A Bioorthogonal Decaging Chemistry of N-Oxide and Silylborane for Prodrug Activation both In Vitro and In Vivo

Novel Light-Promoted Bioorthogonal Reaction via Molecular Recombination for the Synthesis of Polysubstituted Pyrrole and Its Application in In Vitro and In Vivo Studies

Bioorthogonal chemistry has revolutionized organic, medicinal, and biochemical research by designing and developing selective and rapid reactions that do not interfere with biological processes. Despite significant advancements, the existing bioorthogonal reactions can normally introduce only one functional group to a biomolecule, limiting their versatility in biological systems. In this study, we report a novel light-promoting reaction, namely light-promoted bioorthogonal multifunctionalized molecular recombination (LBMR) reaction, that can facilitate the synthesis of polysubstituted pyrroles via molecular editing and recombination of isoxazole-3-carboxylate and isoxazole-3-carboxylic acid derivatives. The proposed LBMR reaction exhibited rapid kinetics, high efficiency, wide substrate scope, and the potential for in situ fluorescence imaging under normal physiological conditions without the need for a catalyst. The LBMR reaction allowed incorporating multiple functional groups and using well-soluble carboxylic salts as bioorthogonal substrates. The in vitro experiments performed in different types of cells and the in vivo studies performed on zebrafish demonstrated the potential applicability of the proposed LBMR for biological imaging. This work not only introduces a new photo-bioorthogonal reaction paradigm but also expands the scope of bioorthogonal chemistry, paving the way for future applications in biomedical research.

Advances in the Delivery, Activation and Therapeutics Applications of Bioorthogonal Prodrugs

Traditional prodrug strategies have been leveraged to overcome many inherent drawbacks of active native drugs in the drug research and development. However, endogenous stimuli such as specific microenvironment or enzymes are relied on to achieve the prodrug activation, resulting in unintended drug release and systemic toxicity. Alternatively, bioorthogonal cleavage reaction-enabled bioorthogonal prodrugs activation via exogenous triggers has emerged as a valuable approach, featuring spatiotemporally controlled drug release. Such bioorthogonal prodrug strategies would ensure targeted drug delivery and/or in situ generation, further circumventing systemic toxicity or premature elimination of active drugs. In recent years, metal-free bioorthogonal cleavage reactions with fast kinetics have boomed in the bioorthogonal prodrug design. Meanwhile, transition-metal-catalyzed and photocatalytic deprotection reactions have also been developed to trigger prodrug activation in biological systems. Besides traditional small molecule prodrugs, gasotransmitters have been successfully delivered to specific organelles or cells via bioorthogonal reactions, and nanosystems have been devised into bioorthogonal triggers as well. Herein, we present an overview of the latest advances in these bioorthogonally-uncaged prodrugs, focused on the delivery, activation and therapeutics applications.

In Vivo Self-Assembly of PROTACs by Bioorthogonal Chemistry for Precision Cancer Therapy

Proteolysis targeting chimeras (PROTACs) hold immense promise for targeted protein degradation; however, challenges such as off-target effects, poor drug-likeness properties, and the "hook effect" remain. This study introduces Nano-Click-formed PROTACs (Nano-CLIPTACs) for precise tumor protein degradation in vivo. Traditional PROTACs with high molecular weight were first divided into two smaller druglike precursors capable of self-assembling to form functional PROTACs through a bioorthogonal reaction. Then, optimal CLIPTACs precursors (W4 and Z2) were encapsulated individually into cyclic RGDfC-peptide-modified liposomes to prepare Nano-CLIPTACs, enabling tumor-targeted delivery and subsequent in situ self-assembly to form PROTACs WZ42 within tumor cells. The degradation abilities of Nano-CLIPTACs in vitro and in vivo were further verified using a key oncology target, anaplastic lymphoma kinase (ALK), validating the safety, efficacy and "anti-hook effect" of this strategy. Overall, Nano-CLIPTACs represent a critical step towards the clinical translation of PROTACs technology for precise targeted anti-cancer therapies.

Transcytosis-Triggering Nanoparticles for Overcoming Stromal Barriers and Reversing Immunosuppression in Pancreatic Cancer Combinatorial Therapy

In pancreatic ductal adenocarcinoma (PDAC), stromal cells and matrix proteins form a dense physical barrier that, while preventing the outward spread of tumor cells, also limits the penetration of drugs and CD8+ T cells inward. Additionally, the overactivated TGF-β/SMAD signaling pathway further promotes matrix proliferation and immune suppression. Therefore, crossing the stromal barrier while preserving the integrity of the stroma, releasing drugs intratumorally, remodeling the stroma, and activating the immune system is a promising drug delivery strategy. In this work, a type of enamine N-oxides modified nanoparticle was prepared, with stearic acid-modified gemcitabine prodrug (GemC18) and pSMAD2/3 inhibitor galunisertib encapsulated. The peripheral enamine N-oxides can trigger transcytosis and then respond to hypoxia and acidic microenvironments, turning the surface charge of the nanoparticles to a positive charge and enhancing penetration. The released galunisertib inhibits the TGF-β/SMAD signaling pathway, reshapes the matrix, activates antitumor immunity, and combines with gemcitabine (Gem) to kill tumor cells.

Drugs from drugs: New chemical insights into a mature concept

Developing new drugs from marketed ones is a well-established and successful approach in drug discovery. We offer a unified view of this field, focusing on the new chemical aspects of the involved approaches: (a) chemical transformation of the original drugs (late-stage modifications, molecular editing), (b) prodrug strategies, and (c) repurposing as a tool to develop new hits/leads. Special focus is placed on the molecular structure of the drugs and their synthetic feasibility. The combination of experimental advances and new computational approaches, including artificial intelligence methods, paves the way for the evolution of the drugs from drugs concept.

Bioorthogonal chemistry-based prodrug strategies for enhanced biosafety in tumor treatments: current progress and challenges

Cancer is a significant global health challenge, and while chemotherapy remains a widely used treatment, its non-specific toxicity and broad distribution can lead to systemic side effects and limit its effectiveness against tumors. Therefore, the development of safer chemotherapy alternatives is crucial. Prodrugs hold great promise, as they remain inactive until they reach the cancer site, where they are selectively activated by enzymes or specific factors, thereby reducing side effects and improving targeting. However, subtle differences in the microenvironments between tumors and normal tissue may still result in unintended cytotoxicity. Bioorthogonal reactions, known for their selectivity and precision without interfering with natural biochemical processes, are gaining attention. When combined with prodrug strategies, these reactions offer the potential to create highly effective chemotherapy drugs. This review examines the safety and efficacy of prodrug strategies utilizing various bioorthogonal reactions in cancer treatment.

A Highly Atom-Efficient Prodrug Approach to Generate Synergy between H2S and Nonsteroidal Anti-inflammatory Drugs and Improve Safety

Efforts to synergize hydrogen sulfide (H2S) with NSAIDs have faced challenges due to complex structural entities and independent release kinetics. This study presents a highly atom-efficient approach of using a thiocarboxylic acid (thioacid) as a novel H2S releasing precursor and successfully employs it to modify NSAIDs, which offers several critical advantages. First, thioacid-modified NSAID is active in inhibiting cyclooxygenase, sometimes with improved potency. Second, this prodrug approach avoids introducing extra structural moieties, allowing for the release of only the intended active principals. Third, the release of H2S and NSAID is concomitant, thus optimally synchronizing the concentration profiles of the two active principals. The design is based on our discovery that esterases can directly and efficiently hydrolyze thiocarboxylic acids, enabling controlled release H2S. This study demonstrates the proof of principle through synthesizing analogs, assesses release kinetics, enzyme inhibition, and pharmacological efficacy, and evaluates toxicity and gut microbiota regulation in animal models.

Click Chemistry: Reaction Rates and Their Suitability for Biomedical Applications

Click chemistry has become a commonly used synthetic method due to the simplicity, efficiency, and high selectivity of this class of chemical reactions. Since their initial discovery, further click chemistry methods have been identified and added to the toolbox of click chemistry reactions for biomedical applications. However, selecting the most suitable reaction for a specific application is often challenging, as multiple factors must be considered, including selectivity, reactivity, biocompatibility, and stability. Thus, this review provides an overview of the benefits and limitations of well-established click chemistry reactions with a particular focus on the importance of considering reaction rates, an often overlooked criterion with little available guidance. The importance of understanding each click chemistry reaction beyond simply the reaction speed is discussed comprehensively with reference to recent biomedical research which utilized click chemistry. This review aims to provide a practical resource for researchers to guide the selection of click chemistry classes for different biomedical applications.

Bioorthogonal Bond Cleavage Chemistry for On-demand Prodrug Activation: Opportunities and Challenges

Time- and space-resolved drug delivery is highly demanded for cancer treatment, which, however, can barely be achieved with a traditional prodrug strategy. In recent years, the prodrug strategy based on a bioorthogonal bond cleavage chemistry has emerged with the advantages of high temporospatial resolution over drug activation and homogeneous activation irrespective of individual heterogeneity. In the past five years, tremendous progress has been witnessed in this field with one such bioorthogonal prodrug entering Phase II clinical trials. This Perspective aims to highlight these new advances (2019-2023) and critically discuss their pros and cons. In addition, the remaining challenges and potential strategic directions for future progress will also be included.