Computational Methods in Cooperation with Experimental Approaches to Design Protein Tyrosine Phosphatase 1B Inhibitors in Type 2 Diabetes Drug Design: A Review of the Achievements of This Century

✅ 全文

计算方法与实验方法协同设计2型糖尿病药物中的蛋白酪氨酸磷酸酶1B抑制剂:本世纪成果综述

作者 Mara Ibeth Campos-Almazán; Alicia Hernández‐Campos; Rafael Castillo; Erick Sierra‐Campos; Mónica Valdez‐Solana; Claudia Avitia‐Domínguez; Alfredo Téllez‐Valencia 期刊 Pharmaceuticals 发表日期 2022 ISSN 1424-8247 DOI 10.3390/ph15070866 类型 原创研究 (Original Research)

📄 英文摘要 English Abstract

EN

Protein tyrosine phosphatase 1B (PTP1B) dephosphorylates phosphotyrosine residues and is an important regulator of several signaling pathways, such as insulin, leptin, and the ErbB signaling network, among others. Therefore, this enzyme is considered an attractive target to design new drugs against type 2 diabetes, obesity, and cancer. To date, a wide variety of PTP1B inhibitors that have been developed by experimental and computational approaches. In this review, we summarize the achievements with respect to PTP1B inhibitors discovered by applying computer-assisted drug design methodologies (virtual screening, molecular docking, pharmacophore modeling, and quantitative structure-activity relationships (QSAR)) as the principal strategy, in cooperation with experimental approaches, covering articles published from the beginning of the century until the time this review was submitted, with a focus on studies conducted with the aim of discovering new drugs against type 2 diabetes. This review encourages the use of computational techniques and includes helpful information that increases the knowledge generated to date about PTP1B inhibition, with a positive impact on the route toward obtaining a new drug against type 2 diabetes with PTP1B as a molecular target.

📄 中文摘要 Chinese Abstract

中文
蛋白酪氨酸磷酸酶1B(PTP1B)可使磷酸酪氨酸残基去磷酸化,是多种信号通路的重要调节因子,如胰岛素、瘦素和ErbB信号网络等。因此,该酶被认为是设计针对2型糖尿病、肥胖症和癌症新药的极具吸引力的靶点。迄今为止,已通过实验和计算方法开发了多种PTP1B抑制剂。在本综述中,我们总结了应用计算机辅助药物设计方法(虚拟筛选、分子对接、药效团建模和定量构效关系(QSAR))作为主要策略,结合实验方法所取得的PTP1B抑制剂研究成果,涵盖从本世纪初至本综述提交时发表的文章,重点聚焦于以发现2型糖尿病新药为目标的研究。

📋 英文结构化总结 English Structured Summary

全文整理

EN

Header:

Background: Protein tyrosine phosphatase 1B (PTP1B) dephosphorylates phosphotyrosine residues and is an important regulator of several signaling pathways, such as insulin, leptin, and the ErbB signaling network, among others. Therefore, this enzyme is considered an attractive target to design new drugs against type 2 diabetes, obesity, and cancer. To date, a wide variety of PTP1B inhibitors that have been developed by experimental and computational approaches. In this review, we summarize the achievements with respect to PTP1B inhibitors discovered by applying computer-assisted drug design methodologies (virtual screening, molecular docking, pharmacophore modeling, and quantitative structure–activity relationships (QSAR)) as the principal strategy, in cooperation with experimental approaches, covering articles published from the beginning of the century until the time this review was submitted, with a focus on studies conducted with the aim of discovering new drugs against type 2 diabetes.

Header:

Methods: The research was carried out using various groups of keywords, such as PTP1B inhibitors, virtual screening, molecular docking, pharmacophore modeling, 3D-QSAR, and computational drug design. The review included only articles published during this century and focused on PTP1B as a target for type 2 diabetes drug design.

Header:

Results: In this review, we summarize the achievements with respect to PTP1B inhibitors discovered by applying computer-assisted drug design methodologies (virtual screening, molecular docking, pharmacophore modeling, and quantitative structure–activity relationships (QSAR)) as the principal strategy, in cooperation with experimental approaches, covering articles published from the beginning of the century until the time this review was submitted, with a focus on studies conducted with the aim of discovering new drugs against type 2 diabetes.

Header:

Data Summary: No quantitative results or key statistics are provided in the extracted text.

Header:

Conclusions: This review encourages the use of computational techniques and includes helpful information that increases the knowledge generated to date about PTP1B inhibition, with a positive impact on the route toward obtaining a new drug against type 2 diabetes with PTP1B as a molecular target.

Header:

Practical Significance: The development of PTP1B inhibitors has increased considerably for the treatment of type 2 diabetes, obesity, and cancer. However, PTP1B inhibitors have not progressed beyond the preclinical stage due to bioavailability and specificity challenges. This review provides helpful information that increases the knowledge generated to date about PTP1B inhibition, with a positive impact on the route toward obtaining a new drug against type 2 diabetes with PTP1B as a molecular target.

📋 中文结构化总结 Chinese Structured Summary

中文

背景:

蛋白酪氨酸磷酸酶1B(PTP1B)可使磷酸酪氨酸残基去磷酸化,是多种信号通路的重要调节因子,如胰岛素、瘦素和ErbB信号网络等。因此,该酶被认为是设计针对2型糖尿病、肥胖症和癌症新药的极具吸引力的靶点。迄今为止,已通过实验和计算方法开发了多种PTP1B抑制剂。在本综述中,我们总结了应用计算机辅助药物设计方法(虚拟筛选、分子对接、药效团建模和定量构效关系(QSAR))作为主要策略,结合实验方法所取得的PTP1B抑制剂研究成果,涵盖从本世纪初至本综述提交时发表的文章,重点聚焦于以发现2型糖尿病新药为目标的研究。

方法:

本研究使用多组关键词进行检索,如PTP1B抑制剂、虚拟筛选、分子对接、药效团建模、3D-QSAR和计算机辅助药物设计。本综述仅收录本世纪内发表的文章,并以PTP1B作为2型糖尿病药物设计靶点的研究为重点。

结果:

在本综述中,我们总结了应用计算机辅助药物设计方法(虚拟筛选、分子对接、药效团建模和定量构效关系(QSAR))作为主要策略,结合实验方法所发现的PTP1B抑制剂研究成果,涵盖从本世纪初至本综述提交时发表的文章,重点聚焦于以发现2型糖尿病新药为目标的研究。

数据摘要:

所提取的文本中未提供定量结果或关键统计数据。

结论:

本综述鼓励运用计算机辅助技术,并提供了有助于增进目前对PTP1B抑制相关知识的积极信息,对以PTP1B为分子靶点开发2型糖尿病新药的研究进程具有积极意义。

实际意义:

PTP1B抑制剂的开发在治疗2型糖尿病、肥胖症和癌症方面已取得显著进展。然而,由于生物利用度和特异性方面的挑战,PTP1B抑制剂尚未进入临床前阶段之后的进一步开发。本综述提供了有助于增进目前对PTP1B抑制相关知识的积极信息,对以PTP1B为分子靶点开发2型糖尿病新药的研究进程具有积极意义。

📖 英文全文 English Full Text

EN

Citation: Campos-Almazán, M.I.; Hernández-Campos, A.; Castillo, R.;

Sierra-Campos, E.; Valdez-Solana, M.; Avitia-Domínguez, C.;

Téllez-Valencia, A. Computational Methods in Cooperation with

Experimental Approaches to Design Protein Tyrosine Phosphatase 1B

Inhibitors in Type 2 Diabetes Drug Design: A Review of the

Achievements of This Century.

Pharmaceuticals 2022, 15, 866. https://doi.org/10.3390/ ph15070866

Academic Editor: Paweł Kafarski Received: 11 June 2022

Accepted: 12 July 2022 Published: 14 July 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations.

Copyright:

© 2022 by the authors.

Licensee MDPI, Basel, Switzerland.

This article is an open access article distributed under the terms and conditions of the Creative Commons

Attribution (CC BY) license (https:// creativecommons.org/licenses/by/

4.0/). pharmaceuticals Review Computational Methods in Cooperation with Experimental

Approaches to Design Protein Tyrosine Phosphatase 1B

Inhibitors in Type 2 Diabetes Drug Design: A Review of the

Achievements of This Century Mara Ibeth Campos-Almazán 1, Alicia Hernández-Campos 2

, Rafael Castillo 2 , Erick Sierra-Campos 3 , Mónica Valdez-Solana 3, Claudia Avitia-Domínguez 1,* and Alfredo Téllez-Valencia 1,*

1 Facultad de Medicina y Nutrición, Universidad Juárez del Estado de Durango,

Avenida Universidad y Fanny Anitúa S/N, Durango 34000, Mexico; maraicamp@gmail.com

2 Facultad de Química, Departamento de Farmacia, Universidad Nacional Autónoma de México,

Ciudad de Mexico 04510, Mexico; hercam@unam.mx (A.H.-C.); rafaelc@unam.mx (R.C.)

3 Facultad de Ciencias Químicas, Universidad Juárez del Estado de Durango Campus Gómez Palacio,

Avenida Artículo 123 S/N, Fracc, Filadelfia, Gómez Palacio 35010, Mexico; ericksier@gmail.com (E.S.-C.); valdezandyval@gmail.com (M.V.-S.)

* Correspondence: claudia.avitia@ujed.mx (C.A.-D.); atellez@ujed.mx (A.T.-V.);

Tel./Fax: +52-6188271382 (C.A.-D. & A.T.-V.) Abstract: Protein tyrosine phosphatase 1B (PTP1B) dephosphorylates phosphotyrosine residues and is an important regulator of several signaling pathways, such as insulin, leptin, and the ErbB signaling network, among others. Therefore, this enzyme is considered an attractive target to design new drugs against type 2 diabetes, obesity, and cancer. To date, a wide variety of PTP1B inhibitors that have been developed by experimental and computational approaches. In this review, we summarize the achievements with respect to PTP1B inhibitors discovered by applying computer- assisted drug design methodologies (virtual screening, molecular docking, pharmacophore modeling, and quantitative structure–activity relationships (QSAR)) as the principal strategy, in cooperation with experimental approaches, covering articles published from the beginning of the century until the time this review was submitted, with a focus on studies conducted with the aim of discovering new drugs against type 2 diabetes. This review encourages the use of computational techniques and includes helpful information that increases the knowledge generated to date about PTP1B inhibition, with a positive impact on the route toward obtaining a new drug against type 2 diabetes with PTP1B as a molecular target.

Keywords: PTP1B inhibitors; computer-assisted drug design; molecular docking; virtual screening; pharmacophore modeling; QSAR; type 2 diabetes

1. Introduction Cancer, obesity, and diabetes mellitus are major health problems worldwide, causing around 9.6, 2.8, and 1.6 million deaths a year, respectively [1]. In addition, all of these disease impose a high expense on the health system and even more when they coexist [2].

Despite the wide variety of oral and injectable therapies available for these diseases, their uses are limited by efficacy, adverse effects, and contraindications [3–7]. Therefore, the increased prevalence of these diseases highlights the necessity of searching for new drugs for their treatment.

In this sense, protein tyrosine phosphatase 1B (PTP1B) has been established as a phar- macological target for these pathologies. Its substrates are involved in multiple cellular processes, such as glucose homeostasis regulated by insulin signaling, decreased food intake, increased energy expenditure, cellular proliferation, and more. PTP1B is considered

Pharmaceuticals 2022, 15, 866. https://doi.org/10.3390/ph15070866 https://www.mdpi.com/journal/pharmaceuticals

Pharmaceuticals 2022, 15, 866 2 of 22 an interesting drug target for the treatment of type 2 diabetes because it dephosphory- lates the insulin receptor (IR) and the insulin receptor substrate 1 (IRS-1), inactivating the downstream pathway of phosphatidylinositol 3-kinase (PI3K)-Akt and preventing the translocation of glucose transporter 4 (GLUT4) [8,9] (Figure 1). In addition, attention has been on PTP1B as a potentially excellent therapeutic target in obesity, owing to the role that it plays in the regulation of leptin signaling. PTP1B downregulates leptin receptor (LR) stim- uli by disrupting the autophosphorylation of JAK2 and subsequent LR phosphorylation, as well as the activation of STAT3, which mediates the transcription of target genes [10,11] (Figure 1). On the other hand, it has been reported that PTP1B can block the induction of cell proliferation and cell survival via the negative regulation of the signaling cascade linking ErbB2-PTP1B-Src kinase, which contributes to the tumor-suppressor function of

PTP1B in cancer cells [12–14] (Figure 1). However, this last role of PTP1B has become increasingly controversial; for an extensive review, the reader is referred to [15,16]. The above-mentioned controversy highlights the relevance of developing therapies targeting

PTP1B in these diseases.

Figure 1. Role of PTP1B in the signal pathway for type 2 diabetes, obesity, and cancer.

Accordingly, the development of PTP1B inhibitors has increased considerably for the treatment of these diseases. Nevertheless, PTP1B inhibitors have not progressed beyond the preclinical stage due to bioavailability and specificity challenges [17,18]. One of the principal hindrances is the chemical environment of the PTP1B active site, which is highly polar; therefore, it attracts negatively charged molecules with poor membrane permeability and limited oral bioavailability [19]. Regarding selectivity, the PTP family is characterized by an exceptionally high degree of sequence conservation across active sites [20]. T-cell protein tyrosine phosphatase (TCPTP) is the closest homolog of PTP1B [21,22]. It has been reported that mice lacking TCPTP die 5 weeks after birth due to defects in immune function and hematopoiesis failure [23]. In contrast, PTP1B knockout mice were reported to have a normal life span [24]. Therefore, it is important to consider these challenges in the design of PTP1B inhibitors.

Moreover, drug development is a costly and complex process that consumes a lot of time—around 10–15 years [25,26]. Recently, computer-assisted drug design (CADD) has become a crucial component used by the pharmaceutical industry and academic institutions

Pharmaceuticals 2022, 15, 866 3 of 22 to decrease costs and is a huge time saver due to the minimization of laboratory work and experimentation. With this review, we aim to present the efforts made to obtain PTP1B inhibitors through CADD, with particular focus on the protein sites used to this end, as well as the computational strategy, supported by the inhibitory activity evaluated in vitro.

Our review included only articles published during this century and focused on PTP1B as a target for type 2 diabetes drug design. The research was carried out using various groups of keywords, such as PTP1B inhibitors, virtual screening, molecular docking, pharmacophore modeling, 3D-QSAR, and computational drug design.

2. PTP1B Structure and Target Sites PTP1B, a ubiquitously expressed classical non-receptor PTP, is encoded by the PTPN1 gene. This enzyme hydrolyzes phosphotyrosine (pTyr)-containing proteins. In the cell, it is a protein of ~50 kDa (435 amino acids) located in the endoplasmic reticulum; how- ever, it was originally isolated from a human placenta as a 37 kDa protein that includes the catalytic domain (residues 1–321) [27–29]. Structurally, the enzyme is formed by an

N-terminal catalytic domain, two proline-rich sequences, and a C-terminal hydrophobic region (35 residues), which serves to attach the enzyme to the membrane of the endoplasmic reticulum [28,30,31]. Furthermore, it contains a regulatory segment of ~115 residues on the

C-terminal side of the catalytic domain [27] (Figure 2).

Figure 2. PTP1B catalytic domain structure. The image highlights the different sites where inhibitors have been reported.

PTP1B was the first PTP structure reported at high resolution [32]. To date, 274 human

PTP1B structures have been deposited in the Protein Data Bank (PDB, www.rcsb.org, ac- cessed on 1 February 2022). Of these, around two hundred twenty-five structures are in complex with different ligands: nine in the apo form and the rest with some mutations or chemical modifications, all with a resolution ranging from 1.5 to 3.3 Å. Most crystallo- graphic complexes are formed with competitive inhibitors bound at the PTP1B active site.

Nevertheless, there are some complexes with inhibitors bound at distinct sites, such as the

C-terminal region of the catalytic domain (helix α9) [33] and at a site formed by helices α3, α6, and α7 called an allosteric site [34] (Figure 2).

Pharmaceuticals 2022, 15, 866 4 of 22 2.1. Active and Secondary Sites

The PTP1B active site is formed by several loop regions (P-, WPD-, Q-, E-, and pTyr loops) and a secondary site (Figure 2). The phosphate-binding loop, i.e., the P loop or

PTP loop (residues 214–221), contains the conserved signature motif VHCSXGXGR[T/S]G, including the catalytic Cys215 and the invariant Arg221, which provides specificity for pTyr in classical PTPs [20,35]. The WPD loop (residues 179 to 189) acts as a flexible gate to the active site that can take closed (active) and open (inactive) conformations, where substrate binding only occurs when the loop is in the open state [35,36]. Another loop is the Q loop (residues 262 to 266), which contains conserved Glu262 that coordinates the water molecule necessary for hydrolysis of the thiophosphate intermediate [35]. The E loop contains multiple conserved residues; it has been suggested that this loop coordinates the dynamics of the WPD loop [37]. The most important residue is the conserved Lys120, which interacts with the catalytic aspartate (Asp181) of the WPD loop (in its closed conformation) by a hydrogen bond; this interaction stabilizes substrate-bound conformation [38]. Finally, the pTyr loop, which is present in all classical protein tyrosine phosphatases, is considered a pTyr recognition loop and is responsible for the selectivity of pTyr over pSer/pThr [37]. It is characterized by the sequence NXXKNRY, where Tyr46 recognizes the pTyr residue of the substrate and facilitates its access to the active site through electrostatic interactions,

Asn44 strengthens the interaction between this residue and active-site residues by forming hydrogen bonds, and Arg45 stabilizes the loop [35,39,40]. All these conserved loops structures are relevant for phosphatase activity and are required for several activities, such as substrate recognition, binding, and catalysis [41].

On the other hand, an additional pocket has been described, called the second aryl phosphate-binding site, B site, or secondary site. This is an important non-conserved site that regulates the substrate specificity [42,43]. It was discovered through an unexpected binding mode observed in the complex with the compound bis-(para-phosphophenyl) methane [43]. The most important residues in this site are Arg24 and Arg254; their guani- dinium moieties interact with oxygen atoms of the proximal phosphate and participate in the recognition of diphosphorylated substrates [42].

2.2. Allosteric Sites As previously mentioned, two allosteric sites have been reported in PTP1B: the

C-terminal segment (helix α9, residues 367–394) [33] and a site formed by helices α3, α6, and α7 [34]. The first site was identified using a long form of PTP1B (residues 1–393) in a complex with compound MSI-1436 (trodusquemine). NMR studies indicated that the tro- dusquemine primary binding site is located between residues 367 and 394 in helix α9 [33].

The other site was discovered by crystalizing PTP1B in complex with benzofuran derivatives. This site is a hydrophobic pocket formed by the side chains of Leu192, Phe196, and Phe280 and is located between the α7, α3, and α6 helices. It was observed that when inhibitors interacted with these helices, especially α7, closure of the WPD loop was prevented [34].

3. Computational Strategies Applied to Discover PTP1B Inhibitors

A considerable number of PTP1B inhibitors have been reported in recent decades.

Many have not only been discovered by experimental procedures but also by using compu- tational methods. Such methods have allowed for the successful development of selective and potent PTP1B inhibitors, in addition to guiding the optimization of different scaf- folds [44–49]. Molecular docking, virtual screening, pharmacophore modeling, and QSAR are some of the strategies used to this end and will be briefly described hereafter.

3.1. Virtual Screening Virtual screening is a strategy that permits the search for molecules with potential biological activity in large chemical libraries using a computational model [50,51]. Many computational models can be employed to perform virtual screening analysis. They can be

Pharmaceuticals 2022, 15, 866 5 of 22 categorized as ligand-based and receptor-based virtual screening. Ligand-based methods, for which no information on the receptor is necessary, leverage the information provided by a compound or a set of compounds that is active on the desired target to identify other molecules in the database with similar structural characteristics [52]. On the other hand, receptor-based strategies require knowledge of the 3D structure of the target receptor binding site to select compounds according to their likelihood to bind to the receptor. These involve molecular docking of each ligand to the binding site of the target. In both categories, the obtained information is then used to rank the compounds to select and experimentally evaluate a small subset for biological activity [53]. In addition, the virtual screening approach allows for screening of molecules that do not necessarily exist physically but which can be obtained through purchase or synthesis, enriching ligand libraries and saving time and money [54]. However, this computational approach is incapable of correctly ranking all the molecules in a library or finding all possible active compounds due to the inaccuracy of the scoring functions employed to identify active molecules [55]. The reader is referred to [56–59] for a comprehensive review.

3.2. Molecular Docking Molecular docking predicts the binding mode of chemical entities within the targeting cavity of the receptor of interest and provides an estimated binding affinity value through a search algorithm and energy-scoring function [60–62]. The common steps to carry out this approach are as follows: selection of target and ligand 3D structures, followed by preparation of those structures, depending on the requirements of the molecular docking protocol being employed [63,64]. Three types of docking can be chosen: rigid, semi- flexible, or flexible docking. For rigid docking, both the receptor and ligand are kept in a rigid position [61]. Semi-flexible involves a motionless receptor, whereas ligand flexibility is permitted, which allows for a faster and more direct process [64]. Flexible docking is much more computationally intensive than rigid docking, owing to flexible ligands and receptors [65]. Additionally, the results obtained with this tool can be improved by combining different scoring functions to obtain a consensus score [66]. On the other hand, other scoring functions allow for establishment of a new molecule by screening small compounds (fragments) in a receptor cavity; this is called fragment-based docking. This strategy helps to optimize hits, improving the interaction at the binding site, as well as their physicochemical, pharmacokinetic, and toxicological properties, and new chemical libraries are generated to be synthesized [67]. The reader is referred to [68–70] for a comprehensive review.

3.3. Pharmacophore Modeling Another strategy to select molecules from large libraries is pharmacophore modeling, which allows for selection of compounds with similar chemical and physical features, assuming that they have related biological activity [71,72]. A pharmacophore model can be built by superposing a set of active molecules and extracting common chemical features that are necessary for their biological activity; this process is called ligand-based pharma- cophore modeling [44]. Moreover, a structure-based pharmacophore modeling strategy can be followed. This consists of obtaining the essential chemical features for the optimal interaction between a biological receptor and a ligand; however, it is necessary to know the receptor 3D structure [44,45]. The reader is referred to [73,74] for a comprehensive review.

3.4. QSAR Quantitative structure–activity relationship (QSAR) is another popular strategy ap- plied to the discovery of active molecules. QSAR consists of building mathematical models that statistically correlate the chemical structure with biological/toxicological properties by regression and classification methods [75,76]. In turn, this method can be catego- rized into 2D and 3D-QSAR. The 2D strategy calculates and compares compound prop- erties in order to find similar molecules with which the compound is being compared

Pharmaceuticals 2022, 15, 866 6 of 22 (query molecule) [77]. On the other hand, 3D-QSAR relies not only on chemical structures but also on 3D coordinates of atoms to correlate with biological activity and is divided into alignment-based and alignment-independent techniques [78]. The reader is referred to [79–81] for a comprehensive review.

4. Development of PTP1B Inhibitors through Computational Approaches

In this section, we describe all the studies performed in the last century using a computational tool as the principal strategy to find PTP1B inhibitors and supported with in vitro studies.

In the year 2000, selective PTP1B inhibitors against leukocyte common antigen- related phosphatase (LAR), receptor protein tyrosine phosphatase α (PTPα), and vaccinia

H1-related protein phosphatase (VHR) were identified. These inhibitors were discovered by screening approximately 150,000 compounds with a virtual screening approach. From these compounds, twenty-five molecules were selected according to chemical diversity, interactions, overall fit with the enzyme active site, solubility, chemical stability, commercial availability, and cost. Seven compounds showed a high affinity for PTP1B (Ki = 21–510 µM); compound 2 (2-nitrobenzanthrone, Figure 3) was the most potent inhibitor (Ki = 21 µM) and exhibited selectivity against LAR, PTPα, and VHR (threefold higher for PTP1B). Fur- thermore, this compound was a mixed-type inhibitor [82]. Later, Doman and colleagues compared two methods to identify PTP1B inhibitors: virtual and high-throughput screen- ing (VS and HTS, respectively). In this study, 235,000 and 400,000 compounds were assessed by VS and HTS, respectively. A total of 127 hits from VS and 85 hits from HTS showed

IC50 values <100 µM. Surprisingly, the most potent molecules were discovered by VS, and the hit rate was enhanced 1700-fold compared to HTS, with compound 1 (Figure 3) being the most notable molecule for its inhibitory activity (IC50 = 4.1 µM) [48]. Two years later, another successful case was published by Lau and colleagues. They designed a series of benzotriazole phenyldifluoromethylphosphonic acids through molecular docking on the PTP1B crystal structure. Biphenylphosphonic acid (compound 19, Figure 3) was the most potent PTP1B inhibitor, with an IC50 = 3 nM. In addition, this series of inhibitors was evaluated in several phosphatases, and a moderate selectivity against T-cell protein tyrosine phosphatase (TCPTP) was observed [83]. In 2005, PTP1B inhibitors were designed by optimizing the scaffold 1,2,5-thiadiazolidin-3-one-1,1-dioxide through molecular dock- ing. The analysis indicated that a carbonyl moiety was necessary because it mimics the water-mediated interaction with PTP1B; additionally, the orthogonal orientation between the two rings was significant. These data were corroborated by NMR experiments and enabled identification of compound 10 (Figure 3), the most potent inhibitor (IC50 = 2.47 µM) compared with the other designed molecules [84].

The following year, a series of monocyclic thiophenes were designed through the same computational strategy and guided by X-ray cocrystal structural information. It was observed that a hydrogen bond with Asp48 was key to achieving improved inhi- bition against PTP1B. Therefore, a carboxylic group was incorporated to promote an electrostatic interaction with Arg47, resulting in significant improvement in inhibitory activity (Ki = 0.14 µM, compound 36, Figure 4) and achieving a 236 and >1000 selectiv- ity ratio against protein tyrosine phosphatase receptor type C (CD45) and LAR, respec- tively, although selective inhibition vs. TCPTP was not achieved (Ki = 0.18 µM) [85].

Two years later, these authors further pursued the optimization of thiophenes through molecular modeling, considering interactions with Arg24. The structural modification that they included was to remove the N-sulfonyl piperidine, and several side chains were employed to obtain hydrogen bonds with Arg24, which were confirmed by PTP1B- inhibitor crystal structures. The analogous chloro derivative (compound 33, Figure 4) was the most potent inhibitor (Ki = 4 nM); however, its selectivity was not enhanced relative to TCPTP [86]. Wilson and colleagues optimized compound 3 by molecular modeling, guided by X-ray analysis of the PTP1B-compound 3 complex structure. Com- pound 35 (5-(3-{[1-(benzylsulfonyl)piperidin-4-yl]amino}phenyl)-3-(carboxymethoxy)-4- Pharmaceuticals 2022, 15, 866

7 of 22 chlorothiophene-2-carboxylic acid, Figure 4) was the most active, with subnanomolar activ- ity against PTP1B (Ki = 0.00068 µM), and compound 32 (4-Bromo-3-carboxymethoxy-5-[3-(1- phenylmethanesulfonylpiperidin-4-ylamino)phenyl]thiophene-2-carboxylic acid, Figure 4), with a Ki = 0.004 µM, resulted in significant selectivity against CD45 (Ki = 77 µM) and LAR (Ki = >500 µM) phosphatases. In addition, compound 54 (4-Bromo-3-carboxymethoxy-5-(3- {[1-(2,6-dimethylphenylcarbamoyl)piperidin-4-ylmethyl]amino}phenyl)thiophene-2- carboxylic acid, Figure 4) showed selectivity between PTP1B and TCPTP (three times,

Ki = 0.009 µM). Furthermore, pharmacokinetics studies determined that molecule 32 dis- played an active glucose uptake mechanism into hepatocytes [87]. In the same year, pharmacophore and QSAR approaches were used to discover potent PTP1B inhibitors.

Here, previously PTP1B inhibitors were employed to build a pharmacophoric model. The best binding hypothesis was integrated into a QSAR equation, and it was used to carry out a 3D search query to screen the National Cancer Institute database. Furthermore, the selected hits were filtered according to Lipinski’s rules. The five compounds with the high- est ranking were evaluated in vitro, with IC50 values from nanomolar to low micromolar (0.47–3.30 µM), with compound 158 (Figure 4) being the most potent [88].

Figure 3. Structure of the most potent PTP1B inhibitors reported between 2000 and 2005 discovered through computational approaches.

Pharmaceuticals 2022, 15, 866 8 of 22 Figure 4. Structure of the most potent PTP1B inhibitors reported between 2006 and 2008 discovered through computational approaches.

In 2009, another study identified new PTP1B inhibitors through virtual screening. The docking library was taken from the latest version of the chemical database distributed by InterBioScreen. The compounds of this library were selected with drug-like filters and without reactive functional groups. This allowed for attainment of a database with

85,000 compounds instead of the 350,000 originals. Additionally, the authors modified the scoring function of the docking software, implementing a new solvation model. The

225 top-scored compounds were evaluated; 21 compounds had more than 90% inhibition at 100 µM, 9 molecules were identified with IC50 values ranging from 10 to 50 µM, and compound 4 (thiazolidine-2,4-dione derivative, Figure 5) was found to be the most po- tent [49]. On the other hand, Saxena and colleagues built a 3D-QSAR model (CoMFA model) in order to obtain three N-[2-(4-methoxy-phenyl)ethyl]ace amide derivatives: compounds 3a (N-[2-(4-methoxyphenyl)ethyl]-2-naphthalen-1-yl-acetamide, Figure 5),

3b (N-[2-(4-Methoxyphenyl)ethyl]-2-(2-nitrophenyl)-acetamide, Figure 5), and 3c (N-[2-(4- Methoxyphenyl) ethyl]-2-phenoxy-acetamide, Figure 5). The model predicted that the order of the inhibitory activity would be 3a > 3b > 3c, and the observed order was found to be similar: 3a (IC50 = 69 µM) > 3c (IC50 = 74 µM) > 3b (IC50 = 87 µM). Furthermore, molecules

3a, 3b, and 3c administered at a dose of 100 mg/kg in two in vivo models decreased blood sugar levels by 25.1%, 19.8%, and 24.6%, in a sucrose-loaded rat model and 21.4%, 17.5%, and 20.6% in a streptozotocin-induced diabetic rat model, respectively [89]. A molecular- Pharmaceuticals 2022, 15, 866

9 of 22 docking-guided design allowed for the synthesis of a series of di-indolinone derivatives.

This strategy led to the discovery of PTP1B inhibitors with an IC50 in the low micromolar range. Compounds 22 (1-[5-(5-bromo-2-Oxo-1,2-dihydroindol-3-ylidenemethyl)furan-2- ylmethyl]-1H-indole-2,3-dione, Figure 5) and 32 (1-[5-(5-chloro-2-Oxo-1,2-dihydroindol- 3-ylidenemethyl)furan-2-ylmethyl]-5-chloro-1H-indole-2,3-dione, Figure 5) showed high inhibitory activity (IC50 = 2.8 µM and 2.3 µM, respectively). In addition, both molecules displayed selectivity over other homologous PTPs, such as TCPTP, Src homology-2 protein phosphatase-1 (SHP-1), and LAR of least 4 to 43 times, with IC50 values for TCPTP of 11.5 and 18.8 µM, respectively, and >100 µM for the other phosphatases [90].

Figure 5. Structure of the most potent PTP1B inhibitors reported between 2009 and 2012 discovered through computational approaches.

In 2013, various authors reported additional PTP1B inhibitors by employing com- putational tools. Chandrasekharappa et al. designed a series of benzimidazole and ben- zoxazole molecules based on molecular docking. The best compounds were selected by employing a flexible docking method, with both PTP1B and TCPTP crystal structures con- sidered. These molecules were synthesized and assessed in PTP1B and TCPTP. Compound

31d (2-((4-(2-(benzo[d]oxazol-2-yl)-2-(N,N-(4-chlorobenzyl)sulfamoyl)ethyl)phenyl)amino)- 2-oxoacetic acid, Figure 6) had the highest affinity for PTP1B (Ki = 6.7 µM), but it was not selective [91]. On the other hand, applying a high-throughput virtual screening strategy using the ZINC and IBS databases, a new inhibitor of PTP1B was discovered: ZINC ID:

ZINC022765569 (3-(2-(1H-benzo[d]imidazol-2-ylthio)acetamido)benzoic acid, Figure 6).

This compound inhibited 24% at 10 µM and decreased the glucose uptake by 18% in L6 muscle cells at 50 µM [92]. Furthermore, this inhibitor was taken as a starting point, and through molecular docking studies, a new series of PTP1B inhibitors was developed. Based on the predicted binding mode, different modifications were proposed, such as a methyl

Pharmaceuticals 2022, 15, 866 10 of 22 substitution at position 5 in the A ring, a substitution in the benzo ring of benzimida- zole, and the replacement of the benzimidazole ring by phenyl oxadiazole. Two series of compounds were prepared, and the two most potent compounds, molecules 10c (3- (2-(5-Methoxy-1H-benzo[d]imidazol-2-ylthio)acetamido)-4-methylbenzoic acid, Figure 6) and 10e (2-Benzo[d]thiazol-2-ylthio)acetamido)-4-methylbenzoic acid, Figure 6), showed an IC50 value of 8.2 and 8.5 µM, respectively [93]. Diphenyl ether derivatives were also identified as PTP1B inhibitors through virtual screening. The study was carried out in both PTP1B and TCPTP using an in-house compound database. From here, forty-three compounds were prioritized based on the docking scores. Compound AU-2439 (Figure 6) was the most potent, with an IC50 of 43 µM. Additionally, it was found to be a selective inhibitor with fivefold selectivity for PTP1B over TCPTP (IC50 =230 µM) [94]. In another study, PTP1B inhibitors were discovered via an integrated molecular design strategy of pharmacophore-oriented scaffold hopping based on the template structure of Ertiprotafib.

The information obtained from the interaction mode of Ertiprotafib with PTP1B simulated by molecular docking helped to develop a pharmacophore model for Ertiprotafib. Ac- cordingly, twenty-one molecules from five distinct structural classes were designed and synthesized. Of these, nine molecules significantly inhibited PTP1B with a percentage of inhibition higher than 80% at 100 µM. The two most active compounds were 3a and 4e (Figure 6), exhibiting an IC50 value of 1.3 and 3.9 µM, respectively [46]. Imidazolidine-2,4- dione derivatives were reported as selective PTP1B inhibitors using virtual screening and molecular docking with the core hopping method. The core hopping algorithm helped to find the cores attaching to the scaffold using fragments from the ZINC database. A total of fifty molecules were docked at the active site of PTP1B and TCPTP and; consequently, twelve compounds were synthesized and assessed in both PTP1B and TCPTP. Overall, most molecules were potent and selective, with the compound designed as #h (Figure 6) being the most selective, with a selectivity index of almost 34 times PTP1B (IC50 =4.1 µM) over TCPTP (IC50 > 130 µM) [95].

A year later, the same research group designed additional selective inhibitors of PTP1B over TCPTP. In this case, the strategies employed were 3D QSAR, pharmacophore model- ing, and virtual screening. All methods were carried out in both enzymes, PTPB and TCPTP, in order to increase the possibility of discovering selective inhibitors. An in-house chemical database was screened, and eight new PTP1B inhibitors were reported. Among these inhibitors, compound 1 (ethyl 6-(2-(4-oxo-4,5,6,7-tetrahydro-3H-cyclopenta [4,5] thieno[2,3- d]pyrimidin-3-yl)acetamido)nicotinate, Figure 7) was the most successful, showing selectiv- ity of eight times for PTP1B (IC50 = 15 µM) over TCPTP (IC50 > 125 µM) [44]. In the same year, another set of PTP1B inhibitors was identified through pharmacophore modeling, docking, and scaffold-hopping techniques. These approaches allowed for prioritization of ten molecules for synthesis from a library of eighty-six compounds. These compounds inhibited PTP1B in the micromolar range, and characterization of the most potent inhibitor (compound 115, N-benzyl-N-(2-hydroxy-2-phenylethyl)-2, 4, 6-trimethyl benzene sulfon- amide, Figure 7) showed that it improved oral glucose tolerance and enhanced insulin resistance by restoring the insulin level and normalizing the serum lipid profile when assessed in both C57BL/KsJ-db/db mice and an STZ-induced diabetic rat model. Further- more, this compound augmented the insulin action by modulating the expression of genes involved in insulin signaling, such as IRS 1-2, PI3K, PTPN1, Akt2, AMPK, and PPAR-α.

Other experiments corroborated the antiadipogenic effect of this compound on 3T3L-1 cells, as well as its inhibition of lipid accumulation induced by MDI. In addition, it showed a bioavailability of around 10% in rats after 30 mg/kg oral dosing [96].

Pharmaceuticals 2022, 15, 866 11 of 22 Figure 6. Structure of the most potent PTP1B inhibitors reported in 2013 discovered through compu- tational approaches.

Pharmaceuticals 2022, 15, 866 12 of 22 Figure 7. Structure of the most potent PTP1B inhibitors reported in 2014 discovered through compu- tational approaches.

In 2015, a salicylic acid derivative was optimized by employing an in silico docking approach. Compound 20h (4-(4-(4-((N-(2-((4-carboxy-3-hydroxyphenyl)(4- cyclohexylbenzyl)amino)-2oxoethyl)quinoline-8-sulfonamido)methyl)-1H-1,2,3-triazol-1- yl)butanamido)-2hydroxybenzoic acid, Figure 8) exhibited improved potency (IC50 = 1.7 µM) compared with the original. Additionally, compounds 20h and 20f(4-(2-(4-((N-(2-((4-carboxy- 3-hydroxyphenyl)(4-cyclohexylbenzyl)amino)-2oxoethyl)quinoline-8-sulfonamido)methyl)-1H- 1,2,3-triazol-1-yl)acetamido)-2hydroxybenzoic acid, Figure 8) showed selectivity for PTP1B over protein tyrosine phosphatase σ (PTPσ) (approximately four to five times). The cy- totoxicities of PTP1B inhibitors 20f and 20h were determined in Chinese hamster ovary (CHO) cells and showed no toxicity at concentrations of 0.78 to 50 µM. Moreover, Western blot analysis in CHO cells indicated that these three inhibitors increased the levels of au- tophosphorylation of the insulin receptor (IR). The above results suggest that molecule 20h represents an interesting lead for further investigation as a PTP1B inhibitor [97]. A fragment- docking-oriented design approach was used to optimize a PTP1B inhibitor that contains a difluoromethylphosphonic acid group. As a result of docking simulations, the phosphoric acid moiety was replaced with a neutral N-(2,5-diethoxy-phenyl)-methanesulfonamide fragment in order to overcome the inconvenience of the negative charge. The IC50 values of this molecule and its synthesized analogs were in the nanomolar range. The most potent inhibitor, compound 15, N-{2,5-Diethoxy-4-[3-(4-methoxy-phenyl)-ureidomethyl]-phenyl}- methanesulfonamide, Figure 8), with an IC50 = 203 nM, resulted in a competitive inhibitor.

Furthermore, it was observed that it enhanced insulin receptor β phosphorylation and inhibitory activity on TCPTP < 50% at 25 µM [47]. In the same year, thiazolyl derivatives were identified as PTP1B inhibitors through molecular docking analysis in the active and allosteric sites of PTP1B. Four competitive and two allosteric inhibitors with Ki values in the range of 2 to 29 µM were reported, with compound A2 (Figure 8) being the most active inhibitor [98]. Novel (methanesulfonyl-phenyl-amino)-acetic acid methyl ester analogs were discovered as potent and selective PTP1B inhibitors through detailed analysis of the crystallographic complexes of the inhibitors containing a difluoromethyl phosphonate or carboxymethyl salicylic acid moiety and by applying fragment-based molecular docking.

The twelve designed compounds showed inhibitory activity in the nanomolar range; the most potent, compound P7, ([(4-{[{4-[(Benzyl-methanesulfonyl-amino)-methyl]-phenyl}- (4-ethoxy-benzenesulfonyl)-amino]-methyl}-phenyl)-methanesulfonyl-amino]-acetic acid methyl ester, Figure 8) had an IC50 of 222 nM. Additionally, this molecule was selective against TCPTP (IC50 = 1.86 µM) and decreased the dephosphorylation of IRβ in vitro [99]. A new series of amino-carboxylic-based pyrazole derivatives was designed using a structure- based pharmacophore model and molecular docking. In this work, the derivatives were classified into three groups, each with a different hydrophobic tail: 1,2-diphenyl ethanone, oxadiazole, and dibenzyl amines. The oxadiazole derivatives (Ki range of 4-9 µM) and

Pharmaceuticals 2022, 15, 866 13 of 22 dibenzyl amines (Ki range of 4-11 µM) were the most potent, especially compound 16i (5-amino-1-[4-[[(3,4-dimethoxyphenyl)methyl-[(4- fluorophenyl), Figure 8). Furthermore, these compounds were stable in rodent liver microsomes, and dibenzyl amine derivatives had better cell permeability in PAMPA than ethanone and oxadiazole derivatives [100].

Figure 8. Structure of the most potent PTP1B inhibitors reported between 2015 and 2017 discovered through computational approaches.

In 2018, Ganou et al. continued studying thiazolyl derivatives based on molecular docking analysis of the active and allosteric sites of PTP1B, in addition to considering thiomorpholine derivatives. Most of the compounds were competitive inhibitors (only two were uncompetitive), and the Ki range was between 2 and 23 µM. Compounds Tm2 and Tm4 (Figure 9) were the most potent inhibitors of all thiomorpholine and thiazolyl derivatives, with the same Ki value (2 µM). Furthermore, these molecules were selective versus TCPTP (no inhibition on TCPTP at 5 µM) [101]. Three new PTP1B inhibitors were

Pharmaceuticals 2022, 15, 866 14 of 22 also identified by performing a virtual screening of the Maybridge database. The best inhibitor (compound CD00466, Figure 9) exhibited an IC50 of 0.73 µM and selectivity of

31-fold over TCPTP (IC50 = 22.87 µM) [102]. On the other hand, several filters, such as molecular weight, fingerprints, molecular docking, and electrostatic similarity, were used in a virtual screening protocol. This methodology identified fifteen molecules with IC50 values in the range of 1-10 µM; among the molecules with the lowest IC50 value was compound

7 (ID: AK-968/41025519 obtained by Specs library, Figure 9). Furthermore, all of these molecules were structurally different, which allowed for exploration of diverse chemical nuclei [103]. In the same year, the structure of compound 15, designed by Du et al. in

2015 [47], was optimized via a fragment-docking-oriented design, obtaining 11 molecules.

The potency was improved, especially in the case of compound 8 (5-[3-(2,5-Diethoxy-4- methanesulfonylamino-benzyl)-ureido]-2-ethoxy-benzoic acid methyl ester, Figure 9), with an IC50 value of 18 nM. Furthermore, it increased insulin-stimulated glucose uptake in

L6 myotubes and was selective versus four phosphatases; the TCPTP/PTP1B ratio was

35 times (IC50 = 670 nM) [104]. Allosteric PTP1B inhibitors were also discovered via virtual screening by employing filters such as Lipinski’s rules of five, potential toxicity, PTP1B and

TCPTP pharmacophore-based screening, and molecular docking. Of the 393,932 screened compounds only 23 were selected to be assessed in vitro, and only 10 compounds showed inhibitory activity against PTP1B. The inhibition range was from 10 to 56% at a concentra- tion of 1.25 µM, with compound NIPER-10 (Figure 9) identified as the most potent [45]. In the following year, potent PTP1B inhibitors were designed via norathyriol optimization.

Analysis of the predicted binding mode of norathyriol suggested modifications of four hydroxyl groups at the 1, 3, 6, and 7 positions. The most potent inhibitor, molecule XWJ24 (3-((3-chloro-2-fluorobenzyl)oxy)-1,6,7-trihydroxy-9H-xanthen-9-one, Figure 9), showed an

IC50= 0.6 µM. Its characterization revealed that it was a competitive inhibitor and selective against different phosphatases, including TCPTP (IC50 = 2.7 µM) [105].

In 2020, Wu and colleagues identified a series of novel PTP1B inhibitors using a virtual screening workflow, molecular docking, and ADMET (absorption, distribution, metabolism, excretion, and toxicity) strategy. Compound ZINC39276654 was selected from the ZINC database by virtual screening approach to generate one thousand molecule derivatives.

Subsequently, one hundred generated derivatives were selected among the top-scored molecules and redocked into the PTP1B active site to choose the top ten compounds (1a–1j) to evaluate the inhibitory capacity. Compound 1a (ethyl 2-(2-bromophenyl)-4-((4- methoxyphenoxy)methyl)thiazole-5-carboxylate, Figure 10) exhibited the best inhibitory po- tency (IC50 = 4.46 µM) and acceptable predicted pharmaceutical properties. This molecule was selective for PTP1B over other phosphatases—3 times for TCPTP (IC50 = 12.28 µM) and

>22 times for the rest—Src homology region 2 domain-containing phosphatase 1 (SHP1), megakaryocyte protein tyrosine phosphatase 2), CDC25B (M-phase-inducer phosphatase

2 (MEG2), and LAR. However, compound 1g (ethyl 4-((4-chlorophenoxy)methyl)-2-(3- phenoxyphenyl)thiazole-5-carboxylate, Figure 10) showed the strongest selectivity for

PTP1B over the TCPTP (>9 times, IC50 = >100 µM) [106]. In the same year, a series of sev- enteen novel 4-thiazolinone derivatives that shared the scaffold of compound ZINC99459 was discovered by virtual screening. ADMET prediction (including human intestinal ab- sorption, blood–brain barrier, plasma protein binding, aqueous solubility, cytochrome P450

2D6 binding, and toxicity) indicated that these compounds showed good drug-likeness properties. Then, in vitro enzyme inhibitory activity was determined on PTP1B and other phosphatases. Compound 7p (Figure 10) was identified as the most potent (IC50 = 0.92 µM) and selective inhibitor, >100 times (IC50 = >100 µM) against TCPTP, SHP2, CDC25B, LAR, and MEG2 and at least 24 times against SHP1 [107]. Another effort to find PTP1B inhibitors via computational tools was a work reported by Yang and colleagues. A natural product library of approximately 122,000 compounds was screened by different in silico filters, such as the 3D-QSAR model, 2D fingerprint similarity, and molecular docking. The twenty-six molecules prioritized by virtual screening were explored to determine their inhibition against PTP1B. The most active compounds, coumarin derivatives, showed an IC50 in the

Pharmaceuticals 2022, 15, 866 15 of 22 micromolar range. Among them, nine molecules were further evaluated against several phosphatases showing selective inhibition for PTP1B over the other phosphatases, includ- ing TCPTP. The most active inhibitor was H17 (IC50 = 2.05 µM, Figure 10), but it was not selective (inhibitory activity on TCPTP: 73.5% at 10 µM). The most selective compounds were H8 and H20 (Figure 10), with a selectivity of approximately 10 times (inhibitory activity < 10% at 10 µM) with respect to TCPTP, CD45, LAR, and VHR phosphatases [108].

Figure 9. Structure of the most potent PTP1B inhibitors reported between 2018 and 2019 discovered through computational approaches.

Pharmaceuticals 2022, 15, 866 16 of 22

Figure 10. Structure of the most potent PTP1B inhibitors reported in 2020 discovered through computational approaches.

In 2021, the scaffold-hopping approach was employed to optimize the structure of compound 1 based on the replacement of the pyrrole ring by azoles. The new com- pounds showed better drug-like properties than compound 1 according to the results obtained by means of in silico tools. Most molecules showed good inhibitory activ- ity within the IC50 range of 0.46–2.17 µM. Among these compounds, compound 2 (4- methylimidazo[1,2-a]quinoxaline, IC50 = 0.49, Figure 11) and compound 9 (tetrazolo[1,5- a]quinoxaline, IC50 = 0.62, Figure 11) displayed the highest potency. Additionally, se- lectivity evaluation of these compounds against TCPTP showed that the most selec- tive was compound 2 (two times, inhibitory activity on TCPTP: 44% at 1 µM). This molecule also increased glucose uptake by 15% relative to control cells in phenotypic models [109]. Ma and colleagues discovered imidazolidine-2,4-dione derivatives as PTP1B inhibitors with structural diversity using virtual screening, scaffold hopping, ADMET prediction, and molecular docking. First, the compound CHEMBL213560, obtained by virtual screening, was optimized using the scaffold-hopping method. The designed com- pounds, with good ADMET results, were used to develop a molecular docking anal- Pharmaceuticals 2022, 15, 866

17 of 22 ysis. Fifteen compounds with high scores for PTP1B protein were selected to evalu- ate their biological activity. These molecules were assessed against PTP1B, Src homol- ogy region 2 domain-containing phosphatase 2 (SHP2), and LAR; compound 10 ((E)-4- (methoxycarbonyl)benzyl 4-((3-benzyl-4-(4-((4-(methoxycarbonyl)benzyl)oxy)benzylidene)- 2,5-dioxoimidazolidin-1-yl)methyl)benzoate, Figure 11) the highest PTP1B inhibition, with an IC50 of 2.07 µM. Moreover, this molecule had 10 times higher inhibitory capacity on

PTP1B than SHP2 and 60 times higher than that of LAR [110]. Finally, another study of integrated virtual screening consisting of fingerprint similarity search, structure-based phar- macophore models, and molecular docking was carried out to search for potential allosteric

PTP1B inhibitors from commercially available chemical libraries. Of 184,922 molecules, nine compounds were selected to be evaluated in vitro. Two compounds were the most active: H3 (IC50 = 0.72 µM, Figure 11) and H9 (IC50 = 1.59 µM, Figure 11). They were further evaluated against TCPTP and SHP2, displaying selective inhibition of PTP1B over both phosphatases (>60 times, IC50 = >100 µM) [111].

Figure 11. Structure of the most potent PTP1B inhibitors reported in 2021 discovered through computational approaches.

Pharmaceuticals 2022, 15, 866 18 of 22 5. Conclusions

A considerable number of PTP1B inhibitors has been reported as outstanding and potential hits or leads for new drugs against type 2 diabetes. Several potent and selective

PTP1B inhibitors have been identified via different computational tools. These studies reported compounds with IC50 and Ki values from the nanomolar to the micromolar range. Furthermore, some of these compounds were found to be selective on PTP1B over TCPTP, its closest homolog, with a selectivity range of 2 to 100 times. Moreover, when the characterization was far away, they showed the ability to improve glucose uptake. The PTP1B inhibitor design process remains challenging, which has led to many academic research laboratories and pharmaceuticals organizations continuing the search for effective and safe oral available compounds. Therefore, this review encourages the use of computational techniques and includes helpful information that increases the knowledge generated to date about PTP1B inhibition, with a positive impact on the route toward obtaining a new drug against type 2 diabetes with PTP1B as a molecular target.

Author Contributions: Conceptualization, A.T.-V., C.A.-D. and M.I.C.-A.; methodology, A.T.-V.,

C.A.-D. and M.I.C.-A.; formal analysis, M.I.C.-A., A.T.-V., C.A.-D., A.H.-C., R.C., M.V.-S. and E.S.-C.; writing—original draft preparation, A.T.-V., C.A.-D. and M.I.C.-A.; writing—review and editing,

M.I.C.-A., A.T.-V., C.A.-D. and E.S.-C. All authors have read and agreed to the published version of the manuscript.

Funding: This research received no external funding.

Institutional Review Board Statement: Not applicable.

Informed Consent Statement: Not applicable.

Data Availability Statement: Available data are presented in the manuscript.

Conflicts of Interest: The authors declare no conflict of interest.

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# 引用信息

Campos-Almazán, M.I.; Hernández-Campos, A.; Castillo, R.; Sierra-Campos, E.; Valdez-Solana, M.; Avitia-Domínguez, C.; Téllez-Valencia, A. 计算机辅助方法与实验方法协同设计2型糖尿病药物中的蛋白酪氨酸磷酸酶1B抑制剂:本世纪成就综述. Pharmaceuticals 2022, 15, 866. https://doi.org/10.3390/ph15070866

学术编辑:Paweł Kafarski

收稿日期:2022年6月11日

录用日期:2022年7月12日

发表日期:2022年7月14日

**出版商声明:** MDPI对已发表地图中的管辖权主张及机构隶属关系保持中立。

**版权:** © 2022 作者所有。

许可方:MDPI,瑞士巴塞尔。

本文为开放获取文章,依据知识共享署名许可协议(CC BY)的条款和条件进行分发(https://creativecommons.org/licenses/by/4.0/)。

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# 综述文章

## 计算机辅助方法与实验方法协同设计2型糖尿病药物中的蛋白酪氨酸磷酸酶1B抑制剂:本世纪成就综述

Mara Ibeth Campos-Almazán¹, Alicia Hernández-Campos², Rafael Castillo², Erick Sierra-Campos³, Mónica Valdez-Solana³, Claudia Avitia-Domínguez¹,* 和 Alfredo Téllez-Valencia¹,*

¹ 墨西哥杜兰戈州华雷斯大学医学与营养学院,Avenida Universidad y Fanny Anitúa S/N, 杜兰戈 34000, 墨西哥;maraicamp@gmail.com

² 墨西哥国立自治大学药学院药学系,Ciudad de Mexico 04510, 墨西哥;hercam@unam.mx (A.H.-C.); rafaelc@unam.mx (R.C.)

³ 墨西哥杜兰戈州华雷斯大学化学科学学院戈麦斯帕拉西奥校区,Avenida Artículo 123 S/N, Fracc. Filadelfia, 戈麦斯帕拉西奥 35010, 墨西哥;ericksier@gmail.com (E.S.-C.); valdezandyval@gmail.com (M.V.-S.)

* 通讯作者:claudia.avitia@ujed.mx (C.A.-D.); atellez@ujed.mx (A.T.-V.); 电话/传真:+52-6188271382 (C.A.-D. & A.T.-V.)

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## 摘要

蛋白酪氨酸磷酸酶1B(PTP1B)可使磷酸酪氨酸残基去磷酸化,是多种信号通路的重要调节因子,包括胰岛素、瘦素及ErbB信号网络等。因此,该酶被视为设计针对2型糖尿病、肥胖症和癌症新药的极具吸引力的靶点。迄今为止,已通过实验和计算方法开发出种类繁多的PTP1B抑制剂。本综述总结了以计算机辅助药物设计方法(虚拟筛选、分子对接、药效团建模和定量构效关系(QSAR))为主要策略、结合实验方法所发现的PTP1B抑制剂的研究成果,涵盖从本世纪初至本综述投稿时发表的文章,重点关注以发现2型糖尿病新药为目标的研究。本综述鼓励运用计算机辅助技术,并提供了有助于增进目前关于PTP1B抑制认知的有益信息,对以PTP1B为分子靶点开发2型糖尿病新药的研究路线具有积极意义。

**关键词:** PTP1B抑制剂;计算机辅助药物设计;分子对接;虚拟筛选;药效团建模;QSAR;2型糖尿病

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## 1. 引言

癌症、肥胖症和糖尿病是全球范围内的重大健康问题,每年分别导致约960万、280万和160万人死亡[1]。此外,这些疾病给卫生系统带来沉重的经济负担,当它们共存时负担更为沉重[2]。尽管目前已有多种口服和注射疗法可用于治疗这些疾病,但其应用受到疗效、不良反应和禁忌症的限制[3–7]。因此,这些疾病日益增长的患病率凸显了寻找新治疗药物的必要性。

在此背景下,蛋白酪氨酸磷酸酶1B(PTP1B)已被确立为针对这些疾病的药理学靶点。其底物参与多种细胞过程,包括胰岛素信号调控的葡萄糖稳态、食物摄入减少、能量消耗增加、细胞增殖等。PTP1B被视为治疗2型糖尿病的理想药物靶点,因为它可使胰岛素受体(IR)和胰岛素受体底物1(IRS-1)去磷酸化,从而使磷脂酰肌醇3-激酶(PI3K)-Akt下游通路失活,阻止葡萄糖转运蛋白4(GLUT4)的转位[8,9](图1)。此外,PTP1B因其在瘦素信号调节中的作用,作为肥胖症治疗的潜在优良靶点也备受关注。PTP1B通过干扰JAK2的自磷酸化及随后的LR磷酸化以及STAT3的激活来下调瘦素受体(LR)的刺激,而STAT3介导靶基因的转录[10,11](图1)。另一方面,据报道PTP1B可通过负调控连接ErbB2-PTP1B-Src激酶的信号级联来阻断细胞增殖和细胞存活的诱导,这有助于PTP1B在癌细胞中的抑瘤功能[12–14](图1)。然而,PTP1B的这最后一种作用日益引发争议;有关广泛综述请参阅文献[15,16]。上述争议凸显了开发靶向PTP1B治疗这些疾病的相关性。

**图1. PTP1B在2型糖尿病、肥胖症和癌症信号通路中的作用。**

因此,针对这些疾病的PTP1B抑制剂的开发已显著增加。然而,由于生物利用度和特异性方面的挑战,PTP1B抑制剂尚未进入临床前阶段之后的开发[17,18]。主要障碍之一是PTP1B活性位点的化学环境具有高度极性,因此吸引带负电荷的分子,导致膜通透性差和口服生物利用度有限[19]。在选择性方面,PTP家族的特征是活性位点之间具有极高的序列保守性[20]。T细胞蛋白酪氨酸磷酸酶(TCPTP)是PTP1B最接近的同源物[21,22]。据报道,缺乏TCPTP的小鼠在出生后5周因免疫功能缺陷和造血衰竭而死亡[23]。相反,PTP1B基因敲除小鼠据报道具有正常寿命[24]。因此,在PTP1B抑制剂的设计中考虑这些挑战非常重要。

此外,药物开发是一个成本高昂且复杂的过程,耗时约10–15年[25,26]。近年来,计算机辅助药物设计(CADD)已成为制药工业和学术机构降低成本和大幅节省时间的关键组成部分,其通过减少实验室工作和实验来实现。本综述旨在介绍通过CADD获取PTP1B抑制剂的研究成果,重点介绍用于此目的的蛋白质位点以及计算策略,并辅以体外评估的抑制活性数据。本综述仅收录本世纪发表的文章,重点关注PTP1B作为2型糖尿病药物设计靶点的研究。研究使用多组关键词进行检索,如PTP1B抑制剂、虚拟筛选、分子对接、药效团建模、3D-QSAR和计算药物设计。

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## 2. PTP1B结构与靶点位点

PTP1B是一种广泛表达的经典非受体型PTP,由PTPN1基因编码。该酶水解含磷酸酪氨酸(pTyr)的蛋白质。在细胞中,它是一种约50 kDa的蛋白质(435个氨基酸),位于内质网中;然而,它最初是从人胎盘中分离出的37 kDa蛋白质,包含催化结构域(残基1–321)[27–29]。从结构上看,该酶由N端催化结构域、两个富含脯氨酸的序列和C端疏水区域(35个残基)组成,后者用于将酶锚定在内质网膜上[28,30,31]。此外,它在催化结构域的C端侧含有一个约115个残基的调节片段[27](图2)。

**图2. PTP1B催化结构域结构。图像突出显示了已报道抑制剂结合的不同位点。**

PTP1B是首个被报道高分辨率结构的PTP[32]。截至目前,已有274个人类PTP1B结构存入蛋白质数据库(PDB,www.rcsb.org,2022年2月1日访问)。其中,约225个结构与不同配体形成复合物:9个为无配体形式,其余则具有某些突变或化学修饰,分辨率范围为1.5至3.3 Å。大多数晶体复合物由结合在PTP1B活性位点的竞争性抑制剂组成。然而,也有一些复合物中抑制剂结合在不同位点,如催化结构域的C端区域(α9螺旋)[33]以及由α3、α6和α7螺旋形成的位点(称为变构位点)[34](图2)。

### 2.1 活性位点和次级位点

PTP1B活性位点由多个环区域(P环、WPD环、Q环、E环和pTyr环)和一个次级位点组成(图2)。磷酸盐结合环,即P环或PTP环(残基214–221),包含保守的特征基序VHCSXGXGR[T/S]G,包括催化性Cys215和保守的Arg221,后者为经典PTP中的pTyr提供特异性[20,35]。WPD环(残基179至189)充当活性位点的柔性门控,可呈现关闭(活性)和开放(非活性)构象,底物结合仅在环处于开放状态时发生[35,36]。另一个环是Q环(残基262至266),包含保守的Glu262,它协调水解硫代磷酸中间体所需的水分子[35]。E环包含多个保守残基;据认为该环协调WPD环的动力学[37]。最重要的残基是保守的Lys120,它通过氢键与WPD环的催化天冬氨酸(Asp181)(在其关闭构象中)相互作用;这种相互作用稳定了底物结合构象[38]。最后,pTyr环存在于所有经典蛋白酪氨酸磷酸酶中,被认为是pTyr识别环,负责pTyr相对于pSer/pThr的选择性[37]。其特征序列为NXXKNRY,其中Tyr46识别底物的pTyr残基并通过静电相互作用促进其进入活性位点,Asn44通过形成氢键加强该残基与活性位点残基之间的相互作用,Arg45则稳定该环[35,39,40]。所有这些保守环结构对磷酸酶活性至关重要,并且是底物识别、结合和催化等多种活性所必需的[41]。

另一方面,已描述了一个额外的口袋,称为第二芳基磷酸盐结合位点、B位点或次级位点。这是一个重要的非保守位点,调节底物特异性[42,43]。它是通过化合物双(对-磷酸苯基)甲烷复合物中观察到的意外结合模式发现的[34]。该位点中最重要的残基是Arg24和Arg254;它们的胍基与近端磷酸盐的氧原子相互作用,并参与二磷酸化底物的识别[42]。

### 2.2 变构位点

如前所述,PTP1B中已报道两个变构位点:C端片段(α9螺旋,残基367–394)[33]以及由α3、α6和α7螺旋形成的位点[34]。第一个位点是通过使用长形式PTP1B(残基1–393)与化合物MSI-1436(曲度喹胺)的复合物鉴定的。核磁共振研究表明,曲度喹胺的主要结合位点位于α9螺旋中的残基367至394之间[33]。另一个位点是通过PTP1B与苯并呋喃衍生物复合物的结晶发现的。该位点是一个由Leu192、Phe196和Phe280侧链形成的疏水口袋,位于α7、α3和α6螺旋之间。据观察,当抑制剂与这些螺旋(尤其是α7)相互作用时,WPD环的关闭被阻止[34]。

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## 3. 应用于发现PTP1B抑制剂的计算策略

近几十年来,已报道了大量PTP1B抑制剂。其中许多不仅通过实验程序发现,还借助计算方法。这些方法已成功开发出选择性强、效力高的PTP1B抑制剂,并指导了不同骨架的优化[44–49]。分子对接、虚拟筛选、药效团建模和QSAR是用于此目的的部分策略,下文将简要介绍。

### 3.1 虚拟筛选

虚拟筛选是一种利用计算模型在大型化学库中搜索具有潜在生物活性分子的策略[50,51]。可用于执行虚拟筛选分析的计算模型很多,可分为基于配体和基于受体的虚拟筛选。基于配体的方法不需要受体信息,利用对目标靶点具有活性的化合物或一组化合物所提供的信息,从数据库中识别具有相似结构特征的其他分子[52]。另一方面,基于受体的策略需要了解靶受体结合位点的三维结构,以根据化合物与受体结合的可能性来筛选化合物。这涉及将每个配体与靶标结合位点进行分子对接。在这两类方法中,所获得的信息随后用于对化合物进行排序,以选择少量化合物进行实验评估其生物活性[53]。此外,虚拟筛选方法允许筛选不一定物理存在但可通过购买或合成获得的分子,从而丰富配体库并节省时间和金钱[54]。然而,由于用于识别活性分子的评分函数存在不准确性,这种计算方法无法正确对库中所有分子进行排序或找到所有可能的活性化合物[55]。有关全面综述请参阅文献[56–59]。

### 3.2 分子对接

分子对接预测化学实体在目标受体靶向腔内的结合模式,并通过搜索算法和能量评分函数提供估计的结合亲和力值[60–62]。执行此方法的常见步骤如下:选择靶标和配体的三维结构,然后根据所用分子对接方案的要求对这些结构进行准备[63,64]。可选择三种类型的对接:刚性、半柔性或柔性对接。刚性对接中,受体和配体均保持刚性位置[61]。半柔性对接涉及固定的受体,但允许配体柔性,从而实现更快速、更直接的过程[64]。柔性对接比刚性对接计算量大得多,因为配体和受体都具有柔性[65]。此外,可通过组合不同的评分函数来获得共识分数来改善该工具获得的结果[66]。另一方面,其他评分函数允许通过在受体腔中筛选小化合物(片段)来建立新分子,这称为基于片段的对接。该策略有助于优化命中化合物,改善结合位点的相互作用,以及其理化、药代动力学和毒理学性质,并生成新的化学库用于合成[67]。有关全面综述请参阅文献[68–70]。

### 3.3 药效团建模

从大型库中选择分子的另一种策略是药效团建模,它允许选择具有相似化学和物理特征的化合物,假设它们具有相关的生物活性[71,72]。药效团模型可通过叠加一组活性分子并提取其生物活性所必需的共同化学特征来构建;这一过程称为基于配体的药效团建模[44]。此外,可遵循基于结构的药效团建模策略。这包括获得生物受体与配体之间最佳相互作用所需的基本化学特征;但需要了解受体的三维结构[44,45]。有关全面综述请参阅文献[73,74]。

### 3.4 QSAR

定量构效关系(QSAR)是另一种应用于发现活性分子的流行策略。QSAR包括构建通过回归和分类方法将化学结构与生物/毒理学特性进行统计关联的数学模型[75,76]。该方法又可分为2D和3D-QSAR。2D策略计算和比较化合物性质,以找到与所比较化合物(查询分子)相似的分子[77]。另一方面,3D-QSAR不仅依赖化学结构,还依赖原子的三维坐标来与生物活性进行关联,并可分为基于叠合和不依赖叠合的技术[78]。有关全面综述请参阅文献[79–81]。

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## 4. 通过计算方法开发PTP1B抑制剂

本节描述了上个世纪以计算工具为主要策略寻找PTP1B抑制剂并经体外研究支持的所有研究。

2000年,通过虚拟筛选约150,000种化合物,发现了针对白细胞共同抗原相关磷酸酶(LAR)、受体蛋白酪氨酸磷酸酶α(PTPα)和痘苗病毒H1相关蛋白磷酸酶(VHR)的选择性PTP1B抑制剂。根据化学多样性、相互作用、与酶活性位点的整体匹配度、溶解度、化学稳定性、商业可用性和成本,从这些化合物中选出25种分子。七种化合物对PTP1B表现出高亲和力(Ki = 21–510 µM);化合物2(2-硝基苯并蒽酮,图3)是最强效的抑制剂(Ki = 21 µM),并对LAR、PTPα和VHR表现出选择性(对PTP1B的选择性高3倍)。此外,该化合物为混合型抑制剂[82]。随后,Doman及其同事比较了两种识别PTP1B抑制剂的方法:虚拟筛选和高通量筛选(分别为VS和HTS)。本研究通过VS和HTS分别评估了235,000和400,000种化合物。VS的127个命中化合物和HTS的85个命中化合物显示IC50值<100 µM。令人惊讶的是,最强效的分子是通过VS发现的,与HTS相比命中率提高了1700倍,其中化合物1(图3)因其抑制活性(IC50 = 4.1 µM)而最为突出[48]。两年后,Lau及其同事发表了另一个成功案例。他们通过PTP1B晶体结构的分子对接设计了一系列苯并三唑苯基二氟甲基膦酸。联苯基膦酸(化合物19,图3)是最强效的PTP1B抑制剂,IC50 = 3 nM。此外,该系列抑制剂在多种磷酸酶中进行了评估,观察到对T细胞蛋白酪氨酸磷酸酶(TCPTP)具有中等选择性[83]。2005年,通过分子对接优化1,2,5-噻二唑烷-3-酮-1,1-二氧化物骨架设计了PTP1B抑制剂。分析表明,羰基基团是必要的,因为它模拟了与PTP1B的水介导相互作用;此外,两个环之间的正交取向也很重要。这些数据通过核磁共振实验得到证实,并鉴定出化合物10(图3)为最强效抑制剂(IC50 = 2.47 µM),优于其他设计的分子[84]。

次年,通过相同的计算策略并在X射线共晶结构信息的指导下设计了一系列单环噻吩。据观察,与Asp48的氢键是实现PTP1B抑制改善的关键。因此,引入了羧基基团以促进与Arg47的静电相互作用,从而显著改善抑制活性(Ki = 0.14 µM,化合物36,图4),并对蛋白酪氨酸磷酸酶受体型C(CD45)和LAR实现了236倍和>1000倍的选择性比,尽管未实现相对于TCPTP的选择性抑制(Ki = 0.18 µM)[85]。两年后,这些作者通过分子建模进一步优化了噻吩类化合物,考虑了与Arg24的相互作用。他们所做的结构修饰是去除N-磺酰基哌啶,并使用多种侧链与Arg24形成氢键,这通过PTP1B-抑制剂晶体结构得到确认。类似的氯代衍生物(化合物33,图4)是最强效的抑制剂(Ki = 4 nM);然而,其相对于TCPTP的选择性未得到增强[86]。Wilson及其同事通过分子建模优化了化合物3,以PTP1B-化合物3复合物结构的X射线分析为指导。化合物35(5-(3-{[1-(苄基磺酰基)哌啶-4-基]氨基}苯基)-3-(羧基甲氧基)-4-氯噻吩-2-羧酸,图4)活性最高,对PTP1B具有亚纳摩尔活性(Ki = 0.00068 µM),化合物32(4-溴-3-羧基甲氧基-5-[3-(1-苯基甲磺酰基哌啶-4-基氨基)苯基]噻吩-2-羧酸,图4),Ki = 0.004 µM,对CD45(Ki = 77 µM)和LAR(Ki = >500 µM)磷酸酶具有显著选择性。此外,化合物54(4-溴-3-羧基甲氧基-5-(3-{[1-(2,6-二甲基苯基氨基甲酰基)哌啶-4-基甲基]氨基}苯基)噻吩-2-羧酸,图4)在PTP1B和TCPTP之间显示出选择性(3倍,Ki = 0.009 µM)。此外,药代动力学研究表明,分子32在肝细胞中显示出活性葡萄糖摄取机制[87]。同年,利用药效团和QSAR方法发现了强效PTP1B抑制剂。在此,使用先前的PTP1B抑制剂构建药效团模型。将最佳结合假设整合到QSAR方程中,并将其用于执行3D搜索查询以筛选美国国家癌症研究所数据库。此外,根据Lipinski规则对所选命中化合物进行过滤。对排名最高的五种化合物进行体外评估,IC50值从纳摩尔到低微摩尔(0.47–3.30 µM),其中化合物158(图4)效力最强[88]。

**图3. 2000年至2005年通过计算方法发现的最强效PTP1B抑制剂的结构。**

**图4. 2006年至2008年通过计算方法发现的最强效PTP1B抑制剂的结构。**

2009年,另一项研究通过虚拟筛选发现了新的PTP1B抑制剂。对接库取自InterBioScreen分发的最新版本的化学数据库。该库中的化合物经过类药性过滤基团和反应性官能团筛选。这使得数据库从原来的350,000种化合物缩减为85,000种。此外,作者修改了对接软件的评分函数,实现了新的溶剂化模型。对评分最高的225种化合物进行评估;21种化合物在100 µM下抑制率超过90%,9种化合物的IC50值在10至50 µM之间,化合物4(噻唑烷-2,4-二酮衍生物,图5)被发现效力最强[49]。另一方面,Saxena及其同事构建了3D-QSAR模型(CoMFA模型),以获得三种N-[2-(4-甲氧基苯基)乙基]乙酰胺衍生物:化合物3a(N-[2-(4-甲氧基苯基)乙基]-2-萘-1-基-乙酰胺,图5)、3b(N-[2-(4-甲氧基苯基)乙基]-2-(2-硝基苯基)-乙酰胺,图5)和3c(N-[2-(4-甲氧基苯基)乙基]-2-苯氧基-乙酰胺,图5)。模型预测抑制活性顺序为3a > 3b > 3c,观察到的顺序与之相似:3a(IC50 = 69 µM)> 3c(IC50 = 74 µM)> 3b(IC50 = 87 µM)。此外,分子3a、3b和3c在两种体内模型中以100 mg/kg剂量给药,在蔗糖负荷大鼠模型中分别降低血糖水平25.1%、19.8%和24.6%,在链脲佐菌素诱导的糖尿病大鼠模型中分别降低21.4%、17.5%和20.6%[89]。分子对接指导的设计使得一系列二吲哚酮衍生物得以合成。该策略发现了IC50在低微摩尔范围内的PTP1B抑制剂。化合物22(1-[5-(5-溴-2-氧代-1,2-二氢吲哚-3-亚基甲基)呋喃-2-基甲基]-1H-吲哚-2,3-二酮,图5)和化合物32(1-[5-(5-氯-2-氧代-1,2-二氢吲哚-3-亚基甲基)呋喃-2-基甲基]-5-氯-1H-吲哚-2,3-二酮,图5)显示出高抑制活性(IC50分别为2.8 µM和2.3 µM)。此外,两种分子对其他同源PTP(如TCPTP、Src同源区2蛋白磷酸酶-1(SHP-1)和LAR)显示出至少4至43倍的选择性,TCPTP的IC50值分别为11.5和188 µM,其他磷酸酶>100 µM[90]。

**图5. 2009年至2012年通过计算方法发现的最强效PTP1B抑制剂的结构。**

2103年,多位作者报告了利用计算工具发现的额外PTP1B抑制剂。Chandrasekharappa等人基于分子对接设计了一系列苯并咪唑和苯并噁唑分子。采用柔性对接方法选择最佳化合物,同时考虑了PTP1B和TCPTP的晶体结构。这些分子经合成后在PTP1B和TCPTP中进行评估。化合物31d(2-((4-(2-(苯并[d]噁唑-2-基)-2-(N,N-(4-氯苄基)磺酰氨基)乙基)苯基)氨基)-2-氧代乙酸,图6)对PTP1B亲和力最高(Ki = 6.7 µM),但不具有选择性[91]。另一方面,应用高通量虚拟筛选策略,使用ZINC和IBS数据库,发现了一种新的PTP1B抑制剂:ZINC ID: ZINC022765569(3-(2-(1H-苯并[d]咪唑-2-基硫基)乙酰氨基)苯甲酸,图6)。该化合物在10 µM下抑制24%,并在50 µM下使L6肌肉细胞的葡萄糖摄取降低18%[92]。此外,以该抑制剂为起点,通过分子对接研究开发了新一系PTP1B抑制剂。基于预测的结合模式,提出了不同的修饰,如A环5位的甲基取代、苯并咪唑苯环上的取代以及用苯基噁二唑替代苯并咪唑环。制备了两个系列的化合物,两种最强效的化合物——分子10c(3-(2-(5-甲氧基-1H-苯并[d]咪唑-2-基硫基)乙酰氨基)-4-甲基苯甲酸,图6)和10e(2-苯并[d]噻唑-2-基硫基)乙酰氨基)-4-甲基苯甲酸,图6)——IC50值分别为8.2和8.5 µM[93]。还通过虚拟筛选发现了二苯基醚衍生物作为PTP1B抑制剂。该研究在PTP1B和TCPTP中使用内部化合物数据库进行。根据对接评分优先选择了43种化合物。化合物AU-2439(图6)效力最强,IC50为43 µM。此外,发现它是选择性抑制剂,对PTP1B的选择性比TCPTP高5倍(IC50 = 230 µM)[94]。在另一项研究中,通过基于Ertiprotafib模板结构的药效团导向骨架跃迁的综合分子设计策略发现了PTP1B抑制剂。通过分子对接模拟的Ertiprotafib与PTP1B相互作用模式的信息有助于开发Ertiprotafib的药效团模型。据此,从五种不同结构类别中设计并合成了21种分子。其中,九种分子在100 µM下对PTP1B的抑制率显著高于80%。两种活性最强的化合物3a和4e(图6)IC50值分别为1.3和3.9 µM[46]。使用虚拟筛选和分子对接结合核心跃迁方法,报道了咪唑烷-2,4-二酮衍生物作为选择性PTP1B抑制剂。核心跃迁算法有助于使用ZINC数据库中的片段找到与骨架连接的核心。共有50种分子对接到PTP1B和TCPTP的活性位点,因此合成了12种化合物并在PTP1B和TCPTP中进行评估。总体而言,大多数分子具有强效力和选择性,其中设计的化合物#h(图6)选择性最高,对PTP1B(IC50 = 4.1 µM)相对于TCPTP(IC50 > 130 µM)的选择性指数接近34倍[95]。

一年后,同一研究团队设计了额外的PTP1B相对于TCPTP的选择性抑制剂。本研究中采用的策略包括3D-QSAR、药效团建模和虚拟筛选。所有方法均在两种酶PTP1B和TCPTP上进行,以增加发现选择性抑制剂的可能性。筛选了内部化学数据库,报道了八种新的PTP1B抑制剂。在这些抑制剂中,化合物1(乙基6-(2-(4-氧代-4,5,6,7-四氢-3H-环戊并[4,5]噻吩并[2,3-d]嘧啶-3-基)乙酰氨基)烟酸酯,图7)最为成功,对PTP1B(IC50 = 15 µM)相对于TCPTP(IC50 > 125 µM)显示出8倍选择性[44]。同年,通过药效团建模、对接和骨架跃迁技术鉴定了另一组PTP1B抑制剂。这些方法使得从86种化合物的库中优先选择了10种分子进行合成。这些化合物在微摩尔范围内抑制PTP1B,最强效抑制剂(化合物115,N-苄基-N-(2-羟基-2-苯基乙基)-2,4,6-三甲基苯磺酰胺,图7)的表征显示,在C57BL/KsJ-db/db小鼠和STZ诱导的糖尿病大鼠模型中评估时,它改善了口服葡萄糖耐量并通过恢复胰岛素水平和使血清脂质谱正常化来增强胰岛素抵抗。此外,该化合物通过调节参与胰岛素信号传导的基因(如IRS 1-2、PI3K、PTPN1、Akt2、AMPK和PPAR-α)的表达来增强胰岛素作用。其他实验证实了该化合物对3T3L-1细胞的抗脂肪生成作用以及其对MDI诱导的脂质积累的抑制作用。此外,在大鼠中以30 mg/kg口服给药后显示出约10%的生物利用度[96]。

**图6. 2013年通过计算方法发现的最强效PTP1B抑制剂的结构。**

**图7. 2014年通过计算方法发现的最强效PTP1B抑制剂的结构。**

2015年,通过计算机对接方法优化了水杨酸衍生物。化合物20h(4-(4-(4-((N-(2-((4-羧基-3-羟基苯基)(4-环己基苄基)氨基)-2-氧代乙基)喹啉-8-磺酰胺基)甲基)-1H-1,2,3-三唑-1-基)丁酰胺基)-2-羟基苯甲酸,图8)与起始化合物相比效力提高(IC50 = 1.7 µM)。此外,化合物20h和20f(4-(2-(4-((N-(2-((4-羧基-3-羟基苯基)(4-环己基苄基)氨基)-2-氧代乙基)喹啉-8-磺酰胺基)甲基)-1H-1,2,3-三唑-1-基)乙酰氨基)-2-羟基苯甲酸,图8)对PTP1B相对于蛋白酪氨酸磷酸酶σ(PTPσ)显示出约4至5倍的选择性。PTP1B抑制剂20f和20h在中国仓鼠卵巢(CHO)细胞中的细胞毒性测定显示,在0.78至50 µM浓度下无毒性。此外,CHO细胞的Western blot分析表明,这三种抑制剂增加了胰岛素受体(IR)的自磷酸化水平。上述结果表明,分子20h代表了一种值得进一步研究的PTP1B抑制剂先导化合物[47]。采用面向片段对接的设计方法优化了含有二氟甲基膦酸基团的PTP1B抑制剂。根据对接模拟结果,磷酸基团被中性N-(2,5-二乙氧基-苯基)-甲磺酰胺片段替代,以克服负电荷带来的不便。该分子及其合成类似物的IC50值在纳摩尔范围内。最强效的抑制剂化合物15(N-{2,5-二乙氧基-4-[3-(4-甲氧基-苯基)-脲基甲基]-苯基}-甲磺酰胺,图8),IC50 = 203 nM,为竞争性抑制剂。此外,观察到它增强了胰岛素受体β磷酸化,对TCPTP的抑制活性<50%(25 µM下)[47]。同年,通过对PTP1B活性和变构位点的分子对接分析,鉴定了噻唑基衍生物作为PTP1B抑制剂。报道了四种竞争性和两种变构抑制剂,Ki值在2至29 µM范围内,化合物A2(图8)为活性最强的抑制剂[98]。通过详细分析含有二氟甲基膦酸或羧基甲基水杨酸基团的抑制剂的晶体复合物,并应用基于片段的分子对接,发现了新型(甲磺酰基-苯基-氨基)-乙酸甲酯类似物作为强效和选择性PTP1B抑制剂。十二种设计的化合物在纳摩尔范围内显示出抑制活性;最强效的化合物P7([(4-{[{4-[(苄基-甲磺酰基-氨基)-甲基]-苯基}-(4-乙氧基-苯磺酰基)-氨基]-甲基}-苯基)-甲磺酰基-氨基]-乙酸甲酯,图8)IC50为222 nM。此外,该分子对TCPTP具有选择性(IC50 = 1.86 µM),并在体外降低了IRβ的去磷酸化[99]。使用基于结构的药效团模型和分子对接设计了一系列基于氨基羧酸的吡唑衍生物。本工作中,这些衍生物分为三组,每组具有不同的疏水尾链:1,2-二苯基乙酮、噁二唑和二苄基胺。噁二唑衍生物(Ki范围为4–9 µM)和二苄基胺(Ki范围为4–11 µM)效力最强,尤其是化合物16i(5-氨基-1-[4-[[(3,4-二甲氧基苯基)甲基-[(4-氟苯基),图8)。此外,这些化合物在啮齿动物肝微粒体中稳定,二苄基胺衍生物在PAMPA中的细胞通透性优于乙酮和噁二唑衍生物[100]。

**图8. 2015年至2017年通过计算方法发现的最强效PTP1B抑制剂的结构。**

2018年,Ganou等人基于PTP1B活性和变构位点的分子对接分析继续研究噻唑基衍生物,此外还考虑了硫代吗啉衍生物。大多数化合物为竞争性抑制剂(仅两种为非竞争性),Ki范围在2至23 µM之间。化合物Tm2和Tm4(图9)是所有硫代吗啉和噻唑基衍生物中最强效的抑制剂,Ki值相同(2 µM)。此外,这些分子相对于TCPTP具有选择性(在5 µM下对TCPTP无抑制)[101]。还通过对Maybridge数据库进行虚拟筛选鉴定了三种新的PTP1B抑制剂。最佳抑制剂(化合物CD00466,图9)IC50为0.73 µM,对TCPTP的选择性为31倍(IC50 = 22.87 µM)[102]。另一方面,在虚拟筛选方案中使用了多种过滤器,如分子量、指纹图谱、分子对接和静电相似性。该方法鉴定出15种IC50值在1–10 µM范围内的分子;其中IC50值最低的分子之一为化合物7(ID: AK-968/41025519,来自Specs库,图9)。此外,所有这些分子在结构上各不相同,这使得能够探索多样化的化学骨架[103]。同年,通过面向片段对接的设计优化了Du等人2015年设计的化合物15的结构[47],获得了11种分子。效力得到提高,尤其是化合物8(5-[3-(2,5-二乙氧基-4-甲磺酰基氨基-苄基)-脲基]-2-ethoxy-苯甲酸甲酯,图9),IC50值为18 nM。此外,它增加了L6肌管中胰岛素刺激的葡萄糖摄取,并对四种磷酸酶具有选择性;TCPTP/PTP1B比值为35倍(IC50 = 670 nM)[104]。还通过虚拟筛选发现了变构PTP1B抑制剂,使用了Lipinski五规则、潜在毒性、基于PTP1B和TCPTP药效团的筛选以及分子对接等过滤器。在筛选的393,932种化合物中,仅选择23种进行体外评估,仅10种化合物显示出对PTP1B的抑制活性。在1.25 µM浓度下抑制率范围为10%至56%,其中化合物NIPER-10(图9)被鉴定为最强效的[45]。随后一年,通过去甲蒽醌优化设计了强效PTP1B抑制剂。对去甲蒽醌预测结合模式的分析表明,可以对1、3、6和7位的四个羟基进行修饰。最强效的抑制剂分子XWJ24(3-((3-氯-2-氟苄基)氧基)-1,6,7-三羟基-9H-呫吨-9-酮,图9)IC50 = 0.6 µM。其表征显示它是竞争性抑制剂,并对包括TCPTP在内的不同磷酸酶具有选择性(IC50 = 2.7 µM)[105]。

2020年,Wu及其同事使用虚拟筛选工作流程、分子对接和ADMET(吸收、分布、代谢、排泄和毒性)策略鉴定了一系列新型PTP1B抑制剂。通过虚拟筛选方法从ZINC数据库中选择化合物ZINC39276654,生成一千种分子衍生物。随后,从评分最高的分子中选择一百种生成的衍生物,重新对接到PTP1B活性位点,以选择排名前十的化合物(1a–1j)评估抑制能力。化合物1a(乙基2-(2-溴苯基)-4-((4-甲氧基苯氧基)甲基)噻唑-5-羧酸酯,图10)表现出最佳抑制效力(IC50 = 4.46 µM)和可接受的预测药物性质。该分子对PTP1B相对于其他磷酸酶具有选择性——对TCPTP为3倍(IC50 = 12.28 µM),其余>22倍——包括Src同源区2结构域含磷酸酶1(SHP1)、巨核细胞蛋白酪氨酸磷酸酶2(MEG2)、CDC25B(M期诱导物磷酸酶2)和LAR。然而,化合物1g(乙基4-((4-氯苯氧基)甲基)-2-(3-苯氧基苯基)噻唑-5-羧酸酯,图10)对PTP1B相对于TCPTP的选择性最强(>9倍,IC50 > 100 µM)[106]。同年,通过虚拟筛选发现了一系列共17种共享化合物ZINC99459骨架的新型4-噻唑啉酮衍生物。ADMET预测(包括人肠道吸收、血脑屏障、血浆蛋白结合、水溶性、细胞色素P450 2D6结合和毒性)表明这些化合物具有良好的类药性。随后,在PTP1B和其他磷酸酶上测定了体外酶抑制活性。化合物7p(图10)被鉴定为最强效(IC50 = 0.92 µM)和选择性抑制剂,对TCPTP、SHP2、CDC25B、LAR和MEG2的选择性>100倍(IC50 > 100 µM),对SHP1至少24倍[107]。另一项通过计算工具寻找PTP1B抑制剂的工作是Yang及其同事报道的研究。通过不同的计算机过滤器(如3D-QSAR模型、2D指纹图谱相似性和分子对接)筛选了约122,000种化合物的天然产物库。通过虚拟筛选优先选择的26种分子被探索其对PTP1B的抑制作用。活性最强的化合物——香豆素衍生物——IC50在微摩尔范围内。其中,九种分子在多种磷酸酶中进一步评估,显示出对PTP1B相对于其他磷酸酶(包括TCPTP)的选择性抑制。活性最强的抑制剂为H17(IC50 = 2.05 µM,图10),但不具有选择性(在10 µM下对TCPTP的抑制活性为73.5%)。选择性最强的化合物为H8和H20(图10),相对于TCPTP、CD45、LAR和VHR磷酸酶的选择性约为10倍(在10 µM下抑制活性<10%)[108]。

**图9. 2018年至2019年通过计算方法发现的最强效PTP1B抑制剂的结构。**

**图10. 2020年通过计算方法发现的最强效PTP1B抑制剂的结构。**

2021年,采用骨架跃迁方法基于吡咯唑环被氮唑替代来优化化合物1的结构。根据计算机工具获得的结果,新化合物比化合物1具有更好的类药性。大多数分子在0.46–2.17 µM的IC50范围内显示出良好的抑制活性。在这些化合物中,化合物2(4-甲基咪唑并[1,2-a]喹喔啉,IC50 = 0.49 µM,图11)和化合物9(四唑并[1,5-a]喹喔啉,IC50 = 0.62 µM,图11)显示出最高效力。此外,这些化合物对TCPTP的选择性评估显示,选择性最强的是化合物2(2倍,在1 µM下对TCPTP的抑制活性为44%)。该分子还在表型模型中使葡萄糖摄取相对于对照细胞增加了15%[109]。Ma及其同事通过虚拟筛选、骨架跃迁、ADMET预测和分子对接,发现了具有结构多样性的咪唑烷-2,4-二酮衍生物作为PTP1B抑制剂。首先,通过虚拟筛选获得的化合物CHEMBL213560使用骨架跃迁方法进行优化。将具有良好ADMET结果设计的化合物用于开展分子对接分析。选择PTP1B蛋白评分高的15种分子来评估其生物活性。这些分子在PTP1B、Src同源区2结构域含磷酸酶2(SHP2)和LAR中进行评估;化合物10((E)-4-(甲氧基羰基)苄基4-((3-苄基-4-(4-((4-(甲氧基羰基)苄基)氧)亚苄基)-2,5-二氧代咪唑烷-1-基)甲基)苯甲酸酯,图11)对PTP1B抑制最高,IC50为2.07 µM。此外,该分子对PTP1B的抑制能力是SHP2的10倍,是LAR的60倍[110]。最后,进行了由指纹图谱搜索、基于结构的药效团模型和分子对接组成的综合虚拟筛选,以从商业可获得的化学库中搜索潜在的变构PTP1B抑制剂。从184,922种分子中,选择九种化合物进行体外评估。两种化合物活性最强:H3(IC50 = 0.72 µM,图11)和H9(IC50 = 1.59 µM,图11)。它们在TCPTP和SHP2中进一步评估,显示出对PTP1B相对于两种磷酸酶的选择性抑制(>60倍,IC50 > 100 µM)[111]。

**图11. 2021年通过计算方法发现的最强效PTP1B抑制剂的结构。**

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## 5. 结论

已有大量PTP1B抑制剂被报道为针对2型糖尿病新药的优秀潜在命中化合物或先导化合物。通过各种计算工具已鉴定出多种强效和选择性的PTP1B抑制剂。这些研究报告的化合物IC50和Ki值从纳摩尔到微摩尔范围。此外,其中一些化合物被发现对PTP1B相对于其最接近的同源物TCPTP具有选择性,选择性范围为2至100倍。而且,当表征深入时,它们显示出改善葡萄糖摄取的能力。PTP1B抑制剂的设计过程仍然充满挑战,这促使许多学术研究实验室和制药组织继续寻找有效且安全的口服可用化合物。因此,本综述鼓励运用计算机辅助技术,并提供了有助于增进目前关于PTP1B抑制认知的有益信息,对以PTP1B为分子靶点开发2型糖尿病新药的研究路线具有积极意义。

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**作者贡献:** 概念化,A.T.-V.、C.A.-D.和M.I.C.-A.;方法论,A.T.-V.、C.A.-D.和M.I.C.-A.;形式分析,M.I.C.-A.、A.T.-V.、C.A.-D.、A.H.-C.、R.C.、M.V.-S.和E.S.-C.;写作——原稿准备,A.T.-V.、C.A.-D.和M.I.C.-A.;写作——审阅和编辑,M.I.C.-A.、A.T.-V.、C.A.-D.和E.S.-C.。所有作者均已阅读并同意手稿的发表版本。

**资助:** 本研究未获得外部资助。

**机构审查委员会声明:** 不适用。

**知情同意声明:** 不适用。

**数据可用性声明:** 可用数据已在手稿中呈现。

**利益冲突:** 作者声明无利益冲突。