Microsampling study designs

Here we include examples of study designs that may be used for microsampling from either main study animals or from satellite groups of animals.  These examples are intended to be a starting point for study design and it may be necessary to amend them to take into account the number of timepoints required for a toxicokinetic profile for a specific compound and the inclusion of additional endpoints (e.g. anti-drug antibody and pharmacodynamic analysis).

[Group sizes will be annotated as XM + XF with X being the number of animals, M representing males and F representing females]

Rat study (four to 13 weeks duration) - example designs

Example study design (1)

Microsampling can reduce the number of satellite animals required to 3M + 3F (rather than 9M + 9F with conventional sampling).  This gives a total reduction of 48 animals.

Using 3M + 3F satellite animals per group is sufficient to give up to six timepoints on day one of the study and again at week four or 13.

Table 1
Dose group Low Medium High Control
No. of animals 10M + 10F 10M + 10F 10M + 10F 10M + 10F
No. of recovery animals     5M + 5F 5M + 5F
No. of toxicokinetic satellites 3M + 3F 3M + 3F 3M + 3F 3M + 3F
Maximum total for one study       124

Example study design (2)

Microsampling can be used to sample from main study animals and avoid the use of satellite animals.  Composite toxicokinetic profiles (made up from samples from sub groups of animals) are obtained from main study animals.  This leads to a total reduction of 72 animals from a standard study design.

Table 2
Dose group Low Medium High  Control
No. of animals 10M + 10F 10M + 10F 10M + 10F 10M + 10F
No. of recovery animals      5M + 5F 5M + 5F
Maximum total for one study       100

An example of how to split the sampling at the different time points is presented below.  This is a balanced study design with ten animals/sex/group, a composite toxicokinetic profile with six time points and three samples per animal.  

Table 3
Sampling timepoint       
Main study rat number 5 6
1 X     X X  
2 X     X   X
3   X   X X  
4   X X     X
5 X   X     X
6 X   X   X  
7 X   X     X
8   X   X X  
9   X X   X  
10   X   X   X

Rat study (six month duration) - example designs

Example study design (1)

Microsampling can reduce the number of satellite animals required to 3M + 3F (rather than 9M + 9F with conventional sampling).  This gives a total reduction of 48 animals.

Using 3M + 3F satellite animals per group is sufficient to give up to six timepoints on day one and again at weeks 13 and/or 26.   

Table 4
Dose group Low Medium High Control
No. of animals 12M + 12F 12M + 12F 12M + 12F 12M + 12F
No. of toxicokinetics 3M + 3F 3M + 3F 3M + 3F 3M + 3F
No. of recovery animals     5M + 5F 5M + 5F
Maximum total for one study       140

Example study design (2)

Microsampling can be used to sample from main study animals and avoid the use of satellite animals.  Composite toxicokinetic profiles (made up from samples from sub groups of animals) are obtained from main study animals.  This leads to a total reduction of 72 animals compared to a standard study design.

Using 15M + 15F main study animals, with composite sampling and each animal being sampled up to three times, a toxicokinetic profile with up to nine timepoints on day one and again at Week 13 and/or 26 can be obtained.  

Table 5
Dose group Low Medium High Control
No. of animals 15M + 15F 15M + 15F 15M + 15F 15M + 15F
No. of recovery animals     5M + 5F 5M + 5F
Maximum total for one study       140

Example study design (3) incorporating male fertility

As Table 5 with an additional five males added to each group for male fertility assessment and 20 undosed females for mating.  This leads to a total reduction of 60-80 animals from a standard study where male fertility was carried out separately. 

Table 6
Dose group Low Medium High Control
No. of animals 15M + 15F 15M + 15F 15M + 15F 15M + 15F
Extra males for mating 5M 5M 5M 5M
Undosed females 20F 20F 20F 20F
Maximum total for one study       220*

Mouse study designs (one and six month)

The following study designs are real examples from two companies demonstrating flexibility in approach while still reducing and refining animal use.

Example study design (1)

Microsampling can reduce the number of satellite animals required to 6M + 6F (rather than 18M + 18F with conventional sampling) giving a total reduction of 102 animals. 

Using 6M + 6F satellite animals per group and composite sampling is sufficient to give up to six timepoints on day one and again at the end of the study.   

Table 7
Dose group Low Medium High Control
No. of animals 12M + 12F 12M + 12F 12M + 12F 12M + 12F
No. of toxicokinetic satellites 6M + 6F 6M + 6F 6M + 6F 3M + 3F
Maximum total for one study       138

Example study design (2)

Microsampling can reduce the number of satellite animals required to 9M + 9F (rather than 18M + 18F with conventional sampling). This is a total reduction of 84 animals. 

Using 9M + 9F satellite animals per group and composite sampling (see table 9), is sufficient to give six timepoints on day one and again at the end of the study.

Table 8
Dose group Low Medium High Control
No. animals  10M + 10F 10M + 10F 10M + 10F 10M + 10F
No. of toxicokinetics satellites 9M + 9F 9M + 9F 9M + 9F 3M + 3F
Maximum total for one study       140

An example of how to split the sampling at the different time points is presented below.  This is a balanced study design with nine animals/sex/group, composite toxicokinetic profile with six time points and two samples per animal.  

Table 9
Hours after dosing           
Satellite mouse number  1   3   6   9   12 24
1 X     X    
2 X     X    
3 X     X    
4   X     X  
5   X     X  
6   X     X  
7     X     X
8     X     X
9     X     X