Randomized, double-blind, double-dummy,vehicle-controlled study of ingenol mebutate gel

0.025% and 0.05% for actinic keratosis

Lawrence Anderson, MD, FACP,a George J. Schmieder, DO,b W. Philip Werschler, MD,c

Eduardo H. Tschen, MD,d Mark R. Ling, MD, PhD,e Dow B. Stough, MD,f and Janelle Katsamasg

Tyler, Texas; Orange Park, Florida; Spokane, Washington; Albuquerque, New Mexico; Newnan, Georgia;

Hot Springs, Arkansas; and Brisbane, Australia

Background: There is a need for improved medical approaches to the treatment of actinic keratosis.Ingenol mebutate, a diterpene ester extracted and purified from the plant Euphorbia peplus, is beingevaluated as a topical therapy for actinic keratosis.

Objective: Assess the efficacy and safety of ingenol mebutate (formerly PEP005) gel at 3 dosing regimensfor the treatment of actinic keratosis.

Methods: Patients with non-facial actinic keratoses applied vehicle gel for 3 days, ingenol mebutate gel,0.025% for 3 days, or ingenol mebutate gel, 0.05% for 2 or 3 days, with an 8-week follow-up period.

Results: All 3 active treatments were significantly more effective than vehicle at clearing actinic keratosislesions, with a dose response observed. The partial clearance rate (primary efficacy end point) for patientstreated with ingenol mebutate gel ranged from 56.0% to 75.4% compared with 21.7% for vehicle gel (P =.0002 to P \ .0001 vs vehicle). The complete clearance rate was also significantly higher (P # .0006) forpatients in the ingenol mebutate gel treatment groups (range: 40.0% to 54.4%) compared with vehicle(11.7%), as was the baseline clearance rate (range: 42.0% to 57.9% for ingenol mebutate gel compared with13.3% for vehicle, P \ .0001 to .0007 vs vehicle). The median percentage reduction in baseline actinickeratosis lesions for patients treated with ingenol mebutate gel ranged from 75% to 100% compared with0% for vehicle gel (P\.0001 vs vehicle). Active treatment was well tolerated at all dosages. The mechanismof action of this agent is the localized induction of necrosis followed by a transient inflammatory response,and this was manifested in most patients as transient local skin responses consisting primarily of erythema,flaking/scaling, and crusting. There was no evidence of treatment-related scarring.

Limitations: Local skin responses may have suggested active treatment to investigators.

Conclusions: Short-course, field-directed therapy with ingenol mebutate gel for actinic keratoses on non-facial sites seems to be effective with a favorable safety profile and potential benefits over topical agentsthat require a more prolonged course of treatment. ( J Am Acad Dermatol 2009;60:934-43.)

From Dermatology Associates of Tylera; Park Avenue Dermatology,

PA, Orange Parkb; Premier Clinical Research, Spokanec; Aca-

demic Dermatology Associates, Albuquerqued; MedaPhase,

Inc., Newnane; Burk Pharmaceutical Research, Hot Springsf;

and Peplin Ltd, Brisbane.g

Funding sources: Peplin Ltd, for Clinical Research and as a member

of the Scientific Advisory Committee.

Disclosure: Dr Anderson was a clinical investigator, chairs a dose

escalation committee on an unrelated clinical trial, and serves

on an advisory board for Peplin Ltd. Ms Katsamas is an

employee of Peplin Ltd. Dr Ling received a research grant for

clinical studies from Graceway and Actavis. Dr Schmieder

934

served as an investigator for Peplin, Genentech, Novum, and

Astellas. Dr Werschler has served as an investigator for Peplin,

Graceway, and Valent/ICN and as an investigator, speaker,

consultant, and on an advisory board for Dermik. Drs Stough

and Tschen report no conflicts of interest.

A list of all clinical investigators participating in the study is found

at the end of the article.

Reprint requests: Lawrence Anderson, MD, FACP, 1367 Dominion

Plaza, Tyler, TX 75703. E-mail: LawrenceA@dermatologytyler.com.

0190-9622/$36.00

ª 2009 by the American Academy of Dermatology, Inc.

doi:10.1016/j.jaad.2009.01.008

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INTRODUCTIONActinic keratosis (AK), or solar keratosis, is a

premalignant lesion that can progress to invasivesquamous cell carcinoma (SCC).1 In fact, a number ofdermatologists and dermatopathologists considerAK to be the earliest clinically recognizable manifes-tation of SCC.2-5 The risk of dermal invasion proba-bly ranges from 8% to 10%,1,6 and one study showedthat progression takes approximately 2 years.1 Inaddition, 60% to 82% of SCC arises directly within orin close proximity to AK lesions.7,8 However, it is notpossible to predict clinically which AK lesions willinvade the dermis and which will not. Therefore, allAK lesions represent targets for treatment.

AK has been described as a field disease that isnot limited to single, clinically apparent lesions.9

Currently available treatment for AK includes topicalfield-directed therapy (principally 5-fluorouracil[5-FU], imiquimod, or diclofenac) or acid peel forcontiguous areas containing multiple AK lesions, aswell as lesion-directed or ‘‘spot’’ therapy (mainlysurgery or destruction by cryotherapy) for discreteAK lesions. However, in the opinion of experts,following a review of the literature, both 5-FU andimiquimod require lengthy treatment and can causeunsightly skin irritation resulting in noncompli-ance.10,11 Diclofenac also requires prolonged treat-ment and has the potential to cause allergicreactions.11 Surgical removal is painful and mayresult in scarring. Cryotherapy can be painful, andpatients are often left with hypopigmented spottingwhere liquid nitrogen was applied. Experts have alsoexpressed the opinion following literature reviewthat patients desire topical therapies offering cos-metic results that are superior to those achieved withcurrently available treatments.11 Accordingly, thereis an unmet medical need for a safe and efficaciousagent for short-course, field-directed treatment thatcan be used in a simple and reliable manner to treatAK.

Ingenol mebutate (ingenol-3-angelate, formerlyPEP005), a diterpene ester extracted and purifiedfrom the plant Euphorbia peplus,12 is being evaluatedas a topical therapy for AK. Ingenol mebutate seemsto possess two mechanisms of antiproliferative ac-tivity: (1) initial chemoablation by disruption of theplasma membrane and mitochondria leading to lossof mitochondrial membrane potential and ultimatelynecrosis of locally affected cells12; and (2) eradica-tion of residual tumor cells via the subsequentgeneration of tumor-specific antibodies, inductionof proinflammatory cytokines, and massive infiltra-tion of neutrophils, ultimately resulting in neutro-phil- and antibody-dependent cellular cytotoxicity.13

Although a mechanism for the selective induction of

necrosis of tumor cells is yet to be reported, theantibody-dependent immune response represents atumor-specific mechanism of action of ingenolmebutate.

Ingenol mebutate has been shown in preclinicalstudies to possess substantial antitumor activity invivo against a variety of murine and human neo-plasms established subcutaneously in mice.12 Aphase 1 study in patients with AK lesions showedthat a single topical application of 0.01% ingenolmebutate in an isopropyl alcoholebased gel formu-lation was associated with a favorable safety profileaccompanied by increased clearance comparedwith vehicle.14 The results of two phase 2a dose-escalation studies suggest that ingenol mebutate gel,0.05% applied to cutaneous AK lesions once dailyfor 2 days may be a suitable concentration and theappropriate dosage regimen.15,16 In one of the phase2a studies, which was conducted in Australia, the rateof complete clinical clearance of individual AKlesions treated once daily for 2 days was 71% withingenol mebutate gel, 0.05% (P \ .0001 vs vehi-cle).16 In the second phase 2a study, which wasconducted in the United States, 70% of patientstreated with ingenol mebutate gel, 0.05% experi-enced a complete clinical response.15 The mostcommon local skin responses (LSRs) were erythema,scabbing and crusting, and scaling/flaking/dry-ness.15,16 Ingenol mebutate and its metaboliteswere not detected in blood samples from twopatients treated with ingenol mebutate gel, 0.05%,suggesting no systemic absorption.15 Samples for PKanalysis were taken at baseline (before day 1 treat-ment) and at 0.5, 1, 2, and 4 hours posttreatment onstudy day 2; the lower limit of quantification was\0.01 ng/mL.

We conducted a phase 2b study to assess furtherthe relative safety and efficacy of ingenol mebutategel, 0.025% and 0.05% as field-directed therapy fornon-facial AK lesions.

METHODSA randomized, double-blind, double-dummy,

vehicle-controlled, sequential cohort dose-findingstudy was conducted at 22 US centers to evaluate the

Abbreviations used:

AE: adverse eventAK: actinic keratosis5-FU: 5-fluorouracilGSR: global severity ratingLSR: local skin responseSCC: squamous cell carcinoma

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safety, tolerability, and efficacy of ingenol mebutategel, 0.025% applied once daily for 3 consecutive daysor ingenolmebutate gel, 0.05% appliedonce daily for 2or 3 consecutive days to a contiguous area ofskin (field-directed therapy) containing AK lesions.Appropriate institutional review boards approved thestudy protocol before the start of the trial. Eligiblepatients (males $ 18 years old and postmenopausalfemales) had 4 to 8 clinically typical, visible, anddiscrete AK lesions within a contiguous 25-cm2 areaon the arm, shoulder, chest, back, or scalp. Among theexclusion criteria were women of childbearing poten-tial, AK lesions on the face, atypical-appearing AKlesions or suspected cutaneous malignancy within theselected AK treatment area, lesion-directed therapywithin 2 cm of the selected AK treatment area duringthe previous 4 weeks, and/or field-directed therapywithin 2 cm of the selected AK treatment area duringthe previous 24 months.

Patients were randomized to treatment with ve-hicle on days 1, 2, and 3; ingenol mebutate gel,0.025% on days 1, 2, and 3; vehicle on day 1 andingenol mebutate gel, 0.05% on days 2 and 3; oringenol mebutate gel, 0.05% on days 1, 2, and 3.Approximately 200 patients were to be enrolled inthe study. Assuming a postdose global severity rating(GSR) incidence of ‘‘severe’’ due to treatment of theselected AK area in 1% of the vehicle group and 20%of the ingenol mebutate gel, 0.05% group, thecalculated odds ratio is 24.75. At a power of 80%and significance level of 0.05, the estimated numberof evaluable patients required per dose group is 41for a one-sided test. If the estimated patient dropoutrate is 10%, the required number of patients per dosegroup increases to 50.

Patients were evaluated at a screening visit andenrolled into the study if they met the study criteria.Between 3 days and 14 days after screening, enrolledpatients were randomized at the day 1 (baseline) visitto 1 of 4 dosing cohorts. Each center was allocated aninitial block of 4 randomization numbers. All en-rolled patients were assigned a patient number atbaseline in ascending order according to the block ofnumbers allocated to the center. Each study patientreceived a study medication kit containing 3 identi-cal-appearing, single-use mini-tubes of study medi-cation labeled day 1, day 2, and day 3; 3 individualfinger gloves for self-application of study medica-tion; and patient safety and study medication in-structions. The randomization number assigned toeach patient appeared on the patient’s study medi-cation kit and on the 3 individual mini-tubes of studymedication. The investigator, center personnel, andpatients were blinded as to which treatment regimenthe patient received.

Randomized patients applied the study medica-tion to the selected AK treatment area as directed onday 1 under the supervision of the investigator.Patients were instructed to apply the study medica-tion at home on day 2 and return for assessment onday 3, at which time the investigator (based on his orher assessment of any LSR and the GSR of the selectedAK treatment area) advised patients whether to applythe study medication at home for the last treatmentday. Patientswere then assessed at follow-up visits ondays 8, 15, 29, and 57 (end-of-study visit). A derma-tologic examination, including assessment of LSRsand monitoring for adverse events (AEs), was per-formed at each visit by a qualified dermatologist.Clinical laboratory tests were performed during thescreening visit and on day 8. Posttreatment follow-upafter day 57 was available for any patient with anunresolved treatment-emergent AE or LSR of theselected AK treatment area (other than pigmentationor scarring) that remained unstable at day 57.

The intent-to-treat population comprised allpatients who were randomized. The modifiedintent-to-treat population (defined as all randomizedpatients who were treated with at least one dose ofstudy medication and who had at least one post-baseline assessment of clearance) was used for allefficacy analyses. Efficacy was assessed by the num-ber of baseline AK lesions still visible clinically in theselected AK treatment area at day 57, the totalnumber of clinically visible AK lesions in the selectedAK treatment area (including baseline lesions) at day57, and patient satisfaction with treatment outcomesat day 57. The primary efficacy end point was thepartial clearance rate, defined as the proportion ofpatients at day 57 with $ 75% reduction in thenumber of AK lesions that were originally identifiedin the selected AK treatment area at baseline.Secondary efficacy end points were (1) the completeclearance rate, defined as the proportion of patientsat day 57 with no clinically visible AK lesions in theselected AK treatment area (lesions present at base-line or emergent during the study period in thetreatment area); (2) the baseline clearance rate,defined as the proportion of patients at day 57 with100% reduction in the number of AK lesions thatwere originally identified in the selected AK treat-ment area at baseline; and (3) the percentage reduc-tion of the number of AK lesions, defined as thenumber of lesions present in the AK treatment area atbaseline minus the number of lesions present at theend of the study divided by the number of lesionspresent in the AK treatment area at baseline. Asubjective assessment of satisfaction with treatmentwas obtained from patients using a questionnairewith a 7-point Likert scale, in which a score of 1 is

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Anderson et al 937

Fig 1. Patient disposition diagram.

very negative, 4 is neutral, and 7 is very positive. Thequestionnaire assessed convenience and ease of use,healing time, cosmetic outcome, satisfaction com-pared with prior AK treatment, and overallsatisfaction.

A safety analysis was performed on the modifiedintent-to-treat population. Safety was assessed by anumber of clinical end points, including the inci-dence rate and grade of LSRs following treatment,the GSR of the selected AK treatment area before andafter treatment, the incidence of treatment-relatedAEs recorded throughout the study, and the meanchange in laboratory tests from the screening visitthrough day 8. LSRs were considered a component ofthe response to treatment and were defined aserythema, flaking/scaling, crusting, swelling, vesic-ulation/pustulation, erosion/ulceration, pigmenta-tion (hyperpigmentation or hypopigmentation),and scarring in the selected treatment area. LSRassessments were made using the following scale:0 = not present; grade 1 = isolated finding specific tolesions; grade 2 = involving less than 50% of thetreated area; grade 3 = involving greater than 50% ofthe treated area; and grade 4 = black eschar orulceration for erosion/ulceration, and extendingoutside treatment area for all other LSRs. The GSRwas developed to capture the investigator’s overallclinical impression of the severity of any local reac-tion to the study drug at the treatment area asassessed at baseline, after the application of studydrug, and at each subsequent study visit using the

following 4-point scale: none = no visible signs orsymptoms present; mild = signs visibly or palpablypresent and/or patient awareness of symptoms;moderate = substantial signs or symptoms; andsevere = extensive signs or symptoms. Treatment-related AEs were those assessed as either unknownrelation, possibly, probably, or definitely related tostudy drug by the investigator.

All statistical analyses were performed usingVersion 8.2 or later of SAS statistical software (SASInstitute Inc, Cary, NC). For discrete/categorical var-iables, the frequency distribution was generatedusing procedure FREQ. The Cochran-Mantel-Haenszel test and the Cochrane-Armitage Trend testwere performed using procedure GLM. TheWilcoxon rank-sum test and Kruskal-Wallis testwere performed using procedure NPAR1WAY.Unless otherwise specified, a result was determinedto be statistically significant when the accompanyingstatistical test (two-tailed) yielded a probability of .05or less.

RESULTSOf 283 patients screened for eligibility, 222 met

the eligibility requirements, were randomized totreatment, and were able to be evaluated for efficacyand safety; 220 completed the study through day 57(1 patient was lost to follow-up and 1 patient had ascheduling issue) (Fig 1). All 222 patients enrolled inthe study were Caucasian, 3 of whom (1.4%) were ofHispanic ethnicity. The age range of patients was 43

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Table I. Efficacy end points

Concentration and Dosage Regimen of ingenol mebutate gel

Efficacy measure

Vehicle

(n = 60)

0.025% Gel 3 3 days

(n = 50)

0.05% Gel 3 2 days

(n = 55)

0.05% Gel 3 3 days

(n = 57)

Partial clearance rate,* No. (%) 13 (21.7) 28 (56.0) 34 (61.8) 43 (75.4)95% CI 11.24-32.09 42.4-69.76 48.98-74.66 64.26-86.61P valuey — .0002 \.0001 \.0001

Complete clearance rate,z No. (%) 7 (11.7) 20 (40.0) 24 (43.6) 31 (54.4)95% CI 3.54-19.79 26.42-53.58 30.53-56.74 41.46-67.32P valuey — .0006 .0001 \.0001

Baseline clearance rate,§ No. (%) 8 (13.3) 21 (42.0) 24 (43.6) 33 (57.9)95% CI 4.73-21.93 28.32-55.68 30.53-56.74 45.08-70.71P valuey — .0007 .0003 \.0001

Median percentage reduction inbaseline lesion

0 75.0 83.3 100

Minimum, maximum �20.0, 100.0 0.0, 100.0 �57.1, 100.0 0.0, 100.0P valuey — .0001 .0001 \.0001

CI, Confidence interval.

*Greater than or equal to 75% of the baseline lesions cleared within the treatment area.yCompared with vehicle.zNo clinically visible lesions (baseline and emergent) within the treatment area.§All (100%) of the baseline lesions cleared within the treatment area.

to 85 years, with a mean age of 67 years. The majorityof patients were male (80.2%), and 68.5% of patientshad Fitzpatrick-Pathak skin types 1 or 2 (burn easilyand tan rarely or minimally). The anatomic distribu-tion of AK lesions was as follows: arm, 66.2%; scalp,27.5%; chest, 3.2%; shoulder, 2.7%; and back, 0.5%.

EfficacyAll 3 active treatments were significantly more

effective than vehicle with respect to reducing thenumber of AK lesions as measured at day 57 by thepartial clearance rate, the complete clearance rate,the baseline clearance rate (overall P \ .0001 vsvehicle for each efficacy end point), and the medianpercentage reduction in baseline lesions. The re-sponses were dose dependent for all measures ofefficacy. The results are summarized in Table I.

For the primary efficacy end point of partialclearance rate, 75.4% (43/57) of the ingenol mebutategel, 0.05% for 3 days group, 61.8% (34/55) of theingenol mebutate gel, 0.05% for 2 days group, and56.0% (28/50) of the ingenol mebutate gel, 0.025% for3 days group met the criteria of $ 75% clearance ofAK lesions, compared with 21.7% (13/60) of thevehicle group. The differences were all statisticallysignificant compared with vehicle (P \ .0001, P \.0001, and P = .0002, respectively).

The complete and baseline clearance rates andthe median percentage reduction of the number ofAK lesions from baseline were also significantlyhigher with active treatment than with vehicle.Complete clearance was achieved in 54.4% (31/57)

of the ingenol mebutate gel, 0.05% for 3 days group,43.6% (24/55) of the ingenol mebutate gel, 0.05% for2 days group, 40.0% (20/50) of the ingenol mebutategel, 0.025% for 3 days group, and 11.7% (7/60) of thevehicle group (P \ .0001, P = .0001, and P = .0006,respectively, compared with vehicle). Completeclearance of baseline lesions was achieved in 57.9%(33/57) of the ingenol mebutate gel, 0.05% for 3 daysgroup, 43.6% (24/55) of the ingenol mebutate gel,0.05% for 2 days group, 42.0% (21/50) of the ingenolmebutate gel, 0.025% for 3 days group, and 13.3%(8/60) of the vehicle group (P\.0001, P = .0003, and

Fig 2. Patient assessment of satisfaction with treatment(mean scores) using a questionnaire with a 7-point scale,where a score of 1 is very negative, 4 is neutral, and 7 isvery positive. a, P = .0779 for all active treatments vsvehicle. b, P = .0005 for all active treatments vs vehicle. c,P \ .0001 for all active treatments vs vehicle. d, P \ .0001for all active treatments vs vehicle. e, P\.0001 for all activetreatments vs vehicle.

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Table II. Local skin responses by study visit for active treatment groups (n = 162)

Patients experiencing LSR

Local skin response Baseline No. (%) Day 3 No. (%) Day 8 No. (%) Day 15 No. (%) Day 57 No. (%)

Erythema 54 (33.3) 158 (97.5) 157 (96.9) 131 (80.9) 55 (34.0)Flaking/scaling 90 (55.6) 124 (76.5) 156 (96.3) 131 (80.9) 47 (29.0)Crusting 22 (13.6) 71 (43.8) 133 (82.1) 69 (42.6) 15 (9.2)Swelling 3 (1.9) 72 (44.4) 50 (30.9) 9 (5.6) 0 (0.0)Vesiculation/pustulation 0 (0.0) 63 (38.9) 28 (17.3) 3 (1.9) 0 (0.0)Erosion/ulceration 1 (0.6) 25 (15.4) 42 (25.9) 10 (6.20) 3 (1.9)Pigmentation (hyper/hypo) 47 (29.0) 35 (21.6) 45 (27.8) 33 (20.4) 32 (19.8)Scarring 3 (1.9) 2 (1.2) 3 (1.9) 2 (1.2) 1 (0.6)

LSR, Local skin response.

P = .0007, respectively, compared with vehicle). Themedian percentage reduction in baseline lesions was0% in patients treated with vehicle compared with100% of patients treated with ingenol mebutate gel,0.05% for 3 days, 83.3% of patients treated withingenol mebutate gel, 0.05% for 2 days, and 75.0% ofpatients treated with ingenol mebutate gel, 0.025%for 3 days (P \ .0001 vs vehicle for each activetreatment).

There was a consistent decline in the number ofAK lesions from day 3 to day 29 for all 3 activetreatments, and the difference between active treat-ments and vehicle was highly significant at day 57(P \ .0001).

Patients’ subjective assessments of satisfactionwith ingenol mebutate gel were positive with meanscores significantly higher for all active treatmentscompared with vehicle for healing time (P = .0005),cosmetic outcome (P \ .0001), results comparedwith previous AK lesion treatment (P \ .001), andoverall satisfaction (P \ .001) (Fig 2). Convenienceand ease of use score, although higher for activetreatments, was not significantly different from thatfor vehicle (P = .0779). The overall median patientsatisfaction score was 7.0 (very positive) for all activetreatments, whereas the overall median score was 4.0(neutral) for the vehicle group.

SafetyThe most common LSRs were erythema, fla-

king/scaling, and crusting, which were most intensebetween day 3 and day 8 (Table II). Erythema wasreported by 97.5% of patients in active treatmentgroups at day 3. At day 8, erythema and flaking/scal-ing were the most frequently reported LSRs (96.9%and 96.3%, respectively). Fig 3 illustrates typical LSRsassociated with ingenol mebutate gel therapy. LSRswere anticipated, and these responses relate to themechanism of action of ingenol mebutate. LSRs weretransient and resolved spontaneously, generally

within 2 to 4 weeks after treatment. Fig 4 shows themean composite LSR score by study visit. The com-posite score represents the sums of the individualLSR scores calculated at each study visit for eachtreatment group. The highest mean composite LSRscores were noted at day 8 for the active drug groups,with a mean composite score of 6.5 for the ingenolmebutate gel, 0.025% for 3 days, and ingenolmebutate gel, 0.05% for 2 days groups, and 7.8 forthe ingenol mebutate gel, 0.05% for 3 days group.Mean composite scores for all 3 active drug groupsdecreased to 1.1 or less by day 57. Mean compositescores for LSR ranged from 1.4 (day 15) to 1.7 (day 3)for vehicle. Mean composite LSR scores showed adose-response effect for grade 3 or grade 4 LSRswithin the active treatment groups from baseline today 8. There was no scarring caused by treatmentwith ingenol mebutate gel; the one patient withscarring at day 57 had scarring at baseline. Theincidence of pigmentation change in the treatmentarea was similar across active treatment groups.Overall, the level of pigmentation LSRs decreasedfrom baseline to day 57 following active treatment,with 29% of lesions showing a pigmentation levelgreater than 0 (not present) at baseline and 20% atthe end of the study (see Table II). At day 57,pigmentation changes that had worsened from base-line were observed in 6 patients: 3 patients each inthe ingenol mebutate gel, 0.05% for 2 days andingenol mebutate gel, 0.05% for 3 days groups.Hyperpigmentation increased from 0 to 1 (slightlyvisible) in 3 patients and from 0 to 2 (present in\50%of the treatment area) in one patient, while hypo-pigmentation increased from 0 to 1 in 1 patient.Both hyperpigmentation and hypopigmentationincreased in 2 separate lesions from 0 to 1 in1 patient.

Across all active treatment groups, 25 patients(15.4%) were deemed not eligible to apply the day 3dose of ingenol mebutate gel because of an LSR (6 of

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Fig 3. Typical local skin responses to ingenol mebutate treatment. Lesions that were identifiedat screening are indicated by numbered dots on the day 1 photograph. A, Ingenol mebutate gel,0.05% on days 1, 2, and 3. B, Ingenol mebutate gel, 0.05% on days 1, 2, and 3. C, Ingenolmebutate gel, 0.05% on days 2 and 3.

50 in the ingenol mebutate gel, 0.025% group, 3 of 55in the ingenol mebutate gel, 0.05% for 2 days group,and 16 of 57 in the ingenol mebutate gel, 0.05% for 3days group).

The summary of GSR for active treatment groupsover time is shown in Table III. In all ingenolmebutate gel groups the predominant GSR wasmild or moderate. The most frequent GSR reportedin the active treatment groups at day 3 was mild (88patients). At day 8, moderate was the most frequentlyreported GSR (78 patients). By day 15 there was asubstantial reduction in the number of patientshaving a moderate or severe GSR (27 and 1, respec-tively). By day 57, the GSRs had returned to baselineor lower.

There were 45 treatment-related AEs reported: 2in the vehicle group, 11 in the ingenol mebutate gel,0.025% group, 11 in the ingenol mebutate gel, 0.05%for 2 days group, and 21 in the ingenol mebutate gel,0.05% for 3 days group. Application site and non-application site treatment-related AEs are summa-rized in Table IV. There were 8 serious AEs in 4patients in the vehicle group, 5 serious AEs in 5patients in the ingenol mebutate gel, 0.025% group, 2

serious AEs in 2 patients in the ingenol mebutate gel,0.05% for 2 days group, and 1 serious AE in 1 patientin the ingenol mebutate gel, 0.05% for 3 days group.No serious AE was reported as being treatmentrelated. All treatment-related or serious AEs had

Fig 4. Summary of mean composite LSR score. A =vehicle; - = Ingenol mebutate gel, 0.025% 3 3 days;m = Ingenol mebutate gel, 0.05% 3 2 days; C = Ingenolmebutate gel, 0.05% 3 3 days. LSR, local skin response.Composite score represents sums of individual LSR scorescalculated at each study visit for each treatment group.

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Table III. GSRs* over time for active treatment groups (n = 162)

GSR rating Baseline No. (%) Day 3 No. (%) Day 8 No. (%) Day 15 No. (%) Day 57 No. (%)

None 112 (69.1) 8 (4.9) 1 (0.6) 18 (11.1) 117 (72.2)Mild 39 (24.1) 88 (54.3) 69 (42.6) 113 (69.8) 40 (24.7)Moderate 11 (6.8) 56 (34.6) 78 (48.1) 27 (16.7) 4 (2.5)Severe 0 (0.0) 10 (6.2) 14 (8.6) 1 (0.6) 0 (0.0)

GSR, Global severity rating.

*GSR assessments were made according to the following definitions: none = no visible signs or symptoms present; mild = signs visibly or

palpably present and/or patient awareness of symptoms; moderate = substantial signs or symptoms; severe = extensive signs or

symptoms.

Table IV. Application site and non-application site treatment-related adverse events*

Adverse event

Vehicle

(n = 60) No. (%)

0.025% Gel 3

3 days (n = 50) No. (%)

0.05% Gel 3

2 days (n = 55) No. (%)

0.05% Gel 3 3 days

(n = 57) No. (%)

Application siteDiscomfort 0 (0.0) 1 (2.0) 0 (0.0) 0 (0.0)Erythema 0 (0.0) 0 (0.0) 0 (0.0) 1 (1.8)Irritation 0 (0.0) 3 (6.0) 3 (5.5) 7 (12.3)Pain 0 (0.0) 4 (8.0) 3 (5.5) 9 (15.3)Paresthesia 0 (0.0) 1 (2.0) 0 (0.0) 1 (1.8)Pruritus 1 (1.7) 4 (8.0) 6 (10.9) 10 (17.5)Reaction 0 (0.0) 0 (0.0) 0 (0.0) 1 (1.8)Vesicles 0 (0.0) 0 (0.0) 0 (0.0) 2 (3.5)Warmth 0 (0.0) 0 (0.0) 1 (1.8) 0 (0.0)Pustules 0 (0.0) 0 (0.0) 0 (0.0) 1 (1.8)

Non-application siteContact dermatitis 0 (0.0) 0 (0.0) 0 (0.0) 1 (1.8)Impetigo 0 (0.0) 0 (0.0) 0 (0.0) 1 (1.8)Chills 0 (0.0) 0 (0.0) 0 (0.0) 1 (1.8)Fever 0 (0.0) 0 (0.0) 1 (1.8) 0 (0.0)Influenza 0 (0.0) 0 (0.0) 1 (1.8) 0 (0.0)Traumatic hematoma 0 (0.0) 0 (0.0) 0 (0.0) 1 (1.8)" Creatine

phosphokinase0 (0.0) 0 (0.0) 1 (1.8) 0 (0.0)

Proteinuria 0 (0.0) 0 (0.0) 1 (1.8) 0 (0.0)Muscle spasms 1 (1.7) 0 (0.0) 1 (1.8) 0 (0.0)Headache 0 (0.0) 0 (0.0) 0 (0.0) 1 (1.8)Nasal congestion 0 (0.0) 1 (2.0) 0 (0.0) 0 (0.0)

*Treatment-related adverse events were those assessed as either unknown relation, possibly, probably, or definitely related to study drug.

resolved by day 57. There were essentially notreatment-related abnormalities in laboratory tests,and there were no discontinuations due to an AE.

DISCUSSIONThis study supports the safety and efficacy of

ingenol mebutate gel as an effective short-course,field-directed therapy with a favorable safety profilefor AK on non-facial sites. Application of ingenolmebutate gel for 2 or 3 days produced a statisticallysignificant, greater AK lesion clearance by all mea-sures of efficacy and at all dosing regimens studiedcompared with vehicle gel. There was a relationshipbetween concentration and therapeutic response. All

3 active treatments were considered to be welltolerated, as application site reactions resolved spon-taneously generally within 2 to 4 weeks, there wereno discontinuations from the study because of an AE,and there were no serious treatment-related AEsduring the 8-week follow-up period. Longer follow-up periods are important to confirm clinical cureover time and to identify recurrence. Subsequentstudies of ingenol mebutate gel in treatment of AKmay use longer follow-up periods.

A comparison of efficacy outcomes with those ofstudies of other topical therapies for AK shows atleast equivalent clearance of lesions over a muchshorter treatment period with ingenol mebutate gel.

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942 Anderson et al

Ranges for partial clearance (56.0% to 75.4% fromlowest to highest dosage) and for complete clear-ance (40.0% to 54.4% from lowest to highest dosage)with ingenol mebutate gel are similar to thosereported historically in phase 3 clinical trials ofcurrent topical therapy for AK lesions includingimiquimod applied for up to 16 weeks,17-19 5-FUapplied for up to 4 weeks,20-22 and diclofenacapplied for up to 90 days.23-25

In this study, ingenol mebutate gel was welltolerated when applied for 2 or 3 days as therapyfor non-facial AK lesions. LSRs, erythema and fla-king/scaling being the most common, peaked be-tween day 3 and day 8 and were largely resolved byday 15. Given that ingenol mebutate has been shownto induce necrosis12 and an acute inflammatoryresponse characterized by a neutrophilic infiltrate,13

the observed LSRs were expected and integral to themechanism of action. Importantly, there was noevidence of significant irritation or sensitization po-tential for ingenol mebutate in a formal, repeatapplication, 21-day skin sensitization study.26 Adose response was observed for the highest rated(Grade 3 and 4) LSRs within the active treatmentgroups (0.05% 3 3 days[0.05% 3 2 days[0.025%3 3 days); all these LSRs cleared during the follow-upperiod. Scarring and pigmentary changes are con-sidered among the most important safety end pointsfor a topical therapy for AK. There was no evidenceof scarring as a result of treatment with ingenolmebutate gel. In addition, although a small numberof patients had hyperpigmentation or hypopigmen-tation after treatment, these pigmentary changeswere mild (most commonly rated as only slightlyvisible) and were not considered clinically meaning-ful by the investigators. Patient approval was high,including satisfaction with respect to tolerability,ease of use, and cosmesis.

In conclusion, ingenol mebutate is a new chem-ical entity with a novel mechanism of action thatseems to be an effective short-course, field-directedtherapy for AK lesions on non-facial sites, with afavorable safety profile when applied as ingenolmebutate gel, 0.025% or 0.05%. A 2- or 3-day courseof therapy with ingenol mebutate gel may providebenefits with respect to patient compliance com-pared with topical agents that require prolongedcourses of treatment. Additional studies are requiredto determine the most appropriate dosage regimen.

The clinical investigators participating in this studywere Lawrence Anderson, MD, FACP, Tyler, TX;Kenneth Beer, MD, West Palm Beach, FL; MelindaBirchmore-Musick, MD, Huntsville, AL; MichaelBond, MD, Clermont, FL; Robert G. Brown, MD,Jacksonville, FL; Michelle Chambers, MD, Columbus,

OH; Armand Cognetta, MD, Tallahassee, FL; StevenA. Davis, MD, San Antonio, TX; Frank Dunlap, MD,Tucson, AZ; John Humeniuk, MD, Greer, SC; TheresaKnoepp, MD, Anderson, SC; Mark R. Ling, MD, PhD,Newnan, GA; Robert T. Matheson, MD, Portland, OR;David Rodriguez, MD, Coral Gables, FL; George J.Schmieder, DO, Orange Park, FL; Pranav Sheth, MD,Cincinnati, OH; Linda Stein Gold, MD, Detroit, MI;Dow B. Stough, MD, Hot Springs, AR; Leonard J.Swinyer, MD, Salt Lake City, UT; Eduardo H. Tschen,MD, Albuquerque, NM; Jeffery M. Weinberg, MD,New York, NY; Jonathan S. Weiss, MD, Snellville, GA;W. Philip Werschler, MD, Spokane, WA; and JoshuaZeichner, MD, Great Neck, NY.

The authors acknowledge the contributions to thedevelopment of this manuscript by Lawrence Nussbaum,MD, Medical Monitor, Omnicare Clinical Research, King ofPrussia, PA, and the analysis of data from the clinical trialby Andrew Barnes, Biostatistician, Omnicare ClinicalResearch, King of Prussia, PA.

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