Species-specific optimization of PEG~SN-38 prodrug pharmacokinetics and antitumor effects in a triple-negative BRCA1-deficient xenograft

Fontaine, Shaun D.; Hann, Byron; Reid, Ralph; Ashley, Gary W.; Santi, Daniel V.

doi:10.1007/s00280-019-03903-5

Cited by 17 publications

(22 citation statements)

References 30 publications

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“…The 4-branched PEG 40kDa provides a neutral, highly flexible, long half-life NC with a hydrodynamic d of approximately 15 nm (13,14) in accord with ideal properties proposed for NC tumor accumulation by EPR (5). Indeed, in preclinical studies, the SN-38 prodrug PLX038 as well as the related EZN-2208, a releasable PEG 40kDa $SN-38 similar to PLX038 except for a faster cleavage rate, showed high tumor accumulation of both prodrugs and released SN-38 that remained high for several weeks, and demonstrated remarkable antitumor effects (12,15,16). These results motivated this study which seeks to investigate the EPR effect of PEG 40kDa NC surrogates of the prodrug PLX038.…”

Section: Introductionsupporting

confidence: 62%

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PET Imaging of the EPR Effect in Tumor Xenografts Using Small 15 nm Diameter Polyethylene Glycols Labeled with Zirconium-89

Beckford-Vera

Fontaine

VanBrocklin

et al. 2020

Molecular Cancer Therapeutics

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The goal was to develop and characterize a companion diagnostic for the releasable PEG 40kDa $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 89 Zr-labeled nanocarriers were determined in tumor and normal tissues in mice using mPET/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 timeactivity 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 halflife, are retained in tumors at higher levels, remain there longer, and afford higher tumor exposure. The small PEG 40kDa 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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Section: Introductionsupporting

confidence: 62%

“…We recently described long-acting PEGylated prodrugs of SN-38, the active metabolite of irinotecan (11,12). The NC-drug conjugate, designated PLX038 ( Fig.…”

Section: Introductionmentioning

confidence: 99%

PET Imaging of the EPR Effect in Tumor Xenografts Using Small 15 nm Diameter Polyethylene Glycols Labeled with Zirconium-89

Beckford-Vera

Fontaine

VanBrocklin

et al. 2020

Molecular Cancer Therapeutics

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“…In the modified procedure, Jones Reagent was substituted by NaOCl/TEMPO to avoid possible introduction of chromium into the drug substance, and individual procedures were optimized to obtain a ∼25% overall yield in large‐scale preparations. 5‐HCO was converted to 5‐HCO‐HSC 9 as previously described 17 …”

Section: Resultsmentioning

confidence: 99%

High‐throughput, aseptic production of injectable Tetra‐PEG hydrogel microspheres for delivery of releasable covalently bound drugs

Henise

Yao

Hearn

et al. 2020

Engineering Reports

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The purpose of this work was to develop equipment and procedures for large‐scale aseptic production of injectable microsphere (MS) drug conjugates. The two major challenges were (a) to prepare sufficient amounts of MSs for clinical trials, and (b) to prepare the MS‐drug product under aseptic conditions. The approach was to prepare the MS‐drug conjugate in two stages. Stage 1 was the preparation of monodisperse tetra‐PEG amine derivatized MSs (amino‐MS) from two soluble PEG prepolymers under low to no bioburden conditions. To accomplish this, custom‐engineered equipment compatible with both aqueous and organic solvents was fabricated for parallel microfluidic preparation of amino‐MS. The system was capable of preparing up to ∼2 L of high quality 50 μm diameter amino‐MS per day. Stage 2 was the sterilization of the starting amino‐MS and aseptic production of the MS‐drug conjugate. The amino‐MS were first sterilized by autoclaving then transferred to a custom‐engineered autoclave‐sterilized washer‐reactor. This apparatus allowed for activation of the amino‐MS and attachment of a linker‐drug under aseptic conditions to give the sterile MS‐drug conjugate drug substance. The final drug product was produced by addition of excipients to form a homogeneous suspension. The entire process is exemplified by an engineering production run of a sterile MS‐peptide drug product.

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“…The 10‐kDa 4‐armed tetra[(cyclooct‐4‐ynyloxycarbonyl)amino]‐PEG (PEG 10kDa (NH‐5HCO) 4 3 (Scheme ) was prepared from PEG 10kDa (NH 2 ) 4 and O‐Cyclooct‐4‐yn‐1‐yl‐O′‐succinimidyl carbonate (5‐HCO‐HSC) as described for the analogous PEG 40kDa (NH‐5HCO) 4 . A solution of 2 (11.2 mg, 19 μmol, 1.3 Eq) in 0.2 mL of acetonitrile was mixed with a solution of 3 (56.6 mM in cyclooctyne, 0.265 mL, 15 μmol cyclooctyne, 1.0 Eq) in 20 mM NaOAc, pH 5, and kept at 50°C for 12 hours.…”

Section: Methodsmentioning

confidence: 99%

“…Similar to a described procedure, Prepolymer A was prepared by reaction of linker HSC 1 with BOC‐Lys, and the product was converted into its HSE and coupled to 4‐arm PEG 20kDa (NH 2 ) 4 . Prepolymer B (4‐arm PEG 20kda ‐NH[HCO] 4 ; ( 3 ) was prepared by coupling 5‐HCO‐HSC with 4‐arm PEG 20kDa (NH 2 ) 4 as described for PEG 40kDa (NH‐5HCO) 4 . Amino‐MSs were prepared from 2.5‐mM solutions of Prepolymer A and Prepolymer B using a reported microfluidic method with the following modifications.…”

Section: Methodsmentioning

confidence: 99%

Autoclave sterilization of tetra‐polyethylene glycol hydrogel biomaterials with β‐eliminative crosslinks

Henise

Yao

Ashley

et al. 2020

Engineering Reports

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Sterilization of degradable polymeric biomaterials intended for injection presents a formidable challenge. Often, either the polymer backbone or labile crosslinks controlling degradation are adversely affected by commonly used sterilization methods. The purpose of this work was to develop an approach to sterilize tetra-polyethylene glycol hydrogel microspheres (MSs) with -eliminative crosslinks that are destined to be carriers for drug delivery. The approach taken was to acidify the medium to compensate for the base-catalyzed cleavage of linkers at high temperatures. We determined that rates of linker cleavage at pH 4 or below were sufficiently slow as to allow autoclaving and showed that precursor amine-derivatized MSs could withstand autoclaving at pH 4 for at least four cycles of 20 minutes each at 121 • C. Thus, amine-MSs need not be prepared aseptically, but instead can be prepared in a low bioburden environment, and then sterilized by autoclaving before drug attachment. K E Y W O R D Sbiodegradable hydrogel, drug delivery, half-life extension, microspheres, tetra-polyethylene glycol INTRODUCTIONWe have developed a general approach for half-life extension of therapeutics, in which a drug is covalently tethered to a long-lived carrier by a linker that slowly cleaves by -elimination to release the native drug (Scheme 1). 1 The cleavage rate of the linker is controlled by the nature of an electron-withdrawing "modulator" (Mod) attached to a carbon containing an acidic C-H bond. After rate-determining proton removal, the intermediate rapidly collapses to provide the free drug. These linkers are not affected by enzymes and are stable for years when stored at low pH and temperature. One carrier we use is a large-pore tetra-polyethylene glycol (PEG) hydrogel polymer. 2-4 These hydrogels-fabricated as uniform 50-μm microspheres (MSs)-are injected subcutaneously (SC) or locally through a small-bore needle where they serve as a depot to slowly release the drug. Importantly, a slower cleaving -eliminative linker is incorporated in crosslinks of these polymers, so gel degradation occurs after drug release. 3,5 Fabrication of tetra-PEG hydrogel MS-drug conjugates is achieved in two stages (Scheme 2). 3,4 Stage 1 involves preparation of amine-derivatized MSs. Here, equimolar amounts of an 8-arm PEG containing 4 amine-and 4 azido-linker end groups and a 4-arm PEG containing cyclooctyne end groups are mixed in a droplet forming device. The azide (A) and cyclooctyne (B) end groups of the PEG prepolymers react within the droplets by strain-promoted alkyne-azide cycloadditions (SPAAC) to form 1,2,3-triazoles and provide homogeneous amine-derivatized tetra-PEG

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Species-specific optimization of PEG~SN-38 prodrug pharmacokinetics and antitumor effects in a triple-negative BRCA1-deficient xenograft

Cited by 17 publications

References 30 publications

PET Imaging of the EPR Effect in Tumor Xenografts Using Small 15 nm Diameter Polyethylene Glycols Labeled with Zirconium-89

PET Imaging of the EPR Effect in Tumor Xenografts Using Small 15 nm Diameter Polyethylene Glycols Labeled with Zirconium-89

High‐throughput, aseptic production of injectable Tetra‐PEG hydrogel microspheres for delivery of releasable covalently bound drugs

Autoclave sterilization of tetra‐polyethylene glycol hydrogel biomaterials with β‐eliminative crosslinks

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