Connecting Bioactive Chemistry Across Documents and Databases
1. Open, Collaborative, and Transformative:
Exploring and Connecting Bioactive
Chemistry Across Biomedical Documents
and Databases with Public Tools
Christopher Southan
TW2Informatics, Göteborg, Sweden,
BioIT Track 11, Boston, April 2013
[1]
3. Abstract
Although there are ~ 50 million chemical structure in public databases, many
millions of bioactive compounds are still entoombed in documents. In addition
linking chemistry between patents, papers, abstracts and databases has been
patchy. However, new tools such as chemicalize.org, OPSIN, OSCA, Venny,
CheS-Mapper and InChIKey indexing by Google, have transformed the
extraction, analysis and connectivity of structures from text. Extractions can also
be triaged against PubChem that now contains 14.5 million patent-extracted
compounds from SureChemOpen, SCRIPDB, Thomson and IBM as well as 1
million from journals via ChEMBL and PubMed. These advances present new
collaborative options such as sharing extracted neglected disease patents with
SAR annotations on figshare.
[3]
4. Getting chemistry out of text and linking to data:
some is done but we have to dig for the rest
[4]
5. Estimates for chemical text tombs
• Journal chemistry public extraction, ~10 to 20 million entombed ?
• Majority of useful patent chemistry already publically extracted, but, ~5
to 10 million still to go?
• PubMed abstracts and MeSH chemistry ~ 0.5 million still entombed ?
• Other unique, useful, text-only (i.e. no database cross-references)
chemistry on the web ~ 0.1 to 0.5 million entombed ?
[5]
6. What’s out there: publically disinterred structures
• InChIKey in Google ~ 50 million
• PubChem = 48 million
• PubChem ROF + 250-800 Mw (lead-like) = 31 million
• ChemSpider = 28 million
• PubChem all docs (papers & patents) = 16 million
• PubChem patents = 15 million
• SureChemOpen = 13 million
• PubChem journal sources (PubMed + ChEMBL) = 1 million
~90% of all structures in databases have their primary origin in text sources
[6]
7. Medicinal chemistry patents (tombs with lids off)
• 18,777,229 patents, 2,208,422 WO’s (i.e. ~ 9 per family)
• WO, C07 or A61= 469,856
• WO , C07D or A61K = 235,854
• WO, C07D = 72,737 (assignee vs. year plots below)
[7]
8. PubMed at 22 mill:
~ 10% with chemistry (guarded tombs)
“Free full text” = 575,513 (24%)
[8]
9. Top-5 Med Chem journals (4% lids off tombs)
“Free full text” = 2671 (4.3%)
[9]
10. Growth:
(escaping the
tombs)
• Patent “big bang”
(SureChem &
SCRIPDB in
2012)
• Literature “slow
burn” (ChEMBL
2009 jump)
• Paradox -
patents:papers
15:1
(both sets of CIDs
cumulative)
[10]
11. Patents in PubChem:
post-bang total vs. unique content
PubChem at 47.3 million CIDs, 32% include patents, 20% patent-only
[11]
12. Citations: connections between tombs
but still need to disinter structures
Papers Abstracts
PubMed
Patents
"relatedness"
heuristics
[12]
14. Post-document retrieval: basic questions
1. What is the name:IUPAC:image:other ratio in the document?
2. Which tools might be appropriate for first-pass extractions?
3. How many and what proportion of strucs can be extracted?
4. Which SAR /in vivo/clinical data is linked to strucs ?
5. Which document sections include the key strucs ?
6. Which database entries have links (back) to this document?
7. Which strucs have InChIKey matches in Google, & database entries?
8. Which strucs have synthesis data?
9. What other documents specify and/or cite this struc ?
10. Which database records for this struc have links to other documents?
11. What realtionship connections can be made using similarity searches?
12. What intersects and differences are discernible within a document set ?
[14]
15. Triaging document or webpage chemistry
• Identify the structure specification types, e.g.
– Semantic names (all sources)
– Code names (press releases, papers and abstracts)
– IUPAC names (papers, patents and abstracts)
– Images (papers, patents, & Google images)
– SMILES (open lab books)
– InChi strings (open lab books)
– SDF files (open lab books, & github)
Convert these to a structure (e.g. SDF, SMILES, InChI) then:
– Search InChIKey in Google
– Search major databases
– Search SureChemOpen
– Compare extracted sets for intersects and diffs
– Extend exact match connectivity with similarity searching
[15]
16. Triage example:
antimalarial
starting point
The MMV390048 code
name is linked to an
image in press reports
but is PubChem and
PubMed -ve
[16]
17. Images: convert and search
Real chemists sketch them in a jiffy;
the rest of us can use OSRA: Optical Structure Recognition Application
(after editing, CS(=O)(=O)c3ccc(C2=CN=C(N)C(C1=CCC(C(F)(F)F)N=C1)C2)cc3)
[17]
28. PubChem -> ChEMBL -> PMID -> assay -> strucs
• CHEMBL2041980 (structure)
• PMID 22390538 (paper)
• CHEMBL2045642 (assay for 32 strucs
from paper)
• The 32 CIDs all have patent matches
•
[28]
29. Venny: intersects, diffs, de-dupes and merges
1) WO2011086531
matches in
PubChem
2) CheS-Mapper
cluster 8 from
WO2011086532
3) ChEMBL
assayed cpds from
PMID 22390538
(handles any
regular strings e.g.
db IDs, SMILES,
IChI or InChIKey)
[29]
30. OSDDMalaria: global sharing test-bed
• Different options being explored
• Team or personal URLs >chemicalize.org
• Github for SD files
• PubChem public collections
• Direct feed to ChEMBL malaria
• G+ for real-time exchange and feedback
[30]
31. The open toolbox facilitates extraction and
collation of 10 to 30 million structures
entombed in text
[31]
32. Conclusions
• The ability to extract chemical structures from text and web sources
has been transformed by an expansion of the public toolbox
• The PubChem big-bang increases probability of extraction having
database exact or similarity matches
• Paradoxically, the patent corpus is now completely open while access
to journal text is still restricted
• However, ChEMBL has extracted ~ 0.8 mill. SAR-linked and target
mapped structures from ~ 50K papers
• The submission of ~15 mill. patent structures to PubChem ensures at
least representation from the majority of medicinal chemistry patents
(many of which spawned the subsequent ChEMBL papers)
• Those who want to share their structures globally (e.g. OSDD) have an
expanding set of options for surfacing their results.
[32]
Notas del editor
70 million substances in CAS suggest a 20-30 million shortfall (i.e. SciFinder only) but they include virtualsand librariesSureChen will continue patent extraction but expect an asymtote of true novels only soonPubMed capture largely dependant on MeSH but a lot of IUPAC chemistry is only anually updated, and some not capturedSureChem, IBM and chemicalize all inticate that, including MeSH terms at least 0.5 million structures could be extracted from PubMedNo idea how much web-unique chemistry (not in documents or databases) is out there but open lab books will increase this
IinChIKeys - estimate of PubChem + ChemSpider in Google – but PubChem currently has a backlog for Key scrapingThe ROF + 250-800 is a very approximate circumscription of the property space that has some possibility of bioactivityProbably a proportion of vendor structures may have never been committed to textThere are some virtuals “out there” including some patent-extractions but difficult to estimate
Note the WO/PCT queries are non-redundant in the patent family senseThe medicinal chemistry corpus is actually quite smallNote big pharma patent decline post-2008 Average exemplified cpds with activity data per patent (family) is unknown but GVKs curation average is ~ 50
Using the top level MeSH term as a filter for “PubMeds with some chemistry”Free full text is ¨ ¼ but there are a lot of biological journals in this set
Select the core journals used for med chem extraction by GVKBIO and ChEMBL. Not a large corpus Both extract ~ 15 cpds per paperNote the proportion of “free full text” is low
Note that cumulative plots include an element of back-mapping i.e. the 2005 matches are to the 2013 total not the just the 2005 documents
PubChem hit 15 million patents in March 2013Largest unique content is SureChemOpen Thomson uniqueness low because a) they include at least 30% journal extractions and b) the Derwent WPI content (was) also in Discovery gateIBM are only pre-2000 patents and the extracted content overlaps with other sources.
Citations are a core tradition but they do not provide direct structure <-> structure linksPatents cite papers but papers rarely cite patents (with the exception of patent reviews)
Only Nature Chemical Biology and Nature Chemistry have direct links from the journal document to PubChemGiven todays technology the major patent offices could put links in the PDFs but are unlikely to do so
The problem “how do I find the chemistry out there relevant to my interests” is a general search retrieval recall and specificity challenge. cannot be addressed here. Beyond PubMed and Google it’s getting better (e.g. indexing of full text patents) but there are still issues (e.g. text mining of chemical journals still very restricted)Once you have found the documents or text, these are the typical set of questions you might want to address, especially in regard to choosing which tools are best for the job.
Need to assess what representational types are being used in the documentEg. Some patents are image-only (but SureChem is pulling most of these out)Then select tools and sources for the job ´Decide how to store your structures locally The default batch search is an upload to PubChemThe default individual search is the InChIKey against Google
Self explanatoryNote my blog post was indexed
The simplest of starting points, at least the press release had a structure diagram OSRA provides good starting points to edit and get SMILESThe structure does not have to be exactly right because a database similarity match is OK to see what it should have been
SMILES from the image hits the CID in PubChemThis links to patents via SureChem and chemicalize.orgChEMBL provides a link to the paper Note none of these sources have MMV390048 as synonym so all the connections are via structure
We can start of with patent linksNote in this case numbered image capture, as oposed to the IUPAC listing, was important to manually collate the structure against the correct IC50
From manual cross-checking between the individual example structures and the IC50 table the Excel sheet can be populated
Useful way to share results that is citableIndexed in Google but no live links in Excel sheet (yet)
Can upload CID lists and download as a saved and public collection
This is the Pistoia /AlexClark SAR Table appDropped the CIDs out of PubChem into DropBox and picked them up on the IPADNice but would be good to automate the decomposition
InChIkey search picks up instantly This was just a choice of one of the activesSo this connects PubChem and figshare
The CID links straight throught to chemicalize and will just re-extract the whole patent in a few seconds The 413 gave 358 hits in pub chem
IUPAC names have a lot of usage variants and OCR mistakes Typically gaps, line breaks 1 instead of 1 and missing bracketsOPSIN is good for indicating where the break is This can then be fixed for a series in chemicalize.org
Total extractions from patents can include a lot of low Mw common reagent chemistryCheS mapper display makes it easy to pick out clusters of lead-like compoundsClusters can then be downloadedFlexibility is high because document sets can be split or merged at the imput stage
ChEMBL extracts structure and dataCant actually select a set of cpds via the PubMed ID but can via the assay ID that is usually unique to that paperIn this case we got 32 structures, all of which came from that patent
Very useful utility for any kind of set operations e.g. sets of extractions Total flexibility e.g. intersecting patents and papers with extractions from abstract setsSets can be de-duplicatedand merged from multiple sets (e.g. 10 patent extractions in one box)Can combine with selected downloaded database records