Recent Progress in Urea‐Containing Compounds as Tyrosine Kinase Inhibitors

ABSTRACT

Cancer remains one of the leading causes of mortality worldwide. Dysregulated cellular signaling pathways play a pivotal role in tumorigenesis, tumor progression, and metastasis. Among these, tyrosine kinases (TKs) constitute a critical class of enzymes that catalyze the phosphorylation of tyrosine residues on target proteins, thereby regulating key cellular processes including growth, differentiation, and survival. TKs have revolutionized cancer therapy by selectively targeting these enzymes, resulting in suppressed tumor growth and improved clinical outcomes for patients. Urea‐containing motifs represent one of the most important bioactive functional groups in medicinal chemistry. In particular, unsymmetrical alkyl‐ and benzylureas are widely employed as key structural components in numerous approved drugs. This structural feature enables versatile modifications that enhance physicochemical properties, including solubility, metabolic stability, and bioavailability. This review explores the current landscape of antineoplastic urea‐based tyrosine kinase inhibitors, presenting an exhaustive examination of contemporary urea‐containing compounds that inhibit TKs while elucidating their mechanisms of action and molecular targets. In recent years, computational technologies have become indispensable in modern drug discovery. They significantly accelerate the identification of new TKIs and support the repurposing of established pharmaceuticals. Ultimately, the review addresses the prevailing challenges and future opportunities in the advancement of urea‐containing tyrosine kinase inhibitors.

Tyrosine kinases (TKs) are key enzymes that phosphorylate tyrosine residues, regulating cell growth, differentiation, and survival. Tyrosine kinase inhibitors (TKIs) have revolutionized cancer therapy by selectively targeting TKs, reducing tumor growth and improving outcomes. This review examines antineoplastic urea‐based TK inhibitors, focusing on urea‐containing compounds—especially unsymmetrical alkyl/benzyl ureas—and their mechanisms of action and molecular targets. It also addresses current challenges and future opportunities in developing these inhibitors.

Abbreviations

A375

melanoma cell line

A431

human lung cancer

ABL

abelson kinase

ADMET

absorption, Distribution, Metabolism, Excretion, and Toxicity

ALK

anaplastic lymphoma kinase

AML

acute myeloid leukemia

ATP

adenosine triphosphate

B16

mouse melanoma

CCK‐8

cell Counting Kit‐8

DFG motif

asp‐Phe‐Gly (Aspartic acid‐Phenylalanine‐Glycine) tripeptide sequence

DNA

deoxyribonucleic acid

DSU

diarylsulfonylurea

EGFR

epidermal growth factor receptor

ERK

extracellular‐signal‐regulated kinase

FDA

food and Drug Administration

FGFRs

fibroblast growth factor receptors

FLT

fms‐like tyrosine kinase

HCC

hepatocellular Carcinoma

HCT116

colon cancer cell line

HDF

normal human dermal fibroblast

Hela

cervical carcinoma

HepG2

hepatoblastoma cell line G2

HER

human epidermal growth factor receptor

HK‐2

human renal epithelial cell line

HT‐29

human colon cancer

JAKs

janus kinases

K562

human chronic myeloid leukemia

KDR

kinase insert domain receptor

MAPK

mitogen‐activated protein kinases

MCF‐7

breast adenocarcinoma

MDA‐MB‐231

md anderson‐metastatic breast‐231

MEK

mitogen‐activated protein kinase

MET

mesenchymal‐epithelial transition factor

MTT

3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide

NADH

nicotinamide adenine dinucleotide (Reduced)

NRTKs

non‐receptor tyrosine kinases

PaCa2

pancreatic cancer cell line

PC3

human prostate cancer

PDGFR

platelet‐derived growth factor receptor

PDGFRs

platelet‐derived growth factor receptors

PK

pharmacokinetics

PTKs

protein tyrosine kinases

Raf

rapidly accelerated fibrosarcoma

RET

receptor tyrosine kinase rearranged during transfection

RTKs

receptor tyrosine kinases

SAR

structure–activity relationship

SiHa

human cervical squamous

SMCl

sorafenib meta‐chlorine

TBS

tert‐Butyldimethylsilyl

TKIs

tyrosine kinase inhibitors

TKs

tyrosine kinases

VEGFRs

vascular endothelial growth factor receptors

1. Introduction

In 1828, the German chemist Friedrich Wöhler accomplished the first laboratory synthesis of urea from inorganic precursors, providing the seminal demonstration that an organic compound previously known only as a metabolic waste product could be produced synthetically [1]. The synthesis of urea marked a significant milestone in the field of synthetic organic chemistry [2]. Urea‐containing compounds constitute an intriguing class of chemicals with a wide range of applications, spanning biological research, coordination chemistry, and beyond [3, 4, 5, 6]. The conventional synthesis of urea derivatives involves the reaction of amines with phosgene, carbon monoxide, or isocyanates, which poses significant toxicological and environmental concerns [7, 8]. Other pathways involving the reactions of amines with urea, ethylene carbonate, or diethyl carbonate have also been identified [9]. Also, several studies have reported the synthesis of urea derivatives through the reaction of amines with carbon dioxide in the presence of catalysts such as 1,8‐diazabicyclo[5.4.0]undec‐7‐ene, CsOH, Cs₂CO₃, Au/poly, [Bmim]OH₂O, or KOH/PEG1000, using ionic liquids as solvents [10, 11, 12]. Urea‐containing scaffolds represent a privileged structural motif in medicinal chemistry, serving as a common framework for numerous drugs and bioactive compounds with diverse therapeutic and pharmacological profiles [13, 14, 15, 16, 17], including antimicrobial, anti‐methicillin‐resistant, antiviral, antiatherosclerotic, antioxidant, anticonvulsant, antidiabetic, hypnotics, sedatives, anti‐inflammatory, antibacterial, and antitumor effects [2, 8, 18, 19, 20, 21, 22, 23, 24, 25].

In recent years, numerous studies have explored the synthesis and mechanisms of action of urea‐based anticancer agents, along with their biological evaluation, structure–activity relationships (SAR), fragmentation patterns, and interactions with key biological targets such as DNA [26, 27]. For example, hydroxyurea is a clinically effective medication for treating both acute and chronic leukemia as well as a variety of solid malignancies [28]. Moreover, diarylsulfonylurea (DSU) derivatives have demonstrated broad‐spectrum anticancer activity across various tumor models. Growing evidence further indicates that topoisomerases serve as the primary intracellular targets for several clinically relevant antitumor urea‐based agents [29].

Cancer remains one of the leading causes of death worldwide. Aberrant cellular signaling pathways play a central role in tumorigenesis, tumor progression, and metastasis. Among these, tyrosine kinases (TKs) represent a critical family of enzymes responsible for phosphorylating tyrosine residues on substrate proteins, thereby regulating essential cellular processes such as growth, differentiation, and survival. Dysregulation of TKs‐frequently through activating mutations or overexpression—is strongly implicated in the pathogenesis of many cancers, rendering them highly attractive therapeutic targets. Tyrosine kinase inhibitors (TKIs) have revolutionized modern cancer therapy by selectively blocking these dysregulated enzymes, resulting in suppressed tumor growth and significantly improved clinical outcomes for patients [30]. Tumorigenesis, defined as the complex, multistep biological process where normal cells transform into cancerous cells, leading to the formation of tumors through uncontrolled growth, division, and survival, is driven by genetic mutations, epigenetic changes, and interactions with the cellular environment [31]. Empirical evidence has established that angiogenesis serves as a rate‐limiting factor in the progression of tumorigenesis [32]. Neoplasms that are deficient in sufficient vascularization tend to undergo necrosis or apoptosis and fail to surpass a certain dimensional threshold. Hence, the suppression of tumor angiogenesis has emerged as a persuasive strategy in the formulation of anticancer pharmacological agents [33, 34, 35, 36]. Urea‐containing compounds assume a significant role in the realm of anticancer pharmacology due to their pronounced inhibitory efficacy against Receptor tyrosine kinases (RTKs), Protein tyrosine kinases (PTKs), and Nicotinamide adenine dinucleotide (NADH) oxidase, all of which are integral to various facets of tumorigenesis [27, 37, 38].

2. Tyrosine Kinase (TKs)

2.1. Definition of Tyrosine Kinases (TKs)

Tyrosine kinases (TKs), a class of enzymes, facilitate the transfer of a phosphate moiety from ATP (adenosine triphosphate) to the tyrosine amino acid residue of proteins [39]. His biochemical process, referred to as phosphorylation, serves as a fundamental mechanism for modulating a multitude of cellular functions, inclusive of:

1. Cell growth and division play a crucial role in the signaling pathways that regulate cell proliferation.

2. Cell Differentiation: It is involved in the processes that determine how cells develop and specialize.

3. Metabolism: Regulating metabolic pathways and energy production within cells.

4. Cell Migration and Adhesion: Important for wound healing and immune responses.

2.2. Tyrosine Kinases Can be Broadly Categorized Into Two Main Groups

2.2.1. Receptor Tyrosine Kinases (RTKs)

These are membrane‐bound proteins that, upon binding with a specific ligand (like a growth factor), activate their kinase activity and trigger downstream signaling pathways. This leads to the phosphorylation of tyrosine residues on themselves (autophosphorylation) and on downstream signaling proteins (Figure 1).

FIGURE 1.

Receptor tyrosine kinase (RTK) pathway [40, 41].

Examples:

• Epidermal growth factor receptor (EGFR)

• Vascular endothelial growth factor receptor (VEGFR)

• Insulin receptor (IR)

• Platelet‐derived growth factor receptor (PDGFR)

2.2.2. Non‐Receptor Tyrosine Kinases (NRTKs)

Unlike RTKs, these kinases are found in the cytoplasm rather than being part of the cell membrane. They are often involved in intracellular signaling pathways, responding to various stimuli.

Examples:

• SRC family kinases

• Janus kinases (JAKs)

• ABL kinase

A predominant subfamily of receptor tyrosine kinases (RTKs) is the vascular endothelial subfamily. The vascular endothelial growth factor receptor (VEGFR) tyrosine kinases, which are specifically localized to vascular endothelial cells, encompass FLT1 (Fms‐like tyrosine kinase 1; VEGFR1), KDR (kinase insert domain‐containing receptor tyrosine kinase; VEGFR2), and FLT4 (VEGFR3). The activation of the VEGFR family of RTKs, notably KDR, by vascular endothelial growth factors (VEGFs) is integral to tumor angiogenesis [42, 43, 44]. Consequently, the inhibition of tyrosine kinases has emerged as a predominant therapeutic approach in oncology, particularly in light of the substantial clinical outcomes observed with Imatinib in the treatment of chronic myeloid leukemia [45, 46].

2.3. Tyrosine Kinase Inhibitors (TKIs)

Tyrosine kinase inhibitors (TKIs) are a class of targeted therapeutic agents. These agents function by inhibiting the activity of tyrosine kinase enzymes. The aforementioned enzymes are integral to the regulation of cellular processes, encompassing cell signaling and the frequency of cellular division. Certain tyrosine kinase inhibitors are employed in the treatment of malignant neoplasms. The mechanism of action of TKIs involves the obstruction of enzymatic activity, thereby preventing the proliferation of neoplastic cells. Tyrosine kinase inhibitors (TKIs) are a class of targeted therapeutic agents used to treat various malignancies [31, 47]. These agents inhibit specific molecular pathways within neoplastic cells that regulate cellular proliferation and division rates. While tyrosine kinase inhibitors do not possess curative properties for cancer, they have the potential to induce prolonged remission or extend survival for individuals afflicted with certain forms of cancer [48].

During the last decade, the Food and Drug Administration (FDA) has granted approval to eleven novel pharmacological agents for the treatment of cancer. These agents function as selective inhibitors of key receptor tyrosine kinases, including anaplastic lymphoma kinase (ALK), epidermal growth factor receptor (EGFR, also designated HER1), human epidermal growth factor receptor 2 (HER2), human epidermal growth factor receptor 4 (HER4), fibroblast growth factor receptors (FGFRs), vascular endothelial growth factor receptors (VEGFRs), mesenchymal‐epithelial transition factor (MET), and RET (rearranged during transfection) [44].

3. Approved Urea‐Containing Drugs Used as Tyrosine Kinase Inhibitors

Sorafenib (Nexavar), is a diaryl urea compound developed by Bayer and Onyx Pharmaceuticals, initially receiving approval in 2005. Sorafenib (Figure 2) functions as a multi‐kinase inhibitor that effectively obstructs VEGFR2, which is a principal facilitator of tumor angiogenesis and growth, by engaging its ATP‐binding site, thereby inhibiting downstream signaling pathways that are essential for endothelial cell viability and proliferation. Consequently, it serves as a prominent anti‐cancer therapeutic agent, with particular efficacy against hepatocellular carcinoma (HCC) and renal malignancies. The blockade of VEGFR2, in conjunction with additional kinases such as VEGFR‐1, ‐3, PDGFR‐β, and B‐Raf, undermines the tumor's vascular supply and cellular proliferation, resulting in a diminished rate of tumor expansion [49, 50].

FIGURE 2.

Chemical structure of approved urea‐containing drugs used as tyrosine kinase inhibitors.

Infigratinib, FGFR2 fusions or rearrangements occur in approximately 10%–16% of intrahepatic cholangiocarcinomas. In 2021, the FDA approved infigratinib, a selective FGFR tyrosine kinase inhibitor, thereby broadening the therapeutic options available for patients with FGFR2 fusion‐positive cholangiocarcinoma (CCA). This approval represents one of the first two targeted treatment modalities developed to improve clinical outcomes in this molecularly defined subgroup (Figure 2) [51].

Tivozanib (Fotivda) is classified as a quinolineurea derivative that exerts its inhibitory effects on VEGFRs through an ATP‐competitive mechanism. Tivozanib is a potent pan‐VEGFR inhibitor with activity against VEGFR‐1, VEGFR‐2, and VEGFR‐3 at picomolar concentrations. By blocking ligand‐stimulated receptor phosphorylation, it exerts direct anticancer activity in addition to suppressing angiogenesis and vascular permeability [52]. In patients with advanced renal cell carcinoma (RCC), tivozanib has been evaluated as a third‐ or fourth‐line therapy, where it significantly prolonged progression‐free survival and showed superior tolerability relative to Sorafenib (Figure 2) [53]. In 2021, the encouraging outcomes associated with Tivozanib culminated in its authorization by the Food and Drug Administration (FDA) for the management of adult patients experiencing relapsed or refractory advanced RCC subsequent to the administration of two or more prior systemic therapies.

Pemigatinib (Pemazyre), an oral small‐molecule inhibitor of FGFR1, FGFR2, and FGFR3 featuring a urea scaffold (Figure 2), was granted accelerated approval by the FDA in April 2020. The approval covers its use in adults with previously treated, locally advanced or metastatic cholangiocarcinoma carrying FGFR2 gene fusions or rearrangements, confirmed by an FDA‐approved diagnostic assay [54].

Lenvatinib (Lenvima and Kisplyx), is a multiple receptor tyrosine kinase (RTK) inhibitor and a prescription anticancer targeted treatment drug. Lenvatinib (Figure 2), a multi‐targeted tyrosine kinase inhibitor bearing a urea scaffold, received FDA approval in 2016 for advanced renal cell carcinoma (in combination with the mTOR inhibitor Everolimus) and for hepatocellular carcinoma. The urea moiety is essential for binding at the kinase hinge region. Crystallographic analysis of the VEGFR2–Lenvatinib complex demonstrates that the urea group establishes a hydrogen‐bond network with the Asp1046 backbone and Glu885 side chain. In addition, Lenvatinib inhibits FGFR1 [55, 56].

Regorafenib (Stivarga), is a fluorinated analog of Sorafenib that targets angiogenic, stromal, and oncogenic receptor tyrosine kinases (RTKs). Regorafenib (Figure 2) was approved in 2012. It targets key receptors, including VEGFRs, PDGFR‐β, and FGFR, as well as intracellular kinases such as BRAF and RAF‐1, thereby inhibiting tumor cell proliferation and new blood vessel formation, thereby starving tumors and slowing their spread. Its use was subsequently expanded to include the treatment of hepatocellular carcinoma [57, 58].

Linifanib (also known as ABT‐869) is a ureido indazole‐based small‐molecule inhibitor that selectively targets vascular endothelial growth factor receptors (VEGFRs) and platelet‐derived growth factor receptors (PDGFRs). Consistent with the mechanism of other tyrosine kinase inhibitors (TKIs), Linifanib competes with ATP for binding to the intracellular tyrosine kinase domain, thereby preventing receptor autophosphorylation and inhibiting subsequent downstream signaling. A novel TKI template called the 3‐aminoindazole motif can imitate the adenine component of ATP by forming two H‐bonding contacts with the hydrophobic pocket of the kinase [59, 60]. Additionally, the insertion of a diaryl urea creates an extra H‐bond binding site that favors the urea moiety's proper orientation inside the pocket and inactivates the receptor. Preliminary research in animals demonstrated a strong anti‐proliferative effect of Linifanib (Figure 2) in inducing cell death in cancer cells driven to proliferate by FLT‐3 and other mutant or constitutively active angiogenic tyrosine kinase receptors [61, 62].

Tandutinib (Figure 2) is a piperazinyl urea derivative that functions as an investigational multi‐targeted tyrosine kinase inhibitor. It has been studied in clinical trials for patients with recurrent or progressive glioblastoma and acute myeloid leukemia (AML). It acts by inhibiting enzymes required for cancer cell growth and can also limit the creation of new blood vessels needed by malignancies. It exerts its antineoplastic effects primarily by inhibiting the phosphorylation of FLT3 (FMS‐like tyrosine kinase 3). This blockade leads to reduced malignant cell proliferation and tumor progression in both in vitro assays and in vivo animal models [63, 64].

Quizartinib (Vanflyta) (Figure 2) is a selective FLT3 tyrosine kinase inhibitor approved by the FDA in 2023 for the treatment of acute myeloid leukemia (AML) harboring FLT3 mutations. By binding to the inactive conformation of the FLT3 receptor, quizartinib inhibits receptor activation and disrupts downstream signaling cascades, including the RAS/RAF/MEK/ERK and PI3K/AKT pathways [65, 66, 67].

4. The Principal Synthetic Approaches to Urea‐Containing Compounds

Given the substantial importance of urea derivatives as pharmacophores in drug design, as well as their utility in material sciences and organocatalytic applications, numerous synthetic strategies have been established for the efficient preparation of these compounds [13, 68]. The synthesis of urea derivatives has evolved significantly, incorporating both classic and modern methodologies. Classic methods typically involve the reaction of isocyanates with amines or alcohols, yielding various urea compounds through straightforward and reliable routes [69, 70, 71]. One notable example is the synthesis of urea via the reaction of ammonia with carbonyl compounds, a process historically recognized for its simplicity [72]. In contrast, modern synthetic approaches leverage advanced techniques such as microwave‐assisted synthesis, which can enhance reaction rates and yields while reducing reaction times [73, 74]. Additionally, the application of green chemistry principles is increasingly prominent, utilizing environmentally friendly solvents and catalysts [75, 76, 77, 78, 79]. These contemporary methods not only improve efficiency but also broaden the scope of urea derivatives synthesized, paving the way for innovative applications in pharmaceuticals and agrochemicals.

4.1. Classic Methods

• Isocyanate route: An amine is reacted with an isocyanate to create the urea derivatives [80, 81, 82, 83, 84].

• Carbamoyl route: An amine is reacted with a carbamoyl halide [85, 86, 87].

• Phosgene/triphosgene: Amines can be reacted with phosgene (a toxic gas) or triphosgene (a solid, safer substitute) to form the urea derivatives [88].

4.2. Modern and Safer Methods

• Reductive carbonylation: This phosgene‐free process uses metal catalysts to react nitro derivatives with carbon monoxide to form urea‐containing compounds [89, 90, 91, 92].

• Carbon dioxide (CO₂) utilization: Reactions involving CO₂ can be used to synthesize urea derivatives [93, 94]. This can include the reaction of silylamines with CO₂ catalyzed by indium compounds or the reaction of alkyl ammonium carbamates (formed from CO₂) with other compounds [95, 96, 97].

• Palladium‐catalyzed cross‐coupling: This is an efficient method for creating unsymmetrical urea derivatives by reacting aryl chlorides and triflates with sodium cyanate, often in a single step [29, 98, 99, 100].

• One‐pot methods: Practical one‐pot syntheses can be achieved by transforming Boc‐protected amines into ureas in situ using reagents like 2‐chloropyridine and trifluoromethanesulfonyl anhydride [101, 102].

5. Recent Developments in Urea‐Containing Compounds as Tyrosine Kinase Inhibitors

Notable among these are aryl‐ and diaryl‐urea derivatives, which exploit networks of hydrogen bonds and hydrophobic/aromatic interactions within a specific pocket near the ATP‐binding site to lock the kinase domain in its inactive state [103, 104]. This pocket includes critical structural features such as the hinge region (with its gatekeeper residue), the P‐loop, the αC‐helix, and the activation loop (A‐loop), the latter featuring the conserved Asp‐Phe‐Gly (DFG) motif at its N‐terminus. Its function is to facilitate the coordination of ATP and magnesium ions within the active site. It exists in two distinct conformational states: a) DFG‐in: the active conformation, wherein the Asp residue is oriented towards the ATP‐binding site; b) DFG‐out: the inactive conformation, characterized by the Asp and Phe side chains transitioning away from the binding site, frequently permitting the binding of specific inhibitors. Thus, urea‐based tyrosine kinase inhibitors (TKIs) generally feature three essential structural elements: (i) a urea group that engages in hydrogen bonding with the hinge region, (ii) a hydrophobic aromatic component that interacts with hydrophobic region I of the kinase, and (iii) a suitable spacer or linker [104, 105, 106, 107].

5.1. Urea‐Containing Compounds as Vascular Endothelial Growth Factor (VEGF) Inhibitors

Phosphorylation serves as a critical mechanism for regulating protein function. Aberrant activation of tyrosine kinases—often caused by mutations or dysregulation—leads to persistent signaling and contributes to the development and progression of cancer. Thus far, around twenty distinct receptor tyrosine kinases (RTKs) have been characterized (Figure 3), encompassing the insulin receptor and several growth factor receptors, including EGFR, FGFR, PDGFR, VEGFR, and NGFR [108].

FIGURE 3.

Structure of the 20 Receptor Tyrosine Kinase Classes [108].

The vascular endothelial growth factor receptor (VEGFR) exhibits the prototypical architecture of receptor tyrosine kinases (RTKs), consisting of an extracellular ligand‐binding domain, a single transmembrane helix, and an intracellular tyrosine kinase domain. The full‐length canonical VEGFR protein comprises 1,356 amino acids. Its overall structure closely resembles that of the platelet‐derived growth factor receptors (PDGFRs). Vascular endothelial growth factors (VEGFs), key mediators of vasculogenesis and angiogenesis, bind to the extracellular domain of VEGFRs on the cell surface. This interaction induces receptor dimerization and subsequent activation of the intracellular kinase domain [109, 110].

Foroumadi et al. reported a novel series of 2‐acetamido‐5‐(phenylthio)‐1,3,4‐thiadiazole derivatives bearing phenylurea substituents as potent VEGFR‐2 inhibitors. The synthesis began with the preparation of 2‐amino‐5‐mercapto‐1,3,4‐thiadiazole (3) from thiosemicarbazide (1) and carbon disulfide (2). Acetylation of 3 gave N‐(5‐mercapto‐1,3,4‐thiadiazol‐2‐yl)acetamide (4), which was then coupled with 1‐chloro‐4‐nitrobenzene (5) to produce intermediate 6. Reduction of the nitro group in 6 with Fe/NH₄Cl yielded aniline derivative (7). Subsequent reaction of 7 with substituted phenyl isocyanates (8) furnished the target compounds 9–18 (Scheme 1) [111]. The anticancer activity of the synthesized compounds was evaluated against three human cancer cell lines—HT‐29 (colon), A431 (lung), and PC‐3 (prostate)—as well as normal human dermal fibroblast (HDF) cells. Most derivatives exhibited moderate to potent antiproliferative activity. Among them, compound 13, bearing 3,4‐dichloro substituents on the terminal phenyl ring (Scheme 1), displayed the highest potency against the A431 cell line, with an IC₅₀ value of 9.23 µM, outperforming Sorafenib (IC₅₀ = 10.42 µM). Further mechanistic studies revealed that compound 13 strongly inhibited the phosphorylation of VEGFR‐2 in A431 cells. Western blot analysis demonstrated that 13 induces apoptosis through upregulation of Bax and downregulation of Bcl‐2 protein expression. These results were corroborated using a three‐dimensional cell culture model generated by the hanging drop technique [111].

SCHEME 1.

Synthesis of 1,3,4‐thiadiazole‐containing phenyl urea derivatives (9‐18) [111].

Recently, Yu et al. reported a new series of diary urea‐bearing chalcone derivatives [112]. As illustrated in Scheme 2, both of 4‐Aminoacetophenone (19) and 4‐chloro‐3‐(trifluoromethyl)phenyl isocyanate (20) reacted in the presence of triethylamine to give diaryl urea (21). Compound 21 was reacted with aromatic aldehydes to form chalcone derivatives 22‐40 using potassium hydroxide or thionyl chloride as catalysts [112]. The aforementioned compounds underwent a rigorous assessment of their in vitro cytotoxic properties against human chronic myeloid leukemia (K562), human renal epithelial cell line (HK‐2), human cervical squamous carcinoma (SiHa), and murine melanoma (B16) cancer cell lines. In contrast to Sorafenib, the investigated compounds exhibited marked cytotoxic effects on K562, SiHa, and B16 cell lines. Specifically, compounds 39, 36, and 33 demonstrated pronounced cytotoxicity against K562, SiHa, and B16, with IC₅₀ values recorded at 0.97, 1.22, and 1.39 µM, respectively. Moreover, 33 exhibited formidable cytotoxicity against K562, SiHa, and B16, with IC50 values ranging from 1.25 to 1.39 µM in comparison to Sorafenib (IC₅₀ ranging from 3.34 to 12.82 µM). In addition, compounds 33 and 36 displayed exceptional inhibitory activity against VEGFR‐2 kinase, with IC₅₀ values measured at 0.42 ± 0.03 and 0.31 ± 0.02 µM, respectively. Analysis through flow cytometry indicated that 33 instigated apoptosis and induced a cell cycle arrest during the G1 and S phases. Compound 33 manifested significant antiproliferative effects on K562, SiHa, and B16 cells. Consequently, compound 33 was chosen for the subsequent apoptosis investigation. The patterns of apoptosis and necrosis in K562 cells were evaluated following treatment with 33 at concentrations of 1.25, 2.5, and 5.0 µM. Early apoptosis exhibited a dose‐dependent increase, attaining 5.80, 8.34, and 57.79% following treatment with 1.25, 2.5, and 5.0 µM of 33, respectively. Late apoptosis similarly increased in a dose‐dependent manner. Negligible necrosis was observed in K562 cells. These findings showed that compound 33 significantly induces apoptosis in K562 cells. Molecular docking analyses were performed on compounds 22‐40 to elucidate their binding modes with VEGFR‐2 proteins (PDB ID: 4ASD). Compounds 22‐40 displayed binding free energies ranging from −8.983 kcal/mol to −10.178 kcal/mol, and both established hydrogen bonds with the amino acid residues Glu885 and Asp1046, whereas Sorafenib demonstrated a binding affinity of −10.230 kcal/mol.

SCHEME 2.

Synthesis of diaryl urea bearing chalcone derivatives (22‐40) [112].

A new series of pyridine derivatives (46‐49) and (53‐55) with urea as the linker were designed and synthesized by reacting isonicotinohydrazide (41) with isocyanates (42‐45 and 50‐52) in a study published by Kroneková and co‐workers, as visualized in Schemes 3 and 4 [113].

SCHEME 3.

Synthesis of urea derivatives (46‐49) [113].

SCHEME 4.

Synthesis of urea derivatives (53‐55) [113].

The in vitro antiproliferative potential of the synthesized pyridine derivatives was systematically assessed against three distinct human cancer cell lines, namely A375 (melanoma), HeLa (cervical carcinoma), and MCF‐7 (breast adenocarcinoma). The findings demonstrated that three derivatives, designated as 49, 53, and 54, exhibited a broad‐spectrum antiproliferative activity characterized by notably low IC₅₀ values. Among the synthesized compounds, derivative 53 exhibited the most pronounced antiproliferative efficacy, with IC₅₀ values of (100 and 70 µM), (66 and 35 µM), and (26 µM) against A375, HeLa, and MCF‐7, respectively, when compared with Gemcitabine (IC₅₀ > 1000 µM). Notably, compound 53 demonstrated a substantial inhibition of VEGFR‐2, with an IC₅₀ value of 0.43 ± 0.011 µM in contrast to Sorafenib (IC₅₀ = 0.078 ± 0.006 µM) and induced apoptosis in MCF‐7 cells at the G2/M phase, reflecting an approximate 6.3‐fold increase in relation to untreated MCF‐7 cells. Ultimately, the in silico ADMET analysis and docking simulation of compound 53 suggested favorable oral bioavailability and a significant binding affinity within the active site of VEGFR‐2 (PDB: 4ASD) [113].

In 2025, Chaft et al. reported a new series of biaryl urea derivatives (58‐62) via the reaction of diisocyanatobenzene derivatives (56) with primary amine derivatives (57) in DMF as depicted in Scheme 5 [114]. HepG2 and MCF‐7 cell viability assays conducted utilizing the MTT methodology demonstrated that compound 59 exhibited the highest efficacy, with IC₅₀ values recorded at 8.4 µM and 9.3 µM, respectively. The inhibition of VEGFR‐2 further corroborated these antitumor findings, with compound 59 displaying significant activity (IC₅₀ = 71.21 nM). Computational binding simulations indicated a robust affinity of the synthesized compounds for the VEGFR‐2 active site, primarily through interactions with Glu885, Asp1046, and crucial water molecules. ADMET assessments confirmed favorable pharmacokinetic profiles and drug‐like characteristics of the evaluated derivatives. This synergistic approach positions compound 59 as a promising candidate for VEGFR‐2‐targeted anticancer therapy, warranting further investigation [114].

SCHEME 5.

Synthesis of aryl‐urea derivatives (58‐62) [114].

Most recently, Girgis and co‐workers reported novel antiproliferative 2‐oxoindolin‐3‐ylidenes incorporating urea as potential VEGFR‐2 inhibitors [115]. The targeted urea derivatives (66‐75) were synthesized in two steps as illustrated in Scheme 6 [115]. Firstly, the appropriate 1‐(3/4‐acetylphenyl)‐3‐phenylurea derivatives (63) were reacted with isatin derivatives (64) to produce a series of appropriate aryl‐ureas (65) in excellent yield. The final products (66‐75) were obtained by Acidic dehydration of 65 in glacial acetic acid containing hydrochloric acid (35%) [115]. Promising antiproliferative characteristics (as determined by MTT assay) were discerned for the majority of these compounds (66‐75) against HCT116 (colon), MCF7 (breast), and PaCa2 (pancreatic) cancer cell lines when compared to Sunitinib. The inhibitory characteristics on VEGFR‐2 are congruent with the antiproliferative effects observed against the evaluated cell lines. Compound 67 (R = 4‐NHCONHPh, R ₁ = H; % inhibition = 87.2) emerges as the most promising and potent anti‐VEGFR‐2 agent synthesized, demonstrating activity that is nearly equivalent to that of Sunitinib (% inhibition = 89.4) at a concentration of 10 µM. Molecular docking analyses (PDB: 3WZE and 3AGD) corroborate the antiproliferative impacts observed against the tested cancer cell lines in conjunction with VEGFR‐2 inhibitory properties. The results are consistent with the collaborative effects of the considered pharmacophores (2‐oxoindolyl heterocycle and urea) in enhancing the bio‐properties [115].

SCHEME 6.

Synthesis of 2‐oxoindolin‐3‐ylidenes incorporating urea derivatives (66‐75) [115].

Küçükgüzel et al. reported a new series of azole‐urea hybrids and tested their activity as VEGFR‐2 inhibitors. As visualized in Scheme 7, this study involved the synthesis of ten 1,2,4‐triazole‐3‐thione (81‐90), two new pyrazoles (94 and 95), six 1,3,4‐oxadiazoles (96‐101), and six 1,3,4‐thiadiazoles (102‐107) derivatives containing a urea moiety with structural characteristics similar to Sorafenib [116].

SCHEME 7.

Synthesis of different heterocycle derivatives bearing urea derivatives [116].

A preliminary investigation was conducted on these compounds alongside the established inhibitors Sorafenib and Staurosporine at a concentration of 10 µM to assess their in vitro efficacy against VEGFR‐2, resulting in the identification of compounds 104, 94, and 81 as the most efficacious derivatives, each exhibiting VEGFR‐2 residual activities below 30%. Among the synthesized derivatives, compound 104 emerged as the most potent VEGFR‐2 inhibitor, with an IC₅₀ value of 0.664 µM. The antiproliferative activity of the series was further assessed against two breast cancer cell lines‐MCF‐7 and the triple‐negative MDA‐MB‐231‐as well as non‐cancerous L929 fibroblasts. Notably, compound 94 exhibited markedly superior potency compared with Sorafenib, showing 7.69‐fold and 1.52‐fold greater efficacy against MCF‐7 and MDA‐MB‐231 cells, respectively, while demonstrating 3.75‐fold lower cytotoxicity toward normal L929 cells. Annexin V binding assays revealed that compound 94 significantly induced both early and late apoptosis in MCF‐7 cells and promoted late apoptosis and necrosis in MDA‐MB‐231 cells.

Molecular docking studies (PDB ID: 4ASD) and ADMET profiling were performed to elucidate the binding mode and drug‐like properties of the compounds. Docking analysis showed that the urea‐NH group of compound 94 forms a strong conventional hydrogen bond with Asp1046. Additionally, the phenyl ring of 94 engages in a π‐sulfur interaction with Cys1045, while the Leu889 side chain forms a π‐sigma interaction. Multiple van der Waals and electrostatic interactions with residues lining the binding pocket further contribute to the high potency of 94 against VEGFR‐2 [116].

In 2021, Li and co‐workers reported a novel series of fifteen 3,4‐dihydroquinazolin‐8‐yl‐3‐phenylurea derivatives through multiple steps, beginning with the treatment of commercially available 2‐amino‐6‐chlorobenzoic acid (108) with formamide to yield 5‐chloroquinazolin‐4(3H)‐one (109). Compound 109 was treated with fuming nitric acid to produce 110, which then reacted with aniline derivatives to yield the corresponding intermediates 111. Compound 111 was reduced by hydrogen on Pd/C to give intermediate 112, which reacted with isocyanate derivatives to produce the target 3,4‐dihydroquinazolin‐8‐yl‐3‐phenylurea derivatives (113‐127) in good yield, as depicted in Scheme 8 [117].

SCHEME 8.

Synthesis of 3,4‐dihydroquinazolin‐8‐yl‐3‐phenylurea derivatives (113‐127) [117].

These compounds (113‐127) were prepared with the extremely conserved VEGFR‐2 active site in mind. Some of those have demonstrated strong inhibitory effect against VEGFR‐2 and anti‐proliferation potency against tumor cells. Compound 120 exhibited the most potent cytotoxic activity against the HeLa cervical cancer cell line (IC₅₀ = 6.10 µM) and demonstrated strong inhibitory activity against VEGFR‐2 (IC₅₀ = 483.1 nM). Molecular docking studies identified compound 120 as a Type II inhibitor of VEGFR‐2. Collectively, these findings highlight 3,4‐dihydroquinazolin‐8‐yl‐3‐phenylurea derivatives as promising VEGFR‐2 inhibitors with potential anti‐angiogenic therapeutic applications [117].

Dastmalchi et al. used a de novo method (a method that designs new molecules or proteins from scratch based on a desired function or target, rather than modifying existing ones). A library of diaryl‐urea derivatives was synthesized and evaluated for in vitro antiproliferative activity against two human cancer cell lines: HT‐29 (colon adenocarcinoma) and A549 (lung adenocarcinoma) [118]. The synthetic route commenced with the reaction of 2‐chloro‐5‐nitrobenzaldehyde (128) and ethyl 2‐mercaptoacetate in the presence of K₂CO₃ at room temperature to afford the benzo[b]thiophene‐2‐carboxylate derivative (129). Subsequent alkaline hydrolysis of 129 with KOH yielded the corresponding carboxylic acid 130, which was converted to the acyl chloride 131 using thionyl chloride (SOCl₂). In the subsequent stage, the reaction involving isocyanate derivatives 132 and para‐aminophenol 133 in dichloromethane (CH₂Cl₂) resulted in the formation of compounds 134 or with benzene‐1,4‐diamine (137) in acetonitrile (AC) to give 138 (Scheme 9). Following this, a nucleophilic substitution reaction of 134 with acyl chloride 131, conducted in the presence of triethylamine (Et₃N) in THF, culminated in the generation of target compounds 135 and 136 with a commendably high yield (Scheme 9) [118].

SCHEME 9.

Synthesis of diaryl‐urea derivatives (135, 136, and 138) as VEGFR2 inhibitors [118].

Likewise, the reaction of 134 and 138 with acyl chlorides (139 or 152) in THF, Et₃N, afforded a novel series of diaryl‐urea derivatives, 140‐151 and 153, 154, respectively, as shown in Scheme 10. Four compounds, 135, 140, 151, and 153, demonstrated enhanced antiproliferative efficacy (with IC₅₀ values of 13.27, 6.62, 12.74, and 3.38 mM, respectively) against the HT‐29 cell line when juxtaposed with the positive control Sorafenib (IC₅₀ = 17.28 mM). Of particular interest, compound 153 exhibited the most pronounced activity, notably inducing apoptosis in HT‐29 cells, elevating intracellular levels of reactive oxygen species, causing cell cycle arrest at the G0/G1 phase, and modulating the expression of proteins pertinent to apoptosis and cell cycle regulation. Furthermore, compound 153 effectively interferes with the Raf/MEK/ERK signaling cascade and inhibits the phosphorylation of VEGFR2. Molecular docking studies indicated that compound 153 possesses a strong binding affinity to the active site of the VEGFR2 receptor. Taken together, compound 153 emerges as a promising candidate warranting further exploration in the quest for novel anticancer therapeutics [118].

SCHEME 10.

Synthesis of diaryl‐urea derivatives as (140‐151, 153, and 154) VEGFR2 inhibitors [118].

5.2. Urea‐Containing Compounds as Epidermal Growth Factor Receptor (EGFR) Inhibitors

The epidermal growth factor receptor (EGFR), along with its three associated proteins comprising the ERBB family, is classified as a receptor tyrosine kinases that fulfill pivotal functions in both normative physiological states and oncogenic environments. Ligand binding induces substantial conformational changes in both the extracellular and intracellular domains of receptor tyrosine kinases (RTKs), resulting in trans‐autophosphorylation of tyrosine residues within the C‐terminal regulatory region. These phosphorylated residues serve as docking sites for downstream signaling adapters and effectors, thereby promoting the activation of pathways that inhibit apoptosis and drive cell proliferation, invasion, and metastasis‐processes central to the oncogenic phenotype. In 2002, activating mutations in the tyrosine kinase domain of the EGFR gene were identified in a subset of non‐small cell lung cancer (NSCLC) patients. Tumors harboring EGFR mutations display markedly increased sensitivity to EGFR tyrosine kinase inhibitors, such as Gefitinib and Erlotinib [119].

Türe and colleagues recently described a series of novel urea derivatives bearing a 4‐phenyl‐5‐thioxo‐4,5‐dihydro‐1H‐1,2,4‐triazole scaffold. These compounds were synthesized and evaluated as potent EGFR inhibitors with promising anticancer activity against breast cancer models [120]. As outlined in Scheme 11, ethyl (4‐acetamidophenoxy)acetate (156) was prepared by esterification of N‐(4‐Hydroxyphenyl)acetamide (155) using ethyl bromoacetate. Compound 156 was treated with hydrazine hydrate to afford 157, which reacted with phenyl isothiocyanate to produce the thiosemicarbazide derivative (158). Treatment of 158 with aqueous sodium hydroxide under heating conditions promoted both the hydrolysis of the acetamide functionality to a free amine and the intramolecular cyclocondensation of the thiosemicarbazide group, yielding the desired 4,5‐dihydro‐1H‐1,2,4‐triazole‐5‐thione derivative 159. The targeted triazole‐urea derivatives (160‐168) were obtained via treatment of 159 with phenyl isothiocyanate derivatives [120]. Compound 162 demonstrated the most pronounced anticancer efficacy against MCF‐7 cells, with an IC₅₀ value of 56.97 ± 4.22 µM, and reduced cytotoxicity towards L929 cells (IC₅₀ = 1651 ± 18.39 µM) compared with Paclitaxel, IC₅₀ = 0.019 ± 0.002 µM against MCF‐7 cells and IC₅₀ = 0.165 ± 0.08 µM towards L929 cells. Furthermore, compound 162 prompted early apoptotic events in MCF‐7 cells, with respective apoptosis rates of 18.40% and 5.28%. In addition, compound 168 revealed the highest degree of EGFR inhibition, as evidenced by an IC₅₀ value of 35.1 nM (compared with Gefitinib, IC₅₀ = 9.4 nM). These findings imply that compound 162 likely mediates its anticancer effects via mechanisms that are independent of EGFR inhibition, while compound 168 manifests considerable promise as an efficacious EGFR inhibitor. Molecular modeling investigations were undertaken to elucidate potential binding interactions of compounds 163, 164, and 168 with wild‐type hEGFR. The crystal structure of human EGFR in complex with TAK‐285 (PDB ID: 3POZ) was selected for the molecular modeling studies. In compounds 163, 164, and 168, the sulfur atom of the thiocarbonyl group engaged in a water‐mediated hydrogen bond with Leu718. Additionally, the ether oxygen of compounds 163 and 164 formed a water‐mediated hydrogen bond with Ser720; this interaction was absent in compound 168. The urea NH groups of all three compounds established hydrogen bonds with the side chain of Asp855. Notably, in compound 168, the urea carbonyl oxygen formed a direct hydrogen bond with Thr790, a water‐mediated hydrogen bond with Cys775, and participated in π–π stacking interactions with Phe997.

SCHEME 11.

Synthesis of triazole‐urea hybrids (160‐168) as EGFR inhibitors [120].

The identification of novel 6‐arylureido‐4‐anilinoquinazoline derivatives functioning as EGFR inhibitors was accomplished by Zhang and collaborators in the year 2021 [121]. As delineated in Scheme 12, compound 170 was synthesized through the cyclization of 2‐amino‐4‐nitrobenzoic acid (169) with formamide; subsequently, compound 160 underwent chlorination utilizing thionyl chloride to yield 171. Compound 161 was subjected to a nucleophilic substitution reaction with various aniline derivatives, resulting in the formation of compound 172. The reduction of compound 172 was conducted in the presence of stannous chloride, leading to the generation of compound 173. The desired 6‐arylureido‐4‐anilinoquinazoline derivatives (176‐195) were synthesized in acetonitrile via the reaction of 173 with isocyanates 175, which were synthesized by treating aniline derivatives (174) with triphosgene [121]. All 20 synthesized compounds (166‐185) underwent biological evaluation employing the standardized CCK‐8 assay and enzyme inhibition assay methodologies. Among the evaluated derivatives, compounds 176, 178, 179, 181, 184, 190, 191, and 192 exhibited significant anti‐proliferative bioactivities, particularly compound 184, which demonstrated exceptional antitumor efficacy against the A549, HT‐29, and MCF‐7 cell lines (IC₅₀ values of 2.25, 1.72, and 2.81 µM, respectively) when compared to Gefitinib, Erlotinib, and Sorafenib. Furthermore, the enzyme activity inhibition assay disclosed that the synthesized compounds possessed sub‐micromolar inhibitory concentrations (IC₅₀ values ranging from 11.66 to 867.1 nM), corroborating the findings from the evaluations of tumor cell line growth inhibition. A comparative assessment of the binding interactions of compound 184 (17.32 nM), Gefitinib (25.42 nM), and Erlotinib (33.25 nM) with the EGFR suggested that compound 184 is capable of accessing the effective binding region, adopting a conformation akin to that of Gefitinib while interacting with the residues L85, D86, and R127, thus enhancing the binding affinity of compound 184 to the EGFR. Through the implementation of a molecular hybridization strategy, 14 compounds exhibiting EGFR inhibitory activity were systematically designed and synthesized, while the underlying mechanisms of action were explored through computational methodologies, thereby providing significant insights for the development of antitumor agents targeting EGFR inhibitors [121].

SCHEME 12.

Synthesis of 6‐arylureido‐4‐anilinoquinazoline derivatives as EGFR inhibitors [121].

Lima and co‐workers reported N‐(3‐(3‐phenylureido) quinoxalin‐6‐yl) acrylamide derivatives as a novel scaffold for EGFR inhibition. The synthesis of the desired N‐(3‐(3‐phenylureido) quinoxalin‐6‐yl) acrylamide derivatives (199‐211) was executed through the synthetic approach illustrated in Scheme 13, utilizing 7‐nitroquinoxaline‐2‐amine (196) as a pivotal intermediate. An efficient multi‐gram procedure for the acquisition of 197 was established, employing the cost‐effective and readily accessible o‐phenylenediamine as the initial substrate. Substituted phenylureas (198) were synthesized via the reaction of a derivative of 7‐nitroquinoxaline‐2‐amine (196) with isocyanates in anhydrous toluene under reflux conditions. The nitro functional group was converted to the respective aniline (198) utilizing tin‐(II)‐chloride dihydrate under reflux. In the concluding phase, the anilines 198 underwent reaction with the previously identified acyl chlorides in anhydrous THF in the presence of DIPEA as an organic base, yielding the target compounds 199‐211 [122].

SCHEME 13.

Synthesis of N‐(3‐(3‐phenylureido) quinoxalin‐6‐yl) acrylamide derivatives (199‐211) as EGFR inhibitors [122].

These compounds (199‐211) were tested against EGFR mutant forms. Compounds 206 and 210 demonstrated biochemical activity within the nanomolar range against both EGFR wild‐type (EGFR_wt) and the EGFR L858R mutant. Analytical investigations utilizing molecular docking techniques and the computation of reaction enthalpy have illuminated the significance of the interaction between reversible and covalent binding mechanisms with EGFR on the effectiveness of inhibition. The inhibitory properties of compound 206 were characterized against a comprehensive selection of patient‐derived tumor cell lines, indicating a preferential reduction in proliferation of EGFR‐associated cells at a concentration of 10 µM across a varied cohort of 30 cell lines derived from tumors of the colon, melanoma, breast, bladder, kidney, prostate, pancreas, and ovary [122].

Zhang and co‐workers reported a new series of 4‐anilinoquinazoline derivatives bearing urea scaffold as potent inhibitors against EGFR‐TK. Intermediate 213 was generated through the process of reductive amination involving methyl 4‐formylbenzoate (212) and a secondary amine. The resultant compound 213 underwent hydrolysis followed by acidification to yield the respective acid. The crude acid product 213 subsequently reacted with thionyl chloride, resulting in the formation of the acid chloride, which then engaged in a reaction with sodium azide to produce acyl azide 214. Alternatively, the reflux of a mixture comprising acyl azide (214), 6‐amino‐4‐anilinoquinazolines (215), and toluene facilitated the synthesis of compounds (217‐231). Furthermore, compound 232 was synthesized by refluxing 214 in conjunction with (R)‐6‐amino‐4‐(1‐phenylethylamino)quinazoline (216) in toluene as visualized in Scheme 14 [123].

SCHEME 14.

4‐anilinoquinazoline derivatives bearing urea scaffold (217‐232) as EGFR inhibitors [123].

The antiproliferative properties of compound 217‐232 were systematically assessed in vitro utilizing the MTT assay against A431 and A549 cell lines. The structure–activity relationship (SAR) of the target compounds was thoroughly analyzed. Compounds 220, 225, and 226, which exhibited significant antiproliferative effects, were assessed for their inhibitory effects on EGFR‐TK. Notably, compound 226 demonstrated robust inhibitory activity against EGFR‐TK. Furthermore, compound 226 demonstrated complete tumor growth inhibition at a dose of 50 mg/kg in a well‐established A549 xenograft model in nude mice. These results suggest that 4‐anilinoquinazoline derivatives bearing a diarylurea moiety and a tertiary amino group at the 6‐position represent promising candidates as anticancer agents and EGFR tyrosine kinase inhibitors [123].

Our research group investigated novel 5‐Fluorouracil analogues (235‐237) and perfluorophenyl derivatives (239‐242) bearing a urea scaffold as EGFR inhibitors [124]. The target 5‐fluorouracil analogs (235‐237) were efficiently synthesized by reacting aryl isocyanates (42, 165, and 233) with 5‐aminouracil (234) in acetonitrile at room temperature (Scheme 15). Similarly, the perfluorophenyl aryl‐urea derivatives (239‐241) were prepared via the reaction of the same aryl isocyanates with 2,3,4,5,6‐pentafluoroaniline (238) under identical conditions (Scheme 15).

SCHEME 15.

5‐Fluorouracil analogues (235‐237) and perfluorophenyl derivatives (239‐241) bearing urea scaffold as EGFR inhibitors [124].

The antiproliferative activity of the synthesized compounds was evaluated against human breast cancer (MCF‐7) and colon cancer (HCT‐116) cell lines, using non‐cancerous skin fibroblast cells (BJ‐1) as a control. MTT assay results revealed that compounds 237 and 241 exhibited potent cytotoxic activity. In particular, compounds 239‐241 showed strong antiproliferative effects against MCF‐7 cells, with IC₅₀ values of 167 ± 0.57 µM (239), 23.4 ± 0.68 µM (240), and 28.8 ± 1.13 µM (241), respectively, compared to 5‐Fluorouracil (5‐FU) (IC₅₀ = 160.7 ± 0.22 µM). Compound 239 displayed a favorable safety profile on BJ‐1 cells, with only 3.9 ± 0.42% cytotoxicity at 100 µM and was therefore selected for further mechanistic studies. At the molecular level, treatment with compound 239 significantly downregulated BCL‐2 gene expression in MCF‐7 cells, achieving greater suppression than 5‐FU. Concurrently, it markedly upregulated the pro‐apoptotic genes p53 and BAX. Cell cycle analysis and apoptosis/necrosis assays demonstrated that 239 induced S and G2/M phase arrest in MCF‐7 cells. Molecular docking studies further revealed that 239 exhibited strong binding affinities to key anticancer target proteins, including EGFR, CDK2, ERα, BAX, BCL‐2, and p53. These interactions involved diverse bonding types (hydrogen bonding, hydrophobic, and π‐stacking), suggesting potential multi‐target inhibitory activity. In addition, ADMET predictions indicated that the compounds comply with Lipinski's rule of five, reflecting favorable drug‐like properties. Finally, molecular dynamics (MD) simulations confirmed the stability of the 239‐protein complexes, as evidenced by low RMSD, RMSF, and appropriate SASA values [124].

In 2023, a new series of aryl‐urea derivatives incorporating trifluoromethyl and sulfonyl moieties was designed and synthesized to explore the influence of these groups on EGFR inhibitory activity. Under mild, metal‐free conditions, the reaction of 4‐tolylsulfonyl isocyanate (233) with various primary amines (242) in acetonitrile at room temperature readily afforded the corresponding 4‐tolylsulfonylurea derivatives (243‐247). Similarly, treatment of 4‐tolyl isocyanate (165) with the same amines yielded the 4‐tolylurea derivatives (248‐252) (Scheme 16) [125]. The anticancer activity of the synthesized compounds was evaluated against eight human cancer cell lines: A549 (lung), HCT116 (colon), PC3 (prostate), A431 (epidermoid), HepG2 (liver), HOS (osteosarcoma), PACA2 (pancreatic), and the non‐cancerous BJ‐1 fibroblast line. Notably, compounds 243, 244, and 245 exhibited superior antiproliferative activity compared to doxorubicin. In particular, compounds 243 and 244 displayed IC₅₀ values of 44.4 µM and 22.4 µM, respectively, against PACA2 cells, outperforming Doxorubicin (IC₅₀ = 52.1 µM). Compound 245 showed potent activity with IC₅₀ values of 17.8 µM (HCT116), 12.4 µM (HePG2), and 17.6 µM (HOS). Quantitative reverse transcription polymerase chain reaction (qRT‐PCR) analysis revealed that compounds 243 and 250 significantly downregulated PALB2 expression in PACA2 cells. In PC3 cells, compound 243 suppressed the expression of both BRCA1 and BRCA2. In A549 cells, compound 244 reduced the expression levels of EGFR and KRAS. Furthermore, compounds 243 and 245 downregulated TP53 and FASN gene expression in HCT116 cells [125].

SCHEME 16.

New diaryl‐urea derivatives (243‐252) as EGFR inhibitors [125].

5.3. Urea‐Containing Compounds as c‐MET Pathway Inhibitors

The c‐Met proto‐oncogene encodes a transmembrane receptor tyrosine kinase (c‐MET) that serves as the sole receptor for hepatocyte growth factor (HGF). Aberrant overexpression of c‐MET is frequently observed in a wide range of human malignancies. Upon binding of HGF to the extracellular domain of c‐MET, receptor dimerization and autophosphorylation of specific intracellular tyrosine residues occur, triggering the activation of multiple downstream signaling cascades [126, 127, 128]. Additionally, c‐MET signaling exerts potent pro‐angiogenic effects by stimulating endothelial cell proliferation, migration, and tube formation, thereby facilitating neovascularization within the tumor microenvironment [129]. The FDA‐approved c‐MET inhibitors, including Amivantamab, Tepotinib, and Crizotinib, represent a significant advancement in targeted cancer therapy. Amivantamab, also a monoclonal antibody, targets both c‐MET and EGFR, providing a dual mechanism to combat cancer effectively. Tepotinib and Crizotinib are inhibitors that target the c‐MET pathway; these inhibitors highlight the therapeutic potential of the c‐MET pathway to improve oncological care [128, 130, 131].

Recently, Shaldam and co‐workers reported a series of aryl pyridine derivatives bearing a 1,3‐diphenylurea scaffold as dual c‐MET and VEGFR‐2 inhibitors with apoptosis‐inducing properties. The synthetic route to the target aryl pyridin‐2‐yl phenylurea derivatives (254‐267) is illustrated in Scheme 17. The synthesis began with the preparation of 1‐(4‐acetylphenyl)‐3‐phenylurea (253) through the reaction of 4‐aminoacetophenone (20) with phenyl isocyanate (42) in refluxing toluene. Subsequent cyclization of 253 with various aldehydes, ethyl cyanoacetate, and ammonium acetate in absolute ethanol under reflux for 24 h afforded the desired pyridine‐containing urea derivatives (254‐267) (Scheme 17) [132]. Regarding biological activity, compounds 257, 259, 263, 264, and 267 displayed potent inhibitory activity against c‐MET, with IC₅₀ values of 65, 24, 150, 170, and 18 nM, respectively. These compounds also exhibited strong inhibition of VEGFR‐2, with IC₅₀ values of 310, 35, 290, 320, and 24 nM, respectively. In cytotoxicity assays, the same derivatives showed potent antiproliferative activity against MCF‐7 breast cancer cells (IC₅₀ = 0.76–21.5 µM) and PC‐3 prostate cancer cells (IC₅₀ = 1.85–3.42 µM), comparable or superior to the reference drug Cabozantinib (IC₅₀ = 1.06 µM in MCF‐7 and 2.01 µM in PC‐3).

SCHEME 17.

Synthesis of aryl pyridine derivatives with 1,3‐diphenylurea scaffold as c‐MET inhibitors [132].

Among them, compound 267 was particularly noteworthy. It induced a marked increase in apoptosis in MCF‐7 cells (total apoptosis rate of 33.19%, comprising 25.15% early and 8.04% late apoptosis), representing an 87.34‐fold increase relative to untreated controls. It also caused cell cycle arrest at the G2/M phase and modulated the expression of apoptosis‐related genes, upregulating P53, Bax, caspase‐3, and caspase‐9, while downregulating the anti‐apoptotic gene Bcl‐2. In vivo studies further confirmed the anticancer efficacy of 267, demonstrating significant reductions in tumor volume and weight (tumor growth inhibition ratio of 56.1%) along with favorable effects on hematological parameters. Consequently, compound 267 can be developed further as a target‐oriented, selective chemotherapeutic for the treatment of breast cancer [132].

Xiong et al. reported 10 novel quinoline derivatives bearing a urea moiety as potential anti‐colorectal‐cancer agents [131]. Among the compounds investigated, compound 277 (Scheme 18) demonstrated exceptional in vitro anticancer activity against COLO 205 cells, evidenced by an IC₅₀ value of 0.11 µM, which surpasses the potency of Regorafenib (IC₅₀ > 10.0 µM) and Fruquintinib (IC₅₀ > 10.0 µM) by more than 90‐fold. Furthermore, compound 277 exhibited an impressive selectivity exceeding 90‐fold towards COLO 205 cells in contrast to human normal colorectal mucosa epithelial FHC cells. A flow cytometry analysis indicated that compound 277 was effective in inducing apoptosis in COLO 205 cells; however, it did not result in cell cycle arrest within these cells. The results from the initial kinase profiling study suggested that compound 277 may serve as a potential dual inhibitor of HGFR and MST1R, with corresponding IC₅₀ values of 0.11 µM and 0.045 µM, respectively [131].

SCHEME 18.

Synthesis of novel quinoline and thiazolidinone semi‐carbazone as c‐MET inhibitor [131].

5.4. Urea‐Containing Compounds as Raf/MEK/ERK Pathway Inhibitors

The RAF‐MEK‐ERK signaling pathway constitutes an essential regulatory cascade that governs cellular processes, including proliferation, differentiation, and survival. Alterations in the constituents of this pathway, especially within RAF kinases, frequently occur in a multitude of malignancies, thus making it a significant focus for therapeutic strategies [133, 134, 135]. Extracellular signal‐regulated kinases (ERKs) serve as crucial signaling entities within the RAS‐RAF‐MEK‐ERK signaling cascade and have surfaced as viable targets for antitumor interventions, presenting a promising avenue for oncological therapeutics. Consequently, the formulation of antitumor pharmacological agents that specifically target ERK proteins has garnered significant scholarly interest [136].

Fu et al. documented a novel diarylurea compound designated as “4‐(4‐(3‐(2‐chloro‐3‐(trifluoromethyl)phenyl) ureido) phenoxy)‐N‐methylpicolinamide,” subsequently naming this innovative compound “Sorafenib meta‐chlorine” and referring to it by the abbreviation SMCl, as shown in Figure 4 [137]. The in vitro anti‐cancer effects of SMCl were rigorously assessed in hepatocellular carcinoma (HCC) cell lines employing MTS, colony formation, and wound healing assays.

FIGURE 4.

Chemical structure of SMCl against Sorafenib [137].

The modulation of the RAS/RAF/MEK/ERK signaling cascade was meticulously assessed employing Western blot methodologies. The in vivo therapeutic efficacy was appraised through the utilization of a xenograft model. The findings derived from the MTS and colony formation assays suggested that SMCl markedly diminished the viability of hepatocellular carcinoma (HCC) cells. The Western blot analysis disclosed that SMCl proficiently curtailed the proliferation of hepatocellular carcinoma via significant attenuation of the RAS/RAF/MEK/ERK signaling pathway, with this inhibitory effect demonstrating both temporal and concentration‐dependent attributes. Moreover, SMCl manifested considerable therapeutic efficacy in the xenograft tumor model, realizing a tumor inhibition rate of 72.37%. Notably, it did not produce a statistically significant effect on spleen weight or body weight in murine subjects, indicating low toxicity towards normal tissues. To facilitate the discovery of a potential active molecule for the clinical management of liver cancer, this investigation initially elucidates the effects of SMCl on HCC cells and its influence on the RAS/RAF/MEK/ERK signaling framework. Figure 5 illustrates the mechanistic action of SMCl [137].

FIGURE 5.

SMCl promotes anti‐HCC effects by targeting the RAS/RAF/MEK/ERK pathway [137].

Tao and colleagues conceptualized and synthesized an innovative scaffold characterized by a pyrrole‐fused urea framework (SHR2415) which serves as a highly efficacious inhibitor of ERK1/2. The synthesis pathway of SHR2415 was executed with relative ease, as delineated in Scheme 19. The synthetic route comprises six pivotal steps, wherein the essential building block (283) was necessitated. Commencing from the commercially accessible chiral alcohol (278), TBS (tert‐butyldimethylsilyl) protection (279) followed by reductive amination with aldehyde (280) yielded a commendable quantity of compound (281). Following this, the Miyaura borylation of 282 afforded boronic ester (283), which upon coupling with intermediate (284) successfully yielded 285. Ultimately, compound 286 = SHR2415, was generated through the deprotection of the TBS moiety in 285 under acidic conditions [138].

SCHEME 19.

Synthesis of the lead compound SHR2415 (286) as a highly potent ERK1/2 inhibitor [138].

As a principal compound, SHR2415 has demonstrated considerable potency as evidenced by the assays performed on the ERK1/2 enzyme and the Colo205 cell line. Furthermore, SHR2415 displayed an advantageous pharmacokinetic profile across diverse species and notable efficacy in the murine Colo205 tumor xenograft model. Moreover, an upcoming preclinical study of SHR2415 will include its efficacy with additional cancer cell lines and its prospective synergistic effects in combination with other MAPK inhibitors [138].

6. Future Prospects and Challenges

Urea‐containing compounds have shown promise in clinical and preclinical studies for treating various malignancies, particularly those characterized by aberrant TK activity. Despite successes, resistance mechanisms‐such as kinase mutations (e.g., EGFR T790M, RET gatekeeper variants), bypass pathways, and polyclonal adaptations‐limit long‐term efficacy. The emergence of combination therapies has further expanded the potential of urea‐based TKIs in oncology. Combination of urea‐containing compounds with other therapeutic agents, such as immune checkpoint inhibitors or chemotherapeutics, could enhance overall effectiveness, mitigate resistance, and improve patient outcomes. Ongoing clinical trials are exploring synergistic effects and optimal dosing regimens, aiming to personalize treatment strategies based on patient‐specific tumor profiles. Moreover, employing green chemistry principles in the synthesis of these compounds can enhance their production efficiency and minimize environmental impact. Encouraging sustainability in pharmaceutical research not only addresses regulatory pressures but also aligns with the evolving landscape of drug development. Another area ripe for exploration is the integration of these compounds into personalized medicine frameworks. Identifying biomarkers that predict responsiveness to specific urea‐containing TKIs will enable more tailored approaches, improving therapeutic success rates and minimizing adverse effects.

Challenges include toxicity management, resistance prediction, and equitable access, particularly in developing regions. Academia‐pharma collaborations will drive selective, multi‐modal therapies, potentially transforming urea‐based TKIs into cornerstones of precision oncology. Prospects lie in the next generation of antineoplastic urea‐based TKI compounds with improved selectivity and pharmacokinetics, along with continued exploration of their mechanisms, structural optimization, and the development of new derivatives. The integration of artificial intelligence and machine learning in drug design could expedite the identification of promising compounds, while high‐throughput screening methods allow for rapid assessment of large chemical libraries.

7. Conclusions

Antineoplastic urea‐containing compounds based on tyrosine kinase inhibition represent a vibrant and evolving field with significant implications for cancer therapy. As our understanding of molecular targets continues to deepen, the development and refinement of these compounds are likely to play an integral role in shaping future cancer treatment paradigms. By harnessing innovative synthetic strategies, exploring combination therapies, and adopting sustainable practices, researchers can propel the field forward, ultimately enhancing patient outcomes and quality of life. The journey from bench to bedside is ongoing, and the future of urea‐based TKIs in oncology holds great promise. By addressing current limitations, future developments hold promise for enhanced efficacy and broader applicability in antineoplastic therapy.

Author Contributions

Farid M. Sroor: conceptualization, supervision, data curation, writing – review and editing, writing – original draft, project administration, and investigation.

Conflicts of Interest

The authors declare no conflicts of interest.

Biography

I, Farid M. Sroor, hailing from Egypt, presently occupy the position of full professor at the National Research Centre (NRC) located in Cairo. I attained my Doctorate degree in the year 2015 under the supervision of Professor Frank Edelmann at the University of Magdeburg in Germany. During the period of 2016‐2017, I was awarded a postdoctoral scholarship by the French embassy in Cairo to conduct a scientific proposal in the field of organometallic chemistry at the LCC institute in Toulouse, France. In the academic year 2021‐2022, I was granted a second postdoctoral scholarship from the Ministry of Higher Education and Scientific Research in Egypt to pursue a scientific proposal in organometallic chemistry at the University of Göttingen in Germany. In 2022‐2023, I was awarded a third postdoctoral fellowship from the French embassy in Cairo to undertake a scientific proposal in organic chemistry at the Faculty of Pharmacy at Aix‐Marseille Université, France. I possess extensive expertise in the synthesis, structural characterization, and catalytic activity of novel organic and organometallic compounds, in addition to my proficiency in managing highly air‐sensitive organolanthanide compounds, including exceedingly sensitive organocerium(III) compounds. My research interests are predominantly centered on the design and synthesis of novel ligands that will alter the properties of metal ions to facilitate the stabilization of uncommon oxidation states or coordination geometries. I am particularly focused on the preparation of new catalysts (organometallic compounds) and their catalytic activity in organic chemistry, specifically in the formation of C─H, C─C, and C─X bonds. Conversely, the current research initiatives within our laboratory are directed towards the development of environmentally benign and economically viable processes of significance to organic synthesis. This endeavor integrates techniques from both organic and organometallic chemistry synthesis to foster the development of more efficient catalytic transformations by employing organometallic and/or organic catalysts through one‐pot synthesis reactions. In addition to my laboratory responsibilities, I am actively engaged in the training and supervision of MSc and PhD candidates, as well as final‐year undergraduate project students.

Data Availability Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.