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Review

Targeting PRMT5: Current Inhibitors and Emerging Strategies for Therapeutic Intervention

by
Zhihang Shen
* and
Chenglong Li
*
Department of Medicinal Chemistry, College of Pharmacy, University of Florida, Gainesville, FL 32610, USA
*
Authors to whom correspondence should be addressed.
Processes 2025, 13(9), 2878; https://doi.org/10.3390/pr13092878
Submission received: 24 June 2025 / Revised: 20 July 2025 / Accepted: 5 September 2025 / Published: 9 September 2025
(This article belongs to the Special Issue Pharmaceutical Development and Bioavailability Analysis, 2nd Edition)
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Abstract

Epigenetic dysregulation is a hallmark of tumorigenesis, with arginine methylation—a post-translational modification—emerging as a key regulatory mechanism in cancer biology. This modification, catalyzed by protein arginine methyltransferases (PRMTs), influences critical cellular processes, including proliferation, differentiation, transcription, RNA splicing, DNA repair, and immune signaling. Among the PRMT family, PRMT5 has garnered significant attention due to its elevated expression across various solid tumors and hematological malignancies, and its strong association with poor clinical outcomes. Notably, PRMT5 exhibits a unique vulnerability in methyl-thio-adenosine phosphorylase (MTAP)-deficient cancers, making it an attractive therapeutic target. Recent advances have led to the development of several PRMT5 inhibitors with diverse binding modes, some of which have progressed into clinical trials for advanced cancers. This review provides a structural and mechanistic overview of PRMT5, summarizes current inhibition strategies, and discusses the challenges and future directions in targeting PRMT5 for cancer therapy.

Graphical Abstract

1. Protein Arginine Methyltransferases 5 (PRMT5) Overview

PRMT5 is a type II arginine methyltransferase that symmetrically di-methylates arginine residues on histone and non-histone proteins, regulating key cellular processes such as transcription [1], RNA splicing [2,3], and DNA repair [4,5]. While essential for normal development and cellular function, PRMT5 is frequently overexpressed in various cancers and linked to poor prognosis [6]. Its role in promoting tumor growth [7,8], immune evasion [9,10,11], and its synthetic lethality in MTAP-deficient cancers has made PRMT5 a compelling therapeutic target, driving significant interest in both its biological functions and pharmacological inhibition.

1.1. PRMT Enzymes

Nine PRMT isoforms (PRMT1-9) are found in mammalian genomes. Type I PRMTs, such as PRMT1, 2, 3, 4, 6, and 8, form monomethyl-arginine (MMA) and asymmetric dimethylarginine (ADMA). Type II PRMTs, such as PRMT5 and 9, form MMA and symmetric dimethylarginine (SDMA). Type III enzymes, such as PRMT7, only produce MMA. PRMT enzymes utilized the cofactor S-adenosylmethionine (SAM or AdoMet) as a methyl donor to transfer the methyl group to protein arginine guanidinium nitrogen, generating a methylated guanidinium moiety and S-adenosylhomocysteine (SAH or AdoHcy), which is salvaged and re-used for methionine biosynthesis. Thus, PRMT family proteins all share a conserved SAM-dependent methyltransferase domain. However, outside the methyltransferase domain, they have distinct motif structures. PRMT1, 6, and 7 only contain catalytic domains, whereas PRMT2-5, 8, and 9 have N-terminal and catalytic domains. In the meanwhile, PRMT7 and 9 both contain a second catalytic domain, although the second domain in PRMT9 is considered a pseudo domain (Figure 1).

1.2. PRMT5 Structure

1.2.1. PRMT54:MEP504 Hetero-Octamer Complex Structure

Among these enzymes, PRMT5 is uniquely structured and functionally significant, particularly in cancer-related processes. In detail, PRMT5 complex with MEP50 (methylosome protein 50) forms a ~453 kDa hetero octamer, which is composed of four PRMT5 proteins in the center of the complex, with four MEP50 proteins (also called WD repeat domain 77) decorating the outer surface. In this complex, the PRMT5 proteins form two dimers in the conserved head-to-tail arrangement, while the PRMT5 tetramer forms the core complex. The dimerization between adjacent PRMT5 monomers occurs by salt bridges. Arg488 and Asp491 from one monomer make salt bridges with Asp491 and Arg488 of an adjacent monomer (Figure 2). Apart from this direct interaction, extensive charged and hydrophobic interactions are mediated by the contacts between the N-terminal triosephosphate isomerase (TIM) barrel and the C-terminal catalytic domain of the adjacent monomer. In addition, the PRMT5:MEP50 complex also requires substrate adaptor proteins (SAPs), such as chloride channel nucleotide sensitive 1A (pICLn), Rio domain-containing protein 1 (RIOK1), and cooperator of PRMT5 (COPR5), to recognize and recruit substrates to the catalytic sites [13,14].

1.2.2. PRMT5:MEP50 Monomer Structure

PRMT5 monomer consists of an N-terminal TIM barrel, an intermediate Rossman-fold, and a C-terminal β-barrel domain [15]. Due to the uniqueness of the N-terminal, MEP50 acts as a binding regulator with PRMT5, among all PRMT family proteins. An MEP50 binds to a PRMT5 through the TIM barrel, which highly increases the methyltransferase activity (Figure 3). This may be partially due to the complex stability improvement after MEP50 binding. The C-terminal catalytic domain consists of a Rossman-fold and a β-barrel domain, which are required for binding cofactor (SAM/AdoMet) and substrate, respectively. In the cofactor binding pocket, the adenine ring of SAM analog (A9145C) forms two hydrogen bonds with Asp419. The hydroxyl groups of the ribose moiety are stabilized by hydrogen bonds to the side chains of Glu392 and Tyr324. The carboxylate group makes a split hydrogen bond to the side chain of Tyr334 and Lys333 in PRMT5.
The PRMT5 substrate pocket shares similarities with all arginine methyltransferases which contain a pair of highly conserved glutamate residues, referred to as the ‘double-E loop’. This loop provides a negative charge towards the bottom of the pocket to coordinate the positively charged guanidinium group of the substrate arginine residue. Although no PRMT5 in complex with a protein substrate has been crystallized so far, a structure with substrate peptide bound to the enzyme has been obtained (PDB:4GQB [15]). Based on this structure, histone 4 is shown as a PRMT5 substrate example. Arginine residue accesses the active site through a narrow tunnel formed by Phe327 and Trp579 and thus stabilizes by four hydrogen bonds with Glu435 and Glu444. In the meanwhile, the peptide substrate forms a sharp β-turn in the active site, which requires specific substrates to achieve the conformation flexibility. This observation is supported by substrate profiling studies: PRMT5 substrates have a fixed pattern, a preference for arginine flanked by glycine (e.g., GRG) [16]. The presence of glycine around the targeted arginine builds conformational flexibility into the region of methylation.

1.3. PRMT5 Inhibition Mechanisms in Cancer Therapy

PRMT5 is upregulated in various types of cancer, and its expression levels are strongly associated with poor prognosis and lower survival rates. As a result, PRMT5 has emerged as a promising target for cancer therapy.

1.3.1. Regulation by Endogenous Ligand

Cancer cells lacking the MTAP gene are particularly sensitive to PRMT5 inhibition. MTAP, often co-deleted with the CDKN2A tumor suppressor in ~15% of cancers, normally metabolizes methyl-thio-adenosine (MTA) in the methionine salvage pathway [17]. MTAP loss leads to 5–20-fold MTA accumulation, which selectively inhibits PRMT5 by occupying its unique catalytic site [18]. This partial inhibition renders MTAP-deficient (MTAP−/−) cells more vulnerable to further PRMT5 suppression, establishing a synthetic lethal interaction that allows PRMT5 inhibitors to selectively target MTAP−/− tumors while sparing normal (MTAP+/+) cells—an approach with significant clinical promise.

1.3.2. Regulation by PTM

In the meanwhile, as a major type II PRMT, PRMT5 controls the methylation level of its substrates, including histone, splicesome, ribosomal proteins and other proteins. Four arginine residues, histone H4 arginine 3 (H4R3me2s), histone H2A arginine 3 (H2AR3me2s), histone H3 arginine 8 (H3R8me2s), and histone H3 arginine 2 (H3R2me2s), are catalyzed within histone proteins [19,20] (Figure 4A). Of those, H4R3me2s and H3R8me2s are largely associated with transcriptional repression, whereas they are also related to transcriptional activation of some genes, such as FGFR3 [21] and elF4E [22] expression in colorectal cancers. H3R2me2s is mainly related to transcriptional activation of target genes, such as SLC7A11 [23], RNF168 [24], and FOXP1 [25], in lung and breast cancer.

1.3.3. Regulation by Protein–Protein Interactions (PPI)

PRMT5 requires additional protein–protein interactions to maintain its enzymatic activity and stability. One of its key partners, MEP50, forms a hetero-octameric complex with PRMT5 that enhances both structural stability and catalytic efficiency. Notably, PRMT5 is the only member of the PRMT family that relies on MEP50, offering a unique feature that may be leveraged for selective therapeutic targeting [15].
In addition to MEP50, PRMT5 interacts with substrate adaptor proteins (SAPs) to recruit specific substrates for methylation. To date, three SAPs have been identified: pICLn, RIOK1, and COPR5 [26]. COPR5 bridges PRMT5 to the N-terminal tail of histone H4, facilitating H4R3 methylation [14]; pICLn is essential for PRMT5-mediated methylation of Sm proteins, influencing RNA splicing [27]; and RIOK1 directs PRMT5 to nucleolin, a regulator of ribosome biogenesis [28] (Figure 4A). Disrupting the interfaces between PRMT5 and its SAPs offers a promising strategy to block substrate-specific methylation events, providing a more precise and potentially less toxic approach to cancer therapy.

1.3.4. Regulation by Ubiquitin–Proteasome System (UPS)

Targeting PRMT5 degradation has emerged as an alternative therapeutic strategy to enzymatic inhibition in cancer therapy. Given PRMT5’s oncogenic role in supporting tumor growth and survival, promoting its degradation through the UPS offers a means to suppress its function regardless of catalytic activity. E3 ubiquitin ligases such as CHIP/Hsp70 (carboxyl terminus of heat shock cognate 70-interacting protein) have been shown to mediate PRMT5 ubiquitination and degradation [29] (Figure 4B). Additionally, TRAF6, an E3 ubiquitin ligase, can also promote PRMT5 ubiquitination and activation in some cancers [30]. Therapeutically, exploiting PRMT5 degradation—potentially through PROTACs—may offer greater selectivity, overcome resistance to catalytic inhibitors, and provide an alternative route for disrupting PRMT5-driven oncogenic programs in cancer cells.

1.3.5. Regulation by Liquid–Liquid Phase Separation (LLPS)

Due to its ubiquitously distributed substrates, PRMT5 methylation has been considered as a whole-cell level effect. Arginine methylation enzymes, including PRMT1 and 5 [31,32,33,34], were found to be involved in modulating protein liquid–liquid phase separation (LLPS) (Figure 4C). Stress granules (SGs), one subtype of LLPS, are ribonucleoprotein assemblies formed in the cytoplasm to prevent mRNA degradation under different types of stress [35,36]. Many known PRMT5 substrates are found in cancer stress granule components [37,38]. These findings suggest that disrupting PRMT5-regulated liquid–liquid phase separation, particularly stress granule formation, may represent a novel therapeutic strategy to inhibit PRMT5 function in cancer. Given that stress granules are closely associated with chemotherapy resistance by protecting mRNAs and promoting cell survival under stress, targeting PRMT5-driven LLPS may help overcome treatment resistance and enhance the efficacy of anticancer therapies.

1.4. Current PRMT5 Inhibitors in Clinical Trials

PRMT5 inhibitors are small molecules that block the enzymatic activity or key interactions of PRMT5. Aberrant PRMT5 activity is linked to cancer progression and poor prognosis [39]. Targeting PRMT5—especially in MTAP-deficient tumors—has shown therapeutic promise, making PRMT5 inhibitors a growing focus in oncology drug development.
In recent years, numerous novel PRMT5 inhibitors with diverse binding mechanisms have been developed, and several have progressed into clinical trials as single agents or in combination therapies for solid and advanced tumors. To date, 17 distinct PRMT5 inhibitors have entered clinical studies, including four SAM-competitive inhibitors [40,41,42,43,44,45], two SAM-cooperative inhibitors [46,47,48,49], two MAT2A inhibitors [50,51], and nine MTA-cooperative inhibitors [52,53,54,55,56,57,58,59,60,61,62,63] (Table 1). As of May 2025, only 12 of these inhibitors continue to be under active investigation (Figure 5).
GSK3326595 [64], the first SAM-cooperative PRMT5 inhibitor, showed manageable side effects in Phase I [49,65] and advanced to Phase II for HR-positive breast cancer [48] and acute myeloid leukemia (AML) [49]. However, the clinical development of GSK3326595 has since been discontinued. SCR-6920, developed by Jiangsu Simcere Pharmaceutical Co., Ltd., completed Phase I studies in advanced malignant tumors and has progressed to Phase II trials in participants with advanced solid tumors (AST) and non-Hodgkin lymphoma (NHL) [46,47]. Unlike GSK3326595, SCR-6920 remains under active clinical investigation.
JNJ-64619178 [66], a SAM-competitive PRMT5 inhibitor, exhibited manageable toxicity and antitumor activity in adults with AST and NHL during Phase I trials [41], though it showed no efficacy in myelodysplastic syndromes [40]. PF-06939999 demonstrated a tolerable safety profile with tumor responses in HNSCC and NSCLC [40,42,43], while PRT811 and PRT543, developed by Prelude Therapeutics, completed Phase I trials for high-grade glioma and hematologic malignancies, respectively [44,67]. However, most clinical trials for SAM-competitive PRMT5 inhibitors have been discontinued, as second-generation PRMT5 inhibitors have shown better efficacy.
The second-generation PRMT5 inhibitors focus on targeting the PRMT5–MTA complex to specifically kill MTAP-deficient cancer cells while sparing normal cells. MRTX1719 (BMS-986504) [68,69,70], developed by Mirati Therapeutics (acquired by Bristol Myers Squibb), is currently applied in patients with advanced or metastatic solid tumors in Phase 1/2 trial [52]. AMG193 is mainly studied in combination therapy, such as in combination with docetaxel or IDE397 in NSCLC [53,54,55,71]. AZD3470 [56,57], TNG462 [58,72], TNG908 [59,73], PEP08 [62], and BAY 3713372 [63] in patients with MTAP-deleted solid tumors are currently in the safety and tolerability testing stage. BGB-58067 and CTS3497 [61], are MTA-cooperative PRMT5 inhibitors developed by BeiGene and CytosinLab Therapeutics, respectively, are being evaluated for safety, tolerability, pharmacokinetics, pharmacodynamics, and preliminary antitumor activity in patients with MTAP-deficient advanced solid tumors [60].
Another PRMT5 inhibition strategy is to target MAT2A, an enzyme that catalyzes SAM production from methionine and ATP. Without SAM as the methyl donor, PRMT5 methyltransferase activity will be inhibited. IDE397 and S095035 are in Phase I clinical trial as a single agent or in combination with other anticancer agents including taxanes (docetaxel, paclitaxel), or sacituzumab govitecan (SG), in adult patients with selected advanced or metastatic MTAP-deleted advanced solid tumors [50,51].

2. Structure-Based PRMT5 Inhibitor Development

This section summarizes PRMT5 inhibitors with available co-crystal or cryo-EM structures deposited in the Protein Data Bank (PDB), alongside recent compounds that act through novel mechanisms. We categorize these inhibitors based on their binding regions and modes of action. Specifically, we review inhibitors that target the C-terminal catalytic pocket, including SAM-cooperative, SAM-competitive, MTA-cooperative synthetic lethal, and allosteric inhibitors. Additionally, we highlight emerging strategies that focus on the N-terminal TIM barrel domain, such as inhibitors that disrupt PRMT5–substrate adaptor and PRMT5–MEP50 interactions—representing promising new directions in PRMT5-targeted therapy.

2.1. PRMT5 Inhibitors Targeting C-Terminal Catalytic Pocket

2.1.1. SAM-Cooperative Inhibitors

EPZ015666, the first discovered PRMT5 inhibitor (GSK3326595 analogue), binds to the peptide-binding site of PRMT5 [64]. The compound interacts directly with the backbone NH of Phe580 and the side chains of Glu444. Additionally, the tertiary nitrogen in its tetra-hydro-isoquinoline (THIQ) ring system forms a water-mediated interaction with Glu435. The THIQ group also engages in a π–π stacking interaction with Phe327, while its phenyl ring participates in a cation–π interaction with the partially positively charged methyl group of SAM. Binding properties revealed that the cation–π interaction contributes at least 3 kcal mol−1 of binding energy, highlighting its SAM-cooperative characteristics (Figure 6A).
In 2020, Shen et al. developed the first-in-class PRMT5 degraders by conjugating EPZ015666 with a VHL E3 ligase ligand to generate MS432251 (Figure 6B) [75]. They initially replaced the oxetane group with an azetidine group, followed by the addition of a linker to this moiety, as the solvent-exposed region does not interact with PRMT5 residues and is unlikely to affect binding. Mechanistic studies demonstrated that MS432251 effectively reduced PRMT5 levels in MCF-7 cells and induced PRMT5 degradation in an E3 ligase- and proteasome-dependent manner. Additionally, this compound exhibited excellent plasma exposure in mice, making it a valuable chemical tool for investigating PRMT5 functions in health and disease.
Inspired by GSK3326595, Zhou et al. from Simcere Pharmaceutical developed SCR-6920, a PRMT5 inhibitor currently in phase 2 clinical trials for the treatment of advanced solid tumors and non-Hodgkin’s lymphoma [46,47,74]. Structurally, the THIQ moiety of SCR-6920 adopts a binding mode similar to that of GSK3326595, relying on SAM-dependent stabilization (Figure 6C). However, unlike GSK3326595, SCR-6920 does not interact with Glu444. Instead, the THIQ ring forms hydrogen bonds with Ser578, and the carbonyl oxygen of the 1,4-diazepane group engages in a hydrogen bond with Phe580, contributing to binding stability. Notably, no preclinical efficacy data have been publicly disclosed.

2.1.2. SAM-Competitive Inhibitors

The development of SAM-competitive PRMT5 inhibitors focuses on designing SAM analogues. LLY-283 [76], the first potent inhibitor developed by Eli Lily, binds the SAM pocket with its adenine and ribose mimicking SAM interactions in PRMT5:MEP50 structures (Figure 7A). Adenine forms hydrogen bonds with Asp419 and Met420, while ribose interacts with Glu392 and Tyr324. Its phenyl group displaces Phe327, inducing a rotamer change with minimal main chain disruption (Figure 7B). A key concern with LLY-283 is its selectivity across different PRMTs. To address this, Prelude Therapeutics developed a covalent compound, Aldehyde 10 (a precursor to PRT543 and PRT811), which targets the unique Cys449 residue in PRMT5, a position occupied by serine in other PRMTs [77]. Co-crystal structures revealed that Cys449 is positioned within bonding distance of the molecule (Figure 7C). Interestingly, instead of the expected -OH group from the addition of -SH to the aldehyde, an unexpected elimination of H2O likely occurred, forming a trans double bond between the sulfur and nitrogen atoms. Additionally, the aminopyrimidine ring forms hydrogen bonds with Asp419, while the ribose hydroxyl groups interact with Glu392 and Tyr324.
Scientists in Janssen identified a 5′ spiro bisamine lead [78] from an adenosine derivative compound library and optimized it through pharmacochemical modifications to develop JNJ-64619178 [66]. Co-crystal structures revealed that it binds non-covalently to the PRMT5 cofactor binding pocket, with its bromo-aminoquinoline moiety extending into the substrate-binding site, forming bidentate hydrogen bonds with the catalytic Glu444 residue. Additionally, the bromine atom establishes a halogen interaction with the backbone oxygen of Ser578 (Figure 8A). Biochemical properties demonstrated that JNJ-64619178 functions as a pseudo-irreversible PRMT5 inhibitor.
PF-06939999 [43] was developed by Pfizer through a two-step optimization process. Initially, an adenosine pharmacophore was defined using a ligand truncation strategy to simplify synthesis. A 3-fluoro-4-chlorobenzene group was then added at the 5′ position to engage the deep binding pocket adjacent to the ribose’s 5′-carbon, resulting in PF-06855800. Guided by the structure of PF-06855800, PF-06939999 was designed by modifying the ribose into a phenyl ether and optimizing the phenyl ring for deeper pocket engagement. A THIQ system was incorporated, with its nitrogen forming key interactions with Glu444, Leu437, and Glu435. Additional fluorine and difluoro-methyl substitutions further enhanced binding affinity. The co-crystal structure confirmed these interactions, demonstrating efficient binding and favorable drug-like properties (Figure 8B).
Like PF-06939999, 5,5-bicyclic scaffolds developed by Merck and Co. were designed to create dual SAM/substrate-competitive inhibitors that occupy the SAM pocket and extend into the narrow groove connecting to Glu444 in the substrate pocket [79,80]. This design aims to enhance potency and prolong compound residence time. To optimize lipophilicity and reduce hepatic clearance, a series of compounds were synthesized to improve oral bioavailability (%F). The crystal structure revealed that the nucleoside diol and nucleobase retained key hydrogen bonding interactions, mimicking the adenosine moiety of SAM. Furthermore, the aminoquinoline moiety extended into the channel linking the SAM and substrate pockets, forming a face-to-face π-stacking interaction with Phe327 and a bidentate hydrogen bond with Glu444 (Figure 8C).

2.1.3. MTA-Cooperative PRMT5 Synthetic Lethal Inhibitors

In 2016, Mavrakis et al. and Kryukov et al. showed that PRMT5 inhibition is effective in MTAP-deficient (MTAP−/−) cancers, which constitute ~15% of human cancers due to frequent co-deletion with the CDKN2A locus [17,18] (Figure 9). MTAP loss causes a 5–20-fold accumulation of MTA, a selective endogenous PRMT5 inhibitor, sensitizing MTAP−/− cells to PRMT5 inhibition [81]. This synthetic lethality allows PRMT5 inhibitors to selectively target MTAP−/− cells while sparing MTAP+/+ cells, offering significant therapeutic potential.
Smith et al. from Mirati Therapeutics, now part of Bristol Myers Squibb, developed MRTX1719 [68], the first synthetic lethal inhibitor of the PRMT5·MTA complex, representing a key milestone in PRMT5 inhibitor development. MRTX1719 exhibits selective inhibition of PRMT5 activity in MTAP-deleted (MTAP−/−) cells compared to MTAP wild-type (MTAP+/+) cells [70]. The development began with a fragment-based lead discovery (FBLD) approach to identify the initial structure, followed by structure-based drug design (SBDD) to optimize and develop MRTX1719. Co-crystal structures revealed that the N-methylpyrazol-4-yl substituent occupies a pocket formed by Gln309, Ser310, Pro311, Leu312, and Val503, forming a key H-bond with the backbone N–H of Leu312 (Figure 10A). Additionally, the 2-cyclopropoxy-4-chloro-5-fluoro-6-yl-benzonitrile group is oriented perpendicular to the N-methyl-pyrazole group, with its fluoro substituent directed toward Leu312 and its nitrile forming an H-bond with the backbone N–H of Phe580 [69].
In the meanwhile, Ghimire-Rijal et al. identified an initial hit from a DNA-encoded library (DEL) that binds PRMT5 in the presence of MTA. Through optimization, AMG 193 was developed [82]. The structure revealed that the amino-dihydrofuro-[1,7] naphthyridine motif in AMG 193 occupies the substrate-binding pocket, forming key interactions: a strong polar bond with the Glu444 side chain, a hydrogen bond with the backbone carbonyl of Glu435, and a tight van der Waals interaction between the dihydrofuran methylene group and the sulfur atom of MTA, which also interacts with AMG 193’s NH2 group. Additionally, the dihydrofuran ring participates in π–π stacking interactions with Trp579 and Phe327, while its oxygen atom forms a hydrogen bond with the amino side chain of Lys333 (Figure 10B). Normally, Lys333 interacts with the carbonyl terminus of SAM, but its position shifts upon AMG 193 binding, moving away from the SAM-binding site. These interactions collectively contribute to the selectivity and MTA cooperativity of AMG 193.
Whittington et al. from Tango Therapeutics developed TNG908, the first brain-penetrant, MTA-cooperative PRMT5 inhibitor [83]. The X-ray structure revealed key binding interactions: the NH2 group at the 6-position of the pyridine forms strong hydrogen bonds with the backbone carbonyl of Glu435 and the side chain of Glu444. The NH of the oxamide creates a hydrogen bond with the carbonyl of Ser578, while its two carbonyl groups form additional hydrogen bonds—one with the backbone NH of Phe580 and another, water-mediated, with Leu312 (Figure 10C). The benzothiazole’s nitrogen engages in a water-mediated hydrogen bond, and its C–S σ* orbital interacts with the carbonyl lone pair of Ser310 [73]. The preclinical data showed that TNG908 demonstrates selective antitumor activity in mouse xenograft models and exhibits favorable physicochemical properties for crossing the blood–brain barrier (BBB). This supports its potential clinical application for treating CNS and non-CNS tumors with MTAP loss.
Smith et al. from AstraZeneca identified compound 28 [84], an orally available lead and precursor to AZD3470 (currently in Phase I/II clinical trials [56,57]). This compound exhibits sub-10 nM PRMT5 cell potency, over 50-fold MTA cooperativity, favorable DMPK properties for oral administration, and significant in vivo efficacy in several MTAP-deficient preclinical cancer models. It was discovered through high-throughput biochemical screening and optimized via structure-based design to enhance oral drug-like properties. The X-ray structure of compound 28 revealed that the lactam and amide groups maintain key hydrogen-bond interactions within the scaffold. Its 5-amino group forms hydrogen bonds with the side chain of Glu444 and the backbone carbonyl of Glu435. Furthermore, the 6-fluoro group of the azaindole induces a slight positional shift (0.7 Å) in the Glu435 side chain, likely due to electronic repulsion, enhancing SDMA MTA cooperativity by approximately twofold in HCT116 cells (Figure 10D).
Li et al. from the University of Florida also identified a pharmacophore for PRMT5 inhibition through a structure-based virtual screening campaign using the Cambridge database. This approach led to the discovery of CMP5 as an initial hit with moderate PRMT5 inhibitory activity [86]. Subsequent structure–activity relationship (SAR) optimization led to the development of 11-2F [85], which exhibited enhanced potency and selectivity. Cryo-EM analysis revealed that the quinoline ring of 11-2F forms hydrogen bonds with Glu435 and Glu444 and engages in a π-stacking interaction with the side chain of Trp579 (Figure 10E). Further refinement produced 16-19F [12], which showed improved binding affinity and strong synthetic lethality in MTAP-deleted cancer cells, selectively inhibiting PRMT5 activity under conditions of elevated MTA while sparing MTAP-wild-type cells. Structural analysis of the PRMT5·SAH·16-19F complex demonstrated that 16-19F occupies the substrate-binding site, forming hydrogen bonds with Glu435 and Glu444, along with a halogen bond with Ser310 (Figure 10F). This binding mode effectively blocks substrate access without interfering with MTA binding, thereby exploiting a key vulnerability in MTAP-deficient tumors.

2.1.4. PRMT5 Allosteric Inhibitors

Palte et al. at Merck and Co. identified a novel conformational state of PRMT5, where the formation of an allosteric binding pocket disrupts the enzyme’s canonical binding site, leading to the discovery of potent small-molecule allosteric PRMT5 inhibitors. Compound 1a [87], previously known as a BACE1 and BACE2 [88] inhibitor, was also identified as a potent PRMT5 inhibitor through an HTS campaign.
To elucidate its binding mode, PRMT5:MEP50 was co-crystallized with 1a, revealing significant structural rearrangements in the protein backbone (Figure 11). The loop spanning Glu435 to Leu445 shifted in orientation, creating a new pocket that obstructs both the cofactor and substrate binding sites. Additionally, 1a forms several key interactions with surrounding protein residues. The adamantane moiety binds within a hydrophobic pocket formed by Leu436, Leu437, Phe519, Phe555, and Tyr468. The methoxyphenyl group is engaged in an edge-to-face π-stacking interaction with Tyr613. Furthermore, the amine of the imino-hydantoin core forms a hydrogen bond with Glu444, contributing to its strong binding affinity. This structural insight provides a foundation for the development of selective allosteric PRMT5 inhibitors.

2.2. PRMT5 Inhibitors Targeting N-Terminal TIM Barrel Domain—Novel Inhibition Strategies

Current PRMT5 inhibitors target the C-terminal catalytic site but struggle with selectivity. Targeting the unique TIM barrel domain of PRMT5 offers a promising solution, though compounds for the N-terminal domain are still in preclinical stages.

2.2.1. PRMT5–Substrate Adaptor Interaction Inhibitors

A large-scale shRNA screening identified PRMT5 SAPs, including pICLn, RIOK1, and its obligate partner MEP50, in MTAP+/+ cancers [89]. Additionally, Mulvaney et al. from the Broad Institute revealed that the interaction between the PRMT5 binding motif and SAPs is essential for recruiting specific substrates, such as histones and spliceosome complexes, to the PRMT5 methylation site (Figure 12A). A conserved seven-residue peptide sequence, GQF(D/E)DA(D/E), was identified in SAPs (pICLn, RIOK1, and COPR5) as the key PBM that mediates adaptor binding to PRMT5 [14]. This mechanism, distinct from catalytic site inhibition, offers a novel therapeutic avenue.
Using the structure of the PBM peptide bound to its site on PRMT5, McKinney et al. initiated a screening campaign, leading to the discovery of BRD0639 (Figure 12B), the first covalent inhibitor targeting the interface between the PRMT5 N-terminal TIM barrel motif (PBM) and SAPs [26]. The refined electron density revealed that the 4-position of the pyridazinone ring forms a covalent bond with Cys278 of PRMT5 through a nucleophilic attack by the Cys278 thiol, accompanied by the loss of a chlorine atom and re-aromatization of the pyridazinone. The pyridyl ethyl side chain reorients toward the molecule’s core through sulfonamide rotation and ethyl linker flexibility, forming a 4-ring π–π stacking interaction involving Tyr286, the pyridine, the aryl core, and Phe243. Additionally, the sulfonamide group forms a hydrogen bond with the Lys241 side chain. Despite these interactions, the compound demonstrated a relatively weak in vitro binding affinity to PRMT5:MEP50 (KD = 13.8 µM), highlighting opportunities for further optimization.
Krzyzanowski et al. designed a cyclopeptide to mimic the consensus sequence GQF [D/E]DA [E/D] found in adaptor proteins pICLn, RIOK1, and COPR5, leveraging the effectiveness of cyclopeptides in disrupting protein–protein interactions (PPIs) involving large surface areas and poorly defined pockets [90]. Initial exploration of various macrocycle sizes and cyclization linkages, combined with peptide library analysis, identified key hot spots for amino acid variation. Incorporating nonproteinogenic amino acids into the macrocyclic peptide yielded a potent PRMT5-binding cyclic peptide (Ki = 66 nM) (Figure 12C), which selectively inhibits PRMT5 interactions with RIOK1 and pICLn (IC50 = 654 nM) while sparing the interaction with the alternative adaptor protein MEP50 [13]. This inhibitor shows great potential as a tool for further biological studies of this intriguing protein interface.
In addition, Shen et al. identified and validated a secondary binding site within the N-terminal TIM barrel domain of PRMT5 that is critical for its interaction with the substrate adaptor protein pICLn. Structural analysis revealed a deep, hydrophobic pocket composed of residues Phe40, Val83, Pro120, Ala121, and Trp152, where pICLn’s Ile211 inserts and is stabilized through van der Waals interactions and key hydrogen bonds (Figure 13A).
To discover small molecules that target this site, two virtual screening strategies were employed. A Schrödinger-based structure-based docking pipeline led to the identification of J021-0199, which binds with moderate affinity (KD = 35 μM). Predicted binding interactions from 200 ns molecular dynamics (MD) simulations showed that J021-0199 forms π–π stacking interactions with Phe40 via its 1-chloro-2-fluorobenzene and 5-methylbenzo [d]oxazole moieties, while its central amide linker forms hydrogen bonds that stabilize its pose [91] (Figure 13B). In addition, a machine learning-based virtual screening pipeline was developed using a fine-tuned CHEM-BERT model. This model achieved a 96% increase in screening efficiency compared to the conventional docking method. The top 10,000 predicted compounds were re-docked using AutoDock Vina, from which Z319334062 (KD = 21.5 μM) was identified [92]. MD simulations showed that Z319334062 formed hydrophobic contacts with Phe40, and hydrogen bonds with Pro120 and Trp152, effectively occupying the TIM barrel pocket (Figure 13C). Both compounds effectively disrupted the PRMT5/pICLn interaction, suppressed PRMT5 activity as measured by SDMA reduction, and selectively reduced cancer cell viability, demonstrating the utility of the PRMT5 secondary site as a novel and druggable interface. Notably, while J021-0199 demonstrated promising activity in disrupting PRMT5/pICLn interactions, follow-up studies revealed potential non-specific effects in prostate cancer cells. In addition to its activity in the resistant 22Rv1 cell line, J021-0199 also reduced cell viability and SDMA levels in LNCaP cells [91]. These findings suggest that J021-0199 may exert partial off-target effects or broader methyltransferase inhibition, underscoring the need for further selectivity profiling and medicinal chemistry optimization.
This therapeutic strategy is further supported by the biological role of the PRMT5/pICLn complex in regulating DNA repair (Figure 13D). In this pathway, the interaction between PRMT5 and pICLn facilitates the transcriptional activation of DNA damage response (DDR) genes, including RAD51, BRCA1, BRCA2, and NHEJ1/XLF, which are essential for homologous recombination and non-homologous end joining repair pathways. Disrupting this interaction impairs the expression of these DDR genes, compromising the cancer cell’s ability to repair double-strand breaks. As a result, targeting the PRMT5/pICLn interface not only inhibits PRMT5 enzymatic activity but also weakens genomic stability, thereby sensitizing cancer cells to DNA-damaging agents and offering a promising avenue for more effective therapeutic intervention.

2.2.2. PRMT5–MEP50 Interaction Inhibitor

In addition to the PBM domain, Andrew et al. identified a novel binding site to inhibit PRMT5/MEP50 protein–protein interactions (PPI) [93]. Since PRMT5 is the only PRMT that requires MEP50 as an obligate cofactor for its function, they proposed that targeting this interaction could enhance selectivity. Through initial virtual screening and analogue refinement, they discovered a novel PPI inhibitor, compound 17 (Figure 13E). In vitro studies demonstrated an IC50 of <500 nM in prostate and lung cancer cells, with selective and specific inhibition of PRMT5:MEP50 substrate methylation and target gene expression. Compound 17 provides proof of concept for targeting PRMT5:MEP50 PPI as an alternative mechanism of action, distinct from catalytic inhibition, and supports further preclinical development of inhibitors in this class.

3. Discussion

The past decade has seen significant advances in the development of PRMT5 inhibitors, driven by the enzyme’s central role in oncogenic processes such as transcriptional regulation, RNA splicing, and DNA damage repair. Traditional PRMT5 inhibitors have largely focused on targeting the catalytic site, employing mechanisms including SAM-competitive, SAM-cooperative, and MTA-cooperative inhibition. While these strategies have led to promising clinical candidates—especially in MTAP-deficient tumors—challenges related to specificity, resistance, and toxicity remain.
Recent structural studies and mechanistic insights have expanded the therapeutic landscape by revealing novel non-catalytic regulatory sites on PRMT5. In particular, the N-terminal TIM barrel domain has emerged as a druggable interface that mediates protein–protein interactions critical for substrate recruitment, particularly through adaptor proteins such as pICLn, RIOK1, and COPR5. Targeting this domain provides an opportunity to selectively disrupt PRMT5 function without directly competing with SAM or substrate binding, offering a new avenue for therapeutic intervention.
Our recent studies identified a previously uncharacterized secondary binding pocket within the PRMT5 TIM barrel [91,92]. Structural and MD simulation analyses revealed that this pocket accommodates pICLn’s Ile211 side chain through a network of hydrophobic and hydrogen bond interactions, making it an attractive target for small-molecule disruption of the PRMT5/pICLn interaction. By combining traditional structure-based screening with a machine learning-accelerated pipeline, we identified two novel compounds—J021-0199 and Z319334062—that bind this pocket with moderate affinity. Functionally, both compounds disrupted PRMT5/pICLn interactions in cell-based assays, reduced symmetric dimethylarginine (SDMA) levels, and selectively inhibited the proliferation of cancer cells overexpressing PRMT5 and pICLn. Mechanistically, this disruption impairs the transcriptional activation of key DNA damage response genes such as RAD51, BRCA1/2, and NHEJ1, ultimately compromising the DNA repair capacity of cancer cells [91]. This dual mechanism—blocking PRMT5 enzymatic activity and impeding DNA repair—highlights the therapeutic potential of targeting the PRMT5/pICLn interface.
These findings also emphasize the value of hybrid drug discovery strategies. The machine learning-guided screening significantly improved computational efficiency (~96%) compared to conventional docking alone [92], demonstrating how artificial intelligence can streamline early-stage hit identification in challenging protein–protein interaction (PPI) targets.

4. Conclusions and Perspectives

This review outlines a comprehensive, multi-tiered strategy for PRMT5-targeted drug development. PRMT5 inhibitors exhibit diverse SAR profiles based on their binding modes. SAM-competitive inhibitors mimic the cofactor and form key interactions in the SAM-binding pocket, while SAM-cooperative inhibitors gain affinity by engaging both the substrate site and SAM simultaneously. MTA-cooperative inhibitors, such as MRTX1719, exploit elevated MTA levels in MTAP-deficient tumors to enhance selectivity. Allosteric inhibitors target distinct conformational pockets outside the active site. Recent strategies also explore non-catalytic regions, including the TIM barrel domain and PRMT5–protein interfaces, providing novel opportunities for selective and context-specific inhibition.
By integrating knowledge from canonical catalytic inhibitors, structural insights into non-catalytic domains, and advanced screening technologies—including machine learning–driven virtual screening—this work presents a strategic roadmap for diversifying the PRMT5 inhibitor landscape. These efforts collectively expand the pharmacological toolbox for targeting PRMT5 and open new opportunities for designing multi-mechanism combination therapies.
Future research should focus on three critical areas to advance PRMT5-targeted therapy. First, a systematic evaluation of both catalytic and non-catalytic inhibitors in in vivo cancer models is essential to validate therapeutic efficacy and to characterize their pharmacokinetic and toxicity profiles. Second, comprehensive resistance profiling will be crucial for understanding the durability of response, identifying potential escape mechanisms, and guiding rational combination strategies. Third, further efforts are needed to identify and characterize novel non-catalytic inhibition mechanisms, particularly those involving protein–protein interaction interfaces, which may offer improved selectivity and reduced toxicity compared to traditional active-site inhibitors.

Author Contributions

The manuscript was written through the contributions of all authors. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Data Availability Statement

No new data were created or analyzed in this study.

Acknowledges

The authors would like to thank colleagues and collaborators in the Department of Medicinal Chemistry at the University of Florida for their insightful discussions and feedback during the preparation of this review.

Conflicts of Interest

The authors declare no competing financial interests.

References

  1. Liu, M.; Yao, B.; Gui, T.; Guo, C.; Wu, X.; Li, J.; Ma, L.; Deng, Y.; Xu, P.; Wang, Y.; et al. PRMT5-dependent transcriptional repression of c-Myc target genes promotes gastric cancer progression. Theranostics 2020, 10, 4437–4452. [Google Scholar] [CrossRef] [PubMed]
  2. Sachamitr, P.; Ho, J.C.; Ciamponi, F.E.; Ba-Alawi, W.; Coutinho, F.J.; Guilhamon, P.; Kushida, M.M.; Cavalli, F.M.G.; Lee, L.; Rastegar, N.; et al. PRMT5 inhibition disrupts splicing and stemness in glioblastoma. Nat. Commun. 2021, 12, 979. [Google Scholar] [CrossRef]
  3. Hoang, P.M.; Torre, D.; Jaynes, P.; Ho, J.; Mohammed, K.; Alvstad, E.; Lam, W.Y.; Khanchandani, V.; Lee, J.M.; Toh, C.M.C.; et al. A PRMT5-ZNF326 axis mediates innate immune activation upon replication stress. Sci. Adv. 2024, 10, eadm9589. [Google Scholar] [CrossRef]
  4. Hamard, P.J.; Santiago, G.E.; Liu, F.; Karl, D.L.; Martinez, C.; Man, N.; Mookhtiar, A.K.; Duffort, S.; Greenblatt, S.; Verdun, R.E.; et al. PRMT5 Regulates DNA Repair by Controlling the Alternative Splicing of Histone-Modifying Enzymes. Cell Rep. 2018, 24, 2643–2657. [Google Scholar] [CrossRef]
  5. Gillespie, M.S.; Chiang, K.; Regan-Mochrie, G.L.; Choi, S.Y.; Ward, C.M.; Sahay, D.; Garcia, P.; Arnold, R.; Davies, C.C. PRMT5-regulated splicing of DNA repair genes drives chemoresistance in breast cancer stem cells. Oncogene 2025, 44, 862–876. [Google Scholar] [CrossRef]
  6. Tan, L.; Xiao, K.; Ye, Y.; Liang, H.; Chen, M.; Luo, J.; Qin, Z. High PRMT5 expression is associated with poor overall survival and tumor progression in bladder cancer. Aging 2020, 12, 8728–8741. [Google Scholar] [CrossRef] [PubMed]
  7. Deng, X.; Shao, G.; Zhang, H.T.; Li, C.; Zhang, D.; Cheng, L.; Elzey, B.D.; Pili, R.; Ratliff, T.L.; Huang, J.; et al. Protein arginine methyltransferase 5 functions as an epigenetic activator of the androgen receptor to promote prostate cancer cell growth. Oncogene 2017, 36, 1223–1231. [Google Scholar] [CrossRef]
  8. Zhang, S.; Ma, Y.; Hu, X.; Zheng, Y.; Chen, X. Targeting PRMT5/Akt signalling axis prevents human lung cancer cell growth. J. Cell Mol. Med. 2019, 23, 1333–1342. [Google Scholar] [CrossRef]
  9. Kim, H.; Kim, H.; Feng, Y.; Li, Y.; Tamiya, H.; Tocci, S.; Ronai, Z.A. PRMT5 control of cGAS/STING and NLRC5 pathways defines melanoma response to antitumor immunity. Sci. Transl. Med. 2020, 12, eaaz5683. [Google Scholar] [CrossRef]
  10. Zhang, H.; Shi, G.; Li, Y.; Wang, C.; Zhang, Y.; Luo, Y.; Xu, J.; Qiu, Y.; Ma, J.; Yang, J.; et al. Epigenetically targeting PRMT5 promotes antitumor immunity by inducing endogenous retroviruses expression and triggering viral mimicry response. Transl. Res. 2025, 281, 55–68. [Google Scholar] [CrossRef] [PubMed]
  11. Meng, S.; Liu, H.; Xu, J.; Deng, C.; Qian, X.; Chu, S.; Zhu, W.G.; Zhu, J.; Yong, H.; Li, Z.; et al. PRMT5-Mediated ALKBH5 Methylation Promotes Colorectal Cancer Immune Evasion via Increasing CD276 Expression. Research 2025, 8, 0549. [Google Scholar] [CrossRef] [PubMed]
  12. Shen, Z.; Yang, X.; Seabra, G.; Xu, X.; Dong, J.; Brant, J.O.; Zhou, W.; Guan, J.; Jiang, W.; Li, C. Discovery and Mechanism of 16–19F, a Novel Synthetic Lethal Inhibitor of the PRMT5•MTA Complex in MTAP-Deleted Cancer Cells. ACS Chem. Biol. 2025, 20, 1333–1346. [Google Scholar] [CrossRef]
  13. Krzyzanowski, A.; Gasper, R.; Adihou, H.; Hart, P.; Waldmann, H. Biochemical Investigation of the Interaction of pICln, RioK1 and COPR5 with the PRMT5-MEP50 Complex. Chembiochem 2021, 22, 1908–1914. [Google Scholar] [CrossRef] [PubMed]
  14. Mulvaney, K.M.; Blomquist, C.; Acharya, N.; Li, R.; Ranaghan, M.J.; O’Keefe, M.; Rodriguez, D.J.; Young, M.J.; Kesar, D.; Pal, D.; et al. Molecular basis for substrate recruitment to the PRMT5 methylosome. Mol. Cell 2021, 81, 3481–3495 e7. [Google Scholar] [CrossRef] [PubMed]
  15. Antonysamy, S.; Bonday, Z.; Campbell, R.M.; Doyle, B.; Druzina, Z.; Gheyi, T.; Han, B.; Jungheim, L.N.; Qian, Y.; Rauch, C.; et al. Crystal structure of the human PRMT5:MEP50 complex. Proc. Natl. Acad. Sci. USA 2012, 109, 17960–17965. [Google Scholar] [CrossRef]
  16. Musiani, D.; Bok, J.; Massignani, E.; Wu, L.; Tabaglio, T.; Ippolito, M.R.; Cuomo, A.; Ozbek, U.; Zorgati, H.; Ghoshdastider, U.; et al. Proteomics profiling of arginine methylation defines PRMT5 substrate specificity. Sci. Signal 2019, 12, eaat8388. [Google Scholar] [CrossRef]
  17. Kryukov, G.V.; Wilson, F.H.; Ruth, J.R.; Paulk, J.; Tsherniak, A.; Marlow, S.E.; Vazquez, F.; Weir, B.A.; Fitzgerald, M.E.; Tanaka, M.; et al. MTAP deletion confers enhanced dependency on the PRMT5 arginine methyltransferase in cancer cells. Science 2016, 351, 1214–1218. [Google Scholar] [CrossRef]
  18. Mavrakis, K.J.; McDonald, E.R., 3rd; Schlabach, M.R.; Billy, E.; Hoffman, G.R.; deWeck, A.; Ruddy, D.A.; Venkatesan, K.; Yu, J.; McAllister, G.; et al. Disordered methionine metabolism in MTAP/CDKN2A-deleted cancers leads to dependence on PRMT5. Science 2016, 351, 1208–1213. [Google Scholar] [CrossRef]
  19. Burgos, E.S.; Wilczek, C.; Onikubo, T.; Bonanno, J.B.; Jansong, J.; Reimer, U.; Shechter, D. Histone H2A and H4 N-terminal tails are positioned by the MEP50 WD repeat protein for efficient methylation by the PRMT5 arginine methyltransferase. J. Biol. Chem. 2015, 290, 9674–9689. [Google Scholar] [CrossRef]
  20. Majumder, S.; Alinari, L.; Roy, S.; Miller, T.; Datta, J.; Sif, S.; Baiocchi, R.; Jacob, S.T. Methylation of histone H3 and H4 by PRMT5 regulates ribosomal RNA gene transcription. J. Cell Biochem. 2010, 109, 553–563. [Google Scholar] [CrossRef] [PubMed]
  21. Zheng, Y.; Lu, J.; Hu, X.; Hu, X.; Gao, X.; Zhou, J. PRMT5/FGFR3/AKT Signaling Axis Facilitates Lung Cancer Cell Metastasis. Technol. Cancer Res. Treat. 2023, 22, 15330338231161139. [Google Scholar] [CrossRef]
  22. Lim, J.H.; Lee, Y.M.; Lee, G.; Choi, Y.J.; Lim, B.O.; Kim, Y.J.; Choi, D.K.; Park, J.W. PRMT5 is essential for the eIF4E-mediated 5′-cap dependent translation. Biochem. Biophys. Res. Commun. 2014, 452, 1016–1021. [Google Scholar] [CrossRef]
  23. Qu, S.; Feng, B.; Xing, M.; Qiu, Y.; Ma, L.; Yang, Z.; Ji, Y.; Huang, F.; Wang, Y.; Zhou, J.; et al. PRMT5 K240lac confers ferroptosis resistance via ALKBH5/SLC7A11 axis in colorectal cancer. Oncogene 2025, 44, 2814–2830. [Google Scholar] [CrossRef]
  24. Du, C.; Hansen, L.J.; Singh, S.X.; Wang, F.; Sun, R.; Moure, C.J.; Roso, K.; Greer, P.K.; Yan, H.; He, Y. A PRMT5-RNF168-SMURF2 Axis Controls H2AX Proteostasis. Cell Rep. 2019, 28, 3199–3211 e5. [Google Scholar] [CrossRef] [PubMed]
  25. Chiang, K.; Zielinska, A.E.; Shaaban, A.M.; Sanchez-Bailon, M.P.; Jarrold, J.; Clarke, T.L.; Zhang, J.; Francis, A.; Jones, L.J.; Smith, S.; et al. PRMT5 Is a Critical Regulator of Breast Cancer Stem Cell Function via Histone Methylation and FOXP1 Expression. Cell Rep. 2017, 21, 3498–3513. [Google Scholar] [CrossRef] [PubMed]
  26. McKinney, D.C.; McMillan, B.J.; Ranaghan, M.J.; Moroco, J.A.; Brousseau, M.; Mullin-Bernstein, Z.; O’Keefe, M.; McCarren, P.; Mesleh, M.F.; Mulvaney, K.M.; et al. Discovery of a First-in-Class Inhibitor of the PRMT5-Substrate Adaptor Interaction. J. Med. Chem. 2021, 64, 11148–11168. [Google Scholar] [CrossRef] [PubMed]
  27. Pesiridis, G.S.; Diamond, E.; Van Duyne, G.D. Role of pICLn in methylation of Sm proteins by PRMT5. J. Biol. Chem. 2009, 284, 21347–21359. [Google Scholar] [CrossRef]
  28. Guderian, G.; Peter, C.; Wiesner, J.; Sickmann, A.; Schulze-Osthoff, K.; Fischer, U.; Grimmler, M. RioK1, a new interactor of protein arginine methyltransferase 5 (PRMT5), competes with pICln for binding and modulates PRMT5 complex composition and substrate specificity. J. Biol. Chem. 2011, 286, 1976–1986. [Google Scholar] [CrossRef]
  29. Zhang, H.T.; Zeng, L.F.; He, Q.Y.; Tao, W.A.; Zha, Z.G.; Hu, C.D. The E3 ubiquitin ligase CHIP mediates ubiquitination and proteasomal degradation of PRMT5. Biochim. Biophys. Acta 2016, 1863, 335–346. [Google Scholar] [CrossRef]
  30. Liu, L.; Yin, S.; Gan, W. TRAF6 Promotes PRMT5 Activity in a Ubiquitination-Dependent Manner. Cancers 2023, 15, 2501. [Google Scholar] [CrossRef]
  31. Yamaguchi, A.; Kitajo, K. The effect of PRMT1-mediated arginine methylation on the subcellular localization, stress granules, and detergent-insoluble aggregates of FUS/TLS. PLoS ONE 2012, 7, e49267. [Google Scholar] [CrossRef]
  32. Huang, C.; Chen, Y.; Dai, H.; Zhang, H.; Xie, M.; Zhang, H.; Chen, F.; Kang, X.; Bai, X.; Chen, Z. UBAP2L arginine methylation by PRMT1 modulates stress granule assembly. Cell Death Differ. 2020, 27, 227–241. [Google Scholar] [CrossRef]
  33. Wall, M.L.; Lewis, S.M. Methylarginines within the RGG-Motif Region of hnRNP A1 Affect Its IRES Trans-Acting Factor Activity and Are Required for hnRNP A1 Stress Granule Localization and Formation. J. Mol. Biol. 2017, 429, 295–307. [Google Scholar] [CrossRef]
  34. Tsai, W.C.; Gayatri, S.; Reineke, L.C.; Sbardella, G.; Bedford, M.T.; Lloyd, R.E. Arginine Demethylation of G3BP1 Promotes Stress Granule Assembly. J. Biol. Chem. 2016, 291, 22671–22685. [Google Scholar] [CrossRef]
  35. Hofweber, M.; Dormann, D. Friend or foe-Post-translational modifications as regulators of phase separation and RNP granule dynamics. J. Biol. Chem. 2019, 294, 7137–7150. [Google Scholar] [CrossRef] [PubMed]
  36. Peng, P.H.; Hsu, K.W.; Wu, K.J. Liquid-liquid phase separation (LLPS) in cellular physiology and tumor biology. Am. J. Cancer Res. 2021, 11, 3766–3776. [Google Scholar] [PubMed]
  37. Jain, S.; Wheeler, J.R.; Walters, R.W.; Agrawal, A.; Barsic, A.; Parker, R. ATPase-Modulated Stress Granules Contain a Diverse Proteome and Substructure. Cell 2016, 164, 487–498. [Google Scholar] [CrossRef] [PubMed]
  38. Wang, Q.; Li, Z.; Zhang, S.; Li, Y.; Wang, Y.; Fang, Z.; Ma, Y.; Liu, Z.; Zhang, W.; Li, D.; et al. Global profiling of arginine dimethylation in regulating protein phase separation by a steric effect-based chemical-enrichment method. Proc. Natl. Acad. Sci. USA 2022, 119, e2205255119. [Google Scholar] [CrossRef]
  39. Vinet, M.; Suresh, S.; Maire, V.; Monchecourt, C.; Nemati, F.; Lesage, L.; Pierre, F.; Ye, M.; Lescure, A.; Brisson, A.; et al. Protein arginine methyltransferase 5: A novel therapeutic target for triple-negative breast cancers. Cancer Med. 2019, 8, 2414–2428. [Google Scholar] [CrossRef]
  40. Haque, T.; Cadenas, F.L.; Xicoy, B.; Alfonso, A.; Platzbecker, U.; Avivi, I.; Brunner, A.M.; Chromik, J.; Morillo, D.; Patel, M.R.; et al. Phase 1 Study of JNJ-64619178, a Protein Arginine Methyltransferase 5 Inhibitor, in Patients with Lower-Risk Myelodysplastic Syndromes. Blood 2021, 138 (Suppl. S1), 2606. [Google Scholar] [CrossRef]
  41. A Phase 1, First-in-Human, Open-Label Study of the Safety, Pharmacokinetics, and Pharmacodynamics of JNJ-64619178, an Inhibitor of Protein Arginine Methyltransferase 5 (PRMT5) in Subjects with Advanced Cancers. 2018. Available online: https://clinicaltrials.gov/study/NCT03573310 (accessed on 18 January 2025).
  42. A Phase 1 Study to Evaluate The Safety, Pharmacokinetics, and Pharmacodynamics of Escalating Doses of PF-06939999 (PRMT5 INHIBITOR) in Participants with Advanced or Metastatic Non-Small Cell Lung Cancer, Head and Neck Squamous Cell Carcinoma, Esophageal Cancer, Endometrial Cancer, Cervical Cancer and Bladder Cancer. 2019. Available online: https://www.clinicaltrials.gov/study/NCT03854227 (accessed on 18 January 2025).
  43. Jensen-Pergakes, K.; Tatlock, J.; Maegley, K.A.; McAlpine, I.J.; McTigue, M.; Xie, T.; Dillon, C.P.; Wang, Y.; Yamazaki, S.; Spiegel, N.; et al. SAM-Competitive PRMT5 Inhibitor PF-06939999 Demonstrates Antitumor Activity in Splicing Dysregulated NSCLC with Decreased Liability of Drug Resistance. Mol. Cancer Ther. 2022, 21, 3–15. [Google Scholar] [CrossRef] [PubMed]
  44. A Phase 1, Open-Label, Multicenter, Dose Escalation and Expansion Study of PRT811 in Subjects with Advanced Solid Tumors, CNS Lymphoma, and Recurrent High-Grade Gliomas. 2019. Available online: https://www.clinicaltrials.gov/study/NCT02048488 (accessed on 18 January 2025).
  45. A Phase 1, Open-Label, Multicenter, Dose Escalation, Dose Expansion Study of PRT543 in Patients with Advanced Solid Tumors and Hematologic Malignancies. 2019. Available online: https://clinicaltrials.gov/study/NCT03886831?cond=myelofibrosis&intr=PRT543&rank=1 (accessed on 18 January 2025).
  46. A Phase I Study to Investigate the Safety, Tolerability, Preliminary Efficacy and Pharmacokinetics(PK) of SCR-6920 Capsule in Patients with Advanced Malignant Tumors. 2022. Available online: https://clinicaltrials.gov/study/NCT05528055?term=PRMT5%20inhibitor&viewType=Table&rank=2 (accessed on 18 January 2025).
  47. Yu, J.; Sun, Y.; Guo, S.; Wang, H.; Wu, J.; Jiang, X.; Chen, J.; Yang, G.; Yang, C. 675P A phase I study of safety, pharmacokinetics, and pharmacodynamics of SCR-6920, a protein arginine methyltransferase 5 (PRMT5) inhibitor, in patients with advanced malignant tumors. Ann. Oncol. 2023, 34, S474. [Google Scholar] [CrossRef]
  48. A Phase II Randomized Window of Opportunity Trial Evaluating Clinical and Biological Effects of PRMT5 Inhibitor, GSK3326595, in Early Stage Breast Cancer. Ontario Institute for Cancer Research; GlaxoSmithKline; London Regional Cancer Program; Canada, Hamilton Health Sciences Corporation (Eds.) 2020. Available online: https://clinicaltrials.gov/study/NCT04676516?intr=GSK3326595&rank=1 (accessed on 18 January 2025).
  49. Watts, J.M.; Bradley, T.J.; Thomassen, A.; Brunner, A.M.; Minden, M.D.; Papadantonakis, N.; Abedin, S.; Baines, A.J.; Barbash, O.; Gorman, S.; et al. A Phase I/II Study to Investigate the Safety and Clinical Activity of the Protein Arginine Methyltransferase 5 Inhibitor GSK3326595 in Subjects with Myelodysplastic Syndrome and Acute Myeloid Leukemia. Blood 2019, 134 (Suppl. S1), 2656. [Google Scholar] [CrossRef]
  50. An Open Label, Phase 1, Treatment Study to Evaluate the Safety, Pharmacokinetics and Pharmacodynamics of IDE397 (MAT2A Inhibitor) in Adult Participants with Advanced Solid Tumors. 2021. Available online: https://www.clinicaltrials.gov/study/NCT04794699 (accessed on 18 January 2025).
  51. A Phase 1, Open-Label, Multicenter Clinical Trial of S095035 (MAT2A Inhibitor) in Adult Participants with Advanced or Metastatic Solid Tumors with Homozygous Deletion of MTAP. Institut de Recherches Internationales Servier (Ed.) 2023. Available online: https://clinicaltrials.gov/study/NCT06188702 (accessed on 18 January 2025).
  52. A Phase 1/2 Multiple Expansion Cohort Trial of MRTX1719 in Patients with Advanced Solid Tumors with Homozygous MTAP Deletion. 2022. Available online: https://www.clinicaltrials.gov/study/NCT05245500 (accessed on 18 January 2025).
  53. A Phase 1/1b/2 Study Evaluating the Safety, Tolerability, Pharmacokinetics, Pharmacodynamics, and Efficacy of AMG 193 Alone and in Combination with Docetaxel in Subjects with Advanced MTAP-Null Solid Tumors. 2021. Available online: https://clinicaltrials.gov/study/NCT05094336 (accessed on 18 January 2025).
  54. A Phase 1b Study Evaluating the Safety, Tolerability, Pharmacokinetics, and Efficacy of AMG 193 Alone or in Combination with Other Therapies in Subjects with Advanced Thoracic Tumors with Homozygous MTAP-Deletion (Master Protocol). 2024. Available online: https://clinicaltrials.gov/study/NCT06333951 (accessed on 18 January 2025).
  55. A Phase 1b Study Evaluating the Safety, Tolerability, Pharmacokinetics, and Efficacy of AMG 193 in Combination with Other Therapies in Subjects with Advanced Gastrointestinal, Biliary Tract, or Pancreatic Cancers with Homozygous MTAP-Deletion. 2024. Available online: https://clinicaltrials.gov/study/NCT06360354 (accessed on 18 January 2025).
  56. A Modular Phase I/II, Open-Label, Multicentre Study to Evaluate the Safety, Tolerability, and Efficacy of AZD3470, a PRMT5 Inhibitor, as Monotherapy and in Combination with Anticancer Agent(s) in Participants with Relapsed/Refractory Haematologic Malignancies. 2023. Available online: https://clinicaltrials.gov/study/NCT06130553 (accessed on 18 January 2025).
  57. PRIMROSE: A Modular Phase I/IIa, Multi-Centre, Dose Escalation, and Expansion Study of AZD3470, a MTA Cooperative PRMT5 Inhibitor, as Monotherapy and in Combination with Anticancer Agents in Patients with Advanced/Metastatic Solid Tumours That Are MTAP Deficient. 2023. Available online: https://clinicaltrials.gov/study/NCT06130553 (accessed on 18 January 2025).
  58. A Phase 1/2, Multi-Center, Open-Label Study to Evaluate the Safety, Tolerability, and Preliminary Anti-Tumor Activity of TNG462 in Patients with MTAP-Deleted Advanced or Metastatic Solid Tumors. 2023. Available online: https://clinicaltrials.gov/study/NCT05732831 (accessed on 18 January 2025).
  59. A Phase 1/2, Multi-Center, Open-Label Study to Evaluate the Safety, Tolerability, and Preliminary Anti-Tumor Activity of TNG908 in Patients with MTAP-Deleted Advanced or Metastatic Solid Tumors. 2022. Available online: https://clinicaltrials.gov/study/NCT05275478 (accessed on 18 January 2025).
  60. A Phase 1a/b Study Investigating the Safety, Tolerability, Pharmacokinetics, Pharmacodynamics, and Preliminary Antitumor Activity of BGB-58067, an MTA-Cooperative PRMT5 Inhibitor in Patients with Advanced Solid Tumors. 2024. Available online: https://clinicaltrials.gov/study/NCT06589596 (accessed on 18 January 2025).
  61. A Multi-Center, Open-Label, Phase I/II Clinical Study to Evaluate the Safety, Tolerability, Pharmacokinetics and Preliminary Anti-Tumor Activity of CTS3497 in Patients with MTAP Deficient Advanced Solid Tumors and Lymphomas. 2025. Available online: https://clinicaltrials.gov/study/NCT06971523 (accessed on 18 January 2025).
  62. A Phase 1a/1b Study Evaluating the Clinical Safety, Tolerability, Pharmacokinetics, Pharmacodynamics, and Preliminary Anti-Tumor Efficacy of PEP08 as Monotherapy and Combination Therapy in MTAP-Del Advanced or Metastatic Solid Tumors. 2025. Available online: https://clinicaltrials.gov/study/NCT06973863 (accessed on 18 January 2025).
  63. A First-in-Human Study to Evaluate the Safety, Tolerability and Pharmacokinetics, Pharmacodynamics and Preliminary Clinical Activity of BAY 3713372, a Novel 2nd Generation PRMT5 Inhibitor, in Participants with MTAP-Deleted Solid Tumors. 2025. Available online: https://clinicaltrials.gov/study/NCT06914128 (accessed on 18 January 2025).
  64. Chan-Penebre, E.; Kuplast, K.G.; Majer, C.R.; Boriack-Sjodin, P.A.; Wigle, T.J.; Johnston, L.D.; Rioux, N.; Munchhof, M.J.; Jin, L.; Jacques, S.L.; et al. A selective inhibitor of PRMT5 with in vivo and in vitro potency in MCL models. Nat. Chem. Biol. 2015, 11, 432–437. [Google Scholar] [CrossRef]
  65. Siu, L.L.; Rasco, D.W.; Vinay, S.P.; Romano, P.M.; Menis, J.; Opdam, F.L.; Heinhuis, K.M.; Egger, J.L.; Gorman, S.A.; Parasrampuria, R. METEOR-1: A phase I study of GSK3326595, a first-in-class protein arginine methyltransferase 5 (PRMT5) inhibitor, in advanced solid tumours. Ann. Oncol. 2019, 30, v159. [Google Scholar] [CrossRef]
  66. Brehmer, D.; Beke, L.; Wu, T.; Millar, H.J.; Moy, C.; Sun, W.; Mannens, G.; Pande, V.; Boeckx, A.; van Heerde, E.; et al. Discovery and Pharmacological Characterization of JNJ-64619178, a Novel Small-Molecule Inhibitor of PRMT5 with Potent Antitumor Activity. Mol. Cancer Ther. 2021, 20, 2317–2328. [Google Scholar] [CrossRef]
  67. A Study of PRT543 in Participants with Advanced Solid Tumors and Hematologic Malignancies. Available online: https://clinicaltrials.gov/ct2/show/NCT03886831 (accessed on 18 January 2025).
  68. Smith, C.R.; Aranda, R.; Bobinski, T.P.; Briere, D.M.; Burns, A.C.; Christensen, J.G.; Clarine, J.; Engstrom, L.D.; Gunn, R.J.; Ivetac, A.; et al. Fragment-Based Discovery of MRTX1719, a Synthetic Lethal Inhibitor of the PRMT5*MTA Complex for the Treatment of MTAP-Deleted Cancers. J. Med. Chem. 2022, 65, 1749–1766. [Google Scholar] [CrossRef]
  69. Smith, C.R.; Aranda, R.; Christensen, J.G.; Engstrom, L.D.; Gunn, R.J.; Ivetac, A.; Ketcham, J.M.; Kuehler, J.; David Lawson, J.; Marx, M.A.; et al. Design and evaluation of achiral, non-atropisomeric 4-(aminomethyl)phthalazin-1(2H)-one derivatives as novel PRMT5/MTA inhibitors. Bioorg Med. Chem. 2022, 71, 116947. [Google Scholar] [CrossRef]
  70. Smith, C.R.; Kulyk, S.; Ahmad, M.U.D.; Arkhipova, V.; Christensen, J.G.; Gunn, R.J.; Ivetac, A.; Ketcham, J.M.; Kuehler, J.; Lawson, J.D.; et al. Fragment optimization and elaboration strategies—The discovery of two lead series of PRMT5/MTA inhibitors from five fragment hits. RSC Med. Chem. 2022, 13, 1549–1564. [Google Scholar] [CrossRef]
  71. Villalona-Calero, M.A.; Patnaik, A.; Maki, R.G.; O’Neil, B.; Abbruzzese, J.L.; Dagogo-Jack, I.; Devarakonda, S.; Wahlroos, S.; Lin, C.C.; Fujiwara, Y.; et al. Design and rationale of a phase 1 dose-escalation study of AMG 193, a methylthioadenosine (MTA)-cooperative PRMT5 inhibitor, in patients with advanced methylthioadenosine phosphorylase (MTAP)-null solid tumors. J. Clin. Oncol. 2022, 40, TPS3167. [Google Scholar] [CrossRef]
  72. Briggs, K.; Tsai, A.; Zhang, M.; Tonini, M.; Haines, B.; Huang, A.; Cottrell, K. TNG462 is a potential best-in-class MTA-cooperative PRMT5 inhibitor for the treatment of peripheral MTAP-deleted solid tumors. Eur. J. Cancer 2022, 174, S84. [Google Scholar] [CrossRef]
  73. Briggs, K.; Cottrell, K.; Tsai, A.; Zhang, M.; Tonini, M.; Yoda, S.; Lombardo, S.; Teng, T.; Davis, C.; Whittington, D.; et al. TNG908 is a brain-penetrant, MTA-cooperative PRMT5 inhibitor for the treatment of MTAP-deleted cancer. Eur. J. Cancer 2022, 174, S84. [Google Scholar] [CrossRef]
  74. Zhou, F.; Zhou, F. PRMT5:MEP50 WITH SCR-6920 AND SAM [PDB ID:8X6L]. 2025. Available online: https://www.rcsb.org/structure/8X6L (accessed on 4 September 2025).
  75. Shen, Y.; Gao, G.; Yu, X.; Kim, H.; Wang, L.; Xie, L.; Schwarz, M.; Chen, X.; Guccione, E.; Liu, J.; et al. Discovery of First-in-Class Protein Arginine Methyltransferase 5 (PRMT5) Degraders. J. Med. Chem. 2020, 63, 9977–9989. [Google Scholar] [CrossRef] [PubMed]
  76. Bonday, Z.Q.; Cortez, G.S.; Grogan, M.J.; Antonysamy, S.; Weichert, K.; Bocchinfuso, W.P.; Li, F.; Kennedy, S.; Li, B.; Mader, M.M.; et al. LLY-283, a Potent and Selective Inhibitor of Arginine Methyltransferase 5, PRMT5, with Antitumor Activity. ACS Med. Chem. Lett. 2018, 9, 612–617. [Google Scholar] [CrossRef]
  77. Lin, H.; Wang, M.; Zhang, Y.W.; Tong, S.; Leal, R.A.; Shetty, R.; Vaddi, K.; Luengo, J.I. Discovery of Potent and Selective Covalent Protein Arginine Methyltransferase 5 (PRMT5) Inhibitors. ACS Med. Chem. Lett. 2019, 10, 1033–1038. [Google Scholar] [CrossRef] [PubMed]
  78. Pande, V.; Sun, W.; Beke, L.; Berthelot, D.; Brehmer, D.; Brown, D.; Corbera, J.; Irving, S.; Meerpoel, L.; Nys, T.; et al. A Chemical Probe for the Methyl Transferase PRMT5 with a Novel Binding Mode. ACS Med. Chem. Lett. 2020, 11, 2227–2231. [Google Scholar] [CrossRef]
  79. Quiroz, R.V.; Reutershan, M.H.; Schneider, S.E.; Sloman, D.; Lacey, B.M.; Swalm, B.M.; Yeung, C.S.; Gibeau, C.; Spellman, D.S.; Rankic, D.A.; et al. The Discovery of Two Novel Classes of 5,5-Bicyclic Nucleoside-Derived PRMT5 Inhibitors for the Treatment of Cancer. J. Med. Chem. 2021, 64, 3911–3939. [Google Scholar] [CrossRef]
  80. Candito, D.A.; Ye, Y.; Quiroz, R.V.; Reutershan, M.H.; Witter, D.; Gadamsetty, S.B.; Li, H.; Sauri, J.; Schneider, S.E.; Lam, Y.H.; et al. Development of a Flexible and Robust Synthesis of Tetrahydrofuro[3,4-b]furan Nucleoside Analogues. J. Org. Chem. 2021, 86, 5142–5151. [Google Scholar] [CrossRef]
  81. Kalev, P.; Hyer, M.L.; Gross, S.; Konteatis, Z.; Chen, C.C.; Fletcher, M.; Lein, M.; Aguado-Fraile, E.; Frank, V.; Barnett, A.; et al. MAT2A Inhibition Blocks the Growth of MTAP-Deleted Cancer Cells by Reducing PRMT5-Dependent mRNA Splicing and Inducing DNA Damage. Cancer Cell 2021, 39, 209–224 e11. [Google Scholar] [CrossRef]
  82. Belmontes, B.; Slemmons, K.K.; Su, C.; Liu, S.; Policheni, A.N.; Moriguchi, J.; Tan, H.; Xie, F.; Aiello, D.A.; Yang, Y.; et al. AMG 193, a Clinical Stage MTA-Cooperative PRMT5 Inhibitor, Drives Antitumor Activity Preclinically and in Patients with MTAP-Deleted Cancers. Cancer Discov. 2024, 15, 139–161. [Google Scholar]
  83. Cottrell, K.M.; Briggs, K.J.; Whittington, D.A.; Jahic, H.; Ali, J.A.; Davis, C.B.; Gong, S.; Gotur, D.; Gu, L.; McCarren, P.; et al. Discovery of TNG908: A Selective, Brain Penetrant, MTA-Cooperative PRMT5 Inhibitor That Is Synthetically Lethal with MTAP-Deleted Cancers. J. Med. Chem. 2024, 67, 6064–6080. [Google Scholar] [CrossRef]
  84. Smith, J.M.; Barlaam, B.; Beattie, D.; Bradshaw, L.; Chan, H.M.; Chiarparin, E.; Collingwood, O.; Cooke, S.L.; Cronin, A.; Cumming, I.; et al. Discovery and In Vivo Efficacy of AZ-PRMT5i-1, a Novel PRMT5 Inhibitor with High MTA Cooperativity. J. Med. Chem. 2024, 67, 13604–13638. [Google Scholar] [CrossRef]
  85. Zhou, W.; Yadav, G.P.; Yang, X.; Qin, F.; Li, C.; Jiang, Q.X. Cryo-EM structure-based selection of computed ligand poses enables design of MTA-synergic PRMT5 inhibitors of better potency. Commun. Biol. 2022, 5, 1054. [Google Scholar] [CrossRef]
  86. Alinari, L.; Mahasenan, K.V.; Yan, F.; Karkhanis, V.; Chung, J.H.; Smith, E.M.; Quinion, C.; Smith, P.L.; Kim, L.; Patton, J.T.; et al. Selective inhibition of protein arginine methyltransferase 5 blocks initiation and maintenance of B-cell transformation. Blood 2015, 125, 2530–2543. [Google Scholar] [CrossRef] [PubMed]
  87. Palte, R.L.; Schneider, S.E.; Altman, M.D.; Hayes, R.P.; Kawamura, S.; Lacey, B.M.; Mansueto, M.S.; Reutershan, M.; Siliphaivanh, P.; Sondey, C.; et al. Allosteric Modulation of Protein Arginine Methyltransferase 5 (PRMT5). ACS Med. Chem. Lett. 2020, 11, 1688–1693. [Google Scholar] [CrossRef] [PubMed]
  88. Malamas, M.S.; Erdei, J.; Gunawan, I.; Turner, J.; Hu, Y.; Wagner, E.; Fan, K.; Chopra, R.; Olland, A.; Bard, J.; et al. Design and synthesis of 5,5′-disubstituted aminohydantoins as potent and selective human beta-secretase (BACE1) inhibitors. J. Med. Chem. 2010, 53, 1146–1158. [Google Scholar] [CrossRef]
  89. McDonald, E.R., 3rd; de Weck, A.; Schlabach, M.R.; Billy, E.; Mavrakis, K.J.; Hoffman, G.R.; Belur, D.; Castelletti, D.; Frias, E.; Gampa, K.; et al. Project DRIVE: A Compendium of Cancer Dependencies and Synthetic Lethal Relationships Uncovered by Large-Scale, Deep RNAi Screening. Cell 2017, 170, 577–592 e10. [Google Scholar] [CrossRef] [PubMed]
  90. Krzyzanowski, A.; Esser, L.M.; Willaume, A.; Prudent, R.; Peter, C.; ‘t Hart, P.; Waldmann, H. Development of Macrocyclic PRMT5-Adaptor Protein Interaction Inhibitors. J. Med. Chem. 2022, 65, 15300–15311. [Google Scholar] [CrossRef]
  91. Shen, Z.; Seabra, G.; Li, C. Virtual High-Throughput Screening of Ligands for Disrupting PRMT5/pICLn Interaction in Prostate Cancer Cells. ACS Med. Chem. Lett. 2025, 16, 875–879. [Google Scholar] [CrossRef]
  92. Shen, Z.; Seabra, G.; Brant, J.; Shirlekar, K.; Deleyrolle, L.; Lewis, B.; Li, C. Discovery of PRMT5 N-Terminal TIM Barrel Ligands from Machine-Learning-Based Virtual Screening. ACS Omega 2025, 10, 1156–1163. [Google Scholar] [CrossRef]
  93. Asberry, A.M.; Cai, X.; Deng, X.; Santiago, U.; Liu, S.; Sims, H.S.; Liang, W.; Xu, X.; Wan, J.; Jiang, W.; et al. Discovery and Biological Characterization of PRMT5:MEP50 Protein-Protein Interaction Inhibitors. J. Med. Chem. 2022, 65, 13793–13812. [Google Scholar] [CrossRef] [PubMed]
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Figure 1. General overview of PRMT family proteins. (A) PRMT family proteins sequence alignment; (B) PRMT family proteins methylation mechanism [12].
Figure 1. General overview of PRMT family proteins. (A) PRMT family proteins sequence alignment; (B) PRMT family proteins methylation mechanism [12].
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Figure 2. PRMT54:MEP504 hetero octamer complex structure. Four PRMT5:MEP50 dimers are depicted in red, yellow, blue, and green, respectively. Within each subunit, PRMT5 is shown in a bright color (e.g., bright red) and MEP50 in the corresponding darker shade (e.g., dark red). Two adjacent PRMT5 subunits form a dimer through conserved salt bridges between Asp491 and Arg488, as highlighted in the enlarged view on the right.
Figure 2. PRMT54:MEP504 hetero octamer complex structure. Four PRMT5:MEP50 dimers are depicted in red, yellow, blue, and green, respectively. Within each subunit, PRMT5 is shown in a bright color (e.g., bright red) and MEP50 in the corresponding darker shade (e.g., dark red). Two adjacent PRMT5 subunits form a dimer through conserved salt bridges between Asp491 and Arg488, as highlighted in the enlarged view on the right.
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Figure 3. PRMT5:MEP50 monomer structure. (A) Three domains and functions of PRMT5. (B) Interactions between SAM and nearby residues in the PRMT5 cofactor binding pocket. (C) Interactions between substrate and nearby residues in the PRMT5 substrate binding pocket.
Figure 3. PRMT5:MEP50 monomer structure. (A) Three domains and functions of PRMT5. (B) Interactions between SAM and nearby residues in the PRMT5 cofactor binding pocket. (C) Interactions between substrate and nearby residues in the PRMT5 substrate binding pocket.
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Figure 4. PRMT5 Inhibition Mechanisms in Cancer Therapy. (A) PRMT5 requires substrate adaptor proteins (SAPs) for substrate specificity. COPR5 facilitates PRMT5 methylation of histones H2A, H3, and H4; pICLn directs methylation of Sm proteins; and RIOK1 mediates PRMT5 methylation of nucleolin. (B) PRMT5 stability is regulated by the ubiquitin–proteasome system. The E3 ligase CHIP, in cooperation with HSP70, promotes PRMT5 ubiquitination and degradation. (C) PRMT5 contributes to liquid–liquid phase separation (LLPS) through methylation of LLPS-related substrates such as MCM7.
Figure 4. PRMT5 Inhibition Mechanisms in Cancer Therapy. (A) PRMT5 requires substrate adaptor proteins (SAPs) for substrate specificity. COPR5 facilitates PRMT5 methylation of histones H2A, H3, and H4; pICLn directs methylation of Sm proteins; and RIOK1 mediates PRMT5 methylation of nucleolin. (B) PRMT5 stability is regulated by the ubiquitin–proteasome system. The E3 ligase CHIP, in cooperation with HSP70, promotes PRMT5 ubiquitination and degradation. (C) PRMT5 contributes to liquid–liquid phase separation (LLPS) through methylation of LLPS-related substrates such as MCM7.
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Figure 5. PRMT5 inhibitors in the clinical trials with disclosed chemical structures.
Figure 5. PRMT5 inhibitors in the clinical trials with disclosed chemical structures.
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Figure 6. SAM-cooperative PRMT5 inhibitors. (A) Chemical and co-crystal structures (PDB: 4X61 [64]) of EPZ015666 and SAM (yellow stick) with PRMT5:MEP50 (gray cartoon). (B) Chemical structure of first-in-class PRMT5 degrader MS4322. (C) Chemical and cryo-EM structures (PDB: 8X6L [74]) of SCR-6920 and SAM (green stick) with PRMT5:MEP50.
Figure 6. SAM-cooperative PRMT5 inhibitors. (A) Chemical and co-crystal structures (PDB: 4X61 [64]) of EPZ015666 and SAM (yellow stick) with PRMT5:MEP50 (gray cartoon). (B) Chemical structure of first-in-class PRMT5 degrader MS4322. (C) Chemical and cryo-EM structures (PDB: 8X6L [74]) of SCR-6920 and SAM (green stick) with PRMT5:MEP50.
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Figure 7. SAM-competitive PRMT5 inhibitors. (A) Chemical structures of LLY-283, aldehyde 10, and PRT543. (B) Co-crystal structure (PDB: 6CKC [76]) of LLY-283 (cyan stick) with PRMT5:MEP50 (gray cartoon). (C) Co-crystal structure (PDB: 6K1S [77]) of aldehyde 10 (deep purple stick) with PRMT5:MEP50 (gray cartoon).
Figure 7. SAM-competitive PRMT5 inhibitors. (A) Chemical structures of LLY-283, aldehyde 10, and PRT543. (B) Co-crystal structure (PDB: 6CKC [76]) of LLY-283 (cyan stick) with PRMT5:MEP50 (gray cartoon). (C) Co-crystal structure (PDB: 6K1S [77]) of aldehyde 10 (deep purple stick) with PRMT5:MEP50 (gray cartoon).
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Figure 8. SAM-competitive PRMT5 inhibitors. (A) Chemical and co-crystal structures (PDB: 6RLQ [66]) of JNJ-64619178 (magenta stick) with PRMT5:MEP50 (gray cartoon). (B) Chemical and co-crystal structure (PDB: 7MX7 [43]) of PF-06939999 (smudge stick) with PRMT5:MEP50 (gray cartoon). (C) Chemical and co-crystal structure (PDB: 7KIB [79]) of 5,5-Bicyclic Nucleoside-derived compound (sky-blue stick) with PRMT5:MEP50 (gray cartoon).
Figure 8. SAM-competitive PRMT5 inhibitors. (A) Chemical and co-crystal structures (PDB: 6RLQ [66]) of JNJ-64619178 (magenta stick) with PRMT5:MEP50 (gray cartoon). (B) Chemical and co-crystal structure (PDB: 7MX7 [43]) of PF-06939999 (smudge stick) with PRMT5:MEP50 (gray cartoon). (C) Chemical and co-crystal structure (PDB: 7KIB [79]) of 5,5-Bicyclic Nucleoside-derived compound (sky-blue stick) with PRMT5:MEP50 (gray cartoon).
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Figure 9. MTAP deletion sensitizes cancer cells to PRMT5 inhibition via MTA accumulation. (A) MTAP deletion induces PRMT5 inhibition. (B) Schematic of the methionine salvage and polyamine synthesis pathways. Loss of MTAP disrupts this salvage process, causing MTA accumulation and enhanced PRMT5 inhibition.
Figure 9. MTAP deletion sensitizes cancer cells to PRMT5 inhibition via MTA accumulation. (A) MTAP deletion induces PRMT5 inhibition. (B) Schematic of the methionine salvage and polyamine synthesis pathways. Loss of MTAP disrupts this salvage process, causing MTA accumulation and enhanced PRMT5 inhibition.
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Figure 10. MTA-cooperative PRMT5 inhibitors. (A) Chemical and co-crystal structures (PDB: 7S1S [68]) of MRTX1719 (orange stick) with PRMT5:MEP50. (B) Chemical and co-crystal structure (PDB: 9C10 [82]) of AMG 193 (deep-green stick) with PRMT5:MEP50. (C) Chemical and co-crystal structure (PDB: 8VEY [83]) of TNG908 (purple stick) with PRMT5:MEP50. (D) Chemical and co-crystal structure (PDB: 9EYX [84]) of AZD3470 (magenta stick) with PRMT5:MEP50. (E) Chemical and cyro-EM structure (PDB: 8CYI [85]) of 11-2F (pink stick) with PRMT5:MEP50. (F) Chemical and cryo-EM structure of 16-19F (green stick) with PRMT5:MEP50.
Figure 10. MTA-cooperative PRMT5 inhibitors. (A) Chemical and co-crystal structures (PDB: 7S1S [68]) of MRTX1719 (orange stick) with PRMT5:MEP50. (B) Chemical and co-crystal structure (PDB: 9C10 [82]) of AMG 193 (deep-green stick) with PRMT5:MEP50. (C) Chemical and co-crystal structure (PDB: 8VEY [83]) of TNG908 (purple stick) with PRMT5:MEP50. (D) Chemical and co-crystal structure (PDB: 9EYX [84]) of AZD3470 (magenta stick) with PRMT5:MEP50. (E) Chemical and cyro-EM structure (PDB: 8CYI [85]) of 11-2F (pink stick) with PRMT5:MEP50. (F) Chemical and cryo-EM structure of 16-19F (green stick) with PRMT5:MEP50.
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Figure 11. PRMT5 allosteric inhibitors. Chemical and co-crystal structures (PDB: 6UXX [87]) of compound 1a (blue stick) with PRMT5:MEP50.
Figure 11. PRMT5 allosteric inhibitors. Chemical and co-crystal structures (PDB: 6UXX [87]) of compound 1a (blue stick) with PRMT5:MEP50.
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Figure 12. PRMT5 N-terminal TIM barrel binding site and ligands. (A) Co-crystal structures (PDB: 6V0O [14]) of pICLn225–235 (yellow stick) with PRMT5:MEP50. (B) Chemical and co-crystal structure (PDB: 7M05 [26]) of BRD6988 and BRD0639 (magenta stick) with PRMT5:MEP50. (C) Chemical and co-crystal structure (PDB: 7BOC [13]) of RIOK18–21 (wheat stick) with PRMT5:MEP50. The yellow dashed line indicates the envisaged macrocyclization site.
Figure 12. PRMT5 N-terminal TIM barrel binding site and ligands. (A) Co-crystal structures (PDB: 6V0O [14]) of pICLn225–235 (yellow stick) with PRMT5:MEP50. (B) Chemical and co-crystal structure (PDB: 7M05 [26]) of BRD6988 and BRD0639 (magenta stick) with PRMT5:MEP50. (C) Chemical and co-crystal structure (PDB: 7BOC [13]) of RIOK18–21 (wheat stick) with PRMT5:MEP50. The yellow dashed line indicates the envisaged macrocyclization site.
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Figure 13. Structural insights and functional impact of PRMT5 N-terminal ligands. (A) Cryo-EM structure of PRMT5 (purple cartoon) in complex with pICLn (wheat cartoon), highlighting the secondary binding pocket. (B) Chemical structure and predicted binding pose of J021-0199 (yellow stick) within the secondary site, based on 200 ns MD simulation. (C) Chemical structure and predicted binding mode of Z319334062 (pink stick). (D) Schematic of PRMT5/pICLn interaction mechanism. (E) Structure of Compound 17, a representative compound for targeting PRMT5:MEP50 interactions.
Figure 13. Structural insights and functional impact of PRMT5 N-terminal ligands. (A) Cryo-EM structure of PRMT5 (purple cartoon) in complex with pICLn (wheat cartoon), highlighting the secondary binding pocket. (B) Chemical structure and predicted binding pose of J021-0199 (yellow stick) within the secondary site, based on 200 ns MD simulation. (C) Chemical structure and predicted binding mode of Z319334062 (pink stick). (D) Schematic of PRMT5/pICLn interaction mechanism. (E) Structure of Compound 17, a representative compound for targeting PRMT5:MEP50 interactions.
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Table 1. PRMT5 inhibitors in clinical trials.
Table 1. PRMT5 inhibitors in clinical trials.
TypeCompoundCompanyClinical StageFirst Identified (Year)Discontinued (Year)Indications
SAM-cooperative inhibitorsGSK3326595GlaxoSmithKlineDiscontinued20172022Advanced solid tumors (AST) and non-Hodgkin’s lymphoma (NHL).
SCR-6920Simcere PharmaceuticalPhase 22022N/AAST and NHL
SAM-competitive inhibitorsJNJ-64619178Janssen PharmaceuticalsDiscontinued20192022AST and NHL
PF-06939999PfizerDiscontinued20192022Advanced or metastatic solid tumors, including endometrial cancer, HNSCC, NSCLC, urothelial cancer, cervical cancer, and esophageal cancer.
PRT811Prelude TherapeuticsDiscontinued20202022AST and high-grade gliomas.
PRT543Prelude TherapeuticsDiscontinued20202022AST and hematologic malignancies.
MTA-cooperative inhibitorsTNG908Tango TherapeuticsPhase 1/22022N/AMTAP-deleted solid tumors, including non-CNS solid tumors such as NSCLC and pancreatic cancer.
TNG462Tango TherapeuticsPhase 1/22023N/AMTAP-deleted solid tumors, including NSCLC and pancreatic cancer.
MRTX1719Mirati TherapeuticsPhase 1/22023N/ASolid tumors harboring MTAP gene deletions.
AMG 193AmgenPhase 1/22024N/AAST with MTAP deletions.
BGB-58067BeiGenePhase 12024N/AAdvanced malignant solid neoplasms.
AZD3470AstraZenecaPhase 1/22024N/AMTAP-Deficient Advanced or Metastatic Solid Tumors
BAY 3713372BayerPhase 12025N/AMTAP-deleted Solid Tumors
PEP08PharmaEnginePhase 12025N/AMTAP-Del Advanced or Metastatic Solid Tumors
CTS3497CytosinLab TherapeuticsPhase 1/22025N/AMTAP Deficient Advanced Solid Tumors and Lymphomas
MAT2A inhibitorsIDE397IDEAYA BiosciencesPhase 1/22024N/AMTAP-deleted solid tumors, including non-small cell lung cancer and urothelial cancer.
S095035Servier PharmaceuticalsPhase 12019N/AAdvanced or metastatic solid tumors with homozygous deletion of MTAP.
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Shen, Z.; Li, C. Targeting PRMT5: Current Inhibitors and Emerging Strategies for Therapeutic Intervention. Processes 2025, 13, 2878. https://doi.org/10.3390/pr13092878

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Shen, Zhihang, and Chenglong Li. 2025. "Targeting PRMT5: Current Inhibitors and Emerging Strategies for Therapeutic Intervention" Processes 13, no. 9: 2878. https://doi.org/10.3390/pr13092878

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Shen, Z., & Li, C. (2025). Targeting PRMT5: Current Inhibitors and Emerging Strategies for Therapeutic Intervention. Processes, 13(9), 2878. https://doi.org/10.3390/pr13092878

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