FGF19 and neoplasm: In silico binding analyses, supported by SPR and ELISA assays, identified pGSN as a key binding partner of DCLK1 isoform 4, with a strong affinity (KD ~ 100 nM) indicative of a critical role in pro-tumorigenic signaling.20,21 Notably, D-peptide 1 enhances pGSN binding, implying allosteric modulation that may alter downstream signaling related to tumor growth and stemness, while its weak interaction with FGF19 underscores the selective nature of these PPIs.