Azobenzene-Based Linker Strategy for Selective Activation of Antibody-Drug Conjugates.

Existing antibody-drug conjugate (ADC) linkers, whether cleavable or non-cleavable, are designed to release highly toxic payloads or payload derivatives upon internalisation of the ADCs into cells. However, clinical studies have shown that only <1 % of the dosed ADCs accumulate in tumour cells. The remaining >99 % of ADCs are nonspecifically distributed in healthy tissue cells, thus inevitably leading to off-target toxicity. Herein, we describe an intelligent tumour-specific linker strategy to address these limitations. A tumour-specific linker is constructed by introducing a hypoxia-activated azobenzene group as a toxicity controller. We show that this azobenzene-based linker is non-cleavable in healthy tissues (O2 >10 %), and the corresponding payload derivative, cysteine-appended azobenzene-linker-monomethyl auristatin E (MMAE), can serve as a safe prodrug to mask the toxicity of MMAE (switched off). Upon exposure to the hypoxic tumour microenvironment (O2<1 %), this linker is cleaved to release MMAE and fully restores the high cytotoxicity of the ADC (switched on). Notably, the azobenzene linker-containing ADC exhibits satisfactory antitumour efficacy in vivo and a larger therapeutic window compared with ADCs containing traditional cleavable or non-cleavable linkers. Thus, our azobenzene-based linker sheds new light on the development of next-generation ADC linkers.

USP2 promotes tumor immune evasion via deubiquitination and stabilization of PD-L1.

The abnormal upregulation of programmed death ligand-1 (PD-L1) on tumor cells impedes T-cell mediated cytotoxicity through PD-1 engagement, and further exploring the mechanisms regulation of PD-L1 in cancers may enhance the clinical efficacy of PD-L1 blockade. Here, using single-guide RNAs (sgRNAs) screening system, we identify ubiquitin-specific processing protease 2 (USP2) as a novel regulator of PD-L1 stabilization for tumor immune evasion. USP2 directly interacts with and increases PD-L1 abundance in colorectal and prostate cancer cells. Our results show that Thr288, Arg292 and Asp293 at USP2 control its binding to PD-L1 through deconjugating the K48-linked polyubiquitination at lysine 270 of PD-L1. Depletion of USP2 causes endoplasmic reticulum (ER)-associated degradation of PD-L1, thus attenuates PD-L1/PD-1 interaction and sensitizes cancer cells to T cell-mediated killing. Meanwhile, USP2 ablation-induced PD-L1 clearance enhances antitumor immunity in mice via increasing CD8+ T cells infiltration and reducing immunosuppressive infiltration of myeloid-derived suppressor cells (MDSCs) and regulatory T cells (Tregs), whereas PD-L1 overexpression reverses the tumor growth suppression by USP2 silencing. USP2-depletion combination with anti-PD-1 also exhibits a synergistic anti-tumor effect. Furthermore, analysis of clinical tissue samples indicates that USP2 is positively associated with PD-L1 expression in cancer. Collectively, our data reveal a crucial role of USP2 for controlling PD-L1 stabilization in tumor cells, and highlight USP2 as a potential therapeutic target for cancer immunotherapy.

Guanidine-modified albumin-MMAE conjugates with enhanced endocytosis ability.

Aiming to address the insufficient endocytosis ability of traditional albumin drug conjugates, this paper reports elegant guanidine modification to improve efficacy for the first time. A series of modified albumin drug conjugates were designed and synthesized with different structures, including guanidine (GA), biguanides (BGA) and phenyl (BA), and different quantities of modifications. Then, the endocytosis ability and in vitro/vivo potency of albumin drug conjugates were systematically studied. Finally, a preferred conjugate A4 was screened, which contained 15 BGA modifications. Conjugate A4 maintains spatial stability similar to that of the unmodified conjugate AVM and could significantly enhance endocytosis ability (p*** = 0.0009) compared with the unmodified conjugate AVM. Additionally, the in vitro potency of conjugate A4 (EC50 = 71.78 nmol in SKOV3 cells) was greatly enhanced (approximately 4 times) compared with that of the unmodified conjugate AVM (EC50 = 286.00 nmol in SKOV3 cells). The in vivo efficacy of conjugate A4 completely eliminated 50% of tumors at 33 mg/kg, which was significantly better than the efficacy of conjugate AVM at the same dose (P** = 0.0026). In addition, theranostic albumin drug conjugate A8 was designed to intuitively realize drug release and maintain antitumor activity similar to conjugate A4. In summary, the guanidine modification strategy could provide new ideas for the development of new generational albumin drug conjugates.

Raddeanin A Enhances Mitochondrial DNA-cGAS/STING Axis-Mediated Antitumor Immunity by Targeting Transactive Responsive DNA-Binding Protein 43.

Immune checkpoint therapies (ICT) have achieved unprecedented efficacy in multiple cancer treatments, but are still limited by low clinical response rates. Identification of immunogenic cell death (ICD)-inducing drugs that can induce tumor cell immunogenicity and reprogram the tumor microenvironment is an attractive approach to enhance antitumor immunity. In the present study, Raddeanin A (RA), an oleanane class triterpenoid saponin isolated from Anemone raddeana Regel, is uncovered as a potent ICD inducer through an ICD reporter assay combined with a T cell activation assay. RA significantly increases high-mobility group box 1 release in tumor cells and promotes dendritic cell (DC) maturation and CD8+ T cell activation for tumor control. Mechanistically, RA directly binds to transactive responsive DNA-binding protein 43 (TDP-43) and induces TDP-43 localization to mitochondria and mtDNA leakage, leading to cyclic GMP-AMP synthase/stimulator of interferon gene-dependent upregulation of nuclear factor κB and type I interferon signaling, thereby potentiating the DC-mediated antigen cross-presentation and T cell activation. Moreover, combining RA with anti-programmed death 1 antibody effectively enhances the efficacy of ICT in animals. These findings highlight the importance of TDP-43 in ICD drug-induced antitumor immunity and reveal a potential chemo-immunotherapeutic role of RA in enhancing the efficacy of cancer immunotherapy.

Development of a nitroreductase-dependent theranostic payload for antibody-drug conjugate.

Antibody-drug conjugates are gradually revolutionizing anticancer therapy. Payload is one of the most crucial components of ADC for high antitumor activity. However, there is no direct and real-time monitoring method for the intracellular release mechanism of the payload. Herein, we developed a theranostic payload that possessed dual functions of therapy and imaging. This payload consisted of the classic payload MMAE and the novel nitro-coumarin probe reported for the first time, which has the dual characteristics of electron transfer ability and the on-off fluorescence property. In this paper, the theranostic property of the novel payload has been preliminarily demonstrated. The fluorescence intensity of the payload in target cells greatly increased approximately 9 times in 120 min through the high content analysis, and the intracellular distribution of the payload could be directly monitored by a confocal microscope. In in vitro cytotoxicity assays, the payload showed broad-spectrum and high antitumor activity (0.09 nM to 1.2 nM), which was equivalent to the MMAE (0.06 nM to 1.1 nM). Moreover, the ADC loaded with L-233 maintained the theranositc property. In conclusion, our work developed a theranostic payload for the first time and provides a new direct and real-time monitoring method for intracellular studies of ADC payloads.

Design, synthesis and biological activity evaluation of a series of bardoxolone methyl prodrugs.

Bardoxolone methyl (CDDO-Me) has exhibited positive therapeutic effects in clinical trials for diabetic nephropathy (DN), but serious safety risks in the heart exist because of the potential off-target response resulting from the highly active part of CDDO-Me. Herein, we reported a novel strategy to prepare Cathepsin B (CTSB) cleavable and improved water-soluble prodrugs of CDDO-Me. CTSB linkers connection to the highly active α-cyano-α, ß-unsaturated ketone (CUK) part of CDDO-Me with the incorporation of polyethylene glycol (PEG) moieties, provided a series of prodrugs of CDDO-Me without CUK part exposure. Theoretically, these prodrugs shielding CUK part can be stably circulated and finally cleaved by CTSB in lysosomes to release CDDO-Me. In this paper, preliminary curative effects and safety of all prodrugs were determined. Wherein, prodrug 20 displayed relatively better activities than other prodrugs in inhibiting the release of NO from RAW264.7 cells, activating Keap1-Nrf2-ARE signaling pathway and inhibiting NF-κB signaling pathway, which were comparable to CDDO-Me. More importantly, prodrug 20 showed relatively lower human ether-a-go-go-related gene (hERG) inhibitory activity compared with CDDO-Me, which demonstrated prodrug 20 might be safer than CDDO-Me. In conclusion, the novel strategy of shielding CUK part with CTSB linkers provided a new idea for solving the limitations of CDDO-Me in clinical application.

Nafamostat mesylate as a broad-spectrum candidate for the treatment of flavivirus infections by targeting envelope proteins.

Epidemics caused by flaviviruses occur globally; however, no antiviral drugs treating flaviviruses infections have yet been developed. Nafamostat (NM) is a protease inhibitor approved for pancreatitis and anti-coagulation. The anti-flavivirus potential of NM has yet to be determined. Here, utilizing in vitro and in vivo infection assays, we present that NM effectively inhibits Zika virus (ZIKV) and other flaviviruses in vitro. NM inhibited the production of ZIKV viral RNA and proteins originating from Asia and African lineage in human-, mouse- and monkey-derived cell lines and the in vivo anti-ZIKV efficacy of NM was verified. Mode-of-action analysis using time-of-drug-addition assay, infectivity inhibition assay, surface plasmon resonance assay, and molecular docking revealed that NM interacted with viral particles and blocked the early stage of infection by targeting the domain III of ZIKV envelope protein. Analysing the anti-flavivirus effects of NM-related compounds suggested that the antiviral effect depended on the unique structure of NM. These findings suggest the potential use of NM as an anti-flavivirus candidate, and a novel drug design approach targeting the flavivirus envelope protein.

Synthesis and evaluation of highly releasable and structurally stable antibody-SN-38-conjugates.

Camptothecins, traditional chemotherapy drugs, have been clinically used in antibody-drug conjugates (ADCs), which refreshes the recognition that ADCs preferably incorporate highly potent payloads. However, SN-38, active metabolite of irinotecan from camptothecins, tended to be incorporated into ADCs with an unstable acid sensitive bond, not with the widely used Cathepsin B (CTSB) sensitive bond, which may pose the risk of off-target. Herein, we reported a novel strategy to construct highly releasable and structurally stable SN-38-conjugates, in which CTSB linkers directly connected to the 10-OH group through ether bond, not to the common 20-OH group of lactones of SN-38. In this paper, rapid release of SN-38 was skillfully demonstrated by utilizing the fluorescence properties of SN-38. The SN-38-ether-ADC displayed highly stable serum stability with the half-life over 10 days. Moreover, the drug-antibody-ratio (DAR) of ADC could be elevated to 7.1 through the introduction of polyethylene glycol (PEG) moieties without aggregation. The optimized ADC exhibited potent in vitro activities up to 5.5 nM, comparable to SN-38. Moreover, this ADC group significantly delayed tumor growth in vivo. In conclusion, the novel strategy has the potential to promote the development of SN38-ADCs and enrich the conjugation approaches for hydroxyl-bearing payloads.

Development of bifunctional anti-PD-L1 antibody MMAE conjugate with cytotoxicity and immunostimulation.

In recent years, tumor immunotherapy, especially the combination of PD1/PD-L1 inhibitors and chemotherapy, has developed rapidly. However, the systemic side effects induced by chemotherapy remain a crucial problem that needs to be addressed. Antibody drug conjugates (ADCs) are exceptional target-specific prodrugs that greatly improve the therapeutic window of chemotherapy drugs. Therefore, designing PD-L1-targeting ADCs is an interesting research project. In this study, we confirmed for the first time that the commercial anti-PD-L1 antibody Atezolizumab has better endocytosis efficiencies than Avelumab, and was more suitable for ADC design. Then, the most popular cytotoxic payload MMAE was conjugated to Atezolizumab via a classical dipeptide (valine-alanine) linker to generate a bifunctional PD-L1 ADC (ADC 3). An in vitro cytotoxicity test indicated the potent tumor cell inhibitory activity of ADC 3, with EC50 values of 9.75 nM to 11.94 nM. In addition, a co-culture of PBMCs in vitro proved that ADC 3 retained the immune activation effect of the Atezolizumab antibody. Moreover, ADC 3 exhibited a higher tumor inhibition rate and tumor regression rate in humanized immune system mice. To the best of our knowledge, this is the most active PD-L1-ADC reported thus far, which may promote the development of immunotherapy and novel ADCs.

Novel antibody-drug conjugate with UV-controlled cleavage mechanism for cytotoxin release.

Antibody-drug conjugates (ADCs) are being developed worldwide with the potential to revolutionize current cancer treatment strategies. However, off-target toxicity caused by the instability of linkers remains one of the main issues to be resolved. Developing a novel photocontrol-ADC with good stability and photocontrolled release seemed to be an attractive and practical solution. In this study, we designed, for the first time, a novel ultraviolet (UV) light-controlled ADC by carefully integrating the UV-cleavable o-nitro-benzyl structure into the linker. Our preliminary work indicated that the ADC exhibited good stability and photocontrollability while maintaining a targeting effect similar to that of the naked antibody. Upon irradiation with UV light, the ADC rapidly released free cytotoxins and exerted significant cytotoxicity toward drug-resistant tumor cells. Compared to those of the unirradiated cells, the EC50 values of ADCs increased by up to 50-fold. Furthermore, our research confirmed that the degradation products of unirradiated ADC, Cys-1a, were relatively less toxic, thus potentially reducing the off-target toxicity caused by nonspecific uptake of ADCs. The novel design strategy of UV light-controlled ADCs may provide new perspectives for future research on ADCs and promote the development of photocontrol systems.

Acid rain: an unsuspected factor predisposing Panzhihua airport landslide, China.

Understanding the effect of acid rain to landslides is crucial for a better landslide risk assessment. This work aims to reveal the unsuspected but key role of acid rain in Panzhihua airport landslide, China. Firstly, we propose a hypothesis that acid rain may aggravate the slaking behavior of mudstone at weak interlayer and make it more fragmented, eventually further reducing its shear strength and predisposing the Panzhihua airport landslide. Subsequently, mudstone samples are subjected to slaking durability test, respectively, using water with a pH of 7 and two dilute hydrochloric acid solution with pH of 5 and 3. Slaking durability index (Idn) is adopted aiming to quantitatively evaluate the impact of acid rain on the slaking. Moreover, the mechanisms of acid rain affecting the slaking behavior of mudstone are revealed by (1) analyzing cation compositions changes in different pH slaking fluid and (2) observing micro-structure change of mudstone-chip before and after acid rain treatment. Finally, three works are conducted as evidences to prove that acid rain indeed plays a key role in the occurrence of Panzhihua airport landslide, including (1) analysis of the link between the slaking behavior of mudstone and its shear strength, (2) comparison of cations between spring water at the edge of the toe of landslide and acid rain, and (3) comparison of mineral contents of mudstone samples collected from different locations. These findings have implications for comprehensively analyzing the formation mechanism of landslide in acid rain area (such as Europe, North America, and China).

A bifunctional molecule-based strategy for the development of theranostic antibody-drug conjugate.

Antibody-drug conjugates (ADCs) are being developed worldwide with the potential to revolutionize current cancer treatment strategies. Developing novel theranostic ADCs with therapeutic utility and imaging capability is an attractive and challenging subject that promises advances in the field of personalized medicine. In this work, we propose a bifunctional molecule-based strategy for the development of theranostic ADCs. Methods: We developed a theranostic ADC consisting of the anti-Her2 antibody Mil40, monomethyl auristatin E (MMAE) as the active payload, and a 7-amino-3-hydroxyethyl-coumarin (7-AHC)-based dipeptide linker, which functions as a novel bifunctional fluorescence probe that allows self-elimination cleavage in the presence of cathepsin B for payload release and fluorophore activation. The on-off fluorescence properties and the antitumor effect in vitro and in vivo were investigated. Results: A 48-fold fluorescence enhancement was observed within 1 h when the 7-AHC-based linker was exposed to cathepsin B. Cleavage upon exposure to cathepsin B allows MMAE and fluorophore intracellular release and the monitoring of MMAE distribution using confocal microscopy. Additionally, the newly developed ADC retains the advantages of traditional p-aminobenzyloxycarbonyl-containing ADCs, such as good stability (t1/2 > 7 days) and high activity in vitro (IC50 = 0.09-3.74 nM). Importantly, the theranostic ADC exhibited the equivalent antitumor efficacy to the marketed ADC T-DM1 in the classic breast cancer model. Conclusion: We suggest that the present strategy can be universally applied in all p-aminobenzyloxycarbonyl-containing ADCs. Overall, theranostic ADCs may play a role in developing new theranostic systems and promoting personalized medicine research.

Antibody-drug conjugates: Recent advances in linker chemistry.

Antibody-drug conjugates (ADCs) are gradually revolutionizing clinical cancer therapy. The antibody-drug conjugate linker molecule determines both the efficacy and the adverse effects, and so has a major influence on the fate of ADCs. An ideal linker should be stable in the circulatory system and release the cytotoxic payload specifically in the tumor. However, existing linkers often release payloads nonspecifically and inevitably lead to off-target toxicity. This defect is becoming an increasingly important factor that restricts the development of ADCs. The pursuit of ADCs with optimal therapeutic windows has resulted in remarkable progress in the discovery and development of novel linkers. The present review summarizes the advance of the chemical trigger, linker‒antibody attachment and linker‒payload attachment over the last 5 years, and describes the ADMET properties of ADCs. This work also helps clarify future developmental directions for the linkers.

The impact and mechanism of ampakine CX1739 on protection against respiratory depression in rats.

Background: Abuse of analgesic and sedative drugs often leads to severe respiratory depression and sometimes death. Approximately 69,000 people worldwide die annually from opioid overdoses. Purpose: This work aimed to investigate whether CX1739 can be used for emergency treatment of acute respiratory depression due to drug abuse. Results: First, the results clarify that CX1739 is a low-impact ampakine that can safely activate α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors without causing excito-neurotoxicity. Second, CX1739 rapidly crossed the blood-brain barrier (Tmax = 2 min), which meets the requirement of rapid onset of action in vivo. Our work provides preliminarily confirmation that high-dose intravenous administration of CX1739 can immediately reverse respiratory depression in animal models of respiratory depression caused by opioid agonist 030418, pentobarbital sodium and ethanol.

Relationship between sedentary behaviour and anxiety symptoms among youth in 24 low- and middle-income countries.

BACKGROUND: Anxiety is burdensome and common in youth. Sedentary behaviour has been identified as potentially modifiable dangerous factors for many diseases. Nevertheless, little is known about the relationship between sedentary behaviour and the risk of anxiety symptoms in youth. Therefore, we aimed to examine the association among youth in 24 low- and middle-income countries (LMICs). METHODS: Data from the Global School-based Student Health Survey (GSHS) were analyzed in 59587 youth aged 12-15 years. Most of the country-wide data were nationally representative. Anxiety symptoms were self-reported. Multivariable logistic regression and meta-analyses of country-wise estimates were conducted. RESULTS: The prevalence of anxiety symptoms was 10.3%. Countrywide meta-analysis demonstrated that sedentary behaviour of >2 h/day (vs.≤2 h/day) was associated with an increased risk of anxiety symptoms (OR = 1.22; 95% CI = 1.10-1.37). CONCLUSIONS: This study provides multi-national evidence of the dangerous effect of sedentary behaviour against anxiety symptoms among youth in LMICs. Decreasing the level of sedentary behaviour during adolescence could be an important target for reducing the prevalence of anxiety.

Anti-SARS-CoV-2 Potential of Artemisinins In Vitro.

The discovery of novel drug candidates with anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) potential is critical for the control of the global COVID-19 pandemic. Artemisinin, an old antimalarial drug derived from Chinese herbs, has saved millions of lives. Artemisinins are a cluster of artemisinin-related drugs developed for the treatment of malaria and have been reported to have multiple pharmacological activities, including anticancer, antiviral, and immune modulation. Considering the reported broad-spectrum antiviral potential of artemisinins, researchers are interested in whether they could be used to combat COVID-19. We systematically evaluated the anti-SARS-CoV-2 activities of nine artemisinin-related compounds in vitro and carried out a time-of-drug-addition assay to explore their antiviral mode of action. Finally, a pharmacokinetic prediction model was established to predict the therapeutic potential of selected compounds against COVID-19. Arteannuin B showed the highest anti-SARS-CoV-2 potential with an EC50 of 10.28 ± 1.12 µM. Artesunate and dihydroartemisinin showed similar EC50 values of 12.98 ± 5.30 µM and 13.31 ± 1.24 µM, respectively, which could be clinically achieved in plasma after intravenous administration. Interestingly, although an EC50 of 23.17 ± 3.22 µM was not prominent among the tested compounds, lumefantrine showed therapeutic promise due to high plasma and lung drug concentrations after multiple dosing. Further mode of action analysis revealed that arteannuin B and lumefantrine acted at the post-entry step of SARS-CoV-2 infection. This research highlights the anti-SARS-CoV-2 potential of artemisinins and provides leading candidates for anti-SARS-CoV-2 drug research and development.

Research progress on repositioning drugs and specific therapeutic drugs for SARS-CoV-2.

SARS-CoV-2 has been widely spread around the world and COVID-19 was declared a global pandemic by the WHO. Limited clinically effective antiviral drugs are available now. The development of anti-SARS-CoV-2 drugs has become an urgent work worldwide. At present, potential therapeutic targets and drugs for SARS-CoV-2 are continuously reported, and many repositioning drugs are undergoing extensive clinical research, including remdesivir and chloroquine. On the other hand, structures of many important viral target proteins and host target proteins, including that of RdRp and Mpro were constantly reported, which greatly promoted structure-based drug design. This paper summarizes the current research progress and challenges in the development of anti-SARS-CoV-2 drugs, and proposes novel short-term and long-term drug research strategies.

Antibody-Drug Conjugate Using Ionized Cys-Linker-MMAE as the Potent Payload Shows Optimal Therapeutic Safety.

Monomethyl auristatin E (MMAE) is the most popular and widely used cytotoxin in the development of antibody-drug conjugates (ADCs). However, current MMAE-based ADCs are all constructed using cleavable linkers, and this design concept still has insurmountable drawbacks. Their potential instabilities and lipophilic MMAE-induced "bystander effect" inevitably increase the toxicity to normal tissues. Herein, we overturn previous negative views of MMAE-based ADCs with non-cleavable linkers and propose using ionized L-Cysteine (Cys)-linker-MMAE as a novel payload, which can ingeniously enrich and enter tumor cells through receptor-mediated endocytosis of antibodies while its lower permeability helps to avoid further off-target toxicity. We demonstrate that Cys-linker-MMAE maintains high potency similar to free MMAE at the tubulin molecular level and can also be efficiently released in target cells. As a result, the preferred ADC (mil40-15) not only exhibits ideal plasma stability and maintains potent cytotoxicity as MMAE (IC50: 10-11 M), but also shows improved safety with lower bystander toxicity (IC50: 10-9 M), its maximum tolerated dose approaching the level of the naked antibody (160 mg/kg). This study indicated that Cys-linker-MMAE has the potential as a potent payload for ADCs, which is expected to provide novel strategies for the development of MMAE-based ADCs.

Design, Synthesis, and Renal Targeting of Methylprednisolone-Lysozyme.

Methylprednisolone (MP) is often used in the treatment of various kidney diseases, but overcoming the systemic side effects caused by its nonspecific distribution in the body is a challenge. This article reports the design, synthesis, and renal targeting of methylprednisolone-lysozyme (MPS-LZM). This conjugate was obtained by covalently linking MP with the renal targeting carrier LZM through a linker containing an ester bond, which could utilize the renal targeting of LZM to deliver MP to renal proximal tubular epithelial cells and effectively release MP. The reaction conditions for the preparation of the conjugate were mild, and the quality was controllable. The number of drug payloads per LZM was 1.1. Cell-level studies have demonstrated the safety and endocytosis of the conjugate. Further pharmacokinetic experiments confirmed that, compared with that of free MP, the conjugate increased the renal exposure (AUC0-t) of active MP from 17.59 to 242.18 h*ng/mL, and the targeting efficiency improved by approximately 14 times. Tissue and organ imaging further revealed that the conjugate could reach the kidneys quickly, and fluorescence could be detected in the kidneys for up to 12 h. This study preliminarily validates the feasibility of a renal targeting design strategy for MPS-LZM, which is expected to provide a new option for improving kidney-specific distribution of glucocorticoids.