Stereoselective Synthesis of the IDO Inhibitor Navoximod.

A highly efficient asymmetric synthesis of the IDO inhibitor navoximod, featuring the stereoselective installation of two relative and two absolute stereocenters from an advanced racemic intermediate, is described. The stereocenters were set via a crystallization-induced dynamic resolution along with two selective ketone reductions: one via a biocatalytic ketoreductase transformation and one via substrate-controlled hydride delivery from LiAlH(Ot-Bu)3. Following this strategy, navoximod was synthesized in 10 steps from 2-fluorobenzaldehyde and isolated in 23% overall yield with 99.7% ee and high purity.

Purification of a GalNAc-cluster-conjugated oligonucleotide by reversed-phase twin-column continuous chromatography.

Multicolumn Countercurrent Solvent Gradient Purification (MCSGP) is a continuous chromatography technique used to maximize purification yields compared to traditional batch purification methods. Here we apply MCSGP for the reversed phase purification of a N-acetylgalactosamine (GalNAc)-cluster-conjugated DNA-LNA gapmer oligonucleotide therapeutic using a twin-column chromatography system. Based on a batch process as a starting point, MCSGP was designed, optimized and compared with the batch process regarding process performance and scale-up requirements. Product yields increased from 52.7% using batch chromatography to 91.5% using MCSGP, with purity, productivity, and buffer consumption otherwise comparable. In a manufacturing scenario, use of MCSGP would allow the downscaling of oligonucleotide synthesis by 42.5%, which would result in a significant cost reduction and increased throughput. Moreover, the equipment, chemicals and methodology used in MCSGP are analogous to a standard reversed phase purification allowing for a "like for like" transition to the upgraded MCSGP process.

Sustainability Challenges and Opportunities in Oligonucleotide Manufacturing.

With a renewed and growing interest in therapeutic oligonucleotides across the pharmaceutical industry, pressure is increasing on drug developers to take more seriously the sustainability ramifications of this modality. With 12 oligonucleotide drugs reaching the market to date and hundreds more in clinical trials and preclinical development, the current state of the art in oligonucleotide production poses a waste and cost burden to manufacturers. Legacy technologies make use of large volumes of hazardous reagents and solvents, as well as energy-intensive processes in synthesis, purification, and isolation. In 2016, the American Chemical Society (ACS) Green Chemistry Institute Pharmaceutical Roundtable (GCIPR) identified the development of greener processes for oligonucleotide Active Pharmaceutical Ingredients (APIs) as a critical unmet need. As a result, the Roundtable formed a focus team with the remit of identifying green chemistry and engineering improvements that would make oligonucleotide production more sustainable. In this Perspective, we summarize the present challenges in oligonucleotide synthesis, purification, and isolation; highlight potential solutions; and encourage synergies between academia; contract research, development and manufacturing organizations; and the pharmaceutical industry. A critical part of our assessment includes Process Mass Intensity (PMI) data from multiple companies to provide preliminary baseline metrics for current oligonucleotide manufacturing processes.

Calculated Nuclear Magnetic Resonance Spectra of Polytwistane and Related Hydrocarbon Nanorods.

Polytwistane is an intriguing hydrocarbon nanorod that has not been experimentally realized to date. To facilitate its identification in complex reaction mixtures, the (1)H and (13)C nuclear magnetic resonance (NMR) spectra of idealized polytwistane were calculated using two distinct quantum chemical approaches. In addition, the NMR spectra of related hydrocarbon nanorods were determined. On the basis of these data, we speculate whether polytwistane and its congeners correspond to a crystalline one-dimensional sp(3) carbon nanomaterial formed by high-pressure solid-state polymerization of benzene.

Synthetic studies toward polytwistane hydrocarbon nanorods.

A synthetic strategy toward the intriguing hydrocarbon nanorod polytwistane is outlined. Our approach aims toward the polymerization of acetylene starting from precursors that would provide a helical bias for the formation of polytwistane. Both transition-metal-catalyzed and radical polymerizations were investigated. Two potential initiator molecules were synthesized that could be used for either approach. Although the intended regioselectivities were not observed, unusual organopalladium complexes and numerous compounds with novel carbon skeletons were obtained.

Polytwistane.

Twistane, C10H16, is a classic D2-symmetric chiral hydrocarbon that has been studied for decades due to its fascinating stereochemical and thermodynamic properties. Here we propose and analyze in detail the contiguous linear extension of twistane with ethano (ethane-1,2-diyl) bridges to create a new chiral, C2-symmetric hydrocarbon nanotube called polytwistane. Polytwistane, (CH)n, has the same molecular formula as polyacetylene but is composed purely of C(sp(3))-H units, all of which are chemically equivalent. The polytwistane nanotube has the smallest inner diameter (2.6 Å) of hydrocarbons considered to date. A rigorous topological analysis of idealized polytwistane and a C236H242 prototype optimized by B3LYP density functional theory reveals that the polymer has a nonrepeating, alternating σ-helix, with an irrational periodicity parameter and an instantaneous rise (or lead) angle near 15 °. A theoretical analysis utilizing homodesmotic equations and explicit computations as high as CCSD(T)/cc-pVQZ yields the enthalpies of formation Delta(f)H(0)°(twistane) = -1.7 kcal mol(-1) and Delta(f)H(0)°(polytwistane) = +1.28 kcal (mol CH)(-1), demonstrating that the hypothetical formation of polytwistane from acetylene is highly exothermic. Hence, polytwistane is synthetically viable both on thermodynamic grounds and also because no obvious pathways exist for its rearrangement to lower-lying isomers. The present analysis should facilitate the preparation and characterization of this new chiral hydrocarbon nanotube.

A step toward polytwistane: synthesis and characterization of C2-symmetric tritwistane.

Twistane is a classic hydrocarbon with fascinating stereochemical properties. Herein we describe a series of oligomers of twistane that converges on a chiral nanorod, which we term polytwistane. A member of this series, C2-symmetric tritwistane, has been synthesized for the first time.

Clinical Trial Educator program - a novel approach to accelerate enrollment in a phase III International Acute Coronary Syndrome Trial.

BACKGROUND: The conduct of current cardiovascular outcome trials requires investigation of thousands of patients at hundreds of investigator sites. Such large trials are clinically and logistically highly demanding and often tend to finish with significant delays, consequently delaying patient access to new medicines. PURPOSE: To address this issue, we designed and implemented a novel approach - a Clinical Trial Educator (CTE) program - to accelerate enrollment in the Thrombin-Receptor Antagonist for Clinical Event Reduction (TRA•CER) trial. This article analyzes the effect of this approach on the study milestones: patient recruitment, site start-up time, and recruitment rate. METHODS: Scientifically qualified and specifically trained CTEs regularly visited TRA•CER investigator sites in 18 European countries where they trained and educated investigators and site personnel to support them address recruitment challenges. Patient recruitment was assessed in absolute numbers and as recruitment rates, both in relation to CTE site visits. RESULTS: CTEs performed 2184 visits at 373 European TRA•CER sites (out of 921 global sites). Of sites visited by a CTE, significantly less remained without enrolling any patient than of sites not visited by a CTE (5.9% vs. 15.3%; p < 0.001). Sites visited within 30 days after initiation showed a significantly shortened median time to recruitment of the first patient (28 vs. 59 days with visits ≤30 or >30 days after initiation; p < 0.001). Mean patient recruitment rates were significantly higher at visited than at not-visited sites (1.13 vs. 0.89 patients per site per month, p < 0.001) and significantly increased after the first CTE site visit (from 0.70 to 1.17 patients per site per month; p < 0.001). Finally, there were fewer low-recruiting sites and more high-recruiting sites among the CTE-visited sites compared to the not-visited sites, and the mean recruitment rate at high-recruiting sites visited by CTEs was significantly higher than at high-recruiting sites without CTE visits (2.07 vs. 1.64 patients per site per month; p < 0.01). LIMITATIONS: The possibility for selection bias is inherent to this post hoc analysis of a nonrandomized data set. The European focus of the CTE program described here might add some geographical bias. Also, other activities such as investigator meetings conducted in parallel with CTE activities might have partly masked the results of our analysis. Finally, the analysis is limited to recruitment-related parameters, and the aspect of cost-effectiveness has not been quantitatively assessed. CONCLUSION: We found a significant positive association between CTE site visits and the assessed recruitment-related study milestones in the TRA•CER trial, and enrollment finished ahead of plan. We propose that a CTE program could efficiently accelerate enrollment in other clinical trials and therapeutic areas and could contribute to shortening patient access time to novel and potential lifesaving treatments in cardiovascular medicine and beyond.