The primary objective of this study is to evaluate the safety and tolerability of JAB-2485 monotherapy to determine the maximum tolerated dose (MTD) and recommended Phase 2 dose (RP2D) during Dose Escalation phase when administered in participants with advanced solid tumors; then to further evaluate preliminary antitumor activity of JAB-2485 monotherapy at the RP2D during Dose Expansion phase in patients with advanced solid tumors such as ER+ breast cancer, triple negative breast cancer (TNBC), AT-rich interaction domain 1A (ARID1A) mutant solid tumors and small cell lung cancer (SCLC).
