Radiolabeled methotrexate as a diagnostic agent of inflammatory target sites: A proof-of-concept study

Abstract

Methotrexate (MTX), as a pharmaceutical, is frequently used in tumor chemotherapy and is also a part of the established treatment of a number of autoimmune inflammatory disorders. Radiolabeled MTX has been studied as a tumor-diagnostic agent in a number of published studies. In the present study, the potential use of technetium-99m-labelled MTX (99mTc-MTX) as a radiotracer was investigated for the identification of inflammatory target sites. The labelling of MTX was carried out via a 99mTc-gluconate precursor. Evaluation studies included in vitro stability, plasma protein binding assessment, partition-coefficient estimation, in vivo scintigraphic imaging and ex vivo animal experiments in an animal inflammation model. MTX was successfully labelled with 99mTc, with a radiochemical purity of >95%. Stability was assessed in plasma, where it remained intact up to 85% at 4 h post-incubation, while protein binding of the radiotracer was observed to be ~50% at 4 h. These preclinical ex vivo and in vivo studies indicated that 99mTc-MTX accumulates in inflamed tissue, as well as in the spinal cord, joints and bones; all areas with relatively high remodeling activity. The results are promising, and set the stage for further work on the development and application of 99mTc-MTX as a radiotracer for inflammation associated with rheumatoid arthritis.

Perspectives of Methotrexate-Based Radioagents for Application in Nuclear Medicine

“…Also, [ 99m Tc]Tc-MTX complex provided clear visualization of chemically induced inflammation on a murine model, despite low selectivity of the radiocomplex. 123 Moreover, the same study reported firm evidence that [ 99m Tc]Tc-MTX exhibited high affinity to the bone-like hydroxyapatite.…”

“…Another study investigated the ability of [ 99m Tc]Tc-MTX complex to detect severe (chemically induced) inflammations. 123 An ex vivo study performed on a small group of three mice with experimentally induced inflammation showed very high uptake of radiocomplex in kidneys and significant accumulation in bones. In parallel, [ 99m Tc]Tc-MTX binding to hydroxyapatite at the level of about 45% after 10 min of incubation was determined.…”

Predictive power of the Triticum root elongation test for the assessment of novel anti‑proliferative therapies

“…It is one of the earliest anticancer drugs, an antifolate that mainly inhibits dihydrofolate reductase, leading to impaired purine synthesis. As a result, malignant cells are unable to synthesize DNA and RNA, leading to cell apoptosis (35). This confirms the findings of previous studies emphasizing the crucial role of folates in root development (36,37).…”

Common Shortcomings in Study on Radiopharmaceutical Design Research: A Case Study of 99mTc-Labelled Methotrexate

“…The procedure of direct method of MTX labelling with technetium-99m one can find in several works [ 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 ]. Generally, the method is based on the reduction of 99m Tc VII (from the pertechnetate anions, [ 99m Tc]TcO 4 − , obtained from 99 Mo/ 99m Tc-generator in all below syntheses) to technetium-99m cation on a lower oxidation state, which allows the formation of [ 99m Tc]Tc-MTX complex.…”

“…Papachristou et al studied the possible use of 99m Tc-labelled MTX as a radiotracer for the identification of chemically induced inflammatory sites [ 12 ]. The labelling reaction of MTX was performed in neutral pH, in presence of sodium gluconate, sodium bicarbonate and stannous chloride at room temperature for 30 min.…”