A Trial to Find the Safe Dose for BI 905681 in Patients With Incurable Tumours or Tumours That Have Spread

Inclusion criteria: * Histologically or cytologically confirmed diagnosis of an advanced, unresectable and/or metastatic non-haematologic malignancy. Patient must have measurable or evaluable lesions (according to Response Evaluation Criteria in Solid Tumours (RECIST) v 1.1). * Patient who has failed conventional treatment or for whom no therapy of proven efficacy exists or who is not eligible for established treatment options. * Patients willing to undergo mandatory tumour biopsy at the time points specified in the protocol. * Eastern Cooperative Oncology Group (ECOG) Score of 0 or 1 (R01-0787). * Adequate organ function defined as all of the following: * Absolute neutrophil count (ANC) ≥1.5 x 10\^9/L; haemoglobin ≥9.0 g/dL; platelets ≥100 x 10\^9/L without the use of haematopoietic growth factors within 4 weeks of start of study medication. * Total bilirubin ≤1.5 x the upper limit of normal (ULN), except for patients with Gilbert's syndrome: total bilirubin ≤3 x ULN or direct bilirubin ≤1.5 x ULN. * Creatinine ≤1.5 x ULN. If creatinine is \>1.5 x ULN, patient is eligible if concurrent creatinine clearance ≥50 ml/min (measured or calculated by the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) formula or Japanese version of CKD-EPI formula for Japanese patients). * Aspartate transaminase (AST) and alanine transaminase (ALT) ≤3 x ULN if no demonstrable liver metastases, or otherwise ≤5 x ULN * Alkaline Phosphatase (ALP) \<5 x ULN * At least 18 years of age at the time of consent or over the legal age of consent in countries where that is greater than 18 years. * Signed and dated written informed consent in accordance with International Conference on Harmonisation (ICH) - Good Clinical Practice (GCP) and local legislation prior to admission to the trial * Life expectancy ≥3 months at the start of treatment in the opinion of the investigator * Further inclusion criteria apply Exclusion criteria: * Osteoporosis ≥ CTCAE Grade 2 * Osteoporotic compression fracture within 12 months prior to informed consent which is clinically significant in the opinion of the investigator. * Further exclusion criteria apply