12FH | pdb_000012fh

Structure of eIF2B bound to a activator

• PDB DOI: https://doi.org/10.2210/pdb12FH/pdb

• Classification: SUGAR BINDING PROTEIN
• Organism(s): Homo sapiens
• Expression System: Homo sapiens
• Mutation(s): No 


• Deposited: 2026-04-01 Released: 2026-06-03 
• Deposition Author(s): Jain, R., Jakob, C.G., Qiu, W.
• Funding Organization(s): Not funded

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Experimental Data Snapshot

• Method: X-RAY DIFFRACTION
• Resolution: 3.50 Å
• R-Value Free: 
  0.271 (Depositor), 0.261 (DCC) 
• R-Value Work: 
  0.215 (Depositor), 0.209 (DCC) 
• R-Value Observed: 
  0.218 (Depositor) 

Starting Model: experimental

Literature

Discovery of Fosigotifator, a Potent eIF2B Activator with Desired Properties for Human Studies.

Frost, J.M., Tong, Y., Xu, X., Shi, L., Pliushchev, M., Murauski, K.J., Kohlhaas, K., Donnelly-Roberts, D.L., Sheehan, M.M., Riedmaier, S., Oberoi, H.S., Chen, J., Prakash, J., Hutchins, C.W., Jakob, C.G., Jain, R., Qiu, W., Henry, R.F., Edalji, R., Sun, C., Carr, T., Basso, A.M., Brown, B.S., Voight, E.A., Sidrauski, C., Dart, M.J.

(2026) J Med Chem 

• PubMed: 42153306 
• DOI: https://doi.org/10.1021/acs.jmedchem.6c00716
• Primary Citation Related Structures: 
  12FH


• PubMed Abstract: 
  

  The integrated stress response (ISR) is a highly conserved cellular pathway triggered by a variety of insults, reducing protein synthesis and inducing ATF4, leading to broadly remodeling the cellular transcriptome and metabolome. ISRIB, 1 , the first identified eIF2B activator, attenuates the ISR restoring protein synthesis, but its poor solubility limits absorption and advancement. To improve drug-like properties, we explored replacements for both the cyclohexyl core and side chains of ISRIB. This effort initially led to truncated analogue, 2BAct, 13 , which demonstrated improved solubility relative to 1 ; however, cardiovascular effects in higher species limited its progression into the clinic. Potent analogue 9 was identified with significantly improved solubility vs 1 but was still projected to have solubility-limited absorption. A prodrug campaign resulted in the identification of compound 26 (fosigotifator), which exhibited significantly improved solubility and is currently being investigated in the clinic.

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Organizational Affiliation: 
• AbbVie, Research and Development, 1 North Waukegan Road, North Chicago, Illinois 60064, United States.
Calico Life Sciences LLC, 1170 Veterans Blvd, South San Francisco, California 94080, United States.

Biological Assembly 1  

Global Symmetry: Asymmetric - C1 
Global Stoichiometry: Hetero 5-mer - A2B2C1 Pseudo Symmetry: Asymmetric - C1 
Pseudo Stoichiometry: Hetero 5-mer - A4B1 Local Symmetry: Cyclic - C2  (Explore in 3D)
Local Stoichiometry: Hetero 4-mer - A2B2 

Local Symmetry: Cyclic - C2  (Explore in 3D)
Local Stoichiometry: Hetero 4-mer - A2B2 

Biological assembly 1 assigned by authors.

Macromolecule Content 

• Total Structure Weight: 203.4 kDa 
• Atom Count: 10,540 
• Modeled Residue Count: 1,346 
• Deposited Residue Count: 1,832 
• Unique protein chains: 3

Macromolecules

Entity ID: 1
Molecule	Chains	Sequence Length	Organism	Details	Image
Isoform 2 of Translation initiation factor eIF2B subunit delta	A, B	542	Homo sapiens	Mutation(s): 0  Gene Names: EIF2B4, EIF2BD
UniProt & NIH Common Fund Data Resources
Find proteins for Q9UI10 (Homo sapiens) Go to UniProtKB:  Q9UI10
PHAROS:  Q9UI10 GTEx:  ENSG00000115211

Entity ID: 2
Molecule	Chains	Sequence Length	Organism	Details	Image
Translation initiation factor eIF2B subunit beta	C, D	366	Homo sapiens	Mutation(s): 0  Gene Names: EIF2B2, EIF2BB
UniProt & NIH Common Fund Data Resources
Find proteins for P49770 (Homo sapiens) Explore P49770  Go to UniProtKB:  P49770
PHAROS:  P49770 GTEx:  ENSG00000119718

Entity ID: 3
Molecule	Chains	Sequence Length	Organism	Details	Image
unidentified protein fragment	E [auth F]	16	Homo sapiens	Mutation(s): 0

Small Molecules

Ligands 2 Unique
ID	Chains	Name / Formula / InChI Key	2D Diagram
A1DBY (Subject of Investigation/LOI)	H [auth D]	N,N'-[(1S,2S,4R)-2-hydroxybicyclo[2.2.2]octane-1,4-diyl]bis[2-(4-chloro-3-fluorophenoxy)acetamide] C24 H24 Cl2 F2 N2 O5 QANASUQVKFAXJZ-NKKJXINNSA-N
SO4	F [auth A], G [auth B]	SULFATE ION O4 S QAOWNCQODCNURD-UHFFFAOYSA-L

Modified Residues  2 Unique
ID	Chains	Type	Formula	2D Diagram	Parent
SEP	A, B	L-PEPTIDE LINKING	C3 H8 N O6 P		SER
TPO	C, D	L-PEPTIDE LINKING	C4 H10 N O6 P		THR
UNK	E [auth F]	L-PEPTIDE LINKING	C4 H9 N O2		--

Experimental Data & Validation

Experimental Data

• Method: X-RAY DIFFRACTION
• Resolution: 3.50 Å
• R-Value Free:  0.271 (Depositor), 0.261 (DCC) 
• R-Value Work:  0.215 (Depositor), 0.209 (DCC) 
• R-Value Observed: 0.218 (Depositor) 

Space Group: P 2₁ 2₁ 2

Unit Cell:

Length ( Å )	Angle ( ˚ )
a = 131.47	α = 90
b = 230.81	β = 90
c = 89.48	γ = 90

Software Package:

Software Name	Purpose
PHENIX	refinement
PDB_EXTRACT	data extraction
autoPROC	data reduction
XSCALE	data scaling
PHENIX	phasing

Structure Validation

Entry History 

& Funding Information

Deposition Data

• Released Date: 2026-06-03 
Deposition Author(s): Jain, R., Jakob, C.G., Qiu, W.

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Funding Organization	Location	Grant Number
Not funded		--

Revision History  

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