Biologic Evaluation of a Novel 188Re-Labeled Porphyrin in Mice Tumor Model

Radiosynthesis, molecular modeling and biodistribution of 99mTc-Protoporphyrin as a preclinical model for tumor diagnosis

Porphyrins are among the most important and widely used compounds involved in a variety of chemical and biochemical applications. These molecules exhibit very special properties that encourage researchers to label many derivatives with diagnostic or therapeutic radionuclides for medical applications. This study reports the radiolabeling and biodistribution of [Formula: see text]Tc-protoporphyrin IX ([Formula: see text]Tc-PPIX) as a novel potential solid-tumor imaging agent. The factors affecting the radiolabeling process were varied to achieve maximum radiochemical yield. [Formula: see text]Tc-PPIX was obtained in high yield of 97.34 ± 0.21% and high stability in serum up to 24 h. The radiochemical yield of [Formula: see text]Tc-PPIX was assessed by a combination of a paper chromatographic technique and HPLC. A computational analysis for all the potential structures that may be formed due to the interaction between protoporphyrin IX and technetium was performed via the DFT method of calculations in gas phase to predict the most likely structure. Molecular docking was further employed to shed light on the nature of the interaction between the most stable complexes with the target protein. Finally, the in-vivo biodistribution of [Formula: see text]Tc-PPIX complex was evaluated in solid-tumor-bearing mice and high tumor/tissue ratio of 5.17 ± 0.34 at 60 min post injection was obtained. Our finding clearly suggests [Formula: see text]Tc-PPIX as a potential SPECT agent for tumor imaging.

Correlation between mouse age and human age in anti-tumor research: Significance and method establishment

Age is closely related with the occurrence and development of tumors, and with treatment outcomes. To improve the accuracy and rigor of preclinical studies, and to enhance consistency between the preclinical research and the clinical reality, the age of experimental animals used in preclinical studies is important. The mouse genome is 99% identical to the human genome, and mice have similar patterns with respect to organs and systemic physiology. Thus, mice have been the most widely used animals in anti-tumor research. However, most mice used in such studies are 6 to 8 weeks old, ignoring the fact that different tumors may often occur in various periods, with a particular tendency to occur in later stages of life. The great difference in age limits the success rate of clinical transformation. Therefore, it is very important to choose mice of suitable age for preclinical studies and to correlate ages of human and mice. Only a few related studies have been reported and there is a lack of consistency in the findings. This review points out that age is one of the important factors in anti-tumor research, and establishes a new method for calculating the age correlation between humans and mice. The equations obtained from the method can help researchers conveniently determine suitable aged mouse for their research, which will improve the rigor of their experimental results. Furthermore, this method can be used beyond anti-tumor research, in studies on other diseases that use mouse as an animal model.

Preparation and evaluation of 99mTc-labeled porphyrin complexes prepared using PNP and HYNIC cores: studying the effects of core selection on pharmacokinetics and tumor uptake in a mouse model

Porphyrins are tetrapyrrolic macrocyclic ligands known for their affinity towards neoplastic tissues and once radiolabeled with a suitable diagnostic radioisotope could potentially be used for the imaging of tumorous lesions. In the present study, an unsymmetrically substituted porphyrin derivative namely 5-(p-amino-propyloxyphenyl)-10,15,20-tris(carboxymethyleneoxyphenyl)-porphyrin was synthesized and modified further to enable radiolabeling with ^99mTc using two different ^99mTc-cores viz. ^99mTc-HYNIC (hydrazino nicotinic acid) and ^99mTc(N)PNP2 (PNP2 = bis-[(2-dimethylphosphino)ethyl]-methoxy-ethylamine) in order to study the effect of employing different ^99mTc-cores on tumor affinity and pharmacokinetic behavior of the resultant ^99mTc-labeled porphyrin complexes. ^99mTc-Porphyrin complexes were characterized by reversed phase HPLC studies and could be prepared with >95% radiochemical purity under optimized radiolabeling conditions. Both ^99mTc-complexes were found to be adequately stable in human blood serum till 3 h post-preparation. Bio-distribution studies, carried out in Swiss mice bearing fibrosarcoma tumors, revealed relatively higher tumor uptake for the ^99mTc-HYNIC-porphyrin complex (3.95 ± 1.42 and 3.28 ± 0.27% IA per g) compared to that exhibited by the ^99mTc(N)PNP-DTC-porphyrin complex (1.52 ± 0.53 and 1.56 ± 0.10% IA per g) at 1.5 and 3 h post-administration, although the former complex exhibited comparatively lower lipophilicity in the octanol-water system. Higher uptake and longer retention in the blood were observed for the ^99mTc-HYNIC-porphyrin complex (6.63 ± 0.75 and 4.36 ± 0.25% IA per g) compared to that exhibited by the ^99mTc(N)PNP-DTC-porphyrin complex (2.41 ± 0.54 and 2.30 ± 0.16% IA per g) at both 1.5 and 3 h post-administration. However, relatively lower liver uptake was observed for the former complex (19.26 ± 3.48 and 18.45 ± 1.05% IA per g) than that exhibited by the latter one (39.37 ± 3.88 and 34.15 ± 8.25% IA per g) at both 1.5 and 3 h post-administration. This study indicates that the in vivo behavior exhibited by the ^99mTc-labeled porphyrins not only depends on their lipophilicity/hydrophilicity but is also governed by the Tc-cores employed for radiolabeling.

Preparation and biological evaluation of a carrier free 90yttrium labelled porphyrin as a possible agent for targeted therapy of tumor

In this research article, 5,10,15,20-tetrakis(phenyl)porphyrin (H2TPP) was produced and characterized. Then, radiolabeling of H2TPP was performed using the carrier free Y-90 which was prepared by the use of a home-made yttrium imprinted sorbent. The radiolabeling procedure was accomplished at 60 [Formula: see text] C during 12 h with a suitable radiochemical purity (95 ± 2% ITLC, 99 ± 0.5% HPLC) and specific activity of (1.0 ± 0.1 GBq/mmol). The obtained radio-labeled H2TPP in final formulation was kept for a week in order to investigate the complex stability. Accordingly, the partition coefficient was calculated as log [Formula: see text] 2.05. Furthermore, the biodistribution of the [Formula: see text]Y–TPP was determined in vital organs of normal wild-type rats using scarification studies. The kidneys could mostly remove the radio-complexes from the blood circulation and in less extends from the liver. As a result it is expected that due to its lipophilicity the higher mitochondrial and thus, tumor cell uptake of this radiolabeled porphyrin happens and therefore [Formula: see text]Y–TPP could act as an efficient potential agent for targeted therapy of tumor.

Production, quality control, biodistribution assessment and preliminary dose evaluation of [177Lu]-tetra phenyl porphyrin complex as a possible therapeutic agent

<p>Due to interesting therapeutic properties of ¹⁷⁷Lu and tumor avidity of tetraphenyl porphyrins (TPPs), ¹⁷⁷Lu-tetraphenyl porphyrin was developed as a possible therapeutic compound. ¹⁷⁷Lu of 2.6-3 GBq/mg specific activity was obtained by irradiation of natural Lu₂O₃sample with thermal neutron flux of 4 × 10¹³ n.cm^-2.s^-1. Tetraphenyl porphyrin was synthetized and labeled with ¹⁷⁷Lu. Radiochemical purity of the complex was studied using Instant thin layer chromatography (ITLC) method. Stability of the complex was checked in final formulation and human serum for 48 h. The biodistribution of the labeled compound in vital organs of wild-type rats was studied up to 7 d. The absorbed dose of each human organ was calculated by medical internal radiation dose (MIRD) method. A detailed comparative pharmacokinetic study was performed for ¹⁷⁷Lu cation and [¹⁷⁷Lu]-TPP. The complex was prepared with a radiochemical purity: >97±1% and specific activity: 970-1000 MBq/mmol. Biodistribution data and dosimetric results showed that all tissues receive approximately an insignificant absorbed dose due to rapid excretion of the complex through the urinary tract. [¹⁷⁷Lu]-TPP can be an interesting tumor targeting agent due to low liver uptake and very low absorbed dose of approximately 0.036 to the total body of human.</p>

Radiolabelled porphyrins in nuclear medicine

Amongst tumour-specific substances, hematoporphyrin and synthetic porphyrin derivatives have been widely investigated to identify and delineate neoplastic and malignant tissue. Whilst the tumour localization exhibited by selected porphyrin species has been exploited through photodynamic therapy, several examples of porphyrin derivatives with varied peripheral functionality have been radiolabelled with the aim of developing porphyrin-based nuclear imaging and therapeutic agents. In this review, we look at the approaches and advances in the preparation and uses of such radiolabelled agents for imaging and therapy.

Development of a (68)Ga-Fluorinated Porphyrin Complex as a Possible PET Imaging Agent

AIM

Due to the interesting pharmacologic properties of porphyrins, the idea of developing a possible tumor imaging agent using PET by incorporating (68)Ga into a suitable porphyrin ligand was investigated.

METHODS

(68)Ga-labeled 5,10,15,20-tetrakis(pentafluoro-13 phenyl) porphyrin ((68)Ga-TFPP) was prepared using freshly eluted [(68)Ga]GaCl3 obtained from a 68Ge/68Ga generator developed in-house and 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin (H2TFPP) for 60 min at 100°C.

RESULTS

The complex was prepared with high radiochemical purity (>99% ITLC, >99% HPLC, specific activity: 13-14 GBq/mmol). Stability of the complex was checked in the final formulation and in human serum for 5 h. The partition coefficient was calculated for the compound (log P = 0.62). The biodistribution of the labeled compound in vital organs of Swiss mice bearing fibrosarcoma tumors was studied using scarification studies and SPECT imaging up to 1 h. The complex was mostly washed out from the circulation through kidneys and liver. The tumor-to-muscle ratio 1 h post injection was 5.13.

CONCLUSION

The radiolabeled porphyrin complex demonstrated potential for further imaging studies in other tumor models.