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: Vistusertib | mTOR Inhibitors | Kinase Inhibitors

Vistusertib [3-[2,4-Bis((3S)-3-methylmorpholin-4-yl)pyrido[5,6-e]pyrimidin-7-yl]-N-methylbenzamide] is an oral, potent and selective dual mTORC1/mTORC2 inhibitor with clear activity in in vivo and in vitro experimental models. It is under clinical trials against various cancers as monotherapy as well in combination with other anti-cancer agents such as Estrogen Receptor Positive (ER+) Metastatic Breast Cancer, Metastatic Renal Cancer, Glioblastoma Multiforme, Ovarian Cancer etc [1, 2].

Vistusertib: 2D and 3D Structure

mTOR as Target for Cancer Treatment

Growth factor/mitogenic activation of the phosphatidylinositol 3-kinase (PI3K)/AKT signalling pathway ultimately leads to the key cell cycle and growth control regulator mTOR, the mammalian target of rapamycin (alternatively referred to as FRAP (FKBP 12 and rapamycin associated protein), RAFTl (rapamycin and FKBP12 target 1), RAPTl (rapamycin target 1) - all derived from the interaction with the FK-506-binding protein FKBP 12, and SEP (sirolimus effector protein)) [3]. 

mTOR is a mammalian serine/threonine kinase of approximately 289 kDa in size and a member of the evolutionary conserved eukaryotic TOR kinases. The mTOR protein is a member of the PB-kinase like kinase (PIKK) family of proteins due to its C-terminal homology (catalytic domain) with PI3-kinase and the other family members, e.g. DNA-PKcs (DNA dependent protein kinase), ATM (Ataxia- telangiectasia mutated).

PI3K-Akt-mTOR pathway is one of the most frequently dysregulated pathways in cancer. The mammalian target of rapamycin (mTOR) is a key target in the development of antitumor therapies. The finding that mTOR can exist in an alternative, rapamycin insensitive, complex that signals to Akt opened up a new line of thinking for the researchers. The existence of both a rapamycin sensitive complex (mTORC1) and a rapamycin insensitive complex (mTORC2) may provide an explanation for the differences observed in the earlier research works. Rapamycin and its analogues have been shown to activate AKT signaling as a consequence of inhibition of the negative feedback loop downstream of mTORC1. Moreover, this is associated with a shorter time to progression in glioblastoma patients treated with rapamycin suggesting that dual mTORC1 and 2 inhibitors that inhibit AKT signaling could offer greater clinical benefit compared with rapalogues. In addition, dual mTORC1 and mTORC2 inhibitors may exhibit a broader spectrum of clinical activity [2].

 Vistusertib as mTOR Inhibitor

Vistusertib is a potent inhibitor of mammalian target of rapamycin (mTOR) kinase (IC₅₀ = 0.0028 uM) and displays a high level of selectivity against other members of the PIKK family (IC₅₀ PI3Kα = 3.8 uM, PI3Kβ, γ, δ greater than 29 uM, respectively). It was inactive against a general panel of over 200 kinases when tested at 10 uM. In in vivo studies, Vistusertib has been shown to modulate downstream markers of mTORC1 (inhibition of pS6 at Ser235/236 IC₅₀ = 0.2 uM) and mTORC2 (inhibition of pAKT at Ser473 IC₅₀ = 0.08 uM). Moreover, it has shown dose-dependent tumor growth inhibition in a mouse MCF7 xenograft model alongside modulation of mTORC1 and mTORC2 biomarkers.

Vistusertib showed excellent aqueous solubility (more than 600 uM), margin to the hERG (IC₅₀ = 47.5 uM) and was shown to have good oral exposure in both rat (100%) and mouse (40%). Vistusertib shows consistent exposure in rodents and a low turnover in human hepatocyte incubations and was subsequently selected for clinical development. Vistusertib is currently in Phase I/II [1, 2].

Dosages and Approvals:

Vistusertib (Tradename: -) is discovered and developed by Kudos Pharmaceuticals, later aquired by AstraZeneca. It is still under clinical trials.

Reported Activities for Vistusertib

IC₅₀ (mTOR enzyme assay) = 2.8 nM

IC₅₀ (PI3Kα enzyme assay) = 3.8 uM

IC₅₀ (PI3Kβ enzyme assay) = greater than 30 uM

IC₅₀ (PI3Kγ enzyme assay) = greater than 30 uM 

IC₅₀ (PI3Kδ enzyme assay) = greater than 29 uM

Summary

Common name: AZD2014; AZD-2014; AZD 2014; Vistusertib

Trademarks: -

Molecular Formula: C25H30N6O3

CAS Registry Number: 1009298-59-2

CAS Name: 3-(2,4-bis((S)-3-methylmorpholino)pyrido[2,3-d]pyrimidin-7-yl)-N-methylbenzamide

Molecular Weight: 462.54

SMILES:C[C@@H](COCC1)N1C2=NC(N3[C@@H](C)COCC3)=NC4=NC(C5=CC(C(NC)=O)=CC=C5)=CC=C42

InChI Key: JUSFANSTBFGBAF-IRXDYDNUSA-N

InChI: InChI=1S/C25H30N6O3/c1-16-14-33-11-9-30(16)23-20-7-8-21(18-5-4-6-19(13-18)24(32)26-3)27-22(20)28-25(29-23)31-10-12-34-15-17(31)2/h4-8,13,16-17H,9-12,14-15H2,1-3H3,(H,26,32)/t16-,17-/m0/s1

Mechanism of Action: Kinase Inhibitors; Dual mTOR Inhibitor

Activity: Various Cancers; Treatment for Breast Cancer; Anti-Cancer Agents

Status: Phase Trials (US)

Chemical Class: Small-molecules; Benzamides; Morpholines; Pyridines; Pyrimidines

Originator: AstraZeneca

Vistusertib Synthesis

WO2008023161A1: It is the oldest reported synthetic procedure for preparing quantitative amounts of Vistusertib and derivatives. The process involves sequential addition of 3S-Methylmorpholine at C4 and C2 position of trichloro intermediate, followed by using suitable boronic acid (or esters) via palladium mediated cross couplings to generate compounds. See also Ref 2.

Identifications:

1H NMR (Estimated) for Vistusertib

Sideeffects: The adverse events (AEs) were gastrointestinal symptoms such as nausea, mucositis, diarrhea and vomiting in 21/41 (51%), 20/41 (49%) 17/41 (42%), and 12/41 (29%) as reported by participants. However, less than 5% of these adverse events were grade 3 or 4. Nausea and vomiting were well controlled by antiemetics, such as domperidone, if necessary, and the grade 1-2 diarrhea did not consistently require treatment. Mucositis was grade 1-2 in most instances and patients responded to mouth-washes and did not require dose interruptions due to it. A predominantly maculopapular rash was observed in 17/41 (42%) of patients and less than 5% of these were grade 3 or higher. Lower respiratory tract infections were seen in 7/41 (17%) and it was grade 3 in only 1/41 (2%). Interestingly, no patients were diagnosed with pneumonitis.

The most common laboratory abnormality was anemia, with 7/41 (17%) having recorded grade 1-2 anemia; given the advanced cancer and degrees of co-morbidities in these patients, it was difficult to attribute this specifically to AZD2014. Hyperglycemia was seen in 5/41 (12%), 0/5 (0%), and 2/4 (50%) of patients treated at 50 mg BD, 70 mg BD and 100 mg BD, respectively [4].

Others: Readers can suggest.

References:

1. Guichard, S. M.; et. al. AZD2014, an Inhibitor of mTORC1 and mTORC2, Is Highly Effective in ER+ Breast Cancer When Administered Using Intermittent or Continuous Schedules. Mol Cancer Ther 2015, 14(11), 2508-2518. (free article)

2. Pike, K. G.; et. al. Optimization of potent and selective dual mTORC1 and mTORC2 inhibitors: the discovery of AZD8055 and AZD2014. Bioorg Med Chem Lett 2013, 23(5), 1212-1216. (FMO only)

3. Duggan, H. M. E.; et. al. 2-methylmorpholine pyrido-, pyrazo- and pyrimido-pyrimidine derivatives as mtor inhibitors. WO2008023161A1

4. Basu, B.; et. al. First-in-Human Pharmacokinetic and Pharmacodynamic Study of the Dual m-TORC 1/2 Inhibitor AZD2014. Clin Cancer Res 2015, 21(15), 3412-3419. (free article)

1 2 3

Drugs in Clinical Pipeline: ABTL0812

ABTL0812 [sodium 2-hydroxylinoleate] is an orally available lipid analogue that hits two clinically validated targets: mTOR and DHFR.  Both these clinically validated targets are responsible for the cytotoxic effect of ABTL0812: mTOR (mammalian target of rapamycin), as shown by the dramatic reduction in S6 phosphorylation, and dihydrofolate reductase (DHFR), as shown by its reduced expression, resulting in autophagic cell death. Moreover, the compound's cellular potency increases with incubation time, and it has a long lasting cytotoxic effect after removing the compound from the incubation medium. This multi-target property increases antitumor efficacy and reduces drug resistance. In addition, preliminary in vivo results indicate that the potential therapeutic margin will be high [1].

ABTL0812 has cytotoxic effect on a wide range of human tumor cell lines, including those which have become resistant to standard therapy. ABTL0812 molecular targets were identified by in silico analysis, comparing ABTL0812 chemical structure against a database including more than one million receptor-ligand interaction data. Functional relevance of the targets was confirmed biochemically and pharmacologically. ABTL0812 mechanism of action was established using human lung and pancreatic tumor cells, MEF KO cells, as well as tumor xenografts.

In silico screening showed that ABTL0812 binds four targets which regulate tumor progression through Akt/mTOR axis. Two of them are the transcription factors PPARα and PPARγ (Peroxisome-Proliferator Activating Receptors). In lung and pancreatic tumor cells ABTL0812 activated PPARα/γ-dependent gene transcription, while pharmacological inhibition with PPARα/γ antagonists impaired ABTL0812 cytotoxic effect. Interestingly, ABTL0812 induced transcription of the endogenous Akt inhibitor TRIB3 (tribbles homologue 3) through PPARα/γ activation. TRIB3 is a pseudokinase that inhibits Akt by direct binding and preventing its phosphorylation by mTORC2 complex. According to this, ABTL0812-induced TRIB3 overexpression resulted in inhibition of Akt phosphorylation, impaired phosphorylation of the Akt substrates TSC2 and PRAS40 and mTORC1 inhibition (pS6), which in turn promoted autophagy-mediated tumor cell death. MEF TRIB3-/- cells were resistant to ABTL0812-induced cell death, indicating that TRIB3 mediates ABTL0812 cytotoxicity. Finally, Akt inhibition was observed in human lung and pancreatic tumor xenograft models treated with ABTL0812 and in human platelets incubated with ABTL0812. This supported the rational for using Akt phosphorylation as a pharmacodynamic biomarker to monitor activity of ABTL0812 in patients included in the Clinical Trial [2].

ABTL0812 was originally developed by Lipopharma and has been licensed to Ability Pharmaceuticals. In Aug 2015 Ability Pharmaceuticals, received orphan drug designation from the U.S. FDA for ABTL0812 in the treatment of neuroblastoma.  The European Medicines Agency (EMA) granted ABTL0812 orphan drug status in April 2015 for the same indication. Neuroblastoma is a rare type of cancer originated from nerve cells and is the most common solid tumor outside the brain in children.  The prognosis for high-risk neuroblastoma cases is poor with no effective treatment.

Common Name: ABTL0812

Synonyms: ABTL0812; ABTL 0812; ABTL-0812

IUPAC Name:  Sodium 2-hydroxylinoleate

CAS Number: -

SMILES:

Mechanism of Action: Kinase Inhibitor; MTOR Inhibitor; AKT Inhibitor; DHFR Inhibitor; Dihydrofolate Reductase Inhibitor

Indication: Various Cancers; Treatment of Neuroblastoma

Development Stage: Phase I

Company: Lipopharma/Ability Pharma

References:

1. Alfon, J.; et. al. Abstract 922: ABTL0812: A new drug class with oral antitumor action inhibiting mTOR activity and DHFR expression. Cancer Res 2012, 72, 922.

2. Gomez-Ferreria, M.; et. al. Abstract 672: ABTL0812, a new antitumor drug that inhibits the axis Akt/mTOR through a novel mechanism of action. Cancer Res 2015, 75, 672.
3. Escriba, R. P. V.; et. al. Use of polyunsaturated fatty acid derivatives as medicaments WO2010106211A1

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: AZD3147

AZD3147 [(S)-1-(4-(4-(1-(cyclopropylsulfonyl)cyclopropyl)-6-(3-methylmorpholino) pyrimidin-2-yl)phenyl)-3-(2-hydroxyethyl)thiourea] is an extremely potent and selective dual inhibitor of mTORC1 and mTORC2 (IC₅₀ mTOR = 0.0015 uM).

AZD3147 has a high degree of selectivity over the PI3K isoforms (PI3K-α,β,δ,γ IC₅₀ = 0.92, 5.5, 9.4, 6.3 uM) and against a general panel of kinases (only 2 hits with greater than 50% inhibition when tested at 10 µM against a panel of 98 kinases). AZD3147 inhibits both mTORC1 and mTORC2 substrates in cells (IC₅₀ mTOR = 0.006 uM), does not appear to inhibit CYP enzymes when tested at concentrations up to 10 µM, and shows no activity against the hERG (human ether-a-go-go-related gene) ion channel (IC₅₀ greater than 100 µM).

Astrazeneca discovered AZD3147 using SAR studies on urea derivatives. Bioavailability of AZD3147 together with its encouraging physicochemical properties resulted in the selection of this compound for preclinical development [1].

Common Name: AZD3147

Synonyms:  AZD3147; AZD-3147; AZD 3147

IUPAC Name: (S)-1-(4-(4-(1-(cyclopropylsulfonyl)cyclopropyl)-6-(3-methylmorpholino) pyrimidin-2-yl)phenyl)-3-(2-hydroxyethyl)thiourea

CAS Number: 1101810-02-9

SMILES:S=C(NCCO)NC1=CC=C(C2=NC(N3[C@@H](C)COCC3)=CC(C4(S(=O)(C5CC5)=O)CC4)=N2)C=C1

Mechanism of Action: Kinase Inhibitor; mTOR Inhibitor

Indication: Various Cancers; Anti-tumor Therapy

Development Stage: Investigational

Company: AstraZeneca

The mammalian target of rapamycin (mTOR), a serine/theronine kinase of approximately 289 kDa in size, is a member of the evolutionary conserved eukaryotic PI3K-related kinase (PIKK) family of atypical protein kinases which also include the protein kinases DNA-PK (DNA dependent protein kinase), ATM (ataxia-telangiectasia mutated) and ATR (ataxiatelangiectasia and Rad3 related). mTOR is a key target in the development of antitumor therapies. Activated by growth factor/mitogenic stimulation activation of the phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway, mTOR is a central regulator of cell growth and proliferation. This PI3K-Akt-mTOR pathway is one of the most frequently dysregulated pathways in cancer [1].

References:
1. Pike, K. G.; et. al. Discovery of AZD3147: A Potent, Selective Dual Inhibitor of mTORC1 and mTORC2. J Med Chem 2015, 58(5), 2326–2349.

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)

Drugs in Clinical Pipeline: Omipalisib

Omipalisib [2,4-difluoro-N-(2-methoxy-5-(4-(pyridazin-4-yl)quinolin-6-yl)pyridin-3-yl)benzenesulfonamide] is a highly potent and selective inhibitor of class I Phosphoinositide 3-kinases (PI3Ks) and the mammalian target of rapamycin (mTOR). 

SAR studies on GSK1059615 eventually led to the identification of Omipalisib, an extraordinarily potent inhibitor of PI3Kα (p110α/p85α) with low picomolar activity (PI3Kα IC₅₀ = 0.04 nM). In biochemical assays, Omipalisib is significantly more potent than GSK1059615 (PI3Kα IC₅₀ = 2 nM) and is the most potent PI3Kα inhibitor reported to date. Omipalisib  is being evaluated in a phase I, open-label, dose-escalation study in subjects with solid tumors or lymphoma.

Omipalisib is also a low picomolar inhibitor of the common activating mutants of p110α (E542K, E545K, and H1047R, K_i = 0.008, 0.008 and 0.009 nM) found in human cancer. Similar to the other reported PI3K inhibitors, Omipalisib is also active against the other class I PI3K isoforms (β, γ, and δ).

The activity of Omipalisib is as follows:

K_i (p110α) = 0.019 nM

K_i (p110β) = 0.13 nM

K_i (p110γ) = 0.024 nM

K_i (p110δ) = 0.06 nM

Common Name: Omipalisib

Synonyms:  GSK-2126458; GSK2126458; GSK 2126458

IUPAC Name: 2,4-difluoro-N-(2-methoxy-5-(4-(pyridazin-4-yl)quinolin-6-yl)pyridin-3-yl)benzenesulfonamide

CAS Number: 1086062-66-9

Mechanism of Action: Kinase Inhibitor; PI3K Inhibitor; PI3Kα Inhibitor, MTOR Inhibitor

Indication: Various Cancers; Solid Tumors

Development Stage: Phase I

Company: GlaxoSmithKline

The phosphoinositide 3-kinase (PI3K) signaling pathway is activated in a broad spectrum of human cancers. Activation of this pathway often occurs indirectly by the activation of receptor tyrosine kinases or the inactivation of the phosphotase and tensin homologue (PTEN) tumor suppressor. Direct activation of PI3K has been demonstrated with the discovery of several activating mutations in the PIK3CA gene itself, the gene that encodes the p110α catalytic subunit of PI3KR. Several of the mutations found in PIK3CA have been shown to increase the lipid kinase activity of PI3KR, induce activation of signaling pathways, and promote transformation of cells both in vitro and in vivo. Furthermore, the PI3K pathway is the most commonly mutated signaling pathway in human cancers. The PI3K family of enzymes is comprised of 15 lipid kinases with distinct substrate specificities, expression patterns, and modes of regulation. In particular, PI3KR has emerged as an attractive target for cancer therapeutics, and several PI3K inhibitors are currently under evaluation in human clinical trials.

Omipalisib shows excellent selectivity over protein kinases (greater than10,000-fold vs more than 240 kinases evaluated) with the notable exception of the class IV PI3K family. mTOR, a class IV PI3K protein kinase, is a central regulator of cell growth and exists in two functional complexes, mTORC1 and mTORC2. mTORC2 is proposed to regulate AKT S473 phosphorylation, and its inhibition is believed to augment the antiproliferative efficacy of a PI3K inhibitor by dual inhibition of the PI3K/AKT pathway. The kinase domain of mTOR is homologous to the p110α catalytic subunit of the class I PI3Ks, and Omipalisib is a potent inhibitor of both mTOR complexes with subnanomolar activity (K_i mTORC1, mTORC2 = 0.18, 0.3 nM). Omipalisib is also a potent inhibitor of the class IV PI3 kinase, DNA-PK (IC₅₀ = 0.28 nM).

Omipalisib induces a G1 cell cycle arrest and inhibits cell proliferation in a large panel of cell lines, including T47D and BT474 breast cancer lines. The PK profile of Omipalisib was studied in four preclinical species (mouse, rat, dog, and monkey). The compound showed low blood clearance and good oral bioavailability. In addition, Omipalisib had minimal potential to inhibit the human cytochrome P450 isoforms [1].

Omipalisib induced morphologic changes in four tumors (two invasive ductal carcinomas, one invasive lobular carcinoma, and one ovarian dysgerminoma), intracellular caspase-3 activity in three tumors (two invasive ductal carcinomas and one poorly differentiated signet ring adenocarcinoma of gastric origin), and immunohistochemical evidence of apoptosis in at least four tumors (three invasive ductal carcinomas and one adenocarcinoma of gastric origin). Two tumors (ovarian serous carcinoma and moderately differentiated adenocarcinoma of colorectal origin) demonstrated no treatment effect [2].

References:

1. Knight, S. D.; et. al. Discovery of GSK2126458, a Highly Potent Inhibitor of PI3K and the Mammalian Target of Rapamycin. ACS Med Chem Lett 2010, 1(1), 39-43.
2. Albawardi, A.; et. al. Cancer Cell Int 2014, 14(1), 90.
3. ClinicalTrials.gov Dose-Escalation Study of GSK2126458 (FTIH). NCT00972686 (retrieved 05-05-2015)
4. ClinicalTrials.gov A Proof of Mechanism Study With GSK2126458 in Patients With Idiopathic Pulmonary Fibrosis (IPF). NCT01725139 (retrieved 05-05-2015)

Drugs in Clinical Pipeline: GNE-317

GNE-317 [5-(6-(3-methoxyoxetan-3-yl)-4-morpholinothieno[3,2-d]pyrimidin-2-yl)pyrimidin-2-amine] is a dual PI3K/mTOR inhibitor with excellent blood-brain barrier penetration. Physicochemical properties of PI3K inhibitors were optimized using in silico tools, leading to the identification of GNE-317. The compound was tested in cells overexpressing P-glycoprotein (P-gp) or breast cancer resistance protein (BCRP). 

GNE-317 was identified as having physicochemical properties predictive of low efflux by P-gp and BCRP. Studies in transfected MDCK cells showed that GNE-317 was not a substrate of either transporter. GNE-317 markedly inhibited the PI3K pathway in mouse brain, causing 40% to 90% suppression of the pAkt and pS6 signals up to 6-hour postdose. GNE-317 was efficacious in the U87, GS2, and GBM10 orthotopic models, achieving tumor growth inhibition of 90% and 50%, and survival benefit, respectively.

Genentech is developing GNE-317. The efficacy of GNE-317 in 3 intracranial models of Glioblastoma (GBM) suggests that this compound could be effective in the treatment of GBM, either as a single agent or in combination therapy.

Common Name: GNE-317

Synonyms:  GNE-317; GNE 317; GNE317

IUPAC Name: 5-(6-(3-methoxyoxetan-3-yl)-4-morpholinothieno[3,2-d]pyrimidin-2-yl)pyrimidin-2-amine

CAS Number: 1394076-92-6

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

Indication: Various Cancers; Glioblastomas

Development Stage: Investigational

Company: Genentech Inc.

PI3K and GBM

The phosphatidylinositol 3-kinase (PI3K) pathway plays a key role in cell survival, growth and proliferation. The lipid kinases belonging to the PI3K family phosphorylate the 3'-hydroxyl group of phophatidylinositols, which lead to the activation of the serine/threonine protein kinase Akt. Further downstream effectors include the mTOR complex 1 and S6 kinase. From the 3 classes of PI3K, class Ia is the most widely involved in cancer and its kinases are composed of a catalytic (p110a, p110b, or p110d) and a regulatory subunit (p85 or p55). The phophatase PTEN acts as a tumor suppressor and inhibits PI3K pathway signaling.

PI3K deregulation, through activating mutations of the p110a catalytic subunit or suppression of PTEN, has been associated with the development of numerous cancers. More specifically, alteration of this pathway has been detected in more than 80% of glioblastoma (GBM). GBM is the most common and aggressive primary tumor of the central nervous system (CNS) in adults. This high grade glioma, characterized by rapid growth and diffuse invasiveness, presents very few treatment options. Tumor progression is controlled only for a limited time with a median survival duration of less than 2 years after initial diagnosis. Key signaling proteins of the PI3K pathway are mutated in a large proportion of GBM, leading to persistent activation of the pathway; EGFR amplification and/or mutation, mutation of the PI3K catalytic and regulatory subunits, and loss of PTEN protein are detected in 45%, 10%, and 50% of GBM, respectively. Thus, targeting the PI3K pathway represents an attractive therapeutic approach for brain tumors.

Inhibitors of mTOR, a key mediator of PI3K signaling, have been evaluated in Phase I and II clinical trials as single agents or in combination with receptor tyrosine kinase inhibitors with limited success. These compounds, analogues of rapamycin, mostly target mTORC1. This in turn can trigger a feedback loop, possibly through mTORC2, which results in the activation of Akt. The disappointing results with rapalogues may also be attributed to the failure of the drugs to fully access their target. These 2 points underscore the potential improvement in activity that could be achieved with dual PI3K/mTOR inhibitors (mTORC1 and mTORC2) as well as the challenge in crossing the blood-brain barrier (BBB) and overcoming the protective effect of efflux transporters to reach the brain and tumors with anticancer agents [1].

GNE-317 and GBM

The marked inhibition of the PI3K pathway in the brain of mice with intact BBB, evidenced by the significant suppression of the PI3K and mTOR markers pAkt, p4EBP1, and pS6, suggested that GNE-317 could be efficacious in intracranial tumors driven by activation of this pathway. Studies in the U87 and GS2 orthotopic models of GBM showed that GNE-317 could reduce tumor volumes by 90% and 50%, respectively [1].

References:

1. Salphati, L.; Targeting the PI3K pathway in the brain--efficacy of a PI3K inhibitor optimized to cross the blood-brain barrier. Clin Cancer Res 2012, 18(22), 6239-6248.