Physicochemical Properties, Bioconversion and Disposition of Lipophilic Prodrugs of 2′,3′-Dideoxycytidine

1996 ◽  
Vol 7 (3) ◽  
pp. 167-172 ◽  
Author(s):  
S.S. Ibrahim ◽  
F.D. Boudinot ◽  
R.F. Schinazi ◽  
C.K. Chu
Keyword(s):  
Mouse Brain ◽  
Half Life ◽  
Liver Homogenate ◽  
Brain Homogenate ◽  
In Vivo Studies ◽  
Mouse Serum ◽  
Lipophilic Prodrugs ◽  
Life Values

Lipophilic prodrugs of 2′,3′-dideoxycytidine (ddC), 4,5′-diacetyI-ddC (DAC), 4,5′-ditrimethylacetyl-ddC (DTMAC), 4,5′-dicyclopentylpropionyl-ddC (DCYPP) and 5′-cholesteryl-ddC (CHOL), were evaluated for their utility in improving brain delivery of the parent nucleoside. The lipophilicity of the prodrugs was greater, compared to ddC., with partition coefficient values increasing from 0.03 for ddC to 0.37,28, 63 and 483 for DAC., DTMAC., DCYPP and CHOL., respectively. Aqueous solubility was decreased proportionally to the increase in lipophilicity. Bioconversion studies were performed in phosphate buffer (pH 7.4), human serum, mouse serum, and mouse brain and liver homogenates. Whereas CHOL was stable in vitro in all media, DAC., DTMAC and DCYPP exhibited stability only in buffer, indicating that the hydrolytic reaction for these compounds was, predominately, enzymatically triggered. DCYPP was rapidly hydrolysed in mouse serum and liver and brain homogenates with degradation half-life values of 0.04, 0.35 and 0.34 h respectively. DAC had a longer half-life in mouse serum than did DTMAC (0.82 h vs. 0.38 h), however, in mouse brain homogenate DTMAC (t1/2=3.9 h) was more stable than DAC (t1/2= 1.6 h). Both of these pro-drugs were rapidly metabolized in the mouse liver homogenate with half-life values of 0.36 h for DAC and 0.23 h for DTMAC. In-vivo studies performed for ddC., DAC and DTMAC in mice showed that the relative brain exposure (re) of ddC was not improved by administering the prodrugs. DTMAC yielded a re value of 0.023 which was similar to that for ddC (re = 0.028), while no ddC was detected in brain after DAC administration. Thus, although all of the prodrugs were more lipophilic than ddC., delivery of ddC to the brain was not enhanced in vivo.

scholarly journals In Vitro Characterization of Rabbit Thrombin, Antithrombin III, and Thrombin-Antithrombin III Complex, and Determination of Their Survival Times in Vivo

1977 ◽  
Author(s):  
Christine N. Vogel ◽  
Kingdon S. Henry ◽  
Roger L. Lundblad
Keyword(s):  
Gel Electrophoresis ◽  
Half Life ◽  
Antithrombin Iii ◽  
Specific Activity ◽  
Sodium Dodecyl ◽  
In Vivo Studies ◽  
Survival Times ◽  
At Iii

Our intention is to study the interaction of rabbit thrombin with antithrombin III (AT-III) in vitro and in vivo. After activation of crude prothrombin with tissue thromboplastin and CaCl2, thrombin was purified and showed two species of thrombin with molecular weights of 36,000 and 39,000 daltons as determined by sodium dodecyl sulfate discontinuous gel electrophoresis. Rabbit AT-III was purified using a heparin agarose column and had a molecular weight of 55,000 daltons. The inhibition of thrombin by AT-III was followed by fibrinogen clotting assays and an AT-III-thrombin complex was observed on gel electrophoresis. For the in vivo studies both thrombin and AT-III were radiolabelled with Na125i using the solid state lactoperoxidase method and retained 99% of the pre-iodinated specific activity. Radiolabelled thrombin and a radiolabelled AT-III-thrombin complex were injected into different rabbits. The rate of removal of both was very similar with a half-life of approximately 9 hours. When radiolabelled AT-III was injected, the half-life was approximately 60 hours. Since the disappearance rate of thrombin more closely approximates that of the preformed AT-III-thrombin complex and is clearly shorter than the turnover rate of AT-III, the possibility is raised that thrombin combines in vivo with a native inhibitor such as AT-III and may in fact be removed from the circulation as a complex rather than as a native molecule.

scholarly journals Once-versus thrice-daily netilmicin combined with amoxicillin, penicillin, or vancomycin against Enterococcus faecalis in a pharmacodynamic in vitro model.

1996 ◽  
Vol 40 (10) ◽  
pp. 2258-2261 ◽  
Author(s):  
S Schwank ◽  
J Blaser
Keyword(s):  
Enterococcus Faecalis ◽  
Half Life ◽  
In Vitro Model ◽  
Bacterial Biofilm ◽  
In Vivo Studies ◽  
Bacterial Killing ◽  
Once Daily ◽  
Vitro Model

Several in vitro and in vivo studies as well as clinical trials have demonstrated that once-daily aminoglycoside regimens are as effective as or more effective than multiple daily dosings. However, the most favorable aminoglycoside dosing regimen for treating enterococcal endocarditis remains controversial. The same total dose of netilmicin was administered as once-daily (24-micrograms/ml peaks) and thrice-daily (8 micrograms/ml) regimens in a pharmacodynamic in vitro model simulating exposure of Enterococcus faecalis to human serum kinetics. Netilmicin was administered in combination with continuous infusions of amoxicillin, vancomycin, or penicillin against a bacterial biofilm adhering to glass beads. No significant differences in bacterial killing were found after 24 or 48 h between the once- and thrice-daily regimens. Additional experiments considering animal kinetics (half-life of netilmicin, 20 min) instead of human kinetics (half-life, 2.5 h) in the pharmacodynamic model also revealed similar results. The addition of netilmicin synergistically increased the activity of vancomycin (P < 0.05). In contrast, amoxicillin alone was as effective as the combination with netilmicin. Thus, it could not be established in this model that once-daily dosing of aminoglycosides is contraindicated for treating infections caused by E. faecalis.

scholarly journals In vivo and in vitro degradation of peptide YY3–36 to inactive peptide YY3–34 in humans

2016 ◽  
Vol 310 (9) ◽  
pp. R866-R874 ◽  
Author(s):  
Signe Toräng ◽  
Kirstine Nyvold Bojsen-Møller ◽  
Maria Saur Svane ◽  
Bolette Hartmann ◽  
Mette Marie Rosenkilde ◽  
...  
Keyword(s):  
Half Life ◽  
Peptide Yy ◽  
Degradation Products ◽  
In Vivo Studies ◽  
Metabolic Clearance ◽  
In Vitro Degradation ◽  
Healthy Men ◽  
Amino Acid Peptide

Peptide YY (PYY) is a 36-amino-acid peptide released from enteroendocrine cells upon food intake. The NH2 terminally truncated metabolite, PYY3–36, exerts anorexic effects and has received considerable attention as a possible antiobesity drug target. The kinetics and degradation products of PYY metabolism are not well described. A related peptide, neuropeptide Y, may be degraded from the COOH terminus, and in vivo studies in pigs revealed significant COOH-terminal degradation of PYY. We therefore investigated PYY metabolism in vitro after incubation in human blood and plasma and in vivo after infusion of PYY1–36 and PYY3–36 in eight young, healthy men. A metabolite, corresponding to PYY3–34, was formed after incubation in plasma and blood and during the infusion of PYY. PYY3–34 exhibited no agonistic or antagonistic effects on the Y2 receptor. PYY1–36 infused with and without coadministration of sitagliptin was eliminated with half-lives of 10.1 ± 0.5 and 9.4 ± 0.8 min (means ± SE) and metabolic clearance rates of 15.7 ± 1.5 and 14.1 ± 1.1 ml·kg−1·min−1 after infusion, whereas PYY3–36 was eliminated with a significantly longer half-life of 14.9 ± 1.3 min and a metabolic clearance rate of 9.4 ± 0.6 ml·kg−1·min−1. We conclude that, upon intravenous infusion in healthy men, PYY is inactivated by cleavage of the two COOH-terminal amino acids. In healthy men, PYY3–36 has a longer half-life than PYY1–36.

Comparison of Biodistributions and Therapeutic Efficacies of Pretargeted Radioimmunoconjugates Targeting the CD20, CD22, and DR Molecules on Human B Cell Lymphomas.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 611-611
Author(s):  
Anastasia Pantelias ◽  
John M. Pagel ◽  
Nathan Hedin ◽  
Yukang Lin ◽  
Donald Axworthy ◽  
...  
Keyword(s):  
Cell Lines ◽  
Half Life ◽  
Lymphoma Cell ◽  
In Vivo Studies ◽  
Cell Binding ◽  
Normal Tissues ◽  
Human Lymphoma ◽  
Anti Cd20

Abstract Radioimmunotherapy (RIT) using anti-CD20 monoclonal antibodies (Ab) produces response rates of 60–95% in relapsed non-Hodgkin’s lymphoma (NHL) patients; however, tumor-to-normal organ ratios of absorbed radiation are low and many patients relapse. The efficacy of RIT is limited by non-specific delivery of radiation to normal tissues due to the long circulating half-life of radiolabeled antibodies. Pretargeted RIT (PRIT) using streptavidin (SA)-Ab conjugates followed by a clearing agent and radiolabeled biotin can augment the efficacy of RIT and decrease toxicity compared with conventional RIT. Although PRIT using anti-CD20-SA Abs have been studied with promising results, targeting multiple antigens may increase efficacy. Since successful clinical trials have been conducted with directly radiolabeled anti-DR and anti-CD22 Abs, we initiated in vitro and in vivo studies comparing pretargeted anti-CD20 Ab-SA conjugate (1F5/SA) with pretargeted anti-CD22-SA (HD39/SA) and anti-HLA-DR-SA (Lym-1/SA) conjugates in three different human B-lymphoma cell lines, RAMOS (Burkitt), RAJI (Burkitt) and FL-18 (transformed follicular). Using standard flow cytometry techniques all three Ab-SA conjugates bound to ≥ 97% of FL18 cells. Cell binding for 1F5/SA, Lym-1/SA, and HD39/SA was 99%, 99%, and 83% to RAJI cells, respectively, and 99%, 22%, and 85% to RAMOS cells. The blood half-life of each conjugate in vivo was measured by injecting groups of 4 mice i.v. with 0.7nmol (150μg) of 125I labeled Ab-SA conjugate and drawing 10μl of blood at various time points to determine the percent injected dose per gram (% ID/g). The half-lives of 1F5/SA, Lym-1/SA and HD39/SA were 18.38, 14.92 and 16.23 hours, respectively. When 5.8nmol (50μg) of a clearing agent (synthetic biotin-N-acetyl-galactosamine) was given 24 hours post 125I-Ab-SA injection, the % ID/g in blood fell by more than 80% of the initial dose within a half-hour. Blood, tumor and non-specific organ uptake was determined by biodistribution experiments in mice (Balb/c nu/nu) bearing human lymphoma xenografts. Athymic mice with s.c. RAMOS, RAJI, or FL-18 xenografts received 1.4nmol (300μg) of either 1F5/SA, HD39/SA, or Lym-1/SA i.v. followed 24 hours later by 5.8nmol (50μg) clearing agent to remove non-localized conjugate from circulation, and 3 hours later by an 111In labeled DOTA-biotin ligand (1μg). The biodistributions of each conjugate were evaluated by sacrificing mice at 24 and 48 hours after 111In-DOTA-biotin. At 24 hours, the ID/g was 18.2±13.6% in FL18 xenografts for pretargeted Lym-1/SA, 18.2±17.4% ID/g for 1F5/SA and 3.3±0.7% ID/g for HD39/SA. Conversely, at 24 hours pretargeted Lym-1/SA uptake in RAJI tumors was 10.8±2.1% ID/g, and 1F5/SA and HD39/SA RAJI tumor localization was 5.2±1.9% ID/g and 2.2±0.5% ID/g. respectively. 1F5/SA had superior uptake (7.1±3.3% ID/g) in RAMOS xenografts compared with Lym-1/SA (3.5±1.5% ID/g) and HD39/SA (2.7±1.0% ID/g). These data suggest a strong correlation between in vitro cell binding results and in vivo biodistributions for all three Ab-SA conjugates in all three human lymphoma cell lines. Using these agents in combination may result in a synergistic effect that has the potential to increase the efficacy of PRIT over using any one of the agents alone. Biodistribution and therapy studies using the Ab-SA conjugates in combination in tumored mice are on-going.

Arginine pharmacokinetics in humans assessed with an enzymatic assay adapted to a centrifugal analyzer.

1989 ◽  
Vol 35 (6) ◽  
pp. 1024-1026 ◽  
Author(s):  
T W van Haeften ◽  
C H Konings
Keyword(s):  
Insulin Secretion ◽  
Half Life ◽  
Volume Of Distribution ◽  
In Vivo Studies ◽  
Metabolic Clearance ◽  
Enzymatic Method ◽  
Automated Assay ◽  
Arginine Concentration

Abstract Arginine is used in supra-physiological concentrations as an insulin secretagogue, in both in vitro and in vivo studies. To investigate the pharmacokinetics of arginine in humans, we have developed a rapid, automated assay of arginine in serum, based on our manual enzymatic method (Clin Chim Acta 1988, 176; 185-94). The limit of linearity of the automated assay was an arginine concentration of 3 mmol/L. Within-run CVs for Ortho control sera with added arginine were 5.5%, 0.8%, and 0.7% at concentrations of 0.16, 1.30, and 2.50 mmol/L, respectively. After 30 min of primed continuous infusions with arginine at infusion rates of 3, 9, 15, and 21 mg/kg per minute, mean (+/- SEM) arginine concentrations in serum from eight volunteers were 1.17 +/- 0.08, 3.44 +/- 0.21, 6.84 +/- 0.58, and 9.25 +/- 0.39 mmol/L, respectively, well within the range of arginine concentrations shown (in vitro) to stimulate insulin secretion. Metabolic clearance of arginine was approximately 11 mL/kg body wt per minute. For the lowest three infusion rates, the half-life (t1/2) of arginine was approximately 15 min and the volume of distribution (Vd) was approximately 290 mL/kg. At the highest infusion rate, t1/2 was significantly increased (27.3 +/- 3.1 min), owing to an increased Vd (446 +/- 83 mL/kg).

scholarly journals Preclinical development of anti-BCMA immunotoxins targeting multiple myeloma

2018 ◽  
Vol 1 (1) ◽  
pp. 19-25 ◽  
Author(s):  
Zoe Shancer ◽  
Matthew Williams ◽  
Austin Igelman ◽  
Satoshi Nagata ◽  
Tomoko Ise ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
B Cell ◽  
Half Life ◽  
Bacterial Toxin ◽  
Mouse Serum ◽  
Serum Albumins ◽  
Preclinical Development ◽  
Binding Domains

ABSTRACT Background Multiple myeloma (MM) is a B-cell malignancy that is incurable for the majority of patients. New treatments are urgently needed. Recombinant immunotoxins (RITs) are chimeric proteins that are composed of the Fv or Fab portion of an antibody fused to a bacterial toxin. B-cell maturation antigen (BCMA) is a lineage-restricted differentiation protein and an ideal target for antibody-based treatments for MM. Methods RITs were produced by expressing plasmids encoding the components of the anti-BCMA RITs in Escherichia coli followed by inclusion body preparation, solubilization, renaturation, and purification by column chromatography. The cytotoxic activity of RITs was tested in vitro by WST-8 assays. We also measured their binding to human and mouse serum albumins and to BCMA and measured their serum half-life in mice. Results Using Fvs from different anti-BCMA antibodies, we produced RITs that specifically kill BCMA-expressing MM cells in vitro. To increase the serum half-life in vivo, we generated RITs that are fused with albumin-binding domains (ABDs). All RITs with ABDs have some decreased activity compared to the parent RIT, which is not due to decreased binding to BCMA. Conclusions Various new anti-BCMA immunotoxins were produced and evaluated. None of these were better than LMB-75 (anti-BCMA BM306-disulfide-stabilized Fv-LRggs) supporting the further preclinical development of LMB-75.

In vitro and in vivo studies of new cationic Zn(II)‐benzonaphthoporphyrazines as photosensitizers for PDT

2001 ◽  
Vol 5 (8) ◽  
pp. 645-651
Author(s):  
M. Peeva ◽  
M. Shopova ◽  
U. Michelsen ◽  
D. Wöhrle ◽  
G. Petrov ◽  
...  
Keyword(s):  
In Vivo Studies

Effect of caffeine on theophyliine on cerebral blood flow response to brain activation: In vitro and in vivo studies

2005 ◽  
Vol 25 (1_suppl) ◽  
pp. S198-S198
Author(s):  
Joseph R Meno ◽  
Thien-son K Nguyen ◽  
Elise M Jensen ◽  
G Alexander West ◽  
Leonid Groysman ◽  
...  
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Brain Activation ◽  
In Vivo Studies ◽  
Blood Flow Response ◽  
Flow Response

Kinetics of Various 99mTc-Sn-Pyrophosphate Compounds in the Rat

1977 ◽  
Vol 16 (04) ◽  
pp. 157-162 ◽  
Author(s):  
C. Schümichen ◽  
B. Mackenbrock ◽  
G. Hoffmann
Keyword(s):  
Normal Saline ◽  
Half Life ◽  
Compound A ◽  
Short Half Life ◽  
Low Concentrations ◽  
The Stability ◽  
Kinetics Of ◽  
In Vitro Stability

SummaryThe bone-seeking 99mTc-Sn-pyrophosphate compound (compound A) was diluted both in vitro and in vivo and proved to be unstable both in vitro and in vivo. However, stability was much better in vivo than in vitro and thus the in vitro stability of compound A after dilution in various mediums could be followed up by a consecutive evaluation of the in vivo distribution in the rat. After dilution in neutral normal saline compound A is metastable and after a short half-life it is transformed into the other 99mTc-Sn-pyrophosphate compound A is metastable and after a short half-life in bone but in the kidneys. After dilution in normal saline of low pH and in buffering solutions the stability of compound A is increased. In human plasma compound A is relatively stable but not in plasma water. When compound B is formed in a buffering solution, uptake in the kidneys and excretion in urine is lowered and blood concentration increased.It is assumed that the association of protons to compound A will increase its stability at low concentrations while that to compound B will lead to a strong protein bond in plasma. It is concluded that compound A will not be stable in vivo because of a lack of stability in the extravascular space, and that the protein bond in plasma will be a measure of its in vivo stability.

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