Phase 1 First-in-Human, Dose Escalation and Dose Expansion Study of RYZ401, a Novel Radiopharmaceutical Therapy Labeled With Actinium-225, in Subjects With Neuroendocrine Tumors and Other Solid Tumors Expressing Somatostatin Receptors.

Inclusion criteria: * At least 18 years old at the time of signing the main study informed consent form (ICF). * Histologically confirmed: Dose Escalation (all cohorts): Grades 1-3 WD, metastatic or locally advanced and unresectable NET at any primary site, including, but not limited to, GI, pancreatic, lung, thyroid, breast, urogenital, and adrenal tumors. * Dose Expansion Cohort A: Grades 1-3 WD, metastatic or locally advanced and unresectable GEP-NETs * Dose Expansion Cohort B: metastatic or locally advanced and unresectable tumors known to frequently express SSTR, limited to the followi…