caerin 1.1

Caerin 1.1 is a natural **host-defense peptide** belonging to the caerin 1 family, originally isolated from the skin secretions of Australian tree frogs, specifically from the Litoria genus, such as Litoria splendida and Litoria gracilenta. It is a cationic antimicrobial peptide of 23 amino acids, demonstrating broad-spectrum antibacterial activity, including activity against Gram-positive and Gram-negative bacteria such as Staphylococcus aureus (MRSA), Acinetobacter baumannii, and Pseudomonas aeruginosa[1][5][11]. Caerin 1.1 also exhibits antiviral activity, inhibiting HIV infection in T cells, and may inhibit the growth of certain fungi and other pathogens[5]. Mechanistically, caerin 1.1 acts by disrupting microbial membranes and activating cellular pathways, leading to the inhibition of biofilm formation and direct cell death[1][5]. In oncology, caerin 1.1 directly induces cancer cell death via apoptosis and pyroptosis, mediated through the activation of caspase 3/GSDME signaling and suppression of survival and proliferation pathways like PI3K/Akt[3][4][7]. It also modulates the tumor microenvironment, enhancing anti-tumor immune responses by improving T cell and NK cell activation, shifting macrophage balance, and activating STAT1/IFN-α pathways[7][10]. Preclinical evidence suggests caerin 1.1 and its radiolabeled forms (^131I-Caerin 1.1) can inhibit tumor growth in multiple cancer models, including non-small cell lung cancer and cervical cancer[3][7]. The peptide is being explored as a potential therapy for antibiotic-resistant bacterial infections, viral infections, and cancer due to its broad antimicrobial and immunomodulatory activities[1][5][7].