Antitumor Efficacy of PKI-587, a Highly Potent Dual PI3K/mTOR Kinase Inhibitor

作者：Mallon Robert^*; Feldberg Larry R; Lucas Judy; Chaudhary Inder; Dehnhardt Christoph; Delos Santos Efren; Chen Zecheng; dos Santos Osvaldo; Ayral Kaloustian Semiramis; Venkatesan Aranapakam; Hollander Irwin

来源：Clinical Cancer Research, 2011, 17(10): 3193-3203.

DOI：10.1158/1078-0432.CCR-10-1694

Purpose: The aim of this study was to show preclinical efficacy and clinical development potential of PKI-587, a dual phosphoinositide 3-kinase (PI3K)/mTOR inhibitor.
Experimental Design: In vitro class 1 PI3K enzyme and human tumor cell growth inhibition assays and in vivo five tumor xenograft models were used to show efficacy.
Results: In vitro, PKI-587 potently inhibited class I PI3Ks (IC(50) vs. PI3K-alpha = 0.4 nmol/L), PI3K-alpha mutants, and mTOR. PKI-587 inhibited growth of 50 diverse human tumor cell lines at IC(50) values of less than 100 nmol/L. PKI-587 suppressed phosphorylation of PI3K/mTOR effectors (e.g., Akt), and induced apoptosis in human tumor cell lines with elevated PI3K/mTOR signaling. MDA-MB-361 [breast; HER2(+), PIK3CA mutant (E545K)] was particularly sensitive to this effect, with cleaved PARP, an apoptosis marker, induced by 30 nmol/L PKI-587 at 4 hours.
In vivo, PKI-587 inhibited tumor growth in breast (MDA-MB-361, BT474), colon (HCT116), lung (H1975), and glioma (U87MG) xenograft models. In MDA-MB-361 tumors, PKI-587 (25 mg/kg, single dose i.v.) suppressed Akt phosphorylation [at threonine(T) 308 and serine(S) 473] for up to 36 hours, with cleaved PARP (cPARP) evident up to 18 hours. PKI-587 at 25 mg/kg (once weekly) shrank large (similar to 1,000 mm(3)) MDA-MB-361 tumors and suppressed tumor regrowth. Tumor regression correlated with suppression of phosphorylated Akt in the MDA-MB-361 model. PKI-587 also caused regression in other tumor models, and efficacy was enhanced when given in combination with PD0325901 (MEK 1/2 inhibitor), irinotecan (topoisomerase I inhibitor), or HKI-272 (neratinib, HER2 inhibitor).
Conclusion: Significant antitumor efficacy and a favorable pharmacokinetic/safety profile justified phase 1 clinical evaluation of PKI-587. Clin Cancer Res; 17(10); 3193-203.

• 出版日期2011-5-15