Background:⁶⁸Ga-NOTA-WL12 is a peptide-based positron emission tomography (PET) imaging agent. We conducted a first-in-human study of ⁶⁸Ga-NOTA-WL12 for PET to study the in vivo biodistribution, metabolism, radiation dosimetry, safety, and potential for quantifying programmed death ligand-1 (PD-L1) expression levels in advanced non-small cell lung cancer (NSCLC) patients. Methods: In vitro assessment of the relationship between PD-L1 expression and cellular uptake of ⁶⁸Ga-NOTA-WL12 was performed, followed by in vivo evaluation of ⁶⁸Ga-NOTA-WL12 uptake in animal models. Nine NSCLC patients with positive PD-L1 expression in lesions were enrolled. ⁶⁸Ga-NOTA-WL12 and paired ¹⁸F-FDG PET/CT imaging were performed. The patients were monitored for adverse events. The uptake (SUV/L and kBq/mL) values of tumors and normal organs were obtained. The biodistribution, radiation dosimetry and relationship of tumor uptake and PD-L1 expression were then evaluated. Follow-up ¹⁸F-FDG PET/CT was performed in patients who had undergone treatment with a combination of pembrolizumab with chemotherapy. Results: The cellular and animal experiments demonstrated that PD-L1 expression correlated with the uptake of ⁶⁸Ga-NOTA-WL12, and PD-L1-positive tumors exhibited high uptake of ⁶⁸Ga-NOTA-WL12. Clinical research showed that ⁶⁸Ga-NOTA-WL12 PET imaging is safe with acceptable radiation dosimetry. Physiological tracer uptake was mainly visible in the liver, spleen, small intestine and kidney. High contrast of tumors was observed, particularly in the lungs with a T/lung ratio of 4.45 ±1.89 at 1 h. One hour was a suitable timepoint for image acquisition because no significant differences were noted in the tumor-to-background ratios between 1 and 2 h. Additionally, a strong relationship was found between the tumor uptake (SUVpeak) and PD-L1 immunohistochemistry results (r = 0.9349; P = 0.002). ⁶⁸Ga-NOTA-WL12 uptake before therapy might indicate the therapeutic efficacy of pembrolizumab plus chemotherapy combination treatment. Conclusion: Our first-in-human findings demonstrate the safety and feasibility of ⁶⁸Ga-NOTA-WL12 for noninvasive in vivo detection of the tumor PD-L1 expression levels, indicating potential benefits for clinical PD-L1 therapy.

Purpose: Nectin-4 is an emerging biomarker for cancer diagnosis and therapy. Recently, enfortumab vedotin (EV) was approved by the FDA as the first nectin-4 targeting antibody–drug conjugate for treating advanced urothelial carcinoma (UC). A PET imaging method to noninvasively quantify nectin-4 expression level would potentially help to select patients most likely to respond to EV and predict the response. Experimental Design: In this study, we designed a bicyclic peptide-based nectin-4 targeting radiotracer 68Ga-N188. Initially, we performed preclinical evaluations of 68Ga-N188 in UC cell lines and xenograft mouse models. Next, we performed the translational study in healthy volunteers and a pilot cohort of patients with advanced UC on uEXPLORER total-body PET/CT. Results: In the preclinical study, 68Ga-N188 showed high affinity to nectin-4, specific uptake in a nectin-4(+) xenograft mouse model, and suitable pharmacokinetic and safety profiles. In the translational study, 2 healthy volunteers and 14 patients with advanced UC were enrolled. The pharmacokinetic profile was determined for 68Ga-N188, and the nectin-4 relative expression level in different organs was quantitatively imaged. Conclusions: A clear correlation between PET SUV value and nectin-4 expression was observed, supporting the application of 68Ga-N188 PET as a companion diagnostic tool for optimizing treatments that target nectin-4. See related commentary by Jiang et al., p. 3259

Prostate-specific membrane antigen (PSMA)-targeted radioligands have played an important role in the diagnosis of prostate cancer. In this study, we developed an Al¹⁸F-labeled radiotracer and evaluated its potential for prostate cancer imaging. Methods: Al¹⁸F-PSMA-BCH was efficiently prepared manually. The binding affinity to PSMA was evaluated in vitro using the 22Rv1 (PSMA+) cell line. Micro-PET imaging, biodistribution studies of Al¹⁸F-PSMA-BCH in mice bearing 22Rv1 and PC-3 (PSMA-)-xenografted tumors and a comparison with ⁶⁸Ga-PSMA-617 in mice bearing LNCaP tumors were performed. PET/CT imaging was performed on 11 newly diagnosed prostate cancer patients at 1 h and 2 h post-injection (p.i.). Biodistribution and preliminary efficacy were evaluated, and radiation dosimetry was estimated using OLINDA/EXM 2.0 software. Results: Al¹⁸F-PSMA-BCH was prepared within 30 min and was found to bind to PSMA with a Kd value of 2.90±0.83 nM. Micro-PET imaging of Al¹⁸F-PSMA-BCH can clearly differentiate 22Rv1 tumors from PC-3 tumors, which was confirmed by ex vivo biodistribution data (7.87±2.37 and 0.54±0.22 ID%/g at 1 h in 22Rv1 and PC-3 tumors, respectively). The uptake of Al¹⁸F-PSMA-BCH in 22Rv1 tumors can be substantially blocked by excess ZJ-43, a PSMA inhibitor. High-level accumulation of Al¹⁸F-PSMA-BCH was observed in PSMA-expressing organs, with increased uptake at later time points. Thirty-seven tumor lesions were detected in 11 patients, and the SUV_max in 27 lesions increased between 1 h and 2 h p.i. (10.60 vs. 14.11). The SUV_max in primary lesions in patients with high-risk prostate cancer was higher than that in patients with intermediate-risk prostate cancer. The kidneys received the highest estimated dose of 0.135 mGy/MBq, and the effective dose was calculated as 0.016 mGy/MBq. Conclusion: Al¹⁸F-PSMA-BCH was conveniently prepared with a reasonable yield within 30 min and showed a promising imaging capability for prostate cancer with proper radiation exposure. Al¹⁸F-PSMA-BCH can be used for prostate cancer imaging as a novel ¹⁸F PET radiotracer.

The purpose of this study was to investigate the feasibility and diagnostic efficacy of ⁶⁸Ga-prostate-specific membrane antigen (PSMA) PET/CT combined with PET/ultrasound-guided biopsy in the diagnosis of prostate cancer (PCa). Methods: In total, 31 patients with a previously negative prostate biopsy but persistent elevated serum prostate-specific antigen (PSA) were imaged with a ⁶⁸Ga-PSMA PET/CT ligand before undergoing repeat prostate biopsy. On the basis of the proposed Prostate Cancer Molecular Imaging Standardized Evaluation criteria, ⁶⁸Ga-PSMA PET/CT results were interpreted as negative (molecular-imaging-for-PSMA expression score [miPSMA-ES] of 0–1) or positive (miPSMA-ES of 2–3). All patients underwent standard template systematic biopsy with up to 4 additional PET/ultrasound-guided biopsy cores. The sensitivity, specificity, positive and negative predictive values, and accuracy of ⁶⁸Ga-PSMA PET/CT were determined. In addition, the correlation between the miPSMA-ES and the detection rate of PCa was also analyzed. Univariate logistic regression models were established using ⁶⁸Ga-PSMA PET/CT semiquantitative analysis parameters to predict the outcome of repeat prostate biopsy. Results: The median age of patients was 65 y (range, 53–81 y), and the median PSA level was 18.0 ng/mL (range, 5.48–49.77 ng/mL). PCa was detected in 15 of 31 patients (48.4%), and 12 of 31 patients (38.7%) had clinically significant PCa (csPCa). The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of ⁶⁸Ga-PSMA PET/CT in the diagnosis of csPCa were 100.0%, 68.4%, 66.7%, 100.0%, and 80.6%, respectively. The detection rate of PCa increased with the increase in miPSMA-ES. The detection rates of csPCa in the miPSMA-ES 0–1, 2, and 3 groups were 0%, 54.5%, and 85.7%, respectively. Semiquantitative analysis of ⁶⁸Ga-PSMA PET/CT images showed that predictive models based on the SUV_max of prostate lesion, tumor–to–normal-prostate background SUV_max, and tumor–to–normal-liver background SUV_max could effectively predict csPCa; area under the curves were 0.930, 0.877, and 0.956, respectively. Conclusion: This study preliminarily confirmed that ⁶⁸Ga-PSMA PET/CT imaging, combined with PET/ultrasound-guided prostate biopsy, can effectively detect csPCa. Prebiopsy ⁶⁸Ga-PSMA PET/CT had predictive value for csPCa in the studied patient population.

Accurately identifying patients who respond to immunotherapy remains clinically challenging. A noninvasive method that can longitudinally capture information about immune cell function and assist in the early assessment of tumor responses is highly desirable for precision immunotherapy. Here, we show that PET imaging using a granzyme B–targeted radiotracer named ⁶⁸Ga-grazytracer, could noninvasively and effectively predict tumor responses to immune checkpoint inhibitors and adoptive T cell transfer therapy in multiple tumor models. ⁶⁸Ga-grazytracer was designed and selected from several radiotracers based on non-aldehyde peptidomimetics, and exhibited excellent in vivo metabolic stability and favorable targeting efficiency to granzyme B secreted by effector CD8⁺ T cells during immune responses. ⁶⁸Ga-grazytracer permitted more sensitive discrimination of responders and nonresponders than did ¹⁸F-fluorodeoxyglucose, distinguishing between tumor pseudoprogression and true progression upon immune checkpoint blockade therapy in mouse models with varying immunogenicity. In a preliminary clinical trial with 5 patients, no adverse events were observed after ⁶⁸Ga-grazytracer injection, and clinical responses in cancer patients undergoing immunotherapy were favorably correlated with ⁶⁸Ga-grazytracer PET results. These results highlight the potential of ⁶⁸Ga-grazytracer PET to enhance the clinical effectiveness of granzyme B secretion–related immunotherapies by supporting early response assessment and precise patient stratification in a noninvasive and longitudinal manner.