Iridium-Catalyzed Enantioselective Transfer Hydrogenation of 1,1-Dialkylethenes with Ethanol: Scope and Mechanism

Despite half a century's advance in the field of transition-metal-catalyzed asymmetric alkene hydrogenation, the enantioselective hydrogenation of purely alkyl-substituted 1,1-dialkylethenes has remained an unmet challenge. Herein, we describe a chiral PCNOx-pincer iridium complex for asymmetric transfer hydrogenation of this alkene class with ethanol, furnishing all-alkyl-substituted tertiary stereocenters. High levels of enantioselectivity can be achieved in the reactions of substrates with secondary/primary and primary/primary alkyl combinations. The catalyst is further applied to the redox isomerization of disubstituted alkenols, producing a tertiary stereocenter remote to the resulting carbonyl group. Mechanistic studies reveal a dihydride species, (PCNOx)Ir(H)2, as the catalytically active intermediate, which can decay to a dimeric species (κ3-PCNOx)IrH(μ-H)2IrH(κ2-PCNOx) via a ligand-remetalation pathway. The catalyst deactivation under the hydrogenation conditions with H2 is much faster than that under the transfer hydrogenation conditions with EtOH, which explains why the (PCNOx)Ir catalyst is effective for the transfer hydrogenation but ineffective for the hydrogenation. The suppression of di-to-trisubstituted alkene isomerization by regioselective 1,2-insertion is partly responsible for the success of this system, underscoring the critical role played by the pincer ligand in enantioselective transfer hydrogenation of 1,1-dialkylethenes. Moreover, computational studies elucidate the significant influence of the London dispersion interaction between the ligand and the substrate on enantioselectivity control, as illustrated by the complete reversal of stereochemistry through cyclohexyl-to-cyclopropyl group substitution in the alkene substrates.

Association between dietary intake of omega-3 polyunsaturated fatty acids and all-cause and cardiovascular mortality among hypertensive adults: Results from NHANES 1999-2018

BACKGROUND

Hypertensive adults are at a higher risk of cardiovascular morbidity and mortality. Dietary omega-3 polyunsaturated fatty acids (N3-PUFA) intake has been associated with cardiovascular benefits. However, few studies have specifically investigated whether dietary intake of N3-PUFA is associated with lower risk of all-cause and cardiovascular mortality among hypertensive adults in the U.S.

METHODS

This prospective cohort study included 26,914 hypertensive individuals 18 years or older who participated in 10 NHANES cycles from 1999 to 2018. Dietary levels of N3-PUFA were obtained from the 24-hour dietary recalls. The dietary data were linked to mortality records from the National Death Index through December 31, 2019. The associations between dietary N3-PUFA levels and mortality were evaluated by constructing the Multivariable Cox Proportional Hazards models.

RESULTS

We observed an increasing trend of dietary N3-PUFA intake levels over the years, mainly driven by alpha-linolenic acid (ALA). Lower all-cause mortality risk was observed among hypertensive adults with higher consumption of total N3-PUFA [adjusted hazards ratio, 95% confidence interval: 0.91 (0.86, 0.97)], plant-based ALA [0.88 (0.83, 0.93)], fish oil-based eicosapentaenoic acid (EPA) + docosahexaenoic acid (DHA) [0.91 (0.83, 0.99)], EPA [0.93 (0.88, 0.98)], docosapentaenoic acid (DPA) [0.73 (0.58, 0.91)], or DHA [0.95 (0.90, 0.99)]. Hypertensive adults were at lower risk of cardiovascular mortality if their diet contained higher levels of total N3-PUFA [0.68 (0.53, 0.88)], ALA [0.89 (0.80, 0.99)], EPA [0.87 (0.79, 0.97)] or DPA [0.86 (0.78, 0.95)]. Weighted quantile sum analysis showed that ALA, EPA, and DPA were the main contributors of the N3-PUFA benefits against mortality among hypertensive adults.

CONCLUSIONS

Dietary intake of N3-PUFA, particularly ALA, EPA, and DPA, was associated with lower risk of all-cause and cardiovascular mortality among U.S. hypertensive adults. These findings suggest that increasing dietary intake of N3-PUFA may serve as a potential strategy to lower hypertension-associated mortality risk.

A Triplet Iron Carbyne Complex

Tuning the spin state of metal carbynes, which have broad applications in organic synthesis and material science, presents a formidable challenge for modern chemists as the strong field nature of carbyne ligands dictates low-spin ground spin states (S = 0 or 1/2) for known metal carbynes. Through the oxidative addition reaction of a low-coordinate iron(0) N-heterocyclic carbene complex with the C-S bond of a thioazole-2-ylidene, we synthesized the first triplet (S = 1) metal terminal carbyne, an iron cyclic carbyne complex. Different from the classical metal carbynes, the triplet complex features an LXZ-type carbyne ligand and a weak Fe≡C triple bond, which endow it with the unique reactivity pattern of facile carbyne coupling, weak affinity toward nucleophiles, and facial addition reactions with electrophiles.

A current and future perspective on T cell receptor repertoire profiling

T cell receptors (TCR) play a vital role in the immune system's ability to recognize and respond to foreign antigens, relying on the highly polymorphic rearrangement of TCR genes. The recognition of autologous peptides by adaptive immunity may lead to the development and progression of autoimmune diseases. Understanding the specific TCR involved in this process can provide insights into the autoimmune process. RNA-seq (RNA sequencing) is a valuable tool for studying TCR repertoires by providing a comprehensive and quantitative analysis of the RNA transcripts. With the development of RNA technology, transcriptomic data must provide valuable information to model and predict TCR and antigen interaction and, more importantly, identify or predict neoantigens. This review provides an overview of the application and development of bulk RNA-seq and single-cell (SC) RNA-seq to examine the TCR repertoires. Furthermore, discussed here are bioinformatic tools that can be applied to study the structural biology of peptide/TCR/MHC (major histocompatibility complex) and predict antigenic epitopes using advanced artificial intelligence tools.

Diimidazolium Salt HBDIM: An Easily Available, Low-Cost CageCarbene Precursor with Broad Applications in Transition Metal-Catalyzed Reactions

The preparation of diimidazolium salt HBDIM 1, a precursor for di-NHCs ligand, from cheap and easily available agent hexabenzylhexaazaisowurtzitane (HBIW) was reported. Under basic conditions, HBDIM underwent facile deprotonation to in situ generate CageCarbene which could efficiently coordinate to transition-metals such as Au, Cu or Pd to give the corresponding bimetallic complexes 2-4. These complexes were isolated and fully characterized including X-ray diffraction of their single crystals. It was found that the steric hinderance of CageCarbene is similar to that of SIMes but smaller than that of IPr, and electronically, CageCarbene is a strong σ-donator silimar to SIMs and a stronger σ-donator than IPr. Further studies showed that complexes 2-4 were highly reactive to catalyze up to 17 reactions. Control experiments utilizing N-benzyl-substituted monoimidazolium salt showed much low catalytic reactivity when it was bounded to Au or Cu, but exhibited similar reactivity for the Pd-complex. Kenetic studies showed that the low reactivity of the monodentate carbene-ligated Au or Cu complex was due to the low stability of the complex under the reaction condions.

Associations of blood lead, cadmium, and mercury with resistant hypertension among adults in NHANES, 1999-2018

BACKGROUND

Resistant hypertension (RHTN), a clinically complex condition with profound health implications, necessitates considerable time and allocation of medical resources for effective management. Unraveling the environmental risk factors associated with RHTN may shed light on future interventional targets aimed at reducing its incidence. Exposure to heavy metal has been linked to an increased risk of hypertension, while the relationship with RHTN remains poorly understood.

METHODS

Using the 1999-2018 National Health and Nutrition Examination Survey (NHANES) data, we examined the association of blood lead (Pb), cadmium (Cd), and mercury (Hg) with RHTN using a multinomial logistic regression model. The combined effects of the metals and the contribution of each metal were assessed using a weighted quantile sum (WQS) analysis.

RESULTS

A total of 38281 participants were included in the analysis. Compared with no resistant hypertension (NRHTN), per 1 µg/dL increase in blood Pb concentration, the proportion of RHTN increased by 16% [adjusted odds ratio (aOR), 1.16; 95% confidence interval (CI) 1.01-1.32]. When analyzed by quartiles (Q), the aOR [95% CI] for Pd was 1.30[1.01,1.67] (Q4 vs. Q1); there was a significant dose-response relationship (p < 0.05). Likewise, as a continuous variable, each 1 µg/dL increase in blood Cd level was associated with a 13% increase in the proportion of RHTN (aOR: 1.13; 95%CI: [1.00,1.27]); when analyzed as quartile, aOR [95% CI] for Cd were 1.30[1.01,1.69] (Q3 vs. Q1), and 1.35[1.03,1.75] (Q4 vs. Q1); the dose-response relationship was significant (p < 0.05). WQS analysis showed a significant combined effects of Pb, Cd, and Hg on RHTN, with Pb as the highest weight (0.64), followed by Cd (0.25) and Hg (0.11). Stratified analysis indicated that the associations for the two heavy metals were significant for participants who were male, ≼ 60 years old, and with kidney dysfunction.

CONCLUSION

Findings of this study with national data provide new evidence regarding the role of environmental heavy metal exposure in RHTN. The prevention strategies aimed at reducing heavy metal exposure should particularly focus on Americans who are middle-aged, male, and afflicted with kidney dysfunction.

POS0287 A PHASE III, RANDOMISED, DOUBLE-BLIND, ACTIVE-CONTROLLED CLINICAL TRIAL TO COMPARE BAT1806/BIIB800, A PROPOSED TOCILIZUMAB BIOSIMILAR, WITH TOCILIZUMAB REFERENCE PRODUCT IN SUBJECTS WITH MODERATE TO SEVERE RHEUMATOID ARTHRITIS WITH AN INADEQUATE RESPONSE TO METHOTREXATE THERAPY

Background

BAT1806/BIIB800 is a proposed biosimilar to reference tocilizumab (TCZ). A Phase III randomised, double-blind, active-controlled clinical trial was conducted as part of a biosimilar development programme.

Objectives

To evaluate the efficacy, pharmacokinetics (PK), safety and immunogenicity of BAT1806/BIIB800 in comparison with EU-sourced TCZ in subjects with moderate to severe rheumatoid arthritis with inadequate response to methotrexate (MTX).

Methods

The study was conducted at 55 centres in China and Europe, between June 2018 and January 2021. Eligible subjects were randomised in a 2:1:1 ratio to one of three treatment groups: (1) BAT1806/BIIB800 up to Week 48, (2) TCZ up to Week 48, or (3) TCZ up to Week 24, followed by BAT1806/BIIB800 from Week 24 to Week 48, administered intravenously every 4 weeks at a dose of 8mg/kg. The primary endpoint was the proportion of subjects achieving an ACR20 response at timepoints pre-specified to meet the requirements of different Regulatory Agencies: Week 12, for EMA; Week 24, for FDA and NMPA. Equivalence margins applied to differences in ACR20 response rates in the BAT1806/BIIB800 and TCZ treatment groups were pre-specified as follows: +/- 14.5% for EMA (95% confidence interval (CI)); -12.0%,15% for FDA (90% CI); +/- 13.6% for NMPA (95% CI). Secondary endpoints included pharmacokinetics, safety and immunogenicity.

The ICH E9(R1) estimands framework including intercurrent events (related or unrelated to the COVID19 pandemic) was implemented for the ACR20 evaluation. A logistic regression model including ‘region’ (China and Eastern Europe) and ‘previous biologic or targeted synthetic DMARD use’ (Yes/No) as captured in Interactive Web Response System as stratification factors was utilised to assess equivalence for the primary endpoint. The difference in response rates was estimated and corresponding confidence intervals were derived to assess equivalence for the primary endpoint. This abstract presents results up to Week 24.

Results

In total, 621 subjects were randomised to receive BAT1806/BIIB800 (N=312), TCZ (N=155), or TCZ followed by BAT1806/BIIB800 (N=154). The groups were comparable in terms of baseline demographics and disease characteristics, including age, gender, disease activity and disease duration. The estimated proportions of subjects achieving an ACR20 response in the BAT1806/BIIB800 vs. the TCZ groups, respectively, were 68.97% vs. 64.82% at Week 12 and 69.89% vs. 67.94% at Week 24. The estimated difference between ACR response rates was 4.15% (95% CI -3.63, 11.93) at week 12, and 1.94% (90% CI -4.04, 7.92; 95% CI -5.18, 9.07) at Week 24. The CIs for the estimated differences between the treatment groups were within the pre-defined equivalence margins (Figure 1). The treatment groups were comparable in terms of serum trough levels, incidence of TEAEs and ADA/NAb positivity (Table 1).

Table 1.

Safety and Immunogenicity up to Week 24, and Pharmacokinetics at Week 24

TCZ (N =309) n (%)BAT1806/BIIB800 (N=312) n (%)TEAE196 (63.4)201 (64.4)Related TEAE151 (48.9)148 (47.4)Serious TEAE13 (4.2)11 (3.5)Related Serious TEAE7 (2.3)2 (0.6)Fatal TEAE1 (0.3)3 (1.0)ADA positive a42 (13.6%)64 (20.5%)NAb positive a42 (13.6%)63 (20.2%)PK, n271276Serum trough level (ug/mL), mean (SD)15.4 (17.1)15.8 (12.3)Serum trough level (ug/mL), geometric mean (CV%)12.3 (140.3)12.9 (121.3)Below limit of quantification, n (%)43 (15.9)28 (10.1)

TEAE, treatment emergent adverse events

a subjects with ≥1 ADA/NAb positive results up to week 24

Conclusion

BAT1806/BIIB800 has demonstrated equivalent efficacy at Week 12 and Week 24 and a similar PK, safety and immunogenicity profile as reference tocilizumab up to Week 24.

Disclosure of Interests

Xiaomei Leng: None declared, Piotr Leszczynski: None declared, Sławomir Jeka: None declared, Shengyun Liu: None declared, Huaxiang Liu: None declared, Malgorzata Miakisz: None declared, Jieruo Gu: None declared, Lali Kilasonia Speakers bureau: Sandoz, Amgen, Takeda, Mykola Stanislavchuk Speakers bureau: Pfizer, Orion, Boehringer Ingelheim, Xiaolei Yang Shareholder of: Employee of the Bio-thera Solutions Ltd. with shares as a part of Stock incentive plan., Employee of: Employee of the Bio-thera Solutions Ltd., Yinbo Zhou Shareholder of: Employee of Bio-thera Solutions Ltd. with share as part of Stock incentive plan, Employee of: Employee of Bio-thera Solutions Ltd., Qingfeng Dong Shareholder of: Employee of Bio-thera Solutions Ltd. with shares as part of Stock incentive plan, Employee of: Employee of Bio-thera Solutions Ltd., Marian Mitroiu Shareholder of: Employee of Biogen and may hold stocks, Employee of: Employee of Biogen, Janet Addison Shareholder of: Employee of Biogen and holds stock in Biogen, Employee of: Employee of Biogen, Xiaofeng Zeng: None declared

MicroRNA-29a attenuates exhaustion and promotes memory-like CD8 T cells

CD8 T cells are crucial for immunity against pathogens and tumor cells. However, persistent antigens during chronic infections and cancers drive the differentiation of exhausted T cells (TEX). TEX do not generate optimal immune responses to persistent antigens. The epigenetic profile of TEX is altered and cannot be reversed with current immunotherapy, such as PD-L1 blockade, providing a challenge for the efficacy of such therapies. Despite considerable work interrogating the transcriptional regulation of TEX, the post-transcriptional control of TEX remains poorly understood. Here, we interrogated the role of microRNAs (miRs) in CD8 T cells responding to acutely resolved or chronic viral infection and identified miR-29a as a key regulator of TEX. Enforced expression of miR-29a improved CD8 T cell responses, attenuated exhaustion, and fostered a memory-like CD8 T cell differentiation state during chronic infection. Importantly, miR-29a combined with anti-PD-L1 therapy increased CD8 T cell accumulation, promoted a progenitor-like TEX subset and enhanced a memory-like phenotype long-term. These data indicate that miR-29a can instruct CD8 T cell differentiation and promote memory-like responses. Therefore, we suggest miR-29a as a novel immunotherapeutic to regulate TEX differentiation and promote functional CD8 T cell responses long-term.

MicroRNA-29a attenuates CD8 T cell exhaustion and induces memory-like CD8 T cells during chronic infection

CD8 T cells mediate protection against intracellular pathogens and tumors. However, persistent antigen during chronic infections or cancer leads to T cell exhaustion, suboptimal functionality, and reduced protective capacity. Despite considerable work interrogating the transcriptional regulation of exhausted CD8 T cells (TEX), the posttranscriptional control of TEX remains poorly understood. Here, we interrogated the role of microRNAs (miRs) in CD8 T cells responding to acutely resolved or chronic viral infection and identified miR-29a as a key regulator of TEX. Enforced expression of miR-29a improved CD8 T cell responses during chronic viral infection and antagonized exhaustion. miR-29a inhibited exhaustion-driving transcriptional pathways, including inflammatory and T cell receptor signaling, and regulated ribosomal biogenesis. As a result, miR-29a fostered a memory-like CD8 T cell differentiation state during chronic infection. Thus, we identify miR-29a as a key regulator of TEX and define mechanisms by which miR-29a can divert exhaustion toward a more beneficial memory-like CD8 T cell differentiation state.

Preparation, Characterization and Reactivity of Trifluoromethoxy Palladium(II) Complexes

The preparation of the first nitrogen- or phosphine-ligated trifluoromethoxylated Pd(II) complexes [(L)Pd(4-CF3Ph)(OCF3)] (L = TMEDA, 4-Mepyridine or tBu-BrettPhos, BrettPhos, RuPhos and CPhos) was described. These complexes were extensively characterized in...

Catalytic Method for the Synthesis of Deuterium-Labeled N-Heterocyclic Carbenes Enabled by a Coordinatively Unsaturated Ruthenium N-Heterocyclic Carbene Catalyst

The wide usage of N-heterocyclic carbenes (NHCs) has raised the quest for their deuterated molecules. Effective synthesis method to obtain them, however, has remained elusive. We present here a catalytic method for the preparation of deuterated NHCs, namely, the catalytic hydrogen-deuterium exchange reaction between NHCs and deuterated benzene using a coordinatively unsaturated Ru NHC catalyst. The catalytic system enables selective deuteration of the C(sp³)-H bonds of the alkyl groups on N-substituents, as well as the sterically nonhindered C(sp²)-H bonds of NHCs as demonstrated by the preparation of 16 deuterium-labeled NHCs that have a deuteration ratio on specified sites higher than 90%. The gram-scale synthesis of deuterated IMes indicated the applicability of this catalytic method. Mechanistic studies revealed that the high regio-selectivity toward those C(sp³)-H bonds on NHCs originates from the regio-selectivity of cyclometalation reactions of coordinatively unsaturated Ru NHC species.

[Application of traction metal clip with fishhook-like device in endoscopic resection]

From July 2020 to June 2021, patients in Jiangyin Hospital Affiliated to Nantong University who met the enrollment criteria were treated with the fishhook-like device during the operation to suture the postoperative wound (group A). Patients with similar conditions and similar size wounds who were treated with a "purse-string suture" to suture the wounds were retrospectively analyzed as the control group (group B). Difference in the suture rate, adverse events, time required for suturing, and number of metal clips were compared between the two groups. The time required for suturing was (7.83±2.41) min in group A and (11.00±3.31) min in group B. The difference was statistically significant (P=0.002). The number of metal clamps used in group A averaged 7.17 pieces/case, and the number of metal clamps used in group B averaged 7.06 pieces/case. The difference was not statistically significant (P>0.05).The traction metal clip with the fishhook-like device is ingeniously designed and easy to operate. It has a good suture effect on the wound after endoscopic resection and effectively prevents postoperative adverse events.

Regio- and enantioselective umpolung gem-difluoroallylation of hydrazones via palladium catalysis enabled by N-heterocyclic carbene ligand

The enantioselective construction of C-CF₂R (R: alkyl or fluoroalkyl) bonds has attracted the attention of synthetic chemists because of the importance of chiral fluorinated compounds in life and materials sciences. Catalytic asymmetric fluoroalkylation has mainly been realized under organocatalysis and Lewis acid catalysis, with substrates limited to carbonyl compounds. Few examples using transition-metal catalysis exist, owing to side reactions including decomposition and isomerization of fluoroalkylating reagents. Herein we report umpolung asymmetric difluoroallylation of hydrazones with 3-bromo-3,3-difluoropropene (BDFP) under palladium catalysis. Difluoroallylation products having quaternary chiral carbon centers are afforded in good yields with high α/γ- and enantioselectivities. The usefulness of the reaction products is demonstrated and an inner-sphere mechanism of the reaction is proposed. The use of chiral N-heterocyclic carbene as ligand is the key for the selectivities as well as the productivity of the reaction.

Mechanistic Insight into Copper-Mediated Trifluoromethylation of Aryl Halides: The Role of CuI

The synthesis, characterization, and reactivity of key intermediates [Cu(CF₃)(X)]^-Q⁺ (X = CF₃ or I, Q = PPh₄) in copper-mediated trifluoromethylation of aryl halides were studied. Qualitative and quantitative studies showed [Cu(CF₃)₂]^-Q⁺ and [Cu(CF₃)(I)]^-Q⁺ were not highly reactive. Instead, a much more reactive species, ligandless [CuCF₃] or DMF-ligated species [(DMF)CuCF₃], was generated in the presence of excess CuI. On the basis of these results, a general mechanistic map for CuI-promoted trifluoromethylation of aryl halides was proposed. Furthermore, on the basis of this mechanistic understanding, a HOAc-promoted protocol for trifluoromethylation of aryl halides with [Ph₄P]⁺[Cu(CF₃)₂]^- was developed.

Markovnikov Hydrosilylation of Alkynes with Tertiary Silanes Catalyzed by Dinuclear Cobalt Carbonyl Complexes with NHC Ligation

Metal-catalyzed hydrosilylation of alkynes is an ideal atom-economic method to prepare vinylsilanes that are useful reagents in the organic synthesis and silicone industry. Although great success has been made in the preparation of β-vinylsilanes by metal-catalyzed hydrosilylation reactions of alkynes, reported metal-catalyzed reactions for the synthesis of α-vinylsilanes suffer from narrow substrate scope and/or poor selectivity. Herein, we present selective Markovnikov hydrosilylation reactions of terminal alkynes with tertiary silanes using a dicobalt carbonyl N-heterocyclic carbene (NHC) complex [(IPr)₂Co₂(CO)₆] (IPr = 1,3-di(2,6-diisopropylphenyl)imidazol-2-ylidene) as catalyst. This cobalt catalyst effects the hydrosilylation of both alkyl- and aryl-substituted terminal alkynes with a variety of tertiary silanes with good functional group compatibility, furnishing α-vinylsilanes with high yields and high α/β selectivity. Mechanistic study revealed that the stoichiometric reactions of [(IPr)₂Co₂(CO)₆] with PhC≡CH and HSiEt₃ can furnish the dinuclear cobalt alkyne and mononuclear cobalt silyl complexes [(IPr)(CO)₂Co(μ-η²:η²-HCCPh)Co(CO)₃], [(IPr)(CO)₂Co(μ-η²:η²-HCCPh)Co(CO)₂(IPr)], and [(IPr)Co(CO)₃(SiEt₃)], respectively. Both dicobalt bridging alkyne complexes can react with HSiEt₃ to yield α-triethylsilyl styrene and effect the catalytic Markovnikov hydrosilylation reaction. However, the mono(NHC) dicobalt complex [(IPr)(CO)₂Co(μ-η²:η²-HCCPh)Co(CO)₃] exhibits higher catalytic activity over the di(NHC)-dicobalt complexes. The cobalt silyl complex [(IPr)Co(CO)₃(SiEt₃)] is ineffective in catalyzing the hydrosilylation reaction. Deuterium labeling experiments with PhC≡CD and DSiEt₃ indicates the syn-addition nature of the hydrosilylation reaction. The absence of deuterium scrambling in the hydrosilylation products formed from the catalytic reaction of PhC≡CH with a mixture of DSiEt₃ and HSi(OEt)₃ hints that mononuclear cobalt species are less likely the in-cycle species. These observations, in addition to the evident of nonsymmetric Co₂C₂-butterfly core in the structure of [(IPr)(CO)₂Co(μ-η²:η²-HCCPh)Co(CO)₃], point out that mono(IPr)-dicobalt species are the genuine catalysts for the cobalt-catalyzed hydrosilylation reaction and that the high α selectivity of the catalytic system originates from the joint play of the dicobalt carbonyl species to coordinate alkynes in the Co(μ-η²:η²-HCCR')Co mode and the steric demanding nature of IPr ligand.

An Isolable Mononuclear Palladium(I) Amido Complex

Mononuclear Pd(I) species are putative intermediates in Pd-catalyzed reactions, but our knowledge about them is limited due to difficulties in accessing them. Herein, we report the isolation of a Pd(I) amido complex, [(BINAP)Pd(NHAr^Trip)] (BINAP = 2,2'-bis(diphenylphosphino)-1,1'-binaphthalene, Ar^Trip = 2,6-bis(2',4',6'-triisopropylphenyl)phenyl), from the reaction of (BINAP)PdCl₂ with LiNHAr^Trip. This Pd(I) amido species has been characterized by X-ray crystallography, electron paramagnetic resonance, and multiedge Pd X-ray absorption spectroscopy. Theoretical study revealed that, while the three-electron-two-center π-interaction between Pd and N in the Pd(I) complex imposes severe Pauli repulsion in its Pd-N bond, pronounced attractive interligand dispersion force aids its stabilization. In accord with its electronic features, reactions of homolytic Pd-N bond cleavage and deprotonation of primary amines are observed on the Pd(I) amido complex.

POS0754 DEVELOPMENT OF A RISK PREDICTION MODEL FOR VENOUS THROMBOEMBOLISM IN PATIENTS WITH SYSTEMIC LUPUS ERYTHEMATOSUS: THE SLE-VTE SCORE

Background:

Patients with systemic lupus erythematosus (SLE) have a substantially increased risk of venous thromboembolism (VTE). An individual VTE risk assessment is important to ensure that all patients are assessed and given adequate thromboprophylaxis.

Objectives:

We conducted this study to develop a risk score for VTE in patients with SLE.

Methods:

Patients with SLE who participated in the Chinese SLE Treatment and Research group were enrolled in this study. Patient baseline information and clinical laboratory indicators were obtained, and VTE events were recorded every 3-6 months during follow-up visits. The risk prediction model was created and internally validated using the bootstrap methods, and a scoring system was established (Figure 1).

Figure 1.

Flow chart of study design.

Results:

Out of 4,502 patients included in this study, 135 had a VTE event. After univariate analysis and Lasso regression, the following 11 variables were identified and included in the risk prediction model: male sex, age, BMI ≥25 kg/m2, hyperlipidemia, hypoalbuminemia, hsCRP>3 mg/L, renal involvement, nervous system involvement, anti-β2-glycoprotein I antibody positivity, lupus anticoagulant positivity, and no use of hydroxychloroquine. The AUC for the SLE-VTE score (Table 1) was 0.947 (95% CI, 0.9249-0.9694). The SLE-VTE score’s sensitivity and specificity with the optimal cutoff value of 13 were 0.919 and 0.881, respectively. The SLE-VTE score was superior to the GAPSS system in predicting the risk of VTE in patients with SLE (AUC= 0.947 vs. 0.680, P< 0.001; integrated discrimination improvement (IDI)= 0.6652, P< 0.001; net reclassification improvement (NRI)= 0.6652, P< 0.001).

Table 1.

Final multivariable analysis for venous thromboembolism risk in patients with SLE

β coefficientsOdds ratio* (95% CI)P-valuePoints in scoring systemMale0.6211.86(0.953-3.503)0.0612Age at study entry(≥50)0.8372.308(1.339-3.915)0.0023BMI02(kg/m20.7922.209(1.333-3.627)0.0023Hyperlipemia0.8382.313(1.246-4.166)0.0063Hypoalbuminemia2.1638.697(5.185-14.794)< 0.0017hsCRP>3 mg/L1.4524.272(2.618-6.968)< 0.0015Anti β2GPI1.0132.754(1.543-4.853)0.0013LA1.5594.752(2.799-8.072)< 0.0015Nervous system2.38210.832(6.163-18.998)< 0.0018Lupus nephritis0.8352.305(1.414-3.756)0.0013No use of hydroxychloroquine1.7715.876(3.722-9.401)< 0.0016

BMI: body mass index; hsCRP: Hypersensitive c-reactive protein; ACL: anticardiolipin, antiβ2GPI: anti-β2-glycoprotein I, LA: lupus anticoagulantm;

Values in bold are statistically significant at p <0.05.

Conclusion:

Various factors are related to the occurrence of VTE in patients with SLE. The proposed SLE-VTE risk score can accurately predict the risk of VTE and help identify SLE patients with a high risk of VTE who may benefit from thromboprophylaxis.

References:

[1]Ramirez GA, Efthymiou M, Isenberg DA, Cohen H. Under crossfire: thromboembolic risk in systemic lupus erythematosus. Rheumatology. 2018;58:940-952.

[2]Chung WS, Lin CL, Chang SN, Lu CC, Kao CH. Systemic lupus erythematosus increases the risks of deep vein thrombosis and pulmonary embolism: a nationwide cohort study. J Thromb Haemost. 2014;12:452-458.

[3]Liew NC, Alemany GV, Angchaisuksiri P, et al. Asian venous thromboembolism guidelines: updated recommendations for the prevention of venous thromboembolism. Int Angiol. 2017;36:1.

[4]Savino S, Giovanni S, Veronica M, Dario R, Khamashta MA, Laura BM. GAPSS: the Global Anti-Phospholipid Syndrome Score. Rheumatology. 2013:8.

[5]Konstantinides SV, Meyer G, Becattini C, et al. 2019 ESC Guidelines for the diagnosis and management of acute pulmonary embolism developed in collaboration with the European Respiratory Society (ERS). Eur Heart J. 2020;41:543-603.

[6]Moghadamyeghaneh Z, Hanna MH, Carmichael JC, Nguyen NT, Stamos MJ. A Nationwide Analysis of Postoperative Deep Vein Thrombosis and Pulmonary Embolism in Colon and Rectal Surgery. J Gastrointest Surg. 2014;18:2169-2177.

Disclosure of Interests:

None declared

Divalent Ytterbium Hydrido Complex Supported by a β-Diketiminato-Based Tetradentate Ligand: Synthesis, Structure, and Reactivity

While the chemistry of trivalent rare-earth metal hydrido complexes has been well developed in the past 40 years, that of the divalent rare-earth metal hydrido complexes remains in its infancy because of the synthetic challenge of such complexes. In this paper, we report the synthesis and structural characterization of a divalent ytterbium hydrido complex supported by a bulky β-diketiminato-based tetradentate ligand. This hydrido complex is a dimer containing two μ-hydrogen ligands, and it easily undergoes a hydrido shift reaction to form a new divalent ytterbium hydrido complex that contains only one hydrido bridge. Furthermore, this hydrido complex reacts with pyridine and pyridine derivatives, showing versatile reactivity [Yb-H addition to pyridine, hydrido shift to ancillary ligand, and ytterbium(II)-center-induced redox reaction with bipyridine]. This hydrido complex reacts with Ph₃P═O, resulting in a P-C^Ph cleavage of Ph₃P═O and an elimination of C₆H₆; on the other hand, the reaction with Ph₃P═S is a hydrido coupling-based redox reaction. The reactions of this hydrido complex with 1 and 2 equiv of PhSSPh clearly indicate that the hydrido coupling-based redox reaction is prior to the ytterbium(II) oxidation-based redox reaction.

Treatment with the Immunomodulator AIC649 in Combination with Entecavir Produces Antiviral Efficacy in the Woodchuck Model of Chronic Hepatitis B

As current interventions for chronic hepatitis B (CHB) rarely induce cure, more effective drugs are needed. Short-term treatment of woodchucks with the novel immunomodulator AIC649, a parapoxvirus-based stimulator of toll-like receptor 9 dependent and independent pathways, has been shown to reduce viral DNA and surface antigen via a unique, biphasic response pattern. The present study evaluated long-term AIC649 treatment in combination with Entecavir for potency and safety in woodchucks. AIC649 monotreatment induced modest reductions in serum viral DNA and surface and e antigens that were associated with the same biphasic response pattern previously observed. Entecavir monotreatment reduced transiently viremia but not antigenemia, while AIC649/Entecavir combination treatment mediated superior viral control. Undetectability of viral antigens and elicitation of antibodies in AIC649/Entecavir-treated woodchucks correlated with the expression of interferons and suppression of viral replication in liver. Combination treatment was well tolerated, and liver enzyme elevations were minor and transient. It was concluded that the AIC649-mediated effects were most likely based on an improvement and/or reconstitution of antiviral immune responses that are typically deficient in CHB. As a combination partner to Entecavir, the antiviral efficacy of AIC649 was markedly enhanced. This preclinical study supports future evaluation of AIC649 for treatment of human CHB.

Insertion of Metal-Substituted Silylene into Naphthalene's Aromatic Ring and Subsequent Rearrangement for Silaspiro-Benzocycloheptenyl and Cyclobutenosilaindan Derivatives

Synthesis of silacycle compounds are of fundamental and application importance. Herein we report the first example of insertion of metal-substituted silylene fragment into naphthalene's aromatic ring. More significantly, this insertion is followed by interesting rearrangements to yield silaspiro-benzocycloheptenyl and cyclobutenosilaindan derivatives. The formation of cyclobutenosilaindan derivative includes the C-C bond cleavage and 4π electrocyclization steps; the formation of silaspiro-benzocycloheptenyl derivative is more complicated, including the C-C bond cleavage, reversible 4π electrocyclization, C-H bond activation and C-Si bond cleavage. DFT investigations were carried out to shed light on the mechanistic aspects of these two rearrangements. The formed cyclobutenosilaindan potassium can readily react with PhOH, MeOTf, EtOTf, PhCH₂ Cl or PhCOCl at room temperature to afford the hydrogen, alkyl, benzyl or benzoyl substituted cyclobutenosilaindans in high yields.

Synthesis and versatile reactivity of scandium phosphinophosphinidene complexes

M=E/M≡E multiple bonds (M = transition metal, E = main group element) are of significant fundamental scientific importance and have widespread applications. Expanding the ranges of M and E represents grand challenges for synthetic chemists and will bring new horizons for the chemistry. There have been reports of M=E/M≡E multiple bonds for the majority of the transition metals, and even some actinide metals. In stark contrast, as the largest subgroup in the periodic table, rare-earth metals (Ln) were scarcely involved in Ln=E/Ln≡E multiple bonds. Until recently, there were a few examples of rare-earth monometallic alkylidene, imido and oxo complexes, featuring Ln=C/N/O bonds. What are in absence are rare-earth monometallic phosphinidene complexes with Ln=P bonds. Herein, we report synthesis and structure of rare-earth monometallic phosphinidene complexes, namely scandium phosphinophosphinidene complexes. Reactivity of scandium phosphinophosphinidene complexes is also mapped out, and appears to be easily tuned by the supporting ligand.

FRI0428 RESULTS FROM A CROSS-SECTIONAL, OBSERVATIONAL STUDY TO ASSESS INADEQUATE PAIN RELIEF IN PATIENTS WITH KNEE AND/OR HIP OSTEOARTHRITIS IN CHINA

Background:

Osteoarthritis (OA) of the knee and hip is a leading cause of disability worldwide, particularly due to the primary symptom of pain in the weight-bearing joints. There is limited data that characterizes patients who experience moderate to severe pain despite analgesic treatment in China.

Objectives:

This study estimates the real-world prevalence of inadequate pain relief (IPR) among patients with knee and/or hip OA who have been prescribed analgesic therapy and characterizes this patient population. The study was conducted in China, the Philippines, Thailand, Russia, and Mexico. This abstract presents results from China.

Methods:

This is a multinational, multi-site, cross-sectional, observational study. Physicians managing patients with OA were recruited and asked to enroll patients over 50 years of age with knee and/or hip OA who had been prescribed topical and/or oral pain medication for at least 30 days prior to study visit. Patients completed a one-time assessment of pain, function, and health-related quality of life (HRQOL) using patient reported outcome (PRO) instruments. Physicians abstracted data from patient charts. IPR was defined as an average pain score of >4/10 on Brief Pain Inventory Question #5 (average pain). Statistical tests including chi-square for categorical variables and Mann-Whitney Wilcoxon test for continuous variables were conducted to assess differences in demographic and clinical characteristics as well as PROs between patients with and without IPR. A multivariate regression analysis was conducted to assess the relationship between IPR and PROs.

Results:

571 patients treated at 10 hospital centers in China were enrolled. 73% were female, the mean (SD) age was 62 (8.32) years. The number of years with OA ranged from less than one year to over 37 years, suggesting a broad sample of patients. Most patients were impacted by knee OA only (90%). Almost half (43%) of the study population met the definition of IPR. Patients with IPR tended to be older, have greater prevalence of obesity, have more comorbidities, and had longer disease duration. The majority (98%) of patients were receiving nonsteroidal anti-inflammatory drugs (NSAIDS), followed by chondroprotective medications (23%). However, more patients with IPR mentioned being dissatisfied with treatment (38% vs. 21%). After adjusting for covariates, patients with IPR reported worse HRQOL, more functional limitations, and reduced work productivity compared to patients without IPR.

Conclusion:

IPR is highly prevalent among individuals with knee and/or hip OA in China and is associated with decreased HRQOL and work productivity, impaired function, and treatment dissatisfaction. Developing awareness among healthcare professionals about the presence and potential impact of IPR is important for the ultimate improvement of OA patient management.

PROmean (SE)No IPR(N=328)IPR(N=243)EQ-5D Index0.72 (0.01)0.49 (0.02)EQ-5D VAS72.3 (0.85)65.5 (1.00)WOMAC Pain Subscale13.1 (0.78)22.7 (1.52)WOMAC Stiffness Subscale4.2 (0.27)7.4(0.51)WOMAC Physical Function Subscale44.8 (2.61)76.9 (5.07)Work Productivity Loss30.0 (4.07)47.5 (10.46)

Multivariate analysis adjusted for age, year since OA diagnosis/follow-up, gender, BMI, number of medication classes, insurance, physician specialty/academic responsibilities, number of affected joints, diabetes, CVD, hyperlipidemia/hypertension, and depression. All differences were statistically significant (p < 0.05) except work productivity loss (p=0.11)

Disclosure of Interests:

Xiaofeng Zeng Consultant of: MSD Pharmaceuticals, Xiaomei Leng Consultant of: MSD Pharmaceuticals, Knightley Wei Employee of: Employed by MSD Pharmaceuticals (China), Wen Min Tang Employee of: Employed by MSD Pharmaceuticals (China), Cai Hua Tang Employee of: Employed by MSD Pharmaceuticals (China), Kaan Tunceli Shareholder of: Holds company stock at Merck Sharp & Dohme Corp., Employee of: Employed by Merck Sharp & Dohme Corp., Jyoti Aggarwal Consultant of: Merck & Co., Inc., Dena Ramey Shareholder of: Holds company stock at Merck Sharp & Dohme Corp., Employee of: Employed by Merck Sharp & Dohme Corp., Fidel Lozano Employee of: Merck & Co. salaried employee, Ishita Doshi Shareholder of: Holds company stock at Merck Sharp & Dohme Corp., Employee of: Employed by Merck Sharp & Dohme Corp., Cynthia Macahilig Consultant of: Consultant to Merck Sharp & Dohme Corp., Shardul Odak Consultant of: Consultant to Merck Sharp & Dohme Corp., Kelly Johnson Employee of: Employed by Merck & Co., Inc.

C(sp3)-CF3 Reductive Elimination from a Five-Coordinate Neutral Copper(III) Complex

The reductive elimination from a high-valent late-transition-metal complex for the formation of a carbon-carbon or carbon-heteroatom bond represents a fundamental product-forming step in a number of catalytic processes. While reductive eliminations from well-defined Pt(IV), Pd(IV), Ni(III)/Ni(IV), and Au(III) complexes have been studied, the analogous reactions from neutral Cu(III) complexes remain largely unexplored. Herein, we report the isolation of a stable, five-coordinate, neutral square pyramidal Cu(III) complex that gives CH₃-CF₃ in quantitative yield via reductive elimination. Mechanistic studies suggest that the reaction occurs through a synchronous bond-breaking/bond-forming process via a three-membered ring transition state.

Samarium(II) Monoalkyl Complex Supported by a β-Diketiminato-Based Tetradentate Ligand: Synthesis, Structure, and Catalytic Hydrosilylation of Internal Alkynes

The synthesis and catalytic applications of trivalent rare-earth metal alkyl complexes have been well developed, but the chemistry of divalent rare-earth metal alkyl complexes lagged much behind. Herein, we report the synthesis, structure, and catalytic applications of a samarium(II) monoalkyl complex supported by a β-diketiminato-based tetradentate ligand, [LSmCH(SiMe₃ )₂ ] (L=[MeC(NDipp)CHC(Me)NCH₂ CH₂ N(Me)CH₂ CH₂ NMe₂ ]^- , Dipp=2,6-(iPr)₂ C₆ H₃ ). This complex is synthesized by the salt metathesis reaction of samarium iodide [LSm(μ-I)]₂ and KCH(SiMe₃ )₂ in 63 % yield. Its structure is characterized by single-crystal X-ray diffraction, showing a distorted square-pyramid coordination geometry. This samarium(II) monoalkyl complex exhibits high catalytic activity in the hydrosilylation of aryl and methyl-substituted unsymmetrical internal alkynes with secondary hydrosilanes, selectively providing the α-(E) products in high yields.

HIV drug resistance in patients in China's national HIV treatment programme who have been on first-line ART for at least 9 months

BACKGROUND

The aim of this study was to assess trends in drug resistance and associated clinical and programmatic factors at a national level during the rapid scale up of ART.

METHODS

Logistic regression was used to identify the factors associated with HIVDR. Variables associated with drug resistance in multivariable logistic regression were included in the Cochran-Armitage test for trend.

RESULTS

A total of 11,976 patients were enrolled in the study. The prevalence of HIVDR among patients who received ART for 9-24 months during 2003-2008, 2009-2012, and 2013-2015 significantly decreased (15.5%, 6.3%, and 2.3%, respectively, P < 0.01). With respect to the class of antiretroviral, there were substantial increases in resistance to both non-nucleoside reverse transcriptase inhibitors (NNRTIs) and nucleoside reverse transcriptase inhibitors (NRTIs) (2003-2008, 2009-2012, and 2013-2015: 49.7%, 58.9%, and 73.0%, respectively, P < 0.01). The prevalence of DR to protease inhibitors (PIs) was low, which supported their continued use as second-line therapy in China.

CONCLUSIONS

Our results provide evidence for the effectiveness of China's "Treat All" approach to guide policy makers to improve training for healthcare providers and education on ART adherence among patients.

α-C–C agostic interactions and C–H bond activation in scandium cyclopropyl complexes

Electron deficient scandium cyclopropyl complexes have been synthesized and fully characterized for the first time, and a combination of solid XRD, solution NMR and theoretical studies well demonstrated the α-C–C agostic interactions in the complexes.