{"entity":{"id":"rk-33","kind":"drug","name":"RK-33","aka":[],"tldr":"RK-33 is an experimental drug from NATSAR Pharmaceuticals that blocks the DDX3 protein in cancer cells. It has been studied in the laboratory and a first trial in people is planned.","summary":"RK-33 is NATSAR Pharmaceuticals' DDX3 inhibitor. The company reports activity across 70 human cancer cell lines, with independent NCI testing, and in animal models alone and with radiation, and plans a phase 1A study of safety and maximum tolerated dose with an intravenous formulation. A National Cancer Institute SBIR award funds its development for breast cancer. No registered trial was found.","status":"preclinical","asOf":"2026-11-04","links":[{"label":"NATSAR Pharmaceuticals","url":"https://www.natsarpharmaceuticals.com/"},{"label":"NIH RePORTER: award 5R44CA295155-02","url":"https://reporter.nih.gov/project-details/11419762"}],"tags":["pipeline"],"related":[],"cancers":[],"sections":[],"technologies":[],"targets":["ddx3x"],"drugs":[],"companies":["natsar-pharmaceuticals"],"institutions":[],"pathways":[],"terms":[],"trials":[],"people":[],"bottlenecks":[],"keyPapers":[],"journals":[],"dependsOn":[],"notes":[],"provenance":{"editedBy":"OnCo startup monitors","editedOn":"2026-11-04"},"code":"RK-33","modality":"Small-molecule inhibitor","mechanism":"Binds the RNA helicase DDX3 and impedes its function, which NATSAR Pharmaceuticals reports activates cell death, inhibits Wnt signalling and blocks non-homologous end-joining DNA repair, making cells more sensitive to radiation.","approvals":[],"mechanismSteps":[],"toxicity":[],"access":[],"regulatoryEvents":[]},"route":"/drugs/rk-33/","neighbours":{"target":[{"id":"ddx3x","kind":"target","name":"DDX3X","route":"/targets/ddx3x/"}],"company":[{"id":"natsar-pharmaceuticals","kind":"company","name":"NATSAR Pharmaceuticals","route":"/companies/natsar-pharmaceuticals/"}]}}