2 research outputs found
Homodimerization of the PAS-B Domains of Hypoxia-Inducible Factors
The Per–Arnt–Sim (PAS) domains of hypoxia-inducible
transcription factors (HIF) mediate heterodimer formation between
the HIF-α forms that are induced in the event of cellular hypoxia
and the constitutive HIF-β variants. Previous efforts toward
structural characterization of the HIF-1α PAS domains were limited
by protein stability. Using homology modeling based on the published
crystal structure of the PAS-B domain of the homologous protein HIF-2α
in complex with the partner HIF-β (also known as ARNT), we have
identified a variant of HIF-1α with improved solubility, monodispersity,
and stability. Purified solutions of the PAS-B domains of HIF-1α
and HIF-2α differ in their propensity for homodimer formation.
In an attempt to understand the structural basis for this difference,
and to document the structural changes that accompany homodimer formation,
we have undertaken a comparative NMR study of the PAS-B domains of
HIF-1α and HIF-2α and mutants of HIF-1α that mimic
the behavior of HIF-2α. The NMR spectra of all of these domains
are very similar, consistent with the similarity of their amino acid
sequences. However, the greater propensity of the HIF-1α PAS-B
domain to form dimers as the concentration was increased allowed us
to determine the site of homodimerization and pointed toward possible
sequence changes in HIF-1α that might discourage the formation
of homodimers
Discovery of a Novel Class of Exquisitely Selective Mesenchymal-Epithelial Transition Factor (c-MET) Protein Kinase Inhibitors and Identification of the Clinical Candidate 2‑(4-(1-(Quinolin-6-ylmethyl)‑1<i>H</i>‑[1,2,3]triazolo[4,5‑<i>b</i>]pyrazin-6-yl)‑1<i>H</i>‑pyrazol-1-yl)ethanol (PF-04217903) for the Treatment of Cancer
The c-MET receptor tyrosine kinase is an attractive oncology
target
because of its critical role in human oncogenesis and tumor progression.
An oxindole hydrazide hit <b>6</b> was identified during a c-MET
HTS campaign and subsequently demonstrated to have an unusual degree
of selectivity against a broad array of other kinases. The cocrystal
structure of the related oxindole hydrazide c-MET inhibitor <b>10</b> with a nonphosphorylated c-MET kinase domain revealed a
unique binding mode associated with the exquisite selectivity profile.
The chemically labile oxindole hydrazide scaffold was replaced with
a chemically and metabolically stable triazolopyrazine scaffold using
structure based drug design. Medicinal chemistry lead optimization
produced 2-(4-(1-(quinolin-6-ylmethyl)-1<i>H</i>-[1,2,3]triazolo[4,5-<i>b</i>]pyrazin-6-yl)-1<i>H</i>-pyrazol-1-yl)ethanol
(<b>2</b>, <b>PF-04217903</b>), an extremely potent and
exquisitely selective c-MET inhibitor. <b>2</b> demonstrated
effective tumor growth inhibition in c-MET dependent tumor models
with good oral PK properties and an acceptable safety profile in preclinical
studies. <b>2</b> progressed to clinical evaluation in a Phase
I oncology setting