Design, synthesis, and structure-activity relationship study of novel plinabulin derivatives as anti-tumor agents based on the co-crystal structure.

Plinabulin, a 2, 5-diketopiperazine-type tubulin inhibitor derived from marine natural products, is currently undergoing Phase III clinical trials for the treatment of non-small cell lung cancer (NSCLC) and chemotherapy-induced neutropenia (CIN). To obtain novel 2, 5-diketopiperazine derivatives with higher biological activity, we designed and synthesized two series of 37 plinabulin derivatives at the C-ring, based on the co-crystal structure of compound 1 and tubulin. Their structures were characterized using NMR and HRMS. All compounds were screened in vitro using the lung cancer cell line NCI-H460 using the MTT method, and the compounds with better activity were further screened in BxPC-3 and HT-29 cells. The compounds 16c (IC50 = 2.0, NCI-H460; IC50 = 1.2 nM, BxPC-3; IC50 = 1.97 nM, HT-29) and 26r (IC50 = 0.96, NCI-H460; IC50 = 0.66 nM, BxPC-3; IC50 = 0.61 nM, HT-29) had the best activity. The cytotoxic activity of compound 26r against various tumor cell lines occurred at less than 1 nM.

Norcantharidin-Encapsulated C60-Modified Nanomicelles: A Potential Approach to Mitigate Cytotoxicity in Renal Cells and Simultaneously Enhance Anti-Tumor Activity in Hepatocellular Carcinoma Cells.

OBJECTIVE: The objective of this study was to examine the preparation process of DSPE-PEG-C60/NCTD micelles and assess the impact of fullerenol (C60)-modified micelles on the nephrotoxicity and antitumor activity of NCTD. METHOD: The micelles containing NCTD were prepared using the ultrasonic method and subsequently optimized and characterized. The cytotoxicity of micelles loaded with NCTD was assessed using the CCK-8 method on human hepatoma cell lines HepG2 and BEL-7402, as well as normal cell lines HK-2 and L02. Acridine orange/ethidium bromide (AO/EB) double staining and flow cytometry were employed to assess the impact of NCTD-loaded micelles on the apoptosis of the HK-2 cells and the HepG2 cells. Additionally, JC-1 fluorescence was utilized to quantify the alterations in mitochondrial membrane potential. The generation of reactive oxygen species (ROS) following micelle treatment was determined through 2',7'-dichlorofluorescein diacetate (DCFDA) staining. RESULTS: The particle size distribution of the DSPE-PEG-C60/NCTD micelles was determined to be 91.57 nm (PDI = 0.231). The zeta potential of the micelles was found to be -13.8 mV. The encapsulation efficiency was measured to be 91.9%. The in vitro release behavior of the micelles followed the Higuchi equation. Cellular experiments demonstrated a notable decrease in the toxicity of the C60-modified micelles against the HK-2 cells, accompanied by an augmented inhibitory effect on cancer cells. Compared to the free NCTD group, the DSPE-PEG-C60 micelles exhibited a decreased apoptosis rate (12%) for the HK-2 cell line, lower than the apoptosis rate observed in the NCTD group (36%) at an NCTD concentration of 75 µM. The rate of apoptosis in the HepG2 cells exhibited a significant increase (49%), surpassing the apoptosis rate observed in the NCTD group (24%) at a concentration of 150 µM NCTD. The HK-2 cells exhibited a reduction in intracellular ROS and an increase in mitochondrial membrane potential (ΔψM) upon exposure to C60-modified micelles compared to the NCTD group. CONCLUSIONS: The DSPE-PEG-C60/NCTD micelles, as prepared in this study, demonstrated the ability to decrease cytotoxicity and ROS levels in normal renal cells (HK-2) in vitro. Additionally, these micelles showed an enhanced antitumor activity against human hepatocellular carcinoma cells (HepG2, BEL-7402).

Design and Synthesis of Novel Phenylahistin Derivatives Based on Co-Crystal Structures as Potent Microtubule Inhibitors for Anti-Cancer Therapy.

Phenylahistin is a naturally occurring marine product with a diketopiperazine structure that can bind to the colchicine site of microtubulin as a possible anticancer agent. To develop more potent microtubule inhibitors, novel phenylahistin derivatives were designed and synthesized based on the co-crystal complexes of phenylahistin derivatives and microtubulin. We established a focused library of imidazole-type molecules for the introduction of different groups to the C-ring and A-ring of phenylahistin. Structure-activity relationship studies indicated that appropriate hydrocarbon substituents and unsaturated alkenyl substituents at the 1-position of the imidazole group are important for improving the activity of such compounds. In addition, this study found that propylamine groups could maintain the activity of these compounds, as exemplified by compound 16d (IC50 = 5.38 nM, NCI-H460). Compound 15p (IC50 = 1.03 nM, NCI-H460) with an allyl group exhibited potent cytotoxic activity at the nanomolar level against human lung cancer cell lines. Immunofluorescence assay indicated that compound 15p could efficiently inhibited microtubule polymerization and induced a high expression of caspase-3. 15p also displayed good pharmacokinetic characteristics in vitro. Additionally, the growth of H22 transplanted tumors was significantly inhibited in BALB/c mice when 15p alone was administered at 4 mg/kg, and the tumor inhibition rate was as much as 65%. Importantly, the continuous administration of 15p resulted in a lower toxicity than that of docetaxel (10 mg/kg) and cyclophosphamide (20 mg/kg). Overall, the novel allyl-imidazole-diketopiperazine-type derivatives could be considered safe and effective potential agents for cancer treatment.

Preparation and Evaluation of the Cytoprotective Activity of Micelles with DSPE-PEG-C60 as a Carrier Against Doxorubicin-Induced Cytotoxicity.

To deliver doxorubicin (DOX) with enhanced efficacy and safety in vivo, fullerenol-modified micelles were prepared with the amphiphilic polymer DSPE-PEG-C60 as a carrier, which was synthesized by linking C60(OH)22 with DSPE-PEG-NH2. Studies of its particle size, PDI, zeta potential, and encapsulation efficiency were performed. DOX was successfully loaded into the micelles, exhibiting a suitable particle size [97 nm, 211 nm, 260 nm, vector: DOX = 5:1, 10:1; 15:1 (W/W)], a negative zeta potential of around -30 mv, and an acceptable encapsulation efficiency [86.1, 95.4, 97.5%, vector: DOX = 5:1, 10:1; 15:1 (W/W)]. The release behaviors of DOX from DSPE-PEG-C60 micelles were consistent with the DSPE-PEG micelles, and it showed sustained release. There was lower cytotoxicity of DSPE-PEG-C60 micelles on normal cell lines (L02, H9c2, GES-1) than free DOX and DSPE-PEG micelles. We explored the protective role of DSPE-PEG-C60 on doxorubicin-induced cardiomyocyte damage in H9c2 cells, which were evaluated with a reactive oxygen species (ROS) assay kit, JC-1, and an FITC annexin V apoptosis detection kit for cellular oxidative stress, mitochondrial membrane potential, and apoptosis. The results showed that H9c2 cells exposed to DSPE-PEG-C60 micelles displayed decreased intracellular ROS, an increased ratio of red fluorescence (JC-1 aggregates) to green fluorescence (JC-1 monomers), and a lower apoptotic ratio than the control and DSPE-PEG micelle cells. In conclusion, the prepared DOX-loaded DSPE-PEG-C60 micelles have great promise for safe, effective tumor therapy.

Structure-based design and synthesis of novel furan-diketopiperazine-type derivatives as potent microtubule inhibitors for treating cancer.

Plinabulin, a synthetic analog of the marine natural product "diketopiperazine phenylahistin," displayed depolymerization effects on microtubules and targeted the colchicine site, which has been moved into phase III clinical trials for the treatment of non-small cell lung cancer (NSCLC) and the prevention of chemotherapy-induced neutropenia (CIN). To develop more potent anti-microtubule and cytotoxic derivatives, the co-crystal complexes of plinabulin derivatives were summarized and analyzed. We performed further modifications of the tert-butyl moiety or C-ring of imidazole-type derivatives to build a library of molecules through the introduction of different groups for novel skeletons. Our structure-activity relationship study indicated that compounds 17o (IC50 = 14.0 nM, NCI-H460) and 17p (IC50 = 2.9 nM, NCI-H460) with furan groups exhibited potent cytotoxic activities at the nanomolar level against various human cancer cell lines. In particular, the 5-methyl or methoxymethyl substituent of furan group could replace the alkyl group of imidazole at the 5-position to maintain cytotoxic activity, contradicting previous reports that the tert-butyl moiety at the 5-position of imidazole was essential for the activity of such compounds. Immunofluorescence assay indicated that compounds 17o and 17p could efficiently inhibit microtubule polymerization. Overall, the novel furan-diketopiperazine-type derivatives could be considered as a potential scaffold for the development of anti-cancer drugs.

Development of novel phenoxy-diketopiperazine-type plinabulin derivatives as potent antimicrotubule agents based on the co-crystal structure.

The co-crystal structure of Compound 6b with tubulin was prepared and solved for indicating the binding mode and for further optimization. Based on the co-crystal structures of tubulin with plinabulin and Compound 6b, a total of 27 novel A/B/C-rings plinabulin derivatives were designed and synthesized. Their biological activities were evaluated against human lung cancer NCI-H460 cell line. The optimum phenoxy-diketopiperazine-type Compound 6o exhibited high potent cytotoxicity (IC50 = 4.0 nM) through SAR study of three series of derivatives, which was more potent than plinabulin (IC50 = 26.2 nM) and similar to Compound 6b (IC50 = 3.8 nM) against human lung cancer NCI-H460 cell line. Subsequently, the Compound 6o was evaluated against other four human cancer cell lines. Both tubulin polymerization assay and immunofluorescence assay showed that Compound 6o could inhibit microtubule polymerization efficiently. Furthermore, theoretical calculation of the physical properties and molecular docking were elucidated for these plinabulin derivatives. The binding mode of Compound 6o was similar to Compound 6b based on the result of molecular docking. The theoretical calculated LogPo/w and PCaco of Compound 6o were better than Compound 6b, which could enhance its cytostatic activity. Therefore, Compound 6o might be developed as a novel potent anti-microtubule agent.

Polymorphs, co-crystal structure and pharmacodynamics study of MBRI-001, a deuterium-substituted plinabulin derivative as a tubulin polymerization inhibitor.

MBRI-001, a deuterium-substituted plinabulin derivative, has been reported to have better pharmacokinetic and similar antitumor effects in comparison with plinabulin. In this approach, we further carried out its polymorphs, co-crystal structure of MBRI-001-tubulin and tubulin inhibition study. Among the different polymorphs, Form F (MBRI-001/H2O) was prepared and evaluated, which had better physical stability and suitable process for scale-up production. Co-crystal structure of MBRI-001-tubulin (PDB:5XI5) was prepared and analyzed. The result of tubulin polymerization assay demonstrated that MBRI-001 could inhibit tubulin polymerization which was similar as plinabulin. Subsequently, the anti-proliferative activities of plinabulin and MBRI-001 were evaluated against two different human lung cancer cell lines. In vivo study, MBRI-001 revealed similar antitumor inhibition in comparison with plinabulin in A549 xenograft tumor model. Therefore, we suggested that MBRI-001 could be developed as a promising anti-cancer agent in near future.

In vitro and in vivo pharmacokinetic and pharmacodynamic study of MBRI-001, a deuterium-substituted plinabulin derivative as a potent anti-cancer agent.

MBRI-001 was demonstrated preliminary better pharmacokinetics and antitumor effects than that of plinabulin in vivo. In this approach, we further carried out systematic pharmacokinetic and pharmacodynamic study of MBRI-001 in vitro and in vivo. MBRI-001 was tested stable in rat plasma and more stable in liver microsomes than plinabulin in vitro. In vivo, MBRI-001 could be distributed rapidly and widely in various tissues, especially the concentration of MBRI-001 in lung was remarkably higher than other tissues. Excretion study indicated that MBRI-001 might been decomposed and excreted as metabolites. Additionally, the combination treatment of MBRI-001 and gefitinib revealed better antitumor inhibition rate than monotherapy in vivo. Therefore, we suggest that MBRI-001 could be developed as a promising anti-cancer agent in near future.

Synthesis of deuterium-enriched and fluorine-substituted plinabulin derivatives and evaluation of their antitumor activities.

Deuterium-enriched and fluorine-substituted compounds have been widely applied in drug discovery due to their advantages in the studies of clinical pharmacokinetics and metabolic profiles. Herein we synthesized a library of deuterated and fluorine-substituted plinabulin derivatives, and all 15 D- or F-compounds were characterized by MS, [Formula: see text] NMR and [Formula: see text]. Their antitumor activities were evaluated against human Jurkat T lymphocyte cells.

Development of MBRI-001, a deuterium-substituted plinabulin derivative as a potent anti-cancer agent.

Plinabulin, a drug targeting microtubule of cancer cells, has been currently tried in its phase III clinical study. However, low efficacy caused by poor pharmacokinetic (PK) properties has been considered to be the main obstacle to approved by the Food and Drug Administration. Herein, we introduced a deuterium atom as an isostere in its structure to become a new compound named (MBRI-001, No. 9 in a series of deuterium-substituted compounds). The structure of MBRI-001 was characterized by HRMS, NMR, IR and a single crystal analysis. MBRI-001 exhibited better pharmacokinetic characteristics than that of plinabulin. Additionally, its antitumor activity is in a low nanomolar level for a variety of cancer cell lines and high activity against human NCI-H460 xenograted in mice intravenous administration. Importantly, continuous administration of MBRI-001 exhibited lower toxicity compared to docetaxel. We thus suggest that MBRI-001 could be developed as a promising anti-cancer agent in near future.