The paper reported a case of a young male patient, with graft-versus-host disease (GVHD) multi-organ involvement lesions after allo-hematopoietic stem cell transplantation. The patient had diverse clinical manifestations, and overlapping acute and chronic disease processes. Acute GVHD were mainly hyperbilirubinemia, with or without elevated transaminase, bloody watery stools; chronic GVHD were highlighted by extensive skin depigmentation, oral mucosal ulcer, sick nails, etc., and chronic signs, such as membranous nephropathy, polyserositis and pulmonary restrictive ventilatory insufficiency. The diagnosis of chronic GVHD mainly relies on medical history combined with clinical manifestations, and it's needed to exclude infections, drugs and tumors. Besides, the rate of missed diagnosis and misdiagnose is high, and it requires multidisciplinary diagnosis and treatment. Combined with the literature review, it indicates that there is a greater risk of GVHD in the male recipient with female donor, and peripheral blood stem cell transplant patients have a higher incidence than bone marrow transplant patients after hematopoietic stem cell transplantation, but the effect of the graft-versus-leukemia exists. Currently, glucocorticoids therapy with or without calcineurin inhibitors are the first-line treatment for GVHD, but the overall prognosis is poor.

[Objective] In view of the crucial role of indole propionic acid in the treatment of tumor immune checkpoint blockade and further revealing its mechanism, our study intended to design and synthesize 1-[¹⁸F]-fluoroethyl-indole propionic acid (1-[¹⁸F]-IPA), and evaluate it as a tumor PET imaging agent. [Methods] The precursor 1-(2-p-toluenesulfonic acid oxygen ethyl)-methyl indole propionate underwent nucleophilic substitution reaction with ¹⁸F^-. The crude product was separated and purified by high-performance liquid chromatography and the intermediates were collected. Finally, 1-[¹⁸F]-IPA was obtained by hydrolysis. The clarity of the product was measured by visual inspection, the pH value was determined by precision test paper, and the radiochemical purity and stability were determined by high-performance liquid chromatography. In order to determine the biodistribution of 1-[¹⁸F]-IPA in normal mice, ICR mice were intravenously injected with 1-[¹⁸F]-IPA (0.2 mL, 7 MBq), and sacrificed at 5, 15, 25, 45, 75 and 120 min and dissected. Micro-PET imaging was performed and analyzed in BxPC-3 tumor-bearing nude mice. Student t test was used to compare the biodistribution of tissues and organs at different time points. [Results] The total preparation time of 1-[¹⁸F]-IPA was 35-40 min, the radiochemical yield was (45±5)%, and the radiochemical purity was more than 95%. The product solution was clear without particles, and the pH value was 6.5, which had good stability in vitro and in vivo. The results of biodistribution in healthy ICR mice showed that except for the brain, 1-[¹⁸F]-IPA had a certain uptake in all major organs, with the most obvious uptake in the liver, gallbladder and kidneys. The radioactivity in the gallbladder gradually increased with time and reached (39.86±6.56)%ID/g at 120 min, but bone uptake did not change significantly with time. Micro-PET/CT showed that there was radioactive uptake at the tumor 30 min after injection of 1-[¹⁸F]-IPA in Dutch BxPC-3 nude mice, but it was not obvious. At this time, SUVmax was about 55.18±14.62. Consistent with the results of biodistribution, the brain uptake was low at each time point. [Conclusion] In summary, 1-[¹⁸F]-IPA with short preparation time and high yield is expected to be a tool to probe tryptophan indole metabolism pathway and further reveal tumor immune resistance.