CA9 and heart failure: Interestingly, in addition to its use for heart failure, angioedema and glaucoma, acetazolamide, a pharmacological inhibitor of CAIX activity, is currently being evaluated in clinical trials as an adjuvant treatment together with temozolomide in patients with malignant astrocytoma (NIH Clinical Trial.gov https://clinicaltrials.gov/ct2/show/NCT03011671, accessed on 20 January 2019) and in combination with platinum and etoposide in patients with localized small cell lung cancer (https://clinicaltrials.gov/ct2/show/NCT03467360, accessed on 20 December 2020).