Discovery of 2-(methylamino)-5,6,7,8-tetrahydropyrido[4,3-d] pyrimidine derivatives as novel HsClpP activators for multiple myeloma therapy.

Chemical activation of Homo sapiens caseinolytic protease P (HsClpP) has been recognized as a promising anticancer strategy for diverse malignancies, yet its applicability to multiple myeloma (MM) remains largely uncharted. Here, we found that D215, a HsClpP activator, exerted anti-MM activity in vitro. Using D215 as the lead compound, we obtained a series of 2-(methylamino)-5,6,7,8-tetrahydropyrido[4,3-d]pyrimidine derivatives via N-methylated modification and structural optimization, among which GU18 was ultimately selected for its remarkable activity and safety. Compared with D215, GU18 had increased HsClpP agonistic activity (EC50 = 0.54 ± 0.12 μM), enhanced anti-MM efficacy in vitro (IC50 = 0.08 ± 0.01 μM) and improved selectivity (selectivity index = 26.13-342.37) across normal cells. Mechanistic studies demonstrated that GU18 induced both structural and functional impairment of mitochondria, leading to the activation of apoptosis in MM cells. Furthermore, GU18 exhibited robust anti-MM activity in vivo, effectively suppressing tumor growth while showing a favorable safety profile. Pharmacokinetic analysis further confirmed its optimal stability and bio-availability in vivo. Collectively, our findings identify GU18 as a promising novel candidate for MM treatment by targeting HsClpP.