e clinical data determined that inhibition of aurora A and aurora B kinases simultaneously produced EX 527 Sirtuin inhibitor a biologic effect and phenotype similar to aurora B kinase inhibition alone.20 However, no clinical data in humans have shown specific AKIs to be more or less therapeutically valuable than multi or pan aurora inhibitors. Evidence of clinical activity of Aurora inhibitors by malignancy and study design are highlighted in Table 2. Emerging data indicate that combination with spindle poisons, such as taxanes or vinca alkaloids, with aurora A kinase inhibitors may prove synergistic.14,21 Similarly, due to interaction of aurora B kinase with histone H3, combination with histone deacetylase inhibitors with AKIs inhibitors may prove synergistic.
22 Therapeutic dosing of aurora kinase specific agents may be difficult to elucidate as higher doses of AKIs may lead to a pan aurora inhibitory effect. 2.1 Selective Inhibitors of Aurora A Kinase 2.1.1 ENMD 981693 and ENMD 2076 The molecule initially described as ENMD 981693 was further developed into ENMD 2076, the L tartrate salt of ENMD 981693.23 ENMD Masitinib 2076 is more selective for aurora A kinase than ENMD 981693, with an IC50 value of 14 nM for aurora A kinase and 350 nM for aurora B kinase, respectively.24 Furthermore, ENMD 2076 also inhibits FGFR3, PDGFR, VEGFR1, and potently inhibits FLT3 with IC50 values ranging from 0.04 �?21 M. Pre clinical studies of ENMD 2076 in murine models have shown promise for multiple myeloma , breast cancer, leukemia and colorectal cancer. 24,25,26,27 Additionally, several phase I and II trials are currently ongoing in ovarian cancer, acute leukemia and multiple myeloma.
28 Green et al. Page 3 Recent Pat Anticancer Drug Discov. Author manuscript, available in PMC 2011 February 15. NIH PA Author Manuscript NIH PA Author Manuscript NIH PA Author Manuscript ENMD 2076 displays favorable pharmacokinetic profile as it is approximately 90% protein bound, displays no significant inhibition of cytochrome P450 isoenzymes CYP1A2, 2A6, 2C19, or 3A4/5 and is orally bioavailable.25,26 The spectrum of antiproliferative, antiangiogenic and cell cycle effects, combined with favorable pharmacokinetic profile makes this agent appealing for investigation in a myriad of tumor types. 2.1.2 MK 5108 MK 5108, also known as VX 689, is a competitive inhibitor of the ATPbinding site of aurora A kinase.
Pre clinical studies show efficacy in a variety of breast, cervix, colorectal, ovary, and pancreas neoplasms. This antitumor effect was enhanced by the addition of docetaxel in vitro and in vivo a murine model with acceptable toxicity, irrespective of treatment sequence.29 The combination of MK 5108 and the HDACI, vorinostat, was investigated in multiple lymphoma cell lines.22 The addition of MK 5108 to vorinostat sensitized the cell lines to apoptosis, with inhibition of c Myc playing a crucial role. A phase 1 study in patients with advanced solid tumors investigated the toxicities of singleagent MK 5108 and MK 5108 in combination with docetaxel 60mg/m2 IV every 21 days.30 Febrile neutropenia and myelotoxicity was identified as the dose limiting toxicity in combination patients, but no DLT was identified in the monotherapy arm.
Disease stabilization was seen in 11 of 34 patients from both arms, while partial response was seen in 2 of 17 patients in the combination arm and 0 of 17 in the monotherapy arm. 2.1.3 MLN8054 MLN8054 potently inhibits aurora A kinase by competitively blocking the ATP binding pocket. Importantly, MLN8054 is structurally and functionally similar to benzodiazepines, leading to the DLT of somnolence at clinically relevant doses.31,32 Preclinical studies in a several cell culture and murine xenograft models displayed potent antitumor activity as determined by di