Discovery of highly potent PARP7 inhibitors for cancer immunotherapy.

PARP7 has been proven to play an important role in immunity. Substantial upregulation of PARP7 is observed in numerous cancerous cell types, consequently resulting in the inhibition of type Ⅰ interferon signaling pathways. Therefore, inhibiting the activity of PARP7 can enhance type Ⅰ interferon signaling to exert an anti-tumor immune response. In this study, we reported the identification of a newly found PARP7 inhibitor (XLY-1) with higher inhibitory activity (IC50 = 0.6 nM) than that of RBN-2397 (IC50 = 6.0 nM). Additionally, XYL-1 displayed weak inhibitory activity on PARP1 (IC50 > 1.0 µM). Mechanism studies showed that XYL-1 could enhance the type Ⅰ interferon signaling in vitro. Pharmacodynamic experiments showed that 50 mg/kg XYL-1 could significantly inhibit tumor growth (TGI: 76.5 %) and related experiments showed that XYL-1 could restore type Ⅰ interferon signaling and promote T cell infiltration in tumor tissues. Taken together, XYL-1 shows promise as a potential candidate for developing cancer immunotherapy agents.

Discovery of novel EGFR-PROTACs capable of degradation of multiple EGFR-mutated proteins.

Although three generations of Epidermal growth factor receptor (EGFR) - TK inhibitors have been approved for the treatment of Non-small-cell lung cancers (NSCLC), their clinical application is still largely hindered by acquired drug resistance mediated new EGFR mutations and side effects. The Proteolysis targeting chimera (PROTAC) technology has the potential to overcome acquired resistance from mutant EGFR through a novel mechanism of action. In this study, we developed the candidate degrader IV-3 by structural modifications of the lead compound 13, which exhibited limited antiproliferative activity against HCC-827 cells. Compared to compound 13, IV-3 exhibited remarkable anti-proliferative activity against HCC-827 cells, NCI-H1975 cells, and NCI-H1975-TM cells (IC50 = 0.009 µM, 0.49 µM and 3.24 µM, respectively), as well as significantly inducing degradation of EGFR protein in these cell lines (DC50 = 17.93 nM, 0.25 µM and 0.63 µM, respectively). Further investigations confirmed that IV-3 exhibited superior anti-tumor activity in all xenograft tumor models through the degradation of mutant EGFR protein. Moreover, IV-3 showed no inhibitory activity against A431 and A549 cells expressing wild-type EGFR, thereby eliminating potential toxic side effects emerging from wild-type EGFR inhibition. Overall, our study provides promising insights into EGFR-PROTACs as a potential therapeutic strategy against EGFR-acquired mutation.

Rational Design of PARP1/c-Met Dual Inhibitors for Overcoming PARP1 Inhibitor Resistance Induced by c-Met Overexpression.

The emergence of resistance to PARP1 inhibitors poses a current therapeutic challenge, necessitating the development of novel strategies to overcome this obstacle. The present study describes the design and synthesis of a series of small molecules that target both PARP1 and c-Met. Among them, compound 16 is identified as a highly potent dual inhibitor, exhibiting excellent inhibitory activities against PARP1 (IC50 = 3.3 nM) and c-Met (IC50 = 32.2 nM), as well as demonstrating good antiproliferative effects on HR-proficient cancer cell lines and those resistant to PARP1 inhibitors. Importantly, compound 16 demonstrates superior antitumor potency compared to the PARP1 inhibitor Olaparib and the c-Met inhibitor Crizotinib, either alone or in combination, in MDA-MB-231 and HCT116OR xenograft models. These findings highlight the potential of PARP1/c-Met dual inhibitors for expanding the indications of PARP1 inhibitors and overcoming tumor cells' resistance to them.

Discovery of the first ataxia telangiectasia and Rad3-related (ATR) degraders for cancer treatment.

The first examples of ataxia telangiectasia and Rad3-related (ATR) PROTACs were designed and synthesized. Among them, the most potent degrader, ZS-7, demonstrated selective and effective ATR degradation in ATM-deficient LoVo cells, with a DC50 value of 0.53 µM. Proteasome-mediated ATR degradation by ZS-7 lasted approximately 12 h after washout in the LoVo cell lines. Notably, ZS-7 demonstrated reasonable PK profiles and, as a single agent or in combination with cisplatin, showed improved antitumor activity and safety profiles compared with the parent inhibitor AZD6738 in a xenograft mouse model of LoVo human colorectal cancer cells upon intraperitoneal (i.p.) administration.

Discovery of Highly Potent Small-Molecule PD-1/PD-L1 Inhibitors with a Novel Scaffold for Cancer Immunotherapy.

Inhibition of the PD-1/PD-L1 interaction through small-molecule inhibitors is a promising therapeutic approach in cancer immunotherapy. Herein, we utilized BMS-202 as the lead compound to develop a series of novel PD-1/PD-L1 small-molecule inhibitors with a naphthyridin scaffold. Among these compounds, X14 displayed the most potent inhibitory activity for the PD-1/PD-L1 interaction (IC50 = 15.73 nM). Furthermore, X14 exhibited good binding affinity to both human PD-L1 (KD = 14.62 nM) and mouse PD-L1 (KD = 392 nM). In particular, X14 showed favorable pharmacokinetic properties (oral bioavailability, F = 58.0%). In the 4T1 (mouse breast cancer cells) syngeneic mouse model, intragastric administration of X14 at 10 mg/kg displayed significant antitumor efficacy (TGI = 66%). Mechanistic investigations revealed that X14 effectively enhanced T-cell infiltration within the tumor microenvironment. Our study demonstrates that compound X14 exhibits potential as a candidate compound for the development of orally effective small-molecule inhibitors targeting PD-1/PD-L1.

Discovery of Highly Selective PARP7 Inhibitors with a Novel Scaffold for Cancer Immunotherapy.

PARP7 plays a crucial role in cancer immunity. The inhibition of PARP7 has shown potential in boosting the immune response against cancer, making it an attractive target for cancer immunotherapy. Herein, we employed a rigid constraint strategy (reduction in molecular flexibility) to design and synthesize a series of novel indazole-7-carboxamide derivatives based on the structure of RBN-2397. Among these derivatives, (S)-XY-05 was identified as the most promising PARP7 inhibitor (IC50: 4.5 nM). Additionally, (S)-XY-05 showed enhanced selectivity toward PARP7 and improved pharmacokinetic properties (oral bioavailability: 94.60%) compared with RBN-2397 (oral bioavailability: 25.67%). In the CT26 syngeneic mouse model, monotherapy with (S)-XY-05 displayed a strong antitumor effect (TGI: 83%) by activating T-cell-mediated immunity within the tumor microenvironment. Collectively, we confirmed that (S)-XY-05 has profound effects on tumor immunity, which paves the way for future studies of PARP7 inhibitors that could be utilized in cancer immunotherapy.

The Characterization of Laser-Induced Particles Generated from Aluminum Alloy in High Power Laser Facility.

Aerosol particle contamination in high-power laser facilities has become a major cause of internal optical component damage resistance and service life reduction. In general, contaminating particles primarily originate from stray light; therefore, it is crucial to investigate the mechanism and dynamics of the dynamic contaminating particle generation to control the cleanliness level. In this study, corresponding research was conducted on experiments and theory. We investigated the particle generation and surface composition modification under the action of a laser. We employed various surface analytical methods to identify the possible variations in the aluminum alloy surface during laser irradiations. A theoretical model for particle ejection from aluminum alloy surfaces was established by taking the adhesion force and laser cleaning force (due to thermal expansion) into account. The results show that the threshold energies for contamination particle generation and damage are around 0.1 and 0.2 J/cm2, respectively. Subsurface impurities are the primary source of particles, and particle adhesion density is related to surface roughness. Pollution particle generation and splashing processes include temperature increases, phase changes, impact diffusion, and adhesion. The results provide a reference for the normal operation of high-energy laser systems. The results also suggest that the laser irradiation pretreatment of aluminum alloy surfaces is essential to improve the cleanliness level.

Design, Synthesis, and Biological Evaluation of Potent and Selective Inhibitors of Ataxia Telangiectasia Mutated and Rad3-Related (ATR) Kinase for the Efficient Treatment of Cancer.

Ataxia telangiectasia mutated and Rad3-related (ATR), a vital member of the phosphatidylinositol 3-kinase-related kinase (PIKK) family, plays a critical role in the DNA damage response (DDR). Tumor cells with a loss of DDR function or defects in the ataxia telangiectasia mutated (ATM) gene are generally more dependent on ATR for survival, suggesting that ATR is an attractive anticancer drug target based on its synthetic lethality. Herein, we present a potent and highly selective ATR inhibitor, ZH-12 (IC50 = 0.0068 µM). It showed potent antitumor activity as a single agent or in combination with cisplatin in the human colorectal adenocarcinoma LoVo tumor xenograft mouse model. Overall, ZH-12 may be a promising ATR inhibitor based on the principle of synthetic lethality and deserves further in-depth study.

Discovery of the Potent and Highly Selective PARP7 Inhibitor as a Novel Immunotherapeutic Agent for Tumors.

PARP7, a polyadenosine diphosphate-ribose polymerase, has been identified as a negative regulator in type I interferon (IFN) signaling. An overexpression of PARP7 is typically found in a wide range of cancers and can lead to the suppression of type I IFN signaling and innate immune response. Herein, we describe the discovery of compound I-1, a novel PARP7 inhibitor with high inhibitory potency (IC50 = 7.6 nM) and selectivity for PARP7 over other PARPs. Especially, I-1 has excellent pharmacokinetic properties and low toxicity in mice and exhibits significantly stronger in vivo antitumor potency (TGI: 67%) than RBN-2397 (TGI: 30%) without the addition of 1-aminobenzotriazole (a nonselective and irreversible inhibitor of cytochrome P450) in CT26 syngeneic mouse models. Our findings reveal that I-1 mainly acts as an immune activator through PARP7 inhibition in the tumor microenvironment, which highlights the potential advantages of I-1 as a tumor immunotherapeutic agent.

Design, Synthesis and Biological Evaluation of Novel and Potent Protein Arginine Methyltransferases 5 Inhibitors for Cancer Therapy.

Protein arginine methyltransferases 5 (PRMT5) is a clinically promising epigenetic target that is upregulated in a variety of tumors. Currently, there are several PRMT5 inhibitors under preclinical or clinical development, however the established clinical inhibitors show favorable toxicity. Thus, it remains an unmet need to discover novel and structurally diverse PRMT5 inhibitors with characterized therapeutic utility. Herein, a series of tetrahydroisoquinoline (THIQ) derivatives were designed and synthesized as PRMT5 inhibitors using GSK-3326595 as the lead compound. Among them, compound 20 (IC50: 4.2 nM) exhibits more potent PRMT5 inhibitory activity than GSK-3326595 (IC50: 9.2 nM). In addition, compound 20 shows high anti-proliferative effects on MV-4-11 and MDA-MB-468 tumor cells and low cytotoxicity on AML-12 hepatocytes. Furthermore, compound 20 possesses acceptable pharmacokinetic profiles and displays considerable in vivo antitumor efficacy in a MV-4-11 xenograft model. Taken together, compound 20 is an antitumor compound worthy of further study.

Rational design, synthesis and biological evaluation of dual PARP-1/2 and TNKS1/2 inhibitors for cancer therapy.

Poly(ADP-ribose) polymerase-1 (PARP-1) inhibitors are the first and most successful drugs designed to exploit the concept of synthetic lethality (SL) between PARP-1 and BRCA1/2, which provides a novel strategy for tumor treatment. However, narrowed indications and resistance to PARP-1 inhibitors have hampered their further clinical application. Inducing "BRCAness" by targeting other targets, which will directly or indirectly disturb the homologous recombination (HR) repair pathway of double-strand DNA breaks (DSBs), is a promising strategy for expanding the clinical application of PARP-1 inhibitors and overcoming resistance to these inhibitors. Tankyrase1/2 (TNKS1/2) are involved in the nonhomologous end-joining (NHEJ) DNA repair pathway by regulating Wnt/ß-catenin signaling. TNKS1/2 can also induce a "BRCAness" phenotype by regulating Wnt signaling, which increases the sensitivity of tumor cells with BRCA proficiency to PARP-1 inhibitors. These results suggest that cotargeting PARP1/2 and TNKS1/2 not only exerts a synergistic effect in the treatment of tumors but also provides a novel strategy for expanding the clinical application of PARP-1 inhibitors and overcoming resistance to PARP-1 inhibitors. Therefore, a series of dual PARP-1/2 and TNKS1/2 inhibitors were rationally designed, synthesized, and evaluated for their pharmacological properties. Among these candidates, compound I-9 showed excellent inhibitory activity as it inhibited PARP-1/2 and TNKS1/2 with IC50 values of 0.25 nM, 1.2 nM, 13.5 nM and 4.15 nM, respectively. I-9 exhibited favorable synergistic antitumor efficacy in both BRCA-mutant and BRCA-wild-type cancer lines. Moreover, I-9 exerted prominent dose-dependent antitumor activity in an HCT116 cell-derived xenograft model and was significantly more efficacious than olaparib and E7449. Overall, the present study indicated that I-9, a dual PARP-1/2 and TNKS1/2 inhibitor, is a novel and promising agent for cancer therapy.

Rational Design for Nitroreductase (NTR)-Responsive Proteolysis Targeting Chimeras (PROTACs) Selectively Targeting Tumor Tissues.

The catalytic properties of proteolysis targeting chimeras (PROTACs) may lead to uncontrolled off-tissue target degradation that causes potential toxicity, limiting their clinical applications. The precise control of this technology in a tissue-selective manner can minimize the potential toxicity. Hypoxia is a hallmark of most solid tumors, accompanied by elevated levels of nitroreductase (NTR). Based on this character, we presented a type of NTR-responsive PROTACs to selectively degrade proteins of interest (POI) in tumor tissues. Compound 17-1 was the first NTR-responsive PROTAC synthesized by incorporating the caging group on the Von Hippel-Lindau (VHL) E3 ubiquitin ligase ligand. It could be activated by NTR to release the active PROTAC 17 to efficiently degrade the EGFR protein and subsequently exert antitumor efficacy. Thus, a general strategy for the precise control of PROTAC to induce POI degradation in tumor tissues by NTR was established, which provided a generalizable platform for the development of NTR-controlled PROTACs to achieve selective degradation.

Discovery of novel potent covalent inhibitor-based EGFR degrader with excellent in vivo efficacy.

Although several Epidermal growth factor receptor (EGFR) inhibitors have been approved for the treatment of non-small-cell lung cancers (NSCLC), acquired drug resistance and side effects largely encumbered their application in clinic. The emerging technology Proteolysis targeting chimera (PROTAC) could be an alternative strategy to overcome these problems. Here, we reported the discovery of Dacomitinib-based EGFR degraders. Promising compound 13 can effectively induce degradation of EGFRdel19 with DC50 value of 3.57 nM in HCC-827 cells, but not to other EGFR mutant, wild-type EGFR protein and the same family receptors (HER2 and HER4). Of note, 13 is the first EGFR-PROTAC to evaluate antitumor effect in vivo, and exhibited excellent antitumor efficacy (TGI = 90%) at a dose of 30 mg/kg without causing observable toxic effects. The preliminary mechanism study demonstrated that 13 can efficiently induce EGFR protein degradation through ubiquitin proteasome pathway and inhibit phosphorylation of downstream pathways in vitro and in vivo, which indicated that 13 exerted antitumor effect by degradation of EGFR protein in tumor tissue. Overall, our study provided further evidence to validate EGFR-PROTACs as a promising strategy for lung cancer therapy.

Design, synthesis and mechanism studies of novel dual PARP1/BRD4 inhibitors against pancreatic cancer.

Inducing the deficiency of homologous recombination (HR) repair is an effective strategy to broaden the indication of PARP inhibitors in pancreatic cancer treatment. Repression of BRD4 has been reported to significantly elevate HR deficiency and sensitize cancer cells to PARP1/2 inhibitors. Inspired by the concept of synthetic lethality, we designed, synthetized and optimized a dual PARP1/BRD4 inhibitor III-7, with a completely new structure and high selectivity against both targets. III-7 repressed the expression and activity of PARP1 and BRD4 to synergistically inhibit the malignant growth of pancreatic cancer cells in vitro and in vivo. Based on the results of bioinformatic analysis, we found that Olaparib induced the acceleration of mitosis and recovery of DNA repair to cause the generation of drug resistance. III-7 reversed Olaparib-induced adaptive resistance and induced cell cycle arrest and DNA damage by perturbing PARP1 and BRD4-involved signaling pathways. We believe that the PARP1/BRD4 dual inhibitors are novel and promising antitumor agents, which provide an efficient strategy for pancreatic cancer treatment.

FDI-6 inhibits the expression and function of FOXM1 to sensitize BRCA-proficient triple-negative breast cancer cells to Olaparib by regulating cell cycle progression and DNA damage repair.

Inducing homologous-recombination (HR) deficiency is an effective strategy to broaden the indications of PARP inhibitors in the treatment of triple-negative breast cancer (TNBC). Herein, we find that repression of the oncogenic transcription factor FOXM1 using FOXM1 shRNA or FOXM1 inhibitor FDI-6 can sensitize BRCA-proficient TNBC to PARP inhibitor Olaparib in vitro and in vivo. Mechanistic studies show that Olaparib causes adaptive resistance by arresting the cell cycle at S and G2/M phases for HR repair, increasing the expression of CDK6, CCND1, CDK1, CCNA1, CCNB1, and CDC25B to promote cell cycle progression, and inducing the overexpression of FOXM1, PARP1/2, BRCA1/2, and Rad51 to activate precise repair of damaged DNA. FDI-6 inhibits the expression of FOXM1, PARP1/2, and genes involved in cell cycle control and DNA damage repair to sensitize TNBC cells to Olaparib by blocking cell cycle progression and DNA damage repair. Simultaneously targeting FOXM1 and PARP1/2 is an innovative therapy for more patients with TNBC.

Discovery of the First Potent IDO1/IDO2 Dual Inhibitors: A Promising Strategy for Cancer Immunotherapy.

Indoleamine 2,3-dioxygenase-1 (IDO1) plays an important role in tumor immune escape. However, unsatisfactory clinical efficacies of selective IDO1 inhibitors have impeded their further development, suggesting that they do not exert sufficient antitumor effects by selectively inhibiting IDO1. IDO2, an isoenzyme of IDO1, is overexpressed in some human tumors, and emerging evidence suggests that concomitant inhibition of IDO1/2 may have synergistic effects in cancer treatment, revealing a promising cancer immunotherapeutic strategy. Herein, we describe the discovery of compound 4t, the first inhibitor targeting both IDO1/2 that has excellent in vitro inhibitory activity (IDO1 IC50 = 28 nM and IDO2 IC50 = 144 nM). Notably, 4t (TGI = 69.7%) exhibited significantly stronger in vivo antitumor potency than epacadostat (TGI = 49.4%) in CT26 xenograft mouse models, highlighting the advantages of IDO1/2 dual inhibitors for tumor immunotherapy. Preliminary mechanistic studies in vivo further identified that 4t exerts its antitumor effect by inhibiting IDO1/2.

Discovery of Potent and Novel Dual PARP/BRD4 Inhibitors for Efficient Treatment of Pancreatic Cancer.

Targeting poly(ADP-ribose) polymerase1/2 (PARP1/2) is a promising strategy for the treatment of pancreatic cancer with breast cancer susceptibility gene (BRCA) mutation. Inducing the deficiency of homologous recombination (HR) repair is an effective way to broaden the indication of PARP1/2 inhibitor for more patients with pancreatic cancer. Bromodomain-containing protein 4 (BRD4) repression has been reported to elevate HR deficiency. Therefore, we designed, synthetized, and optimized a dual PARP/BRD4 inhibitor III-16, with a completely new structure and high selectivity against PARP1/2 and BRD4. III-16 showed favorable synergistic antitumor efficacy in pancreatic cancer cells and xenografts by arresting cell cycle progression, inhibiting DNA damage repair, and promoting autophagy-associated cell death. Moreover, III-16 reversed Olaparib-induced acceleration of cell cycle progression and recovery of DNA repair. The advantages of III-16 over Olaparib suggest that dual PARP/BRD4 inhibitors are novel and promising agents for the treatment of advanced pancreatic cancer.

Discovery of novel IDO1 inhibitors targeting the protein's apo form through scaffold hopping from holo-IDO1 inhibitor.

Immunomodulating enzyme IDO1 plays an important role in tumor immune resistance. Inhibiting IDO1 by small molecules with new mechanism of action is a potential strategy in IDO1 inhibitor development. Based on our urea derived compound originally binding with holo-IDO1, through scaffold hopping, a series of diisobutylaminophenyl hydroxyamidine compounds were designed. Unexpectedly, this novel class of IDO1 inhibitor does not target the holo form of IDO1 protein but displaces heme and binds to its apo form. Representative compound I-4 exhibits moderate potency with IC50 value of 0.44 µM in cell-based IDO1 assay, which has the potential to be developed for IDO1-related cancer treatment.

Discovery of Novel Small-Molecule Inhibitors of PD-1/PD-L1 Interaction via Structural Simplification Strategy.

Blockade of the programmed cell death 1 (PD-1)/programmed cell death-ligand 1 (PD-L1) interaction is currently the focus in the field of cancer immunotherapy, and so far, several monoclonal antibodies (mAbs) have achieved encouraging outcomes in cancer treatment. Despite this achievement, mAbs-based therapies are struggling with limitations including poor tissue and tumor penetration, long half-life time, poor oral bioavailability, and expensive production costs, which prompted a shift towards the development of the small-molecule inhibitors of PD-1/PD-L1 pathways. Even though many small-molecule inhibitors targeting PD-1/PD-L1 interaction have been reported, their development lags behind the corresponding mAb, partly due to the challenges of developing drug-like small molecules. Herein, we report the discovery of a series of novel inhibitors targeting PD-1/PD-L1 interaction via structural simplification strategy by using BMS-1058 as a starting point. Among them, compound A9 stands out as the most promising candidate with excellent PD-L1 inhibitory activity (IC50 = 0.93 nM, LE = 0.43) and high binding affinity to hPD-L1 (KD = 3.64 nM, LE = 0.40). Furthermore, A9 can significantly promote the production of IFN-γ in a dose-dependent manner by rescuing PD-L1 mediated T-cell inhibition in Hep3B/OS-8/hPD-L1 and CD3-positive T cells co-culture assay. Taken together, these results suggest that A9 is a promising inhibitor of PD-1/PD-L1 interaction and is worthy for further study.

Design, synthesis and biological evaluation of novel molecules as potent PARP-1 inhibitors.

Two series of novel compounds with inhibition activity against PARP-1 were designed and synthesized. All target compounds were evaluated for their PARP-1 inhibition activity, and compounds with high PARP-1 inhibition activity were selected to assess for cellular assays in vitro. Among them, compound II-4 displayed impressive results in both PARP-1 enzyme inhibition with IC50 value of 0.51 nM and anti-proliferation activity against HCT116 and HCC1937 cell lines with IC50 values of 6.62 nM and 12.65 nM, respectively. Also, II-4 exhibited good metabolic stability in vitro with t1/2 of 173.25 min and CLint of 0.04 mL/min/mg. Prediction of molecular properties and protein docking were applied to structure design. Our study provides potential lead compounds and design directions for the development of PARP-1 inhibitors.