This is a global, first-in-human (FIH), Phase 1/2, open-label, multicenter, dose-escalation, and dose-optimization study to evaluate the safety, tolerability, and antitumor activity of PARP1 selective inhibitor, EIK1004, as monotherapy in participants with advanced solid tumors.

The study will be conducted in 2 parts:

Part 1 (monotherapy dose escalation): The MTD (or MAD) will be investigated, and safety, tolerability, PK, PD, and preliminary antitumor activity of EIK1004 monotherapy will be assessed in participants. 

Part 2 (dose optimization): Further evaluation of the safety, tolerability, PK, PD, and preliminary antitumor activity of selected dose levels of EIK1004 in participants with advanced HER2‑negative breast cancer who have not received prior PARPi therapy with deleterious or suspected deleterious mutations of one of the genes: BRCA1, BRCA2, PALB2, RAD51B, RAD51C, or RAD51D