Development of (2-(Benzyloxy)phenyl)methanamine Derivatives as Potent and Selective Inhibitors of CARM1 for the Treatment of Melanoma.

Coactivator-associated arginine methyltransferase 1 (CARM1), an important member of type I protein arginine methyltransferases (PRMTs), has emerged as a promising therapeutic target for various cancer types. In our previous study, we have identified a series of type I PRMT inhibitors, among which ZL-28-6 (6) exhibited increased activity against CARM1 while displaying decreased potency against other type I PRMTs. In this work, we conducted chemical modifications on compound 6, resulting in a series of (2-(benzyloxy)phenyl)methanamine derivatives as potent inhibitors of CARM1. Among them, compound 17e displayed remarkable potency and selectivity for CARM1 (IC50 = 2 ± 1 nM), along with notable antiproliferative effects against melanoma cell lines. Cellular thermal shift assay and western blot experiments confirmed that compound 6 effectively targets CARM1 within cells. Furthermore, compound 17e displayed good antitumor efficacy in a melanoma xenograft model, indicating that this compound warrants further investigation as a potential anticancer agent.

Inhibition of PRMT5-mediated regulation of DKK1 sensitizes colorectal cancer cells to chemotherapy.

The Dickkopf family proteins (DKKs) are strong Wnt signaling antagonists that play a significant role in colorectal cancer (CRC) development and progression. Recent work has shown that DKKs, mainly DKK1, are associated with the induction of chemoresistance in CRC and that DKK1 expression in cancer cells correlates with that of protein arginine N-methyltransferase 5 (PRMT5). This points to the presence of a regulatory loop between DKK1 and PRMT5. Herein, we addressed the question of whether PRMT5 contributes to DKK1 expression in CRC and hence CRC chemoresistance. Both in silico and in vitro approaches were used to explore the relationship between PRMT5 and different DKK members. Our data demonstrated that DKK1 expression is significantly upregulated in CRC clinical samples, KRAS-mutated CRC in particular and that the levels of DKK1 positively correlate with PRMT5 activation. Chromatin immunoprecipitation (ChIP) data indicated a possible epigenetic role of PRMT5 in regulating DKK1, possibly through the symmetric dimethylation of H3R8. Knockdown of DKK1 or treatment with the PRMT5 inhibitor CMP5 in combination with doxorubicin yielded a synergistic anti-tumor effect in KRAS mutant, but not KRAS wild-type, CRC cells. These findings suggest that PRMT5 regulates DKK1 expression in CRC and that inhibition of PRMT5 modulates DKK1 expression in such a way that reduces CRC cell growth.

Discovery of TNG908: A Selective, Brain Penetrant, MTA-Cooperative PRMT5 Inhibitor That Is Synthetically Lethal with MTAP-Deleted Cancers.

It has been shown that PRMT5 inhibition by small molecules can selectively kill cancer cells with homozygous deletion of the MTAP gene if the inhibitors can leverage the consequence of MTAP deletion, namely, accumulation of the MTAP substrate MTA. Herein, we describe the discovery of TNG908, a potent inhibitor that binds the PRMT5·MTA complex, leading to 15-fold-selective killing of MTAP-deleted (MTAP-null) cells compared to MTAPintact (MTAP WT) cells. TNG908 shows selective antitumor activity when dosed orally in mouse xenograft models, and its physicochemical properties are amenable for crossing the blood-brain barrier (BBB), supporting clinical study for the treatment of both CNS and non-CNS tumors with MTAP loss.

The antidepressant effects of protein arginine methyltransferase 2 involve neuroinflammation.

Protein arginine methyltransferase (PRMT) 2 catalyzes the methylation of arginine residues in histones. Depression is associated with histone methylation; however, more comprehensive research is needed on how PRMT2 regulates depression. The present study aimed to investigate the effects and possible mechanism(s) of PRMT2 overexpression on depression-like behavior induced by chronic unpredictable mild stress (CUMS) in rats, and whether lentivirus-mediated PRMT2 overexpression in the hippocampus suppresses depression-like behavior. Furthermore, the PRMT2 inhibitor MS023 was administered to the animals to investigate whether the antidepressant effect of PRMT2 overexpression could be reversed. Behavioral experiments were performed to detect depression-like behavior in rats. Western blotting was used to determine protein expression levels of PRMT2, histone H3R8 asymmetric dimethylation (H3R8me2a), inducible nitric oxide synthase (iNOS), and arginase 1 (Arg1) in rat hippocampal tissues. Hippocampal microglia and PRMT2 were stained using immunofluorescence techniques. Enzyme-linked immunosorbent assay was used to determine the levels of various inflammatory factors in rat hippocampal tissue. Results of analysis revealed that PRMT2 overexpression in the hippocampus exerted an antidepressant effect. PRMT2 overexpression in the hippocampus reduced the proportion of activated microglia in the hippocampus, upregulated Arg1 and H3R8me2a expression, and downregulated iNOS expression. PRMT2 overexpression in the hippocampus inhibited the release of pro-inflammatory factors and promoted the release of anti-inflammatory factors. In summary, PRMT2 overexpression in the hippocampus promoted the conversion of microglia from the M1 to M2 type, resulting in an antidepressant effect. These results suggest that PRMT2 may be a potential therapeutic target to prevent and treat depression.

Combined inhibition of MTAP and MAT2a mimics synthetic lethality in tumor models via PRMT5 inhibition.

Homozygous 5'-methylthioadenosine phosphorylase (MTAP) deletions occur in approximately 15% of human cancers. Co-deletion of MTAP and methionine adenosyltransferase 2 alpha (MAT2a) induces a synthetic lethal phenotype involving protein arginine methyltransferase 5 (PRMT5) inhibition. MAT2a inhibitors are now in clinical trials for genotypic MTAP-/- cancers, however the MTAP-/- genotype represents fewer than 2% of human colorectal cancers (CRCs), limiting the utility of MAT2a inhibitors in these and other MTAP+/+ cancers. Methylthio-DADMe-immucillin-A (MTDIA) is a picomolar transition state analog inhibitor of MTAP that renders cells enzymatically MTAP-deficient to induce the MTAP-/- phenotype. Here, we demonstrate that MTDIA and MAT2a inhibitor AG-270 combination therapy mimics synthetic lethality in MTAP+/+ CRC cell lines with similar effects in mouse xenografts and without adverse histology on normal tissues. Combination treatment is synergistic with a 104-fold increase in drug potency for inhibition of CRC cell growth in culture. Combined MTDIA and AG-270 decreases S-adenosyl-L-methionine and increases 5'-methylthioadenosine in cells. The increased intracellular methylthioadenosine:S-adenosyl-L-methionine ratio inhibits PRMT5 activity, leading to cellular arrest and apoptotic cell death by causing MDM4 alternative splicing and p53 activation. Combination MTDIA and AG-270 treatment differs from direct inhibition of PRMT5 by GSK3326595 by avoiding toxicity caused by cell death in the normal gut epithelium induced by the PRMT5 inhibitor. The combination of MTAP and MAT2a inhibitors expands this synthetic lethal approach to include MTAP+/+ cancers, especially the remaining 98% of CRCs without the MTAP-/- genotype.

CARM1 arginine methyltransferase as a therapeutic target for cancer.

Coactivator-associated arginine methyltransferase 1 (CARM1) is an arginine methyltransferase that posttranslationally modifies proteins that regulate multiple levels of RNA production and processing. Its substrates include histones, transcription factors, coregulators of transcription, and splicing factors. CARM1 is overexpressed in many different cancer types, and often promotes transcription factor programs that are co-opted as drivers of the transformed cell state, a process known as transcription factor addiction. Targeting these oncogenic transcription factor pathways is difficult but could be addressed by removing the activity of the key coactivators on which they rely. CARM1 is ubiquitously expressed, and its KO is less detrimental in embryonic development than deletion of the arginine methyltransferases protein arginine methyltransferase 1 and protein arginine methyltransferase 5, suggesting that therapeutic targeting of CARM1 may be well tolerated. Here, we will summarize the normal in vivo functions of CARM1 that have been gleaned from mouse studies, expand on the transcriptional pathways that are regulated by CARM1, and finally highlight recent studies that have identified oncogenic properties of CARM1 in different biological settings. This review is meant to kindle an interest in the development of human drug therapies targeting CARM1, as there are currently no CARM1 inhibitors available for use in clinical trials.

Identification of a Protein Arginine Methyltransferase 7 (PRMT7)/Protein Arginine Methyltransferase 9 (PRMT9) Inhibitor.

Less studied than the other protein arginine methyltransferase isoforms, PRMT7 and PRMT9 have recently been identified as important therapeutic targets. Yet, most of their biological roles and functions are still to be defined, as well as the structural requirements that could drive the identification of selective modulators of their activity. We recently described the structural requirements that led to the identification of potent and selective PRMT4 inhibitors spanning both the substrate and the cosubstrate pockets. The reanalysis of the data suggested a PRMT7 preferential binding for shorter derivatives and prompted us to extend these structural studies to PRMT9. Here, we report the identification of the first potent PRMT7/9 inhibitor and its binding mode to the two PRMT enzymes. Label-free quantification mass spectrometry confirmed significant inhibition of PRMT activity in cells. We also report the setup of an effective AlphaLISA assay to screen small molecule inhibitors of PRMT9.

Comparative Study of Adenosine Analogs as Inhibitors of Protein Arginine Methyltransferases and a Clostridioides difficile-Specific DNA Adenine Methyltransferase.

S-Adenosyl-l-methionine (SAM) analogs are adaptable tools for studying and therapeutically inhibiting SAM-dependent methyltransferases (MTases). Some MTases play significant roles in host-pathogen interactions, one of which is Clostridioides difficile-specific DNA adenine MTase (CamA). CamA is needed for efficient sporulation and alters persistence in the colon. To discover potent and selective CamA inhibitors, we explored modifications of the solvent-exposed edge of the SAM adenosine moiety. Starting from the two parental compounds (6e and 7), we designed an adenosine analog (11a) carrying a 3-phenylpropyl moiety at the adenine N6-amino group, and a 3-(cyclohexylmethyl guanidine)-ethyl moiety at the sulfur atom off the ribose ring. Compound 11a (IC50 = 0.15 µM) is 10× and 5× more potent against CamA than 6e and 7, respectively. The structure of the CamA-DNA-inhibitor complex revealed that 11a adopts a U-shaped conformation, with the two branches folded toward each other, and the aliphatic and aromatic rings at the two ends interacting with one another. 11a occupies the entire hydrophobic surface (apparently unique to CamA) next to the adenosine binding site. Our work presents a hybrid knowledge-based and fragment-based approach to generating CamA inhibitors that would be chemical agents to examine the mechanism(s) of action and therapeutic potentials of CamA in C. difficile infection.

Medicinal chemistry strategies targeting PRMT5 for cancer therapy.

Protein arginine methyltransferases 5 (PRMT5), a therapeutic target whose main physiological function is mono- and symmetric dimethylation of arginine, has drawn significant attention from researchers in the field. PRMT5 has been reported to participate in many cellular functions including cell growth, migration, and development. Upregulation of PRMT5 occurs in different kinds of tumors and is strongly associated with poor prognosis. In recent years, several PRMT5 inhibitors have entered clinical trials for the treatment of various cancers, such as advanced or recurrent solid tumors with MTAP deletion. Herein, we reviewed the binding modes and structure-activity relationships of novel PRMT5 inhibitors and discussed prospects of PRMT5 inhibitors in cancer therapy, aiming to provide insights on drug development of PRMT5 inhibitors.

PRMT5-mediated RNF4 methylation promotes therapeutic resistance of APL cells to As2O3 by stabilizing oncoprotein PML-RARα.

Acute promyelocytic leukemia (APL) is a hematological malignancy driven by the oncoprotein PML-RARα, which can be treated with arsenic trioxide (As2O3) or/and all-trans retinoic acid. The protein arginine methyltransferase 5 (PRMT5) is involved in tumorigenesis. However, little is known about the biological function and therapeutic potential of PRMT5 in APL. Here, we show that PRMT5 is highly expressed in APL patients. PRMT5 promotes APL by interacting with PML-RARα and suppressing its ubiquitination and degradation. Mechanistically, PRMT5 attenuates the interaction between PML-RARα and its ubiquitin E3 ligase RNF4 by methylating RNF4 at Arg164. Notably, As2O3 treatment triggers the dissociation of PRMT5 from PML nuclear bodies, attenuating RNF4 methylation and promoting RNF4-mediated PML-RARα ubiquitination and degradation. Moreover, knockdown of PRMT5 and pharmacological inhibition of PRMT5 with the specific inhibitor EPZ015666 significantly inhibit APL cells growth. The combination of EPZ015666 with As2O3 shows synergistic effects on As2O3-induced differentiation of bone marrow cells from APL mice, as well as on apoptosis and differentiation of primary APL cells from APL patients. These findings provide mechanistic insight into the function of PRMT5 in APL pathogenesis and demonstrate that inhibition of PRMT5, alone or in combination with As2O3, might be a promising therapeutic strategy against APL.

PRMT inhibition induces a viral mimicry response in triple-negative breast cancer.

Triple-negative breast cancer (TNBC) is the most aggressive breast cancer subtype with the worst prognosis and few effective therapies. Here we identified MS023, an inhibitor of type I protein arginine methyltransferases (PRMTs), which has antitumor growth activity in TNBC. Pathway analysis of TNBC cell lines indicates that the activation of interferon responses before and after MS023 treatment is a functional biomarker and determinant of response, and these observations extend to a panel of human-derived organoids. Inhibition of type I PRMT triggers an interferon response through the antiviral defense pathway with the induction of double-stranded RNA, which is derived, at least in part, from inverted repeat Alu elements. Together, our results represent a shift in understanding the antitumor mechanism of type I PRMT inhibitors and provide a rationale and biomarker approach for the clinical development of type I PRMT inhibitors.

Fragment-Based Discovery of MRTX1719, a Synthetic Lethal Inhibitor of the PRMT5•MTA Complex for the Treatment of MTAP-Deleted Cancers.

The PRMT5•MTA complex has recently emerged as a new synthetically lethal drug target for the treatment of MTAP-deleted cancers. Here, we report the discovery of development candidate MRTX1719. MRTX1719 is a potent and selective binder to the PRMT5•MTA complex and selectively inhibits PRMT5 activity in MTAP-deleted cells compared to MTAP-wild-type cells. Daily oral administration of MRTX1719 to tumor xenograft-bearing mice demonstrated dose-dependent inhibition of PRMT5-dependent symmetric dimethylarginine protein modification in MTAP-deleted tumors that correlated with antitumor activity. A 4-(aminomethyl)phthalazin-1(2H)-one hit was identified through a fragment-based screen, followed by X-ray crystallography, to confirm binding to the PRMT5•MTA complex. Fragment growth supported by structural insights from X-ray crystallography coupled with optimization of pharmacokinetic properties aided the discovery of development candidate MRTX1719.

Fascinating Transformation of SAM-Competitive Protein Methyltransferase Inhibitors from Nucleoside Analogues to Non-Nucleoside Analogues.

The abnormal expression of protein methyltransferase (PMT) has been linked with many diseases such as diabetes, neurological disorders, and cancer. S-Adenyl-l-methionine (SAM) is a universal methyl donor and gets converted to S-adenyl-l-homocysteine (SAH), an endogenous competitive inhibitor of SAM. Initially developed SAM/SAH mimetic nucleoside analogues were pan methyltransferase inhibitors. The gradual understanding achieved through ligand-receptor interaction paved the way for various rational approaches of drug design leading to potent and selective nucleoside inhibitors. The present perspective is based on the systematic evolution of selective SAM-competitive heterocyclic non-nucleoside inhibitors from nucleoside inhibitors. This fascinating transition has resolved several issues inherent to nucleoside analogues such as poor pharmacokinetics leading to poor in vivo efficacy. The perspective has brought together various concepts and strategies of drug design that contributed to this rational transition. We firmly believe that the strategies described herein will serve as a template for the future development of drugs in general.

Explore the effect of LLY-283 on the ototoxicity of auditory cells caused by cisplatin: A bioinformatic analysis based on RNA-seq.

BACKGROUND: Cisplatin is a commonly used chemotherapeutic drug in clinics, and long-term application will lead to hearing impairment. LLY-283, an inhibitor of PRMT5, has not been reported in deafness. Our study aimed to explore the mechanism of LLY-283 in hearing impairment. MATERIALS AND METHODS: First, we performed RNA-seq (cisplatin in the experimental group and DMSO in the control group) to obtain the biological processes mainly involved in differentially expressed genes (DEGs). CCK-8 and LDH experiments were used to observe the effect of LLY-283 on cisplatin-induced auditory cell injury. ROS experiment was used to monitor the impact of LLY-283 on oxidative damage of auditory cells. Effect of LLY-283 on apoptosis of auditory cells detected by TUNEL experiment. PCR and Western blotting were used to detect the expression of genes and proteins related to auditory cell apoptosis in LLY-283 cells. Meanwhile, we explored the effect of LLY-283 on the expression of PRMT5 in cisplatin-induced hearing impaired cells at RNA and protein levels. RESULTS: Biological process analysis showed that DEGs were mainly enriched in the apoptotic process involved in morphogenesis (-Log10 P = 3.71). CCK-8 and LDH experiments confirmed that LLY-283 could save cisplatin-induced auditory cell injury. ROS experiments confirmed that LLY-283 could rescue cisplatin-induced oxidative damage to auditory cells. TUNEL experiments confirmed that LLY-283 could protect cisplatin-induced apoptosis of auditory cells. Meanwhile, LLY-283 could inhibit the expression of PRMT5 in auditory cells induced by cisplatin. CONCLUSION: LLY-283 can rescue cisplatin-induced auditory cell apoptosis injury. LLY-283 can inhibit the increase in PRMT5 expression induced by cisplatin.

PRMT3 inhibitor SGC707 reduces triglyceride levels and induces pruritus in Western-type diet-fed LDL receptor knockout mice.

Protein arginine methyltransferase 3 (PRMT3) is a co-activator of liver X receptor capable of selectively modulating hepatic triglyceride synthesis. Here we investigated whether pharmacological PRMT3 inhibition can diminish the hepatic steatosis extent and lower plasma lipid levels and atherosclerosis susceptibility. Hereto, male hyperlipidemic low-density lipoprotein receptor knockout mice were fed an atherogenic Western-type diet and injected 3 times per week intraperitoneally with PRMT3 inhibitor SGC707 or solvent control. Three weeks into the study, SGC707-treated mice developed severe pruritus and scratching-associated skin lesions, leading to early study termination. SGC707-treated mice exhibited 50% lower liver triglyceride stores as well as 32% lower plasma triglyceride levels. Atherosclerotic lesions were virtually absent in all experimental mice. Plasma metabolite analysis revealed that levels of taurine-conjugated bile acids were ~ threefold increased (P < 0.001) in response to SGC707 treatment, which was paralleled by systemically higher bile acid receptor TGR5 signalling. In conclusion, we have shown that SGC707 treatment reduces hepatic steatosis and plasma triglyceride levels and induces pruritus in Western-type diet-fed LDL receptor knockout mice. These findings suggest that pharmacological PRMT3 inhibition can serve as therapeutic approach to treat non-alcoholic fatty liver disease and dyslipidemia/atherosclerosis, when unwanted effects on cholesterol and bile acid metabolism can be effectively tackled.

SAM-Competitive PRMT5 Inhibitor PF-06939999 Demonstrates Antitumor Activity in Splicing Dysregulated NSCLC with Decreased Liability of Drug Resistance.

Protein arginine methyltransferase 5 (PRMT5) overexpression in hematologic and solid tumors methylates arginine residues on cellular proteins involved in important cancer functions including cell-cycle regulation, mRNA splicing, cell differentiation, cell signaling, and apoptosis. PRMT5 methyltransferase function has been linked with high rates of tumor cell proliferation and decreased overall survival, and PRMT5 inhibitors are currently being explored as an approach for targeting cancer-specific dependencies due to PRMT5 catalytic function. Here, we describe the discovery of potent and selective S-adenosylmethionine (SAM) competitive PRMT5 inhibitors, with in vitro and in vivo characterization of clinical candidate PF-06939999. Acquired resistance mechanisms were explored through the development of drug resistant cell lines. Our data highlight compound-specific resistance mutations in the PRMT5 enzyme that demonstrate structural constraints in the cofactor binding site that prevent emergence of complete resistance to SAM site inhibitors. PRMT5 inhibition by PF-06939999 treatment reduced proliferation of non-small cell lung cancer (NSCLC) cells, with dose-dependent decreases in symmetric dimethyl arginine (SDMA) levels and changes in alternative splicing of numerous pre-mRNAs. Drug sensitivity to PF-06939999 in NSCLC cells associates with cancer pathways including MYC, cell cycle and spliceosome, and with mutations in splicing factors such as RBM10. Translation of efficacy in mouse tumor xenograft models with splicing mutations provides rationale for therapeutic use of PF-06939999 in the treatment of splicing dysregulated NSCLC.

Ribavirin inhibits the growth and ascites formation of hepatocellular carcinoma through downregulation of type I CARM1 and type II PRMT5.

Type I co-activator-associated arginine methyltransferase 1 (CARM1) and type II protein arginine methyltransferase 5 (PRMT5) are highly expressed in multiple cancers including liver cancer and their overexpression contributes to poor prognosis, thus making them promising therapeutic targets. Here, we evaluated anti-tumor activity of ribavirin in hepatocellular carcinoma (HCC). We found that ribavirin significantly inhibited the proliferation of HCC cells in a time- and dose-dependent manner. Furthermore, ribavirin suppressed the growth of subcutaneous and orthotopic xenograft of HCC in mice, decreased vascular endothelial growth factor (VEGF) and peritoneal permeability to reduce ascites production, and prolonged the survival of mice in HCC ascites tumor models. Mechanistically, ribavirin potently down-regulated global protein expression of CARM1 and PRMT5, and concurrently decreased accumulation of H3R17me2a and H3R8me2s/H4R3me2s. However, ribavirin did not affect the activity and mRNA levels of both CARM1 and PRMT5 in vivo and in vitro HCC cells. In addition, our ChIP results shown that ribavirin inhibited CARM1 which in turn decreased the H3R17me2a, binds to the eukaryotic translation initiation factor 4E (eIF4E) and VEGF promoter region, and reduced the relative mRNA expression level of eIF4E and VEGF in HCC cells. Our findings suggested a potential therapeutic strategy for patients with HCC through inhibition of the abnormal activation/expression of both CARM1 and PRMT5.

PRMT4 inhibitor TP-064 impacts both inflammatory and metabolic processes without changing the susceptibility for early atherosclerotic lesions in male apolipoprotein E knockout mice.

BACKGROUND AND AIMS: Atherosclerotic cardiovascular disease is a metabolic and inflammatory disorder. In vitro studies have suggested that protein arginine methyltransferase 4 (PRMT4) may act as a transcriptional coactivator to modulate inflammatory and metabolic processes. Here we investigated the potential anti-atherogenic effect of PRMT4 inhibitor TP-064 in vivo. METHODS: Male apolipoprotein E knockout mice fed a high cholesterol/high fat Western-type diet were intraperitoneally injected three times a week with 2.5 mg/kg (low dose) or 10 mg/kg (high dose) TP-064 or with DMSO control. RESULTS: TP-064 induced a dose-dependent decrease in lipopolysaccharide-induced ex vivo blood monocyte Tnfα secretion (p < 0.05 for trend) in the context of unchanged blood monocyte concentrations and neutrophilia induction (p < 0.01 for trend). A dose-dependent decrease in gonadal white adipose tissue expression levels of PPARγ target genes was detected, which translated into a reduced body weight gain after high dose TP-064 treatment (p < 0.05). TP-064 treatment also dose-dependently downregulated gene expression of the glycogen metabolism related protein G6pc in the liver (p < 0.001 for trend). In addition, a trend towards lower plasma insulin and higher blood glucose levels was observed, which was paralleled by a reduction in hepatic mRNA expression levels of the insulin-responsive genes Fasn (-55%; p < 0.001) and Gck (-47%; p < 0.001) in high dose-treated mice. Plasma triglyceride levels were reduced by high dose TP-064 treatment (-30%; p < 0.05). However, no change was observed in the size or composition of aortic root atherosclerotic lesions. CONCLUSIONS: The PRMT4 inhibitor TP-064 impacts both inflammatory and metabolic processes without changing atherosclerosis susceptibility of male apolipoprotein E knockout mice.

Cellular pathways influenced by protein arginine methylation: Implications for cancer.

Arginine methylation is an influential post-translational modification occurring on histones, RNA binding proteins, and many other cellular proteins, affecting their function by altering their protein-protein and protein-nucleic acid interactions. Recently, a wealth of information has been gathered, implicating protein arginine methyltransferases (PRMTs), enzymes that deposit arginine methylation, in transcription, pre-mRNA splicing, DNA damage signaling, and immune signaling with major implications for cancer therapy, especially immunotherapy. This review summarizes this recent progress and the current state of PRMT inhibitors, some in clinical trials, as promising drug targets for cancer.