Covalent Radiopharmaceuticals: Precision Imaging and Therapy for Cancer.

Covalent radiopharmaceuticals are emerging as a powerful new class of agents for cancer imaging and therapy, offering durable target engagement that overcomes the key limitations of conventional, reversible tracers. By forming covalent bonds with nucleophilic residues on or near disease-relevant proteins, covalent radiopharmaceuticals can achieve prolonged tumor retention, improved target selectivity, and enhanced imaging contrast, or therapeutic efficacy. This strategy is particularly well-suited to addressing biological challenges such as rapid internalization, low target abundance, and tumor heterogeneity, where noncovalent agents often underperform. Recent advances have demonstrated the versatility of covalent radiopharmaceuticals across a range of molecular formats, including small molecules, protein binders, and peptidomimetics. These agents have been engineered with diverse covalent targeting moieties that enable selective and stable binding under physiological conditions. In preclinical and early clinical studies, covalent tracers have shown superior tumor retention and, in some cases, improved performance over standard-of-care agents. Importantly, covalent design also allows for greater alignment between tracer pharmacokinetics and radionuclide decay, improving dosimetry and expanding therapeutic windows. While challenges remain in optimizing covalent handle reactivity and minimizing off-target effects, ongoing innovations in synthetic chemistry and protein engineering are rapidly advancing the field. As the mechanistic and translational advantages of covalency become increasingly clear, covalent radiopharmaceuticals are poised to redefine molecular imaging and therapy. They are not merely specialized tools but are foundational components of next-generation precision oncology.