John Maxwell

Discovery of Thienoimidazole-Based HCV NS5A Genotype 1a and 1b Inhibitors.

The discovery of potent thienoimidazole-based HCV NS5A inhibitors is herein reported. A novel method to access the thienoimidazole [5,5]-bicyclic system is disclosed. This method gave access to a common key intermediate (6) that was engaged in Suzuki or Sonogashira reactions with coupling partners bearing different linkers. A detailed study of the structure-activity relationship (SAR) of the linkers revealed that aromatic linkers with linear topologies are required to achieve high potency for both 1a and 1b HCV genotypes. Compound 20, with a para-phenyl linker, was identified as a potential lead displaying potencies of 17 and 8 pM against genotype 1a and 1b replicons, respectively.

Synthesis and evaluation of NS5A inhibitors containing diverse heteroaromatic cores.

Inhibitors of the HCV NS5A nonstructural protein are showing promising clinical potential in the treatment of hepatitis C when used in combination with other direct-acting antiviral agents. Current NS5A clinical candidates such as daclatasvir, ledipasvir, and ombitasvir share a common pharmacophore that features a pair of (S)-methoxycarbonylvaline capped pyrrolidines linked to various cores by amides, imidazoles and/or benzimidazoles. In this Letter, we describe the evaluation of NS5A inhibitors which contain alternative heteroaromatic replacements for these amide mimetics. The SAR knowledge gleaned in the optimization of scaffolds containing benzoxazoles was parlayed toward the identification of potent NS5A inhibitors containing other heteroaromatic replacements such as indoles and imidazopyridines.

Benzimidazole-containing HCV NS5A inhibitors: effect of 4-substituted pyrrolidines in balancing genotype 1a and 1b potency.

The treatment of HCV with highly efficacious, well-tolerated, interferon-free regimens is a compelling clinical goal. Trials employing combinations of direct-acting antivirals that include NS5A inhibitors have shown significant promise in meeting this challenge. Herein, we describe our efforts to identify inhibitors of NS5A and report on the discovery of benzimidazole-containing analogs with subnanomolar potency against genotype 1a and 1b replicons. Our SAR exploration of 4-substituted pyrrolidines revealed that the subtle inclusion of a 4-methyl group could profoundly increase genotype 1a potency in multiple scaffold classes.

Discovery of thienoimidazole-based HCV NS5A inhibitors. Part 2: Non-symmetric inhibitors with potent activity against genotype 1a and 1b

The discovery of non-symmetric thienoimidazole-containing HCV NS5A inhibitors is described. The inhibitors herein reported display high potencies against both genotype 1a and 1b. In this follow-up manuscript, we discuss the importance of the linker aromaticity to achieve high potency, particularly against genotype 1a.

Discovery of thienoimidazole-based HCV NS5A inhibitors. Part 1: C2-Symmetric inhibitors with diyne and biphenyl linkers

The discovery of C2-symmetric bis-thienoimidazoles HCV NS5A inhibitors is herein reported. Two straightforward approaches to access the requisite diyne and biphenyl linker moieties are described. This study revealed the paramount importance of the aromatic character of the linker to achieve high genotype 1a potency.

Abstract P5-06-05: Preclinical characterization of VX-984, a selective DNA-dependent protein kinase (DNA-PK) inhibitor in combination with doxorubicin in breast and ovarian cancers

Background: The efficacy of chemotherapeutic agents such as doxorubicin, which cause lethal DNA double-strand breaks (DSBs), is diminished by efficient repair of the damaged DNA in cancer cells. DNA-PK is a key regulator of the non-homologous end joining (NHEJ) pathway, which is responsible for repairing DSBs. Studies of nonselective inhibitors of DNA-PK have shown that cancer cells depend on DNA-PK for survival following treatment with DSB-inducing agents. However, a comprehensive characterization of DNA-PK inhibition has been hampered by a lack of selective inhibitors. Here we describe VX-984, a potent and selective inhibitor of DNA-PK, and its preclinical profile in combination with doxorubicin both in vitro and in vivo. Methods: VX-984 was examined as a single agent and in combination with doxorubicin or pegylated liposomal doxorubicin (PLD) in a panel of breast cancer cell lines and in mouse xenograft models, respectively. Results: In vitro, inhibition of DNA-PK by VX-984 enhanced the cytotoxic activity of doxorubicin in established breast cancer cell lines and in primary ovarian tumor explants. Notably, mean Bliss DE >10% (strong synergy) were observed for doxorubicin in the presence of VX-984 in 22 of 35 breast cancer cell lines and 21 of 44 ovarian cancer cell lines in a broad cancer cell line screen. Further, the efficacy observed with VX-984 was associated with increased DNA damage as measured by phosphorylated histone H2AX (gamma-H2AX) and phosphorylated Kruppel-associated protein (pKAP1) in DU4475, MDA-MB-436 and MDA-MB-468 breast cancer cell lines, which is consistent with diminished DSB repair. In vivo, VX-984 significantly enhanced the efficacy of PLD in ovarian cancer patient-derived xenograft models and in cell line xenograft models. Conclusions: These data provide evidence that inhibition of DNA-PK by VX-984 enhances the efficacy of doxorubicin in preclinical models and support the use of VX-984 in combination with DSB agents such as anthracyclines including PLD for the treatment of breast and ovarian cancers. VX-984 is currently in a Phase 1 clinical trial in combination with PLD. Sponsored by Vertex Pharmaceuticals Incorporated. Citation Format: Boucher D, Newsome D, Takemoto D, Hillier S, Wang Y, Arimoto R, Maxwell J, Charifson P, Fields SZ, Tanner K, Penney MS. Preclinical characterization of VX-984, a selective DNA-dependent protein kinase (DNA-PK) inhibitor in combination with doxorubicin in breast and ovarian cancers [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P5-06-05.

Abstract 3716: Potent radiation enhancement with VX-984, a selective DNA-PKcs inhibitor for the treatment of NSCLC

Ionizing radiation (IR), which is widely used for the treatment of cancer, causes double-strand breaks (DSBs) in DNA. If left unrepaired, these DSBs are lethal to the cell. DNA-dependent protein kinase (DNA-PK) is a key enzyme in the non-homologous end joining (NHEJ) pathway that repairs DSBs caused by IR, or chemotherapeutic agents that cause DSBs such as doxorubicin. The goal of these studies was to characterize the radiation enhancing effects of VX-984, a selective and potent ATP-competitive inhibitor of the catalytic subunit of DNA-PK (DNA-PKcs), with a focus on non-small cell lung cancer (NSCLC) cells and tumor xenografts. VX-984 enhances the cytotoxicity of IR in a panel of cancer cell lines including NSCLC cell lines in vitro with dose enhancement factors (DEF) greater than 3. Notably, VX-984 combined with IR in normal human lung fibroblasts minimally enhanced the cytotoxicity compared to IR alone. Additionally, VX-984 decreased DNA-PKcs autophosphorylation on S2056 both in vitro and in vivo in NSCLC cells and attenuated the decay of the DNA damage markers γH2AX and pKAP1 in response to IR. In NSCLC PDX models VX-984, in combination with IR (2 Gy x 3), caused durable complete responses while IR alone only led to a delay in tumor growth, consistent with delayed DNA damage repair. In these models, the combination of VX-984 and IR was well tolerated. These data demonstrate that VX-984 is a potent radiation-enhancing agent and provide a strong rationale for the use of VX-984 in combination with IR for the treatment of NSCLC. Citation Format: Diane Boucher, Russell Hoover, Yuxin Wang, Yong Gu, David Newsome, Pamella Ford, Cameron Moody, Veronique Damagnez, Reiko Arimoto, Shawn Hillier, Mark Wood, William Markland, Brenda Eustace, Kevin Cottrell, Marina Penney, Brinley Furey, Kirk Tanner, John Maxwell, Paul Charifson. Potent radiation enhancement with VX-984, a selective DNA-PKcs inhibitor for the treatment of NSCLC. [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 3716.