BI 894999 First in Human Dose Finding Study in Advanced Malignancies

Inclusion criteria: For all patients * Age 18 years or older at the time of signature of the informed consent. * Life expectancy of at least 12 weeks after the start of the treatment according to the investigator's judgement * Male or female patients. Women of childbearing potential\* must be ready and able to use highly effective methods of birth control per ICH M3(R2) that result in a low failure rate of less than 1% per year when used consistently and correctly. A list of contraception methods meeting these criteria is provided in the patient information. For women of childbearing potential using a contraceptive pill, an additional barrier method is necessary due to the potential CYP3A4 inducing effect of BI894999. Male patients having a partner of childbearing potential must use condoms and ensure their partner is using a highly effective method of birth control as described above, during the trial and for at least three months after the end of the trial \* Any female who has experienced menarche and does not meet the criteria for "women not of childbearing potential" as described below. Women not of childbearing potential are defined as: women who are postmenopausal (12 months with no menses without an alternative medical cause) or who are permanently sterilized (e.g., tubal occlusion, hysterectomy, bilateral oophorectomy or bilateral salpingectomy). \- Written informed consent consistent with ICH-GCP and local legislation For patients with solid tumours * Patients with a histologically or cytologically confirmed diagnosis of an advanced unresectable and/or metastatic, malignant solid tumour, who have failed conventional treatment or for whom no therapy of proven efficacy exists, or who are not amenable to standard therapies * Age ≥ legal age to be adult for the given country at the time of signature of the informed consent. For NC patients, age 15 years or older at the time of signature of the informed consent ( in Germany and South Korea, only legally adult patients may be included * Eastern Cooperative Oncology Group (ECOG, R01-0787) performance score 0 or 1 at the time of screening. A score of 2 is allowed for NUT carcinoma patients * Recovery of therapy-related toxicities from previous chemotherapy, tyrosine kinase inhibitors, hormone therapy, immunotherapy, antibodies, vaccine therapy, or radiotherapy to CTCAE ≤ grade 1 (with the exception of alopecia, peripheral sensory neuropathy grade 2) * Life expectancy of at least 12 weeks after the start of the treatment according to the investigator's judgement * Male or female patients. Women of childbearing potential\* must be ready and able to use highly effective methods of birth control per ICH M3(R2) that result in a low failure rate of less than 1% per year when used consistently and correctly. A list of contraception methods meeting these criteria is provided in the patient information. For women of childbearing potential using a contraceptive pill, an additional barrier method is necessary due to the potential CYP3A4 inducing effect of BI894999. Male patients having a partner of childbearing potential must use condoms and ensure their partner is using a highly effective method of birth control as described above, during the trial and for at least three months after the end of the trial treatment * Written informed consent consistent with ICH-GCP and local legislation. For adolescent NC patients aged 15 years to \< legal adult age, written assent of the patient and written informed consent of the parents (both or one according to national regulation) or legal guardian of the adolescent * Written informed consent for tumour biopsies in the escalation phase Ia * Optional for those patients until extension of the MTD cohort, * Optional for the patients in the extension of MTD cohort at the same time points as described below for the expansion phase. For these patients in the extension of the MTD cohort, if they have an accessible lesion for biopsy, they will be offered optional consent for tumour biopsies * In addition, all patients included in the expansion Phase Ib must: * Have been diagnosed with one of the four types of tumours selected: * small cell lung cancer (SCLC) * metastatic castrate resistant prostate cancer (mCRPC) * colorectal cancer (CRC) * NUT carcinoma (NC) (for which the "midline" origin is not a prerequisite) * Have failed conventional treatments or who are not amenable to standard therapies (per criterion 1) that specifically include for: * SCLC: a platinum-based therapy (previous treatment with topotecan is not mandatory) * mCRPC: a hormonal agent (abiraterone, enzalutamide, or apalutamide) and a taxane (docetaxel or cabazitaxel) * CRC: fluoropyrimidine, oxaliplatin and irinotecan, bevacizumab for patients eligible to this treatment and an anti-epidermal growth factor receptor (EGFR) in RAS (Rat Sarcoma Virus) wild type metastatic CRC. * Have measurable disease (radiated lesions and lesions used for biopsy do not qualify as target lesions), according to RECIST 1.1 (R09-0262) (for NC patients only nonmeasurable disease is acceptable); or according to PCWG3 (R17-3377) for the mCRPC cohort (see point 5 of inclusion criteria below, specific to mCRPC patients) * Have progressive disease within the last 6 months, according to RECIST 1.1 (R09-0262) or according to PCWG3 (R17-3377) for the mCRPC cohort (see point 5 of inclusion criteria below, specific to mCRPC patients). NC patients do not need to show progression per RECIST 1.1 (for example, if newly diagnosed). * Have a tumour lesion accessible for biopsies (pre- and at steady state under treatment in Cycle 1, ideally from the same anatomic lesion) (except for mCRPC patients having only bone metastases or for patients with therapeutic INR because of treatment with a vitamin K antagonist or a novel oral anticoagulant. Biopsies are optional for NC patients * Give written informed consent for two tumour biopsies, one at screening and one after start of treatment, between Day 8 and Day 11 of Cycle 1 (or between day 3 and day 8 if the day of biopsy in Cycle 1 needs to be moved as explained in Section 3.1) (when applicable) * In addition, all patients in the mCRPC expansion cohort of Phase Ib must have: * Histologically or cytologically confirmed adenocarcinoma of the prostate * Radiographic evidence of metastatic prostate cancer (stage M1 or D2). Distant metastases evaluable by bone scan, CT scan, or MRI within 28 days before the start of study treatment. * PSA ≥ 5 ng/mL (if no measurable disease by RECIST 1.1) * Prior surgical or chemical castration with a serum testosterone of \<50 ng/dL (\< 1.7 nmol/L) by luteinizing hormone releasing level hormone (LHRH) agonist or antagonist, or by abiraterone or by enzalutamide or apalutamide. If the actual method of castration is LHRH agonist or antagonist, the patient must be willing to continue the use of LHRH agonist or antagonist during protocol treatment. * Progressive disease defined as at least one of the following: * Progressive measurable disease: using conventional solid tumour criteria RECIST 1.1 * Bone scan progression: at least two new lesions on bone scan plus a rising PSA as described in point c below * Increasing PSA level: at least two consecutive rising PSA values over a reference value (PSA no.1) taken at least 1 week apart. A third PSA (PSA no. 3) is required to be \> than PSA no. 2; if not, a fourth PSA (PSA no. 4) is required to be \> to PSA no. 2 In patients with DLBCL * Patients with histologically confirmed DLBCL who have failed 2 or more lines of systemic therapy including an anti-CD-20 therapy and an anthracycline or who are not amenable to standard therapies but have an indication for therapy as per investigator's judgement. Standard therapies may also include but are not limited to CAR-T cells therapy, depending on approved therapies in the country where the patient is treated * ECOG Performance Status 0, 1 or 2 at the time of screening * Measurable disease (radiated lesions do not qualify as target lesions) according to according to RECIL 2017 on the CT scan part of the FDG/PET-CT scan * Recovery of therapy-related toxicities from previous anti-lymphoma therapy to CTCAE \<= grade 1 (with the exception of alopecia, peripheral sensory neuropathy grade 2) * written informed consent for tumour biopsies (optional) * Further inclusion criteria apply Exclusion criteria: For all patients: * Inability to swallow tablets * Additional other serious illness, concomitant non-oncological disease (e.g. active infectious disease including an active infection with SARS-CoV-2 confirmed by a PCR test or had one in the prior 6 weeks or active hepatitis (Hep) B infection as defined by positive Hep B DNA test, active Hep C infection as defined by positive Hep C RNA test and human immunodeficiency virus (HIV) infection (positive result in established HIV diagnostic assay), or ongoing toxicity from prior therapies considered by the investigator to potentially compromise patient's safety in this trial * Serum creatinine greater than 1.5 mg/dL (\>132 µmol/L, SI unit equivalent) * Women who are pregnant, nursing, or who plan to become pregnant while in the trial * Treatment with other investigational drugs or participation in another clinical interventional trial within the past four weeks or within five times the half-life of the previous investigational drug, whichever is shorter, before start of therapy or concomitant with this trial * Patients unable to comply with the protocol * Patients who are actively abusing alcohol or drugs. Since no alcohol or drug testing is required per protocol, it is at the investigator's discretion to determine abuse. For patients with solid tumours: * Additional other serious illness , concomitant non-oncological disease (e.g. active infectious disease or known chronic Hepatitis B/Hepatitis C infection and HIV), or ongoing toxicity from prior therapies considered by the investigator to potentially compromise patient's safety in this trial * History or presence of cardiovascular abnormalities deemed clinically relevant by the investigator such as uncontrolled hypertension, congestive heart failure NYHA classification of 3, unstable angina or poorly controlled arrhythmia. Myocardial infarction within 6 months prior to study entry.Left Ventricular Ejection Fraction (LVEF) less than 50% at baseline * Clinical evidence of symptomatic progressive brain or leptomeningeal disease during the last 28 days before the start of treatment with BI 894999 * Absolute neutrophil count less than 1500/mm\^3 * Platelet count less than 100 000/mm\^3 * Bilirubin greater than 1.5 mg/dL (\>26 µmol/L, SI unit equivalent) (except known Gilbert's syndrome, accepted up to 2 mg/dL or up to 34.2 µmol/L in this case) * Aspartate amino transferase (AST) and/or alanine amino transferase (ALT) greater than 2.5 times the upper limit of normal (if related to liver metastases, greater than five times the upper limit of normal) * Treatment with other investigational drugs or participation in another clinical interventional trial within the past four weeks (past two weeks for NC patients) or within five times the half-life of the previous investigational drug, whichever is the shorter, before start of therapy or concomitant with this trial * Systemic anti-cancer therapy within four weeks (past two weeks for NC patients) or five times the half-life of the drug, whichever is shorter. Radiotherapy given for curative intent or other than palliative radiotherapy within the past four weeks before start of therapy or concomitantly with this trial. This These restrictions does not apply to LHRH agonists or antagonists, steroids (given at a stable dose in the last four weeks) used for palliative intent, bisphosphonates, and denosumab and to palliative radiotherapy (no wash out required) For patients with DLBCL: * Patient is eligible for curative salvage high dose therapy followed by stem cell transplant. * Primary central nervous system (CNS) lymphoma or known CNS involvement * Prior allogeneic bone marrow or stem cell transplant * High-dose therapy with stem cell support \<3 months prior to visit 1 * AST or ALT \>2.5 x upper limit of normal (CTCAE grade 2 or higher) * Total bilirubin \>1.5 x upper limit of normal (CTCAE grade 2 or higher) * Absolute neutrophil count \<1.0 x 10\^9/L(without growth factor support) * Platelets \<100 x 10\^9/L (without transfusions) * Significant concurrent medical disease or condition which according to the investigator's judgement would either compromise patient safety or interfere with the evaluation of the safety of the test drug, e.g. symptomatic congestive heart failure, unstable angina pectoris, myocardial infarction within 6 months prior to study entry, cardiac arrhythmia requiring therapy with the exception of extra systoles or minor conduction abnormalities * Chronic or ongoing infection requiring treatment at the time of enrolment or within the previous two weeks, e.g. active infectious disease or known Hepatitis B/Hepatitis C infection, HIV * Systemic anti-DLBCL therapy within the past two weeks or five times the half-life of the drug, whichever is shorter (palliative radiotherapy and agents used for palliative reasons for example steroids and bisphosphonates, are allowed) * Further exclusion criteria apply