Not all Projects Start at the First Stage
There can be many situations where a particular company finds it can start a project at some stage other than the first stage.
In-Licensing. If a company or non-profit laboratory has developed a particular target (and any related small molecules or biologicals) through one or more stages and publishes the information that led to project progression or offers its work for sale, another company may be enticed to initiate in-house work at that point in the pipeline (see Section In-House vs In-License).
Paralogue Synergy. Targets often bear genetic similarities to other biological targets, such targets are called paralogues. Thus work on Target A1 could allow a company to readily initiate work on Target A2, which is its genetic sibling, starting at or near the same stage as Target A1, depending on how readily transferable the work is from Target A1 to Target A2. It is often the case that the project team working on Target A1 will develop selectivity assays to ensure that they develop agents that act on Target A1 and not Target A2. In the process they may discover agents that are more efficacious against Target A2 than A1. Such agents would be shelved by the project team, but should be made available to a project team that forms around Target A2 should a relevant potential disease indication be envisioned. This synergy within a company is particularly useful. The inter-company synergy is what in-licensing tends to promote.