DAREON™-5: A Study to Test Whether Different Doses of BI 764532 Help People With Small Cell Lung Cancer or Other Neuroendocrine Cancers

Inclusion criteria:

1. Male or female participants ≥18 years old and at least at the legal age of consentin countries where it is greater than 18 years at the time of signature of theinformed consent form (ICF).

2. Signed and dated written informed consent in accordance with International Councilfor Harmonisation-Good Clinical Practice (ICH-GCP) and local legislation prior toadmission to the trial.

3. Part 1: Histologically or cytologically confirmed, cancer of the followinghistologies:

• Small cell lung cancer (SCLC)

• Extra-pulmonary neuroendocrine carcinoma (epNEC) (except Merkel cell carcinoma (MCC), Medullary thyroid cancer (MTC) and Neuroendocrine prostate cancer (NEPC))

• Large cell neuroendocrine carcinoma (LCNEC) of the lung Patients with tumourswith mixed histologies for any above type are eligible only if theneuroendocrine carcinoma/small tumour cells component is predominant andrepresents at least 50% of the overall tumour tissue. Patients must have progressed or recurred after standard of care therapy

• SCLC: after at least two prior lines of therapy, including at least oneplatinum-based regimen; in countries where standard of care in first linetherapy includes PD-L1 inhibitor treatment patients should have received thecombination of platinum-based regimen plus PD-L1 inhibitor unless they havebeen unable to receive checkpoint inhibitor treatment.

• Therapy includes PD-L1 inhibitor treatment; patients should have received thecombination of platinum-based regimen plus PD-L1 inhibitor unless they havebeen unable to receive checkpoint inhibitor treatment.

• epNEC/LCNEC: after at least one platinum-based regimen. Part 2 and part 3:Histologically or cytologically confirmed epNEC (except MCC, MTC and NEPC) withcentrally assessed DLL3 high expression status. Patients must have progressedor recurred after at least one platinum-based regimen.

4. Eastern Cooperative Oncology Group (ECOG) score of 0 or 1.,

5. Measurable lesions as defined per Response Evaluation Criteria In Solid Tumours (RECIST) v 1.1 within 21 days prior to the first dose of BI 764532.

6. Part 1: Availability of archival tumour tissue sample Part 2 and part 3:Availability of archival formalin-fixed paraffin-embedded (FFPE) tumour tissuesample. Following specimens are not allowed: Fine Needle Aspiration (FNA), Cytologysamples, decalcified bone samples.

7. Adequate organ function as defined in the protocol.

8. All toxicities related to previous anti-cancer therapies have resolved = CommonTerminology Criteria for Adverse Events (CTCAE) Grade 1 prior to trial treatmentadministration (except for alopecia, peripheral neuropathy, fatigue andendocrinopathies controlled by replacement therapy which must be = CTCAE Grade 2 andamenorrhea/menstrual disorders which can be any grade).

9. Women of childbearing potential (WOCBP) and men able to father a child must be readyand able to use acceptable methods of birth control per ICH M3 (R2) that result in alow failure rate of less than 1% per year when used consistently and correctly. Alist of contraception methods meeting these criteria and instructions on theduration of their use is provided in the participant information

10. Only for Part 3, at the timepoint of Screening 02:

• For Cycle 1, patients should be willing to stay within 1 hour driving distancefor 48 hours after IMP administration and confirm availability of a caregiverfor the same timeframe.

• Patients should be considered suitable by the investigator to followinstructions applicable to the reduced monitoring cohort, such as taking theirtemperature and administration of oral medication at home if needed.

Exclusion criteria:

1. Untreated or symptomatic brain metastases. (Part 2 and part 3: identified during themandatory assessment by brain MRI within 21 days before first trial drugadministration.) Participants with treated, stable brain metastases are eligibleprovided they meet the following criteria:

• Radiotherapy or surgery for brain metastases was completed at least 2 weeksprior to the first administration of BI 764532.

• Patient is off steroids for at least 7 days (physiologic doses of steroids arepermitted), and the patient is off anti-epileptic drugs for at least 7 days oron stable doses of anti-epileptic drugs for malignant central nervous system (CNS) disease.

2. Presence of leptomeningeal disease or, part 2 and part 3: epidural disease includingspinal cord compression.

3. Part 1: Active/previous history of interstitial lung disease or non-infectiouspneumonitis (any grade). Part 2 and part 3: Active/previous history of interstitial lung disease, pulmonaryfibrosis, organizing pneumonia or non-infectious pneumonitis (any grade). Patientswith a history of therapy-related pneumonitis that is considered clinically resolvedare eligible.

4. Participants who experienced severe, life-threatening immune-mediated adverse eventsor infusion-related reactions including those that lead to permanent discontinuationwhile on treatment with immuno-oncology agents.

5. Prior anti-cancer therapy:

• Patients who have been treated with any other anti-cancer drug within 4 weeksor within 5 half-life periods (whichever is shorter) prior to firstadministration of BI 764532.

• Patients who have been treated with extensive field radiotherapy includingwhole brain irradiation within 2 weeks prior to first administration of BI

764533. Previous treatment with Delta-like ligand 3 (DLL3)-targeting T cell engagers or celltherapies.

764534. Diagnosis of immunodeficiency or systemic steroid therapy or any other form ofimmunosuppressive therapy within 7 days prior to the first dose of BI 764532.Physiological replacement of steroids is allowed.

764535. Unresolved toxicity from prior anti-tumour therapy, defined in the inclusioncriteria.

Further exclusion criteria apply.