Empagliflozin and pioglitazone do not appear to have adverse DDI (drug drug interactions), at least short term. Why is this important - because this was in healthy people.
Pharmacokinetics of Empagliflozin and Pioglitazone After Coadministration in Healthy Volunteers
Regarding bladder cancer and lack of treatment options - progress is being made:
New treatment eliminates bladder cancer in 82% of patients