Tarlatamab for SCLC Brain Metastases

Inclusion Criteria: In order to be eligible to participate in this study, a subject must meet all of the following criteria: 1. Signed and written informed consent 2. Age 18 years or older 3. Patients with pathology proven metastatic SCLC 4. Pretreated with at least platinum-doublet chemotherapy with or without immunotherapy, no maximum of previous lines of systemic therapy 5. WHO/ECOG PS 0-1 6. Estimated life expectancy 12 weeks or more 7. At least one asymptomatic active (newly diagnosed or unequivocally progressive) untreated brain metastasis ≥ 5mm: 1. Subjects with largest measurable intracranial lesion ≥5 mm but \<10mm may be allowed to enroll upon agreement with investigator (for patients with target lesions of ≥ 5mm but \<10 mm, 1.5 mm slice thickness brain MRI is required). 2. "Untreated" refers to the lesion not being previously treated with stereotactic radiosurgery/therapy (SRS/SRT) or surgery. 3. Prior treatment with whole brain radiation therapy or local surgery is permissible provided unequivocal progression in the lesion has since occurred 8. For at least 7 days prior to study start: Patient must be asymptomatic from CNS metastases and on a stable dose of anti-epileptics and corticosteroids. Maximum dose of steroids is 10 mg prednisolone or equivalent/day, dose should be noted. 9. Adequate organ and bone marrow function, defined as: a. Hematological function: i. Absolute neutrophil count ≥1.5 x109/L ii. Platelet count ≥ 100 x109/L iii. Hemoglobin ≥ 5.6 mmol/l b. Coagulation function: i. Protrombin time (PT)/ international normalized ratio (INR) and partial thromboplastin time (PTT) or activated partial thromboplastin time (APTT) ≤ 1.5 x institutional upper limit of normal (ULN) except for subjects receiving anticoagulation, who must be on a stable dose of anticoagulant therapy for 6 weeks prior to start of study treatment. c. Renal function: i. Estimated glomerular filtration rate (eGFR) based on Modification of Dietin Renal Disease (MDRD) calculation \> 30 mL/min/1.73 m2 d. Hepatic function: i. Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) \< 3x ULN (or \< 5x ULN for subjects with liver metastases) ii. Total bilirubin \< 1.5x ULN (or \< 2x ULN for subjects with liver metastases), except for subjects with Gilberts disease e. Pulmonary function: i. No clinically significant pleural effusion. Pleural effusions managed with indwelling pleural catheter (eg, PleurX) are allowed. ii. Baseline oxygen saturation \> 90% on room air f. Cardiac function: i. Cardiac ejection fraction ≥50%, no clinically significant pericardial effusion as determined by an echocardiogram (ECHO) or multigated acquisition (MUGA) scan, and no clinically significant electrocardiogram (ECG) finding Exclusion Criteria: A potential subject who meets any of the following criteria will be excluded from participation in this study: 1. Symptomatic BM (if asymptomatic with corticosteroids with a maximum dose of steroids of 10 mg prednisolone or equivalent/day, the patient is eligible). If in doubt, discussion with the sponsor is necessary 2. Leptomeningeal metastases (evaluated with MRI brain) 3. BM in eloquent area (to be discussed with neuro-oncologist) 4. Contra-indication for MRI 5. Prior history of severe or life-threatening events from any immune-mediated therapy 6. Grade 2 or higher toxicity from previous systemic therapy, except for alopecia 7. History of other malignancy within the past 2 years, with the following exceptions: 1. Malignancy treated with curative intent before enrolment, with no known active disease and felt to be at low risk for recurrence by the treating physician, after discussion with the sponsor 2. Adequately treated non-melanoma skin cancer or lentigo maligna without evidence of disease 3. adequately treated cervical cancer in situ without evidence of disease 4. adequately treated breast ductal carcinoma in situ without evidence of disease 5. prostatic intraepithelial neoplasia without evidence of prostate cancer 6. adequately treated urothelial papillary non-invasive carcinoma or carcinoma in situ 8. Active or prior documented autoimmune or inflammatory disorders (including inflammatory bowel disease \[e.g. colitis or Crohn's disease\], systemic lupus erythematosus, sarcoidosis, granulomatosis with polyangiitis, Graves' disease, rheumatoid arthritis, hypophysitis, uveitis, etc), autoimmune pneumonitis, and autoimmune myocarditis. The following are exceptions to this criterion: 1. Subjects with vitiligo or alopecia 2. Subjects with hypothyroidism (e.g. following Hashimoto syndrome) stable on hormone replacement 3. Any chronic skin condition that does not require systemic therapy 4. Subjects without active disease in the last 5 years may be included but only after consultation with the sponsor 5. Subjects with coeliac disease controlled by diet alone 9. Myocardial infarction and/or symptomatic congestive heart failure (New York Heart Association \> class II, appendix 2), within 6 months prior to first dose of study treatment 10. History of arterial thrombosis (e.g. stroke or transient ischemic attack) within 6 months prior to first dose of study treatment 11. Evidence of ILD or active, non-infectious pneumonitis 12. History of solid organ transplant 13. Major surgical procedures within 28 days prior to first dose of study treatment 14. Presence of active HIV or hepatitis infection 1. HIV infection: subjects with HIV infection on antiviral therapy and undetectable viral load are permitted with a requirement for regular monitoring for reactivation for the duration of the treatment on study per local or institutional guidelines 2. Active hepatitis C infection (subjects with detectable hepatitis C antibody \[HCV Ab\] and hepatitis C virus (HCV) RNA viral load above the limit of quantification) are not allowed. Subjects with presence of HCV antibody (HCV Ab positive) and HCV RNA viral load below the li