This study proposes to test if the study drug triapine is an effective radiation sensitizer that can be safely combined with peptide receptor radionuclide therapy (PRRT) and can improve antitumor activity of the PRRT Lutetium Lu 177 Dotatate for well-differentiated somatostatin receptor-positive neuroendocrine tumors.

Triapine is a type of drug called a ribonucleotide reductase (RNR) inhibitor. RNR is a key enzyme involved in DNA synthesis, is directly involved in the cellular response to radiation. RNR is the only enzyme responsible for the formation of deoxyribonucleotide diphosphate (dNDP), the key building blocks for DNA synthesis.

The purpose of this study is to compare the usual treatment of PRRT alone to using triapine plus PRRT. This study will help the study doctors find out if this different approach is better, the same, or worse than the usual approach.

This targeted radiation-based treatment, Lutetium Lu 177 Dotatate, is already approved by the U.S. Food and Drug Administration (FDA) to treat neuroendocrine cancer, but it is considered investigational in this study because it is not yet approved by the FDA in combination with triapine. 

Participants will be randomly assigned to one of two study groups. Randomization is like flipping a coin and there is a 50/50 chance of being assigned to either group.

Group 1 will receive Lutetium Lu 177 Dotatate through a vein in the arm once each cycle on Day 1, for a total of 4 cycles. Each cycle lasts 8 weeks (56 days). Lutetium Lu 177 Dotatate will be administered by slow intravenous infusion (IV) over a 30-minute time span.

Group 2 will receive triapine plus Lutetium Lu 177 Dotatate. Lutetium Lu 177 Dotatate will be administered through a vein in the arm once each cycle on Day 1, for a total of 4 cycles. Lutetium Lu 177 Dotatate will be administered by slow intravenous infusion (IV) over a 30-minute time span. Triapine will be taken by mouth once a day on Days 1-14 of each cycle, for a total of 4 cycles. Each cycle lasts 8 weeks (56 days).