Improving Drug Delivery While Tailoring Prodrug Activation to Modulate Cmax and Cmin by Optimization of (Carbonyl)oxyalkyl Linker-Based Prodrugs of Atazanavir.

Structure-property relationships associated with a series of (carbonyl)oxyalkyl amino acid ester prodrugs of the marketed HIV-1 protease inhibitor atazanavir (1), designed to enhance the systemic drug delivery, were examined. Compared to previously reported prodrugs, optimized candidates delivered significantly enhanced plasma exposure and trough concentration (Cmin at 24 h) of 1 in rats while revealing differentiated PK paradigms based on the kinetics of prodrug activation and drug release. Prodrugs incorporating primary amine-containing amino acid promoieties offered the benefit of rapid bioactivation that translated into low circulating levels of the prodrug while delivering a high Cmax value of 1. Interestingly, the kinetic profile of prodrug cleavage could be tailored for slower activation by structural modification of the amino terminus to either a tertiary amine or a dipeptide motif, which conferred a circulating depot of the prodrug that orchestrated a sustained release of 1 along with substantially reduced Cmax and a further enhanced Cmin.

Conformational-Analysis-Guided Discovery of 2,3-Disubstituted Pyridine IDO1 Inhibitors.

IDO1 inhibitors have shown promise as immunotherapies for the treatment of a variety of cancers, including metastatic melanoma and renal cell carcinoma. We recently reported the identification of several novel heme-displacing IDO1 inhibitors, including the clinical molecules linrodostat (BMS-986205) and BMS-986242. Both molecules contain quinolines that, while being present in successful medicines, are known to be potentially susceptible to oxidative metabolism. Efforts to swap this quinoline with an alternative aromatic system led to the discovery of 2,3-disubstituted pyridines as suitable replacements. Further optimization, which included lowering ClogP in combination with strategic fluorine incorporation, led to the discovery of compound 29, a potent, selective IDO1 inhibitor with robust pharmacodynamic activity in a mouse xenograft model.

Discovery of Imidazopyridines as Potent Inhibitors of Indoleamine 2,3-Dioxygenase 1 for Cancer Immunotherapy.

Indoleamine 2,3-dioxygenase 1 (IDO1) has been identified as a target for small-molecule immunotherapy for the treatment of a variety of cancers including renal cell carcinoma and metastatic melanoma. This work focuses on the identification of IDO1 inhibitors containing replacements or isosteres for the amide found in BMS-986205, an amide-containing, IDO1-selective inhibitor currently in phase III clinical trials. Detailed subsequently are efforts to identify a structurally differentiated IDO1 inhibitor via the pursuit of a variety of heterocyclic isosteres, leading to the discovery of highly potent, imidazopyridine-containing IDO1 inhibitors.

(Carbonyl)oxyalkyl linker-based amino acid prodrugs of the HIV-1 protease inhibitor atazanavir that enhance oral bioavailability and plasma trough concentration.

We describe the design, synthesis and pharmacokinetic (PK) evaluation of a series of amino acid-based prodrugs of the HIV-1 protease inhibitor atazanavir (1) derivatized on the pharmacophoric secondary alcohol using a (carbonyl)oxyalkyl linker. Prodrugs of 1 incorporating simple (carbonyl)oxyalkyl-based linkers and a primary amine in the promoiety were found to exhibit low chemical stability. However, chemical stability was improved by modifying the primary amine moiety to a tertiary amine, resulting in a 2-fold enhancement of exposure in rats following oral dosing compared to dosing of the parent drug 1. Further refinement of the linker resulted in the discovery of 22 as a prodrug that delivered the parent 1 to rat plasma with a 5-fold higher AUC and 67-fold higher C24 when compared to oral administration of the parent drug. The PK profile of 22 indicated that plasma levels of this prodrug were higher than that of the parent, providing a more sustained release of 1 in vivo.

Design, Synthesis, and Pharmacokinetic Evaluation of Phosphate and Amino Acid Ester Prodrugs for Improving the Oral Bioavailability of the HIV-1 Protease Inhibitor Atazanavir.

Phosphate and amino acid prodrugs of the HIV-1 protease inhibitor (PI) atazanavir (1) were prepared and evaluated to address solubility and absorption limitations. While the phosphate prodrug failed to release 1 in rats, the introduction of a methylene spacer facilitated prodrug activation, but parent exposure was lower than that following direct administration of 1. Val amino acid and Val-Val dipeptides imparted low plasma exposure of the parent, although the exposure of the prodrugs was high, reflecting good absorption. Screening of additional amino acids resulted in the identification of an l-Phe ester that offered an improved exposure of 1 and reduced levels of the circulating prodrug. Further molecular editing focusing on the linker design culminated in the discovery of the self-immolative l-Phe-Sar dipeptide derivative 74 that gave four-fold improved AUC and eight-fold higher Ctrough values of 1 compared with oral administration of the drug itself, demonstrating a successful prodrug approach to the oral delivery of 1.

Effect of pretreatment regimens of 1-aminobenzotriazole on metabolism and gastric emptying of probe compounds in rat.

1-Aminobenzotriazole (ABT) is a mechanism-based inactivator of major cytochrome P450 (CYP) enzymes, which is used in multiple mechanistic studies. The purpose was to evaluate the effect of 2 and 16-h pretreatment regimens of ABT on the exposures of triazolam in rat. Another objective was to evaluate the effect of ABT on gastric emptying of acetaminophen. Plasma area under the curve (AUC) of triazolam was increased by 101-fold and 81-fold for the rats pretreated with ABT at 2 and 16 h, respectively, compared to control rats. Time to reach maximum concentration was 0.3, 4.8 and 3.7 h in control, 2 and 16-h pretreatment animals, respectively. In the case of acetaminophen, where Tmax was not delayed, the mean absorption time (MAT) in control, 2 and 16 h ABT pretreatment groups were 0.3, 4.6 and 2.9 h, respectively, suggesting delayed absorption. This hypothesis was further supported by GastroPlusTM simulation. In summary, extent of triazolam absorption was increased to a similar extent with both 2 and 16 h ABT pretreatment regimens, suggesting that either of the regimen can be used to increase parent exposures in rat. With ABT pretreatment, delayed absorption of triazolam and acetaminophen was observed, as suggested by delay in Tmax and MAT, respectively.

Coupling of an Acyl Migration Prodrug Strategy with Bio-activation To Improve Oral Delivery of the HIV-1 Protease Inhibitor Atazanavir.

HIV-1 protease inhibitors (PIs), which include atazanavir (ATV, 1), remain important medicines to treat HIV-1 infection. However, they are characterized by poor oral bioavailability and a need for boosting with a pharmacokinetic enhancer, which results in additional drug-drug interactions that are sometimes difficult to manage. We investigated a chemo-activated, acyl migration-based prodrug design approach to improve the pharmacokinetic profile of 1 but failed to obtain improved oral bioavailability over dosing the parent drug in rats. This strategy was refined by conjugating the amine with a promoiety designed to undergo bio-activation, as a means of modulating the subsequent chemo-activation. This culminated in a lead prodrug that (1) yielded substantially better oral drug delivery of 1 when compared to the parent itself, the simple acyl migration-based prodrug, and the corresponding simple l-Val prodrug, (2) acted as a depot which resulted in a sustained release of the parent drug in vivo, and (3) offered the benefit of mitigating the pH-dependent absorption associated with 1, thereby potentially reducing the risk of decreased bioavailability with concurrent use of stomach-acid-reducing drugs.

Identification of a Potent, Selective, and Efficacious Phosphatidylinositol 3-Kinase δ (PI3Kδ) Inhibitor for the Treatment of Immunological Disorders.

PI3Kδ plays an important role controlling immune cell function and has therefore been identified as a potential target for the treatment of immunological disorders. This article highlights our work toward the identification of a potent, selective, and efficacious PI3Kδ inhibitor. Through careful SAR, the successful replacement of a polar pyrazole group by a simple chloro or trifluoromethyl group led to improved Caco-2 permeability, reduced Caco-2 efflux, reduced hERG PC activity, and increased selectivity profile while maintaining potency in the CD69 hWB assay. The optimization of the aryl substitution then identified a 4'-CN group that improved the human/rodent correlation in microsomal metabolic stability. Our lead molecule is very potent in PK/PD assays and highly efficacious in a mouse collagen-induced arthritis model.

Prediction of pH dependent absorption using in vitro, in silico, and in vivo rat models: Early liability assessment during lead optimization.

Weakly basic compounds which have pH dependent solubility are liable to exhibit pH dependent absorption. In some cases, a subtle change in gastric pH can significantly modulate the plasma concentration of the drug and can lead to sub-therapeutic exposure of the drug. Evaluating the risk of pH dependent absorption and potential drug-drug interaction with pH modulators are important aspects of drug discovery and development. In order to assess the risk around the extent of decrease in the systemic exposure of drugs co-administered with pH modulators in the clinic, a pH effect study is carried out, typically in higher species, mostly dog. The major limitation of a higher species pH effect study is the resource and material requirement to assess this risk. Hence, these studies are mostly restricted to promising or advanced leads. In our current work, we have used in vitro aqueous solubility, in silico simulations using GastroPlus™ and an in vivo rat pH effect model to provide a qualitative assessment of the pH dependent absorption liability. Here, we evaluate ketoconazole and atazanavir with different pH dependent solubility profiles and based on in vitro, in silico and in vivo results, a different extent of gastric pH effect on absorption is predicted. The prediction is in alignment with higher species and human pH effect study results. This in vitro, in silico and in vivo (IVISIV) correlation is then extended to assess pH absorption mitigation strategy. The IVISIV predicts pH dependent absorption for BMS-582949 whereas its solubility enhancing prodrug, BMS-751324 is predicted to mitigate this liability. Overall, the material requirement for this assessment is substantially low which makes this approach more practical to screen multiple compounds during lead optimization.

Modulation of mitomycin C-induced genotoxicity by acetyl- and thio- analogues of salicylic acid.

BACKGROUND: Recent reports regarding acetylsalicylic acid (ASA) and its metabolites suggest suppressive effects against mitomycin C (MMC)-induced genotoxicity in a mice chromosomal aberration assay. Keeping this in mind, the potential anti-genotoxic effect of the thio-analogue of salicylic acid namely thio-salicylic acid (TSA) was speculated upon. The present study investigated and compared the anti-genotoxic potential of ASA and TSA. MATERIALS AND METHODS: The study was performed in male swiss mice (20+/-2 g) using single-cell gel electrophoresis and a peripheral blood micronucleus assay. ASA and TSA (5, 10 or 20 mg/kg) were administered 15 minutes after MMC (1 mg/kg) once daily for 3 or 7 days. RESULTS: Both ASA and TSA significantly decreased the DNA damage induced by MMC as indicated by a decrease in the comet parameters in bone marrow cells and decreased frequencies of micronucleated reticulocytes in peripheral blood. CONCLUSION: The results clearly demonstrate the anti-genotoxic potential of ASA and TSA.