This is what I have understood,

In order for patients to be enrolled in these clinical studies, they have to first satisfy certain criteria. The preceding steps referred to are those previously mentioned in the Guideline; i.e. 4.1 In vitro studies, 4.2 Determination of the need for in vivo studies and 4.3 In vivo studies.

The more productive (or positive) the results are (commensurate with the level of evidence), the easier it is to compare those results (support comparability) from the two different studies 1. Non-clinical studies 2. Clinical studies

Therefore, only those patients who meet this requirement are normally selected (enrolled) .

This is what I have understood,

In order for patients to be enrolled in these clinical studies, they have to first satisfy certain criteria. The previous step(s) referred to are those previously mentioned in the Guideline; i.e. 4.1 In vitro studies, 4.2 Determination of the need for in vivo studies and 4.3 In vivo studies.

The (s) in step(s) suggests that one or more steps may be taken into account.

The more productive (or positive) the results are (commensurate with the level of evidence), the easier it is to compare those results (support comparability) from the two different studies 1. Non-clinical studies 2. Clinical studies

Therefore, only those patients who meet this requirement are normally selected (enrolled) .