Granzyme B PET imaging inflammation and remodeling in myocardial infarction.

PURPOSE: This study aimed to evaluate whether granzyme B (GzmB)-targeted positron emission tomography (PET) imaging agent (68 Ga-grazytracer) can characterize cardiac inflammation and remodeling in myocardial infarction (MI). METHODS: Rats with MI were subjected to GzmB-targeted PET/CT on post-operative days 1, 3, 6, 14, and 28. Autoradiography, Masson staining, immunohistochemistry, and ELISA were performed to verify the inflammatory response and remodeling after MI in vitro. Rats were treated with GzmB inhibitor Z-IETD-FMK to improve cardiac remodeling. Cardiac function tests were performed by echocardiography at 6 weeks after MI. RESULTS: The highest uptake of 68 Ga-grazytracer was observed on day 3 after MI compared with the values obtained on the other days (0.294 ± 0.03% ID/g at 3 days vs. 0.122 ± 0.01% ID/g in the sham group, P < 0.001). Immunohistochemistry showed significantly high expression of GzmB and CD8, in line with the PET/CT imaging results. Autoradiography revealed 68 Ga-grazytracer accumulation in the infarcted myocardium. The 68 Ga-grazytracer uptake of treated rats was significantly reduced compared with that in the MI groups (0.184 ± 0.03%ID/g vs. 0.286 ± 0.03%ID/g; P < 0.001). Echocardiography showed that the left ventricular ejection fraction was lower in the MI groups than in the ischemia reperfusion group. GzmB inhibitor treatment was shown to be effective in improving cardiac function without significantly shortening infarct size. CONCLUSIONS: This study demonstrated the potential of 68 Ga-grazytracer imaging to delineate adverse inflammatory responses and pathological cardiac remodeling, which can help predict heart function. PET/CT imaging-guided therapy may reduce myocardial injury and improve heart function in MI.

Early detection of anthracycline-induced cardiotoxicity using [68 Ga]Ga-FAPI-04 imaging.

PURPOSE: Anthracycline-induced cardiotoxicity (AIC), whose major manifestation is diffuse myocardial fibrosis, is an important clinical problem in cancer therapy. Therefore, early identification and treatment are clinically important. This study aims to explore the feasibility of using 68 Ga-labelled fibroblast activation protein (FAP) inhibitor ([68 Ga]Ga-FAPI) positron emission tomography/computed tomography (PET/CT) for the early identification of the fibrotic process and guidance of antifibrosis therapy in AIC. METHODS: An AIC rat model was induced by the intravascular administration of doxorubicin (DOX) once per week for 1, 2, 3 and 6 weeks (2.5 mg/kg/injection, groups 1-4), whereas intravascular saline was administered to control rats. Experimental and control groups (n = 4) underwent [68 Ga]Ga-FAPI PET/CT following disease induction. Groups 5 and 6 received DOX injections for 3 and 6 weeks, treated with angiotensin-converting enzyme (ACE) inhibitor starting at 3 weeks, treated with enalapril (20 mg/kg, gastric gavage) daily and underwent echocardiography and [68 Ga]Ga-FAPI PET/CT at 3 weeks after treatment. Rat hearts were subjected to haematoxylin and eosin staining, FAP immunohistochemistry, Sirius red staining and Masson's trichrome staining to investigate the pathological changes and deposition of collagen fibres. Rat blood was sampled weekly for the enzyme-linked immunosorbent assay of various markers of myocardial injury, such as plasma cardiac troponin I, B-type natriuretic peptide and angiotensin II. RESULTS: [68 Ga]Ga-FAPI-04 uptake by the heart was significantly higher in the cardiotoxicity group than in the control group at weeks 3 (SUVmax: 1.21 ± 0.23 vs 0.67 ± 0.01, P < 0.05) and 6 (SUVmax: 1.48 ± 0.28 vs 0.67 ± 0.08, P < 0.001), whereas left ventricle ejection fraction (LVEF) did not significantly differ between normal and AIC rats at week 3. FAP+ expression began to increase starting at week 3, before irreversible fibrotic changes were detected, until week 6. After 3 weeks of enalapril treatment, [68 Ga]Ga-FAPI-04 accumulation decreased in groups 5 and 6 (SUVmax decreased from 1.21 ± 0.23 to 0.77 ± 0.08 and 1.48 ± 0.28 to 1.09 ± 1.06, P < 0.05). Cardiac function was preserved (LVEF was 75.7% ± 7.38% in group 3 vs 74.5% ± 2.45% in group 5, P > 0.05) and improved (LVEF increased from 51.6% ± 9.03% in group 4 to 65.2% ± 4.27% in group 6, P < 0.05), and myocardial fibrosis attenuated (from 6.5% ± 1.2% in group 4 to 4.31% ± 0.37% in group 6, P < 0.01). CONCLUSION: [68 Ga]Ga-FAPI PET/CT can be used for the early detection of active myocardial fibrosis in AIC and the evaluation of the efficacy of therapeutic interventions. Early treatment guided by [68 Ga]Ga-FAPI PET/CT may reduce anthracycline-induced myocardial injury and improve heart function.

A self-triggered radioligand therapy agent for fluorescence imaging of the treatment response in prostate cancer.

PURPOSE: Radioligand therapy (RLT) targeting prostate-specific membrane antigen (PSMA) is emerging as an effective treatment option for metastatic castration-resistant prostate cancer (mCRPC). An imaging-based method to quantify early treatment responses can help to understand and optimize RLT. METHODS: We developed a self-triggered probe 2 targeting the colocalization of PSMA and caspase-3 for fluorescence imaging of RLT-induced apoptosis. RESULTS: The probe binds to PSMA potently with a Ki of 4.12 nM, and its fluorescence can be effectively switched on by caspase-3 with a Km of 67.62 µM. Cellular and in vivo studies demonstrated its specificity for imaging radiation-induced caspase-3 upregulation in prostate cancer. To identify the detection limit of our method, we showed that probe 2 could achieve 1.79 times fluorescence enhancement in response to 177Lu-RLT in a medium PSMA-expressing 22Rv1 xenograft model. CONCLUSION: Probe 2 can potently bind to PSMA, and the fluorescence signal can be sensitively switched on by caspase-3 both in vitro and in vivo. This method may provide an effective tool to investigate and optimize PSMA-RLT.

Optimization of ODAP-Urea-based dual-modality PSMA targeting probes for sequential PET-CT and optical imaging.

Prostate-specific membrane antigen (PSMA) is emerging as a promising target to specifically image prostate cancer. Dual-modality probe combining radionuclide imaging and near-infrared fluorescence navigation targeting PSMA would enable both the preoperative staging and intraoperative detection of the tumor lesions. To overcome one of the key barriers for achieving high contrast imaging at both early and late time points, we optimized the pharmacokinetics of dual-modality probes based on oxalyldiaminopropionic acid-urea (ODAP-Urea) PSMA inhibitors recently developed. Four dual-modality probes with variable hydrophilicity were synthesized and evaluated. They displayed good optical properties (λem max = 835 nm, QY = 0.67%-1.50%), high affinity to PSMA (Ki = 2.09 ± 1.71-4.15 ± 2.20 nM) and PSMA specific cellular uptake (0.48 ± 0.01% - 0.64 ± 0.04% IA/105 LNCaP cells) upon labeled with 68Ga. In vivo studies showed that [68Ga]Ga-P3 exhibited an optimum pharmacokinetic property with high specific tumor uptake (SUVmax = 1.88 ± 0.36, at 1 h) in medium level PSMA expressing 22Rv1 tumor model and high tumor-to-muscle ratio (12.56 ± 2.63, at 1 h). Specific fluorescence imaging could also be achieved with high contrast for later time points (tumor-to-background ratio = 11.63 ± 4.16 at 24 h). This study demonstrates that ODAP-Urea-based P3 has the potential for PET imaging and intraoperative optical imaging of prostate cancer.

Discovery of N-substituted-3-phenyl-1,6-naphthyridinone derivatives bearing quinoline moiety as selective type II c-Met kinase inhibitors against VEGFR-2.

New N-substituted-3-phenyl-1,6-naphthyridinone derivatives are designed and synthesized, based on structural modification of our previously reported compound 3. Extensive enzyme-based SAR studies and PK evaluation led to the discovery of compound 4r, with comparable c-Met potency to that of Cabozantinib and high VEGFR-2 selectivity, while Cabozantinib displayed no VEGFR-2 selectivity. More importantly, at oral doses of 45 mg/kg (Q.D.), compound 4r exhibits significant tumor growth inhibition (93%) in a U-87MG human gliobastoma xenograft model. The promising selectivity against VEGFR-2 and excellent tumor growth inhibition of compound 4r suggest that it could be used as a new lead molecule for further discovery of selective type II c-Met inhibitors.

Platinum(II)-Based Convex Trigonal-Prismatic Cages via Coordination-Driven Self-Assembly and C60 Encapsulation.

The development of three-dimensional (3D) supramolecular coordination complexes is of great interest from both fundamental and application points of view because these materials are useful in molecular catalysis, separation and purification, sensing, etc. Herein, we describe the synthesis of two Klärner's molecular-clip-based tetrapyridyl donors, which possess a C-shaped structure as shown by X-ray analysis, and subsequently use them to prepare four convex trigonal-prismatic cages via coordination-driven self-assembly with two 180° diplatinum(II) acceptors. The cages are fully characterized by multinuclear NMR (31P and 1H) analysis, diffusion-ordered spectroscopy, electrospray ionization time-of-flight mass spectrometry, and UV/vis absorption spectroscopy. Moreover, the incorporation of molecular-clip-based ligands provides these cages with free cavities to encapsulate fullerene C60 via aromatic interactions, which may be useful for fullerene separation and purification. The studies described herein enlarge the scope of the platinum(II)-based directional bonding approach in the preparation of curved 3D metallacages and their host-guest chemistry.

Pharmacogenomic profiling of intra-tumor heterogeneity using a large organoid biobank of liver cancer.

Inter- and intra-tumor heterogeneity is a major hurdle in primary liver cancer (PLC) precision therapy. Here, we establish a PLC biobank, consisting of 399 tumor organoids derived from 144 patients, which recapitulates histopathology and genomic landscape of parental tumors, and is reliable for drug sensitivity screening, as evidenced by both in vivo models and patient response. Integrative analysis dissects PLC heterogeneity, regarding genomic/transcriptomic characteristics and sensitivity to seven clinically relevant drugs, as well as clinical associations. Pharmacogenomic analysis identifies and validates multi-gene expression signatures predicting drug response for better patient stratification. Furthermore, we reveal c-Jun as a major mediator of lenvatinib resistance through JNK and ß-catenin signaling. A compound (PKUF-01) comprising moieties of lenvatinib and veratramine (c-Jun inhibitor) is synthesized and screened, exhibiting a marked synergistic effect. Together, our study characterizes the landscape of PLC heterogeneity, develops predictive biomarker panels, and identifies a lenvatinib-resistant mechanism for combination therapy.

Conformational adjustment overcomes multiple drug-resistance mutants of tropomyosin receptor kinase.

Mutation-induced resistance to targeted drug treatment poses a serious threat to successful chemotherapy. Multiple mutations underlying drug resistance remain a largely unsolved scientific issue. Tropomyosin receptor kinases (TRKs) are promising therapeutic targets for several malignant human cancers, but they have become less effective due to multiple resistance mutations. Thus, TRKs are representative cases to explore the problem of multiple resistance mutations. Here, we proposed a conformational adjustment strategy of drug design to overcome multiple resistance mutations in cancer treatments. A representative inhibitor, TIY-7, exhibited remarkable inhibitory activity against five TRK mutants, showing an IC50 value of 1.1 nM against the most severe mutant TRKA-G595R. Moreover, it displayed superior tumor growth inhibitory activity compared with the clinically used drug selitrectinib. These results validated our strategy to design a new inhibitor structure to overcome multiple resistance mutations.

Discovery of 3-pyrazolyl-substituted pyrazolo[1,5-a]pyrimidine derivatives as potent TRK inhibitors to overcome clinically acquired resistance.

Several secondary tropomyosin receptor kinase (TRK) mutations located in the solvent front, xDFG, and gatekeeper regions, are a common cause of clinical resistance. Mutations in the xDFG motif in particular limit sensitivity to second-generation TRK inhibitors, which represent an unmet clinical need. We designed a series of 3-pyrazolyl-substituted pyrazolo[1,5-a]pyrimidine derivatives toward these secondary mutations using ring-opening and scaffold-hopping strategies. Compound 5n was the most potent, with IC50 values of 2.3 nM, 0.4 nM, and 0.5 nM against TRKAG667C, TRKAF589L, and TRKAG595R, compared to selitrectinib with IC50 values of 12.6 nM, 5.8 nM, and 7.6 nM, respectively (approximately 5.4, 14.5, and 15.2-fold increases). Furthermore, 5n displayed favorable pharmacokinetic properties and satisfactory antitumor efficacy (tumor growth inhibition of 97% at 30 mg/kg and 73% at 100 mg/kg) in TRKAWT and TRKAG667C xenograft mouse models. Collectively, 5n is a promising TRK inhibitor lead compound for overcoming clinically acquired resistance to second-generation inhibitors, particularly for resistant tumors harboring the TRKAG667C mutation in the xDFG motif.

Noninvasive interrogation of CD8+ T cell effector function for monitoring early tumor responses to immunotherapy.

Accurately identifying patients who respond to immunotherapy remains clinically challenging. A noninvasive method that can longitudinally capture information about immune cell function and assist in the early assessment of tumor responses is highly desirable for precision immunotherapy. Here, we show that PET imaging using a granzyme B-targeted radiotracer named 68Ga-grazytracer, could noninvasively and effectively predict tumor responses to immune checkpoint inhibitors and adoptive T cell transfer therapy in multiple tumor models. 68Ga-grazytracer was designed and selected from several radiotracers based on non-aldehyde peptidomimetics, and exhibited excellent in vivo metabolic stability and favorable targeting efficiency to granzyme B secreted by effector CD8+ T cells during immune responses. 68Ga-grazytracer permitted more sensitive discrimination of responders and nonresponders than did 18F-fluorodeoxyglucose, distinguishing between tumor pseudoprogression and true progression upon immune checkpoint blockade therapy in mouse models with varying immunogenicity. In a preliminary clinical trial with 5 patients, no adverse events were observed after 68Ga-grazytracer injection, and clinical responses in cancer patients undergoing immunotherapy were favorably correlated with 68Ga-grazytracer PET results. These results highlight the potential of 68Ga-grazytracer PET to enhance the clinical effectiveness of granzyme B secretion-related immunotherapies by supporting early response assessment and precise patient stratification in a noninvasive and longitudinal manner.

Insights into SARS-CoV-2: Medicinal Chemistry Approaches to Combat Its Structural and Functional Biology.

Coronavirus disease 2019, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is still a pandemic around the world. Currently, specific antiviral drugs to control the epidemic remain deficient. Understanding the details of SARS-CoV-2 structural biology is extremely important for development of antiviral agents that will enable regulation of its life cycle. This review focuses on the structural biology and medicinal chemistry of various key proteins (Spike, ACE2, TMPRSS2, RdRp and Mpro) in the life cycle of SARS-CoV-2, as well as their inhibitors/drug candidates. Representative broad-spectrum antiviral drugs, especially those against the homologous virus SARS-CoV, are summarized with the expectation they will drive the development of effective, broad-spectrum inhibitors against coronaviruses. We are hopeful that this review will be a useful aid for discovery of novel, potent anti-SARS-CoV-2 drugs with excellent therapeutic results in the near future.

Discovery of Next-Generation Tropomyosin Receptor Kinase Inhibitors for Combating Multiple Resistance Associated with Protein Mutation.

Tropomyosin receptor kinase (TRK) inhibition is an effective therapeutic approach for treatment of a variety of cancers. Despite the use of first-generation TRK inhibitor (TRKI) larotrectinib (1) resulting in significant therapeutic response in patients, acquired resistance develops invariably. The emergence of secondary mutations occurring at the solvent-front, xDFG, and gatekeeper regions of TRK represents a common mechanism for acquired resistance. However, xDFG mutations remain insensitive to second-generation macrocyclic TRKIs selitrectinib (3) and repotrectinib (4) designed to overcome the resistance mediated by solvent-front and gatekeeper mutations. Here, we report the structure-based drug design and discovery of a next-generation TRKI. The structure-activity relationship studies culminated in the identification of a promising drug candidate 8 that showed excellent in vitro potency on a panel of TRK mutants, especially TRKAG667C in the xDFG motif, and improved in vivo efficacy than 1 and 3 in TRK wild-type and mutant fusion-driven tumor xenograft models, respectively.

Efficient Arylation of 2,7-Naphthyridin-1(2H)-one with Diaryliodonium Salts and Discovery of a New Selective MET/AXL Kinase Inhibitor.

New 8-chloro-2-phenyl-2,7-naphthyridin-1(2H)-one building blocks bearing diverse substitutes on the 2-phenyl group were synthesized via an efficient diaryliodonium salt-based N-arylation strategy with the advantage of mild conditions, short reaction times, and high yields. A small combinatorial library of 8-amino substituted 2-phenyl-2,7-naphthyridin-1(2H)-one was further conveniently constructed based on the above chlorinated naphthyridinones and substituted aniline. Preliminary biochemical screening resulted in the discovery of the new 2,7-naphthyridone-based MET/AXL kinase inhibitors. More importantly, 17c (IC50,MET of 13.8 nM) or 17e (IC50,AXl of 17.2 nM) and 17i (IC50,AXl of 31.8 nM) can efficient selectively inhibit MET or AXL kinase, respectively, while commercial cabozantinib showed no selectivity. The further exploration of the 8-substituted 2-phenyl-2,7-naphthyridin-1(2H)-one combinatorial library would significantly accelerate the discovery of more potent and selective inhibitors against diverse kinases.

Structure-activity relationship study of novel quinazoline-based 1,6-naphthyridinones as MET inhibitors with potent antitumor efficacy.

As a privileged scaffold, the quinazoline ring is widely used in the development of EGFR inhibitors, while few quinazoline-based MET inhibitors are reported. In our ongoing efforts to develop new MET-targeted anticancer drug candidates, a series of quinazoline-based 1,6-naphthyridinone derivatives were designed, synthesized, and evaluated for their biological activities. The preliminary SARs studies indicate that the quinazoline scaffold was also acceptable for the block A of class II MET inhibitors. The further pharmacokinetic studies led to the identification of the most promising compound 22a with favorable in vitro potency (MET, IC50 = 9.0 nM), human microsomal metabolic stability (t1/2 = 621.2 min) and oral bioavailability (F = 42%). Moreover, 22a displayed good in vivo antitumor efficacy (IR of 81% in 75 mg/kg) in MET-positive human glioblastoma U-87 MG xenograft model. These positive results indicated that 22a is a potential new MET-targeted antitumor drug lead, which is worthy of further development.

Ultrafast 2,7-Naphthyridine-Based fluorescent probe for detection of thiophenol with a remarkable Stokes shift and its application In vitro and in vivo.

2,7-Naphthyridine derivatives were developed as fluorophores for the first time to design two fluorescence probes, AND-DNP and ND-DNP, which can be applied for detecting thiophenol in aqueous media. Comparing with ND-DNP, AND-DNP showed more favorable properties such as lower background, larger Stokes shift, and higher fluorescence quantum yield for detecting thiophenol. Moreover, the experimental results were verified by theoretical calculations. Hence, AND-DNP was selected as the superior fluorescence probe to detect thiophenol because of its high sensitivity and selectivity. Based on the experimental results, AND-DNP showed a remarkably larger Stokes shift (225 nm), faster response speed (30 s) and higher fluorescence enhancement (240-fold) than most other fluorescent probes for thiophenol reported in the literature. For an extended application, AND-DNP was applied to detect thiophenol quantitatively in real water samples. Meanwhile, AND-DNP also detected thiophenol via red emission in living A549 cells and zebrafish. All these results proved AND-DNP's potential value as an accurate probe for imaging thiophenol in different environments.

2,7-naphthyridinone-based MET kinase inhibitors: A promising novel scaffold for antitumor drug development.

As part of our effort to develop new molecular targeted antitumor drug, a novel 2,7-naphthyridone-based MET kinase inhibitor, 8-((4-((2-amino-3-chloropyridin-4-yl)oxy)- 3-fluorophenyl)amino)-2-(4-fluorophenyl)-2,7-naphthyridin-1(2H)-one (13f), was identified. Knowledge of the binding mode of BMS-777607 in MET led to the design of new inhibitors that utilize novel 2,7-naphthyridone scaffold to conformationally restrain the key pharmacophoric groups (block C). Detailed SAR studies resulted in the discovery of a new MET inhibitor 13f, displaying favorable in vitro potency and oral bioavailability. More importantly, 13f exhibited excellent in vivo efficacy (tumor growth inhibition/TGI of 114% and 95% in 50 mg/kg, respectively) both in the U-87 MG and HT-29 xenograft models. The favorable drug-likeness of 13f indicated that 2,7-naphthyridinone may be used a promising novel scaffold for antitumor drug development. The preclinical studies of 13f are under way.