An overview of current advances of PD-L1 targeting immuno-imaging in cancers

68Ga-Labeled Peptide for Noninvasive Quantifying Tumor Exposure of PD-L1 Therapeutics

PURPOSE

Targeting the programmed death protein 1/programmed death-ligand 1 (PD-1/PD-L1) immune checkpoint blockade therapy plays a critical role in cancer therapy. However, not all patients benefit from this approach, with PD-L1 expression levels being a significant contributing factor. Positron emission tomography (PET) imaging of PD-L1 offers a noninvasive, whole-body, and dynamic assessment of its expression. This study aims to develop a novel peptide-based PD-L1 tracer, [68Ga]HF12, to quantitatively evaluate PD-L1 expression in tumors, thereby offering clinical guidance.

METHODS

HF12 was successfully synthesized and radiolabeled with 68Ga to yield [68Ga]HF12. In vitro binding assays confirmed the specific binding affinity of HF12 for PD-L1 using CHO-hPD-L1 and CHO cell lines. Subsequent in vivo positron emission tomography (PET) imaging and biodistribution studies assessed [68Ga]HF12 for monitoring PD-L1 expression levels in tumor-bearing mice, including those subjected to immunotherapy. Furthermore, PD-L1 expression in tumor tissues was evaluated by using autoradiography, Western blotting, and immunohistochemical (IHC) analysis.

RESULTS

The synthesis of [68Ga]HF12 was successfully achieved with a radiochemical purity and yield exceeding 95%. Cellular uptake studies indicated that [68Ga]HF12 demonstrated both high specificity and significant uptake in PD-L1-positive CHO-hPD-L1 cells. Micro-PET imaging and biodistribution studies revealed that [68Ga]HF12 was preferentially accumulated in CHO-hPD-L1 tumors compared to PD-L1-negative CHO tumors. Treatment with Atezolizumab resulted in a significant reduction in [68Ga]HF12 uptake in CHO-hPD-L1 tumors relative to pretreatment levels, whereas no significant changes were observed in the phosphate-buffered saline (PBS) control group. Subsequent biodistribution studies, along with Western blotting and immunohistochemical analyses, confirmed that PD-L1 expression levels in tumors were reduced following immunotherapy, consistent with the results obtained from PET imaging.

CONCLUSIONS

[68Ga]HF12 was successfully synthesized as a radiotracer for noninvasive quantitative PET imaging of PD-L1 expression levels. This radiotracer exhibited the potential to quantify PD-L1 expression across various tumors, thereby facilitating the prediction of patient response to anti-PD-1 and anti-PD-L1 immunotherapies and monitoring therapeutic efficacy.

Preclinical and first‑in‑human evaluation of [68Ga]Ga-DOTA-PEG2-Asp2-PDL1P PET imaging to assess tumor PD-L1 expression

PURPOSE

PD-L1 PET imaging can provide a non-invasively and real-time assessment of PD-L1 expression status at tumor sites. This study aimed to evaluate the targeting efficacy and biodistribution of a novel peptide-based PD-L1 PET agent, [68Ga]Ga-DOTA-PEG2-Asp2-PDL1P, in preclinical studies and human participants.

METHODS

[68Ga]Ga-DOTA-PEG2-Asp2-PDL1P was synthesized and the probe stability was analyzed in vitro and in vivo. Cellular uptake of the probe was evaluated using tumor cell lines with different PD-L1 expression levels. Small animal PET imaging and semi-quantitative studies were conducted in PC3, H1975 and A549 tumor-bearing mice models, with tumor PD-L1 expression confirmed through immunofluorescence and immunohistochemistry. Furthermore, [68Ga]Ga-DOTA-PEG2-Asp2-PDL1P PET imaging was performed in 1 healthy volunteer and 14 lung cancer patients to assess biodistribution and PD-L1 expression at tumor sites.

RESULTS

[68Ga]Ga-DOTA-PEG2-Asp2-PDL1P exhibited a radiochemical purity of > 99% and had good stability both in vitro and in vivo. In vitro cellular uptake and in vivo small animal PET imaging revealed the probe binding to PD-L1 with high affinity and specificity, consistent with the results of immunofluorescence and immunohistochemistry. In the clinical study involving 15 participants, [68Ga]Ga-DOTA-PEG2-Asp2-PDL1P was proven safe with demonstrating low uptake in normal organs and physiologically excreting via the urinary system. Lung cancer patients with high PD-L1 expression (TPS 70-90%) exhibited higher tumor uptake and tumor-to-background ratios than those with negative or low PD-L1 expression (TPS < 1-10%), with SUVmax of 1.89-2.27 vs. 0.87-1.01, tumor-to-lung ratios of 4.73-7.68 vs. 1.61-2.35, and tumor-to-muscle ratios of 6.73-12.61 vs. 4.35-5.61.

CONCLUSION

[68Ga]Ga-DOTA-PEG2-Asp2-PDL1P showed promising as a PET agent to assess tumor PD-L1 expression in preclinical and first-in-human studies, offering a non-invasive, real-time and accurate tool to address clinical challenges in predicting and assessing the efficacy of immunotherapy.

Clinical features and prognosis analysis of stage III/IV patients with lung cancer after treatment with toripalimab: A real-world retrospective

AIM

Toripalimab is the first antitumor programmed cell death protein 1 (PD-1) antibody approved in China. For better patient management, it is important to understand the real-world outcomes of toripalimab in treating patients with lung cancer in the real world outside of clinical trials to improve patient care.

METHODS

We retrospectively examined the clinical data of 80 patients with lung cancer who received the PD-1 inhibitor (toripalimab). The Chi-square test was performed to identify clinical factors associated with the advancement of the disease. Multivariate Cox regression analysis was used to screen prognostic variables linked to real-world progression-free survival (PFS) and overall survival (OS). OS and PFS were calculated using the Kaplan-Meier method, and the comparisons were determined using the log-rank test, and continuous and categorical variables were explained using median and percentage, respectively.

RESULT

The median OS of the estimated 80 patients was 15.85 months (95% confidence interval [CI]: 14.103-17.949 months), and the estimated PFS was 5.650 months (95% CI: 7.226-11.264 months). The longer OS and PFS correlate with the patient's staging and number of treatment lines. The PD-1 drug gave stage III patients a significantly longer PFS and OS compared to stage IV patients (PFS: 14.65 vs. 6.68, P = 0.004; OS: 21.1 vs. 13.7, P = 0.003). First- or second-line immunotherapy patients have significantly longer PFS and OS than third- or fourth-line (PFS: 6.4 vs. 3.6, P = 0.009; OS: 20.0 vs. 10.5, P = 0.003). In patients with stage IV (n = 60) with extensive metastasis, the site of metastasis is mostly 1-3 sites after receiving toripalimab. The duration of PD-1 inhibitor OS in progressive patients (n = 56) was significantly prolonged (P = 0.038).

CONCLUSION

For patients with lung cancer, toripalimab can considerably extend PFS and OS in the first or second line and in stage III. PD-1 inhibitors are administered to patients with stage IV extensively metastatic lung cancer, which indicates an oligometastatic progression pattern, primarily in 1-3 locations, who are treated with PD-1 inhibitors. Continuing toripalimab beyond disease progression significantly prolonged OS.

Targeting anticancer immunity in melanoma tumour microenvironment: unleashing the potential of adjuvants, drugs, and phytochemicals

Melanoma poses a challenge in oncology because of its aggressive nature and limited treatment modalities. The tumour microenvironment (TME) in melanoma contains unique properties such as an immunosuppressive and high-density environment, unusual vasculature, and a high number of stromal and immunosuppressive cells. In recent years, numerous experiments have focused on boosting the immune system to effectively remove malignant cells. Adjuvants, consisting of phytochemicals, toll-like receptor (TLR) agonists, and cytokines, have shown encouraging results in triggering antitumor immunity and augmenting the therapeutic effectiveness of anticancer therapy. These adjuvants can stimulate the maturation of dendritic cells (DCs) and infiltration of cytotoxic CD8+ T lymphocytes (CTLs). Furthermore, nanocarriers can help to deliver immunomodulators and antigens directly to the tumour stroma, thereby improving their efficacy against malignant cells. The remodelling of melanoma TME utilising phytochemicals, agonists, and other adjuvants can be combined with current modalities for improving therapy outcomes. This review article explores the potential of adjuvants, drugs, and their nanoformulations in enhancing the anticancer potency of macrophages, CTLs, and natural killer (NK) cells. Additionally, the capacity of these agents to repress the function of immunosuppressive components of melanoma TME, such as immunosuppressive subsets of macrophages, stromal and myeloid cells will be discussed.

Preliminary Research of Radiolabeled Atezolizumab for the Noninvasive Evaluation of TNBC PD-L1 Expression In Vivo

Programmed death-ligand 1 (PD-L1) expression is related to the efficacy and prognosis in triple-negative breast cancer. This study employed an indirect labeling method to synthesize [125I]PI-Atezolizumab. The in vitro stability of [125I]PI-Atezolizumab was assessed through incubation in phosphate buffered saline and fetal bovine serum, revealing sustained stability. Specific binding of [125I]PI-Atezolizumab to MDA-MB-231 cells expressing humanized PD-L1 was assessed through in vitro incubation, yielding a Kd value comparable to that of Atezolizumab. This suggests that the labeling process did not compromise the affinity of the Atezolizumab to PD-L1. Subsequently, pharmacokinetic studies were conducted in normal mice and biodistribution experiments in tumor-bearing mice. A comparison of the biodistribution results between [125I]PI-Atezolizumab and 125I-labeled Atezolizumab indicated better in vivo stability for the former. Single photon emission computed tomography (SPECT)/CT imaging further confirmed the targeted specificity of [125I]PI-Atezolizumab for PD-L1 in MDA-MB-231 xenografts, which were validated by immunohistochemistry staining. This research underscores the utility of [125I]PI-Atezolizumab, prepared via indirect labeling, for monitoring PD-L1 in triple-negative breast cancer models.

Toripalimab plus chemotherapy in the treatment of metastatic triple-negative breast cancer: a cost-effectiveness analysis

Objective

This study focuses on assessing the cost-effectiveness of incorporating toripalimab alongside chemotherapy for the treatment of patients diagnosed with metastatic triple-negative breast cancer from the perspective of the Chinese healthcare system.

Methods

A partitioned survival model was constructed to simulate the costs and health outcomes over the lifetime of patients with mTNBC. Clinical data regarding overall survival, progression-free survival, and treatment-related adverse events were derived from the TORCHLIGHT clinical trials. Incremental cost-effectiveness ratio (ICER) were calculated based on the gains in quality-adjusted life-year (QALY). The willingness-to-pay (WTP) threshold was defined as $39,855.79 per QALY. Additionally, sensitivity analyses were conducted to examine the robustness of the model.

Results

The total cost incurred by the group receiving toripalimab was $38,040.62, while the placebo plus chemotherapy was $26,102.07. The utilization of the toripalimab regimen resulted in an increase of 0.74 QALYs and an incremental cost of $11,938.55 compared to the placebo plus chemotherapy group. The ICER was $16,133.18/QALY, indicating that toripalimab plus chemotherapy is a cost-effective strategy according to the WTP threshold. Sensitivity analyses confirmed the robustness of the results.

Conclusion

This study suggests that the addition of toripalimab to chemotherapy for the treatment of mTNBC is a cost-effective strategy. The findings provide valuable evidence to guide decision-making regarding treatment selection for patients with mTNBC in China.

Navigating the landscape of PD-1/PD-L1 imaging tracers: from challenges to opportunities

Immunotherapy targeted to immune checkpoint inhibitors, such as the program cell death receptor (PD-1) and its ligand (PD-L1), has revolutionized cancer treatment. However, it is now well-known that PD-1/PD-L1 immunotherapy response is inconsistent among patients. The current challenge is to customize treatment regimens per patient, which could be possible if the PD-1/PD-L1 expression and dynamic landscape are known. With positron emission tomography (PET) imaging, it is possible to image these immune targets non-invasively and system-wide during therapy. A successful PET imaging tracer should meet specific criteria concerning target affinity, specificity, clearance rate and target-specific uptake, to name a few. The structural profile of such a tracer will define its properties and can be used to optimize tracers in development and design new ones. Currently, a range of PD-1/PD-L1-targeting PET tracers are available from different molecular categories that have shown impressive preclinical and clinical results, each with its own advantages and disadvantages. This review will provide an overview of current PET tracers targeting the PD-1/PD-L1 axis. Antibody, peptide, and antibody fragment tracers will be discussed with respect to their molecular characteristics and binding properties and ways to optimize them.

ICG-labeled PD-L1-antagonistic affibody dimer for tumor imaging and enhancement of tumor photothermal-immunotherapy

In clinical practice, tumor-targeting diagnosis and immunotherapy against programmed death ligand 1 (PD-L1) have a significant impact. In this research, a PD-L1-antagonistic affibody dimer (ZPD-L1) was successfully prepared through Escherichia coli expression system, and conjugated with the photosensitizer of ICG via N-hydroxysuccinimide (NHS) ester to develop a novel tumor-targeting agent (ICG-ZPD-L1) for both tumor imaging diagnosis and photothermal-immunotherapy simultaneously. In vitro, ZPD-L1 could specifically bind to PD-L1-positive LLC and MC38 tumor cells, and ICG-ZPD-L1-mediated photothermal therapy (PTT) also showed excellent phototoxicity to these tumor cells. In vivo, ICG-ZPD-L1 selectively enriched into the PD-L1-positive MC38 tumor tissues, and the high-contrast optical imaging of tumors was obtained. ICG-ZPD-L1-mediated PTT exhibited a potent anti-tumor effect in vivo due to its remarkable photothermal properties. Furthermore, ICG-ZPD-L1-mediated PTT significantly induced the immunogenic cell death (ICD) of primary tumors, promoted maturation of dendritic cells (DCs), up-regulated anti-tumor immune response, enhanced immunotherapy, and superiorly inhibited the growth of metastatic tumors. In addition, ICG-ZPD-L1 showed favorable biosafety throughout the brief duration of treatment. In summary, these results suggest that ICG-ZPD-L1 is a multifunctional tumor-targeting drug integrating tumor imaging diagnosis and photothermal-immunotherapy, and has great guiding significance for the diagnosis and treatment of clinical PD-L1-positive tumor patients.

New advances in the treatment of chondrosarcoma under the PD-1/PD-L1 pathway

ABSTRACT

Bone sarcomas encompass a group of spontaneous mesenchymal malignancies, among which osteosarcoma, Ewing sarcoma, chondrosarcoma, and chordoma are the most common subtypes. Chondrosarcoma, a relatively prevalent malignant bone tumor that originates from chondrocytes, is characterized by endogenous cartilage ossification within the tumor tissue. Despite the use of aggressive treatment approaches involving extensive surgical resection, chemotherapy, and radiotherapy for patients with osteosarcoma, chondrosarcoma, and chordoma, limited improvements in patient outcomes have been observed. Furthermore, resistance to chemotherapy and radiation therapy has been observed in chondrosarcoma and chordoma cases. Consequently, novel therapeutic approaches for bone sarcomas, including chondrosarcoma, need to be uncovered. Recently, the emergence of immunotherapy and immune checkpoint inhibitors has garnered attention given their clinical success in various diverse types of cancer, thereby prompting investigations into their potential for managing chondrosarcoma. Considering that circumvention of immune surveillance is considered a key factor in the malignant progression of tumors and that immune checkpoints play an important role in modulating antitumor immune effects, blockers or inhibitors targeting these immune checkpoints have become effective therapeutic tools for patients with tumors. One such checkpoint receptor implicated in this process is programmed cell death protein-1 (PD-1). The association between PD-1 and programmed cell death ligand-1 (PD-L1) and cancer progression in humans has been extensively studied, highlighting their remarkable potential as biomarkers for cancer treatment. This review comprehensively examines available studies on current chondrosarcoma treatments and advancements in anti-PD-1/PD-L1 blockade therapy for chondrosarcoma.