Development of a high-throughput screening system targeting the protein-protein interactions between PRL and CNNM.

Phosphatase of regenerating liver (PRL) is an oncogenic protein that promotes tumor progression by directly binding to cyclin M (CNNM) membrane proteins and inhibiting their Mg2+ efflux activity. In this study, we have developed a high-throughput screening system to detect the interactions between PRL and CNNM proteins based on homogenous time-resolved fluorescence resonance energy transfer (HTR-FRET, HTRF). We optimized the tag sequences attached to the recombinant proteins of the CNNM4 CBS domains and PRL3 lacking the carboxyl terminal CAAX motif, and successfully detected the interaction by observing the FRET signal in the mixture of the tagged proteins and fluorophore-conjugated antibodies. Moreover, we performed compound library screening using this system and discovered several compounds that could efficiently inhibit the PRL-CNNM interaction. Characterization of one candidate compound revealed that it was relatively stable compared with thienopyridone, a known inhibitor of the PRL-CNNM interaction. The candidate compound can also inhibit PRL function in cells: suppression of CNNM-dependent Mg2+ efflux, and has sufficient in vitro drug metabolism and pharmacokinetic properties. Overall, these results demonstrate the effectiveness of this screening system for identifying novel inhibitors of the PRL-CNNM interaction, which could contribute to the development of novel anti-cancer drugs.

Survival of men with metastatic hormone-sensitive prostate cancer and adrenal-permissive HSD3B1 inheritance.

BACKGROUNDMetastatic hormone-sensitive prostate cancer (mHSPC) is androgen dependent, and its treatment includes androgen deprivation therapy (ADT) with gonadal testosterone suppression. Since 2014, overall survival (OS) has been prolonged with addition of other systemic therapies, such as adrenal androgen synthesis blockers, potent androgen receptor blockers, or docetaxel, to ADT. HSD3B1 encodes the rate-limiting enzyme for nongonadal androgen synthesis, 3ß-hydroxysteroid dehydrogenase-1, and has a common adrenal-permissive missense-encoding variant that confers increased synthesis of potent androgens from nongonadal precursor steroids and poorer prostate cancer outcomes.METHODSOur prespecified hypothesis was that poor outcome associated with inheritance of the adrenal-permissive HSD3B1 allele with ADT alone is reversed in patients with low-volume (LV) mHSPC with up-front ADT plus addition of androgen receptor (AR) antagonists to inhibit the effect of adrenal androgens. HSD3B1 genotype was obtained in 287 patients with LV disease treated with ADT + AR antagonist only in the phase III Enzalutamide in First Line Androgen Deprivation Therapy for Metastatic Prostate Cancer (ENZAMET) trial and was associated with clinical outcomes.RESULTSPatients who inherited the adrenal-permissive HSD3B1 allele had more favorable 5-year clinical progression-free survival and OS when treated with ADT plus enzalutamide or ADT plus nonsteroidal antiandrogen compared with their counterparts who did not have adrenal-permissive HSD3B1 inheritance. HSD3B1 was also associated with OS after accounting for known clinical variables. Patients with both genotypes benefited from early enzalutamide.CONCLUSIONThese data demonstrated an inherited physiologic driver of prostate cancer mortality is associated with clinical outcomes and is potentially pharmacologically reversible.FUNDINGNational Cancer Institute, NIH; Department of Defense; Prostate Cancer Foundation, Australian National Health and Medical Research Council.

Clinical Assessment of Breast Cancer Resistance Protein (BCRP)-Mediated Drug-Drug Interactions of Sepiapterin with Curcumin and Rosuvastatin in Healthy Volunteers.

BACKGROUND AND OBJECTIVE: Sepiapterin, also known as PTC923 and CNSA-001, is a synthetic form of endogenous sepiapterin being developed as a novel oral treatment for phenylketonuria. Sepiapterin is a natural precursor of tetrahydrobiopterin (BH4) and, when orally administered, is converted to BH4 via the pterin salvage pathway. In vitro studies have demonstrated that both sepiapterin and BH4 are both substrates and inhibitors of the breast cancer resistance protein (BCRP) transporter. This phase I study investigated BCRP-mediated drug-drug interactions of sepiapterin as a victim and as a perpetrator. METHODS: An open-label, fixed-sequence, four-period, crossover, single-dose study was conducted in adult male and female healthy volunteers (18-55 years of age). In a given treatment period, subjects received a single oral dose of sepiapterin (20 mg/kg), sepiapterin (20 mg/kg) plus curcumin (2 g), rosuvastatin (10 mg), or rosuvastatin (10 mg) plus sepiapterin (60 mg/kg). The pharmacokinetics of sepiapterin, its metabolite BH4, and rosuvastatin were studied, and geometric mean ratios of exposures in the presence and absence of the BCRP inhibitor curcumin or sepiapterin were estimated. The presence of the BCRP c.421C>A polymorphism was evaluated in all subjects. RESULTS: A total of 29 subjects were enrolled and included in the safety analysis. Among them, 26 subjects were included in the pharmacokinetic and drug-drug interaction analyses. Following oral administration 20 mg/kg sepiapterin, sepiapterin was rapidly and extensively converted to BH4, and BH4 maximum observed concentration (415.0 ng/mL) was observed 4.95 h (time to maximum observed concentration) post-dose. Sepiapterin maximum observed concentration and area under the concentration-time curve from time 0 to time of the last quantifiable measurement or the last sample collection time (AUClast) were <1% of BH4 values. Coadministration of the BCRP inhibitor curcumin (2 g) increased BH4 maximum observed concentration, AUClast, and area under the concentration-time curve from time 0 extrapolated to infinity by 24%, 21%, and 20%, respectively. When sepiapterin was coadministered with the BCRP substrate rosuvastatin, there was no effect on the pharmacokinetics of rosuvastatin. BCRP c.421C/A carriers (n = 4) had higher plasma exposures of BH4 (1.39 × for AUClast) and rosuvastatin (1.61 × for AUClast) than c.421C/C carriers (n = 22). Greater increases in BH4 exposures (1.33 vs 1.18 for AUClast) were observed in c.421C/A carriers compared with c.421C/C carriers when sepiapterin was coadministered with curcumin. All treatments were well tolerated during the study. CONCLUSIONS: Oral coadministration of the BCRP inhibitor curcumin slightly increased the plasma exposure of sepiapterin and its metabolite BH4 in healthy volunteers. This modest increase was deemed not clinically meaningful. Sepiapterin did not alter the pharmacokinetics of the BCRP substrate rosuvastatin.

A phase I drug-drug interaction study to assess the effect of futibatinib on P-gp and BCRP substrates and of P-gp inhibition on the pharmacokinetics of futibatinib.

Futibatinib, an inhibitor of fibroblast growth factor receptor 1-4, is approved for the treatment of patients with advanced cholangiocarcinoma with FGFR2 fusions/rearrangements. In this phase I drug-drug interaction study, the effects of futibatinib on P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP) substrates, and of P-gp inhibition on futibatinib pharmacokinetics (PK) were investigated in healthy adults aged 18-55 years. In part 1, 20 participants received digoxin (P-gp substrate) and rosuvastatin (BCRP substrate). Following a ≥10-day washout, futibatinib was administered for 7 days, with digoxin and rosuvastatin coadministered on the third day. In part 2, 24 participants received futibatinib. Following a ≥3-day washout, quinidine (P-gp inhibitor) was administered for 4 days, with futibatinib coadministered on day 4. Blood samples were collected predose and for 24 (futibatinib), 72 (rosuvastatin), and 120 h (digoxin) postdose. Urine samples (digoxin) were collected predose and for 120 h postdose. PK parameters were compared between treatments using analysis of variance. Coadministration with futibatinib had no effect on the PK of digoxin and rosuvastatin, and coadministration with quinidine had minimal effects on the PK of futibatinib. Differences in Cmax and AUC with and without futibatinib and quinidine, respectively, were <20%. The most common treatment-emergent adverse events were diarrhea (80%) and increased blood phosphorous (75%) in part 1 and prolonged electrocardiogram QT interval (38%) in part 2. The data show that futibatinib has no clinically meaningful effects on the PK of P-gp or BCRP substrates and that the effect of P-gp inhibition on futibatinib PK is not clinically relevant.

Short Communication: Novel Di- and Triselenoesters as Effective Therapeutic Agents Inhibiting Multidrug Resistance Proteins in Breast Cancer Cells.

Breast cancer has the highest incidence rate among all malignancies worldwide. Its high mortality is mainly related to the occurrence of multidrug resistance, which significantly limits therapeutic options. In this regard, there is an urgent need to develop compounds that would overcome this phenomenon. There are few reports in the literature that selenium compounds can modulate the activity of P-glycoprotein (MDR1). Therefore, we performed in silico studies and evaluated the effects of the novel selenoesters EDAG-1 and EDAG-8 on BCRP, MDR1, and MRP1 resistance proteins in MCF-7 and MDA-MB-231 breast cancer cells. The cytometric analysis showed that the tested compounds (especially EDAG-8) are inhibitors of BCRP, MDR1, and MRP1 efflux pumps (more potent than the reference compounds-novobiocin, verapamil, and MK-571). An in silico study correlates with these results, suggesting that the compound with the lowest binding energy to these transporters (EDAG-8) has a more favorable spatial structure affecting its anticancer activity, making it a promising candidate in the development of a novel anticancer agent for future breast cancer therapy.

Multitargeted molecular docking and dynamics simulation studies of 1,3,4-thiadiazoles synthesised from (R)-carvone against specific tumour protein markers: An In-silico study of two diastereoisomers.

In the present work, we describe the synthesis of new 1,3,4-thiadiazole derivatives from natural (R)-carvone in three steps including, dichloro-cyclopropanation, a condensation with thiosemicarbazide and then a 1,3-dipolar cycloaddition reaction with various nitrilimines. the targeted compounds were structurally identified by 1H & 13C NMR and HRMS analyses. The cytotoxic assay demonstrated that some synthesized novel compounds were potent on certain cancer cell lines. Molecular modeling studies were undertaken to rationalize the wet lab study results. Furthermore, molecular docking was performed to unveil the binding potential of the most active derivatives, 3a and 6c, to caspase-3 and COX-2. The stabilities of the protein-compound complexes obtained from the docking were evaluated using MD simulation. Furthermore, FMO and related parameters of the active compounds and their stereoisomers were examined through DFT studies. The docking study showed compound 6c had a higher binding potential than caspase-3. However, the binding strength of 6c was found to be less than that of the standard drug, doxorubicin, as it formed lower conventional hydrogen bonds. On the other hand, compound 3a had a higher binding potential to COX-2. However, the binding potential 3a was much lower than that of the standard COX-2 inhibitor, celecoxib. The MD simulation demonstrated that the caspase-3-6c complex was less stable than the caspase-3-doxorubicin complex. In contrast, the COX-2-3a complex was stable, and 3a was anticipated to remain inside the protein's binding pocket. The DFT study showed that 3a had higher chemical stability than 6c. The electron exchange capacity, chemical stability, and molecular orbital distributions of the stereoisomers of the active compounds were also found to be alike.

Development of Ligands and Degraders Targeting MAGE-A3.

Type I melanoma antigen (MAGE) family members are detected in numerous tumor types, and expression is correlated with poor prognosis, high tumor grade, and increased metastasis. Type I MAGE proteins are typically restricted to reproductive tissues, but expression can recur during tumorigenesis. Several biochemical functions have been elucidated for them, and notably, MAGEs regulate proteostasis by serving as substrate recognition modules for E3 ligase complexes. The repertoire of E3 ligase complexes that can be hijacked for targeted protein degradation continues to expand, and MAGE-E3 complexes are an especially attractive platform given their cancer-selective expression. Additionally, type I MAGE-derived peptides are presented on cancer cell surfaces, so targeted MAGE degradation may increase antigen presentation and improve immunotherapy outcomes. Motivated by these applications, we developed novel, small-molecule ligands for MAGE-A3, a type I MAGE that is widely expressed in tumors and associates with TRIM28, a RING E3 ligase. Chemical matter was identified through DNA-encoded library (DEL) screening, and hit compounds were validated for in vitro binding to MAGE-A3. We obtained a cocrystal structure with a DEL analog and hypothesize that the small molecule binds at a dimer interface. We utilized this ligand to develop PROTAC molecules that induce MAGE-A3 degradation through VHL recruitment and inhibit the proliferation of MAGE-A3 positive cell lines. These ligands and degraders may serve as valuable probes for investigating MAGE-A3 biology and as foundations for the ongoing development of tumor-specific PROTACs.

Effect of midostaurin on the pharmacokinetics of P-gp, BCRP, and CYP2D6 substrates: assessing potential drug-drug interactions in healthy participants : Brief title: Drug-drug interaction of midostaurin.

PURPOSE: Midostaurin, approved for FLT3-mutated acute myeloid leukemia and advanced systemic mastocytosis, is mainly metabolized by cytochrome P450 (CYP) 3A4. Midostaurin exhibited potential inhibitory effects on P-glycoprotein (P-gp), breast cancer resistance protein (BCRP), organic anion-transporting polyprotein 1B1, and CYP2D6 in in vitro studies. This study investigated the pharmacokinetic (PK) effects of midostaurin on P-gp (digoxin), BCRP (rosuvastatin) and CYP2D6 (dextromethorphan) substrates in healthy adults. METHODS: This was an open-label, single-sequence, phase I clinical study evaluating the effect of single-dose midostaurin (100 mg) on the PK of digoxin and rosuvastatin (Arm 1), and dextromethorphan (Arm 2). Participants were followed up for safety 30 days after last dose. In addition, the effect of midostaurin on the PK of dextromethorphan metabolite (dextrorphan) was assessed in participants with functional CYP2D6 genes in Arm 2. RESULTS: The effect of midostaurin on digoxin was minor and resulted in total exposure (AUC) and peak plasma concentration (Cmax) that were only 20% higher. The effect on rosuvastatin was mild and led to an increase in AUCs of approximately 37-48% and of 100% in Cmax. There was no increase in the primary PK parameters (AUCs and Cmax) of dextromethorphan in the presence of midostaurin. The study treatments were very well tolerated with no occurance of severe adverse events (AEs), AEs of grade ≥ 2, or deaths. CONCLUSION: Midostaurin showed only a minor inhibitory effect on P-gp, a mild inhibitory effect on BCRP, and no inhibitory effect on CYP2D6. Study treatments were well tolerated in healthy adults.

Discovery of a novel highly specific, fully human PSCA antibody and its application as an antibody-drug conjugate in prostate cancer.

Prostate stem cell antigen (PSCA) is expressed in all stages of prostate cancer, including in advanced androgen-independent tumors and bone metastasis. PSCA may associate with prostate carcinogenesis and lineage plasticity in prostate cancer. PSCA is also a promising theranostic marker for a variety of other solid tumors, including pancreatic adenocarcinoma and renal cell carcinoma. Here, we identified a novel fully human PSCA antibody using phage display methodology. The structure-based affinity maturation yielded a high-affinity binder, F12, which is highly specific and does not bind to 6,000 human membrane proteins based on a membrane proteome array assay. F12 targets PSCA amino acids 63-69 as tested by the peptide scanning microarray, and it cross-reacts with the murine PSCA. IgG1 F12 efficiently internalizes into PSCA-expressing tumor cells. The antimitotic reagent monomethyl auristatin E (MMAE)-conjugated IgG1 F12 (ADC, F12-MMAE) exhibits dose-dependent efficacy and specificity in a human prostate cancer PC-3-PSCA xenograft NSG mouse model. This is a first reported ADC based on a fully human PSCA antibody and MMAE that is characterized in a xenograft murine model, which warrants further optimizations and investigations in additional preclinical tumor models, including prostate and other solid tumors.

Ticagrelor modestly raises plasma riboflavin concentration in humans and inhibits riboflavin transport by BCRP and MRP4.

Riboflavin (vitamin B2) has been proposed as a biomarker for breast cancer resistance protein (BCRP) activity. In recent studies in mice, cynomolgus monkeys, and humans, BCRP-inhibiting drugs increased the plasma concentration of riboflavin. We showed recently that ticagrelor inhibits BCRP and raises the plasma concentrations of the BCRP substrate rosuvastatin in healthy volunteers. In the same drug-drug interaction study, we now investigated whether ticagrelor affects the plasma concentrations of riboflavin. Intake of 90 mg ticagrelor increased the ratio between the peak plasma riboflavin concentration and the fasting riboflavin concentration before ticagrelor administration by 1.20-fold (90% confidence interval, 1.10-1.32; P = 0.006) compared to placebo. In vitro, riboflavin was transported by BCRP and multidrug-resistance-associated protein 4 (MRP4) but no clear transport was observed by MRP2, MRP3, or the P-glycoprotein. Moreover, ticagrelor inhibited the transport of riboflavin in BCRP- and MRP4-expressing membrane vesicles with unbound 50% inhibitory concentrations of 0.020 and 1.1 µM, respectively. Based on vesicle and tissue protein expression data, the small intestinal MRP4-mediated efflux clearance of riboflavin (1.2-1.4 nL/min/mg) was estimated to be similar to that mediated by BCRP (0.23-1.3 nL/min/mg). As MRP4 is expressed in the basolateral membrane of enterocytes, it may facilitate the absorption of riboflavin and impair the utility of riboflavin as a biomarker of intestinal BCRP. To conclude, ticagrelor modestly raises the plasma concentration of riboflavin probably by inhibiting intestinal BCRP. Inhibition of intestinal MRP4 may have reduced the absorption of riboflavin and limited the effect of ticagrelor on riboflavin levels.

Structural and theoretical basis for drug development targeting TMEM16A: Inhibition mechanism of tracheloside analogs.

Ion channels play a crucial role in the electrophysiological activities of organisms. The calcium-activated chloride channel TMEM16A is involved in various physiological processes. Therefore, inhibitors of TMEM16A are used to treat diseases caused by TMEM16A dysfunction. However, the unclear inhibition mechanism hinders the progress of drug development. Based on our previous study, we found that the molecular structures of TMEM16A inhibitors tracheloside, matairesinoside and arctigenin are similar. In this study, we conducted a structure-based virtual screening of tracheloside analogs from the PubChem database. The six tracheloside analogs with the highest affinity to TMEM16A were selected, and their inhibitory effects were detected by fluorescence and electrophysiological experiments. Subsequently, the interaction between the tracheloside analogs and TMEM16A was investigated through molecular docking and site-directed mutagenesis. Based on the above results, the mechanism of inhibition of TMEM16A gated conformation by tracheloside analogs was proposed. These findings provide a structural and theoretical basis for drug development targeting TMEM16A.

HIV-protease inhibitors potentiate the activity of carfilzomib in triple-negative breast cancer.

BACKGROUND: Resistance to chemotherapy is a major problem in the treatment of patients with triple-negative breast cancer (TNBC). Preclinical data suggest that TNBC is dependent on proteasomes; however, clinical observations indicate that the efficacy of proteasome inhibitors in TNBC may be limited, suggesting the need for combination therapies. METHODS: We compared bortezomib and carfilzomib and their combinations with nelfinavir and lopinavir in TNBC cell lines and primary cells with regard to their cytotoxic activity, functional proteasome inhibition, and induction of the unfolded protein response (UPR). Furthermore, we evaluated the involvement of sXBP1, ABCB1, and ABCG2 in the cytotoxic activity of drug combinations. RESULTS: Carfilzomib, via proteasome ß5 + ß2 inhibition, is more cytotoxic in TNBC than bortezomib, which inhibits ß5 + ß1 proteasome subunits. The cytotoxicity of carfilzomib was significantly potentiated by nelfinavir or lopinavir. Carfilzomib with lopinavir induced endoplasmic reticulum stress and pro-apoptotic UPR through the accumulation of excess proteasomal substrate protein in TNBC in vitro. Moreover, lopinavir increased the intracellular availability of carfilzomib by inhibiting carfilzomib export from cells that express high levels and activity of ABCB1, but not ABCG2. CONCLUSION: Proteasome inhibition by carfilzomib combined with nelfinavir/lopinavir represents a potential treatment option for TNBC, warranting further investigation.

Exploring the potential of cryptochlorogenic acid as a dietary adjuvant for multi-target combined lung cancer treatment.

BACKGROUND: Lung cancer is a highly malignant disease with limited treatment options and significant adverse effects. It is urgent to develop novel treatment strategies for lung cancer. In recent years, TMEM16A has been confirmed as a specific drug target for lung cancer. The development of TMEM16A-targeting drugs and combined administration for the treatment of lung cancer has become a research hotspot. METHODS: Fluorescence screening and electrophysiological experiments were conducted to confirm the inhibitory effect of CCA on TMEM16A. Molecular dynamics simulation and site-directed mutagenesis were employed to analyze the binding mode of CCA and TMEM16A. CCK-8, colony formation, wound healing, transwell, and annexin-V experiments were conducted to explore the regulatory effects and mechanisms of CCA on the proliferation, migration, and apoptosis of lung cancer cells. Tumor model mice and pharmacokinetic experiments were used to examine the efficacy and safety of CCA and cisplatin in vivo. RESULTS: This study firstly confirmed that CCA effectively inhibits TMEM16A to exert anticancer effects and analyzed the pharmacological mechanism. CCA bound to S517/N546/E623/E633/Q637 of TMEM16A through hydrogen bonding and electrostatic interactions. It inhibited the proliferation and migration, and induced apoptosis of lung cancer cells by targeting TMEM16A. In addition, the combined administration of CCA and cisplatin exhibited a synergistic effect, enhancing the efficacy of lung cancer treatment while reducing side effects. CONCLUSION: CCA is an effective novel inhibitor of TMEM16A, and it synergizes with cisplatin in anticancer treatment. These findings will provide new research ideas and lead compound for the combination therapy of lung cancer.

Anticancer Effect of Hemin through ANO1 Inhibition in Human Prostate Cancer Cells.

Anoctamin1 (ANO1), a calcium-activated chloride channel, is overexpressed in a variety of cancer cells, including prostate cancer, and is involved in cancer cell proliferation, migration, and invasion. Inhibition of ANO1 in these cancer cells exhibits anticancer effects. In this study, we conducted a screening to identify novel ANO1 inhibitors with anticancer effects using PC-3 human prostate carcinoma cells. Screening of 2978 approved and investigational drugs revealed that hemin is a novel ANO1 inhibitor with an IC50 value of 0.45 µM. Notably, hemin had no significant effect on intracellular calcium signaling and cystic fibrosis transmembrane conductance regulator (CFTR), a cyclic AMP (cAMP)-regulated chloride channel, and it showed a weak inhibitory effect on ANO2 at 3 µM, a concentration that completely inhibits ANO1. Interestingly, hemin also significantly decreased ANO1 protein levels and strongly inhibited the cell proliferation and migration of PC-3 cells in an ANO1-dependent manner. Furthermore, it strongly induced caspase-3 activation, PARP degradation, and apoptosis in PC-3 cells. These findings suggest that hemin possesses anticancer properties via ANO1 inhibition and could be considered for development as a novel treatment for prostate cancer.

In Vitro Investigations into the Potential Drug Interactions of Pseudoginsenoside DQ Mediated by Cytochrome P450 and Human Drug Transporters.

Pseudoginsenoside DQ (PDQ), an ocotillol-type ginsenoside, is synthesized with protopanaxadiol through oxidative cyclization. PDQ exhibits good anti-arrhythmia activity. However, the inhibitory effect of PDQ on the cytochrome 450 (CYP450) enzymes and major drug transporters is still unclear. Inhibition of CYP450 and drug transporters may affect the efficacy of the drugs being used together with PDQ. These potential drug-drug interactions (DDIs) are essential for the clinical usage of drugs. In this study, we investigated the inhibitory effect of PDQ on seven CYP450 enzymes and seven drug transporters with in vitro models. PDQ has a significant inhibitory effect on CYP2C19 and P-glycoprotein (P-gp) with a half-inhibitory concentration (IC50) of 0.698 and 0.41 µM, respectively. The inhibition of CYP3A4 and breast cancer-resistant protein (BCRP) is less potent, with IC50 equal to 2.02-6.79 and 1.08 µM, respectively.

RNASEH2B loss and PARP inhibition in advanced prostate cancer.

BACKGROUNDClinical trials have suggested antitumor activity from PARP inhibition beyond homologous recombination deficiency (HRD). RNASEH2B loss is unrelated to HRD and preclinically sensitizes to PARP inhibition. The current study reports on RNASEH2B protein loss in advanced prostate cancer and its association with RB1 protein loss, clinical outcome, and clonal dynamics during treatment with PARP inhibition in a prospective clinical trial.METHODSWhole tumor biopsies from multiple cohorts of patients with advanced prostate cancer were interrogated using whole-exome sequencing (WES), RNA-Seq (bulk and single nucleus), and IHC for RNASEH2B and RB1. Biopsies from patients treated with olaparib in the TOPARP-A and TOPARP-B clinical trials were used to evaluate RNASEH2B clonal selection during olaparib treatment.RESULTSShallow codeletion of RNASEH2B and adjacent RB1 - colocated at chromosome 13q14 - was common, deep codeletion infrequent, and gene loss associated with lower mRNA expression. In castration-resistant prostate cancer (CRPC) biopsies, RNASEH2B and RB1 mRNA expression correlated, but single nucleus RNA-Seq indicated discordant loss of expression. IHC studies showed that loss of the 2 proteins often occurred independently, arguably due to stochastic second allele loss. Pre- and posttreatment metastatic CRPC (mCRPC) biopsy studies from BRCA1/2 WT tumors, treated on the TOPARP phase II trial, indicated that olaparib eradicated RNASEH2B-loss tumor subclones.CONCLUSIONPARP inhibition may benefit men suffering from mCRPC by eradicating tumor subclones with RNASEH2B loss.TRIAL REGISTRATIONClinicaltrials.gov NCT01682772.FUNDINGAstraZeneca; Cancer Research UK; Medical Research Council; Cancer Research UK; Prostate Cancer UK; Movember Foundation; Prostate Cancer Foundation.

Minimal Involvement of P-gp and BCRP in Oral Absorption of Ensitrelvir, An Oral SARS-CoV-2 3C-like Protease Inhibitor, in a Non-Clinical Investigation.

P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP) are important transporters causing drug-drug interaction (DDI). Here, we investigated the involvement of P-gp and BCRP in the oral absorption of ensitrelvir in non-clinical studies and estimated the DDI risk mediated by P-gp and BCRP inhibition in humans. Although ensitrelvir is an in vitro P-gp and BCRP substrate, it demonstrated high bioavailability in rats and monkeys after oral administration. Plasma exposures of ensitrelvir following oral administration were comparable in wild type (WT) and Bcrp (-/-) mice. On the other hand, the area under the plasma concentration-time curve (AUC) ratio of ensitrelvir in the Mdr1a/1b (-/-) mice to the WT mice was 1.92, indicating that P-gp, but not BCRP, was involved in the oral absorption of ensitrelvir. Based on our previous retrospective analyses, such a low AUC ratio (<3) in the Mdr1a/1b (-/-) mice indicates a minimal impact of P-gp on the oral absorption in humans. In conclusion, our studies demonstrate that the involvement of both P-gp and BCRP in the oral absorption of ensitrelvir is minimal, and suggest that ensitrelvir has a low risk for DDIs mediated by P-gp and BCRP inhibition in humans.

Evaluation of the Clinical Drug-Drug Interaction Potential of Pritelivir on Transporters and CYP450 Enzymes Using a Cocktail Approach.

Pritelivir is a novel viral helicase-primase inhibitor active against herpes simplex virus. In vitro drug-drug interaction studies indicated that pritelivir has the potential for clinically relevant interactions on the cytochrome P450 (CYP) enzymes 2C8, 2C9, 3A4, and 2B6, and intestinal uptake transporter organic anion transporting polypeptide (OATP) 2B1 and efflux transporter breast cancer resistance protein (BCRP). This was evaluated in 2 clinical trials. In 1 trial the substrates flurbiprofen (CYP2C9), bupropion (CYP2B6), and midazolam (CYP3A4) were administered simultaneously as part of the Geneva cocktail, while the substrate celiprolol (OAPT2B1) was administered separately. In another trial, the substrates repaglinide (CYP2C8) and rosuvastatin (BCRP) were administered separately. Exposure parameters of the substrates and their metabolites (flurbiprofen and bupropion only) were compared after administration with or without pritelivir under therapeutic concentrations. The results of these trials indicated that pritelivir has no clinically relevant effect on the exposure of substrates for the intestinal uptake transporter OATP2B1 and the CYP enzymes 3A4, 2B6, 2C9, and 2C8, and has a weak inhibitory effect on the intestinal efflux transporter BCRP. In summary, the results suggest that pritelivir has a low drug-drug interaction potential.

BET bromodomain inhibition potentiates radiosensitivity in models of H3K27-altered diffuse midline glioma.

Diffuse midline glioma (DMG) H3K27-altered is one of the most malignant childhood cancers. Radiation therapy remains the only effective treatment yet provides a 5-year survival rate of only 1%. Several clinical trials have attempted to enhance radiation antitumor activity using radiosensitizing agents, although none have been successful. Given this, there is a critical need for identifying effective therapeutics to enhance radiation sensitivity for the treatment of DMG. Using high-throughput radiosensitivity screening, we identified bromo- and extraterminal domain (BET) protein inhibitors as potent radiosensitizers in DMG cells. Genetic and pharmacologic inhibition of BET bromodomain activity reduced DMG cell proliferation and enhanced radiation-induced DNA damage by inhibiting DNA repair pathways. RNA-Seq and the CUT&RUN (cleavage under targets and release using nuclease) analysis showed that BET bromodomain inhibitors regulated the expression of DNA repair genes mediated by H3K27 acetylation at enhancers. BET bromodomain inhibitors enhanced DMG radiation response in patient-derived xenografts as well as genetically engineered mouse models. Together, our results highlight BET bromodomain inhibitors as potential radiosensitizer and provide a rationale for developing combination therapy with radiation for the treatment of DMG.

Anoctamin pharmacology.

TMEM16 proteins, also known as anoctamins, are a family of ten membrane proteins with various tissue expression and subcellular localization. TMEM16A (anoctamin 1) is a plasma membrane protein that acts as a calcium-activated chloride channel. It is expressed in many types of epithelial cells, smooth muscle cells and some neurons. In airway epithelial cells, TMEM16A expression is particularly enhanced by inflammatory stimuli that also promote goblet cell metaplasia and mucus hypersecretion. Therefore, pharmacological modulation of TMEM16A could be beneficial to improve mucociliary clearance in chronic obstructive respiratory diseases. However, the correct approach to modulate TMEM16A activity (activation or inhibition) is still debated. Pharmacological inhibitors of TMEM16A could also be useful as anti-hypertensive agents given the TMEM16A role in smooth muscle contraction. In contrast to TMEM16A, TMEM16F (anoctamin 6) behaves as a calcium-activated phospholipid scramblase, responsible for the externalization of phosphatidylserine on cell surface. Inhibitors of TMEM16F could be useful as anti-coagulants and anti-viral agents. The role of other anoctamins as therapeutic targets is still unclear since their physiological role is still to be defined.