A novel bispecific antibody drug conjugate targeting HER2 and HER3 with potent therapeutic efficacy against breast cancer.

Antibody drug conjugate (ADC) therapy has become one of the most promising approaches in cancer immunotherapy. Bispecific targeting could enhance the efficacy and safety of ADC by improving its specificity, affinity and internalization. In this study we constructed a HER2/HER3-targeting bispecific ADC (BsADC) and characterized its physiochemical properties, target specificity and internalization in vitro, and assessed its anti-tumor activities in breast cancer cell lines and in animal models. The HER2/HER3-targeting BsADC had a drug to antibody ratio (DAR) of 2.89, displayed a high selectivity against the target JIMT-1 breast cancer cells in vitro, as well as a slightly higher level of internalization than HER2- or HER3-monospecific ADCs. More importantly, the bispecific ADC potently inhibited the viability of MCF7, JIMT-1, BT474, BxPC-3 and SKOV-3 cancer cells in vitro. In JIMT-1 breast cancer xenograft mice, a single injection of bispecific ADC (3 mg/kg, i.v.) significantly inhibited the tumor growth with an efficacy comparable to that caused by combined injection of HER2 and HER3-monospecific ADCs (3 mg/kg for each). Our study demonstrates that the bispecific ADC concept can be applied to development of more potent new cancer therapeutics than the monospecific ADCs.

Long-term passaging of pseudo-typed SARS-CoV-2 reveals the breadth of monoclonal and bispecific antibody cocktails.

The continuous emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants poses challenges to the effectiveness of neutralizing antibodies. Rational design of antibody cocktails is a realizable approach addressing viral immune evasion. However, evaluating the breadth of antibody cocktails is essential for understanding the development potential. Here, based on a replication competent vesicular stomatitis virus model that incorporates the spike of SARS-CoV-2 (VSV-SARS-CoV-2), we evaluated the breadth of a number of antibody cocktails consisting of monoclonal antibodies and bispecific antibodies by long-term passaging the virus in the presence of the cocktails. Results from over two-month passaging of the virus showed that 9E12 + 10D4 + 2G1 and 7B9-9D11 + 2G1 from these cocktails were highly resistant to random mutation, and there was no breakthrough after 30 rounds of passaging. As a control, antibody REGN10933 was broken through in the third passage. Next generation sequencing was performed and several critical mutations related to viral evasion were identified. These mutations caused a decrease in neutralization efficiency, but the reduced replication rate and ACE2 susceptibility of the mutant virus suggested that they might not have the potential to become epidemic strains. The 9E12 + 10D4 + 2G1 and 7B9-9D11 + 2G1 cocktails that picked from the VSV-SARS-CoV-2 system efficiently neutralized all current variants of concern and variants of interest including the most recent variants Delta and Omicron, as well as SARS-CoV-1. Our results highlight the feasibility of using the VSV-SARS-CoV-2 system to develop SARS-CoV-2 antibody cocktails and provide a reference for the clinical selection of therapeutic strategies to address the mutational escape of SARS-CoV-2.

Interaction of Wnt pathway related variants with type 2 diabetes in a Chinese Han population.

Aims. Epistasis from gene set based on the function-related genes may confer to the susceptibility of type 2 diabetes (T2D). The Wnt pathway has been reported to play an important role in the pathogenesis of T2D. Here we applied tag SNPs to explore the association between epistasis among genes from Wnt and T2D in the Han Chinese population. Methods. Variants of fourteen genes selected from Wnt pathways were performed to analyze epistasis. Gene-gene interactions in case-control samples were identified by generalized multifactor dimensionality reduction (GMDR) method. We performed a case-controlled association analysis on a total of 1,026 individual with T2D and 1,157 controls via tag SNPs in Wnt pathway. Results. In single-locus analysis, SNPs in four genes were significantly associated with T2D adjusted for multiple testing (rs7903146(C) in TCF7L2, p = 3.21∗10(-3), OR = 1.39, 95% CI [1.31-1.47], rs12904944(G) in SMAD3, p = 2.51∗10(-3), OR = 1.39, 95% CI [1.31-1.47], rs2273368(C) in WNT2B, p = 4.46∗10(-3), OR = 1.23, 95% CI [1.11-1.32], rs6902123(C) in PPARD, p = 1.14∗10(-2), OR = 1.40, 95% CI [1.32-1.48]). The haplotype TGC constructed by TCF7L2 (rs7903146), DKK1 (rs2241529) and BTRC (rs4436485) showed a significant association with T2D (OR = 0.750, 95% CI [0.579-0.972], P = 0.03). For epistasis analysis, the optimized combination was the two locus model of WNT2B rs2273368 and TCF7L2rs7903146, which had the maximum cross-validation consistency. This was 9 out of 10 for the sign test at 0.0107 level. The best combination increased the risk of T2D by 1.47 times (95% CI [1.13-1.91], p = 0.0039). Conclusions. Epistasis between TCF7L2 and WNT2B is associated with the susceptibility of T2D in a Han Chinese population. Our results were compatible with the idea of the complex nature of T2D that would have been missed using conventional tools.

Expression profiles of miRNAs in Gossypium raimondii.

miRNAs are a class of conserved, small, endogenous, and non-protein-coding RNA molecules with 20-24 nucleotides (nt) in length that function as post-transcriptional modulators of gene expression in eukaryotic cells. Functional studies have demonstrated that plant miRNAs are involved in the regulation of a wide range of plant developmental processes. To date, however, no research has been carried out to study the expression profiles of miRNAs in Gossypium raimondii, a model cotton species. We selected 16 miRNAs to profile their tissue-specific expression patterns in G. raimondii four different tissues, and these miRNAs are reported to play important roles in plant growth and development. Our results showed that the expression levels of these miRNAs varied significantly from one to another in a tissue-dependent manner. Eight miRNAs, including miR-159, miR-162, miR-164, miR-172, miR-390, miR-395, miR-397, and miR-398, exhibited exclusively high expression levels in flower buds, suggesting that these miRNAs may play significant roles in floral development. The expression level of miR-164 was relatively high in shoots beside flower buds, implying that the function of miR-164 is not only limited to floral development but it may also play an important role in shoot development. Certain miRNAs such as miR-166 and miR-160 were extremely highly expressed in all of the four tissues tested compared with other miRNAs investigated, suggesting that they may play regulatory roles at multiple development stages. This study will contribute to future studies on the functional characterization of miRNAs in cotton.

Thyroid hormone attenuates vascular calcification induced by vitamin D3 plus nicotine in rats.

Thyroid hormones (THs) including thyroxine (T4) and triiodothyronine (T3) play critical roles in bone remodeling. However, the role and mechanism of THs in vascular calcification (VC) have been unclear. To explore the pathophysiological roles of T3 on VC, we investigated the changes in plasma and aortas of THs concentrations and the effect of T3 on rat VC induced by vitamin D3 plus nicotine (VDN). VDN-treated rat showed decreased plasma T3 content, increased vascular calcium deposition, and alkaline phosphatase (ALP) activity. Administration of T3 (0.2 mg/kg body weight IP) for 10 days greatly reduced vascular calcium deposition and ALP activity in calcified rat aortas when compared with controls. Concurrently, the loss of smooth muscle lineage markers α-actin and SM22a was restored, and the increased bone-associated molecules, such as runt-related transcription factor2 (Runx2), Osterix, and osteopontin (OPN) levels in calcified aorta, were reduced by administration of T3. The suppression of klotho in calcified rat aorta was restored by T3. Methimazole (400 mg/L) blocked the beneficial effect of T3 on VC. These results suggested that T3 can inhibit VC development.

Cinchona alkaloids from Cinchona succirubra and Cinchona ledgeriana.

Seven new cinchona alkaloids, cinchonanines A-G (1-7), and 29 known alkaloids were isolated from the barks of Cinchona surrirubra and C. ledgeriana collected from Yunnan Province in China. The new structures were elucidated by extensive spectroscopic analysis. All compounds were evaluated for their cytotoxicity against five human cancer cell lines. Compounds 2, 13, 14, and 15 showed moderate cytotoxicity.

Melosuavines A-H, cytotoxic bisindole alkaloid derivatives from Melodinus suaveolens.

Eight new bisindole alkaloids, melosuavines A-C (1-3), having an aspidosperma-scandine linkage, melosuavines D-F (4-6), possessing an aspidosperma-aspidosperma skeleton, and melosuavines G and H (7 and 8) of the aspidosperma-venalatonine type, tenuicausine (9), and melodinine J (10) were isolated from the twigs and leaves of Melodinus suaveolens. The structures of 1-8 were elucidated by extensive spectroscopic methods, and compounds 9 and 10 were identified by comparison with data in the literature. The relative configuration 9 was determined from the ROESY spectrum, and some NMR signals were reassigned. Compounds 1, 2, 4-6, 8, and 10 exhibited low micromolar cytotoxicity against one or more of five human cancer cell lines.

Gardovatine, a novel Strychnos-Strychnos bisindole alkaloid with cytotoxicity from Gardneria oveta.

Gardovatine (1), the first Strychnos-Strychnos alkaloid with a C3/C7 cleaved backbone, was isolated from twigs and leaves of Gardneria ovate, together with an analogue divarine (2). The structure was established by extensive spectroscopic methods. Both compounds showed potential cytotoxicities against five human cancer cell lines.

Intermedin1-53 attenuates vascular smooth muscle cell calcification by inhibiting endoplasmic reticulum stress via cyclic adenosine monophosphate/protein kinase A pathway.

We previously reported that endoplasmic reticulum (ER) stress-mediated apoptosis participated in vascular calcification. Importantly, a novel paracrine/autocrine peptide intermedin1-53 (IMD1-53) in the vasculature inhibited vascular calcification in rats. But the mechanisms needed to be fully elucidated. Vascular smooth muscle cells (VSMCs) calcification was induced by CaCl2 and ß-glycerophosphate. Tunicamycin (Tm) or dithiothreitol (DTT) was used to induce ER stress. We found that IMD1-53 (10(-7)mol/L) treatment significantly alleviated the protein expression of ER stress hallmarks activating transcription factor 4 (ATF4), ATF6, glucose-regulated protein 78 (GRP78) and GRP94 induced by Tm or DTT. ER stress occurred in early and late calcification of VSMCs but was inhibited by IMD1-53. These inhibitory effects of IMD1-53 were abolished by treatment with the protein kinase A (PKA) inhibitor H89. Pretreatment with IMD1-53 decreased the number of apoptotic VSMCs and downregulated protein expression of cleaved caspase 12 and C/EBP homologous protein (CHOP) in calcified VSMCs. Concurrently, IMD1-53 restored the loss of VSMC lineage markers and ameliorated calcium deposition and alkaline phosphatase activity in calcified VSMCs as well. The observation was further verified by Alizarin Red S staining, which showed that IMD1-53 reduced positive red nodules among calcified VSMCs. In conclusion, IMD1-53 attenuated VSMC calcification by inhibiting ER stress through cAMP/PKA signalling.

Activating transcription factor 4 is involved in endoplasmic reticulum stress-mediated apoptosis contributing to vascular calcification.

Our previous work reported that endoplasmic reticulum stress (ERS)-mediated apoptosis was activated during vascular calcification (VC). Activating transcription factor 4 (ATF4) is a critical transcription factor in osteoblastogenesis and ERS-induced apoptosis. However, whether ATF4 is involved in ERS-mediated apoptosis contributing to VC remains unclear. In the present study, in vivo VC was induced in rats by administering vitamin D3 plus nicotine. Vascular smooth muscle cell (VSMC) calcification in vitro was induced by incubation in calcifying media containing ß-glycerophosphate and CaCl2. ERS inhibitors taurine or 4-phenylbutyric acid attenuated ERS and VSMC apoptosis in calcified rat arteries, reduced calcification and retarded the VSMC contractile phenotype transforming into an osteoblast-like phenotype in vivo. Inhibition of ERS retarded the VSMC phenotypic transition into an osteoblast-like cell phenotype and reduced VSMC calcification and apoptosis in vitro. Interestingly, ATF4 was activated in calcified aortas and calcified VSMCs in vitro. ATF4 knockdown attenuated ERS-induced apoptosis in calcified VSMCs. ATF4 deficiency blocked VSMC calcification and negatively regulated the osteoblast phenotypic transition of VSMCs in vitro. Our results demonstrate that ATF4 was involved at least in part in the process of ERS-mediated apoptosis contributing to VC.

Transforming growth factor-ß1 gene mutations and phenotypes in pediatric patients with Camurati­Engelmann disease.

The aim of the present study was to investigate the clinical characteristics and major causative gene in pediatric patients with Camurati­Engelmann disease (CED). Biochemical and radiographic examinations, bone scintigraphy and genetic analyses were performed in two affected males and their parents. The two patients experienced waddling gait, muscular weakness and growth developmental delay. X-ray radiography revealed typical fusiform thickening of the diaphyseal portions of the long bones. The abnormal uptake of tracer Tc-99m was visualized in the skull and both sides of the upper humeri, ulnas, radii, femurs and tibias using bone scintigraphy. Serum levels of the bone formation marker procollagen type I N-terminal propeptide (PINP) and the bone resorption marker ß­isomerized C-terminal cross-linked telopeptide of type I collagen (ß-CTX) in the 6-year-old patient were significantly increased compared with the normal value range, while only the ß-CTX levels were elevated in the 16-year-old patient. A heterozygous missense mutation p.Arg218Cys in exon 4 of the transforming growth factor ß1 (TGFß1) gene was detected in the two patients, while their parents had normal wild­type genotypes. In conclusion, the p.Arg218Cys mutation was shown to contribute to the clinical phenotypes in two pediatric patients with CED. The results of this study suggest that abnormal bone turnover marker levels, typical radiological findings and mutations in the TGFß1 gene are three important factors in the diagnosis of sporadic CED cases.

The A242T mutation in the low-density lipoprotein receptor-related protein 5 gene in one Chinese family with osteosclerosis.

OBJECTIVE: Osteosclerosis (OMIM: 144750) is a type of autosomal dominant bone disease caused by a mutation in the low-density lipoprotein receptor-related protein 5 (LRP5) gene. The case of a Chinese family with two affected individuals is reported in the present study in order to investigate the clinical characteristics and virulence genes of this sclerosing bone disorder. METHODS: Biochemical and radiographic examinations and bone mineral density (BMD) and genetic analyses were performed in two patients and eight other family members. RESULTS: The 40-year-old proband (II-1) and her 64-year-old mother (I-2) both had chronic lumbodorsal pain, an elongated mandible and torus palatinus in the center of the hard palate. No fractures were observed in any of the family members. Skull, mandibular and pelvic X-rays in each of the two patients revealed thickened cranial plates, an enlarged sella turcica, an elongated mandible and cortical thickening of the long bones. The BMD values of the two patients was significantly higher than the standard age- and sex-matched adult mean reference values. Both patients had higher serum sclerostin levels, while their renal function markers and serum calcium, phosphonium, parathyroid hormone (PTH) and 25(OH)D levels were within the normal ranges. The heterozygous missense mutation p.Ala242Thr in exon 4 of the LRP5 gene was detected in the two patients, while the other family members and 200 healthy donors had normal wild-type genotypes. CONCLUSION: The A242T mutation in the LRP5 gene resulted in a high bone mass phenotype with an elongated mandible and torus palatinus in this osteosclerotic family.

Angiotensin-(1-7) inhibits vascular calcification in rats.

Angiotensin-(1-7) [Ang-(1-7)] is a new bioactive heptapeptide in the renin-angiotensin-aldosterone system (RAAS) with potent protective effects in cardiovascular diseases, opposing many actions of angiotensin II (Ang II) mediated by Ang II type 1 (AT1) receptor. It is produced mainly by the activity of angiotensin-converting enzyme 2 (ACE2) and acts through the Mas receptor. However, the role of Ang-(1-7) in vascular calcification (VC) is still unclear. In this study, we investigated the protective effects of Ang-(1-7) on VC in an in vivo rat VC model induced by vitamin D3 plus nicotine. The levels of ACE2 and the Mas receptor, as well as ACE, AT1 receptor, Ang II type 2 receptor and angiotensinogen, were significantly increased in calcified aortas, and Ang-(1-7) reversed the increased levels. Ang-(1-7) restored the reduced expression of lineage markers, including smooth muscle (SM) α-actin, SM22α, calponin and smoothelin, in vascular smooth muscle cells (VSMCs) and retarded the osteogenic transition of VSMCs by decreasing the expression of bone-associated proteins. It reduced alkaline phosphatase activity and calcium deposition in VC and alleviated the hemodynamic disorders of rats with VC. We provide the first in vivo evidence that Ang-(1-7) can inhibit the development of VC by inhibiting the osteogenic transition of VSMCs, at least in part by decreasing levels of the ACE/Ang II/AT1 axis. The increased expression of ACE2 and the Mas receptor in calcified aortas suggests the involvement of the ACE2/Ang-(1-7)/Mas axis during VC. Ang-(1-7) might be an efficient endogenous vasoprotective factor for VC.

[The relationship between hyperuricaemia and clinic pathology of IgA nephropathy].

OBJECTIVE: To analyze the correlation between the level of serum uric acid and the clinical and pathological features of IgA nephropathy. METHODS: Totally 148 patients diagnosed as IgA nephropathy by renal biopsy in our hospital from January 2007 to December 2010 were divided into hyperuricaemic group (41 cases) and non-hyperuricaemic group (107 cases) according to the level of serum uric acid. The clinical parameters and renal pathology grade were compared. RESULTS: There were significant differences between hyperuricaemic group and non-hyperuricaemic group in the incidences of hypertension (63.4% vs 38.3%), disease duration [(18.90 ± 10.12) months vs (9.46 ± 3.91) months] and body mass index [(22.81 ± 3.60) kg/m(2) vs (15.32 ± 2.54) kg/m(2)] (all P < 0.05), while no differences in age and sex (both P > 0.05). The blood urea nitrogen (BUN) [(8.93 ± 4.28) mmol/L vs (5.21 ± 2.18) mmol/L], creatinine (Cr) [(155.96 ± 107.72) µmol/L vs (79.52 ± 40.01) µmol/L], serum triglycerides [(2.11 ± 1.06) mmol/L vs (1.86 ± 1.20) mmol/L] and 24-hour urine protein amount [(4328.16 ± 1434.25) mg/24 h vs (2885.10 ± 1388.15) mg/24 h] were significantly different between the two groups (all P < 0.05). The percentage of Lee's grade I + II in hyperuricaemic group was 12.2%, and IV + V grade was 39.0%, while percentage of Lee's grade I + II in non-hyperuricaemic group was 25.2%, and IV + V grade was 16.9% (P < 0.05). Tubulointerstitial lesions (TIL) grade III + IV was more in hyperuricaemic group, which was 68.3%, while TIL grade II was more in non-hyperuricaemic group, which was 76.6%. Renal artery damage grade II + III was more in hyperuricaemic group, which was 73.2%, while renal artery damage grade 0 + I was more in non-hyperuricaemic group, which was 69.2%. CONCLUSIONS: The level of serum uric acid was related with 24-hour urine protein amount, blood pressure and kidney function in IgA nephropathy, and Lee's grade, TIL grade and renal artery damage grade were severe in hyperuricaemic group.

Adrenomedullin protects against fructose-induced insulin resistance and myocardial hypertrophy in rats.

Adrenomedullin (ADM) has been recognized as a multipotent multifunctional peptide. To explore the pathophysiological roles of ADM in insulin resistance (IR), we studied the changes in ADM mRNA level in the myocardium and vessels and the effect of ADM supplementation on rats with IR induced by fructose feeding. Rats were fed 4% fructose in drinking water for 8 weeks, and ADM was administered subcutaneously in pure water through an Alzet Mini-osmotic Pump at 300 ng/kg/h for the last 4 weeks. Compared with controls, rats with IR showed increased levels of fasting blood sugar and serum insulin, by 95% and 67%, respectively (all P<0.01), and glycogen synthesis and glucose transport activity of the soleus decreased by 54% and 55% (all P<0.01). mRNA level and content of brain natriuretic peptide (BNP) in myocardial were all increased significantly. Fructose-fed rats showed increased immunoreactive-ADM content in plasma by 110% and in myocardia by 55% and increased mRNA level in myocardia and vessels (all P<0.01). ADM administration ameliorated the induced IR and myocardial hypertrophy. The glycogen synthesis and glucose transport activity of the soleus muscle increased by 41% (P<0.01) and 32% (P<0.05). ADM therapy attenuated myocardial and soleus lipid peroxidation injury and enhanced the antioxidant ability. Our results showed upregulation of endogenous ADM during fructose-induced IR and the protective effect of ADM on fructose-induced IR and concomitant cardiovascular hypertrophy probably by its antioxidant effect, which suggests that ADM could be an endogenous protective factor in IR.

Deep sequencing identifies novel and conserved microRNAs in peanuts (Arachis hypogaea L.).

BACKGROUND: MicroRNAs (miRNAs) are a new class of small, endogenous RNAs that play a regulatory role in the cell by negatively affecting gene expression at the post-transcriptional level. miRNAs have been shown to control numerous genes involved in various biological and metabolic processes. There have been extensive studies on discovering miRNAs and analyzing their functions in model species, such as Arabidopsis and rice. Increasing investigations have been performed on important agricultural crops including soybean, conifers, and Phaselous vulgaris but no studies have been reported on discovering peanut miRNAs using a cloning strategy. RESULTS: In this study, we employed the next generation high through-put Solexa sequencing technology to clone and identify both conserved and species-specific miRNAs in peanuts. Next generation high through-put Solexa sequencing showed that peanuts have a complex small RNA population and the length of small RNAs varied, 24-nt being the predominant length for a majority of the small RNAs. Combining the deep sequencing and bioinformatics, we discovered 14 novel miRNA families as well as 75 conserved miRNAs in peanuts. All 14 novel peanut miRNAs are considered to be species-specific because no homologs have been found in other plant species except ahy-miRn1, which has a homolog in soybean. qRT-PCR analysis demonstrated that both conserved and peanut-specific miRNAs are expressed in peanuts. CONCLUSIONS: This study led to the discovery of 14 novel and 22 conserved miRNA families from peanut. These results show that regulatory miRNAs exist in agronomically important peanuts and may play an important role in peanut growth, development, and response to environmental stress.

Genome-wide computational identification of microRNAs and their targets in the deep-branching eukaryote Giardia lamblia.

Using a combined computational program, we identified 50 potential microRNAs (miRNAs) in Giardia lamblia, one of the most primitive unicellular eukaryotes. These miRNAs are unique to G. lamblia and no homologues have been found in other organisms; miRNAs, currently known in other species, were not found in G. lamblia. This suggests that miRNA biogenesis and miRNA-mediated gene regulation pathway may evolve independently, especially in evolutionarily distant lineages. A majority (43) of the predicted miRNAs are located at one single locus; however, some miRNAs have two or more copies in the genome. Among the 58 miRNA genes, 28 are located in the intergenic regions whereas 30 are present in the anti-sense strands of the protein-coding sequences. Five predicted miRNAs are expressed in G. lamblia trophozoite cells evidenced by expressed sequence tags or RT-PCR. Thirty-seven identified miRNAs may target 50 protein-coding genes, including seven variant-specific surface proteins (VSPs). Our findings provide a clue that miRNA-mediated gene regulation may exist in the early stage of eukaryotic evolution, suggesting that it is an important regulation system ubiquitous in eukaryotes.

Effect and mechanism of nociceptin/orphanin FQ reversing multi-drug resistance in K562/ADM cell.

OBJECTIVE: To investigate the effect and mechanism of nociceptin/orphanin FQ (OFQ) reversing multi-drug resistance of K562/ADM cells in vitro. METHODS: MTT assay, Wright staining, flow cytometry, transmission electron microscope and gel electrophoresis were used to evaluate the effect and mechanism of OFQ in reversing multi-drug resistance of K562/ADM cells. RESULTS: OFQ could time-dependently reverse the ADM resistance of K562/ADM cell. After treatment with OFQ (1 x 10(-7) mol x L(-1)), K562/ADM cells were cultured for 24, 48 and 72 h. The reversal index (RI) was 1.33, 1.42 and 1.53, respectively. Furthermore, OFQ significantly increased the intracellular accumulation of ADM in K562/ADM cells and percentage apoptosis in K562/ADM cells. OFQ down-regulated the level of P-gp time-dependently, while the level of Fas and FasL were up-regulated. There were evidently significant differences compared with the control (P < 0.01). After treating K562/ADM cells with OFQ (1 x 10(-7) mol x L(-1)) and ADM (20 microg x ml(-1)) for 48 hours, the cells showed apoptotic nuclear fragmentation, which was characterized by the appearance of a DNA ladder pattern in genomic DNA gel electrophoresis. CONCLUSION: OFQ can reverse the ADM resistance of K562/ADM cells. The mechanism involves OFQ up-regulating the expression of Fas/FasL, down-regulating the level of P-gp, and decreasing the intracellular level of calcium in K562/ADM cells.

Preclinical pharmacokinetics of a HepDirect prodrug of a novel phosphonate-containing thyroid hormone receptor agonist.

The prodrug [(2R,4S)-4-(3-chlorophenyl)-2-[(3,5-dimethyl-4-(4'-hydroxy-3'-isopropylbenzyl)phenoxy)methyl]-2-oxido-[1,3,2]-dioxaphosphonane (MB07811)] of a novel phosphonate-containing thyroid hormone receptor agonist [3,5-dimethyl-4-(4'-hydroxy-3'-isopropylbenzyl)phenoxylmethylphosphonic acid (MB07344)] is the first application of the HepDirect liver-targeting approach to a non-nucleotide agent. The disposition of MB07811 was characterized in rat, dog, and monkey to assess its liver specificity, which is essential in limiting the extrahepatic side effects associated with this class of lipid-lowering agents. MB07811 was converted to MB07344 in liver microsomes from all species tested (CL(int) 1.23-145.4 microl/min/mg). The plasma clearance and volume of distribution of MB07811 matched or exceeded 1 l/h/kg and 3 l/kg, respectively. Although absorption of prodrug was good, its absolute oral bioavailability as measured systemically was low (3-10%), an indication of an extensive hepatic first-pass effect. This effect was confirmed by comparison of systemic exposure levels of MB07811 after portal and jugular vein administration to rats, which demonstrated a hepatic extraction ratio of >0.6 with liver CYP3A-mediated conversion to MB07344 being a major component. The main route of elimination of MB07811 and MB07344 was biliary, with no evidence for enterohepatic recirculation of MB07344. Similar metabolic profiles of MB07811 were obtained in liver microsomes across the species tested. Tissue distribution and whole body autoradiography confirmed that the liver is the major target organ of MB07811 and that conversion to MB07344 was high in the liver relative to that in other tissues. Hepatic first-pass extraction and metabolism of MB07811, coupled with possible selective distribution of MB07811-derived MB07344, led to a high degree of liver targeting of MB07344.