A Study to Test How Different Doses of BI 1703880 in Combination With Ezabenlimab Are Tolerated in People With Different Types of Advanced Cancer (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