aMCI subjects had higher values in the global cortical, precuneus, frontal, occipital and posterior cingulate areas. There were negative correlations of MMSE scores with SUVRs in the global cortical, precuneus, frontal, parietal, occipital, temporal, posterior cingulate and anterior cingulate areas on a combined subject pool of the three groups after age and education attainment adjustment.</p> <p>Conclusions</p><p>Amyloid deposition occurs relatively early in precuneus, frontal and posterior cingulate in aMCI subjects. Higher [¹⁸F]AV-45 accumulation is present in parietal, occipital and temporal gyri in AD subjects compared to the aMCI group. Significant correlation between MMSE scores and [¹⁸F]AV-45 SUVRs can be observed among CN, aMCI and AD subjects.</p> </div

Statistical parametric mapping analysis: Localization of increased [¹⁸F]AV-45 retention between CN, aMCI and AD subjects.

<p>Comparisons of [¹⁸F]AV-45 SUVRs between cognitively normal (CN) and amnestic mild cognitively impairment (aMCI) subjects (A), and between aMCI and Alzheimer's disease (AD) subjects (B) (Uncorrected for multiple comparisons and the color bar values indicate the value of the T-statistic in each display). Surface rendering was used to illustrate the cortical areas where [¹⁸F]AV-45 SUVRs were increased in aMCI than CN subjects (red) and increased in AD than aMCI subjects (green) (C).</p

Scatter plots showing general and individual region-to-cerebellum ratios between different groups.

<p>Comparisons of [¹⁸F]AV-45 SUVR in the predefined VOIs of the global cortical (A), precuneus (B), frontal (C), parietal (D), occipital (E), temporal (F), posterior cingulate (G) and anterior cingulate (H) areas among the cognitively normal (CN), amnestic mild cognitive impairment (aMCI), and Alzheimer's disease (AD) subjects. (* <i>p</i><0.05, ** <i>p</i><0.005, *** <i>p</i><0.0005, when comparing SUVR among CN, aMCI and AD subjects with the Kruskal–Wallis ANOVA test. † <i>p</i><0.05 versus CN subjects with Dunn's post hoc analysis).</p

Relationship between MMSE scores and global and regional cortical [¹⁸F]AV-45 retention.

<p>Results of the negative regressions between MMSE scores and global and regional cortical [¹⁸F]AV-45 SUVRs among the cognitive normal, amnestic mild cognitive impairment, and Alzheimer's disease subjects with age and years of education as covariates.</p