RT Journal Article SR Electronic T1 A Phase I/IIa Clinical Trial to Evaluate Safety and Adrenal Uptake of Para-Chloro-2-[18F]Fluoroethyletomidate in Healthy Volunteers and Patients with Primary Aldosteronism JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 434 OP 440 DO 10.2967/jnumed.124.268425 VO 66 IS 3 A1 Gillett, Daniel A1 Senanayake, Russell A1 MacFarlane, James A1 Bashari, Waiel A1 Palma, August A1 Hu, Lihua A1 Harper, Ines A1 Mendichovszky, Iosif A. A1 Antoni, Gunnar A1 Hellman, Per A1 Sundin, Anders A1 Hird, Matthew A1 Boros, István A1 Brown, Morris J. A1 Cheow, Heok A1 Aloj, Luigi A1 Aigbirhio, Franklin A1 Gurnell, Mark YR 2025 UL http://jnm.snmjournals.org/content/66/3/434.abstract AB Primary aldosteronism (PA) is a common, potentially reversible, cause of hypertension. Distinguishing unilateral from bilateral PA is critical when deciding who should be offered surgery (unilateral adrenalectomy). Recent studies have shown that PET/CT with [11C]metomidate can accurately identify unilateral PA, with localization of the causative aldosterone-producing adenoma (APA). However, the availability of [11C]metomidate is limited to centers with an on-site cyclotron. Here, we report an early-phase human study with the 18F-labeled analog, para-chloro-2-[18F]fluoroethyletomidate ([18F]CETO). Methods: We conducted a phase I/IIa, single-center, open-label, microdosing study. The primary objective was to evaluate the safety of up to 2 administrations of [18F]CETO in 6 patients with PA (3 unilateral disease, 3 bilateral disease) and 5 healthy volunteers. Safety evaluation included assessment of adrenal function after the first [18F]CETO administration. The biodistribution of [18F]CETO was assessed in a 90-min dynamic PET acquisition. In patients with PA, the effect of pretreatment with oral dexamethasone on [18F]CETO uptake by normal adrenal tissue and APAs was also assessed. Results: Eleven participants were recruited to the trial, including 6 patients and 5 healthy volunteers. No subjects experienced serious adverse events or reactions, and all participants had normal adrenal function after [18F]CETO administration. [18F]CETO demonstrated high selectivity for the adrenal glands with low uptake in other tissues. Visualization of APAs was enhanced after dexamethasone pretreatment, which suppressed [18F]CETO uptake by normal adrenal tissue. Conclusion: [18F]CETO is a safe radiopharmaceutical for PET imaging of the adrenal glands, with no observed adverse reactions or impairment of adrenal function in this study. [18F]CETO demonstrates selective high affinity for adrenal tissue, particularly APAs. Distinction between APAs and normal adrenal tissue is enhanced by dexamethasone pretreatment to suppress [18F]CETO uptake by normal glands. This positions [18F]CETO as a promising imaging tool for evaluation in the context of PA.