Phase Ia, First in Human Open Label Dose Escalation Trial Evaluating Intravenous BI 1703880 in Combination With Intravenous Ezabenlimab for Treatment of Advanced Solid Tumours

Inclusion Criteria: * Histologically or cytologically confirmed diagnosis of an advanced, unresectable and/or metastatic or relapsed/refractory solid tumour. Patient must have at least one measurable lesion (according to Response Criteria in Solid Tumours (RECIST 1.1)). * Patient must have exhausted or refused established treatment options for the malignant disease, or is not eligible for established treatment options. * Has a lesion amenable to pre-treatment and on-treatment biopsy and patient consents to both biopsies. * Medically fit and willing to undergo all mandatory trial procedures. * Eastern Cooperative Oncology Group (ECOG) performance status score of 0 or 1. * Adequate organ function or bone marrow reserve as demonstrated at screening by the following laboratory values: * Absolute neutrophil count ≥ 1.5x10\^9/L (≥ 1.5x10\^3/μL, ≥ 1500/mm3); platelet count ≥ 100x10\^9/L (≥ 100x10\^3/μL, ≥ 100x10\^3/mm3), without the use of hematopoietic growth factors within 4 weeks of start of trial medication * Haemoglobin ≥ 90 g/L (≥ 9.0 g/dL, ≥ 5.6 mmol/L) * Estimated glomerular filtration rate (eGFR) ≥60 ml/min/1.73m\^2 (as determined by the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) formula) * Aspartate transaminase (AST) and alanine transaminase (ALT) ≤ 3 x ULN if no demonstrable liver metastases, or otherwise ≤ 5 x ULN if transaminase elevation is attributable to liver metastases. * Total bilirubin ≤ 1.5 x ULN, except for patients with Gilbert's syndrome: total bilirubin ≤ 3.0 x ULN or direct bilirubin ≤ 1.5 x ULN * partial thromboplastin time (PTT) / activated partial thromboplastin time (aPTT) \<1.5 x ULN * Patients ≥18 years of age or over the legal age of consent in countries where that is greater than 18 years at the time of signature of the informed consent form (ICF). * Signed and dated written ICF in accordance with International Council for Harmonisation- Good Clinical Practice (ICH-GCP) and local legislation, obtained before performing any protocol related procedures that are not part of normal standard of practice care. Note: If a patient declines to participate in the voluntary biobanking component of the trial, he/she will not be excluded from other aspects of the trial. Further inclusion criteria apply Exclusion Criteria: * Any investigational or antitumour treatment within 4 weeks or 5 half-life periods prior to the first treatment whichever is shorter. * Prior STING agonist therapy. * Prior intolerability of a anti-programmed cell death protein 1 (PD-1) or anti-programmed cell death ligand 1 (PD-L1) therapy. * History of allergy or hypersensitivity to study agent components. * Immunosuppressive therapies including, but not limited to, systemic corticosteroids at doses exceeding \>10 mg/day of prednisone or equivalent, and tumour necrosis factor-alpha blockers. * Persistent toxicity from previous treatments (including immune related Adverse Events (irAEs)) that has not resolved to Grade ≤1, except for alopecia, xerostomia, and immunotherapy related endocrinopathies. * Evidence of active, non-treatment related autoimmune disease, except for endocrinopathies. * History or complication of pneumonitis or interstitial lung disease within the last 12 months, or any prior pneumonitis related to immunotherapy. Further exclusion criteria apply