p110α (Ki = 0.019 nM); p110α-E545K (Ki = 0.008 nM); p110α-E542K (Ki = 0.008 nM); p110α-H1047R (Ki = 0.009 nM); p110β (Ki = 0.13 nM); p110δ (Ki = 0.024 nM); p110γ (Ki = 0.06 nM); mTORC1 (Ki = 0.18 nM); mTORC2 (Ki = 0.3 nM)

GSK2126458 potently inhibits the activity of common activating mutants of p110α (E542K, E545K, and H1047R) found in human cancer with Ki of 8 pM, 8 pM and 9 pM, respectively.[1] GSK2126458 significantly lowers the levels of pAkt-S473 in T47D and BT474 cells with a remarkable potency, with IC50 values of 0.41 nM and 0.18 nM, respectively. Additionally, GSK2126458 causes a G1 cell cycle arrest and has an inhibitory effect on cell proliferation in a variety of cell lines, including the T47D and BT474 breast cancer lines with IC50 values of 3 nM and 2.4 nM, respectively.[1]

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These studies eventually led to the identification of Omipalisib/1, an extraordinarily potent inhibitor of PI3Kα (p110α/p85α) with low picomolar activity (PI3Kα IC50 = 0.04 nM). In biochemical assays, compound 1 is significantly more potent than 2 (PI3Kα IC50 = 2 nM) and is the most potent PI3Kα inhibitor reported to date. In comparison with other clinical PI3K inhibitors, 1 is ∼100-fold more potent than BEZ235 (IC50 = 6 nM) and GDC-0941 (IC50 = 9 nM) and ∼1000-fold more active than XL-765 (IC50 = 39 nM). Importantly, 1 is also a low picomolar inhibitor of the common activating mutants of p110α (E542K, E545K, and H1047R) found in human cancer (Table 3). Similar to the other reported PI3K inhibitors, 1 is also active against the other class I PI3K isoforms (β, γ, and δ). [1]

Compound 1/Omipalisib shows excellent selectivity over protein kinases (>10,000-fold vs >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. (25) 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 1 is a potent inhibitor of both mTOR complexes with subnanomolar activity (Table 4). Compound 1 is also a potent inhibitor of the class IV PI3 kinase, DNA-PK (IC50 = 0.28 nM).[1]

A cocrystal structure of PI3Kγ in complex with 1/Omipalisib shows the inhibitor bound in the ATP-binding site of the enzyme (Figure 3). The structure was determined to 2.7 Å resolution and shows, like 6e, that the pyridyl nitrogen forms a key hydrogen bond with the conserved water molecule. The sulfonamide interacts with Lys833, making a strong charged interaction. On the basis of the pKa of the sulfonamide-NH (6.56), ∼87% of the moiety exists in its deprotonated form at physiological pH. This charged interaction may help to explain the superior potency of 1 as compared to the other reported PI3K inhibitors. In addition, the difluorophenyl group fills a hydrophobic region in the back pocket of the enzyme, while the quinoline nitrogen forms an interaction with the hinge (Val882).[1]

In mechanistic cellular assays, 1/Omipalisib caused a significant reduction in the levels of pAKT-S473 with remarkable potency (Table 5). Consistent with its activity against both PI3Kα and mTOR, 1 also inhibits phosphorylation of AKT-T308 and p70S6K at low nanomolar concentrations (data not shown). Compound 1 induces a G1 cell cycle arrest and inhibits cell proliferation in a large panel of cell lines, including T47D and BT474 breast cancer lines. [1]

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Inhibition of MAPK and PI3K/mTOR pathways enhances cell growth inhibition in the acquired resistant clones [2]
Although the combination of GSK2118436 and GSK1120212 profoundly inhibited proliferation of the resistant clones, phosphorylation of S6P was not inhibited completely. Because S6P phosphorylation can be induced by activation of the PI3K/mTOR pathway, we evaluated the combination of GSK2118436 or GSK1120212 with Omipalisib/GSK2126458 (PI3K/mTOR inhibitor). All clones displayed modest sensitivity cell growth inhibition by GSK2126458 (Table 1). GSK2126458 treatment of representative resistant clones decreased AKT phosphorylation and had minimal effect on S6P phosphorylation (Fig. 5A). Omipalisib/GSK2126458 in combination with GSK2118436 or GSK1120212 reduced S6P phosphorylation in the resistant clones, whereas GSK2118436 or GSK1120212 alone was sufficient to reduce S6P phosphorylation in A375. The reduction in pS6P with either GSK2118436 or GSK1120212 in combination with GSK2126458 was greater than the reduction observed with the GSK2118436 and GSK1120212 combination. MEK and ERK phosphorylation was similar to treatment with GSK2118436 or GSK1120212 alone. Cleaved PARP and caspase-3/7 activity, indicators of apoptosis, were increased slightly by GSK2126458 in combination with either GSK2118436 or GSK1120212 in clones 16R6-4 and 16R6-2, although basal apoptosis levels were higher in all of the resistant clones compared with A375 (Fig. 5A and data not shown). The addition of GSK2118436 to GSK2126458 enhanced cell growth inhibition (EOSHA >10 ppts) in 5/7 clones with NRAS mutations and the 2 clones harboring MEK1K59del (Table 1). The combination of GSK1120212 and GSK2126458 was synergistic (CI <0.8) in 8/9 clones and enhanced cell growth inhibition (EOSHA >20 ppts) in all 9 clones regardless of NRAS or MEK1 mutation (Table 1). Long-term proliferation assays confirmed the enhancement of growth inhibition by the combination of GSK2118436 or GSK1120212 with GSK2126458 (Fig. 5B). In general, the resistant clones were more sensitive to cell growth inhibition with the combination of GSK2126458 and GSK1120212 at the concentrations used; however, appreciable activity was also observed with 1 μmol/L GSK2118436 and 0.03 μmol/L Omipalisib/GSK2126458. The antiproliferative effect of GSK2118436 in combination with GSK2126458 was not as potent as that observed with the GSK2118436 and GSK1120212 combination, or the GSK1120212 and GSK2126458 combination. Benefits were observed for these combinations in the YUSIT1 GSK2118436–resistant clones, although the combination of GSK2126458 with GSK2118436 or GSK1120212 was moderately synergistic to nearly additive in these clones (Supplementary Table S1).

In a BT474 human tumor xenograft model, Omipalisib/GSK2126458 treatment reduces pAkt-S473 levels in a dose-dependent manner and inhibits tumor growth in a dose-dependent manner at a low dose of 300 μg/kg. The oral bioavailability of GSK2126458 is also good in four preclinical species (mouse, rat, dog, and monkey), and its blood clearance is low.[1]

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In an in vivo setting, Omipalisib/1 exhibited a dose-dependent reduction in pAKT-S473 levels in human BT474 tumors implanted in mice. In the study, designed to measure the magnitude and duration of the pharmacodynamic (PD) response, mice were treated orally with drug, and pAKT levels were determined over the course of 24 h. Following a single 300 μg/kg dose, 1 showed a profound and sustained PD response over the 10 h observation period with pAKT levels returning to those of control by 24 h (Figure 4). Remarkably, the sustained PD response was achieved with very low circulating levels of drug, consistent with the high in vitro potency of 1.[1]

Compound 1/Omipalisib was also evaluated in a BT474 human tumor xenograft growth efficacy model where mice were administered a single oral dose five times per week for 3 weeks. Consistent with inhibition of the PI3K/AKT/mTOR pathway, the drug exhibited dose-dependent tumor growth inhibition (Figure 5). The top dose (3 mg kg−1) was well-tolerated in the study. As reported previously, compound 2 exhibited efficacy in BT474 xenografts following twice daily dosing at 25 mg kg−1. In comparison, compound 1 exhibited similar efficacy at a much lower dose and less frequent administration. [1]

HTRF In vitro Profiling Assays for PI3K Inhibition [1]
The PI3-Kinase profiling assays were developed to measure the compound-dependent inhibition of the alpha, beta, delta, and gamma isoforms of PI3Kin an in vitro catalytic assay. This assay was developed and optimized from a kit produced by Upstate. Briefly, this procedure utilizes a pre-formed HTRF (Homogeneous Time-Resolved Fluorescence energy transfer) complex between four binding partners: 1) biotinylated PIP3, 2) GST tagged pleckstrin homology (PH) domain, 3) Europium labeled anti-GST monoclonal antibody, and 4) StreptavidinAllophycocyanin (APC). The native PIP3 produced by PI 3-Kinase activity displaces biotin-PIP3 from the PH domain, resulting in the dissociation of the HTRF complex and a decrease in the fluorescence signal. The format of this assay is the same for all 4 isoforms of PI3K; the differences lie in the concentration of enzyme used to achieve the most robust signal. The alpha and delta assays are run at 400pM enzyme; the beta assay is at 200pM enzyme and the gamma assay is run at 1nM enzyme. In addition, the alpha, beta and delta assays are run with 150mM NaCl while the gamma assay is run in the absence of NaCl. The ATP concentration is 100uM in the alpha, beta, and delta assays and 15uM ATP in the gamma assay. All reactions are run at 10uM PIP2.

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The Multidrop Combi is used to add 2.5 μL of stop solution (Stop A and Stop B pre-mixed at a ratio of 5:1, respectively) to all wells in order to quench reactions. The quenched reactions are then processed to identify product formation by adding 2.5 μL of detection solution using the Multidrop Combi (Detection mix C, Detection mix A, and Detection mix B combined together in an 18:1:1 ratio, i.e., for a 6000 μL total volume, mix 5400 μL Detection mix C, 300 μL Detection mix A, and 300 μL Detection mix B). Please take note that this solution needs to be prepared two hours before use. The HTRF signal is measured on the Envision plate reader set for 330nm excitation after an hour of dark incubation.

BT474, HCC1954 and T-47D (human breast) are cultured in RPMI-1640 containing 10% fetal bovine serum at 37 °C in 5% CO2 incubator. Prior to assay setup, cells are divided into T75 flasks at a density that results in 70–80% confluence at the time of assay harvest. Trypsin-EDTA 0.25% is used to harvest cells. Utilizing Trypan Blue exclusion staining, cell counts are carried out on cell suspension. Then, cells are plated in 384-well black flat-bottom polystyrene dishes with 1,000 cells per well and 48 μL of culture medium per dish. GSK2126458 is added the following day after all plates have been overnighted at 5% CO2, 37 °C. One plate is given a CellTiter-Glo treatment for a day 0 (t=0) measurement and read as per the instructions below. GSK2126458 is made in 384 well clear bottom polypropylene plates using successive two fold dilutions. 2 μL of these dilutions are added to each well of the cell plates after 4 μL of these dilutions are added to 105 μL of culture media and the solution is mixed. The final DMSO concentration in each well is 0.15%. 72 hours are spent incubating the cells at 37 °C and 5% CO2. Each plate is developed and read 72 hours after being incubated with GSK2126458. Using a volume equal to the cell culture volume in the wells, CellTiter-Glo reagent is added to assay plates. After about 30 minutes of incubation at room temperature and two minutes of shaking, the plates are read using the Analyst GT reader for the chemiluminescent signal. Results are plotted against the concentration of GSK2126458 and expressed as a percentage of the t=0. For GSK2126458, the concentration (gIC50) that inhibits 50% of the cell growth with Y min as the t=0 and Y max as the DMSO control is determined by fitting the dose response with a 4 or 6 parameter curve fit using the XLfit software. For background correction, the value from wells without cells is subtracted from all samples.

Human BT474 tumors implanted in mice.
≤300 μg /kg
Administered via p.o.

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The pharmacokinetics of 1 (free base) were studied following single intravenous and/or oral administration to the male mouse, rat, dog and monkey. The IV and PO solution formulations contained 40% (v/v) PEG-400, 16% (w/v) encapsin in saline and water, respectively. The pH was adjusted to within 3.0-4.0 for the mouse, rat, dog and monkey solutions. Oral bioavailability was estimated using a cross-over study design for the dog and monkey (n = 3). Oral bioavailability in the rat was estimated using crossover (n = 1) and non-crossover (n = 2) designs and a non-crossover serial design was employed in the mouse (n = 2 IV and n = 3 PO). Blood samples were assayed for Omipalisib (GSK2126458, GSK458) using protein precipitation with acetonitrile followed by HPLC/MS/MS analysis employing positive-ion Turbo IonSpray ionization. Blood concentration-time data were analyzed by non-compartmental methods. Mouse and rat data reported as mean ± range. Dog and monkey data reported as mean ± standard deviation. [1]

The PK profile of 1/Omipalisib was studied in four preclinical species (mouse, rat, dog, and monkey). The compound showed low blood clearance and good oral bioavailability (Table 6). In addition, 1 had minimal potential to inhibit the human cytochrome P450 isoforms (IC50 > 25 μM vs CYPs 3A4, 1A2, 2C9, 2C19, and 2D6). [1]

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Pharmacokinetic analyses for Omipalisib[3]
Following single daily dosing, the median tmax ranged from 1 to 4 hours. Mean AUC0–24hrs and Cmax increased approximately in proportion with doses from 0.1 to 0.4 mg daily and then from 0.75 mg to 3.0 mg/day but not across the whole dose range (Supplementary Table S1 and Fig. 1A). As expected due to accumulation of OmipalisibGSK458, the mean AUC0–12hrs and Cmax were generally higher following the second dose versus the first dose with the twice-daily dosing schedule. The average time spent > 20 ng/mL (the target dose level based on preclinical data) was greater with twice-daily than once-daily dosing (21.2 hours at 2 mg twice daily vs. 14.5 hours at the once-daily MTD of 2.5 mg; Fig. 1B). The terminal T1/2 and AUC0–>∞ could not be determined due to the large %AUC extrapolation in >20% of patients. Because of between-subject variability, pharmacokinetic values overlapped across doses.

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The study results also highlight the importance of pharmacokinetic/pharmacodynamic data to define the optimal biologic dose in a first-in-patient study of a targeted anticancer therapy. Pharmacokinetic/pharmacodynamic modeling using mouse BT474 xenografts yielded a sustained mean target serum concentration of >20 ng/mL as the expected IC67 for AKT phosphorylation with range of 6.6 to 60 ng/mL to account for potential translation differences between mice and humans. Pharmacokinetic data from the daily dosing schedule suggested that the target serum concentration of >20 ng/mL was not being sustained over a 24-hour interval. In addition, significant interpatient variability in drug exposure was observed across the once-daily dosing levels. These two factors likely contributed to the lack of dose- and exposure-dependent effect observed in the pharmacodynamic analyses with daily dosing of Omipalisib/GSK458 and may have impacted the observed antitumor activity. The twice-daily dosing schedule achieved more consistent serum levels above the target exposure. Whether twice-daily dosing of GSK458 translates into more effective target inhibition and enhanced antitumor activity requires further clinical evaluation as pharmacodynamic analyses were nearly entirely limited to the once-daily dosing cohort and the MTD was not reached with twice-daily dosing.[3]

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GSK458/Omipalisib was fairly well tolerated. The frequency of adverse events appeared to be similar with once-daily versus twice-daily dosing. Diarrhea was a common clinical event; however, it was largely grade 1–2 in severity for most patients, with grade 3 diarrhea (>7 stools above baseline/day) observed in 8% of enrolled patients. Diarrhea appeared to be self-limiting and responsive to temporary dose interruptions and resolved in more than 80% of patients at the time of last study reporting. Hyperglycemia, a class effect (and potential pharmacodynamic biomarker) of PI3K pathway inhibition, was observed in 18% of patients on study and was mostly grade 1–2 in severity. Hyperglycemia was commonly managed with oral agents (e.g., metformin); the initiation of insulin during protocol therapy was a rare event. Other class effects of PI3K pathway inhibition were observed, including rash and mucositis, both managed effectively with temporary dose holds and/or initiation of topical steroid treatment. Interestingly, in contrast to other PI3K inhibitors such as BKM120, effects on mood were uncommon, suggesting potentially a differential penetration across the blood–brain barrier or other off-target differences in receptor inhibition.[3]

Determination of MTD for Omipalisib In the once-daily dose-escalation part of the study, 8 dose levels were explored (Table 3). The first DLT (grade 3 diarrhea) occurred at the 1.5 mg once-daily dose. This cohort was expanded without further dose limiting events. Three DLTs (all grade 3 diarrhea events) occurred at the 3 mg once-daily dose level, rendering this the nontolerated dose (NTD). Patients were subsequently treated at dose levels of 2 mg and 2.5 mg once daily without any observed DLTs, establishing 2.5 mg as the MTD with once daily dosing schedule.
Because of the observation of a shorter duration of Omipalisib/GSK458 drug levels above target range with daily dosing, twice-daily dose escalation was initiated at a dose of 0.75 mg twice daily, and 5 dose levels were studied (Table 3). No DLTs were observed at the 2 mg twice-daily dose level. One of the three patients experienced a DLT (grade 3 fatigue + grade 3 rash) at 2.5 mg twice daily; however, due to the decision to discontinue single-agent testing of GSK458, further patients were not treated at this dose level; and therefore, the MTD with twice-daily dosing could not be determined.

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Safety results for Omipalisib The most common adverse events (any grade severity) experienced on study were fatigue (45%), diarrhea (45%), nausea (42%), decreased appetite (30%), and vomiting (26%; Table 4). The most common grade ≥ 3 adverse events included diarrhea (8%), hyperglycemia (>250 mg/dL; 6%), and skin rash (5%). Nine patients (5%) experienced a treatment-related serious adverse event, including four patients with diarrhea. Diarrhea appeared to be an intermittent, self-limiting event for most patients, with resolution reported in 82% of patients. Rash was noted in 21 patients (12%), with most patients experiencing a single occurrence (81%). The most common type of rash was maculopapular in appearance; acneiform rash was rare (2 patients). Hyperglycemia was noted in 37 patients (22%), was mostly grade 1 or 2 in severity, and did not require dose adjustment in the majority of patients (92%). Cardiac toxicity was minimal with 2 (1%) patients experiencing post-baseline decreases in ejection fraction below the lower limit of normal and >10% from baseline. There were no significant effects on mood noted. There were no treatment-related grade 5 adverse events.

[1]. 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]. Combinations of BRAF, MEK, and PI3K/mTOR inhibitors overcome acquired resistance to the BRAF inhibitor GSK2118436 dabrafenib, mediated by NRAS or MEK mutations. Mol Cancer Ther. 2012 Apr;11(4):909-20.

[3]. First-in-Human Phase I Study of GSK2126458, an Oral Pan-Class I Phosphatidylinositol-3-Kinase Inhibitor, in Patients with Advanced Solid Tumor Malignancies. Clin Cancer Res. 2016 Apr 15;22(8):1932-9.

Omipalisib is a member of the class of quinolines that is quinoline which is substituted by pyridazin-4-yl and 5-[(2,4-difluorobenzene-1-sulfonyl)amino]-6-methoxypyridin-3-yl groups at positions 4 and 6, respectively. It is a highly potent inhibitor of PI3K and mTOR developed by GlaxoSmithKline and was previously in human phase 1 clinical trials for the treatment of idiopathic pulmonary fibrosis and solid tumors. It has a role as an autophagy inducer, an EC 2.7.1.137 (phosphatidylinositol 3-kinase) inhibitor, a mTOR inhibitor, an antineoplastic agent, a radiosensitizing agent and an anticoronaviral agent. It is a member of quinolines, a difluorobenzene, a sulfonamide, an aromatic ether, a member of pyridines and a member of pyridazines.
Omipalisib has been used in trials studying the treatment of CANCER, Solid Tumours, and Idiopathic Pulmonary Fibrosis.
Omipalisib is a small-molecule pyridylsulfonamide inhibitor of phosphatidylinositol 3-kinase (PI3K) with potential antineoplastic activity. Omipalisib binds to and inhibits PI3K in the PI3K/mTOR signaling pathway, which may trigger the translocation of cytosolic Bax to the mitochondrial outer membrane, increasing mitochondrial membrane permeability and inducing apoptotic cell death. Bax is a member of the proapoptotic Bcl2 family of proteins. PI3K, often overexpressed in cancer cells, plays a crucial role in tumor cell regulation and survival.

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Phosphoinositide 3-kinase α (PI3Kα) is a critical regulator of cell growth and transformation, and its signaling pathway is the most commonly mutated pathway in human cancers. The mammalian target of rapamycin (mTOR), a class IV PI3K protein kinase, is also a central regulator of cell growth, and mTOR inhibitors are believed to augment the antiproliferative efficacy of PI3K/AKT pathway inhibition. 2,4-Difluoro-N-{2-(methyloxy)-5-[4-(4-pyridazinyl)-6-quinolinyl]-3-pyridinyl}benzenesulfonamide (Omipalisib/GSK2126458, 1) has been identified as a highly potent, orally bioavailable inhibitor of PI3Kα and mTOR with in vivo activity in both pharmacodynamic and tumor growth efficacy models. Compound 1 is currently being evaluated in human clinical trials for the treatment of cancer.[1]

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In conclusion, we report the discovery of 1/Omipalisib, a structurally novel inhibitor of the PI3K/AKT/mTOR signaling pathway with picomolar activity against PI3Kα and mTOR. Compound 1 displays remarkable potency in both mechanistic and antiproliferative cellular assays. Compound 1 also exhibits excellent in vivo activity, highlighted by a sustained PD effect at very low circulating drug levels. Inhibition of the PI3K/AKT/mTOR pathway is expected to have a beneficial effect on cancer therapy, and 1 has been advanced into a phase I, open-label, dose-escalation study in subjects with solid tumors or lymphoma.[1]

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Recent results from clinical trials with the BRAF inhibitors GSK2118436 (dabrafenib) and PLX4032 (vemurafenib) have shown encouraging response rates; however, the duration of response has been limited. To identify determinants of acquired resistance to GSK2118436 and strategies to overcome the resistance, we isolated GSK2118436 drug-resistant clones from the A375 BRAF(V600E) and the YUSIT1 BRAF(V600K) melanoma cell lines. These clones also showed reduced sensitivity to the allosteric mitogen-activated protein/extracellular signal-regulated kinase (MEK) inhibitor GSK1120212 (trametinib). Genetic characterization of these clones identified an in-frame deletion in MEK1 (MEK1(K59del)) or NRAS mutation (NRAS(Q61K) and/or NRAS(A146T)) with and without MEK1(P387S) in the BRAF(V600E) background and NRAS(Q61K) in the BRAF(V600K) background. Stable knockdown of NRAS with short hairpin RNA partially restored GSK2118436 sensitivity in mutant NRAS clones, whereas expression of NRAS(Q61K) or NRAS(A146T) in the A375 parental cells decreased sensitivity to GSK2118436. Similarly, expression of MEK1(K59del), but not MEK1(P387S), decreased sensitivity of A375 cells to GSK2118436. The combination of GSK2118436 and GSK1120212 effectively inhibited cell growth, decreased ERK phosphorylation, decreased cyclin D1 protein, and increased p27(kip1) protein in the resistant clones. Moreover, the combination of GSK2118436 or GSK1120212 with the phosphoinositide 3-kinase/mTOR inhibitor Omipalisib/GSK2126458 enhanced cell growth inhibition and decreased S6 ribosomal protein phosphorylation in these clones. Our results show that NRAS and/or MEK mutations contribute to BRAF inhibitor resistance in vitro, and the combination of GSK2118436 and GSK1120212 overcomes this resistance. In addition, these resistant clones respond to the combination of GSK2126458 with GSK2118436 or GSK1120212. Clinical trials are ongoing or planned to test these combinations.[2]

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Purpose: Omipalisib/GSK2126458 (GSK458) is a potent inhibitor of PI3K (α, β, γ, and δ), with preclinical studies demonstrating broad antitumor activity. We performed a first-in-human phase I study in patients with advanced solid tumors.
Materials and methods: Patients received oral GSK458 once or twice daily in a dose-escalation design to define the maximum tolerated dose (MTD). Expansion cohorts evaluated pharmacodynamics, pharmacokinetics, and clinical activity in histologically and molecularly defined cohorts.
Results: One hundred and seventy patients received doses ranging from 0.1 to 3 mg once or twice daily. Dose-limiting toxicities (grade 3 diarrhea,n= 4; fatigue and rash,n= 1) occurred in 5 patients (n= 3 at 3 mg/day). The MTD was 2.5 mg/day (MTD with twice daily dosing undefined). The most common grade ≥3 treatment-related adverse events included diarrhea (8%) and skin rash (5%). Pharmacokinetic analyses demonstrated increased duration of drug exposure above target level with twice daily dosing. Fasting insulin and glucose levels increased with dose and exposure of Omipalisib/GSK458. Durable objective responses (ORs) were observed across multiple tumor types (sarcoma, kidney, breast, endometrial, oropharyngeal, and bladder cancer). Responses were not associated withPIK3CAmutations (OR rate: 5% wild-type vs. 6% mutant).
Conclusions: Although the MTD of GSK458 was 2.5 mg once daily, twice-daily dosing may increase duration of target inhibition. Fasting insulin and glucose levels served as pharmacodynamic markers of drug exposure. Select patients achieved durable responses; however,PIK3CAmutations were neither necessary nor predictive of response. Combination treatment strategies and novel biomarkers may be needed to optimally target PI3K.[3]

C25H17F2N5O3S

505.4960

505.102

C, 59.40; H, 3.39; F, 7.52; N, 13.85; O, 9.50; S, 6.34

1086062-66-9

1086062-66-9

25167777

light yellow solid powder

1.5±0.1 g/cm3

715.6±70.0 °C at 760 mmHg

187-189℃

386.6±35.7 °C

0.0±2.3 mmHg at 25°C

1.660

3.81

1

10

6

36

833

0

S(C1C([H])=C([H])C(=C([H])C=1F)F)(N([H])C1=C(N=C([H])C(=C1[H])C1C([H])=C([H])C2C(=C(C([H])=C([H])N=2)C2=C([H])N=NC([H])=C2[H])C=1[H])OC([H])([H])[H])(=O)=O

CGBJSGAELGCMKE-UHFFFAOYSA-N

InChI=1S/C25H17F2N5O3S/c1-35-25-23(32-36(33,34)24-5-3-18(26)12-21(24)27)11-17(13-29-25)15-2-4-22-20(10-15)19(7-8-28-22)16-6-9-30-31-14-16/h2-14,32H,1H3

2,4-difluoro-N-[2-methoxy-5-(4-pyridazin-4-ylquinolin-6-yl)pyridin-3-yl]benzenesulfonamide

Omipalisib; GSK2126458; GSK 2126458; 2,4-difluoro-N-(2-methoxy-5-(4-(pyridazin-4-yl)quinolin-6-yl)pyridin-3-yl)benzenesulfonamide; 2,4-difluoro-N-[2-methoxy-5-(4-pyridazin-4-ylquinolin-6-yl)pyridin-3-yl]benzenesulfonamide; GSK-212; GSK-2126458

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

DMSO: ~100 mg/mL (~197.8 mM)
Water: <1 mg/mL
Ethanol: <1 mg/mL

Solubility in Formulation 1: ≥ 2.5 mg/mL (4.95 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: 1%DMSO+30% polyethylene glycol+1%Tween 80: 18mg/mL

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 (Please use freshly prepared in vivo formulations for optimal results.)