Symplocamide A as marine-derived proteasome inhibitor: a promising scaffold for targeted cancer therapy

Symplocamide A (Sym A), a 3-amino-6-hydroxy-2-piperidone (Ahp)-containing cyclodepsipeptide derived from the marine cyanobacterium Symploca sp., has emerged as a promising candidate in anticancer research. With potent serine protease and proteasome inhibition, Sym A has demonstrated nanomolar cytotoxicity across several cancer cell lines, including lung and neuroblastoma models. This review critically assesses the anti-cancer mechanisms, pharmacokinetic properties, synthetic approaches, and translational limitations of Symplocamide A, highlighting its potential and challenges as a therapeutic agent in oncology. A systematic literature review was performed using PubMed, Scopus, Web of Science, Google Scholar, and the TRIP database, incorporating studies published until March 2025. Articles were selected based on predefined inclusion criteria focusing on Sym A's anticancer activity, mechanisms of action, bioavailability, synthesis, and toxicity profiles. Sym A exhibits selective cytotoxicity toward various cancer cell lines, notably inhibiting chymotrypsin with over 200-fold greater potency than trypsin. Structural analysis underscores the role of Ahp and brominated tyrosine residues in target affinity and stability. Pharmacokinetic modeling indicates favorable intestinal absorption and drug-likeness, although brain penetration is limited. Synthetic production remains inefficient, with low overall yield. No in vivo or clinical studies have yet been reported. Toxicological concerns are heightened by its structural similarity to cyanotoxins, necessitating cautious evaluation. Symplocamide A demonstrates high preclinical anticancer potential through protease inhibition and favorable bioavailability traits. Nonetheless, its clinical translation is hindered by synthesis challenges, the absence of in vivo validation, and undefined toxicity. Further studies are warranted to evaluate its therapeutic window, optimize synthetic accessibility, and assess safety in vivo.