SB-T-121205, a next-generation taxane, enhances apoptosis and inhibits migration/invasion in MCF-7/PTX cells

Transgelin-2, a novel cancer stem cell-related biomarker, is a diagnostic and therapeutic target for biliary tract cancer

BACKGROUND

Biliary tract cancer (BTC) is a relatively rare but aggressive gastrointestinal cancer with a high mortality rate. Cancer stem cell (CSC) populations play crucial roles in tumor biology and are responsible for the low response to anti-cancer treatment and the high recurrence rate. This study investigated the role of Transgelin-2 (TAGLN2), overexpressed in CSC in BTC cells, and analyzed its expression in patient tissues and serum to identify potential new targets for BTC.

METHODS

TAGLN2 expression was suppressed by small-interfering or short hairpin RNAs, and its effects on tumor biology were assessed in several BTC cell lines. Furthermore, the effects of TAGLN2 silencing on gemcitabine-resistant BTC cells, differentially expressed genes, proteins, and sensitivity to therapeutics or radiation were assessed. TAGLN2 expression was also assessed using western blotting and immunohistochemistry in samples obtained from patients with BTC to validate its clinical application.

RESULTS

Suppression of TAGLN2 in BTC cell lines decreased cell proliferation, migration, invasion, and tumor size, in addition to a reduction in CSC features, including clonogenicity, radioresistance, and chemoresistance. TAGLN2 was highly expressed in BTC tissues, especially in cancer-associated fibroblasts in the stroma. Patients with a low stromal immunohistochemical index had prolonged disease-free survival compared to those with a high stromal immunohistochemical index (11.5 vs. 7.4 months, P = 0.013). TAGLN2 expression was higher in the plasma of patients with BTC than that in those with benign diseases. TAGLN2 had a higher area under the curve (0.901) than CA19-9, a validated tumor biomarker (0.799; P < 0.001).

CONCLUSION

TAGLN2 plays a critical role in promoting BTC cell growth and motility and is involved in regulating BTC stemness. Silencing TAGLN2 expression enhanced cell sensitivity to radiation and chemotherapeutic drugs. The expression of TAGLN2 in patient tissue and plasma suggests its potential to serve as a secretory biomarker for BTC. Overall, targeting TAGLN2 could be an appropriate therapeutic strategy against advanced cancer following chemotherapy failure.

Strategies for the drug discovery and development of taxane anticancer therapeutics

INTRODUCTION

Paclitaxel and docetaxel have been extensively used in the clinic over the past three decades. Although the patents of these first-generation taxanes have expired, their clinical applications, particularly new formulations and combination therapies, are under active investigations. Inspired by the notable success of Abraxane and Lipusu, new formulations have been extensively developed. In parallel, to overcome multidrug resistance (MDR) and to eradicate cancer stem cells, immense efforts have been made on the discovery and development of new-generation taxanes with improved potency and superior pharmacological properties.

AREAS COVERED

This review covers (a) natural sources of advanced intermediates used for semi-synthesis of taxane API, (b) new formulations, (c) the major issues of FDA approved taxanes, (d) the design and development of next-generation taxanes, (e) new mechanisms of action, and (f) a variety of taxane-based drug delivery systems.

EXPERT OPINION

As the highly potent next-generation taxanes can eradicate cancer stem cells and overcome MDR, the priority is to develop these compounds as an integral part of cancer therapy, especially for pancreatic, colon and prostate cancers which hardly respond to checkpoint inhibitors. In order to mitigate undesirable side effects, the exploration of effective nanoformulations and tumor-targeted drug delivery systems are essential.

A new core–shell-type nanoparticle loaded with paclitaxel/norcantharidin and modified with APRPG enhances anti-tumor effects in hepatocellular carcinoma

Nanoparticle delivery systems have been shown to improve the therapeutic efficacy of anti-cancer drugs, including a variety of drugs for the treatment of hepatocellular carcinoma (HCC). However, the current systems show some limitations, and the delivery of more effective nanoparticle systems for anti-HCC drugs with better targeting ability are needed. Here, we created paclitaxel (PTX)/norcantharidin (NCTD)-loaded core–shell lipid nanoparticles modified with a tumor neovasculature-targeted peptide (Ala-Pro-Arg-Pro-Gly, APRPG) and investigated their anti-tumor effects in HCC. Core–shell-type lipid nanoparticles (PTX/NCTD-APRPG-NPs) were established by combining poly(lactic-co-glycolic acid) (PLGA)-wrapped PTX with phospholipid-wrapped NCTD, followed by modification with APRPG. For comparison, PTX-loaded PLGA nanoparticles (PTX-NPs) and PTX/NCTD-loaded core–shell-type nanoparticles without APRPG (PTX/NCTD-NPs) were prepared. The in vitro and in vivo anti-tumor effects were examined in HepG2 cells and tumor-bearing mice, respectively. Morphological and release characterization showed that PTX/NCTD-APRPG-NPs were prepared successfully and achieved up to 90% release of PTX in a sustained manner. Compared with PTX/NCTD-NPs, PTX/NCTD-APRPG-NPs significantly enhanced the uptake of PTX. Notably, the inhibition of proliferation and migration of hepatoma cells was significantly higher in the PTX/NCTD-APRPG-NP group than those in the PTX-NP and PTX/NCTD-NP groups, which reflected significantly greater anti-tumor properties as well. Furthermore, key molecules in cell proliferation and apoptosis signaling pathways were altered most in the PTX/NCTD-APRPG-NP group, compared with the PTX-NP and PTX/NCTD-NP groups. Collectively, PTX/NCTD-loaded core–shell lipid nanoparticles modified with APRPG enhance the effectiveness of anti-HCC drugs and may be an effective system for the delivery of anti-HCC drugs.

Design, synthesis and SAR study of Fluorine-containing 3rd-generation taxoids

It has been shown that the incorporation of fluorine or organofluorine groups into pharmaceutical and agricultural drugs often induces desirable pharmacological properties through unique protein-drug interactions involving fluorine. We have reported separately remarkable effects of the 2,2-difluorovinyl (DFV) group at the C3' position, as well as those of the CF₃O and CHF₂O groups at the 3-position of the C2-benzoyl moiety of the 2nd- and 3rd-generation taxoids on their potency and pharmacological properties. Thus, it was very natural for us to investigate the combination of these two modifications in the 3rd-generation taxoids and to find out whether these two modifications are cooperative at the binding site in the β-tubulin or not, as well as to see how these effects are reflected in the biological activities of the new 3rd-generation DFV-taxoids. Accordingly, we designed, synthesized and fully characterized 14 new 3rd-generation DFV-taxoids. These new DFV-taxoids exhibited remarkable cytotoxicity against human breast, lung, colon, pancreatic and prostate cancer cell lines. All of these new DFV-taxoids exhibited subnanomolar IC₅₀ values against drug-sensitive cell lines, A549, HT29, Vcap and PC3, as well as CFPAC-1. All of the novel DFV-taxoids exhibited 2-4 orders of magnitude greater potency against extremely drug-resistant cancer cell lines, LCC6-MDR and DLD-1, as compared to paclitaxel, indicating that these new DFV-taxoids can overcome MDR caused by the overexpression of Pgp and other ABC cassette transporters. Dose-response (kill) curve analysis of the new DFV-taxoids in LCC6-MDR and DLD-1 cell lines revealed highly impressive profiles of several new DFV-taxoids. The cooperative effects of the combination of the 3'-DFV group and 3-CF₃O/CHF₂O-benzoyl moiety at the C2 position were investigated in detail by molecular docking analysis. We found that both the 3'-DFV moiety and the 3-CF₃O/3-CHF₂O group of the C2-benzoate moiety are nicely accommodated to the deep hydrophobic pocket of the paclitaxel/taxoid binding site in the β-tubulin, enabling an enhanced binding mode through unique attractive interactions between fluorine/CF₃O/CHF₂O and the protein beyond those of paclitaxel and new-generation taxoids without bearing organofluorine groups, which are reflected in the remarkable potency of the new 3rd-generation DFV-taxoids.

The Role of TRIP6, ABCC3 and CPS1 Expression in Resistance of Ovarian Cancer to Taxanes

The main problem precluding successful therapy with conventional taxanes is de novo or acquired resistance to taxanes. Therefore, novel experimental taxane derivatives (Stony Brook taxanes; SB-Ts) are synthesized and tested as potential drugs against resistant solid tumors. Recently, we reported alterations in ABCC3, CPS1, and TRIP6 gene expression in a breast cancer cell line resistant to paclitaxel. The present study aimed to investigate gene expression changes of these three candidate molecules in the highly resistant ovarian carcinoma cells in vitro and corresponding in vivo models treated with paclitaxel and new experimental Stony Brook taxanes of the third generation (SB-T-121605 and SB-T-121606). We also addressed their prognostic meaning in ovarian carcinoma patients treated with taxanes. We estimated and observed changes in mRNA and protein profiles of ABCC3, CPS1, and TRIP6 in resistant and sensitive ovarian cancer cells and after the treatment of resistant ovarian cancer models with paclitaxel and Stony Brook taxanes in vitro and in vivo. Combining Stony Brook taxanes with paclitaxel caused downregulation of CPS1 in the paclitaxel-resistant mouse xenograft tumor model in vivo. Moreover, CPS1 overexpression seems to play a role of a prognostic biomarker of epithelial ovarian carcinoma patients’ poor survival. ABCC3 was overexpressed in EOC tumors, but after the treatment with taxanes, its up-regulation disappeared. Based on our results, we can suggest ABCC3 and CPS1 for further investigations as potential therapeutic targets in human cancers.

Microtubule Targeting Agents in Disease: Classic Drugs, Novel Roles

Microtubule-targeting agents (MTAs) represent one of the most successful first-line therapies prescribed for cancer treatment. They interfere with microtubule (MT) dynamics by either stabilizing or destabilizing MTs, and in culture, they are believed to kill cells via apoptosis after eliciting mitotic arrest, among other mechanisms. This classical view of MTA therapies persisted for many years. However, the limited success of drugs specifically targeting mitotic proteins, and the slow growing rate of most human tumors forces a reevaluation of the mechanism of action of MTAs. Studies from the last decade suggest that the killing efficiency of MTAs arises from a combination of interphase and mitotic effects. Moreover, MTs have also been implicated in other therapeutically relevant activities, such as decreasing angiogenesis, blocking cell migration, reducing metastasis, and activating innate immunity to promote proinflammatory responses. Two key problems associated with MTA therapy are acquired drug resistance and systemic toxicity. Accordingly, novel and effective MTAs are being designed with an eye toward reducing toxicity without compromising efficacy or promoting resistance. Here, we will review the mechanism of action of MTAs, the signaling pathways they affect, their impact on cancer and other illnesses, and the promising new therapeutic applications of these classic drugs.

Detection of phenotype-specific therapeutic vulnerabilities in breast cells using a CRISPR loss-of-function screen

Cellular phenotype plasticity between the epithelial and mesenchymal states has been linked to metastasis and heterogeneous responses to cancer therapy, and remains a challenge for the treatment of triple-negative breast cancer (TNBC). Here, we used isogenic human breast epithelial cell lines, D492 and D492M, representing the epithelial and mesenchymal phenotypes, respectively. We employed a CRISPR-Cas9 loss-of-function screen targeting a 2240-gene 'druggable genome' to identify phenotype-specific vulnerabilities. Cells with the epithelial phenotype were more vulnerable to the loss of genes related to EGFR-RAS-MAPK signaling, while the mesenchymal-like cells had increased sensitivity to knockout of G₂ -M cell cycle regulators. Furthermore, we discovered knockouts that sensitize to the mTOR inhibitor everolimus and the chemotherapeutic drug fluorouracil in a phenotype-specific manner. Specifically, loss of EGFR and fatty acid synthase (FASN) increased the effectiveness of the drugs in the epithelial and mesenchymal phenotypes, respectively. These phenotype-associated genetic vulnerabilities were confirmed using targeted inhibitors of EGFR (gefitinib), G₂ -M transition (STLC), and FASN (Fasnall). In conclusion, a CRISPR-Cas9 loss-of-function screen enables the identification of phenotype-specific genetic vulnerabilities that can pinpoint actionable targets and promising therapeutic combinations.

Preparation of hydroxy genkwanin nanosuspensions and their enhanced antitumor efficacy against breast cancer

Hydroxy genkwanin (HGK), a flavonoid compound from natural resources, showed good inhibition against the growth of breast tumor cells. However, the poor solubility restricted the further study and the in vivo drug delivery of HGK. We prepared HGK nanosuspensions by antisolvent precipitation method and investigated their characterization, stability, hemolysis probability, release behavior in vitro, antitumor activity in vitro and in vivo, and preliminary safety through acute toxicity experiments. The resultant HGK nanosuspensions (HGK-NSps) showed an average diameter of (261.1 ± 4.8 nm), a narrow particle size distribution (PDI of 0.12 ± 0.01), spherical morphology, high drug-loading content (39.9 ± 2.3%, w/w), and good stability in various physiological media. HGK-NSps was safe for intravenous injection at low concentration and HGK was slowly released from the obtained nanosuspensions. HGK-NSps showed stronger cytotoxicity than free HGK against many tumor cells in vitro. Especially against MCF-7 cells, the IC₅₀ value was decreased to 1.0 μg/mL, 5-fold lower than the HGK solution. In the in vivo antitumor activity study HGK-NSps (40 mg/kg) displayed a similar therapeutic effect to that of the paclitaxel injection (8 mg/kg). The preliminary acute toxicity test showed that even at the highest dose of 360 mg/kg (iv), HGK-NSps had 100% of mice survival and all the mice were in a good state, suggesting a maximum tolerated dose more than 360 mg/kg. The effective antitumor effect and good tolerance showed HGK-NSps were likely to become a safe and effective antitumor drug for the treatment of breast cancer in the future.

Hydrous icaritin nanorods with excellent stability improves the in vitro and in vivo activity against breast cancer

Due to their various biological activities that are beneficial to human health and antitumor effect, flavonoid compounds have attracted much attention in recent years. Hydrous icaritin (HICT) was such a flavonoid that can inhibit the growth of breast cancer and cancer stem cells. In order to overcome the insolubility problem, HICT was fabricated into nanorods (NRs) through anti-solvent precipitation in this paper using D-α tocopherol acid polyethylene glycol succinate and sodium oleate as a co-stabilizer meanwhile using the mixture of ethanol and acetone (1:2, v/v) as the organic solvent. The obtained HICT NRs showed an average particle size 222.0 nm with a small polydispersity index value of 0.124 and a high zeta potential of – 49.5 mV. HICT NRs could maintain similar particle size in various physiological medium and could be directly lyophilized without the addition of any cytoprotectants and then reconstituted into a colloidal system of similar size. The resultant HICT NRs had a high drug loading content of 55.6% and released HICT in a steady and constant pattern. MTT assay indicated NRs enhanced HICT’s antitumor activity to ninefold against MCF-7 breast carcinoma cells. In vivo studies demonstrated oral administration free HICT had almost no tumor inhibitory effect while HICT NRs showed a tumor inhibition rate of 47.8%. When intravenously injected, HICT NRs displayed similar therapeutic efficacy to paclitaxel injections (70.4% vs. 74.5%, TIR). This may be partly due to the high accumulation of the injected HICT NRs in tumor ranking only second to that in the liver but much higher than in other organs. These results demonstrated that HICT NRs could be a promising antitumor agent for the treatment of breast cancer in clinic.

A novel taxane, difluorovinyl-ortataxel, effectively overcomes paclitaxel-resistance in breast cancer cells

Paclitaxel (PTX) is widely used to treat breast and ovarian cancers, but innate and acquired resistance often compromises its applications. The objective of this study was to screen new-generation taxanes for their efficiency against both PTX-sensitive and PTX-resistant breast cancer cells. From twelve compounds, difluorovinyl-ortataxel (DFV-OTX) displayed potent cytotoxic activities against both PTX-sensitive and PTX-resistant breast cancer cells. Moreover, DFV-OTX effectively induced tubulin/microtubule polymerization and G2/M phase arrest, leading to apoptosis in both PTX-sensitive and PTX-resistant cancer cells. Molecular docking analysis showed that DFV-OTX possesses unique hydrogen-bonding and van der Waals interactions with β-tubulin. LC-MS/MS analysis also demonstrated that the intracellular drug amount of DFV-OTX was lower than that of PTX, which would be critical to overcome PTX-resistance. Furthermore, DFV-OTX exhibited clear efficacy in the MCF-7R and MDA-MB-231R tumor xenografts in mouse models. Taken together, our results demonstrate that the novel taxane, DFV-OTX, can effectively overcome PTX-resistance in MDA-MB-231R cells, wherein the drug resistance was attributed to ABCB1/ABCG2 upregulation and a distinct mode of action in MCF-7R cells. Our results strongly indicate that DFV-OTX is a promising chemotherapeutic agent for the treatment of PTX-resistant cancers.

Microtubule-targeting agents and their impact on cancer treatment

Microtubule-targeting agents (MTAs) constitute a diverse group of chemical compounds that bind to microtubules and affect their properties and function. Disruption of microtubules induces various cellular responses often leading to cell cycle arrest or cell death, the most common effect of MTAs. MTAs have found a plethora of practical applications in weed control, as fungicides and antiparasitics, and particularly in cancer treatment. Here we summarize the current knowledge of MTAs, the mechanisms of action and their role in cancer treatment. We further outline the potential use of MTAs in anti-metastatic therapy based on inhibition of cancer cell migration and invasiveness. The two main problems associated with cancer therapy by MTAs are high systemic toxicity and development of resistance. Toxic side effects of MTAs can be, at least partly, eliminated by conjugation of the drugs with various carriers. Moreover, some of the novel MTAs overcome the resistance mediated by both multidrug resistance transporters as well as overexpression of specific β-tubulin types. In anti-metastatic therapy, MTAs should be combined with other drugs to target all modes of cancer cell invasion.

Design, synthesis and SAR study of 3rd-generation taxoids bearing 3-CH3, 3-CF3O and 3-CHF2O groups at the C2-benzoate position

It has been shown that inclusion of CF₃O and CHF₂O groups to drug candidates often improve their pharmacological properties, especially metabolic stability, membrane permeability and PK profile. Moreover, the unique non-spherical structure of the OCHF₂ group can provide interesting and beneficial characteristics. Accordingly, new 3rd-generation taxoids, bearing 3-OCF₃ or 3-OCF₂H (and 3-CH₃ for comparison) at the C2 benzoate moiety, were synthesized and their potencies against drug-sensitive and drug-resistant cancer cell lines examined. In this study, our previous SAR studies on 3rd-generation taxoids were expanded to disclose that CH₃, CF₃O and CHF₂O groups are well tolerated at this position and enhance potency, especially against MDR-cancer cell lines so that these taxoids can virtually overcome MDR. These new taxoids exhibit up to 7 times higher cytotoxicity (IC₅₀) than paclitaxel against drug-sensitive cancer cell lines (MCF7 and LCC6-WT) and 2-3 orders of magnitude higher potency than paclitaxel against drug-resistant ovarian, breast and colon cancer cell lines with MDR-phenotype (NCI/ADR, LCC6-MDR and LDL-1), as well as pancreatic cancer cell line, CFPAC-1. Since it has been shown that a bulky group at this position reduces potency, it is noteworthy that rather bulky CF₃O and CHF₂O groups are well tolerated. Molecular modeling analysis indicated the favorable van der Waals interactions of CF₃O and CHF₂O groups in the binding site. It is also worthy of note that new taxoids, bearing a CHF₂O group at the C2 benzoate position (1-06 series), exhibited the highest potencies against MDR-cancer cell lines and cancer stem cell (CSC)-enriched cancer cell lines. These new 3rd-generation taxoids are promising candidates for highly potent chemotherapeutic agents, as well as payloads for tumor-targeting drug conjugates such as antibody-drug conjugates (ADCs).

Transgelin-2: Biochemical and Clinical Implications in Cancer and Asthma

Transgelin-2 has been regarded as an actin-binding protein that induces actin gelation and regulates actin cytoskeleton. However, transgelin-2 has recently been shown to relax the myosin cytoskeleton of the airway smooth muscle cells by acting as a receptor for extracellular metallothionein-2. From a clinical perspective, these results support transgelin-2 as a promising therapeutic target for diseases such as cancer and asthma. The inhibition of transgelin-2 prevents actin gelation and thereby cancer cell proliferation, invasion, and metastasis. Conversely, the activation of transgelin-2 with specific agonists relaxes airway smooth muscles and reduces pulmonary resistance in asthma. Here, we review new studies on the biochemical properties of transgelin-2 and discuss their clinical implications for the treatment of immune, oncogenic, and respiratory disorders.

Recent progress in the strategic incorporation of fluorine into medicinally active compounds

This account exemplifies our recent progress on the strategic incorporation of fluorine and organofluorine groups to (i) taxoid anticancer agents, (ii) acylhydrazone-based antifungal agents and (iii) inhibitors of matrix metalloproteinase 9 (MMP9) for medicinal chemistry and chemical biology studies. In the case study (i), a series of next-generation fluorotaxoids, bearing m-OCF3 or m-OCF2H group in the C2-benzoate moiety was designed, synthesized and examined for their potencies. A number of these fluorotaxoids possess two orders of magnitude greater potency in different drug-resistant cancer cell lines as compared to paclitaxel. One of these next-generation fluorotaxoids, SB--121205wasselected for detailed mechanistic study against highly paclitaxel-resistant human breast cancer cell line, MCF-7/PTX, which disclosed a unique mechanism of action. Recently, glucosylceramide (GlcCer) synthesis emerged as a promising target for next-generation antifungal agents, especially against cryptococcosis, candidiasis and pulmonary aspergillosis. The HTP screening of compound libraries identified several acylhydrazones as hit compounds. In the case study (ii), fluoro-acylhydrazones containing F, OCF3, OCHF2, o-F/p-OCF3, as well as o-F/p-CF3 functional groups in the ring A and ring B were designed based on these hit compounds, synthesized and examined for their potencies against C. neoformans. A number of those novel fluoro-acylhydrazones exhibited high potency and excellent killing properties. The hemopexin-like domain of matrix metalloproteinases (MMPs) is a highly promising target to circumvent the critical issue in the development of MMP inhibitors for the treatment of various cancers. In the case study (iii), a small optimization library of compounds, based on the OCHF2-containing hit compound, SB-M-001, was generated and evaluated, which identified a fluorine-containing new lead compound, SB-M-103. SB-M-103 was found to inhibit tumor cell growth, migration, and invasion by effectively disrupting the MMP-9 homodimerization.

Transgelin-2 is a novel target of KRAS-ERK signaling involved in the development of pancreatic cancer

Background

The KRAS mutation is the driving force of pancreatic ductal adenocarcinoma (PDAC). Downstream effectors of KRAS signal pathways are crucial to the development of PDAC. The purpose of this study was to investigate the relationship between KRAS mutation and transgelin-2. Transgelin-2 is highly expressed in PDAC tissues compared with adjacent normal tissues. The underlying mechanism for upregulating transgelin-2 is largely unknown.

Methods

Expression of transgelin-2 was analyzed by microarray data and qRT-PCR. The effect of KRAS signaling on transgelin-2 expression was examined in PDAC cells in the presence or absence of the ERK inhibitor. The interaction of transgelin-2 with ERK was confirmed by immunoprecipitation. ERK-mediated Phosphorylation of transglein-2 was detected by in vivo and in vitro kinase assays. The gain-of-function and loss-of-function approaches were used to examine the role of phosphorylation of transgelin-2 on cell proliferation. Phosphorylation of transgelin-2 was detected by immunohistochemistry in PDAC tissues.

Results

Here we found transgelin-2 expression was induced by KRAS mutation. In the case of KRAS mutation, ERK2 interacted with 29–31 amino acids of transgelin-2 and subsequently phosphorylated the S145 residue of transgelin-2. S145 phosphorylation of transgelin-2 played important roles in cell proliferation and tumorigenesis of PDAC. In addition, S145 phosphorylation of transgelin-2 was associated with a poor prognosis in patients with PDAC.

Conclusions

This study indicated that KRAS-ERK-mediated transeglin-2 phosphorylation played an important role in the development of PDAC. Inhibition of transgelin-2 phosphorylation may be a potential therapeutic strategy for targeting PDAC with KRAS mutation.

Quest for Efficacious Next-Generation Taxoid Anticancer Agents and Their Tumor-Targeted Delivery

Paclitaxel and docetaxel are among the most widely used chemotherapeutic drugs against various types of cancer. However, these drugs cause undesirable side effects as well as drug resistance. Therefore, it is essential to develop next-generation taxoid anticancer agents with better pharmacological properties and improved activity especially against drug-resistant and metastatic cancers. The SAR studies by the authors have led to the development of numerous highly potent novel second- and third-generation taxoids with systematic modifications at the C-2, C-10, and C-3' positions. The third-generation taxoids showed virtually no difference in potency against drug-resistant and drug-sensitive cell lines. Some of the next-generation taxoids also exhibited excellent potency against cancer stem cells. This account summarizes concisely investigations into taxoids over 25 years based on a strong quest for the discovery and development of efficacious next-generation taxoids. Discussed herein are SAR studies on different types of taxoids, a common pharmacophore proposal for microtubule-stabilizing anticancer agents and its interesting history, the identification of the paclitaxel binding site and its bioactive conformation, characteristics of the next-generation taxoids in cancer cell biology, including new aspects of their mechanism of action, and the highly efficacious tumor-targeted drug delivery of potent next-generation taxoids.