Thiocoraline is a depsipeptide and DNAbis-intercalator originally isolated fromMicromonosporawith antibacterial and anticancer activities.1,2It is active against the Gram-positive bacteriaS. aureus,B. subtilis, andM. luteus(MICs = 0.05, 0.05, and 0.03 μg ml, respectively) but not Gram-negativeE. coli,K. pneumoniae, orP. aeruginosa(MICs = >100 μg ml for all).1Thiocoraline inhibits RNA and DNApolymerase and thymidylate synthase (IC50s = 6, 6, and 15 μg ml, respectively), as well as RNA and DNA synthesisin vitro(IC50s = 0.008 and 0.4 μg ml, respectively). It is cytotoxic to P388, A549, HT-29, and MEL-28 cancer cells (IC50s = 0.002, 0.002, 0.01, and 0.002 μg ml, respectively). 1.Romero, F., Espilego, F., Pérez Baz, J., et al.Thiocoraline, a new depsipeptide with antitumor activity produced by a marine Micromonospora. I. Taxonomy, fermentation, isolation, and biological activitiesJ. Antibiot. (Tokyo)50(9)734-737(1997) 2.Negri, A., Marco, E., García-Hernández, V., et al.Antitumor activity, X-ray crystal structure, and DNA binding properties of thiocoraline A, a natural bisintercalating thiodepsipeptideJ. Med. Chem.50(14)3322-3333(2007)
Pidnarulex HCl is the salt form of CX-5461, a first-in-class non-genotoxic small molecule targeted inhibitor of RNA polymerase I (Pol I) that activates the p53 pathway without causing DNA damage. CX-5461 selectively inhibits rRNA synthesis by Pol I in the nucleolus, but does not inhibit mRNA synthesis by RNA Polymerase II (Pol II) and does not inhibit DNA replication or protein synthesis. Inhibition of Pol I results in nucleolar stress and release of ribosomal proteins (RP) from the nucleolus. The RP bind to Mdm2 and liberate p53 to orchestrate apoptosis in cancer cells. CX-5461 demonstrates a favorable preclinical profile, potently and selectively kills cancer cells, demonstrates robust in vivo efficacy in multiple models, and has demonstrated oral bioavailability in multiple species.