An allosteric Akt inhibitor effectively blocks Akt signaling and tumor growth with only transient effects on glucose and insulin levels in vivo.
The PI3K-Akt pathway is dysregulated in the majority of solid tumors. Pharmacological inhibition of Akt is a promising strategy for treating tumors resistant to growth factor receptor antagonists due to mutations in PI3K or PTEN. We have developed allosteric, isozyme-specific inhibitors of Akt activity and activation, as well as ex vivo kinase assays to measure inhibition of individual Akt isozymes in tissues. Here we describe the relationship between PK, Akt inhibition, hyperglycemia and tumor efficacy for a selective inhibitor of Akt1 and Akt2 (AKTi). In nude mice, AKTi treatment caused transient insulin resistance and reversible, dose-dependent hyperglycemia and hyperinsulinemia. Akt1 and Akt2 phosphorylation was inhibited in mouse lung with EC50 values of 1.6 and 7 μM, respectively, and with similar potency in other tissues and xenograft tumors. Weekly subcutaneous dosing of AKTi resulted in dose-dependent inhibition of LNCaP prostate cancer xenografts, an AR-dependent tumor with PTEN deletion and constitutively activated Akt. Complete tumor growth inhibition was achieved at 200 mpk, a dose that maintained inhibition of Akt1 and Akt2 of greater than 80% and 50%, respectively, for at least 12 hours in xenograft tumor and mouse lung. Hyperglycemia could be controlled by reducing C(max), while maintaining efficacy in the LNCaP model, but not by insulin administration. AKTi treatment was well tolerated, without weight loss or gross toxicities. These studies supported the rationale for clinical development of allosteric Akt inhibitors and provide the basis for further refining of pharmacokinetic properties and dosing regimens of this class of inhibitors.
Department of Cancer Research, Merck Research Laboratories, Rahway, NJ 07065, USA.
Craig
C
Cherrin
Kathleen
K
Haskell
Bonnie
B
Howell
Raymond
R
Jones
Karen
K
Leander
Ronald
R
Robinson
Aubrey
A
Watkins
Mark
M
Bilodeau
Jacob
J
Hoffman
Philip
P
Sanderson
George
G
Hartman
Elizabeth
E
Mahan
Thomayant
T
Prueksaritanont
Guoqiang
G
Jiang
Qing-Bai
QB
She
Neal
N
Rosen
Laura
L
Sepp-Lorenzino
Deborah
D
Defeo-Jones
Hans E
HE
Huber
D000494:Allosteric Regulation; D000818:Animals; D005947:Glucose / Q000378:metabolism*; D006801:Humans; D006943:Hyperglycemia / Q000188:drug therapy / Q000378:metabolism; D007191:Indazoles / Q000493:pharmacokinetics / Q000494:pharmacology*; D007211:Indoles / Q000493:pharmacokinetics / Q000494:pharmacology*; D007328:Insulin / Q000378:metabolism*; D007527:Isoenzymes; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D009287:Naphthyridines / Q000493:pharmacokinetics / Q000494:pharmacology*; D051059:PTEN Phosphohydrolase / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011471:Prostatic Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000517:prevention & control*; D021381:Protein Transport; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors* / Q000378:metabolism; D015398:Signal Transduction; D014018:Tissue Distribution; D023041:Xenograft Model Antitumor Assays
C504035:A 443654; D007191:Indazoles; D007211:Indoles; D007328:Insulin; D007527:Isoenzymes; D009287:Naphthyridines; D051057:Proto-Oncogene Proteins c-akt; D051059:PTEN Phosphohydrolase; C494929:PTEN protein, human; D005947:Glucose