A Phase I/IIa Open-label, Multi-center Study to Evaluate the Safety, Tolerability, Whole-body Distribution, Radiation Dosimetry and Anti-tumor Activity of [177Lu]-NeoB Administered in Patients With Advanced Solid Tumors Known to Overexpress Gastrin-releasing Peptide Receptor (GRPR)

• Signed informed consent must be obtained prior to participation in the study.

• Adult patients (age >= 18 years old) with any of the following advanced or metastatic solid tumors:

• For Phase I: breast cancer, lung cancer, prostate cancer, GIST, GBM

• For Phase IIa:

• Cohort A: Breast cancer with histology as follows: HR-positive with ER > 10% of nuclei stain, HER-2 negative as assessed on the primary diagnosis

• Cohort B: Prostate cancer

• Cohort C: GIST

• Cohort D: patients affected by any metastatic solid tumor type suspected to overexpress GRPR, and with moderate impaired renal function defined as creatinine clearance (calculated using the Cockcroft-Gault formula, or measured) ≥ 30mL/min and < 60mL/min

• At least one measurable lesion per RECIST 1.1, RANO (applicable for GBM only) criteria detected on the low-dose CT/MRI (for GBM MRI only) acquired together with the [68Ga]-NeoB PET.

• The same identified measurable lesion shows [68Ga]-NeoB uptake on PET/CT or PET/MRI. If the only matching lesion is located in the bone, the patient will still be eligible.

• Patients for whom no standard therapy is available, tolerated or appropriate in both Phase I and Phase IIa. Specifically in the Phase IIa breast cancer cohort, patients need to have completed at least two prior treatments of endocrine therapy (including CDk4/6i) and at least one prior chemotherapy (unless contraindicated) in the metastatic setting.

• Patient Eastern Cooperative Oncology Group (ECOG) performance status =< 2.