Cysteine metabolic engineering and selective disulfide reduction produce superior antibody-drug-conjugates.

Next-generation site-specific cysteine-based antibody-drug-conjugates (ADCs) broaden therapeutic index by precise drug-antibody attachments. However, manufacturing such ADCs for clinical validation requires complex full reduction and reoxidation processes, impacting product quality. To overcome this technical challenge, we developed a novel antibody manufacturing process through cysteine (Cys) metabolic engineering in Chinese hamster ovary cells implementing a unique cysteine-capping technology. This development enabled a direct conjugation of drugs after chemoselective-reduction with mild reductant tris(3-sulfonatophenyl)phosphine. This innovative platform produces clinical ADC products with superior quality through a simplified manufacturing process. This technology also has the potential to integrate Cys-based site-specific conjugation with other site-specific conjugation methodologies to develop multi-drug ADCs and exploit multi-mechanisms of action for effective cancer treatments.

Evaluation of single-use tangential flow filtration technology for purification of activated polysaccharides used in conjugate vaccine manufacturing.

Over the past decade, single-use tangential flow filtration (TFF) technologies have emerged to reduce system preparation time, promote fast and flexible product change over, and ultimately shorten process development and manufacturing time/cost. In this study, the performance of a recently developed Pellicon® single-use TFF capsule was compared against traditional Pellicon® cassettes by assessing TFF process performance (such as flux, residuals clearance, and yield) and post-purification product attributes (such as concentration and mass-weighted average molecular weight). Good scaling was shown by comparing process performance and product attributes across different scales and formats. Additionally, similar TFF process performance and post-purification product attributes were observed for the single-use capsule compared to the reusable TFF cassettes. The capsule requires a smaller flush than the cassette, and it is easier to use since it does not require a compression holder or pre-sanitization. The results provide insight into the application of the single-use TFF capsule and scalability of TFF processes for the purification of conjugate vaccines.

Mechanistic understanding of the cysteine capping modifications of antibodies enables selective chemical engineering in live mammalian cells.

Protein modifications by intricate cellular machineries often redesign the structure and function of existing proteins to impact biological networks. Disulfide bond formation between cysteine (Cys) pairs is one of the most common modifications found in extracellularly-destined proteins, key to maintaining protein structure. Unpaired surface cysteines on secreted mammalian proteins are also frequently found disulfide-bonded with free Cys or glutathione (GSH) in circulation or culture, the mechanism for which remains unknown. Here we report that these so-called Cys-capping modifications take place outside mammalian cells, not in the endoplasmic reticulum (ER) where oxidoreductase-mediated protein disulfide formation occurs. Unpaired surface cysteines of extracellularly-arrived proteins such as antibodies are uncapped upon secretion before undergoing disulfide exchange with cystine or oxidized GSH in culture medium. This observation has led to a feasible way to selectively modify the nucleophilic thiol side-chain of cell-surface or extracellular proteins in live mammalian cells, by applying electrophiles with a chemical handle directly into culture medium. These findings provide potentially an effective approach for improving therapeutic conjugates and probing biological systems.

Small molecule inhibitors of HIV RT Ribonuclease H.

Two classes of compounds, thiocarbamates 1 and triazoles 2, have been identified as HIV RT RNase H inhibitors using a novel FRET-based HTS assay. The potent analogs in each series exhibited selectivity and were active in cell-based assays. In addition, saturable, 1:1 stoichiometric binding to target was established and time of addition studies were consistent with inhibition of RT-mediated HIV replication.

C-5 substituted heteroaryl-3-pyridinecarbonitriles as PKCtheta inhibitors: part II.

We previously reported that a 3-pyridinecarbonitrile analog with a furan substituent at C-5 and a 4-methylindol-5-ylamino substituent at C-4, 1, was a potent inhibitor of PKCtheta (IC50=4.5 nM). Replacement of the C-5 furan ring of 1 with bicyclic heteroaryl rings, led to compounds with significantly improved potency against PKCtheta. Analog 6b with a 4-methylindol-5-ylamino group at C-4 and a 5-[(4-methylpiperazin-1-yl)methyl]-1-benzofuran-2-yl group at C-5 had an IC50 value of 0.28 nM for the inhibition of PKCtheta.

Optimization of 5-phenyl-3-pyridinecarbonitriles as PKCtheta inhibitors.

The key intermediate, 4-chloro-5-iodo-3-pyridinecarbonitrile, allowed for ready optimization of the PKCtheta inhibitory activity of a series of 3-pyridinecarbonitriles. Analog 13b with a 4-methylindol-5-ylamino group at C-4 and a 4-(2-(4-methylpiperazin-1-yl)ethoxy)phenyl group at C-5 had an IC(50) value of 7.4nM for the inhibition of PKCtheta.

Spirocyclopropyl beta-lactams as mechanism-based inhibitors of serine beta-lactamases. Synthesis by rhodium-catalyzed cyclopropanation of 6-diazopenicillanate sulfone.

Class A-class C mechanism-based beta-lactamase inhibitors were designed on the basis of the intermediacy of an oxycarbenium species capable of cross-linking with amino acids residues in the active site. Penams 24 and 27 were very potent against AmpC in vitro. The MIC values of 24 in combination with piperacillin against class A and class C producing organisms showed improvement over clinically used tazobactam.

Resistance to beta-lactam antibiotics: structure and mechanism based design of beta-lactamase inhibitors.

Resistance to antibiotics is currently a major health concern in treating infectious diseases. The most common mechanism of resistance to beta-lactam antibiotics is the production of beta-lactamases, which destroy beta-lactam antibiotics before they reach the bacterial target. Combination therapy, which involves treatment with a beta-lactam antibiotic and a beta-lactamase inhibitor, has been successfully used to control resistance during last two decades. Due to the lack of effectiveness of the currently available beta-lactamase inhibitors against class C enzymes and new variants of beta-lactamases, there is a need to develop an inhibitor with broad-spectrum activity. Since the discovery of clavulanic acid, there has been an enormous research effort in this area to identify better antibiotic/inhibitor combinations and to understand the molecular bases for interactions between beta-lactam antibiotics, beta-lactamases, and beta-lactamase inhibitors. This review describes some of the structure- and mechanism-based approaches to design of new beta-lactamase inhibitors and the study of probable mechanisms of inhibition using X-ray, electrospray ionization mass spectrometry, and molecular modeling techniques.