Development of a Series of Pyrrolopyridone MAT2A Inhibitors

The optimization of an allosteric fragment, discovered by differential scanning fluorimetry, to an in vivo MAT2a tool inhibitor is discussed. The structure-based drug discovery approach, aided by relative binding free energy calculations, resulted in AZ'9567 (21), a potent inhibitor in vitro with excellent preclinical pharmacokinetic properties. This tool showed a selective antiproliferative effect on methylthioadenosine phosphorylase (MTAP) KO cells, both in vitro and in vivo, providing further evidence to support the utility of MAT2a inhibitors as potential anticancer therapies for MTAP-deficient tumors.

Discovery of AZD4747, a Potent and Selective Inhibitor of Mutant GTPase KRASG12C with Demonstrable CNS Penetration

The glycine to cysteine mutation at codon 12 of Kirsten rat sarcoma (KRAS) represents an Achilles heel that has now rendered this important GTPase druggable. Herein, we report our structure-based drug design approach that led to the identification of 14, AZD4747, a clinical development candidate for the treatment of KRAS^G12C-positive tumors, including the treatment of central nervous system (CNS) metastases. Building on our earlier discovery of C5-tethered quinazoline AZD4625, excision of a usually critical pyrimidine ring yielded a weak but brain-penetrant start point which was optimized for potency and DMPK. Key design principles and measured parameters that give high confidence in CNS exposure are discussed. During optimization, divergence between rodent and non-rodent species was observed in CNS exposure, with primate PET studies ultimately giving high confidence in the expected translation to patients. AZD4747 is a highly potent and selective inhibitor of KRAS^G12C with an anticipated low clearance and high oral bioavailability profile in humans.

Chemical Biology Approaches Confirm MCT4 as the Therapeutic Target of a Cellular Optimized Hit

Lactic acid transport is a key process maintaining glycolytic flux in tumors. Inhibition of this process will result in glycolytic shutdown, impacting on cell growth and survival and thus has been pursued as a therapeutic approach for cancers. Using a cell-based screen in a MCT4-dependent cell line, we identified and optimized compounds for their ability to inhibit the efflux of intracellular lactic acid with good physical and pharmacokinetic properties. To deconvolute the mechanism of lactic acid efflux inhibition, we have developed three assays to measure cellular target engagement. Specifically, we synthesized a biologically active photoaffinity probe (IC₅₀ < 10 nM), and using this probe, we demonstrated selective engagement of MCT4 of our parent molecule through a combination of confocal microscopy and in-cell chemoproteomics. As an orthogonal assay, the cellular thermal shift assay (CETSA) confirmed binding to MCT4 in the cellular system. Comparisons of lactic acid efflux potencies in cells with differential expression of MCT family members further confirmed that the optimized compounds inhibit the efflux of lactic acid through the inhibition of MCT4. Taken together, these data demonstrate the power of orthogonal chemical biology methods to determine cellular target engagement, particularly for proteins not readily amenable to traditional biophysical methods.

Discovery of Clinical Candidate AZD0095, a Selective Inhibitor of Monocarboxylate Transporter 4 (MCT4) for Oncology

Due to increased reliance on glycolysis, which produces lactate, monocarboxylate transporters (MCTs) are often upregulated in cancer. MCT4 is associated with the export of lactic acid from cancer cells under hypoxia, so inhibition of MCT4 may lead to cytotoxic levels of intracellular lactate. In addition, tumor-derived lactate is known to be immunosuppressive, so MCT4 inhibition may be of interest for immuno-oncology. At the outset, no potent and selective MCT4 inhibitors had been reported, but a screen identified a triazolopyrimidine hit, with no close structural analogues. Minor modifications to the triazolopyrimidine were made, alongside design of a constrained linker and broad SAR exploration of the biaryl tail to improve potency, physical properties, PK, and hERG. The resulting clinical candidate 15 (AZD0095) has excellent potency (1.3 nM), MCT1 selectivity (>1000×), secondary pharmacology, clean mechanism of action, suitable properties for oral administration in the clinic, and good preclinical efficacy in combination with cediranib.

Optimization of hERG and Pharmacokinetic Properties for Basic Dihydro-8H-purin-8-one Inhibitors of DNA-PK

The DNA-PK complex is activated by double-strand DNA breaks and regulates the non-homologous end-joining repair pathway; thus, targeting DNA-PK by inhibiting the DNA-PK catalytic subunit (DNA-PKcs) is potentially a useful therapeutic approach for oncology. A previously reported series of neutral DNA-PKcs inhibitors were modified to incorporate a basic group, with the rationale that increasing the volume of distribution while maintaining good metabolic stability should increase the half-life. However, adding a basic group introduced hERG activity, and basic compounds with modest hERG activity (IC50 = 10-15 μM) prolonged QTc (time from the start of the Q wave to the end of the T wave, corrected by heart rate) in an anaesthetized guinea pig cardiovascular model. Further optimization was necessary, including modulation of pK a, to identify compound 18, which combines low hERG activity (IC50 = 75 μM) with excellent kinome selectivity and favorable pharmacokinetic properties.

The Discovery of 7-Methyl-2-[(7-methyl[1,2,4]triazolo[1,5-a]pyridin-6-yl)amino]-9-(tetrahydro-2H-pyran-4-yl)-7,9-dihydro-8H-purin-8-one (AZD7648), a Potent and Selective DNA-Dependent Protein Kinase (DNA-PK) Inhibitor

DNA-PK is a key component within the DNA damage response, as it is responsible for recognizing and repairing double-strand DNA breaks (DSBs) via non-homologous end joining. Historically it has been challenging to identify inhibitors of the DNA-PK catalytic subunit (DNA-PKcs) with good selectivity versus the structurally related PI3 (lipid) and PI3K-related protein kinases. We screened our corporate collection for DNA-PKcs inhibitors with good PI3 kinase selectivity, identifying compound 1. Optimization focused on further improving selectivity while improving physical and pharmacokinetic properties, notably co-optimization of permeability and metabolic stability, to identify compound 16 (AZD7648). Compound 16 had no significant off-target activity in the protein kinome and only weak activity versus PI3Kα/γ lipid kinases. Monotherapy activity in murine xenograft models was observed, and regressions were observed when combined with inducers of DSBs (doxorubicin or irradiation) or PARP inhibition (olaparib). These data support progression into clinical studies (NCT03907969).

Abstract 4478: Discovery of AZD5363, an orally bioavailable, potent ATP-competitive inhibitor of AKT kinases

AKT is a key node in the most frequently de-regulated signaling pathway in human cancer and has been shown to mediate resistance to a range of cytotoxic, anti-hormonal and targeted therapies. We decided to explore inhibitors of AKT as potential new anti-cancer therapeutics. Here we disclose for the first time the discovery and structure of AZD5363, an orally bioavailable, potent ATP-competitive inhibitor of AKT. We evaluated a range of chemical starting points arising from our previous collaboration with the Institute of Cancer Research and Astex Therapeutics Ltd. Ultimately AZD5363 was discovered following a long journey that started from a pyrrolopyrimidine series of compounds. Our first challenge was to improve potency and a second challenge was to improve ROCK selectivity. ROCK is an AGC kinase like AKT but is involved in regulation of vascular tone and thus blood pressure. Extensive SAR studies exploring the series revealed that achieving selectivity over ROCK while retaining AKT potency was quite challenging. Eventually we discovered ways which could improve both selectivity and potency. However, these compounds had significant activity against the hERG ion channel which is implicated in the development of Torsades de Pointes and cardiac death. The next phase of work therefore had to focus on reducing hERG activity, while at the same time not adversely impacting either AKT potency or ROCK selectivity. Finally we discovered that introduction of a key substituent group provided a compound that achieved reduced hERG potency and, surprisingly, also achieved a further small improvement in both AKT potency and ROCK selectivity. This compound was AZD5363. A crystal structure of AZD5363 bound to AKT has revealed some of the key interactions that may contribute to its potency. For example, the pyrrolopyrimidine appears to form hydrogen bonds to the hinge region of the kinase. AZD5363 inhibits all known AKT isoforms with a potency of &lt;10 nM and inhibits phosphorylation of the AKT substrate, PRAS40 in BT474c cells with a potency of 0.31 μM. Activity in in vivo pharmacodynamic and xenograft models has also been demonstrated. A synthetic route suitable for scale-up has been developed. In conclusion, AZD5363 is a potent inhibitor of AKT in vitro and in cells. It has good hERG and ROCK selectivity. It has pharmacodynamic and xenograft activity in vivo. AZD5363 has potential in cancer therapy and is currently in phase 1 clinical trials.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4478. doi:10.1158/1538-7445.AM2011-4478

Proximal colonic response and gastrointestinal transit after high and low fat meals

The fat component of meals has been thought to make a major contribution to the colonic response to feeding. We have combined gamma scintigraphy and radiotelemetry to noninvasively study the response of the normally inaccessible proximal colon after ingestion of either a high or low fat meal. Separate studies were performed to measure the rate of passage of the same meals through the whole gut. Gastric emptying and small bowel transit of the two meals to the colon was similar, 50% of meal marker reaching the ascending colon 4.8 +/- 0.2 and 4.5 +/- 0.3 hr after the high and low fat meals respectively (N = 8, difference not significant). The low fat meal caused a consistent increase in motility index, which rose from a basal value of 1.0 +/- 0.3 to 2.6 +/- 0.7 mm Hg in the 2 hr after the meal (N = 8, P < 0.01). Response to the high fat meal was less consistent, motility index increasing from 1.6 +/- 0.6 basally to 2.3 +/- 0.7 mm Hg postprandially (N = 8, P = 0.21). Despite these increases in motor activity there was no net caudal propulsion of colonic contents after either meal. The geometric center was comparable, being 3.2 +/- 0.4 and 3.7 +/- 0.4 before the high and low fat meals. This did not change significantly after either meal, being then 3.5 +/- 0.4 and 3.6 +/- 0.4 2 hr after the high and low fat meals, respectively. We conclude that in normal subjects equicaloric high and low fat meals transit the whole gut at a similar rate.(ABSTRACT TRUNCATED AT 250 WORDS)