Pathophysiological significance of the TRPM2 ion channel as a potential target in cancer, neurological disorders, and ischemia/reperfusion injury.

1.
Introduction
The transient receptor potential melastatin 2 (TRPM2) ion channel belongs to the transient receptor potential melastatin (TRPM) subfamily of the transient receptor potential (TRP) superfamily. TRP channels constitute a large and functionally diverse group of tetrameric, non-selective cation channels that were originally identified in Drosophila melanogaster and later in mammals and various other species. In mammals, the TRP superfamily is classified into six major subfamilies: TRPA (ankyrin), TRPC (canonical), TRPM (melastatin), TRPV (vanilloid), TRPML (mucolipin), and TRPP (polycystin). Among these, the TRPM subfamily is the most diverse and ubiquitously expressed, comprising eight members (TRPM1–TRPM8) [1,2] (Fig. 1). Within this subfamily, TRPM2 has attracted considerable attention due to its unique role as a redox-sensitive cation channel [3–5].
TRPM2 is a non-specific cation channel that is permeable to Ca2+ and plays a vital role in the maintenance of intracellular Ca2+ homeostasis and cellular response to oxidative stress [2,5,6]. The structural feature that distinguishes TRPM2 from other members of the TRPM subfamily is the presence of the C-terminal NUDT9-H domain, which is an important adenosine diphosphate ribose (ADPR) binding site required for the channel activation [7,8]. TRPM2 is widely distributed across multiple tissues, including the brain (neurons and glial cells), heart, liver, pancreatic beta cells, lungs, immunocytes, hematopoietic cells, eyes, and spleen [9–11]. Functionally, TRPM2-mediated Ca2+ influx modulates diverse downstream cell signaling pathways involved in insulin secretion, temperature regulation, inflammation, autophagy, mitochondrial integrity, transcriptional regulation, endothelial barrier function, cell survival, and death under oxidative stress conditions, etc. [12,13]. While physiological TRPM2 activity contributes to stress adaptation and immune regulation, its sustained or aberrant activation promotes pathological outcomes, including tumor progression, neuroinflammation, neuronal degeneration, and vascular dysfunction [14–18].
Growing evidence has now positioned TRPM2 as a key mediator in diseases characterized by oxidative stress and Ca2+ dysregulation. In these contexts, TRPM2 integrates redox signaling with inflammatory and metabolic pathways, often modulating the balance from cellular adaptation toward tissue injury and disease progression [6, 19–23]. In this review, we provide a comprehensive and integrative analysis of TRPM2, emphasizing its diverse functional roles across multiple disease systems, including cancers, neurological disorders, and ischemia/reperfusion (I/R) injury. This review explores the regulatory complexity of TRPM2 by detailing its alternative splice variants and the emerging role of the TRPM2 antisense long non-coding RNA (TRPM2-AS) in tumor progression and therapeutic resistance. By systematically dissecting disease-specific signaling pathways, including oxidative stress, autophagy, and transcriptional networks, this review not only consolidates existing knowledge but also presents in-depth mechanistic insights with translational relevance.

2.
Structural characteristics of the TRPM2 ion channel
Human TRPM2 (hTRPM2) protein is composed of 1503 amino acid (aa) residues, encoded by the Trpm2 gene located on chromosome 21q22.3. The approximate size of the gene is 90 kB with a molecular weight of around 170 kDa [14,24,25]. Four identical subunits assemble to form a functional tetrameric-transmembrane channel. Each TRPM2 subunit is composed of multi-domain proteins, and based on the advanced cryogenic electron microscopy (Cryo-EM) structures, it can be characterized into three tiers [26–30]. The top tier consists of the transmembrane (TM) domains (S1-S6), pre-S1 region, and the TRP helices (H1 and H2). The S1–S4 segments are a voltage sensor-like domain (VSLD), and a binding site for Ca2+ is located within the TM region. The S5–S6 domains form a re-entrant pore-forming loop and contain the ‘979FGQI982’ motif, which serves as an ion selectivity filter and is involved in the regulation of gating. The middle tier is comprised of the rib helix and MHR4 domain. The TRP helices strongly interact with this MHR4 domain and the Trp1078 residue of S4-S5 linkers that support the channel in its apo (closed) state. The bottom tier of the TRPM2 subunit represents the intracellular layer that includes the N-terminal MHR1/2 and MHR3 domains, the pole helices, and the C-terminal NUDT9-H domain. The pole helices form an intertwined coiled-coil domain (CCD) and build a central structural scaffold with the rib helix that supports the tetrameric channel assembly [30]. The previous study by Wang et. al. has reported that NUDT9-H domain is the primary binding site for ADPR; however, a later cryo-EM study in hTRPM2 by Huang et. al. demonstrated that MHR1/2 is the orthosteric binding site for ADPR, while a second ADPR binding to the NUDT9-H domain is important for conformational changes, opening the channel with Ca2+ [27,30]. This finding was recently confirmed in 2024 by Wang et. al., where the RCSB Protein Data Bank (PDB) structure (PDB ID: 8E6Q) shows ADPR binding to both MHR1/2 and NUDT9-H domains. In the apo state, the NUDT9-H domain engages in extensive interactions with the MHR1/2 domains with its core region, both its own subunit (cis) and neighboring subunits (trans). These interactions stabilize the inactive conformation of the channel by restraining inter-subunit movements. Upon binding of a second ADPR to the NUDT9-H domain, this strong interaction with MHR1/2 undergoes conformational changes that relay the signal to the transmembrane domains through MHR3 and MHR4 linker domains [26–30] (Fig. 2).
TRPM2 also has a non-canonical IQ-like calmodulin-binding (CaM) motif in its N-terminal region (aa 406–416) that modulates Ca2+ sensitivity [31]. An additional Ca2+-CaM binding site is present in the NUDT9-H domain that makes the channel sensitive to temperature [32] (Fig. 3A). Previously, TRPM2 was termed as “chanzyme,” because of the assumption that it has both channel-like and enzymatic activity, due to the resemblance of the NUDT9-H domain to mitochondrial NUDT9 (mitNUDT9), an enzyme that catalyzes the cleavage of ADPR into AMP and Ribose-5-Phosphate [7]. However, recent studies proved that NUDT9-H of TRPM2 does not hydrolyze the ADPR, thus making it a simple ligand-gated channel [33]. This loss of enzymatic activity relative to NUDT9 is due to the substitution of an amino acid in the NUDT9-H motif at E1405I/F1406L [34,35].
In addition to functional full-length TRPM2 (TRPM2-L), TRPM2 has multiple splice variants that do not transport Ca2+ across the membrane, rather co-regulate the activation of TRPM2-L with varying activity. These include TRPM2-S (short), TRPM2-SSF (striatum short form), TRPM2-ΔN (truncated N-terminal), TRPM2-ΔC (truncated C-terminal), TRPM2-ΔNΔC (truncated N- and C-termini), and TRPM2-TE (terminal exon) [14, 36–38]. The TRPM2-S (short) isoform acts as an inhibitor of TRPM2-L. It has 845 aa residues with only two transmembrane fragments [38,39]. TRPM2-S can directly bind to TRPM2-L within the membrane and prevent its activation [40]. The activity of TRPM2 can be reinstated in oxidative stress, where activated protein kinase Cα (PKCα) can dissociate TRPM2-S from TRPM2 by phosphorylation of TRPM2-S at Ser39. It results in increased intracellular Ca2+ influx through TRPM2 and promotes cellular apoptosis [38,41]. TRPM2-TE is of 184 or 218 amino acid residues from the C-terminal of TRPM2. It is overexpressed in tumor cells like lung cancer and melanoma and was identified during a search for tumor suppressor genes in melanoma. It may have some potential to protect against apoptosis [36]. Other variants include TRPM2-ΔN, missing amino acids 538–557 in the N-tail; TRPM2-ΔC, lacking 1292–1325 in the C-tail; TRPM2-ΔNΔC, lacking both amino acids 538–557 and 1292–1325; SSF-TRPM2, with deletion of 1–214 amino acids [14,25,37].

3.
Regulation and activation mechanisms of TRPM2 ion channel
The TRPM2 ion channel is activated by a range of physiological and pathological stimuli, including ADPR, calcium ions (Ca2+), reactive oxygen species (ROS), tumor necrosis factor alpha (TNFα), zinc ions (Zn2+), and amyloid β peptide [3, 4, 42–47]. Among these, ADPR is the most potent and well-characterized endogenous activator, with an EC50 typically between 10–80 μM. ADPR is generated from nicotinamide adenine dinucleotide (NAD+) in both the nucleus and mitochondria during oxidative stress [4,42,48]. Other molecules stimulate the channel activation via ADPR production rather than acting as a direct agonist. Oxidative stress triggers nuclear DNA damage, which activates two enzymes: poly-ADP-ribose polymerase (PARP) and poly-ADP-ribose glycohydrolase (PARG). PARP converts NAD+ into poly-ADPR, which then cleaves into ADPR by PARG. In mitochondria, ADPR is directly produced from NAD+ by the NUDT9 enzyme. Once formed, ADPR binds to both the NUDT9-H domain in the C-terminal and the MHR1/2 domain in the N-terminal region of TRPM2 (Fig. 3A). This dual binding triggers a structural change, specifically a 27° rigid-body rotation between subunits that primes the channel for opening. The subsequent binding of intracellular Ca2+ near the S2-S3 domains and TRP region of primed TRPM2 further rotates the subunits by 15°. This causes tilting of the TRP H1 helix and twisting of the S6 domain, resulting in the opening of the TRPM2 channel [30] (Fig. 3B).
The intracellular Ca2+-binding to the channel is crucial for facilitating ADPR-mediated channel activation. Without the Ca2+-binding, ADPR alone cannot efficiently activate the channel [4,30,42]. According to the literature, Ca2+ alone can also activate full-length TRPM2 (TRPM2-L), although to a lesser extent than when ADPR is present. Even in certain splice isoforms of TRPM2, lacking canonical ADPR-binding sites, Ca2+ acts as the only activator [48,49]. Therefore, Ca2+-binding plays a critical role in the conformational changes that are required for the channel opening.
Temperature is another factor that plays a role in activating TRPM2, which makes the channel thermally sensitive. TRPM2 is found to be activated in rat insulinoma cells at temperatures above 35°C [50]. On prolonged exposure to heat, TRPM2 expression is increased in the embryonic mouse brain, which affects embryonic development as well as neurogenesis [51]. TRPM2, present in the preoptic area of the brain, is involved in regulating body temperature. It is activated when temperatures rise above 37°C, preventing fever and tissue damage [52]. Even though the role of TRPM2 in temperature sensing is known, the precise mechanisms behind this remain elusive.

4.
TRPM2 as a potential therapeutic target for cancer treatment
Overexpression of TRPM2 promotes cancer cell survival in various malignancies, including neuroblastoma, lung, stomach, prostate, and pancreatic cancer. Research has shown that TRPM2-mediated elevated intracellular Ca2+ levels contribute to cancer cell proliferation by increasing the antioxidant level, reducing oxidative stress, stimulating mitochondrial functionality, ATP production, mitophagy/autophagic system, and other cell-signaling pathways [53–57].
4.1.
Roles and therapeutic targeting of TRPM2 in neuroblastoma
TRPM2 is notably upregulated in neuroblastoma and plays a role in cancer cell survival and tumor growth. The role of TRPM2 in promoting tumor growth is validated in mouse xenograft models implanted with SH-SY5Y neuroblastoma cells engineered to stably express either of the TRPM2 isoforms: TRPM2-L or TRPM2-S. A marked decrease in tumor growth was observed in TRPM2-S expressing mice compared to those with TRPM2-L. TRPM2-S has inhibitory function in the activity of TRPM2-L, lowering the Ca2+ influx and further reduction of hypoxia-inducible transcription factors-1α and −2α (HIF-1/2α) and mitophagy led to increased cancer cell death that primarily contributed to the suppression of tumor growth in TRPM2-S expressing mice [58]. Mechanistically, in the absence of TRPM2, Ca2+ influx becomes lower in cancer cell, which in turn suppresses the expression of HIF-1/2α along with its target proteins, including fork-head box transcription factor 3a (FOXO3a), lactate dehydrogenase, enolase 2, NADH dehydrogenase (ubiquinone) 1α subcomplex, 4-like 2 (NDUFAL2), BCL2/ adenovirus E1B 19 kDa interacting protein 3 (BNIP3) and vascular endothelial growth factor (VEGF). Reduction of FOXO3a leads to decreased levels of antioxidant enzymes such as superoxide dismutase 1 and 2 (SOD1/2), elevating superoxide production and overall ROS level. In parallel, lower expression of mitochondrial protein NDUFA4L2 and cytochrome c oxidase subunit IV isoform 1 and 2 (COX 4.1/2) impairs the electron transport chain (ETC) and ATP production. Additionally, suppression of mitophagy marked by a significant reduction of BNIP3 promotes the accumulation of damaged mitochondria. Collectively, these alterations disrupt mitochondrial bioenergetics and weaken antioxidant defense. Thereby, cancer cells become unable to effectively limit oxidative stress, and the resulting ROS accumulation ultimately diminishes cancer cell viability [53,58]. TRPM2 inhibition also downregulates phosphorylated Src (pSrc), CREB (in mitochondria and nucleus), and mitochondrial proline-rich tyrosine kinase 2 (Pyk2), resulting in reduced mitochondrial Ca2+ uptake (MCU) in neuroblastoma cells [59]. A recent extension of this mechanism involves E2F transcription factor 1 (E2F1) and fork-head box protein M1 (FOXM1), which play a major role in cell proliferation, angiogenesis, and DNA damage repair in cancer cells. The expression of FOXM1 is associated with many key transcription factors, including E2F1, HIF-1/2α, CREB, and CREB-binding protein (CBP/p300). Deletion or inhibition of TRPM2 significantly lowers these regulators and decreases the activity of FOXM1. Consequently, it affects the expression of its downstream targets, including cyclin B1, PLK1, CSK1, CDK1, and DNA repair proteins. TRPM2 deletion also reduces protein phosphatase Mg2+/Mn2+-dependent 1D (PPM1D) expression, which promotes p53 and p21 expression that are involved in DNA damage and cell cycle arrest. Decreased activity of CKS1 also contributes to p21 elevation by lowering the ubiquitination; thus, all these together trigger cell cycle arrest at G2/M phase, causing cellular death. Genetic knockdown of TRPM2 has shown significant suppression of tumor growth compared to TRPM2 wild-type (TRPM2-WT) or scrambled control in the SH-SY5Y mouse xenograft model [60]. Additionally, TRPM2 inhibition prevents migration and invasion in neuroblastoma by inhibiting protein kinase B (AKT), extracellular signal-regulated kinase (ERK), FOXM1, E2F1, and Pyk2, and reducing the expression of integrins [61] (Table 1). Collectively, these studies outline a comprehensive mechanistic understanding of TRPM2 in neuroblastoma progression, emphasizing its potential role as a novel therapeutic target in this pediatric cancer.

4.2.
Roles and therapeutic targeting of TRPM2 in lung cancer
Several studies have confirmed the upregulation of TRPM2 in lung adenocarcinoma and squamous cell carcinoma that contributes to cancer cell proliferation, migration, and invasion [62–65]. A bioinformatic analysis on 60 paired lung adenocarcinoma and normal tissues showed TRPM2 to be overexpressed in non-small cell lung cancer (NSCLC) [54]. Recently, a study identified TRPM2 as a biomarker in lung cancer based on IHC staining of lung cancer tissues obtained from 30 lung cancer patients, showing a higher median value of TRPM2 in cancerous cells compared to the noncancerous cells [65]. TRPM2 induces lung cancer cell proliferation by maintaining DNA integrity and promotes metastasis through the regulation of the epithelial-mesenchymal transition (EMT) markers [54,66,67]. In the TRPM2-KO lung cancer models, lower mRNA expression of the EMT markers has been observed with increased cellular apoptosis and suppression of tumor growth in vivo. As mentioned earlier, in the absence of TRPM2, cancer cells become unable to limit ROS production. The elevated oxidative stress in turn activates the c-Jun N-terminal kinase (JNK) signaling pathway that mediates cellular apoptosis in lung cancer. JNK protein is involved in the regulation of DNA damage, cell cycle arrest, apoptotic cell death, and metastasis. Accordingly, on silencing TRPM2, expression of phosphorylated JNK (p-JNK) significantly increases, along with DNA damage marker phospho-Histone H2A.X and G2/M phase marker cyclin B1 in vitro in NSCLC cells. Thus, these findings indicate that TRPM2 inhibition suppresses lung cancer progression and metastasis through activation of the JNK signaling pathway [54, 68–71]. Moreover, recently, a pharmacological inhibitor of TRPM2, D9, has shown efficacy in EGFR mutant NSCLC. It not only triggers cancer cell death but also enhances the susceptibility of the mutant NSCLC cells to the third-generation EGFR-tyrosine kinase inhibitor (EGFR-TKI) osimertinib. In in vivo experimental model, D9 reportedly potentiates the efficacy of osimertinib and significantly suppresses tumor growth, which further corroborates the promising role of TRPM2 inhibition in overcoming acquired resistance to this first-line targeted therapy in NSCLC [67] (Table 1).
4.2.1.
Roles and therapeutic targeting of TRPM2-AS in lung cancer
TRPM2-AS is the long noncoding antisense RNA (lncRNA) of TRPM2. TRPM2-AS stabilizes TRPM2 mRNA by recruiting RNA-binding protein TAF15 rather than directly interacting with TRPM2 mRNA. TAF15 protein interacts with TRPM2 mRNA, thus protecting it from degradation and promoting TRPM2 protein translation [36,72]. TRPM2-AS was first discovered in melanoma, and later, overexpression of TRPM2-AS has been identified as a diagnostic and prognostic biomarker in various cancer types, including lung, gastric, prostate, bladder, ovarian, and esophageal cancers. Additionally, it is marked to be strongly associated with enhanced tumor growth and TNM (Tumor, Nodes, and Metastasis) stage III-IV with poor overall survival in these cancer types [36, 73–80]. TRPM2-AS primarily acts as a competing endogenous RNA (ceRNA) and sponges several tumor suppressive microRNAs (miRNAs) such as miR-138–5p, miR-195, miR-497–5p, and miR-140–3p. Thereby, TRPM2-AS modulates several key oncogenic signaling pathways that ultimately promote cancer cell proliferation, metastasis, and drug resistance [81,82].
TRPM2-AS is highly upregulated in NSCLC cell lines and patient-derived lung cancer tissues compared to adjacent non-tumorous tissues [80,83,84]. TRPM2-AS promotes tumorigenesis in lung cancer by sponging miR-138–5p [80]. MiR-138–5p plays a complex function in suppressing tumor growth, promoting metastasis, and imparting drug resistance by inhibiting oncogenes such as epidermal growth factor receptor (EGFR), plasminogen activator, urokinase (PLAU), and syndecan 3 (SDC3) [74,78,80,85]. In NSCLC, TRPM2-AS directly interacts with miR-138–5p, diminishing its antitumorigenic activity, and thereby, activates the EGFR-mediated phosphatidylinositol 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) signaling pathway. As a result, it promotes the tumor cell survival, migration, and invasion. However, inhibition of TRPM2-AS by short hairpin RNAs showed significant suppression of tumor growth in an in vivo model with lower EGFR and Ki67 expression. Thus, targeting the TRPM2-AS/-miR-138–5p/EGFR axis represents a novel strategy for inducing cell death in NSCLC [80]. SHC-transforming protein 1 (Shc1) is another protein that is expressed in the absence of TRPM2-AS and promotes cancer cell apoptosis by the p53-p66Shc signaling pathway [86]. Downregulation or inhibition of TRPM2-AS promotes apoptosis in NSCLC cells and potentially overcomes cisplatin resistance in cisplatin-resistant A549 (A549/DDP) cells via activation of this pathway [84,86] (Table 1).
Therefore, collectively, these findings suggest that targeting both TRPM2 and TRPM2-AS holds promise for suppressing tumor progression and overcoming resistance to current therapies in lung cancer.

4.3.
Roles and therapeutic targeting of TRPM2 in stomach cancer
Growing evidence suggests that TRPM2 inhibition plays a crucial role in inhibiting stomach cancer progression. It disrupts the autophagic system and mitochondrial function through downregulation of the JNK signaling pathway that impairs cellular adaptation to stress [57,87]. The JNK-mediated autophagy system is involved in the survival of many cancer types, including neuroblastoma, bladder, and gastric cancer. In contrast to lung cancer, where JNK activation triggers apoptotic cell death in the absence of TRPM2, in gastric cancer, JNK downregulation is associated with reduced or dysfunctional autophagy system, diminishing gastric cancer cell survival and proliferation [88–90]. Experimental studies using TRPM2-KO in vitro and in vivo stomach cancer models have shown a significant reduction in autophagy- and mitophagy-related markers, including ATG3, ATG7, ATG12, and BNIP3 [87]. In parallel, TRPM2 depletion suppresses expression of the EMT markers and inhibits phosphatase and tensin homolog (PTEN)/AKT-cell signaling axis, further limiting cancer cell migration and invasion [57]. Moreover, deletion of TRPM2 sensitizes stomach cancer cells to chemotherapeutic treatments such as paclitaxel and doxorubicin, which highlights the potential function of TRPM2 to overcome chemotherapeutic resistance [87] (Table 1).
TRPM2 also supports stomach cancer cell survival by suppressing ferroptosis, a non-apoptotic cell death pathway marked by excessive lipid peroxidation and Fe2+ accumulation. TRPM2 limits ferroptotic stress and promotes cellular adaptation to oxidative damage by regulating two key ferroptosis-associated transcription factors: nuclear factor erythroid 2-related factor 2 (Nrf2) and hypoxia inducible factor-1α (HIF-1α), through intracellular Ca2+ signaling [91–95]. Functional studies demonstrate that silencing TRPM2 significantly enhances the effects of ferroptosis inducers- erastin and RAS-selective lethal 3 (RSL3), leading to reduced antioxidant activity marked by depletion of glutathione (GSH), glutathione peroxidase (GPx), increased intracellular Fe2+ and ROS accumulation, and diminished viability of SGC7901 and MGC803 gastric cancer cells. While these cancer cells are relatively less sensitive to erastin and RSL3, TRPM2 depletion markedly sensitizes these cancer cells to the treatment and triggers ferroptotic cell death. Moreover, TRPM2 knockdown markedly decreases the expression of HIF-1α and Nrf2 proteins, suggesting enhanced proteasomal degradation of these proteins in the absence of TRPM2 during ferroptosis [91] (Table 1).
4.3.1.
Roles and therapeutic targeting of TRPM2-AS in stomach cancer
Bioinformatic analysis of public RNA sequence data obtained from GEO (GSE70880) and TCGA- stomach adenocarcinoma (TCGA-STAD) datasets shows higher expression of TRPM2-AS in stomach cancer tissues relative to normal tissues [77,96]. It is markedly correlated with lymphatic metastasis, advanced TNM stage, and reduced overall survival in patients with stomach cancer [97]. As mentioned earlier in 4.2.1, TRPM2-AS functions by sponging certain tumor suppressive miRNAs and promotes cancer progression. In stomach cancer, TRPM2-AS sponges the functional miRNAs such as miR-195, miR-138–5p, and miR-612 [73,74,77,97]. By sequestering miR-195 and miR-138–5p, TRPM2-AS relieves repression of oncogenic targets such as high-mobility group AT-hook 1 (HMGA1) and plasminogen activator urokinase (PLAU), thereby promoting cancer cell proliferation, migration, and invasion [73,74]. Additionally, TRPM2-AS sponges miR-612 and upregulates its downstream targets, including insulin-like growth factor 2 mRNA-binding protein 1 (IGF2BP1) and FOXM1 [97]. IGF2BP1 is an oncogenic RNA-binding protein that stabilizes cellular myelocytomatosis oncogene (c-Myc) mRNA and promotes cancer cell proliferation, while FOXM1 functions in DNA damage repair and suppression of cellular senescence. Thereby, upregulating these proteins, TRPM2-AS promotes stomach cancer progression and imparts resistance to radiotherapy [97–101]. However, silencing TRPM2-AS has been found to restore the functionality of these miRNAs that eventually block these downstream oncogenic targets and diminish the tumor progression [73,74]. Moreover, TRPM2-AS silencing has been shown to induce enhanced apoptosis in stomach cancer cells by activating p38 mitogen-activated protein kinase (MAPK) and inhibiting signal transducer and activator of transcription 3 (STAT3) pathway [77]. Collectively, this evidence suggests multiple oncogenic signaling axes by which TRPM2-AS regulates stomach cancer progression. Thus, inhibition of TRPM2-AS provides a new direction for serving as a potential therapeutic target in this malignancy (Table 1).

4.4.
Roles and therapeutic targeting of TRPM2 in prostate cancer
TRPM2 elevation has been identified as a prognostic marker for prostate cancer (PCa). Studies show that TRPM2 inhibition suppresses the PCa cell survival and tumor progression both in vitro and in vivo [55,102,103]. Mechanistically, inhibition of TRPM2 induces cell death in PCa by upregulating certain genes involved in the apoptosis and autophagy pathways, including autophagy and BECN1-regulator 1 (AMBRA1), autophagy-related 7 (ATG7), unc-51 like kinase 1/2 (ULK1/2), BCL2-associated X (BAX), Beclin-1 (BECN1), Beclin-1-associated rough-endoplasmic reticulum (ER)-localized protein (BARKOR), lysosomal-associated membrane protein 2 (LAMP2), autophagy related 10 (ATG10), and autophagy related 16 like 1 (ATG16L1) [103]. A recent study has uncovered a novel molecular axis involving TRPM2 and the pro-tumorigenic cytokine interleukin-6 (IL-6). IL-6 directly interacts with TRPM2, promoting cellular adaptation and proliferation through HIF-1α expression, which eliminates excessive ROS generation [102,104,105]. Thus, pharmacological inhibition of IL-6 using tocilizumab significantly downregulates TRPM2 expression along with HIF-1α and impairs PCa cell proliferation and tumor growth in in vivo mouse xenograft model [102]. Additionally, TRPM2 inhibition by 2-APB and siRNA significantly lowers PCa cell migration compared to the control group through Zn2+-dependent actin remodeling. Fluorescent staining of actin filaments demonstrates that TRPM2 depletion markedly suppresses the formation of lamellipodia and filopodia, cytoskeletal structures essential for directed cell migration in PC3 and DU145 PCa cell lines [106] (Table 1).
4.4.1.
Roles and therapeutic targeting of TRPM2-AS in prostate cancer
In addition to TRPM2, TRPM2-AS overexpression is found to be associated with PCa cell survival and poor therapeutic outcome [107–109]. Microarray analysis reveals that TRPM2-AS is involved in regulating the expression of several cell-cycle and survival genes, such as aurora kinase A (AURKA), E2F transcription factor 2 (E2F2), cell division cycle 20 (CDC20), baculoviral IAP repeat containing 5 (BIRC5), as well as several stress-responsive and inflammatory genes [108,110]. Additionally, TRPM2-AS contributes to prostate tumor progression by sponging miR-497–5p and inducing the expression of oncogenic transcription factor Forkhead Box K1 (FOXK1). Thereby, silencing TRPM2-AS using siRNA elevates miR-497–5p levels, suppresses FOXK1 expression, and induces apoptosis in PCa cells [109,111]. Moreover, TRPM2-AS inhibition sensitizes paclitaxel-resistant PC3 (PC3/PR) and DU145 (DU145/PR) PCa cells to paclitaxel in vitro via this pathway and significantly suppresses tumor growth in paclitaxel-resistant PCa xenograft model in vivo. Thus, targeting the TRPM2-AS/miR-497–5p/FOXK1 axis may represent a novel therapeutic approach to counteract prostate cancer prognosis and improve treatment outcome [108,109,111] (Table 1).

4.5.
Roles and therapeutic targeting of TRPM2 in pancreatic cancer
Clinical data analysis has revealed a significant negative correlation of TRPM2-overexpression with progression-free survival rate in patients with pancreatic ductal adenocarcinoma (PDAC) [56]. Functional studies demonstrate that TRPM2-overexpression promotes pancreatic cancer cell proliferation and migration in both in vitro and in vivo models [56,112]. Analyses of human and murine PDAC tissues reveal that TRPM2 promotes tumor progression predominantly through activation of protein kinase C (PKC)/MAPK signaling cascade. Aberrant activation of PKC and MAPK pathways is a well-established regulator of tumorigenesis across multiple malignancies, including prostate, breast, lung, melanoma, colorectal, and pancreatic cancers [113–116]. At the molecular level, TRPM2-mediated Ca2+ influx cooperates with diacylglycerol (DAG) to activate PKC, which subsequently stimulates downstream MAPK signaling and supports pancreatic tumor progression. Experimentally, inhibition of the PKC significantly increases cell death in TRPM2-overexpressed Bx-PC3 cells, providing functional evidence that the PKC/MAPK axis is a critical pathway through which TRPM2 supports pancreatic cancer cell viability [56,112]. Additionally, gene expression analysis reported several well-established oncogenes, including toll-like receptor-7 (TLR7), SCM-like with four MBT domains protein 2 (SFMBT2), γ-parvin (PARVG), and phospholipid-transporting ATPase IM (ATP8B4) that may be modulated by TRPM2 and contribute to tumor progression [56,117,118] (Table 1). Although mechanistic studies of TRPM2 in prostate cancer remain limited, this growing evidence underscores the promising function of inhibition of TRPM2 in suppressing pancreatic tumor progression, highlighting the need for further investigation to corroborate its therapeutic role.
Beyond the role of TRPM2 in cancer cell intrinsic pathways, TRPM2 is reported to be associated with the remodeling of the tumor microenvironment (TME) in a manner that favors tumor growth. TRPM2-regulated Ca2+ signaling promotes the recruitment of immunosuppressive immune populations such as regulatory T cells, and polarization of pro-tumorigenic M2 macrophages, thereby facilitating immune evasion, angiogenesis, and metastatic potential [119]. However, in contrast, TRPM2 also regulates neutrophil chemoattraction by inducing the expression of C-X-C motif chemokine 2 (CXCL2) in tumor cells, while cancer cells with low TRPM2 expression resist the neutrophil-mediated cytotoxicity [120]. Therefore, an in-depth investigation is required to understand how TRPM2 regulates TME supporting tumor progression.

5.
TRPM2 as a potential therapeutic target for neurological disorders
The TRPM2 channel is abundantly present in the central nervous system, including hippocampal and cortical neurons, the substantia nigra, as well as microglia and astrocytes. Aberrant activation of TRPM2 in response to oxidative stress has been strongly implicated in the pathogenesis of many neurological diseases, such as Alzheimer’s disease (AD), Parkinson’s disease (PD), and epilepsy. TRPM2-mediated sustained elevation of intracellular Ca2+ level is primarily involved in neurotoxicity and neuronal death in these pathologic conditions. Moreover, excessive Ca2+ influx through TRPM2 activates the glial cells (microglia and astrocytes), triggering neuroinflammatory responses that further exacerbate disease progression, as demonstrated in various preclinical models of AD, PD, and epilepsy [121–123].
5.1.
Roles and therapeutic targeting of TRPM2 in Alzheimer’s disease
Abnormal accumulation of amyloid-beta (Aβ) plaque in the brain is a hallmark of AD [124]. In AD, Aβ reportedly induces neurotoxicity, neuroinflammation, neurovascular dysfunction, and neuronal death through the activation of the TRPM2 ion channel [15,47,122,124,125]. In neurons, Aβ activates protein kinase C (PKC), NADPH-dependent oxidases (NOX), and triggers the ROS generation. It stimulates the mitogen-activated protein kinase (MEK)/extracellular signal-regulated kinase (ERK) signaling pathway that induces PARP/ADPR-mediated TRPM2 activation. TRPM2 activation in lysosomes dysregulates its activity, causing excessive lysosomal Zn2+ release, which accumulates in mitochondria. Zn2+ targets complex III of the electron transport chain (ETC) in the mitochondria, releasing electrons and thereby facilitating superoxide formation. Consequently, mitochondrial function becomes disrupted, and cytochrome C (cyt C) is released, triggering the mitochondrial apoptotic pathway and elevating the ROS production. These events altogether ultimately result in neuronal death and progression of AD pathogenesis [122,125,126]. TRPM2 also mediates Aβ-triggered neuroinflammation, activating the glial cells. In glial cells, excessive Ca2+ influx by TRPM2 induces inflammatory signals like p38, ERK, c-JNK, and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) that trigger the release of pro-inflammatory cytokines, TNF-α, and IL-6, and initiate inflammation. Simultaneously, elevated Ca2+ level activates NLRP3-mediated caspase-1 activation and expression of IL-1β. In addition, Ca2+ activates Pyk2, which forms a positive loop by stimulating the MEK/ERK pathway and further inducing PARP/ADPR-mediated TRPM2 activation [15,127,128]. Altogether, this results in decreasing the phagocytosis efficiency of microglial cells to eliminate the Aβ plaque and contributes to the progression of AD [129,130]. Additionally, TRPM2 activation plays a key role in Aβ-induced disruption of cerebrovascular homeostasis. Aβ triggers the production of superoxide in the endothelial cells that generate peroxynitrite by reacting with nitric oxide (NO). This damages the DNA and stimulates PARP/ADPR-mediated TRPM2 activation. Sequentially, TRPM2 elevates Ca2+ influx that disrupts the endothelial cells’ barrier function and permeability, leading to neurovascular dysfunction. Consequently, it impairs the blood supply to the brain and further aids the accumulation of Aβ [131–133]. Functional experiments have shown that genetic knockout of TRPM2 and inhibition by TRPM2-S overexpression or pharmacological inhibitors (N-(p-amyl cinnamoyl) anthranilic acid (ACA), 2-APB prevent Aβ-induced neuronal toxicity and cell death in primary striatal and hippocampal (HPC) neurons [125] (Fig. 4).

5.2.
Roles and therapeutic targeting of TRPM2 in Parkinson’s disease
TRPM2 is responsible for oxidative stress-triggered dopaminergic (DA) neuronal cell death and contributes to the pathogenesis of Parkinson’s disease (PD). TRPM2 is found to be overexpressed in the substantia nigra pars compacta (SNpc) in MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) neurotoxin-induced PD mouse models and postmortem brain tissues of PD patients. Mechanistically, in in vivo PD models, MPTP converts into MPP+ that crosses the blood-brain barrier (BBB) and activates TRPM2 in the DA neurons. It also stimulates NADPH oxidase 2 (NOX2) to generate ROS, forming a positive loop for activation of the channel. TRPM2-mediated elevated cytosolic Ca2+ influx triggers Zn2+-mediated overproduction of mitochondrial ROS. In parallel, Ca2+ overload suppresses AKT activation (phosphorylated AKT), thereby relieving inhibition of glycogen synthase kinase-3 beta (GSK-3β). As a result, GSK-3β induces the caspase 3 (Cas-3) apoptotic signaling pathway. Consequently, the mitochondrial and cellular dysfunctions downregulate the anti-apoptotic proteins and suppress antioxidant activity, ultimately triggering DA neuronal death. In MPTP induced PD model, the expression of Cas-3 along with the pro-apoptotic proteins such as Bcl-2 homologous antagonist/killer (BAK), BH3-interacting domain death agonist (Bid), and Bcl-2-like protein 4 (Bad) and mitochondrial cyt-C significantly increases that is reversed by TRPM2 inhibition by flufenamic acid (FFA), or siRNA indicating the role of TRPM2 in mediating DA neuronal damage [121,134,135]. Following DA neuronal loss, the elevated oxidative stress further stimulates TRPM2 activation in glial cells. TRPM2-regulated intracellular Ca2+ signals the release of pro-inflammatory cytokines (TNF-α, IL-6, IL-1β) and activates NLRP3 inflammasome, in a similar manner as observed in AD, which eventually stimulates the glial cells activation and neuroinflammation in PD [121,130]. However, genetic knockdown and pharmacological inhibition of TRPM2 by 2-APB or AG490 have demonstrated neuroprotective function in both in vitro and in vivo PD models [121,134,136]. Functional experiments have shown that in the absence of TRPM2, MPP+ is unable to trigger the mitochondrial intrinsic apoptotic pathway in neurons and microglia-mediated neuroinflammation in TRPM2-KO mice. Whereas in the TRPM2-wild type (TRPM2-WT) PD model, expression of pro-inflammatory cytokines, including TNF-α, IL-6, IL-β and intracellular Ca2+ and Zn2+ levels are significantly elevated [134,135]. Consistent with these findings, in the 6-hydroxydopamine (6-OHDA) PD mouse model, both partial or complete genetic deletion of TRPM2 significantly lowers microglial accumulation, and normalizes microglial morphology, decreases CD68 expression and pro-inflammatory cytokine production, as well as reduces DA loss, motor impairment, and improves overall neuronal survival irrespective of sex [130,137]. Pharmacological inhibition further supports this protective role, as intervention with the tyrphostin compound- AG490 downregulates TRPM2 expression in SNpc and caudate/putamen (CPu), lowers GFAP protein expression (astroglia activation indicator), and reverses the altered microglial morphology, indicating the promising function of the channel inhibition in developing a therapeutic strategy in PD [136] (Fig. 4).

5.3.
Roles and therapeutic targeting of TRPM2 in epilepsy
Epilepsy is characterized by recurrent seizures that promote excessive oxidative stress in the brain, leading to neuronal damage and neuroinflammation [138]. TRPM2, as a redox-sensitive channel, plays a critical role in mediating epileptic pathogenesis. TRPM2 has been observed to be overexpressed in the pentylenetetrazol (PTZ)- and pilocarpine-induced temporal lobe epileptic mouse model [123,139]. In epilepsy, oxidative stress induces PARP/ADPR-mediated TRPM2 activation, allowing sustained Ca2+ influx in cortical and HPC neurons. It stimulates the downstream BNIP3/apoptosis-inducing factor (AIF)/endonuclease G (Endo G) signaling cascade that damages nuclear DNA and activates caspase-independent apoptosis. Additionally, TRPM2 activation disrupts mitochondrial functionality, inducing autophagy and triggering apoptotic neuronal cell death [139]. Functional studies demonstrate that genetic deletion of TRPM2 diminishes neuronal apoptosis, suppresses excessive autophagy, and alleviates epilepsy induced pathological damage in in vivo epileptic models. Additionally, TRPM2-deletion lowers the neuroinflammation marked by significant downregulation of the neuroinflammatory cytokines, including IL-6, IL-1β, CXCL2, TNF-α, NLRP3, the adapter protein ASC of the NLRP3 inflammasome complex, and caspase-1 in microglia, as observed in AD and PD in vivo mouse models [123,139]. A recent study demonstrated that microglial TRPM2-KO ameliorates neuroinflammation and diminishes microglia activation through upregulation of AMPK/mTOR–dependent autophagy system, which is essential for the removal of damaged organelles and for promoting the transition of glial cells toward a non-inflammatory, homeostatic state [140–142]. Additionally, TRPM2-KO has been observed to attenuate reactive astrogliosis in the HPC CA1 region by inhibiting the TRPM2/PKC/NF-κβ cascade and to increase the epilepsy threshold [143] (Fig. 4). Further in vivo studies have observed that deletion of TRPM2 significantly suppresses neuronal hyperexcitability in epileptic mice and improves impaired cognitive function compared to the TRPM2-WT group [123]. Additionally, whole cell patch clamping in PTZ-induced SH-SY5Y cells shows that valproic acid (VA), a widely used epileptic drug, significantly reduces ADPR-activated TRPM2-mediated Ca2+ current compared to control groups (PTZ + ADPR and PTZ + ADPR + ACA). Moreover, VA co-stimulated with ADPR markedly drops the Ca2+ current to the level of the ADPR + ACA group, further confirming the effect of the drug in suppressing TRPM2 activity [144].
Collectively, evidence across Alzheimer’s disease, Parkinson’s disease, and epilepsy identifies TRPM2 as an oxidative stress-responsive mediator of neuronal injury and neuroinflammation, positioning its inhibition as a promising disease-modifying therapeutic strategy in neurological disorders.

6.
TRPM2- as a potential therapeutic target for ischemia/reperfusion (I/R) injury
Ischemia/reperfusion (I/R) injury is a major pathological event associated with stroke, myocardial infarction, hepatic failure, and renal damage, where oxidative stress and Ca2+ overload drive extensive tissue injury. TRPM2 acts as a key mediator by connecting ischemia-induced excessive ROS generation and elevated intracellular Ca2+ influx that exacerbates the cellular injuries and organ dysfunctions during I/R [145–148].
Several studies have demonstrated TRPM2 as a critical regulator in causing delayed neuronal cell death in ischemia/reperfusion (I/R) in the brain. Mechanistically, TRPM2 mediates neuronal cell death by inhibiting the N-methyl-D-aspartate (NMDA) receptor’s pro-survival pathway and activating the NMDA receptor’s pro-death pathway. In I/R, TRPM2 expression stimulates the transport of GluN2B, a subunit of the NMDA receptor, to the cell surface by postsynaptic density protein 95 (PSD-95). It promotes the extrasynaptic Ca2+ influx and prevents the activation of pro-survival signaling molecules such as ERK1/2 and AKT. On the other hand, TRPM2 expression inhibits GluN2A, another NMDA receptor subunit that typically plays a neuroprotective role. Inhibition of GluN2A results in a reduction of synaptic Ca2+ influx and inhibition of downstream MAPK and PI3K survival pathways that ultimately activate pro-apoptotic GSK3β and cause neuronal death [149,150] (Table 2). Recently, a study reported that protein kinase C gamma (PKCγ) binds to the M2PBM binding motif of TRPM2, which further potentiates the extrasynaptic NMDAR (esNMDAR) excitation and Ca2+ overload, thereby aggravating the effect. However, deletion of the M2PBM motif of TRPM2 or intervention with interfering peptides TAT-EE3 and TAT-M2PBM attenuates I/R brain injury both in vitro and in vivo by inhibiting the interaction of esNMDAR and PKCγ with TRPM2 [151, 152]. Recent findings demonstrate that TRPM2 elevates postsynaptic GABAA receptors clustering, enhancing GABAergic inhibition in postsynaptic inhibitory synapses through activation of the Ca2+/CaMKII pathway. This excessive inhibitory signaling suppresses HPC long-term potentiation (LTP) and contributes to cognitive impairment in global cerebral ischemia (GCI) following cardiac arrest (CA) [153] (Table 2). In addition, astroglial CD38, which upregulates following ischemia, contributes to this effect by stimulating TRPM2 activation in the HPC CA1 pyramidal neurons [154]. However, intervention with pharmacological inhibitors of TRPM2, such as tat-M2NX (peptide molecule), A23, ACA, 2-APB, FFA, clotrimazole (CTZ), as well as genetic knockdown of TRPM2 with shRNA, significantly reduces cortical and HPC neuronal death, preserves HPC synaptic plasticity, and diminishes the incidence of I/R injury in the brain [153,155]. Additionally, intervention with pharmacological inhibitors of TRPM2, such as ACA, 2-APB, FFA, CTZ, A23, and tat-M2NX, as well as genetic knockdown of TRPM2 with shRNA, significantly reduces cortical and HPC neuronal death and diminishes the incidence of I/R injury [155]I. Interestingly, the protective role of TRPM2 inhibition is reported to be sex-specific in I/R models, including oxygen-glucose deprivation followed by reoxygenation (OGD/R) and middle cerebral artery occlusion-reperfusion (MCAO-R). TRPM2 inhibition preferentially prevents neuronal death and reduces cerebral infarct volume in male mice compared to females [145,155]. Supporting this, a recent finding also demonstrates less brain injury in male mice relative to female mice in the TRPM2-KO traumatic brain injury (TBI) model. Additionally, TRPM2 inhibition with tat-M2NX recovers HPC plasticity and prevents memory impairment in TBI-induced mice, even 30 days after the trauma recovery [156]. Thus, TRPM2 inhibition exhibits a protective function in brain injuries and memory impairment, but its role in sexual dimorphism is still poorly understood and needs further investigation.
TRPM2 inhibition confers a hepatoprotective role during ischemia/reperfusion injury by activating autophagy, mitophagy, and down-regulating the ferroptosis pathway. Functional studies demonstrate that genetic deletion or pharmacological inhibition of TRPM2 by a selective TRPM2 antagonist, A10, significantly ameliorates liver damage post-ischemia, as evidenced by reduced neutrophil infiltration and lower serum levels of alanine aminotransferase (ALT) and aspartate amino-transferase (AST) in the hepatic I/R model [157]. Unlike in epilepsy, where excessive autophagy contributes to neuronal loss and deletion of TRPM2 reduces autophagy-related neuronal death, in I/R, depletion of TRPM2 enhances autophagic flux and exerts a protective role [139,157]. In the absence of TRPM2, expression of autophagy-related markers, including microtubule-associated protein 1A/1B light chain 3 (LC3-II) and autophagic substrate p62, are upregulated. Concurrently, mTOR, a known autophagy inhibitor, and components of the NLRP3 inflammasome pathway, including NLRP3, interleukin-1β (IL-1β), and caspase-1, are downregulated [157]. Additionally, TRPM2 depletion suppresses mitochondrial lipid peroxidation during ferroptosis, as marked by lower levels of arachidonate lipoxygenase 12 (ALOX12) and the key oxidative stress marker 4-hydroxy-2-nonenal (4-HNE) [158]. Consequently, it prevents excessive ROS generation and pro-inflammatory cytokines release, protecting hepatocytes from inflammation and hepatocellular death in I/R [157,158] (Table 2). This is further corroborated by recent findings that TRPM2-depletion protects the chicken hepatocytes and murine pulmonary endothelial cells from cadmium (Cd)- and H9N2 influenza virus-induced ferroptosis in a similar mechanism [159,160].
In the context of renal I/R, experiments in chimeric mice with TRPM2-KO in parenchymal cells revealed that the presence of TRPM2 in kidney parenchymal cells is primarily responsible for renal I/R injury. TRPM2 induces Ras-related C3 neurotoxin 1 (RAC1), a key NADPH oxidase regulator that forms a positive feedback loop further stimulating TRPM2 expression. As a result, it diminishes antioxidant activity, elevates the oxidative stress, and eventually triggers the mitochondrial apoptotic pathway, which exacerbates renal I/R damage [146]. However, functional analysis shows that inhibition of TRPM2 with 2-APB and ACA markedly attenuates glomerular and tubular damage and lowers the level of renal dysfunction biomarkers, including blood urea nitrogen (BUN), cystatin C (CysC), neutrophil gelatinase-associated lipocalin (NGAL), creatinine, kidney injury molecule-1 (KIM-1), and IL-18 in in vivo renal I/R model [146,161,162] (Table 2). Moreover, pharmacological inhibition of TRPM2 by 2-APB in combination with selenium significantly lowers Cd-induced renal tissue damage, depicting the potential therapeutic role of the channel’s inhibition in alleviating nephrotoxicity [163].
Cardiac I/R occurs as the secondary effect of myocardial infarction (MI) on reperfusion of blood after cardiac ischemia, followed by excessive oxidative stress, Ca2+ overload, and release of inflammatory cytokines [164]. TNF-α, a major pro-inflammatory cytokine, stimulates PARP/ADPR-mediated TRPM2 activation and elevates the intracellular Ca2+ level. It disrupts the mitochondrial function, induces mitochondrial membrane depolarization, and activates caspase-8, ultimately resulting in elevated oxidative stress and cardiomyocyte death. Thereby, inhibition of TRPM2 by CTZ, ACA, and FFA shows a significant reduction in the TNF-α-induced TRPM2 currents and Ca2+ level in the ventricular myocytes of adult mice [46]. In the left coronary artery (LCA) ligation I/R model, genetic deletion or pharmacological inhibition of TRPM2 by econazole markedly reduces myocardial infarct volume and improves cardiac contractility. Additionally, immunostaining results show significantly lower neutrophil infiltration in the reperfused area of TRPM2-KO myocardium compared to the WT, which further confirms the attenuation of cardiac I/R injury by TRPM2 inhibition [165] (Table 2).
Collectively, these findings underscore the emerging role of TRPM2 inhibition as a therapeutic target in I/R injury of multiple organs. Notably, in cerebral I/R models, TRPM2 inhibition demonstrates sex-specific effects, with male mice showing greater susceptibility to I/R injury but also a more significant neuroprotective response to TRPM2 blockade than female mice. In contrast, such sexual dimorphism is not observed in Parkinson’s disease models, and therefore, the role of TRPM2 in gender specific outcomes needs further investigation [130, 137,145,155,166]. In neurological disorders and I/R injury, TRPM2 has been implicated in the activation of the NLRP3 inflammasome, which is also a central mediator of the pyroptotic cell death program [157, 167–169]. This association suggests that TRPM2-mediated Ca2+ signaling promotes inflammasome-dependent pyroptotic signaling. Consistent with this, correlations between TRPM2 expression and pyroptosis-related genes have also been reported in ovarian cancer [119]. In summary, TRPM2 regulates several cell death pathways, including apoptosis, ferroptosis, and pyroptosis, causing tissue injury in multiple organs under pathological conditions. Therefore, inhibition of TRPM2 represents a promising therapeutic strategy for these diseases.

7.
Agents inhibiting TRPM2 functionality
Recognizing the therapeutic potential of TRPM2 inhibition, research efforts have been undertaken since the early 2000s to identify TRPM2 inhibitors. These efforts have resulted in the discovery of several chemical and peptide agents with demonstrable TRPM2 inhibitory activity. Whereas early TRPM2 inhibitors exhibited limited potency and selectivity for TRPM2 channels, more recently developed agents demonstrate improved selectivity profiles and efficacy in in vivo ischemic stroke model, although none has advanced to clinical trials yet. These agents can be broadly classified into three categories: a. ADPR analogues, b. Small molecules and c. Peptides (Fig. 5).
ADPR analogues:
ADPR is a naturally occurring metabolite derived from NAD+ and serves as an important second messenger in multiple cellular processes. In the context of TRPM2 signaling, as mentioned in 2, ADPR activates the channel by binding to two separate intracellular ADPR-sensing regions, i.e. the N-terminal MHR1/2 domain and C-terminal NUDT9-H domain [27].
In efforts to identify ADPR analogues capable of blocking ADPR-dependent TRPM2 signaling, Partida-Sánchez et al. (2007) developed 8-bromo-ADPR, a modified ADPR analogue with a bromine atom introduced at the C8 position of the adenine. This compound exhibited clear antagonistic activity against ADPR-induced TRPM2 activation in Jurkat T cells, resulting in a marked suppression of Ca2+ influx [170]. Recent cryo-EM structures further elucidate the molecular basis of this inhibition, demonstrating that 8-bromo-ADPR binds to both the N-terminal MHR1/2 domain and the C-terminal NUDT9-H domain (PDB ID: 8E6T) in a binding pose closely resembling that of native ADPR (PDB ID: 8E6Q) (Fig. 6). Together, these findings provide compelling structural and functional evidence that chemical modification of the ADPR scaffold can preserve high-affinity engagement with TRPM2 while selectively preventing channel opening, establishing 8-bromo-ADPR as a prototypical orthosteric antagonist and a valuable lead for the mechanistic studies for TRPM2 inhibition by ADPR-analogues.
Building on these findings, in 2013, Moreau et al. performed an extensive Structure-Activity Relationship (SAR) study on the ADPR scaffold for TRPM2 inhibition by making systematic structural modifications to adenine, adenosine ribose, pyrophosphate linker, and terminal ribose of ADPR. This work identified 8-Phenyl-2’-deoxy-ADPR, as a potent TRPM2 antagonist with a half-maximal inhibitor concentration (IC50) of 3 μM, reinforcing the notion that steric interference at the adenine binding pocket can decouple the ligand binding from TRPM2 activation [171]. This also suggests the potential modifiability of the adenosine ribose.
Further scaffold optimization efforts focusing on masking of hydroxyl groups of adenosine and/or terminal ribose with ethers, changing the bridge oxygen of the pyrophosphate group to methylene or difluoromethylene, and optional introduction of chlorine to the 8th position of adenosine of ADPR or 2’-deoxy-ADPR yielded two potent ADPR analogues, i.e., 7i and 8a, that selectively inhibit TRPM2 with IC50 values of 5.7 μM and 5.4 μM [172]. The SAR studies were extended to explore the role of the terminal ribose of ADPR, revealing that the terminal ribose is critical for the activation of TRPM2 by ADPR, and at high concentrations, α−1”-O-methyl-ADPR and THF-ADP can act as competitive antagonists for ADPR-induced TRPM2 activation [173]. Additional optimizations focusing on the removal or the masking of hydroxyl groups on the terminal ribose of ADPR or 2’-deoxy-ADPR also yielded several TRPM2 inhibitors, but their antagonistic effects are weaker than 8-bromo-ADPR and 8-Phenyl-2’-deoxy-ADPR [174].
Although some ADPR-based TRPM2 inhibitors demonstrate potent antagonistic activity and functional selectivity towards TRPM2 over other TRP channels, the ubiquitous involvement of ADPR in NAD+-dependent signaling necessitates further investigations into the specificity and selectivity of these agents. Furthermore, ADPR analogues are highly polar and often negatively charged at physiological pH, limiting their membrane permeability, and so these agents are only effective at TRPM2 inhibition when administered intracellularly. On the other hand, the inherent rapid metabolism of ADPR raises concerns about the metabolic stability of the ADPR-analogues, which are often addressed with the replacement of the phosphate-oxygen-phosphate linkage with the phosphate-carbon-phosphate linkage. In summary, the ADPR-analogues are promising mechanistic tools for the investigation of TRPM2 inhibition, but the challenges associated with their pharmacokinetic (PK) properties often make them unattractive from a translational point of view.
Small molecules:
A wide range of small-molecule inhibitors has been reported to suppress TRPM2-mediated Ca2+ influx, spanning chemically diverse classes such as anthranilic acid–based fenamates, boron-containing modulators, azole antifungals, and natural products. While most of the early TRPM2 inhibitors were identified as functional tool compounds, they often have limited selectivity and specificity for TRPM2, show off-target effects on intracellular Ca2+ homeostasis, or have suboptimal pharmacokinetic properties. More recent SAR-driven and high-throughput screening efforts have yielded mechanistically distinct and more selective TRPM2 inhibitors, including extracellular pore-loop binders with nanomolar potency, that demonstrate in vivo efficacy in ischemic stroke models.
Fenamates are anthranilic acid derivatives that are structurally related to N-(p-amylcinnamoyl) anthranilic acid (ACA), a compound known to have phospholipase A2 (PLA2) inhibitory properties. In 2006, Kraft et al. demonstrated that 20 μM of ACA completely inhibits the ADPR-induced whole cell current in hTRPM2-transfected HEK293 cells in a concentration-dependent manner, with an IC50 value of 1.7 μM. This inhibition is voltage independent and kinetically potentiated at acidic pH conditions. Furthermore, the inhibition is not observed when ACA is administered intracellularly, suggesting that it binds to the extracellular domain of TRPM2. ACA also demonstrates inhibition of other TRP channels, including TRPM8 and TRPC6 [175]. ACA has also been reported to reduce brain infarct at 25 mg/kg dose in the tMCAO model of stroke in mice. This effect is attributed to TRPM2 inhibition by ACA, as no such reduction of infarct size is observed in TRPM2-KO mice [176]. Flufenamic acid (FFA) is another widely studied fenamate that has been shown to inhibit the TRPM2 channel at concentrations ranging from 50 μM to 1 mM with pH-dependent kinetics [177]. The IC50 of FFA for hTRPM2-transfected HEK293 has been determined to be 70 μM. Although FFA shows a prominent TRPM2 inhibition at higher concentrations, the effect is non-specific, and this causes a significant intracellular calcium ion leakage, mainly through mitochondrial Ca2+ release. SAR studies with several FFA derivatives revealed that the nature and the position of substituents are important for the activity as well as the selectivity for TRPM2 inhibition, leading to the discovery of 3-Mefenamic acid (3-MFA), which has similar potency (IC50 76 μM) as FFA for TRPM2 inhibition with better selectivity for TRPM2 inhibition [178]. A recent study by Zhang et al. in 2021 explored the SAR for ACA analogues for their TRPM2 inhibition properties. Their work revealed that the replacement of the n-pentyl group of ACA with a substituted phenyl ring can lead to improvement in potencies, leading to the discovery of A23, an anthranilic acid derivative with good pharmacokinetic properties (in vivo half-life of 1.7 h following intravenous administration and clearance of 52.9 mL/hr/kg), and has selectivity for TRPM2 (IC50: 788 nM), over TRPM8 and TRPV1 (IC50s: >10 μM). This compound also shows significantly less PLA2 inhibition (IC50: >10 μM) compared to ACA itself, despite having the same anthranilic acid core structure. A23 also demonstrates significant protective action in SH-SY5Y (human neuroblastoma) cells against OGD/R injury in vitro, and this protective activity was also translated in vivo at a dose as low as 0.3 mg/kg in tMCAO stroke model [179].
While ADPR is among the primary activators of the TRPM2 channel, one of its metabolites i.e., adenosine monophosphate (AMP), acts as an inhibitor of TRPM2 with an IC50 of 70 μM, essentially forming a negative feedback loop [180]. Despite this inhibitory effect, structural analogues of AMP cannot be developed as drug molecules because of their hydrophilic and ionic nature. To overcome this hurdle, Zhang et al. performed a 3D similarity-based virtual screening to identify hits that have structural and electronic similarities with AMP and can be developed into pharmacologically relevant molecules. The virtual screening yielded H1, a hit compound that showed a significant reduction in H2O2-induced calcium fluorescence increase in hTRPM2-overexpressed HEK293 cells. This hit did not show any inhibition when administered intracellularly, implying binding to the extracellular domain of the channel. SAR studies on the H1 scaffold demonstrated that the 6- and 8-positions of the dihydroquinazolinone core, as well as the phenyl ring, are amenable to modification. These optimizations led to the synthesis and biological evaluation of compounds A1, A10, D1, and D9, which exhibit TRPM2 inhibition with single-digit micromolar potencies. Moreover, inhibition by D9 (IC50: 3.7 μM) was selective towards TRPM2 channels over TRPM8, laying the foundation for the development of this scaffold for selective TRPM2 inhibition [181]. In 2024, Chen et al. demonstrated that TRPM2 expression and activity are associated with resistance to tyrosine kinase inhibitors (TKIs) and showed that D9 synergizes with Osimertinib, improving its efficacy and delaying acquired resistance to it in lung cancer. The combination of D9 and Osimertinib also significantly reduced tumor size in EGFR-mutant NSCLC [67].
In 2019, Fourgeaud et al. screened the entire chemical library available at Janssen R&D with the FLIPR (Fluorescence Imaging Plate Reader) assay for their TRPM2 inhibitory property and reported the discovery of JNJ-28583113 as a potent TRPM2 inhibitor. This compound has been reported to be active in inhibiting chimpanzee, rat, and human TRPM2 proteins with IC50 values of 100 nM, 25 nM, and 126 nM, respectively. This work also validated that the compound does not induce changes in calcium current by inhibiting the PARP or PARG enzymes, indicating direct action on the TRPM2 channel. The TRPM2 inhibitory action of JNJ-28583113 was further corroborated with whole cell patch-clamp studies on hTRPM2 overexpressing HEK293 cells, where it was applied extracellularly. The activity of this compound was also screened against a panel of known kinases, GPCRs, and ion channels, and in these screening studies, JNJ-28583113 did not demonstrate any significant activity against any of these proteins. Next, the selectivity of JNJ-28583113 was evaluated by investigating its activity against other TRP channels. Interestingly, this compound does not exhibit significant agonistic or antagonistic activity against other TRP channels, except for TRPM5, for which it has a sub-micromolar IC50. The pharmacokinetic profiling of JNJ-28583113 indicated that this compound shows significant blood-brain-barrier permeation but is unstable in plasma, possibly due to degradation by plasma esterases. Overall, JNJ-28583113 shows low nanomolar potency for TRPM2 inhibition and a good distribution into the brain tissue, but its poor metabolic stability obstructs the in vivo studies with this compound [182].
In a recent study, Lu et al. identified a novel class of extracellular TRPM2 inhibitors through screening of a proprietary nitrogen-containing heterocyclic compound library using fluorescent Ca2+ imaging in doxycycline-inducible TRPM2-overexpressing HEK-293T cells. From this screen, compound A1 emerged as a potent inhibitor that markedly reduced H2O2-induced cytosolic Ca2+ elevation, an effect subsequently confirmed by whole-cell patch-clamp electrophysiology, where extracellular application of A1 almost completely abolished TRPM2 currents at 30 μM (IC50 = 3.28 μM). Importantly, A1 displayed high selectivity, showing no significant inhibition of closely related TRP channels (TRPM8, TRPV1, TRPV4, TRPC6) or other excitatory ion channels (NMDAR and ASIC1a) at the same concentration. Site-directed mutagenesis studies revealed that Glu994, His995, Glu1010, and Glu1022 residues are critical for the activity of compound A1. It is important to note that all these residues are located on the extracellular “pore loop domain” of TRPM2, providing strong evidence for an extracellular binding mode distinct from the canonical intracellular ADPR-sensing mechanism of TRPM2. It also has an acceptable in vivo half-life of 1.81 h when administered at 8 mg/kg dose via intravenous (IV) route in SD rats. Subsequent scaffold optimization yielded several active analogues, among which D10 demonstrated enhanced TRPM2 inhibition (IC50 = 2.29 μM), neuroprotective efficacy, and favorable pharmacokinetics (in vivo t1/2: 0.86 h at 1 mg/kg IV dosing, and 2.62 h at 20 mg/kg intragastric dosing), including oral bioavailability (~50 %). In vivo efficacy studies with D10 in tMCAO model of stroke in mice show a significant reduction in infarct volume and improvement in neurological scores at 1 mg/kg and 3 mg/kg doses [183]. Despite the favorable PK properties and in vivo efficacy, later studies revealed that D10 inhibited the human ether-à-go-go-related gene (hERG) potassium channel with an IC50 of 1.75 μM, raising concerns about the potential cardiotoxicity of this compound. To mitigate this liability, a more hydrophilic analogue, D14, was selected for further optimization, leading to the development of LC4, an adamantyl-based TRPM2 inhibitor with substantially improved potency (IC50 = 660 nM), enhanced selectivity (TRPM8, TRPV1 IC50s > 10 μM), reduced hERG liability (hERG IC50: 21.61 μM for LC4 vs 1.75 μM for D10), and a 3.2-fold improvement in in vivo half-life. Although LC4 displays diminished oral bioavailability, it retained robust in vivo efficacy, significantly reducing infarct volume and improving neurological outcomes in the tMCAO model when administered intravenously after reperfusion at 1 mg/kg and 3 mg/kg. Collectively, these studies establish LC4 as a potent, selective, and mechanistically distinct extracellular TRPM2 inhibitor with improved safety and pharmacokinetic properties, positioning it as a compelling preclinical candidate for ischemic stroke intervention [184].
2-Aminoethoxydiphenyl borate (2-APB) is an inositol 1,4, 5-triphosphate (InsP3) antagonist that has also shown inhibition of TRPC3, TRPC5, TRPC6, TRPC7, TRPM7 and TRPM8 [185–188]. On the other hand, 2-APB activates several TRPV channels, including TRPV1, TRPV2, and TRPV3 [189]. In 2008, Togashi et al. reported that 2-APB also inhibits ADPR and/or heat-activated TRPM2 current with an IC50 value of about 1 μM [190]. In 2021, Zhao et al. utilized three-dimensional molecular shape and electrostatic potential similarity–based virtual screening based on the 2-APB scaffold, and identified Z-4 as a virtual screening hit compound. Whole-cell patch-clamping studies validated TRPM2 inhibition by Z-4, further optimization of which yielded compounds ZA10 and ZA18, which demonstrate significant TRPM2 inhibition with low-micromolar potencies (IC50: 8.1 and 6.2 μM, respectively). The selectivity of ZA10 and ZA18 toward TRPM2 was limited, as both compounds exhibited modest inhibitory activity against TRPM8 and TRPV1. In addition, ZA10 produced pronounced inhibition of TRPC3, comparable to 2-APB. ZA10 and ZA18 did not show any inhibition of InsP3 and Orai-evoked Ca2+ release [191].
Scalaradial is a natural compound isolated from the extract of an undescribed species of Cacospongia and has been reported to demonstrate strong inhibition of TRPM2-mediated current in HEK293 cells that overexpress TRPM2 protein in whole-cell patch--clamp experiments. The inhibition is concentration- and time-dependent with an IC50 of 210 nM. Scalaradial also inhibits TRPM7 but with a 3.6-fold reduction in potency (IC50 760 nM), and did not inhibit CRAC, TRPM4, and TRPV1 currents. The inhibitory action of scalaradial on TRPM2 is independent of its effects in secreted PLA2, extracellular signal-regulated kinases (ERK) and Akt pathways. The 12-deacetylated derivative of scalaradial has also demonstrated similar inhibitory action on TRPM2 current [192]. While the nanomolar potency makes scalaradial a promising hit for TRPM2 inhibition, the presence of an α,β-unsaturated aldehydic group can make it act as a Michael acceptor, potentially leading to covalent modification of cellular proteins and nucleic acids, necessitating extensive optimization to mitigate potential toxic effects [193–196].
Clotrimazole and econazole are two widely used antifungal agents that have an imidazole ring in their structures. Apart from their sterol-14-α-demethylase-mediated antifungal action, these drugs have demonstrated interactions with a plethora of mammalian ion channels [197]. In 2004, Hill et al. reported that clotrimazole and econazole also irreversibly and non-selectively inhibited TRPM2 with low micromolar potencies [198]. Jia et al. demonstrated that TRPM2 inhibition with 25 mg/kg dose of clotrimazole significantly reduces infarct volume in tMCAO model [155]. However, the lack of selectivity, combined with irreversible channel inhibition and extensive off-target ion channel effects, substantially limits their suitability as lead scaffolds for medicinal chemistry optimization toward clinically viable TRPM2 inhibitors.
In summary, over the past decade, substantial progress has been made in the discovery and optimization of small-molecule TRPM2 inhibitors, evolving from non-selective functional tool compounds toward mechanistically distinct, target-engaging, and in vivo active agents. Anthranilic acid–based inhibitors such as A23 demonstrate that rational SAR optimization can yield compounds with improved potency, selectivity, and pharmacokinetic properties, although further validation of off-target profiles and safety of the acrylamide moiety remains necessary. High-throughput screening efforts have identified highly potent inhibitors such as JNJ-28583113, whose nanomolar activity and exceptional selectivity underscore the tractability of TRPM2 as a druggable ion channel, yet whose metabolic instability highlights the importance of scaffold refinement for in vivo application. Among currently reported inhibitors, LC4 represents the most balanced preclinical candidate, combining sub-micromolar potency, improved selectivity, reduced hERG liability, and robust neuroprotective efficacy in ischemic stroke models, albeit with limitations in oral bioavailability. Collectively, these studies establish TRPM2 as a pharmacologically addressable target in ischemic and neuroinflammatory diseases, as well as cancer, and illustrate multiple viable chemical strategies for its inhibition. Future efforts should focus on confirmation of direct binding with X-ray crystal-lography or cryo-electron microscopy, improving metabolic stability and oral exposure, rigorously defining selectivity across broader ion channel and enzyme panels, and clarifying potential sex-dependent or disease-context–specific responses, thereby advancing TRPM2 inhibitors toward clinical translation.
Peptides:
In recent years, the discovery and development of peptide-based therapeutics has gained substantial momentum, highlighted by the clinical approval of several peptides, most notably oral semaglutide for the treatment of type 2 diabetes and long-term weight management. These peptide therapeutics often retain close structural resemblance to endogenous peptide or protein interaction motifs, enabling highly specific target engagement. The rational design of these agents confers high efficacy, predictable pharmacological behavior, and a well-defined mechanism of action, making peptides an increasingly attractive modality in modern drug discovery [199].
In 2016, Shimizu et al. reported the discovery of tat-M2NX (also referred to as tatM2NX), a novel, cell-permeable, peptide molecule that selectively inhibits the TRPM2 channel. This peptide-based TRPM2 inhibitor was engineered by fusing a C-terminal segment of TRPM2, which shares over 90 % sequence identity with its Nudix domain (23 amino acid residues), to the cell-penetrating tat-inducer sequence (11 amino acid residues) derived from the human immunodeficiency virus (HIV). Fluorescent calcium imaging shows that Tat-M2NX inhibits H2O2-induced TRPM2-mediated Ca2+ influx in hTRPM2-expressing HEK-293 cells in a concentration-dependent manner. The IC50 value for TRPM2 inhibition by tat-M2NX has been determined to be 396 nM, with significant inhibitions achieved at concentrations as low as 500 nM, making it one of the most potent TRPM2 inhibitors reported. Coimmunoprecipitation experiment with the biotinylated tat-M2NX peptide shows that the peptide forms a complex with FLAG-TRPM2, corroborating direct binding of tat-M2NX with TRPM2. Site-directed mutagenesis studies, in which tryptophan at position 33 and valine at position 34 of tat-M2NX were modified to alanine residues, resulted in a complete loss of TRPM2 inhibition, indicating the role of these residues in binding to TRPM2. These results are also supported by computational modelling and molecular dynamics simulation studies. Following the promising in vitro activity, the effects of treatment as well as pretreatment with tat-M2NX were also investigated in the transient MCAO model of stroke in both male and female mice. In the pretreatment studies, tat-M2NX or tat-SCR (the scrambled version of tat-M2NX, which has been shown to possess no TRPM2 inhibition and thus serves as a control) was administered 20 min before the transient MCAO that was reperfused after 60 min, and the infarct volumes were analyzed after 24 h of reperfusion. Interestingly, the male mice treated with tat-M2NX had a significant reduction in the infarct volume compared to the control group (29 % vs 43.4 %, p < 0.01), but no such reduction in infarct size was observed in female mice. For the post-stroke treatment model, MCA was occluded for 1 h and then reperfused, and tat-M2NX was administered retro-orbitally 3 h after the reperfusion. The brain samples analyzed 24 h after reperfusion showed a significant reduction in infarct volume in the treatment group of male mice compared to the control (28.3 % vs 46.5 %, p < 0.05). These results are comparable to the pretreatment model, and no significant effects were observed for the female mice in the treatment model as well, indicating a male-specific extended treatment window of tat-M2NX for neuronal ischemia/reperfusion injury that is observed in ischemic stroke. The neuroprotective effect of tat-M2NX is not observed in TRPM2 knockout male mice, indicating sec-specific TRPM2-mediated activity of this peptide [200,201].
In 2019, Dietz et al. validated the role of sustained TRPM2 activation in hippocampal injury and cognitive function impairment following global cerebral ischemia using a cardiac arrest/cardiopulmonary resuscitation (CA/CPR) model of TRPM2-KO male mice. CA/CPR-induced global ischemia disrupts synaptic plasticity in the CA1 region of the hippocampus, as evidenced by a pronounced impairment of LTP, leading to deficits in learning and memory performances. Acute and delayed inhibition of TRPM2 with tat-M2NX demonstrates outcomes similar to that of TRPM2-KO and results in the protection of LTP and recovery of synaptic plasticity following CA/CPR-induced global ischemia [202]. A similar study using a controlled cortical impact (CCI) model to generate traumatic brain injury (TBI) revealed that TRPM2-KO male mice had significantly smaller cortical injury compared to the wild-type, associating TRPM2 activation with TBI, though no such effects were observed in female mice. Building up on these results, tat-M2NX was administered intravenously at 2 h post injury at 2, 10, and 20 mg/kg doses, and neurological injury and performance were evaluated at 7 days post injury. The study revealed that acute inhibition of the TRPM2 channel by tat-M2NX can preserve synaptic plasticity and memory function following TBI, although no significant reduction in cortical injury was observed [156].
Tat-EE3 and tat-M2PBM are two other TRPM2-based peptides that have shown significant activity in vitro as well as in vivo ischemic stroke model, but their activity is not attributable to direct inhibition of TRPM2 channel, rather, it results from inhibition of TRPM2-mediated NMDAR-induced excitotoxicity in neurons [151,152].
Collectively, these studies establish TRPM2 as a critical mediator of neuronal dysfunction across ischemic stroke, global cerebral ischemia, and traumatic brain injury models, and validate tat-M2NX as a powerful mechanistic probe for investigating TRPM2-dependent pathology. This peptide exhibits sub-micromolar potency, robust target engagement, and reproducible neuroprotection in male animals across both prophylactic and delayed treatment paradigms, with effects abolished in TRPM2-deficient mice, confirming on-target activity. However, the pronounced sex-specific efficacy, absence of comprehensive pharmacokinetic and brain exposure data, and the inherent translational liabilities associated with peptide therapeutics, including limited stability, parenteral administration, immunogenicity, etc., substantially constrain its clinical potential [203,204]. Moreover, the lack of direct comparative studies with emerging small-molecule TRPM2 inhibitors limits assessment of its relative therapeutic value. As such, tat-M2NX should be viewed as a potent TRPM2-inhibiting peptide, whose efficacy, pharmacokinetic properties, and safety should be further explored for possible clinical translation.
In conclusion, TRPM2 inhibition is emerging as a promising pharmacological strategy for the treatment of neurological conditions, cancer, and I/R injury, and the discovery and development of different classes of small-molecule and peptide-based TRPM2 inhibitors has laid the foundation in this aspect. Despite significant progress, the development of TRPM2 inhibitors is still in the early stages, necessitating both intensive and extensive evaluation of pharmacology, toxicity, off-target effects, and pharmacokinetic properties of the reported agents, so that further optimization of these agents can lead to the discovery of clinical lead(s). Interestingly, even though most of the recent drug discovery efforts focus on targeting neurological conditions, they often overlook the blood-brain barrier permeation properties of these agents, which can limit their future development. While different approaches are undertaken to identify and characterize TRPM2 inhibitors, the general scheme is to use whole-cell patch clamping in hTRPM2 overexpressing cells to determine the effect at particular concentration(s), followed by potency determination. Once potent compounds are identified, their pharmacokinetic properties are characterized in vivo, and compounds with desirable properties are evaluated in in vivo efficacy models of TRPM2-mediated disease conditions. It should be noted that, due to the variability in models used for characterization, it may be difficult to perform direct comparisons among different properties of these TRPM2-inhibiting agents. The table below summarizes the important properties of the reported TRPM2 inhibitors that were available at the time of writing this review.

8.
Conclusion and perspectives
TRPM2 is one of the critical regulators of intracellular Ca2+ homeostasis under oxidative stress, which plays a complex role across various pathological conditions, especially in cancer, neurological diseases, and I/R injury. As described in this review, TRPM2-activated Ca2+ influx modulates different downstream signaling pathways and cellular bioenergetics in pathologic settings. TRPM2 and TRPM2-AS have been widely studied in different cancer models. Overexpressions of TRPM2 and TRPM2-AS boost antioxidant activity, mitochondrial metabolic functionality, and autophagy, which allows cancer cells to adapt under stressful conditions and promotes cancer cell survivability. Additionally, TRPM2 supports an immune suppressive TEM promoting tumor growth and metastasis. Thus, inhibition of TRPM2 and TRPM2-AS is a novel therapeutic approach for inhibiting cancer cell growth and overcoming resistance to certain chemotherapeutic agents. In neurological diseases, such as epilepsy, Alzheimer’s, and Parkinson’s diseases, TRPM2-mediated Ca2+ overload induces neuronal cell death and neuroinflammation through disruption of mitochondrial functionality and glial cell activation. TRPM2-regulated Ca2+ accumulation also exacerbates I/R-related damage in the brain, kidney, liver, and cardiac muscles through excessive ROS generation and triggering the downstream cell death pathways. Therefore, inhibition of TRPM2 holds great promise as a therapeutic target in these disease conditions.
Despite the identification of multiple TRPM2 inhibitors, spanning ADPR analogues, small molecules, and peptide-based approaches, none have yet advanced into clinical trials. While the earlier TRPM2 inhibitors, such as 2-APB, ACA, and clotrimazole, econazole, are non-specific and had suboptimal potency, recently reported inhibitors like JNJ-28583113, LC4, and the peptide tat-M2NX have shown improved potency and selectivity toward TRPM2. The development of small-molecule TRPM2 inhibitors is still limited by the lack of detailed pharmacokinetic studies, structural biology insights, mechanistic investigation, and assessment of the reported agents for specificity and toxicity. On the other hand, the evaluations of specificity, immunogenic interaction of peptide-based TRPM2 inhibitors, as well as their metabolic stability, distribution into brain tissue, and sex-specific responses are necessary for their development.
In conclusion, TRPM2 is a compelling therapeutic target. With the development of selective inhibitors and careful alignment of mechanisms to disease context, TRPM2-directed therapies could open new avenues across multiple severe conditions.