Automated Radiosynthesis, Quality Control, and Biodistribution of Ga-68 Pentixafor: First Indian Experience

68 Ga-Pentixafor PET/CT for In Vivo Imaging of CXCR4 Receptors in Glioma Demonstrating a Potential for Response Assessment to Radiochemotherapy: Preliminary Results

PURPOSE

The aim of this study was to evaluate the diagnostic potential of 68 Ga-pentixafor PET/CT for in vivo CXCR4 receptors imaging in glioma and its possible role in response assessment to radiochemotherapy (R-CT).

METHODS

Nineteen (12 men, 7 women) patients with glioblastoma multiforme (GBM) underwent 68 Ga-pentixafor PET/CT, contrast-enhanced MR, and MR spectroscopy. Patients were divided in to 2 groups, that is, group I was the presurgical (n = 9) group in which the scanning was done before surgery, and PET findings were correlated with CXCR4 receptors' density. The group II was the postsurgical (n = 10) group in which the scanning was done before and after R-CT and used for treatment response evaluation. The quantitative analysis of 68 Ga-pentixafor PET/CT evaluated the mean SUV max , SUV mean , SUV peak , and T/B values. MR spectroscopy data evaluated the ratios of tumor metabolites (choline, NAA, creatine).

RESULTS

68 Ga-Pentixafor uptake was noted in all (n = 19) the patients. In the group I, the mean SUV max , SUV mean , SUV peak , and T/B values were found to be 4.5 ± 1.6, 0.60 ± 0.26, 1.95 ± 0.8, and 6.9 ± 4.6, respectively. A significant correlation ( P < 0.005) was found between SUV mean and choline/NAA ratio. Immunohistochemistry performed in 7/9 showed CXCR4 receptors' positivity (intensity 3 + ; stained cells >50.0%). In the group II, the mean SUV max at baseline was 4.6 ± 2.1 and did not differ (4.4 ± 1.6) significantly from the value noted at post-R-CT follow-up PET/CT imaging. At 6 months' clinical follow-up, 4 patients showed stable disease. SUV max and T/B ratios at follow-up imaging were lower (3.70 ± 0.90, 2.64 ± 1.35) than the corresponding values (4.40 ± 2.8; 2.91 ± 0.93) noted at baseline. Six (6/10) patients showed disease progression, and the mean SUV max , and T/B ratio in these patients were significantly ( P < 0.05) higher than the corresponding values at baseline and also higher than that noted in the stable patients.

CONCLUSIONS

68 Ga-Pentixafor PET/CT can be used for in vivo mapping of CXCR4 receptors in GBM. The technique after validation in a large cohort of patients may have added diagnostic value for the early detection of GBM recurrence and for treatment response evaluation.

68 Ga-Pentixafor PET/CT for in-vivo mapping of CXCR4 receptors as potential radiotheranostic targets in soft tissue and bone sarcoma: preliminary results

OBJECTIVE

To evaluate the diagnostic utility of 68 Ga-Pentixafor PET/CT for in vivo imaging of CXCR4 receptors in soft tissue/bone sarcoma.

METHODS

Ten (7M: 3F; mean age = 24.7 ± 14.2 years) consecutive patients with clinical and radiological evidence of bone/soft tissue sarcoma were recruited prospectively whole body 68 Ga-Pentixafor PET/CT imaging was performed at 60-min after tracer administration. After performing standard CT, PET acquisition from head to toe was done (3 min/bed position) in a caudocranial direction. PET/CT data was reconstructed and SUV max , SUV mean values, target-to-background ratio (TBR) and active tumor volume (cc) were computed for the tracer avid lesions. Histopathological and IHC analysis was performed on the surgically excised primary tumors. CXCR4 receptors' intensity was evaluated by visual scoring.

RESULTS

The mean SUV max and SUV mean values in the primary tumors were 4.80 ± 1.0 (3.9-7.7) and 2.40 ± 0.60 (0.9-4.0). The mean TBR and tumor volume (cc) were 1.84 ± 1.3 and 312.2 ± 285. Diagnosis of osteosarcoma in 7, chondrosarcoma, leiomyosarcoma and synovial sarcoma in 1 patient each was confirmed on HP analysis. Distant metastatic lesions were seen in 3/10 patients. Nuclear CXCR4 receptors' positivity was seen in 5, cytoplasmic in 4 and both pattern seen in 1 patient. The mean CXCR4 receptors' intensity was found to be 7.6 ± 2. The highest SUV max value of 7.7 was observed in the patient having both cytoplasmic and nuclear CXCR4 expression. SUV max was found to be poorly correlated ( r  = 0.441) with CXCR4 expression.

CONCLUSION

68 Ga-Pentixafor PET/CT detects CXCR4 receptors over-expressed in sarcoma, its radio-theranostics potential needs detailed evaluation.

[68Ga]Ga-Pentixafor PET/CT imaging for in vivo CXCR4 receptor mapping in different lung cancer histologic sub-types: correlation with quantitative receptors' density by immunochemistry techniques

PURPOSE

In vivo CXCR4 receptor quantification in different lung cancer (LC) sub-types using [⁶⁸Ga]Ga-Pentixafor PET/CT and to study correlation with quantitative CXCR4 receptors' tissue density by immunochemistry analyses.

METHODS

[⁶⁸Ga]Ga-Pentixafor PET/CT imaging was performed prospectively in 94 (77 M: 17F, mean age 60.1 ± 10.1 years) LC patients. CXCR4 receptors' expression on lung mass in all the patients was estimated by immunohistochemistry (IHC) and fluorescence-activated cell sorting (FACS) analyses. SUV_max on PET, intensity score on IHC, and mean fluorescence index (MFI) on FACS analyses were measured.

RESULTS

A total of 75/94 (79.8%) cases had non-small cell lung cancer (NSCLC), 14 (14.9%) had small cell lung cancer (SCLC), and 5 (5.3%) had lung neuroendocrine neoplasm (NEN). All LC types showed increased CXCR4 expression on PET (SUV_max) and FACS (MFI). However, both these parameters (mean SUV_max = 10.3 ± 5.0; mean MFI = 349.0 ± 99.0) were significantly (p = 0.005) higher in SCLC as compared to those in NSCLC and lung NEN. The mean SUV_max in adenocarcinoma (n = 16) was 8.0 ± 1.9 which was significantly (p = 0.003) higher than in squamous cell carcinoma (n = 54; 6.2 ± 2.1) and in not-otherwise specified (NOS) sub-types (n = 5; 5.8 ± 1.5) of NSCLC. A significant correlation (r = 0.697; p = 001) was seen between SUV_max and MFI values in squamous cell NSCLC as well as in NSCLC adenocarcinoma (r = 0.538, p = 0.031) which supports the specific in vivo uptake of [⁶⁸Ga]Ga-Pentixafor by CXCR4 receptors. However, this correlation was not significant in SCLC (r = 0.435, p = 0.121) and NEN (r = 0.747, p = 0.147) which may be due to the small sample size. [⁶⁸Ga]Ga-Pentixafor PET/CT provided good sensitivity (85.7%) and specificity (78.1%) for differentiating SCLC from NSCLC (ROC cutoff SUV_max = 7.2). This technique presented similar sensitivity (87.5%) and specificity (71.4%) (ROC cutoff SUV_max = 6.7) for differentiating adenocarcinoma and squamous cell variants of NSCLC.

CONCLUSION

The high sensitivity and specificity of [⁶⁸Ga]Ga-Pentixafor PET/CT for in vivo targeting of CXCR4 receptors in lung cancer can thus be used effectively for the response assessment and development of CXCR4-based radioligand therapies in LC.

Automated synthesis and quality control of [68Ga]Ga-PentixaFor using the Gaia/Luna Elysia-Raytest module for CXCR4 PET imaging

BACKGROUND

[⁶⁸Ga]Ga-PentixaFor is a promising radiotracer for positron emission tomography imaging of several human tumors overexpressing the chemokine receptor-4 (CXCR4). CXCR4 overexpression has been demonstrated in patients with hematologic malignancies, solid cancers, as well as cardiovascular pathologies of inflammatory origins. However, its radio synthesis is not yet fully developed in France, and existing methods do not use our type of synthesis module. Therefore, we aimed at developing a [⁶⁸Ga]Ga-PentixaFor synthesis with Gaia/Luna Elysia-Raytest module to use it in clinical purpose.

RESULTS

12 syntheses were carried out by varying the temperature conditions and radiolabeling times, and led to choose specific labelling conditions with the Gaia/Luna Elysia-Raytest module: 97 °C, 4 min. The mean synthesis time of the 3 validation runs under good manufacturing practice (GMP) was 24 min 27 s (± 8 s), and the mean radiochemical yield was 87.0% [standard deviation (SD) 6.67%]. Different quality control parameters were also evaluated in accordance with European Pharmacopeia: radiochemical and radionuclidic purity, pH, sterility, stability and endotoxins levels. The average radiochemical purity was 99.1% (SD 0.25%) assessed by instant thin layer chromatography and 99.8% (SD 0.092%) assessed by high pressure liquid chromatography. average [⁶⁸Ge] breakthrough was 1.48 × 10^-5%, under the recommended level of 0.001%. We assessed the stability of the radiotracer up to 4 h at room temperature (no augmentation of the [⁶⁸Ga] chloride in the final product, i.e. radiochemical purity (RCP) > 98.5%). The endotoxins levels were < 5 EU/mL, and the pH was 6.5 (same for the three syntheses).

CONCLUSION

The [⁶⁸Ga]Ga-PentixaFor synthesis process developed on the Gaia/Luna Elysia-Raytest module has fulfilled all acceptance criteria for injectable radiopharmaceutical products regarding the European Pharmacopeia. The radiochemical purity, stability, efficacy, as well as the microbiological quality of the three GMP batches were found to be good. The robustness of the synthesis process may be suitable for multi-dose application in clinical settings.

CAM-Xenograft Model Provides Preclinical Evidence for the Applicability of [68Ga]Ga-Pentixafor in CRC Imaging

Colorectal cancer is one of the leading causes of cancer-related deaths worldwide. Increased expression of CXCR4 has been associated with liver metastasis, disease progression, and shortened survival. Using in vitro cell binding studies and the in ovo model, we aimed to investigate the potential of [⁶⁸Ga]Ga-Pentixafor, a radiotracer specifically targeting human CXCR4, for CRC imaging. Specific membrane binding and internalisation of [⁶⁸Ga]Ga-Pentixafor was shown for HT29 cells, but not for HCT116 cells. Accordingly, [⁶⁸Ga]Ga-Pentixafor accumulated specifically in CAM-xenografts derived from HT29 cells, but not in HCT116 xenografts, as determined by µPET/MRI. The CAM-grown xenografts were histologically characterised, demonstrating vascularisation of the graft, preserved expression of human CXCR4, and viability of the tumour cells within the grafts. In vivo viability was further confirmed by µPET/MRI measurements using 2-[¹⁸F]FDG as a surrogate for glucose metabolism. [⁶⁸Ga]Ga-Pentixafor µPET/MRI scans showed distinct radiotracer accumulation in the chick embryonal heart, liver, and kidneys, whereas 2-[¹⁸F]FDG uptake was predominantly found in the kidneys and joints of the chick embryos. Our findings suggest that [⁶⁸Ga]Ga-Pentixafor is an interesting novel radiotracer for CRC imaging that is worth further investigation. Moreover, this study further supports the suitability of the CAM-xenograft model for the initial preclinical evaluation of targeted radiopharmaceuticals.

Gallium-68-Pentixafor PET/CT demonstrating in vivo CXCR4 receptors' overexpression in rare lung malignancies: Correlation with the histological and histochemical findings

Objectives: Gallium-68 [⁶⁸Ga] Pentixafor PET/CT imaging allows non-invasive assessment of CXCR4 expression in various malignancies, but its use in rare lung cancer variants is not reported. Methods: [⁶⁸Ga] Pentixafor PET/CT imaging was performed in 6 patients (3M:3F; mean age=57.0±16.80 years) with suspected lung masses. Whole-body PET/CT images were acquired at 1-h after the i.v. injection of 148.0-185.0 MBq of the tracer. PET/CT images were reconstructed and analysed. The image findings were correlated with histopathological and quantitative (CXCR4-receptors) FACS analysis. Results: Histopathological diagnosis of haemangioendothelioma, sarcomatoid carcinoma and hemangiopericytoma was confirmed in 1-patient each. Lung metastasis was diagnosed in the remaining 3/6 patients with primary sarcoma (n = 1), RCC (n = 1) and unknown primary (n = 1). Increased tracer uptake in the primary lung mass with SUV_max values of 3.0, 6.3 and 13.0 were noted in hemangiopericytoma, sarcomatoid carcinoma and haemangioendothelioma cases respectively. The mean values of SUV_max, MFI and % stained cells were highest in haemangioendothelioma. Among 3 patients with lung metastases, the highest SUV_max value of 9.5 was observed in primary sarcoma patient. Conclusion: [⁶⁸Ga] Pentixafor selectively targets the in vivo whole-body disease burden of CXCR4 receptors. This approach thus holds good promise for developing suitable radio-theranostics in lung cancers expressing these targets.