The hypoxia-inducible factor 2α (HIF-2α) is a key oncogenic driver in clear cell renal cell carcinoma (ccRCC). Our first HIF-2α inhibitor PT2385 demonstrated promising proof of concept clinical ...activity in heavily pretreated advanced ccRCC patients. However, PT2385 was restricted by variable and dose-limited pharmacokinetics resulting from extensive metabolism of PT2385 to its glucuronide metabolite. Herein we describe the discovery of second-generation HIF-2α inhibitor PT2977 with increased potency and improved pharmacokinetic profile achieved by reduction of phase 2 metabolism. Structural modification by changing the geminal difluoro group in PT2385 to a vicinal difluoro group resulted in enhanced potency, decreased lipophilicity, and significantly improved pharmacokinetic properties. In a phase 1 dose-escalation study, the clinical pharmacokinetics for PT2977 supports the hypothesis that attenuating the rate of glucuronidation would improve exposure and reduce variability in patients. Early evidence of clinical activity shows promise for PT2977 in the treatment of ccRCC.
HIF-2α, a member of the HIF family of transcription factors, is a key oncogenic driver in cancers such as clear cell renal cell carcinoma (ccRCC). A signature feature of these cancers is the ...overaccumulation of HIF-2α protein, often by inactivation of the E3 ligase VHL (von Hippel-Lindau). Herein we disclose our structure based drug design (SBDD) approach that culminated in the identification of PT2385, the first HIF-2α antagonist to enter clinical trials. Highlights include the use of a putative n → π*
interaction to guide early analog design, the conformational restriction of an essential hydroxyl moiety, and the remarkable impact of fluorination near the hydroxyl group. Evaluation of select compounds from two structural classes in a sequence of PK/PD, efficacy, PK, and metabolite profiling identified 10i (PT2385, luciferase EC
= 27 nM) as the clinical candidate. Finally, a retrospective crystallographic analysis describes the structural perturbations necessary for efficient antagonism.
HIF-2α, a member of the HIF family of transcription factors, is a key oncogenic driver in cancers such as clear cell renal cell carcinoma (ccRCC). A signature feature of these cancers is the ...overaccumulation of HIF-2α protein, often by inactivation of the E3 ligase VHL (von Hippel–Lindau). Herein we disclose our structure based drug design (SBDD) approach that culminated in the identification of PT2385, the first HIF-2α antagonist to enter clinical trials. Highlights include the use of a putative n → π*Ar interaction to guide early analog design, the conformational restriction of an essential hydroxyl moiety, and the remarkable impact of fluorination near the hydroxyl group. Evaluation of select compounds from two structural classes in a sequence of PK/PD, efficacy, PK, and metabolite profiling identified 10i (PT2385, luciferase EC50 = 27 nM) as the clinical candidate. Finally, a retrospective crystallographic analysis describes the structural perturbations necessary for efficient antagonism.
Pharmacokinetic properties of our first-generation HIF-2α antagonist PT2385, including modest solubility, resulted in a high recommended phase 2 dose (RP2D) of 800 mg BID and motivated the pursuit of ...novel scaffolds which could improve solubility and formulation parameters with the goal of improved pharmacokinetics. Herein we disclose our successful efforts to identify such HIF-2α antagonists through an optimization strategy characterized by: (1) increasing the fraction of sp
3
hybridized carbons (Fsp
3
), (2) replacing the aromatic portion of the indane core with pyridine heterocycles, and (3) improving a putative O
lp
→π*
Ar
interaction, an underutilized electrostatic contact in medicinal chemistry. These efforts emphasize the importance of employing multiple strategies in parameter optimization. In isolation, modifications to areas (1) and (2) improved solubility, but with the compromise of reduced potency. In area (3), understanding the importance of an O
lp
→π*
Ar
interaction, as documented through a wealth of crystal structures and retrospective calculations, proved essential in guiding SAR and identifying the trifluoromethyl group as a suitable replacement of the sulfone. Only by combining these three strategies could inhibitors with substantially improved solubility and comparable potency be discovered. Finally, the overall improvement in pharmacokinetic properties of the newly identified inhibitors is highlighted through a battery of ADME and in vivo data, including use of pharmacodynamic biomarkers indicative of HIF-2α antagonism.
Cancer presents a difficult challenge for oncologists, as there are few therapies that specifically target disease cells.
Existing treatment strategies rely heavily on physical and chemical agents ...that nonspecifically affect DNA metabolism. To
improve the effectiveness of these treatments, we have identified a new class of protein kinase inhibitor that targets a major
DNA repair pathway. A representative of this class, 1-(2-hydroxy-4-morpholin-4-yl-phenyl)-ethanone, inhibits the DNA-dependent
protein kinase (DNA-PK) and differs significantly from previously studied DNA-PK inhibitors both structurally and functionally.
DNA-PK participates in the cellular response to and repair of chromosomal DNA double-strand breaks (DSBs). These new selective
inhibitors recapitulate the phenotype of DNA-PK defective cell lines including those from SCID mice. These compounds directly
inhibit the repair of DNA DSBs and consequently enhance the cytotoxicity of physical and chemical agents that induce DSBs
but not other DNA lesions. In contrast to previously studied DNA-PK inhibitors, these compounds appear benign, exhibiting
no toxic effects in the absence of DSB-inducing treatments. Most importantly, 1-(2-hydroxy-4-morpholin-4-yl-phenyl)-ethanone
synergistically enhances radiation-induced tumor control in a mouse-human xenograft assay. These studies validate DNA-PK as
a cancer drug target and suggest a new approach for enhancing the effects of existing cancer therapies.
The in silico construction of a PDGFRβ kinase homology model and ensuing medicinal chemistry guided by molecular modeling, led to the identification of potent, small molecule inhibitors of PDGFR. ...Subsequent exploration of structure–activity relationships (SAR) led to the incorporation of a constrained secondary amine to enhance selectivity. Further refinements led to the integration of a fluorine substituted piperidine, which resulted in significant reduction of P-glycoprotein (Pgp) mediated efflux and improved bioavailability. Compound 28 displayed oral exposure in rodents and had a pronounced effect in a pharmacokinetic–pharmacodynamic (PKPD) assay.
A series of pyrimidine thioethers was synthesized and evaluated for inhibitory properties against wild-type HIV-1 reverse transcriptase (RT) and an RT carrying the resistance-conferring mutation ...P236L. Modifications of both the pyrimidine and the functionality attached through the thioether yielded several analogues, which demonstrated activity against both enzyme types, with IC50 values as low as 190 nM against wild-type and 66 nM against P236L RT. Evaluation of a select number of pyrimidine thioethers in cell culture showed that these compounds have excellent activity against HIV-1IIIB-WT and retain good activity against a laboratory-derived HIV-1MF delavirdine-resistant variant.
Vinylidenebisphosphonic acid tetraethyl ester (1) and diazo ketones 7a-1 in ether at 22 degrees C yield pyrazoline bisphosphonate tetraethyl esters 8a-1 in moderate to good yield. These compounds ...were evaluated in animal models of arthritis: rat adjuvant-induced polyarthritis (AIP) and murine antigen-induced arthritis (AIA) and a murine model of chronic inflammation, the delayed type hypersensitivity granuloma reaction (DTH-GRA). (5-Benzoyl-2,4-dihydro-3H-pyrazol-3-ylidene)-bisphosphonic acid tetraethyl ester (8a), and 5-(3-fluorobenzoyl)-2,4-dihydro-3H-pyraxol-3-ylidene- bisphosphonic acid tetraethyl ester (8d) significantly inhibited the arthritis models, AIP (15 mg/kg) and AIA (25 mg/kg), as well as the DTH-GRA (25 mg/kg). Conversion of 8a to the corresponding bisphosphonic acid, 10a, resulted in loss of activity. Compounds with alkyl substituents on the pyrazoline nitrogen, 9a-d, were inactive in the DTH-GRA. These results show that 8a and 8d have novel antiinflammatory activity and are capable of inhibiting chronic arthritis and inflammation in animals. Such compounds might be useful in man for treating chronic tissue injury associated with arthropathies such as inflammatory joint disease as well as other chronic inflammatory diseases.
Abstract
Hypoxia-inducible factor 2a (HIF-2a), a transcription factor, has been established as an oncogenic driver in clear cell renal cell cancer (ccRCC). The first HIF-2a antagonist being evaluated ...in clinical development, PT2385, has demonstrated clinical activity in ccRCC patients who had previously been treated with multiple lines of therapy. There is continuing effort to characterize additional HIF-2a antagonists possessing attributes that may contribute to enhanced clinical activity. PT2977 is a novel HIF-2a antagonist with improved potency in preclinical tumor models compared to PT2385. This improvement arises from enhanced biochemical and cellular potency, an improvement in plasma protein binding, and diminished metabolic clearance in vivo relative to PT2385. PT2977 exhibits favorable metabolic stability and pharmacokinetic characteristics when dosed orally in multiple preclinical species. Allometric scaling of the preclinical data predicts PT2977 to be suitable for oral once-daily dosing in humans. PT2977 inhibits expression of HIF-2a target genes in tumor cells and induces complete stasis or regression in ccRCC xenografts. A strong pharmacokinetics/pharmacodynamics correlation is observed in tumors from xenograft models treated with PT2977. Gene expression analyses of ccRCC xenografts treated with PT2977 reveal extensive modulation of genes in the tumor cells as well as in immune cells. Immune phenotyping of tumors treated with PT2977 confirms that HIF-2a antagonism results in a reduction in the number of immunosuppressive myeloid-derived cells, including neutrophils and macrophages. Treatment with PT2977 also results in an influx of mature dendritic cells. These observations are consistent with HIF-2a exerting an immunosuppressive effect on the tumor microenvironment, in addition to driving angiogenesis and the proliferation and viability of tumor cells. With its favorable preclinical profile, PT2977 is well positioned to further reveal the broader therapeutic potential of HIF-2a antagonism for the treatment of cancer, as a single agent or in combination with other immune-modulating agents.
Citation Format: Tai W. Wong, Rajeev Shrimali, Cristina Contreras, Tzuling Cheng, Robert M. Czerwinski, Daryl D. Dixon, Xinlin Du, Craig Fett, Jessica Goree, Jonas A. Grina, Guangzhou Han, Heli Huang, Jim Rizzi, Stephen T. Schlachter, Bin Wang, Keshi Wang, Paul M. Wehn, Shanhai Xie, Rui Xu, Hanbiao Yang, John A. Josey, Eli M. Wallace. PT2977, a novel HIF-2a antagonist, has potent antitumor activity and remodels the immunosuppressive tumor microenvironment in clear cell renal cell cancer abstract. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr B140.
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