Ron M. Versteegen

Supramolecular polymer materials; chain extension of telechelic polymers using a reactive hydrogen bonding synthon

Functionalizing the termini of low-molecular-weight telechelic polymers with strongly associating hydrogen bonding units (see Figure) results in a new set of supramolecular materials, as reported here. These materials possess the unique combination of polymer-like properties at room temperature and monomer-like properties at elevated temperatures.

Highly reactive trans-cyclooctene tags with improved stability for Diels-Alder chemistry in living systems.

One of the challenges of pretargeted radioimmunotherapy, which centers on the capture of a radiolabeled probe by a preinjected tumor-bound antibody, is the potential immunogenicity of biological capturing systems. A bioorthogonal chemical approach may circumvent this drawback, but effective in vivo chemistry in mice, larger animals, and eventually humans, requires very high reagent reactivity, sufficient stability, and retained selectivity. We report here that the reactivity of the fastest bioorthogonal reaction, the inverse-electron-demand-Diels-Alder cycloaddition between a tetrazine probe and a trans-cyclooctene-tagged antibody, can be increased 10-fold (k2 = 2.7 × 10(5) M(-1) s(-1)) via the trans-cyclooctene, approaching the speed of biological interactions, while also increasing its stability. This was enabled by the finding that the trans-cyclooctene tag is probably deactivated through isomerization to the unreactive cis-cyclooctene isomer by interactions with copper-containing proteins, and that increasing the steric hindrance on the tag can impede this process. Next, we found that the higher reactivity of axial vs equatorial linked TCO can be augmented by the choice of linker. The new, stabilized, and more reactive tag allowed for improved tumor-to-nontumor ratios in pretargeted tumor-bearing mice.

Click to Release: Instantaneous Doxorubicin Elimination upon Tetrazine Ligation†

Eliminated without a trace: The fastest click reaction, the highly selective inverse-electron-demand Diels-Alder reaction, has been modified to enable selective bioorthogonal release. Thus, the click reaction of a tetrazine with a drug-bound trans-cyclooctene caused the instantaneous release of the drug and CO2 (see scheme). One possible application is the chemically triggered release, and thereby activation, of a drug from a tumor-bound antibody-drug conjugate.

[n]-polyurethanes : synthesis and characterization

More than 50 years after Otto Bayers detailed description of [m,n]-polyurethanes, the first general synthesis of [n]-polyurethanes 1 is described. This series of aliphatic [n]-polyurethanes is synthesized by the in situ polymerization of the corresponding alpha,omega-isocyanato alcohol monomers, which in turn are made out of linear alpha,omega-amino alcohols and di-tert-butyltricarbonate. Polymers of high molecular weight possessing a uniform microstructure are obtained, while their melting points show a strong odd-even effect.

Triggered Drug Release from an Antibody–Drug Conjugate Using Fast “Click-to-Release” Chemistry in Mice

The use of a bioorthogonal reaction for the selective cleavage of tumor-bound antibody-drug conjugates (ADCs) would represent a powerful new tool for ADC therapy, as it would not rely on the currently used intracellular biological activation mechanisms, thereby expanding the scope to noninternalizing cancer targets. Here we report that the recently developed inverse-electron-demand Diels-Alder pyridazine elimination reaction can provoke rapid and self-immolative release of doxorubicin from an ADC in vitro and in tumor-bearing mice.

Efficient functionalization of additives at supramolecular material surfaces

Selective surface modification reactions can be performed on additives that are supramolecularly incorporated into supramolecular materials. Hereby, processing of the material, that regularly requires harsh processing conditions (i.e., the use of organic solvents and/or high temperatures), and functionalization can be decoupled. Moreover, high-resolution depth profiling by time-of-flight (ToF) secondary-ion mass spectrometry clearly shows distinct differences in surface and bulk material composition.

[n]-Polyurethane: Synthese und Charakterisierung

Uber 50 Jahre nach Otto Bayers detaillierter Beschreibung der [m,n]-Polyurethane wird nun eine allgemeine Synthese der [n]-Polyurethane 1 beschrieben. Diese Reihe aliphatischer [n]-Polyurethane wird durch In-situ-Polymerisation der entsprechenden α,ω-Isocyanatalkoholmonomere erhalten, die ihrerseits aus linearen α,ω-Aminoalkoholen und Di-tert-butyltricarbonat hergestellt werden. Man erhalt so Polymere mit hohem Molekulargewicht und einheitlicher Mikrostruktur, deren Schmelzpunkte einen starke Alternanz (Gerade-Ungerade-Effekt) zeigen.

DOTA-tetrazine probes with modified linkers for tumor pretargeting

INTRODUCTION Pretargeted radioimmunoimaging and -therapy approaches building on the bioorthogonal inverse-electron-demand Diels-Alder (IEDDA) reaction between strained trans-cyclooctenes (TCO) and electron-deficient tetrazines (Tz) have yielded impressive results in recent years and have proven a vital alternative to biological pretargeting systems. After improvement of the TCO-antibody conjugates, we here report on our evaluation of a new series of radiolabeled Tz-probes. METHODS Four new Tz-probes were synthesized, radiolabeled with lutetium-177, and characterized in vitro in terms of lipophilicity, reactivity, and stability in PBS and mouse serum. The in vivo biodistribution profile and tumor-targeting potential of the probes were evaluated in LS174T tumor-bearing mice pretargeted with TCO-antibody conjugates using non-pretargeted mice as control. RESULTS Radiolabeling of all probes proceeded in high yields providing the 177Lu-labeled tetrazines in >95% radiochemical purity without any further purification. In mouse serum, half-lives of the probes varied between 8 and 13 h, with the exception of the most lipophilic probe, [177Lu]1b, with a serum half-life of less than 1 h. This probe also showed the fastest blood clearance (t1/2 = 5.4 min), more than 2-fold faster than PEG-linked probes [177Lu]3 and [177Lu]4, and even 3-fold faster than the other small probes without the PEG-linker, [177Lu]1a and [177Lu]2. In the pretargeting experiments, tumor uptake of the lead probe [177Lu]4 (~6 %ID/g) was most closely approached by [177Lu]2, followed by [177Lu]3 and [177Lu]1a. While all the smaller and more lipophilic probes suffered from increased liver uptake, the PEG-linked probe [177Lu]3 with its additional negative charge surprisingly showed the highest kidney uptake among all of the probes. CONCLUSION The in vitro performance of some of the new tetrazine probes turned out to be comparable to the established lead probe [177Lu]Lu-DOTA-PEG11-Tz ([177Lu]4). However, tumor pretargeting studies in vivo showed lower tumor uptake and increased uptake in non-target organs.

Chemically triggered drug release from an antibody-drug conjugate leads to potent antitumour activity in mice

Current antibody-drug conjugates (ADCs) target internalising receptors on cancer cells leading to intracellular drug release. Typically, only a subset of patients with solid tumours has sufficient expression of such a receptor, while there are suitable non-internalising receptors and stroma targets. Here, we demonstrate potent therapy in murine tumour models using a non-internalising ADC that releases its drugs upon a click reaction with a chemical activator, which is administered in a second step. This was enabled by the development of a diabody-based ADC with a high tumour uptake and very low retention in healthy tissues, allowing systemic administration of the activator 2 days later, leading to efficient and selective activation throughout the tumour. In contrast, the analogous ADC comprising the protease-cleavable linker used in the FDA approved ADC Adcetris is not effective in these tumour models. This first-in-class ADC holds promise for a broader applicability of ADCs across patient populations.Current antibody-drug conjugates (ADCs) target internalising receptors on cancer cells. Here, the authors report the development and in vivo validation of a non-internalising ADC with the capacity to target cancer cells and release its therapeutic cargo extracellularly via a chemical trigger.

Click‐to‐Release from trans‐Cyclooctenes: Mechanistic Insights and Expansion of Scope from Established Carbamate to Remarkable Ether Cleavage

The bioorthogonal cleavage of allylic carbamates from trans-cyclooctene (TCO) upon reaction with tetrazine is widely used to release amines. We disclose herein that this reaction can also cleave TCO esters, carbonates, and surprisingly, ethers. Mechanistic studies demonstrated that the elimination is mainly governed by the formation of the rapidly eliminating 1,4-dihydropyridazine tautomer, and less by the nature of the leaving group. In contrast to the widely used p-aminobenzyloxy linker, which affords cleavage of aromatic but not of aliphatic ethers, the aromatic, benzylic, and aliphatic TCO ethers were cleaved as efficiently as the carbamate, carbonate, and esters. Bioorthogonal ether release was demonstrated by the rapid uncaging of TCO-masked tyrosine in serum, followed by oxidation by tyrosinase. Finally, tyrosine uncaging was used to chemically control cell growth in tyrosine-free medium.