Drugs in Clinical Pipeline: Apitolisib

Apitolisib [(S)-1-(4-((2-(2-aminopyrimidin-5-yl)-7-methyl-4-morpholinothieno[3,2-d]pyrimidin-6-yl)methyl)piperazin-1-yl)-2-hydroxypropan-1-one] is a selective, potent, orally bioavailable inhibitor of Class I PI3 kinase (PI3K) and mTOR kinase (TORC1/2) with excellent pharmacokinetic and pharmaceutical properties. Apitolisib displayed excellent potency against class I PI3K isoforms (IC₅₀ PI3K-α, β, δ and γ = 4.8, 27, 6.7 and 14 nM) and mTOR kinase (IC₅₀ = 17 nM) and selectivity against a large panel of other kinases, including closely related PIKK family members DNA-PK (K_i = 623 nM), VPS34 (IC₅₀ = 2000 nM), c2alpha (IC₅₀ = 1300 nM), and c2beta (IC₅₀ = 794 nM) [1, 2].

References:
1. Sutherlin, D. P.; et. al. Discovery of a potent, selective, and orally available class I phosphatidylinositol 3-kinase (PI3K)/mammalian target of rapamycin (mTOR) kinase inhibitor (GDC-0980) for the treatment of cancer. J Med Chem 2011, 54(21), 7579-7587.
2. Wallin, J. J.; et. al. GDC-0980 is a novel class I PI3K/mTOR kinase inhibitor with robust activity in cancer models driven by the PI3K pathway. Mol Cancer Ther 2011, 10(12), 2426-2436.

Drugs in Clinical Pipeline: GSK-2269557 | Treatment of COPD | Treatment of Asthma | Treatment of Autoimmune Diseases I PIK3d Inhibitor

GSK-2269557 [2-(6-(1H-indol-4-yl)-1H-indazol-4-yl)-5-((4-isopropylpiperazin-1-yl)methyl)oxazole] is a potent, selective nanomolar inhibitor of the delta isoform of the 110 kDa catalytic subunit of class IA phosphoinositide-3 kinases (PI3K). GSK-2269557 is more selective for PI3Kδ relative to other PI3K class I enzymes (pK_i: PI3Kδ = 9.9) with greater than 1000-fold selectivity over PI3Kα, PI3Kγ and PI3Kβ. It has a pIC₅₀ value greater than 7, with at least ten-fold selectivity for PI3Kδ over PI3Kα, PI3Kγ and PI3Kβ [1, 2].

GSK-2269557: 2D and 3D Structure

GSK-2269557 and GSK-2292767 are designed especially for the treatment of respiratory indications via inhalation. Both the drugs meet the criteria necessary for compounds to be delivered as aerosolized dry powder formulations. The advantages of delivering such inhibitors by this route are that it can minimize the risk of systemic, mechanism-related side effects and it also facilitates exploring combinations of the PI3Kδ inhibitors with other anti-asthma agents such as the corticosteroids [3]. 

GSK-2269557 is currently in Phase 2 clinical trials for chronic obstructive pulmonary disease (COPD) and asthma.

The activity of GSK-2269557 is as follows:

pIC₅₀ (PI3Kδ enzyme assay) = greater than 7

pK_i (PI3Kδ enzyme assay) = 9.9

Common Name: GSK-2269557

Synonyms: GSK-2269557; GSK2269557; GSK 2269557

IUPAC Name: 2-(6-(1H-indol-4-yl)-1H-indazol-4-yl)-5-((4-isopropylpiperazin-1-yl)methyl)oxazole

SMILES: 

CAS Number: 1254036-71-9; 1254036-77-5 (hydrochloride)

Mechanism of Action: Kinase Inhibitor; PI3K Inhibitor; PI3K delta Inhibitor

Indication: Treatment of COPD; Treatment of Asthma; Treatment of Autoimmune Diseases

Development Stage: Phase II

Company: GlaxoSmithKline

1H NMR (Estimated) for GSK-2269557

References:
1. Hamblin, J. N.; et. al. Oxazole substituted indazoles as pi3-kinase inhibitors. WO2010125082A1
2. Down, K.; et. al. Optimization of Novel Indazoles as Highly Potent and Selective Inhibitors of Phosphoinositide 3-Kinase d for the Treatment of Respiratory Disease. J Med Chem 2015, 58(18), 7381-7399.
3. Norman, P. Evaluation of WO2012032067 and WO2012055846: two selective PI3Kd inhibitors, which is GSK-2269557? Expert Opin Ther Pat 2012, 22(8), 965-970.

Drugs in Clinical Pipeline: GSK2636771 | PI3K Inhibitor | PI3Kbeta Inhibitor | Cancer Drug

GSK2636771 [2-methyl-1-(2-methyl-3-(trifluoromethyl)benzyl)-6-morpholino-1H-benzo[d]imidazole-4-carboxylic acid] is a potent, orally bioavailable and selective nanomolar inhibitor of the beta isoform of the 110 kDa catalytic subunit of class IA phosphoinositide-3 kinases (PI3K). GSK2636771 was more selective for PI3Kβ relative to other PI3K class I enzymes (IC₅₀: PI3Kβ = 0.89 nM) with greater than 900-fold selectivity over PI3Kα/PI3Kγ and more than 10-fold over PI3Kδ. It inhibits AKT phosphorylation and downstream signalling measured as decrease of PRAS40-, GSK3β-, and RPS6-phosphorylation in PTEN mutant cell lines [1].

GSK2636771: 2D and 3D Structure

The activity of GSK2636771 is as follows:

IC₅₀ (PI3Kβ enzyme assay) = 0.89 nM

Common Name: GSK2636771

Synonyms: GSK2636771; GSK-2636771; GSK 2636771

IUPAC Name: 2-methyl-1-(2-methyl-3-(trifluoromethyl)benzyl)-6-morpholino-1H-benzo[d]imidazole-4-carboxylic acid

CAS Number: 1372540-25-4

Mechanism of Action: Kinase Inhibitor; PI3K Inhibitor; PI3Kbeta Inhibitor

Indication: Various Cancers; Anti-Tumor Agents

Development Stage: Phase I/II
Company: GlaxoSmithKline

1H NMR (Estimated) for GSK2626771

References:
1. Arkenau, H. -T.; et. al. Abstract 2514: A phase I/II, first-in-human dose-escalation study of GSK2636771 in patients (pts) with PTEN-deficient advanced tumors. J Clin Oncol  2014, 32, (suppl).
2. Qu, J.; et. al. Benzimidazole derivatives as pi3 kinase inhibitors. WO2012047538A1 (For synthesis and activity see Example 31)

Drugs in Clinical Pipeline: Acalisib

Acalisib [(S)-2-(1-((7H-purin-6-yl)amino)ethyl)-6-fluoro-3-phenylquinazolin-4(3H)-one] is a potent, selective nanomolar inhibitor of the delta isoform of the 110 kDa catalytic subunit of class IA phosphoinositide-3 kinases (PI3K). 

Acalisib was more selective for PI3Kδ relative to other PI3K class I enzymes (IC₅₀: PI3Kδ = 12.7 nM; PI3Kα = 5441 nM; PI3Kβ = 3377 nM and PI3Kγ = 1389 nM). Acalisib was also 1000-fold more selective against PI3Kδ than against related kinases, such as CIIβ, hVPS34, DNAPK, and mammalian target of rapamycin (mTOR) [1].

Acalisib was also assayed for its potential binding interaction with kinases by screening a comprehensive panel of 393 kinases, including mutants, in the Ambit KINOMEscan. No binding outside of PI3K was observed at 10 µM Acalisib, further demonstrating a high degree of selectivity. Acalisib was considered active if less than 35% of binding to immobilized probes remained compared to DMSO control. Various PI3K isoforms have %control binding values in the 0.25-14 range. The next kinase target was PIP5K2B with a value of 49% [1].

Acalisib is under investigation for the treatment of lymphoid malignancies including non-Hodgkin lymphoma (NHL) and chronic lymphocytic leukemia (CLL) [2].

The activity of Acalisib is as follows:

IC₅₀ (PI3Kδ enzyme assay) = 12.7 nM

IC₅₀ (PI3Kα enzyme assay) = 5441 nM

IC₅₀ (PI3Kβ enzyme assay) = 3377 nM

IC₅₀ (PI3Kγ enzyme assay) = 1389 nM

IC₅₀ (DNA-PK enzyme assay) = 18.7 uM

IC₅₀ (mTOR enzyme assay) = greater than 1 uM

IC₅₀ (CIIβ enzyme assay) = greater than 1 uM

IC₅₀ (hVPS34 enzyme assay) = 12.6 uM

Common Name: Acalisib

Synonyms: GS-9820; GS9820; GS 9820; CAL-120; CAL 120; CAL120

IUPAC Name: (S)-2-(1-((7H-purin-6-yl)amino)ethyl)-6-fluoro-3-phenylquinazolin-4(3H)-one

CAS Number: 870281-34-8

Mechanism of Action: Kinase Inhibitor; PI3K Inhibitor; PI3Kdelta Inhibitor

Indication: Various Cancers; Anti-Tumor Agents; Autoimmune Disease Treatment

Development Stage: Phase I

Company: Gilead Sciences

References:
1. Shugg, R. P.; et. al. Effects of isoform-selective phosphatidylinositol 3-kinase inhibitors on osteoclasts: actions on cytoskeletal organization, survival, and resorption. J Biol Chem 2013, 288(49), 35346-35357.
2. Jun, S.; et. al. Interim Analysis Of A Phase 1B Study Evaluating The Safety Of GS-9820, A Second-Generation PI3Kd-Inhibitor, In Relapsed/Refractory Lymphoid Malignancies. 13th International Conference on Malignant Lymphoma. 17-20 June 2015 Lugano, Switzerland.

Drugs in Clinical Pipeline: VS-5584

VS-5584 [5-(9-isopropyl-8-methyl-2-morpholin-4-yl-9H-purin-6-yl)-pyrimidin-2-ylamine] is a novel low-molecular weight compound with high and equivalent potency against Mammalian target of Rapamycin (mTOR) and all Phosphoinositide 3-kinase (PI3K) class I isoforms but with no relevant activity for more than 400 lipid and protein kinases. VS-5584 is a potent inhibitor of mTOR (IC₅₀ = 37 nM) as well as class I PI3K isoforms (IC₅₀: PI3Kα = 16 nM; PI3Kβ = 68 nM; PI3Kγ = 25 nM; PI3Kδ = 42 nM). The Ambit full panel screening revealed that besides mTOR and the PI3K family, only NEK2 and BTK showed potential binding (less than 5%) of VS-5584. All other evaluated kinases showed negligible binding when tested up to 10 µM VS-5584. Further analysis of 320 kinases (including NEK2 and BTK) in a radiometric kinase assay platform showed that no kinase showed an IC₅₀ less than 300 nM except for the PIKK family [1].

VS-5584 shows robust modulation of cellular PI3K/mTOR pathways, inhibiting phosphorylation of substrates downstream of PI3K and mTORC1/2. A large human cancer cell line panel screen (436 lines) revealed broad antiproliferative sensitivity and that cells harboring mutations in PI3KCA are generally more sensitive toward VS-5584 treatment. VS-5584 exhibits favorable pharmacokinetic properties after oral dosing in mice and is well tolerated. VS-5584 induces long-lasting and dose-dependent inhibition of PI3K/mTOR signaling in tumor tissue, leading to tumor growth inhibition in various rapalog-sensitive and -resistant human xenograft models. Furthermore, VS-5584 is synergistic with an EGF receptor inhibitor in a gastric tumor model [1].

VS-5584, a novel purine analog, was generated with the aid of computational chemistry as a small-molecule ATP competitive inhibitor of PI3K and mTOR kinases with favorable pharmaceutical properties by S*BIO Pte Ltd (Singapore). It has been licensed to Verastem which now has patent protection of VS-5584 through 2029. VS-5584 has undergone IND-enabling testing and is in Phase 1 trial in patients with advanced cancer since the second half of 2013.

The activity of VS-5584 is as follows:

IC₅₀ (mTOR enzyme assay) = 37 ± 7 nM

IC₅₀ (PI3Kα enzyme assay) = 16 ± 3 nM

IC₅₀ (PI3Kβ enzyme assay) = 68 ± 9 nM

IC₅₀ (PI3Kγ enzyme assay) = 25 ± 5 nM

IC₅₀ (PI3Kδ enzyme assay) = 42 ± 8 nM

IC₅₀ (DNA-PK enzyme assay) = 1270 ± 321 nM

IC₅₀ (Vps34 enzyme assay) = 7470 ± 1300 nM

Common Name: VS-5584

Synonyms:  VS-5584; VS 5584; VS5584; SB2343; SB-2343; SB 2343

IUPAC Name: 5-(9-isopropyl-8-methyl-2-morpholin-4-yl-9H-purin-6-yl)-pyrimidin-2-ylamine

CAS Number: 1246560-33-7

Mechanism of Action: Kinase Inhibitor; Dual-Kinase Inhibitor; mTOR Inhibitor; PI3K Inhibitor

Indication: Various Cancers

Development Stage: Phase I

Company: S*BIO Pte Ltd/Verastem

In mammals, mTOR is the catalytic subunit in 2 distinct complexes, mTORC1 and mTORC2. mTORC1 controls cellular growth by integrating signals from growth factor receptors and intracellular nutrient status. mTORC2 is less well understood but plays a role in the regulation of cellular survival and cell migration. The mTOR signaling pathway has been suggested to be involved in multiple anticancer drug resistance mechanisms toward chemotherapeutics but also signal transduction inhibitors. Rapamycin and its analogs block mTORC1 activity and have shown single-agent activity in a small subsets of cancers. However, resistance has been shown to develop through activation of the PI3K signaling pathway including activation of mTORC2.

The phosphoinositide-3-kinase (PI3K) family of lipid kinases is involved in a diverse set of cellular functions, including cell growth, proliferation, motility, differentiation, glucose transport, survival, etc. PI3K’s can be categorized into class I, II, or III, depending on their subunit structure, regulation, and substrate selectivity. Class IA PI3K’s are activated by receptor tyrosine kinases and consist of a regulatory subunit (p85) and a catalytic subunit (p110). There are three catalytic isoforms: p110α, β, and δ. A single class IB PI3K, activated by GPCRs, consists of only one member: a p110γ catalytic subunit and a p101 regulatory subunit. The primary in vivo substrate of the class I PI3K’s is phosphatidylinositol (4,5) diphosphate (PtdIns(4,5)P2), which upon phosphorylation at the 3-position of the inositol ring to form phosphatidylinositol triphosphate (3,4,5)P3 (PIP3) serves as a second messenger by activating a series of downstream effectors that mediate the cellular functions mentioned above. The PI3K isoforms have different distributions and share similar cellular functions, which are context dependent. In particular, p110α pathway deregulation has been demonstrated in ovarian, breast, colon, and brain cancers. Hence, inhibitors targeting PI3K activities are major interest area for cancer treatment and therapy.

Important finding about VS5584:

Modulation of PI3K/mTOR signaling pathways by VS-5584: The effects of VS-5584 was tested in various cell lines such as PC3 (a prostate cancer cell line with PTEN deletion), MV4-11 cells (harboring FLT3-ITD), Colo205 (BRAF V600E, mTOR P1193L) and MDA-MB-231 (BRAF G464V, KRAS G13D). The researchers report that  data shows VS-5584 effectively permeates cells to modulate signaling pathways downstream of PI3K/mTOR independent of the genetic background of the cells.

VS-5584 potently blocks proliferation in a broad spectrum of tumor cells: As the PI3K/mTOR signaling pathway regulates important functional responses including cell proliferation, the effects of VS-5584 on a panel of 51 cancer cell lines derived from both liquid and solid tumors of human origin were investigated. Overall, VS-5584 showed high antiproliferative activity in a broad spectrum of cancer cells, with H929 (multiple myeloma) showing the highest sensitivity in our panel (IC₅₀ = 48 nM).

VS-5584 is efficacious in a PTEN^null human prostate PC3 xenograft model.

Therapeutic effects of VS-5584 in a rapamycin-resistant human colorectal COLO-205 xenograft model: a well-tolerated dose of VS-5584 blocks mTOR and PI3K signaling in tumor tissue and reduces the number of functional blood vessels in the tumor and is efficacious in a rapalog-resistant COLO-205 xenograft model.

VS-5584 is efficacious in a FLT3-ITD AML xenograft model: VS-5584 is also efficacious at low and well-tolerated dose in liquid tumor model, namely the FLT3-ITD harboring MV4-11 xenograft model.

VS-5584 is efficacious as a single agent and has synergistic effects in combination with an EGFRi in a gastric xenograft model.

VS-5584 has very good pharmacokinetic properties and effectively blocks mTORC1 and 2 as well as PI3K signaling in tumor tissue after once daily oral dosing. It is highly efficacious and well tolerated in all xenograft models tested so far, including models resistant to rapalogs and standard of care therapies [1].

VS-5584 potently inhibited survival and proliferation of established (A375, A-2058 and SK-MEL-3 lines) and primary human melanoma cells, but was non-cytotoxic to non-cancerous human skin keratinocytes and B10BR murine melanocytes. VS-5584 induced caspase-dependent apoptotic death in melanoma cells, and its cytotoxicity was alleviated by the caspase inhibitors. At the molecular level, VS-5584 blocked AKT-mTOR activation and downregulated cyclin D1 expression in melanoma cells, while the expressions of Bcl-xL and Bcl-2 were not affected by VS-5584 treatment [2]. VS-5584 failed to affect Bcl-xL and Bcl-2 expressions in tested melanoma cells. Importantly, the Bcl-xL/Bcl-2 inhibitor ABT-737, or siRNA-mediated knockdown of Bcl-xL/Bcl-2, remarkably enhanced the activity of VS-5584 against melanoma cells in vitro and in vivo.

References:
1. Hart, S.; et. al. VS-5584, a Novel and Highly Selective PI3K/mTOR Kinase Inhibitor for the Treatment of Cancer. Mol Cancer Ther 2013, 12(2), 151-161.
2. Shao, Z.; et. al. VS-5584, a Novel PI3K-mTOR Dual Inhibitor, Inhibits Melanoma Cell Growth In Vitro and In Vivo. PLoS One 2015, 10(7), e0132655.

Drugs in Clinical Pipeline: Buparlisib

Buparlisib [5-(2,6-dimorpholinopyrimidin-4-yl)-4-(trifluoromethyl)pyridin-2-amine] is an orally available pan-class I Phosphoinositide-3-kinase (PI3K) inhibitor. It does not significantly inhibit mTOR and is highly selective against other protein or lipid kinases. Buparlisib was identified upon optimization of drug-like and in vivo protein kinase properties from a 2-morpholino-6-aminopyridyl-pyrimidine scaffold [1].

Buparlisib is approximately equipotent against the class IA PI3Ks α, β, and δ (IC₅₀ = 52, 166 and 116 nM, respectively) and modestly less potent against the class IB γ isoform (IC₅₀ = 262 nM). The compound also shows comparable potency against activating p110α somatic mutations (IC₅₀ H1047R, E545K = 58 ± 2, 99 ± 6 nM, respectively) that have been described in a wide array of human cancers [1, 2].  

Buparlisib is significantly less potent in biochemical assays against the PI3K class III family member Vps34 (IC₅₀ = 2410 ± 150 nM), the related class IV PIKK protein kinases mTOR, ATR, (IC₅₀ = 2866 ± 1671, 8091 ± 2038 nM) and DNA-PK (IC₅₀ greater than 10), and the distinct lipid kinase PI4Kβ (IC₅₀ greater than 25) [1, 2]. 

Buparlisib was shown to be mostly inactive against all the kinases tested in an in-house selectivity panel with the exception of colony-stimulating factor 1 receptor (CSF1R, IC₅₀ = 582 nM). This inhibitory activity was confirmed at a concentration of 5 µM in the Invitrogen functional kinase panel but no effect was observed in a cell-based CSF1R autophosphorylation assay. Buparlisib was further profiled in the Ambit kinase competition panel, in which EphA2 and fibroblast growth factor receptor 2 (FGFR2) kinases were found to be inhibited by more than 90% at a concentration of 1 µM.

The pharmacological, biologic, and preclinical safety profile of Buparlisib supports its clinical development and the compound is undergoing phase II clinical trials in patients with cancer.

The activity of Buparlisib is as follows:

IC₅₀ (PI3Kα Filter binding assay; Kinase-Glo assay) = 52 ± 37 nM; 0.035 ± 0.017 uM

IC₅₀ (PI3Kβ Filter binding assay; Kinase-Glo assay) = 166 ± 29 nM; 0.175 ± 0.067 uM

IC₅₀ (PI3Kδ Filter binding assay; Kinase-Glo assay) = 116 nM; 0.108 ± 0.048 uM

IC₅₀ (PI3Kγ Filter binding assay; Kinase-Glo assay) = 262 ± 94 nM; 0.348 ± 0.013 uM

Common Name: Buparlisib

Synonyms:  NVP-BKM120; NVP BKM120; BKM120; BKM 120

IUPAC Name: 5-(2,6-dimorpholinopyrimidin-4-yl)-4-(trifluoromethyl)pyridin-2-amine

CAS Number: 944396-07-0

Mechanism of Action: Kinase Inhibitor; PI3K Inhibitor

Indication: Various Cancers

Development Stage: Phase II

Company: Novartis

The phosphoinositide-3-kinase (PI3K) family of lipid kinases is involved in a diverse set of cellular functions, including cell growth, proliferation, motility, differentiation, glucose transport, survival, etc. PI3K’s can be categorized into class I, II, or III, depending on their subunit structure, regulation, and substrate selectivity. Class IA PI3K’s are activated by receptor tyrosine kinases and consist of a regulatory subunit (p85) and a catalytic subunit (p110). There are three catalytic isoforms: p110α, β, and δ. A single class IB PI3K, activated by GPCRs, consists of only one member: a p110γ catalytic subunit and a p101 regulatory subunit. The primary in vivo substrate of the class I PI3K’s is phosphatidylinositol (4,5) diphosphate (PtdIns(4,5)P2), which upon phosphorylation at the 3-position of the inositol ring to form phosphatidylinositol triphosphate (3,4,5)P3 (PIP3) serves as a second messenger by activating a series of downstream effectors that mediate the cellular functions mentioned above. The PI3K isoforms have different distributions and share similar cellular functions, which are context dependent. In particular, p110α pathway deregulation has been demonstrated in ovarian, breast, colon, and brain cancers. Hence, inhibitors targeting PI3K activities are major interest area for cancer treatment and therapy [1, 2].

Consistent with its mechanism of action, Buparlisib decreases the cellular levels of p-Akt in mechanistic models and relevant tumor cell lines, as well as downstream effectors in a concentration-dependent and pathway-specific manner. Tested in a panel of 353 cell lines, Buparlisib exhibited preferential inhibition of tumor cells bearing PIK3CA mutations, in contrast to either KRAS or PTEN mutant models. Buparlisib shows dose-dependent in vivo pharmacodynamic activity as measured by significant inhibition of p-Akt and tumor growth inhibition in mechanistic xenograft models. Buparlisib behaves synergistically when combined with either targeted agents such as MEK or HER2 inhibitors or with cytotoxic agents such as docetaxel or temozolomide.

As found with other PI3K inhibitors, Buparlisib possesses strong antiangiogenic activity. Hence, highly angiogenic tumors could be very sensitive to the compound. Buparlisib could, therefore, be used efficiently as second line treatment upon failure of approved antiangiogenic drugs such as sutent, or sorafenib, in the case of metastatic renal cell carcinoma. Of interest is the fact that Buparlisib possesses excellent brain penetration, hence, there is the possibility to treat advanced nonresectable highly angiogenic GBM, mostly in combination with temozolomide-based therapies [1].

Target modulation and good pharmacokinetic and pharmacodynamic correlation was achieved with Buparlisib in tumor-bearing mice. Significant and dose-dependent antitumor activity was observed at dose levels sufficient to shut down the PI3K pathway, showing the strong relationship between compound concentration, pathway inhibition and efficacy. Suboptimal dose of Buparlisib was enough to strongly enhance the antitumor activity of standard of care (cytotoxic or targeted agents) in various cancer types such as prostate (with Taxotere), HER2-amplified breast cancer, or gastric cancer (with Herceptin/trastuzumab) and GBM (with temozolomide) [1].

Researchers tested the biologic effects of Buparlisib in a set of glioma cell lines. Buparlisib treatment for 72 hours resulted in a dose-dependent growth inhibition and effectively blocked the PI3K/Akt signaling cascade. Although they found no obvious relationship between the cell line's sensitivity to Buparlisib and the phosphatase and tensin homolog (PTEN) and epidermal growth factor receptor (EGFR) statuses, reserachers did observe a differential sensitivity pattern with respect to p53 status, with glioma cells containing wild-type p53 more sensitive than cells with mutated or deleted p53. Buparlisib showed differential forms of cell death on the basis of p53 status of the cells with p53 wild-type cells undergoing apoptotic cell death and p53 mutant/deleted cells having a mitotic catastrophe cell death [3].

In a review researchers have reported intense investigation of the potential biomarkers that explain response or resistance to buparlisib and inspire strategies to rationally explore the therapeutic potential of this drug with special emphasis on breast cancer [4].

References:

1. Burger, M. T.; et. al. Identification of NVP-BKM120 as a Potent, Selective, Orally Bioavailable Class I PI3 Kinase Inhibitor for Treating Cancer. ACS Med Chem Lett 2011, 2(10), 774–779.
2. Maira, S. M.; et. al. Identification and characterization of NVP-BKM120, an orally available pan-class I PI3-kinase inhibitor. Mol Cancer Ther 2012, 11(2), 317-328.
3. Koul, D.; et. al. Antitumor activity of NVP-BKM120--a selective pan class I PI3 kinase inhibitor showed differential forms of cell death based on p53 status of glioma cells. Clin Cancer Res 2012, 18(1), 184-195. (Kinase Glo assay data)
4. Geuna, E.; et. al. Buparlisib , an oral pan-PI3K inhibitor for the treatment of breast cancer. Expert Opin Investig Drugs 2015, 24(3), 421-431.

Drugs in Clinical Pipeline: AZD6482

AZD6482 [(R)-2-((1-(7-methyl-2-morpholino-4-oxo-4H-pyrido[1,2-a]pyrimidin-9-yl)ethyl)amino)benzoic acid] is a potent, selective and ATP competitive Phosphoinositide 3-Kinase β (PI3Kβ) inhibitor (IC₅₀ = 0.01 uM). PI3Kβ is given an important role in platelet adhesion and aggregation. AZD6482 showed a maximal anti-platelet effect at 1 uM in the in vitro and ex vivo tests both in dog and in man [1].

This novel isoform-selective inhibitor of PI3Kβ was originally developed as a racemic mixture named KN-309 (later AZ12379678) [2]. The racemate (AZ12379678) and the S-enantiomer (AZ12502334) were about three-fold (IC₅₀ = 0.03 uM) and greater than 200-fold (IC₅₀ = 2.3 uM) less potent inhibitor of PI3Kβ as compared with the R-enantiomer AZD6482, respectively. AZD6482 was assessed in functional assays against 88 protein kinases including the closely related PI3K-like protein kinases; DNA-dependent protein kinase (DNA-PK, IC₅₀ = 0.42 uM), ataxia telangiectasia mutated protein (ATM, IC₅₀ greater than 30 uM) and mammalian target of rapamycin (mTOR, IC₅₀ = 8 uM). The selective ratio was high (greater than 200-fold) with the exception of the other PI3K isoforms and one related protein kinase (DNA-PK), 8-08-fold, whereas ATM and mTOR displayed high selectivity in spite of also being PI3K like.

AZD6482 had a short plasma half-life owing to a high clearance and a relatively small distribution volume. With this profile, AZD6482 may be useful as a parenteral antiplatelet agent in situations where a low bleeding risk is desirable such as during acute stroke and cardiothoracic surgery.

The activity of AZD6482 is as follows:

IC₅₀ (PI3Kα enzyme assay) = 0.87 uM

IC₅₀ (PI3Kδ enzyme assay) = 0.08 uM

IC₅₀ (PI3Kβ enzyme assay) = 0.01 uM

IC₅₀ (PI3Kγ enzyme assay) = 1.09 uM

Common Name: AZD6482

Synonyms: AZD6482; AZD-6482; AZD 6482; KN-309; KN309; KN 309

IUPAC Name: (R)-2-((1-(7-methyl-2-morpholino-4-oxo-4H-pyrido[1,2-a]pyrimidin-9-yl)ethyl)amino)benzoic acid

CAS Number: 1173900-33-8

Mechanism of Action: Kinase Inhibitor; PI3K Inhibitor; PI3Kβ Inhibitor

Indication: Anti-platelet Therapy; Treatment for Strokes

Development Stage: Phase I

Company: AstraZeneca

Phosphoinositide 3-kinases (PI3Ks) are lipid kinases that phosphorylate the D3 hydroxyl group of membrane phosphoinositides (PIs). They are divided into three distinct classes (Class I, II and III) based on their primary structure, mode of regulation and substrate specificity. Class I PI3Ks are heterodimers with a catalytic (p110α, β, γ and δ) and a regulatory subunit (p85 or p101). They are involved in signal transduction through tyrosine kinase receptors and G protein-coupled receptors and are responsible for agonist-induced production of the second messenger phosphatidylinositol (3,4,5)trisphosphate (PIP3) by phosphorylation of the 3-position in the inositol ring of phosphatidylinositol (4,5)bisphosphate (PIP2) using ATP as a phosphate donor.

PI3Kα and β are ubiquitously expressed whereas PI3Kδ is mainly expressed in leukocytes and PI3Kγ in leukocytes, platelets and cardiomyocytes. PI3Ks have been attributed a central role in cell signaling from a number of receptors involved in proliferation, motility, immune system function etc. Insulin signaling is also modulated through PI3Ks, which promotes glucose uptake and lipogenesis. The literature indicates that the effect on insulin signaling is mediated via PI3Kα but a minor role for PI3Kβ cannot be excluded.

Platelets contain all class I isoforms (α, β, γ and δ) although the levels of PI3Kδ are very low. The role of the individual PI3K isoforms in regulating platelet functional responses has started to be defined during the recent years and PI3Kβ has been attributed the most prominent role of the four. Inhibition of PI3Kβ has been shown to inhibit thrombus formation in different in vivo models without significantly affecting primary hemostasis [1].

AZD6482 potently inhibited Akt(Ser 473) phosphorylation in adenocarcinoma MDA-MB- 468 cells (IC₅₀ = 0.04 uM).

The human anti-platelet potency of AZD6482 was evaluated in a number of in vitro assays using several agonists. The most potent effect was seen on shear induced platelet adhesion and aggregation. In this assay, 5 uM AZD6482 appears not to inhibit primary adhesion but has a strong effect on aggregate formation. The racemate, AZ12379678, had about 25% the potency of AZD6482, close to the theoretical 50%, using ADP as an agonist (impedance aggregometry) whereas the S-enantiomer, AZ12502334, was inactive with no inhibition detected at concentrations less than 10 uM. AZD6482 was also evaluated in vitro in dog and rat blood using ADP-induced impedance aggregometry. AZD6482 was more potent in human blood than in dog and rat blood with IC₅₀ values of 0.27, 1.4 and 1.8 uM in human, dog and rat blood, respectively. Protein binding in man, dog and rat was 8%, 10% and 11% free unbound, respectively. In vivo in dog, AZD6482 produced a complete antithrombotic effect without significantly compromising hemostasis as no increase in bleeding time or blood loss was seen at plasma exposure that achieved a full anti-thrombotic effect, 1 uM. The anti-platelet effect measured ex vivo in dog directly mirrors the antithrombotic effect in vivo and full inhibition of both occurred at approximately 1 uM plasma exposure [1].

References:

1. Nylander, S.; et. al. Human target validation of phosphoinositide 3-kinase (PI3K)β: effects on platelets and insulin sensitivity, using AZD6482 a novel PI3Kß inhibitor. J Thromb Haemost 2012, 10(10), 2127-2136.

2. Jackson, S. P.; et. al. Preparation of morpholinyl- and pyridinyl-substituted heterobicyclic ketones as selective inhibitors of phosphoinositide 3- kinase b for use against thrombosis. WO2004016607

3. ClinicalTrials.gov Study to Investigate Safety and Tolerability of a Single Dose of AZD6482. NCT00688714 (retrieved on 01-07-2015).

4. ClinicalTrials.gov Bleeding Time Study With AZD6482, Clopidogrel and ASA. NCT00853450 (retrieved on 01-07-2015).

Idelalisib I Kinase Inhibitor | PI3Kdelta Inhibitor | Treatment of Chronic Lymphocytic Leukemia | Treatment of Follicular B-cell Non-Hodgkin Lymphoma | Treatment of Small Lymphocytic Lymphoma

Common name: Idelalisib; CAL-101; CAL 101; CAL101; GS-1101; GS 1101; GS1101; Zydelig

Trademarks: Zydelig

Molecular Formula: C22H18FN7O

CAS Registry Number: 870281-82-6

CAS Name: 5-Fluoro-3-phenyl-2-[(1S)-1-(7H-purin-6-ylamino)propyl]-4(3H)-quinazolinone

Molecular Weight: 415.42 g/mol

SMILES:CCC(C1=NC2=C(C(=CC=C2)F)C(=O)N1C3=CC=CC=C3)NC4=NC=NC5=C4NC=N5

InChI Key: IFSDAJWBUCMOAH-HNNXBMFYSA-N

InChI: InChI=1S/C22H18FN7O/c1-2-15(28-20-18-19(25-11-24-18)26-12-27-20)21-29-16-10-6-9-14(23)17(16)22(31)30(21)13-7-4-3-5-8-13/h3-12,15H,2H2,1H3,(H2,24,25,26,27,28)/t15-/m0/s1

Mechanism of Action: Protein Kinase Inhibitor; Kinase Inhibitor; PI3K Inhibitor; PI3Kdelta Inhibitor; Antineoplastic Drugs 

Indication: Various Cancers; Treatment of Chronic Lymphocytic Lymphoma (CLL); Treatment of Follicular B-cell non-Hodgkin Lymphoma (FL); Treatment of Small Lymphocytic Lymphoma (SLL) 

Status: Launched 2014 (US, EU)

Originator: Calistoga Pharmaceuticals/Gilead

Idelalisib: 2D and 3D Structure

Idelalisib as Medicine:

The first-in-class Phosphatidylinositol-3-kinase p110δ (PI3Kδ) inhibitor Idelalisib (Zydelig) is approved in the treatment of chronic lymphocytic leukemia (CLL) and for 2 types of lymphoma in patients who have relapsed after previous treatment. The US Food and Drug Administration (FDA) granted a full approval for Idelalisib in relapsed CLL, specifically for its use in combination with rituximab (Rituxan) in patients for whom rituximab alone would be considered appropriate therapy due to other existing medical conditions (comorbidities).

The approval of this indication was based on a placebo-controlled trial in 220 patients that was stopped early for benefit. The first prespecified interim analysis showed a significantly longer progression-free survival in patients treated with idelalisib plus rituximab (10.7 months) compared with those on placebo plus rituximab (5.5 months). Results from a second interim analysis continued to show a statistically significant improvement, the FDA noted [1].

The other two approved for indications are:

Follicular B-cell non-Hodgkin Lymphoma (FL) when the disease has come back after treatment with at least two prior medicines.

Small Lymphocytic Lymphoma (SLL) when the disease comes back after treatment with at least two prior medicines.

Idelalisib had both breakthrough therapy designation and orphan drug designation.

The FDA also granted accelerated approval for Idelalisib for use in relapsed follicular B-cell non-Hodgkin's lymphoma (FL) and relapsed small lymphocytic lymphoma (SLL), another type of non-Hodgkin's lymphoma. Idelalisib is intended to be used in patients who have received at least 2 prior systemic therapies. These lymphoma patients had become refectory to both rituximab and alkylating agents but when treated with Idelalisib, the results showed an overall response rate of 54% in patients with relapsed FL and 58% in patients with SLL [2].

Idelalisib [5-fluoro-3-phenyl-2-[(S)-1-(9H-purin-6-ylamino)-propyl]-3H-quinazolin-4-one] is an oral, highly selective and potent small molecule inhibitor of Phosphatidylinositol-3-kinase p110δ (PI3Kδ). Idelalisib was 40- to 300-fold more selective for p110d relative to other PI3K class I enzymes (IC₅₀ p110δ = 2.5 nM; p110α, p110β, and p110γ IC₅₀ were 820, 565, and 89 nM, respectively). Greater selectivity (400- to 4000-fold) was seen against related kinases C2β, mTOR (IC₅₀ for both greater than 1000 nM), hVPS34, DNA-PK (IC₅₀ = 978, 6729 nM, respectively), whereas no activity was observed against a panel of 402 diverse kinases at 10µM. Idelalisib is currently under clinical evaluation in patients with B-cell malignancies [3].

In cell-based assays, Idelalisib had 240- to 2500-fold selectivity for PI3Kδ over the other class I PI3K isoforms. The following results highlight this selectivity:

In fibroblasts, the receptor tyrosine kinase platelet-derived growth factor receptor signals through p110α and the G-protein–coupled receptor for lysophosphatidic acid (LPA) signals through p110 β. Researchers stimulated murine embryonic fibroblasts with PDGF or LPA and monitored phosphorylation of Akt to measure pathway activation. Idelalisib reduced PDGF-induced pAkt by only 25% at 10 µM, whereas the positive control, PI-103, had a half-maximal effective concentration (EC₅₀) of 90 nM. Idelalisib inhibited LPA-induced pAkt with an EC₅₀ of 1.9 µM.

Expression of p110δ and p110γ is normally restricted to leukocytes. In basophils, FcεRI signals through p110δ, whereas formyl-methionyl-leucyl-phenylalanine (fMLP) signals through G-protein-coupled receptor- p110γ, and activation through either stimulus results in surface expression of CD63 that can be monitored by flow cytometry. CAL-101 blocked FcεRI p110δ-mediated CD63 expression with an EC₅₀ of 8 nM, whereas formyl-methionyl-leucyl-phenylalanine activation of p110γ was inhibited with an EC₅₀ of 3.0 µM.

Idelalisib as Chemical Compound:

Idelalisib is a quinazolinone derivative. Specifically it is a quinazolin-4-one molecule with a purine unit present in it. Other important chemical classifications are:

1. Fluoro compound

2. Purine derivatives

3. Quinazolin-4-one derivatives

4. Quinazolinones

5. Alkylhalides

Side-Effects

Common laboratory abnormalities include neutropenia, hypertriglyceridemia, hyperglycemia, and elevated levels of liver enzymes. Common adverse effects include diarrhea, pyrexia, fatigue, nausea, cough, pneumonia, abdominal pain, chills, and rash. Idelalisib carries a boxed warning alerting patients/healthcare professionals of fatal and serious toxicities that can occur, including liver toxicity, diarrhea and colon inflammation (colitis), lung inflammation (pneumonitis), and intestinal perforation.

References:

1. Furman, R. R.; et. al. Idelalisib and rituximab in relapsed chronic lymphocytic leukemia. N Engl J Med 2014, 370(11), 997-1007.

2. Keating, G. M.; et. al. Idelalisib: a review of its use in chronic lymphocytic leukaemia and indolent non-Hodgkin's lymphoma. Target Oncol 2015, 10(1), 141-151.

3. Lannutti, B. J.; et. al. CAL-101, a p110d selective phosphatidylinositol-3-kinase inhibitor for the treatment of B-cell malignancies, inhibits PI3K signaling and cellular viability. Blood 2011, 117(2), 591-594.
4. FDA approves Zydelig for three types of blood cancers. Food and Drug Administration. July 23, 2014.
5. European Medicines Agency recommends approval of two new treatment options for rare cancers. European Medicines Agency. July 25, 2014.

Drugs in Clinical Pipeline: Gedatolisib

Gedatolisib [1-(4-(4-(dimethylamino)piperidine-1-carbonyl)phenyl)-3-(4-(4,6-dimorpholino-1,3,5-triazin-2-yl)phenyl)urea] is an exceptionally potent, selective, ATP-competitive, and reversible dual Phosphoinositide 3-kinase (PI3K)/mTOR inhibitor. It is administered intravenously.

Gedatolisib suppressed phosphorylation of PI3K/mTOR effectors (e.g., Akt), and induced apoptosis in human tumor cell lines with elevated PI3K/mTOR signaling. MDA-MB-361 [breast; HER2+, PIK3CA mutant (E545K)] was particularly sensitive to this effect, with cleaved PARP, an apoptosis marker, induced by 30 nM of Gedatolisib PKI-587 at 4 hours.

In vitro, Gedatolisib potently inhibited class I PI3Ks (IC₅₀ PI3K-α = 0.4 nM, PI3K-β = 60 nM, PI3K-γ = 60 nM), PI3K-α mutants (IC₅₀ E545K = 0.6 nM, H1047R = 0.8 nM), and mTOR (IC₅₀ = 10 nM). Gedatolisib inhibited growth of 50 diverse human tumor cell lines at IC₅₀ values of less than 100 nM.

The activity of Gedatolisib is as follows:

IC₅₀ (PI3K-α enzyme assay) = 0.4 nM

IC₅₀ (PI3K-β enzyme assay) = 60 nM

IC₅₀ (PI3K-γ enzyme assay) = 60 nM

IC₅₀ (mTOR enzyme assay) = 10 nM

Common Name: Gedatolisib

Synonyms:  PKI-587; PF-05212384; PF05212384; PF 05212384; PF5212384

IUPAC Name: 1-(4-(4-(dimethylamino)piperidine-1-carbonyl)phenyl)-3-(4-(4,6-dimorpholino-1,3,5-triazin-2-yl)phenyl)urea

CAS Number: 1197160-78-3

SMILES:O=C(NC1=CC=C(C2=NC(N3CCOCC3)=NC(N4CCOCC4)=N2)C=C1)NC5=CC=C(C(N6CCC(N(C)C)CC6)=O)C=C5

Mechanism of Action: Kinase Inhibitor; PI3K Inhibitor; mTOR Inhibitor; Dual-Kinase Inhibitor

Indication: Various Cancers; Treatment of Solid Tumors

Development Stage: Phase I

Company: Pfizer

Class 1 phosphoinositide 3-kinases (PI3K) play a key role in the biology of human cancer. The gene encoding the PI3K-α isoform (PIK3CA) is amplified or mutated in a wide range of cancers. Aberrantly elevated PI3K/Akt/mTOR pathway signaling has been implicated in poor prognosis and survival in patients with lymphatic, breast, prostate, lung, glioblastoma, melanoma, colon, and ovarian cancers. In addition, PI3K/Akt/mTOR pathway activation contributes to resistance of cancer cells to both targeted anticancer therapies and conventional cytotoxic agents. An effective inhibitor of the PI3K/Akt/mTOR pathway could prevent cancer cell proliferation and induce programmed cell death [1].

Gedatolisib, a potent pan–class I phosphoinositide 3-kinase (PI3K)/mTOR inhibitor, showed single-agent efficacy in multiple preclinical tumor models. Tumor regression was observed in several models. This effect was most pronounced against MDA-MB-361 (breast), which has elevated HER2 levels and mutant PI3K-α. Preclinical data suggest utility of PKI-587 in the treatment of cancers with elevated PI3K/mTOR signaling, including those resistant to agents that target HER2 or epidermal growth factor (EGF) receptors (EGFR).PKI-587 efficacy was enhanced when combined with a MEK1,2 kinase inhibitor (PD0325901), or irinotecan in a colon tumor model (HCT116) with mutant K-Ras. PKI-587 showed single-agent efficacy against a non–small cell lung cancer model (H1975) with mutant EGFR (L858R/T790M), and this activity was also enhanced when combined with the irreversible HER2 kinase inhibitor, HKI-272 [1].

Gedatolisib showed single-agent efficacy in both xenograft and orthotopic versions of the H1975 [NSCLC; EGFR (L858R/T790M)] model. In H1975 xenografts, continuous dosing of PKI-587 (at >5 mg/kg) caused early time point tumor regression. In the H1975 orthotopic model, 25 mg/kg PKI-587 (weekly) kept (9 of 10) treated mice alive, whereas all control mice (10 of 10) were dead by day 40. This suggests that PKI-587 could be used against lung tumors that have acquired resistance to EGFR inhibitors such as Iressa or Tarceva.

Phase I Study in Patients with Advanced Cancer

The part 1 of this open-label phase I study was designed to estimate the maximum-tolerated dose (MTD) in patients with nonselected solid tumors, using a modified continual reassessment method to guide dose escalation. Objectives of part 2 were MTD confirmation and assessment of preliminary activity in patients with selected tumor types and PI3K pathway dysregulation [3].

Methodology and Findings

Seventy-seven of the 78 enrolled patients received treatment. The MTD for Gedatolisib, administered intravenously once weekly, was estimated to be 154 mg. The most common treatment-related adverse events (AE) were mucosal inflammation/stomatitis (58.4%), nausea (42.9%), hyperglycemia (26%), decreased appetite (24.7%), fatigue (24.7%), and vomiting (24.7%). The majority of patients treated at the MTD experienced only grade 1 treatment-related AEs. Grade 3 treatment-related AEs occurred in 23.8% of patients at the MTD. No treatment-related grade 4-5 AEs were reported at any dose level. Antitumor activity was noted in this heavily pretreated patient population, with two partial responses (PR) and an unconfirmed PR. Eight patients had long-lasting stable disease (greater than 6 months). Pharmacokinetic analyses showed a biphasic concentration-time profile for Gedatolisib (half-life, 30-37 hours after multiple dosing). Gedatolisib inhibited downstream effectors of the PI3K pathway in paired tumor biopsies.

Results

Gedatolisib has potential to advance into further clinical development for patients with advanced solid malignancies.

References:

1. Mallon, R.; et. al. Antitumor efficacy of PKI-587, a highly potent dual PI3K/mTOR kinase inhibitor. Clin Cancer Res 2011, 17(10), 3193-3203.
2. Venkatesan, A. M.; et. al. Bis(morpholino-1,3,5-triazine) derivatives: potent adenosine 5'-triphosphate competitive phosphatidylinositol-3-kinase/mammalian target of rapamycin inhibitors: discovery of compound 26 (PKI-587), a highly efficacious dual inhibitor. J Med Chem 2010, 53(6), 2636-2645. (synthesis)
3. Shapiro, G. I.; et. al. First-in-Human Study of PF-05212384 (PKI-587), a Small-Molecule, Intravenous, Dual Inhibitor of PI3K and mTOR in Patients with Advanced Cancer. Clin Cancer Res 2015, 21(8), 1888-1895.
4. ClinicalTrials.gov  Study of PF-05212384 (Also Known as PKI-587) Administered Intravenously To Subjects With Solid Tumors (B2151001). NCT00940498 (retrieved 19-05-2015)
5. ClinicalTrials.gov Investigation Of The Metabolism, And Excretion Of [14c]-PF-05212384 In Healthy Male Volunteers. NCT02142920 (retrieved 19-05-2015)
6. ClinicalTrials.gov A Study Of PF-05212384 In Combination With Other Anti-Tumor Agents. NCT01920061 (retrieved 19-05-2015)