Discovery of HC-7366: An Orally Bioavailable and Efficacious GCN2 Kinase Activator

A series of activators of GCN2 (general control nonderepressible 2) kinase have been developed, leading to HC-7366, which has entered the clinic as an antitumor therapy. Optimization resulted in improved permeability compared to that of the original indazole hinge binding scaffold, while maintaining potency at GCN2 and selectivity over PERK (protein kinase RNA-like endoplasmic reticulum kinase). The improved ADME properties of this series led to robust in vivo compound exposure in both rats and mice, allowing HC-7366 to be dosed in xenograft models, demonstrating that activation of the GCN2 pathway by this compound leads to tumor growth inhibition.

Abstract 6231: Activation of GCN2 by HC-7366 results in significant antitumor efficacy as monotherapy and in combination with multiple standard of care agents in various solid cancer models

The integrated stress response (ISR) is an adaptive signaling pathway that cells utilize to respond to a wide range of extrinsic and intrinsic stresses, which are important for tumorigenesis. Activation of ISR is suggested to play a dual role in cell fate decisions. While the ISR promotes survival, prolonged activation of ISR induces apoptosis. We are developing HC-7366, a first-in-class, first-in-human GCN2 activator, and are currently evaluating it in a phase 1 clinical trial in solid tumors (NCT05121948). In this study, we present the characterization of the antitumor effects of HC-7366 in solid tumors.

In vivo efficacy studies using HC-7366 montherapy showed significant tumor growth inhibition (TGI%) in preclinical cancer models of colorectal (78-95%), head and neck (33% regression), sarcoma (80%) and prostate (65%). HC-7366 activated the ISR in tumors from treated mice as evidenced by induction of the ATF4 target genes ASNS and PSAT1. Additionally, HC-7366 induced the proapoptotic protein PUMA and reduced HIF1⍺ and HIF2⍺ levels. Furthermore, HC-7366 showed significant benefit in colorectal models when combined with DC101 (anti-VEGFR2 antibody), 5-fluorouracil (chemotherapy), alpelisib (PI3Kα inhibitor), or trametinib (MEK1/2 inhibitor). Using GCN2 CRISPR-knockout cells, we confirmed that the HC-7366 mediated reduction of cell growth and induction of ISR markers was dependent on GCN2. We performed multi-omics analyses to further understand the mechanism of action. Metabolomics analysis of tumors treated with HC-7366 revealed that HC-7366 altered several metabolites involved in amino acid metabolism, oxidative stress, the urea cycle, and pyrimidine biosynthesis. Additionally, proteomics analysis showed that HC-7366 significantly reduced proteins involved in oxidative phosphorylation. Analysis of the transcriptome in tumors from treated mice demonstrated that HC-7366 reduced the activity of HIF and E2F1-driven transcription, including expression of metaphase-anaphase transition genes, consistent with decreased Ki67 staining in tumors. ATF4 and JUN transcriptional activity was enhanced with HC-7366 treatment consistent with activation of ISR. Collectively, our in vitro and in vivo results demonstrate that HC-7366 is a potent GCN2 activator with strong antitumor activity across multiple solid tumor models as a monotherapy or in combination with standard of care agents.

Citation Format: Feven Tameire, Paulina Wojnarowicz, Crissy Dudgeon, Sho Fujisawa, Sharon Huang, Owen B. Reilly, Nicholas Collette, Jeremy Drees, Kathryn Bieging-Rolett, Takashi O. Kangas, Weiyu Zhang, Maria Fumagalli, Iman Dewji, Yunfang Li, Anissa SH Chan, Xiaohong Qiu, Ben Harrison, Ashley LaCayo, Ricardo A. Cordova, Kirk A. Staschke, Alan C. Rigby, Savithri Ramurthy, Eric S. Lightcap, David Surguladze, Nandita Bose. Activation of GCN2 by HC-7366 results in significant antitumor efficacy as monotherapy and in combination with multiple standard of care agents in various solid cancer models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6231.

Towards the sustainable discovery and development of new antibiotics

An ever-increasing demand for novel antimicrobials to treat life-threatening infections caused by the global spread of multidrug-resistant bacterial pathogens stands in stark contrast to the current level of investment in their development, particularly in the fields of natural-product-derived and synthetic small molecules. New agents displaying innovative chemistry and modes of action are desperately needed worldwide to tackle the public health menace posed by antimicrobial resistance. Here, our consortium presents a strategic blueprint to substantially improve our ability to discover and develop new antibiotics. We propose both short-term and long-term solutions to overcome the most urgent limitations in the various sectors of research and funding, aiming to bridge the gap between academic, industrial and political stakeholders, and to unite interdisciplinary expertise in order to efficiently fuel the translational pipeline for the benefit of future generations.

Antimicrobial resistance is an increasing threat to public health and encouraging the development of new antimicrobials is one of the most important ways to address the problem. This Roadmap article aims to bring together industrial, academic and political partners, and proposes both short-term and long-term solutions to this challenge.

Structural and Biological Basis of Small Molecule Inhibition of Escherichia coli LpxD Acyltransferase Essential for Lipopolysaccharide Biosynthesis

LpxD, acyl-ACP-dependent N-acyltransferase, is the third enzyme of lipid A biosynthesis in Gram-negative bacteria. A recent probe-based screen identified several compounds, including 6359-0284 (compound 1), that inhibit the enzymatic activity of Escherichia coli (E. coli) LpxD. Here, we use these inhibitors to chemically validate LpxD as an attractive antibacterial target. We first found that compound 1 was oxidized in solution to the more stable aromatized tetrahydro-pyrazolo-quinolinone compound 1o. From the Escherichia coli strain deficient in efflux, we isolated a mutant that was less susceptible to compound 1o and had an lpxD missense mutation (Gly268Cys), supporting the cellular on-target activity. Using surface plasma resonance, we showed direct binding to E. coli LpxD for compound 1o and other reported LpxD inhibitors in vitro. Furthermore, we determined eight cocrystal structures of E. coli LpxD/inhibitor complexes. These costructures pinpointed the 4'-phosphopantetheine binding site as the common ligand binding hotspot, where hydrogen bonds to Gly269 and/or Gly287 were important for inhibitor binding. In addition, the LpxD/compound 1o costructure rationalized the reduced activity of compound 1o in the LpxD_Gly268Cys mutant. Moreover, we obtained the LpxD structure in complex with a previously reported LpxA/LpxD dual targeting peptide inhibitor, RJPXD33, providing structural rationale for the unique dual targeting properties of this peptide. Given that the active site residues of LpxD are conserved in multidrug resistant Enterobacteriaceae, this work paves the way for future LpxD drug discovery efforts combating these Gram-negative pathogens.

Design and Discovery of N-(3-(2-(2-Hydroxyethoxy)-6-morpholinopyridin-4-yl)-4-methylphenyl)-2-(trifluoromethyl)isonicotinamide, a Selective, Efficacious, and Well-Tolerated RAF Inhibitor Targeting RAS Mutant Cancers: The Path to the Clinic

Direct pharmacological inhibition of RAS has remained elusive, and efforts to target CRAF have been challenging due to the complex nature of RAF signaling, downstream of activated RAS, and the poor overall kinase selectivity of putative RAF inhibitors. Herein, we describe 15 (LXH254, Aversa, R.; et al. Int. Patent WO2014151616A1, 2014), a selective B/C RAF inhibitor, which was developed by focusing on drug-like properties and selectivity. Our previous tool compound, 3 (RAF709; Nishiguchi, G. A.; et al. J. Med. Chem. 2017, 60, 4969), was potent, selective, efficacious, and well tolerated in preclinical models, but the high human intrinsic clearance precluded further development and prompted further investigation of close analogues. A structure-based approach led to a pyridine series with an alcohol side chain that could interact with the DFG loop and significantly improved cell potency. Further mitigation of human intrinsic clearance and time-dependent inhibition led to the discovery of 15. Due to its excellent properties, it was progressed through toxicology studies and is being tested in phase 1 clinical trials.

Design and synthesis of potent RSK inhibitors

Utilizing the already described 3,4-bi-aryl pyridine series as a starting point, incorporation of a second ring system with a hydrogen bond donor and additional hydrophobic contacts yielded the azaindole series which exhibited potent, picomolar RSK2 inhibition and the most potent in vitro target modulation seen thus far for a RSK inhibitor. In the context of the more potent core, several changes at the phenol moiety were assessed to potentially find a tool molecule appropriate for in vivo evaluation.

Abstract DDT01-04: Pharmacological profile and anti-tumor properties of LXH254, a highly selective RAF kinase inhibitor

The mitogen-activated protein kinase (MAPK) signaling pathway is frequently activated in human cancers due to genetic alterations that can occur at multiple nodes, the most prevalent of which are mutations in RAS or BRAF. While BRAFV600 mutant tumors are responsive to RAF inhibitors such as dabrafenib and vemurafenib, these drugs are ineffective in RAS mutant cancers and tumors expressing other RAF mutations. CRAF kinase functions as a critical effector in mutant RAS and Class II/III BRAF mutant tumors and plays a role in feedback-mediated pathway reactivation following MEK inhibition. Thus, selective inhibitors that potently inhibit the activity of CRAF could be both effective in blocking mutant RAS and BRAF signaling and in inhibiting feedback-mediated activation in combination with a MEK inhibitor. LXH254 is a type II ATP-competitive inhibitor that inhibits both B- and CRAF kinase activities at picomolar concentrations with a high degree of selectivity against a panel of 456 human kinases and in cell-based assays. LXH254 not only inhibits MAPK signaling activity in tumor models harboring BRAFV600 mutation, but also inhibits mutant N- and KRAS-driven signaling due to its ability to inhibit both RAF monomers and dimers with similar potencies. LXH254 is orally bioavailable, demonstrates a direct PK/PD relationship and causes tumor regression in multiple cell line and primary human tumor derived xenograft models at well-tolerated doses. LXH254 represents a next generation RAF inhibitor that is differentiated from other RAF inhibitors in this class due to the high degree of selectivity. In preclinical efficacy and toxicology studies, LXH254 demonstrated a relatively wide therapeutic index which should enable effective interrogation of RAF inhibition in patients with decreased risk for off-target toxicity. LXH254 is currently in a Phase I trial in patients with solid tumors expressing MAPK pathway mutations.

Citation Format: Darrin D. Stuart, Wenlin Shao, Yuji Mishina, Yun Feng, Giordano Caponigro, Vesselina G. Cooke, Stacey Rivera, Fang Shen, Joshua Korn, Lesley A. Mathews Griner, Giselle Nishiguchi, Benjamin Taft, Lifeng Wan, Sharadha Subramanian, Yan Lou, Lina Setti, Matthew Burger, Victor Tamez, Alice Rico, Robert Aversa, John Tellew, Jacob R. Haling, Valery Polyakov, Amy Lambert, Richard Zang, Ann Van Abbema, Mohamad Hekmat-Nejad, Payman Amiri, Mallika Singh, Nicholas Keen, Michael P. Dillon, Emma Lees, William R. Sellers, Savithri Ramurthy. Pharmacological profile and anti-tumor properties of LXH254, a highly selective RAF kinase inhibitor [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr DDT01-04.

Antitumor Properties of RAF709, a Highly Selective and Potent Inhibitor of RAF Kinase Dimers, in Tumors Driven by Mutant RAS or BRAF

Resistance to the RAF inhibitor vemurafenib arises commonly in melanomas driven by the activated BRAF oncogene. Here, we report antitumor properties of RAF709, a novel ATP-competitive kinase inhibitor with high potency and selectivity against RAF kinases. RAF709 exhibited a mode of RAF inhibition distinct from RAF monomer inhibitors such as vemurafenib, showing equal activity against both RAF monomers and dimers. As a result, RAF709 inhibited MAPK signaling activity in tumor models harboring either BRAF^V600 alterations or mutant N- and KRAS-driven signaling, with minimal paradoxical activation of wild-type RAF. In cell lines and murine xenograft models, RAF709 demonstrated selective antitumor activity in tumor cells harboring BRAF or RAS mutations compared with cells with wild-type BRAF and RAS genes. RAF709 demonstrated a direct pharmacokinetic/pharmacodynamic relationship in in vivo tumor models harboring KRAS mutation. Furthermore, RAF709 elicited regression of primary human tumor-derived xenograft models with BRAF, NRAS, or KRAS mutations with excellent tolerability. Our results support further development of inhibitors like RAF709, which represents a next-generation RAF inhibitor with unique biochemical and cellular properties that enables antitumor activities in RAS-mutant tumors.Significance: In an effort to develop RAF inhibitors with the appropriate pharmacological properties to treat RAS mutant tumors, RAF709, a compound with potency, selectivity, and in vivo properties, was developed that will allow preclinical therapeutic hypothesis testing, but also provide an excellent probe to further unravel the complexities of RAF kinase signaling. Cancer Res; 78(6); 1537-48. ©2018 AACR.

Inhibition of prenylated KRAS in a lipid environment

RAS mutations lead to a constitutively active oncogenic protein that signals through multiple effector pathways. In this chemical biology study, we describe a novel coupled biochemical assay that measures activation of the effector BRAF by prenylated KRAS^G12V in a lipid-dependent manner. Using this assay, we discovered compounds that block biochemical and cellular functions of KRAS^G12V with low single-digit micromolar potency. We characterized the structural basis for inhibition using NMR methods and showed that the compounds stabilized the inactive conformation of KRAS^G12V. Determination of the biophysical affinity of binding using biolayer interferometry demonstrated that the potency of inhibition matches the affinity of binding only when KRAS is in its native state, namely post-translationally modified and in a lipid environment. The assays we describe here provide a first-time alignment across biochemical, biophysical, and cellular KRAS assays through incorporation of key physiological factors regulating RAS biology, namely a negatively charged lipid environment and prenylation, into the in vitro assays. These assays and the ligands we discovered are valuable tools for further study of KRAS inhibition and drug discovery.

Abstract 330: Development of a highly selective B/CRAF kinase inhibitor that exhibits antitumor activities in RAS and BRAF mutant tumors with minimal paradoxical activation

The mitogen-activated protein kinase (MAPK) signaling pathway is frequently activated in human cancers due to genetic alterations that can occur at multiple nodes in the pathway, the most prevalent of which are mutations in RAS or BRAF. While BRAFV600 mutant tumors are effectively treated with existing RAF inhibitors, RAS mutant cancers and tumors expressing atypical BRAF mutants remain an unmet medical need. Emerging biology has demonstrated that the CRAF kinase functions as a critical mediator of mutant KRAS-driven cell proliferation and tumor development. CRAF was also shown to be the mediator of feedback-mediated pathway reactivation following MEK inhibitor treatment in KRAS mutant cancers. Hence selective inhibitors that potently inhibit the activity of CRAF could be both effective in blocking mutant RAS-driven tumorigenesis and in alleviating feedback activation. We have developed a type II ATP-competitive inhibitor that inhibits both B- and CRAF kinase activities at picomolar IC50 values in biochemical assays with high selectivity profile against a panel of 456 human kinases. The inhibitor not only inhibits MAPK signaling activity in tumor models harboring BRAFV600 mutation, but also inhibits mutant N- and KRAS-driven signaling with minimum paradoxical activation, likely due to its activity in inhibiting both RAF monomers and dimers with similar potencies. Correspondingly, profiling data of the inhibitor in a panel of 480 human cancer cell lines shows that it has higher antitumor activities in cell lines harboring BRAF or RAS mutations as compared to those that are wild-type. The inhibitor is orally bioavailable, it demonstrates a direct PK/PD relationship and causes tumor regression in multiple cell line and primary human tumor derived xenograft models that have BRAF, NRAS or KRAS mutations with good tolerability. Thus, we have developed a next generation RAF inhibitor with unique biochemical and cellular properties that enables its antitumor activities in RAS mutant tumors.

Citation Format: Wenlin Shao, Yuji Mishina, Yun Feng, Giordano Caponigro, Savithri Ramurthy, Vesselina Cooke, Lesley Griner, Gisele Nishiguchi, Alice Rico, Ben Taft, Matthew Burger, Huw Tanner, Valery Polyakov, Brent Appleton, John Tellew, Richard Zang, Mohammad Hekmat-Nejad, Payman Amiri, Mallika Singh, Darrin Stuart. Development of a highly selective B/CRAF kinase inhibitor that exhibits antitumor activities in RAS and BRAF mutant tumors with minimal paradoxical activation. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 330.

Discovery of RAF265: A Potent mut-B-RAF Inhibitor for the Treatment of Metastatic Melanoma

Abrogation of errant signaling along the MAPK pathway through the inhibition of B-RAF kinase is a validated approach for the treatment of pathway-dependent cancers. We report the development of imidazo-benzimidazoles as potent B-RAF inhibitors. Robust in vivo efficacy coupled with correlating pharmacokinetic/pharmacodynamic (PKPD) and PD-efficacy relationships led to the identification of RAF265, 1, which has advanced into clinical trials.

Discovery of Potent and Selective RSK Inhibitors as Biological Probes

While the p90 ribosomal S6 kinase (RSK) family has been implicated in multiple tumor cell functions, the full understanding of this kinase family has been restricted by the lack of highly selective inhibitors. A bis-phenol pyrazole was identified from high-throughput screening as an inhibitor of the N-terminal kinase of RSK2. Structure-based drug design using crystallography, conformational analysis, and scaffold morphing resulted in highly optimized difluorophenol pyridine inhibitors of the RSK kinase family as demonstrated cellularly by the inhibition of YB1 phosphorylation. These compounds provide for the first time in vitro tools with an improved selectivity and potency profile to examine the importance of RSK signaling in cancer cells and to fully evaluate RSK as a therapeutic target.

Abstract B38: Inhibiting mutated KRAS, a broken switch of effector pathways

Mutated forms of KRAS are no longer able to switch effectors between “on” and “off” states. It is known that the function of KRAS is controlled by key parts in the C-terminus, including six consecutive lysines, a terminal prenyl moiety and a terminal carboxymethyl functional group. We set out to discover compounds which would inhibit the function of mutated KRAS as an activator for effectors. This campaign yielded several compounds that blocked biochemical and cellular functions of KRAS with low micromolar activity while not affecting markers outside of KRAS pathways in cells. In order to understand the mode of binding of these compounds to KRAS, we generated different forms of the protein, including unprenylated truncated and fully processed full-length protein. NMR studies with truncated protein (amino acids 1-169) identified a site at which compound binding stabilized the inactive conformation of KRAS. This site is located adjacent to switch-II and is similar to sites described by others. The Kd determined for this binding event is almost 3 orders of magnitude higher than the IC50 and EC50 values measured in biochemical and cellular assays. In order to understand this difference, we developed a biophysical assay using the Fortebio system which enabled binding studies in a system with full-length prenylated protein in the presence of lipids, to match the context of the biochemical and cellular assays. Micromolar binding to the full-length prenylated KRAS protein was observed in the Fortebio assay and binding was not observed in the absence of prenylation, consistent with the near millimolar Kd observed by NMR for truncated KRAS. Curiously, similar micromolar binding was seen to a peptide derived from the C-terminus of KRAS (amino acids 168-185) with and without prenyl modification while related compounds that do not bind to the full-length prenylated KRAS also do not bind to these peptides. It is still unclear whether binding to the terminal peptide in lipid context is related to the binding site adjacent to switch-II. From a drug discovery perspective, it remains to be confirmed whether current inhibitors can be optimized.

Citation Format: Johanna Jansen, Wolfgang Jahnke, Susan Fong, Laura Tandeske, Charles Wartchow, Keith Pfister, Tatiana Zavorotinskaya, Anke Blechschmidt, Dirksen Bussiere, Yumin Dai, Jeff Dove, Eric Fang, David Farley, Jean-Michel Florent, John Fuller, Simona Gokhin, Alvar Gossert, Mohammad Hekmat-Nejad, Chrystèle Henry, Julia Klopp, Bill Lenahan, Andreas Lingel, Arndt Meyer, Jamie Narberes, Gwynn Pardee, C Gregory Paris, Savithri Ramurthy, Paul Renhowe, Sebastien Rieffel, Kevin Shoemaker, Sharadha Subramanian, Tiffany Tsang, Stephania Widger, Armin Widmer, Isabel Zaror, Stephen Hardy. Inhibiting mutated KRAS, a broken switch of effector pathways. [abstract]. In: Proceedings of the AACR Special Conference on RAS Oncogenes: From Biology to Therapy; Feb 24-27, 2014; Lake Buena Vista, FL. Philadelphia (PA): AACR; Mol Cancer Res 2014;12(12 Suppl):Abstract nr B38. doi: 10.1158/1557-3125.RASONC14-B38

Structure-Based Drug Design of Novel, Potent, and Selective Azabenzimidazoles (ABI) as ATR Inhibitors

Compound 13 was discovered through morphing of the ATR biochemical HTS hit 1. The ABI series was potent and selective for ATR. Incorporation of a 6-azaindole afforded a marked increase in cellular potency but was associated with poor PK and hERG ion channel inhibition. DMPK experiments established that CYP P450 and AO metabolism in conjunction with Pgp and BCRP efflux were major causative mechanisms for the observed PK. The series also harbored the CYP3A4 TDI liability driven by the presence of both a morpholine and an indole moiety. Incorporation of an adjacent fluorine or nitrogen into the 6-azaindole addressed many of the various medicinal chemistry issues encountered.

Correction to Design and Synthesis of Orally Bioavailable Benzimidazole Reverse Amides as Pan RAF Kinase Inhibitors

[This corrects the article DOI: 10.1021/ml5002272.].

Design and Synthesis of Orally Bioavailable Benzimidazole Reverse Amides as Pan RAF Kinase Inhibitors

Benzimidazole reverse amides were designed and synthesized as Pan RAF kinase inhibitors. Investigation of the structure-activity relationship of the compounds revealed that they were potent in vitro and exhibited desirable in vivo properties.

2-Amino-7-substituted benzoxazole analogs as potent RSK2 inhibitors

2-Amino-7-substituted benzoxazole analogs were identified by HTS as inhibitors of RSK2. Molecular modeling and medicinal chemistry techniques were employed to explore the SAR for this series with a focus of improving in vitro and target modulation potency and physicochemical properties.

4-(Aminoalkylamino)-3-benzimidazole-quinolinones as potent CHK-1 inhibitors

CHK-1 is one of the key enzymes regulating checkpoints in cellular growth cycles. Novel 4-(amino-alkylamino)-3-benzimidazole-quinolinones were prepared and assayed for their ability to inhibit CHK-1. These compounds are potent cell permeable CHK-1 inhibitors and showed synergistic effect with a DNA-damaging agent, camptothecin.

The synthesis of enantiomerically pure, highly functionalized heterocycles: the products of amino acid based acylnitroso hetero Diels-Alder reactions

The diastereoselectivities of several chiral acylnitroso dienophiles (9a-h, 12 and 15) derived from optically pure, N-protected alpha-amino hydroxamic acids (2a-h, 4 and 7) were determined in an intermolecular hetero Diels-Alder reaction with cyclopentadiene. The diastereomeric excesses ranged from 0 to 72%. Hydroxamic acids with polar functionality were examined extensively to determine the effect of hydrogen bonding on the cycloaddition. The largest increase in diastereoselectivity was observed with increasing the steric bulk at the alpha-position of the hydroxamic acids and not with potential hydrogen bonding interactions. The cycloadditions afforded synthetically useful quantities of functionally rich, enantiomerically pure heterocycles (10a-h, 11a-h, 13, 14, 16 and 17), which have been elaborated into a variety of biologically interesting products.

Framework-Reactive Siderophore Analogs as Potential Cell-Selective Drugs. Design and Syntheses of Trimelamol-Based Iron Chelators

Currently, the role of DNA-directed alkylating agents as potential anticancer/ antimicrobial drugs is of wide interest. Most of the alkylating agents used clinically as drugs damage DNA in cells without specificity, and this can lead to undesired toxicity problems. Minimizing serum residence time by targeting the drug to select pathogens or organs might diminish the effects of nonselective reactivity. This paper describes the syntheses and preliminary studies of analogs of siderophores (microbial iron chelators) 2 and 20 that incorporate centers within the siderophore framework capable of generating potent electrophiles (iminium ions), hopefully after directed cellular recognition and uptake. Formation of N-aminals from trimelamol (3) and substituted hydroxamic acid 4 or 5was critical for the design and synthesis of the targets. In preliminary biological testing, compound 2, a trimelamol-based siderophore analog, was active against Escherichia coli X580, illustrating the therapeutic potential of this new type of siderophore-mediated drug design and delivery.

Peptidomimetic antagonists designed to inhibit the binding of CD4 to HIV GP120

Attempts to enhance the efficacy of our previously reported CD4 CDR2-like (residues 40-45) mimetic 1 by incorporation of the critical guanidine residue Arg-59 of CD4 are described.

Peptidomimetics of the immunoglobulin supergene family--a review

An important goal of structural biochemistry is the reduction of complex molecules to small functional units that are amenable to high-resolution structural analysis and rapid modification. The dissection of multidomain proteins into small synthetic conformationally restricted components is an important step in the design of low-molecular-weight nonpeptides that mimic the activity of the native protein. Mimetics of critical functional domains might possess beneficial properties in comparison to the intact proteinaceous species with regard to specificity and therapeutic potential, and are valuable probes for the study of molecular recognition events.