Rongqi Wang

Developing Lipid Nanoparticle-Based siRNA Therapeutics for Hepatocellular Carcinoma Using an Integrated Approach

Successful siRNA therapeutics requires the optimal integration of multiple components, including an efficient delivery system, a disease indication that is appropriate for siRNA-based therapy, and a potent and nontoxic siRNA against a robust therapeutic target. Although all currently available delivery systems have limitations, it is important to recognize that a careful selection of the disease indication, therapeutic target, and siRNA molecule could partially compensate for deficiencies associated with the delivery system and makes it possible to advance a therapeutic siRNA regimen. In this study, we present the development of siRNA therapeutics for hepatocellular carcinoma using an integrated approach, including the development of an efficient lipid nanoparticle delivery system, the identification of a robust therapeutic target that does not trigger liver toxicity upon target knockdown, and the selection of potent and nonimmunogenic siRNA molecules against the target. The resulting siRNA-containing lipid nanoparticles produced significant antitumor efficacy in orthotopic hepatocellular carcinoma models, and, thus, represent a promising starting point for the development of siRNA therapeutics for hepatocellular carcinoma. Mol Cancer Ther; 12(11); 2308–18. ©2013 AACR.

Fragment-Based, Structure-Enabled Discovery of Novel Pyridones and Pyridone Macrocycles as Potent Bromodomain and Extra-Terminal Domain (BET) Family Bromodomain Inhibitors

Members of the BET family of bromodomain containing proteins have been identified as potential targets for blocking proliferation in a variety of cancer cell lines. A two-dimensional NMR fragment screen for binders to the bromodomains of BRD4 identified a phenylpyridazinone fragment with a weak binding affinity (1, Ki = 160 μM). SAR investigation of fragment 1, aided by X-ray structure-based design, enabled the synthesis of potent pyridone and macrocyclic pyridone inhibitors exhibiting single digit nanomolar potency in both biochemical and cell based assays. Advanced analogs in these series exhibited high oral exposures in rodent PK studies and demonstrated significant tumor growth inhibition efficacy in mouse flank xenograft models.

Discovery of N-(4-(2,4-difluorophenoxy)-3-(6-methyl-7-oxo-6,7-dihydro-1H-pyrrolo[2,3-c]pyridin-4-yl)phenyl)ethanesulfonamide (ABBV-075/mivebresib), a Potent and Orally Available Bromodomain and Extraterminal domain (BET) Family Bromodomain Inhibitor

The development of bromodomain and extraterminal domain (BET) bromodomain inhibitors and their examination in clinical studies, particularly in oncology settings, has garnered substantial recent interest. An effort to generate novel BET bromodomain inhibitors with excellent potency and drug metabolism and pharmacokinetics (DMPK) properties was initiated based upon elaboration of a simple pyridone core. Efforts to develop a bidentate interaction with a critical asparagine residue resulted in the incorporation of a pyrrolopyridone core, which improved potency by 9-19-fold. Additional structure-activity relationship (SAR) efforts aimed both at increasing potency and improving pharmacokinetic properties led to the discovery of the clinical candidate 63 (ABBV-075/mivebresib), which demonstrates excellent potency in biochemical and cellular assays, advantageous exposures and half-life both in animal models and in humans, and in vivo efficacy in mouse models of cancer progression and inflammation.

Discovery and optimization of novel constrained pyrrolopyridone BET family inhibitors

Novel conformationally constrained BET bromodomain inhibitors have been developed. These inhibitors were optimized in two similar, yet distinct chemical series, the 6-methyl-1H-pyrrolo[2,3-c]pyridin-7(6H)-ones (A) and the 1-methyl-1H-pyrrolo[2,3-c]pyridin-7(6H)-ones (B). Each series demonstrated excellent activity in binding and cellular assays, and lead compounds from each series demonstrated significant efficacy in in vivo tumor xenograft models.

Abstract 4695: Functional group elaboration of a low molecular weight fragment to yield the novel BET family bromodomain inhibitor ABBV-075

Phenotypic cell-based screening assays combined with affinity chromatography and mass-spectrometry identified the BET family of bromodomains as potential targets for blocking proliferation in a variety of cancer cell lines. Lead-finding investigations included screening a library of compounds with an average molecular weight of 225 for binding to the 13C-labeled 2nd bromodomain of BRD4 using 2-dimensional NMR. A pyridazinone fragment emerged from this effort that possessed weak binding affinity (Kd = 130 uM). The binding affinity was improved by roughly 100,000-fold through an X-ray structure enabled medicinal chemistry program that included moving to a pyrrolopyridone core along with judicious placement of additional functional groups. Antiproliferative potencies strongly correlated with potencies in a cell-based target engagement assay, suggesting that the antiproliferative effects resulted from the inhibition of BRD4/BET protein function. In vitro metabolite ID studies in rat liver microsomes helped identify sites of oxidative metabolism. The addition of fluorine atoms at these locations improved rat in vitro microsomal stability that translated to low in vivo clearance and high oral exposure in rat. The final molecule, ABBV-075, exhibited long half-lives and low unbound clearances in rat, mouse, dog and monkey. ABBV-075 demonstrated significant tumor growth inhibition in mouse flank xenograft studies representing diverse hematological and solid tumor malignancies and recently entered Phase I clinical studies. Disclosures: All authors are employees of AbbVie. The design, study conduct, and financial support for this research were provided by AbbVie. AbbVie participated in the interpretation of data, review, and approval of the publication. Citation Format: Keith McDaniel, Le Wang, George Sheppard, Steve Fidanze, John Pratt, Dachun Liu, Lisa Hasvold, Robert Mantei, Chang Park, Aparna Sarthy, Leiming Li, Daniel H. Albert, Xiaoyu Lin, Scott Warder, Emily Faivre, Mai H. Bui, Xiaoli Huang, Denise Wilcox, Rongqi Wang, Terry Magoc, Ganesh Rajaraman, Andrew Petros, Sanjay Panchal, Chaohong Sun, Guowei Fang, Steven W. Elmore, Saul Rosenberg, Yu Shen, Warren Kati. Functional group elaboration of a low molecular weight fragment to yield the novel BET family bromodomain inhibitor ABBV-075. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4695.

Abstract 3770: HEXIM1 as a pharmacodynamic marker for monitoring target engagement of ABBV-075

Bromodomain and extra-terminal (BET) family are dual bromodomain-containing proteins that play an important role in transcription regulation. ABBV-075 is a small molecule BET bromodomain inhibitor currently in phase 1 clinical trials. Here we report the identification of Hexim1 and other BET-responsive genes as robust pharmacodynamic markers for monitoring ABBV-075 target engagement in tumors and in surrogate tissues such as whole blood and skin. Transcription profiling of cancer cell lines for their responses to BET inhibitors identified a set of 9 BET-regulated genes, including Hexim1, that responded to BET inhibition across cancer cell lines and in xenograft tumors. Further characterization of BET-responsive genes in surrogate tissues such as mouse skin, mouse/human PBMCs and whole blood revealed that the mRNA level of Hexim1 exhibited the best response to BETi treatment across different settings. A dose-dependent increase of Hexim1 expression was detected in the whole blood of ABBV-075 treated tumor bearing mice, and the Hexim1 response was closely correlated with the plasma drug concentration and largely reflected the anti-tumor efficacy at various dose levels of ABBV-075. Hexim1 is part of a protein/RNA complex that sequesters pTEFb and prevents its recruitment by BRD4. It also reportedly mediates the anti-proliferative activity of BRD4 in AML. Taken together, Hexim1 could serve as a functional relevant pharmacodynamic marker for monitoring ABBV-075 target engagement in animal models and in the clinical setting. Citation Format: Xiaoli Huang, Xiaoyu Lin, Leiming Li, Rongqi Wang, Lisa Roberts, Paul Hessler, Tamar Uziel, Lloyd Lam, Terry Magoc, Daniel H. Albert, Steven W. Elmore, Guowei Fang, Saul H. Rosenberg, Keith McDaniel, Warren Kati, Yu Shen. HEXIM1 as a pharmacodynamic marker for monitoring target engagement of ABBV-075. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3770.