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Jain AN, Brueckner AC, Jorge C, Cleves AE, Khandelwal P, Cortes JC, Mueller L. Complex peptide macrocycle optimization: combining NMR restraints with conformational analysis to guide structure-based and ligand-based design. J Comput Aided Mol Des 2023; 37:519-535. [PMID: 37535171 PMCID: PMC10505130 DOI: 10.1007/s10822-023-00524-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/20/2023] [Indexed: 08/04/2023]
Abstract
Systematic optimization of large macrocyclic peptide ligands is a serious challenge. Here, we describe an approach for lead-optimization using the PD-1/PD-L1 system as a retrospective example of moving from initial lead compound to clinical candidate. We show how conformational restraints can be derived by exploiting NMR data to identify low-energy solution ensembles of a lead compound. Such restraints can be used to focus conformational search for analogs in order to accurately predict bound ligand poses through molecular docking and thereby estimate ligand strain and protein-ligand intermolecular binding energy. We also describe an analogous ligand-based approach that employs molecular similarity optimization to predict bound poses. Both approaches are shown to be effective for prioritizing lead-compound analogs. Surprisingly, relatively small ligand modifications, which may have minimal effects on predicted bound pose or intermolecular interactions, often lead to large changes in estimated strain that have dominating effects on overall binding energy estimates. Effective macrocyclic conformational search is crucial, whether in the context of NMR-based restraints, X-ray ligand refinement, partial torsional restraint for docking/ligand-similarity calculations or agnostic search for nominal global minima. Lead optimization for peptidic macrocycles can be made more productive using a multi-disciplinary approach that combines biophysical data with practical and efficient computational methods.
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Affiliation(s)
- Ajay N Jain
- Research and Development, BioPharmics LLC, Sonoma County, CA, USA.
| | | | | | - Ann E Cleves
- Research and Development, BioPharmics LLC, Sonoma County, CA, USA
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2
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Jain AN, Brueckner AC, Cleves AE, Reibarkh M, Sherer EC. A Distributional Model of Bound Ligand Conformational Strain: From Small Molecules up to Large Peptidic Macrocycles. J Med Chem 2023; 66:1955-1971. [PMID: 36701387 PMCID: PMC9923749 DOI: 10.1021/acs.jmedchem.2c01744] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The internal conformational strain incurred by ligands upon binding a target site has a critical impact on binding affinity, and expectations about the magnitude of ligand strain guide conformational search protocols. Estimates for bound ligand strain begin with modeled ligand atomic coordinates from X-ray co-crystal structures. By deriving low-energy conformational ensembles to fit X-ray diffraction data, calculated strain energies are substantially reduced compared with prior approaches. We show that the distribution of expected global strain energy values is dependent on molecular size in a superlinear manner. The distribution of strain energy follows a rectified normal distribution whose mean and variance are related to conformational complexity. The modeled strain distribution closely matches calculated strain values from experimental data comprising over 3000 protein-ligand complexes. The distributional model has direct implications for conformational search protocols as well as for directions in molecular design.
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Affiliation(s)
- Ajay N. Jain
- Research
& Development, BioPharmics LLC, Sonoma County, California95404, United States,
| | - Alexander C. Brueckner
- Molecular
Structure & Design, Bristol Myers Squibb, Princeton, New Jersey08543, United States
| | - Ann E. Cleves
- Research
& Development, BioPharmics LLC, Sonoma County, California95404, United States
| | - Mikhail Reibarkh
- Analytical
Research and Development, Merck & Co.
Inc., Rahway, New Jersey07065, United States
| | - Edward C. Sherer
- Analytical
Research and Development, Merck & Co.
Inc., Rahway, New Jersey07065, United States,
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3
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Wankowicz SA, de Oliveira SH, Hogan DW, van den Bedem H, Fraser JS. Ligand binding remodels protein side-chain conformational heterogeneity. eLife 2022; 11:e74114. [PMID: 35312477 PMCID: PMC9084896 DOI: 10.7554/elife.74114] [Citation(s) in RCA: 26] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2021] [Accepted: 03/18/2022] [Indexed: 12/15/2022] Open
Abstract
While protein conformational heterogeneity plays an important role in many aspects of biological function, including ligand binding, its impact has been difficult to quantify. Macromolecular X-ray diffraction is commonly interpreted with a static structure, but it can provide information on both the anharmonic and harmonic contributions to conformational heterogeneity. Here, through multiconformer modeling of time- and space-averaged electron density, we measure conformational heterogeneity of 743 stringently matched pairs of crystallographic datasets that reflect unbound/apo and ligand-bound/holo states. When comparing the conformational heterogeneity of side chains, we observe that when binding site residues become more rigid upon ligand binding, distant residues tend to become more flexible, especially in non-solvent-exposed regions. Among ligand properties, we observe increased protein flexibility as the number of hydrogen bonds decreases and relative hydrophobicity increases. Across a series of 13 inhibitor-bound structures of CDK2, we find that conformational heterogeneity is correlated with inhibitor features and identify how conformational changes propagate differences in conformational heterogeneity away from the binding site. Collectively, our findings agree with models emerging from nuclear magnetic resonance studies suggesting that residual side-chain entropy can modulate affinity and point to the need to integrate both static conformational changes and conformational heterogeneity in models of ligand binding.
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Affiliation(s)
- Stephanie A Wankowicz
- Department of Bioengineering and Therapeutic Sciences, University of California, San FranciscoSan FranciscoUnited States
- Biophysics Graduate Program, University of California San FranciscoSan FranciscoUnited States
| | | | - Daniel W Hogan
- Department of Bioengineering and Therapeutic Sciences, University of California, San FranciscoSan FranciscoUnited States
| | - Henry van den Bedem
- Department of Bioengineering and Therapeutic Sciences, University of California, San FranciscoSan FranciscoUnited States
- Atomwise Inc.San FranciscoUnited States
| | - James S Fraser
- Department of Bioengineering and Therapeutic Sciences, University of California, San FranciscoSan FranciscoUnited States
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4
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Adpressa DA, Reibarkh M, Jiang Y, Saurí J, Makarov AA. Interrogation of solution conformation of complex macrocyclic peptides utilizing a combined SEC-HDX-MS, circular dichroism, and NMR workflow. Analyst 2021; 147:325-332. [PMID: 34927633 DOI: 10.1039/d1an01619a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Recent technological and synthetic advances have led to a resurgence in the exploration of peptides as potential therapeutics. Understanding peptide conformation in both free and protein-bound states remains one of the most critical areas for successful development of peptide drugs. In this study it was demonstrated that the combination of Size-Exclusion Chromatography with Hydrogen-Deuterium Exchange Mass Spectrometry (SEC-HDX-MS) and Circular Dichroism Spectroscopy (CD) can be used to guide the selection of peptides for further NMR analysis. Moreover, the insights from this workflow guide the choice of the best biologically relevant conditions for NMR conformational studies of peptide ligands in a free state in solution. Combined information about solution conformation character and stability across temperatures and co-solvent compositions greatly expedites selection of optimal conditions for NMR analysis. In total, the combination of SEC-HDX-MS, CD, and NMR into a single complementary workflow greatly accelerates conformational analysis of peptides in the drug discovery lead optimization process.
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Affiliation(s)
- Donovon A Adpressa
- Analytical Research & Development, Merck & Co. Inc., Boston, Massachusetts 02115, USA.
| | - Mikhail Reibarkh
- Analytical Research & Development, Merck & Co. Inc., Rahway, New Jersey 07065, USA.
| | - Yuan Jiang
- Analytical Research & Development, Merck & Co. Inc., Boston, Massachusetts 02115, USA.
| | - Josep Saurí
- Analytical Research & Development, Merck & Co. Inc., Boston, Massachusetts 02115, USA.
| | - Alexey A Makarov
- Analytical Research & Development, Merck & Co. Inc., Boston, Massachusetts 02115, USA.
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5
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Caldararu O, Ekberg V, Logan DT, Oksanen E, Ryde U. Exploring ligand dynamics in protein crystal structures with ensemble refinement. Acta Crystallogr D Struct Biol 2021; 77:1099-1115. [PMID: 34342282 PMCID: PMC8329865 DOI: 10.1107/s2059798321006513] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2021] [Accepted: 06/21/2021] [Indexed: 11/10/2022] Open
Abstract
Understanding the dynamics of ligands bound to proteins is an important task in medicinal chemistry and drug design. However, the dominant technique for determining protein-ligand structures, X-ray crystallography, does not fully account for dynamics and cannot accurately describe the movements of ligands in protein binding sites. In this article, an alternative method, ensemble refinement, is used on six protein-ligand complexes with the aim of understanding the conformational diversity of ligands in protein crystal structures. The results show that ensemble refinement sometimes indicates that the flexibility of parts of the ligand and some protein side chains is larger than that which can be described by a single conformation and atomic displacement parameters. However, since the electron-density maps are comparable and Rfree values are slightly increased, the original crystal structure is still a better model from a statistical point of view. On the other hand, it is shown that molecular-dynamics simulations and automatic generation of alternative conformations in crystallographic refinement confirm that the flexibility of these groups is larger than is observed in standard refinement. Moreover, the flexible groups in ensemble refinement coincide with groups that give high atomic displacement parameters or non-unity occupancy if optimized in standard refinement. Therefore, the conformational diversity indicated by ensemble refinement seems to be qualitatively correct, indicating that ensemble refinement can be an important complement to standard crystallographic refinement as a tool to discover which parts of crystal structures may show extensive flexibility and therefore are poorly described by a single conformation. However, the diversity of the ensembles is often exaggerated (probably partly owing to the rather poor force field employed) and the ensembles should not be trusted in detail.
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Affiliation(s)
- Octav Caldararu
- Department of Theoretical Chemistry, Lund University, Chemical Centre, PO Box 124, SE-221 00 Lund, Sweden
| | - Vilhelm Ekberg
- Department of Theoretical Chemistry, Lund University, Chemical Centre, PO Box 124, SE-221 00 Lund, Sweden
| | - Derek T. Logan
- Biochemistry and Structural Biology, Centre for Molecular Protein Science, Department of Chemistry, Lund University, Chemical Centre, PO Box 124, SE-221 00 Lund, Sweden
| | - Esko Oksanen
- European Spallation Source Consortium ESS ERIC, PO Box 176, SE-221 00 Lund, Sweden
| | - Ulf Ryde
- Department of Theoretical Chemistry, Lund University, Chemical Centre, PO Box 124, SE-221 00 Lund, Sweden
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6
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Liebeschuetz JW. The Good, the Bad, and the Twisted Revisited: An Analysis of Ligand Geometry in Highly Resolved Protein-Ligand X-ray Structures. J Med Chem 2021; 64:7533-7543. [PMID: 34060310 DOI: 10.1021/acs.jmedchem.1c00228] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
An analysis of the rotatable bond geometry of drug-like ligand models is reported for high-resolution (<1.1 Å) crystallographic protein-ligand complexes. In cases where the ligand fit to the electron density is very good, unusual torsional geometry is rare and, most often, though not exclusively, associated with strong polar, metal, or covalent ligand-protein interactions. It is rarely associated with a torsional strain of greater than 2 kcal mol-1 by calculation. An unusual torsional geometry is more prevalent where the fit to electron density is not perfect. Multiple low-strain conformer bindings were observed in 21% of the set and, it is suggested, may also lie behind many of the 35% of single-occupancy cases, where a poor fit to the e-density was found. It is concluded that multiple conformer ligand binding is an under-recognized phenomenon in structure-based drug design and that there is a need for more robust crystallographic refinement methods to better handle such cases.
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Affiliation(s)
- John W Liebeschuetz
- Skilos Chemoinformatics, 159 Water Street, Cambridge CB4 1PB, United Kingdom.,Astex Pharmaceuticals, 436 Cambridge Science Park, Milton Road, Milton, Cambridge CB4 0QA, United Kingdom
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7
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Brueckner AC, Deng Q, Cleves AE, Lesburg CA, Alvarez JC, Reibarkh MY, Sherer EC, Jain AN. Conformational Strain of Macrocyclic Peptides in Ligand-Receptor Complexes Based on Advanced Refinement of Bound-State Conformers. J Med Chem 2021; 64:3282-3298. [PMID: 33724820 DOI: 10.1021/acs.jmedchem.0c02159] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Macrocyclic peptides are an important modality in drug discovery, but molecular design is limited due to the complexity of their conformational landscape. To better understand conformational propensities, global strain energies were estimated for 156 protein-macrocyclic peptide cocrystal structures. Unexpectedly large strain energies were observed when the bound-state conformations were modeled with positional restraints. Instead, low-energy conformer ensembles were generated using xGen that fit experimental X-ray electron density maps and gave reasonable strain energy estimates. The ensembles featured significant conformational adjustments while still fitting the electron density as well or better than the original coordinates. Strain estimates suggest the interaction energy in protein-ligand complexes can offset a greater amount of strain for macrocyclic peptides than for small molecules and non-peptidic macrocycles. Across all molecular classes, the approximate upper bound on global strain energies had the same relationship with molecular size, and bound-state ensembles from xGen yielded favorable binding energy estimates.
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Affiliation(s)
- Alexander C Brueckner
- Computational & Structural Chemistry, Merck & Co Inc, 2000 Galloping Hill Road, Kenilworth, New Jersey 07033, United States
| | - Qiaolin Deng
- Computational & Structural Chemistry, Merck & Co Inc, 2000 Galloping Hill Road, Kenilworth, New Jersey 07033, United States
| | - Ann E Cleves
- Bioengineering and Therapeutic Sciences, University of California San Francisco, Box 0128, San Francisco, California 94158, United States
| | - Charles A Lesburg
- Computational and Structural Chemistry, Merck and Co Inc, 33 Avenue Louis Pasteur, Boston, Massachusetts 02115, United States
| | - Juan C Alvarez
- Computational and Structural Chemistry, Merck and Co Inc, 33 Avenue Louis Pasteur, Boston, Massachusetts 02115, United States
| | - Mikhail Y Reibarkh
- Analytical Research and Development, Merck & Co Inc, 126 East Lincoln Avenue, Rahway, New Jersey 07065, United States
| | - Edward C Sherer
- Analytical Research and Development, Merck & Co Inc, 126 East Lincoln Avenue, Rahway, New Jersey 07065, United States
| | - Ajay N Jain
- Bioengineering and Therapeutic Sciences, University of California San Francisco, Box 0128, San Francisco, California 94158, United States
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