Inclusion
1. Aged at least 18 years (inclusive at the time of informed consent).
2. Must be able and willing to provide written informed consent prior to start of any study procedures and assessments and must be willing to comply with all study procedures.
3. Histologically or cytologically confirmed ES-SCLC.
4. Adequate organ and marrow function within 7 days of first dose of 177Lu-SSO110 as defined below:
a. absolute neutrophil count greater than or equal to 1,000/µL;
b. platelets of greater than or equal to 100,000/µL;
c. total bilirubin less than or equal to 1.5 × upper limit of normal (ULN) or less than or equal to 3.0 × ULN for participants with hereditary benign hyperbilirubinaemia;
d. AST (aspartate aminotransferase or serum glutamic oxaloacetic transaminase, SGOT) and ALT (alanine aminotransferase or serum glutamic pyruvic transaminase, SGPT) less than or equal to 3 × ULN (or less than or equal to 5 × ULN if liver metastases are present);
e. serum creatinine less than or equal to 1.5 × ULN;
f. estimated glomerular filtration rate greater than or equal to 45 mL/min/1.73 m2;
g. serum albumin greater than or equal to 30 g/L.
5. Life expectancy of >18 weeks at confirmation of eligibility, in the opinion of the Investigator.
6. Women of childbearing potential (WOCBP) must have a negative beta-human chorionic gonadotropin test within 72 hours before the first dose of study drug and must not be breastfeeding. WOCBP are defined as those who are not surgically sterile or post-menopausal. Female participants will be considered post-menopausal if they have been amenorrhoeic for 12 months without an alternative medical cause. Female participants <50 years old who meet the criteria for post-menopausal status without previous surgical sterilization should be considered for further investigation with luteinising hormone and follicle stimulating hormone levels to confirm serological post-menopausal status.
7. WOCBP must agree to use a highly effective method of contraception during the study and for 90 days after the last dose of study drug.
8. Male participants who are able to father a child must agree to avoid impregnating a partner and to adhere to a highly effective method of contraception during the study and for 90 days after the last dose of study drug. All male participants must agree to not donate sperm during the study and for 90 days after the last dose of study drug.
9. Either positive 68Ga-SSO120 scan at screening (positive being a lesion concordant with a known lesion based on CT or FDG-PET/CT with uptake visually assessed as greater than the liver on 68Ga-SSO120 scan) or at the Investigator’s discretion, in the case of no/insufficient visible lesions at screening, a positive test for SST2 from archival tissue or histology report (positive being a H-score >50).
10. To receive the first dose of 177Lu-SSO110, participants must have received at least 1 and no more than 2 doses of maintenance atezolizumab after induction therapy consisting of a platinum-based agent (e.g., cisplatin/carboplatin), etoposide and atezolizumab.
11. Participants with previously treated brain metastases are eligible to participate if:
a. they are clinically and radiologically stable disease (no evidence of progression by imaging; same imaging modality [magnetic resonance imaging or CT scan]) must be used for each assessment) for at least 28 days prior to the first dose of study drug;
b. any neurologic symptoms returned to baseline;
c. no longer on steroids.
Note: Participants with a history of leptomeningeal disease may not participate even if stable clinically.
Exclusion
A participant who meets any of the following exclusion criteria must be excluded from the study:
1. Any previous radioligand therapy (e.g., peptide receptor radionuclide therapy).
2. Any concurrent malignancy. Patients with a malignancy whose natural history or treatment does not have the potential to interfere with the safety or efficacy assessment of the investigational regimen and participants with a prior malignancy that have shown evidence of complete remission are eligible for this study at the Investigator’s discretion.
3. Any condition that precludes the adequate performance of PET and/or CT scan.
4. History of clinically significant allergic reactions attributed to compounds of similar chemical composition to 68Ga, 177Lu, SSO110, SSO120, atezolizumab, somatostatin analogue peptides or other agents used in the study.
5. Any Grade >3 immune-related adverse event (irAE) during prior or current therapy with any immunotherapy agent(s). Previous irAEs thought not to increase participant’s risk of an investigational medicinal product-related AE, may be approved at the Investigator’s discretion, if it is determined as unlikely to put the participant at an increased risk of treatment-related toxicity and/or impact the integrity of study outcome (e.g., hypothyroidism on stable thyroxine replacement, adrenal insufficiency on stable hormone replacement therapy, diabetes on stable insulin therapy).
6. Use of immunosuppressive medication >10 mg prednisolone per day or equivalent within 14 days prior to the first dose of 177Lu-SSO110.
Note: Use of immunosuppressive medications as prophylaxis in participants with contrast allergies are acceptable. In addition, temporary uses of corticosteroids considered non-clinically relevant may be approved at the Investigator’s discretion.
7. Any unresolved AEs Grade >1 from prior anticancer therapy except for alopecia. Participants with residual AEs Grade >1 considered unlikely to put the participant at an increased risk of treatment-related toxicity and/or impact the integrity of study outcome may be permitted on a case-by-case basis at the Investigator’s discretion (e.g., thyroid disorders or cortisol insufficiency on stable hormone replacement therapy).
8. Any uncontrolled intercurrent illness or clinically significant uncontrolled condition(s); active bacterial, fungal, or viral infections requiring systemic therapy.
9. Live vaccine administration less than or equal to 21 days prior to the first dose of study drug.
10. Active or previous autoimmune diseases, with the following exemptions:
a. Hashimoto’s thyroiditis on stable thyroid replacement therapy;
b. Type 1 diabetes mellitus on stable insulin therapy;
c. Other autoimmune disorders not considered to put participant at a higher risk of irAE may be approved at the Investigator’s discretion.
11. History of primary immunodeficiency, bone marrow (BM) transplantation, or solid organ transplantation.
12. History of inflammatory bowel disease, interstitial lung disease (pneumonitis), myocarditis, Stevens-Johnson syndrome, or toxic epidermal necrolysis.
13. History of known alcohol or substance abuse and/or a known psychiatric illness/social situation that would limit compliance with study requirements.
14. Has had or is scheduled to have major surgery <28 days prior to the first dose of study drug.
15. Known active human immunodeficiency virus or known active hepatitis B or C virus.
16. Known history within 4 months prior to first dose of study treatment or current symptomatic heart failure as per New York Heart Association classes III-IV, unstable angina, myocardial infarction, serious/uncontrolled/unstable cardiac arrhythmia, cerebral vascular accident, coronary/peripheral artery bypass graft surgery, transient ischemic attack, or pulmonary embolism.
17. Known history of severe asthma and/or chronic obstructive airways disease requiring systemic steroid therapy within 6 months prior to first dose of study treatment. Baseline oxygen saturation reading at room air must be >90% by pulse oximetry.
18. Known history of severe eczema and other skin/pruritic conditions requiring systemic steroid therapy within 6 months prior to first dose of study treatment.
19. Any extensive radiotherapy less than or equal to 3 months before first 177Lu-SSO110 administration, defined as external beam radiation (e.g., stereotactic ablative radiotherapy) to >25% of the BM or brachytherapy.
20. A known superscan indicating extensive bony metastatic disease.
21. Received anticancer therapy (other than atezolizumab), including chemotherapy, immunotherapy, biologic, herbal therapy, or any investigational therapy or investigational device, within 18 days (or 5 half-lives for biologic/non-cytotoxic agents, whichever is shorter), prior to the first dose of the study drug.