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Data driven life sciences The Pyramids meet the Tower of Babel
Rajarshi Guha NIH Chemical Genomics Center
2010 ACS Na;onal Mee;ng, Boston, MA
Characteris9cs
• Large sizes (but this is rela;ve) – Chemistry datasets are not really that big
• Mul;‐dimensional
• Mul;ple sources (and hence, types)
• Challenges – Handling and processing large datasets – Integra;ng mul;ple data types / sources
– Get a coherent story out of it all
How Useful is More Data?
• Alterna;vely, can we stop doing science and just do paMern recogni;on on increasingly large datasets?
• According to Chris Anderson, yes. There is now a better way. Petabytes allow us to say: "Correlation is enough." We can stop looking for models. We can analyze the data without hypotheses about what it might show. We can throw the numbers into the biggest computing clusters the world has ever seen and let statistical algorithms find patterns where science cannot.
hMp://www.wired.com/science/discoveries/magazine/16‐07/pb_theory
How Useful is More Data?
• The u;lity of more data is obvious in many scenarios – Sta;s;cal models on 10 observa;ons is not a good idea
• But can there be such a thing as too much data? – Sta;s;cal models on 106 observa;ons may not be a good idea
Big Data for Some Problems
• Halevy et al discuss the effec;veness of extremely large datasets
• Their applica;on focuses on machine transla;on – see the Google n‐gram corpus
• They suggest that such extremely large datasets are useful because they effec;vely encompass all n‐grams (phrases) commonly used
• Domain is rela;vely constrained
Halevy et al, IEEE Intelligent Systems, 2009, 24, 8‐12
Google Scale in Chemistry?
• What would be the equivalent of an n‐gram corpus in chemistry? – Fragments – A more direct analogy can be made by using LINGO’s
• It is possible to generate arbitrarily large (virtual) compound and fragment collec;ons
• But would such a collec;on span all of “commonly used” chemistry? – Depending on the ini;al compound set, yes – But we’re also interested in going beyond such a “commonly used” set
Fink T, Reymond JL, J Chem Inf Model, 2007, 47, 342
Fragment Diversity
• Consider a set of bioac;ves such as the LOPAC collec;on, 1280 compounds
• Using exhaus;ve fragmenta;on we get 2,460 unique fragments
• On the MLSMR (~ 400K compounds), we get 164,583 fragments
log Fragment Frequency
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Fragment Diversity
• Distribu;on of MLSMR fragments in BCUT space
PC 1
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All fragments Fragments occurring in 5 to 50 molecules
What Do We Do with Fragments?
• Assuming we obtain fragments from a large enough collec;on what do we do? – Learning from fragments – QSARs, genera;ve models
– Use fragments as filters, alterna;ve to clustering
– Explore chemotypes and ac;vity
White, D and Wilson, RC, J Chem Inf Model, 2010, ASAP
Scaffold Ac9vity Diagrams
• Network oriented view of fragment (scaffold) collec;ons – Similar in idea to Scaffold Hunter etc
– Not purely hierarchical • Color by arbitrary proper;es
• Quickly assess u;lity of a scaffold
• Try it online
What Makes a Good Scaffold?
• What makes a good scaffold? – Size, complexity, … – Do the members represent an SAR or not?
– Intui;on and experience also play a role
Scaffold QSAR
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Evaluate topological and physicochemical descriptors for the R‐groups
Fit PLS or ridge regression model
Characterize the SAR landscape
Scaffold QSAR ‐ Drawbacks
• Many scaffolds have few (5 to 10) members • Invariably, more features than observa;ons • If the number of R‐groups is large, the feature matrix can be very sparse – Less of a problem for combinatorial libraries
• A linear fit may not be the best approach to correla;ng R‐groups to the ac;vi;es – Difficult to choose a model type a priori
• S;ll working on it …
Fragments for Automa9on
• What is the mo;va;on for scaffold QSAR? • Automate a high throughput screen
• Try and develop heuris;cs to automa;cally push chemotypes into secondary screening
Big Data and Chemistry
• But in the end, the fundamental problem with big data is the issue of domain applicability
• Tradi;onal models are developed on small datasets and perform well within the training domain
• But models trained on very large datasets will not necessarily perform well, even though the training domain is now much larger
Helgee et al, J Chem Inf Model, 2010, 50, 677‐689
Processing Large Datasets
• Most cheminforma;cs tasks are not algorithmically parallel
• Rather, they are applied to large numbers of inputs and hence embarrassingly parallel – Start up lots of jobs
• Hadoop is useful technology for those problems that follow the map/reduce paradigm – Not aware of cheminforma;cs methods that work in this manner
– But can also be used like a job submission system
Common HTS Analysis Tasks
How do we beMer automate such tasks?
• Iden;fica;on of Series and Singletons – Clustering of ac;ves, iden;fica;on of top scaffolds – Profiling of series across all assays – Series and singleton priori;za;on
• Compound Selec;on for Followup – Assessment of structure ac;vity rela;onships – Rapid iden;fica;on of key compounds to confirm, new compounds to test – Mining of commercially available chemical libraries
• Analysis of Ac;vity – Concentra;on response across mul;ple phenotypes, mul;ple assays – Assay interference (differen;a;ng ac;vity from ar;facts) – Assay ontology (biological rela;onships, assay plaqorms) – Compound annota;ons, known ligand‐target network, prior art assessment – Profile data (PubChem, BindingDB, ChEMBL, PDSP, etc, physical proper;es)
A Smorgasbord of Data
Data Integra9on
• It’s nice to simplify data, but we can s;ll be faced with a mul;tude of data types
• We want to explore these data in a linked fashion
• How we explore and what we explore is generally influenced by the task at hand
• At one point, make inferences over all the data
Data Integra9on
User’s Network
Network of Public Data
Content: ‐ Drugs ‐ Compounds ‐ Scaffolds ‐ Assays ‐ Genes ‐ Targets ‐ Pathways ‐ Diseases ‐ Clinical Trials ‐ Documents
Links: ‐Manually curated ‐Derived from algorithms
Record View of an Assay
Access Disease Hierarchy & Network
Ar9cles, Patents, Drug Labels, …
Going Beyond Explora9on?
• Simply being able to explore data in an integrated manner is useful as an idea generator
• Can we integrate heterogenous data types & sources to get a systems level view? – Current research problem in genomics and systems biology
– Some aMempts have been made to merge chemical data with other data types
Young, D.W. et al, Nat. Chem. Biol., 2008, 4, 59‐68
RNAi & Compound Screens
Goal: Develop systems level view of small molecule acDvity
• Reuse pre‐exis;ng MLI data • Develop new annotated libraries
TACGGGAACTACCATAATTTA
CAGCATGAGTACTACAGGCCA
• Run parallel RNAi screen
What targets mediate ac;vity of siRNA and compound
Pathway elucida;on, iden;fica;on of interac;ons
Target ID and valida;on
Link RNAi generated pathway peturba;ons to small molecule ac;vi;es. Could provide insight into polypharmacology
Small Molecule HTS Summary
• 2,899 FDA‐approved compounds screened
• 55 compounds retested ac;ve • Which components of the NF‐κB pathway do they hit? – 17 molecules have target/pathway informa;on in GeneGO
– Literature searches list a few more
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Most Potent AcDves Proscillaridin A
Trabec;din
Digoxin
Miller, S.C. et al, Biochem. Pharmacol., 2010, ASAP
RNAi HTS Summary
• Qiagen HDG library – 6886 genes, 4 siRNA’s per gene
• A total of 567 genes were knocked down by 1 or more siRNA’s – We consider >= 2 as a “reliable” hit
– 16 reliable hits – Added in 66 genes for follow up via triage procedure
RNAi & Small Molecule
• Based on reporter assays, the only conclusions one can draw are the obvious ones
• Limited by 1‐D signal
• Going to high content gives us much richer data, but more complexity – Shown to be useful for compounds
– Much more difficult when the phenotypic parameters come from different systems
Summary
• Mul;ple data types are probably the most challenging aspect of data driven discovery
• Size issues can be addressed with more hardware or wai;ng (a bit) longer
• Integra;on issues require new approaches both at the presenta;on & algorithmic levels
Acknowledgements
• Ruili Huang • Ajit Jadhav • Trung Ngyuen • Noel Southall
Job Openings at NCGC/NCTT
• Sowware development (focusing on Tripod) – Java, Swing UI, algorithms
• Research Informa;cs Scien;st – Generalist, cheminforma;cs, comp chem, med chem
• Collaborate with chemists, biologists • Cuxng edge problems • Lots of fresh data • Fun!