Although the underlying mechanisms are potentially intriguing and require further investigation, copanlisib (PI3K-α/δ) demonstrated the most potent anti-tumor efficacy on MCC-3, MCC-9, and MCC-21 cell lines, in which PI3K-δ and -α are the two most abundantly expressed PI3K isoforms. The gene discussed is PIK3CB; the disease is neoplasm.