Influences of hydrocarbon linkers on the receptor binding affinities of gonadotropin-releasing hormone peptides

Three new DOTA-conjugated GnRH peptides with various hydrocarbon linkers were synthesized to evaluate the influences of the linkers on their receptor binding affinities. The hydrocarbon linker displayed a profound impact on the receptor binding affinities of DOTA-conjugated GnRH peptides. The Aun linker was better than Gaba, Ahx and Aoc linkers in retaining strong receptor binding affinity of the GnRH peptide. DOTA-Aun-(d-Lys⁶-GnRH) displayed 22.8 nM GnRH receptor binding affinity. ¹¹¹In-DOTA-Aun-(d-Lys⁶-GnRH) exhibited fast tumor uptake and urinary clearance in MDA-MB-231 human breast cancer-xenografted nude mice. The cellular and biological results provided an insight into the design of new GnRH peptides in the future.     

Introduction of d-Phenylalanine enhanced the receptor binding affinities of gonadotropin-releasing hormone peptides

The purpose of this study was to examine whether the introduction of d-Phe could improve the GnRH receptor binding affinities of DOTA-conjugated d-Lys⁶-GnRH peptides. Building upon the construct of DOTA-Ahx-(d-Lys⁶-GnRH1) we previously reported, an aromatic amino acid of d-Phe was inserted either between the DOTA and Ahx or between the Ahx and d-Lys⁶ to generate new DOTA-d-Phe-Ahx-(d-Lys⁶-GnRH) or DOTA-Ahx-d-Phe-(d-Lys⁶-GnRH) peptides. Compared to DOTA-Ahx-(d-Lys⁶-GnRH1) (36.1 nM), the introduction of d-Phe improved the GnRH receptor binding affinities of DOTA-d-Phe-Ahx-(d-Lys⁶-GnRH) (16.3 nM) and DOTA-Ahx-d-Phe-(d-Lys⁶-GnRH) (7.6 nM). The tumor targeting and pharmacokinetic properties of ¹¹¹In-DOTA-Ahx-d-Phe-(d-Lys⁶-GnRH) was determined in MDA-MB-231 human breast cancer-xenografted nude mice. Compared to ¹¹¹In-DOTA-Ahx-(d-Lys⁶-GnRH1), ¹¹¹In-DOTA-Ahx-d-Phe-(d-Lys⁶-GnRH) exhibited comparable tumor uptake with faster renal and liver clearance. The MDA-MB-231 human breast cancer-xenografted tumors were clearly visualized by single photon emission computed tomography (SPECT) using ¹¹¹In-DOTA-Ahx-d-Phe-(d-Lys⁶-GnRH) as an imaging probe, providing a new insight into the design of new GnRH peptides in the future.     

Synthesis and evaluation of novel gonadotropin-releasing hormone receptor-targeting peptides

The purpose of this study was to develop novel radiolabeled gonadotropin-releasing hormone (GnRH) receptor-targeting peptides for breast cancer imaging. Three novel 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA)-conjugated GnRH peptides were designed and synthesized. The radiometal chelator DOTA was conjugated to the epsilon or alpha amino group of D-lysine, or the epsilon amino group of L-lysine via an Ahx {aminohexanoic acid} linker to generate DOTA-Ahx-(D-Lys(6)-GnRH1), DOTA-Ahx-(D-Lys(6)-GnRH2) and DOTA-Ahx-(L-Lys(6)-GnRH3), respectively. The conjugation of the DOTA to the epsilon amino group of D-lysine (rather than alpha amino group of D-lysine nor epsilon amino group of L-lysine) maintained the nanomolar GnRH receptor binding affinity. The IC(50) values of DOTA-Ahx-(D-Lys(6)-GnRH1), DOTA-Ahx-(D-Lys(6)-GnRH2) and DOTA-Ahx-(L-Lys(6)-GnRH3) were 36.1 nM, 10.6 mM and 4.3 mM, respectively. Since only DOTA-Ahx-(D-Lys(6)-GnRH1) displayed nanomolar receptor binding affinity, the specific GnRH receptor binding of (111)In-DOTA-Ahx-(D-Lys(6)-GnRH1) was determined in human GnRH receptor membrane preparations. Furthermore, the biodistribution and tumor imaging properties of (111)In-DOTA-Ahx-(D-Lys(6)-GnRH1) were examined in MDA-MB-231 human breast cancer-xenografted nude mice. (111)In-DOTA-Ahx-(D-Lys(6)-GnRH1) exhibited specific GnRH receptor binding and rapid tumor uptake (1.76 ± 0.58% ID/g at 0.5 h postinjection) coupled with fast whole-body clearance through the urinary system. The MDA-MB-231 human breast cancer-xenografted tumor lesions were clearly visualized by single photon emission computed tomography (SPECT)/CT at 1 h postinjection of (111)In-DOTA-Ahx-(D-Lys(6)-GnRH1). The profound impact of DOTA position on the binding affinity of the GnRH peptide provided a new insight into the design of novel radiolabeled GnRH peptides. The successful imaging of MDA-MB-231 human breast cancer-xenografted tumor lesions using (111)In-DOTA-Ahx-(D-Lys(6)-GnRH1) suggested its potential as a novel imaging probe for human breast cancer imaging.     

A novel indium-111-labeled gonadotropin-releasing hormone peptide for human prostate cancer imaging

The purpose of this study was to evaluate the tumor targeting and imaging properties of a novel (111)In-labeled gonadotropin-releasing hormone (GnRH) peptide {1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA)-Ahx-(D-Lys(6)-GnRH1)} for human prostate cancer. The biodistribution and tumor imaging properties of (111)In-DOTA-Ahx-(D-Lys(6)-GnRH1) were determined in DU145 human prostate cancer-xenografted nude mice. (111)In-DOTA-Ahx-(d-Lys(6)-GnRH1) exhibited rapid tumor uptake (1.27 ± 0.40% ID/g at 0.5h post-injection) coupled with fast whole-body clearance through the urinary system. The DU145 human prostate cancer-xenografted tumor lesions were clearly visualized by single photon emission computed tomography (SPECT)/CT at 0.5h post-injection of (111)In-DOTA-Ahx-(D-Lys(6)-GnRH1). The successful imaging of DU145 human prostate cancer-xenografted tumor lesions using (111)In-DOTA-Ahx-(d-Lys(6)-GnRH1) highlighted its potential as a novel imaging probe for human prostate cancer imaging.     

Synthesis and evaluation of 18F-labeled CJ-042794 for imaging prostanoid EP4 receptor expression in cancer with positron emission tomography

The potent and selective prostanoid EP4 receptor antagonist CJ-042794 was radiolabeled with ¹⁸F, and evaluated for imaging EP4 receptor expression in cancer with positron emission tomography (PET). The fluorination precursor, arylboronic acid pinacol ester 4, was prepared in 4 steps with 42% overall yield. ¹⁸F-CJ-042794 was synthesized via a copper-mediated ¹⁸F-fluorination reaction followed by base hydrolysis, and was obtained in 1.5 ± 1.1% (n = 2) decay-corrected radiochemical yield. PET/CT imaging and biodistribution studies in mice showed that ¹⁸F-CJ-042794 was excreted through both renal and hepatobiliary pathways with significant retention in blood. The EP4-receptor-expressing LNCaP prostate cancer xenografts were clearly visualized in PET images with 1.12 ± 0.08%ID/g (n = 5) uptake value and moderate tumour-to-muscle contrast ratio (2.73 ± 0.22) at 1 h post-injection. However, the tumour uptake was nonspecific as it could not be blocked by co-injection of cold standard, precluding the application of ¹⁸F-CJ-042794 for PET imaging of EP4 receptor expression in cancer.     

Antitumor properties of substituted (αE)-α-(1H-indol-3-ylmethylene)benzeneacetic acids or amides

A novel class of indole derivatives characterized by a (αE)-α-(1H-indol-3-ylmethylene)benzeneacetic acid or amide scaffold was synthesized. These derivatives, assayed for cell-growth inhibition activity against a panel of six different tumor cell lines, showed strong antiproliferative activity and selectivity mainly towards DU145 cell line. In particular, compounds 2d–m and 5 stand out for their cell growth inhibitory activity and, among them, compound 2d emerged for its selectivity towards DU145 with respect to other tested tumor cell lines. DU145 treated with 1 μM of 2d for 72 h showed p21^Cip1 induction and suppression of Akt signaling together with induction of Rb. From a computational point of view, two different approaches were used in order to study topology and electronic properties of the novel compounds and to shed light on their drug-likeness properties. Firstly, topological and electronic features of the compounds endowed with the most relevant biological activity were deepened; in parallel, some ADME properties like solubility and permeability were predicted.     

Ultrasound Elastography of the Prostate Using an Unconstrained Modulus Reconstruction Technique: A Pilot Clinical Study

A novel full-inversion-based technique for quantitative ultrasound elastography was investigated in a pilot clinical study on five patients for non-invasive detection and localization of prostate cancer and quantification of its extent. Conventional-frequency ultrasound images and radiofrequency (RF) data (~5 MHz) were collected during mechanical stimulation of the prostate using a transrectal ultrasound probe. Pre and post-compression RF data were used to construct the strain images. The Young's modulus (YM) images were subsequently reconstructed using the derived strain images and the stress distribution estimated iteratively using finite element (FE) analysis. Tumor regions determined based on the reconstructed YM images were compared to whole-mount histopathology images of radical prostatectomy specimens. Results indicated that tumors were significantly stiffer than the surrounding tissue, demonstrating a relative YM of 2.5 ± 0.8 compared to normal prostate tissue. The YM images had a good agreement with the histopathology images in terms of tumor location within the prostate. On average, 76% ± 28% of tumor regions detected based on the proposed method were inside respective tumor areas identified in the histopathology images. Results of a linear regression analysis demonstrated a good correlation between the disease extents estimated using the reconstructed YM images and those determined from whole-mount histopathology images (r² = 0.71). This pilot study demonstrates that the proposed method has a good potential for detection, localization and quantification of prostate cancer. The method can potentially be used for prostate needle biopsy guidance with the aim of decreasing the number of needle biopsies. The proposed technique utilizes conventional ultrasound imaging system only while no additional hardware attachment is required for mechanical stimulation or data acquisition. Therefore, the technique may be regarded as a non-invasive, low cost and potentially widely-available clinical tool for prostate cancer diagnosis.     

3D-QSAR (CoMFA,CoMSIA), molecular docking and molecular dynamics simulations study of 6-aryl-5-cyano-pyrimidine derivatives to explore the structure requirements of LSD1 inhibitors

Recently, Histone Lysine Specific Demethylase 1 (LSD1) was regarded as a promising anticancer target for the novel drug discovery. And several small molecules as LSD1 inhibitors in different structures have been reported. In this work, we carried out a molecular modeling study on the 6-aryl-5-cyano-pyrimidine fragment LSD1 inhibitors using three-dimensional quantitative structure–activity relationship (3D-QSAR), molecular docking and molecular dynamics simulations. Comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) were used to generate 3D-QSAR models. The results show that the best CoMFA model has q² = 0.802, r²_ncv = 0.979, and the best CoMSIA model has q² = 0.799, r²_ncv = 0.982. The electrostatic, hydrophobic and H-bond donor fields play important roles in the models. Molecular docking studies predict the binding mode and the interactions between the ligand and the receptor protein. Molecular dynamics simulations results reveal that the complex of the ligand and the receptor protein are stable at 300 K. All the results can provide us more useful information for our further drug design.     

Cyclic ferrocenylnaphthalene diimide derivative as a new class of G-quadruplex DNA binding ligand

To identify an effective ligand that binds to a G-quadruplex structure but not a double-stranded DNA (dsDNA), a set of biophysical and biochemical experiments were carried out using newly synthesized cyclic ferrocenylnaphthalene diimide (cFNDI, 1) or the non-cyclic derivative (2) with various structures of G-quadruplex DNAs and dsDNA. Compound 1 bound strongly to G-quadruplexes DNAs (10⁶ M^?1 order) with diminished binding to dsDNA (10⁴ M^?1 order) in 100 mM AcOH-AcOK buffer (pH 5.5) containing 100 mM KCl. Interestingly, 1 showed an approximately 50-fold higher selectivity to mixed hybrid-type telomeric G-quadruplex DNA (K = 3.4 × 10⁶ M^?1 and a 2:1 stoichiometry) than dsDNA (K = 7.5 × 10⁴ M^?1) did. Furthermore, 1 showed higher thermal stability to G-quadruplex DNAs than it did to dsDNA with a preference for c-kit and c-myc G-quadruplex DNAs over telomeric and thrombin binding aptamers. Additionally, 1 exhibited telomerase inhibitory activity with a half-maximal inhibitory concentration (IC₅₀) of 0.4 μM. Compound 2 showed a preference for G-quadruplex; however, the binding affinity magnitude and preference were improved in 1 because the former had a cyclic structure.     

Y-shaped bis-arylethenesulfonic acid esters: Potential potent and membrane permeable protein tyrosine phosphatase 1B inhibitors

Known PTP1B inhibitors with bis-anionic moieties exhibit potent inhibitory activity, good selectivity, however, they are incapable of penetrating cellular membranes. Based upon our finding of a new pharmacophoric group in inhibition of PTP1B and the structural characteristics of the binding pocket of PTP1B, a series of bis-arylethenesulfonic acid ester derivatives were designed and synthesized. These novel molecules, particularly Y-shaped bis-arylethenesulfonic acid ester derivatives, exhibited high PTP1B inhibitory activity, moderate selectivity, and great potential in penetrating cellular membranes (compound 7p, CLog P = 9.73, P_app = 9.6 × 10^-6 cm/s; IC₅₀ = 140, 1290 and 920 nM on PTP1B, TCPTP and SHP2, respectively). Docking simulations suggested that these Y-shaped inhibitors might interact with multiple secondary binding sites in addition to the catalytic site of PTP1B.     

Original endomorphin-1 analogues exhibit good analgesic effects with minimal implications for human sperm motility

To search a novel analgesic characterizes the effects on human sperm motility as minimal as possible. A new class of endomorphin-1 (EM-1) analogues was synthesized by combining successful chemical modifications including N-terminal guanidino modification, Phe⁴ was chlorinated, replaced of l-Pro²-Trp³ by d-Ala²-Gly³ or d-Pro²-Gly³ at position 2 and 3. Their bioactivities were measured by radioligand binding assay, metabolic stability, antinociception activity and sperm motility effects. In radioligand binding assays, analogue GAGP shown a μ-opioid receptor affinity about 17.7-fold higher and a 57.3-fold higher δ-opioid receptor affinity than EM-1. In the metabolic stability assays, GAGP had the longest half-lives and 16.6-fold higher than EM-1. In the tail-flick test in mice, GAGP showed the best analgesia. In sperm motility assays, the group of GAGP (10^?5, 10^?7 mol/L) decreased of the percentage of a + b grade, and no significant when compared with initial value. In GAGP (10^?6 mol/L) group, sperm motility was progressively increased, although it was not statistically significant. But at the groups of morphine (10^?7 mol/L) and GAGD (10^?7 mol/L), these caused significant reduction between 0 and 90 min. We found that analogues GAGP, activating μ-opioid receptor and partial δ-opioid receptor, exhibit good analgesic effects with minimal implications for human sperm motility. It might be important in potential application as drug candidates of analgesic without implications for human sperm motility.     

Radiosynthesis and evaluation of new PET ligands for peripheral cannabinoid receptor type 1 imaging

Cannabinoid receptor type 1 (CB1) is mainly expressed in the brain, as well as being expressed in functional relevant concentrations in various peripheral tissues. 1-(4-Chlorophenyl)-3-(3-(6-(pyrrolidin-1-yl)pyridin-2-yl)phenyl)urea (PSNCBAM-1, 1) was developed as a potent allosteric antagonist for CB1 and its oral administration led to reductions in the appetite and body weight of rats. Several analogs of 1 (compounds 2 and 3) were recently identified through a series of structure-activity relationship studies. Herein, we report the synthesis of radiolabeled analogs of these compounds using [¹¹C]COCl₂ and an evaluation of their potential as PET ligands for CB1 imaging using in vitro and in vivo techniques. [¹¹C]2 and [¹¹C]3 were successfully synthesized in two steps using [¹¹C]COCl₂. The radiochemical yields of [¹¹C]2 and [¹¹C]3 were 17 ± 8% and 20 ± 9% (decay-corrected to the end of bombardment, based on [¹¹C]CO₂). The specific activities of [¹¹C]2 and [¹¹C]3 were 42 ± 36 and 37 ± 13 GBq/μmol, respectively. The results of an in vitro binding assay using brown adipose tissue (BAT) homogenate showed that the binding affinity of 2 for CB1 (K_D = 15.3 µM) was much higher than that of 3 (K_D = 26.0 µM). PET studies with [¹¹C]2 showed a high uptake of radioactivity in BAT, which decreased in animals pretreated with AM281 (a selective antagonist for CB1). In conclusion, [¹¹C]2 may be a useful PET ligand for imaging peripheral CB1 in BAT.     

DNA methylation profiles in African American prostate cancer patients in relation to disease progression

This study examined whether differential DNA methylation is associated with clinical features of more aggressive disease at diagnosis and prostate cancer recurrence in African American men, who are more likely to die from prostate cancer than other populations. Tumor tissues from 76 African Americans diagnosed with prostate cancer who had radical prostatectomy as their primary treatment were profiled for epigenome-wide DNA methylation levels. Long-term follow-up identified 19 patients with prostate cancer recurrence. Twenty-three CpGs were differentially methylated (FDR q ≤ 0.25, mean methylation difference ≥ 0.10) in patients with vs. without recurrence, including CpGs in GCK, CDKL2, PRDM13, and ZFR2. Methylation differences were also observed between men with metastatic-lethal prostate cancer vs. no recurrence (five CpGs), regional vs. local pathological stage (two CpGs), and higher vs. lower tumor aggressiveness (one CpG). These results indicate that differentially methylated CpG sites identified in tumor tissues of African American men may contribute to prostate cancer aggressiveness.     

In silico selection and cell-based characterization of selective and bioactive compounds for androgen-dependent prostate cancer cell

Prostate cancer is one of the most prevalent types of cancer in male population. It is a hormone driven disease, especially in its initial phase. Hence, androgen deprivation therapy (ADT) is the major chemotherapeutic effort and novel AR inhibitors with improved pharmacological profiles are needed. In this report, a novel bioactive compound was selected and investigated using in silico and cell-based assays. Neq0502 compound was selective for the testosterone stimulated AR-dependent prostate cancer cell (LNCaP, GI₅₀ = 22.4 μM) when compared with unstimulated LNCaP or AR-insensitive (DU145 and PC-3) cell lines. Cell cycle arrest study provided the same profile for Neq0502 and the reference drug enzalutamide. Moreover, this compound is not cytotoxic for fibroblast Balb/C 3T3 clone A31 cells up to 250 μM, with a good selectivity ratio (SI > 11), which could be used in compound optimization effort to a novel therapeutic alternative.     

[Lys(DOTA)4]BVD15, a novel and potent neuropeptide Y analog designed for Y1 receptor-targeted breast tumor imaging

We substituted a truncated neuropeptide Y (NPY) analog, [Pro³⁰, Tyr³², Leu³⁴]NPY(28-36)NH₂ also called BVD15, at various positions with DOTA (1,4,7,10-tetraazacyclododecane-1,4,7-10-tetraacetic acid) and evaluated the effect of the coupling position with the binding affinity for NPY Y₁ receptors (NPY1R). Our data suggest that [Lys(DOTA)⁴]BVD15 (K_i = 63 ± 25 nM vs. K_i = 39 ± 34 nM for BVD15) is a potent NPY analog suitable for radiolabeling with metallo positron emitters for PET imaging of breast cancer.     

Design and synthesis of potent tyr(OMe)5-gonadotropin-releasing hormone (GnRH) analogues with modifications at positions 6, 9 and 10

We have recently reported the synthesis and the conformational properties of some Gonadotropin-releasing hormone (GnRH) analogues in which the tyrosine residue at position 5 is substituted with tyrosine-O-methyl (Keramida et al., Let. Pept. Sci., 3 (1996) 257/Matsoukas et al., Eur. J. Med. Chem., 32 (1997) 927). The analogue [Tyr-(OMe)⁵]-GnRH was found to exert a lower degree of desensitization than the native GnRH peptides in terms of pituitary gonadotropin (GTH) release in goldfish. Compared to GnRH, however, [Tyr-(OMe)⁵]-GnRH exerted a lower GTH-release potency in cultured goldfish pituitary fragments, and was bound with a lower binding affinity to the rat pituitary GnRH receptors. In order to increase the potency of [Tyr-(OMe)⁵]-GnRH, we have synthesized a group of GnRH peptides containing Tyr-(OMe)⁵ in combination with other substitutions at positions 6, 9 and 10 and we have estimated their binding affinity for the rat pituitary receptors and gonadotropin (GTH) release potency in the goldfish pituitary. A selected number of these analogues was also tested for their ability to induce ovulation in seabass. The important structural modifications that increased the binding and gonadotropic activity of [Tyr(OMe)⁵]-GnRH in vitro and in vivo were found to include the replacement of the proline at position 9 with azetidine, glycine amide terminus with an alkyl amide group and Gly⁶ residue with hydrophilic D-amino acids such as D-Arg⁶. Overall, the findings provide SAR information on a group of novel GnRH peptides that can be also used to induce ovulation in teleosts.     

Radiolabeling and initial biological evaluation of [18F]KBM-1 for imaging RAR-α receptors in neuroblastoma

Retinoic acid receptor alpha (RAR-α) plays a significant role in a number of diseases, including neuroblastoma. Children diagnosed with high-risk neuroblastoma are treated 13-cis-retinoic acid, which reduces risk of cancer recurrence. Neuroblastoma cell death is mediated via RAR-α, and expression of RAR-α is upregulated after treatment. A molecular imaging probe that binds RAR-α will help clinicians to diagnose and stratify risk for patients with neuroblastoma, who could benefit from retinoid-based therapy. In this study, we report the radiolabeling, and initial in vivo evaluation of [¹⁸F]KBM-1, a novel RAR-α agonist. The radiochemical synthesis of [¹⁸F]KBM-1 was carried out through KHF₂ assisted substitution of [¹⁸F]^? from aryl-substituted pinacolatoesters-based retinoid precursor. In vitro cell uptake assay in human neuroblastoma cell line showed that the uptake of [¹⁸F]KBM-1 was significantly inhibited by all three blocking agents (KBM-1, ATRA, BD4) at all the selected incubation times. Standard biodistribution in mice bearing neuroblastoma tumors demonstrated increased tumor uptake from 5 min to 60 min post radiotracer injection and the uptake ratios for target to non-target (tumor: muscle) increased 2.2-fold to 3.7-fold from 30 min to 60 min post injection. Tumor uptake in subset of 30 min blocking group was 1.7-fold lower than unblocked. These results demonstrate the potential utility of [¹⁸F]KBM-1 as a RAR-α imaging agent.     

Diversity-oriented sustainable synthesis of antimicrobial spiropyrrolidine/thiapyrrolizidine oxindole derivatives: New ligands for a metallo-β-lactamase from Klebsiella pneumonia

A simple, environmentally benign and highly proficient microwave assisted one-pot approach for the synthesis of antimicrobial spiropyrrolidine/thiapyrrolizidine oxindole derivatives is reported assembling two pharmacophoric moieties (1,3-indanedione and pyrrolidine/thiapyrrolizidine) in a single molecular framework via three-component 1,3-dipolar cycloaddition reaction of substituted isatin, sarcosine/1,3-thiazoles-4-carboxylic acid and Knoevenagel adduct (2-Cyano-3-phenyl-acrylic acid ethyl ester or 2-Benzylidene-malononitrile) in 2,2,2-trifluoroethanol as a reusable green solvent. Good functional group tolerance and broad scope of usable substrates are other prominent features of the present methodology with high degree of chemo-, regio- and stereoselectivity. The stereochemistry of synthesized compounds was confirmed by single crystal X-ray analysis. All the synthetic compounds were examined for their antimicrobial potential. The synthesized compounds having pyrrolothiazole moiety showed excellent activity against K. pneumoniae as compared to others and even more inhibitory activity than the mentioned drugs, i.e. compounds 6a (MIC = 0.09 μg/mL), 6b (MIC = 0.045 μg/mL), 6c (MIC = 0.005 μg/mL), 6d (MIC = 0.19 μg/mL). Additionally, compound 6c has shown better binding affinity against New Delhi Metallo-beta-Lactamase-1 (NDM-1) protein in computational docking studies.     

Bifunctional bisphosphonate derivatives and platinum complexes with high affinity for bone hydroxyapatite

A series of ethylenediamine/1,3-propanediamine derivatives containing bifunctional bisphosphonate substituents and their corresponding dichloroplatinum(II) complexes have been synthesized and characterized by elemental analysis, ¹H NMR, ¹³C NMR, ³¹P NMR, and HRMS spectra. Based on WST-8 assay with CCK-8, in general, the newly synthesized dichloroplatinum complexes 1–6 showed higher in vitro antitumor activity than platinum-free compounds L1–L6 against three tumor cell lines (especially osteosarcoma MG-63). According to hydroxyapatite binding experiment, complexes 2, 3, and 6 showed much higher affinity (K′ = 3.7, 4.0, and 3.0, respectively) for bone hydroxyapatite than cisplatin (K′ < 0.1), comparable to zoledronate (K′ = 2.8). It can be found that representative complex 2 with high cytotoxicity and in vitro antiproliferative activity against osteosarcoma cell line, as well as promising hydroxyapatite binding ability has been screened as a potential bone-targeting antitumor agent for subsequent in vivo study. In addition, flow cytometry experiment was applied to investigate the mode of action of representative complex 2.     

Design and synthesis of a fluorinated quinazoline-based type-II Trk inhibitor as a scaffold for PET radiotracer development

NTRK1/2/3 fusions have recently been characterized as low incidence oncogenic alterations across various tumor histologies. Tyrosine kinase inhibitors (TKIs) of the tropomyosin receptor kinase family TrkA/B/C (encoded by NTRK1/2/3) are showing promises in the clinic for the treatment of cancer patients whose diseases harbor NTRK tumor drivers. We describe herein the development of [¹⁸F]QMICF ([¹⁸F]-(R)-9), a quinazoline-based type-II pan-Trk radiotracer with nanomolar potencies for TrkA/B/C (IC₅₀ = 85–650 nM) and relevant TrkA fusions including TrkA-TPM3 (IC₅₀ = 162 nM). Starting from a racemic FLT3 (fms like tyrosine kinase 3) inhibitor lead with off-target TrkA activity ((±)-6), we developed and synthesized the fluorinated derivative (R)-9 in three steps and 40% overall chemical yield. Compound (R)-9 displays a favorable selectivity profile on a diverse set of kinases including FLT3 (>37-fold selectivity for TrkB/C). The mesylate precursor 16 required for the radiosynthesis of [¹⁸F]QMICF was obtained in six steps and 36% overall yield. The results presented herein support the further exploration of [¹⁸F]QMICF for imaging of Trk fusions in vivo.