A Dose Escalation and Expansion Study of [177Lu]Lu-SN201 in Participants With Advanced Cancer

Inclusion criteria:

1. Male or female participants ≥ 18 years of age on the day of signing informed consent.
2. Histologically or cytologically documented, recurrent, locally advanced, or metastaticsolid malignancy that has failed at least one prior systemic standard therapy, or forwhich standard therapy is not appropriate, or for which no standard therapy exists.
3. Eastern Cooperative Oncology Group (ECOG) performance status 0-2.
4. Life expectancy ≥ 3 months.
5. Adequate bone marrow, liver, and renal function, as assessed by the followinglaboratory requirements, to be conducted within 28 days before the start of the studyIMP administration:
6. Hemoglobin ≥ 9.0 g/dL (transfusions are allowed).
7. Absolute neutrophil count (ANC) ≥ 1500/mm3.
8. Platelet count ≥ 100,000 mm3.
9. Total bilirubin ≤ 2.5 x upper limit of normal (ULN) (in participants with livermetastases ≤ 5 ULN).
10. Alanine transaminase (ALT) and aspartate transaminase (AST) ≤ 5 x ULN.
11. On a stable dose of anti-coagulation therapy will be allowed to participate if theyhave no sign of bleeding or clotting and prothrombin/international normalized ratioand partial thromboplastin time (PT/INR and PTT, respectively) test results arecompatible with the acceptable benefit-risk ratio at the Investigator's discretion.
12. Serum creatinine ≤ 1.5 x ULN and estimated glomerular filtration rate (eGFR) > 30mL/min/1.73 m2 (per local values).
13. Contraceptive use by men and women should be consistent with local regulationsregarding the methods of contraception for those participating in clinical studies.
14. Male participants must agree to use a highly effective method of birth control asdefined in ICH M3(R2) starting with the first dose of study medication through 120 days after the last dose of study medication.
15. Female participants of childbearing potential* must have a negative pregnancytest documented at Screening and Baseline and be willing to use a highlyeffective method of contraception** or practice abstinence starting from ICFsignature through to 120 days after the last dose of study medication.

• A female of childbearing potential is a sexually mature female who 1) hasnot undergone a hysterectomy or bilateral oophorectomy, or 2) has not beennaturally postmenopausal for at least 24 consecutive months (i.e., had hadmenses at any time in the preceding 24 consecutive months).
• Effective contraception is defined as contraceptive methods with afailure rate of < 1% to prevent pregnancy (combined [estrogen andprogestogen containing] hormonal contraception associated withinhibition of ovulation [oral, intravaginal, transdermal],progestogen-only hormonal contraception associated with inhibition ofovulation [oral, injectable, implantable], intrauterine device [IUD] orintrauterine hormone-releasing system).

9. Written informed consent to study participation.
10. Be able to understand and comply with the requirements of the study, as judged by theInvestigator.
11. Phase I: At least one lesion as per RECIST v1.1.
12. Phase IIa: At least one measurable lesion as per RECIST v1.1.

Exclusion criteria:

1. Unstable systemic disease (including but not limited to active infection, hepatic,renal, or metabolic disease).
2. Clinically significant cardiac disease including any of the following:
3. Congestive heart failure requiring treatment (New York Heart Association Grade ≥ 2).
4. LVEF of < 50%, as determined by MUGA or ECHO.
5. Uncontrolled hypertension, defined as persistent systolic blood pressure ≥ 150mmHg or diastolic blood pressure ≥ 100 mmHg despite current therapy.
6. History or presence of clinically significant ventricular arrhythmias or atrialfibrillation.
7. Clinically significant resting bradycardia.
8. Unstable angina pectoris ≤ 3 months before the start of study treatment.
9. Acute myocardial infarction ≤ 3 months before the start of study treatment.
10. Mean triplicate QT interval corrected for heart rate using Fridericia's formula (QTcF) value > 480 msec (as specified in Section 10.5).
11. Known hypersensitivity to pegylated drugs or vaccines (e.g., covid-19 vaccines).
12. Concurrent or active solid or hematologic malignancy within the last 2 years with adistinct primary site or histology from the cancer being evaluated in this studyexcept for the following cancer types: cervical cancer in situ, treated basal cellcarcinoma, superficial bladder tumors (Ta and Tis).
13. Infections not responding to therapy or active clinically serious infections.
14. Known human immunodeficiency virus (HIV) infection, active hepatitis B virus (HBV), orhepatitis C virus (HCV) infection requiring treatment. Participants with chronic HBVor HCV infection are eligible at the Investigator's discretion provided that thedisease is stable and sufficiently controlled under treatment. NB: Participants with CNS metastases may be included after discussion with Sponsor,except for the sentinel participants.
15. Chemotherapy, experimental cancer therapy, biologic therapy, or immunotherapy within 2weeks (or 5 half-lives, whatever is shortest) before the start of the study IMPadministration.
16. Palliative radiotherapy completed less than 2 weeks before the start of the study IMPadministration will be allowed as long as no more than 10% of the participant's bonemarrow was irradiated.
17. Not recovered to Grade 1 from any prior anti-cancer therapy, excluding alopecia.
18. Previous high-dose chemotherapy needing hemopoietin-stem-cell-rescue.
19. Major surgery, open biopsy, or significant trauma within 4 weeks before the start ofstudy treatment.
20. A psychiatric or functional disorder that prevents participants from providinginformed consent or following protocol instructions.
21. A participant that has a condition or is in a situation, in the Investigator's opinionmay put the individual at significant risk, may confound the study results, or mayinterfere significantly with their participation in the study.
22. Is currently participating and receiving study therapy or has participated in a studyof an investigational agent and received study therapy or used an investigationaldevice within 2 weeks or 5 half-lives of the agent, whichever is the shortest.