peter Mac, page-33

MEsoblast and others have these for their products. It's essentially step 1 towards trying to get accelerated approval when strong results are in or pending but it's by no means in the bag.

https://www.fda.gov/patients/fast-track-breakthrough-therapy-accelerated-approval-priority-review/priority-review

It just means if they submit an application the FDA will look at it twice as fast as a normal application (within 6 months instead of 10 I think.

MSB has had one for its products for over a year and still no approval yet but it's a positive sign.
Given PTX are not close to approval with a P3 trial outcome it seems unlikely soon however, as @MrGold points out, they could get a pharma partnership or major re-rating based on the market figuring it is a likely outcome, or worth backing in case it does you know..... end up as a cure for certain types of cancer!