Animal research is defended on the ground that it has produced treatments, which is true and incomplete.
It is opposed on the ground that it causes suffering, which is also true and also incomplete.
The interesting question is how much of it predicts what happens in a human body.
Reviews that traced from animal studies into human trials found a low rate of successful .
Many failures are attributed to species difference and a substantial share to study design.
Animal experiments have been slower than clinical trials to adopt and assessment.
Studies that used them reported smaller effects than studies that did not, in the same field and the same year.
That comparison indicates that a portion of the published animal literature its results.
The ethical argument changes once the scientific one is admitted.
Suffering imposed for a result that does not translate is not a difficult trade-off but a waste.
Improving therefore reduces both the number of animals used and the harm done per finding.
The regulatory framework in several countries already requires replacement, reduction and .
Enforcement concentrates on , which is the least demanding of the three.
Replacement requires a alternative, and validating one is expensive research that nobody's grant funds.
Organ-on-a-chip systems and human cell models have advanced considerably and replace a narrow set of tests.
They cannot yet reproduce a whole organism responding over months.
Claiming otherwise damages the case for funding them, since a regulator who tests the claim will find it false.
The credible position is that replacement is partial today and will remain partial for a long time.