Pharmacological Enhancement of Radionuclide Therapy Using Radiopharmaceutical–Drug Combinations in Oncology

Despite the ability of radionuclide therapy to significantly prolong progression-free survival and overall survival in several different cancer types, most patients show only partial tumor responses or stable disease, while some patients show progressive disease in spite of therapy. Co-administration or sequential administration of selected drugs whose mechanism of action complement the properties of radionuclide therapy may provide a pharmacological basis to potentially overcome some of the limitations of radiopharmaceutical therapy and may enhance clinical efficacy by additive or synergistic cytotoxic effects. The rational design and evaluation of novel radiopharmaceutical-drug combinations and optimization of dosage and administration schedules, within the complex context of individualized multimodal cancer treatment, requires a multidisciplinary approach, principally including clinical pharmacology. Potential strategies include upregulation of target receptors, co-administration of cytotoxic chemotherapeutic drugs, co-administration of drugs that inhibit DNA damage repair, co-administration of drugs that inhibit the mammalian (or mechanistic) target of rapamycin signaling pathway, co-administration of drugs that activate immune responses, and co-administration aimed at modifying pharmacokinetics to prolong retention time of radiopharmaceuticals and increase the absorbed radiation dose. Several phase II trials are currently underway, highlighting a role for clinical pharmacology in the exploration of methods to further improve efficacy of radionuclide therapy.