PAR -v- CUV, page-44

Yes drug repurposing is an industry in itself and very much part of the mainstream. This article is of interest.....
https://www.ddw-online.com/drug-discovery/p303678-therapeutic-drug-repurposingrepositioning-and-rescue-part-iii:-market-exclusivity-using-intellectual-property-and-regulatory-pathways.html
The IP path for repurposed drugs is well trodden and there are protections available to encourage development in this area ('method of use' patents being just as strong as 'composition of matter' ones). Interesting that ~30% of all new drugs are repurposed (including viagra!).