reduce & repeat

Reduce & Repeat

Non-Clinical Statistics Conference 2014, BruggeOctober 2014

More Precise XC50s Using Fewer Wells (in vitro) and Fewer Animals (in vivo)

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Innovative Medicines | Discovery Sciences

Raw Conc-Response Data

2 Jonathan Bright | September 2014


Only Half of the Concs



Only Half of the Replicates



Only Half of the Concs and Half of the Replicates



Only Half of the Concs and Half of the Replicates and Half of the Controls



IC50 and 95% Confidence Interval



Findings #1

• For a “well-behaved” assay, the resource (wells) may be dramatically reduced with little impact on either the estimate of the XC50 or its confidence interval

• “Well-behaved”- Max and min controls that safely position the curve top and

bottom- Conc-response data that have the right sort of sigmoid

shape- Acceptable to overlook details such as biphasic and partial

inhibition• May be exploited

- Throughput- Cost- Compound use



Second Set of Raw Conc-Response Data



Findings #2

• Run-to-run differences in XC50 are massive compared to the small changes in XC50 that occur as a result of reducing the resource (wells) on any given run

• Put in terms of components of variation- Between run variation dominates within-run variation- Within-run variation changes hardly at all as the number of

concs and number of replicates changes• May be exploited

- Reduce the resource per run- Repeat- Average



IC50 vs Run



In Vivo

• A situation similar to the in vitro case has been observed, whereby study-to-study differences are the main component of variation

- Was it a “good day” or a “bad day” for compound X• 2 Start Strategy (Brian Middleton)

- Start half the planned animals (reduce)- Independently run the second half (repeat)- Average

• Gives a superior estimate of the e.g. XC50 or XD50• Provides in some cases a chance to change doses for the

second start



Summary

• In both in vitro and in vivo settings there are large run-to-run or study-to-study differences when a compound is retested

- Root cause analysis• Exploit by

- reducing the resource (wells or animals) on a given occasion- repeating the experiment- averaging across the experiments

• Reduce- Throughput, cost and compound benefits

• Reduce and Repeat- Precision benefit +



Acknowledgement and Reference

• Siller H, Taylor JD, Middleton B. Two-start design within a Sephadex inflammatory model – A means to generate reliable ED50 data whilst significantly reducing the number of animals used. Pulm Pharmacol Ther 2012; 25:223-227.



Extra Slide


Innovative Medicines | Discovery Sciences23 Jonathan Bright | September 2014

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reduce & repeat

Documents

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confidence intervals7findings

confidence intervals

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replicates4jonathan

controls6jonathan bright

replicates5jonathan

concs3jonathan bright