This was an open-label, dose-finding study evaluating BI 894999 for diffuse large B-cell lymphoma (DLBCL; phase Ia extension) and solid tumors [colorectal cancer (CRC), nuclear protein in testis (NUT) carcinoma, metastatic castration-resistant prostate cancer (mCRPC) and small-cell lung cancer (SCLC); phase Ib cohort]. This evidence concerns the gene CD44 and diffuse large B-cell lymphoma.