Chien-Huang Wu

Discovery of 2-[5-(4-chloro-phenyl)-1-(2,4-dichloro-phenyl)-4-ethyl-1H-pyrazol-3-yl]-1,5,5-trimethyl-1,5-dihydro-imidazol-4-thione (BPR-890) via an active metabolite. A novel, potent and selective cannabinoid-1 receptor inverse agonist with high antiobesity efficacy in DIO mice.

By using the active metabolite 5 as an initial template, further structural modifications led to the identification of the titled compound 24 (BPR-890) as a highly potent CB1 inverse agonist possessing an excellent CB2/1 selectivity and remarkable in vivo efficacy in diet-induced obese mice with a minimum effective dose as low as 0.03 mg/kg (po qd) at the end of the 30-day chronic study. Current SAR studies along with those of many existing rimonabant-mimicking molecules imply that around the pyrazole C3-position, a rigid and deep binding pocket should exist for CB1 receptor. In addition, relative to the conventional carboxamide carbonyl, serving as a key hydrogen-bond acceptor during ligand-CB1 receptor interaction, the corresponding polarizable thione carbonyl might play a more critical role in stabilizing the Asp366-Lys192 salt bridge in the proposed CB1-receptor homology model and inducing significant selectivity for CB1R over CB2R.

Discovery of 1‐(2,4‐Dichlorophenyl)‐4‐ethyl‐5‐(5‐(2‐(4‐(trifluoromethyl)phenyl)ethynyl)thiophen‐2‐yl)‐N‐(piperidin‐1‐yl)‐1H‐pyrazole‐3‐carboxamide as a Potential Peripheral Cannabinoid‐1 Receptor Inverse Agonist

Cannabinoid-1 receptor (CB1R) is one of the most abundant neuroregulatory receptors in the brain, and it is involved in regulating feeding and appetite. In addition to expression in brain, this receptor is also found in the peripheral organs, such as adipose tissues, muscle, and liver. In sharp contrast, the structurally closely related cannabinoid-2 receptor (CB2R) is expressed almost exclusively in the immune system and is primarily involved in immune regulation and neurodegeneration. The therapeutic potential of CB1R antagonists has been extensively reviewed, and at least one compound (1; also called rimonabant or SR141716A) has shown clinical evidence of weight reducing action. However, after its launch in 2006, it was subsequently withdrawn (2008) in Europe due to severe psychiatric effects including depression, anxiety and stress disorders. Currently, only two drugs, orlistat and sibutramine, are available for the long-term treatment of obesity; however, both have met with moderate success because of their limited weight-loss efficacy and many accompanying adverse effects, including high blood pressure and flatulence.

Bioisosteric Replacement of the Pyrazole 5-Aryl Moiety of N-(Piperidin-1-yl)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide (SR141716A). A Novel Series of Alkynylthiophenes as Potent and Selective Cannabinoid-1 Receptor Antagonists

Replacing the conventional pyrazole 5-aryl substituent of 1 (SR141716A) with the 2-thienyl moiety appended with an appropriate alkynyl unit, a novel class of 5-(5-alkynyl-2-thienyl)pyrazole derivatives, behaving as highly potent CB1 receptor antagonists with good CB1/2 selectivity, was discovered, many of which, as typified by compound 18, showed significant weight reduction in diet-induced obese mouse model, thus pharmacologically validating that the bioisosteric replacement described above is viable. Also encouraging was the finding that a subtle structural modification of the newly developed series could result in a distinct difference in the intrinsic property, as demonstrated by compounds 12 (NA) and its methylated structural isomers 15 (PA) and 18 (IA). Moreover, current structure-activity relationship studies revealed that around the pyrazole 5-position of 1, a deep and flat crevice surrounded by a sequence of hydrophobic/aromatic residues as indicated by the CB1-receptor homology model might exist in the binding site.

Discovery of 1-(2,4-Dichlorophenyl)-N-(piperidin-1-yl)-4-((pyrrolidine-1-sulfonamido)methyl)-5-(5-((4-(trifluoromethyl)phenyl)ethynyl)thiophene-2-yl)-1H-pyrazole-3-carboxamide as a Novel Peripherally Restricted Cannabinoid-1 Receptor Antagonist with Significant Weight-Loss Efficacy in Diet-Induced Obese Mice

After extensive synthetic efforts, we found that many structurally diverse bioisosteres could be generated via derivatizing the C-4 alkyl chain on the pyrazole ring of compound 3 (B/P = 1/33) with different electronegative groups. Especially when a sulfonamide or sulfamide moiety was added, resulting compounds exhibited not only potent CB1R activity but also a desired tPSA value over 90 Å(2), a threshold considered to possess a low probability to cross BBB, leading to the identification of compound 4 (B/P = 1/64) as a peripherally restricted CB1R antagonist. Apart from its significant weight-loss efficacy in DIO mice, compound 4 also displays 163 clean off-target profiles and is currently under development for treating obesity and the related metabolic syndrome.

Function-oriented development of CXCR4 antagonists as selective human immunodeficiency virus (HIV)-1 entry inhibitors.

Motivated by the pivotal role of CXCR4 as an HIV entry co-receptor, we herein report a de novo hit-to-lead effort on the identification of subnanomolar purine-based CXCR4 antagonists against HIV-1 infection. Compound 24, with an EC50 of 0.5 nM against HIV-1 entry into host cells and an IC50 of 16.4 nM for inhibition of radioligand stromal-derived factor-1α (SDF-1α) binding to CXCR4, was also found to be highly selective against closely related chemokine receptors. We rationalized that compound 24 complementarily interacted with the critical CXCR4 residues that are essential for binding to HIV-1 gp120 V3 loop and subsequent viral entry. Compound 24 showed a 130-fold increase in anti-HIV activity compared to that of the marketed CXCR4 antagonist, AMD3100 (Plerixafor), whereas both compounds exhibited similar potency in mobilization of CXCR4(+)/CD34(+) stem cells at a high dose. Our study offers insight into the design of anti-HIV therapeutics devoid of major interference with SDF-1α function.

Discovery of novel stem cell mobilizers that target the CXCR4 receptor.

The chemokine CXCL12 (also known as stromal cell-derived factor-1, SDF-1) consists of 68 amino acids and is a highly positively charged member of the CXC chemokines. It was originally cloned from bone marrow stromal cell lines and was found to act as a growth factor for progenitor B cells. The physiological function of SDF-1 is mediated by the CXCR4 receptor, a G-protein-coupled seven-transmembrane receptor (GPCR), and is broadly expressed in a variety of human tissues, particularly those of the immune and central nervous systems. CXCR4 was also identified as the main co-receptor by which T-lymphotropic HIV strains enter target cells. Although the initial interest in CXCR4 antagonists was focused on their potential application in the treatment of HIV infection, 6] it is now recognized that the SDF-1/CXCR4 axis is also involved in many diseases such as rheumatoid arthritis, asthma, leukemia, and tumor metastasis ; it also helps in recruiting stem cells to sites of injury. AMD3100 (plerixafor, Mozobil), the first highly potent and specific CXCR4 antagonist, was originally intended to treat HIV infection, but failed in phase II clinical trials. Nevertheless, it

Stem Cell Mobilizers Targeting Chemokine Receptor CXCR4: Renoprotective Application in Acute Kidney Injury

We have discovered a novel series of quinazoline-based CXCR4 antagonists. Of these, compound 19 mobilized CXCR4(+) cell types, including hematopoietic stem cells and endothelial progenitor cells, more efficiently than the marketed 1 (AMD3100) with subcutaneous administration at the same dose (6 mg/kg) in mice. This series of compounds thus provides a set of valuable tools to study diseases mediated by the CXCR4/SDF-1 axis, including myocardial infarction, ischemic stroke, and cancer metastasis. More importantly, treatment with compound 19 significantly lowered levels of blood urea nitrogen and serum creatinine in rats with renal ischemia-reperfusion injury, providing evidence for its therapeutic potential in preventing ischemic acute kidney injury. CXCR4 antagonists such as 19 might also be useful to increase circulating levels of adult stem cells, thereby exerting beneficial effects on damaged and/or inflamed tissues in diseases that currently are not treated by standard approaches.

A novel CXCR4 antagonist CX549 induces neuroprotection in stroke brain

C-X-C chemokine receptor type 4 (CXCR4) is a receptor for a pleiotropic chemokine CXCL12. Previous studies have shown that the acute administration of the CXCR4 antagonist AMD3100 reduced neuroinflammation in stroke brain and mobilized bone marrow hematopoietic stem cells (HSCs). The purpose of this study was to characterize the neuroprotective and neurotrophic effect of a novel CXCR4 antagonist CX549. We demonstrated that CX549 had a higher affinity for CXCR4 and was more potent than AMD3100 to inhibit CXCL12-mediated chemotaxis in culture. CX549 effectively reduced the activation of microglia and improved neuronal survival after injury in neuron/microglia cocultures. Early poststroke treatment with CX549 significantly improved behavioral function, reduced brain infarction, and suppressed the expression of inflammatory markers. Compared to AMD3100, CX549 has a higher affinity for CXCR4, is more efficient to mobilize HSCs for transplantation, and induces behavioral improvement. Our data support that CX549 is a potent anti-inflammatory agent, is neuroprotective against ischemic brain injury, and may have clinical implications for the treatment of stroke.

Targeting Tumor Associated Phosphatidylserine with New Zinc Dipicolylamine-Based Drug Conjugates

A series of zinc(II) dipicolylamine (ZnDPA)-based drug conjugates have been synthesized to probe the potential of phosphatidylserine (PS) as a new antigen for small molecule drug conjugate (SMDC) development. Using in vitro cytotoxicity and plasma stability studies, PS-binding assay, in vivo pharmacokinetic studies, and maximum tolerated dose profiles, we provided a roadmap and the key parameters required for the development of the ZnDPA based drug conjugate. In particular, conjugate 24 induced tumor regression in the COLO 205 xenograft model and exhibited a more potent antitumor effect with a 70% reduction of cytotoxic payload compared to that of the marketed irinotecan when dosed at the same regimen. In addition to the validation of PS as an effective pharmacodelivery target for SMDC, our work also provided the foundation that, if applicable, a variety of therapeutic agents could be conjugated in the same manner to treat other PS-associated diseases.

Abstract 4413: Zinc-dipicolylamine directed pharmaceutical delivery system (ZAPS) as an innovative cancer drug delivery platform

Drug delivered by conjugate with antibody is expected to increase drug concentrations at the tumor sites for improved antitumor effects. Showing some successes, the antibody-drug conjugate system has certain limitations such as difficulties in protein characterization, high cost and individual variations in expression of the epitope, which might abrogate the antibody recognition and cause premature drug release arising from antibody-drug linker instability and thus ineffectiveness. Phosphatidylserine (PS) exists in bulk amount in the tumor microenvironment. Studies showed that a small sized Zinc (II)-dipicolylamine (Zn-DPA) molecule was superior in locating PS surrounding the apoptotic sites in vivo. Although Zn-DPA has been constructed incorporating fluorescent dyes as optical tools for imaging the PS-exposed cell membranes to identify tumor sites from healthy cells in animals, drug conjugates with Zn-DPA has never been described. We aimed to design, synthesize and evaluate a Zinc-dipicolylAmine directed Pharmaceutical delivery System (ZAPS), a platform for spatial- and temporal-release of drug specifically at the targeted tumor site. Zn-DPA was conjugated through standard coupling conditions with various linkers to SN-38 and the Zn-DPA-linker-SN-38 conjugates were obtained and investigated for structure-activity relationships on the chemical stability in plasma and cytotoxicity against cancer cells. Promising ZAPS-SN-38 conjugates were evaluated for activities against tumor growths in nude mice. CPT-11 and SN-38 were included for comparisons. ZAPS-SN-38 conjugates were examined for tolerable doses in mice. Among the ZAPS-SN-38 conjugates synthesized, ZAPS001 was found chemically stable in mouse plasma and in vitro active against several cancer cells. ZAPS001 dose-dependently inhibited the growth of Colo205 tumors in nude mice. Zn-DPA-linker001 (ZAPS001 without SN-38) showed no inhibition effect on the tumor growth. Intriguingly, employing only 40% of the SN-38 delivered by CPT-11 (40 mg/kg), ZAPS001 resulted in 8-fold increase in antitumor activity compared to that of CPT-11 given at the same dose regimen. Furthermore, ZAPS001 is also active against pancreatic Mia-Paca2 and BxPC-3 tumors in mice. An increased SN-38 level delivered by ZAPS001 to the tumors in mice was also observed. ZAPS is thus capable of selectively associating with PS-exposing tumor cells/tissues to achieve site-specific delivery of anticancer agents. Our findings strongly support that ZAPS conferred an “in situ dose amplification” effect, i.e., the cytotoxics-induced PS exposure could specifically recruit more ZAPS-drug conjugates to the tumor site and further enhance its therapeutic effect. ZAPS provides spatial and temporal controls to increase drug concentration at targeted disease sites, reduce drug dosage, lessen the toxic side effects, and thus increase therapeutic index of the anticancer drugs. Citation Format: Lun K. Tsou, Yu-Wei Liu, Yun-Yu Chen, Chen-Fu Lo, Teng-Kuang Yeh, Chien-Huang Wu, Kak-Shan Shia, Joe C. Shih, Brian D. Gary, Koon Y. Pak, Chiung-Tong Chen. Zinc-dipicolylamine directed pharmaceutical delivery system (ZAPS) as an innovative cancer drug delivery platform. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4413. doi:10.1158/1538-7445.AM2015-4413