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Meher N, Ashley GW, Bobba KN, Wadhwa A, Bidkar AP, Dasari C, Mu C, Sankaranarayanan RA, Serrano JAC, Raveendran A, Bulkley DP, Aggarwal R, Greenland NY, Oskowitz A, Wilson DM, Seo Y, Santi DV, VanBrocklin HF, Flavell RR. Prostate-Specific Membrane Antigen Targeted StarPEG Nanocarrier for Imaging and Therapy of Prostate Cancer. Adv Healthc Mater 2024:e2304618. [PMID: 38700450 DOI: 10.1002/adhm.202304618] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2023] [Revised: 04/29/2024] [Indexed: 05/05/2024]
Abstract
BACKGROUND The uptake of large (>10 nm) non-targeted nanocarriers by bulk tumors is thought to be dominated by passive extravasation through porous tumor vessels and limited lymphatic drainage, the enhanced permeability and retention (EPR) effect. Prior studies demonstrated radiolabeled tumor-targeted and non-targeted 4-arm 40 kDa star polyethylene glycol (StarPEG) polymers for cancer imaging. By adding small molecule ligands targeting prostate-specific membrane antigen (PSMA) to the StarPEG polymer, marked increase in tumor uptake, penetration and retention in the tumor core was observed. These prior studies support the application of imaging surrogates for the evaluation of targeted delivery of chemotherapeutic nanomedicines and the potential for therapy using analogous β-emitting radiopharmaceuticals. METHODS To evaluate the delivery and therapeutic efficacy of PSMA-targeted StarPEG nanocarriers, StarPEG nanodrugs with or without three copies of PSMA-targeting, ACUPA, ligands were designed and synthesized. One copy of the radiometal chelator, DOTA, was conjugated to each nanocarrier for labelling with b-emitting 177Lu, providing non-targeted [177Lu]PEG-(DOTA)1 and PSMA targeting [177Lu]PEG-(DOTA)1(ACUPA)3, for SPECT imaging and therapy. The radiolabeled nanodrugs were evaluated in vitro and in vivo using PSMA+ PC3-Pip and/or PSMA- PC3-Flu cell lines, subcutaneous xenografts and disseminated metastatic models. RESULTS The nanocarriers PEG-(DOTA)1 and PEG-(DOTA)1(ACUPA)3 were efficiently radiolabeled with 177Lu with molar activities of 10.8-15.8 MBq/nmol. Along with excellent in vitro PSMA binding affinity (kD = 51.7 nM in PC3-Pip cells), the targeted nanocarrier [177Lu]PEG-(DOTA)1(ACUPA)3 demonstrated excellent in vivo single-photon emission computed tomography (SPECT) imaging contrast with 21.3% ID/g uptake in PC3-Pip tumors at 192 h post injection. Single doses of 18.5 MBq [177Lu]PEG-(DOTA)1(ACUPA)3 showed complete resolution of the PC3-Pip xenografts, without any regrowth up to 138 days. CONCLUSIONS AND FUTURE DIRECTIONS The StarPEG nanocarriers demonstrated high PSMA-targeted delivery of the therapeutic isotope 177Lu with excellent imaging contrast. The targeted nanocarrier eliminated subcutaneous and metastatic PC3-Pip tumors. Overall, these preclinical results demonstrated high treatment efficacy of the PSMA-targeted nanocarrier [177Lu]PEG-(DOTA)1(ACUPA)3 for prostate cancer, with potential for clinical translation. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Niranjan Meher
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, 94143, USA
- National Institute of Pharmaceutical Education and Research, Raebareli, Lucknow, UP, 226002, India
| | | | - Kondapa Naidu Bobba
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, 94143, USA
| | - Anju Wadhwa
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, 94143, USA
| | - Anil P Bidkar
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, 94143, USA
| | - Chandrashekhar Dasari
- Helen Diller Family Comprehensive Cancer Center, University of California San Francisco, San Francisco, CA, 94143-0981, USA
| | - Changhua Mu
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, 94143, USA
| | | | - Juan A Camara Serrano
- Division of Vascular and Endovascular Surgery, University of California, San Francisco, CA, 94143-0957, USA
| | - Athira Raveendran
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, 94143, USA
| | - David P Bulkley
- Department of Pathology, University of California, San Francisco, CA, 94143, USA
| | - Rahul Aggarwal
- Division of Vascular and Endovascular Surgery, University of California, San Francisco, CA, 94143-0957, USA
| | - Nancy Y Greenland
- Department of Pharmaceutical Chemistry, University of California, San Francisco, CA, 94158-2517, USA
| | - Adam Oskowitz
- Helen Diller Family Comprehensive Cancer Center, University of California San Francisco, San Francisco, CA, 94143-0981, USA
| | - David M Wilson
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, 94143, USA
- Division of Vascular and Endovascular Surgery, University of California, San Francisco, CA, 94143-0957, USA
| | - Youngho Seo
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, 94143, USA
- Division of Vascular and Endovascular Surgery, University of California, San Francisco, CA, 94143-0957, USA
| | | | - Henry F VanBrocklin
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, 94143, USA
- Division of Vascular and Endovascular Surgery, University of California, San Francisco, CA, 94143-0957, USA
| | - Robert R Flavell
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, 94143, USA
- Division of Vascular and Endovascular Surgery, University of California, San Francisco, CA, 94143-0957, USA
- Department of Biochemistry and Biophysics, University of California, San Francisco, CA, 94158, USA
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Carreras CW, Fontaine SD, Reid RR, Ashley GW, Santi DV. Long-Acting Poly(ADP-ribose) Polymerase Inhibitor Prodrug for Humans. Bioconjug Chem 2024; 35:551-558. [PMID: 38591781 DOI: 10.1021/acs.bioconjchem.4c00112] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/10/2024]
Abstract
Poly(ADP-ribose) polymerase inhibitors (PARPi) have been approved for once or twice daily oral use in the treatment of cancers with BRCA defects. However, for some patients, oral administration of PARPi may be impractical or intolerable, and a long-acting injectable formulation is desirable. We recently developed a long-acting PEGylated PARPi prodrug, PEG∼talazoparib (TLZ), which suppressed the growth of PARPi-sensitive tumors in mice for very long periods. However, the release rate of TLZ from the conjugate was too fast to be optimal in humans. We prepared several new PEG∼TLZ prodrugs having longer half-lives of drug release and accurately measured their pharmacokinetics in the rat. Using the rates of release of TLZ from these prodrugs and the known pharmacokinetics of free TLZ in humans, we simulated the pharmacokinetics of the macromolecular prodrugs and released TLZ in humans. From several possibilities, we chose two conjugates that could be administered intravenously every 2 weeks and maintain TLZ within its known therapeutic window. We describe situations where the PEG∼TLZ conjugates would find utility in humans and suggest how the intravenously administered long-acting prodrugs could in fact be more effective than daily oral administration of free TLZ.
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Affiliation(s)
| | - Shaun D Fontaine
- ProLynx, Inc., 135 Mississippi Street, San Francisco, California 94107, United States
| | - Ralph R Reid
- ProLynx, Inc., 135 Mississippi Street, San Francisco, California 94107, United States
| | - Gary W Ashley
- ProLynx, Inc., 135 Mississippi Street, San Francisco, California 94107, United States
| | - Daniel V Santi
- ProLynx, Inc., 135 Mississippi Street, San Francisco, California 94107, United States
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Santi DV, Ashley GW, Cabel L, Bidard FC. Could a Long-Acting Prodrug of SN-38 be Efficacious in Sacituzumab Govitecan-Resistant Tumors? BioDrugs 2024; 38:171-176. [PMID: 38236523 PMCID: PMC10912420 DOI: 10.1007/s40259-024-00643-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/02/2024] [Indexed: 01/19/2024]
Abstract
We previously proposed that sacituzumab govitecan (SG, Trodelvy®) likely acts as a simple prodrug of systemic SN-38 as well as an antibody drug conjugate (ADC). In the present commentary, we assess whether a long-acting SN-38 prodrug, such as PLX038, might be efficacious in SG-resistant patients. We first describe possible mechanisms of action of SG, with new insights on pharmacokinetics and TROP2 receptor occupancy. We argue that SG is not an optimal conventional ADC and that the amount of systemic SN-38 spontaneously hydrolyzed from the ADC is so high it must have activity. Then, we describe the concept of time-over-target as related to the pharmacology of SG and PLX038 as SN-38 prodrugs. To be clear, we are not in any way suggesting that PLX038 or any SN-38 prodrug is superior to SG as an anticancer agent. Clearly, SG has the benefit over antigen-independent SN-38 prodrugs in that it targets cells with the TROP2 receptor. However, we surmise that PLX038 should be a more efficacious and less toxic prodrug of systemic SN-38 than SG. Finally, we suggest possible mechanisms of SG resistance and how PLX038 might perform in the context of each. Taken together, we argue that-contrary to many opinions-SG does not exclusively act as a conventional ADC, and propose that PLX038 may be efficacious in some settings of SG-resistance.
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Affiliation(s)
- Daniel V Santi
- Prolynx, Inc., 135 Mississippi Street, San Francisco, CA, 94107, USA.
- Pharmaceutical Chemistry, UCSF, San Francisco, CA, USA.
| | - Gary W Ashley
- Prolynx, Inc., 135 Mississippi Street, San Francisco, CA, 94107, USA
| | - Luc Cabel
- Medical Oncology, Institut Curie, Paris, France
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Fontaine SD, Carreras CW, Reid RR, Ashley GW, Santi DV. A Very Long-acting Exatecan and Its Synergism with DNA Damage Response Inhibitors. Cancer Res Commun 2023; 3:908-916. [PMID: 37377899 PMCID: PMC10208276 DOI: 10.1158/2767-9764.crc-22-0517] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/19/2022] [Revised: 03/03/2023] [Accepted: 04/18/2023] [Indexed: 06/29/2023]
Abstract
Exatecan (Exa) is a very potent inhibitor of topoisomerase I and anticancer agent. It has been intensively studied as a single agent, a large macromolecular conjugate and as the payload component of antigen-dependent antibody-drug conjugates. The current work describes an antigen-independent conjugate of Exa with polyethylene glycol (PEG) that slowly releases free Exa. Exa was conjugated to a 4-arm 40 kDa PEG through a β-eliminative cleavable linker. Pharmacokinetic studies in mice showed that the conjugate has an apparent circulating half-life of 12 hours, which reflects a composite of both the rate of renal elimination (half-life ∼18 hours) and release of Exa (half-life ∼40 hours). Remarkably, a single low dose of 10 μmol/kg PEG-Exa-only approximately 0.2 μmol/mouse-caused complete suppression of tumor growth of BRCA1-deficient MX-1 xenografts lasting over 40 days. A single low dose of 2.5 μmol/kg PEG-Exa administered with low but efficacious doses of the PARP inhibitor talazoparib showed strong synergy and caused significant tumor regression. Furthermore, the same low, single dose of PEG-Exa administered with the ATR inhibitor VX970 at doses of the DNA damage response inhibitor that do not affect tumor growth show high tumor regression, strong synergy, and synthetic lethality. Significance A circulating conjugate that slowly releases Exa is described. It is efficacious after a single dose and synergistic with ATR and PARP inhibitors.
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Meher N, Ashley GW, Bidkar AP, Dhrona S, Fong C, Fontaine SD, Beckford Vera DR, Wilson DM, Seo Y, Santi DV, VanBrocklin HF, Flavell RR. Prostate-Specific Membrane Antigen Targeted Deep Tumor Penetration of Polymer Nanocarriers. ACS Appl Mater Interfaces 2022; 14:50569-50582. [PMID: 36318757 PMCID: PMC9673064 DOI: 10.1021/acsami.2c15095] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2022] [Accepted: 10/24/2022] [Indexed: 05/05/2023]
Abstract
Tumoral uptake of large-size nanoparticles is mediated by the enhanced permeability and retention (EPR) effect, with variable accumulation and heterogenous tumor tissue penetration depending on the tumor phenotype. The performance of nanocarriers via specific targeting has the potential to improve imaging contrast and therapeutic efficacy in vivo with increased deep tissue penetration. To address this hypothesis, we designed and synthesized prostate cancer-targeting starPEG nanocarriers (40 kDa, 15 nm), [89Zr]PEG-(DFB)3(ACUPA)1 and [89Zr]PEG-(DFB)1(ACUPA)3, with one or three prostate-specific membrane antigen (PSMA)-targeting ACUPA ligands. The in vitro PSMA binding affinity and in vivo pharmacokinetics of the targeted nanocarriers were compared with a nontargeted starPEG, [89Zr]PEG-(DFB)4, in PSMA+ PC3-Pip and PSMA- PC3-Flu cells, and xenografts. Increasing the number of ACUPA ligands improved the in vitro binding affinity of PEG-derived polymers to PC3-Pip cells. While both PSMA-targeted nanocarriers significantly improved tissue penetration in PC3-Pip tumors, the multivalent [89Zr]PEG-(DFB)1(ACUPA)3 showed a remarkably higher PC3-Pip/blood ratio and background clearance. In contrast, the nontargeted [89Zr]PEG-(DFB)4 showed low EPR-mediated accumulation with poor tumor tissue penetration. Overall, ACUPA conjugated targeted starPEGs significantly improve tumor retention with deep tumor tissue penetration in low EPR PC3-Pip xenografts. These data suggest that PSMA targeting with multivalent ACUPA ligands may be a generally applicable strategy to increase nanocarrier delivery to prostate cancer. These targeted multivalent nanocarriers with high tumor binding and low healthy tissue retention could be employed in imaging and therapeutic applications.
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Affiliation(s)
- Niranjan Meher
- Department
of Radiology and Biomedical Imaging, University
of California, San Francisco, California 94143, United States
| | - Gary W. Ashley
- ProLynx
Inc., San Francisco, California 94158, United States
| | - Anil P. Bidkar
- Department
of Radiology and Biomedical Imaging, University
of California, San Francisco, California 94143, United States
| | - Suchi Dhrona
- Department
of Radiology and Biomedical Imaging, University
of California, San Francisco, California 94143, United States
| | - Cyril Fong
- Department
of Radiology and Biomedical Imaging, University
of California, San Francisco, California 94143, United States
| | | | - Denis R. Beckford Vera
- Department
of Radiology and Biomedical Imaging, University
of California, San Francisco, California 94143, United States
| | - David M. Wilson
- Department
of Radiology and Biomedical Imaging, University
of California, San Francisco, California 94143, United States
- Helen
Diller Family Comprehensive Cancer Center, University of California San Francisco, San Francisco, California 94143-0981, United States
| | - Youngho Seo
- Department
of Radiology and Biomedical Imaging, University
of California, San Francisco, California 94143, United States
- Helen
Diller Family Comprehensive Cancer Center, University of California San Francisco, San Francisco, California 94143-0981, United States
| | - Daniel V. Santi
- ProLynx
Inc., San Francisco, California 94158, United States
| | - Henry F. VanBrocklin
- Department
of Radiology and Biomedical Imaging, University
of California, San Francisco, California 94143, United States
- Helen
Diller Family Comprehensive Cancer Center, University of California San Francisco, San Francisco, California 94143-0981, United States
| | - Robert R. Flavell
- Department
of Radiology and Biomedical Imaging, University
of California, San Francisco, California 94143, United States
- Helen
Diller Family Comprehensive Cancer Center, University of California San Francisco, San Francisco, California 94143-0981, United States
- Department
of Pharmaceutical Chemistry, University
of California, San Francisco, California 94158-2517, United States
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Thomas A, Fontaine SD, Diolaiti ME, Desai P, Kumar R, Takahashi N, Sciuto L, Nichols S, Ashworth A, Feng FY, Ashley GW, Nguyen M, Pommier Y, Santi DV. PLX038: A Long-Acting Topoisomerase I Inhibitor With Robust Antitumor Activity in ATM-Deficient Tumors and Potent Synergy With PARP Inhibitors. Mol Cancer Ther 2022; 21:1722-1728. [PMID: 35999657 PMCID: PMC10673686 DOI: 10.1158/1535-7163.mct-22-0217] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Revised: 06/02/2022] [Accepted: 08/15/2022] [Indexed: 11/16/2022]
Abstract
Alterations in the ATM gene are among the most common somatic and hereditary cancer mutations, and ATM-deficient tumors are hypersensitive to DNA-damaging agents. A synthetic lethal combination of DNA-damaging agents and DNA repair inhibitors could have widespread utility in ATM-deficient cancers. However, overlapping normal tissue toxicities from these drug classes have precluded their clinical translation. We investigated PLX038, a releasable polyethylene glycol-conjugate of the topoisomerase I inhibitor SN-38, in ATM wild-type and null isogenic xenografts and in a BRCA1-deficient xenograft. PLX038 monotherapy and combination with PARP inhibition potently inhibited the growth of both BRCA1- and ATM-deficient tumors. A patient with an ATM-mutated breast cancer treated with PLX038 and the PARP inhibitor rucaparib achieved rapid, symptomatic, and radiographic complete response lasting 12 months. Single-agent PLX038 or PLX038 in combination with DNA damage response inhibitors are novel therapeutic paradigms for patients with ATM-loss cancers.
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Affiliation(s)
| | | | - Morgan E. Diolaiti
- UCSF Helen Diller Family Comprehensive Cancer Center, San Francisco, California
| | | | | | | | | | | | - Alan Ashworth
- UCSF Helen Diller Family Comprehensive Cancer Center, San Francisco, California
| | - Felix Y. Feng
- UCSF Helen Diller Family Comprehensive Cancer Center, San Francisco, California
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Hearn BR, Fontaine SD, Schneider EL, Kraemer Y, Ashley GW, Santi DV. Attenuation of the Reaction of Michael Acceptors with Biologically Important Nucleophiles. Bioconjug Chem 2021; 32:794-800. [PMID: 33822591 DOI: 10.1021/acs.bioconjchem.1c00075] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
β-Elimination of drugs tethered to macromolecular carbamates provides a platform for drug half-life extension. However, the macromolecular Michael acceptor products formed upon drug release can potentially react with biological amines and thiols and may raise concerns about safety. We desired to mitigate this possibility by developing linkers that have predictable rates of β-elimination but suppressed rates of nucleophilic addition to their Michael acceptor products. We prepared Michael acceptor products of β-eliminative linkers that contained a methyl group at the Cβ carbon or a gem-dimethyl group at the Cγ carbon and studied the kinetics of their reactions with the most prevalent biological nucleophiles-amine and thiol groups. Aza-Michael reactions with glycine are slowed about 20-fold by methylation of the β-carbon and 175-fold with a gem-dimethyl group at the γ-carbon. Likewise, addition of the glutathione thiol to γ-gem-dimethyl Michael acceptors was retarded 7-24-fold compared to parent unsubstituted linkers. It was estimated that in an in vivo environment of ∼0.5 mM macromolecular thiols or ∼20 mM macromolecular amines-as in plasma-the reaction half-life of a typical Michael acceptor with a γ-gem-dimethyl linker could exceed 3 years for thiols or 25 years for amines. We also prepared a large series of γ-gem-dimethyl β-eliminative linkers and showed excellent structure-activity relationships of elimination rates with corresponding unsubstituted parent linkers. Finally, we compared the first-generation unsubstituted and new gem-dimethyl β-eliminative linkers in a once-monthly drug delivery system of a 39 amino acid peptide. Both linkers provided the desired half-life extension of the peptide, but the Michael acceptor formed from the gem-dimethyl linker was much less reactive. We conclude that the γ-gem-dimethyl β-eliminative linkers provide high flexibility and greatly reduce potential reactions of Michael acceptor products with biologically important nucleophiles.
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Affiliation(s)
- Brian R Hearn
- ProLynx, 455 Mission Bay Boulevard South, Suite 341, San Francisco, California 94158, United States
| | - Shaun D Fontaine
- ProLynx, 455 Mission Bay Boulevard South, Suite 341, San Francisco, California 94158, United States
| | - Eric L Schneider
- ProLynx, 455 Mission Bay Boulevard South, Suite 341, San Francisco, California 94158, United States
| | - Yannick Kraemer
- ProLynx, 455 Mission Bay Boulevard South, Suite 341, San Francisco, California 94158, United States
| | - Gary W Ashley
- ProLynx, 455 Mission Bay Boulevard South, Suite 341, San Francisco, California 94158, United States
| | - Daniel V Santi
- ProLynx, 455 Mission Bay Boulevard South, Suite 341, San Francisco, California 94158, United States
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Fontaine SD, Ashley GW, Houghton PJ, Kurmasheva RT, Diolaiti M, Ashworth A, Peer CJ, Nguyen R, Figg WD, Beckford-Vera DR, Santi DV. A Very Long-Acting PARP Inhibitor Suppresses Cancer Cell Growth in DNA Repair-Deficient Tumor Models. Cancer Res 2020; 81:1076-1086. [PMID: 33323380 DOI: 10.1158/0008-5472.can-20-1741] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Revised: 10/21/2020] [Accepted: 12/10/2020] [Indexed: 11/16/2022]
Abstract
PARP inhibitors are approved for treatment of cancers with BRCA1 or BRCA2 defects. In this study, we prepared and characterized a very long-acting PARP inhibitor. Synthesis of a macromolecular prodrug of talazoparib (TLZ) was achieved by covalent conjugation to a PEG40kDa carrier via a β-eliminative releasable linker. A single injection of the PEG∼TLZ conjugate was as effective as ∼30 daily oral doses of TLZ in growth suppression of homologous recombination-defective tumors in mouse xenografts. These included the KT-10 Wilms' tumor with a PALB2 mutation, the BRCA1-deficient MX-1 triple-negative breast cancer, and the BRCA2-deficient DLD-1 colon cancer; the prodrug did not inhibit an isogenic DLD-1 tumor with wild-type BRCA2. Although the half-life of PEG∼TLZ and released TLZ in the mouse was only ∼1 day, the exposure of released TLZ from a single safe, effective dose of the prodrug exceeded that of oral TLZ given daily over one month. μPET/CT imaging showed high uptake and prolonged retention of an 89Zr-labeled surrogate of PEG∼TLZ in the MX-1 BRCA1-deficient tumor. These data suggest that the long-lasting antitumor effect of the prodrug is due to a combination of its long t 1/2, the high exposure of TLZ released from the prodrug, increased tumor sensitivity upon continued exposure, and tumor accumulation. Using pharmacokinetic parameters of TLZ in humans, we designed a long-acting PEG∼TLZ for humans that may be superior in efficacy to daily oral TLZ and would be useful for treatment of PARP inhibitor-sensitive cancers in which oral medications are not tolerated. SIGNIFICANCE: These findings demonstrate that a single injection of a long-acting prodrug of the PARP inhibitor talazoparib in murine xenografts provides tumor suppression equivalent to a month of daily dosing of talazoparib.
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Affiliation(s)
| | | | - Peter J Houghton
- Greehey Children's Cancer Research Institute, UT Health San Antonio, Texas
| | | | - Morgan Diolaiti
- UCSF Helen Diller Family Comprehensive Cancer Center, San Francisco, California
| | - Alan Ashworth
- UCSF Helen Diller Family Comprehensive Cancer Center, San Francisco, California
| | - Cody J Peer
- Pharmacology Program, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland
| | - Ryan Nguyen
- Pharmacology Program, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland
| | - William D Figg
- Pharmacology Program, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland
| | - Denis R Beckford-Vera
- Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, California
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Fontaine SD, Ashley GW, Houghton PJ, Kurmasheva R, Diolati M, Ashworth A, Santi DV. Abstract LB-060: A very long-acting poly(ADP-ribose) polymerase inhibitor. Cancer Res 2020. [DOI: 10.1158/1538-7445.am2020-lb-060] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Abstract
Purpose: The purpose of this work was to prepare and characterize the anti-tumor properties of a prodrug for a very long-acting of poly(ADP-ribose) polymerase (PARP) inhibitor. Background: Four PARP inhibitors (PARPi) have been approved for QD oral use in treatment of human cancers. It is believed that PARP requires continuous inhibition for optimal anti-tumor effects, but, as with any drug with a short t1/2, daily administered PARPi exhibit high Cmax values and peak-to-trough excursions. We speculated that the prolonged exposure and lower Cmax and Cmax/Cmin of a long-acting PARPi might provide a more effective, less toxic therapeutic. In choosing which PARPi to target, a major consideration was whether the carrier has capacity to deliver sufficient levels of the drug over a long dosing interval. Talazoparib (TLZ) was chosen for this study because it is the most potent of the PARP inhibitors, requiring only 1 mg/day in adults compared to hundreds of mg/day for other PARPi's. Experimental procedures: We prepared a long-acting prodrug of TLZ by attaching it to a PEG40kDa carrier by a β-eliminative releasable linker. The chemistry was achieved by a novel alkylation of TLZ at the poorly acidic 2-NH of the phthalazinone moiety with an O-azidoalkyl-N-alkyl-N-chloromethyl carbamate, followed by coupling to PEG-cyclooctyne. Daily PO doses of TLZ or a single IP injection of the PEG-TLZ conjugate were administered to xenografts in mice possessing defects in homologous recombination - either a PALB2 mutation in the KT-10 Wilms tumor, or a BRCA1-deficient MX-1 triple-negative breast cancer. New data: PEG~TLZ was highly effective in treating both KT-10 and MX-1 xenografts. Although the t1/2 of TLZ in the mouse is only ~3 hr, tumor growth in animals treated with PEG~TLZ was suppressed for about one month. The EFS T/C values - the ratio of the median time to event between treated and control groups - of single injections of ~5 mg TLZ/kg as PEG~TLZ in either tumor was more than 4, indicating the drug is a highly active agent at low doses. The amount of TLZ in a single efficacious dose of the PEG~TLZ conjugate was equivalent to the same amount of free TLZ administered in divided daily doses for 4 or more weeks. Although we did not investigate scheduling, dosing PEG~TLZ once every 3 to 4 weeks should be sufficient to suppress tumor growth for extended periods. Conclusion: We developed a novel method of conjugating linkers to the 2N of the phthalazinone moiety of PARPi. We prepared a cleavable PEG~TLZ that releases TLZ with a t1/2 of 160 hr at pH 7.4. In mouse xenografts of tumors with defective HR, single non-toxic doses of PEG~TLZ suppresses tumor growth for ~1 month, and are equi-effective to QD administration of TLZ over that period. We posit that the long lasting effect is due to the long t1/2 of the prodrug, increased sensitivity of the tumor upon continued exposure to TLZ, tumor accumulation of the 15 nm nanomolecule, and counteracting drug resistance by efflux pumps.
Citation Format: Shaun D. Fontaine, Gary W. Ashley, Peter J. Houghton, Raushan Kurmasheva, Morgan Diolati, Alan Ashworth, Daniel V. Santi. A very long-acting poly(ADP-ribose) polymerase inhibitor [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr LB-060.
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Affiliation(s)
| | | | | | | | - Morgan Diolati
- 3UCSF Helen Diller Family Comprehensive Cancer Center, San Francisco, CA
| | - Alan Ashworth
- 3UCSF Helen Diller Family Comprehensive Cancer Center, San Francisco, CA
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Schneider EL, Reid R, Parkes DG, Lutz TA, Ashley GW, Santi DV. A once-monthly GLP-1 receptor agonist for treatment of diabetic cats. Domest Anim Endocrinol 2020; 70:106373. [PMID: 31479925 DOI: 10.1016/j.domaniend.2019.07.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Revised: 06/28/2019] [Accepted: 07/01/2019] [Indexed: 12/23/2022]
Abstract
There is growing evidence that peptidic glucagon-like peptide-1 receptor agonists (GLP-1RA), such as exenatide, may provide useful therapeutic options for treatment of feline diabetes. However, because such drugs are administered subcutaneously, it is desirable that they be long-acting and not require frequent injections. We have developed a chemically controlled delivery system to support half-life extension of peptidic therapeutics. Here, the peptide is covalently attached to hydrogel microspheres by a self-cleaving β-eliminative linker; after subcutaneous injection of the microspheres, the peptide is slowly released from the depot to the systemic circulation. Using this technology, we developed a delivery system that supports once-monthly administration of a stable exenatide analog, [Gln28]exenatide, in rodents (Schneider, et al, ACS Chem Biol 12, 2107 to 2116, 2017). The purposes of the present study were a) to demonstrate pharmacokinetic and pharmacodynamic similarities of the deamidation-sensitive GLP-1RA exenatide and the closely related, more stable [Gln28]exenatide and b) to develop a long-acting GLP-1RA in cats. The results show that exenatide and [Gln28]exenatide injected intravenously or subcutaneously at 10 μg/kg have nearly identical pharmacokinetics in the cat-both having elimination half-lives of ∼40 min-but subcutaneously administered [Gln28]exenatide has superior bioavailability-93% for [Gln28]exenatide vs 52% for exenatide. The results also show that exenatide and [Gln28]exenatide have similar insulinotropic activities in the cat during a high-dose intravenous glucose tolerance test; they increased the area under the curve (AUC) for insulin to a similar extent but had no effect on glucose AUC. Finally, subcutaneous injection of a microsphere-[Gln28]exenatide conjugate containing an appropriate self-cleaving linker in the cat provides plasma [Gln28]exenatide with a half-life of about 40 d vs 40 min with the injected free peptide. Hence, the large body of information available for exenatide can be used to facilitate clinical development of [Gln28]exenatide as a treatment for feline diabetes, and the microsphere-[Gln28]exenatide conjugate is quite suitable for once-monthly subcutaneous administration of the peptide in the cat.
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Affiliation(s)
| | - R Reid
- ProLynx, San Francisco, CA, USA
| | | | - T A Lutz
- University of Zurich, Institute of Veterinary Physiology, Zurich, Switzerland
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Beckford Vera DR, Fontaine SD, VanBrocklin HF, Hearn BR, Reid R, Ashley GW, Santi DV. PET Imaging of the EPR Effect in Tumor Xenografts Using Small 15 nm Diameter Polyethylene Glycols Labeled with Zirconium-89. Mol Cancer Ther 2019; 19:673-679. [PMID: 31744896 DOI: 10.1158/1535-7163.mct-19-0709] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2019] [Revised: 09/18/2019] [Accepted: 11/12/2019] [Indexed: 11/16/2022]
Abstract
The goal was to develop and characterize a companion diagnostic for the releasable PEG40kDa∼SN-38 oncology drug, PLX038, that would identify tumors susceptible to high accumulation of PLX038. PEG conjugates of the zirconium ligand desferroxamine B (DFB) of similar size and charge to PLX038 were prepared that contained one or four DFB, as well as one that contained three SN-38 moieties and one DFB. Uptake and associated kinetic parameters of the 89Zr-labeled nanocarriers were determined in tumor and normal tissues in mice using μPET/CT imaging. The data were fit to physiologically based pharmacokinetic models to simulate the mass-time profiles of distribution of conjugates in the tissues of interest. The time-activity curves for normal tissues showed high levels at the earliest time of measurement due to vascularization, followed by a monophasic loss. In tumors, levels were initially lower than in normal tissues but increased to 9% to 14% of injected dose over several days. The efflux half-life in tumors was very long, approximately 400 hours, and tumor levels remained at about 10% injected dose 9 days after injection. Compared with diagnostic liposomes, the PEG nanocarriers have a longer serum half-life, are retained in tumors at higher levels, remain there longer, and afford higher tumor exposure. The small PEG40kDa nanocarriers studied here show properties for passive targeting of tumors that are superior than most nanoparticles and might be effective probes to identify tumors susceptible to similar size therapeutic nanocarriers such as PLX038.
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Affiliation(s)
- Denis R Beckford Vera
- Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, California
| | | | - Henry F VanBrocklin
- Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, California
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Fontaine SD, Santi AD, Reid R, Smith PC, Ashley GW, Santi DV. PLX038: a PEGylated prodrug of SN-38 independent of UGT1A1 activity. Cancer Chemother Pharmacol 2019; 85:225-229. [PMID: 31707444 DOI: 10.1007/s00280-019-03987-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2019] [Accepted: 10/29/2019] [Indexed: 11/30/2022]
Abstract
PURPOSE The purpose of this study was to determine the importance of UGT1A1 activity on the metabolism and pharmacokinetics of a releasable PEG ~ SN-38 conjugate, PLX038A. Irinotecan (CPT-11) is converted to the topoisomerase 1 inhibitor SN-38 by first-pass hepatic metabolism and is converted to its glucuronide SN-38G by UGT1A1. With diminished UGT1A1 activity, the high liver exposure to SN-38 can cause increased toxicity of CPT-11. In contrast, releasable PEG ~ SN-38 conjugates-such as PLX038-release SN-38 in the vascular compartment, and only low levels of SN-38 are expected to enter the liver by transport through the OATP1B1 transporter. METHODS We measured CPT-11 and PLX038A metabolites in plasma and bile, and determined pharmacokinetics of PLX038A in UGT1A-deficient and replete rats. RESULTS Compared to CPT-11, treatment of rats with PLX038A results in very low levels of biliary SN-38 and SN-38G, a low flux through UGT1A, and a low SN-38G/SN-38 ratio in plasma. Further, the pharmacokinetics of plasma PLX038A and SN-38 in rats deficient in UGT1A is unchanged compared to normal rats. CONCLUSIONS The disposition of PEGylated SN-38 is independent of UGT1A activity in rats, and PLX038 may find utility in full-dose treatment of patients who are UGT1A1*28 homozygotes or have metastatic disease with coincidental or incidental liver dysfunction.
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Affiliation(s)
- Shaun D Fontaine
- ProLynx, 455 Mission Bay Blvd. South, Suite 341, San Francisco, CA, 94158, USA
| | - Angelo D Santi
- ProLynx, 455 Mission Bay Blvd. South, Suite 341, San Francisco, CA, 94158, USA
| | - Ralph Reid
- ProLynx, 455 Mission Bay Blvd. South, Suite 341, San Francisco, CA, 94158, USA
| | - Philip C Smith
- Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Gary W Ashley
- ProLynx, 455 Mission Bay Blvd. South, Suite 341, San Francisco, CA, 94158, USA
| | - Daniel V Santi
- ProLynx, 455 Mission Bay Blvd. South, Suite 341, San Francisco, CA, 94158, USA.
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Fontaine SD, Hann B, Reid R, Ashley GW, Santi DV. Species-specific optimization of PEG~SN-38 prodrug pharmacokinetics and antitumor effects in a triple-negative BRCA1-deficient xenograft. Cancer Chemother Pharmacol 2019; 84:729-738. [PMID: 31321449 DOI: 10.1007/s00280-019-03903-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2019] [Accepted: 07/04/2019] [Indexed: 10/26/2022]
Abstract
PURPOSE Optimal efficacy of a macromolecular prodrug requires balancing the rate of drug release with the rate of prodrug elimination. Since circulating macromolecules have different elimination rates in different species, a prodrug optimal for one species will likely not be for another. The objectives of this work were (a) to develop an approach to optimize pharmacokinetics of a PEG~SN-38 prodrug in a particular species, (b) to use the approach to predict the pharmacokinetics of various prodrugs of SN-38 in the mouse and human, and (c) to develop a PEG~SN-38 conjugate that is optimized for mouse tumor models. METHODS We developed models that describe the pharmacokinetics of a drug released from a prodrug by the relationship between the rates of drug release and elimination of the prodrug. We tested the model by varying the release rate of SN-38 from PEG~SN-38 conjugates in the setting of a constant prodrug elimination rate in the mouse. Finally, we tested the antitumor efficacy of a PEG~SN-38 optimized for the mouse. RESULTS Optimization of a PEG~SN-38 prodrug was achieved by adjusting the rate of SN-38 release such that the ratio of t1/2,β of released SN-38 to the t1/2 of prodrug elimination was 0.2-0.8. Using this approach, we could rationalize the efficacy of previous PEGylated SN-38 prodrugs in the mouse and human. Finally, a mouse-optimized PEG~SN-38 showed remarkable antitumor activity in BRCA1-deficient MX-1 xenografts; a single dose gave tumor regression, suppression, and shrinkage of massive tumors. CONCLUSIONS The efficacy of a macromolecular prodrug can be optimized for a given species by balancing the rate of drug release from the carrier with the rate of prodrug elimination.
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Affiliation(s)
- Shaun D Fontaine
- ProLynx, 455 Mission Bay Boulevard South, Suite 341, San Francisco, CA, 94158, USA
| | - Byron Hann
- University of California San Francisco, 1450 3rd Street, San Francisco, CA, 94158, USA
| | - Ralph Reid
- ProLynx, 455 Mission Bay Boulevard South, Suite 341, San Francisco, CA, 94158, USA
| | - Gary W Ashley
- ProLynx, 455 Mission Bay Boulevard South, Suite 341, San Francisco, CA, 94158, USA
| | - Daniel V Santi
- ProLynx, 455 Mission Bay Boulevard South, Suite 341, San Francisco, CA, 94158, USA.
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Machinaga N, Ashley GW, Reid R, Yamasaki A, Tanaka K, Nakamura K, Yabe Y, Yoshigae Y, Santi DV. A Controlled Release System for Long-Acting Intravitreal Delivery of Small Molecules. Transl Vis Sci Technol 2018; 7:21. [PMID: 30174998 PMCID: PMC6114027 DOI: 10.1167/tvst.7.4.21] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2018] [Accepted: 06/15/2018] [Indexed: 01/03/2023] Open
Abstract
Purpose The short half lives of small molecules in the vitreous requires frequent repeated intravitreal injections that are impractical for treatment of chronic eye diseases. We sought to develop a method for increasing the intravitreal half-life of small-molecule drugs. Methods We adapted a technology for controlled release of drugs from macromolecular carriers for use as a long-acting intravitreal delivery system for small molecules. As a prototype, a small molecule complement factor D inhibitor with an intravitreal half-life of 7 hours was covalently attached to a 4-arm PEG40kDa by a self-cleaving β-eliminative linker with a cleavage half-life of approximately 1 week. Results After intravitreal injection in rabbits, the drug was slowly released in the vitreous, and equilibrated with the retina and choroid. The intravitreal half-life of the intact PEG-drug conjugate in the rabbit was 7 days, and that of the released drug was 3.6 days. We simulated the anticipated pharmacokinetics of the delivery system in human vitreous, and estimated that the half-life of a 4-arm PEG40kDa conjugate would be approximately 2 weeks, and that of the released drug would be approximately 5 days. Conclusions We posit that a linker with a cleavage half life of 2 weeks would confer a half life of approximately 7 days to a released small molecule drug in humans, comparable to the half life of approved intravitreal injected macromolecular drugs. Translational Relevance With this technology, a potent small molecule with an appropriate therapeutic window should be administrable by intravitreal injections in the human at once-monthly intervals.
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Affiliation(s)
- Nobuo Machinaga
- Pain & Neuroscience Laboratories, Daiichi Sankyo Co., Ltd, Tokyo, Japan
| | | | | | - Atsushi Yamasaki
- Pain & Neuroscience Laboratories, Daiichi Sankyo Co., Ltd, Tokyo, Japan
| | - Kyosuke Tanaka
- Pain & Neuroscience Laboratories, Daiichi Sankyo Co., Ltd, Tokyo, Japan
| | - Koichi Nakamura
- Drug Metabolism & Pharmacokinetics Research Laboratories, Daiichi Sankyo Co., Ltd, Tokyo, Japan
| | - Yoshiyuki Yabe
- Drug Metabolism & Pharmacokinetics Research Laboratories, Daiichi Sankyo Co., Ltd, Tokyo, Japan
| | - Yasushi Yoshigae
- Pain & Neuroscience Laboratories, Daiichi Sankyo Co., Ltd, Tokyo, Japan
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Schneider EL, Hearn BR, Pfaff SJ, Reid R, Parkes DG, Vrang N, Ashley GW, Santi DV. A Hydrogel-Microsphere Drug Delivery System That Supports Once-Monthly Administration of a GLP-1 Receptor Agonist. ACS Chem Biol 2017; 12:2107-2116. [PMID: 28605180 DOI: 10.1021/acschembio.7b00218] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
We have developed a chemically controlled very long-acting delivery system to support once-monthly administration of a peptidic GLP-1R agonist. Initially, the prototypical GLP-1R agonist exenatide was covalently attached to hydrogel microspheres by a self-cleaving β-eliminative linker; after subcutaneous injection in rats, the peptide was slowly released into the systemic circulation. However, the short serum exenatide half-life suggested its degradation in the subcutaneous depot. We found that exenatide undergoes deamidation at Asn28 with an in vitro and in vivo half-life of approximately 2 weeks. The [Gln28]exenatide variant and exenatide showed indistinguishable GLP-1R agonist activities as well as pharmacokinetic and pharmacodynamic effects in rodents; however, unlike exenatide, [Gln28]exenatide is stable for long periods. Two different hydrogel-[Gln28]exenatide conjugates were prepared using β-eliminative linkers with different cleavage rates. After subcutaneous injection in rodents, the serum half-lives for the released [Gln28]exenatide from the two conjugates were about 2 weeks and one month. Two monthly injections of the latter in the Zucker diabetic fatty rat showed pharmacodynamic effects indistinguishable from two months of continuously infused exenatide. Pharmacokinetic simulations indicate that the delivery system should serve well as a once-monthly GLP-1R agonist for treatment of type 2 diabetes in humans.
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Affiliation(s)
- Eric L. Schneider
- ProLynx, 455 Mission Bay Blvd. South, Suite
145, San Francisco, California 94158, United States
| | - Brian R. Hearn
- ProLynx, 455 Mission Bay Blvd. South, Suite
145, San Francisco, California 94158, United States
| | - Samuel J. Pfaff
- ProLynx, 455 Mission Bay Blvd. South, Suite
145, San Francisco, California 94158, United States
| | - Ralph Reid
- ProLynx, 455 Mission Bay Blvd. South, Suite
145, San Francisco, California 94158, United States
| | - David G. Parkes
- DGP Scientific Inc., Del Mar, California 92014, United States
| | - Niels Vrang
- Gubra ApS, Horsholm Kongevej
11B, 2970 Horsholm, Denmark
| | - Gary W. Ashley
- ProLynx, 455 Mission Bay Blvd. South, Suite
145, San Francisco, California 94158, United States
| | - Daniel V. Santi
- ProLynx, 455 Mission Bay Blvd. South, Suite
145, San Francisco, California 94158, United States
- Department
of Pharmaceutical Chemistry, University of California, San Francisco, 600 16th Street, San Francisco, California 94158, United States
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Schneider EL, Hearn BR, Pfaff SJ, Fontaine SD, Reid R, Ashley GW, Grabulovski S, Strassberger V, Vogt L, Jung T, Santi DV. Approach for Half-Life Extension of Small Antibody Fragments That Does Not Affect Tissue Uptake. Bioconjug Chem 2016; 27:2534-2539. [DOI: 10.1021/acs.bioconjchem.6b00469] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Eric L. Schneider
- ProLynx, 455 Mission Bay Blvd. South, Suite
145, San Francisco, California 94158, United States
| | - Brian R. Hearn
- ProLynx, 455 Mission Bay Blvd. South, Suite
145, San Francisco, California 94158, United States
| | - Samuel J. Pfaff
- ProLynx, 455 Mission Bay Blvd. South, Suite
145, San Francisco, California 94158, United States
| | - Shaun D. Fontaine
- ProLynx, 455 Mission Bay Blvd. South, Suite
145, San Francisco, California 94158, United States
| | - Ralph Reid
- ProLynx, 455 Mission Bay Blvd. South, Suite
145, San Francisco, California 94158, United States
| | - Gary W. Ashley
- ProLynx, 455 Mission Bay Blvd. South, Suite
145, San Francisco, California 94158, United States
| | | | | | - Lorenz Vogt
- Delenex Therapeutics AG, Wagistrasse
27, CH-8952 Schlieren, Germany
| | - Thomas Jung
- Delenex Therapeutics AG, Wagistrasse
27, CH-8952 Schlieren, Germany
| | - Daniel V. Santi
- ProLynx, 455 Mission Bay Blvd. South, Suite
145, San Francisco, California 94158, United States
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Schneider EL, Henise J, Reid R, Ashley GW, Santi DV. Subcutaneously Administered Self-Cleaving Hydrogel–Octreotide Conjugates Provide Very Long-Acting Octreotide. Bioconjug Chem 2016; 27:1638-44. [DOI: 10.1021/acs.bioconjchem.6b00188] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Eric L. Schneider
- ProLynx, 455 Mission Bay Boulevard South,
Suite 145, San Francisco, California 94158, United States
| | - Jeff Henise
- ProLynx, 455 Mission Bay Boulevard South,
Suite 145, San Francisco, California 94158, United States
| | - Ralph Reid
- ProLynx, 455 Mission Bay Boulevard South,
Suite 145, San Francisco, California 94158, United States
| | - Gary W. Ashley
- ProLynx, 455 Mission Bay Boulevard South,
Suite 145, San Francisco, California 94158, United States
| | - Daniel V. Santi
- ProLynx, 455 Mission Bay Boulevard South,
Suite 145, San Francisco, California 94158, United States
- Department
of Pharmaceutical Chemistry, University of California, San Francisco, 600 16th Street, San Francisco, California 94158, United States
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Henise J, Hearn BR, Santi DV, Kamata H, Sakai T, Ashley GW. Surgical sealants with tunable swelling, burst pressures, and biodegradation rates. J Biomed Mater Res B Appl Biomater 2016; 105:1602-1611. [PMID: 27149244 DOI: 10.1002/jbm.b.33701] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2015] [Revised: 04/06/2016] [Accepted: 04/14/2016] [Indexed: 11/07/2022]
Abstract
We developed two types of polyethylene glycol (PEG)-based surgical sealants, which we have termed the PER and PRO series. In one, the PRO series, an 8-arm PEG containing activated carbonyl end-groups was reacted with a 4-armed amino-PEG. In the second, the PER series, a 4-arm PEG containing bi-functional end groups with four azides and four activated esters was reacted by strain-promoted alkyne-azide cycloaddition with a 4-arm cyclooctyne-PEG to give a near-ideal Tetra-PEG hydrogel. The sealants showed predictably tunable strength, swelling, adhesion, and gelation properties. The gels were compared to commercially available PEG-based sealants and exhibit physical properties equivalent to or better than the standards. Variants of each gel-format were prepared that contained a β-eliminative cleavable linker in the crosslinks to control degradation rate. Linkers of this type self-cleave with half-lives spanning from hours to years, and offer the unique ability to precisely tune the degradation to match the healing process. In addition, these linkers could serve as cleavable tethers for controlled drug release. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1602-1611, 2017.
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Affiliation(s)
- Jeff Henise
- ProLynx, 455 Mission Bay Blvd. South, Suite 145, San Francisco, California, 94158
| | - Brian R Hearn
- ProLynx, 455 Mission Bay Blvd. South, Suite 145, San Francisco, California, 94158
| | - Daniel V Santi
- ProLynx, 455 Mission Bay Blvd. South, Suite 145, San Francisco, California, 94158
| | - Hiroyuki Kamata
- Department of Bioengineering, Graduate School of Engineering, the University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, Japan
| | - Takamasa Sakai
- Department of Bioengineering, Graduate School of Engineering, the University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, Japan
| | - Gary W Ashley
- ProLynx, 455 Mission Bay Blvd. South, Suite 145, San Francisco, California, 94158
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Schneider EL, Henise J, Reid R, Ashley GW, Santi DV. Hydrogel Drug Delivery System Using Self-Cleaving Covalent Linkers for Once-a-Week Administration of Exenatide. Bioconjug Chem 2016; 27:1210-5. [DOI: 10.1021/acs.bioconjchem.5b00690] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Eric L. Schneider
- ProLynx, 455 Mission Bay Boulevard South, Suite 145, San Francisco, California 94158, United States
| | - Jeff Henise
- ProLynx, 455 Mission Bay Boulevard South, Suite 145, San Francisco, California 94158, United States
| | - Ralph Reid
- ProLynx, 455 Mission Bay Boulevard South, Suite 145, San Francisco, California 94158, United States
| | - Gary W. Ashley
- ProLynx, 455 Mission Bay Boulevard South, Suite 145, San Francisco, California 94158, United States
| | - Daniel V. Santi
- ProLynx, 455 Mission Bay Boulevard South, Suite 145, San Francisco, California 94158, United States
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Schneider EL, Ashley GW, Dillen L, Stoops B, Austin NE, Malcolm BA, Santi DV. Half-life extension of the HIV-fusion inhibitor peptide TRI-1144 using a novel linker technology. Eur J Pharm Biopharm 2015; 93:254-9. [DOI: 10.1016/j.ejpb.2015.04.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2015] [Revised: 04/01/2015] [Accepted: 04/08/2015] [Indexed: 11/30/2022]
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Henise J, Hearn BR, Ashley GW, Santi DV. Biodegradable Tetra-PEG Hydrogels as Carriers for a Releasable Drug Delivery System. Bioconjug Chem 2015; 26:270-8. [DOI: 10.1021/bc5005476] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Affiliation(s)
- Jeff Henise
- ProLynx, 455 Mission Bay Boulevard South, Suite 145, San Francisco, California 94158, United States
| | - Brian R. Hearn
- ProLynx, 455 Mission Bay Boulevard South, Suite 145, San Francisco, California 94158, United States
| | - Gary W. Ashley
- ProLynx, 455 Mission Bay Boulevard South, Suite 145, San Francisco, California 94158, United States
| | - Daniel V. Santi
- ProLynx, 455 Mission Bay Boulevard South, Suite 145, San Francisco, California 94158, United States
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Affiliation(s)
- Shaun D. Fontaine
- ProLynx, 455 Mission
Bay Blvd. South, Suite 145, San Francisco, California 94158, United States
| | - Ralph Reid
- ProLynx, 455 Mission
Bay Blvd. South, Suite 145, San Francisco, California 94158, United States
| | - Louise Robinson
- ProLynx, 455 Mission
Bay Blvd. South, Suite 145, San Francisco, California 94158, United States
| | - Gary W. Ashley
- ProLynx, 455 Mission
Bay Blvd. South, Suite 145, San Francisco, California 94158, United States
| | - Daniel V. Santi
- ProLynx, 455 Mission
Bay Blvd. South, Suite 145, San Francisco, California 94158, United States
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Santi DV, Schneider EL, Ashley GW. Macromolecular prodrug that provides the irinotecan (CPT-11) active-metabolite SN-38 with ultralong half-life, low C(max), and low glucuronide formation. J Med Chem 2014; 57:2303-14. [PMID: 24494988 DOI: 10.1021/jm401644v] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
We have recently reported a chemical approach for half-life extension that utilizes β-eliminative linkers to attach amine-containing drugs or prodrugs to macromolecules. The linkers release free drug or prodrug over periods ranging from a few hours to over 1 year. We adapted these linkers for use with phenol-containing drugs. Here, we prepared PEG conjugates of the irinotecan (CPT-11) active metabolite SN-38 via a phenyl ether that release the drug with predictable long half-lives. Pharmacokinetic studies in the rat indicate that, in contrast to other SN-38 prodrugs, the slowly released SN-38 shows a very low C(max), is kept above target concentrations for extended periods, and forms very little SN-38 glucuronide (the precursor of enterotoxic SN-38). The low SN-38 glucuronide is attributed to low hepatic uptake of SN-38. These macromolecular prodrugs have unique pharmacokinetic profiles that may translate to less intestinal toxicity and interpatient variability than the SN-38 prodrugs thus far studied.
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Affiliation(s)
- Daniel V Santi
- ProLynx , 455 Mission Bay Boulevard South, Suite 145, San Francisco, California 94158, United States
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Schneider EL, Robinson L, Reid R, Ashley GW, Santi DV. β-Eliminative Releasable Linkers Adapted for Bioconjugation of Macromolecules to Phenols. Bioconjug Chem 2013; 24:1990-7. [DOI: 10.1021/bc4002882] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Eric L. Schneider
- ProLynx, 455 Mission Bay Boulevard
South, Suite 145, San Francisco, California 94158, United States
| | - Louise Robinson
- ProLynx, 455 Mission Bay Boulevard
South, Suite 145, San Francisco, California 94158, United States
| | - Ralph Reid
- ProLynx, 455 Mission Bay Boulevard
South, Suite 145, San Francisco, California 94158, United States
| | - Gary W. Ashley
- ProLynx, 455 Mission Bay Boulevard
South, Suite 145, San Francisco, California 94158, United States
| | - Daniel V. Santi
- ProLynx, 455 Mission Bay Boulevard
South, Suite 145, San Francisco, California 94158, United States
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Czudnochowski N, Ashley GW, Santi DV, Alian A, Finer-Moore J, Stroud RM. The mechanism of pseudouridine synthases from a covalent complex with RNA, and alternate specificity for U2605 versus U2604 between close homologs. Nucleic Acids Res 2013; 42:2037-48. [PMID: 24214967 PMCID: PMC3919597 DOI: 10.1093/nar/gkt1050] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
RluB catalyses the modification of U2605 to pseudouridine (Ψ) in a stem-loop at the peptidyl transferase center of Escherichia coli 23S rRNA. The homolog RluF is specific to the adjacent nucleotide in the stem, U2604. The 1.3 Å resolution crystal structure of the complex between the catalytic domain of RluB and the isolated substrate stem-loop, in which the target uridine is substituted by 5-fluorouridine (5-FU), reveals a covalent bond between the isomerized target base and tyrosine 140. The structure is compared with the catalytic domain alone determined at 2.5 Å resolution. The RluB-bound stem-loop has essentially the same secondary structure as in the ribosome, with a bulge at A2602, but with 5-FU2605 flipped into the active site. We showed earlier that RluF induced a frame-shift of the RNA, moving A2602 into the stem and translating its target, U2604, into the active site. A hydrogen-bonding network stabilizes the bulge in the RluB–RNA but is not conserved in RluF and so RluF cannot stabilize the bulge. On the basis of the covalent bond between enzyme and isomerized 5-FU we propose a Michael addition mechanism for pseudouridine formation that is consistent with all experimental data.
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Affiliation(s)
- Nadine Czudnochowski
- Department of Biochemistry and Biophysics, University of California, San Francisco, 600 16th Street, San Francisco, CA 94158, USA, ProLynx, 455 Mission Bay Blvd., Suite 145, San Francisco, CA 94158, USA and Faculty of Biology, Technion-Israel Institute of Technology, Technion City, Haifa 320003, Israel
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Santi DV, Schneider EL, Reid R, Robinson L, Ashley GW. Predictable and tunable half-life extension of therapeutic agents by controlled chemical release from macromolecular conjugates. Proc Natl Acad Sci U S A 2012; 109:6211-6. [PMID: 22474378 PMCID: PMC3341049 DOI: 10.1073/pnas.1117147109] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Conjugation to macromolecular carriers is a proven strategy for improving the pharmacokinetics of drugs, with many stable polyethylene glycol conjugates having reached the market. Stable conjugates suffer several limitations: loss of drug potency due to conjugation, confining the drug to the extracellular space, and the requirement for a circulating conjugate. Current research is directed toward overcoming such limitations through releasable conjugates in which the drug is covalently linked to the carrier through a cleavable linker. Satisfactory linkers that provide predictable cleavage rates tunable over a wide time range that are useful for both circulating and noncirculating conjugates are not yet available. We describe such conjugation linkers on the basis of a nonenzymatic β-elimination reaction with preprogrammed, highly tunable cleavage rates. A set of modular linkers is described that bears a succinimidyl carbonate group for attachment to an amine-containing drug or prodrug, an azido group for conjugation to the carrier, and a tunable modulator that controls the rate of β-eliminative cleavage. The linkers provide predictable, tunable release rates of ligands from macromolecular conjugates both in vitro and in vivo, with half-lives spanning from a range of hours to >1 y at physiological pH. A circulating PEG conjugate achieved a 56-fold half-life extension of the 39-aa peptide exenatide in rats, and a noncirculating s.c. hydrogel conjugate achieved a 150-fold extension. Using slow-cleaving linkers, the latter may provide a generic format for once-a-month dosage forms of potent drugs. The releasable linkers provide additional benefits that include lowering C(max) and pharmacokinetic coordination of drug combinations.
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Menzella HG, Tran TT, Carney JR, Lau-Wee J, Galazzo J, Reeves CD, Carreras C, Mukadam S, Eng S, Zhong Z, Timmermans PBMWM, Murli S, Ashley GW. Potent Non-Benzoquinone Ansamycin Heat Shock Protein 90 Inhibitors from Genetic Engineering of Streptomyces hygroscopicus. J Med Chem 2009; 52:1518-21. [DOI: 10.1021/jm900012a] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Hugo G. Menzella
- Kosan Biosciences Incorporated, 3832 Bay Center Place, Hayward, California 94545
| | - Thomas-Toan Tran
- Kosan Biosciences Incorporated, 3832 Bay Center Place, Hayward, California 94545
| | - John R. Carney
- Kosan Biosciences Incorporated, 3832 Bay Center Place, Hayward, California 94545
| | - Janice Lau-Wee
- Kosan Biosciences Incorporated, 3832 Bay Center Place, Hayward, California 94545
| | - Jorge Galazzo
- Kosan Biosciences Incorporated, 3832 Bay Center Place, Hayward, California 94545
| | | | - Christopher Carreras
- Kosan Biosciences Incorporated, 3832 Bay Center Place, Hayward, California 94545
| | - Sophie Mukadam
- Kosan Biosciences Incorporated, 3832 Bay Center Place, Hayward, California 94545
| | - Sara Eng
- Kosan Biosciences Incorporated, 3832 Bay Center Place, Hayward, California 94545
| | - Ziyang Zhong
- Kosan Biosciences Incorporated, 3832 Bay Center Place, Hayward, California 94545
| | | | - Sumati Murli
- Kosan Biosciences Incorporated, 3832 Bay Center Place, Hayward, California 94545
| | - Gary W. Ashley
- Kosan Biosciences Incorporated, 3832 Bay Center Place, Hayward, California 94545
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Ashley GW, Burlingame M, Desai R, Fu H, Leaf T, Licari PJ, Tran C, Abbanat D, Bush K, Macielag M. Preparation of Erythromycin Analogs Having Functional Groups at C-15. J Antibiot (Tokyo) 2006; 59:392-401. [PMID: 17025015 DOI: 10.1038/ja.2006.56] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Chemobiosynthesis has been used to prepare analogs of erythromycins having unique functional groups at the 15-position. Using diketide thioester feeding to genetically engineered Streptomyces coelicolor, analogs of 6-deoxyerythronolide B were prepared having 15-fluoro, 15-chloro, and 15-azido groups. Bioconversion using a genetically engineered mutant of Saccharopolyspora erythraea was used to produce 15-fluoroerythromycin A and 15-azidoerythromycin A. These new erythromycin analogs provide antibacterial macrolides with unique physicochemical properties and functional groups that allow for selective derivatization.
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Affiliation(s)
- Gary W Ashley
- Kosan Biosciences, Inc., 3832, Bay Center Place, Hayward, California 94545, USA.
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Abstract
Three new ascomycins produced by genetic engineering of Streptomyces hygroscopicus ATCC 14891 have been purified and characterized. Replacement of the 13-methoxyl group of ascomycin was accomplished by substitution of the corresponding acyltransferase domain of the polyketide synthase with a domain specific for either malonyl-CoA or methylmalonyl-CoA. The strain containing the methylmalonyl-specific acyltransferase domain produced a compound with properties consistent with those expected for 13-demethoxy-13-methylascomycin. NMR analysis revealed this material to be predominantly the cis amide rotamer, similar to ascomycin. The strain containing the malonyl-specific acyltransferase domain produced a mixture of two compounds, 13-demethoxyascomycin and the 9,14-hemiacetal isomer of 13-demethoxyascomycin, in nearly equal amounts. NMR analysis revealed both compounds to be predominantly the trans amide rotamers.
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Affiliation(s)
- John R Carney
- Department of Chemistry and Process Science, Kosan Biosciences, Inc., 3832 Bay Center Place, Hayward, CA 94545, USA.
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Murli S, MacMillan KS, Hu Z, Ashley GW, Dong SD, Kealey JT, Reeves CD, Kennedy J. Chemobiosynthesis of novel 6-deoxyerythronolide B analogues by mutation of the loading module of 6-deoxyerythronolide B synthase 1. Appl Environ Microbiol 2005; 71:4503-9. [PMID: 16085842 PMCID: PMC1183267 DOI: 10.1128/aem.71.8.4503-4509.2005] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Chemobiosynthesis (J. R. Jacobsen, C. R. Hutchinson, D. E. Cane, and C. Khosla, Science 277:367-369, 1997) is an important route for the production of polyketide analogues and has been used extensively for the production of analogues of 6-deoxyerythronolide B (6-dEB). Here we describe a new route for chemobiosynthesis using a version of 6-deoxyerythronolide B synthase (DEBS) that lacks the loading module. When the engineered DEBS was expressed in both Escherichia coli and Streptomyces coelicolor and fed a variety of acyl-thioesters, several novel 15-R-6-dEB analogues were produced. The simpler "monoketide" acyl-thioester substrates required for this route of 15-R-6-dEB chemobiosynthesis allow greater flexibility and provide a cost-effective alternative to diketide-thioester feeding to DEBS KS1(o) for the production of 15-R-6-dEB analogues. Moreover, the facile synthesis of the monoketide acyl-thioesters allowed investigation of alternative thioester carriers. Several alternatives to N-acetyl cysteamine were found to work efficiently, and one of these, methyl thioglycolate, was verified as a productive thioester carrier for mono- and diketide feeding in both E. coli and S. coelicolor.
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Affiliation(s)
- Sumati Murli
- Kosan Biosciences Inc., 3832 Bay Center Place, Hayward, CA 94545, USA
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Affiliation(s)
- Leonard Katz
- Kosan Biosciences, Incorporated, 3832 Bay Center Place, Hayward, California 94545, USA.
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Shaw SJ, Abbanat D, Ashley GW, Bush K, Foleno B, Macielag M, Zhang D, Myles DC. 15-Amido Erythromycins: Synthesis and in Vitro Activity of a New Class of Macrolide Antibiotics. J Antibiot (Tokyo) 2005; 58:167-77. [PMID: 15895524 DOI: 10.1038/ja.2005.19] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
An array of 15-amido substituted erythromycin A compounds was synthesized using a chemobiosynthesis approach. It was found that while the in vitro antibacterial activities of aryl amides were inferior to erythromycin A, substituted benzylamides showed equivalent and in some cases improved activity against the macrolide-resistant strains. The 15-amidoerythromycins represent a new class of antibacterial macrolides.
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Affiliation(s)
- Simon J Shaw
- Kosan Biosciences, Inc., 3832, Bay Center Place, Hayward, California 94545, USA.
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Abstract
The API-MS spectra of 6-deoxyerythronolide B (6-dEB) and a number of its analogs have been studied to gain information into the fragmentation patterns of 6-deoxyerythronolides under atmospheric pressure ionization conditions. The API-MS spectrum of 6-dEB shows five major families of fragments. The spectra of a series of desmethyl-6-dEBs allow assignment of these fragment families to structural subunits as well as provide information regarding the fragmentation mechanisms. The spectrum of [9-(18)O]-6-dEB is consistent with loss of the ketone oxygen during the first dehydration, and the spectra of other oxygen-modified analogs implicate the non-obligate formation of a 5,9-hemiacetal in the initial stages of fragmentation. These results taken together are used to propose a model for the fragmentation of 6-dEB and its analogs under API conditions.
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Affiliation(s)
- Gary W Ashley
- Department of Chemistry, Kosan Biosciences, Inc., 3832 Bay Center Place, Hayward, CA 94545, USA.
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Abstract
The fragmentation of delta-lactones, particularly triketide lactones, has been studied to provide information on the behavior of polyketides under atmospheric pressure ionization mass spectrometry (API-MS). The principal fragmentation patterns of triketide lactones are characterized by two sequential dehydrations followed by loss of CO to give hydrocarbon fragments. A particular goal of this study was an understanding of the origins of the two water molecules from the dehydrations. 18O- and 2H-isotope labeling experiments with delta-valerolactone suggest a mechanism for lactone fragmentation in which ionization by proton transfer is followed by rapid equilibration of ring-opened and ring-closed forms, which results in exchange of the ionizing proton into the hydrocarbon framework of the compound and randomization of the oxygens of the lactone. Subsequent fragmentation primarily involves sequential loss of water and CO. Similar experiments with the more complex triketide lactones show that their mass spectra share common features with that of delta-valerolactone, together with an additional water loss from the 3-hydroxyl group.
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Affiliation(s)
- Gary W Ashley
- Department of Chemistry, Kosan Biosciences, Inc. 3832 Bay Center Place, Hayward, CA 94545, USA.
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Reeves CD, Murli S, Ashley GW, Piagentini M, Hutchinson CR, McDaniel R. Alteration of the substrate specificity of a modular polyketide synthase acyltransferase domain through site-specific mutations. Biochemistry 2001; 40:15464-70. [PMID: 11747421 DOI: 10.1021/bi015864r] [Citation(s) in RCA: 150] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Cassette replacement of acyltransferase (AT) domains in 6-deoxyerythronolide B synthase (DEBS) with heterologous AT domains with different substrate specificities usually yields the predicted polyketide analogues. As reported here, however, several AT replacements in module 4 of DEBS failed to produce detectable polyketide under standard conditions, suggesting that module 4 is sensitive to perturbation of the protein structure when the AT is replaced. Alignments between different modular polyketide synthase AT domains and the Escherichia coli fatty acid synthase transacylase crystal structure were used to select motifs within the AT domain of module 4 to re-engineer its substrate selectivity and minimize potential alterations to protein folding. Three distinct primary regions of AT4 believed to confer specificity for methylmalonyl-CoA were mutated into the sequence seen in malonyl-CoA-specific domains. Each individual mutation as well as the three in combination resulted in functional DEBSs that produced mixtures of the natural polyketide, 6-deoxyerythronolide B, and the desired novel analogue, 6-desmethyl-6-deoxyerythronolide B. Production of the latter compound indicates that the identified sequence motifs do contribute to AT specificity and that DEBS can process a polyketide chain incorporating a malonate unit at module 4. This is the first example in which the extender unit specificity of a PKS module has been altered by site-specific mutation and provides a useful alternate method for engineering AT specificity in the combinatorial biosynthesis of polyketides.
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Affiliation(s)
- C D Reeves
- Kosan Biosciences, Inc., 3832 Bay Center Place, Hayward, California 94545, USA
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Fardis M, Ashley GW, Carney JR, Chu DT. Synthesis of 14,15-dehydroerythromycin A ketolides: effects of the 13-substituent on erythromycin tautomerism. J Antibiot (Tokyo) 2001; 54:278-84. [PMID: 11372784 DOI: 10.7164/antibiotics.54.278] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A ketolide was prepared from 14,15-dehydroerythromycin A by two different routes. The first approach involving oxidation of the 3-OH of 3-descladinosyl-14,15-dehydroerythromycin A 2'-O-acetate gave unexpectedly high levels of 3,11-double oxidation. This may be due to greater formation of the 9,12-hemiketal in 14,15-dehydroerythromycin A and concomitant exposure of the 11-OH group for oxidation. NMR studies of 14,15-dehydroerythromycin A support this hypothesis, revealing a 9:1 ratio of 9-ketone to 9,12-hemiketal in CDCl3 and a 1:1 ratio in CD3OD as contrasted with the corresponding tautomer ratios of 30:1 in CDCl3, and 6: 1 in CD3OD with erythromycin A. Alteration of the 13-substituent on the erythronolide A ring from ethyl to vinyl thus favors formation of the 9,12-hemiketal. A second route to the ketolides was developed based on these findings, in which the 11-OH is eliminated prior to oxidation of the 3-OH.
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Affiliation(s)
- M Fardis
- Department of Chemistry, Kosan Biosciences, Inc, Hayward, CA 94545, USA
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Carreras CW, Ashley GW. Manipulation of polyketide biosynthesis for new drug discovery. EXS 2001; 89:89-108. [PMID: 10997284 DOI: 10.1007/978-3-0348-8393-1_6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Modular polyketide synthases (PKS) are large multifunctional proteins which direct the condensation of activated short chain carboxylic acids into products of defined length and functionality using a dedicated set of active sites, or module, for each step in the polymerization. The structure of the product is directly related to the number, content and sequence of modules in a PKS. Technology is described which allows the rational manipulation of the biosynthesis of these compounds and enables the generation of specific novel polyketide structures. Examples of polyketide drugs whose structures may be manipulated using this technology are given.
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Affiliation(s)
- C W Carreras
- Department of New Technologies, Kosan Biosciences, Inc., Hayward, CA 94545, USA
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Miller JR, Busby RW, Jordan SW, Cheek J, Henshaw TF, Ashley GW, Broderick JB, Cronan JE, Marletta MA. Escherichia coli LipA is a lipoyl synthase: in vitro biosynthesis of lipoylated pyruvate dehydrogenase complex from octanoyl-acyl carrier protein. Biochemistry 2000; 39:15166-78. [PMID: 11106496 DOI: 10.1021/bi002060n] [Citation(s) in RCA: 174] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The Escherichia coli lipA gene product has been genetically linked to carbon-sulfur bond formation in lipoic acid biosynthesis [Vanden Boom, T. J., Reed, K. E., and Cronan, J. E., Jr. (1991) J. Bacteriol. 173, 6411-6420], although in vitro lipoate biosynthesis with LipA has never been observed. In this study, the lipA gene and a hexahistidine tagged lipA construct (LipA-His) were overexpressed in E. coli as soluble proteins. The proteins were purified as a mixture of monomeric and dimeric species that contain approximately four iron atoms per LipA polypeptide and a similar amount of acid-labile sulfide. Electron paramagnetic resonance and electronic absorbance spectroscopy indicate that the proteins contain a mixture of [3Fe-4S] and [4Fe-4S] cluster states. Reduction with sodium dithionite results in small quantities of an S = 1/2 [4Fe-4S](1+) cluster with the majority of the protein containing a species consistent with an S = 0 [4Fe-4S](2+) cluster. LipA was assayed for lipoate or lipoyl-ACP formation using E. coli lipoate-protein ligase A (LplA) or lipoyl-[acyl-carrier-protein]-protein-N-lipoyltransferase (LipB), respectively, to lipoylate apo-pyruvate dehydrogenase complex (apo-PDC) [Jordan, S. W., and Cronan, J. E. (1997) Methods Enzymol. 279, 176-183]. When sodium dithionite-reduced LipA was incubated with octanoyl-ACP, LipB, apo-PDC, and S-adenosyl methionine (AdoMet), lipoylated PDC was formed. As shown by this assay, octanoic acid is not a substrate for LipA. Confirmation that LipA catalyzes formation of lipoyl groups from octanoyl-ACP was obtained by MALDI mass spectrometry of a recombinant PDC lipoyl-binding domain that had been lipoylated in a LipA reaction. These results provide information about the mechanism of LipA catalysis and place LipA within the family of iron-sulfur proteins that utilize AdoMet for radical-based chemistry.
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Affiliation(s)
- J R Miller
- Howard Hughes Medical Institute, Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48109-0606, USA
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MacDonald RC, Ashley GW, Shida MM, Rakhmanova VA, Tarahovsky YS, Pantazatos DP, Kennedy MT, Pozharski EV, Baker KA, Jones RD, Rosenzweig HS, Choi KL, Qiu R, McIntosh TJ. Physical and biological properties of cationic triesters of phosphatidylcholine. Biophys J 1999; 77:2612-29. [PMID: 10545361 PMCID: PMC1300535 DOI: 10.1016/s0006-3495(99)77095-5] [Citation(s) in RCA: 112] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The properties of a new class of phospholipids, alkyl phosphocholine triesters, are described. These compounds were prepared from phosphatidylcholines through substitution of the phosphate oxygen by reaction with alkyl trifluoromethylsulfonates. Their unusual behavior is ascribed to their net positive charge and absence of intermolecular hydrogen bonding. The O-ethyl, unsaturated derivatives hydrated to generate large, unilamellar liposomes. The phase transition temperature of the saturated derivatives is very similar to that of the precursor phosphatidylcholine and quite insensitive to ionic strength. The dissociation of single molecules from bilayers is unusually facile, as revealed by the surface activity of aqueous liposome dispersions. Vesicles of cationic phospholipids fused with vesicles of anionic lipids. Liquid crystalline cationic phospholipids such as 1, 2-dioleoyl-sn-glycero-3-ethylphosphocholine triflate formed normal lipid bilayers in aqueous phases that interacted with short, linear DNA and supercoiled plasmid DNA to form a sandwich-structured complex in which bilayers were separated by strands of DNA. DNA in a 1:1 (mol) complex with cationic lipid was shielded from the aqueous phase, but was released by neutralizing the cationic charge with anionic lipid. DNA-lipid complexes transfected DNA into cells very effectively. Transfection efficiency depended upon the form of the lipid dispersion used to generate DNA-lipid complexes; in the case of the O-ethyl derivative described here, large vesicle preparations in the liquid crystalline phase were most effective.
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Affiliation(s)
- R C MacDonald
- Department of Biochemistry, Molecular Biology, and Cell Biology, Northwestern University, Evanston, Illinois 60208, USA.
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Betlach MC, Kealey JT, Ashley GW, McDaniel R. Characterization of the macrolide P-450 hydroxylase from Streptomyces venezuelae which converts narbomycin to picromycin. Biochemistry 1998; 37:14937-42. [PMID: 9778370 DOI: 10.1021/bi981699c] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The post-polyketide synthase (PKS) biosynthetic tailoring of macrolide antibiotics usually involves one or more oxidation reactions catalyzed by cytochrome P450 monooxygenases. As the specificities of members from this class of enzymes vary significantly among PKS gene clusters, the identification and study of new macrolide P450s are important to the growing field of combinatorial biosynthesis. We have isolated the cytochrome P450 gene picK from Streptomyces venezuelae which is responsible for the C-12 hydroxylation of narbomycin to picromycin. The gene was located by searching regions proximal to modular PKS genes with a probe for macrolide P450 monooxygenases. The overproduction of PicK with a C-terminal six-His affinity tag (PicK/6-His) in Escherichia coli aided the purification of the enzyme for kinetic analysis. PicK/6-His was shown to catalyze the in vitro C-12 hydroxylation of narbomycin with a kcat of 1.4 s-1, which is similar to the value reported for the related C-12 hydroxylation of erythromycin D by the EryK hydroxylase. The unique specificity of this enzyme should be useful for the modification of novel macrolide substrates similar to narbomycin, in particular, ketolides, a promising class of semisynthetic macrolides with activity against erythromycin-resistant pathogens.
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Affiliation(s)
- M C Betlach
- KOSAN Biosciences, Inc., Burlingame, California 94010, USA
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Labeots LA, Clare SE, Ashley GW, Letsinger RL. Stereochemical assignment of chiral phosphotriester analogues with Alu I sites. J Biomol Struct Dyn 1996; 14:111-6. [PMID: 8877567 DOI: 10.1080/07391102.1996.10508934] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The stereochemistry of the diastereomers of a DNA duplex with the 2,2,2-trichloro-1,1,-dimethylethyl (TCDME) phosphotriester backbone substitution has been assigned by the use of 2D NMR spectroscopy. The duplex [G1G2A3A4G5p(TCDME)C6T7A8G9G10]-[C11C12T13A14G15C16 T17T18C19C20] is a substrate of the restriction endonuclease Alu I, with placement of the TCDME group at the G5-C6 cleavage site of one strand. The stereochemical orientation of the TCDME group in relation to the structure of the double helix regulates the ability of Alu I to hydrolyze the complementary recognition site. The phosphotriester group of the isomer 1 duplex blocks cleavage of the complementary strand, while that of the isomer 2 duplex allows cleavage to proceed. Within the phosphotriester recognition site, no hydrolysis is detected nor is any seen when the single-stranded DNA substrate is utilized. Data from the 2D NOESY spectra demonstrate that both DNA duplexes retain basic B-form geometry. The isomer 1 duplex shows NOE cross-relaxation from the protons of the two methyl groups of the TCDME modification (1.99, 2.00 ppm) to the G5 H3'(5.30 ppm), G5 H4' (4.53 ppm), and C6 H5'/H5" (4.52, 4.62 ppm) protons. The isomer 2 duplex shows NOE cross-relaxation from the methyl protons of the TCDME modification (2.01, 2.03 ppm) to the C6 H6 (7.15 ppm), C6 H4' (4.30 ppm), C6 H5'/H5" (4.48, 4.62 ppm), G5 H3' (5.26 ppm), and G5 H4' (4.48 ppm) protons. Thus the NOE cross-relaxation between the methyl protons of the TCDME modification and the C6 H6 and C6 H4' protons in isomer 2 is not found in the spectra of the isomer 1 duplex. These NMR data confirm the stereochemical assignment of the chirality of the TCDME phosphotriester group in isomer 1 as the Sp configuration and in isomer 2 as the Rp configuration. The Sp isomer features the TCDME group pointing away from the helix, while the Rp isomer shows the TCDME group pointing towards the major groove. Thus through the use of 2D NMR techniques, the stereochemistry of chiral phosphotriester linkages may be assigned in chemically modified DNA.
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Affiliation(s)
- L A Labeots
- Department of Chemistry, Northwestern University, Evanston, IL 60208, USA.
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Abstract
The DNA hairpins d[CGATCG-Tn-CGATCG] (n = 3, 4) have been studied by NMR in order to gain information on hairpin conformation and flexibility. Resonance assignments were made using a combination of DQF-COSY, DQF-COSY[31P], NOESY, and 1H-31P-COSY. These data also provide approximate coupling constant information which points out exceptionally flexible regions of the phosphate backbone. The data for both hairpins reveal substantial flexibility within the loop segments. For n = 4, NOESY data alone are insufficient to distinguish between two loop-folding motifs, although coupling constant data favor a conformation in which Tb is folded toward the minor groove and is highly exposed to solvent. This is in agreement with chemical shift data and susceptibility to modification by KMnO4. The phosphate backbone between Tc and Td is exceptionally flexible, undergoing a facile exchange between (beta t,gamma+) and (beta+,gamma t) conformers. A similar flexible phosphate is observed between Tc and C7 when n = 3. Differences in stem conformation and dynamics in both hairpins are restricted to the two base pairs adjacent to the stem-loop junction. The C7pG8 stem phosphate appears to flip easily between (zeta-,alpha-) and (zeta-,alpha t) conformers when n = 4 but not when n = 3. Hairpin loop size thus affects the conformational flexibility of the adjacent stem segment.
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Affiliation(s)
- S M Baxter
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208
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46
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Cheah E, Austin C, Ashley GW, Ollis D. Substrate-induced activation of dienelactone hydrolase: an enzyme with a naturally occurring Cys-His-Asp triad. Protein Eng 1993; 6:575-83. [PMID: 8234228 DOI: 10.1093/protein/6.6.575] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The Cys-His-Asp catalytic triad found in dienelactone hydrolase (DLH) is unusual for several reasons. It has not been observed in other hydrolytic enzymes and it is virtually inactive when it is produced by site-directed mutagenesis in the proteases. We propose a model to explain why this triad is catalytically active in DLH but not in the proteases. In the resting state of DLH, His202 forms an ion pair with Asp171 and Cys123 exists as a thiol. The resting state thiol does not interact with His202 in the active site but instead forms a hydrogen bond with Glu36 in the interior of the molecule. In the absence of substrate, Glu36 is also ion paired with Arg206. When substrate binds, Arg206 forms a second ion pair with the anionic substrate and the Arg206/Glu36 ion pair weakens. The destabilized Glu36 carboxylate shifts towards and deprotonates the Cys123 thiol, thereby activating the nucleophile. As the thiolate anion is not energetically favoured in the hydrophobic interior of the enzyme, it swings into the active site where it can be stabilized by the His202 imidazolium and the dipole of helix C. The Cys123 thiolate which now lies adjacent to the acyl carbon of the substrate, is thus generated only in the presence of substrate. The mode of thiolate activation reduces the susceptibility of DLH towards thiol alkylating agents.
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Affiliation(s)
- E Cheah
- Research School of Chemistry, Australian National University, Canberra
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47
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Abstract
Dienelactone hydrolase (DLH), an enzyme from the beta-ketoadipate pathway, catalyzes the hydrolysis of dienelactone to maleylacetate. Our inhibitor binding studies suggest that its substrate, dienelactone, is held in the active site by hydrophobic interactions around the lactone ring and by the ion pairs between its carboxylate and Arg-81 and Arg-206. Like the cysteine/serine proteases, DLH has a catalytic triad (Cys-123, His-202, Asp-171) and its mechanism probably involves the formation of covalently bound acyl intermediate via a tetrahedral intermediate. Unlike the proteases, DLH seems to protonate the incipient leaving group only after the collapse of the first tetrahedral intermediate, rendering DLH incapable of hydrolyzing amide analogues of its ester substrate. In addition, the triad His probably does not protonate the leaving group (enolate) or deprotonate the water for deacylation; rather, the enolate anion abstracts a proton from water and, in doing so, supplies the hydroxyl for deacylation.
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Affiliation(s)
- E Cheah
- Research School of Chemistry, Australian National University, Canberra
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48
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Hayden MA, Huang IY, Iliopoulos G, Orozco M, Ashley GW. Biosynthesis of lipoic acid: characterization of the lipoic acid auxotrophs Escherichia coli W1485-lip2 and JRG33-lip9. Biochemistry 1993; 32:3778-82. [PMID: 8466915 DOI: 10.1021/bi00065a033] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The abilities of the Escherichia coli lipoic acid auxotrophs W1485-lip2 and JRG33-lip9 to grow on succinate medium in the presence of octanoate, 8-mercaptooctanoate, or 6-mercaptooctanoate have been determined. Both organisms are mutated in lipA. Neither organism can use octanoate or 6-mercaptooctanoate for production of lipoate, but the lip2 allele can use 8-mercaptooctanoate. Chromosomal DNA from the auxotrophs was amplified by PCR using primers derived from the DNA sequence of wild-type lipA and then sequenced. Both mutants contain single G/C to A/T mutations in lipA, resulting in conversion of Ser307 into Phe in W1485-lip2 and Glu195 into Lys in JRG33-lip9. These results support the hypothesis that lipA is involved in the sulfur insertion step(s) of lipoate biosynthesis and indicate that it is possible to selectively block formation of the C8-S bond through suitable mutation in lipA.
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Affiliation(s)
- M A Hayden
- Department of Chemistry and of Biochemistry, Northwestern University, Evanston, Illinois 60208
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49
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Meschwitz SM, Schultz RG, Ashley GW, Goldberg IH. Selective abstraction of 2H from C-1' of the C residue in AGC.ICT by the radical center at C-2 of activated neocarzinostatin chromophore: structure of the drug/DNA complex responsible for bistranded lesion formation. Biochemistry 1992; 31:9117-21. [PMID: 1390698 DOI: 10.1021/bi00153a001] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Glutathione-activated neocarzinostatin chromophore (NCS-Chrom) generates bistranded lesions at AGC.GCT sequences in DNA, consisting of an abasic site at the C residue and a strand break at the T residue on the complementary strand, due to hydrogen atom abstraction from C-1' and C-5', respectively. Earlier work showed that 2H from C-5' of T was selectively abstracted by the radical center at C-6 of activated NCS-Chrom, supporting a proposed model of the active-drug/DNA complex. However, since under the conditions used breaks at the T exceeded their inclusion in bistranded lesions, it was not clear what fraction of the hydrogen transfer represented bistranded lesions. Since virtually all abasic sites at the C are part of a bistranded lesions, hydrogen transfer from C-1' of C into the drug should reflect only the bistranded reaction. Accordingly, a self-complementary oligodeoxynucleotide 5'-GCAGCICTGC-3' was synthesized in which the C contained 2H at the C-1' position. In order to eliminate an 2H isotope effect on the transfer and to increase the extent of the bistranded reaction, an I residue was substituted for the G opposite the C residue. Sequencing gel electrophoretic analysis revealed that under one-hit kinetics, 37% of the damage reaction was associated with abasic site (alkali-labile break) formation at the C residue and 48% with direct strand breaks at the T residue. Thus, 74% of the damage involved a bistranded lesion. 1H NMR spectroscopic analysis of the reacted chromophore showed that 2H had been selectively transferred into the C-2 position to the extent of approximately 22%.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- S M Meschwitz
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115
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50
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Hayden MA, Huang I, Bussiere DE, Ashley GW. The biosynthesis of lipoic acid. Cloning of lip, a lipoate biosynthetic locus of Escherichia coli. J Biol Chem 1992; 267:9512-5. [PMID: 1577793] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
The lip gene of Escherichia coli has been cloned and sequenced. Subcloning of a 3-kilobase EcoRI/EcoRV restriction fragment from Clark-Carbon plasmid pLC15-5 into pUC18 gives a plasmid that complements two lipoate auxotrophs, W1485-lip2 and JRG33-lip9, and which expresses a protein of approximately 36,000 Da. Sequencing suggests that lip codes for a protein of 281 amino acids (31,350 Da), showing sequence similarity to biotin synthase. It is thus likely that lip encodes a sulfur insertion enzyme analogous to biotin synthase and that the sulfur insertion chemistries of the two systems are related. Unidirectional nested deletion experiments show that both lipoate auxotrophs are complemented by the same 500-base pair region at the 3' terminus of the lip gene, indicating that the mutations affecting lipoate biosynthesis are located in this region of the protein. A small open reading frame located immediately downstream of the lip gene codes for a small protein of unknown function.
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Affiliation(s)
- M A Hayden
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208
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