What modifier describes a situation where obtaining approval / access from one organisation will lead to others following suit?

One example I can think of is trend-setting; however, it's not quite that although I can't put my finger on why.

For further context, a company tries to get approval for a drug to be paid for by insurance companies. If one particular insurance company says that it will pay for it, the likelihood is that other insurance companies will do the same.

Solution 1:

The event is called a precedent:

An earlier event or action that is regarded as an example or guide to be considered in subsequent similar circumstances.

‘I want the kind of precedent I have seen in Europe followed here.’
‘So the planners want to look at what precedent they are setting.’

— Lexico

So you could use precedent-setting, although I would probably favour recasting the sentence entirely.