Potent Selective Inhibitor Research Articles

The Current Landscape for METex14 Skipping Mutations in Non-Small Cell Lung Cancer.

Capmatinib and tepotinib received US Food and Drug Administration (FDA) approval for mesenchymal-epithelial transition (MET) exon 14 (METex14) skipping alteration in 2020 and 2021, respectively. Capmatinib was FDA approved in May 2020 under accelerated approval for the treatment of patients with metastatic non–small cell lung cancer (NSCLC) whose tumors have a mutation that leads to METex14 skipping. Accelerated approval was based on overall response rate and response duration to capmatinib, and it was granted orphan drug and breakthrough therapy designation. Capmatinib is a potent selective kinase inhibitor of the MET receptor, crosses the blood-brain barrier, and has shown low-grade adverse events. Based on phase II data, capmatinib demonstrated an overall response rate (ORR) of 41% and a median duration of response (DOR) of 9.7 months in those who previously received one or two lines of therapy. In treatment-naive patients, capmatinib demonstrated a 68% ORR with a median DOR of 12.6 months. The FDA also granted accelerated approval to tepotinib for adult patients with metastatic NSCLC harboring METex14 skipping alteration. Accelerated approval for tepotinib was based on an ORR of 43% with a median DOR of 10.8 months in treatment-naive patients. Among previously treated patients, the ORR was 43% with a median DOR of 11.1 months. Continued approval for capmatinib and tepotinib is contingent upon confirmatory trials. Both agents are now considered first-line therapy or a subsequent therapy option in patients with metastatic NSCLC who are positive for METex14 skipping alterations.

Radiobrominated probe targeting activated p38α in inflammatory diseases.

p38α, a member of the mitogen-activated protein kinase superfamily, is activated by external stimuli, followed by nuclear translocation for the regulation of inflammatory responses at the transcriptional and translational levels in inflammatory diseases. Thus, activated p38α would be an appropriate target molecule for in vivo noninvasive imaging and targeted radionuclide therapy. For this purpose, we designed a radiobrominated compound, 6-(4-[77Br]bromo-2-fluorophenoxy)-8-methyl-2-(tetrahydro-2H-pyran-4-ylamino)-pyrido[2,3-d]pyrimidin-7(8H)-one ([77Br]4-BR), based on a potent p38α selective inhibitor, R1487, for use with single-photon emission computed tomography. We synthesized [77Br]4-BR and evaluated its effectiveness as an activated p38α imaging probe compared with our previous radioiodinated probe (6-(2-fluoro-4-[125I]iodophenoxy)-8-methyl-2-(tetrahydro-2H-pyran-4-ylamino)-pyrido[2,3-d]pyrimidin-7(8H)-one ([125I]4-IR)) in a mouse inflammatory model. We designed [77Br]4-BR by replacing the radioiodine of [125I]4-IR or the fluorine of R1487 with radiobromine at the 4-position of the phenoxy ring. We synthesized 4-BR via a four-step process. The inhibitory potency of 4-BR was measured using an ADP-Glo™ kinase assay system. Radiosynthesis of [77Br]4-BR was performed via an organotin-radiobromine exchange reaction using the corresponding tributyltin precursor. Radioactivity biodistribution was evaluated in normal ddY mice and turpentine oil-induced inflammation model mice for 120min after intravenous administration of [77Br]4-BR. The temporal changes in radioactivity in blood fractions were compared between [77Br]4-BR and [125I]4-IR. 4-BR was synthesized at a total yield of 9.1% and showed a p38α inhibitory potency similar to that of 4-IR. [77Br]4-BR was successfully obtained from a tributyltin precursor with high radiochemical yield (89.9%), purity (95.9%), and molar activity (2.0 TBq/µmol). [77Br]4-BR showed accumulation of high radioactivity in the inflamed tissue (3.4% ± 0.9% ID/g, peaking at 15min), rapid delivery throughout the body, and rapid blood clearance with approximately half of the blood radioactivity existing as an intact form at 60min. Although the maximum radioactivity accumulation in inflamed tissue after [77Br]4-BR administration was approximately half that of [125I]4-IR because of its faster blood clearance and lower free fraction in the input function, the inflamed tissue-to-blood ratio was comparable between [77Br]4-BR and [125I]4-IR. [77Br]4-BR would be a promising imaging agent for detecting activated p38α in inflammatory diseases.

Abstract 5434: Discovery of SCR-7952, a novel, potent and high selective MAT2A inhibitor shows robust anti-tumor activities and better safety profile

Abstract The metabolic enzyme methionine adenosyltransferase 2A (MAT2A) was identified as a synthetic lethal target in methylthioadenosine phosphorylase (MTAP)-deleted cancers. The co-deletion of MTAP and CDKN2A was observed in approximately 15% of all cancers and predicted worse outcomes, which provides MAT2A a potential therapeutic target. AG-270, a first MAT2A inhibitor, is currently evaluated in early clinical study. Given the inhibitory activity on UGT1A1, a bilirubin uridine diphosphate glucuronosyl transferase regulating the homeostasis of bilirubin, treatment of AG-270 led to the bilirubin increase in patients, which limited the further dose escalation. Therefore, to avoid those off-targeted side effects and maximize benefit from the MAT2A targeted therapy, it is necessary to develop a new generation of MAT2A inhibitor with better activity and higher selectivity, especially, removal of UGT1A1 activity. Here, we report SCR-7952 is a novel MAT2A inhibitor with greater potency and higher selectivity. In biochemical assay, SCR-7952 exhibited potent inhibitory activity on MAT2A enzyme with IC50 of 21 nM, which was more potent than AG-270 (IC50, 68 nM). In HCT116 MTAP-/- cells, SCR-7952 strongly inhibited the cellular SAM production with IC50 of 2 nM, which was significantly more potent than AG-270 (IC50, 6 nM). And SCR-7952 potently inhibited HCT116 MTAP-/- cell growth with IC50 of 53 nM, which was almost 6-fold more potent than AG-270 tested in parallel (IC50, 300 nM). Meanwhile, SCR-7952 displayed more than 20-fold selectivity over the HCT116 parent cells on proliferation assay. However, AG-270 only demonstrated 4-fold selectivity in the same assay. Furthermore, inhibition of SCR-7952 on a panel of 47 life-dependent targets was determined at 10 μM, result showed that there is no significant inhibition observed. In addition to MTAP KO cells, SCR-7952 showed potently inhibited cell growth in multiple cell lines with natural MTAP-deficiency. SCR-7952 revealed excellent oral bioavailability and PK properties in pre-clinical species. In the HCT-116 MTAP-/- xenograft model, SCR-7952 demonstrated robust anti-tumor activity and achieved 72% tumor growth inhibition (TGI) at 1 mpk, QD, which was more potent than AG-270 (TGI 56% at 200 mpk, QD). Furthermore, SCR-7952 was well tolerant and no elevation of bilirubin was observed. In contrast, AG-270 at 200mpk resulted in significant increase of bilirubin. In conclusion, the above data demonstrate that SCR-7952 is a more potent and higher selective MAT2A, and will be filed IND in 2022. Citation Format: Feng Zhou, Feng Tang, Zhiyong Yu, Zhen Li, Wenqing Yang, Liting Xue, Ping Chen, Renhong Tang. Discovery of SCR-7952, a novel, potent and high selective MAT2A inhibitor shows robust anti-tumor activities and better safety profile [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5434.

Abstract 2157: SCR-6277, a potent and high selective arginine methyltransferase 5 (PRMT5) inhibitor with high tumor/plasma distribution ratio demonstrated robust anti-tumor activities and decreased hematological toxicities

Abstract Protein arginine methyltransferase 5 (PRMT5) is observed dysregulation in both solid and hematological tumors. Increasing evidences demonstrated that PRMT5 is a potential therapeutic target. Given the essential role in maintenance of adult hematopoietic cells, inhibition of PRMT5 leads to hematological toxicity. Anemia is the most common treatment related adverse event observed by PRMT5 inhibitor, such as GSK3326595, which limited the dose escalation. Therefore, developing a PRMT5 inhibitor with tumor-biased distribution could be an effective approach to avoid these target related toxicities. In this study, a novel and high selective PRMT5 inhibitor, SCR-6277 was identified. SCR-6277 inhibited the PRMT5 enzyme with an IC50 of 1.5 nM, and showed a high selectivity against other five methyltransferase isoforms (selectivity folds >1000). SCR-6277 potently inhibited the PRMT5-mediated SDMA production in Z-138 cells (IC50, 0.6 nM) and the cell proliferation (IC50, 3 nM). SCR-6277 also demonstrated robustly anti-proliferation activities on multiple PRMT5 proficient solid tumor cell lines (IC50 values ranging from 20 - 130 nM) and no inhibitory effects on PRMT5 deficient cell lines. SCR-6277 had good oral bioavailability and favorable pharmacokinetic properties. In Z-138 and 5637 xenograft models, SCR-6277 robustly inhibited tumor growth. In contrast to GSK3326595, SCR-6277 showed tumor biased distribution. Exposure of SCR-6277 in tumors were 50 folds higher than that in plasma. The extremely high T/P ratio made SCR-6277 achieve the better anti-tumor activities at lower blood exposure (Table 1). In conclusion, SCR-6277 is a novel, potent and high selective PRMT5 inhibitor. And higher tumor/plasma distribution ratio predicts SCR-6277 is a more tolerant and effective PRMT5 inhibitor in human. Table 1. Distribution and anti-tumor activity of SCR-6277 Dose TGI Plasma Conc. (ng/mL) * Tumor Conc. (ng/g) * T/P ratio GSK3326595 50 mpk,BID 87% 45 106 2 SCR-6277 15 mpk,BID 117% 20 668 50 Citation Format: Feng Zhou, Guimei Yang, Feng Tang, Liting Xue, Wenqing Yang, Ping Chen, Renhong Tang. SCR-6277, a potent and high selective arginine methyltransferase 5 (PRMT5) inhibitor with high tumor/plasma distribution ratio demonstrated robust anti-tumor activities and decreased hematological toxicities [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2157.

Abstract 170: Development of diacylglycerol kinase assays to facilitate isoform specific inhibitor discovery

Abstract Diacylglycerol (DAG) and phosphatidic acid (PA) are two key second messengers in signaling and metabolic pathways. Diacylglycerol kinase (DGK) phosphorylate DAG to produce PA, acting as a central switch between the various signal transduction pathways activated by these second messengers. Ten DGK isoforms (α, β, γ, δ, ε, ζ, η, θ, ι, and κ) have been identified and categorized into five classes based on their structural features. DGKα is highly expressed in several cancers including hepatoma, lymphoma and melanoma, and has been shown to promote cancer survival by positively regulating proliferative activity through several signaling pathways, attracting interest to DGKα as a potential therapeutic target. DGKα and ζ are expressed at high levels in T cells, and shown to promote T cell anergy, pointing to inhibition of these DGK isoforms as a means of enhancing T cell anti-tumor activity and restoring T cells function. Several DGK isoforms have also been implicated in disease contexts such as hypertension, autoimmunity, type II diabetes, epilepsy, and bipolar disorder. Current DGK inhibitor discovery efforts are focused on DGKα and ζ, but to our knowledge no compounds have proceeded to clinical trial-to date. To facilitate these efforts, we have developed a DGK screening panel including compound profiling assays for all DGK isoforms. This is an essential tool for identification of potent and isoform selective inhibitors towards therapeutically relevant DGK isoforms. Further, we present kinetic characterization of all isoforms and lipid substrate specificity studies of DGKs. Citation Format: Safnas F. AbdulSalam, Mia M. Eason, Holly A. Fowle, Anna L. Stuart, Kurumi Y. Horiuchi. Development of diacylglycerol kinase assays to facilitate isoform specific inhibitor discovery [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 170.

Identification of novel HDAC8 selective inhibitors through ligand and structure based studies: Exploiting the acetate release channel differences among class I isoforms

Histone deacetylases (HDACs) are key regulators of gene expression and have emerged as crucial therapeutic targets for cancer. Among the HDACs, inhibition of HDAC8 enzyme has been reported to be a novel strategy in the treatment of female-specific cancers. Most of the HDAC inhibitors discovered so far inhibit multiple HDAC isoforms causing toxicities in the clinic thus limiting their potential. Therefore, the discovery of isoform-selective HDAC8 inhibitors is highly desirable. In the present study, a combination of ligand and structure based drug design tools were utilized to build a statistically significant pharmacophore based 3D QSAR model with statistical parameters R 2 : 0.9964, and Q 2 : 0.7154, from a series of 31 known HDAC8 inhibitors. Top 1000 hits obtained from Virtual screening of Phase database were subjected to docking studies against HDAC8. Top 100 hits obtained were redocked into HDAC Class I (HDAC 1,2,3) and Class II isoforms (HDAC 4, 6) and rescored with XP Glide Score. Based on fitness score, XP glide score and interacting amino acid residues, five HDAC8 inhibitors ( 1 – 5 ) were selected for in vitro studies. The HDAC8 activity assay followed by enzyme kinetics clearly indicated Compounds 1 , 2 and 3 to be potent HDAC8 selective inhibitors with IC 50 of 126 pM, 112 nM, and 442 nM respectively. These compounds were cytotoxic to HeLa cells where HDAC8 is overexpressed but not to normal cells, HEK293. Also, they were able to induce apoptosis by modulating Bax/Bcl2, cleavage of PARP and release of Cytochrome C . Molecular Dynamics simulations observed most favorable interaction patterns and presented a rationale for the activities of the identified compounds. Selectivity against HDAC8 was due to exploitation of the architectural difference in the acetate release channel among class I HDAC isoforms.

First-in-human phase 1/2 dose escalation and expansion study evaluating first-in-class eIF4A inhibitor zotatifin in patients with solid tumors.

3081 Background: Zotatifin (eFT226) is a first in class, potent and sequence selective inhibitor of RNA helicase eIF4A1 that promotes stable mRNA:eIF4A:drug ternary complex at specific polypurine motifs within the 5’-UTR, preventing ribosome docking and thus, efficient translation of select transcripts. In preclinical models zotatifin treatment simultaneously down-regulated translation of numerous oncogenes with complex 5’ mRNA structures, including ERBB2, FGFR1/2, EGFR, KRAS, and CCND1. Methods: Patients (pts) with select advanced solid tumors harboring mutations/amplification of ERBB2, FGFR1, FGFR2, EGFR, or KRAS or with pancreatic cancer were enrolled into 3+3 dose escalation portion of the protocol (Part 1), and indication specific expansions continue to enroll at recommended phase 2 dose (RP2D; Part 2). The primary endpoints of Part 1 include determination of safety, tolerability, and maximum tolerated dose (MTD)/RP2D; additional endpoints include characterization of pharmacokinetic, pharmacodynamic (including from blood-based assay during escalation and from pre- and on-treatment biopsy at/near MTD with reverse phase protein array (RPPA)), and initial efficacy. Results: As of cut-off date Jan 13, 2022, Dose escalation phase (Part 1) included 37 patients treated with zotatifin at dose levels: 0.005, 0.01, 0.02, 0.035 mg/Kg IV weekly, and 0.035, 0.05, 0.07, 0.1 mg/kg IV 2 weeks-on and 1 week-off. DLTs were observed in 3 patients: Gr 2 thrombocytopenia (0.035 mg/kg weekly), Gr 3 anemia (0.1 mg/kg) and Gr 3 gastrointestinal bleed resulting in anemia (0.1 mg/kg). MTD/RP2D is 0.07 mg/Kg IV 2 weeks-on and 1 week-off. The most common treatment emergent adverse events (TEAEs) in Part 1 include: fatigue, anemia, diarrhea and dyspnea. The most common AEs at RP2D (n = 16 pts; Part 1 and Part 2) include: anemia (25% all gr 1 or 2), fatigue (25% all gr 1 or 2) and dyspnea (19%; 13% Gr 3) diarrhea (13%, all Gr 1 or 2). Pharmacokinetics were generally linear and dose proportional and exposures at MTD/RP2D are consistent with target pharmacologic levels in preclinical models. Blood based biomarkers showed dose- and time- dependent evidence of target engagement. Pre- and on-treatment biopsy data in expansion patients showed decreased expression of target proteins. No patient in dose escalation experienced an objective tumor response; initial efficacy data from Part 2 and at RP2D will be presented. Conclusions: eIF4A inhibitor zotatifin achieves pharmacologically relevant exposures with on-target AEs that are manageable at the MTD, with evidence of target knockdown from on-treatment biopsies. Part 2 indication-specific expansions (including in ER+ FGFR-amplified MBC as single agent, ER+ MBC in combination with fulvestrant and abemaciclib, and KRAS NSCLC in combination with sotorasib) are on-going. Clinical trial information: NCT04092673.

Inhibiting UCH-L5: Rational Design of a Cyclic Ubiquitin-Based Peptide Inhibitor.

The ubiquitin-proteasome system is an essential regulator of many cellular processes including controlling protein homeostasis. The degradation of proteins by the multi-subunit proteasome complex is tightly regulated through a series of checkpoints, amongst which are a set of deubiquitinating proteases (DUBs). The proteasome-associated DUBs, UCH-L5 (Ubiquitin carboxyl-terminal hydrolase isozyme L5) and USP14 (Ubiquitin-specific protease 14), and the integral-DUB in the proteasome, Rpn11, is known to regulate proteasomal degradation by deubiquitination of distinct substrates. Although selective inhibitors for USP14 and Rpn11 have been recently developed, there are no known inhibitors that selectively bind to UCH-L5. The X-ray structure of the Ubiquitin (Ub) bound to UCH-L5 shows a β-sheet hairpin in Ub that contains a crucial hydrophobic patch involved in the interaction with UCH-L5. Herein, we designed and developed both a Ub sequence-based linear- and cyclic- β-sheet hairpin peptide that was found to preferably inhibit UCH-L5. We show that these peptides have low micromolar IC50 values and the cyclic peptide competes with the activity-based UbVME (Ubiquitin-Vinyl-Methyl-Ester) probe for UCH-L5, binding in a concentration-dependent manner. We further establish the selectivity profile of the cyclic peptide for UCH-L5 compared to other members of the UCH-DUB family and other cysteine DUBs in cell lysate. Furthermore, the cyclic peptide infiltrated cells resulting in the accumulation of polyUb chains, and was found to be non-toxic at the concentrations used here. Taken together, our data suggest that the cyclic peptide permeates the cell membrane, inhibits UCH-L5 by possibly blocking its deubiquitinating function, and contributes to the accumulation of polyubiquitinated substrates. The implications of inhibiting UCH-L5 in the context of the 26S proteasome render it an attractive candidate for further development as a potential selective inhibitor for therapeutic purposes.

Transcriptome‑based drug repositioning identifies TPCA‑1 as a potential selective inhibitor of esophagus squamous carcinoma cell viability.

Esophageal squamous cell carcinoma (ESCC) is a cancer type with limited treatment options. The present study aimed to screen for small molecules that may inhibit ESCC cell viability. The small-molecule-perturbed signatures were extrapolated from the library of integrated network-based cellular signatures (LINCS) database. Since LINCS does not include small-molecule-perturbed signatures of ESCC cells, it was hypothesized that non-ESCC cell lines that display transcriptome profiles similar to those of ESCC may have similar small-molecule-perturbated responses to ESCC cells and that identifying small molecules that inhibit the viability of these non-ESCC cells may also inhibit the viability of ESCC cells. The transcriptomes of >1,000 cancer cell lines from the Cancer Cell Line Encyclopedia database were analyzed and 70 non-ESCC cell lines exhibiting similar transcriptome profiles to those of ESCC cells were identified. Among them, six cell lines with transcriptome signatures upon drug perturbation were available in the LINCS, which were used as reference signatures. A total of 20 ESCC datasets were analyzed and 522 downregulated and 461 upregulated differentially expressed genes (DEGs) that were consistently altered across >50% of the datasets were identified. These DEGs together with the reference signatures were then used as inputs of the ZhangScore method to score small molecules that may reverse transcriptome alterations of ESCC. Among the top-ranked 50 molecules identified by the ZhangScore, four candidates that may inhibit ESCC cell viability were experimentally verified. Furthermore, 2-[(aminocarbonyl)amino]-5-(4-fluorophenyl)-3-thiophenecarboxamide (TPCA-1), an inhibitor of the NF-κB pathway, was able to preferentially inhibit the viability of ESCC cells compared with non-tumorigenic epithelial Het-1A cells. Mechanistically, TPCA-1 induced ESCC KYSE-450 cell apoptosis by inhibiting the phosphorylation of inhibitor of NF-κB kinase subunit β, leading to IκBα stabilization and NF-κB signaling pathway inhibition. Collectively, these results demonstrated that LINCS-based drug repositioning may facilitate drug discovery and that TPCA-1 may be a promising candidate molecule in the treatment of ESCC.

28P Dose determination and pharmacokinetics (PK) of pralsetinib: Results from the phase I ARROW study

The phase 1/2 ARROW (NCT03037385) study supported approval of pralsetinib, a highly potent oral selective RET inhibitor, for RET-altered non-small cell lung cancer (NSCLC) in the US, EU, and other countries, and thyroid cancer (TC) in the US. Here we report data from the phase 1 dose-escalation part of ARROW.

Hit evaluation results in 5-benzyl-1,3,4-thiadiazole-2-carboxamide based SIRT2-selective inhibitor with improved affinity and selectivity

Sirtuin 2 (SIRT2), member of sirtuin family, belongs to class III histone deacetylases (HDACs) and is majorly cytosolic with occasional nuclear translocation. The enzymatic activity of SIRT2 is dependent on nicotinamide adenine dinucleotide (NAD+) and SIRT2 regulates post-translational modifications that are responsible for deacetylation of lysine residues in histone and non-histone substrates. SIRT2, thus affects most likely multiple cellular processes, such as signaling, gene expression, aging, autophagy, and has been identified as potential drug target in relation to inflammation, neurodegenerative diseases and cancer. Therefore, probing potential selective inhibitors is essential for the accurate understanding of enzyme functions. Here, we report a series of heteroaryl-2-carboxamide hybrids bearing substituted benzyl or substituted phenoxy group at the 5-position of the central heterocyclic ring. The synthesized compounds were screened against SIRT1-3 and MCF-7 human breast cancer cell line to evaluate their biological activity. The best SIRT2 inhibition profiles were displayed by ST29 (SIRT2 IC50 = 38.69 μM) and ST30 (SIRT2 IC50 = 43.29 μM) with excellent selectivity against SIRT2 over SIRT1 and SIRT3. Molecular docking study of the synthesized compounds into SIRT2 active site was performed to rationalize the remarkable SIRT2 inhibitory activity. Furthermore, we performed all-atom, explicit-solvent molecular dynamics (MD) simulations and end-point binding free energy calculations using molecular mechanics/generalized Born surface area (MM/GBSA) method to evaluate whether this design strategy was successfully deployed. The results implied that the binding poses and ligand affinities were predicted without significant loss of accuracy. Conclusively, the developed chemotypes were advocated as promising leads for SIRT2 inhibition and required further investigation for SIRT2-targeted drug discovery and development.

Evaluation of phototoxicity induced by the anticancer drug rucaparib

Rucaparib (RCP) is a potent selective inhibitor of both PARP-1 and PARP-2 enzymes that induces synthetic lethality in cancer cells. It is used for the treatment of breast and ovarian tumors harboring deleterious germline or somatic cancer susceptibility genes mutations. Although RCP has an indole chromophore in its structure, it displays a bathochromic shift of the absorption band towards the UVA region of sunlight, thus extending the active fraction of solar light able to produce photosensitivity reactions. In this context, it is highly interesting to study the photo(geno)toxicity disorders associated with this drug, bearing in mind that, for dermatologists it is crucial to understand the toxicity mechanism to improve clinical management. In the present work, RCP has shown to be potentially phototoxic, as observed in the neutral red uptake phototoxicity test. Moreover, this significant phototoxicity is attributed to both proteins and genomic DNA, as revealed in the protein photooxidation and comet assays. The results obtained are highly relevant concerning RCP photosafety and become clinically important in the context of identification of the cutaneous adverse events that can be associated with the targeted therapies. Interestingly, this is the first example of a PARP inhibitor able to induce photosensitized damage to biomolecules.

Updated overall survival (OS) analysis for ProCAID: A randomized, double-blind, placebo-controlled phase II trial of capivasertib with docetaxel versus docetaxel alone in metastatic castration-sensitive prostate cancer (mCRPC).

108 Background: The AKT pathway is frequently deregulated in mCRPC. ProCAID tested addition of capivasertib, a potent selective inhibitor of all three AKT isoforms (AKT1/2/3) to docetaxel chemotherapy vs. placebo plus docetaxel for mCRPC. The primary analysis showed no difference between treatment arms for the primary endpoint of composite progression free survival (cPFS). However, OS, which was a secondary endpoint, was extended in the capivasertib plus docetaxel arm. cPFS and OS results were consistent irrespective of PI3K/AKT/PTEN pathway biomarker status (Crabb et al, J Clin Oncol 2021;39(3):190-201). Methods: An updated analysis of mature OS data was undertaken once events reached ≥65% by Cox proportional hazards model, adjusted for minimisation factors, within the intent to treat (ITT) population (n = 150). Patients (pts) and investigators remained blinded to treatment allocation. We also investigated OS outcomes within subsets based on prior androgen receptor targeted agent (ARTA) exposure to abiraterone and/or enzalutamide (abi/enza) and the balance of post-trial life extending treatment use by treatment arm. Funding: Cancer Research UK (C9317/A16029, CRUK/12/042) and AstraZeneca. Results: At this OS update, 99 pts (66.0%) had died, with 88 of these deaths (88.9%) due to prostate cancer. 5 pts (3.3%) remained on capivasertib or placebo. Median OS was 25.3 months for the capivasertib plus docetaxel arm vs. 20.3 months for placebo plus docetaxel (hazard ratio (HR) 0.70, 95% confidence interval (CI) 0.47 to 1.05; nominal p = 0.09). One, or more, subsequent life extending treatment options, including abiraterone, enzalutamide, radium-223 and cabazitaxel, were received by 99 pts (66.0%) and were balanced between treatment arms (68% capivasertib, 64% placebo). 101 pts (67.3%; 51 capivasertib, 50 placebo) had received abi/enza prior to entering ProCAID. Within this subgroup, OS benefit for capivasertib plus docetaxel (median OS 31.1 months) was maintained vs. placebo plus docetaxel (median OS 19.3 months; HR 0.57, 95% CI 0.36 to 0.91), but not in the remaining 49 pts who were naive to prior abi/enza (median OS 31.1 vs. not reached respectively; HR 1.43, 95% CI 0.63 to 3.23). These updated OS results remained consistent irrespective of biomarker status for PI3K/AKT/PTEN pathway activation. No clinically significant differences from the previously reported safety outcomes were seen with extended follow up of this trial. Conclusions: OS remains longer within the ProCAID ITT population with the addition of capivasertib to docetaxel for mCRPC. This does not appear to be explained by subsequent treatment choices. Exploratory analysis found prolonged OS with capivasertib within a subset of pts previously exposed to an ARTA which should be evaluated in prospective trials. Clinical trial information: NCT02121639.

Abstract OT2-14-01: CAPItello-292: A phase Ib/III study of capivasertib, palbociclib and fulvestrant, versus placebo, palbociclib and fulvestrant, for endocrine therapy-resistant HR+/HER2− advanced breast cancer

Abstract Background: More than two-thirds of advanced breast cancer (ABC) is hormone receptor-positive/human epidermal growth factor receptor 2-negative (HR+/HER2-). Endocrine therapy (ET) is the core treatment for patients with HR+/HER2- ABC, most commonly an aromatase inhibitor (AI), tamoxifen, or the selective estrogen receptor degrader (SERD), fulvestrant. ET is increasingly also combined with a cyclin-dependent kinase (CDK) 4/6 inhibitor, and this has become the first-line standard of care for HR+/HER2- ABC in many countries. However, despite the fact that combination therapy prolongs life compared with ET alone, most patients eventually develop therapy resistance and HR+/HER2- ABC is considered incurable. Overcoming therapy resistance is a major challenge, partially because it is associated with several different mechanisms. The phosphoinositide 3-kinase/protein kinase/phosphatase and tensin homologue (PI3K/AKT/PTEN) pathway regulates cell growth, proliferation and survival. Increased PI3K/AKT/PTEN pathway activity has been observed as one of the key mechanisms driving resistance to the combination therapy of ET and CDK4/6 inhibitors. Capivasertib is a potent selective inhibitor of all three AKT isoforms that suppresses PI3K/AKT/PTEN pathway activity. Capivasertib has demonstrated synergistic anticancer activity with standard ET agents in in vitro and in vivo experimental models. Moreover, the Phase II FAKTION trial found that patients with AI-resistant HR+/HER2- ABC had longer progression-free survival (PFS) when capivasertib was added to fulvestrant therapy, compared with fulvestrant alone. CAPItello-292 is a Phase Ib/III trial examining the safety, tolerability and clinical benefit of adding AKT inhibition (with capivasertib) to combined CDK4/6 inhibition (with palbociclib) and ET (with fulvestrant) for patients with ET-resistant HR+/HER2- ABC. Trial design: CAPItello-292 (NCT04862663) is enrolling patients with HR+/HER2- locally advanced or metastatic breast cancer whose disease progressed or recurred while receiving ET or within 12 months of completing an ET (neo)adjuvant regimen. The Phase Ib trial will identify the recommended Phase III dose (RP3D) for combined capivasertib, palbociclib and fulvestrant therapy. Up to 72 patients will be enrolled for the Phase Ib part. The initial regimen will be capivasertib (320 mg twice daily; 4 days on, 3 days off through each 28-day cycle), palbociclib (125 mg once daily for 21 days of each 28-day cycle) and fulvestrant (500 mg once every 28 days, plus a loading dose on day 15 of the first cycle). In the Phase III part, approximately 628 patients will be randomized 1:1 to receive either the RP3D of the triplet or placebo plus palbociclib and fulvestrant until disease progression, unacceptable toxicity or withdrawal of consent. The Phase III primary endpoint is PFS. Secondary endpoints include safety, tolerability and overall survival, as well as PFS of patients whose tumors have PIK3CA/AKT1/PTEN alterations. The first site for the study was activated in mid-May 2021. As of July 2021, two patients have been dosed in the first cohort. Funding and acknowledgements: CAPItello-292 is funded and overseen by AstraZeneca. AstraZeneca funded medical writing support provided by Rose Goodchild, PhD, of Oxford PharmaGenesis, Oxford, UK. This abstract was previously presented at the 2021 European Society for Medical Oncology (ESMO) Annual Meeting, 3019TiP, Erika Hamilton et al. - Reused with permission. Citation Format: Hope S Rugo, Gaia Schiavon, Lynda M Grinsted, Elza C De Bruin, Maria Teresa Catanese, Erika Hamilton. CAPItello-292: A phase Ib/III study of capivasertib, palbociclib and fulvestrant, versus placebo, palbociclib and fulvestrant, for endocrine therapy-resistant HR+/HER2− advanced breast cancer [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr OT2-14-01.

Selinexor in Combination with Carboplatin and Pemetrexed in Patients with Advanced or Metastatic Solid Tumors: Results of an Open-Label, Single-Center, Multi-Arm Phase 1b Study.

Selinexor in Combination with Carboplatin and Pemetrexed in Patients with Advanced or Metastatic Solid Tumors: Results of an Open-Label, Single-Center, Multi-Arm Phase 1b Study.

Metabolic Disposition of Lurbinectedin, a Potent Selective Inhibitor of Active Transcription of Protein-Coding Genes, in Nonclinical Species and Patients.

Lurbinectedin is a novel and potent selective inhibitor of active transcription of protein-coding genes, triggering apoptosis of cancerous cells. It has been approved for the treatment of patients with metastatic small-cell lung cancer with disease progression on or after platinum-based chemotherapy. Studies exploring the disposition and metabolism of lurbinectedin were performed in vitro and in vivo (by intravenous administration of lurbinectedin). Low blood cell partitioning for lurbinectedin in rats, nonhuman primates (NHP), and humans was determined as 23.4%, 29.8%, and 9.8%, respectively. Protein binding was very high (>95%) in total plasma (rat, NHP, and human), albumin, and α-1-acid glycoprotein (both human). In vitro, lurbinectedin underwent intense liver microsome-mediated metabolism-in 10 minutes, 80% of the compound is metabolized in human-with CYP3A4 being the isoform involved in that metabolism. Results also showed NHPs being the nonclinical species which, metabolically, most closely resembles humans. Mass balance studies performed in rats (both genders), NHPs (male only), and patients (both genders) demonstrated that the principal route of excretion of 14C-lurbinectedin-related radioactivity was through the feces (88.7% ± 10.1% in patients), with only a minor fraction recovered from the urine (5.6% ± 2.0% in patients). In plasma samples, the majority of lurbinectedin-related radioactivity was attributed to unchanged compound (95% ± 3.1% and 70.2% ± 10.9% in NHPs and humans, respectively). Plasma metabolic profiling demonstrated the major (% compared with unchanged compound) circulating metabolites were N-Desmethyl-lurbinectedin (0.4% ± 0.2% and 10.4% ± 2.2% in NHPs and patients, respectively) and 1',3'-Desmethylene-lurbinectedin (0.9% ± 0.7% and 14.3% ± 10.4% in NHP and patients, respectively). SIGNIFICANCE STATEMENT: Lurbinectedin is a novel and potent selective inhibitor of active transcription of protein-coding genes, triggering apoptosis of cancerous cells, and was recently approved for the treatment of patients with metastatic small-cell lung cancer with disease progression on or after platinum-based chemotherapy. The present study provides a complete set of information on the pharmacokinetics, biotransformation, and elimination of 14C-lurbinectedin and its metabolites, following a single intravenous administration to nonclinical species (rats and nonhuman primates) and patients.

Optimization of a novel piperazinone series as potent selective peripheral covalent BTK inhibitors

BTK is a tyrosine kinase playing an important role in B cell and myeloid cell functions through B cell receptor (BCR) signaling and Fc receptor (FcR) signaling. Selective inhibition of BTK has the potential to provide therapeutical benefits to patients suffering from autoimmune diseases. Here we report the design, optimization, and characterization of novel potent and highly selective covalent BTK inhibitors. Starting from a piperazinone hit derived from a selective reversible inhibitor, we solved the whole blood cellular potency issue by introducing an electrophilic warhead to reach Cys481. This design led to a covalent irreversible BTK inhibitor series with excellent kinase selectivity as well as good whole blood CD69 cellular potency. Optimization of metabolic stability led to representative compounds like 42, which demonstrated strong cellular target occupancy and inhibition of B-cell proliferation measured by proximal and distal functional activity.

Additive Effect of CD73 Inhibitor in Colorectal Cancer Treatment With CDK4/6 Inhibitor Through Regulation of PD-L1.

Background & AimsAlthough cancer immunotherapies are effective for advanced-stage cancers, there are no clinically approved immunotherapies for colon cancers (CRCs). Therefore, there is a high demand for the development of novel therapies. Extracellular adenosine-mediated signaling is considered a promising target for advanced-stage cancers that are nonresponsive to programmed death 1 (PD-1)-/programmed death-ligand 1 (PD-L1)-targeted immunotherapies. In this study, we aimed to elucidate novel tumorigenic mechanisms of extracellular adenosine.MethodsTo investigate the effects of extracellular adenosine on tumor-associated macrophages, peripheral blood-derived human macrophages were treated with adenosine and analyzed using flow cytometry and Western blot. Changes in adenosine-treated macrophages were further assessed using multi-omics analysis, including total RNA sequencing and proteomics. Colon cancer mouse models were used to measure the therapeutic efficacy of AB680 and palbociclib. We also used tissue microarrays of patients with CRC, to evaluate their clinical relevance.ResultsExtracellular adenosine-mediated reduction of cyclin D1 (CCND1) was found to be critical for the regulation of immune checkpoint molecules and PD-L1 levels in human macrophages, indicating that post-translational modification of PD-L1 is affected by adenosine. A potent CD73 selective inhibitor, AB680, reversed the effects of adenosine on CCND1 and PD-L1. This result strongly suggests that AB680 is a combinatory therapeutic option to overcome the undesired side effects of the cyclin-dependent kinase 4/6 inhibitor, palbociclib, which increases PD-L1 expression in tumors. Because palbociclib is undergoing clinical trials for metastatic CRC in combination with cetuximab (clinical trial number: NCT03446157), we validated that the combination of AB680 and palbociclib significantly improved anti-tumor efficacy in CRC animal models, thereby highlighting it as a novel immunotherapeutic strategy. We further assessed whether the level of CCND1 in tumor-associated macrophages was indeed reduced in tumor sections obtained from patients with CRC, for evaluating the clinical relevance of this strategy.ConclusionsIn this study, we demonstrated that a novel combination therapy of AB680 and palbociclib may be advantageous for the treatment of CRC.

Synthesis and In Vitro Biological Evaluation of 3-ethyl1,5-Naphthyridin-2(1H)-One Derivatives As Novel, Potent PARP-1 Selective Inhibitors and PARP-1 DNA Trappers

Synthesis and In Vitro Biological Evaluation of 3-ethyl1,5-Naphthyridin-2(1H)-One Derivatives As Novel, Potent PARP-1 Selective Inhibitors and PARP-1 DNA Trappers

QSAR STUDY OF PYRAZOLE-UREA HYBRID COMPOUNDS AS ANTIMALARIAL AGENT VIA PROLYL-tRNA SYNTHETASE INHIBITION

Aminoacyl-tRNA synthetase is one of the emerging potential targets for various tropical diseases such as malaria. One of which, prolyl-tRNA synthetase, has known to possess diverse binding modes such as dual inhibitor with febrifugine and the recently elucidated allosteric site. A recent study showed that pyrazole-urea hybrid analogues are a potential selective inhibitor agent against this enzyme. Here, we have created a quantitative structure-activity relationship (QSAR) model using multiple linear regression (MLR) and a partial least square (PLS) regression approach. Due to the limited amount of available data, the double cross-validation (DCV) method was employed to overcome a bias which resulted due to some data points being held out for validation. Several optimizations were performed to obtain the best result, namely different data splitting strategies (random and rational) and different correlation threshold values (0.8 and 0.9). Finally, the two best equations obtained from MLR and PLS approaches were evaluated by checking their applicability domain. It is found that the MLR output model yielded the best result, which indicated the significance of Geary autocorrelation and CATS-2D-based descriptors in representing the correlation between pyrazole-urea hybrid analogues and their enzymatic activity.