B-cell-directed CAR-T cell therapy activates CD8+ cytotoxic CARneg bystander T-cells in non-human primates and patients

CAR-T cells hold promise as a therapy for B-cell-derived malignancies, yet despite their impressive initial response rates, a significant proportion of patients ultimately experience relapse. While recent studies have explored the mechanisms of in vivo CAR-T cell function, little is understood about the activation of surrounding CARneg bystander T-cells and their potential to enhance tumor responses. We performed single-cell RNA-Seq (scRNA-Seq) on non-human primate (NHP) and patient-derived T-cells to identify the phenotypic and transcriptomic hallmarks of bystander activation of CARneg T-cells following B-cell targeted CAR-T cell therapy. Utilizing a highly translatable CD20 CAR NHP model, we observed a distinct population of activated CD8+ CARneg T-cells emerging during CAR-T cell expansion. These bystander CD8+ CARneg T-cells exhibited a unique transcriptional signature with upregulation of NK-cell markers (KIR3DL2, CD160, KLRD1), chemokines and chemokine receptors (CCL5, XCL1, CCR9), and downregulation of naive T-cell-associated genes (SELL, CD28). A transcriptionally similar population was identified in patients following Tisagenlecleucel infusion. Mechanistic studies revealed that IL-2 and IL-15 exposure induced bystander-like CD8+ T-cells in a dose dependent manner. In vitro activated and patient-derived T-cells with the bystander phenotype efficiently killed leukemic cells through a TCR-independent mechanism. Collectively, this dataset provides the first comprehensive identification and profiling of CARneg bystander CD8+ T-cells following B-cell targeting CAR-T cell therapy and suggests a novel mechanism through which CAR-T cell infusion might trigger enhanced anti-leukemic responses.

Abstract 2296: Inhibition of the PI3K/Akt pathway during CAR T cell production results in enhanced efficacy across multiple in vivo tumor models

Patients treated with chimeric antigen receptor (CAR) T cells targeting CD19 for B cell malignancies have experienced rapid and durable tumor regressions. Manufacture of CAR T cells for treatment requires ex vivo culture to facilitate CAR gene transfer and to achieve a therapeutic dose of the modified cells. Recent data suggests that specific T cell subtypes can provide enhanced anti-tumor efficacy, spurring efforts to optimize the production of therapeutic T cells via the cumbersome physical isolation of central memory T cells or culture in cytokines such as IL-7 and IL-15. Here we explored the potential for a simple culture modification to improve the therapeutic potential of CAR T cells without adding manufacturing complexity. To this end, we produced CAR T cells specific to B cell maturation antigen (BCMA) using standard IL-2 culture conditions supplemented with a PI3K inhibitor, or with IL-7 and IL-15 in place of IL-2. The in vivo activity of CAR T cells was studied in mouse models of human Burkitt's lymphoma (Daudi) and multiple myeloma (RPMI-8226), both of which express BCMA. In the Daudi model, NSG mice were injected intravenously with 2 × 106 tumor cells and allowed to accumulate a large tumor burden to model late stage disease observed in relapsed and refractory lymphoma. In this advanced disease model, anti-BCMA CAR T cells (4 × 106/mouse) cultured either in IL-2 or IL-7 and IL-15 had little or no effect on tumor growth (p = 0.22 and 0.23, respectively) and all mice succumbed to tumors within two weeks of treatment. In contrast, all animals treated with the same number of anti-BCMA CAR T cells cultured with PI3K inhibition survived and had complete long-term tumor regression (p = 0.003). The same anti-BCMA CAR T cells were studied in a model of multiple myeloma. NSG mice were injected subcutaneously with 107 RPMI-8226 cells and 22 days later received a single administration of anti-BCMA CAR T cells (4 × 105/mouse) cultured under various conditions. In this model, tumor regression occurred regardless of in vitro culture conditions. To model tumor relapse and evaluate CAR T cell durability, surviving animals were re-challenged with RPMI-8226 cells on the opposite flank two weeks after initial tumor clearance. In contrast to other conditions, all animals treated with anti-BCMA CAR T cells cultured with PI3K inhibition were protected against subsequent tumor challenge (p = 0.005). This improved therapeutic activity of anti-BCMA CAR T cells cultured with PI3K inhibition was associated with an increased frequency of CD62L+ CD8+ T cells in the drug product (p < 0.001) suggesting enrichment of this distinct CD8 T cell subset. These data suggest that inhibition of PI3K during ex vivo expansion

with IL-2 may generate an improved anti-BCMA CAR T cell product for clinical use. Furthermore, this approach could potentially be used in the manufacture of other T cell therapies.

Citation Format: Shannon Grande, Molly R. Perkins, Amanda Hamel, Holly M. Horton, Fay Eng, Claire J. Rhodes, Tracy E. Garrett, Sara M. Miller, John W. Evans, Howard J. Latimer, Christopher Horvath, Michael Kuczewski, Kevin Friedman, Richard A. Morgan. Inhibition of the PI3K/Akt pathway during CAR T cell production results in enhanced efficacy across multiple in vivo tumor models. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2296.

gp180, a host cell glycoprotein that binds duck hepatitis B virus particles, is encoded by a member of the carboxypeptidase gene family

Duck hepatitis B virus particles bearing the L and S envelope proteins bind a cellular glycoprotein of 180 kDa (gp180) with high affinity and specificity. Binding is mediated by the pre-S region of the L protein and is blocked by neutralizing but not by non-neutralizing monoclonal antibodies to the virus. These and other properties have suggested that gp180 may be a component of the viral entry machinery. Here we report the purification of gp180 from duck liver and the isolation and characterization of cDNA encoding it. DNA sequence analysis of this cDNA indicates that gp180 is a novel member of the basic carboxypeptidase gene family.

Mechanistic study on toxicity of positively charged liposomes containing stearylamine to blood

We studied the interaction of stearylamine (SA) containing liposomes (SA-liposomes) with erythrocyte ghost (EG) or platelets, utilizing the Tb/dipicolinate (Tb/DPA) assay for the mixing of aqueous contents and a resonance energy transfer (RET) assay for the mixing of lipid. The results demonstrate that SA-liposomes and EG, after aggregation, have a great tendency to mix their lipid before the mixing of the internal contents. The mixing of their contents takes place inside the vesicles due to the fusion of SA-liposomes and EG, followed by the leakage of the contents from the vesicles. In the presence of carboxymethyl chitin (CM-chitin), SA-liposomes-EG interaction was inhibited, indicating that CM-chitin reduces the tendency of SA-liposomes to interact with EG. The lipid mixing between SA-liposomes and platelets was not affected by CM-chitin or phagocytosis inhibitors: EDTA, cytochalasin B, or 2,4-dinitrophenol and iodoacetate, indicating the importance of glycoproteins on the platelet membrane surface in the interaction of SA-liposomes with platelets.

Ibogaine modulates cocaine responses which are altered due to environmental habituation: in vivo microvoltammetric and behavioral studies

Ibogaine, a serotonergic (5-HTergic) indole alkaloid, was studied for cocaine modulatory effects on four parameters of behavior by computerized infrared photocell beam detection. The behavioral parameters were: a) locomotor activity (ambulations), b) rearing, c) stereotypy (fine movements, primarily grooming), and d) agoraphobia [(thigmotaxis) a natural tendency to avoid the center of the behavioral chamber]. With each behavioral data point, dopamine (DA) release, and serotonin (5-HT) release were detected within seconds in nucleus accumbens (NAcc) of the same behaving male Sprague-Dawley rats, using in vivo electrochemistry (voltammetry). Ibogaine was administered (40 mg/kg IP) for 4 consecutive days. Importantly, the DAergic and the 5-HTergic responses to (SC) cocaine and two behavioral responses, ambulations and central ambulations, were reduced in intensity due to extended time spent in the novel behavioral chamber (habituated). Rearing and fine movement patterns were not habituated. The results show that ibogaine downmodulated the (SC) cocaine-induced increase in NAcc DA release (p < 0.0001) and potentiated the (SC) cocaine-induced decrease in NAcc 5-HT release (p < 0.0001). Concurrently, ibogaine downmodulated cocaine-induced ambulation (p < 0.0001) and central ambulation behavior (p < 0.0001). On the other hand, the behavioral parameters that did not exhibit habituation, i.e., rearing behavior and fine movement behavior, were not downmodulated by ibogaine (p < 0.1558) (p < 0.3763), respectively. Furthermore, ibogaine itself did not significantly alter NAcc DA release over the 2-h period studied (p < 0.9113) although individual time points were significantly affected bidirectionally. Concurrently ibogaine significantly increased 5-HT release (p < 0.0155). Behaviorally, ibogaine appears to be a weak psychostimulant. The data show a critical modulatory role for 5-HT in ibogaine-cocaine interactions. Also elucidated as critical is the efficacy of ibogaine when the response to (SC) cocaine is decreased due to the habituation of the animals to their environment.

Long-term alterations in the permeability of the blood-testis barrier following a single intratesticular injection of dilute aqueous glycerol

The mechanism whereby glycerol exerts its antispermatogenic action is not known. The objective of this study was to determine, with the use of [3H]inulin and [125I]albumin by in vivo and in vitro methods, whether glycerol exerts its effect by altering the permeability of the blood-testis barrier (BTB). Adult male rats received a single intratesticular injection of either glycerol (10% or 20%; treated) or saline (control), and 2, 4, 8, 26, and 56 weeks after treatment, either [3H]inulin or [125I]albumin was administered either by infusion or directly to the testicular tissues. Radioactivity was measured in testicular tissue, rete testis fluid, and seminiferous tubular fluid. Following in vivo administration, the uptake of [3H]inulin by seminiferous tubules, rete testis fluid, and seminiferous tubule fluid was significantly greater in the treated than in the control testes at all times after treatment. Radiolabeled inulin, injected into isolated testes or added to medium in which isolated tubules were incubated, accumulated at significantly higher levels in the seminiferous tubule compartment of treated than control tissues. Rete testis fluid from treated testes, collected by micropuncture following efferent duct ligation, contained about 5- to 13-fold more radioactivity than fluid from controls. Following infusion of 50 microCi of [125I]albumin into the jugular vein, the accumulated radioactivity was significantly greater in testicular and epididymal tissues and in the seminiferous tubule fluid from treated than from control animals. In all experiments the significant differences between treated and control were maintained during the period of 2-56 weeks following glycerol treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Real time detection of acute (IP) cocaine-enhanced dopamine and serotonin release in ventrolateral nucleus accumbens of the behaving Norway rat

Cocaine (10 mg/kg), administered intraperitoneal (IP), was studied for its effects on dopamine (DA) and serotonin (5-HT) release in ventrolateral nucleus accumbens (vlNAcc) of conscious and behaving male, virus-free, Sprague-Dawley rats with in vivo electrochemistry (voltammetry). Miniature stearate probes detected DA and 5-HT release, on line and within a temporal resolution of seconds. Psychostimulant behaviors, in the form of four behavioral components (i.e., the classically DA-dependent behaviors of locomotor activity [ambulations], rearing, and stereotypy, and a 5-HT-ergic behavior, central ambulations) were studied concurrently with infrared photobeam detection. The results show that (IP) cocaine significantly increased vlNAcc DA release (p < 0.0001) and 5-HT release (p < 0.0012). Each of the four parameters of cocaine-induced psychostimulant behavior was concurrently and significantly increased as well (ambulations: p < 0.0001); rearing p < 0.0008; stereotypy: p < 0.0004; central ambulations: p < 0.0082). Moreover, exactly coincident data points for DA and 5-HT release occurred 10 and 40 min after (IP) cocaine administration. Cocaine-induced DA and 5-HT release were highly and positively correlated during the first hour of study (p < 0.01). As expected, increased DA release in vlNAcc after cocaine administration was significantly and positively correlated with classically DA-dependent behaviors (first- and second-hour effects) (p < 0.01) and with the 5-HT-ergic behavior, central ambulations (p < 0.01). Also, cocaine-induced 5-HT release was significantly and positively correlated with 5-HT behavior (p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Novel deletion and a new missense mutation (Glu 217 Lys) at the catalytic site in two adenosine deaminase alleles of a patient with neonatal onset adenosine deaminase- severe combined immunodeficiency

Mutations at the adenosine deaminase (ADA) locus result in a spectrum of disorders, encompassing a fulminant neonatal onset severe combined immunodeficiency (SCID) and childhood onset immunodeficiency, as well as apparently normal immune function. The extent of accumulation of the toxic metabolite, deoxyATP, correlates directly with severity of disease. We have now determined the mutations on both alleles of a child with fulminant, neonatal onset ADA- SCID and accumulation of extremely high concentrations of deoxyATP. The genotype was consistent with the severely affected phenotype. One allele carried a large deletion that arose by non-homologous recombination and included the first five exons and promoter region. The second allele carried a missense mutation (G649A) resulting in replacement of Glu217, an amino acid involved in the catalytic site, by Lys and predicting a major alteration in charge. Expression of the mutant cDNA in Cos cells confirmed that the mutation abolished enzyme activity. We have previously reported that a missense mutation at the preceding codon is similarly associated with neonatal onset ADA- SCID and accumulation of extremely high deoxyATP. These findings suggest that genotype-phenotype correlations may be apparent for ADA- SCID, despite the role that random variation in exposure to environmental pathogens may play in the initial phenotype. Such genotype-phenotype correlations may be important to consider in evaluating results of ongoing trials of "gene" and enzyme replacement therapy.

Novel deletion and a new missense mutation (Glu 217 Lys) at the catalytic site in two adenosine deaminase alleles of a patient with neonatal onset adenosine deaminase- severe combined immunodeficiency

Mutations at the adenosine deaminase (ADA) locus result in a spectrum of disorders, encompassing a fulminant neonatal onset severe combined immunodeficiency (SCID) and childhood onset immunodeficiency, as well as apparently normal immune function. The extent of accumulation of the toxic metabolite, deoxyATP, correlates directly with severity of disease. We have now determined the mutations on both alleles of a child with fulminant, neonatal onset ADA- SCID and accumulation of extremely high concentrations of deoxyATP. The genotype was consistent with the severely affected phenotype. One allele carried a large deletion that arose by non-homologous recombination and included the first five exons and promoter region. The second allele carried a missense mutation (G649A) resulting in replacement of Glu217, an amino acid involved in the catalytic site, by Lys and predicting a major alteration in charge. Expression of the mutant cDNA in Cos cells confirmed that the mutation abolished enzyme activity. We have previously reported that a missense mutation at the preceding codon is similarly associated with neonatal onset ADA- SCID and accumulation of extremely high deoxyATP. These findings suggest that genotype-phenotype correlations may be apparent for ADA- SCID, despite the role that random variation in exposure to environmental pathogens may play in the initial phenotype. Such genotype-phenotype correlations may be important to consider in evaluating results of ongoing trials of "gene" and enzyme replacement therapy.

Morphology of the bile ducts of the brook lamprey, Lampetra lamottenii (Le Sueur) before and during infection with the nematode, Truttaedacnitis stelmioides (Vessichelli, 1910) (Nematoda: Cucullanidae)

Routine light microscopy and transmission and scanning electron microscopy were used to describe and compare the biliary tree of larval Lampetra lamottenii before and during infestation of the bile ducts with the nematode, Truttaedacnitis stelmioides. The most prominent changes to the biliary tree following infection by the parasite are the dilation of the bile ducts, alterations to their epithelial cells, and an increase in periductal fibrous tissue. In recently infected animals, the simple epithelium of dilated bile ducts often contains many mitotic figures. In long-term infestations, the epithelium is stratified or pseudostratified. Changes to the fine structure of the biliary epithelial cells include increase and/or dilation of the RER and SER, and increases in microfilaments, intermediate filaments, and microtubules. The abundance of dense bodies may reflect enhance reabsorption of biliary constituents, and their accumulation may ultimately result in cytolysis. There are increased mucous granules in the apical cytoplasm of biliary epithelial cells and an abundance of mucinous material within the bile duct lumen, and the basal lamina appears thickened. The changes to the liver of L. lamottenii following infection are discussed and compared to those reported in small mammals following bile duct ligation, in patients with extrahepatic biliary obstruction, and in parasitic infection of the biliary tree.

Morphology of the liver of the brook lamprey, Lampetra lamottenii before and during infection with the nematode, Truttaedacnitis stelmioides, hepatocytes, sinusoids, and perisinusoidal cells

Routine light microscopy and transmission and scanning electron microscopy were used to describe and compare the livers of larval lampreys, Lampetra lamottenii before and during infection of the bile ducts by the nematode, Truttaedacnitis stelmioides. The hepatocytes of uninfected animals differ from other lamprey species in that they contain abundant glycogen, smooth endoplasmic reticulum (SER), and lipoprotein indicating that the liver may be involved in glucose metabolism. Infestation of the biliary tree by T. stelmioides coincides with alterations to the hepatocytes. These changes include dilation of the bile canaliculi, smooth endoplasmic reticulum (SER), rough endoplasmic reticulum (RER), and Golgi apparatus, swollen mitochondria in cells showing a high degree of hypertrophy, and an abundance of dense bodies. Following infection, the sinusoidal lumina became dilated and contain a moderate electron-dense precipitate, an abundance of melanomacrophages, lipocytes, and mononuclear cells. There is also a widening of the fenestrae of the sinusoidal endothelium following infection. Many of the changes in hepatocytes and sinusoids following parasite infections closely resemble those observed in hepatocytes in various pathologies and following experimental bile duct ligation and, therefore, are likely a consequence of increased biliary pressure due to bile duct obstruction.

Biliverdin in the serum of ammocoetes of Lampetra lamottenii (Le Sueur)

Green sera collected from larval lampreys of Lampetra lamottenii were assayed and were shown to contain biliverdin at a concentration ranging from 141.5 to 305.0 μmol/L (mean 231.0 ± 27.4). These levels of serum biliverdin are compared with those of other lower vertebrates and with those observed during several human pathological conditions and are discussed with regard to the location of larval nematodes of Truttaedacnitis stelmioides within the bile ducts of these lampreys.

Identification and characterization of nine RFLPs at the adenosine deaminase (ADA) locus

We have identified and/or characterized at least nine RFLPs at the adenosine deaminase (ADA) locus, detected by digestion of DNA with MspI, BanII, PstI, BalI, and PvuII. The RFLPs were distributed over approximately 15 kb of the gene, from IVS 2 to IVS 10. They exhibited Mendelian inheritance and were in Hardy-Weinberg equilibrium. For seven fully characterized RFLPs, the gene frequencies of the rare alleles in 90 chromosomes examined ranged from .33 to .04, the PIC from .34 to .07, and the heterozygosity from .09 to .58. In kindreds examined (58 independent chromosomes), a total of nine haplotypes could be defined on the basis of seven fully characterized RFLPs with a heterozygosity of .62 and PIC of .53. Because there was considerable linkage disequilibrium, only three haplotypes accounted for 90% of individuals. Similar heterozygosity and PIC values (.59 and .51, respectively) could be obtained on the basis of haplotypes defined by the two sites that were the most polymorphic and that were in the least degree of linkage disequilibrium. A strategy for use of the RFLPs in linkage studies is suggested. We have also examined DNA from 17 patients with complete genetic deficiency of ADA (resulting in severe combined immunodeficiency [ADA-SCID] and from 10 patients with partial ADA deficiency (deficient in erythrocytes, with varying levels of ADA in other cells and normal immune function). Although the RFLPs detected genetic compounds among both types of patients, there was, as expected, a decreased incidence of heterozygosity (ADA-SCIDs, .29; partial ADA deficients, .20). Two additional haplotypes not found in the normal population were identified in homozygous form in patients. This information should be useful in developing a rational approach to delineation of mutations at the ADA locus as well as in distinguishing recurrent mutations of independent origin from those derived from a common progenitor.

Metrizamide compared with iohexol for cervical myelography: a double-blind study

A double-blind comparative study of iohexol and metrizamide for use in cervical myelography through lumbar puncture was carried out in a group of 30 patients. No difference was found in the quality of radiographic examinations of the cervical or lumbar regions nor in the postmyelographic computed tomographic examinations of the cervical spine. The overall incidence of side effects was significantly higher in the metrizamide group (93.4%) than in the iohexol group (40%) (p = 0.002). The differences in incidence of nausea (53% in the metrizamide group compared with 13% in the iohexol group) and vomiting (46.6% with metrizamide, 6.6% with iohexol) were also significant (p = 0.02). Pyramidal signs and seizures occurred only after metrizamide myelography.

Determination of tricyclic antidepressant drugs by gas chromatography with the use of a capillary column

A universal gas chromatographic procedure for the determination of the commonly prescribed tricyclic antidepressant drugs in 1 mL of plasma is described. After the addition of internal standards the samples are washed with pentane at acidic pH and extracted with pentane at alkaline pH. The pentane extract is evaporated after the addition of acetic anhydride. Aliquots of a methanolic solution of the residue of evaporated extract are analyzed isothermally on a Durabond 30 m fused silica column. This column is well suited for use with a nitrogen selective detector. The liquid phase is not extracted by repeated injections of methanolic solutions of plasma extracts. When compared to a packed column, this column allows shorter analysis time.

Liquid-chromatographic determination of pentobarbital in plasma with use of a resin column and an alkaline mobile phase

We describe a liquid-chromatographic method involving a new, nonsilica column (XAD-2, Hamilton Co.) for pentobarbital in plasma. Plasma is extracted with chloroform after addition of the internal standard, 5-ethyl-5-p-tolyl-barbituric acid. Acidic drugs are back-extracted into alkali, then chromatographed on the resin-base reversed-phase column. The use of alkaline mobile phase allows enhanced sensitivity and detection of barbiturates at 240 nm. The within-run CV for 10 samples was 1.9%, the between-run CV 1.8%. Ten commonly used barbiturates are separated isocratically in less than 15 min. Other commonly prescribed acidic drugs do not interfere with determination of pentobarbital.

Liquid-chromatographic determination of pentobarbital in plasma with use of a resin column and an alkaline mobile phase

We describe a liquid-chromatographic method involving a new, nonsilica column (XAD-2, Hamilton Co.) for pentobarbital in plasma. Plasma is extracted with chloroform after addition of the internal standard, 5-ethyl-5-p-tolyl-barbituric acid. Acidic drugs are back-extracted into alkali, then chromatographed on the resin-base reversed-phase column. The use of alkaline mobile phase allows enhanced sensitivity and detection of barbiturates at 240 nm. The within-run CV for 10 samples was 1.9%, the between-run CV 1.8%. Ten commonly used barbiturates are separated isocratically in less than 15 min. Other commonly prescribed acidic drugs do not interfere with determination of pentobarbital.

Liquid-chromatographic determination of ethylene glycol in plasma

In this novel procedure for determining ethylene glycol in plasma by liquid chromatography, benzoyl esters of ethylene glycol and of benzyl alcohol (used as the internal standard) are prepared directly in plasma. The benzoyl esters, highly ultraviolet-absorbing chromogens, are ideal compounds for analysis by reversed-phase liquid chromatography with methanol/water as the mobile phase. The benzoyl derivative of ethylene glycol is well separated from the derivative of the internal standard and from plasma constituents. The standard curve is linear to 400 mg of ethylene glycol per liter. As little as 10 mg of ethylene glycol per liter of plasma can be measured. Other commonly ingested alcohols do not interfere.

Liquid-chromatographic determination of ethylene glycol in plasma

In this novel procedure for determining ethylene glycol in plasma by liquid chromatography, benzoyl esters of ethylene glycol and of benzyl alcohol (used as the internal standard) are prepared directly in plasma. The benzoyl esters, highly ultraviolet-absorbing chromogens, are ideal compounds for analysis by reversed-phase liquid chromatography with methanol/water as the mobile phase. The benzoyl derivative of ethylene glycol is well separated from the derivative of the internal standard and from plasma constituents. The standard curve is linear to 400 mg of ethylene glycol per liter. As little as 10 mg of ethylene glycol per liter of plasma can be measured. Other commonly ingested alcohols do not interfere.

Gas-chromatographic analysis for valproic acid as phenacyl esters

We describe a novel isothermal gas-chromatographic procedure for measuring valproic acid. Plasma, with cyclohexanecarboxylic acid added as internal standard, is selectively extracted with pentane to minimize the extraction of other acidic drugs. To convert carboxylic acids to their phenacyl esters, alpha-bromoacetophenone is added to the organic extract before evaporating the solvent. These esters are relatively less volatile than the acids themselves and the extracting solvent can be removed without any loss of valproic acid or internal standard. The phenacyl esters, when chromatographed on 3% OV-17, produce sharp, well-shaped peaks and show high response for the flame ionization detector. Valproic acid is well separated from the internal standard, from reagents and plasma constituents, and from some commonly prescribed drugs that we examined. When alpha-bromo-p-nitroacetophenone is sued as the derivatizing agent, the resulting nitrophenacyl esters can be analyzed with use of a nitrogen-specific detector.

Gas-chromatographic analysis for valproic acid as phenacyl esters

We describe a novel isothermal gas-chromatographic procedure for measuring valproic acid. Plasma, with cyclohexanecarboxylic acid added as internal standard, is selectively extracted with pentane to minimize the extraction of other acidic drugs. To convert carboxylic acids to their phenacyl esters, alpha-bromoacetophenone is added to the organic extract before evaporating the solvent. These esters are relatively less volatile than the acids themselves and the extracting solvent can be removed without any loss of valproic acid or internal standard. The phenacyl esters, when chromatographed on 3% OV-17, produce sharp, well-shaped peaks and show high response for the flame ionization detector. Valproic acid is well separated from the internal standard, from reagents and plasma constituents, and from some commonly prescribed drugs that we examined. When alpha-bromo-p-nitroacetophenone is sued as the derivatizing agent, the resulting nitrophenacyl esters can be analyzed with use of a nitrogen-specific detector.

Estimation of theophylline in plasma by thin-layer chromatography

1. A quantitative thin-layer chromatographic procedure for theophylline has been evaluated. An internal standard, 3-isobutyl-1-methylxanthine, a compound similar in properties to those of theophylline is added to the specimen prior to extraction to eliminate the need for accurate measurements of volume during extraction or analysis. 2. This method does not show interference from other xanthines and from a number of drugs commonly prescribed with thephylline. It has an acceptable correlation with a reference gas-liquid chromatographic procedure. 3. This procedure is capable of handling batches of six or more samples faster than the serial processing of either high performance liquid chromatography or gas-liquid chromatography.