The Experts below are selected from a list of 390 Experts worldwide ranked by ideXlab platform
Katharina Roellecke - One of the best experts on this subject based on the ideXlab platform.
-
Influence of Stereochemistry on the Bioactivation and Glucuronidation of 4-Ipomeanol
The Journal of pharmacology and experimental therapeutics, 2018Co-Authors: Aaron M. Teitelbaum, Katharina Roellecke, Oliver T. Parkinson, Dale Whittington, Matthew G. Mcdonald, John P. Kowalski, Michele Scian, Helmut Hanenberg, Constanze Wiek, Allan E. RettieAbstract:A potential CYP4B1 suicide gene application in engineered T-cell treatment of blood cancers has revived interest in the use of 4-Ipomeanol (IPO) in gene-directed enzyme prodrug therapy, in which disposition of the administered compound may be critical. IPO contains one chiral center at the carbon bearing a secondary alcohol group; it was of interest to determine the effect of stereochemistry on 1) CYP4B1-mediated bioactivation and 2) (UGT)-mediated glucuronidation. First, (R)-IPO and (S)-IPO were synthesized and used to assess cytotoxicity in HepG2 cells expressing rabbit CYP4B1 and re-engineered human CYP4B1, where the enantiomers were found to be equipotent. Next, a sensitive UPLC-MS/MS assay was developed to measure the IPO-glucuronide diastereomers and product stereoselectivity in human tissue microsomes. Human liver and kidney microsomes generated (R)- and (S)-IPO-glucuronide diastereomers in ratios of 57:43 and 79:21, respectively. In a panel of 13 recombinantly expressed UGTs, UGT1A9 and UGT2B7 were the major isoforms responsible for IPO glucuronidation. (R)-IPO-glucuronide diastereoselectivity was apparent with each recombinant UGT, except UGT2B15 and UGT2B17, which favored the formation of (S)-IPO-glucuronide. Incubations with IPO and the UGT1A9-specific chemical inhibitor niflumic acid significantly decreased glucuronidation in human kidney, but only marginally in human liver microsomes, consistent with known tissue expression patterns of UGTs. We conclude that IPO glucuronidation in human kidney is mediated by UGT1A9 and UGT2B7. In human liver, it is mediated primarily by UGT2B7 and, to a lesser extent, UGT1A9 and UGT2B15. Overall, the lack of pronounced stereoselectivity for IPO's bioactivation in CYP4B1-transfected HepG2 cells, or for hepatic glucuronidation, suggests the racemate is an appropriate choice for use in suicide gene therapies.
-
Ligand characterization of CYP4B1 isoforms modified for high-level expression in Escherichia coli and HepG2 cells.
Protein engineering design & selection : PEDS, 2017Co-Authors: Katharina Roellecke, Allan E. Rettie, John P. Kowalski, Helmut Hanenberg, Constanze Wiek, Vera D. Jäger, Veselin H Gyurov, Stephanie Mielke, Marco GirhardAbstract:Human CYP4B1, a cytochrome P450 monooxygenase predominantly expressed in the lung, inefficiently metabolizes classical CYP4B1 substrates, such as the naturally occurring furan pro-toxin 4-Ipomeanol (4-IPO). Highly active animal forms of the enzyme convert 4-IPO to reactive alkylating metabolite(s) that bind(s) to cellular macromolecules. By substitution of 13 amino acids, we restored the enzymatic activity of human CYP4B1 toward 4-IPO and this modified cDNA is potentially valuable as a suicide gene for adoptive T-cell therapies. In order to find novel pro-toxins, we tested numerous furan analogs in in vitro cell culture cytotoxicity assays by expressing the wild-type rabbit and variants of human CYP4B1 in human liver-derived HepG2 cells. To evaluate the CYP4B1 substrate specificities and furan analog catalysis, we optimized the N-terminal sequence of the CYP4B1 variants by modification/truncation and established their heterologous expression in Escherichia coli (yielding 70 and 800 nmol·l-1 of recombinant human and rabbit enzyme, respectively). Finally, spectral binding affinities and oxidative metabolism of the furan analogs by the purified recombinant CYP4B1 variants were analyzed: the naturally occurring perilla ketone was found to be the tightest binder to CYP4B1, but also the analog that was most extensively metabolized by oxidative processes to numerous non-reactive reaction products.
-
optimized human cyp4b1 in combination with the alkylator prodrug 4 Ipomeanol serves as a novel suicide gene system for adoptive t cell therapies
Gene Therapy, 2016Co-Authors: Katharina Roellecke, E L Virts, R Einholz, K Z Edson, Claudia Rossig, Martin Wagenmann, Dorothee Von Laer, Bianca Altvater, K Scheckenbach, Dirk ReinhardtAbstract:Optimized human CYP4B1 in combination with the alkylator prodrug 4-Ipomeanol serves as a novel suicide gene system for adoptive T-cell therapies
-
Optimized human CYP4B1 in combination with the alkylator prodrug 4-Ipomeanol serves as a novel suicide gene system for adoptive T-cell therapies
Gene Therapy, 2016Co-Authors: Katharina Roellecke, E L Virts, R Einholz, K Z Edson, Claudia Rossig, Martin Wagenmann, Bianca Altvater, K Scheckenbach, D Von Laer, Dirk ReinhardtAbstract:Engineering autologous or allogeneic T cells to express a suicide gene can control potential toxicity in adoptive T-cell therapies. We recently reported the development of a novel human suicide gene system that is based on an orphan human cytochrome P450 enzyme, CYP4B1, and the naturally occurring alkylator prodrug 4-Ipomeanol. The goal of this study was to systematically develop a clinically applicable self-inactivating lentiviral vector for efficient co-expression of CYP4B1 as an ER-located protein with two distinct types of cell surface proteins, either MACS selection genes for donor lymphocyte infusions after allogeneic stem cell transplantation or chimeric antigen receptors for retargeting primary T cells. The U3 region of the myeloproliferative sarcoma virus in combination with the T2A site was found to drive high-level expression of our CYP4B1 mutant with truncated CD34 or CD271 as MACS suitable selection markers. This lentiviral vector backbone was also well suited for co-expression of CYP4B1 with a codon-optimized CD19 chimeric antigen receptor (CAR) construct. Finally, 4-Ipomeanol efficiently induced apoptosis in primary T cells that co-express mutant CYP4B1 and the divergently located MACS selection and CAR genes. In conclusion, we here developed a clinically suited lentiviral vector that supports high-level co-expression of cell surface proteins with a potent novel human suicide gene.
-
Identification of Amino Acid Determinants in CYP4B1 for Optimal Catalytic Processing of 4-Ipomeanol
The Biochemical journal, 2014Co-Authors: Constanze Wiek, Katharina Roellecke, Edward J. Kelly, Christof M. Kramm, Eva M. Schmidt, Marcel Freund, Mariko Nakano, Wolfgang Kaisers, Vladimir Yarov-yarovoy, Allan E. RettieAbstract:Mammalian CYP4B1 enzymes are cytochrome P450 mono-oxygenases that are responsible for the bioactivation of several exogenous pro-toxins including 4-Ipomeanol (4-IPO). In contrast with the orthologous rabbit enzyme, we show here that native human CYP4B1 with a serine residue at position 427 is unable to bioactivate 4-IPO and does not cause cytotoxicity in HepG2 cells and primary human T-cells that overexpress these enzymes. We also demonstrate that a proline residue in the meander region at position 427 in human CYP4B1 and 422 in rabbit CYP4B1 is important for protein stability and rescues the 4-IPO bioactivation of the human enzyme, but is not essential for the catalytic activity of the rabbit CYP4B1 protein. Systematic substitution of native and p.S427P human CYP4B1 with peptide regions from the highly active rabbit enzyme reveals that 18 amino acids in the wild-type rabbit CYP4B1 protein are key for conferring high 4-IPO metabolizing activity. Introduction of 12 of the 18 amino acids that are also present at corresponding positions in other human CYP4 family members into the p.S427P human CYP4B1 protein results in a mutant human enzyme (P+12) that is as stable and as active as the rabbit wild-type CYP4B1 protein. These 12 mutations cluster in the predicted B-C loop through F-helix regions and reveal new amino acid regions important to P450 enzyme stability. Finally, by minimally re-engineering the human CYP4B1 enzyme for efficient activation of 4-IPO, we have developed a novel human suicide gene system that is a candidate for adoptive cellular therapies in humans.
Allan E. Rettie - One of the best experts on this subject based on the ideXlab platform.
-
Structure-Activity Relationships for CYP4B1 Bioactivation of 4-Ipomeanol Congeners: Direct Correlation between Cytotoxicity and Trapped Reactive Intermediates.
Chemical research in toxicology, 2019Co-Authors: John P. Kowalski, Dale Whittington, Matthew G. Mcdonald, Michele Scian, Helmut Hanenberg, Constanze Wiek, Miklos Guttman, Marco Girhard, Allan E. RettieAbstract:Cytochrome P450 4B1 (CYP4B1) has been explored as a candidate enzyme in suicide gene systems for its ability to bioactivate the natural product 4-Ipomeanol (IPO) to a reactive species that causes cytotoxicity. However, metabolic limitations of IPO necessitate discovery of new "pro-toxicant" substrates for CYP4B1. In the present study, we examined a series of synthetically facile N-alkyl-3-furancarboxamides for cytotoxicity in HepG2 cells expressing CYP4B1. This compound series maintains the furan warhead of IPO while replacing its alcohol group with alkyl chains of varying length (C1-C8). Compounds with C3-C6 carbon chain lengths showed similar potency to IPO (LD50 ≈ 5 μM). Short chain analogs ( 6 carbons) exhibited reduced toxicity, resulting in a parabolic relationship between alkyl chain length and cytotoxicity. A similar parabolic relationship was observed between alkyl chain length and reactive intermediate formation upon trapping of the putative enedial as a stable pyrrole adduct in incubations with purified recombinant rabbit CYP4B1 and common physiological nucleophiles. These parabolic relationships reflect the lower affinity of shorter chain compounds for CYP4B1 and increased ω-hydroxylation of the longer chain compounds by the enzyme. Furthermore, modest time-dependent inhibition of CYP4B1 by N-pentyl-3-furancarboxamide was completely abolished when trapping agents were added, demonstrating escape of reactive intermediates from the enzyme after bioactivation. An insulated CYP4B1 active site may explain the rarely observed direct correlation between adduct formation and cell toxicity reported here.
-
Influence of Stereochemistry on the Bioactivation and Glucuronidation of 4-Ipomeanol
The Journal of pharmacology and experimental therapeutics, 2018Co-Authors: Aaron M. Teitelbaum, Katharina Roellecke, Oliver T. Parkinson, Dale Whittington, Matthew G. Mcdonald, John P. Kowalski, Michele Scian, Helmut Hanenberg, Constanze Wiek, Allan E. RettieAbstract:A potential CYP4B1 suicide gene application in engineered T-cell treatment of blood cancers has revived interest in the use of 4-Ipomeanol (IPO) in gene-directed enzyme prodrug therapy, in which disposition of the administered compound may be critical. IPO contains one chiral center at the carbon bearing a secondary alcohol group; it was of interest to determine the effect of stereochemistry on 1) CYP4B1-mediated bioactivation and 2) (UGT)-mediated glucuronidation. First, (R)-IPO and (S)-IPO were synthesized and used to assess cytotoxicity in HepG2 cells expressing rabbit CYP4B1 and re-engineered human CYP4B1, where the enantiomers were found to be equipotent. Next, a sensitive UPLC-MS/MS assay was developed to measure the IPO-glucuronide diastereomers and product stereoselectivity in human tissue microsomes. Human liver and kidney microsomes generated (R)- and (S)-IPO-glucuronide diastereomers in ratios of 57:43 and 79:21, respectively. In a panel of 13 recombinantly expressed UGTs, UGT1A9 and UGT2B7 were the major isoforms responsible for IPO glucuronidation. (R)-IPO-glucuronide diastereoselectivity was apparent with each recombinant UGT, except UGT2B15 and UGT2B17, which favored the formation of (S)-IPO-glucuronide. Incubations with IPO and the UGT1A9-specific chemical inhibitor niflumic acid significantly decreased glucuronidation in human kidney, but only marginally in human liver microsomes, consistent with known tissue expression patterns of UGTs. We conclude that IPO glucuronidation in human kidney is mediated by UGT1A9 and UGT2B7. In human liver, it is mediated primarily by UGT2B7 and, to a lesser extent, UGT1A9 and UGT2B15. Overall, the lack of pronounced stereoselectivity for IPO's bioactivation in CYP4B1-transfected HepG2 cells, or for hepatic glucuronidation, suggests the racemate is an appropriate choice for use in suicide gene therapies.
-
Ligand characterization of CYP4B1 isoforms modified for high-level expression in Escherichia coli and HepG2 cells.
Protein engineering design & selection : PEDS, 2017Co-Authors: Katharina Roellecke, Allan E. Rettie, John P. Kowalski, Helmut Hanenberg, Constanze Wiek, Vera D. Jäger, Veselin H Gyurov, Stephanie Mielke, Marco GirhardAbstract:Human CYP4B1, a cytochrome P450 monooxygenase predominantly expressed in the lung, inefficiently metabolizes classical CYP4B1 substrates, such as the naturally occurring furan pro-toxin 4-Ipomeanol (4-IPO). Highly active animal forms of the enzyme convert 4-IPO to reactive alkylating metabolite(s) that bind(s) to cellular macromolecules. By substitution of 13 amino acids, we restored the enzymatic activity of human CYP4B1 toward 4-IPO and this modified cDNA is potentially valuable as a suicide gene for adoptive T-cell therapies. In order to find novel pro-toxins, we tested numerous furan analogs in in vitro cell culture cytotoxicity assays by expressing the wild-type rabbit and variants of human CYP4B1 in human liver-derived HepG2 cells. To evaluate the CYP4B1 substrate specificities and furan analog catalysis, we optimized the N-terminal sequence of the CYP4B1 variants by modification/truncation and established their heterologous expression in Escherichia coli (yielding 70 and 800 nmol·l-1 of recombinant human and rabbit enzyme, respectively). Finally, spectral binding affinities and oxidative metabolism of the furan analogs by the purified recombinant CYP4B1 variants were analyzed: the naturally occurring perilla ketone was found to be the tightest binder to CYP4B1, but also the analog that was most extensively metabolized by oxidative processes to numerous non-reactive reaction products.
-
Species Differences in Microsomal Oxidation and Glucuronidation of 4-Ipomeanol: Relationship to Target Organ Toxicity
Drug metabolism and disposition: the biological fate of chemicals, 2016Co-Authors: Oliver T. Parkinson, Edward J. Kelly, Dale Whittington, Aaron M. Teitelbaum, Allan E. RettieAbstract:4-Ipomeanol (IPO) is a model pulmonary toxicant that undergoes P450-mediated metabolism to reactive electrophilic intermediates that bind to tissue macromolecules and can be trapped in vitro as the NAC/NAL adduct. Pronounced species and tissue differences in IPO toxicity are well documented, as is the enzymological component of phase I bioactivation. However, IPO also undergoes phase II glucuronidation, which may compete with bioactivation in target tissues. To better understand the organ toxicity of IPO, we synthesized IPO-glucuronide and developed a new quantitative mass spectrometry-based assay for IPO glucuronidation. Microsomal rates of glucuronidation and P450-dependent NAC/NAL adduct formation were compared in lung, kidney, and liver microsomes from seven species with different target organ toxicities to IPO. Bioactivation rates were highest in pulmonary and renal microsomes from all animal species (except dog) known to be highly susceptible to the extrahepatic toxicities induced by IPO. In a complementary fashion, pulmonary and renal IPO glucuronidation rates were uniformly low in all experimental animals and primates, but hepatic glucuronidation rates were high, as expected. Therefore, with the exception of the dog, the balance between microsomal NAC/NAL adduct and glucuronide formation correlate well with the risk for IPO-induced pulmonary, renal, and hepatic toxicities across species.
-
Identification of Amino Acid Determinants in CYP4B1 for Optimal Catalytic Processing of 4-Ipomeanol
The Biochemical journal, 2014Co-Authors: Constanze Wiek, Katharina Roellecke, Edward J. Kelly, Christof M. Kramm, Eva M. Schmidt, Marcel Freund, Mariko Nakano, Wolfgang Kaisers, Vladimir Yarov-yarovoy, Allan E. RettieAbstract:Mammalian CYP4B1 enzymes are cytochrome P450 mono-oxygenases that are responsible for the bioactivation of several exogenous pro-toxins including 4-Ipomeanol (4-IPO). In contrast with the orthologous rabbit enzyme, we show here that native human CYP4B1 with a serine residue at position 427 is unable to bioactivate 4-IPO and does not cause cytotoxicity in HepG2 cells and primary human T-cells that overexpress these enzymes. We also demonstrate that a proline residue in the meander region at position 427 in human CYP4B1 and 422 in rabbit CYP4B1 is important for protein stability and rescues the 4-IPO bioactivation of the human enzyme, but is not essential for the catalytic activity of the rabbit CYP4B1 protein. Systematic substitution of native and p.S427P human CYP4B1 with peptide regions from the highly active rabbit enzyme reveals that 18 amino acids in the wild-type rabbit CYP4B1 protein are key for conferring high 4-IPO metabolizing activity. Introduction of 12 of the 18 amino acids that are also present at corresponding positions in other human CYP4 family members into the p.S427P human CYP4B1 protein results in a mutant human enzyme (P+12) that is as stable and as active as the rabbit wild-type CYP4B1 protein. These 12 mutations cluster in the predicted B-C loop through F-helix regions and reveal new amino acid regions important to P450 enzyme stability. Finally, by minimally re-engineering the human CYP4B1 enzyme for efficient activation of 4-IPO, we have developed a novel human suicide gene system that is a candidate for adoptive cellular therapies in humans.
Dirk Reinhardt - One of the best experts on this subject based on the ideXlab platform.
-
optimized human cyp4b1 in combination with the alkylator prodrug 4 Ipomeanol serves as a novel suicide gene system for adoptive t cell therapies
Gene Therapy, 2016Co-Authors: Katharina Roellecke, E L Virts, R Einholz, K Z Edson, Claudia Rossig, Martin Wagenmann, Dorothee Von Laer, Bianca Altvater, K Scheckenbach, Dirk ReinhardtAbstract:Optimized human CYP4B1 in combination with the alkylator prodrug 4-Ipomeanol serves as a novel suicide gene system for adoptive T-cell therapies
-
Optimized human CYP4B1 in combination with the alkylator prodrug 4-Ipomeanol serves as a novel suicide gene system for adoptive T-cell therapies
Gene Therapy, 2016Co-Authors: Katharina Roellecke, E L Virts, R Einholz, K Z Edson, Claudia Rossig, Martin Wagenmann, Bianca Altvater, K Scheckenbach, D Von Laer, Dirk ReinhardtAbstract:Engineering autologous or allogeneic T cells to express a suicide gene can control potential toxicity in adoptive T-cell therapies. We recently reported the development of a novel human suicide gene system that is based on an orphan human cytochrome P450 enzyme, CYP4B1, and the naturally occurring alkylator prodrug 4-Ipomeanol. The goal of this study was to systematically develop a clinically applicable self-inactivating lentiviral vector for efficient co-expression of CYP4B1 as an ER-located protein with two distinct types of cell surface proteins, either MACS selection genes for donor lymphocyte infusions after allogeneic stem cell transplantation or chimeric antigen receptors for retargeting primary T cells. The U3 region of the myeloproliferative sarcoma virus in combination with the T2A site was found to drive high-level expression of our CYP4B1 mutant with truncated CD34 or CD271 as MACS suitable selection markers. This lentiviral vector backbone was also well suited for co-expression of CYP4B1 with a codon-optimized CD19 chimeric antigen receptor (CAR) construct. Finally, 4-Ipomeanol efficiently induced apoptosis in primary T cells that co-express mutant CYP4B1 and the divergently located MACS selection and CAR genes. In conclusion, we here developed a clinically suited lentiviral vector that supports high-level co-expression of cell surface proteins with a potent novel human suicide gene.
Eric K. Rowinsky - One of the best experts on this subject based on the ideXlab platform.
-
Phase II Study of 4-Ipomeanol, a Naturally Occurring Alkylating Furan, in Patients with Advanced Hepatocellular Carcinoma
Investigational New Drugs, 2001Co-Authors: Shailendra Lakhanpal, Ross C. Donehower, Eric K. RowinskyAbstract:Background/purpose : 4-Ipomeanol (IPO; NSC394438), anaturally occurring furan isolated from common sweet potatoes(Ipomoea batatas) infected with the fungus Fusariumsolani was the first agent to be developed by theNationalCancer Institute based on a biochemical-biological rationaleas an anticancer agent targeted specifically against lungcancer. Prior to clinical development, IPO was shown to inducepulmonary toxicity in the lungs of several mammalian speciesbecause the agent is metabolized to a highly reactive furanepoxide by specific cytochrome P450 monooxygenases found inpulmonary Clara cells and type II pneumocytes, which sharebiochemical features with bronchogenic carcinoma. However,instead of inducing the anticipated lung toxicity in patientswith lung cancer in disease-directed phase I studies,hepatotoxicity was the principal toxic effect of IPO inhumans. Based on the presumption that IPO may bepreferentially activated by cytochrome P450 monooxygenases inliver cells and biochemically-related hepatic malignancies, aphase II study was conducted to determine the activity andevaluate the toxicity of IPO in patients with advancedhepatocellular carcinoma. Patients and methods : Nineteen patients with advancedmeasurable hepatocellular carcinoma were enrolled on the phaseII trial. All patients had an Eastern Cooperative OncologyGroup performance status of at least two, no evidence ofpulmonary dysfunction, and had either no prior treatment orminimal prior therapy. Patients were treated with IPO at adose of either 1032 mg/m^2, which was the maximumtolerated and recommended phase II dose previously derived forpatients with normal hepatic function (15 patients) or 826mg/m^2 if they had serum bilirubin concentrations intherange of 2.0 to 3.0 mg/dL (four patients). Treatment wasrepeated every three weeks. Objective tumor response, theprimary endpoint of the study, was assessed after every twocourses of treatment, and both pulmonary function and lungdensity were rigorously monitored using successive pulmonaryfunction testing and computerized tomography. Results : All nineteen patients were evaluable forbothresponse and toxicity. No major objective responses wereobserved. One patient had a minor, brief reduction in lungmetastases. Although marker lesions and overall diseaseremained stable for at least 12 and 24 months in three and twopatients, respectively, the median time to progression wasthree months and the median survival was five months for allpatients. The principal toxicity was reversible elevations inhepatic transaminases, which occasionally resulted in dosereduction. No clinically-significant pulmonary toxicity wasnoted. Conclusion : IPO at a dose of either 826 or 1032mg/m^2 administered every three weeks did notdemonstratea relevant degree of clinical activity against advancedhepatocellular carcinoma. Further evaluations of TO is notrecommended for this disease.
-
Phase I and Pharmacological Study of the Pulmonary Cytotoxin 4-Ipomeanol on a Single Dose Schedule in Lung Cancer Patients: Hepatotoxicity Is Dose Limiting in Humans
Cancer research, 1993Co-Authors: Eric K. Rowinsky, Michael R. Boyd, Michaele C. Christian, Dennis A. Noe, David S. Ettinger, B G Lubejko, Elliot K. Fishman, Susan E. Sartorius, Ross C. DonehowerAbstract:4-Ipomeanol (IPO), a naturally occurring pulmonary toxin, is the first cytotoxic agent to undergo clinical development based on a biochemicalbiological rationale as an antineoplastic agent targeted specifically against lung cancer. This rationale is based on preclinical observations that metabolic activation and intracellular binding of IPO, as well as cytotoxicity, occurred selectively in tissues and cancers derived from tissues that are rich in specific P450 mixed function oxidase enzymes. Although tissues capable of activating IPO to cytotoxic intermediates in vitro include liver, lung, and kidney, IPO has been demonstrated in rodents and dogs to undergo in situ activation, bind covalently, and induce cytotoxicity preferentially in lung tissue at doses not similarly affecting liver or kidneys. Although the drug was devoid of antitumor activity in the conventional murine preclinical screening models, cytotoxic activity was observed in human lung cancers in vitro and in human lung cancer xenografts in vivo , adding to the rationale for clinical development. Somewhat unexpectantly, hepatocellular toxicity was the dose-limiting principal toxicity of IPO administered as a 30-min infusion every 3 weeks to patients with lung cancer. In this study, 55 patients received 254 courses at doses almost spanning 3 orders of magnitude, 6.5 to 1612 mg/m2. Transient and isolated elevations in hepatocellular enzymes, predominately alanine aminotransferase, occurred in the majority of courses of IPO at 1032 mg/m2, which is the recommended IPO dose for subsequent phase II trials. At higher doses, hepatocellular toxicity was more severe and was often associated with right upper quadrant pain and severe malaise. Toxic effects were also noted in other tissues capable of activating IPO, including possible nephrotoxicity in a patient treated with one course of IPO at 154 mg/m2 and severe, reversible pulmonary toxicity in another patient who received nine courses of IPO at doses ranging from 202 to 826 mg/m2. Although individual plasma drug disposition curves were well described by a two-compartment first order elimination model, the relationship between IPO dose and are under the disposition curve was curvilinear, suggesting saturable elimination kinetics. At the maximum tolerated dose, the mean half-lives (λ1 and λ2) were 6.7 and 114.5 min, respectively. Renal excretion of parent compound accounted for less than 2% of the administered dose of IPO. An unidentified metabolite was detected in the plasma of patients treated at higher doses. No objective antitumor responses were observed; however, stable disease persisted for at least eight courses in 27% of patients. The preponderance of clinical toxicity observed in liver rather than lung suggests that IPO may be preferentially activated and bound in liver rather than lung or other tissues in humans or that human lung tissue is more effective at detoxifying and/or is more tolerant to activated IPO than other species. In any event, these observations suggest further that the rationale for the clinical evaluation of IPO should be extended to include liver cancers and possibly renal cancers, as well as lung cancers.
Ross C. Donehower - One of the best experts on this subject based on the ideXlab platform.
-
Phase II Study of 4-Ipomeanol, a Naturally Occurring Alkylating Furan, in Patients with Advanced Hepatocellular Carcinoma
Investigational New Drugs, 2001Co-Authors: Shailendra Lakhanpal, Ross C. Donehower, Eric K. RowinskyAbstract:Background/purpose : 4-Ipomeanol (IPO; NSC394438), anaturally occurring furan isolated from common sweet potatoes(Ipomoea batatas) infected with the fungus Fusariumsolani was the first agent to be developed by theNationalCancer Institute based on a biochemical-biological rationaleas an anticancer agent targeted specifically against lungcancer. Prior to clinical development, IPO was shown to inducepulmonary toxicity in the lungs of several mammalian speciesbecause the agent is metabolized to a highly reactive furanepoxide by specific cytochrome P450 monooxygenases found inpulmonary Clara cells and type II pneumocytes, which sharebiochemical features with bronchogenic carcinoma. However,instead of inducing the anticipated lung toxicity in patientswith lung cancer in disease-directed phase I studies,hepatotoxicity was the principal toxic effect of IPO inhumans. Based on the presumption that IPO may bepreferentially activated by cytochrome P450 monooxygenases inliver cells and biochemically-related hepatic malignancies, aphase II study was conducted to determine the activity andevaluate the toxicity of IPO in patients with advancedhepatocellular carcinoma. Patients and methods : Nineteen patients with advancedmeasurable hepatocellular carcinoma were enrolled on the phaseII trial. All patients had an Eastern Cooperative OncologyGroup performance status of at least two, no evidence ofpulmonary dysfunction, and had either no prior treatment orminimal prior therapy. Patients were treated with IPO at adose of either 1032 mg/m^2, which was the maximumtolerated and recommended phase II dose previously derived forpatients with normal hepatic function (15 patients) or 826mg/m^2 if they had serum bilirubin concentrations intherange of 2.0 to 3.0 mg/dL (four patients). Treatment wasrepeated every three weeks. Objective tumor response, theprimary endpoint of the study, was assessed after every twocourses of treatment, and both pulmonary function and lungdensity were rigorously monitored using successive pulmonaryfunction testing and computerized tomography. Results : All nineteen patients were evaluable forbothresponse and toxicity. No major objective responses wereobserved. One patient had a minor, brief reduction in lungmetastases. Although marker lesions and overall diseaseremained stable for at least 12 and 24 months in three and twopatients, respectively, the median time to progression wasthree months and the median survival was five months for allpatients. The principal toxicity was reversible elevations inhepatic transaminases, which occasionally resulted in dosereduction. No clinically-significant pulmonary toxicity wasnoted. Conclusion : IPO at a dose of either 826 or 1032mg/m^2 administered every three weeks did notdemonstratea relevant degree of clinical activity against advancedhepatocellular carcinoma. Further evaluations of TO is notrecommended for this disease.
-
Phase I and Pharmacological Study of the Pulmonary Cytotoxin 4-Ipomeanol on a Single Dose Schedule in Lung Cancer Patients: Hepatotoxicity Is Dose Limiting in Humans
Cancer research, 1993Co-Authors: Eric K. Rowinsky, Michael R. Boyd, Michaele C. Christian, Dennis A. Noe, David S. Ettinger, B G Lubejko, Elliot K. Fishman, Susan E. Sartorius, Ross C. DonehowerAbstract:4-Ipomeanol (IPO), a naturally occurring pulmonary toxin, is the first cytotoxic agent to undergo clinical development based on a biochemicalbiological rationale as an antineoplastic agent targeted specifically against lung cancer. This rationale is based on preclinical observations that metabolic activation and intracellular binding of IPO, as well as cytotoxicity, occurred selectively in tissues and cancers derived from tissues that are rich in specific P450 mixed function oxidase enzymes. Although tissues capable of activating IPO to cytotoxic intermediates in vitro include liver, lung, and kidney, IPO has been demonstrated in rodents and dogs to undergo in situ activation, bind covalently, and induce cytotoxicity preferentially in lung tissue at doses not similarly affecting liver or kidneys. Although the drug was devoid of antitumor activity in the conventional murine preclinical screening models, cytotoxic activity was observed in human lung cancers in vitro and in human lung cancer xenografts in vivo , adding to the rationale for clinical development. Somewhat unexpectantly, hepatocellular toxicity was the dose-limiting principal toxicity of IPO administered as a 30-min infusion every 3 weeks to patients with lung cancer. In this study, 55 patients received 254 courses at doses almost spanning 3 orders of magnitude, 6.5 to 1612 mg/m2. Transient and isolated elevations in hepatocellular enzymes, predominately alanine aminotransferase, occurred in the majority of courses of IPO at 1032 mg/m2, which is the recommended IPO dose for subsequent phase II trials. At higher doses, hepatocellular toxicity was more severe and was often associated with right upper quadrant pain and severe malaise. Toxic effects were also noted in other tissues capable of activating IPO, including possible nephrotoxicity in a patient treated with one course of IPO at 154 mg/m2 and severe, reversible pulmonary toxicity in another patient who received nine courses of IPO at doses ranging from 202 to 826 mg/m2. Although individual plasma drug disposition curves were well described by a two-compartment first order elimination model, the relationship between IPO dose and are under the disposition curve was curvilinear, suggesting saturable elimination kinetics. At the maximum tolerated dose, the mean half-lives (λ1 and λ2) were 6.7 and 114.5 min, respectively. Renal excretion of parent compound accounted for less than 2% of the administered dose of IPO. An unidentified metabolite was detected in the plasma of patients treated at higher doses. No objective antitumor responses were observed; however, stable disease persisted for at least eight courses in 27% of patients. The preponderance of clinical toxicity observed in liver rather than lung suggests that IPO may be preferentially activated and bound in liver rather than lung or other tissues in humans or that human lung tissue is more effective at detoxifying and/or is more tolerant to activated IPO than other species. In any event, these observations suggest further that the rationale for the clinical evaluation of IPO should be extended to include liver cancers and possibly renal cancers, as well as lung cancers.
