Hi Hassaine - I know that we have standard content and we have an adapter to integrate it through XI/PI.
But without using PI i doubt it's possible.
However I just came across the below documentation where it mentioned that 7.5 has REST Api for external application integration but i'm not sure what functionalities does it offer.
I would suggest you to contact Maximo to get additional information or post the same query in their forum Tivoli:Tivoli:Maximo and process automation solutions (if not done.)
If you have the restful services that you need then you can directly consume them in SAP.
Reference : IBM Maximo Asset Management