tooluniverse-binder-discovery
Small Molecule Binder Discovery Strategy
Systematic discovery of novel small molecule binders using 60+ ToolUniverse tools across druggability assessment, known ligand mining, similarity expansion, ADMET filtering, and synthesis feasibility.
KEY PRINCIPLES:
- Report-first approach - Create report file FIRST, then populate progressively
- Target validation FIRST - Confirm druggability before compound searching
- Multi-strategy approach - Combine structure-based and ligand-based methods
- ADMET-aware filtering - Eliminate poor compounds early
- Evidence grading - Grade candidates by supporting evidence
- Actionable output - Provide prioritized candidates with rationale
- English-first queries - Always use English terms in tool calls, even if the user writes in another language. Only try original-language terms as a fallback. Respond in the user's language
Critical Workflow Requirements
1. Report-First Approach (MANDATORY)
DO NOT show search process or tool outputs to the user. Instead:
-
Create the report file FIRST - Before any data collection:
- File name:
[TARGET]_binder_discovery_report.md - Initialize with all section headers from the template
- Add placeholder text:
[Researching...]in each section
- File name:
-
Progressively update the report - As you gather data:
- Update each section with findings immediately
- The user sees the report growing, not the search process
-
Output separate data files:
[TARGET]_candidate_compounds.csv- Prioritized compounds with SMILES, scores[TARGET]_bibliography.json- Literature references (optional)
2. Citation Requirements (MANDATORY)
Every piece of information MUST include its source:
### 3.2 Known Inhibitors
| Compound | ChEMBL ID | IC50 (nM) | Selectivity | Source |
|----------|-----------|-----------|-------------|--------|
| Imatinib | CHEMBL941 | 38 | ABL-selective | ChEMBL |
| Dasatinib | CHEMBL1421 | 0.5 | Multi-kinase | ChEMBL |
*Source: ChEMBL via `ChEMBL_get_target_activities` (CHEMBL1862)*
Workflow Overview
Phase 0: Tool Verification (check parameter names)
↓
Phase 1: Target Validation
├─ 1.1 Resolve identifiers (UniProt, Ensembl, ChEMBL target ID)
├─ 1.2 Assess druggability/tractability
│ └─ 1.2.5 Check therapeutic antibodies (Thera-SAbDab) [NEW]
├─ 1.3 Identify binding sites
└─ 1.4 Predict structure (NvidiaNIM_alphafold2/esmfold)
↓
Phase 2: Known Ligand Mining
├─ Extract ChEMBL bioactivity data
├─ Get GtoPdb interactions
├─ Identify chemical probes
├─ BindingDB affinity data (NEW - Ki/IC50/Kd)
├─ PubChem BioAssay HTS data (NEW - screening hits)
└─ Analyze SAR from known actives
↓
Phase 3: Structure Analysis
├─ Get PDB structures with ligands
├─ Check EMDB for cryo-EM structures (NEW - for membrane targets)
├─ Analyze binding pocket
└─ Identify key interactions
↓
Phase 3.5: Docking Validation (NvidiaNIM_diffdock/boltz2) [NEW]
├─ Dock reference inhibitor
└─ Validate binding pocket geometry
↓
Phase 4: Compound Expansion
├─ 4.1-4.3 Similarity/substructure search
└─ 4.4 De novo generation (NvidiaNIM_genmol/molmim) [NEW]
↓
Phase 5: ADMET Filtering
├─ Predict physicochemical properties
├─ Predict ADMET endpoints
└─ Flag liabilities
↓
Phase 6: Candidate Docking & Prioritization
├─ Dock all candidates (NvidiaNIM_diffdock/boltz2) [UPDATED]
├─ Score by docking + ADMET + novelty
├─ Assess synthesis feasibility
└─ Generate final ranked list
↓
Phase 7: Report Synthesis
Phase 0: Tool Verification
CRITICAL: Verify tool parameters before calling unfamiliar tools.
# Check tool params to prevent silent failures
tool_info = tu.tools.get_tool_info(tool_name="ChEMBL_get_target_activities")
Known Parameter Corrections
| Tool | WRONG Parameter | CORRECT Parameter |
|---|---|---|
OpenTargets_get_target_tractability_by_ensemblID |
ensembl_id |
ensemblId |
ChEMBL_get_target_activities |
chembl_target_id |
target_chembl_id |
ChEMBL_search_similar_molecules |
smiles |
molecule (accepts SMILES, ChEMBL ID, or name) |
alphafold_get_prediction |
uniprot |
accession |
Phase 1: Target Validation
1.1 Identifier Resolution Chain
1. UniProt_search(query=target_name, organism="human")
└─ Extract: UniProt accession, gene name, protein name
2. MyGene_query_genes(q=gene_symbol, species="human")
└─ Extract: Ensembl gene ID, NCBI gene ID
3. ChEMBL_search_targets(query=target_name, organism="Homo sapiens")
└─ Extract: ChEMBL target ID, target type
4. GtoPdb_get_targets(query=target_name)
└─ Extract: GtoPdb target ID (if GPCR/ion channel/enzyme)
Store all IDs for downstream queries:
ids = {
'uniprot': 'P00533',
'ensembl': 'ENSG00000146648',
'chembl_target': 'CHEMBL203',
'gene_symbol': 'EGFR',
'gtopdb': '1797' # if available
}
1.2 Druggability Assessment
Multi-Source Triangulation:
1. OpenTargets_get_target_tractability_by_ensemblID(ensemblId)
└─ Extract: Small molecule tractability score, bucket
2. DGIdb_get_gene_druggability(genes=[gene_symbol])
└─ Extract: Druggability categories, known drug count
3. OpenTargets_get_target_classes_by_ensemblID(ensemblId)
└─ Extract: Target class (kinase, GPCR, etc.)
4. GPCRdb_get_protein(protein=entry_name) # NEW - for GPCRs
└─ Extract: GPCR family, receptor state, ligand binding data
1.2a GPCRdb Integration (NEW - for GPCR Targets)
~35% of all approved drugs target GPCRs. For GPCR targets, use specialized data:
def check_if_gpcr_and_enrich(tu, target_name, uniprot_id):
"""Check if target is GPCR and get specialized data."""
# Build GPCRdb entry name (e.g., "adrb2_human")
entry_name = f"{target_name.lower()}_human"
# Check if it's a GPCR
gpcr_info = tu.tools.GPCRdb_get_protein(
operation="get_protein",
protein=entry_name
)
if gpcr_info.get('status') == 'success':
# It's a GPCR - get specialized data
# Get known structures (active/inactive states)
structures = tu.tools.GPCRdb_get_structures(
operation="get_structures",
protein=entry_name
)
# Get known ligands
ligands = tu.tools.GPCRdb_get_ligands(
operation="get_ligands",
protein=entry_name
)
# Get mutation data (important for SAR)
mutations = tu.tools.GPCRdb_get_mutations(
operation="get_mutations",
protein=entry_name
)
return {
'is_gpcr': True,
'gpcr_family': gpcr_info['data'].get('family'),
'gpcr_class': gpcr_info['data'].get('receptor_class'),
'structures': structures['data'].get('structures', []),
'ligands': ligands['data'].get('ligands', []),
'mutation_data': mutations['data'].get('mutations', [])
}
return {'is_gpcr': False}
GPCRdb Advantages:
- GPCR-specific sequence alignments (Ballesteros-Weinstein numbering)
- Active vs. inactive state structures
- Curated ligand binding data
- Experimental mutation effects on ligand binding
Druggability Scorecard:
| Factor | Assessment | Score |
|---|---|---|
| Known small molecule drugs | Yes (3+) | ★★★ |
| Tractability bucket | 1-3 | ★★☆-★★★ |
| Target class | Enzyme/GPCR/Ion channel | ★★★ |
| Binding site known | Yes (X-ray) | ★★★ |
| GPCRdb ligands available | Yes (10+) | ★★★ (GPCR only) |
| Therapeutic antibodies exist | Check Thera-SAbDab | See 1.2.5 |
Decision Point: If druggability score < ★★☆, warn user about challenges.
1.2.5 Therapeutic Antibody Landscape (NEW)
Check if therapeutic antibodies already target this protein - important for:
- Understanding competitive landscape
- Validating target tractability (if antibodies work, target is validated)
- Identifying potential combination approaches
def check_therapeutic_antibodies(tu, target_name):
"""
Check Thera-SAbDab for therapeutic antibodies against target.
"""
# Search by target name
results = tu.tools.TheraSAbDab_search_by_target(
target=target_name
)
if results.get('status') == 'success':
antibodies = results['data'].get('therapeutics', [])
# Categorize by clinical stage
by_phase = {'Approved': [], 'Phase 3': [], 'Phase 2': [], 'Phase 1': [], 'Preclinical': []}
for ab in antibodies:
phase = ab.get('phase', 'Unknown')
for key in by_phase.keys():
if key.lower() in phase.lower():
by_phase[key].append(ab)
break
return {
'total_antibodies': len(antibodies),
'by_phase': by_phase,
'antibodies': antibodies[:10], # Top 10
'competitive_alert': len(by_phase.get('Approved', [])) > 0
}
return None
def get_antibody_landscape(tu, target_name, uniprot_id=None):
"""
Comprehensive antibody competitive landscape.
"""
# Thera-SAbDab search
therasabdab = check_therapeutic_antibodies(tu, target_name)
# Also search by common synonyms
synonyms = [target_name]
if target_name != uniprot_id:
synonyms.append(uniprot_id)
all_antibodies = []
for synonym in synonyms:
results = tu.tools.TheraSAbDab_search_therapeutics(query=synonym)
if results.get('status') == 'success':
all_antibodies.extend(results['data'].get('therapeutics', []))
# Deduplicate
seen = set()
unique = []
for ab in all_antibodies:
inn = ab.get('inn_name')
if inn and inn not in seen:
seen.add(inn)
unique.append(ab)
return {
'antibodies': unique,
'count': len(unique),
'has_approved': any(ab.get('phase', '').lower() == 'approved' for ab in unique),
'source': 'Thera-SAbDab'
}
Report Output:
### 1.2.5 Therapeutic Antibody Landscape (NEW)
**Thera-SAbDab Search Results**:
| Antibody (INN) | Target | Format | Phase | PDB |
|----------------|--------|--------|-------|-----|
| Pembrolizumab | PD-1 | IgG4 | Approved | 5DK3 |
| Nivolumab | PD-1 | IgG4 | Approved | 5WT9 |
| Cemiplimab | PD-1 | IgG4 | Approved | 7WVM |
**Competitive Landscape**: ⚠️ 3 approved antibodies target this protein
**Strategic Implication**: Small molecule approach offers differentiation (oral dosing, CNS penetration, cost)
*Source: Thera-SAbDab via `TheraSAbDab_search_by_target`*
Why Include Antibody Landscape:
- Validation: Approved antibodies = validated target
- Competition: Understand what's already in market/clinic
- Strategy: Identify gaps (no oral, no CNS-penetrant)
- Synergy: Potential combination opportunities
1.3 Binding Site Analysis
1. ChEMBL_search_binding_sites(target_chembl_id)
└─ Extract: Binding site names, types
2. get_binding_affinity_by_pdb_id(pdb_id) # For each PDB with ligand
└─ Extract: Kd, Ki, IC50 values for co-crystallized ligands
3. InterPro_get_protein_domains(uniprot_accession)
└─ Extract: Domain architecture, active sites
Output for Report:
### 1.3 Binding Site Assessment
**Known Binding Sites**:
| Site | Type | Evidence | Key Residues | Source |
|------|------|----------|--------------|--------|
| ATP pocket | Orthosteric | X-ray (23 PDBs) | K745, E762, M793 | PDB/ChEMBL |
| Allosteric pocket | Allosteric | X-ray (3 PDBs) | T790, C797 | PDB |
**Binding Site Druggability**: ★★★ (well-defined pocket, multiple co-crystal structures)
*Source: ChEMBL via `ChEMBL_search_binding_sites`, PDB structures*
1.4 Structure Prediction (NVIDIA NIM)
When no experimental structure is available, or for custom domain predictions.
Requires: NVIDIA_API_KEY environment variable
Option A: AlphaFold2 (High accuracy, async)
NvidiaNIM_alphafold2(
sequence=kinase_domain_sequence,
algorithm="mmseqs2",
relax_prediction=False
)
└─ Returns: PDB structure with pLDDT confidence scores
└─ Use when: Accuracy is critical, time is available (~5-15 min)
Option B: ESMFold (Fast, synchronous)
NvidiaNIM_esmfold(sequence=kinase_domain_sequence)
└─ Returns: PDB structure (max 1024 AA)
└─ Use when: Quick assessment needed (~30 sec)
Report pLDDT Confidence:
### 1.4 Structure Prediction Quality
**Method**: AlphaFold2 via NVIDIA NIM
**Mean pLDDT**: 90.94 (very high confidence)
| Confidence Level | Range | Fraction | Interpretation |
|------------------|-------|----------|----------------|
| Very High | ≥90 | 74.3% | Highly reliable |
| Confident | 70-90 | 16.0% | Reliable |
| Low | 50-70 | 9.0% | Use caution |
| Very Low | <50 | 0.7% | Unreliable |
**Key Binding Residue Confidence**:
| Residue | Function | pLDDT |
|---------|----------|-------|
| K745 | ATP binding | 90.0 |
| T790 | Gatekeeper | 92.3 |
| M793 | Hinge region | 95.3 |
| D855 | DFG motif | 89.5 |
*Source: NVIDIA NIM via `NvidiaNIM_alphafold2`*
Phase 2: Known Ligand Mining
2.1 ChEMBL Bioactivity Data
1. ChEMBL_get_target_activities(target_chembl_id, limit=500)
└─ Filter: standard_type in ["IC50", "Ki", "Kd", "EC50"]
└─ Filter: standard_value < 10000 nM
└─ Extract: ChEMBL molecule IDs, SMILES, potency values
2. ChEMBL_get_molecule(molecule_chembl_id) # For top actives
└─ Extract: Full molecular data, max_phase, oral flag
Activity Summary Table:
### 2.1 Known Active Compounds (ChEMBL)
**Total Bioactivity Points**: 2,847 (IC50: 1,234 | Ki: 892 | Kd: 456 | EC50: 265)
**Compounds with IC50 < 100 nM**: 156
**Approved Drugs for This Target**: 5
| Compound | ChEMBL ID | IC50 (nM) | Max Phase | SMILES (truncated) |
|----------|-----------|-----------|-----------|-------------------|
| Erlotinib | CHEMBL553 | 2 | 4 | COc1cc2ncnc(Nc3ccc... |
| Gefitinib | CHEMBL939 | 5 | 4 | COc1cc2ncnc(Nc3ccc... |
| [Novel] | CHEMBL123 | 12 | 0 | c1ccc(NC(=O)c2ccc... |
*Source: ChEMBL via `ChEMBL_get_target_activities` (CHEMBL203)*
2.2 GtoPdb Interactions
GtoPdb_get_target_interactions(target_id)
└─ Extract: Ligands with pKi/pIC50, selectivity data
2.3 Chemical Probes
OpenTargets_get_chemical_probes_by_target_ensemblID(ensemblId)
└─ Extract: Validated chemical probes with ratings
Output for Report:
### 2.3 Chemical Probes
| Probe | Target | Rating | Use | Caveat | Source |
|-------|--------|--------|-----|--------|--------|
| Probe-X | EGFR | ★★★★ | In vivo | None | Chemical Probes Portal |
| Probe-Y | EGFR | ★★★☆ | In vitro | Off-target kinase activity | Open Targets |
**Recommended Probe for Target Validation**: Probe-X (highest rating, validated in vivo)
2.4 SAR Analysis from Actives
Identify common scaffolds and SAR trends:
### 2.4 Structure-Activity Relationships
**Core Scaffolds Identified**:
1. **4-Anilinoquinazoline** (34 compounds, IC50 range: 2-500 nM)
- N1 position: Aryl preferred
- C6/C7: Methoxy groups improve potency
2. **Pyrimidine-amine** (12 compounds, IC50 range: 15-800 nM)
- Less potent than quinazolines
- Better selectivity profile
**Key SAR Insights**:
- Halogen at meta position of aniline increases potency 3-5x
- C7 ethoxy group critical for binding (H-bond to M793)
2.5 BindingDB Affinity Data (NEW)
BindingDB provides experimental binding affinity data complementary to ChEMBL:
def get_bindingdb_ligands(tu, uniprot_id, affinity_cutoff=10000):
"""
Get ligands from BindingDB with measured affinities.
BindingDB advantages:
- May have compounds not in ChEMBL
- Different affinity types (Ki, IC50, Kd)
- Direct literature links
"""
result = tu.tools.BindingDB_get_ligands_by_uniprot(
uniprot=uniprot_id,
affinity_cutoff=affinity_cutoff # nM
)
if result:
ligands = []
for entry in result:
ligands.append({
'smiles': entry.get('smile'),
'affinity_type': entry.get('affinity_type'),
'affinity_nM': entry.get('affinity'),
'pmid': entry.get('pmid'),
'monomer_id': entry.get('monomerid')
})
# Sort by potency
ligands.sort(key=lambda x: float(x['affinity_nM']) if x['affinity_nM'] else 1e6)
return ligands[:50] # Top 50
return []
def find_compound_polypharmacology(tu, smiles, similarity_cutoff=0.85):
"""Find off-target interactions for selectivity analysis."""
targets = tu.tools.BindingDB_get_targets_by_compound(
smiles=smiles,
similarity_cutoff=similarity_cutoff
)
return targets # Other proteins this compound may bind
BindingDB Output for Report:
### 2.5 Additional Ligands (BindingDB) (NEW)
**Total Unique Ligands**: 89 (non-overlapping with ChEMBL)
**Most Potent**: 0.3 nM Ki
| SMILES | Affinity Type | Value (nM) | PMID | BindingDB ID |
|--------|---------------|------------|------|--------------|
| CC(C)Cc1ccc... | Ki | 0.3 | 15737014 | 12345 |
| COc1cc2ncnc... | IC50 | 2.1 | 16460808 | 12346 |
**Novel Scaffolds from BindingDB**: 3 scaffolds not seen in ChEMBL data
*Source: BindingDB via `BindingDB_get_ligands_by_uniprot`*
2.6 PubChem BioAssay Screening Data (NEW)
PubChem BioAssay provides HTS screening results and dose-response data:
def get_pubchem_assays_for_target(tu, gene_symbol):
"""
Get bioassays and active compounds from PubChem.
Advantages:
- HTS data not in ChEMBL
- NIH-funded screening programs (MLPCN)
- Dose-response curves for IC50 calculation
"""
# Search assays targeting this gene
assays = tu.tools.PubChem_search_assays_by_target_gene(
gene_symbol=gene_symbol
)
results = {
'assays': [],
'total_active_compounds': 0
}
if assays.get('data', {}).get('aids'):
for aid in assays['data']['aids'][:10]: # Top 10 assays
# Get assay summary
summary = tu.tools.PubChem_get_assay_summary(aid=aid)
# Get active compounds
actives = tu.tools.PubChem_get_assay_active_compounds(aid=aid)
active_cids = actives.get('data', {}).get('cids', [])
results['assays'].append({
'aid': aid,
'summary': summary.get('data', {}),
'active_count': len(active_cids)
})
results['total_active_compounds'] += len(active_cids)
return results
def get_dose_response_data(tu, aid):
"""Get dose-response curves for IC50/EC50 determination."""
dr_data = tu.tools.PubChem_get_assay_dose_response(aid=aid)
return dr_data
def get_compound_bioactivity_profile(tu, cid):
"""Get all bioactivity data for a compound."""
profile = tu.tools.PubChem_get_compound_bioactivity(cid=cid)
return profile
PubChem BioAssay Output for Report:
### 2.6 PubChem HTS Screening Data (NEW)
**Assays Found**: 45
**Total Active Compounds Across Assays**: ~1,200
| AID | Assay Type | Active Compounds | Target | Description |
|-----|------------|------------------|--------|-------------|
| 504526 | HTS | 234 | EGFR | qHTS inhibition screen |
| 1053104 | Dose-response | 12 | EGFR kinase | Confirmatory IC50 |
| 651564 | Cellular | 8 | EGFR | Cell proliferation assay |
**Novel Actives** (not in ChEMBL/BindingDB):
- CID 12345678: Active in AID 504526, IC50 = 45 nM
- CID 23456789: Active in AID 1053104, IC50 = 120 nM
*Source: PubChem via `PubChem_search_assays_by_target_gene`, `PubChem_get_assay_active_compounds`*
Why Use Both BindingDB and PubChem:
| Source | Strengths | Best For |
|---|---|---|
| ChEMBL | Curated, standardized, SAR data | Primary ligand source |
| BindingDB | Direct affinity measurements | Ki/Kd values, PMIDs |
| PubChem BioAssay | HTS data, NIH screens | Novel scaffolds, broad coverage |
Phase 3: Structure Analysis
3.1 PDB Structure Retrieval
1. PDB_search_similar_structures(query=uniprot_accession, type="sequence")
└─ Extract: PDB IDs with ligands
2. get_protein_metadata_by_pdb_id(pdb_id)
└─ Extract: Resolution, method, ligand codes
3. alphafold_get_prediction(accession=uniprot_accession)
└─ Extract: Predicted structure (if no experimental)
3.1b EMDB Cryo-EM Structures (NEW)
Prioritize EMDB for: Membrane proteins (GPCRs, ion channels), large complexes, targets with multiple conformational states.
def get_cryoem_structures(tu, target_name, uniprot_accession):
"""Get cryo-EM structures for membrane targets."""
# Search EMDB
emdb_results = tu.tools.emdb_search(
query=f"{target_name} membrane receptor"
)
structures = []
for entry in emdb_results[:5]:
details = tu.tools.emdb_get_entry(entry_id=entry['emdb_id'])
# Get associated PDB model (essential for docking)
pdb_models = details.get('pdb_ids', [])
structures.append({
'emdb_id': entry['emdb_id'],
'resolution': entry.get('resolution', 'N/A'),
'title': entry.get('title', 'N/A'),
'conformational_state': details.get('state', 'Unknown'),
'pdb_models': pdb_models
})
return structures
When to use cryo-EM over X-ray:
| Target Type | Prefer cryo-EM? | Reason |
|---|---|---|
| GPCR | Yes | Native membrane conformation |
| Ion channel | Yes | Multiple functional states |
| Receptor-ligand complex | Yes | Physiological state |
| Kinase | Usually X-ray | Higher resolution typically |
Structure Summary:
### 3.1 Available Structures
| PDB ID | Resolution | Method | Ligand | Affinity | State |
|--------|------------|--------|--------|----------|-------|
| 1M17 | 2.6 Å | X-ray | Erlotinib | Ki=0.4 nM | Active |
| 4HJO | 2.1 Å | X-ray | Lapatinib | Ki=3 nM | Inactive |
| AF-P00533 | - | Predicted | None | - | - |
### 3.1b Cryo-EM Structures (EMDB)
| EMDB ID | Resolution | PDB Model | Conformation | Ligand |
|---------|------------|-----------|--------------|--------|
| EMD-12345 | 3.2 Å | 7ABC | Active | Agonist |
| EMD-23456 | 3.5 Å | 8DEF | Inactive | Antagonist |
**Best Structure for Docking**: 1M17 (high resolution, relevant ligand)
*Source: RCSB PDB, EMDB, AlphaFold DB*
3.2 Binding Pocket Analysis
get_binding_affinity_by_pdb_id(pdb_id)
└─ Extract: Binding affinities for co-crystallized ligands
Output for Report:
### 3.2 Binding Pocket Characterization
**Pocket Volume**: ~850 ų (well-defined)
**Key Interaction Residues**:
- **Hinge region**: M793 (backbone H-bond donor/acceptor)
- **Gatekeeper**: T790 (small residue, allows access)
- **DFG motif**: D855 (active conformation)
- **Selectivity pocket**: L788, G796 (unique to EGFR)
**Druggability Assessment**: High (enclosed pocket, conserved interactions)
Phase 3.5: Docking Validation (NVIDIA NIM)
Validate structure and score compounds using molecular docking.
Requires: NVIDIA_API_KEY environment variable
3.5.1 Reference Compound Docking
Dock a known inhibitor to validate the structure captures the binding pocket correctly.
Option A: DiffDock (Blind docking, PDB + SDF input)
NvidiaNIM_diffdock(
protein=pdb_content, # PDB text content
ligand=reference_sdf, # SDF/MOL2 content
num_poses=10
)
└─ Returns: Docking poses with confidence scores
└─ Use: When you have PDB structure and ligand SDF file
Option B: Boltz2 (From sequence + SMILES)
NvidiaNIM_boltz2(
polymers=[{"molecule_type": "protein", "sequence": kinase_sequence}],
ligands=[{"smiles": "COc1cc2ncnc(Nc3ccc(C#C)cc3)c2cc1OCCOC"}],
sampling_steps=50,
diffusion_samples=1
)
└─ Returns: Protein-ligand complex structure
└─ Use: When starting from SMILES, no SDF needed
3.5.2 Docking Score Interpretation
| Score vs Reference | Priority | Symbol |
|---|---|---|
| Higher than reference | Top priority | ★★★★ |
| Within 5% of reference | High priority | ★★★ |
| Within 20% of reference | Moderate priority | ★★☆ |
| >20% lower | Low priority | ★☆☆ |
Report Format:
### 3.5 Docking Validation Results
**Reference Compound**: Erlotinib
**Method**: DiffDock via NVIDIA NIM
| Metric | Value | Interpretation |
|--------|-------|----------------|
| Best Pose Confidence | 0.906 | Excellent |
| Steric Clashes | None | Clean binding pose |
**Validation Status**: ✓ Structure captures binding pocket correctly
*Source: NVIDIA NIM via `NvidiaNIM_diffdock`*
Phase 4: Compound Expansion
4.1 Similarity Search
Starting from top actives, expand chemical space:
1. ChEMBL_search_similar_molecules(molecule=top_active_smiles, similarity=70)
└─ Extract: Similar compounds not yet tested on target
2. PubChem_search_compounds_by_similarity(smiles, threshold=0.7)
└─ Extract: PubChem CIDs with similar structures
Strategy:
- Use 3-5 diverse actives as seeds
- Similarity threshold: 70-85% (balance novelty vs. activity)
- Prioritize compounds NOT in ChEMBL bioactivity for target
4.2 Substructure Search
1. ChEMBL_search_substructure(smiles=core_scaffold)
└─ Extract: Compounds containing scaffold
2. PubChem_search_compounds_by_substructure(smiles=core_scaffold)
└─ Extract: Additional scaffold-containing compounds
4.3 Cross-Database Mining
1. STITCH_get_chemical_protein_interactions(identifier=target_gene)
└─ Extract: Additional chemical-protein links
2. DGIdb_get_drug_gene_interactions(genes=[gene_symbol])
└─ Extract: Approved/investigational drugs
Output for Report:
### 4. Compound Expansion Results
**Starting Seeds**: 5 diverse actives (IC50 < 100 nM)
**Similarity Expansion**: 847 compounds (70% threshold)
**Substructure Search**: 234 scaffold matches
**Cross-Database**: 45 additional hits
**After Deduplication**: 923 unique candidate compounds
| Source | Compounds | Already Tested | Novel Candidates |
|--------|-----------|----------------|------------------|
| ChEMBL similarity | 456 | 234 | 222 |
| PubChem similarity | 391 | 156 | 235 |
| ChEMBL substructure | 178 | 89 | 89 |
| STITCH | 45 | 23 | 22 |
| **Total Unique** | **923** | **355** | **568** |
4.4 De Novo Molecule Generation (NVIDIA NIM)
When database mining yields insufficient candidates, generate novel molecules.
Requires: NVIDIA_API_KEY environment variable
Option A: GenMol (Scaffold Hopping with Masked Regions)
NvidiaNIM_genmol(
smiles="COc1cc2ncnc(Nc3ccc([*{3-8}])c([*{1-3}])c3)c2cc1OCCCN1CCOCC1",
num_molecules=100,
temperature=2.0,
scoring="QED"
)
└─ Input: SMILES with [*{min-max}] masked regions
└─ Output: Generated molecules with QED/LogP scores
└─ Use: Explore specific positions while keeping scaffold
Mask Design Strategy:
| Position | Mask | Purpose |
|---|---|---|
| Aniline substituent | [*{1-3}] |
Small groups (halogen, methyl) |
| Solubilizing group | [*{5-10}] |
Morpholine, piperazine variants |
| Linker region | [*{3-6}] |
Spacer variations |
Example Masked SMILES for EGFR:
# Keep quinazoline core, vary aniline and tail
COc1cc2ncnc(Nc3ccc([*{1-3}])c([*{1-3}])c3)c2cc1[*{5-12}]
Option B: MolMIM (Controlled Generation from Reference)
NvidiaNIM_molmim(
smi="COc1cc2ncnc(Nc3ccc(Cl)cc3)c2cc1OCCN1CCOCC1",
num_molecules=50,
algorithm="CMA-ES"
)
└─ Input: Reference SMILES (known active)
└─ Output: Optimized analogs with property scores
└─ Use: Generate close analogs of top actives
Generation Workflow:
- Identify top 3-5 actives from Phase 2
- Design masked SMILES for GenMol OR use as reference for MolMIM
- Generate 50-100 molecules per seed
- Pass generated molecules to Phase 5 (ADMET filtering)
- Dock survivors in Phase 6 for final ranking
Report Format:
### 4.4 De Novo Generation Results
**Method**: GenMol via NVIDIA NIM
**Seed Scaffold**: 4-anilinoquinazoline (from erlotinib)
**Masked Positions**: Aniline (3,4), solubilizing tail
| Metric | Value |
|--------|-------|
| Molecules Generated | 100 |
| Passing Lipinski | 95 (95%) |
| Mean QED Score | 0.72 |
| Unique Scaffolds | 12 |
**Top Generated Compounds**:
| ID | SMILES | QED | LogP | Novelty |
|----|--------|-----|------|---------|
| GEN-001 | COc1cc2ncnc(Nc3ccc(Cl)c(Cl)c3)c2cc1OCCCN1CCOCC1 | 0.81 | 4.2 | Novel substitution |
| GEN-002 | COc1cc2ncnc(Nc3ccc(C#N)c(F)c3)c2cc1OCCCN1CCOCC1 | 0.78 | 3.8 | Novel substitution |
*Source: NVIDIA NIM via `NvidiaNIM_genmol`*
Phase 5: ADMET Filtering
5.1 Physicochemical Properties
ADMETAI_predict_physicochemical_properties(smiles=[compound_list])
└─ Filter: Lipinski violations ≤ 1
└─ Filter: QED > 0.3
└─ Filter: MW 200-600
5.2 ADMET Endpoints
1. ADMETAI_predict_bioavailability(smiles=[compound_list])
└─ Filter: Oral bioavailability > 0.3
2. ADMETAI_predict_toxicity(smiles=[compound_list])
└─ Filter: AMES < 0.5, hERG < 0.5, DILI < 0.5
3. ADMETAI_predict_CYP_interactions(smiles=[compound_list])
└─ Flag: CYP3A4 inhibitors (drug interaction risk)
5.3 Structural Alerts
ChEMBL_search_compound_structural_alerts(smiles=compound_smiles)
└─ Flag: PAINS, reactive groups, toxicophores
ADMET Filter Summary:
### 5. ADMET Filtering Results
| Filter Stage | Input | Passed | Failed | Pass Rate |
|--------------|-------|--------|--------|-----------|
| Physicochemical (Lipinski) | 568 | 456 | 112 | 80% |
| Drug-likeness (QED > 0.3) | 456 | 398 | 58 | 87% |
| Bioavailability (> 0.3) | 398 | 312 | 86 | 78% |
| Toxicity filters | 312 | 267 | 45 | 86% |
| Structural alerts | 267 | 234 | 33 | 88% |
| **Final Candidates** | **568** | **234** | **334** | **41%** |
**Common Failure Reasons**:
1. High molecular weight (>600): 67 compounds
2. Low predicted bioavailability: 86 compounds
3. hERG liability: 28 compounds
4. PAINS alerts: 18 compounds
Phase 6: Candidate Prioritization
6.1 Scoring Framework
Score each candidate on multiple dimensions:
| Dimension | Weight | Scoring Criteria |
|---|---|---|
| Structural Similarity | 25% | Tanimoto to actives (0.7-1.0 → 1-5) |
| Novelty | 20% | Not in ChEMBL bioactivity = +2; Novel scaffold = +3 |
| ADMET Score | 25% | Composite of property predictions |
| Synthesis Feasibility | 15% | SA score (1-10), commercial availability |
| Scaffold Diversity | 15% | Cluster representative bonus |
6.2 Synthesis Feasibility
### 6.2 Synthesis Feasibility Assessment
| Candidate | SA Score | Commercial | Estimated Steps | Flag |
|-----------|----------|------------|-----------------|------|
| Compound-1 | 2.3 | Yes (Enamine) | 0 | ★★★ |
| Compound-2 | 3.5 | Building block | 2-3 | ★★☆ |
| Compound-3 | 5.8 | No | 6-8 | ★☆☆ |
**SA Score Interpretation**:
- 1-3: Easy synthesis
- 3-5: Moderate complexity
- 5-10: Challenging synthesis
6.3 Final Prioritized List
### 6.3 Top 20 Candidate Compounds
| Rank | ID | SMILES | Sim. Score | ADMET | Novelty | Overall | Rationale |
|------|-----|--------|------------|-------|---------|---------|-----------|
| 1 | CPD-001 | Cc1ccc... | 0.82 | 4.5 | Novel scaffold | 4.2 | High similarity, clean ADMET |
| 2 | CPD-002 | COc1cc... | 0.78 | 4.3 | Not tested | 4.0 | Quinazoline analog |
| 3 | CPD-003 | Nc1ccc... | 0.75 | 4.1 | Novel core | 3.9 | New chemotype |
| ... | ... | ... | ... | ... | ... | ... | ... |
**Scaffold Diversity**: 7 distinct scaffolds in top 20
**Commercial Availability**: 12/20 available for purchase
**Estimated Hit Rate**: 15-25% (based on similarity to actives)
Phase 6.5: Literature Evidence (NEW)
6.5.1 Literature Search for Validation
Search literature to validate candidate compounds and understand target context.
def search_binder_literature(tu, target_name, compound_scaffolds):
"""Search literature for compound and target evidence."""
# PubMed: Published SAR studies
sar_papers = tu.tools.PubMed_search_articles(
query=f"{target_name} inhibitor SAR structure-activity",
limit=30
)
# BioRxiv: Latest unpublished findings
preprints = tu.tools.BioRxiv_search_preprints(
query=f"{target_name} small molecule discovery",
limit=15
)
# MedRxiv: Clinical data on inhibitors
clinical = tu.tools.MedRxiv_search_preprints(
query=f"{target_name} inhibitor clinical trial",
limit=10
)
# Citation analysis for key papers
key_papers = sar_papers[:10]
for paper in key_papers:
citation = tu.tools.openalex_search_works(
query=paper['title'],
limit=1
)
paper['citations'] = citation[0].get('cited_by_count', 0) if citation else 0
return {
'published_sar': sar_papers,
'preprints': preprints,
'clinical_preprints': clinical,
'high_impact_papers': sorted(key_papers, key=lambda x: x.get('citations', 0), reverse=True)
}
6.5.2 Output for Report
## 6.5 Literature Evidence
### Published SAR Studies
| PMID | Title | Year | Key Insight |
|------|-------|------|-------------|
| 34567890 | Discovery of novel EGFR inhibitors... | 2024 | C7 substitution critical |
| 33456789 | Structure-activity relationship of... | 2023 | Fluorine improves potency |
### Recent Preprints (⚠️ Not Peer-Reviewed)
| Source | Title | Posted | Relevance |
|--------|-------|--------|-----------|
| BioRxiv | Novel scaffolds for EGFR... | 2024-02 | New chemotype discovery |
| MedRxiv | Clinical activity of... | 2024-01 | Phase 2 results |
### High-Impact References
| PMID | Citations | Title |
|------|-----------|-------|
| 32123456 | 523 | Landmark EGFR inhibitor study... |
| 31234567 | 312 | Comprehensive SAR analysis... |
*Source: PubMed, BioRxiv, MedRxiv, OpenAlex*
Report Template
File: [TARGET]_binder_discovery_report.md
# Small Molecule Binder Discovery: [TARGET]
**Generated**: [Date] | **Query**: [Original query] | **Status**: In Progress
---
## Executive Summary
[Researching...]
---
## 1. Target Validation
### 1.1 Target Identifiers
[Researching...]
### 1.2 Druggability Assessment
[Researching...]
### 1.3 Binding Site Analysis
[Researching...]
---
## 2. Known Ligand Landscape
### 2.1 ChEMBL Bioactivity Summary
[Researching...]
### 2.2 Approved Drugs & Clinical Compounds
[Researching...]
### 2.3 Chemical Probes
[Researching...]
### 2.4 SAR Insights
[Researching...]
---
## 3. Structural Information
### 3.1 Available Structures
[Researching...]
### 3.2 Binding Pocket Analysis
[Researching...]
### 3.3 Key Interactions
[Researching...]
---
## 4. Compound Expansion
### 4.1 Similarity Search Results
[Researching...]
### 4.2 Substructure Search Results
[Researching...]
### 4.3 Cross-Database Mining
[Researching...]
---
## 5. ADMET Filtering
### 5.1 Physicochemical Filters
[Researching...]
### 5.2 ADMET Predictions
[Researching...]
### 5.3 Structural Alerts
[Researching...]
### 5.4 Filter Summary
[Researching...]
---
## 6. Candidate Prioritization
### 6.1 Scoring Methodology
[Researching...]
### 6.2 Synthesis Feasibility
[Researching...]
### 6.3 Top 20 Candidates
[Researching...]
---
## 7. Recommendations
### 7.1 Immediate Actions
[Researching...]
### 7.2 Experimental Validation Plan
[Researching...]
### 7.3 Backup Strategies
[Researching...]
---
## 8. Data Gaps & Limitations
[Researching...]
---
## 9. Data Sources
[Will be populated as research progresses...]
---
## 10. Methods Summary
| Step | Tool | Purpose |
|------|------|---------|
| Sequence retrieval | UniProt_search | Get protein sequence |
| Structure prediction | NvidiaNIM_alphafold2 / NvidiaNIM_esmfold | 3D structure with pLDDT |
| Docking validation | NvidiaNIM_diffdock / NvidiaNIM_boltz2 | Validate binding pocket |
| Known ligands | ChEMBL_get_target_activities | Bioactivity data |
| Similarity search | ChEMBL_search_similar_molecules | Expand chemical space |
| De novo generation | NvidiaNIM_genmol / NvidiaNIM_molmim | Novel molecule design |
| ADMET filtering | ADMETAI_predict_* | Drug-likeness assessment |
| Candidate docking | NvidiaNIM_diffdock / NvidiaNIM_boltz2 | Final scoring |
Evidence Grading
| Tier | Symbol | Description | Example |
|---|---|---|---|
| T0 | ★★★★ | Docking score > reference inhibitor | Better than erlotinib |
| T1 | ★★★ | Experimental IC50/Ki < 100 nM | ChEMBL bioactivity |
| T2 | ★★☆ | Docking within 5% of reference OR IC50 100-1000 nM | High priority |
| T3 | ★☆☆ | Structural similarity > 80% to T1 | Predicted active |
| T4 | ☆☆☆ | Similarity 70-80%, scaffold match | Lower confidence |
| T5 | ○○○ | Generated molecule, ADMET-passed, no docking | Speculative |
Docking-Enhanced Grading: When NVIDIA NIM docking is available, compounds gain evidence:
- Docking > reference → upgrade to T0 (★★★★)
- Docking within 5% → upgrade to T2 (★★☆)
- Docking within 20% → maintain current tier
- Docking >20% worse → downgrade one tier
Apply to all candidate compounds:
| Compound | Evidence | Docking vs Ref | Rationale |
|----------|----------|----------------|-----------|
| CPD-001 | ★★★★ | +8.3% | 85% similar, docking > erlotinib |
| CPD-002 | ★★★ | -2.1% | IC50=45nM, validated by docking |
| CPD-003 | ★★☆ | -4.5% | 78% similar, good docking |
| GEN-001 | ★☆☆ | -15% | Generated, ADMET-passed |
Mandatory Completeness Checklist
Phase 1: Target Validation
- UniProt accession resolved
- ChEMBL target ID obtained
- Druggability assessed (≥2 sources)
- Target class identified
- Binding site information (or "No structural data")
Phase 2: Known Ligands
- ChEMBL activities queried (≥100 or all available)
- Activity statistics (count, potency range)
- Top 10 actives listed with IC50
- Chemical probes identified (or "None available")
- SAR insights summarized
Phase 3: Structure
- PDB structures listed (or "No experimental structure")
- Best structure for docking identified
- Binding pocket described (or "Predicted from AlphaFold")
Phase 4: Expansion
- ≥3 seed compounds used
- Similarity search completed (≥100 results or exhausted)
- Substructure search completed
- Deduplicated candidate count reported
Phase 5: ADMET
- Physicochemical filters applied
- Toxicity predictions run
- Structural alerts checked
- Filter funnel table included
Phase 6: Prioritization
- ≥20 candidates ranked (or all if fewer)
- Scoring methodology explained
- Synthesis feasibility assessed
- Scaffold diversity noted
Phase 7: Recommendations
- ≥3 immediate actions listed
- Experimental validation plan outlined
- Data gaps aggregated
Tool Reference by Phase
Phase 1: Target Validation
| Tool | Purpose |
|---|---|
UniProt_search |
Resolve UniProt accession |
MyGene_query_genes |
Get Ensembl/NCBI IDs |
ChEMBL_search_targets |
Get ChEMBL target ID |
OpenTargets_get_target_tractability_by_ensemblID |
Tractability assessment |
DGIdb_get_gene_druggability |
Druggability categories |
ChEMBL_search_binding_sites |
Binding site info |
InterPro_get_protein_domains |
Domain architecture |
Phase 2: Known Ligands
| Tool | Purpose |
|---|---|
ChEMBL_get_target_activities |
Bioactivity data |
ChEMBL_get_molecule |
Molecule details |
GtoPdb_get_target_interactions |
Pharmacology data |
OpenTargets_get_chemical_probes_by_target_ensemblID |
Chemical probes |
OpenTargets_get_associated_drugs_by_target_ensemblID |
Known drugs |
Phase 1.4: Structure Prediction (NVIDIA NIM)
| Tool | Purpose |
|---|---|
NvidiaNIM_alphafold2 |
High-accuracy structure prediction with pLDDT |
NvidiaNIM_esmfold |
Fast structure prediction (max 1024 AA) |
NvidiaNIM_msa_search |
MSA generation for AlphaFold |
Phase 3: Structure
| Tool | Purpose |
|---|---|
PDB_search_similar_structures |
Find PDB structures |
get_protein_metadata_by_pdb_id |
Structure metadata |
get_binding_affinity_by_pdb_id |
Ligand affinities |
alphafold_get_prediction |
Predicted structure (AlphaFold DB) |
get_ligand_smiles_by_chem_comp_id |
Ligand structures |
emdb_search |
Search cryo-EM structures (NEW) |
emdb_get_entry |
Get EMDB entry details (NEW) |
Phase 3.5: Docking Validation (NVIDIA NIM)
| Tool | Purpose |
|---|---|
NvidiaNIM_diffdock |
Blind molecular docking (PDB + SDF) |
NvidiaNIM_boltz2 |
Protein-ligand complex (sequence + SMILES) |
Phase 4: Expansion
| Tool | Purpose |
|---|---|
ChEMBL_search_similar_molecules |
Similarity search |
PubChem_search_compounds_by_similarity |
PubChem similarity |
ChEMBL_search_substructure |
Substructure search |
PubChem_search_compounds_by_substructure |
PubChem substructure |
STITCH_get_chemical_protein_interactions |
Cross-database |
Phase 4.4: De Novo Generation (NVIDIA NIM)
| Tool | Purpose |
|---|---|
NvidiaNIM_genmol |
Scaffold hopping with masked regions |
NvidiaNIM_molmim |
Controlled generation from reference |
Phase 5: ADMET
| Tool | Purpose |
|---|---|
ADMETAI_predict_physicochemical_properties |
Drug-likeness |
ADMETAI_predict_bioavailability |
Oral absorption |
ADMETAI_predict_toxicity |
Toxicity flags |
ADMETAI_predict_CYP_interactions |
CYP liabilities |
ChEMBL_search_compound_structural_alerts |
PAINS, alerts |
Phase 6: Candidate Docking (NVIDIA NIM)
| Tool | Purpose |
|---|---|
NvidiaNIM_diffdock |
Score all candidates by docking |
NvidiaNIM_boltz2 |
Alternative docking from SMILES |
Phase 6.5: Literature Evidence (NEW)
| Tool | Purpose |
|---|---|
PubMed_search_articles |
Published SAR studies |
BioRxiv_search_preprints |
Latest biology preprints |
MedRxiv_search_preprints |
Clinical preprints |
openalex_search_works |
Citation analysis |
SemanticScholar_search |
AI-ranked papers |
Fallback Chains
| Primary Tool | Fallback 1 | Fallback 2 | Use When |
|---|---|---|---|
ChEMBL_get_target_activities |
GtoPdb_get_target_interactions |
PubChem_search_assays |
No ChEMBL data |
ChEMBL_search_similar_molecules |
PubChem_search_compounds_by_similarity |
STITCH_get_chemical_protein_interactions |
ChEMBL exhausted |
PDB_search_similar_structures |
NvidiaNIM_alphafold2 |
alphafold_get_prediction |
No PDB structure |
alphafold_get_prediction |
NvidiaNIM_alphafold2 |
NvidiaNIM_esmfold |
AlphaFold DB unavailable |
NvidiaNIM_alphafold2 |
NvidiaNIM_esmfold |
alphafold_get_prediction |
AlphaFold2 NIM error |
NvidiaNIM_diffdock |
NvidiaNIM_boltz2 |
Skip docking, use similarity | Docking error |
NvidiaNIM_genmol |
NvidiaNIM_molmim |
Manual scaffold hopping | Generation error |
OpenTargets_get_target_tractability |
DGIdb_get_gene_druggability |
Document "Unknown" | Open Targets error |
ADMETAI_* |
SwissADME tools | Basic Lipinski | Invalid SMILES |
PDB_search_similar_structures |
emdb_search + PDB |
NvidiaNIM_alphafold2 |
Membrane proteins |
PubMed_search_articles |
openalex_search_works |
SemanticScholar_search |
Literature search |
BioRxiv_search_preprints |
MedRxiv_search_preprints |
Skip preprints | Preprint sources |
NVIDIA NIM API Key Required: Tools with NvidiaNIM_ prefix require NVIDIA_API_KEY environment variable. Check availability at start:
import os
nvidia_available = bool(os.environ.get("NVIDIA_API_KEY"))
# If not available, fall back to non-NIM alternatives
Common Use Cases
Well-Characterized Target
User: "Find novel binders for EGFR" → Rich ChEMBL data; focus on novel scaffolds, selectivity, ADMET
Novel Target
User: "Find small molecules for [new target with no known ligands]" → Limited bioactivity; rely on structure-based assessment, similar target ligands
Lead Optimization
User: "Find analogs of compound X for target Y" → Deep similarity search around specific compound; focus on SAR
Selectivity Challenge
User: "Find selective inhibitors for kinase X vs kinase Y" → Include selectivity analysis; filter by off-target predictions
When NOT to Use This Skill
- Drug research → Use tooluniverse-drug-research (existing drug profiling)
- Target research only → Use tooluniverse-target-research
- Single compound ADMET → Call ADMET tools directly
- Literature search → Use tooluniverse-literature-deep-research
- Protein structure only → Use tooluniverse-protein-structure-retrieval
Use this skill for discovering new compounds for a protein target.
Additional Resources
- Checklist: CHECKLIST.md - Pre-delivery verification
- Examples: EXAMPLES.md - Detailed workflow examples
- Tool corrections: TOOLS_REFERENCE.md - Parameter corrections