MRIA9

MRIA9 is a preclinical **small-molecule kinase inhibitor** developed as a chemical probe targeting the salt-inducible kinase family, with particular relevance to **SIK2** biology in ovarian cancer. Published medicinal chemistry and cell biology studies describe MRIA9 as a **dual SIK/PAK inhibitor** derived from a pyrido[2,3-d]pyrimidin-7-one scaffold and optimized from the PAK inhibitor G-5555. In ovarian cancer models, MRIA9 inhibits SIK2-dependent mitotic functions, blocks centrosome disjunction, disrupts spindle positioning, increases chromosomal instability, and enhances sensitivity to **paclitaxel**, supporting investigation of SIK2 inhibition as a strategy to overcome taxane resistance. The available public evidence is limited to peer-reviewed preclinical research rather than clinical development, and later work suggests MR22 was designed to retain pan-SIK activity while removing PAK activity seen with MRIA9.