In this field, our research group has reported many studies concerning the development of efficient oxindole-based anticancer hybrids (hybrids I–III [32,33,34], Figure 1) that exhibited different enzymatic and cellular targets such as apoptosis induction in different human cancer cell lines [35,36], inhibition of cancer-related carbonic anhydrase IX isoform [37,38], in addition to inhibition of tyrosine kinases [39,40]. This evidence concerns the gene CA9 and cancer.