Preclinical assessment of Alzheimer's disease using novel designed ^99mTc‐labeled RGD‐based pro‐apoptotic cyclic peptide as a promising SPECT agent

Abstract

The increased prevalence of neurodegenerative disorders such as Alzheimer's disease, Parkinson's disease, and glioma results in increased risks to abolish the healthy life. This is because of inducing alternation causes into the intracellular compartment as well as noncell compartments. Therefore, herein, a simple and facile radiosynthesis strategy was employed for the development of a novel 99mTc (t1/2 = 6 h, Er = 140 keV) labeled diethylenetriamine pentaacetic acid (DTPA) conjugated cyclic heptapeptide (99mTc‐DTPA‐c[RGDKLAK]; cPT). The radiotracer was characterized using various analytical techniques to evaluate the identity, radiolabeling, biocompatibility, in vitro stability, and amenability for preclinical use. The biological specificity and efficacy of the radiolabeled cyclic peptide analog were confirmed by in vivo biodistribution and single‐photon emission computed tomography (SPECT) studies in Alzheimer disease (AD)‐induced animal models. The results demonstrated that 99mTc(CO)3‐DTPA‐cPT showed high radioactivity concentration at the site of αvβ3, α5β1‐integrins expressing brain regions while decreasing radioactivity levels in kidneys and increasing urinary bladder over the period of 3 h suggested the renal clearance route of the radiotracer. The diagnostic outcomes obtained from planar SPECT study are consistent with that of the biodistribution study with a target‐to‐nontarget ratio (T/NT = 28.47 ± 2.53) at 3‐h postinjection. The results are surprisingly supportive to our hypothesis that the small cyclic peptide‐based radiotracer is well‐oriented towards targeted drug delivery and envisaged that our proposed radiotracer 99mTc(CO)3‐DTPA‐cPT has potential diagnostic applications for Alzheimer's disease as a novel SPECT agent.

Identification of a pH-Responsive Peptide–Paclitaxel Conjugate as a Novel Drug with Improved Therapeutic Potential

“…Hence, the tumor inhibitory abilities of PDC were significantly improved compared with PTX alone, which highlighted the considerable antitumor efficacy with an increased order of anticancer activity as PDC > PTX > CPP. Further, it can be seen from Figure 7a−c that c[RGDKLAK] being a potent cell-targeting 27 and cell-penetrating peptide 49 itself shows limited anticancer activity, which is comparatively smaller than that of free PTX and our designed PDC. This small anticancer effect of this dual-targeting peptide sequence is because of the proapoptotic KLA tri motif, which specifically targets the cancer cell mitochondria and disrupts its membrane potential to induce apoptosis via the intrinsic pathway as reported previously.…”

“…For in vivo tumor-model studies, technetium-99mlabeled diethylenetriamine pentaacetic acid ( 99m Tc-DTPA) was conjugated with the ε-amino group of a terminal lysine residue of the peptide by a simple condensation reaction as a protocol reported in the literature. 49 Briefly, cDTPA (0.061 g, 0.17 mmol, 1.13 equiv) in 150 μL of DMSO and HATU (0.064 g, 0.17 mmol, 1.13 equiv) in 150 μL of DMF were mixed and stirred for 20 min at room temperature. The white crystals of PDC (0.255 g, 0.15 mmol, 1.0 equiv) were dissolved in Milli-Q water (600 μL), added dropwise to the cDTPA mixture, and stirred for another 30 min at room temperature.…”

“…To evaluate the binding affinity of PDC in comparison with CPP and PTX alone, we performed the western blot analysis by following the protocol reported previously. 49 Briefly, the glioblastoma tumor tissue samples were denatured for 30 min at 37 °C temperature, followed by fractionation in SDS-PAGs (8% in PBS). Later, the denatured samples were mixed with a poly(vinylidene difluoride) membrane and blocked with a TBST solution in 5% BSA for 1 h at 4 °C.…”

Peptide-Drug Conjugates: Design, Chemistry, and Drug Delivery System as a Novel Cancer Theranostic

“…Furthermore, the same group synthesized a novel radiotracer ( 99m Tc-DTPA-c­[RGDKLAK]) and studied its efficacy to diagnose Alzheimer’s disease preclinically. The results showed that radiotracer was highly accumulated in α v β 3 -integrin expressing brain region with decreased uptake in the liver and kidneys having target-to-nontarget ratio 28.47 ± 2.53 at 3 h postinjection . Moreover, Rizvi et al for the first time reported the synthesis of synergistic cell-penetrating peptide (cRGD-KLAK) conjugated with paclitaxel via ester linkage with succinic acid as cleavable linker.…”

“…The results showed that radiotracer was highly accumulated in α v β 3integrin expressing brain region with decreased uptake in the liver and kidneys having target-to-nontarget ratio 28.47 ± 2.53 at 3 h postinjection. 152 Moreover, Rizvi et al for the first time reported the synthesis of synergistic cell-penetrating peptide (cRGD-KLAK) conjugated with paclitaxel via ester linkage with succinic acid as cleavable linker. The proposed PDC was observed to possess improved solubility in water, enhanced stability in blood circulatory system (≥90%), as well as promising tumor-growth inhibitory effect (2.82−3.24-folds) in glioblastoma models.…”