Beyond Small Molecules: Antibodies and Peptides for Fibroblast Activation Protein Targeting Radiopharmaceuticals

Sulphostin-inspired N-phosphonopiperidones as selective covalent DPP8 and DPP9 inhibitors

Covalent chemical probes and drugs combine unique pharmacologic properties with the availability of straightforward compound profiling technologies via chemoproteomic platforms. These advantages have fostered the development of suitable electrophilic "warheads" for systematic covalent chemical probe discovery. Despite undisputable advances in the last years, the targeted development of proteome-wide selective covalent probes remains a challenge for dipeptidyl peptidase (DPP) 8 and 9 (DPP8/9), intracellular serine hydrolases of the pharmacologically relevant dipeptidyl peptidase 4 activity/structure homologues (DASH) family. Here, we show the exploration of the natural product Sulphostin, a DPP4 inhibitor, as a starting point for DPP8/9 inhibitor development. The generation of Sulphostin-inspired N-phosphonopiperidones leads to derivatives with improved DPP8/9 inhibitory potency, an enhanced proteome-wide selectivity and confirmed DPP8/9 engagement in cells, thereby representing that structural fine-tuning of the warhead's leaving group may represent a straightforward strategy for achieving target selectivity in exoproteases such as DPPs.

Determining the Multivalent Effects of d-Peptide-Based Radiotracers

Dextrorotary (d) peptides, composed of d-amino acids, are hyper-resistant to proteolytic hydrolysis, making them valuable ligands with excellent in vivo stability for radiopharmaceutical development. Multimerization is a well-established strategy for enhancing the in vivo performance of l-peptide-based radiopharmaceuticals. However, the effect of multimerization on the in vivo fate of d-peptide-based radiopharmaceuticals remains largely unexplored. Here, we synthesized the d-peptide DPA, which targets PD-L1, along with its dimer (DP2) and trimer (DP3). PET/CT imaging and ex vivo biodistribution studies were performed to delineate the pharmacokinetics and target interactions of [68Ga]DPA, [68Ga]DP2, and [68Ga]DP3 in both normal and tumor-bearing mice. Our results revealed that tumor uptake and kidney retention increased with higher valency ([68Ga]DP3 > [68Ga]DP2 > [68Ga]DPA). No significant differences were observed in the liver, heart, lung, spleen, intestine, or bone among the three radiotracers. Interestingly, a significant reduction of radioactivity in the bloodstream was detected for the [68Ga]DP3-treated group compared to the other two groups. Data analysis revealed that chiral configuration of amino acids and the linking chemistry used in multimerization are the two dominant factors in the in vivo fate of d-peptide multimers. These findings indicate that d-peptide multimerization exerts a distinct influence on in vivo profiles compared to l-peptide multimerization. This study deepens our understanding of how mirror-imaged peptides/proteins interact with the living systems, paving the way for the development of radiopharmaceuticals that harness d-peptides as targeting moieties.

Drug Delivery System Targeting Cancer-Associated Fibroblast for Improving Immunotherapy

Cancer-associated fibroblasts (CAFs) are a heterogeneous population of non-malignant cells that play a crucial role in the tumor microenvironment, increasingly recognized as key contributors to cancer progression, metastasis, and treatment resistance. So, targeting CAFs has always been considered an important part of cancer immunotherapy. However, targeting CAFs to improve the efficacy of tumor therapy is currently a major challenge. Nanomaterials show their unique advantages in the whole process. At present, nanomaterials have achieved significant accomplishments in medical applications, particularly in the field of cancer-targeted therapy, showing enormous potential. It has been confirmed that nanomaterials can not only directly target CAFs, but also interact with the tumor microenvironment (TME) and immune cells to affect tumorigenesis. As for the cancer treatment, nanomaterials could enhance the therapeutic effect in many ways. Therefore, in this review, we first summarized the current understanding of the complex interactions between CAFs and TME, immune cells, and tumor cells. Next, we discussed common nanomaterials in modern medicine and their respective impacts on the TME, CAFs, and interactions with tumors. Finally, we focus on the application of nano drug delivery system targeting CAFs in cancer therapy.

Radiopharmaceuticals and their applications in medicine

Radiopharmaceuticals involve the local delivery of radionuclides to targeted lesions for the diagnosis and treatment of multiple diseases. Radiopharmaceutical therapy, which directly causes systematic and irreparable damage to targeted cells, has attracted increasing attention in the treatment of refractory diseases that are not sensitive to current therapies. As the Food and Drug Administration (FDA) approvals of [177Lu]Lu-DOTA-TATE, [177Lu]Lu-PSMA-617 and their complementary diagnostic agents, namely, [68Ga]Ga-DOTA-TATE and [68Ga]Ga-PSMA-11, targeted radiopharmaceutical-based theranostics (radiotheranostics) are being increasingly implemented in clinical practice in oncology, which lead to a new era of radiopharmaceuticals. The new generation of radiopharmaceuticals utilizes a targeting vector to achieve the accurate delivery of radionuclides to lesions and avoid off-target deposition, making it possible to improve the efficiency and biosafety of tumour diagnosis and therapy. Numerous studies have focused on developing novel radiopharmaceuticals targeting a broader range of disease targets, demonstrating remarkable in vivo performance. These include high tumor uptake, prolonged retention time, and favorable pharmacokinetic properties that align with clinical standards. While radiotheranostics have been widely applied in tumor diagnosis and therapy, their applications are now expanding to neurodegenerative diseases, cardiovascular diseases, and inflammation. Furthermore, radiotheranostic-empowered precision medicine is revolutionizing the cancer treatment paradigm. Diagnostic radiopharmaceuticals play a pivotal role in patient stratification and treatment planning, leading to improved therapeutic outcomes in targeted radionuclide therapy. This review offers a comprehensive overview of the evolution of radiopharmaceuticals, including both FDA-approved and clinically investigated agents, and explores the mechanisms of cell death induced by radiopharmaceuticals. It emphasizes the significance and future prospects of theranostic-based radiopharmaceuticals in advancing precision medicine.