Macrocyclic Inhibitors Research Articles

Mirror-Image Random Nonstandard Peptides Integrated Discovery (MI-RaPID) Technology Yields Highly Stable and Selective Macrocyclic Peptide Inhibitors for Matrix Metallopeptidase 7.

Matrix metallopeptidase 7 (MMP7) plays a crucial role in cancer metastasis and progression, making it an attractive target for therapeutic development. However, the development of selective MMP7 inhibitors is challenging due to the conservation of active sites across various matrix metalloproteinases (MMPs). Here, we have developed mirror-image random nonstandard peptides integrated discovery (MI-RaPID) technology to discover innate protease-resistant macrocyclic peptides that specifically bind to and inhibit human MMP7. One identified macrocyclic peptide against D-MMP7, termed D20, was synthesized in its mirror-image form, D'20, consisting of 12 D-amino acids, one cyclic β-amino acid, and a thioether bond. Notably, it potently inhibited MMP7 with an IC50 value of 90 nM, and showed excellent selectivity over other MMPs with similar substrate specificity. Moreover, D'20 inhibited the migration of pancreatic cell line CFPAC-1, but had no effect on the cell proliferation and viability. D'20 exhibited excellent stability in human serum, as well as in simulated gastric and intestinal fluids. This study highlights that MI-RaPID technology can serve as a powerful tool to develop in vivo stable macrocyclic peptides for therapeutic applications.

Mirror‐Image Random Nonstandard Peptides Integrated Discovery (MI‐RaPID) Technology Yields Highly Stable and Selective Macrocyclic Peptide Inhibitors for Matrix Metallopeptidase 7

AbstractMatrix metallopeptidase 7 (MMP7) plays a crucial role in cancer metastasis and progression, making it an attractive target for therapeutic development. However, the development of selective MMP7 inhibitors is challenging due to the conservation of active sites across various matrix metalloproteinases (MMPs). Here, we have developed mirror‐image random nonstandard peptides integrated discovery (MI‐RaPID) technology to discover innate protease‐resistant macrocyclic peptides that specifically bind to and inhibit human MMP7. One identified macrocyclic peptide against D‐MMP7, termed D20, was synthesized in its mirror‐image form, D’20, consisting of 12 D‐amino acids, one cyclic β‐amino acid, and a thioether bond. Notably, it potently inhibited MMP7 with an IC50 value of 90 nM, and showed excellent selectivity over other MMPs with similar substrate specificity. Moreover, D’20 inhibited the migration of pancreatic cell line CFPAC‐1, but had no effect on the cell proliferation and viability. D’20 exhibited excellent stability in human serum, as well as in simulated gastric and intestinal fluids. This study highlights that MI‐RaPID technology can serve as a powerful tool to develop in vivo stable macrocyclic peptides for therapeutic applications.

Rational Design of Macrocyclic Noncovalent Inhibitors of SARS-CoV-2 Mpro from a DNA-Encoded Chemical Library Screening Hit That Demonstrate Potent Inhibition against Pan-Coronavirus Homologues and Nirmatrelvir-Resistant Variants.

The recent global COVID-19 pandemic has highlighted treatments for coronavirus infection as an unmet medical need. The main protease (Mpro) has been an important target for the development of SARS-CoV-2 direct-acting antivirals. Nirmatrelvir as a covalent Mpro inhibitor was the first such approved therapy. Although Mpro inhibitors of various chemical classes have been reported, they are generally less active against nirmatrelvir-resistant variants and have limited pan-coronavirus potential, presenting a significant human health risk upon future outbreaks. We here present a novel approach and utilized DNA-encoded chemical library screening to identify the noncovalent Mpro inhibitor 5, which demonstrated a distinct binding mode to nirmatrelvir. A macrocyclization strategy designed to lock the active conformation resulted in lactone 12 with significantly improved antiviral activity. Further optimization led to the potent lactam 26, which demonstrated exceptional potency against nirmatrelvir-resistant variants as well as against a panel of viral main proteases from other coronaviruses.

151 (PB139): CFON-026, a best-in-class macrocyclic non-covalent inhibitor of BTK (WT) and all clinically relevant BTK resistance mutations

151 (PB139): CFON-026, a best-in-class macrocyclic non-covalent inhibitor of BTK (WT) and all clinically relevant BTK resistance mutations

Macrocyclic Inhibitors Targeting the Prime Site of the Fibrinolytic Serine Protease Plasmin.

Two series of macrocyclic inhibitors addressing the S1 pocket and the prime site of the fibrinolytic serine protease plasmin have been developed. In the first series, a P1 tranexamoyl residue was coupled to 4-aminophenylalanine in P1' position, which provided moderately potent inhibitors with inhibition constants around 1 μM. In the second series, a substituted biphenylalanine was incorporated as P1' residue leading to approximately 1000-fold stronger plasmin inhibitors, the best compounds possess subnanomolar inhibition constants. The most effective compounds already exhibit a certain selectivity as plasmin inhibitors compared to other trypsin-like serine proteases such as trypsin, plasma kallikrein, thrombin, activated protein Ca, as well as factors XIa and Xa. For inhibitor 28 of the second series, the co-crystal structure in complex with a Ser195Ala microplasmin mutant revealed that the P2' residue adopts multiple conformations. Most polar contacts to plasmin and surrounding water molecules are mediated through the P1 tranexamoyl residue, whereas the bound conformation of the macrocycle is mainly stabilized by two intramolecular hydrogen bonds.

Brain Exposure to the Macrocyclic ALK Inhibitor Zotizalkib is Restricted by ABCB1, and Its Plasma Disposition is Affected by Mouse Carboxylesterase 1c.

Zotizalkib (TPX-0131), a fourth-generation macrocyclic anaplastic lymphoma kinase (ALK) inhibitor, is designed to overcome resistance due to secondary ALK mutations in non-small cell lung cancer (NSCLC). We here evaluated the pharmacokinetic roles of the ABCB1 (P-gp/MDR1) and ABCG2 (BCRP) efflux transporters, OATP1 influx transporters and the metabolizing enzymes CES1 and CYP3A in plasma and tissue disposition of zotizalkib after oral administration in relevant mouse models. Zotizalkib was efficiently transported by hABCB1 in vitro. In vivo, a significant ∼9-fold higher brain-to-plasma ratio was observed in Abcb1a/b-/- and Abcb1a/b;Abcg2-/- compared to wild-type mice. No change in brain disposition was observed in Abcg2-/- mice, suggesting that mAbcb1a/b markedly restricts the brain accumulation of zotizalkib. ABCB1-mediated efflux of zotizalkib was completely inhibited by elacridar, a dual ABCB1/ABCG2 inhibitor, increasing brain exposure without any signs of acute CNS-related toxicities. In Oatp1a/b-/- mice, no marked changes in plasma exposure or tissue-to-plasma ratios were observed, indicating that zotizalkib is not a substantial in vivo substrate for mOatp1a/b. Zotizalkib may further be metabolized by CYP3A4 but only noticeably at low plasma concentrations. In Ces1-/- mice, a 2.5-fold lower plasma exposure was seen compared to wild-type, without alterations in tissue distribution. This suggests increased plasma retention of zotizalkib by binding to the abundant mouse plasma Ces1c. Notably, the hepatic expression of human CES1 did not affect zotizalkib plasma exposure or tissue distribution. The obtained pharmacokinetic insights may be useful for the further development and optimization of therapeutic efficacy and safety of zotizalkib and related compact macrocyclic ALK inhibitors.

Discovery of Thioether-Cyclized Macrocyclic Covalent Inhibitors by mRNA Display.

Macrocyclic peptides are promising scaffolds for the covalent ligand discovery. However, platforms enabling the direct identification of covalent macrocyclic ligands in a high-throughput manner are limited. In this study, we present an mRNA display platform allowing selection of covalent macrocyclic inhibitors using 1,3-dibromoacetone-vinyl sulfone (DBA-VS). Testcase selections on TEV protease resulted in potent covalent inhibitors with diverse cyclic structures, among which cTEV6-2, a macrocyclic peptide with a unique C-terminal cyclization, emerged as the most potent covalent inhibitor of TEV protease described to-date. This study outlines the workflow for integrating chemical functionalization─installation of a covalent warhead─with mRNA display and showcases its application in targeted covalent ligand discovery.

TKI type switching overcomes ROS1 L2086F in ROS1 fusion-positive cancers

ROS1 tyrosine kinase inhibitors (TKIs) are highly effective in ROS1-positive non-small cell lung cancer, but resistance remains a challenge. We investigated the activity of various TKIs against wildtype and mutant ROS1, focusing on the emerging L2086F resistance mutation. Using Ba/F3 and NIH3T3 cell models, CRISPR/Cas9-edited isogenic wildtype and mutant patient-derived cell lines, and in vivo tumor growth studies, we compared type I TKIs (crizotinib, entrectinib, taletrectinib, lorlatinib, and repotrectinib) to type II TKIs (cabozantinib and merestinib) and the type I FLT3 inhibitor gilteritinib. The ROS1 L2086F mutant kinase showed resistance to type I TKIs, while type II TKIs retained activity. Gilteritinib inhibited both wildtype and L2086F mutant ROS1 but was ineffective against the G2032R mutation. Structural analyses revealed distinct binding poses for cabozantinib and gilteritinib, explaining their efficacy against L2086F. Clinical cases demonstrated cabozantinib’s effectiveness in patients with TKI-resistant, ROS1 L2086F mutant NSCLCs. This study provides the first comprehensive report of ROS1 L2086F in the context of later-generation TKIs, including macrocyclic inhibitors. While cabozantinib effectively inhibits ROS1 L2086F, its multi-kinase inhibitor nature highlights the need for more selective and better-tolerated TKIs to overcome kinase-intrinsic resistance. Gilteritinib may offer an alternative for targeting ROS1 L2086F with distinct off-target toxicities, but further studies are required to fully evaluate its potential in this setting.

Cyclin A/B RxL Macrocyclic Inhibitors to Treat Cancers with High E2F Activity.

Cancer cell proliferation requires precise control of E2F1 activity; excess activity promotes apoptosis. Here, we developed cell-permeable and bioavailable macrocycles that selectively kill small cell lung cancer (SCLC) cells with inherent high E2F1 activity by blocking RxL-mediated interactions of cyclin A and cyclin B with select substrates. Genome-wide CRISPR/Cas9 knockout and random mutagenesis screens found that cyclin A/B RxL macrocyclic inhibitors (cyclin A/Bi) induced apoptosis paradoxically by cyclin B- and Cdk2-dependent spindle assembly checkpoint activation (SAC). Mechanistically, cyclin A/Bi hyperactivate E2F1 and cyclin B by blocking their RxL-interactions with cyclin A and Myt1, respectively, ultimately leading to SAC activation and mitotic cell death. Base editor screens identified cyclin B variants that confer cyclin A/Bi resistance including several variants that disrupted cyclin B:Cdk interactions. Unexpectedly but consistent with our base editor and knockout screens, cyclin A/Bi induced the formation of neo-morphic Cdk2-cyclin B complexes that promote SAC activation and apoptosis. Finally, orally-bioavailable cyclin A/Bi robustly inhibited tumor growth in chemotherapy-resistant patient-derived xenograft models of SCLC. This work uncovers gain-of-function mechanisms by which cyclin A/Bi induce apoptosis in cancers with high E2F activity, and suggests cyclin A/Bi as a therapeutic strategy for SCLC and other cancers driven by high E2F activity.

Discovery of macrocyclic covalent inhibitors for severe acute respiratory syndrome coronavirus 2 3CL protease

The coronavirus disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been spread worldwide for more than 3 years. Although the hospitalization rate and mortality have decreased dramatically due to wide vaccination effort and improved treatment options, the disease is still a global health issue due to constant viral mutations, causing negative impact on social and economic activities. In addition, long COVID and complications arising from COVID-19 weeks after infection have become a concern for public health experts. Therefore, better treatments for COVID-19 are still needed. Herein, we describe a class of macrocyclic peptidomimetic compounds that are potent inhibitors of SARS-Cov-2 3CL protease (3CLpro). Significantly, some of the compounds showed a higher stability against human liver microsomes (HLM t1/2 > 180 min) and may be suitable for oral administration without the need for a pharmacokinetic (PK) boosting agent such as ritonavir.

A review on macrocyclic kinase inhibitors in clinical trials

Macrocyclic kinase inhibitors have high binding affinity and selectivity towards a variety of kinases including mammalian target of rapamycin complex 1/2, janus kinases/ Fms like tyrosine kinase, cyclin-dependent kinases and anaplastic lymphoma kinase1. Recently, few macrocyclic kinase inhibitors have entered clinical trial for treatment different types of cancers including leukemia, non-small cell lung cancer, myelofibrosis, breast cancer, glioblastoma and lymphoma. Of them, ridaforomilus has completed Phase III clinical trial and is waiting to be approved for treatment of breast cancer and advanced leukemia. Pacritinib is also currently being tested in phase III clinical trial for treatment of myelofibrosis and, loratinib is being evaluated for advanced ALK gene positive nonsmall cell lung carcinoma. The broad-spectrum cyclin-dependent kinases inhibitor, TGO2, has also entered phase II clinical trial for treatment of glioblastoma and advanced leukemia.

PAS-004: A novel macrocyclic MEK inhibitor to inhibit cancer cell growth in vitro and tumor growth in mouse xenograft studies.

3126 Background: Three MEK inhibitors have been approved to date to treat melanomas driven by RAS pathway mutations and a 4th compound (selumetinib) is approved to treat Neurofibromatosis type 1 (NF1) in pediatric patients. PAS-004 is the first macrocyclic MEK inhibitor in development for solid tumors and NF1. Methods: Ten NRAS mutant cancer cell lines were cultured for 48 hrs in the presence of the MEK inhibitor PAS-004, trametinib, binimetinib (bini) and selumetinib (selu) and cell proliferation was assayed using a Cell Titer Glo luminescence assay. The anti-tumor activity of PAS-004 was compared with selu and bini in two mouse xenograft studies using NRAS mutant human hepatocellular carcinoma (HCC) and lung carcinoma cell lines. Dose response was assessed with treatment initiated when the tumor reached a volume of 150 mm3 and mice treated for 20 days. Body weights and tumor volumes were measured twice weekly. Tumors were excised at the end of the study and pERK inhibition was assessed by Western blot. Terminal plasma was collected for PK analysis. Results: PAS-004 strongly inhibited 5/10 NRAS mutant cancer lines with IC50 values ranging from 0.024 to 0.306 µM. Maximal growth inhibition of >50% was achieved by PAS-004 in 8 cell lines and PAS-004 achieved greater maximal inhibition in 7/10 lines vs selu and bini. PAS-004 inhibition was comparable to trametinib in 5/10 cell lines tested. However, in contrast to trametinib PAS-004 did not reach a plateau at the highest dose tested in three of these lines. In the HCC xenograft study the highest dose of PAS-004 completely prevented tumor growth and the same dose caused a 69% reduction in tumor volume in the lung carcinoma xenograft study. The anti-tumor efficacy of PAS-004, when taken at equivalent doses, was shown to be superior to that of bini and selu. Specifically, PAS-004 at dose levels of 10 mg/kg and 5 mg/kg, once daily, exhibited higher efficacy compared to bini and selu at dose levels of 5 mg/kg and 2.5 mg/kg, when administered twice daily, respectively. No significant differences in body weight loss were seen between the compounds. Conclusions: The novel macrocyclic MEK inhibitorPAS-004 inhibited NRAS mutant tumor growth in mouse xenograft studies with similar activity as the approved MEK inhibitors selu and bini. In vitro, PAS-004 provided greater maximal growth inhibition of NRAS lines than selu and bini. These results support investigating PAS-004 further and a clinical trial in patients with advanced solid tumors carrying RAS pathway mutations, including NRAS variants, is ongoing.

Recent Advances in the Development of RET Inhibitors

Background: Rearranged during transfection (RET) is a receptor tyrosine kinase and a bona fide oncogene that drives various cancers. Oncogenic RET induces abnormal activation of RET kinase, causing tumorigenesis. RET can be abnormally activated through RET point mutations and RET fusions. Although RET kinase has been discovered in tumors more than 30 years ago, patients with RET-altered tumors gain limited benefits from multikinase inhibitors (MKIs). In 2020, pralsetinib and selpercatinib were approved by FDA for the treatment of RET-altered tumors. Objective: Recently reported RET inhibitors were reviewed to provide an overview of the development of novel RET inhibitors. Methods: Literatures, patents, and conference proceedings published in the past five years were collected. Only RET inhibitors with novel scaffolds or in vivo efficacy were discussed in this review. The enzymebased and cell-based activities, PK profiles, antitumor activities in vivo, and clinical efficacy of the selected RET inhibitors were described. Results: Great efforts have been spent on the development of RET inhibitors, leading to increased RETtargeted therapies. Due to high potency and specificity, pralsetinib and selpercatinib resulted in a >8- month improvement in overall survival, compared to MKIs. However, solvent-front mutants emerged and contributed to the acquired resistance to pralsetinib and selpercatinib. To overcome solvent front mutants, TPX-0046, TAS0953, and LOX-260 are investigated in early clinical studies. Conclusion: Zeteletinib, SYHA1815, TPX-0046, TAS0953, and LOX-260 are potential therapies for RET-altered cancers. In addition, macrocyclic inhibitors, allosteric inhibitors, and PROTACs are three promising strategies to address the potential drug resistance of RET.

Synthesis and structural characterization of new macrocyclic inhibitors of the Zika virus NS2B-NS3 protease.

Three new series of macrocyclic active site-directed inhibitors of the Zika virus (ZIKV) NS2B-NS3 protease were synthesized. First, attempts were made to replace the basic P3 lysine residue of our previously described inhibitors with uncharged and more hydrophobic residues. This provided numerous compounds with inhibition constants between 30 and 50 nM. A stronger reduction of the inhibitory potency was observed when the P2 lysine was replaced by neutral residues, all of these inhibitors possess Ki values >1 µM. However, it is possible to replace the P2 lysine with the less basic 3-aminomethylphenylalanine, which provides a similarly potent inhibitor of the ZIKV protease (Ki = 2.69 nM). Crystal structure investigations showed that the P2 benzylamine structure forms comparable interactions with the protease as lysine. Twelve additional structures of these inhibitors in complex with the protease were determined, which explain many, but not all, SAR data obtained in this study. All individual modifications in the P2 or P3 position resulted in inhibitors with low antiviral efficacy in cell culture. Therefore, a third inhibitor series with combined modifications was synthesized; all of them contain a more hydrophobicd-cyclohexylalanine in the linker segment. At a concentration of 40 µM, two of these compounds possess similar antiviral potency as ribavirin at 100 µM. Due to their reliable crystallization in complex with the ZIKV protease, these cyclic compounds are very well suited for a rational structure-based development of improved inhibitors.

Structural Analysis of the Macrocyclic Inhibitor BI-4020 Binding to EGFR Kinase.

A novel macrocyclic inhibitor of mutant EGFR (BI-4020) has shown promise in pre-clinical studies of T790M and C797S drug-resistant non-small cell lung cancer. To better understand the molecular basis for BI-4020 selectivity and potency, we have carried out biochemical activity assays and structural analysis with X-ray crystallography. Biochemical potencies agree with previous studies indicating that BI-4020 is uniquely potent against drug-resistant L858R/T790M and L858R/T790M/C797S variants. X-ray structures with wild-type (2.4 Å) and T790M/V948R (3.1 Å) EGFR kinase domains show that BI-4020 is likely rendered selective due to interactions with the kinase domain hinge region as well as T790M, akin to Osimertinib. Additionally, BI-4020 is also rendered more potent due to its constrained macrocycle geometry as well as additional H-bonds to conserved K745 and T845 residues in both active and inactive conformations. These findings taken together show how this novel macrocyclic inhibitor is both highly potent and selective for mutant EGFR in a reversible mechanism and motivate structure-inspired approaches to developing targeted therapies in medicinal oncology.

Concurrent Optimizations of Efficacy and Blood-Brain Barrier Permeability in New Macrocyclic LRRK2 Inhibitors for Potential Parkinson's Disease Therapeutics.

The elevated activity of leucine-rich repeat kinase 2 (LRRK2) is implicated in the pathogenesis of Parkinson's disease (PD). The quest for effective LRRK2 inhibitors has been impeded by the formidable challenge of crossing the blood-brain barrier (BBB). We leveraged structure-based de novo design and developed robust three-dimensional quantitative structure-activity relationship (3D-QSAR) models to predict BBB permeability, enhancing the likelihood of the inhibitor's brain accessibility. Our strategy involved the synthesis of macrocyclic molecules by linking the two terminal nitrogen atoms of HG-10-102-01 with an alkyl chain ranging from 2 to 4 units, laying the groundwork for innovative LRRK2 inhibitor designs. Through meticulous computational and synthetic optimization of both biochemical efficacy and BBB permeability, 9 out of 14 synthesized candidates demonstrated potent low-nanomolar inhibition and significant BBB penetration. Further assessments of in vitro and in vivo effectiveness, coupled with pharmacological profiling, highlighted 8 as the promising new lead compound for PD therapeutics.

Process Development of a Macrocyclic Peptide Inhibitor of PD-L1.

This article outlines the process development leading to the manufacture of 800 g of BMS-986189, a macrocyclic peptide active pharmaceutical ingredient. Multiple N-methylated unnatural amino acids posed challenges to manufacturing due to the lability of the peptide to cleavage during global side chain deprotection and precipitation steps. These issues were exacerbated upon scale-up, resulting in severe yield loss and necessitating careful impurity identification, understanding the root cause of impurity formation, and process optimization to deliver a scalable synthesis. A systematic study of macrocyclization with its dependence on concentration and pH is presented. In addition, a side chain protected peptide synthesis is discussed where the macrocyclic protected peptide is extremely labile to hydrolysis. A computational study explains the root cause of the increased lability of macrocyclic peptide over linear peptide to hydrolysis. A process solution involving the use of labile protecting groups is discussed. Overall, the article highlights the advancements achieved to enable scalable synthesis of an unusually labile macrocyclic peptide by solid-phase peptide synthesis. The sustainability metric indicates the final preparative chromatography drives a significant fraction of a high process mass intensity (PMI).

Brain-Permeable Immunoproteasome-Targeting Macrocyclic Peptide Epoxyketones for Alzheimer's Disease.

Previously, we demonstrated that linear peptide epoxyketones targeting the immunoproteasome (iP) could ameliorate cognitive deficits in mouse models of Alzheimer's disease (AD) independently of amyloid deposition. We also reported the first iP-targeting macrocyclic peptide epoxyketones, which exhibit improved metabolic stability compared with their linear counterparts. Here, we prepared additional macrocyclic peptide epoxyketones and compared them with existing macrocyclic iP inhibitors by assessing Caco2 cell-based permeability and microsomal stability, providing the four best macrocyclic iP inhibitors. We then evaluated the four compounds using the Ames test and the potency assays in BV2 cells, selecting compound 5 as our AD drug lead. When 5 was administered intravenously (40 mg/kg) or orally (150 mg/kg) into healthy BALB/c mice, we observed considerable iP inhibition in the mouse brain, indicating good blood-brain barrier permeability and target engagement. Combined results suggest that 5 is a promising AD drug lead that may need further investigation.

Abstract CT196: First-in-human phase 1/2a trial of a macrocyclic ATR inhibitor (ATRN-119) in patients with advanced solid tumors

Abstract Background: ATRN-119 is an orally bioavailable, potent, selective macrocyclic small molecule inhibitor of Ataxia Telangiectasia and Rad3- related (ATR) kinase. As the master regulator of DNA damage response (DDR), ATR orchestrates cellular response to DNA replication stress to preserve DNA replication fork integrity. Cancer cells with markedly increased oncogenic stress or dysfunctional DDR are more reliant on ATR for genome stabilization. Thus, inhibition of ATR can result in cancer cell-selective replication fork collapse and cancer cell death. Methods: This ongoing, first-in-human, multi-site phase 1/2a trial (NCT04905914) is investigating ATRN-119 safety and pharmacokinetic properties (primary objectives), preliminary efficacy in various solid tumors (secondary objective), and biomarker profile (exploratory objective). This study uses an open-label, standard 3+3 dose escalation and dose expansion study design. Key inclusion criteria include: advanced solid tumor, measurable disease (RECIST v1.1), tumor with at least 1 DDR mutation by next-generation-sequencing, at least 1 failed standard-of-care therapy, ECOG PS 0 or 1, and adequate organ function. Key exclusion criteria are cancer therapy within 4 weeks or at least 5 half-lives, unresolved therapy-related AEs, investigational agent within 5 half-lives or 30 days of study drug, CNS metastases or unstable involvement, and concomitant treatment with strong CYP3A4 or CYP2D6 inhibitors or inducers. Results: This trial is currently enrolling at Dose level 5 (550 mg). Among 12 patients in the first four dose levels, the median age is 62 years (range: 48 to 79), where 67% (n=8) are female, 75% (n=9) are White, and 25% (n=3) are Black. The median number of prior treatments is 3 (range: 1 to 6, and 92% have received platinum-based chemotherapy). The majority of tumors, 75% (n=9), had a TP53 mutation. There have been no reports of dose-limiting toxicities, treatment-related serious adverse events (AE), and treatment-related AEs Grade 3 or higher in these cohorts. The three most commonly reported all-cause AEs are fatigue (33%, n=4), nausea (25%, n=3), and diarrhea (25%, n=3). Increasing exposure and maximum serum concentrations (Cmax) were observed by dose level. The half-life of ATRN-119 is ~5 hours. Two of 12 patients achieved stable disease (SD): one patient from Dose level 1 (50 mg) who progressed on Day 112 and one patient from Dose level 3 (200 mg) who remains on treatment as of Day 118 (data cut off date: January 2, 2024). Conclusion: In these early cohorts, once-daily oral ATRN-119 appears to be well tolerated with a manageable safety profile, exhibits near dose proportionality, and demonstrates disease stabilization warranting further investigation. Further studies to explore a twice-daily schedule are being considered. Citation Format: Fiona Simpkins, Amit Mahipal, Patricia LoRusso, Reva Schneider, Crystal Miller, David Stenehjem, Eric J. Brown, Mike Carleton, Joachim Gullbo, Nadeem Q. Mirza. First-in-human phase 1/2a trial of a macrocyclic ATR inhibitor (ATRN-119) in patients with advanced solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr CT196.

Discovery of novel macrocyclic derivatives as potent and selective cyclin-dependent kinase 2 inhibitors

Cyclin-dependent kinase 2 (CDK2) is a member of CDK family of kinases (CDKs) that regulate the cell cycle. Its inopportune or over-activation leads to uncontrolled cell cycle progression and drives numerous types of cancers, especially ovarian, uterine, gastric cancer, as well as those associated with amplified CCNE1 gene. However, developing selective lead compound as CDK2 inhibitors remains challenging owing to similarities in the ATP pockets among different CDKs. Herein, we described the optimization of compound 1, a novel macrocyclic inhibitor targeting CDK2/5/7/9, aiming to discover more selective and metabolically stable lead compound as CDK2 inhibitor. Molecular dynamic (MD) simulations were performed for compound 1 and 9 to gain insights into the improved selectivity against CDK5. Further optimization efforts led to compound 22, exhibiting excellent CDK2 inhibitory activity, good selectivity over other CDKs and potent cellular effects. Based on these characterizations, we propose that compound 22 holds great promise as a potential lead candidate for drug development.