The SOS1 Inhibitor MRTX0902 Blocks KRAS Activation and Demonstrates Antitumor Activity in Cancers Dependent on KRAS Nucleotide Loading

KRAS is the most frequently mutated oncogene in human cancer and facilitates uncontrolled growth through hyperactivation of the RTK/MAPK pathway. The Son of Sevenless homolog 1 (SOS1) protein functions as a guanine nucleotide exchange factor (GEF) for the RAS subfamily of small GTPases and represents a druggable target in the pathway. Using a structure-based drug discovery approach, MRTX0902 was identified as a selective and potent SOS1 inhibitor that disrupts the KRAS:SOS1 protein-protein interaction to prevent SOS1-mediated nucleotide exchange on KRAS and translates into an anti-proliferative effect in cancer cell lines with genetic alterations of the KRAS-MAPK pathway. MRTX0902 augmented the antitumor activity of the KRAS G12C inhibitor adagrasib when dosed in combination in eight out of twelve KRAS G12C-mutant human non-small cell lung cancer (NSCLC) and colorectal cancer (CRC) xenograft models. Pharmacogenomic profiling in preclinical models identified cell cycle genes and the SOS2 homolog as genetic co-dependencies and implicated tumor suppressor genes (NF1, PTEN) in resistance following combination treatment. Lastly, combined vertical inhibition of RTK/MAPK pathway signaling by MRTX0902 with inhibitors of EGFR or RAF/MEK led to greater downregulation of pathway signaling and improved antitumor responses in KRAS-MAPK pathway-mutant models. These studies demonstrate the potential clinical application of dual inhibition of SOS1 and KRAS G12C and additional SOS1 combination strategies that will aide in the understanding of SOS1 and RTK/MAPK biology in targeted cancer therapy.

Discovery of Pyridopyrimidinones that Selectively Inhibit the H1047R PI3Kα Mutant Protein

The H1047R mutation of PIK3CA is highly prevalent in breast cancers and other solid tumors. Selectively targeting PI3KαH1047R over PI3KαWT is crucial due to the role that PI3KαWT plays in normal cellular processes, including glucose homeostasis. Currently, only one PI3KαH1047R-selective inhibitor has progressed into clinical trials, while three pan mutant (H1047R, H1047L, H1047Y, E542K, and E545K) selective PI3Kα inhibitors have also reached the clinical stage. Herein, we report the design and discovery of a series of pyridopyrimidinones that inhibit PI3KαH1047R with high selectivity over PI3KαWT, resulting in the discovery of compound 17. When dosed in the HCC1954 tumor model in mice, 17 provided tumor regressions and a clear pharmacodynamic response. X-ray cocrystal structures from several PI3Kα inhibitors were obtained, revealing three distinct binding modes within PI3KαH1047R including a previously reported cryptic pocket in the C-terminus of the kinase domain wherein we observe a ligand-induced interaction with Arg1047.

Stereoselective Amine Synthesis Mediated by a Zirconocene Hydride to Accelerate a Drug Discovery Program

Chiral amine synthesis remains a significant challenge in accelerating the design cycle of drug discovery programs. A zirconium hydride, due to its high oxophilicity and lower reactivity, gave highly chemo- and stereoselective reductions of sulfinyl ketimines. The development of this zirconocene-mediated reduction helped to accelerate our drug discovery efforts and is applicable to several motifs commonly used in medicinal chemistry. Computational investigation supported a cyclic half-chair transition state to rationalize the high selectivity in benzyl systems.

Discovery of Five SOS2 Fragment Hits with Binding Modes Determined by SOS2 X-Ray Cocrystallography

SOS1 and SOS2 are guanine nucleotide exchange factors that mediate RTK-stimulated RAS activation. Selective SOS1:KRAS PPI inhibitors are currently under clinical investigation, whereas there are no reports to date of SOS2:KRAS PPI inhibitors. SOS2 activity is implicated in MAPK rebound when divergent SOS1 mutant cell lines are treated with the SOS1 inhibitor BI-3406; therefore, SOS2:KRAS inhibitors are of therapeutic interest. In this report, we detail a fragment-based screening strategy to identify X-ray cocrystal structures of five diverse fragment hits bound to SOS2.

MRTX1719 Is an MTA-Cooperative PRMT5 Inhibitor That Exhibits Synthetic Lethality in Preclinical Models and Patients with MTAP-Deleted Cancer

Previous studies implicated protein arginine methyltransferase 5 (PRMT5) as a synthetic lethal target for MTAP-deleted (MTAP del) cancers; however, the pharmacologic characterization of small-molecule inhibitors that recapitulate the synthetic lethal phenotype has not been described. MRTX1719 selectively inhibited PRMT5 in the presence of MTA, which is elevated in MTAP del cancers, and inhibited PRMT5-dependent activity and cell viability with >70-fold selecti-vity in HCT116 MTAP del compared with HCT116 MTAP wild-type (WT) cells. MRTX1719 demonstrated dose-dependent antitumor activity and inhibition of PRMT5-dependent SDMA modification in MTAP del tumors. In contrast, MRTX1719 demonstrated minimal effects on SDMA and viability in MTAP WT tumor xenografts or hematopoietic cells. MRTX1719 demonstrated marked antitumor activity across a panel of xenograft models at well-tolerated doses. Early signs of clinical activity were observed including objective responses in patients with MTAP del melanoma, gallbladder adenocarcinoma, mesothelioma, non-small cell lung cancer, and malignant peripheral nerve sheath tumors from the phase I/II study.

SIGNIFICANCE

PRMT5 was identified as a synthetic lethal target for MTAP del cancers; however, previous PRMT5 inhibitors do not selectively target this genotype. The differentiated binding mode of MRTX1719 leverages the elevated MTA in MTAP del cancers and represents a promising therapy for the ∼10% of patients with cancer with this biomarker. See related commentary by Mulvaney, p. 2310. This article is featured in Selected Articles from This Issue, p. 2293.

Selected Approaches to Disrupting Protein-Protein Interactions within the MAPK/RAS Pathway

Within the MAPK/RAS pathway, there exists a plethora of protein-protein interactions (PPIs). For many years, scientists have focused efforts on drugging KRAS and its effectors in hopes to provide much needed therapies for patients with KRAS-mutant driven cancers. In this review, we focus on recent strategies to inhibit RAS-signaling via disrupting PPIs associated with SOS1, RAF, PDEδ, Grb2, and RAS.

Fragment optimization and elaboration strategies - the discovery of two lead series of PRMT5/MTA inhibitors from five fragment hits

Here we describe the early stages of a fragment-based lead discovery (FBLD) project for a recently elucidated synthetic lethal target, the PRMT5/MTA complex, for the treatment of MTAP-deleted cancers. Starting with five fragment/PRMT5/MTA X-ray co-crystal structures, we employed a two-phase fragment elaboration process encompassing optimization of fragment hits and subsequent fragment growth to increase potency, assess synthetic tractability, and enable structure-based drug design. Two lead series were identified, one of which led to the discovery of the clinical candidate MRTX1719.

Design and evaluation of achiral, non-atropisomeric 4-(aminomethyl)phthalazin-1(2H)-one derivatives as novel PRMT5/MTA inhibitors

MRTX1719 is an inhibitor of the PRMT5/MTA complex and recently entered clinical trials for the treatment of MTAP-deleted cancers. MRTX1719 is a class 3 atropisomeric compound that requires a chiral synthesis or a chiral separation step in its preparation. Here, we report the SAR and medicinal chemistry design strategy, supported by structural insights from X-ray crystallography, to discover a class 1 atropisomeric compound from the same series that does not require a chiral synthesis or a chiral separation step in its preparation.

Anti-tumor efficacy of a potent and selective non-covalent KRASG12D inhibitor

Recent progress in targeting KRAS^G12C has provided both insight and inspiration for targeting alternative KRAS mutants. In this study, we evaluated the mechanism of action and anti-tumor efficacy of MRTX1133, a potent, selective and non-covalent KRAS^G12D inhibitor. MRTX1133 demonstrated a high-affinity interaction with GDP-loaded KRAS^G12D with K_D and IC₅₀ values of ~0.2 pM and <2 nM, respectively, and ~700-fold selectivity for binding to KRAS^G12D as compared to KRAS^WT. MRTX1133 also demonstrated potent inhibition of activated KRAS^G12D based on biochemical and co-crystal structural analyses. MRTX1133 inhibited ERK1/2 phosphorylation and cell viability in KRAS^G12D-mutant cell lines, with median IC₅₀ values of ~5 nM, and demonstrated >1,000-fold selectivity compared to KRAS^WT cell lines. MRTX1133 exhibited dose-dependent inhibition of KRAS-mediated signal transduction and marked tumor regression (≥30%) in a subset of KRAS^G12D-mutant cell-line-derived and patient-derived xenograft models, including eight of 11 (73%) pancreatic ductal adenocarcinoma (PDAC) models. Pharmacological and CRISPR-based screens demonstrated that co-targeting KRAS^G12D with putative feedback or bypass pathways, including EGFR or PI3Kα, led to enhanced anti-tumor activity. Together, these data indicate the feasibility of selectively targeting KRAS mutants with non-covalent, high-affinity small molecules and illustrate the therapeutic susceptibility and broad dependence of KRAS^G12D mutation-positive tumors on mutant KRAS for tumor cell growth and survival.

Atropisomeric Racemization Kinetics of MRTX1719 Using Chiral Solvating Agent-Assisted 19F NMR Spectroscopy

With renewed interest in atropisomerism of drug molecules, efficient methods to experimentally determine torsion rotational energy barriers are needed. Here, we describe use of the chiral phosphoric acid solvating agent (+)-TiPSY to resolve the signals of atropisomers in ¹⁹F NMR and to use the data to study the kinetics of racemization and determine the rotational energy barrier of clinical compound MRTX1719. This method is complimentary to traditional chiral high-performance liquid chromatography (HPLC) and enhances the toolkit for chiral analysis techniques.

Design and Discovery of MRTX0902, a Potent, Selective, Brain-Penetrant, and Orally Bioavailable Inhibitor of the SOS1:KRAS Protein-Protein Interaction

SOS1 is one of the major guanine nucleotide exchange factors that regulates the ability of KRAS to cycle through its “on” and “off” states. Disrupting the SOS1:KRAS^G12C protein–protein interaction (PPI) can increase the proportion of GDP-loaded KRAS^G12C, providing a strong mechanistic rationale for combining inhibitors of the SOS1:KRAS complex with inhibitors like MRTX849 that target GDP-loaded KRAS^G12C. In this report, we detail the design and discovery of MRTX0902—a potent, selective, brain-penetrant, and orally bioavailable SOS1 binder that disrupts the SOS1:KRAS^G12C PPI. Oral administration of MRTX0902 in combination with MRTX849 results in a significant increase in antitumor activity relative to that of either single agent, including tumor regressions in a subset of animals in the MIA PaCa-2 tumor mouse xenograft model.

Abstract LB505: Design and discovery of MRTX0902, a potent, selective, and orally bioavailable SOS1 inhibitor

KRAS mutations are the most common activating mutations in human cancer that ultimately lead to hyperactivation of the MAPK pathway and uncontrolled growth. KRAS functions as a small GTPase that cycles through its GTP-loaded “on” state and its GDP-loaded “off” state, a highly regulated process that is crucial for normal cell proliferation and survival. The guanine nucleotide exchange factor (GEF) SOS1 plays a critical role in this process by regulating the “on/off” state of KRAS. The protein-protein interaction between SOS1 and KRAS facilitates turnover of KRAS from the GDP-loaded inactive state to its activated and GTP-loaded state, a critical step to enable productive KRAS effector binding and activation of downstream signaling. The KRASG12C inhibitor, adagrasib (MRTX849), irreversibly binds to the GDP-loaded inactive conformation of KRASG12C and has recently shown encouraging clinical activity across several cancer types. As adagrasib binds preferentially to the inactive state of KRAS, blockade of SOS1 is anticipated to shift KRASG12C into the adagrasib-susceptible GDP-loaded state. Furthermore, this combination strategy could be used to target other mutant-driven cancers within the MAPK pathway using the appropriate KRASmut inhibitors and/or inhibitors of other targets within the MAPK pathway including MEK or EGFR. MRTX0902 was identified using iterative structure-based design as a selective inhibitor of SOS1 that demonstrates an IC50 value of 2 nM in a SOS1 HTRF binding assay and 30 nM in an MKN1 cellular assay. In pharmacokinetic evaluation across species, MRTX0902 demonstrated low extraction ratios and moderate to high bioavailability in mice, rats, and dogs. In preclinical models, MRTX0902 augmented the antitumor activity of adagrasib and other selected therapies. The design, discovery, and preclinical characterization of the potential best-in-class candidate MRTX0902 will be described.

Citation Format: John M. Ketcham, David M. Briere, Aaron C. Burns, James G. Christensen, Robin J. Gunn, Jacob Haling, Anthony Ivetac, Shilpi Khare, Jon Kuehler, Svitlana Kulyk, Jade Laguer, John D. Lawson, Krystal Moya, Natalie Nguyen, Peter Olson, Lisa Rahbaek, Christopher R. Smith, Niranjan Sudhakar, Nicole C. Thomas, Darin Vanderpool, Xiaolun Wang, Matthew A. Marx. Design and discovery of MRTX0902, a potent, selective, and orally bioavailable SOS1 inhibitor [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 LB505.

Abstract ND02: MRTX0902: A SOS1 inhibitor for therapeutic intervention of KRAS-driven cancers

KRAS is the most frequently mutated oncogene in cancer and drives uncontrolled growth through hyperactivation of the MAPK pathway. Significant progress has been made in the past several years to directly target KRASG12C with the FDA approval of sotorasib and the reported clinical activity of adagrasib (MRTX849). Despite these remarkable breakthroughs, additional therapies that enhance the depth and duration of response to KRASG12C inhibitors provide the opportunity to build upon the initial progress. SOS proteins are guanine nucleotide exchange factors (GEFs) that transduce receptor tyrosine kinase (RTK) signaling from the cell surface and facilitate the activation of RAS family proteins. In addition, SOS1 is a target of negative feedback signaling following RAS-mediated activation of the RAF-MEK-ERK cascade. Thus, SOS proteins represent a significant therapeutic node that maintains RAS pathway equilibrium as well as oncogenic signaling dynamics. Here we highlight the discovery and preclinical evaluation of MRTX0902, a potent, selective, and orally bioavailable inhibitor of SOS1 presently in IND-enabling studies. A structure-based approach was used to identify a novel chemical series that disrupts the protein-protein interaction between SOS1 and KRAS, thereby preventing SOS1-mediated GTP-exchange on GDP-bound KRAS. Considering MRTX849 preferentially binds to inactive GDP-bound KRASG12C, targeting SOS1 in this genetic context increases the ability of MRTX849 to bind and inhibit KRASG12C. The combination of MRTX0902 with MRTX849 enhances the depth and durability of an anti-tumor response when compared to MRTX849 alone in pre-clinical KRASG12C tumor models. MRTX0902 augments additional targeted therapies across a variety of RAS-addicted tumors, indicating that SOS1 inhibition is effective against a broad spectrum of mutations within the MAPK pathway. Furthermore, drug-anchored CRISPR experiments with MRTX0902 and MRTX849 uncovered a previously underappreciated functional role of the SOS1 paralog, SOS2, in KRAS-addicted tumors. In addition to aiding in the understanding of SOS and RAS family signaling dynamics, these studies implicate SOS2 as a potential cancer drug target in the context of SOS1/KRASG12C inhibition. In summary, we have used a structure-based approach to discover a SOS1 inhibitor that augments the anti-tumor activity of MRTX849 and additional targeted MAPK pathway inhibitors. We anticipate our findings to translate into the clinic and make an impact in patients with RAS-addicted tumors.

Citation Format: John M. Ketcham, Shilpi Khare, Niranjan Sudhakar, David M. Briere, Larry Yan, Jade Laguer, Laura Vegar, Darin Vanderpool, Jill Hallin, Lauren Hargis, Vickie Bowcut, David Lawson, Robin J. Gunn, Anthony Ivetac, Nicole C. Thomas, Barbara Saechao, Natalie Nguyen, Jeffrey Clarine, Lisa Rahbaek, Christopher R. Smith, Aaron C. Burns, Matthew A. Marx, James G. Christensen, Peter Olson, Jacob R. Haling. MRTX0902: A SOS1 inhibitor for therapeutic intervention of KRAS-driven cancers [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 ND02.

Abstract 1131: Pharmacogenomic insight into targetable vulnerabilities and modifiers of response to MRTX1133 in KRASG12D-mutant models

The ability to effectively target mutated KRAS has remained elusive despite decades of research. Recently, the identification of selective KRASG12C inhibitors has provided an effective treatment option for patients harboring this particular mutation and has also provided insight toward targeting other KRAS mutants, including KRASG12D. MRTX1133 was identified via a structure-based drug design strategy as a potent, selective, and non-covalent KRASG12D inhibitor directed at the switch II binding pocket. MRTX1133 exhibited dose dependent KRAS pathway and tumor growth inhibition and demonstrated marked anti-tumor activity across a panel of models in vivo, including tumor regression &gt;30% in 8 out of 11 pancreatic ductal adenocarcinoma (PDAC) models. While evaluation of MRTX1133 across a panel of cell and patient-derived xenograft models demonstrated strong single agent activity in the majority of models tested, a subset of models were less responsive. Focused sgRNA libraries targeting ~5,000 genes were tested in MRTX1133-anchored CRISPR/Cas9 screens in vitro and in vivo in PDAC and colorectal KRASG12D-mutant cell lines. Similar to what was seen in a targeted genetic screen with our selective KRASG12C inhibitor MRTX849, several genes that act either upstream or downstream of KRAS were depleted with MRTX1133 treatment which illuminate specific targetable vulnerabilities in the context of KRASG12D inhibition. sgRNAs targeting EGFR, PIK3CA, PTPN11, mTOR, and CDK2/4/6 were depleted in MRTX1133-treated (or vehicle-treated) cell lines or xenograft models, while hallmark tumor suppressor genes RB1, KEAP1, NF1 and PTEN were enriched. The enrichment of KEAP1 sgRNAs in PDAC models parallels findings with MRTX849 in preclinical models and is in line with emerging clinical data suggesting increased capacity to scavenge reactive oxygen species (ROS) may represent a mechanism of partial resistance to a non-covalent, non-electrophilic warhead-containing KRASG12D-selective inhibitor in PDAC. Treatment using small molecules targeting selected vulnerabilities in vitro and in vivo confirmed these genetic findings. Further evaluation of dependencies utilizing an integrated analysis of RNAseq data also revealed KRAS regulates and is critically dependent on pro-survival and cell cycle genes for cancer cell viability. These data lend further insight into tumor response to KRASG12D inhibition and provide key insight into the genes that mediate the mechanism of action of, as well as confer partial resistance to MRTX1133, and identify combination targets that can augment the anti-tumor effect of MRTX1133.

Citation Format: Vickie Bowcut, Andrew Calinisan, David M. Briere, Lauren Hargis, Lars D. Engstrom, Jade Laguer, Darin Vanderpool, Xiaolun Wang, J David Lawson, Nicole Thomas, Robin Gunn, Christopher R. Smith, Julio Fernandez-Banet, Leo He, Adam Pavlicek, Lisa Rahbaek, Matthew A. Marx, Peter Olson, James G. Christensen, Jill Hallin. Pharmacogenomic insight into targetable vulnerabilities and modifiers of response to MRTX1133 in KRASG12D-mutant models [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 1131.

Fragment-Based Discovery of MRTX1719, a Synthetic Lethal Inhibitor of the PRMT5•MTA Complex for the Treatment of MTAP-Deleted Cancers

The PRMT5•MTA complex has recently emerged as a new synthetically lethal drug target for the treatment of MTAP-deleted cancers. Here, we report the discovery of development candidate MRTX1719. MRTX1719 is a potent and selective binder to the PRMT5•MTA complex and selectively inhibits PRMT5 activity in MTAP-deleted cells compared to MTAP-wild-type cells. Daily oral administration of MRTX1719 to tumor xenograft-bearing mice demonstrated dose-dependent inhibition of PRMT5-dependent symmetric dimethylarginine protein modification in MTAP-deleted tumors that correlated with antitumor activity. A 4-(aminomethyl)phthalazin-1(2H)-one hit was identified through a fragment-based screen, followed by X-ray crystallography, to confirm binding to the PRMT5•MTA complex. Fragment growth supported by structural insights from X-ray crystallography coupled with optimization of pharmacokinetic properties aided the discovery of development candidate MRTX1719.

Identification of MRTX1133, a Noncovalent, Potent, and Selective KRASG12D Inhibitor

KRAS^G12D, the most common oncogenic KRAS mutation, is a promising target for the treatment of solid tumors. However, when compared to KRAS^G12C, selective inhibition of KRAS^G12D presents a significant challenge due to the requirement of inhibitors to bind KRAS^G12D with high enough affinity to obviate the need for covalent interactions with the mutant KRAS protein. Here, we report the discovery and characterization of the first noncovalent, potent, and selective KRAS^G12D inhibitor, MRTX1133, which was discovered through an extensive structure-based activity improvement and shown to be efficacious in a KRAS^G12D mutant xenograft mouse tumor model.

Abstract P165: MRTX1719: A first-in-class MTA-cooperative PRMT5 inhibitor that selectively elicits antitumor activity in MTAP/CDKN2A deleted cancer models

Nearly all oncology therapies target proteins that are hyperactivated in cancer; however, developing precision medicines for cancers that harbor a specific tumor suppressor gene loss remains one of the most significant challenges in cancer research. Previous studies demonstrated cancer cell lines harboring homozygous deletion of the MTAP gene (MTAP del) are selectively vulnerable to shRNA-mediated PRMT5 inhibition based on the concept of synthetic lethality. MTAP is adjacent to, and co-deleted with, the most commonly deleted tumor suppressor gene, CDKN2A. MTAP is deleted in ~10% of all cancers and is enriched in NSCLC, pancreatic cancer, mesothelioma, MPNST, and several other cancers. MTAP del cells accumulate the metabolite methylthioadenosine (MTA) which binds to, and partially inhibits, PRMT5 activity; however, current clinical-stage small molecule PRMT5 inhibitors have binding modes that are mutually exclusive with MTA binding and therefore are not selective for MTAP del cancers. To develop a potential precision medicine for MTAP del cancers, compounds that selectively bind to the PRMT5/MTA complex were discovered via a fragment-based approach using SPR complemented with structural insight utilizing X-ray crystallography. Optimization of the lead series identified MRTX1719, a potent inhibitor of PRMT5 activity (8 nM IC50) and cell viability (12 nM IC50) in HCT116 MTAP del cells with greater than 50-fold selectivity compared with HCT116 MTAP WT cells. MRTX1719 possesses favorable drug-like characteristics and human predicted oral PK properties. Daily oral administration of MRTX1719 to tumor xenograft-bearing mice demonstrated dose-dependent inhibition of PRMT5-dependent symmetric dimethylarginine (SDMA) protein modification in MTAP del tumors that correlated with antitumor activity. In contrast, minimal inhibition of PRMT5-dependent SDMA and tumor growth inhibition was observed in MTAP WT tumor xenografts. Repeat dosing in mice also showed reduced effects in bone marrow compared to nonselective PRMT5 inhibitors currently in clinical trials, suggesting MRTX1719 may have an improved therapeutic index relative to these agents. MRTX1719 treatment resulted in dysregulated post-translational modification of key cancer and cell growth-related proteins, dysregulated RNA splicing, decreased proliferation and increased apoptosis in MTAP del cancer cells. Screens evaluating the effect of MRTX1719 on cell viability across panels of cancer cell lines and/or patient-derived xenograft tumor models demonstrated broad anti-tumor activity across MTAP-deleted tumor models. Select targeted therapy and chemotherapy combinations augmented the activity of MRTX1719 and in some models converged on phospho-Rb inhibition to block tumor growth. Together, these data demonstrate that MRTX1719, a selective PRMT5/MTA inhibitor, represents a promising therapeutic strategy for patients with MTAP del cancers.

Citation Format: Christopher R. Smith, Lars D. Engstrom, Svitlana Kulyk, Ruth Aranda, Laura Waters, Krystal Moya, Victoria Bowcut, Allan Hebbert, David Trinh, David M. Briere, J. David Lawson, Jeff Clarine, Lisa Rahbaek, James G. Christensen, Matthew A. Marx, Peter Olson. MRTX1719: A first-in-class MTA-cooperative PRMT5 inhibitor that selectively elicits antitumor activity in MTAP/CDKN2A deleted cancer models [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2021 Oct 7-10. Philadelphia (PA): AACR; Mol Cancer Ther 2021;20(12 Suppl):Abstract nr P165.

Discovery of the Bruton's Tyrosine Kinase Inhibitor Clinical Candidate TAK-020 (S)-5-(1-((1-Acryloylpyrrolidin-3-yl)oxy)isoquinolin-3-yl)-2,4-dihydro-3H-1,2,4-triazol-3-one, by Fragment-Based Drug Design

This publication details the successful use of FBDD (fragment-based drug discovery) principles in the invention of a novel covalent Bruton's tyrosine kinase inhibitor, which ultimately became the Takeda Pharmaceuticals clinical candidate TAK-020. Described herein are the discovery of the fragment 5-phenyl-2,4-dihydro-3H-1,2,4-triazol-3-one, the subsequent optimization of this hit molecule to the candidate, and synthesis and performance in pharmacodynamic and efficacy models along with direct biophysical comparison of TAK-020 with other clinical-level assets and the marketed drug Ibrutinib.

In Vivo Elongation Patterns of the Collateral Ligaments in Healthy Knees During Functional Activities

BACKGROUND

Improved knowledge of in vivo function of the collateral ligaments is essential for enhancing rehabilitation and guiding surgical reconstruction as well as soft-tissue balancing in total knee arthroplasty. The aim of this study was to quantify in vivo elongation patterns of the collateral ligaments throughout complete cycles of functional activities.

METHODS

Knee kinematics were measured using radiographic images captured with a mobile fluoroscope while healthy subjects performed level walking, downhill walking, and stair descent. The registered in vivo tibiofemoral kinematics were then used to drive subject-specific multibody knee models to track collateral ligament elongation.

RESULTS

The elongation patterns of the medial collateral ligament varied distinctly among its bundles, ranging from lengthening of the anterior fibers to shortening of the posterior bundle with increases in the knee flexion angle. The elongation patterns of the lateral collateral ligament varied considerably among subjects. It showed an average 4% shortening with increasing flexion until 60% to 70% of the gait cycle, and then recovered during the terminal-swing phase until reaching its reference length (defined at heel strike).

CONCLUSIONS

The observed nonuniform elongation of the medial collateral ligament bundles suggests that single-bundle reconstruction techniques may not fully restore healthy ligament function. Moreover, the observed ligament elongation patterns indicate greater varus than valgus laxity in the loaded knee.

CLINICAL RELEVANCE

Through providing key knowledge about the in vivo elongation patterns of the collateral ligaments throughout complete cycles of functional activities, this study offers in vivo evidence for benchmarking ligament reconstruction and soft-tissue balancing in total knee arthroplasty.

Abstract LB003: Fragment based discovery of MRTX9768, a synthetic lethal-based inhibitor designed to bind the PRMT5-MTA complex and selectively target MTAP/CDKN2A-deleted tumors

The MTAP gene is proximal to and co-deleted in nearly all CDKN2A-deleted cancers. This genetic alteration is present in an estimated 9% of all cancers and is especially prevalent in cancers with high unmet medical need (e.g. mesothelioma (32%), pancreatic (22%), lung squamous (20%)). Multiple independent research teams have demonstrated that tumor cell lines with homozygous MTAP deletions are hypersensitive to shRNA-mediated knock down of PRMT5. MTAP is required for the methionine salvage pathway and MTAP-del cells accumulate MTA, an inhibitory co-factor which competes for binding to the co-factor binding site of PRMT5 with the activating co-factor SAM. PRMT5 is a methyltransferase that adds symmetric dimethylarginine (SDMA) modification to proteins and is essential for mammalian cell survival. A small molecule that selectively binds and stabilizes the catalytically inactive PRMT5•MTA complex may represent a synthetic lethal-based precision medicine for the treatment of MTAP/CDKN2A—del tumors. Notably, 1st generation PRMT5 small molecule inhibitors do not target MTA-complexed PRMT5 and do not exhibit selective inhibition of MTAP-del cancer cells. Here we report a new series of compounds discovered via a fragment-based approach that selectively bind to the PRMT5•MTA complex. A fragment hit was identified in an SPR binding assay with PRMT5•MTA (KD 18 μM). The binding mode was determined by X-ray crystallography and revealed that the fragment makes productive interactions with K333, F327, E435, E444, E435, and W579 of PRMT5 as well as with the co-liganded MTA. Fragment growing aided by structure-based design identified a key interaction with the L312 backbone N-H that enhances binding to PRMT5•MTA (MRTX4646, SPR KD 57 nM). Further exploration highlighted an interaction with the F580 backbone N-H as important for cellular activity and selectivity. This interaction with F580 was illustrated by MRTX7512 which exhibits an IC50 value of 633 nM for inhibition of SDMA in engineered HCT116 MTAP-del cells and demonstrates 15-fold selectivity compared with HCT116 MTAP-WT cells (IC50 9763 nM). Further optimization of cellular potency and pharmacokinetic properties identified MRTX9768, a potent inhibitor of SDMA and cell proliferation in HCT116 MTAP-del cells (SDMA IC50 3 nM; prolif. IC50 11 nM) with marked selectivity over HCT116 MTAP-WT cells (SDMA IC50 544 nM; prolif. IC50 861 nM). In xenograft studies, oral administration of MRTX9768 demonstrates dose-dependent inhibition of SDMA in MTAP-del tumors, with less SDMA modulation observed in bone marrow. In summary, we have used a fragment-based approach to discover a new class of orally active PRMT5•MTA inhibitors that demonstrate selective antitumor activity in MTAP-del tumor cells while sparing MTAP-WT cells.

Citation Format: Christopher R. Smith, Svitlana Kulyk, J. D. Lawson, Lars D. Engstrom, Ruth Aranda, David M. Briere, Robin Gunn, Krystal Moya, Lisa Rahbaek, Laura Waters, Anthony Ivetac, James G. Christensen, Peter Olson, Matthew A. Marx. Fragment based discovery of MRTX9768, a synthetic lethal-based inhibitor designed to bind the PRMT5-MTA complex and selectively target MTAP/CDKN2A-deleted tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr LB003.

Comparison of LI-RADS with other non-invasive liver MRI criteria and radiological opinion for diagnosing hepatocellular carcinoma in cirrhotic livers using gadoxetic acid with histopathological explant correlation

AIM

To establish the diagnostic accuracy of the Liver Imaging Reporting and Data System (LI-RADS) for hepatocellular carcinoma (HCC) and compare its performance to that of international criteria from European Assofor the Study of the Liver (EASL), Japan Society of Hepatology (JSH), Asian Pacific Association for the Study of the Liver (APASL), and Organ Procurement and Transplantation Network (OPTN), and to the reporting radiologist's overall opinion regarding the probability of a nodule being a HCC by correlating with a histological diagnosis from whole liver explants.

MATERIALS AND METHODS

The present single-centre, retrospective review selected participants based on the following criteria: adults (≥18 years) listed for liver transplantation in 2014/2015, with liver cirrhosis at the time of magnetic resonance imaging (MRI) with hepatocyte specific contrast agent, and at least one liver lesion ≥10 mm on MRI with histology from subsequent liver explant for comparison. Each lesion was assessed against international criteria and given a "radiologist opinion" score of 1-5 (1 = definitely benign, 5 = definitely HCC).

RESULTS

Total 268 patient records were reviewed, with 105 eligible lesions identified from 47 patients. Median lesion size was 15.5 mm (range 10-68 mm). Sensitivity (%), specificity (%), and positive predictive value (PPV; %) for LI-RADS LR5 was 45, 89, and 89, for LI-RADS LR4+5 + TIV was 61, 80, and 86, for EASL was 44, 86 and 86, for JSH/APASL was 64, 81, and 87, for OPTN was 36, 90, and 88, and for "radiologist impression" of probably or definitely HCC was 79, 79, and 88 respectively.

CONCLUSIONS

MRI has moderate sensitivity and good specificity for the diagnosis of HCC with considerable variation depending on criteria used. OPTN criteria have the best specificity, but low sensitivity. "Radiologist opinion" gives highest overall accuracy with increases in sensitivity and reduction in specificity when compared to the imaging criteria.

Feature extraction via similarity search: application to atom finding and denoising in electron and scanning probe microscopy imaging

We develop an algorithm for feature extraction based on structural similarity and demonstrate its application for atom and pattern finding in high-resolution electron and scanning probe microscopy images. The use of the combined local identifiers formed from an image subset and appended Fourier, or other transform, allows tuning selectivity to specific patterns based on the nature of the recognition task. The proposed algorithm is implemented in Pycroscopy, a community-driven scientific data analysis package, and is accessible through an interactive Jupyter notebook available on GitHub.

Conserved roles of Osiris genes in insect development, polymorphism and protection

Much of the variation among insects is derived from the different ways that chitin has been moulded to form rigid structures, both internal and external. In this study, we identify a highly conserved expression pattern in an insect-only gene family, the Osiris genes, that is essential for development, but also plays a significant role in phenotypic plasticity and in immunity/toxicity responses. The majority of Osiris genes exist in a highly syntenic cluster, and the cluster itself appears to have arisen very early in the evolution of insects. We used developmental gene expression in the fruit fly, Drosophila melanogaster, the bumble bee, Bombus terrestris, the harvester ant, Pogonomyrmex barbatus, and the wood ant, Formica exsecta, to compare patterns of Osiris gene expression both during development and between alternate caste phenotypes in the polymorphic social insects. Developmental gene expression of Osiris genes is highly conserved across species and correlated with gene location and evolutionary history. The social insect castes are highly divergent in pupal Osiris gene expression. Sets of co-expressed genes that include Osiris genes are enriched in gene ontology terms related to chitin/cuticle and peptidase activity. Osiris genes are essential for cuticle formation in both embryos and pupae, and genes co-expressed with Osiris genes affect wing development. Additionally, Osiris genes and those co-expressed seem to play a conserved role in insect toxicology defences and digestion. Given their role in development, plasticity, and protection, we propose that the Osiris genes play a central role in insect adaptive evolution.

Dietary cation-anion difference may explain why ammonium urate nephrolithiasis occurs more frequently in common bottlenose dolphins () under human care than in free-ranging common bottlenose dolphins

Ammonium urate nephrolithiasis frequently develops in common bottlenose dolphins () managed under human care but is rare in free-ranging common bottlenose dolphins. In other species, the dietary cation-anion difference (DCAD) can affect ammonium urate urolith formation by increasing proton excretion as ammonium ions. Therefore, differences in diet between the 2 dolphin populations could affect urolith formation, but the DCAD of most species consumed by free-ranging and managed dolphins is unknown. To compare the nutrient composition of diets consumed by free-ranging and managed bottlenose dolphins, samples ( = 5) of the 8 species of fish commonly consumed by free-ranging bottlenose dolphins in Sarasota Bay, FL, and the 7 species of fish and squid commonly fed to managed bottlenose dolphins were analyzed for nutrient content. Metabolizable energy was calculated using Atwater factors; the DCAD was calculated using 4 equations commonly used in people and animals that use different absorption coefficients. The nutrient composition of individual species was used to predict the DCAD of 2 model diets typically fed to managed common bottlenose dolphins and a model diet typically consumed by common bottlenose dolphins in Sarasota Bay. To mimic differences in postmortem handling of fish for the 2 populations of bottlenose dolphins, "free-ranging" samples were immediately frozen at -80°C and minimally thawed before analysis, whereas "managed" samples were frozen for 6 to 9 mo at -18°C and completely thawed. "Free-ranging" species contained more Ca and P and less Na and Cl than "managed" fish and squid species. As a consequence, the DCAD of both model managed dolphin diets obtained using 3 of the 4 equations was much more negative than the DCAD of the model free-ranging bottlenose dolphin diet ( < 0.05). The results imply that managed bottlenose dolphins must excrete more protons in urine than free-ranging bottlenose dolphins, which will promote nephrolith formation. The nutrient composition of the free-ranging bottlenose dolphin diet, determined for the first time here, can be used as a guide for feeding managed bottlenose dolphins, but research in vivo is warranted to determine whether adding more cations to the diet will prevent urolith formation in managed dolphins.

A Targeted Metabolomics Assay to Measure Eight Purines in the Diet of Common Bottlenose Dolphins, Tursiops truncatus

Bottlenose dolphins managed under human care, human beings and Dalmatian dogs are prone to forming urate uroliths. Limiting dietary purine intake limits urate urolith formation in people and dogs because purines are metabolized to uric acid, which is excreted in urine. Managed dolphins develop ammonium urate nephroliths, whereas free-ranging dolphins do not. Free-ranging dolphins consume live fish, whereas managed dolphins consume different species that have been stored frozen and thawed. Differences in the purine content of fish consumed by dolphins under human care versus in the wild may be responsible for the difference in urolith prevalence. Commercially available purine assays measure only four purines, but reported changes in purines during frozen storage suggest that a wider range of metabolites should be measured when comparing fresh and stored fish. A method using high performance liquid chromatography with tandem mass spectrometry was developed to quantify eight purine metabolites in whole fish and squid commonly consumed by dolphins. The coefficient of variation within and among days was sometimes high for purines present in small amounts but was acceptable (≤ 25%) for guanine, hypoxanthine, and inosine, which were present in high concentrations. This expanded assay identified a total purine content up to 2.5 times greater than the total that would be quantified if only four purines were measured. Assuming additional purines are absorbed, these results suggest that additional purine metabolites should be measured to better understand the associated risk when fish or other purine-rich foods are consumed by people or animals prone to developing uroliths.

A Targeted Metabolomics Assay to Measure Eight Purines in the Diet of Common Bottlenose Dolphins, Tursiops truncatus

Bottlenose dolphins managed under human care, human beings and Dalmatian dogs are prone to forming urate uroliths. Limiting dietary purine intake limits urate urolith formation in people and dogs because purines are metabolized to uric acid, which is excreted in urine. Managed dolphins develop ammonium urate nephroliths, whereas free-ranging dolphins do not. Free-ranging dolphins consume live fish, whereas managed dolphins consume different species that have been stored frozen and thawed. Differences in the purine content of fish consumed by dolphins under human care versus in the wild may be responsible for the difference in urolith prevalence. Commercially available purine assays measure only four purines, but reported changes in purines during frozen storage suggest that a wider range of metabolites should be measured when comparing fresh and stored fish. A method using high performance liquid chromatography with tandem mass spectrometry was developed to quantify eight purine metabolites in whole fish and squid commonly consumed by dolphins. The coefficient of variation within and among days was sometimes high for purines present in small amounts but was acceptable (≤ 25%) for guanine, hypoxanthine, and inosine, which were present in high concentrations. This expanded assay identified a total purine content up to 2.5 times greater than the total that would be quantified if only four purines were measured. Assuming additional purines are absorbed, these results suggest that additional purine metabolites should be measured to better understand the associated risk when fish or other purine-rich foods are consumed by people or animals prone to developing uroliths.

Fragment-Based Discovery of a Small Molecule Inhibitor of Bruton's Tyrosine Kinase

The discovery and optimization of a series of 4-aminocinnoline-3-carboxamide inhibitors of Bruton's tyrosine kinase are reported. A fragment-based screening approach incorporating X-ray co-crystallography was used to identify a cinnoline fragment and characterize its binding mode in the ATP binding site of Btk. Optimization of the fragment hit resulted in the identification of a lead compound which reduced paw swelling in a dose- and exposure-dependent fashion in a rat model of collagen-induced arthritis.

Erratum: Seasonal dynamics of megafauna on the deep West Antarctic Peninsula shelf in response to variable phytodetrital influx

[This corrects the article DOI: 10.1098/rsos.140294.].

Deciphering the peptidome of urine from ovarian cancer patients and healthy controls

Background

Ovarian cancer (OvCa) is the most lethal gynecological malignancy. The emergence of high-throughput technologies, such as mass spectrometry, has allowed for a paradigm shift in the way we search for novel biomarkers. Urine-based peptidomic profiling is a novel approach that may result in the discovery of noninvasive biomarkers for diagnosing patients with OvCa. In this study, the peptidome of urine from 6 ovarian cancer patients and 6 healthy controls was deciphered.

Results

Urine samples underwent ultrafiltration and the filtrate was subjected to solid phase extraction, followed by fractionation using strong cation exchange chromatography. These fractions were analyzed using an Orbitrap mass spectrometer. Over 4600 unique endogenous urine peptides arising from 713 proteins were catalogued, representing the largest urine peptidome reported to date. Each specimen was processed in triplicate and reproducibility at the protein (69-76%) and peptide (58-63%) levels were noted. More importantly, over 3100 unique peptides were detected solely in OvCa specimens. One such promising biomarker was leucine-rich alpha-2-glycoprotein (LRG1), where multiple peptides were found in all urines from OvCa patients, but only one peptide was found in one healthy control urine sample.

Conclusions

Mining the urine peptidome may yield highly promising novel OvCa biomarkers.

Deciphering the ovarian cancer ascites fluid peptidome

Background

Conventional proteomic approaches have thus far been unable to identify novel serum biomarkers for ovarian cancer that are more sensitive and specific than the current clinically used marker, CA-125. Because endogenous peptides are smaller and may enter the circulation more easily than proteins, a focus on the low-molecular-weight region may reveal novel biomarkers with enhanced sensitivity and specificity. In this study, we deciphered the peptidome of ascites fluid from 3 ovarian cancer patients and 3 benign individuals (ascites fluid from patients with liver cirrhosis).

Results

Following ultrafiltration of the ascites fluids to remove larger proteins, each filtrate was subjected to solid phase extraction and fractionated using strong cation exchange chromatography. The resultant fractions were analyzed using an Orbitrap mass spectrometer. We identified over 2000 unique endogenous peptides derived from 259 proteins. We then catalogued over 777 peptides that were found only in ovarian cancer ascites. Our list of peptides found in ovarian cancer specimens includes fragments derived from the proteins vitronectin, transketolase and haptoglobin.

Conclusions

Peptidomics may uncover previously undiscovered disease-specific endogenous peptides that warrant further investigation as biomarkers for ovarian cancer.

Glycoproteomic identification of potential glycoprotein biomarkers in ovarian cancer proximal fluids

BACKGROUND

Ovarian cancer is the leading cause of death among all gynecological disorders. Aberrant glycosylation, or more specifically, increased sialylation of proteins has been observed in ovarian cancer. Several sialyltransferase genes have been shown to be up-regulated at both the mRNA and protein levels in a number of cancers, including that of the ovary. ST6GAL1 (β-galactosamide α2,6-sialyltranferase 1) gene expression has previously been shown to be upregulated in ovarian cancers of all major subtypes.

METHODS

We have identified the sialome (i.e., sialic acid containing glycoproteins) of biological fluids from ovarian cancer patients and ovarian cancer cell lines utilizing tandem mass spectrometry as a potential pool of novel biomarker candidates. The sialoglycopeptides from four ovarian cancer cell lines, pooled ascites (n=13) and ovarian cyst (n=14) fluids from ovarian cancer patients were enriched utilizing affinity to agarose-immobilized Elderberry lectin (Sambucus nigra agglutinin) and magnetic hydrazide beads folowing periodate-mediated oxidation of sialic acids. Benign ovarian cyst (n=10) and peritoneal effusion (n=20) fluids were analyzed in the same fashion to serve as controls. PNGase F deglycosylated peptides were identified using electrospray ionization-LTQ Orbitrap tandem mass spectrometry.

RESULTS

In all of the samples analyzed in the glycoproteomic portion of the study, we have identified 579 glycosylation sites on 333 proteins. Of these, 13 were exclusively identified in biological fluids from ovarian cancer patients, and another eight were common to these fluids and the ovarian cancer cell line supernatants.

CONCLUSIONS

The proteins identified in the present study could form the basis for future studies examining and quantifying their sialylation status as biomarkers of ovarian cancer.

Volatile food attractants forOryzaephilus surinamensis (L.) from oats

The sawtoothed grain beetle,Oryzaephilus surinamensis (L.) (Coleoptera: Cucujidae), is attracted to certain volatile components that occur in whole and rolled oats as determined by a laboratory pitfall chamber bioassay. More than 100 components were detected in the attractive carbonyl-containing fractions; 14 of these, making up 60% of the total, were identified and bioassayed. Although hexanal, heptanal, octanal, (E)-2-heptenal, and 2-furaldehyde, at doses ranging variously from 1 to 100 μg, were all significantly attractive, only 1 /10 to 1 /100 as much (E)-2-nonenal or (E,E)-2,4-nonadienal was necessary to produce comparable insect response. In addition, propanal and formaldehyde (previously reported in oats but not detected by us) were bioassayed and found to be attractive.

Structure-activity relationships among maytansinoids in their effect on the European corn borer,Ostrinia nubilalis (Hübner)

Five maytansinoids fromMaytenus (Celastraceae) andPutterlickia (Rhamnaceae) species were tested for biological activity against the European corn borerOstrinia nubilalis. Maytanbutine, maytansine, and maytanvaline, all of which contain an amino acid residue at C-3, were active and comparable in their effect on larvae to trewiasine, a known active, amino acid-containing maytansinoid fromTrewia nudiflora. Maytanacine, which has an acetate group at C-3, was not as active as maytansine, maytanvaline, maytanbutine, or trewiasine, but significantly retarded the development of the larvae. Normaysine, which has no oxygen substituent at C-3, had no significant effect on mortality and only moderate effect on development of the larvae. The presence of the amino acid moiety at C-3 appears to be an important factor for the biological activity of maytansinoids.

From principles to practice: a spatial approach to systematic conservation planning in the deep sea

Increases in the demand and price for industrial metals, combined with advances in technological capabilities have now made deep-sea mining more feasible and economically viable. In order to balance economic interests with the conservation of abyssal plain ecosystems, it is becoming increasingly important to develop a systematic approach to spatial management and zoning of the deep sea. Here, we describe an expert-driven systematic conservation planning process applied to inform science-based recommendations to the International Seabed Authority for a system of deep-sea marine protected areas (MPAs) to safeguard biodiversity and ecosystem function in an abyssal Pacific region targeted for nodule mining (e.g. the Clarion-Clipperton fracture zone, CCZ). Our use of geospatial analysis and expert opinion in forming the recommendations allowed us to stratify the proposed network by biophysical gradients, maximize the number of biologically unique seamounts within each subregion, and minimize socioeconomic impacts. The resulting proposal for an MPA network (nine replicate 400 × 400 km MPAs) covers 24% (1 440 000 km(2)) of the total CCZ planning region and serves as example of swift and pre-emptive conservation planning across an unprecedented area in the deep sea. As pressure from resource extraction increases in the future, the scientific guiding principles outlined in this research can serve as a basis for collaborative international approaches to ocean management.

Video image analysis in the Australian meat industry - precision and accuracy of predicting lean meat yield in lamb carcasses

A wide selection of lamb types of mixed sex (ewes and wethers) were slaughtered at a commercial abattoir and during this process images of 360 carcasses were obtained online using the VIAScan® system developed by Meat and Livestock Australia. Soft tissue depth at the GR site (thickness of tissue over the 12th rib 110 mm from the midline) was measured by an abattoir employee using the AUS-MEAT sheep probe (PGR). Another measure of this thickness was taken in the chiller using a GR knife (NGR). Each carcass was subsequently broken down to a range of trimmed boneless retail cuts and the lean meat yield determined. The current industry model for predicting meat yield uses hot carcass weight (HCW) and tissue depth at the GR site. A low level of accuracy and precision was found when HCW and PGR were used to predict lean meat yield (R(2)=0.19, r.s.d.=2.80%), which could be improved markedly when PGR was replaced by NGR (R(2)=0.41, r.s.d.=2.39%). If the GR measures were replaced by 8 VIAScan® measures then greater prediction accuracy could be achieved (R(2)=0.52, r.s.d.=2.17%). A similar result was achieved when the model was based on principal components (PCs) computed from the 8 VIAScan® measures (R(2)=0.52, r.s.d.=2.17%). The use of PCs also improved the stability of the model compared to a regression model based on HCW and NGR. The transportability of the models was tested by randomly dividing the data set and comparing coefficients and the level of accuracy and precision. Those models based on PCs were superior to those based on regression. It is demonstrated that with the appropriate modeling the VIAScan® system offers a workable method for predicting lean meat yield automatically.

cis-5,cis-9,cis-12-octadecatrienoic and some unusual oxygenated acids inXeranthemum annuum seed oil

Seed oil ofXeranthemum annuum (family Compositae) contains a number of unusual fatty acids in addition to palmitic, stearic, oleic, linoleic and linolenic. These acids includecis-5,cis-9,cis-12-octadecatrienoic, 5%;cis-9-L: ,10-L: -epoxyoctadecanoic, 3%;cis-9-L: ,10-L: -epoxy-cis-12-octadecenoic (coronaric), 8%; andcis-12-D: ,13-D: -epoxy-cis-9-octadecenoic (vernolic), 2%; as well as a mixture of two hydroxy acids, 11%. The absolute configurations of the two 9,10-epoxy acids are established for the first time.

Caltha palustris L. Seed Oil. A source of four fatty acids withcis-5-unsaturation

The seed oil ofCaltha palustris L. yields two unusual polyunsaturated components, all-cis-5,11,14-eicosatrienoic acid (23%) and all-cis-5,11,14,17-eicosatetraenoic acid (1%). The C(18) monoene fraction (26%) is a mixture ofcis-5- andcis-9-octadecenoic acids (2ratio1). The C(20) monoene fraction (12%) is a mixture ofcis-11- andcis-5-isomers (3ratio1).

Separation of kallikrein 6 glycoprotein subpopulations in biological fluids by anion-exchange chromatography coupled to ELISA and identification by mass spectrometry

Kallikrein 6 (KLK6) has been shown to be aberrantly glycosylated in ovarian cancer. Here, we report a novel HPLC anion exchange method, coupled to a KLK6-specific ELISA, capable of differentiating KLK6 glycoform subgroups in biological fluids. Biological fluids were fractionated using anion exchange and resulting fractions were analyzed for KLK6 content by ELISA producing a four-peak elution profile. Using this assay, the KLK6 elution profile and distribution across peaks of a set (n = 7) of ovarian cancer patient matched serum and ascites fluid samples was found to be different than the profile of serum and cerebrospinal fluid (CSF) of normal individuals (n = 7). Glycosylation patterns of recombinant KLK6 (rKLK6) were characterized using tandem mass spectrometry (MS/MS), and found to consist of a highly heterogeneous KLK6 population. This protein was found to contain all of the four diagnostic KLK6 peaks present in the previously assayed biological fluids. The rKLK6 glycoform composition of each peak was assessed by lectin affinity and MS/MS based glycopeptide quantification by product ion monitoring. The combined results showed an increase in terminal alpha 2-6 linked sialic acid in the N-glycans found on KLK6 from ovarian cancer serum and ascites, as opposed to CSF and serum of normal individuals.