Characterization of the mechanism of action of the pan class I PI3K inhibitor NVP-BKM120 across a broad range of concentrations.
The pan-phosphoinositide 3-kinase (PI3K) inhibitor BKM120 was found, at high concentrations, to cause cell death in various cellular systems, irrespective of their level of PI3K addiction. Transcriptional and biochemical profiling studies were used to identify the origin of these unexpected and apparently PI3K-independent effects. At 5- to 10-fold, the concentration needed to half-maximally inhibit PI3K signaling. BKM120 treatment caused changes in expression of mitotic genes and the induction of a robust G(2)-M arrest. Tubulin polymerization assays and nuclear magnetic resonance-binding studies revealed that BKM120 inhibited microtubule dynamics upon direct binding to tubulin. To assess the contribution of this off-target activity vis-à-vis the antitumor activity of BKM120 in PI3K-dependent tumors, we used a mechanistic PI3K-α-dependent model. We observed that, in vivo, daily treatment of mice with doses of BKM120 up to 40 mg/kg led to tumor regressions with no increase in the mitotic index. Thus, strong antitumor activity can be achieved in PI3K-dependent models at exposures that are below those necessary to engage the off-target activity. In comparison, the clinical data indicate that it is unlikely that BKM120 will achieve exposures sufficient to significantly engage the off-target activity at tolerated doses and schedules. However, in preclinical settings, the consequences of the off-target activity start to manifest themselves at concentrations above 1 μmol/L in vitro and doses above 50 mg/kg in efficacy studies using subcutaneous tumor-bearing mice. Hence, careful concentration and dose range selection is required to ensure that any observation can be correctly attributed to BKM120 inhibition of PI3K.
NIBR Oncology Disease Area, Novartis Pharma AG, Basel CH4002, Switzerland. saskia.brachmann@novartis.com
Saskia M
SM
Brachmann
Julia
J
Kleylein-Sohn
Swann
S
Gaulis
Audrey
A
Kauffmann
Marcel J J
MJ
Blommers
Malika
M
Kazic-Legueux
Laurent
L
Laborde
Marc
M
Hattenberger
Fabian
F
Stauffer
Juliane
J
Vaxelaire
Vincent
V
Romanet
Chrystèle
C
Henry
Masato
M
Murakami
Daniel Alexander
DA
Guthy
Dario
D
Sterker
Sebastian
S
Bergling
Christopher
C
Wilson
Thomas
T
Brümmendorf
Christine
C
Fritsch
Carlos
C
Garcia-Echeverria
William R
WR
Sellers
Francesco
F
Hofmann
Sauveur-Michel
SM
Maira
D000631:Aminopyridines / Q000494:pharmacology*; D000818:Animals; D059447:Cell Cycle Checkpoints / Q000187:drug effects; D045744:Cell Line, Tumor; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D007191:Indazoles / Q000494:pharmacology; D051379:Mice; D008938:Mitosis / Q000187:drug effects; D009025:Morpholines / Q000494:pharmacology*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D055503:Protein Multimerization / Q000187:drug effects; D051381:Rats; D013449:Sulfonamides / Q000494:pharmacology; D014404:Tubulin / Q000378:metabolism
C532162:2-(1H-indazol-4-yl)-6-(4-methanesulfonylpiperazin-1-ylmethyl)-4-morpholin-4-ylthieno(3,2-d)pyrimidine; D000631:Aminopyridines; D007191:Indazoles; D009025:Morpholines; C571178:NVP-BKM120; D000081082:Phosphoinositide-3 Kinase Inhibitors; D013449:Sulfonamides; D014404:Tubulin