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---
name: chembl-database
description: "Query ChEMBL's bioactive molecules and drug discovery data. Search compounds by structure/properties, retrieve bioactivity data (IC50, Ki), find inhibitors, perform SAR studies, for medicinal chemistry."
---
# ChEMBL Database
## Overview
ChEMBL is a manually curated database of bioactive molecules maintained by the European Bioinformatics Institute (EBI), containing over 2 million compounds, 19 million bioactivity measurements, 13,000+ drug targets, and data on approved drugs and clinical candidates. Access and query this data programmatically using the ChEMBL Python client for drug discovery and medicinal chemistry research.
## When to Use This Skill
This skill should be used when:
- **Compound searches**: Finding molecules by name, structure, or properties
- **Target information**: Retrieving data about proteins, enzymes, or biological targets
- **Bioactivity data**: Querying IC50, Ki, EC50, or other activity measurements
- **Drug information**: Looking up approved drugs, mechanisms, or indications
- **Structure searches**: Performing similarity or substructure searches
- **Cheminformatics**: Analyzing molecular properties and drug-likeness
- **Target-ligand relationships**: Exploring compound-target interactions
- **Drug discovery**: Identifying inhibitors, agonists, or bioactive molecules
## Installation and Setup
### Python Client
The ChEMBL Python client is required for programmatic access:
```bash
uv pip install chembl_webresource_client
```
### Basic Usage Pattern
```python
from chembl_webresource_client.new_client import new_client
# Access different endpoints
molecule = new_client.molecule
target = new_client.target
activity = new_client.activity
drug = new_client.drug
```
## Core Capabilities
### 1. Molecule Queries
**Retrieve by ChEMBL ID:**
```python
molecule = new_client.molecule
aspirin = molecule.get('CHEMBL25')
```
**Search by name:**
```python
results = molecule.filter(pref_name__icontains='aspirin')
```
**Filter by properties:**
```python
# Find small molecules (MW <= 500) with favorable LogP
results = molecule.filter(
molecule_properties__mw_freebase__lte=500,
molecule_properties__alogp__lte=5
)
```
### 2. Target Queries
**Retrieve target information:**
```python
target = new_client.target
egfr = target.get('CHEMBL203')
```
**Search for specific target types:**
```python
# Find all kinase targets
kinases = target.filter(
target_type='SINGLE PROTEIN',
pref_name__icontains='kinase'
)
```
### 3. Bioactivity Data
**Query activities for a target:**
```python
activity = new_client.activity
# Find potent EGFR inhibitors
results = activity.filter(
target_chembl_id='CHEMBL203',
standard_type='IC50',
standard_value__lte=100,
standard_units='nM'
)
```
**Get all activities for a compound:**
```python
compound_activities = activity.filter(
molecule_chembl_id='CHEMBL25',
pchembl_value__isnull=False
)
```
### 4. Structure-Based Searches
**Similarity search:**
```python
similarity = new_client.similarity
# Find compounds similar to aspirin
similar = similarity.filter(
smiles='CC(=O)Oc1ccccc1C(=O)O',
similarity=85 # 85% similarity threshold
)
```
**Substructure search:**
```python
substructure = new_client.substructure
# Find compounds containing benzene ring
results = substructure.filter(smiles='c1ccccc1')
```
### 5. Drug Information
**Retrieve drug data:**
```python
drug = new_client.drug
drug_info = drug.get('CHEMBL25')
```
**Get mechanisms of action:**
```python
mechanism = new_client.mechanism
mechanisms = mechanism.filter(molecule_chembl_id='CHEMBL25')
```
**Query drug indications:**
```python
drug_indication = new_client.drug_indication
indications = drug_indication.filter(molecule_chembl_id='CHEMBL25')
```
## Query Workflow
### Workflow 1: Finding Inhibitors for a Target
1. **Identify the target** by searching by name:
```python
targets = new_client.target.filter(pref_name__icontains='EGFR')
target_id = targets[0]['target_chembl_id']
```
2. **Query bioactivity data** for that target:
```python
activities = new_client.activity.filter(
target_chembl_id=target_id,
standard_type='IC50',
standard_value__lte=100
)
```
3. **Extract compound IDs** and retrieve details:
```python
compound_ids = [act['molecule_chembl_id'] for act in activities]
compounds = [new_client.molecule.get(cid) for cid in compound_ids]
```
### Workflow 2: Analyzing a Known Drug
1. **Get drug information**:
```python
drug_info = new_client.drug.get('CHEMBL1234')
```
2. **Retrieve mechanisms**:
```python
mechanisms = new_client.mechanism.filter(molecule_chembl_id='CHEMBL1234')
```
3. **Find all bioactivities**:
```python
activities = new_client.activity.filter(molecule_chembl_id='CHEMBL1234')
```
### Workflow 3: Structure-Activity Relationship (SAR) Study
1. **Find similar compounds**:
```python
similar = new_client.similarity.filter(smiles='query_smiles', similarity=80)
```
2. **Get activities for each compound**:
```python
for compound in similar:
activities = new_client.activity.filter(
molecule_chembl_id=compound['molecule_chembl_id']
)
```
3. **Analyze property-activity relationships** using molecular properties from results.
## Filter Operators
ChEMBL supports Django-style query filters:
- `__exact` - Exact match
- `__iexact` - Case-insensitive exact match
- `__contains` / `__icontains` - Substring matching
- `__startswith` / `__endswith` - Prefix/suffix matching
- `__gt`, `__gte`, `__lt`, `__lte` - Numeric comparisons
- `__range` - Value in range
- `__in` - Value in list
- `__isnull` - Null/not null check
## Data Export and Analysis
Convert results to pandas DataFrame for analysis:
```python
import pandas as pd
activities = new_client.activity.filter(target_chembl_id='CHEMBL203')
df = pd.DataFrame(list(activities))
# Analyze results
print(df['standard_value'].describe())
print(df.groupby('standard_type').size())
```
## Performance Optimization
### Caching
The client automatically caches results for 24 hours. Configure caching:
```python
from chembl_webresource_client.settings import Settings
# Disable caching
Settings.Instance().CACHING = False
# Adjust cache expiration (seconds)
Settings.Instance().CACHE_EXPIRE = 86400
```
### Lazy Evaluation
Queries execute only when data is accessed. Convert to list to force execution:
```python
# Query is not executed yet
results = molecule.filter(pref_name__icontains='aspirin')
# Force execution
results_list = list(results)
```
### Pagination
Results are paginated automatically. Iterate through all results:
```python
for activity in new_client.activity.filter(target_chembl_id='CHEMBL203'):
# Process each activity
print(activity['molecule_chembl_id'])
```
## Common Use Cases
### Find Kinase Inhibitors
```python
# Identify kinase targets
kinases = new_client.target.filter(
target_type='SINGLE PROTEIN',
pref_name__icontains='kinase'
)
# Get potent inhibitors
for kinase in kinases[:5]: # First 5 kinases
activities = new_client.activity.filter(
target_chembl_id=kinase['target_chembl_id'],
standard_type='IC50',
standard_value__lte=50
)
```
### Explore Drug Repurposing
```python
# Get approved drugs
drugs = new_client.drug.filter()
# For each drug, find all targets
for drug in drugs[:10]:
mechanisms = new_client.mechanism.filter(
molecule_chembl_id=drug['molecule_chembl_id']
)
```
### Virtual Screening
```python
# Find compounds with desired properties
candidates = new_client.molecule.filter(
molecule_properties__mw_freebase__range=[300, 500],
molecule_properties__alogp__lte=5,
molecule_properties__hba__lte=10,
molecule_properties__hbd__lte=5
)
```
## Resources
### scripts/example_queries.py
Ready-to-use Python functions demonstrating common ChEMBL query patterns:
- `get_molecule_info()` - Retrieve molecule details by ID
- `search_molecules_by_name()` - Name-based molecule search
- `find_molecules_by_properties()` - Property-based filtering
- `get_bioactivity_data()` - Query bioactivities for targets
- `find_similar_compounds()` - Similarity searching
- `substructure_search()` - Substructure matching
- `get_drug_info()` - Retrieve drug information
- `find_kinase_inhibitors()` - Specialized kinase inhibitor search
- `export_to_dataframe()` - Convert results to pandas DataFrame
Consult this script for implementation details and usage examples.
### references/api_reference.md
Comprehensive API documentation including:
- Complete endpoint listing (molecule, target, activity, assay, drug, etc.)
- All filter operators and query patterns
- Molecular properties and bioactivity fields
- Advanced query examples
- Configuration and performance tuning
- Error handling and rate limiting
Refer to this document when detailed API information is needed or when troubleshooting queries.
## Important Notes
### Data Reliability
- ChEMBL data is manually curated but may contain inconsistencies
- Always check `data_validity_comment` field in activity records
- Be aware of `potential_duplicate` flags
### Units and Standards
- Bioactivity values use standard units (nM, uM, etc.)
- `pchembl_value` provides normalized activity (-log scale)
- Check `standard_type` to understand measurement type (IC50, Ki, EC50, etc.)
### Rate Limiting
- Respect ChEMBL's fair usage policies
- Use caching to minimize repeated requests
- Consider bulk downloads for large datasets
- Avoid hammering the API with rapid consecutive requests
### Chemical Structure Formats
- SMILES strings are the primary structure format
- InChI keys available for compounds
- SVG images can be generated via the image endpoint
## Additional Resources
- ChEMBL website: https://www.ebi.ac.uk/chembl/
- API documentation: https://www.ebi.ac.uk/chembl/api/data/docs
- Python client GitHub: https://github.com/chembl/chembl_webresource_client
- Interface documentation: https://chembl.gitbook.io/chembl-interface-documentation/
- Example notebooks: https://github.com/chembl/notebooks

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# ChEMBL Web Services API Reference
## Overview
ChEMBL is a manually curated database of bioactive molecules with drug-like properties maintained by the European Bioinformatics Institute (EBI). It contains information about compounds, targets, assays, bioactivity data, and approved drugs.
The ChEMBL database contains:
- Over 2 million compound records
- Over 1.4 million assay records
- Over 19 million activity values
- Information on 13,000+ drug targets
- Data on 16,000+ approved drugs and clinical candidates
## Python Client Installation
```bash
pip install chembl_webresource_client
```
## Key Resources and Endpoints
ChEMBL provides access to 30+ specialized endpoints:
### Core Data Types
- **molecule** - Compound structures, properties, and synonyms
- **target** - Protein and non-protein biological targets
- **activity** - Bioassay measurement results
- **assay** - Experimental assay details
- **drug** - Approved pharmaceutical information
- **mechanism** - Drug mechanism of action data
- **document** - Literature sources and references
- **cell_line** - Cell line information
- **tissue** - Tissue types
- **protein_class** - Protein classification
- **target_component** - Target component details
- **compound_structural_alert** - Structural alerts for toxicity
## Query Patterns and Filters
### Filter Operators
The API supports Django-style filter operators:
- `__exact` - Exact match
- `__iexact` - Case-insensitive exact match
- `__contains` - Contains substring
- `__icontains` - Case-insensitive contains
- `__startswith` - Starts with prefix
- `__endswith` - Ends with suffix
- `__gt` - Greater than
- `__gte` - Greater than or equal
- `__lt` - Less than
- `__lte` - Less than or equal
- `__range` - Value in range
- `__in` - Value in list
- `__isnull` - Is null/not null
- `__regex` - Regular expression match
- `__search` - Full text search
### Example Filter Queries
**Molecular weight filtering:**
```python
molecules.filter(molecule_properties__mw_freebase__lte=300)
```
**Name pattern matching:**
```python
molecules.filter(pref_name__endswith='nib')
```
**Multiple conditions:**
```python
molecules.filter(
molecule_properties__mw_freebase__lte=300,
pref_name__endswith='nib'
)
```
## Chemical Structure Searches
### Substructure Search
Search for compounds containing a specific substructure using SMILES:
```python
from chembl_webresource_client.new_client import new_client
similarity = new_client.similarity
results = similarity.filter(smiles='CC(=O)Oc1ccccc1C(=O)O', similarity=70)
```
### Similarity Search
Find compounds similar to a query structure:
```python
similarity = new_client.similarity
results = similarity.filter(smiles='CC(=O)Oc1ccccc1C(=O)O', similarity=85)
```
## Common Data Retrieval Patterns
### Get Molecule by ChEMBL ID
```python
molecule = new_client.molecule.get('CHEMBL25')
```
### Get Target Information
```python
target = new_client.target.get('CHEMBL240')
```
### Get Activity Data
```python
activities = new_client.activity.filter(
target_chembl_id='CHEMBL240',
standard_type='IC50',
standard_value__lte=100
)
```
### Get Drug Information
```python
drug = new_client.drug.get('CHEMBL1234')
```
## Response Formats
The API supports multiple response formats:
- JSON (default)
- XML
- YAML
## Caching and Performance
The Python client automatically caches results locally:
- **Default cache duration**: 24 hours
- **Cache location**: Local file system
- **Lazy evaluation**: Queries execute only when data is accessed
### Configuration Settings
```python
from chembl_webresource_client.settings import Settings
# Disable caching
Settings.Instance().CACHING = False
# Adjust cache expiration (in seconds)
Settings.Instance().CACHE_EXPIRE = 86400 # 24 hours
# Set timeout
Settings.Instance().TIMEOUT = 30
# Set retries
Settings.Instance().TOTAL_RETRIES = 3
```
## Molecular Properties
Common molecular properties available:
- `mw_freebase` - Molecular weight
- `alogp` - Calculated LogP
- `hba` - Hydrogen bond acceptors
- `hbd` - Hydrogen bond donors
- `psa` - Polar surface area
- `rtb` - Rotatable bonds
- `ro3_pass` - Rule of 3 compliance
- `num_ro5_violations` - Lipinski rule of 5 violations
- `cx_most_apka` - Most acidic pKa
- `cx_most_bpka` - Most basic pKa
- `molecular_species` - Molecular species
- `full_mwt` - Full molecular weight
## Bioactivity Data Fields
Key bioactivity fields:
- `standard_type` - Activity type (IC50, Ki, Kd, EC50, etc.)
- `standard_value` - Numerical activity value
- `standard_units` - Units (nM, uM, etc.)
- `pchembl_value` - Normalized activity value (-log scale)
- `activity_comment` - Activity annotations
- `data_validity_comment` - Data validity flags
- `potential_duplicate` - Duplicate flag
## Target Information Fields
Target data includes:
- `target_chembl_id` - ChEMBL target identifier
- `pref_name` - Preferred target name
- `target_type` - Type (PROTEIN, ORGANISM, etc.)
- `organism` - Target organism
- `tax_id` - NCBI taxonomy ID
- `target_components` - Component details
## Advanced Query Examples
### Find Kinase Inhibitors
```python
# Get kinase targets
targets = new_client.target.filter(
target_type='SINGLE PROTEIN',
pref_name__icontains='kinase'
)
# Get activities for these targets
activities = new_client.activity.filter(
target_chembl_id__in=[t['target_chembl_id'] for t in targets],
standard_type='IC50',
standard_value__lte=100
)
```
### Retrieve Drug Mechanisms
```python
mechanisms = new_client.mechanism.filter(
molecule_chembl_id='CHEMBL25'
)
```
### Get Compound Bioactivities
```python
activities = new_client.activity.filter(
molecule_chembl_id='CHEMBL25',
pchembl_value__isnull=False
)
```
## Image Generation
ChEMBL can generate SVG images of molecular structures:
```python
from chembl_webresource_client.new_client import new_client
image = new_client.image
svg = image.get('CHEMBL25')
```
## Pagination
Results are paginated automatically. To iterate through all results:
```python
activities = new_client.activity.filter(target_chembl_id='CHEMBL240')
for activity in activities:
print(activity)
```
## Error Handling
Common errors:
- **404**: Resource not found
- **503**: Service temporarily unavailable
- **Timeout**: Request took too long
The client automatically retries failed requests based on `TOTAL_RETRIES` setting.
## Rate Limiting
ChEMBL has fair usage policies:
- Be respectful with query frequency
- Use caching to minimize repeated requests
- Consider bulk downloads for large datasets
## Additional Resources
- Official API documentation: https://www.ebi.ac.uk/chembl/api/data/docs
- Python client GitHub: https://github.com/chembl/chembl_webresource_client
- ChEMBL interface docs: https://chembl.gitbook.io/chembl-interface-documentation/
- Example notebooks: https://github.com/chembl/notebooks

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#!/usr/bin/env python3
"""
ChEMBL Database Query Examples
This script demonstrates common query patterns for the ChEMBL database
using the chembl_webresource_client Python library.
Requirements:
pip install chembl_webresource_client
pip install pandas (optional, for data manipulation)
"""
from chembl_webresource_client.new_client import new_client
def get_molecule_info(chembl_id):
"""
Retrieve detailed information about a molecule by ChEMBL ID.
Args:
chembl_id: ChEMBL identifier (e.g., 'CHEMBL25')
Returns:
Dictionary containing molecule information
"""
molecule = new_client.molecule
return molecule.get(chembl_id)
def search_molecules_by_name(name_pattern):
"""
Search for molecules by name pattern.
Args:
name_pattern: Name or pattern to search for
Returns:
List of matching molecules
"""
molecule = new_client.molecule
results = molecule.filter(pref_name__icontains=name_pattern)
return list(results)
def find_molecules_by_properties(max_mw=500, min_logp=None, max_logp=None):
"""
Find molecules based on physicochemical properties.
Args:
max_mw: Maximum molecular weight
min_logp: Minimum LogP value
max_logp: Maximum LogP value
Returns:
List of matching molecules
"""
molecule = new_client.molecule
filters = {
'molecule_properties__mw_freebase__lte': max_mw
}
if min_logp is not None:
filters['molecule_properties__alogp__gte'] = min_logp
if max_logp is not None:
filters['molecule_properties__alogp__lte'] = max_logp
results = molecule.filter(**filters)
return list(results)
def get_target_info(target_chembl_id):
"""
Retrieve information about a biological target.
Args:
target_chembl_id: ChEMBL target identifier (e.g., 'CHEMBL240')
Returns:
Dictionary containing target information
"""
target = new_client.target
return target.get(target_chembl_id)
def search_targets_by_name(target_name):
"""
Search for targets by name or keyword.
Args:
target_name: Target name or keyword (e.g., 'kinase', 'EGFR')
Returns:
List of matching targets
"""
target = new_client.target
results = target.filter(
target_type='SINGLE PROTEIN',
pref_name__icontains=target_name
)
return list(results)
def get_bioactivity_data(target_chembl_id, activity_type='IC50', max_value=100):
"""
Retrieve bioactivity data for a specific target.
Args:
target_chembl_id: ChEMBL target identifier
activity_type: Type of activity (IC50, Ki, EC50, etc.)
max_value: Maximum activity value in nM
Returns:
List of activity records
"""
activity = new_client.activity
results = activity.filter(
target_chembl_id=target_chembl_id,
standard_type=activity_type,
standard_value__lte=max_value,
standard_units='nM'
)
return list(results)
def find_similar_compounds(smiles, similarity_threshold=85):
"""
Find compounds similar to a query structure.
Args:
smiles: SMILES string of query molecule
similarity_threshold: Minimum similarity percentage (0-100)
Returns:
List of similar compounds
"""
similarity = new_client.similarity
results = similarity.filter(
smiles=smiles,
similarity=similarity_threshold
)
return list(results)
def substructure_search(smiles):
"""
Search for compounds containing a specific substructure.
Args:
smiles: SMILES string of substructure
Returns:
List of compounds containing the substructure
"""
substructure = new_client.substructure
results = substructure.filter(smiles=smiles)
return list(results)
def get_drug_info(molecule_chembl_id):
"""
Retrieve drug information including indications and mechanisms.
Args:
molecule_chembl_id: ChEMBL molecule identifier
Returns:
Tuple of (drug_info, mechanisms, indications)
"""
drug = new_client.drug
mechanism = new_client.mechanism
drug_indication = new_client.drug_indication
try:
drug_info = drug.get(molecule_chembl_id)
except:
drug_info = None
mechanisms = list(mechanism.filter(molecule_chembl_id=molecule_chembl_id))
indications = list(drug_indication.filter(molecule_chembl_id=molecule_chembl_id))
return drug_info, mechanisms, indications
def find_kinase_inhibitors(max_ic50=100):
"""
Find potent kinase inhibitors.
Args:
max_ic50: Maximum IC50 value in nM
Returns:
List of kinase inhibitor activities
"""
target = new_client.target
activity = new_client.activity
# Find kinase targets
kinase_targets = target.filter(
target_type='SINGLE PROTEIN',
pref_name__icontains='kinase'
)
# Get target IDs
target_ids = [t['target_chembl_id'] for t in kinase_targets[:10]] # Limit to first 10
# Find activities
results = activity.filter(
target_chembl_id__in=target_ids,
standard_type='IC50',
standard_value__lte=max_ic50,
standard_units='nM'
)
return list(results)
def get_compound_bioactivities(molecule_chembl_id):
"""
Get all bioactivity data for a specific compound.
Args:
molecule_chembl_id: ChEMBL molecule identifier
Returns:
List of all activity records for the compound
"""
activity = new_client.activity
results = activity.filter(
molecule_chembl_id=molecule_chembl_id,
pchembl_value__isnull=False
)
return list(results)
def export_to_dataframe(data):
"""
Convert ChEMBL data to pandas DataFrame (requires pandas).
Args:
data: List of ChEMBL records
Returns:
pandas DataFrame
"""
try:
import pandas as pd
return pd.DataFrame(data)
except ImportError:
print("pandas not installed. Install with: pip install pandas")
return None
# Example usage
if __name__ == "__main__":
print("ChEMBL Database Query Examples")
print("=" * 50)
# Example 1: Get information about aspirin
print("\n1. Getting information about aspirin (CHEMBL25)...")
aspirin = get_molecule_info('CHEMBL25')
print(f"Name: {aspirin.get('pref_name')}")
print(f"Formula: {aspirin.get('molecule_properties', {}).get('full_molformula')}")
# Example 2: Search for EGFR inhibitors
print("\n2. Searching for EGFR targets...")
egfr_targets = search_targets_by_name('EGFR')
if egfr_targets:
print(f"Found {len(egfr_targets)} EGFR-related targets")
print(f"First target: {egfr_targets[0]['pref_name']}")
# Example 3: Find potent activities for a target
print("\n3. Finding potent compounds for EGFR (CHEMBL203)...")
activities = get_bioactivity_data('CHEMBL203', 'IC50', max_value=10)
print(f"Found {len(activities)} compounds with IC50 <= 10 nM")
print("\n" + "=" * 50)
print("Examples completed successfully!")