13 research outputs found
OPTIMIZING AN ENZYME FOR ITS PHYSIOLOGICAL ROLE: STRUCTURAL AND FUNCTIONAL COMPARISONS OF ATP SULFURYLASES FROM THREE DIFFERENT ORGANISMS
No full textMechanism of Resistance to GS-9148 Conferred by the Q151L Mutation in HIV-1 Reverse Transcriptase
No full textABSTRACT
GS-9148 is an investigational phosphonate nucleotide analogue inhibitor of reverse transcriptase (RT) (NtRTI) of human immunodeficiency virus type 1 (HIV-1). This compound is an adenosine derivative with a 2′,3′-dihydrofuran ring structure that contains a 2′-fluoro group. The resistance profile of GS-9148 is unique in that the inhibitor can select for the very rare Q151L mutation in HIV-1 RT as a pathway to resistance. Q151L is not stably selected by any of the approved nucleoside or nucleotide analogues; however, it may be a transient intermediate that leads to the related Q151M mutation, which confers resistance to multiple compounds that belong to this class of RT inhibitors. Here, we employed pre-steady-state kinetics to study the impact of Q151L on substrate and inhibitor binding and the catalytic rate of incorporation. Most importantly, we found that the Q151L mutant is unable to incorporate GS-9148 under single-turnover conditions. Interference experiments showed that the presence of GS-9148–diphosphate, i.e., the active form of the inhibitor, does not reduce the efficiency of incorporation for the natural counterpart. We therefore conclude that Q151L severely compromises binding of GS-9148–diphosphate to RT. This effect is highly specific, since we also demonstrate that another NtRTI, tenofovir, is incorporated with selectivity similar to that seen with wild-type RT. Incorporation assays with other related compounds and models based on the RT/DNA/GS-9148–diphosphate crystal structure suggest that the 2′-fluoro group of GS-9148 may cause steric hindrance with the side chain of the Q151L mutant.</jats:p
The HIV-1 Reverse Transcriptase M184I Mutation Enhances the E138K-Associated Resistance to Rilpivirine and Decreases Viral Fitness
No full textDesign and Synthesis of Novel HIV‑1 NNRTIs with Bicyclic Cores and with Improved Physicochemical Properties
No full textNon-nucleoside reverse transcriptase inhibitors (NNRTIs)
represent
cornerstones of current regimens for treatment of human immunodeficiency
virus type 1 (HIV-1) infections. However, NNRTIs usually suffer from
low aqueous solubility and the emergence of resistant viral strains.
In the present work, novel bicyclic NNRTIs derived from etravirine
(ETV) and rilpivirine (RPV), bearing modified purine, tetrahydropteridine,
and pyrimidodiazepine cores, were designed and prepared. Compounds 2, 4, and 6 carrying the acrylonitrile
moiety displayed single-digit nanomolar activities against the wild-type
(WT) virus (EC50 = 2.5, 2.7, and 3.0 nM, respectively),
where the low nanomolar activity was retained against HXB2 (EC50 = 2.2–2.8 nM) and the K103N and Y181C mutated strains
(fold change, 1.2–6.7×). Most importantly, compound 2 exhibited significantly improved phosphate-buffered saline
solubility (10.4 μM) compared to ETV and RPV (≪1 μM).
Additionally, the binding modes of compounds 2, 4, and 6 to the reverse transcriptase were studied
by X-ray crystallography
Crystal Structures of HIV-1 Reverse Transcriptase with Etravirine (TMC125) and Rilpivirine (TMC278): Implications for Drug Design
No full textDiarylpyrimidine (DAPY) non-nucleoside reverse transcriptase inhibitors (NNRTIs) have inherent flexibility, helping to maintain activity against a wide range of resistance mutations. Crystal structures were determined with wild-type and K103N HIV-1 reverse transcriptase with etravirine (TMC125) and rilpivirine (TMC278). These structures reveal a similar binding mode for TMC125 and TMC278, whether bound to wild-type or K103N RT. Comparison to previously published structures reveals differences in binding modes for TMC125 and differences in protein conformation for TMC278
Structural and Binding Analysis of Pyrimidinol Carboxylic Acid and <i>N</i> -Hydroxy Quinazolinedione HIV-1 RNase H Inhibitors
No full textABSTRACT
HIV-1 RNase H breaks down the intermediate RNA-DNA hybrids during reverse transcription, requiring two divalent metal ions for activity. Pyrimidinol carboxylic acid and
N
-hydroxy quinazolinedione inhibitors were designed to coordinate the two metal ions in the active site of RNase H. High-resolution (1.4 Å to 2.1 Å) crystal structures were determined with the isolated RNase H domain and reverse transcriptase (RT), which permit accurate assessment of the metal and water environment at the active site. The geometry of the metal coordination suggests that the inhibitors mimic a substrate state prior to phosphodiester catalysis. Surface plasmon resonance studies confirm metal-dependent binding to RNase H and demonstrate that the inhibitors do not bind at the polymerase active site of RT. Additional evaluation of the RNase H site reveals an open protein surface with few additional interactions to optimize active-site inhibitors.
</jats:p
Design and Synthesis of Novel HIV‑1 NNRTIs with Bicyclic Cores and with Improved Physicochemical Properties
No full textNon-nucleoside reverse transcriptase inhibitors (NNRTIs)
represent
cornerstones of current regimens for treatment of human immunodeficiency
virus type 1 (HIV-1) infections. However, NNRTIs usually suffer from
low aqueous solubility and the emergence of resistant viral strains.
In the present work, novel bicyclic NNRTIs derived from etravirine
(ETV) and rilpivirine (RPV), bearing modified purine, tetrahydropteridine,
and pyrimidodiazepine cores, were designed and prepared. Compounds 2, 4, and 6 carrying the acrylonitrile
moiety displayed single-digit nanomolar activities against the wild-type
(WT) virus (EC50 = 2.5, 2.7, and 3.0 nM, respectively),
where the low nanomolar activity was retained against HXB2 (EC50 = 2.2–2.8 nM) and the K103N and Y181C mutated strains
(fold change, 1.2–6.7×). Most importantly, compound 2 exhibited significantly improved phosphate-buffered saline
solubility (10.4 μM) compared to ETV and RPV (≪1 μM).
Additionally, the binding modes of compounds 2, 4, and 6 to the reverse transcriptase were studied
by X-ray crystallography
Discovery of Lanraplenib (GS-9876): A Once-Daily Spleen Tyrosine Kinase Inhibitor for Autoimmune Diseases
No full textSpleen tyrosine kinase (SYK) is a
critical regulator of signaling
in a variety of immune cell types such as B-cells, monocytes, and
macrophages. Accordingly, there have been numerous efforts to identify
compounds that selectively inhibit SYK as a means to treat autoimmune
and inflammatory diseases. We previously disclosed GS-9973 (entospletinib)
as a selective SYK inhibitor that is under clinical evaluation in
hematological malignancies. However, a BID dosing regimen and drug
interaction with proton pump inhibitors (PPI) prevented development
of entospletinib in inflammatory diseases. Herein, we report the discovery
of a second-generation SYK inhibitor, GS-9876 (lanraplenib), which
has human pharmacokinetic properties suitable for once-daily administration
and is devoid of any interactions with PPI. Lanraplenib is currently
under clinical evaluation in multiple autoimmune indications
Discovery of GS-9973, a Selective and Orally Efficacious Inhibitor of Spleen Tyrosine Kinase
No full textSpleen
tyrosine kinase (Syk) is an attractive drug target in autoimmune,
inflammatory, and oncology disease indications. The most advanced
Syk inhibitor, R406, 1 (or its prodrug form fostamatinib, 2), has shown efficacy in multiple therapeutic indications,
but its clinical progress has been hampered by dose-limiting adverse
effects that have been attributed, at least in part, to the off-target
activities of 1. It is expected that a more selective
Syk inhibitor would provide a greater therapeutic window. Herein we
report the discovery and optimization of a novel series of imidazo[1,2-a]pyrazine Syk inhibitors. This work culminated in the identification
of GS-9973, 68, a highly selective and orally efficacious
Syk inhibitor which is currently undergoing clinical evaluation for
autoimmune and oncology indications
