ATO联合抗坏血酸治疗淋巴瘤的2期研究

Publishedonline31July2008inWileyInterScience(www.interscience.wiley.com)DOI:10.1002/hon.870

ResearchArticle

PhaseIIstudyofarsenictrioxideandascorbicacidforrelapsedorrefractorylymphoidmalignancies:aWisconsinOncologyNetworkstudyzJEChang1,PMVoorhees1y,JMKolesar1,HGAhuja2,FASanchez3,GARodriguez3,KKim1,JWerndli1,HHBailey1andBSKahl1*

12PaulP.CarboneComprehensiveCancerCenter,UniversityofWisconsin,Madison,WI,USAAspirusRegionalCancerCenter,Wausau,WI,USA3OncologyAssociates,Waukesha,WI,USA

*Correspondenceto:

BSKahl,UniversityofWisconsin,600HighlandAvenue,H4/534CSC,Madison,WI53792,USA.E-mail:bsk@medicine.wisc.eduyCurrentaddress:LinebergerComprehensiveCancerCenterattheUniversityofNorthCarolina,ChapelHill,NC.zParticipatinginstitutions:

UniversityofWisconsinPaulP.CarboneComprehensiveCancerCenter,Madison,WI;AspirusRegionalCancerCenter,Wausau,WI;OncologyAssociates,Waukesha,WI;St.Vincent’sRegionalCancerCenter,GreenBay,WI.

Abstract

Arsenictrioxide(As2O3)hasestablishedclinicalactivityinacutepromyelocyticleukaemiaandhaspre-clinicaldatasuggestingactivityinlymphoidmalignancies.CelldeathfromAs2O3maybetheresultofoxidativestress.Agentswhichdepleteintracellularglutathione,suchasascorbicacid(AA),maypotentiatearsenic-mediatedapoptosis.Thismulti-institutionphaseIIstudyinvestigatedanoveldosingscheduleofAs2O3andAAinpatientswithrelapsedorrefractorylymphoidmalignancies.PatientsreceivedAs2O30.25mg/kgIVandAA1000mgIVforfiveconsecutivedaysduringthefirstweekofeachcyclefollowedbytwiceweeklyinfusionsduringweeks2–6.Cycleswererepeatedevery8weeks.Theprimaryendpointwasobjectiveresponse.Inasubsetofpatients,sequentiallevelsofintracellularglutathioneandmeasuresofBcl-2andBaxgeneexpressionwereevaluatedinperipheralbloodmononuclearcellsduringtreatment.SeventeenpatientswereenrolledbetweenMarch2002andFebruary2004.Themedianagewas71,andthemajorityofenrolledpatientshadnon-Hodgkin’slymphoma(12/17).Sixteenpatientswereevaluable,andonepatientwithmantlecelllymphomaachievedanunconfirmedcompleteresponseafterfivecyclesoftherapyforanoverallresponserateof6%.Thetrial,whichhadbeendesignedasatwo-stagestudy,wasclosedafterthefirststageanalysisduetolackofactivity.Haematologictoxicitieswerethemostcommonlyreportedeventsinthisheavilypre-treatedpopulation,andcomprisedthemajorityofgrade3and4toxicities.Intracellulardepletionofglutathionewasnotconsistentlyobservedduringtreatment.As2O3andAAinthisnoveldosingstrategywasgenerallywelltoleratedbuthadlimitedactivityinpatientswithrelapsedandrefractorylymphoidmalignancies.Copyright#2008JohnWiley&Sons,Ltd.

Keywords:

arsenictrioxide;ascorbicacid;lymphoma

Received:28February2008Revised:26June2008Accepted:30June2008

Introduction

Arsenictrioxide(As2O3)hasdemonstratedimpressivesingleagentactivityinacutepromyelocyticleukaemia(APL)[1–4],andclinicalactivityhasalsobeenshowninthetreatmentofmultiplemyelomaandmyelodysplasticsyndromes[5–11].Severalpre-clinicalstudieshavesuggestedactivityofAs2O3inlymphoidmalignancies[12–16].Themechanismofactionisunclear,andAs2O3mayhavedifferentmechanismsatdifferentdosinglevelsandindifferenttumourtypes.InAPL,As2O3atlowdosesappearstoinducedifferentiationofleukaemicblasts[17].Inothermalignancies,As2O3inhighdosesappearstocausecelldeathbyinducingapoptosis[17,18].As2O3-inducedapoptosisisahydrogenperoxide(H2O2)-mediatedprocess,andthesensitivityoftumourcellstoAs2O3iscorrelatedwithintracellularlevelsofH2O2andtheactivityofenzymesinvolved

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inH2O2metabolism,mainlycatalaseandglutathioneperoxidase[19,20].Inpre-clinicalmodels,depletionofintracellularglutathionewithagentssuchasascorbicacid(AA)enhancesAs2O3-mediatedapoptosis[21–25].

Basedonthepre-clinicaldata,wehypothesizedthatAs2O3plusAAwouldbeeffectivetherapyforrelapsedlymphoidmalignancies.ThemajorityofclinicalexperiencewithAs2O3hasemployeddailyinfusionsofAs2O3givenforprolongedperiodsofatleastseveralweeks.Intheinterestofexploringamoreconvenientadministrationschedule,wedevisedadosingstrategybasedontheprincipleofaloadingdosefollowedbytwiceweeklyinfusions.Describedhereinaretheresultsofamulti-centre,prospectiveclinicaltrialinvestigatingaregimenofAs2O3andAAadministeredinanoveldosingscheduleforthetreatmentofrelapsedandrefractorylymphoidmalignancies.

12PatientsandmethodsStudydesign

Thisstudywasdesignedasamulti-centrephaseIItrialofAs2O3andAAinpatientswithrelapsedorrefractorylymphoidmalignancies.Thestudydesigncalledforonecohortofpatientswithamixofhistologies.ThestudyprotocolwasconductedattheUniversityofWisconsinComprehensiveCancerCenterandparticipatinginstitu-tionsintheWisconsinOncologyNetwork(WON).TheInstitutionalReviewBoardateachparticipatingcentreapprovedthestudyandallpatientssignedaninformedconsentdocumentdescribingtheinvestigationalnatureoftheprotocoltreatment.

Patientselection

Patientswereeligibleforthisstudyiftheyhadhistologicallyconfirmeddiagnosesofrelapsedorrefrac-torynon-Hodgkinlymphoma(allsubtypeseligible),Hodgkinlymphoma,chroniclymphocyticleukaemia(CLL)orotherlymphoidneoplasms.Relapseddiseasewasdefinedasdiseaseprogressionafterhavingatleastapartialresponsetothemostrecentsystemictherapy.Refractorydiseasewasdefinedashavinghadlessthanapartialresponsetothemostrecentlyadministeredsystemictherapy.Patientswererequiredtohavemeasurable/evaluabledisease,priortreatmentwithatleastonesystemictherapy,andanECOGperformancestatus 3.Priortostudyenrolment,patientswererequiredtobeatleast4weeksfromtheirlastsystemictherapyand2weeksfromtheirlastradiotherapytreatment.

Otherstudycriteriaincluded3adequatehaematologicpara-meters(ANC!1000/mm,plateletcount!50000/mm3),adequateliverfunction(totalbilirubin 2.0mg/dL,AST 2.5XULN),andadequaterenalfunction(creatinineclearance>50mL/min).Cytopeniaswerenotexclusionaryifrelatedtosplenomegalyordiseasereplacementofbonemarrow.Patientswereexcludediftheywerepregnantorbreast-feeding,hadpre-existinggrade!3neuropathy,hadahistoryofseizuresoractiveCNSdiseaseinvolvement,hadanactivesecondmalignancyoractiveanduncontrolledinfection(includingHIVinfection).Otherexclusionarycriteriaincludedahistoryofventri-culardysrhythmias,significantunderlyingcardiacdys-functionorbaselineQTcintervalprolongation(!0.48s).Therewerenoexclusionsforthenumberofpriortreatmentsreceived.

Studytreatment

PatientsweretreatedwithAs2O30.25mg/kgIVinfusedover1hfollowedbyAA1000mgIVinfusedover15min.TheAAinfusionwasadministeredwithin30minaftercompletionoftheAs2O3infusion.Atreatmentcyclewasdefinedas8weeks,consistingof6weeksoftreatmentfollowedbya2weekrecoveryperiod.Duringthefirstweekofeachcycle,patientsreceivedinfusionsofAs2O3andAAforfiveconsecutivedays.Duringweeks2–6,

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JEChangetal.

patientsreceivedthesamedosesofAs2O3andAAtwiceweekly.Cycleswererepeateduntiltherewasevidenceofacompleteresponse,partialresponsewithastablediseasestatusontwoconsecutivecycles,diseasepro-gressionornoevidenceofresponse,unacceptabletoxicityorpatient/physicianpreferencefordiscontinu-ation.Restagingoccurredaftereachtreatmentcycle.Patientsachievingonlystablediseaseatreassessmentwerenoteligibletocontinuetherapy.

Assessmentofresponse

Measurementsofresponseincasesofnon-HodgkinandHodgkinlymphomaweredefinedaccordingtocriteriaestablishedbytheInternationalWorkingGroup[26].AssessmentofresponseincasesofCLLusedNCIWG-definedcriteria[27].

Assessmentofsafety

GiventheconcernforcardiacconductionproblemswithAs2O3basedonpriorreportsofheartblockandventriculardysrhythmias,patientsweremonitoredwithweeklyelectrocardiogramsthroughoutthecourseoftreatment,withtreatmentheldfordysrhythmiasorprolongationoftheQTcinterval.Inaddition,weeklyserummagnesiumandpotassiumlevelswereevaluatedduringtreatment,andcompleteserumchemistrieswererepeatedpriortoeachcycleoftreatment.OthertoxicitieswereassessedpriortoeachtreatmentcycleusingtheCommonTerminologyCriteriaforAdverseEvents,version2.0.

Statisticalconsiderations

Theprimaryendpointofthisprotocolwasobjectiveresponse(completeandpartialresponses)totreatmentwithAs2O3andAA.Treatmentfailurewasdefinedasstabledisease(SD),progressivedisease(PD)ordeathfromanycause.Secondaryendpointsincludedtreatment-relatedtoxicity,progression-freesurvival(PFS)andoverallsurvival(OS).PFSwasdefinedasthetimefromstudyentryuntildeathfromanycauseorPD.OSwasdefinedasthetimefromstudyentryuntildeathfromanycause.Atwo-stagedesignforpatientaccrualwasplannedtoallowforearlyterminationforlackofefficacy.Theprotocolwasdesignedtoinitiallyaccrue15evaluablepatients,withplanstoaccrueanadditional16evaluablepatientsshouldtherebeoneormoreresponsesobservedinthefirstcohortofpatients.Thisprocedureteststhenullhypothesisthatthetrueresponserateisatmost10%versusthealternativehypothesisthatitisatleast25%withasignificancelevelof8.3%andapowerof83%.

Correlativestudies

Previousobservationsinpre-clinicalmodelshavesuggestedthatdepletionofintracellularglutathionewithAAenhancesAs2O3mediatedapoptosis,withproposedreductioninBcl-2andamplificationofBaxexpression.In

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ordertotestthishypothesis,seriallevelsofintracellularglutathioneandmeasurementsofBcl-2andBaxexpres-sionwereevaluatedinasubsetofpatientsduringtreatment.Duetologisticalissueswithsamplecollectionandprocessing,onlypatientsenrolledattheUniversityofWisconsinsiteparticipatedinthecorrelativestudyportionoftheprotocol.

QuantitativeglutathionelevelsandgeneexpressionofBcl-2andBaxincirculatingperipheralbloodmononuclearcells(PBMC)wereassessedpriortotherapyandat5hpost-therapyduringthefirstcycleoftreatment.Gluta-thioneactivityinPBMCsweremeasuredusingthestandardTietzeassay,aspreviouslydescribed[28].Briefly,PBMCsweresonicatedandresuspended,andglutathioneactivitywasdeterminedbyreductionofDTNB(5-50dithiobis[2-nitrobenzoic])asmeasuredspectropho-tometricallyatl412.Cellswerecountedandactivitywasnormalizedto1Â106cells.RNAwasextractedbystandardmethodsandstoredatÀ808Cuntilanalysis.TheRNAwasquantifiedviaNanoDropND-1000(NanoDropTechnologies,Wilmington,DE).TwelvemicrolitresofRNAextractwasreversetranscribedusingrandomprimersfollowingthemanufacturer’sdirections.ThefinalcDNAvolumewas24mL.Bcl-2andBaxgeneexpressionanalysiswasperformedontheBio-RadMyIQreal-timethermocyclerwiththeiCyclerparametersasfollows:958C/2minÂ1cycle,958C/30s,61.78C/1min,728C/30sfor50cycles,608C/7sþ0.58CÂ70cycles.TheresultingdatawereanalysedwiththeEragenMultiCodeRTxAnalysisSoftwarev1.0.14.TheBcl-2assaywasvalidatedusingcDNAobtainedfromtheDU145prostatecancercellline.ThetotalcDNAconcentrationwasdeterminedspectrophotometrically,andthestandardcurvewasgeneratedbyamplifyingin39ngto2500ngoftotalDNAon4daysoveraperiodof4weeks.Thestandardcurveislinearfrom39to2500ng,withanintradayvariabilityof3.536%andaninterdayvariabilityover4weeksof3.26%.TheBaxassaywasalsovalidatedusingcDNAobtainedfromtheDU145prostatecancercellline.ThetotalcDNAconcentrationwasdeterminedspectrophotometricallyandthestandardcurvewasgeneratedbyamplifyingin6.25–100ngoftotalDNAon6daysoveraperiodof6weeks.Thestandardcurveislinearfrom6.25to100ng,withanintradayvariabilityof14.14%andaninterdayvariabilityover6weeksof2.93%.

Results

Patientenrollment

Seventeenpatientswereenrolledfromfiveinstitutionsbetween27March2002and20February2004.Ofthe17patientsenrolled,1patientdied3daysfollowingenrolmentfromprogressivelymphomabeforereceivinganyprotocoltreatment,andwassubsequentlyexcludedfromanalysis.Althoughtheprotocolmetthepre-determinedcriteriaforcontinuationbeyondfirststageaccrualwithoneobjectiveresponseobserved,themodestefficacyledtowaningenthusiasmforthestudyandagreementamongsttheinvestigatorstoclosethetrialearly.

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Patientcharacteristics

Baselinedemographicandclinicalcharacteristicsof16evaluablepatientsareshowninTable1.Patientsrangedinagefrom37to88years,withamedianageof71.Twelveofthe16patientshadanECOGPS 1,andnoneofthepatientshadanECOGperformancestatus>2.Variouslymphoidmalignancieswererepresented,withfollicularlymphoma(3patients),diffuselargeBcelllymphoma(3patients),mantlecelllymphoma(3patients)andCLL(4patients)representingthemostcommonhistologicalsubtypes.Patientswereheavilypre-treated,withallpatientshavingreceived!2systemictherapiesatenrolment.Ofthe11patientswithNHL,8patientshadanInternationalPrognosticIndexscore!3[29].

Diseaseresponse

Ofthe16evaluablepatients,8patientsdidnotcompletecycleone,5duetoevidenceofPDduringcycle1and3duetotoxicity.Ofthe8patientswhocompletedatleast1cycleoftreatment,allhadevidenceofPDfollowingcycle1exceptfor2patients.OnepatientwithmarginalzonelymphomacompletedthreecyclesoftreatmentbeforeexperiencingPD.Thetreatingcentrehadmisinterpretedthecriteriaforprotocolcontinuation,andthispatienthadreceivedtwocyclesoftherapywithevidenceofSDbeforedemonstratingPDfollowingcycle3.OnepatientwithmantlecelllymphomacompletedfivecyclesoftreatmentandachievedanunconfirmedCR(CRu),witharesponsedurationexceeding12months(Table2).Theoverallresponseratewas6%(1/16)witha95%confidenceintervalof(0–30%).

Table1.Baselinecharacteristics(n¼16)

Age

Median71Range37–88SexMale10(63%)Female

6(38%)Performancestatus05(31%)17(44%)2

4(25%)Priorsystemictherapies2–374–!65Median4Range

2–12DiseasestatusatenrolmentRefractory12(75%)Relapsed

4(25%)Internationalprognosticindexy0–12(18%)2–34(36%)4–5

5(45%)

yInternationalprognosticindexscoringincludesonlythe11patientswithNHL.

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14Table2.Responseratebydiseasehistology

Histology

Responses

Non-HodgkinlymphomaBurkitt’s10/1Follicular

30/3Diffuselargecell30/3Marginalzone10/1Mantlecell

31/3ChronicleukaemiaCLL

40/4Hairycell

10/1N¼16

1/16(6%)

Survival

Fourteenofthe16evaluablepatientshavedied,and2patientswithfollicularlymphomaarealiveatthedateoflastcontact.ThemedianPFSwas1.8months(95%CI0.6–5.7),andthemedianOSwas7.6months(95%CI3.7–1).The1-yearsurvivalratewas37.5%(95%CI19.9–70.6%).

Toxicityassessment

Sixteenpatientswereassessablefortoxicity,withatotalof14cyclescompleted.Toxicitiesweremodestgiventheheavilypre-treatednatureofthispatientpopulation,withthemajorityofgrade!3toxicitiescomprisedofhaematologictoxicities.Grade3–5toxicitiesareshowninTable3.Onepatientwithknowncoronaryarterydiseaseexperiencedgrade5heartfailureaftersufferingamyocardialinfarction3daysintotreatment.Onepatientdiscontinuedtreatmentduringcycle1foradecliningperformancestatus.Onepatientwasrequiredtodis-continuetreatmentduringcycle1forrecurrentgrade4hyperglycaemia.Non-haematologictoxicitiesweregener-

Table3.Eventsofgrade3–5toxicities

Toxicity

Grade3Grade4Grade5Total

Anaemia

61—7Thrombocytopenia61—7Leukopaenia41—5Neutopenia

13—4Neutropenicfever3——3Infectiony3——3Hyperglycaemia

—1—1Elevatedserumtransaminases1——1Anorexia1——1Stomatitis1——1Fatigue31—4Pain

1——1Dizziness/light-headedness1——1Dyspnea3——3Hypoxia

2——2Pleuraleffusions4——4Oedema

1——1Cardiacischemia/infarct—1—1Heartfailure

1—12

yInfectionsoccurringintheabsenceofneutropenia.

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allymild,withnoelectrolyticimbalancesorchangesinrenalfunctionreportedas>grade2inseverity.Gastrointestinalsideeffectsweretolerable,withonlyonepatientexperiencinggrade3stomatitis.Oneeventofgrade3serumtransaminaseelevationwasreported,whichwasreversiblewithabreakfromtherapy.Sixgrade1or2infectionswerereported,fourofwhichwererelatedtoherpeszoster.Twopatientsexperiencedgrade1QTcintervalprolongationonelectrocardiogramevaluation,whichwasreversibleineachcasewithabreakfromtherapy.Bothpatientsexperiencedthegrade1QTcintervalprolongationduringcycle1ondays4and7,respectively.

Correlativestudyresults

OfthefourpatientsenrolledattheUniversityofWisconsinsite,threepatientsparticipatedinthecorrelativeanalysis.Amongthesethreepatients,onepatientdidnotcompletecycle1duetoPD,andtheremainingtwopatientshadSDaftercycle1.SeriallevelsofintracellularglutathioneandgeneexpressionofBcl-2andBaxweremeasuredinthesethreestudypatientsduringtherapywithAs2O3andAA,withresultsshowninTable4.Althoughmoderatereductionsinintracellularglutathionewereobservedinoneofthepatientsfollowingtreatment,thetworemainingpatientshadminimaltonoreductioninintracellularglutathioneorwereobservedtohaveanincreaseinintracellularglutathionewithtreatment.Overall,meanglutathionelevelswerenotsignificantlydifferentbeforeand5haftertreatmentinthissmallsubsetofpatients.MeasurementofBcl-2geneexpressiondemonstratedconsistentreductionsduringtreatment,asshowninTable4.Anearly10-foldreductioninBcl-2expressionwasobserved5haftertreatmentwithAs2O3andAAwithBaxexpressionremainingconstant.

Discussion

SeveralinvitrostudieshavedemonstratedactivityofAs2O3inlymphoidmalignancies[12–15].Thispre-clinicalworkaswellasstudiessuggestingpotentiationofAs2O3withAAledustohypothesizethatthiscombinationwouldprovideanactiveandrelativelynon-toxiccombinationinrelapsedlymphoidmalignancies.DespitepriorevidencesuggestingsynergybetweenAs2O3andAAandshowingpromisingactivityofAs2O3inlymphoidmalignancies,theresponseratewiththeregimenofAs2O3andAAadministeredinthisstudywasonly6%andthestudywasclosedatthefirstinterimanalysis.

Table4.IntracellularglutathionelevelsandgeneexpressionofBcl-2andBaxduringtreatmentwithAs2O3andAA

Analyte

n

Pre5hPost(MeanÆSE)

(MeanÆSE)

Glutathione(ng/106cells)3239Æ280239Æ121Bcl-2(ng/ngcDNA)349070Æ3218524Æ36Bax(ng/ngcDNA)

3262Æ57329Æ71

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As2O3hasalreadydemonstratedactivityinmultiplehaematologicmalignancies,mostimportantlyinthetreatmentofAPL[1–3].TwosmallUStrialsinrelapsedAPLdemonstratedCRratesof92%and100%[4,30].ArecentpublicationexaminedtheroleofsingleagentAs2O3usedforremissioninduction,consolidationandmainten-ancefornewlydiagnosedAPL[31].Thecompleteresponseratewas86%andthe3-yearestimatesforEFSandOSwere75%and86%,respectively.Althoughthedurationoffollow-upinthisstudyisrelativelyshort,theseprovocativeresultsarecomparabletothoseobtainedwithconventionalchemotherapy.

ModestactivityofAs2O3hasalsobeenreportedinmultiplemyelomaandmyelodysplasticsyndromes(MDS)[5–11,32,33].Twolargemulti-centrephaseIIstudieshaverecentlybeenpublishedinMDS.InaUStrial,haematologicimprovementwasnotedin34%oflowriskpatientsand6%ofhighriskpatients[5].InaEuropeantrial,whichutilizedadosingstrategysimilartotheoneinourstudy,haematologicresponseratesof26%and17%wereobservedinlow-riskandhigh-riskcohorts,respectively[6].Whenevaluatedasasingleagentinmultiplemyeloma,As2O3producedobjectiveresponsesin2/9(23%)patients[9,10].

As2O3hasdual,dose-dependentmechanismsofactionagainstmalignantcelllines.Atlowdoses(0.1–0.5mmol/L),As2O3appearstoinducepartialdifferen-tiationofAPLcelllinesandprimaryculturesofblasts.Athigherdoses(0.5–2.0mmol/L),As2O3inducesapoptosis,includingcelllinesthatoverexpressMDR,MRP,Bcl-2andBcl-XL[34].

Arsenic-inducedapoptosisislikelyduetothepro-ductionofreactiveoxygenspecies,andresistancetooxidativedamageislargelymediatedbyintracellularglutathione[17,19,35].PreviousexperiencewithNB-4celllines(anAPLcellline)haveshownthatthesecellswithlowbaselinelevelsofglutathioneareexquisitelysensitivetotreatmentwithAs2O3,whereasHL-60cells(non-APLacutemyeloidleukaemiacellline)withincreasedlevelsofglutathionearemoreresistanttoAs2O3[19,20].AgentswhichdepleteintracellularglutathioneshouldsensitizecellstoAs2O3.ArecentpublicationfromTaiwandemonstratesthatHL-60cellsquicklydevelopresistancetoAs2O3bycompensatoryincreasesinintracellularglutathione,anddepletionofglutathionewithbuthioninesulphoximine(BSO)reversedthedrugresistanceinvitro[36].WhileBSOisanattractiveagentforglutathionedepletion,availabilityofthisagentforclinicaluseislimited[37,38].

AAisanotheragentcapableofdepletingintracellularglutathione[39].AAatconcentrationsof62.5mmolhasbeenshowntolowerglutathionelevelsinNB-4,HL-60andsu-DHL-4(B-celllymphoma)celllines,andthecombinationofAAandAs2O3leadstoincreasedapoptosisinthesecelllinescomparedwithtreatmentusingeitheragentalone[20].OtherinvestigatorshavealsoshownpotentiationofAs2O3-mediatedcytotoxicitywhencom-binedwithAA[22–25,40,41].WewereunabletodemonstrateasimilardeclineinglutathioneaftertreatmentwithAA,althoughthismaybeafunctionofoursmall

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samplesize,thelimitedsamplingscheduleordosingofAAthatwasinsufficienttolowerglutathione.

Amodifieddosingschedulewasusedinthisstudytofacilitatepatientcomplianceandlimittreatmenttimeandtoxicity.OnepatientwithmantlecelllymphomaachievedanunconfirmedCRthatwasdurableforover12months.ThissuggeststhatfurtherinvestigationofAs2O3andAAmaybereasonablebutwilllikelyrequireabetterunderstandingofbiologicalfeaturespredictiveofresponse.OnestudyindicatedAs2O3mediatesapoptosisthroughinhibitionofNFkB[42].Ifthisprovestobeamajormechanismofapoptosis,thentumourtypesknownforconstitutiveNFkBexpression(e.g.mantlecelllymphoma)maybebettertargetsforfurtherstudy.Alternatively,itispossiblethatAs2O3doesnothavesufficientactivityoutsideofAPLtowarrantfurtherstudyandnegativephaseIIstudieshavebeenreportedinmelanoma,germcelltumoursandacutelymphoblasticleukaemia[43–45].Inadequatedose-intensitymayalsobeafactor,particularlyasthepercycledoseofAs2O33.75mg/kgutilizedinourstudyissimilartothedose-intensityofAs2O3utilizedintheconsolidationphaseofAPLtherapy(totalof3.75mg/kg)ratherthanthehigherdose-intensityutilizedduringAPLinductiontherapy(upto9mg/kg).Wecannotdiscernwhetherthelackofactivityinourstudywasduetoasuboptimaldosingstrategy,theheavilypre-treatednatureofourpatientpopulation,orduesimplytoinactivityofthiscombination.Itispossiblethatalternativedosingstrategiesinasimilarpatientpopulationcouldprovetobemoreefficacious.

Acknowledgements

ThisstudywassupportedbyfundingfromtheUniversityofWisconsinPaulP.CarboneComprehensiveCancerCenterandCellTherapeutics,Inc.CellTherapeutics,Inc.alsoprovidedtheAs2O3forstudyadministration.Noneoftheauthorshaveconflictsofinteresttodiscloserelativetothisstudy.

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DOI:10.1002/hon