Synthetically obtained derivatives of the pyrazolo[4,3-e][1,2,4]triazine ring system have been extensively studied for their antitumor activity [13,14,15] and as inhibitors of tyrosine kinases [16], tyrosinase [17,18], urease [18], phosphodiesterase 5 (PDE5) [17], carbonic anhydrase (CA), and especially its two isoenzymes associated with cancer i.e., CAIX and CAXII [13,19,20]. The gene discussed is CA9; the disease is cancer.