Development of programmable gemcitabine-GnRH pro-drugs bearing linker controllable "click" oxime bond tethers and preclinical evaluation against prostate cancer

Recent progress in the development of peptide-drug conjugates (PDCs) for cancer therapy

Peptide-drug conjugates (PDCs) are emerging therapeutic agents composed of peptides, linkers, and payloads, which possess favorable targeting capability and can deliver enough payloads to the tumor sites with minimized impact on healthy tissues. However, only a few PDCs have been approved for clinical use so far. To advance the research on PDCs, this review summarizes the approved PDCs, and PDCs in clinical and preclinical stages based on the payload types. Additionally, the biological activity and pharmacokinetic properties of preclinical PDCs are detailedly described. Lastly, the challenges and future development directions of PDCs are discussed. This review aims to inspire insights into the development of PDCs for cancer treatment.

Design of pH-Responsive Nanomaterials Based on the Tumor Microenvironment

The metabolic activity of tumor cells leads to the acidification of the surrounding microenvironment, which provides new strategies for the application of nanotechnology in cancer therapy. Researchers have developed various types of pH-responsive nanomaterials based on the tumor acidic microenvironment. This review provides an in-depth discussion on the design mechanisms, drug-loading strategies, and application pathways of tumor acidic microenvironment-responsive nanodrug delivery systems. These materials trigger drug release upon reaching the tumor microenvironment, enhancing therapeutic targeting and reducing toxicity to healthy cells. pH-responsive nanomaterials include organic nanomaterials, inorganic nanomaterials, and composite nanomaterials. Additionally, this review outlines the drug-loading strategies, application prospects, and challenges of pH-responsive nanomaterials, aiming to promote the development and clinical translation of this field.

Peptides for microbe-induced cancers: latest therapeutic strategies and their advanced technologies

Cancer is a significant global health concern associated with multiple distinct factors, including microbial and viral infections. Numerous studies have elucidated the role of microorganisms, such as Helicobacter pylori (H. pylori), as well as viruses for example human papillomavirus (HPV), hepatitis B virus (HBV), and hepatitis C virus (HCV), in the development of human malignancies. Substantial attention has been focused on the treatment of these microorganism- and virus-associated cancers, with promising outcomes observed in studies employing peptide-based therapies. The current paper provides an overview of microbe- and virus-induced cancers and their underlying molecular mechanisms. We discuss an assortment of peptide-based therapies which are currently being developed, including tumor-targeting peptides and microbial/viral peptide-based vaccines. We describe the major technological advancements that have been made in the design, screening, and delivery of peptides as anticancer agents. The primary focus of the current review is to provide insight into the latest research and development in this field and to provide a realistic glimpse into the future of peptide-based therapies for microbe- and virus-induced neoplasms.

Engineering peptide drug therapeutics through chemical conjugation and implication in clinics

The development of peptide drugs has made tremendous progress in the past few decades because of the advancements in modification chemistry and analytical technologies. The novel-designed peptide drugs have been modified through various biochemical methods with improved diagnostic, therapeutic, and drug-delivery strategies. Researchers found it a helping hand to overcome the inherent limitations of peptides and bring continued advancements in their applications. Furthermore, the emergence of peptide-drug conjugates (PDCs)-utilizes target-oriented peptide moieties as a vehicle for cytotoxic payloads via conjugation with cleavable chemical agents, resulting in the key foundation of the new era of targeted peptide drugs. This review summarizes the various classifications of peptide drugs, suitable chemical modification strategies to improve the ADME (adsorption, distribution, metabolism, and excretion) features of peptide drugs, and recent (2015-early 2024) progress/achievements in peptide-based drug delivery systems as well as their fruitful implication in preclinical and clinical studies. Furthermore, we also summarized the brief description of other types of PDCs, including peptide-MOF conjugates and peptide-UCNP conjugates. The principal aim is to provide scattered and diversified knowledge in one place and to help researchers understand the pinching knots in the science of PDC development and progress toward a bright future of novel peptide drugs.

Design Principles and Applications of Fluorescent Kinase Inhibitors for Simultaneous Cancer Bioimaging and Therapy

Kinase inhibitors are potent therapeutic agents in cancer treatment, but their effectiveness is frequently restricted by the inability to image the tumor microenvironment. To address this constraint, kinase inhibitor-fluorophore conjugates have emerged as promising theranostic agents, allowing for simultaneous cancer diagnosis and treatment. These conjugates are gaining attention for their ability to visualize malignant tissues and concurrently enhance therapeutic interventions. This review explores the design principles governing the development of multimodal inhibitors, highlighting their potential as platforms for kinase tracking and inhibition via bioimaging. The structural aspects of constructing such theranostic agents are critically analyzed. This work could shed light on this intriguing field and provide adequate impetus for developing novel theranostic compounds based on small molecule inhibitors and fluorophores.

Hypoxia-Activated Theragnostic Prodrugs (HATPs): Current State and Future Perspectives

Hypoxia is a significant feature of solid tumors and frequently poses a challenge to the effectiveness of tumor-targeted chemotherapeutics, thereby limiting their anticancer activity. Hypoxia-activated prodrugs represent a class of bio-reductive agents that can be selectively activated in hypoxic compartments to unleash the toxic warhead and thus, eliminate malignant tumor cells. However, their applicability can be further elevated by installing fluorescent modalities to yield hypoxia-activated theragnostic prodrugs (HATPs), which can be utilized for the simultaneous visualization and treatment of hypoxic tumor cells. The scope of this review is to summarize noteworthy advances in recent HATPs, highlight the challenges and opportunities for their further development, and discuss their potency to serve as personalized medicines in the future.

Design, Synthesis, and Antitumor Evaluation of an Opioid Growth Factor Bioconjugate Targeting Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) presents a formidable challenge with high lethality and limited effective drug treatments. Its heightened metastatic potential further complicates the prognosis. Owing to the significant toxicity of current chemotherapeutics, compounds like [Met5]-enkephalin, known as opioid growth factor (OGF), have emerged in oncology clinical trials. OGF, an endogenous peptide interacting with the OGF receptor (OGFr), plays a crucial role in inhibiting cell proliferation across various cancer types. This in vitro study explores the potential anticancer efficacy of a newly synthesized OGF bioconjugate in synergy with the classic chemotherapeutic agent, gemcitabine (OGF-Gem). The study delves into assessing the impact of the OGF-Gem conjugate on cell proliferation inhibition, cell cycle regulation, the induction of cellular senescence, and apoptosis. Furthermore, the antimetastatic potential of the OGF-Gem conjugate was demonstrated through evaluations using blood platelets and AsPC-1 cells with a light aggregometer. In summary, this article demonstrates the cytotoxic impact of the innovative OGF-Gem conjugate on pancreatic cancer cells in both 2D and 3D models. We highlight the potential of both the OGF-Gem conjugate and OGF alone in effectively inhibiting the ex vivo pancreatic tumor cell-induced platelet aggregation (TCIPA) process, a phenomenon not observed with Gem alone. Furthermore, the confirmed hemocompatibility of OGF-Gem with platelets reinforces its promising potential. We anticipate that this conjugation strategy will open avenues for the development of potent anticancer agents.

Peptide-Drug Conjugates: Design, Chemistry, and Drug Delivery System as a Novel Cancer Theranostic

The emergence of peptide-drug conjugates (PDCs) that utilize target-oriented peptide moieties as carriers of cytotoxic payloads, interconnected with various cleavable/noncleavable linkers, resulted in the key-foundation of the new era of targeted therapeutics. They are capable of retaining the integrity of conjugates in the blood circulatory system as well as releasing the drugs at the tumor microenvironment. Other valuable advantages are specificity and selectivity toward targeted-receptors, higher penetration ability, and drug-loading capacity, making them a suitable candidate to play their vital role as promising carrier agents. In this review, we summarized the types of cell-targeting (CTPs) and cell-penetrating peptides (CPPs) that have broad applications in the advancement of targeted drug-delivery systems (DDS). Moreover, the techniques to overcome the limitations of peptide-chemistry for their extensive implementation to construct the PDCs. Besides this, the diversified breakthrough of linker chemistry, and ample knowledge of various cytotoxic payloads used in PDCs in recent years, as well as the mechanism of action of PDCs was critically discussed. The principal aim is to provide scattered and diversified knowledge in one place and to help researchers understand the pinching knots in the science of PDC development, also their progression toward a bright future for PDCs as novel theranostics in clinical practice.

Peptide-drug conjugates: A new paradigm for targeted cancer therapy

Peptide-drug conjugates (PDCs) are the new hope for targeted therapy after antibody-drug conjugates (ADCs). Compared with ADCs, the core advantages of PDCs are enhanced tissue penetration, easier chemical synthesis, and lower production costs. Two PDCs have been approved by the US Food and Drug Administration (FDA) for the treatment of cancer. The therapeutic effects of PDCs are remarkable, but PDCs also encounter problems when used as targeted therapeutics, such as poor stability, a short blood circulation time, a long research and development time frame, and a slow clinical development process. Therefore, it is very urgent and important to understand the latest research progress of cancer cells targeting PDC, the solution to its stability problem, the scheme of computer technology to assist its research and development, and the direction of its future development. In this manuscript, based on the structure and function of PDCs, the latest research progress on PDCs from the aspects of cancer cell-targeting peptide (CTP) selection, pharmacokinetic characteristics, stability regulation and so on were systematically reviewed, hoping to highlight the current problems and future development directions of PDCs.

Oxime-Linked Peptide-Daunomycin Conjugates as Good Tools for Selection of Suitable Homing Devices in Targeted Tumor Therapy: An Overview

Chemotherapy is still one of the main therapeutic approaches in cancer therapy. Nevertheless, its poor selectivity causes severe toxic side effects that, together with the development of drug resistance in tumor cells, results in a limitation for its application. Tumor-targeted drug delivery is a possible choice to overcome these drawbacks. As well as monoclonal antibodies, peptides are promising targeting moieties for drug delivery. However, the development of peptide-drug conjugates (PDCs) is still a big challenge. The main reason is that the conjugates have to be stable in circulation, but the drug or its active metabolite should be released efficiently in the tumor cells. For this purpose, suitable linker systems are needed that connect the drug molecule with the homing peptide. The applied linker systems are commonly categorized as cleavable and non-cleavable linkers. Both the groups possess advantages and disadvantages that are summarized briefly in this manuscript. Moreover, in this review paper, we highlight the benefit of oxime-linked anthracycline-peptide conjugates in the development of PDCs. For instance, straightforward synthesis as well as a conjugation reaction proceed in excellent yields, and the autofluorescence of anthracyclines provides a good tool to select the appropriate homing peptides. Furthermore, we demonstrate that these conjugates can be used properly in in vivo studies. The results indicate that the oxime-linked PDCs are potential candidates for targeted tumor therapy.

Metabolism investigation of the peptide-drug conjugate LN005 in rats using UHPLCHRMS

LN005, as a peptide-drug conjugate (PDC), is a conjugate of the homing peptide VAP and doxorubicin (DOX). The exceptional targeting ability of the homing peptide VAP is directed toward glucose-regulated protein (GRP78), a highly expressed protein primarily found in the endoplasmic reticulum of various solid tumors. However, there are limited reports regarding the metabolism of peptide-drug conjugates (PDCs), and the in vivo metabolism of LN005 has yet to be investigated. After intravenous injection of 18 mg/kg LN005 in SD rats, biological samples including plasma, urine, fecal, and bile samples, were collected and analyzed by ultra-high performance liquid chromatography-high resolution mass spectrometry (UHPLC-HRMS). A total of 11 possible metabolites of LN005 were identified. Unchanged LN005 was found to be the main component in rat blood and urine, accounting for 46.46% and 63.79% of the total peak areas, respectively. M1057 was the most abundant metabolite in feces, accounting for 57.65% of the total peak area. Only one metabolite, M398, was identified in rat bile. The metabolism of LN005 is closely related to DOX, and the primary metabolic pathways involved oxidative deamination or hydrolysis, reductive glycosidic cleavage, hydrolytic glycosidic cleavage, and dehydrogenation.

Is it still worth renewing nucleoside anticancer drugs nowadays?

Nucleoside has situated the convergence point in the discovery of novel drugs for decades, and a large number of nucleoside derivatives have been constructed for screening novel pharmacological properties at various experimental platforms. Notably, nearly 20 nucleosides are approved to be used in the clinic treatment of various cancers. Nevertheless, the blossom of synthetic nucleoside analogs in comparison with the scarcity of nucleoside anticancer drugs leads to a question: Is it still worth insisting on the screening of novel anticancer drugs from nucleoside derivatives? Hence, this review attempts to emphasize the importance of nucleoside analogs in the discovery of novel anticancer drugs. Firstly, we introduce the metabolic procedures of nucleoside anticancer drug (such as 5-fluorouracil) and summarize the designing of novel nucleoside anticancer candidates based on clinically used nucleoside anticancer drugs (such as gemcitabine). Furthermore, we collect anticancer properties of some recently synthesized nucleoside analogs, aiming at emphasizing the availability of nucleoside analogs in the discovery of anticancer drugs. Finally, a variety of synthetic strategies including the linkage of sugar moiety with nucleobase scaffold, modifications on the sugar moiety, and variations on the nucleobase structure are collected to exhibit the abundant protocols in the achievement of nucleoside analogs. Taken the above discussions collectively, nucleoside still advantages for the finding of novel anticancer drugs because of the clearly metabolic procedures, successfully clinic applications, and abundantly synthetic routines.

Metabolite characterisation of the peptide-drug conjugate LN005 in liver S9s by UHPLC-Orbitrap-HRMS

LN005 is a peptide-drug conjugate (PDC) targeting glucose-regulated protein 78 (GRP78) to treat several types of cancer, such as breast, colon, and prostate cancer.As a new drug modality, understanding its metabolism and elimination pathways will help us to have a whole picture of it. Currently, there are no metabolic studies on LN005; therefore, this study aimed to investigate the metabolism of LN005, clarify its metabolic profile in the liver S9s of different species, and identify the major metabolic pathways and differences between species.The incubation samples were measured by ultra-high performance liquid chromatography combined with orbitrap tandem mass spectrometry (UHPLC-Orbitrap-HRMS).The results showed that LN005 was metabolised by liver S9s, and four metabolites were identified. The main metabolic pathway of LN005 in liver S9s was oxidative deamination to ketone or hydrolysis. Similar metabolic profiles were observed in mouse, rat, dog, monkey, and human liver S9s, indicating no differences between these four animal species and humans.This study provides information for the structural modification and optimisation of LN005 and affords a reference for subsequent animal experiments and human metabolism of other PDCs.

Dual targeting pH responsive chitosan nanoparticles for enhanced active cellular internalization of gemcitabine in non-small cell lung cancer

Lung cancer (LC), related with the enhanced expression of epidermal growth factor receptor (EGFR) and sialic acid binding receptors (glycan) brought about the development of EGFR and glycan receptor specific anticancer therapeutics. The current study assessed the formulation, physiochemical characterization, in vitro and in vivo effects of sialic acid (SA) and cetuximab (Cxmab) decorated chitosan nanoparticles (CSN-NPs) loaded with gemcitabine (GMC) targeted to glycan and EGFR over-expressing non-small-cell lung-cancer (NSCLC) A-549 cells. Chitosan (CSN) was conjugated with sialic acid via EDC/NHS chemistry followed by gemcitabine loaded sialic acid conjugated chitosan nanoparticles (GMC-CSN-SA-NPs) were prepared by ionic gelation method decorated with Cxmab by electrostatic interaction. In vitro cytotoxicity of NPs quantified using cell based MTT, DAPI and Annexing-V/PI apoptosis assays showed superior antiproliferative activity of targeted nanoformulations (GMC-CSN-SA-Cxmab-NPs ≫ GMC-CSN-SA-NPs, GMC-CSN-Cxmab-NPs) over non-targeted nanoformulation (GMC-CSN-NPs) against A-549 cells. In vivopharmacokinetic study showed superior bioavailability and in vivo therapeutic efficacy investigation exhibited strongest anticancer activity of glycan and EGFR targeted NPs (GMC-CSN-SA-Cxmab-NPs). GMC-CSN-SA-Cxmab-NPs demonstrated enhanced cellular internalization and better therapeutic potential, by specifically targeting glycan and EGFR on NSCLC A-549 cells and B[a]P induced lung cancer mice model, hence it might be a good substitute for non-targeted, conventional chemotherapy.

Stimuli-Responsive Prodrug Chemistries for Cancer Therapy

Prodrugs are pharmacologically inactive, chemically modified derivatives of active drugs, which, following in vivo administration, are converted to the parent drugs through chemical or enzymatic cleavage. The prodrug approach holds tremendous potential to create the enhanced version of an existing pharmacological agent and leverage those improvements to augment the drug molecules' bioavailability, targeting ability, therapeutic efficacy, safety, and marketability. Especially in cancer therapy, prodrug application has received substantial attention. A prodrug can effectively broaden the therapeutic window of its parent drug by enhancing its release at targeted tumor sites while reducing its access to healthy cells. The spatiotemporally controlled release can be achieved by manipulating the chemical, physical, or biological stimuli present at the targeted tumor site. The critical strategy comprises drug-carrier linkages that respond to physiological or biochemical stimuli in the tumor milieu to yield the active drug form. This review will focus on the recent advancements in the development of various fluorophore-drug conjugates that are widely used for real-time monitoring of drug delivery. The use of different stimuli-cleavable linkers and the mechanisms of linker cleavage will be discussed. Finally, the review will conclude with a critical discussion of the prospects and challenges that might impede the future development of such prodrugs.

A Brief Guide to Preparing a Peptide-Drug Conjugate

Peptide-drug conjugates (PDCs) have recently emerged as interesting hybrid constructs not only for targeted therapy, but also for the early diagnosis of different pathologies. In most cases, the crucial step in the PDC synthesis is the final conjugation step, where a specific drug is bound to a particular peptide-/peptidomimetic-targeting unit. Thus, this concept paper aims to give a short guide to determining the finest conjugation reaction, by considering in particular the reaction conditions, the stability of the linker and the major pros and cons of each reaction. Based on the recent PDCs reported in literature, the most common and efficient conjugation methods will be systematically presented and compared, generating a short guide to consult while planning the synthesis of a novel peptide-drug conjugate.

Research advances in peptide‒drug conjugates

Peptide‒drug conjugates (PDCs) are drug delivery systems consisting of a drug covalently coupled to a multifunctional peptide via a cleavable linker. As an emerging prodrug strategy, PDCs not only preserve the function and bioactivity of the peptides but also release the drugs responsively with the cleavable property of the linkers. Given the ability to significantly improve the circulation stability and targeting of drugs in vivo and reduce the toxic side effects of drugs, PDCs have already been extensively applied in drug delivery. Herein, we review the types and mechanisms of peptides, linkers and drugs used to construct PDCs, and summarize the clinical applications and challenges of PDC drugs.

Peptide-drug conjugates (PDCs): a novel trend of research and development on targeted therapy, hype or hope?

Peptide-drug conjugates (PDCs) are the next generation of targeted therapeutics drug after antibody-drug conjugates (ADCs), with the core benefits of enhanced cellular permeability and improved drug selectivity. Two drugs are now approved for market by US Food and Drug Administration (FDA), and in the last two years, the pharmaceutical companies have been developing PDCs as targeted therapeutic candidates for cancer, coronavirus disease 2019 (COVID-19), metabolic diseases, and so on. The therapeutic benefits of PDCs are significant, but poor stability, low bioactivity, long research and development time, and slow clinical development process as therapeutic agents of PDC, how can we design PDCs more effectively and what is the future direction of PDCs? This review summarises the components and functions of PDCs for therapeutic, from drug target screening and PDC design improvement strategies to clinical applications to improve the permeability, targeting, and stability of the various components of PDCs. This holds great promise for the future of PDCs, such as bicyclic peptide‒toxin coupling or supramolecular nanostructures for peptide-conjugated drugs. The mode of drug delivery is determined according to the PDC design and current clinical trials are summarised. The way is shown for future PDC development.

Recent Progress in Bio-Responsive Drug Delivery Systems for Tumor Therapy

Spatially- and/or temporally-controlled drug release has always been the pursuit of drug delivery systems (DDSs) to achieve the ideal therapeutic effect. The abnormal pathophysiological characteristics of the tumor microenvironment, including acidosis, overexpression of special enzymes, hypoxia, and high levels of ROS, GSH, and ATP, offer the possibility for the design of stimulus-responsive DDSs for controlled drug release to realize more efficient drug delivery and anti-tumor activity. With the help of these stimulus signals, responsive DDSs can realize controlled drug release more precisely within the local tumor site and decrease the injected dose and systemic toxicity. This review first describes the major pathophysiological characteristics of the tumor microenvironment, and highlights the recent cutting-edge advances in DDSs responding to the tumor pathophysiological environment for cancer therapy. Finally, the challenges and future directions of bio-responsive DDSs are discussed.

Design Principles Governing the Development of Theranostic Anticancer Agents and Their Nanoformulations with Photoacoustic Properties

The unmet need to develop novel approaches for cancer diagnosis and treatment has led to the evolution of theranostic agents, which usually include, in addition to the anticancer drug, an imaging agent based mostly on fluorescent agents. Over the past few years, a non-invasive photoacoustic imaging modality has been effectively integrated into theranostic agents. Herein, we shed light on the design principles governing the development of theranostic agents with photoacoustic properties, which can be formulated into nanocarriers to enhance their potency. Specifically, we provide an extensive analysis of their individual constituents including the imaging dyes, drugs, linkers, targeting moieties, and their formulation into nanocarriers. Along these lines, we present numerous relevant paradigms. Finally, we discuss the clinical relevance of the specific strategy, as also the limitations and future perspectives, and through this review, we envisage paving the way for the development of theranostic agents endowed with photoacoustic properties as effective anticancer medicines.

Stimuli-Responsive Delivery Strategies for Controllable Gene Editing in Tumor Therapeutics

CRISPR system has attracted significant interest due to its great potential in tumour therapy. Developing effective, precise and safe delivery vectors is a prerequisite for CRISPR applications. Some disease-related biological...

Development of novel GnRH and Tat48-60 based luminescent probes with enhanced cellular uptake and bioimaging profile

There is a clear need to develop photostable chromophores for bioimaging with respect to the classically utilized green fluorescent dye fluorescein. Along these lines, we utilized a phosphorescent carboxy-substituted ruthenium(ii) polypyridyl [Ru(bipy)2(mcb)]2+ (bipy = 2,2'-bipyridyl and mcb = 4-carboxy-4'-methyl-2,2'-bipyridyl) complex. We developed two luminescent peptide conjugates of the cell-penetrating peptide Tat48-60 consisting of either [Ru(bipy)2(mcb)]2+ or 5(6)-carboxyfluorescein (5(6)-FAM) tethered on the Lys50 of the peptide through amide bond. We confirmed the efficient cellular uptake of both bioconjugates in HeLa cells by confocal microscopy and flow cytometry and proved that the ruthenium-based chromophore possesses enhanced photostability compared to a 5(6)-FAM-based peptide, after continuous laser scanning. Furthermore, we designed and developed a luminescent agent with high photostability, based on the ruthenium core, that could be selectively localized in cancer cells overexpressing the GnRH receptor (GnRH-R). To achieve this, we took advantage of the tumor-homing character of d-Lys6-GnRH which selectively recognizes the GnRH-R. The [Ru(bipy)2(mcb)]2+-d-Lys6-GnRH peptide conjugate was synthesized, and its cellular uptake was evaluated through flow cytometric analysis and live-cell imaging in HeLa and T24 bladder cancer cells as negative and positive controls of GnRH-R, respectively. Besides the selective targeting that the specific conjugate could offer, we also recorded high internalization levels in T24 bladder cancer cells. The ruthenium(ii) polypyridyl peptide-based conjugates we developed is an intriguing approach that offers targeted cell imaging in the Near Infrared region, and simultaneously paves the way for further advancements in the dynamic studies on cellular imaging.

Recent Advances in pH- or/and Photo-Responsive Nanovehicles

The combination of nanotechnology and chemotherapy has resulted in more effective drug design via the development of nanomaterial-based drug delivery systems (DDSs) for tumor targeting. Stimulus-responsive DDSs in response to internal or external signals can offer precisely controlled delivery of preloaded therapeutics. Among the various DDSs, the photo-triggered system improves the efficacy and safety of treatment through spatiotemporal manipulation of light. Additionally, pH-induced delivery is one of the most widely studied strategies for targeting the acidic micro-environment of solid tumors. Accordingly, in this review, we discuss representative strategies for designing DDSs using light as an exogenous signal or pH as an endogenous trigger.

Stimulus-cleavable chemistry in the field of controlled drug delivery

Stimulus-cleavable nanoscale drug delivery systems are receiving significant attention owing to their capability of achieving exquisite control over drug release via the exposure to specific stimuli. Central to the construction of such systems is the integration of cleavable linkers showing susceptibility to one stimulus or several stimuli with drugs, prodrugs or fluorogenic probes on the one hand, and nanocarriers on the other hand. This review summarises recent advances in stimulus-cleavable linkers from various research areas and the corresponding mechanisms of linker cleavage and biological applications. The feasibility of extending their applications to the majority of nanoscale drug carriers including nanomaterials, polymers and antibodies are further highlighted and discussed. This review also provides general design guidelines to incorporate stimulus-cleavable linkers into nanocarrier-based drug delivery systems, which will hopefully spark new ideas and applications.