This source text is weirdly phrased, because it says "rights of a medicine." In licensing, rights are "in" something (rights in a medicine, rights in a patent) or sometimes "to" something (rights to the novel). That's obviously what this means; it's just phrased wrong (I'm guessing it wasn't written by a lawyer).

I've seen two common ways to talk about rights in/to something, in FR: (1) les droits attachés à la/au... or (2) les droits rattachés à la/au...
I leave it to the FR native speakers to explain whether it makes a difference which verb you choose.

Also, in the spirit of credit where credit is due, Bertrand Leduc posted a link explaining in-licensing and out-licensing on the other Kudoz page (the out-licensing question): https://www.quora.com/What-is-in-licensing-and-out-licensing...

In sum, to out-license is to grant someone else a license to make pharmaceutical drugs covered by your patent. To in-license is to obtain a license to make drugs covered by someone else's patent.

So normally you would translate in-licensing by obtenir une licence. However, here the source text says "in-license exclusive rights of [should be in/to] a medicine," so you don't use the normal translation.