6 research outputs found
Evaluation of the metabolism, bioactivation and pharmacokinetics of triaminopyrimidine analogs toward selection of a potential candidate for antimalarial therapy
<p>1. During the course of metabolic profiling of lead Compound <b>1</b>, glutathione (GSH) conjugates were detected in rat bile, suggesting the formation of reactive intermediate precursor(s). This was confirmed by the identification of GSH and <i>N</i>-acetylcysteine (NAC) conjugates in microsomal incubations.</p> <p>2. It was proposed that bioactivation of Compound <b>1</b> occurs via the formation of a di-iminoquinone reactive intermediate through the involvement of the C-2 and C-5 nitrogens of the pyrimidine core.</p> <p>3. To further investigate this hypothesis, structural analogs with modifications at the C-5 nitrogen were studied for metabolic activation in human liver microsomes supplemented with GSH/NAC.</p> <p>4. Compounds <b>1</b> and <b>2</b>, which bear secondary nitrogens at the C-5 of the pyrimidine core, were observed to form significant amounts of GSH/NAC-conjugates <i>in vitro</i>, whereas compounds with tertiary nitrogens at C-5 (Compound <b>3</b> and <b>4</b>) formed no such conjugates.</p> <p>5. These observations provide evidence that electron/hydrogen abstraction is required for the bioactivation of the triaminopyrimidines, potentially via a di-iminoquinone intermediate. The lack of a hydrogen and/or steric hindrance rendered Compound <b>3</b> and <b>4</b> incapable of forming thiol conjugates.</p> <p>6. This finding enabled advancement of compound <b>4</b>, with a desirable potency, safety and PK profile, as a lead candidate for further development in the treatment of malaria.</p
Left-Hand Side Exploration of Novel Bacterial Topoisomerase Inhibitors to Improve Selectivity against hERG Binding
Structure–activity
relationship (SAR) exploration on the
left-hand side (LHS) of a novel class of bacterial topoisomerase inhibitors led to a significant improvement
in the selectivity against hERG cardiac channel binding with concomitant
potent antimycobacterial activity. Bulky polar substituents at the
C-7 position of the naphthyridone ring did not disturb its positioning
between two base pairs of DNA. Further optimization of the polar substituents
on the LHS of the naphthyridone ring led to potent antimycobacterial
activity (Mtb MIC = 0.06 ÎĽM) against <i>Mycobacterium tuberculosis</i> (Mtb). Additionally, this knowledge provided a robust SAR understanding
to mitigate the hERG risk. This compound class inhibits Mtb DNA gyrase
and retains its antimycobacterial activity against moxifloxacin-resistant
strains of Mtb. Finally, we demonstrate <i>in vivo</i> proof
of concept in an acute mouse model of TB following oral administration
of compound <b>19</b>
Novel N‑Linked Aminopiperidine-Based Gyrase Inhibitors with Improved hERG and in Vivo Efficacy against Mycobacterium tuberculosis
DNA
gyrase is a clinically validated target for developing drugs
against Mycobacterium tuberculosis (Mtb).
Despite the promise of fluoroquinolones (FQs) as anti-tuberculosis
drugs, the prevalence of pre-existing resistance to FQs is likely
to restrict their clinical value. We describe a novel class of N-linked
aminopiperidinyl alkyl quinolones and naphthyridones that kills Mtb
by inhibiting the DNA gyrase activity. The mechanism of inhibition
of DNA gyrase was distinct from the fluoroquinolones, as shown by
their ability to inhibit the growth of fluoroquinolone-resistant Mtb.
Biochemical studies demonstrated this class to exert its action via
single-strand cleavage rather than double-strand cleavage, as seen
with fluoroquinolones. The compounds are highly bactericidal against
extracellular as well as intracellular Mtb. Lead optimization resulted
in the identification of potent compounds with improved oral bioavailability
and reduced cardiac ion channel liability. Compounds from this series
are efficacious in various murine models of tuberculosis
Azaindoles: Noncovalent DprE1 Inhibitors from Scaffold Morphing Efforts, Kill Mycobacterium tuberculosis and Are Efficacious <i>in Vivo</i>
We report 1,4-azaindoles as a new
inhibitor class that kills Mycobacterium tuberculosis <i>in vitro</i> and demonstrates efficacy in mouse tuberculosis
models. The series emerged from scaffold morphing efforts and was
demonstrated to noncovalently inhibit decaprenylphosphoryl-β-d-ribose2′-epimerase (DprE1). With “drug-like”
properties and no expectation of pre-existing resistance in the clinic,
this chemical class has the potential to be developed as a therapy
for drug-sensitive and drug-resistant tuberculosis
Discovery of Imidazo[1,2‑<i>a</i>]pyridine Ethers and Squaramides as Selective and Potent Inhibitors of Mycobacterial Adenosine Triphosphate (ATP) Synthesis
The approval of bedaquiline
to treat tuberculosis has validated
adenosine triphosphate (ATP) synthase as an attractive target to kill Mycobacterium tuberculosis (Mtb). Herein, we report
the discovery of two diverse lead series imidazoÂ[1,2-<i>a</i>]Âpyridine ethers (IPE) and squaramides (SQA) as inhibitors of mycobacterial
ATP synthesis. Through medicinal chemistry exploration, we established
a robust structure–activity relationship of these two scaffolds,
resulting in nanomolar potencies in an ATP synthesis inhibition assay.
A biochemical deconvolution cascade suggested cytochrome c oxidase
as the potential target of IPE class of molecules, whereas characterization
of spontaneous resistant mutants of SQAs unambiguously identified
ATP synthase as its molecular target. Absence of cross resistance
against bedaquiline resistant mutants suggested a different binding
site for SQAs on ATP synthase. Furthermore, SQAs were found to be
noncytotoxic and demonstrated efficacy in a mouse model of tuberculosis
infection
Discovery of Imidazo[1,2‑<i>a</i>]pyridine Ethers and Squaramides as Selective and Potent Inhibitors of Mycobacterial Adenosine Triphosphate (ATP) Synthesis
The approval of bedaquiline
to treat tuberculosis has validated
adenosine triphosphate (ATP) synthase as an attractive target to kill Mycobacterium tuberculosis (Mtb). Herein, we report
the discovery of two diverse lead series imidazoÂ[1,2-<i>a</i>]Âpyridine ethers (IPE) and squaramides (SQA) as inhibitors of mycobacterial
ATP synthesis. Through medicinal chemistry exploration, we established
a robust structure–activity relationship of these two scaffolds,
resulting in nanomolar potencies in an ATP synthesis inhibition assay.
A biochemical deconvolution cascade suggested cytochrome c oxidase
as the potential target of IPE class of molecules, whereas characterization
of spontaneous resistant mutants of SQAs unambiguously identified
ATP synthase as its molecular target. Absence of cross resistance
against bedaquiline resistant mutants suggested a different binding
site for SQAs on ATP synthase. Furthermore, SQAs were found to be
noncytotoxic and demonstrated efficacy in a mouse model of tuberculosis
infection