10SB | pdb_000010sb

PCSK9 in complex with cyclic peptide 21


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.83 Å
  • R-Value Free: 
    0.238 (Depositor), 0.229 (DCC) 
  • R-Value Work: 
    0.196 (Depositor), 0.189 (DCC) 
  • R-Value Observed: 
    0.199 (Depositor) 

Starting Model: experimental
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wwPDB Validation 3D Report Full Report

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Ligand Structure Quality Assessment 


This is version 1.0 of the entry. See complete history

Literature

Discovery Process of Enlicitide, a Highly Engineered Macrocyclic Peptide Therapeutic, through Issue-Driven Fragment-Based Synthetic Assembly and SAR.

Josien, H.Nair, A.G.Ding, F.X.Guo, Y.Chen, Y.H.Rao, A.U.Liu, J.Tong, L.Sun, Z.Lo, M.M.Tucker, T.J.Embrey, M.W.Shahripour, A.Wu, C.Bianchi, E.Branca, D.Kuethe, J.T.Lee, J.Thaisrivongs, D.A.Bulger, P.G.Zhu, X.Ha, S.N.Johnston, J.M.Klein, D.J.Orth, P.Hong, M.R.Buevich, A.V.Gao, Q.Zokian, H.J.Koeplinger, K.A.Tracy, R.W.Hafey, M.J.Buist, N.Bueters, T.Alleyne, C.Bass, A.Campeau, L.C.Johns, D.G.Garbaccio, R.M.Vachal, P.Walji, A.Wood, H.B.

(2026) J Med Chem 

  • DOI: https://doi.org/10.1021/acs.jmedchem.6c00463
  • Primary Citation Related Structures: 
    10SB

  • PubMed Abstract: 

    Herein, we report the discovery process of enlicitide (MK-0616, compound 18 ), an orally active macrocyclic peptide therapeutic against PCSK9 for LDL-C reduction. To overcome development bottlenecks in a prior lead (compound 1a ) in a timely manner (sulfur oxidation liability, low solubility, azido potential manufacturing hazard, and alkene isomeric complexity), we deployed a novel scalable solution-phase modular fragment assembly (North/East/South/West/tail), which allowed us to accelerate the design-make-test-analyze (DMTA) cycle and preclinical profiling. Design solutions were quickly validated through this approach (a northern lactam staple, an N -benzylamide southern spacer, an RCM-derived cross-link in conjunction with solvent-exposed motifs to modulate solubility) and delivered compounds with low picomolar potency, improved solubility, stability, and PK from which enlicitide (MK-0616, compound 18 ) was selected for clinical progression. This modular strategy may act as a template to accelerate late-stage issue-driven SAR in highly engineered macrocyclic peptides.


  • Organizational Affiliation
    • Department of Medicinal Chemistry, Merck &Co., Inc., Rahway, New Jersey 07065, United States.

Macromolecule Content 

  • Total Structure Weight: 48.17 kDa 
  • Atom Count: 3,192 
  • Modeled Residue Count: 385 
  • Deposited Residue Count: 439 
  • Unique protein chains: 3

Macromolecules

Find similar proteins by:|  3D Structure
Entity ID: 1
MoleculeChains  Sequence LengthOrganismDetailsImage
Propeptide of Proprotein convertase subtilisin/kexin type 9122Homo sapiensMutation(s): 0 
Gene Names: PCSK9NARC1PSEC0052
EC: 3.4.21
UniProt & NIH Common Fund Data Resources
Find proteins for Q8NBP7 (Homo sapiens)
Explore Q8NBP7 
Go to UniProtKB:  Q8NBP7
PHAROS:  Q8NBP7
GTEx:  ENSG00000169174 
Entity Groups
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupQ8NBP7
Sequence Annotations
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Reference Sequence
Find similar proteins by:|  3D Structure
Entity ID: 2
MoleculeChains  Sequence LengthOrganismDetailsImage
Proprotein convertase subtilisin/kexin type 9308Homo sapiensMutation(s): 0 
Gene Names: PCSK9NARC1PSEC0052
EC: 3.4.21
UniProt & NIH Common Fund Data Resources
Find proteins for Q8NBP7 (Homo sapiens)
Explore Q8NBP7 
Go to UniProtKB:  Q8NBP7
PHAROS:  Q8NBP7
GTEx:  ENSG00000169174 
Entity Groups
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupQ8NBP7
Sequence Annotations
Expand
Reference Sequence
Find similar proteins by:  Sequence   |   3D Structure  
Entity ID: 3
MoleculeChains  Sequence LengthOrganismDetailsImage
Cyclic peptide 21C [auth D]9synthetic constructMutation(s): 0 

Small Molecules

Modified Residues  4 Unique
IDChains TypeFormula2D DiagramParent
0A1
Query on 0A1
C [auth D]L-PEPTIDE LINKINGC10 H13 N O3TYR
2RA
Query on 2RA
C [auth D]D-PEPTIDE LINKINGC3 H8 N2 O2ALA
3WX
Query on 3WX
C [auth D]PEPTIDE-LIKEC6 H11 N O2PRO
FTR
Query on FTR
C [auth D]L-PEPTIDE LINKINGC11 H11 F N2 O2TRP

Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.83 Å
  • R-Value Free:  0.238 (Depositor), 0.229 (DCC) 
  • R-Value Work:  0.196 (Depositor), 0.189 (DCC) 
  • R-Value Observed: 0.199 (Depositor) 
Space Group: P 32 2 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 70.741α = 90
b = 70.741β = 90
c = 159.125γ = 120
Software Package:
Software NamePurpose
BUSTERrefinement
XDSdata reduction
STARANISOdata scaling
PHASERphasing

Structure Validation

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Ligand Structure Quality Assessment 


Entry History 

& Funding Information

Deposition Data


Funding OrganizationLocationGrant Number
Not funded--

Revision History  (Full details and data files)

  • Version 1.0: 2026-06-03
    Type: Initial release