Ester Prodrug Research Articles

P-2030. Remdesivir and Obeldesivir Retain Potent Activity Against SARS-CoV-2 Omicron Variants

Abstract Background Remdesivir (RDV), a nucleotide analog prodrug that targets the viral RNA-dependent RNA polymerase, Nsp12, is approved to treat COVID-19 in hospitalized and nonhospitalized patients. Obeldesivir (ODV), an oral mono-5’-isobutyryl ester prodrug, is metabolized into the same active triphosphate as RDV. The antiviral activity of RDV and ODV against previous Omicron subvariants (BA.1 to XBF) was maintained with respect to the ancestral WA1 strain. Here, RDV and ODV antiviral activity data against recent Omicron subvariants (XBB.2.3.2, EG.5.1, EG.1.2, BA.2.86, XBC.1.6, HK.3, and JN.1) are reported using clinical isolates and site directed mutants (SDMs) in replicons bearing Nsp12 substitutions observed in these subvariants. Methods The prevalence of Nsp12 substitutions in Omicron subvariants was assessed using Global Initiative on Sharing Avian Influenza Data (GISAID) EpiCoV database sequences. Structures of identified substitutions were analyzed using a previously established cryo-electron microscopy-based model of the replication-transcription complex. Antiviral activity (half-maximal effective concentration [EC50]) of RDV and ODV against subvariant clinical isolates was assessed by nucleoprotein ELISA in A549-hACE2-TMPRSS2 cells and by SDMs in a replicon system. Results Genomic analysis of >2.5 million Omicron subvariant sequences revealed unique substitutions in Nsp12 vs WA1. Two new defining mutations (≥75% of sequences; D63N [HK.3] and G823insD [XBC.1.6]) were found compared with earlier Omicron subvariants. Less prevalent substitutions (1.0% to 15.9%; T26I, D40G, T85I, I171V, Y175H, I223M, T225I, D258N, Y289H, D303N, T394M, P461S, V476A, M666I, T803I, and V848I) were also observed; none had direct interaction with the incoming nucleotide triphosphate or the viral RNA. Phenotyping of individual substitutions using SDMs showed no loss of RDV or ODV susceptibility (≤1.60-fold change). Phenotyping of clinical isolates of XBB.2.3.2, EG.5.1, EG.1.2, BA.2.86, XBC.1.6, HK.3, and JN.1 indicated no change of RDV or ODV in vitro antiviral activity (< 1.05-fold change). Conclusion RDV and ODV retained potent in vitro antiviral activity against all tested Omicron subvariants and Nsp12 substitutions with potencies comparable to reference strains. Disclosures Lauren Rodriguez, PhD, Gilead Sciences, Inc.: Employee|Gilead Sciences, Inc.: Stocks/Bonds (Public Company) J. Lizbeth Reyes Zamora, PhD, Gilead Sciences, Inc.: Employee|Gilead Sciences, Inc.: Stocks/Bonds (Public Company) Dong Han, MS, Gilead Sciences, Inc.: Employee|Gilead Sciences, Inc.: Stocks/Bonds (Public Company) Nadine Peinovich, MPH, Gilead Sciences, Inc.: Employee|Gilead Sciences, Inc.: Stocks/Bonds (Public Company) Clarissa Martinez, MPH, Gilead Sciences, Inc.: Employee|Gilead Sciences, Inc.: Stocks/Bonds (Public Company) Pui Yan Ho, PhD, Gilead Sciences, Inc.: Employee|Gilead Sciences, Inc.: Stocks/Bonds (Public Company) Jiani Li, PhD, Gilead Sciences, Inc.: Employee|Gilead Sciences, Inc.: Stocks/Bonds (Public Company) Thomas Aeschbacher, PhD, Gilead Sciences, Inc.: Employee|Gilead Sciences, Inc.: Stocks/Bonds (Public Company) John P. Bilello, PhD, Gilead Sciences, Inc.: Employee|Gilead Sciences, Inc.: Stocks/Bonds (Public Company) Jason K. Perry, PhD, Gilead Sciences, Inc.: Employee|Gilead Sciences, Inc.: Stocks/Bonds (Public Company) Charlotte Hedskog, PhD, Gilead Sciences, Inc.: Employee|Gilead Sciences, Inc.: Stocks/Bonds (Public Company)

Structure-Based Virtual Screening Identifies 2-Arylthiazole-4-Carboxylic Acids as a Novel Class of Nanomolar Affinity Ligands for the CaMKIIα Hub Domain.

The Ca2+/calmodulin-dependent protein kinase II α (CaMKIIα) plays a crucial role in regulating neuronal signaling and higher brain functions, being involved in various brain diseases. Utilization of small molecules targeting the CaMKIIα hub domain has proved to be a promising strategy for specific CaMKIIα modulation and future therapy. Through an in silico structure-based virtual screening campaign, we herein identified 2-arylthiazole-4-carboxylic acids as a new class of high-affinity CaMKIIα hub ligands. Particularly, the 2,6-dichlorophenyl analog, PTCA (compound 1a), displayed mid-nanomolar affinity (pKi = 7.2) and substantial stabilization of the CaMKIIα hub oligomer upon binding. Moreover, the tert-butyl ester prodrug, 14a, was developed to facilitate the brain delivery of PTCA and demonstrated remarkable enhancement in brain penetration compared to PTCA per se after systemic administration. Altogether, our study highlights that PTCA represents a novel and powerful tool compound for future pharmacological interventions targeting CaMKII kinase in the brain.

Design of (R)-3-(5-Thienyl)carboxamido-2-aminopropanoic Acid Derivatives as Novel NMDA Receptor Glycine Site Agonists: Variation in Molecular Geometry to Improve Potency and Augment GluN2 Subunit-Specific Activity.

NMDA receptor ligands have therapeutic potential in neurological and psychiatric disorders. We designed (R)-3-(5-thienyl)carboxamido-2-aminopropanoic acid derivatives with nanomolar agonist potencies at NMDA receptor subtypes (GluN12/A-D). These compounds are superagonists at GluN1/2C compared to glycine and partial to full agonists at GluN1/2A and GluN1/2D but display functional antagonism at GluN1/2B due to low agonist efficacy. Notably, 8d display 864% agonist efficacy at GluN1/2C relative to glycine, and 8j has high potency at GluN1/2A (0.018 μM), GluN1/2C (0.0029 μM), and GluN1/2D (0.016 μM). We evaluated the binding mode in the glycine site using molecular modeling and mutagenesis. In vitro absorption, distribution, metabolism, and excretion (ADME) assays predict high metabolic stability but poor blood-brain barrier permeability. However, an ester prodrug for the carboxylate group of 7j display moderately high blood-brain barrier permeability. The thiophenecarboxamide agonists expand the synthetic pharmacology of NMDA receptors and provide structural insights that facilitate the design of GluN1 agonists with GluN2 subunit-specific activity.

In Vitro Rooting of Poplar: Effects and Metabolism of Dichlorprop Auxin Ester Prodrugs.

Efficient adventitious root formation is essential in micropropagation. Auxin prodrugs, inactive precursors that convert into active auxins within the plant, offer potentially improved rooting control and reduced phytotoxicity. This study investigated the efficacy of dichlorprop ester (DCPE), commercialized as Corasil® and Clemensgros® (originally intended to increase grapefruit size), in promoting in vitro root initiation in the model plant Populus × canadensis, compared to its hydrolyzed form DCP and the related compound C77. DCPE displayed a stronger root-inducing effect than DCP, especially at lower concentrations (0.01 and 0.1 µM). Notably, at 1 µM, both DCP and DCPE induced abundant aerial root formation, a phenomenon not previously observed in poplar with traditional auxin treatments. Metabolite analysis revealed distinct patterns. DCPE treatment resulted in rapid hydrolysis to DCP, leading to faster and more systemic distribution of the active auxin throughout the plant, compared to direct DCP application. C77 treatments showed slower uptake and limited translocation combined with slow metabolism to DCP. These results highlight the potential of auxin prodrugs like DCPE as an effective and controllable auxin source for optimizing in vitro rooting protocols in woody plant species.

Intracorneal iontophoretic delivery of triamcinolone acetonide prodrugs: Physicochemical parameters guiding electrotransport.

Intracorneal delivery of ten amino acid (alanine, arginine, asparagine, glutamine, glycine, histidine, isoleucine, lysine, methionine and valine) ester prodrugs of triamcinolone acetonide (TA-AA) was investigated in vitro, using a corneal iontophoresis device (IONTOFOR-CXL; SOOFT Italia S.p.A.) approved for clinical use in the treatment of keratoconus. Short duration iontophoresis (1mA for 5min) was performed and intracorneal deposition of TA was quantified by HPLC-UV and UHPLC-MS/MS. The data evidenced the clear advantage of TA-AA prodrug iontophoresis compared to passive delivery and revealed unexpected and prodrug dependent deposition profiles. Despite their superior electrical mobility, intracorneal delivery of dications, TA-Arg and TA-Lys, did not outperform that of TA-Ala and TA-Gly. In silico investigations to relate the TA-AA prodrugs' physicochemical properties to their electrotransport confirmed that increased lipophilicity potential did not favour iontophoretic transport. For TA-Ala and TA-Gly, it was hypothesized that the greater charge distribution and decreased tendency to interact with the corneal tissue via electrostatic and H-bonds contributed to their successful iontophoretic delivery. Intracorneal biodistribution of TA confirmed that TA-Gly iontophoresis resulted in supratherapeutic concentrations in deep corneal stroma, exceeding TA IC50 by∼104-fold. The results clearly demonstrated the successful combination of the clinically approved SOOFT iontophoretic device and the TA-AA prodrugs for targeted corneal iontophoretic delivery.

Pharmacokinetic Evaluation of Neutral Sphinghomyelinase2 (nSMase2) Inhibitor Prodrugs in Mice and Dogs.

Background: Extracellular vesicles (EVs) can carry pathological cargo, contributing to disease progression. The enzyme neutral sphingomyelinase 2 (nSMase2) plays a critical role in EV biogenesis, making it a promising therapeutic target. Our lab previously identified a potent and selective inhibitor of nSMase2, named DPTIP (IC50 = 30 nM). Although promising, DPTIP exhibits poor pharmacokinetics (PKs) with a low oral bioavailability (%F < 5), and a short half-life (t1/2 ≤ 0.5 h). To address these limitations, we previously developed DPTIP prodrugs by masking its phenolic hydroxyl group, demonstrating improved plasma exposure in mice. Recognizing that species-specific metabolic differences can influence prodrug PK, we expanded our studies to evaluate selected prodrugs in both mice and dogs. Methods: The scaleup of selected prodrugs was completed and two additional valine- ester based prodrugs were synthesized. Mice were dosed prodrugs via peroral route (10 mg/kg equivalent). For dog studies DPTIP was dosed via intravenous (1 mg/kg) or peroral route (2 mg/kg) and prodrugs were given peroral at a dose 2 mg/kg DPTIP equivalent. Plasma samples were collected at predetermined points and analyzed using developed LC/MS-MS methods. Results: In mice, several of the tested prodrugs showed similar or improved plasma exposures compared to DPTIP. However, in dog studies, the double valine ester prodrug 9, showed significant improvement with an almost two-fold increase in DPTIP plasma exposure (AUC0-t = 1352 vs. 701 pmol·h/mL), enhancing oral bioavailability from 8.9% to 17.3%. Conclusions: These findings identify prodrug 9 as a promising candidate for further evaluation and underscore the critical role of species-specific differences in prodrug PKs.

Advancements in NMDA Receptor-Targeted Antidepressants: From d-Cycloserine Discovery to Preclinical Efficacy of Lu AF90103.

The discovery of d-cycloserine (DCS), a partial agonist of the NMDA receptor that exhibits antidepressant effects without the psychotomimetic effects of ketamine, has fueled interest in new NMDA-targeting antidepressants. Our objective was to identify potent partial agonists mirroring DCS, particularly tailored for the GluN2B subtype of the NMDA receptor. Through a structure-based drug design approach, we discovered compound 42d. This compound acts as a partial agonist of the GluN1/GluN2B complex, exhibiting 24% efficacy, and has an EC50 value of 78 nM. Subsequent investigations led us to 42e (Lu AF90103), a methyl ester prodrug of 42d capable of penetrating the blood-brain barrier, as confirmed by rat microdialysis studies. In different rat in vivo models relevant to neuropsychiatric diseases, administering 42e led to 42d demonstrating both acute effects, observed in a seizure model and EEG, and lasting effects in the stress-sensitive hippocampal pathway and an antidepressant-sensitive model.

Facile Synthesis of Valsartan and Ribose Prodrug and Studying its Influence on the Pancreatic Lipase

Valsartan is a widely used drug that belongs to the type of angiotensin receptor blockers generally specified to control high blood pressure (hypertension) and heart failure. In the present work, a new ester prodrug utilizes ribose sugar as a carrier for the valsartan through an esterification reaction. The synthesized compound was characterized by the FT-IR and 1H NMR spectroscopic. The investigation furthermore involved measuring the activity of the lipase enzyme in the blood serum of individuals with high blood pressure and healthy individuals and purifying the lipase enzyme utilizing gel filtration technology. Besides, the investigation studied the kinetics of the lipase enzyme, the impact of various substrate concentrations, the impact of pH and optimal temperature on the enzyme's activity, and the impact of reaction time on the enzyme's effectiveness. It was found that the effectiveness of the lipase enzyme reduced with raising the concentration of the synthesized compound, and the sort of inhibition was determined as competitive.

Prodrug Nanomedicine for Synovium Targeted Therapy of Inflammatory Arthritis: Insights from Animal Model and Human Synovial Joint Fluid.

Many patients cannot tolerate low-dose weekly methotrexate (MTX) therapy for inflammatory arthritis treatment due to life-threatening toxicity. Although biologics offer a target-specific therapy, it raises the risk of serious infections and even cancer due to immune system suppression. We introduce an anti-inflammatory arthritis MTX ester prodrug using a long-circulating biocompatible polymeric macromolecule: folic acid (FA) functionalized hyperbranched polyglycerol (HPG). In vitro the drug MTX is incrementally released through pH and enzymatic degradation over 2 weeks. The role of matrix metalloproteinases (MMPs) in site-specific prodrug activation was verified using synovial fluid (SF) of 26 rheumatology patients and 4 healthy controls. Elevated levels of specific MMPs-markers of joint inflammation-positively correlated with enhanced prodrug release explained by acid-catalyzed hydrolysis of esters by proteases. Intravenously administered 111In-radiolabeled prodrug confirmed by SPECT/CT imaging that it accumulated preferentially in inflamed joints while reducing off-target side-effects in a mouse model of rheumatoid arthritis (RA). Added FA as a targeting vector prolonged prodrug action; prodrug with 4x less MTX applied every 2 weeks was as effective as weekly MTX therapy. The preclinical results suggest a prodrug-based strategy for the treatment of inflammatory joint diseases, with potential for other chronic inflammatory diseases and cancer.

Synthesis, Characterization and Antibacterial Studies of New Crown Ether Prodrugs.

New three esters (E1, E2 and E3) from crown ethers and drugs were prepared by Stiglich esterification. These procedures began with the reaction of certain quinolones (levofloxacin, ciprofloxacin, and nalidixic acid) with thionyl chloride to produce a considerably more potent acylating agent. Next, for the production of ester prodrugs, 2-hydroxymethyl-15-crown-5 ether (a lariat crown ether) was esterified using an acid chloride in the presence of pyridine. These molecules were synthesized as carrier-mediated prodrugs in order to solve different pharmacokinetic and pharmacological difficulties, enhance physicochemical features, and augment the antibacterial efficacy of the parent drugs by structural modifications while avoiding bacterial resistance. The compounds` structures were verified by FTIR, UV, H1 &amp; 13C-NMR spectroscopy and certain physiochemical qualities. In a concentration-dependent manner, all of the synthesized prodrugs’ biological studies revealed improved activity against certain bacterial species.

Synthesis and release studies on amylose-based ester prodrugs of fenamic acid NSAIDs.

Aim: To achieve colon-targeted release of mefenamic acid from its ester-linked amylose prodrugs.Materials & methods: The prodrug was characterized by 1H NMR and IR spectroscopy. Drug activation and release profile was studied in enzyme enriched simulated physiological media via UV-vis spectroscopy and was validated with HPLC analysis. ELISA assay was employed for evaluating the % inhibition of COX-1 and COX-2 inhibition at different concentrations of the prodrug preincubated with ester and/ or amylose hydrolyzing enzymes. SEM studies further validated the performance of the prodrug under simulated physiological conditions.Results: Pancreatin was essential for the prodrug activation in SIM to make the ester bonds in prodrug vulnerable to hydrolysis by esterase. This evidence was confirmed by drug release studies, HPLC analysis, ELISA assay and SEM investigation where the ester conjugated prodrug showed marked stability in physiological media only to get activated in the presence of amylose degrading enzyme.Conclusion: Ester linked amylose-mefenamic acid conjugate showed both enzyme responsive activation and release in SIM.

Design, synthesis, and antitumor activity evaluation of 1,2,3-triazole derivatives as potent PD-1/PD-L1 inhibitors

A series of 1,2,3-triazole derivatives targeting the PD-1/PD-L1 pathway were designed, synthesized, and evaluated both in vitro and in vivo. Among them, compound III-4 demonstrated exceptional inhibitory activity against the interaction of PD-1/PD-L1 and showed great binding affinity with hPD-L1, with an IC50 value of 2.9 nM and a KD value of 3.33 nM. In the co-culture of Hep3B/OS-8/hPD-L1 cells and CD3+ T cells assay, III-4 relieved the inhibition of PD-L1 on PD-1 and promoted the expression of IFN-γ, which shared a comparable effect to that of the PD-1 monoclonal antibody Pembrolizumab (5 μg/mL). Moreover, compound III-5, an ester prodrug derived from III-4, demonstrated significant antitumor effects in the hPD-L1-MC38 C57BL/6 mouse model (TGI: 49.6 %) by oral administration. These findings suggest that compound III-5 holds promise as an inhibitor of the PD-1/PD-L1 interaction for cancer immunotherapy.

Prodrug activation in malaria parasites mediated by an imported erythrocyte esterase, acylpeptide hydrolase (APEH).

The continued emergence of antimalarial drug resistance highlights the need to develop new antimalarial therapies. Unfortunately, new drug development is often hampered by poor drug-like properties of lead compounds. Prodrugging temporarily masks undesirable compound features, improving bioavailability and target penetration. We have found that lipophilic diester prodrugs of phosphonic acid antibiotics, such as fosmidomycin, exhibit significantly higher antimalarial potency than their parent compounds (1). However, the activating enzymes for these prodrugs were unknown. Here, we show that an erythrocyte enzyme, acylpeptide hydrolase (APEH) is the major activating enzyme of multiple lipophilic ester prodrugs. Surprisingly, this enzyme is taken up by the malaria parasite, Plasmodium falciparum, where it localizes to the parasite cytoplasm and retains enzymatic activity. Using a novel fluorogenic ester library, we characterize the structure activity relationship of APEH, and compare it to that of P. falciparum esterases. We show that parasite-internalized APEH plays an important role in the activation of substrates with branching at the alpha carbon, in keeping with its exopeptidase activity. Our findings highlight a novel mechanism for antimicrobial prodrug activation, relying on a host-derived enzyme to yield activation at a microbial target. Mutations in prodrug activating enzymes are a common mechanism for antimicrobial drug resistance (2-4). Leveraging an internalized host enzyme would circumvent this, enabling the design of prodrugs with higher barriers to drug resistance.

Development of LC-MS/MS methods affording identification and measurement of active metabolites in rat and dog plasma after oral dosing of a penta-ethyl ester prodrug of diethylenetriamine pentaacetic acid

Development of LC-MS/MS methods affording identification and measurement of active metabolites in rat and dog plasma after oral dosing of a penta-ethyl ester prodrug of diethylenetriamine pentaacetic acid

The ester-containing prodrug NT-0796 enhances delivery of the NLRP3 inflammasome inhibitor NDT-19795 to monocytic cells expressing carboxylesterase-1

NT-0796 is an ester prodrug which is metabolized by carboxylesterase-1 (CES1) to yield the carboxylic acid NDT-19795, an inhibitor of the NLR family pyrin domain-containing protein 3 (NLRP3) inflammasome. When applied to human monocytes/macrophages which express CES1, however, NT-0796 is much more potent at inhibiting NLRP3 inflammasome activation than is NDT-19795. Comparison of the binding of NDT-19795 and NT-0796 in a cell-based NLRP3 target engagement assay confirms that NDT-19795 is the active species. Moreover, microsomes expressing CES1 efficiently convert NT-0796 to NDT-19795, confirming CES1-dependent activation. To understand the basis for the enhanced potency of the ester prodrug species in human monocytes, we analyzed the accumulation and de-esterification of NT-0796 in cultured cells. Our studies reveal NT-0796 rapidly accumulates in cells, achieving estimated cellular concentrations above those applied to the medium, with concomitant metabolism to NDT-19795 in CES1-expressing cells. Using cells lacking CES1 or a poorly hydrolysable NT-0796 analog demonstrated that de-esterification is not required for NT-0796 to achieve high cellular levels. As a result of a dynamic equilibrium whereby NDT-19795 formed intracellularly is subsequently released to the medium, concentrations of NT-0796 sufficient to inhibit NLRP3 can be completely metabolized to NDT-19795 resulting in a transient pharmacodynamic response. In contrast, when NDT-19795 is applied directly to cells, observed cell-associated levels are below those present in the medium and remain stable over time. Dynamics observed within the context of a closed tissue culture system highlight the utility of NT-0796 as a vehicle for delivering the NDT-19795 acid payload to CES1 expressing cells.

Enantioselective Synthesis of β-l-5-[(E)-2-Bromovinyl)-1-((2S,4S)-2-(hydroxymethyl)-1,3-(dioxolane-4-yl) Uracil)] (l-BHDU) via Chiral Pure l-Dioxolane.

β-l-5-((E)-2-Bromovinyl)-1-((2S,4S)-2-(hydroxymethyl)-1,3-(dioxolane-4-yl) uracil (l-BHDU, 17) is a potent and selective inhibitor of the varicella-zoster virus (VZV). l-BHDU (17) has demonstrated excellent anti-VZV activity and is a preclinical candidate to treat chickenpox, shingles (herpes zoster), and herpes simplex virus 1 (HSV-1) infections. Its monophosphate prodrug (POM-l-BHDU-MP, 24) demonstrated an enhanced pharmacokinetic and antiviral profile. POM-l-BHDU-MP (24), in vivo, effectively reduced the VZV viral load and was effective for the topical treatment of VZV and HSV-1 infections. Therefore, a viable synthetic procedure for developing POM-l-BHDU-MP (24) is needed. In this article, an efficient approach for the synthesis of l-BHDU (17) from a readily available starting material is described in 7 steps. An efficient and practical methodology for both chiral pure l- & d-dioxolane 11 and 13 were developed via diastereomeric chiral amine salt formation. Neutralization of the amine carboxylate salt of l-dioxolane 10 provides enantiomerically pure l-dioxane 11 (ee ≥ 99%). Optically pure 11 was utilized to construct the final nucleoside l-BHDU (17) and its monophosphate ester prodrug (POM-l-BHDU-MP, 24). Notably, the reported process eliminates expensive chiral chromatography for the synthesis of chiral pure l- & d-dioxolane, which offers avenues for the development and structure-activity relationship studies of l- & d-dioxolane-derived nucleosides.

Chiral Isothiourea‐Catalyzed Acylative Dynamic Kinetic Resolution of 3‐Hydroxyphthalides for Enantioselective Synthesis of Phthalidyl Esters

Comprehensive SummaryPhthalides serve as core structures pervasive in a wide array of natural products and drug molecules, which display a diverse array of biological activities. We report herein a highly efficient dynamic kinetic resolution of 3‐hydroxyphthalides by chiral isothioureas (ITUs) catalyzed asymmetric acylation, facilitating the effective synthesis of a variety of chiral phthalidyl esters with good yields and enantioselectivities. Notably, this reaction features mild reaction conditions, expansive substrate scope as well as good functional group compatibility. In addition, the practicality of this method is underscored by the large‐scale synthesis, reduced catalyst loading experiment and the synthesis of the chiral phthalidyl ester prodrug.

Differential Bioactivation Profiles of Different GS-441524 Prodrugs in Cell and Mouse Models: ProTide Prodrugs with High Cell Permeability and Susceptibility to Cathepsin A Are More Efficient in Delivering Antiviral Active Metabolites to the Lung.

We assessed factors that determine the tissue-specific bioactivation of ProTide prodrugs by comparing the disposition and activation of remdesivir (RDV), its methylpropyl and isopropyl ester analogues (MeRDV and IsoRDV, respectively), the oral prodrug GS-621763, and the parent nucleotide GS-441524 (Nuc). RDV and MeRDV yielded more active metabolite remdesivir-triphosphate (RDV-TP) than IsoRDV, GS-621763, and Nuc in human lung cell models due to superior cell permeability and higher susceptivity to cathepsin A. Intravenous administration to mice showed that RDV and MeRDV delivered significantly more RDV-TP to the lung than other compounds. Nevertheless, all four ester prodrugs exhibited very low oral bioavailability (<2%), with Nuc being the predominant metabolite in blood. In conclusion, ProTides prodrugs, such as RDV and MeRDV, are more efficient in delivering active metabolites to the lung than Nuc, driven by high cell permeability and susceptivity to cathepsin A. Optimizing ProTides' ester structures is an effective strategy for enhancing prodrug activation in the lung.

Lymphatic Uptake of a Highly Lipophilic Protease Inhibitor Prodrug from a Lipid-Based Formulation is Limited by Instability in the Intestine

Dabigatran etexilate (DABE) is a lipophilic double alkyl ester prodrug of dabigatran (DAB) which is a serine protease inhibitor used clinically as an anticoagulant. Recently, translocation of serine protease enzymes, including trypsin, from the gut into the mesenteric lymph and then blood has been associated with organ failure in acute and critical illnesses (ACIs). Delivery of DABE into mesenteric lymph may thus be an effective strategy to prevent organ failure in ACIs. Most drugs access the mesenteric lymph in low quantities following oral administration, as they are rapidly transported away from the intestine via the blood. Here, we examine the potential to deliver DABE into the mesenteric lymph by promoting association with lymph lipid transport pathways via co-administration with a lipid-based formulation (LBF). A series of self-emulsifying LBFs were designed and tested in vitro for their potential to form stable DABE loaded emulsions and keep DABE solubilised and stable over time in simulated gastrointestinal conditions. The LBFs were found to form fine emulsions with a droplet size of 214 ± 30 nm and DABE was stable in the formulation. The stability of DABE in vitro in simulated intestinal conditions, plasma and lymph samples was also evaluated to ensure stability in collected samples and to evaluate whether the prodrug is likely to release active DAB. Ultimately, a highly uniform and stable self-emulsifying Type III A LBF of DABE was chosen for progression into in vivo studies in male Sprague Dawley rats to confirm the lymphatic uptake and plasma pharmacokinetics. Both in vitro and in vivo in plasma and lymph, DABE was rapidly converted to an intermediate and DAB. The main species present in vivo in both plasma and lymph was DAB and mass transport of DABE and DAB in lymph was minimal (∼0.5 % of dose). Importantly, the concentration of DABE in lymph was substantially (20–176 fold) higher than in plasma, supporting that if the prodrug were stable and did not convert to DAB in the intestine, it would be lymphatically transported. Future studies will therefore focus on optimizing the design of the prodrug and formulation to improve stability during absorption and further promote lymphatic uptake.

Abstract 1818: Novel efficient isolation and water-soluble prodrug preparation of anti-cancer natural product narciclasine

Abstract Narciclasine is a promising anti-cancer agent produced by plants of the family Amaryllidaceae. Narciclasine has been shown to be a potent anti-cancer agent against a variety of cancers carrying dismal outcomes, including glioblastoma, non-small cell lung cancer, and non-Hodgkin’s lymphoma. It is particularly effective in animal studies of brain cancer both primary, such as glioblastoma, metastatic tumors to the brain, such as melanoma and non-small cell lung cancer. Its isolation from plants has generally been accompanied with variable success as it depends on the plant species, their location and the time of plant collection. In this study, an optimized procedure for the extraction of narciclasine yielding 300 mg/kg of dried plant material. This represents a crucial step towards the development of optimized narciclasine derivatives, as the price of narciclasine from commercial sources ranges from $100-$500 per milligram. Additionally, clinical advancement of narciclasine and its derivatives has been severely thwarted, potentially owing to its sparing water-solubility. Insolubility in water makes administration at therapeutic dosages difficult and can lead to unfavorable pharmacokinetic and pharmacodynamic characteristics. To this effort, the synthesis of five prodrug esters of narciclasine is presented, with the target of a water-soluble narciclasine prodrug. Citation Format: Alexander Kornienko, Ryan Rutledge. Novel efficient isolation and water-soluble prodrug preparation of anti-cancer natural product narciclasine [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1818.