Benoît Moreau

Discovery of Hepatitis C Virus NS3-4A Protease Inhibitors with Improved Barrier to Resistance and Favorable Liver Distribution

Given the emergence of resistance observed for the current clinical-stage hepatitis C virus (HCV) NS3 protease inhibitors, there is a need for new inhibitors with a higher barrier to resistance. We recently reported our rational approach to the discovery of macrocyclic acylsulfonamides as HCV protease inhibitors addressing potency against clinically relevant resistant variants. Using X-ray crystallography of HCV protease variant/inhibitor complexes, we shed light on the complex structural mechanisms by which the D168V and R155K residue mutations confer resistance to NS3 protease inhibitors. Here, we disclose SAR investigation and ADME/PK optimization leading to the identification of inhibitors with significantly improved potency against the key resistant variants and with increased liver partitioning.

Molecular Mechanism by Which a Potent Hepatitis C Virus NS3-NS4A Protease Inhibitor Overcomes Emergence of Resistance

Background: Antivirals must often be given in combinations to avoid rapid emergence of resistance. Results: We identified and structurally characterized protease inhibitors that maintain potency against genotype and resistant variants. Conclusion: Pan-variant potency was achieved by targeting invariant regions and incorporating flexibility where pocket variability occurs. Significance: Such inhibitors may yield simplified and/or more successful treatments for hepatitis C infections. Although optimizing the resistance profile of an inhibitor can be challenging, it is potentially important for improving the long term effectiveness of antiviral therapy. This work describes our rational approach toward the identification of a macrocyclic acylsulfonamide that is a potent inhibitor of the NS3-NS4A proteases of all hepatitis C virus genotypes and of a panel of genotype 1-resistant variants. The enhanced potency of this compound versus variants D168V and R155K facilitated x-ray determination of the inhibitor-variant complexes. In turn, these structural studies revealed a complex molecular basis of resistance and rationalized how such compounds are able to circumvent these mechanisms.

Simple Method Provides Resolution of Albumin, Lipoprotein, Free Fraction, and Chylomicron To Enhance the Utility of Protein Binding Assays

Medicinal chemists have been encouraged in recent years to embrace high speed protein binding assays. These methods employ dialysis membranes in 96-well format or spin filters. Membrane-based methods do not separate lipoprotein binding from albumin binding and introduce interference despite membrane binding controls. Ultracentrifugation methods, in contrast, do not introduce interference if density gradients can be avoided and they resolve lipoprotein from albumin. A new generation of compact, fast ultracentrifuges facilitates the rapid and fully informative separation of plasma into albumin, albumin/fatty acid complex, lipoprotein, protein-free, and chylomicron fractions with no need of salt or sugar density gradients. We present a simple and fast ultracentrifuge method here for two platinum compounds and a taxane that otherwise bound irreversibly to dialysis membranes and which exhibited distinctive lipoprotein binding behaviors. This new generation of ultracentrifugation methods underscores a need to further discuss protein binding assessments as they relate to medicinal chemistry efforts.

Abstract 3674: Pentarins: Improved tumor targeting through nanoparticle encapsulation of miniaturized biologic drug conjugates

The specific targeting of cytotoxic drugs to solid tumors has achieved success with the advent of antibody drug conjugates (ADCs). This approach has had notable success but has also met with limitations. The most common issue limiting ADC effectiveness is believed to be low tumor permeation by these large (∼150 kDa) molecules. Attempts to address this limitation have been focused on the design of miniaturized biologic drug conjugates such as those with small protein or small molecule targeting moieties. However, these efforts uniformly result in conjugates with poor pharmacokinetics in contrast to the extended plasma pharmacokinetics observed with ADCs. The Pentarin platform encapsulates miniaturized biological drug conjugates within nanoparticles to improve the biodistribution of these classes of conjugates. There are multiple benefits to this strategy. Through the enhanced permeability and retention (EPR) effect the nanoparticles accumulate in the perivascular space of the tumor tissue. Next the nanoparticles release the permeable miniaturized conjugate that can penetrate in to the tumor, bind to an over-expressed target on the cancer cell surface, internalize the payload and elicit a strong biological effect. All of this is further enhanced by the extended plasma pharmacokinetics of the nanoparticle when compared to the conjugate alone. To exemplify the Pentarin platform we have designed novel miniaturized biologic drug conjugates to an over-expressed target found in small cell lung cancer. In vitro data has shown the designed conjugates specifically and potently target tumor cells expressing the receptor of interest. When encapsulated in nanoparticles, these miniaturized biologic drug conjugates have improved plasma pharmacokinetics, the amount of payload delivered to xenograft tumors is increased and the xenograft efficacy is significantly more pronounced over drug conjugate not in a nanoparticle. These observations correlate with in vivo mechanistic assays in the xenograft tissue. These data will be presented, together with the name of the target, to demonstrate the impact of the Pentarin platform and to show progress towards the first clinical candidate from this work. Citation Format: Mark T. Bilodeau, Rajesh Shinde, Brian White, Patrick Bazinet, Kerry Whalen, Michelle Dupont, Kristina Kriksciukaite, Jamie Quinn, Beata Sweryda-Krawiec, Rossitza Alargova, Adam Brockman, Patrick Lim Soo, Kristan Meetze, Benoit Moreau, Haley Oller, Mike Ramstack, Danielle Rockwood, Sukhjeet Singh, Tsun Au Yeung, Sudha Kadiyala, Craig Dunbar, Richard Wooster. Pentarins: Improved tumor targeting through nanoparticle encapsulation of miniaturized biologic drug conjugates. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3674. doi:10.1158/1538-7445.AM2015-3674

Abstract 39: Discovery of PEN-221, an SSTR2-targeting maytansinoid conjugate with potent activity in vitro and in vivo

Here we describe the discovery and the structure of PEN-221, a somatostatin receptor 2 (SSTR2) targeting peptide conjugated to DM1. PEN-221 is the first clinical compound from Tarveda’s Pentarin platform, which utilizes miniaturized drug conjugates that diffuse rapidly and deeply into solid tumors. Antibody drug conjugates (ADCs) have garnered a significant amount of attention in their ability to direct cytotoxic drugs to cancer cells; however, the efficacy of ADCs in solid tumors is limited by the slow diffusion of such large molecules through solid tumor tissue. Pentarins are designed to improve the efficacy of targeted therapies through effective tumor cell targeting and enhanced tumor penetration. SSTR2, a GPCR overexpressed in multiple types of neuroendocrine tumors, including small cell lung cancers, internalizes rapidly upon agonist stimulation, making it an ideal vector for delivering cytotoxic payloads. Examination of a variety of SSTR2 targeting ligands, as well as several potential conjugation sites, led to the identification of the C-terminal side chain of [Tyr3]-octreotate amide as the best conjugation site for a lipophilic payload. The use of DM1 as a payload afforded superior receptor affinity and receptor internalization when compared to other similarly potent microtubule-targeting agents. In vitro studies show that PEN-221 has receptor-dependent cytotoxic effects, and preclinical studies demonstrate PEN-221 induces tumor regression in several SSTR2 expressing xenograft models. Citation Format: Brian H. White, Patrick Bazinet, Kerry Whalen, Michelle DuPont, James M. Quinn, Rossitza Alargova, Tsun Au Yeung, Adam Brockman, James Gifford, Haley Oller, Kristina Kriksciukaite, Charles-Andre Lemelin, Patrick Lim Soo, Benoit Moreau, Samantha Perino, Gitanjali Sharma, Rajesh Shinde, Beata Sweryda-Krawiec, Mary Simcox, Richard Wooster, Mark T. Bilodeau. Discovery of PEN-221, an SSTR2-targeting maytansinoid conjugate with potent activity in vitro and in vivo [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 39. doi:10.1158/1538-7445.AM2017-39