brequinar (DUP 785)

Human stromal cell lines HS-5 and HS-27, as well as primary MSCs isolated from patient bone marrow, were superior in promoting AML differentiation compared to mouse cells in response to AICAr and brequinar, with the inhibitors not significantly affecting the stromal cells themselves. In conclusion, our study highlights the supportive role of human BM MSCs in enhancing the differentiation effects of pyrimidine synthesis inhibitors on AML cells, suggesting that AML treatment strategies focusing on differentiation rather than cell killing may be successful in clinical settings.

Here, we rationally designed a hollow iron-doped SiO2-based nanozyme (FeSHS) loaded with brequinar (BQR) and lificiguat (YC-1), named FeSHS/BQR/YC-1-PEG, for tumor ferroptosis activation...The elevation of levels of iron and PUFAs while simultaneously disrupting the GPX4/DHODH/FSP1 inhibitory pathways by our designed nanoplatform displayed high therapeutic efficacy both in vitro and in vivo. This work elucidates rationally designing smart nanoplatforms for ferroptosis activation and future tumor treatments.

In vivo studies demonstrated synergetic tumor growth inhibition in xenograft models with brequinar and venetoclax combination treatment. These results provide preliminary evidence for the rational combination of DHODH and BCL2 blockade in HGBCL with abnormal MYC and BCL2.

The negatively charged nanomedicine ensured good blood stability and high tumor accumulation, while the charge-reversal to positive in response to the acidic pH in the tumor microenvironment (TME) and lysosomes enhanced the uptake by tumor cells and lysosome escape, achieving accumulation in mitochondria. The subsequently released Na+ in mitochondria not only contributed to the formation of mitomiR-494 induced G-quadruplexes for AIE imaging diagnosis but also led to an osmolarity surge that was enhanced by brequinar to achieve effective ion-interference therapy.

Furthermore, the in vivo studies revealed that BQR@MLipo could remarkably accumulate into the bladder tumor and successfully initiate the infiltration of CD8 T cells into tumor microenvironment for enabling efficient CBI to inhibit bladder tumor growth. Therefore, BQR@MLipo may represent a clinically promising modality for enhancing CBI in bladder tumor.

Their poor prognosis is linked to the presence of glioblastoma stem cells (GSC), which support resistance to therapy, notably to temozolomide (TMZ)...Finally, we provide a mechanism whereby mitochondrial transfer from MSCs to GSCs contributes to GBM resistance to TMZ therapy, by demonstrating that inhibition of orotate production by Brequinar (BRQ) restores TMZ sensitivity in GSCs with acquired mitochondria...Mitochondria acquired from MSCs enhance the chemoresistance of GBMs. The discovery that they also generate metabolic vulnerability in GSCs paves the way for novel therapeutic approaches.

TUS-resistant cells (TUS/R) were 60-fold resistant to gilteritinib (FLT3 inhibitor) but not to quizartinib (FLT3 inhibitor). There was no observed resistance to azacitidine, luxeptinib (lymphoid & myeloid kinase inhibitor), brequinar (DHODH inhibitor), zelavespib (HSP90 inhibitor), or IMP-1088 (NMT1/2 inhibitor), and a small degree of hypersensitivity (<2-fold) of TUS/R cells to luxeptinib, brequinar, and IMP-1088... Resistance to TUS in MOLM-14 cells required prolonged high-level drug exposure. The fact that FLT3 remained fully inhibited in TUS/R cells growing in 75 nM TUS suggests that resistance is not due to a mutation of FLT3. Drug resistance in TUS/R cells in the absence of TUS over 60 days indicates a stable phenotype, distinct from "persister cell resistance" in which resistance fades during subsequent passages.

Inducing oxidative stress by SOD2 inhibition sensitized nasopharyngeal carcinoma cells to ionizing radiation via ferroptosis induction. This was found to be dependent on DHODH activity. This suggests that DHODH inhibitors should be used with caution during radiotherapy in nasopharyngeal carcinoma patients.

Herein, shRNA and brequinar were used to knock down DHODH and directly inhibit DHODH, respectively. A combination of DHODH inhibition and cisplatin synergistically induced both in vitro and in vivo ferroptosis and downregulated the ferroptosis defender mTOR pathway. Therefore, the combination of DHODH inhibition and cisplatin exhibits synergistic effects on ferroptosis induction via inhibiting the mTOR pathway could provide a promising way for cervical cancer therapy.

Moreover, brequinar facilitated myeloid maturation and inhibited immune-suppressive features in human bone marrow culture systems. These findings advance the concept of MDSC differentiation therapy in immuno-oncology.

To probe for druggable mediators of DHODH inhibitor resistance, we performed a combination screen with a small molecule library against pancreatic cancer cell lines that are highly resistant to the DHODH inhibitor brequinar (BQ)...In an aggressive, immunocompetent pancreatic cancer mouse model, combined targeting of DHODH and ENT1 dramatically suppressed tumor growth and prolonged mouse survival. Overall, our study defines CNX-774 as a previously uncharacterized ENT1 inhibitor and provides strong proof of concept support for dual targeting of DHODH and ENT1 in pancreatic cancer.

The emergence of dihydroorotate dehydrogenase as an appealing mechanistic target in AML has propelled the development of several clinical candidate DHODH inhibitors (DHODHi) such as brequinar...Collectively, we provide a thorough preclinical assessment for HOSU-53 for treatment in hematological malignancy both as a monotherapy and combined with other effective approved therapies including decitabine, monoclonal antibodies and gilteritinib. We have initiated IND enabling studies including GLP toxicity studies planned for late 2022 and have initiated human dose projection models based on our multi-species PK/PD analysis. We anticipate filing an IND application in 2023 for a phase 1 clinical trial in AML and MM.

Using an in silico/crystallography supported design, we identified compound 4 (IC 7.2 nM), characterized by the presence of a decorated aryloxyaryl moiety that replaced the biphenyl scaffold, with potent inhibition and pro-differentiating abilities on AML THP1 cells (EC 74 nM), superior to those of brequinar (EC 249 nM) and boosted when in combination with dipyridamole. Finally, compound 4 has an extremely low cytotoxicity on non-AML cells as well as MEDS433; it has shown a significant antileukemic activity in vivo in a xenograft mouse model of AML.

A combination of brequinar and temozolomide was curative in the majority of transgenic TH-MYCN neuroblastoma mice, indicating a highly active clinical combination therapy. Overall, DHODH inhibition combined with temozolomide has therapeutic potential in neuroblastoma and we propose this combination for clinical testing.

We have previously reported that 5-aminoimidazole-4-carboxamide ribonucleoside (AICAr) and brequinar, a DHODH inhibitor, induced differentiation of myeloid leukemia by activating the ataxia telangiectasia and Rad3-related (ATR)/checkpoint kinase 1 (Chk1) via pyrimidine depletion. In addition, cytarabine induces differentiation ex vivo in a subset of primary AML samples that are sensitive to AICAr and DHODH inhibitor. The results of our study suggest that leukemic cell differentiation stimulated by low doses of cytarabine depends on the activation of Chk1 and thus shares the same pathway as pyrimidine synthesis inhibitors.

Functional Assays : RNA interference and inhibitors that selectively target GLS (CB-839), DHODH (Teriflunomide, Leflunomide, Vidofludimus, Brequinar and BAY 2402234) or BRD4 (MZ-1; JQ1; AZD5153; Mivebresib and Birabresib) potently and specifically diminish the clonogenic potential of several SCCHN cell lines. However, none of these treatments induce comparable apoptosis in the ex vivo SCCHN tumour tissue. Conclusion The challenges presented by the tumour microenvironment in diminishing the potential of several promising therapies will have to be characterised further, which is the primary focus of our current studies.

Aims To develop and assess new therapeutics, we investigated the effects of the DHODH inhibitor brequinar in DHL lymphoma cell lines and the synthetic effects of brequinar and venetoclax. Thus, it can be reasonably expected that a clinical-grade DHODH inhibitor combined with venetoclax might improve outcomes for patients with DHL or double-expression lymphoma and other cancers with high expression of MYC and BCL2 or MYC and MCL-1. Our findings provide new insights into the molecular basis of this effect and offer opportunities to design new targeted treatments for lymphoma.

We recently discovered compound 1, a potent hDHODH inhibitor (IC = 1.2 nM), able to induce myeloid differentiation in AML cell lines (THP1) in the low nM range (EC = 32.8 nM) superior to brequinar's phase I/II clinical trial (EC = 265 nM)...Moreover, in order to identify a backup compound, we investigate the SAR of this class of compounds. Inside the series, 17 is characterized by higher potency in inducing myeloid differentiation (EC = 17.3 nM), strong proapoptotic properties (EC = 20.2 nM), and low cytotoxicity toward non-AML cells (EC(Jurkat) > 100 μM).

Glioblastoma is the most common and aggressive type of cancer in the brain; its poor prognosis is often marked by reoccurrence due to resistance to the chemotherapeutic agent temozolomide, which is triggered by an increase in the expression of DNA repair enzymes such as MGMT...Pharmacological inhibition of DHODH with the specific inhibitors brequinar or ML390 effectively depleted the pool of pyrimidines in glioblastoma cells grown in vitro and in vivo and impaired rDNA transcription, leading to nucleolar stress...Our in vivo data indicate that while inhibition of DHODH caused a dramatic reduction in pyrimidines in tumor cells, it did not affect the overall pyrimidine levels in normal brain and liver tissues, suggesting that pyrimidine production by the salvage pathway may play an important role in maintaining these nucleotides in normal cells. Our study demonstrates that glioblastoma cells heavily rely on the de novo pyrimidine biosynthesis pathway to generate ribosomal RNA (rRNA) and thus, we identified an approach to inhibit ribosome production and consequently the proliferation of glioblastoma cells through the specific inhibition of the de novo pyrimidine biosynthesis pathway.

AICAr induces differentiation in a subset of primary non-APL AML blasts, and these effects correlate with sensitivity to a well-known, potent DHODH inhibitor.