当前位置：文档库 › Refametinib

Refametinib

C 19H

Mol wt: 572.337

CAS: 923032-37-5

CAS: 923032-36-4 (undefined stereochemistry)

CAS: 923032-38-6 (enantiomer)

EN: 444804

SUMMARY

The Ras/Raf/MEK/ERK pathway has been well researched and impli-cated as a novel target for potential molecular inhibition in the treat-ment of human cancers. The mitogen-activated protein kinase (MAPK) pathway through Ras/Raf/MEK/ERK signal transduction is an ideal site for molecularly directed therapies, which are involved in approxi-mately one-third of all tumor cell lines. MEK activation of ERK through

the MAPK pathway is especially appealing considering that MEK’s only known substrate is ERK. Refametinib is a small, potent and orally available, noncompetitive inhibitor with impressively high affinity for MEK 1/2 and a favorable therapeutic index. It has been studied both as monotherapy and as combination therapy in colon, pancreatic, thy-roid, melanoma and hepatocellular tumor xenograft models. While monotherapy in treating these malignancies has shown significant tumor growth inhibition, combination therapy using agents within compensatory alternative pathways has also shown promise in the treatment of cancer.

Key words: MEK 1/2 inhibitor – Cancer –Combination therapy –Refametinib – RDEA-119 – BAY-86-9766

SYNTHESIS*

Condensation of 1,2,3,5-tetrafluoro-4-nitrobenzene (I) with 2-fluoro-4-iodoaniline (II) by means of LiHMDS in THF gives diaryl amine (III), which undergoes selective fluoride substitution with NaOMe in THF to yield 5-methoxy-6-nitroaniline derivative (IV). Nitro group reduc-tion in intermediate (IV) by means of Fe and NH

Cl in refluxing EtOH provides the corresponding diamine (V), which is then condensed with 1-allylcyclopropanesulfonyl chloride (VI) in the presence of pyri-dine at 40 °C to produce the sulfonamide (VII). Dihydroxylation of

the allyl group of compound (VII) with OsO

and NMMO in TH F affords racemic refametinib, which is finally resolved using chiral HPLC (1, 2). Scheme 1.

In an alternative method, coupling of the primary amine (V) with the chiral sulfonyl chloride (VIII) in the presence of pyridine yields the corresponding sulfonamide (IX), which is finally hydrolyzed at the acetonide moiety with HCl in THF (3). Scheme 1.

1-Allylcyclopropanesulfonyl chloride intermediate (VI) is prepared as follows. Treatment of 3-chloro-1-propanesulfonyl chloride (X) with BuOH affords butyl 3-chloro-1-propanesulfonate (XI), which cyclizes in the presence of BuLi to yield butyl cyclopropanesulfonate (XII),

THOMSON REUTERS

Drugs of the Future 2013, 38(1): 19-26

DOI: 10.1358/dof.2013.38.1.1902801

A. Lammers, MD1, and C.D. Weekes, MD, PhD1,2. 1University of Colorado Denver, Depart-ment of Medicine, Aurora, Colorado, USA; 2University of Colorado Cancer Center, 12801 E. 17th Ave., R C-1 South, Rm. 8123, Aurora, CO 80045, USA. E-mail: colin.weekes@https://www.wendangku.net/doc/602786748.html,.

*Synthesis prepared by J. Bolòs, R. Casta?er. Thomson Reuters, Proven?a 398, 08025 Barcelona, Spain.MONOGRAPH

REFAMETINIB Dual MEK 1/2 Inhibitor Rec INN Oncolytic AR-119

BAY-86-9766

BAY-869766

RDEA-119

(–)-N-[3,4-Difluoro-2-(2-fluoro-4-iodophenylamino)-6-methoxyphenyl]-1-[2(S),3-dihydroxypropyl]cyclopropanesulfonamide

InChI: 1S/C19H20F3IN2O5S/c1-30-15-7-13(21)16(22)18(24-14-3-2-10(23)6-12(14)20)17(15)25-31(28,29)19(4-5-19)8-11(27)9-26/h2-3,6-

7,11,24-27H,4-5,8-9H2,1H3/t11-/m0/s1

REFAMETINIB A. Lammers and C.D. Weekes

which can also be obtained by treatment of cyclopropanesulfonyl chloride (XIII) with BuOH in the presence of pyridine. Alkylation of butyl cyclopropanesulfonate (XII) with allyl iodide (XIV) using BuLi in THF at –78 °C yields butyl 1-allylcyclopropanesulfonate (XV), which is hydrolyzed by treatment with KSCN in DME/H 2O at reflux produc-ing potassium 1-allylcyclopropanesulfonate (XVI). Finally, the potas-sium sulfonate (XVI) is chlorinated with refluxing SOCl 2in the pres-ence of a catalytic amount of DMF (1, 2). Scheme 1.

Chiral cyclopropanesulfonyl chloride intermediate (VIII) can be pre-pared as follows. Lithiation of (trimethylsilyl)acetylene (XVII) with t -BuLi in THF at –78 °C, and subsequent coupling with TBDMS-pro-tected (S )-glycidol (XVIII) in the presence of BF 3·Et 2O at –78 °C affords the (S )-pentynol derivative (XIX). Then, the TMS-protecting group of intermediate (XIX) is selectively removed by means of K 2CO 3in MeOH to give alkyne (XX). Iodoboration of alkyne (XX) with B-I-9-BBN in CH 2Cl 2at 0 °C followed by deborination with AcOH yields 4-iodo-4-pentene-1,2(S )-diol (XXI). O -Protection of diol (XXI)with TBDMSOTf and pyridine in TH F provides the bis-silyl ether (XXII), which is then submitted to Simmons-Smith cyclopropanation with CH 2I 2in the presence of Et 2Zn and TFA in DCE to produce 1,2-O -bis-TBDMS-3-(1-iodocyclopropyl)propane-1,2(S )-diol (XXIII).Desilylation of compound (XXIII) using HCl in THF gives 3-(1-iodocy-clopropyl)propane-1,2(S )-diol (XXIV), which by trans -ketalization with 2,2-dimethoxypropane (XXV) by means of PPTS in CH 2Cl 2gives 4(S )-(1-iodocyclopropylmethyl)-2,2-dimethyl-1,3-dioxolane (XXVI).Finally, alkyl iodide (XXVI) is treated with t -BuLi in Et 2O at –78 °C,followed by chlorosulfonation with SO 2Cl 2in Et 2O (3). Scheme 2.Alternatively, deprotonation of dicyclopropyl disulfide (XXVII) with BuLi in TH F, followed by alkylation with 4(R )-(bromomethyl)-2,2-dimethyl-1,3-dioxolane (XXVIII) at –78 °C affords the dimeric bis-ace-tonide (XXIX), which is reductively cleaved to the corresponding thiol monomer (XXX) by treatment with PPh 3and HCl in dioxane/H 2O. Air oxidation of cyclopropanethiol derivative (XXX) in the presence of NaOH in DMF gives sodium cyclopropanesulfonate derivative (XXXI), which can also be obtained by direct oxidation of disulfide (XXIX) with H 2O 2and NaOAc in AcOH at 80 °C. Finally, sulfonate (XXXI) is chlorinated using POCl 3at 80 °C. Alternatively, sulfonyl chloride (VIII) can be directly obtained from disulfide (XXIX) by oxidative cleavage with NCS in the presence of H Cl in MeCN (3).Scheme 2.BACKGROUND

Despite significant strides in research and advancing therapeutic options in the fight against cancer, it remains the second most com-mon cause of death in the U.S. (4). In recent years, the focus of can-cer therapy has shifted toward molecular-targeted therapy and genetic pathways responsible for the development and maintenance of the disease (5). Within these pathways, there are many viable sites for manipulation in treating cancer. Several specific paths that have been viewed as potential targets include the following: 1) extracellu-lar neutralization of transition points within a signaling cascade prior to receptor binding; 2) direct receptor inhibition; and 3) signal inhi-bition within the cytoplasm through secondary messengers (6).While there are numerous crucial growth factors and cytokines linked with human cancer, the mitogen-activated protein kinase (MAPK) pathway through Ras/Raf/MEK/ERK signal transduction

A. Lammers and C.D. Weekes REFAMETINIB

has been implicated as an ideal target for the development of strate-gies utilizing molecularly directed therapies in the treatment of can-cer (7). Within this pathway, there are numerous possible sites for the manipulation of signal transduction that can be used in cancer therapy, as the MAPK pathway itself is uniquely linked with cancer progression, including cell proliferation, differentiation and apopto-sis (Fig. 1) (8).

When extracellular growth factors such as epidermal growth factor (EGF) bind to cell surface receptors, conformational changes there-in lead to phosphorylation, dimerization and recruitment of proteins such as Ras within the cytoplasm to promote MAPK signal transduc-tion (9). Alternatively, The MAPK pathway can be activated through various mechanisms, including gain-of-function mutations in KRAS or BRAF genes and hyperactivation of receptor tyrosine kinases,resulting in unchecked pathway activation (10). KRAS -activating mutations occur in pancreatic (95%), colorectal (40%) and non-small cell lung cancer (5-10%) (11). Likewise, activated BRAF muta-tions occur in papillary thyroid (36-53%), colorectal (5-22%), non-small cell lung and pancreatic cancer, as well as malignant melanoma (27-70%) (12).

The resulting inappropriate activation of ERK, through aberrant expression or loss of ERK phosphatase, leads to activation of ERK via phosphorylation (pERK). pERK subsequently interacts with vari-ous intracellular substrates, leading to cell proliferation, growth,survival, angiogenesis and differentiation (13). This cascade of events results in constitutive activation of tumor growth, leading to pro-gression of human cancers. Further research has elucidated that the MAPK pathway is important in oncogenesis. The MEK (MAP/ERK kinase) kinases are particularly essential within this cascade, with dual kinase activity and phosphorylation of both serine/threonine and tyrosine residues. MEK is imperative in the MAPK pathway, as MEK activation leads to transformation of all cell lines (14, 15). More-over, constitutive activation of MEK 1 results in cellular transforma-tion (16, 17). These two kinases, MEK 1 and MEK 2, are nearly identi-cal, with > 80% amino acid sequence structure; therefore, individual small-molecule inhibitors can bind equally to MEK 1 and MEK 2 (18,19). These small-molecule inhibitors are themselves highly selective and show minimal cross-reactivity with other protein kinases; there-fore, MEK represents an ideal target for pharmacological interven-tion in cancer.

Evaluation of the MEK inhibitors has shown that they bind to a unique site adjacent to the ATP binding pocket rather than the ATP binding site itself, and therefore serve as noncompetitive inhibitors.MEK inhibitors prevent MEK binding to its substrate ERK, which in turn blocks ERK phosphorylation (20). The first generation of MEK 1/2 inhibitors displayed potent in vitro effects but lacked in vivo activ-ity, with profound CNS toxicity (21). However, the second generation of MEK 1/2 inhibitors (i.e., AZD-6244, PD-0325901, RDEA-119 and others) proved to have improved in vivo profiles and current phase I and II trials provide initial evidence of clinical activity in the treat-ment of human cancers (22-24).PRECLINICAL PHARMACOLOGY

Refametinib (RDEA-119, BAY-86-9766) is a potent, orally bioavail-able, small-molecule inhibitor of MEK kinases. In vivo evaluation has shown that it potently inhibits MEK activity in a non-ATP-competitive

manner. Refametinib binds to an allosteric site adjacent to the Mg-ATP binding region within the activation loop and interacts exten-sively with ATP. This is consistent with the site of interaction of other MEK inhibitors, such as PD-318088 and AZD-6244. This binding configuration results in noncompetitive inhibition of MEK 1, allowing ATP binding yet preventing ERK phosphorylation. Refametinib exclusively inhibits only MEK 1/2. Specifically, MEK 1 and MEK 2 were inhibited by 97% and 99%, respectively, when tested at 10 μmol/L (19). MEK enzymatic inhibition assays demonstrate that refametinib potently inhibits MEK 1 and MEK 2 activity (IC

= 19 nmol/L and 47 nmol/L, respectively) in a non-ATP-competitive manner. By compar-ison, PD-0325901 has an inhibition equilibrium constant of 1 nmol/L

REFAMETINIB A. Lammers and C.D. Weekes

in vitro. AZD-6244 has an IC 50of 10-14 nmol/L, leading to 70-80%pERK inhibition at plasma concentrations of > 200 ng/mL (22-25).Refametinib-mediated MEK inhibition results in anchorage-depend-ent inhibition of human cancer cells harboring BRAF gain-of-func-tion mutations. Interestingly, growth inhibition was achieved at lower concentrations with anchorage-independent cell lines in com-parison to anchorage-dependent conditions, especially in the set-ting of wild-type BRAF mutations (26). These findings suggest that there is increased dependence on the MEK pathway for the anchor-age-independent cell lines (27).

The in vivo evaluation of refametinib demonstrated preclinical evi-dence of tumor growth inhibition in cell line-based xenograft mod-els. Refametinib administered orally on a daily schedule for 14 days in human malignant melanoma A-375 tumor xenografts in mice at doses of 25 and 50 mg/kg/day resulted in significant tumor growth inhibition (TGI) of 54% and 68%, respectively. Five to eight complete or partial responses (CRs/PRs) and up to six tumor-free survivors (TFSs) were observed in these experiments. A schedule-dependent antitumor efficacy profile for refametinib was observed in the A-375tumor xenografts. Refametinib administration at 100 mg/kg every other day was less effective than daily dosing at either 25 or 50mg/kg. Furthermore, twice-daily dosing was more effective than once-daily dosing. These observations correlated with minimum

concentration (C min ) levels, supporting a continuous dosing schedule to maximize refametinib-induced tumor growth-inhibitory proper-ties. Refametinib primarily induced cell cycle arrest rather than apoptosis to promote inhibition of A-375 proliferation. Apoptosis-related cellular membrane integrity disruption was minimally affect-ed by refametinib. Similarly, flow cytometry revealed a G 1phase cell cycle arrest without sub-G 1population generation (26).

Refametinib resulted in similar results in the human colon adeno-carcinoma COLO 205 xenograft model. Doses of 25 and 50 mg/kg administered daily produced marked TGI during drug treatment (e.g., TGI = 123% at 25 mg/kg). Tumor regressions were also noted,with seven PRs, two CRs and two TFSs observed in the nine animals treated with 25 mg/kg, and nine PRs seen in the group treated with 50 mg/kg. COLO 205-bearing animals were subsequently treated with refametinib on a daily dosing schedule for 14 days to estimate an ED 50at doses lower than 25 mg/kg (2.5-25 mg/kg). The ED 50doses for TGI in these xenograft experiments ranged from 2.5 to 10mg/kg, for which 43-53% TGI was observed, respectively. In addition,A-431 and human colon adenocarcinoma HT-29 cells harboring con-stitutive ERK pathway activation due to epidermal growth factor receptor (EGFR) overexpression and a BRAF V600E mutation,respectively, also exhibited tumor growth inhibition upon refame-tinib exposure (28). The tumor growth-inhibitory effects observed in

A. Lammers and C.D. Weekes REFAMETINIB

Figure 1.The Ras/Raf/MEK/ERK pathway. Reproduced with permission from the American Association for Cancer Research, Iverson, C., Larson, G., Lai, C. et al. RDEA119/BAY 869766: A potent, selective, allosteric inhibitor of MEK1/2 for the treatment of cancer

. Cancer Res 2009, 69(17): 6839-47.

these studies occurred in the absence of significant weight loss or signs of neurological and gastrointestinal toxicity.

Mammalian target of rapamycin (mTOR) represents a compensatory pathway that could be utilized by cancer cells to promote tumor cell proliferation and survival observed with MEK inhibition. A combina-tion study has been performed with refametinib and the mTOR inhibitor rapamycin in a human orthotopic primary pancreatic can-cer xenograft model. Combination therapy of rapamycin and refametinib in this model resulted in an additive tumor growth inhi-bition in comparison to the individual drug treatments (26). Refame-tinib treatment alone and in combination with rapamycin resulted in intratumoral ERK 1/2 dephosphorylation. Rapamycin exposure inhibited mTOR-mediated Ser235/236 and Ser240/244 phosphoryl-ation of S6 ribosomal protein, as well as increased Akt Ser473 phos-phorylation, as expected. Interestingly, combination therapy with refametinib and rapamycin augmented the intratumoral signal transduction effects of either drug while promoting enhanced tumor growth inhibition (29, 30). These data provide evidence supporting the development of multifaceted combinatorial signal transduction inhibition strategies with refametinib. Combined, the xenograft experiments utilizing melanoma, colon carcinoma and pancreas cancer xenografts provided preclinical evidence of refametinib tumor growth inhibition as a single agent or in combination with other molecular-targeted agents (26).

Initial xenograft experiments analyzed refametinib-mediated MEK inhibition by evaluating ERK phosphorylation in various murine tis-sues to include brain, lung, peripheral bone marrow mononuclear cells (PBMCs), plasma and tumor in comparison to the first-genera-tion MEK inhibitor PD-325901. The EC 50was 42 ng/mL (73 nmol/L)for MEK inhibition. By comparison, the PD-325901 EC 50for MEK inhibition was 641 ng/mL. Refametinib failed to inhibit ERK phos-phorylation in brain samples. In fact, refametinib demonstrated tis-sue-specific MEK inhibition relegated primarily to tumor tissue, with minimal lung inhibition of ERK phosphorylation and none occurring in the brain. Mathematical modeling suggests that a > 3000 ng/mL plasma concentration would be required to induce 50% inhibition of ERK phosphorylation in the brain. The levels of refametinib were similar in the lung and plasma, while much lower concentrations were appreciated in the brain. In contrast, PD-325901 administra-tion yielded equal concentrations in brain, lung and plasma (22).This observation was associated with equal MEK inhibition across tissues, as measured by ERK phosphorylation. These data suggest that refametinib would possess significantly less CNS toxicity than has been observed with PD-325901 and other first-generation MEK inhibitors.

PHARMACOKINETICS AND METABOLISM

Preclinical pharmacokinetic analyses were first assessed in mouse models. The pharmacokinetics of refametinib in these models were assessed over a 24-hour time course following oral exposure to a single dose of 25 mg/kg. The time to maximal concentration (t max )was 2 hours, with a total maximum serum concentration (C max ) of 9.85 μg/mL, a t max consistent with other MEK inhibitors (AZD-6244and PD-0325901). The minimum serum concentration (C min ) values at 12 and 24 hours were 1.37 and 0.03 μg/mL, respectively. The half-life (t 1/2) following oral exposure in the mouse model was 2.6 hours

and the area under the curve from 0 to 24 hours (AUC 0-24h ) was 55μg·h/mL. A simulated twice-daily dosing of 12.5 mg/kg was admin-istered and projected a total serum C max of approximately 5 μg/mL,with C min values at 12 and 24 hours of 1.2 μg/mL. In comparison, the concentrations of refametinib necessary to inhibit cellular pERK in vitro were 1.4-9.0 ng/mL (conversion from nmol/L to ng/mL =0.572) or 23-48 ng/mL for anchorage-independent cell proliferation across the cancer cell lines tested in 10% FBS (22).

A multicenter, dose-escalation phase I trial of refametinib analyzed 57 of 69 patients with advanced cancer and found that C max and AUC 0-24 values increased with dose in a dose-linear manner follow-ing single or multiple doses up to 100 mg/day and doses ranging from 20 to 100 mg/day orally. Accumulation overall was modest (median accumulation ratio of C max : 1.4 ng/mL [range 0.4-3.8ng/mL]; AUC 0-24: 1.6 ng/mL [range 0.9-2.5 ng/mL]) in all patients following multiple doses. However, the half-life of refametinib was sustained and remained approximately 10-20 hours following a sin-gle dose on day 1, significantly prolonged compared to other MEK inhibitors, specifically AZD-6244 (t 1/2= 8.3 hours) and PD-325901(t 1/2= 7.8 hours) (31).

A dose-escalation phase I clinical trial has now been completed with refametinib. The average terminal half-life was 12 hours. C max and steady-state AUC 0-24 values increased nearly dose-proportionally in the 2- to 100-mg dose range with daily dosing. Continuous daily dosing resulted in moderate refametinib accumulation at most dose levels, including the 50mg b.i.d. group in the expanded maximum tolerated dose cohort, where approximately a twofold accumulation was observed. Refametinib exposure on days 22 and 35 was gener-ally comparable, indicating that a steady-state condition was achieved within 2 weeks of continuous dosing (31).

Overall the drug was well tolerated, with an adverse event (AE) pro-file similar to other MEK inhibitors. The most frequent drug-related AE was dermatological toxicity in the form of an acneiform rash.Generally, the rash was grade 1 or 2; however, grade 3 and no grade 4 rash was observed in 4% of patients (31). This is in comparison to AZD-6244, which developed grade 3-4 rash in 16% of patients (22).Patients receiving refametinib had gastrointestinal toxicity predom-inantly in the form of diarrhea. This was well controlled with the ini-tiation of loperamide therapy. Fatigue was another common toxicity observed, occurring in 25% of patients, which was reversible upon drug discontinuation (28). H ematological toxicity was remarkably absent. By comparison, both AZD-6244 and PD-0325901 resulted in hematological toxicity (23, 24). PD-0325901 displayed several grade 4 hematological AEs, including lymphopenia (4.8%), neu-tropenia (3.2%) and anemia (1.6%) (23).

Neurological toxicity remains the most deleterious and concerning MEK inhibitor-related toxicity. Preclinical testing of refametinib pre-dicted that it would have less frequent neurological toxicity than first-generation MEK inhibitors. Neurological toxicity occurred rarely at doses less than the recommended phase II dose of 100 mg cumu-lative daily dose in the dose-escalation phase I study. These were all grade 1 and consisted of abnormal dreams. All grade 3 CNS AEs occurred at doses > 100 mg (31). Ocular toxicity occurred in seven (10%) evaluable patients, including reversible chorioretinopathy and retinal vein occlusion (28). By comparison, other second-generation MEK inhibitors, such as trametinib, demonstrated a treatment-relat-REFAMETINIB A. Lammers and C.D. Weekes

ed ocular toxicity in 15% of patients, including central serous retinopathy and retinal vein occlusion (32). The recommended phase II dose was determined to be 100 mg administered either as a single daily dose or 50 mg twice daily based upon these data.

As a result of these observations, a biomarker analysis strategy was employed as a component of the dose-escalation phase I clinical trial (31). Refametinib demonstrated the ability to inhibit MEK activa-tion in ex vivo PBMCs stimulated with phorbol ester in the expansion cohort of patients. In addition, tumors were evaluated for the pres-ence of KRAS, BRAF, PTEN and PIK3mutations and correlated with patient outcome in the expansion cohort. These results were inde-terminate due to a small sample size. H owever, prolonged stable disease was observed in 10 patients on study (32). Refametinib demonstrated evidence of clinical activity in the early phase I clinical trial, warranting further investigation in phase II clinical studies. CLINICAL STUDIES

A multicenter, dose-escalation phase I clinical trial of refametinib has recently completed enrollment. The study identified the recom-mended phase II dose to be 100 mg/day administered as a single daily dose or 50 mg twice daily (31).

Refametinib has been evaluated in Asia in combination with sorafenib in patients with previously untreated Child-Pugh A hepa-tocellular carcinoma in a phase II study. Eighty-three percent of patients had cirrhosis and 93% of patients had either hepatitis B or C viral hepatitis. The disease control rate of this study was 43%, with three (5%) patients attaining a confirmed PR. The primary therapy-related AEs were rash and diarrhea, occurring in 60% and 59% of patients, respectively (33).

Additionally, refametinib is being evaluated in combination with gemcitabine in a phase I/II study as first-line therapy for patients with locally advanced or metastatic pancreas adenocarcinoma. The initial presentation of the phase I clinical trial demonstrated that the combination of gemcitabine 1000 mg/m2administered weekly for 3 weeks of a 4-week cycle combined with twice-daily dosing of refametinib 30 mg was safe. The most frequent therapy-related AE was grade 1 and 2 acneiform rash. The primary grade 3 and 4 thera-py-related AE was neutropenia, occurring in 6 of 17 (35%) patients (34). Overall, this combination was deemed to be tolerable and the phase II component of the study is currently enrolling patients with a refametinib dose of 50 mg twice daily.

These studies demonstrate that refametinib can be safely combined with both cytotoxic chemotherapy, as well as molecularly targeted agents. The efficacy benefit remains to be defined for both of these clinical trials. Unfortunately, pharmacodynamic biomarker analysis was not reported in either study.

CONCLUSIONS

Refametinib is a small-molecule, potent and orally bioavailable agent that strongly inhibits MEK activity in a non-ATP-competitive manner. It has a robust affinity for both MEK 1 and MEK 2, with exclu-sive specificity for only MEK 1 and 2 (22). In vivo studies have shown refametinib to have preferential growth inhibition in cancer cells har-boring BRAF V600E mutations. Xenograft tumor modeling demon-strated a tumor growth-inhibitory effect across a wide range of his-tological cancer subtypes. Its affinity appears to be superior to other MEK inhibitors, with a more ideal IC

compared to its counterparts (26). Additionally, it has a favorable side effect profile compared to other first- and second-generation MEK inhibitors, with only minimal CNS effects by comparison at clinically relevant doses (11). Ongoing combination studies with gemcitabine and sorafenib demonstrate that refametinib can be safely combined with both cytotoxic chemotherapy and molecularly targeted agents. As with other small-molecule inhibitors in this class, biomarker-driven clini-cal trials provide an opportunity to realize the ultimate clinical effi-cacy of this compound. The genetic abnormalities may vary depend-ing on the histological subtype of the malignancy. Defining the compensatory pathways utilized by cancer cells in response to refametinib-induced MEK inhibition will dictate the appropriate combination strategies in the future.

SOURCES

Ardea Biosciences, Inc. (US) (a wholly owned subsidiary of AstraZeneca); licensed to Bayer H ealthCare Pharmaceuticals, Inc. (US).

DISCLOSURES

The authors state no conflicts of interest.

REFERENCES

1.Maderna, A., Vernier, J., Barawkar, D., Chamakura, V., El Abdellaoui, H.,

H ong, Z. (Ardea Biosciences, Inc.). Derivatives of N-(arylamino)sulfon-

amides as inhibitors of MEK. US 2008058340, US 8101799.

2.Maderna, A., Vernier, J.-M., Barawkar, D., Chamakura, V., Abdellaoui,

H.E., H ong, Z. (Ardea Biosciences, Inc.). N-(Arylamino)-sulfonamide

inhibitors of MEK. EP 1912636, US 2012022076, WO 2007014011.

3.Maderna, A., Vernier, J.-M. (Ardea Biosciences, Inc.). Preparation of (R)-

and (S)-N-(3,4-difluoro-2-(2-fluoro-4-iodophenylamino)-6-methoxyphen-yl)-1-(2, 3-dihydroxypropyl)cyclopropane-1-sulfonamide and protected derivatives thereof. EP 2462111, JP 2013500242, KR 2012032536, WO 2011009541.

4.Hayat, M.J., Howlader, N., Reichman, M.E., Edwards, B.K. Cancer statis-

tics, trends and multiple primary cancer analyses from the Surveillance, Epidemiology, and End Results (SEER) Program. Oncologist 2007, 12(1): 20-37.

5.Pang, R.W., Poon, R.T. From molecular biology to targeted therapies for

hepatocellular carcinoma: The future is now. Oncology 2007, 72(Suppl. 1): 30-44.

6.Meyerhardt, J.A., Mayer, R.J. Systemic therapy for colorectal cancer. N

Engl J Med 2005, 352(5): 476-87.

7.Friday, B.B., Adjei, A.A. Advances in targeting the Ras/Raf/MEK/Erk mito-

gen-activated protein kinase cascade with MEK inhibitors for cancer thera-py. Clin Cancer Res 2008, 14(2): 342-6.

8.Sebolt-Leopold, J.S. MEK inhibitors: A therapeutic approach to targeting

the Ras-MAP kinase pathway in tumors.Curr Pharm Des 2004, 10(16): 1907-14.

9.Seger, R., Krebs, E.G. The MAPK signaling cascade. FASEB J 1995, 9(9):

726-35.

10.McCormick, F. Signal transduction. How receptors turn Ras on. Nature

1993, 363(6424): 15-6.

A. Lammers and C.D. Weekes REFAMETINIB

11.Adelstein, B.A. ,Dobbins, T.A. ,H arris, C.A.,Marschner, I.C.,Ward,

R.L. A systematic review and meta-analysis of KRAS status as the deter-minant of response to anti-EGFR antibodies and the impact of partner chemotherapy in metastatic colorectal cancer.Eur J Cancer 2011, 47(9): 1343-54.

12.Garnett, M.J., Marias, R. Guilty as charged: B-RAF in a human oncogene.

Cancer Cell 2004, 6(4): 313-9.

13.Trujillo, J.I. MEK inhibitors: A patent review 2008 - 2010. Expert OpinTher

Pat 2011, 21(7): 1045-69.

14.Cowley, S., Paterson, H., Kemp, P., Marshall, C.J. Activation of MAP

kinase kinase is necessary and sufficient for PC12 differentiation and for transformation of NIH 3T3 cells. Cell 1994, 77(6): 841-52.

15.Mansour, S.J., Matten, W.T., Hermann, A.S. et al. Transformation of mam-

malian cells by constitutively active MAP kinase kinase. Science 1994, 265(5174): 966-70.

16.Cowley, S., Paterson, H., Kemp, P., Marshall, C.J. Activation of MAP kinase

kinase is necessary and sufficient for PC12 differentiation and for transfor-mation of NIH3T3 cells.Cell 1994, 77(6): 841-52.

17.Mansour, S.J., Matten, W.T., Hermann, A.S. et al. Transformation of mam-

malian cells by constitutively active MAP kinase kinase. Science 1994, 265(5174): 966-70.

18.Brott, B.K., Alessandrini, A., Largaespada, D.A. et al. MEK2 is a kinase

related to MEK1 and is differentially expressed in murine tissues. Cell Growth Differ 1993, 4(11): 921-9.

19.Ohren, J.F., Chen, H., Pavlovsky, A. et al. Structures of human MAP kinase

kinase 1 (MEK1) and MEK2 describe novel noncompetitive kinase inhibition.

Nat Struct Mol Biol 2004, 11(12): 1192-7.

20.Seger, R., Ahn, N.G., Posada, J. et al. Purification and characterization of

mitogen-activated protein kinase activator(s) from epidermal growth fac-tor-stimulated A431 cells. J Biol Chem 2003, 267(20): 14373-81.

21.Allen, L.F., Sebolt-Leopold, J., Meyer, M.B. CI-1040 (PD184352), a target-

ed signal transduction inhibitor of MEK (MAPKK).Semin Oncol 2003, 30(5, Suppl. 16): 105-16.

22.Iverson, C., Larson, G., Lai, C. et al. RDEA119/BAY 869766: A potent, selec-

tive, allosteric inhibitor of MEK1/2 for the treatment of cancer. Cancer Res 2009, 69(17): 6839-47.

23.LoRusso, P.M., Krishnamurthi, S.S., Rinehart, J.J. et al. Phase I pharma-

cokinetic and pharmacodynamic study of the oral MAPK/ERK kinase inhibitor PD-0325901 in patients with advanced cancers. Clin Cancer Res 2010, 16(6): 1924-37.

24.Adjei, A., Cohen, C., Franklin, W. et al. Phase I pharmacokinetic and phar-

macodynamic study of the oral, small-molecule mitogen-activated protein

kinase kinase1/2 inhibitor AZD6244 (ARRY-142886) in patients with advanced cancers. J Clin Oncol 2008, 26(13): 2139-46.

25.Leijen, S., Middleton, M.R., Tresca, P. et al. Phase I dose-escalation study

of the safety, pharmacokinetics and pharmacodynamics of the MEK Inhibitor RO4987655 (CH4987655) in patients with advanced solid tumors. Clin Cancer Res2012, 18(17): 4794-805.

26.Chang, Q., Chapman, M.S., Miner, J.N., Hedley, D.W. Antitumour activity

of a potent MEK inhibitor RDEA119/BAY 869766 combined with rapamycin in human orthotopic primary pancreatic cancer xenografts.BMC Cancer 2010, 10: 515.

27.Bos, J.L. Ras oncogenes in human cancer: A review. Cancer Res 1989,

49(17):4682-9.

28.Thompson, D.M., Gill, G.N. The EGF receptor: Structure, regulation and

potential role in malignancy.Cancer Surv 1985,4(4):767-88.

29.Chang, Q., Chen, E., Hedley, D.W. Effects of combined inhibition of MEK

and mTOR on downstream signaling and tumor growth in pancreatic can-cer xenograft models. Cancer Biol Ther 2009, 8(20): 1893-901.

30.Birle, D.C., H edley, D.W. Signaling interactions of rapamycin combined

with erlotinib in cervical carcinoma xenografts. Mol Cancer Ther 2006, 5(10): 2494-502.

31.Weekes, C.D., Von Hoff, D.D., Adjel, A.A. et al. A multi-center phase 1, dose

escalation trial to determine the safety and pharmacokinetics/pharmaco-dynamics of BAY 86-9766 (RDEA119), an MEK inhibitor, in advanced can-cer patients. 22nd EORTC-NCI-AACR Symp Mol Targets Cancer Ther (Nov 16-19, Berlin) 2010, Abst 368.

32.Gore, L., Lewis, K., Von H off, D.D. et al. Safety, pharmacokinetics, and

pharmacodynamics results from a phase I trial of BAY 86-9766 (RDEA119),

a MEK inhibitor, in patients with advanced cancer.J Clin Oncol [47th Annu

Meet Am Soc Clin Oncol (ASCO) (June 3-7, Chicago) 2011] 2011, 29(Suppl.): Abst 3007.

33.Ho, Y.L., Yen, C.J., Tak, W.Y. et al. A phase II trial of MEK inhibitor BAY 86-

9766 in combination with sorafenib as first-line systemic treatment for patients with unresectable hepatocellular carcinoma (HCC).J Clin Oncol [48th Annu Meet Am Soc Clin Oncol (ASCO) (June 1-5, Chicago) 2012] 2012, 30(Suppl.): Abst 4103.

34.Van Laethem, J.L., Heinemann, V., Martens, U.M. A phase I/II study of the

MEK inhibitor BAY 86-9766 (BAY) in combination with gemcitabine (GEM) in patients with nonresectable, locally advanced or metastatic pancreatic cancer (PC): Phase I dose-escalation results.J Clin Oncol [48th Annu Meet Am Soc Clin Oncol (ASCO) (June 1-5, Chicago) 2012] 2012, 30(Suppl.): Abst 4050.

REFAMETINIB A. Lammers and C.D. Weekes