- Email: [email protected]
Treatment of genital warts with an immune-response modifier (imiquimod)
Treatment of genital warts with an immune-response modifier (imiquimod) Karl R. Beutner, MD, PhD,a,b Spotswood L. Spruance, MD,c Andrina J. Hougham, BA,d Terry L. Fox, MS,d Mary L. Owens, MD,d and John M. Douglas, Jr., MDe San Francisco and Vallejo, California; Salt Lake City, Utah; St. Paul, Minnesota; and Denver, Colorado Background: Genital warts are a common sexually transmitted disease caused by human papillomavirus. Imiquimod is a novel immune-response modifier capable of inducing a variety of cytokines, including interferon alfa, tumor necrosis factor–α, as well as interleukins 1, 6, and 8. In animal models imiquimod has demonstrated antiviral, antitumor, and adjuvant activity. In vitro, imiquimod has no antiviral or antitumor activity. Objective: Our purpose was to determine the safety and efficacy of topical imiquimod for the treatment of external genital warts. Methods: This prospective double-blind, placebo-controlled, parallel design clinical trial was performed in three outpatient centers, a public health clinic, a university-based clinic, and a private practice. One hundred eight patients with external genital warts (predominantly white men) were entered into the trial. Fifty-one patients were randomly selected to receive 5% imiquimod cream; 57 patients were randomly chosen to receive placebo cream. Study medication was applied three times weekly for up to 8 weeks. Patients whose warts cleared completely were observed for up to 10 weeks to determine recurrence rates. Results: In the intent-to-treat analysis, the warts of 37% (19 of 51) of the imiquimodtreated patients and 0% (0 of 57) of the placebo group cleared completely (p < 0.001). In addition, many patients experienced a partial response. A reduction in baseline wart area of 80% or more was observed in 62% of imiquimod-treated patients (28 of 45) and 4% of the placebo group (2 of 50) (p < 0.001); a 50% reduction or more in wart area was noted in 76% of imiquimod-treated patients (34 of 45) and 8% of placebo recipients (4 of 50) (p < 0.001). Of imiquimod-treated patients whose warts cleared completely and who finished the 10-week follow-up period, 19% (3 of 16) experienced recurrences of warts. Imiquimod-treated patients experienced a significantly greater number of local inflammatory reactions than the placebo group. Symptoms and signs associated with the local inflammatory reactions included itching (54.2%), erythema (33.3%), burning (31.3%), irritation (16.7%), tenderness (12.5%), ulceration (10.4%), erosion (10.4%), and pain (8.3%). There were no differences in systemic reactions or laboratory abnormalities between treatment groups. Conclusion: Topical 5% imiquimod cream appears to have a significant therapeutic effect in the treatment of external genital warts. (J Am Acad Dermatol 1998;38:230-9.)
It has been estimated that 30% to 50% of sexually active adults have genital human papilloFrom the Department of Dermatology, University of California, San Franciscoa; the Department of Medicine, Sutter-Solano Medical Center, Vallejob; the Division of Infectious Diseases, University of Utah, Salt Lake Cityc; 3M Pharmaceuticals, St. Pauld; and the Disease Control Service, Denver Department of Public Health.e Clinical Trial R837-017. Supported by a grant from 3M Pharmaceuticals, St. Paul, Minn. Reprint requests: Karl R. Beutner, 127 Hospital Dr., Suite 204, Vallejo, CA 94589. 16/1/86468
230
mavirus (HPV) infection and that 1% have genital warts.1 Genital warts may clear without therapy; this is thought to be mediated by immunologic responses.2 A variety of treatments are available for genital warts. Of these, only intralesional interferon3-5 and patient-applied podofilox6-8 have been proved to be safe and effective in placebo-controlled clinical trials. Other treatments such as surgery (laser, electrocautery, excision), cryotherapy, podo-
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phyllin resin, and caustic agents (trichloro-acetic or dichloroacetic acid) are regarded as safe and effective but have not been systematically evaluated in controlled trials.9 The major theoretical limitation of current therapies is that, with the exception of the interferons, all are cytodestructive or ablative. Although these modalities can remove the warts, they are inherently limited in their ability to address the primary problem, a viral infection. Imiquimod, 1-(2-methylpropyl)-1H-imidazo[4,5-c]quinolin-4-amine (also known as R-837 and S-26308) (Fig. 1), a non-nucleoside heterocyclic amine, is a member of a new class of immune-response modifying agents. Imiquimod is a potent inducer of interferon alfa (IFN-α). In mice, imiquimod induces a variety of cytokines, including tumor necrosis factor–α (TNF-α) and interleukin-6 (IL-6), but not IL-2.10-14 In the guinea pig model, imiquimod has potent antiherpetic activity because of the induction of cytokines and enhanced cell-mediated immunity.15-20 Imiquimod has also demonstrated in vivo activity against cytomegalovirus21 and Rift Valley Fever virus.22 In vitro, imiquimod has no direct antiviral activity, but it has in vivo antitumor activity in several murine models.23-25 Imiquimod has a greater adjuvant effect than Freund's complete adjuvant in guinea pigs immunized with herpes simplex virus glycoproteins.26 The current study was designed to evaluate the safety and efficacy of topically applied imiquimod for the treatment of genital warts. MATERIAL AND METHODS
Study design This study was a double-blind, randomized, placebo-controlled, parallel design conducted at three centers. There were three phases: prestudy, treatment, and follow-up. Prestudy At the prestudy visit, the study was explained to each patient, eligibility was determined, and all patients signed written informed consent approved by the Institutional Review Board at each center. The diagnosis of genital warts was established by physical examination and confirmed by histopathology when indicated. Only clinically visible, external anogenital warts were evaluated and treated. The wart area was determined by measuring the two greatest perpendicular dimensions of each wart and taking the product of these two measurements. Total wart area was the sum
Beutner et al. 231
Fig. 1. Chemical structure of imiquimod.
of areas for each wart. Included in the study were HIVseronegative men and women (neither lactating nor pregnant) at least 18 years of age and in good general health. Women with vaginal warts or low- or highgrade cervical squamous intraepithelial lesions were excluded. Treatment period Patients were instructed in the use of the study medication and the first dose was applied by the patient under supervision. The active cream contained 5% imiquimod, and the placebo control cream was physically indistinguishable. Patients were instructed to bathe or shower before drug application (but not during the 24-hour period when the cream was on the skin), to apply the cream three times per week (Monday, Wednesday, Friday or Tuesday, Thursday, Saturday), and to apply enough cream to cover the wart area. Patients were requested to avoid sexual contact when the study cream was on the skin. During the 8-week treatment period, patients made one initiation visit and seven once-a-week interval visits. At these visits, wart evaluations, skin irritation assessments, and vital-sign measurements were recorded. Patients were queried regarding adverse events and concomitant medications, as well as pain, itching, and burning at the site of cream application or adjacent
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Table I. Demographic and wart characteristics of study population Imiquimod (n = 51)
Demographics Males (%) Age (yr) mean (SD) Race (%) White Black Asian/Pacific Islander Tobacco (%) No Current Past use Baseline wart characteristics, median (range) Wart area (mm2) No. of warts Months since diagnosis Months since onset Previous treatment (%)‡ None Podophyllin resin Cryotherapy Surgical excision Electrocautery Laser Trichloroacetic acid Condylox Cornstarch Unknown/other medication Mean No. of previous treatments (SD)
Placebo (n = 57)
46 (90) 29 (8)
52 (91) 30 (9)
48 (94) 3 (6) 0 (0)
54 (95) 1 (2) 2 (4)
22 (43) 22 (43) 7 (14)
19 (33) 35 (61) 3 (5)
47 (6-1785) 6 (1-29) 16 (0-144) 28 (2-181)
63 (4-8784) 7 (1-105) 9 (0-275) 14 (1-277)
p Value
> 0.50* > 0.50† 0.29*
0.11*
16 (31) 26 (51) 18 (35) 0 (0) 4 (8) 0 (0) 4 (8) 0 (0) 0 (0) 2 (4) 1.06 (0.91)
18 (32) 21 (37) 20 (35) 1 (2) 3 (5) 1 (2) 8 (14) 2 (4) 1 (2) 4 (7) 1.05 (0.93)
0.14† > 0.50† > 0.50† 0.18† > 0.50* 0.18* > 0.50* > 0.50* > 0.50* > 0.50* 0.37* 0.50* > 0.50* > 0.50* > 0.50†
*p Value is from Fisher's exact test. †p Value is from Wilcoxon rank-sum test. ‡A patient may have had more than one previous wart treatment.
areas. They were asked to quantify these symptoms as mild, moderate, or severe during each visit. Objective evidence of inflammation at the site of cream application and at adjacent sites was evaluated by means of the following scale: 0 = no visible reaction; 1 = equivocal response; 2 = mild erythema; 3 = moderate erythema; 4 = intense erythema; 5 = intense erythema with edema; and 6 = intense erythema with edema and vesicles. Safety monitoring during the interval visits included hemoglobin, hematocrit, leukocyte count and differential, red blood cell count and platelet count, ALT, and AST. Follow-up phase Patients who experienced complete clearing of warts during the treatment period entered into a treatment-free follow-up period of up to 10 weeks or until recurrence was noted. Patients who had a partial response at the end of the 8-week treatment period were evaluated again at week 2 of follow-up to determine whether they had achieved complete clearing.
Statistical considerations For selection of sample size it was estimated that 20% of placebo patients would achieve complete clearing of warts. A clinically meaningful difference between placebo and imiquimod was determined to be 30% (i.e., 50% of imiquimod patients with complete clearing). With a chi-square test, a total of at least 78 patients (39 per treatment) would be needed to have 80% power to detect this treatment difference, assuming a two-sided test with alpha equal to 0.05. Patients who discontinued the study during the treatment period because of local skin reactions and for increase/no change in wart area were considered treatment failures and included in the denominator of the clearance proportions in the treatment-failures analysis. Patients who discontinued for personal reasons, who were judged to be noncompliant with dosing schedules, or who were lost to follow-up were excluded from this analysis.
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Table II. Percent reduction in baseline wart area from treatment- failures analysis* % Reduction in wart area
Imiquimod (n = 45)
Placebo (n = 50)
p Value†
100 ≥ 90 ≥ 80 ≥ 70 ≥ 60 ≥ 50 ≥ 40 ≥ 30 ≥ 20 ≥ 10 ≥0
18 (40%) 21 (47%) 28 (62%) 28 (62%) 31 (69%) 34 (76%) 35 (78%) 37 (82%) 38 (84%) 40 (89%) 42 (93%)
0 (0%) 2 (4%) 2 (4%) 2 (4%) 3 (6%) 4 (8%) 5 (10%) 9 (18%) 12 (24%) 13 (26%) 26 (52%)
< 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001
*This is the last evaluation including follow-up week 2 for patients whose warts did not completely clear in the 8-week treatment period. †p Value is from Fisher's exact test.
A secondary efficacy analysis was a comparison of the reduction in wart area over time. The median percentage reduction in wart area during the 8 weeks in the treatment period and through week 2 of follow-up was calculated for each treatment group and compared by the Wilcoxon rank-sum test. In this analysis, if a patient's warts completely cleared at a certain week and the patient then went into the follow-up period, the reduction of 100% was carried forward for the remaining weeks of the treatment period. If a patient discontinued the study at a certain week for skin irritation or for increase/no change in wart area, that patient's last reduction in area was carried forward for the remaining weeks. Patients who were lost to follow-up were included for the weeks they had data available. RESULTS
A total of 108 patients were entered into the trial from three centers. Fifty-one patients were randomly selected to receive imiquimod and 57 were randomly selected to receive placebo. The population was predominantly white men. There were no significant differences between the groups in terms of age, race, or tobacco use (Table I). The median wart area was 47 mm2 for the imiquimod group and 63 mm2 for placebo. The median number of warts was six for imiquimod versus seven for placebo. In men, the genital warts were predominantly (90% to 91%) on the shaft of the penis and less commonly on the perianal, scrotal, inguinal, pubic, thigh, and perineal areas. In
Fig. 2. Product limit estimate of proportion of patients with complete clearing of baseline warts during treatment period (upper panel). Median percent reduction in baseline wart area and wart count for imiquimodtreated patients (lower panel).
women, warts were located on vulvar, perineal, and perianal areas, as well as the mons pubis and thigh. Some patients had warts at multiple sites. Approximately 30% of both treatment groups had no previous treatment. Those with a history of previous treatment averaged 1.5 treatments and received a variety of treatments (Table I). The time since first diagnosis or onset of genital warts was not significantly different between the treatment groups. No significant differences were found between study groups with respect to overall rate or for any individual reason for discontinuation. A total of seven imiquimod-treated patients (14%) discontinued versus 12 placebo-treated patients (21%). Of the seven patients receiving imiquimod who
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234 Beutner et al.
Table III. Number of patients reporting skin irritation at wart site during treatment period
Week
Group
No. of patients
1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8
Imiquimod Placebo Imiquimod Placebo Imiquimod Placebo Imiquimod Placebo Imiquimod Placebo Imiquimod Placebo Imiquimod Placebo Imiquimod Placebo
47 55 45 50 46 52 43 50 39 49 39 45 34 42 35 45
No. of reactions
28 (59.6%) 47 (85.5%) 20 (44.4%) 41 (82.0%) 19 (41.3%) 45 (86.5%) 17 (39.5%) 43 (86.0%) 17 (43.6%) 42 (85.7%) 18 (46.2%) 39 (86.7%) 21 (61.8%) 38 (90.5%) 20 (57.1%) 41 (91.1%)
Equivocal response or mild erythema
17 (36.2%) 8 (14.5%) 12 (26.7%) 7 (14.0%) 14 (30.4%) 5 (9.6%) 16 (37.2%) 6 (12.0%) 10 (25.6%) 7 (14.3%) 12 (30.8%) 5 (11.1%) 7 (20.6%) 3 (7.1%) 8 (22.9%) 3 (6.7%)
Moderate erythema
Intense erythema
Intense erythema with edema ± vesicles
1 (2.1%) 0 (0.0%) 6 (13.3%) 1 (2.0%) 6 (13.0%) 1 (1.9%) 3 (7.0%) 0 (0.0%) 7 (17.9%) 0 (0.0%) 8 (20.5%) 1 (2.2%) 5 (14.7%) 1 (2.4%) 5 (14.3%) 1 (2.2%)
0 (0.0%) 0 (0.0%) 3 (6.7%) 1 (2.0%) 5 (10.9%) 1 (1.9%) 5 (11.6%) 1 (2.0%) 3 (7.7%) 0 (0.0%) 1 (2.6%) 0 (0.0%) 1 (2.9%) 0 (0.0%) 1 (2.9%) 0 (0.0%)
1 (2.1%) 0 (0.0%) 4 (8.9%) 0 (0.0%) 2 (4.3%) 0 (0.0%) 2 (4.7%) 0 (0.0%) 2 (5.1%) 0 (0.0%) 0 (0.0%) 0 (0.0%) 0 (0.0%) 0 (0.0%) 1 (2.9%) 0 (0.0%)
p Value*
0.002 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 0.002 < 0.001
*p Value is from Wilcoxon rank-sum test.
discontinued, four were lost to follow-up (three patients were lost after the initiation visit and one patient after week 2), two discontinued for local skin reaction, and one discontinued for increase/no change in wart area. Of the 12 patients receiving placebo who discontinued, six were lost to follow-up (two after the initiation visit, and four after treatment had started), five patients discontinued for increase/no change in wart area, and one patient discontinued for a personal reason. Of the 51 patients randomly selected to receive imiquimod, four were excluded from the treatment-failures analysis because they were lost to follow-up, and two were excluded because of poor treatment compliance. Of the 57 patients receiving placebo, the six who were lost to follow-up and the one who dropped out for personal reasons were excluded from the treatment-failures analysis. Of the 45 patients remaining in the imiquimod group, 18 patients (40%) had complete clearance of their warts; none of the 50 patients in the placebo group had completely cleared (p < 0.001). By intent-to-treat analysis, the proportions with complete wart clearance were 19 of 51 (37%) for the imiquimod group versus 0 of 57 (0%) for the placebo group (p < 0.001). The median time to complete clearance was 7 weeks with 22% (4 of 18) of complete responders
clear by week 4 of treatment, 83% (15 of 18) clear by the end of treatment, and 100% by the first follow-up visit. Estimates of proportions of patients with complete clearing of warts relative to time on treatment were established by the Kaplan-Meier product-limit method (Fig. 2). At the end of treatment (follow-up week 2), the product limit estimate of the proportion of imiquimod patients with complete clearing of warts was 0.407 (with standard error of 0.074) and for the placebo group was 0 (p < 0.001). In addition to complete clearance (100% reduction) of baseline wart area, many patients achieved partial reductions during the treatment period (Table II). For imiquimod, 62% (28 of 45) experienced an 80% or greater reduction in baseline wart area, compared with 4% of the placebo group (2 of 50). Of imiquimod and placebo recipients, 76% (34 of 45) versus 8% (4 of 50), respectively, experienced a 50% or more reduction in wart area (p ≤ 0.001). The median percent reduction in wart area improved each week to a maximum of 90% at week 8 for patients receiving imiquimod (Fig. 2), but there was no reduction in those receiving placebo. The median percent of baseline warts cleared at week 8 was 66.7%. A total of 19 imiquimod-treated patients had complete clearing of their warts during the treatment period and entered the follow-up period. A
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Table IV. Application-site reactions* and intensity and duration of reactions Sign or symptom
Itching Erythema Burning Irritation Tenderness Ulceration Erosion Pain
Incidence for imiquimod-treated patients (n = 48)
Total no. of reactions reported†
26 (54.2%) 16 (33.3%) 15 (31.3%) 8 (16.7%) 6 (12.5%) 5 (10.4%) 5 (10.4%) 4 (8.3%)
59 66 32 15 7 9 12 6
Intensity of reactions Mild (%) Moderate (%) Severe (%)
71 49 47 67 43 67 42 17
20 38 41 27 57 11 25 17
9 14 13 7 0 22 33 67
Duration of reactions Median No. Interquartile of days range (days)
6 12 4 5 7 12 10 8
3–13 7–21 1–13 1–11 2–9 7–14 7–13 2–16
*Incidence for patients in the imiquimod group was significantly (p < 0.05) higher than the incidence for patients in the placebo group. †A patient may report a given reaction more than once during the study.
total of three patients were lost to follow-up during this 10-week period. Of the remaining 16 patients, 3 (19%) experienced a recurrence. Two were noted at week 2 and one at week 6 of the 10week follow-up period. A total of 14 of 48 imiquimod-treated patients (29%) and 20 of 55 patients receiving placebo (36%) experienced new warts during the treatment period (p > 0.50). For 5 of these 14 imiquimodtreated patients (36%), the new warts completely cleared during the treatment period, and by the end of the treatment period, these 14 patients had a median of one new wart. In the placebo group, only 1 of 20 patients (5%) had clearing of new warts, and by the end of treatment, the 20 placebo-treated patients had a median of two new warts. The greatest incidence of clinically significant (score ≥ 4) wart-site inflammation occurred during weeks 2 through 5, and these responses abated promptly even with continued application (Table III). One patient in the imiquimod group had a score of 4 at follow-up weeks 2 and 4; from follow-up week 6 on, no patient had a score greater than 2 (mild erythema). Inflammation at the wart site was noted significantly more often in imiquimod recipients than in placebo recipients. Imiquimod-treated patients made a total of 328 clinic visits in the treatment phase (an average of 6.8 visits per patient). Clinically significant inflammation (score ≥ 4) was noted at 31 of the 328 visits (9.5%). A score of 6 (highest possible inflammation score) was noted in 10.4% of imiquimod-treated patients (5 of 48) at some point during treatment. However, a score of 6 was reported at only 2.1% of the visits
(7 of 328). Thus a majority of imiquimod-treated patients experienced inflammatory reactions, but they were relatively short-lived despite continued therapy (Table III). In addition to objective measures of inflammation at each visit, patients were queried about pain, itching, burning, and other symptoms noted at the treatment site. The most frequently reported application-site symptoms for imiquimod-treated patients were itching (54.2%), erythema (33.3%), burning (31.3%), irritation (16.7%), tenderness (12.5%), ulceration (10.4%), erosion (10.4%), and pain (8.3%). Each symptom occurred significantly more frequently (p < 0.05) in imiquimod recipients than in placebo recipients. These symptoms were predominantly reported as mild or moderate and rarely as severe and were of a relatively short duration, lasting a median of 4 to 12 days (Table IV). There were no serious systemic adverse reactions or clinical laboratory abnormalities reported in either group. There were no differences between the groups in terms of frequency or nature of other medical events. Among patients included in the treatment-failures efficacy analysis (n = 45 for imiquimod and n = 50 for placebo), the Spearman rank correlation was used to investigate the relation between final wart area reduction in the treatment period and maximal intensity of wart-site inflammation during the treatment period. For the imiquimod group, a significant positive correlation was found (p < 0.001). No significant correlation was found between wart reduction and months since onset of warts, wart area, or tobacco use. Fig. 3 depicts a typical local inflammatory reaction and a partial response.
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236 Beutner et al.
A
B
C
D Fig. 3. Genital wart before treatment (A); at treatment week 5 (B); at treatment week 7 (C); and at week 2 of follow-up (D). This was a partial response.
DISCUSSION
The complete response rate of 40% noted with imiquimod is comparable to other currently available therapies. The complete response rates reported in controlled trials of podofilox and intralesional interferon(s) are 45% to 58%6-8 and 36% to 62%,3-5 respectively. The complete response rates for other modalities have been less well characterized and are as follows: podophyllin resin, 22% to 77%27-33; trichloroacetic acid, 81%34; cryotherapy, 54% to 92%30,35,36; and laser surgery, 27% to 100%.35,37-40 In addition to patients with complete clearance of warts (18 of 45), an additional 35.6% (16 of 45) had a greater than 50% reduction in wart area. There are a number of potential explanations for partial responses. A median time to complete response of 7 weeks, given a maximum treatment period of 8 weeks, would suggest that a longer treatment period may increase the number of
patients with a complete response. The three times weekly dosing regimen was empirically chosen largely on the basis of results with intralesional interferon.3,4 This study treated predominantly warts on the shaft of the penis, a site traditionally difficult to treat with topical medications. For example, treatment of warts on the shaft of the penis with patient-applied podofilox resulted in a 50% complete response.6 The same treatment given to men with warts predominantly under the foreskin produced a 92% complete response rate.41 For this reason warts on the penile shaft should be considered a stringent test of efficacy for a topical medication. The recurrence rates with interferon and patient-applied podofilox have been determined in rigorous clinical trials. For podofilox the recurrence rate has ranged from 33% to 91%.6-8 For intralesional interferon the recurrence rates have
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been 21%,4 25%,5 and 33%.42 The recurrence rate of 19% noted with imiquimod is lower than that reported with other modalities. Because traditional genital wart therapy uses primarily ablative methods, there has been a tendency to stop treatment as soon as the warts appear to be gone. Although this is consistent with a surgical strategy, it is contrary to antimicrobial chemotherapy, which is usually continued for a time even after symptoms have abated. Because most recurrences (two of three) were noted early (2 weeks) in the follow-up period, the treatment duration may not have been adequate to ensure a sustained response. In addition to recurrent warts, new warts appearing during a course of therapy have been noted in other studies6 and demonstrate the dynamic nature of this infection. Inflammation, erosion, burning, and pain were reported in 64%, 63%, 59%, and 46%, respectively, of patients treated with podofilox.6 With imiquimod treatment, these were reported in 33.3%, 10.4%, 31.3%, and 8.3%, respectively, of subjects at some time during the study. In general, these reactions were mild. Wart-site inflammation scores associated with imiquimod treatment peaked at treatment weeks 2 to 3 and then declined despite continued application of medication. With conventional ablative therapies, pain, burning, inflammation, erosions, and ulcerations are essentially universal. Unlike intralesional interferon treatment of genital warts, which has been associated with a 50% incidence of systemic reactions,3-5 no such reactions were noted with imiquimod. In human peripheral blood mononuclear cells, imiquimod induces IFN-α, IL-1, and TNF-α but not IL-2.10-13 Human keratinocytes exposed to imiquimod demonstrate an increase in messenger RNA for IL-1, IL-6, and IL-8.14 Which of these cytokines accounts for the clinical response is not yet known. IFN-α could be involved in the response noted with imiquimod because intralesional interferons have efficacy in the treatment of genital warts. The inflammation noted with imiquimod appeared to be necessary for wart clearing. IFN-α can enhance antigen presentation by increasing the major histocompatibility complex class I antigen expression. Furthermore, IFNα can favor development of Th1 helper T cells and, thus, a cell-mediated response.43 Warts treated with intralesional interferon frequently regress,
Beutner et al. 237 but characteristically do so without an inflammatory response, such as that seen with imiquimod, suggesting that the response to imiquimod may be caused by factors other than or in addition to interferon. The effect of TNF-α, IL-1, IL-6, and IL-8 in wart clearance is not known, although IL-6 can increase the cytotoxicity of natural killer cells and stimulate acute phase proteins and B cell growth.44 Induction of these cytokines could be anticipated to produce an inflammatory reaction in the epidermis that may stimulate specific and nonspecific host defense mechanisms. TNF-α can induce the expression of intracellular adhesion molecule I (ICAM-1) on keratinocytes45 that may influence T-cell infiltration in the epidermis. In the guinea pig model of genital herpes simplex virus, topical treatment with imiquimod reduced both acute and latent neural infections and acute and recurrent genital disease.15-18 In this model, topical imiquimod had a systemic effect as evidenced by enhanced cell-mediated cytolytic activity. Which one or combination of the potential biologic activities of imiquimod accounts for its therapeutic effect on genital warts remains to be defined. Imiquimod stimulation of a specific immune response is at least suggested by the relatively long time (median, 7 weeks) from onset of therapy to complete response, an inflammatory reaction before wart clearing, and a relatively low recurrence rate. The inflammatory response noted with imiquimod is reminiscent of the inflammation often observed in molluscum contagiosum before natural regression. REFERENCES 1. Koutsky LA, Galloway DA, Holmes KK. Epidemiology of genital human papillomavirus infection. Epidemiol Rev 1983;10:122-63. 2. Jablonska S, Majewski S. Immunology of genital papillomavirus infections. In: Gross G, Jablonska S, Pfister H, Stegner HE, editors. Genital papillomavirus infections. Berlin: Springer-Verlag; 1990. p. 263-81. 3. Vance JC, Bart BJ, Hansen RC, Reichman RC, McEwen C, Hatch KD. Intralesional recombinant alpha-2 interferon for the treatment of patients with condyloma acuminatum or verruca plantaris. Arch Dermatol 1986;122: 272-7. 4. Eron LJ, Judson F, Tucker S. Interferon therapy for condylomata acuminata. N Engl J Med 1986;315:105964. 5. Friedman-Kien AE, Eron LJ, Conant M, Growdon W, Badiak H, Bradstreet PW, et al. Natural interferon alfa for treatment of condylomata acuminata. JAMA 1988;259:533-8. 6. Beutner KR, Conant MA, Friedman-Kien AE, Illeman
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20. 21. 22.
M, Artman NN, Thisted RA, et al. Patient-applied podofilox for treatment of genital warts. Lancet 1989;1: 831-4. Greenberg MD, Rutledge LH, Reid R, Berman NR, Precop SL, Elswick RK Jr. A double-blind, randomized trial of 0.5% podofilox and placebo for the treatment of genital warts in women. Obstet Gynecol 1991;77:735-9. Kirby P, Dunne A, King DH, Corey L. Double-blind randomized clinical trial of self-administered podofilox solution versus vehicle in the treatment of genital warts. Am J Med 1990;88:465-9. Kling AR. Genital warts: therapy. Semin Dermatol 1992;11:247-55. Reiter MJ, Testerman TL, Miller RL, Weeks CE, Tomai MA. Cytokine induction in mice by the immunomodulator imiquimod. J Leukoc Biol 1994;55:234-40. Weeks CE, Gibson SJ. Alpha interferon induction in human blood cell culture by immunomodulator candidate R-837. J Interferon Res 1989;9(Suppl 2):S215. Miller RL, Imbertson LM, Reiter MJ, Pecore SE, Gerster JF. Interferon induction by antiviral S-26308 in guinea pigs. 26th Interscience Conference on Antimicrobial Agents and Chemotherapy, New Orleans, La., Sept 28–Oct 1, 1986. Abstract 385. Weeks CE, Gibson SJ, Imbertson LM, Reiter MJ, Miller RL, Gerster JF. Preclinical pharmacology and efficacy of immunomodulator R-837. J Interferon Res 1990;10 (Suppl 1):S89. Kono T, Kondo S, Pastore S, Shiuji GM, Tomai MA, McKenzie RC, et al. Effects of a novel topical immunomodulator, imiquimod, on keratinocyte cytokine gene expression. Lymphokine Cytokine Res 1994;13: 71-6. Miller RL, Imbertson LM, Reiter MJ, Schwartzmiller DH, Pecore SE, Gerster JF. Inhibition of herpes simplex virus infections in a guinea pig model by S-26308. 25th Interscience Conference on Antimicrobial Agents and Chemotherapy, Minneapolis, Minn., Sept 29-Oct 2, 1985. Abstract 775. Harrison CJ, Jenski L, Voychehovski T, Bernstein DI. Modification of immunological responses and clinical disease during topical R-837 treatment of genital HSV-2 infection. Antiviral Res 1988;10:209-24. Bernstein DI, Miller RL, Harrison CJ. Effect of R837 (an immunomodulator) and acyclovir on genital HSV infection when begun after lesion development in the guinea pig. 31st Interscience Conference on Antimicrobial Agents and Chemotherapy, Chicago: Sept 29-Oct 2, 1991. Abstract 1229. Bernstein DI, Harrison CJ. Effects of immunomodulating agent R837 on acute and latent herpes simplex virus type 2 infections. Antimicrob Agents Chemother 1989;33:1511-5. Harrison CJ, Stanberry LR, Bernstein DI. Effects of cytokines and R-837, a cytokine inducer, on UV-irradiation augmented recurrent genital herpes in guinea pigs. Antiviral Res 1991;15:315-22. Harrison CJ, Jenski L, Miller RL, Bernstein DI. Treatment of genital HSV2 with R-837 [abstract]. Antiviral Res 1988;9:125. Chen M, Griffith BP, Lucia HL, Hsiung GD. Efficacy of S26308 against guinea pig cytomegalovirus infection. Antimicrob Agents Chemother 1988;32:678-83. Kende M, Lupton HW, Canonica PG. Treatment of experimental viral infections with immunomodulators. Adv Biosci 1988;68:51-63.
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23. Sidky YA, Weeks CE, Hatcher J, Bryan GT, Borden EC. Effects of treatment with the oral interferon inducer, R837, on the growth of mouse colon carcinoma, MC-26 [abstract]. Proc Am Assoc Cancer Res 1990;31:433. 24. Sidky YA, Bryan GT, Weeks CE, Hatcher JM, Borden EC. Effects of treatment with an oral interferon inducer, imidazoquinolinamine (R-837), on the growth of mouse bladder carcinoma FCB. J Interferon Res 1990;10(Suppl 1):S123. 25. Borden EC, Sidky YA, Weeks CE. Mechanism of antitumor action of the interferon inducer R-837 [abstract]. Proc Am Assoc Cancer Res 1991;32:258. 26. Bernstein DI, Miller RL, Harrison CJ. Adjuvant effects of imiquimod on a herpes simplex virus type 2 glycoprotein vaccine in guinea pigs. J Infect Dis 1993;167:731-5. 27. Simmons PD. Podophyllin 10% and 25% in the treatment of ano-genital warts. Br J Venereol Dis 1981;57: 208-9. 28. Gabriel G, Thin RN. Treatment of anogenital warts: comparison of trichloracetic acid and podophyllin versus podophyllin alone. Br J Venereol Dis 1983;59:124-6. 29. Mazurkiewicz W, Jablonska S. Comparison between the therapeutic efficacy of 0.5% podophyllotoxin preparations and 20% podophyllin ethanol solution in condylomata acuminata. Z Hautkr 1985;61:1387-95. 30. Stone KM, Becker TM, Hadgu A, Kraus SJ. Treatment of external genital warts: a randomised clinical trial comparing podophyllin, cryotherapy, and electrodesiccation. Genitourin Med 1990;66:16-9. 31. Lassus A, Haukka K, Forsstrom S. Podophyllotoxin for treatment of genital warts in males: a comparison with conventional podophyllin therapy. Eur J Sex Transm Dis 1984;2:31-3. 32. Jensen SL. Comparison of podophyllin application with simple surgical excision in clearance and recurrence of perianal condylomata acuminata. Lancet 1985;2:1146-8. 33. Edwards A, Atma-Ram A, Thin RN. Podophyllotoxin 0.5% versus podophyllin 20% to treat penile warts. Genitourin Med 1988;64:263-5. 34. Godley MJ, Bradbear CS, Gellan M, Thin RNT. Cryotherapy compared with trichloracetic acid in treating genital warts. Genitourin Med 1987;63:390-2. 35. Yliskoski M, Saarikoski S, Syrjänen K, Syrjänen S, Castrén O. Cryotherapy and CO2-laser vaporization in the treatment of cervical and vaginal human papillomavirus (HPV) infections. Acta Obstet Gynecol Scand 1989;68:619-25. 36. Damstra RJ, van Vloten WA. Cryotherapy in the treatment of condylomata acuminata: a controlled study of 64 patients. J Dermatol Surg Oncol 1991;17:273-6. 37. Rosemberg SK. Carbon dioxide laser treatment of external genital lesions. Urology 1985;25:555-8. 38. Larsen J, Petersen CS. The patient with refractory genital warts in the STD-clinic. Dan Med Bull 1990;37: 194-5. 39. Graversen PH, Bagi P, Rosenkilde P. Laser treatment of recurrent urethral condylomata acuminata in men. Scand J Urol Nephrol 1990;24:163-6. 40. Krebs H-B, Wheelock JB. The CO2 laser for recurrent and therapy-resistant condylomata acuminata. J Reprod Med 1985;30:489-92. 41. von Krogh G. Penile condylomata acuminata: an experimental model for evaluation of topical self-treatment with 0.5-1.0% ethanolic preparations of podophyllotoxin for three days. Sex Transm Dis 1981;8:179-86. 42. Reichman RC, Oakes D, Bonnez W, Greisberger C,
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Tyring S, Miller L, et al. Treatment of condyloma acuminatum with three different interferons administered intralesionally: a double-blind, placebo-controlled trial. Ann Intern Med 1988;108:675-9. 43. Parronchi P, De Carli M, Manetti R, Simonelli C, Sampognaro S, Piccinni MP, et al. IL-4 and IFN (α and γ) exert opposite regulatory effects on the development of cytolytic potential by Th1 or Th2 human T cell clones. J Immunol 1992;I49:2977-83.
O
44. McKenzie RC, Sauder DN. Keratinocyte cytokines and growth factors: functions in skin immunity and homeostasis. Dermatol Clin 1990;8:649-54. 45. Griffiths CEM, Voorhees JJ, Nickoloff BJ. Characterization of intercellular adhesion molecule-1 and HLA-DR expression in normal and inflamed skin: modulation by recombinant gamma interferon and tumor necrosis factor. J Am Acad Dermatol 1989;20:617-29.
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It has been estimated that 30% to 50% of sexually active adults have genital human papilloFrom the Department of Dermatology, University of California, San Franciscoa; the Department of Medicine, Sutter-Solano Medical Center, Vallejob; the Division of Infectious Diseases, University of Utah, Salt Lake Cityc; 3M Pharmaceuticals, St. Pauld; and the Disease Control Service, Denver Department of Public Health.e Clinical Trial R837-017. Supported by a grant from 3M Pharmaceuticals, St. Paul, Minn. Reprint requests: Karl R. Beutner, 127 Hospital Dr., Suite 204, Vallejo, CA 94589. 16/1/86468
230
mavirus (HPV) infection and that 1% have genital warts.1 Genital warts may clear without therapy; this is thought to be mediated by immunologic responses.2 A variety of treatments are available for genital warts. Of these, only intralesional interferon3-5 and patient-applied podofilox6-8 have been proved to be safe and effective in placebo-controlled clinical trials. Other treatments such as surgery (laser, electrocautery, excision), cryotherapy, podo-
Journal of the American Academy of Dermatology Volume 38, Number 2, Part 1
phyllin resin, and caustic agents (trichloro-acetic or dichloroacetic acid) are regarded as safe and effective but have not been systematically evaluated in controlled trials.9 The major theoretical limitation of current therapies is that, with the exception of the interferons, all are cytodestructive or ablative. Although these modalities can remove the warts, they are inherently limited in their ability to address the primary problem, a viral infection. Imiquimod, 1-(2-methylpropyl)-1H-imidazo[4,5-c]quinolin-4-amine (also known as R-837 and S-26308) (Fig. 1), a non-nucleoside heterocyclic amine, is a member of a new class of immune-response modifying agents. Imiquimod is a potent inducer of interferon alfa (IFN-α). In mice, imiquimod induces a variety of cytokines, including tumor necrosis factor–α (TNF-α) and interleukin-6 (IL-6), but not IL-2.10-14 In the guinea pig model, imiquimod has potent antiherpetic activity because of the induction of cytokines and enhanced cell-mediated immunity.15-20 Imiquimod has also demonstrated in vivo activity against cytomegalovirus21 and Rift Valley Fever virus.22 In vitro, imiquimod has no direct antiviral activity, but it has in vivo antitumor activity in several murine models.23-25 Imiquimod has a greater adjuvant effect than Freund's complete adjuvant in guinea pigs immunized with herpes simplex virus glycoproteins.26 The current study was designed to evaluate the safety and efficacy of topically applied imiquimod for the treatment of genital warts. MATERIAL AND METHODS
Study design This study was a double-blind, randomized, placebo-controlled, parallel design conducted at three centers. There were three phases: prestudy, treatment, and follow-up. Prestudy At the prestudy visit, the study was explained to each patient, eligibility was determined, and all patients signed written informed consent approved by the Institutional Review Board at each center. The diagnosis of genital warts was established by physical examination and confirmed by histopathology when indicated. Only clinically visible, external anogenital warts were evaluated and treated. The wart area was determined by measuring the two greatest perpendicular dimensions of each wart and taking the product of these two measurements. Total wart area was the sum
Beutner et al. 231
Fig. 1. Chemical structure of imiquimod.
of areas for each wart. Included in the study were HIVseronegative men and women (neither lactating nor pregnant) at least 18 years of age and in good general health. Women with vaginal warts or low- or highgrade cervical squamous intraepithelial lesions were excluded. Treatment period Patients were instructed in the use of the study medication and the first dose was applied by the patient under supervision. The active cream contained 5% imiquimod, and the placebo control cream was physically indistinguishable. Patients were instructed to bathe or shower before drug application (but not during the 24-hour period when the cream was on the skin), to apply the cream three times per week (Monday, Wednesday, Friday or Tuesday, Thursday, Saturday), and to apply enough cream to cover the wart area. Patients were requested to avoid sexual contact when the study cream was on the skin. During the 8-week treatment period, patients made one initiation visit and seven once-a-week interval visits. At these visits, wart evaluations, skin irritation assessments, and vital-sign measurements were recorded. Patients were queried regarding adverse events and concomitant medications, as well as pain, itching, and burning at the site of cream application or adjacent
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Table I. Demographic and wart characteristics of study population Imiquimod (n = 51)
Demographics Males (%) Age (yr) mean (SD) Race (%) White Black Asian/Pacific Islander Tobacco (%) No Current Past use Baseline wart characteristics, median (range) Wart area (mm2) No. of warts Months since diagnosis Months since onset Previous treatment (%)‡ None Podophyllin resin Cryotherapy Surgical excision Electrocautery Laser Trichloroacetic acid Condylox Cornstarch Unknown/other medication Mean No. of previous treatments (SD)
Placebo (n = 57)
46 (90) 29 (8)
52 (91) 30 (9)
48 (94) 3 (6) 0 (0)
54 (95) 1 (2) 2 (4)
22 (43) 22 (43) 7 (14)
19 (33) 35 (61) 3 (5)
47 (6-1785) 6 (1-29) 16 (0-144) 28 (2-181)
63 (4-8784) 7 (1-105) 9 (0-275) 14 (1-277)
p Value
> 0.50* > 0.50† 0.29*
0.11*
16 (31) 26 (51) 18 (35) 0 (0) 4 (8) 0 (0) 4 (8) 0 (0) 0 (0) 2 (4) 1.06 (0.91)
18 (32) 21 (37) 20 (35) 1 (2) 3 (5) 1 (2) 8 (14) 2 (4) 1 (2) 4 (7) 1.05 (0.93)
0.14† > 0.50† > 0.50† 0.18† > 0.50* 0.18* > 0.50* > 0.50* > 0.50* > 0.50* 0.37* 0.50* > 0.50* > 0.50* > 0.50†
*p Value is from Fisher's exact test. †p Value is from Wilcoxon rank-sum test. ‡A patient may have had more than one previous wart treatment.
areas. They were asked to quantify these symptoms as mild, moderate, or severe during each visit. Objective evidence of inflammation at the site of cream application and at adjacent sites was evaluated by means of the following scale: 0 = no visible reaction; 1 = equivocal response; 2 = mild erythema; 3 = moderate erythema; 4 = intense erythema; 5 = intense erythema with edema; and 6 = intense erythema with edema and vesicles. Safety monitoring during the interval visits included hemoglobin, hematocrit, leukocyte count and differential, red blood cell count and platelet count, ALT, and AST. Follow-up phase Patients who experienced complete clearing of warts during the treatment period entered into a treatment-free follow-up period of up to 10 weeks or until recurrence was noted. Patients who had a partial response at the end of the 8-week treatment period were evaluated again at week 2 of follow-up to determine whether they had achieved complete clearing.
Statistical considerations For selection of sample size it was estimated that 20% of placebo patients would achieve complete clearing of warts. A clinically meaningful difference between placebo and imiquimod was determined to be 30% (i.e., 50% of imiquimod patients with complete clearing). With a chi-square test, a total of at least 78 patients (39 per treatment) would be needed to have 80% power to detect this treatment difference, assuming a two-sided test with alpha equal to 0.05. Patients who discontinued the study during the treatment period because of local skin reactions and for increase/no change in wart area were considered treatment failures and included in the denominator of the clearance proportions in the treatment-failures analysis. Patients who discontinued for personal reasons, who were judged to be noncompliant with dosing schedules, or who were lost to follow-up were excluded from this analysis.
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Table II. Percent reduction in baseline wart area from treatment- failures analysis* % Reduction in wart area
Imiquimod (n = 45)
Placebo (n = 50)
p Value†
100 ≥ 90 ≥ 80 ≥ 70 ≥ 60 ≥ 50 ≥ 40 ≥ 30 ≥ 20 ≥ 10 ≥0
18 (40%) 21 (47%) 28 (62%) 28 (62%) 31 (69%) 34 (76%) 35 (78%) 37 (82%) 38 (84%) 40 (89%) 42 (93%)
0 (0%) 2 (4%) 2 (4%) 2 (4%) 3 (6%) 4 (8%) 5 (10%) 9 (18%) 12 (24%) 13 (26%) 26 (52%)
< 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001
*This is the last evaluation including follow-up week 2 for patients whose warts did not completely clear in the 8-week treatment period. †p Value is from Fisher's exact test.
A secondary efficacy analysis was a comparison of the reduction in wart area over time. The median percentage reduction in wart area during the 8 weeks in the treatment period and through week 2 of follow-up was calculated for each treatment group and compared by the Wilcoxon rank-sum test. In this analysis, if a patient's warts completely cleared at a certain week and the patient then went into the follow-up period, the reduction of 100% was carried forward for the remaining weeks of the treatment period. If a patient discontinued the study at a certain week for skin irritation or for increase/no change in wart area, that patient's last reduction in area was carried forward for the remaining weeks. Patients who were lost to follow-up were included for the weeks they had data available. RESULTS
A total of 108 patients were entered into the trial from three centers. Fifty-one patients were randomly selected to receive imiquimod and 57 were randomly selected to receive placebo. The population was predominantly white men. There were no significant differences between the groups in terms of age, race, or tobacco use (Table I). The median wart area was 47 mm2 for the imiquimod group and 63 mm2 for placebo. The median number of warts was six for imiquimod versus seven for placebo. In men, the genital warts were predominantly (90% to 91%) on the shaft of the penis and less commonly on the perianal, scrotal, inguinal, pubic, thigh, and perineal areas. In
Fig. 2. Product limit estimate of proportion of patients with complete clearing of baseline warts during treatment period (upper panel). Median percent reduction in baseline wart area and wart count for imiquimodtreated patients (lower panel).
women, warts were located on vulvar, perineal, and perianal areas, as well as the mons pubis and thigh. Some patients had warts at multiple sites. Approximately 30% of both treatment groups had no previous treatment. Those with a history of previous treatment averaged 1.5 treatments and received a variety of treatments (Table I). The time since first diagnosis or onset of genital warts was not significantly different between the treatment groups. No significant differences were found between study groups with respect to overall rate or for any individual reason for discontinuation. A total of seven imiquimod-treated patients (14%) discontinued versus 12 placebo-treated patients (21%). Of the seven patients receiving imiquimod who
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234 Beutner et al.
Table III. Number of patients reporting skin irritation at wart site during treatment period
Week
Group
No. of patients
1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8
Imiquimod Placebo Imiquimod Placebo Imiquimod Placebo Imiquimod Placebo Imiquimod Placebo Imiquimod Placebo Imiquimod Placebo Imiquimod Placebo
47 55 45 50 46 52 43 50 39 49 39 45 34 42 35 45
No. of reactions
28 (59.6%) 47 (85.5%) 20 (44.4%) 41 (82.0%) 19 (41.3%) 45 (86.5%) 17 (39.5%) 43 (86.0%) 17 (43.6%) 42 (85.7%) 18 (46.2%) 39 (86.7%) 21 (61.8%) 38 (90.5%) 20 (57.1%) 41 (91.1%)
Equivocal response or mild erythema
17 (36.2%) 8 (14.5%) 12 (26.7%) 7 (14.0%) 14 (30.4%) 5 (9.6%) 16 (37.2%) 6 (12.0%) 10 (25.6%) 7 (14.3%) 12 (30.8%) 5 (11.1%) 7 (20.6%) 3 (7.1%) 8 (22.9%) 3 (6.7%)
Moderate erythema
Intense erythema
Intense erythema with edema ± vesicles
1 (2.1%) 0 (0.0%) 6 (13.3%) 1 (2.0%) 6 (13.0%) 1 (1.9%) 3 (7.0%) 0 (0.0%) 7 (17.9%) 0 (0.0%) 8 (20.5%) 1 (2.2%) 5 (14.7%) 1 (2.4%) 5 (14.3%) 1 (2.2%)
0 (0.0%) 0 (0.0%) 3 (6.7%) 1 (2.0%) 5 (10.9%) 1 (1.9%) 5 (11.6%) 1 (2.0%) 3 (7.7%) 0 (0.0%) 1 (2.6%) 0 (0.0%) 1 (2.9%) 0 (0.0%) 1 (2.9%) 0 (0.0%)
1 (2.1%) 0 (0.0%) 4 (8.9%) 0 (0.0%) 2 (4.3%) 0 (0.0%) 2 (4.7%) 0 (0.0%) 2 (5.1%) 0 (0.0%) 0 (0.0%) 0 (0.0%) 0 (0.0%) 0 (0.0%) 1 (2.9%) 0 (0.0%)
p Value*
0.002 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 0.002 < 0.001
*p Value is from Wilcoxon rank-sum test.
discontinued, four were lost to follow-up (three patients were lost after the initiation visit and one patient after week 2), two discontinued for local skin reaction, and one discontinued for increase/no change in wart area. Of the 12 patients receiving placebo who discontinued, six were lost to follow-up (two after the initiation visit, and four after treatment had started), five patients discontinued for increase/no change in wart area, and one patient discontinued for a personal reason. Of the 51 patients randomly selected to receive imiquimod, four were excluded from the treatment-failures analysis because they were lost to follow-up, and two were excluded because of poor treatment compliance. Of the 57 patients receiving placebo, the six who were lost to follow-up and the one who dropped out for personal reasons were excluded from the treatment-failures analysis. Of the 45 patients remaining in the imiquimod group, 18 patients (40%) had complete clearance of their warts; none of the 50 patients in the placebo group had completely cleared (p < 0.001). By intent-to-treat analysis, the proportions with complete wart clearance were 19 of 51 (37%) for the imiquimod group versus 0 of 57 (0%) for the placebo group (p < 0.001). The median time to complete clearance was 7 weeks with 22% (4 of 18) of complete responders
clear by week 4 of treatment, 83% (15 of 18) clear by the end of treatment, and 100% by the first follow-up visit. Estimates of proportions of patients with complete clearing of warts relative to time on treatment were established by the Kaplan-Meier product-limit method (Fig. 2). At the end of treatment (follow-up week 2), the product limit estimate of the proportion of imiquimod patients with complete clearing of warts was 0.407 (with standard error of 0.074) and for the placebo group was 0 (p < 0.001). In addition to complete clearance (100% reduction) of baseline wart area, many patients achieved partial reductions during the treatment period (Table II). For imiquimod, 62% (28 of 45) experienced an 80% or greater reduction in baseline wart area, compared with 4% of the placebo group (2 of 50). Of imiquimod and placebo recipients, 76% (34 of 45) versus 8% (4 of 50), respectively, experienced a 50% or more reduction in wart area (p ≤ 0.001). The median percent reduction in wart area improved each week to a maximum of 90% at week 8 for patients receiving imiquimod (Fig. 2), but there was no reduction in those receiving placebo. The median percent of baseline warts cleared at week 8 was 66.7%. A total of 19 imiquimod-treated patients had complete clearing of their warts during the treatment period and entered the follow-up period. A
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Beutner et al. 235
Table IV. Application-site reactions* and intensity and duration of reactions Sign or symptom
Itching Erythema Burning Irritation Tenderness Ulceration Erosion Pain
Incidence for imiquimod-treated patients (n = 48)
Total no. of reactions reported†
26 (54.2%) 16 (33.3%) 15 (31.3%) 8 (16.7%) 6 (12.5%) 5 (10.4%) 5 (10.4%) 4 (8.3%)
59 66 32 15 7 9 12 6
Intensity of reactions Mild (%) Moderate (%) Severe (%)
71 49 47 67 43 67 42 17
20 38 41 27 57 11 25 17
9 14 13 7 0 22 33 67
Duration of reactions Median No. Interquartile of days range (days)
6 12 4 5 7 12 10 8
3–13 7–21 1–13 1–11 2–9 7–14 7–13 2–16
*Incidence for patients in the imiquimod group was significantly (p < 0.05) higher than the incidence for patients in the placebo group. †A patient may report a given reaction more than once during the study.
total of three patients were lost to follow-up during this 10-week period. Of the remaining 16 patients, 3 (19%) experienced a recurrence. Two were noted at week 2 and one at week 6 of the 10week follow-up period. A total of 14 of 48 imiquimod-treated patients (29%) and 20 of 55 patients receiving placebo (36%) experienced new warts during the treatment period (p > 0.50). For 5 of these 14 imiquimodtreated patients (36%), the new warts completely cleared during the treatment period, and by the end of the treatment period, these 14 patients had a median of one new wart. In the placebo group, only 1 of 20 patients (5%) had clearing of new warts, and by the end of treatment, the 20 placebo-treated patients had a median of two new warts. The greatest incidence of clinically significant (score ≥ 4) wart-site inflammation occurred during weeks 2 through 5, and these responses abated promptly even with continued application (Table III). One patient in the imiquimod group had a score of 4 at follow-up weeks 2 and 4; from follow-up week 6 on, no patient had a score greater than 2 (mild erythema). Inflammation at the wart site was noted significantly more often in imiquimod recipients than in placebo recipients. Imiquimod-treated patients made a total of 328 clinic visits in the treatment phase (an average of 6.8 visits per patient). Clinically significant inflammation (score ≥ 4) was noted at 31 of the 328 visits (9.5%). A score of 6 (highest possible inflammation score) was noted in 10.4% of imiquimod-treated patients (5 of 48) at some point during treatment. However, a score of 6 was reported at only 2.1% of the visits
(7 of 328). Thus a majority of imiquimod-treated patients experienced inflammatory reactions, but they were relatively short-lived despite continued therapy (Table III). In addition to objective measures of inflammation at each visit, patients were queried about pain, itching, burning, and other symptoms noted at the treatment site. The most frequently reported application-site symptoms for imiquimod-treated patients were itching (54.2%), erythema (33.3%), burning (31.3%), irritation (16.7%), tenderness (12.5%), ulceration (10.4%), erosion (10.4%), and pain (8.3%). Each symptom occurred significantly more frequently (p < 0.05) in imiquimod recipients than in placebo recipients. These symptoms were predominantly reported as mild or moderate and rarely as severe and were of a relatively short duration, lasting a median of 4 to 12 days (Table IV). There were no serious systemic adverse reactions or clinical laboratory abnormalities reported in either group. There were no differences between the groups in terms of frequency or nature of other medical events. Among patients included in the treatment-failures efficacy analysis (n = 45 for imiquimod and n = 50 for placebo), the Spearman rank correlation was used to investigate the relation between final wart area reduction in the treatment period and maximal intensity of wart-site inflammation during the treatment period. For the imiquimod group, a significant positive correlation was found (p < 0.001). No significant correlation was found between wart reduction and months since onset of warts, wart area, or tobacco use. Fig. 3 depicts a typical local inflammatory reaction and a partial response.
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236 Beutner et al.
A
B
C
D Fig. 3. Genital wart before treatment (A); at treatment week 5 (B); at treatment week 7 (C); and at week 2 of follow-up (D). This was a partial response.
DISCUSSION
The complete response rate of 40% noted with imiquimod is comparable to other currently available therapies. The complete response rates reported in controlled trials of podofilox and intralesional interferon(s) are 45% to 58%6-8 and 36% to 62%,3-5 respectively. The complete response rates for other modalities have been less well characterized and are as follows: podophyllin resin, 22% to 77%27-33; trichloroacetic acid, 81%34; cryotherapy, 54% to 92%30,35,36; and laser surgery, 27% to 100%.35,37-40 In addition to patients with complete clearance of warts (18 of 45), an additional 35.6% (16 of 45) had a greater than 50% reduction in wart area. There are a number of potential explanations for partial responses. A median time to complete response of 7 weeks, given a maximum treatment period of 8 weeks, would suggest that a longer treatment period may increase the number of
patients with a complete response. The three times weekly dosing regimen was empirically chosen largely on the basis of results with intralesional interferon.3,4 This study treated predominantly warts on the shaft of the penis, a site traditionally difficult to treat with topical medications. For example, treatment of warts on the shaft of the penis with patient-applied podofilox resulted in a 50% complete response.6 The same treatment given to men with warts predominantly under the foreskin produced a 92% complete response rate.41 For this reason warts on the penile shaft should be considered a stringent test of efficacy for a topical medication. The recurrence rates with interferon and patient-applied podofilox have been determined in rigorous clinical trials. For podofilox the recurrence rate has ranged from 33% to 91%.6-8 For intralesional interferon the recurrence rates have
Journal of the American Academy of Dermatology Volume 38, Number 2, Part 1
been 21%,4 25%,5 and 33%.42 The recurrence rate of 19% noted with imiquimod is lower than that reported with other modalities. Because traditional genital wart therapy uses primarily ablative methods, there has been a tendency to stop treatment as soon as the warts appear to be gone. Although this is consistent with a surgical strategy, it is contrary to antimicrobial chemotherapy, which is usually continued for a time even after symptoms have abated. Because most recurrences (two of three) were noted early (2 weeks) in the follow-up period, the treatment duration may not have been adequate to ensure a sustained response. In addition to recurrent warts, new warts appearing during a course of therapy have been noted in other studies6 and demonstrate the dynamic nature of this infection. Inflammation, erosion, burning, and pain were reported in 64%, 63%, 59%, and 46%, respectively, of patients treated with podofilox.6 With imiquimod treatment, these were reported in 33.3%, 10.4%, 31.3%, and 8.3%, respectively, of subjects at some time during the study. In general, these reactions were mild. Wart-site inflammation scores associated with imiquimod treatment peaked at treatment weeks 2 to 3 and then declined despite continued application of medication. With conventional ablative therapies, pain, burning, inflammation, erosions, and ulcerations are essentially universal. Unlike intralesional interferon treatment of genital warts, which has been associated with a 50% incidence of systemic reactions,3-5 no such reactions were noted with imiquimod. In human peripheral blood mononuclear cells, imiquimod induces IFN-α, IL-1, and TNF-α but not IL-2.10-13 Human keratinocytes exposed to imiquimod demonstrate an increase in messenger RNA for IL-1, IL-6, and IL-8.14 Which of these cytokines accounts for the clinical response is not yet known. IFN-α could be involved in the response noted with imiquimod because intralesional interferons have efficacy in the treatment of genital warts. The inflammation noted with imiquimod appeared to be necessary for wart clearing. IFN-α can enhance antigen presentation by increasing the major histocompatibility complex class I antigen expression. Furthermore, IFNα can favor development of Th1 helper T cells and, thus, a cell-mediated response.43 Warts treated with intralesional interferon frequently regress,
Beutner et al. 237 but characteristically do so without an inflammatory response, such as that seen with imiquimod, suggesting that the response to imiquimod may be caused by factors other than or in addition to interferon. The effect of TNF-α, IL-1, IL-6, and IL-8 in wart clearance is not known, although IL-6 can increase the cytotoxicity of natural killer cells and stimulate acute phase proteins and B cell growth.44 Induction of these cytokines could be anticipated to produce an inflammatory reaction in the epidermis that may stimulate specific and nonspecific host defense mechanisms. TNF-α can induce the expression of intracellular adhesion molecule I (ICAM-1) on keratinocytes45 that may influence T-cell infiltration in the epidermis. In the guinea pig model of genital herpes simplex virus, topical treatment with imiquimod reduced both acute and latent neural infections and acute and recurrent genital disease.15-18 In this model, topical imiquimod had a systemic effect as evidenced by enhanced cell-mediated cytolytic activity. Which one or combination of the potential biologic activities of imiquimod accounts for its therapeutic effect on genital warts remains to be defined. Imiquimod stimulation of a specific immune response is at least suggested by the relatively long time (median, 7 weeks) from onset of therapy to complete response, an inflammatory reaction before wart clearing, and a relatively low recurrence rate. The inflammatory response noted with imiquimod is reminiscent of the inflammation often observed in molluscum contagiosum before natural regression. REFERENCES 1. Koutsky LA, Galloway DA, Holmes KK. Epidemiology of genital human papillomavirus infection. Epidemiol Rev 1983;10:122-63. 2. Jablonska S, Majewski S. Immunology of genital papillomavirus infections. In: Gross G, Jablonska S, Pfister H, Stegner HE, editors. Genital papillomavirus infections. Berlin: Springer-Verlag; 1990. p. 263-81. 3. Vance JC, Bart BJ, Hansen RC, Reichman RC, McEwen C, Hatch KD. Intralesional recombinant alpha-2 interferon for the treatment of patients with condyloma acuminatum or verruca plantaris. Arch Dermatol 1986;122: 272-7. 4. Eron LJ, Judson F, Tucker S. Interferon therapy for condylomata acuminata. N Engl J Med 1986;315:105964. 5. Friedman-Kien AE, Eron LJ, Conant M, Growdon W, Badiak H, Bradstreet PW, et al. Natural interferon alfa for treatment of condylomata acuminata. JAMA 1988;259:533-8. 6. Beutner KR, Conant MA, Friedman-Kien AE, Illeman
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M, Artman NN, Thisted RA, et al. Patient-applied podofilox for treatment of genital warts. Lancet 1989;1: 831-4. Greenberg MD, Rutledge LH, Reid R, Berman NR, Precop SL, Elswick RK Jr. A double-blind, randomized trial of 0.5% podofilox and placebo for the treatment of genital warts in women. Obstet Gynecol 1991;77:735-9. Kirby P, Dunne A, King DH, Corey L. Double-blind randomized clinical trial of self-administered podofilox solution versus vehicle in the treatment of genital warts. Am J Med 1990;88:465-9. Kling AR. Genital warts: therapy. Semin Dermatol 1992;11:247-55. Reiter MJ, Testerman TL, Miller RL, Weeks CE, Tomai MA. Cytokine induction in mice by the immunomodulator imiquimod. J Leukoc Biol 1994;55:234-40. Weeks CE, Gibson SJ. Alpha interferon induction in human blood cell culture by immunomodulator candidate R-837. J Interferon Res 1989;9(Suppl 2):S215. Miller RL, Imbertson LM, Reiter MJ, Pecore SE, Gerster JF. Interferon induction by antiviral S-26308 in guinea pigs. 26th Interscience Conference on Antimicrobial Agents and Chemotherapy, New Orleans, La., Sept 28–Oct 1, 1986. Abstract 385. Weeks CE, Gibson SJ, Imbertson LM, Reiter MJ, Miller RL, Gerster JF. Preclinical pharmacology and efficacy of immunomodulator R-837. J Interferon Res 1990;10 (Suppl 1):S89. Kono T, Kondo S, Pastore S, Shiuji GM, Tomai MA, McKenzie RC, et al. Effects of a novel topical immunomodulator, imiquimod, on keratinocyte cytokine gene expression. Lymphokine Cytokine Res 1994;13: 71-6. Miller RL, Imbertson LM, Reiter MJ, Schwartzmiller DH, Pecore SE, Gerster JF. Inhibition of herpes simplex virus infections in a guinea pig model by S-26308. 25th Interscience Conference on Antimicrobial Agents and Chemotherapy, Minneapolis, Minn., Sept 29-Oct 2, 1985. Abstract 775. Harrison CJ, Jenski L, Voychehovski T, Bernstein DI. Modification of immunological responses and clinical disease during topical R-837 treatment of genital HSV-2 infection. Antiviral Res 1988;10:209-24. Bernstein DI, Miller RL, Harrison CJ. Effect of R837 (an immunomodulator) and acyclovir on genital HSV infection when begun after lesion development in the guinea pig. 31st Interscience Conference on Antimicrobial Agents and Chemotherapy, Chicago: Sept 29-Oct 2, 1991. Abstract 1229. Bernstein DI, Harrison CJ. Effects of immunomodulating agent R837 on acute and latent herpes simplex virus type 2 infections. Antimicrob Agents Chemother 1989;33:1511-5. Harrison CJ, Stanberry LR, Bernstein DI. Effects of cytokines and R-837, a cytokine inducer, on UV-irradiation augmented recurrent genital herpes in guinea pigs. Antiviral Res 1991;15:315-22. Harrison CJ, Jenski L, Miller RL, Bernstein DI. Treatment of genital HSV2 with R-837 [abstract]. Antiviral Res 1988;9:125. Chen M, Griffith BP, Lucia HL, Hsiung GD. Efficacy of S26308 against guinea pig cytomegalovirus infection. Antimicrob Agents Chemother 1988;32:678-83. Kende M, Lupton HW, Canonica PG. Treatment of experimental viral infections with immunomodulators. Adv Biosci 1988;68:51-63.
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23. Sidky YA, Weeks CE, Hatcher J, Bryan GT, Borden EC. Effects of treatment with the oral interferon inducer, R837, on the growth of mouse colon carcinoma, MC-26 [abstract]. Proc Am Assoc Cancer Res 1990;31:433. 24. Sidky YA, Bryan GT, Weeks CE, Hatcher JM, Borden EC. Effects of treatment with an oral interferon inducer, imidazoquinolinamine (R-837), on the growth of mouse bladder carcinoma FCB. J Interferon Res 1990;10(Suppl 1):S123. 25. Borden EC, Sidky YA, Weeks CE. Mechanism of antitumor action of the interferon inducer R-837 [abstract]. Proc Am Assoc Cancer Res 1991;32:258. 26. Bernstein DI, Miller RL, Harrison CJ. Adjuvant effects of imiquimod on a herpes simplex virus type 2 glycoprotein vaccine in guinea pigs. J Infect Dis 1993;167:731-5. 27. Simmons PD. Podophyllin 10% and 25% in the treatment of ano-genital warts. Br J Venereol Dis 1981;57: 208-9. 28. Gabriel G, Thin RN. Treatment of anogenital warts: comparison of trichloracetic acid and podophyllin versus podophyllin alone. Br J Venereol Dis 1983;59:124-6. 29. Mazurkiewicz W, Jablonska S. Comparison between the therapeutic efficacy of 0.5% podophyllotoxin preparations and 20% podophyllin ethanol solution in condylomata acuminata. Z Hautkr 1985;61:1387-95. 30. Stone KM, Becker TM, Hadgu A, Kraus SJ. Treatment of external genital warts: a randomised clinical trial comparing podophyllin, cryotherapy, and electrodesiccation. Genitourin Med 1990;66:16-9. 31. Lassus A, Haukka K, Forsstrom S. Podophyllotoxin for treatment of genital warts in males: a comparison with conventional podophyllin therapy. Eur J Sex Transm Dis 1984;2:31-3. 32. Jensen SL. Comparison of podophyllin application with simple surgical excision in clearance and recurrence of perianal condylomata acuminata. Lancet 1985;2:1146-8. 33. Edwards A, Atma-Ram A, Thin RN. Podophyllotoxin 0.5% versus podophyllin 20% to treat penile warts. Genitourin Med 1988;64:263-5. 34. Godley MJ, Bradbear CS, Gellan M, Thin RNT. Cryotherapy compared with trichloracetic acid in treating genital warts. Genitourin Med 1987;63:390-2. 35. Yliskoski M, Saarikoski S, Syrjänen K, Syrjänen S, Castrén O. Cryotherapy and CO2-laser vaporization in the treatment of cervical and vaginal human papillomavirus (HPV) infections. Acta Obstet Gynecol Scand 1989;68:619-25. 36. Damstra RJ, van Vloten WA. Cryotherapy in the treatment of condylomata acuminata: a controlled study of 64 patients. J Dermatol Surg Oncol 1991;17:273-6. 37. Rosemberg SK. Carbon dioxide laser treatment of external genital lesions. Urology 1985;25:555-8. 38. Larsen J, Petersen CS. The patient with refractory genital warts in the STD-clinic. Dan Med Bull 1990;37: 194-5. 39. Graversen PH, Bagi P, Rosenkilde P. Laser treatment of recurrent urethral condylomata acuminata in men. Scand J Urol Nephrol 1990;24:163-6. 40. Krebs H-B, Wheelock JB. The CO2 laser for recurrent and therapy-resistant condylomata acuminata. J Reprod Med 1985;30:489-92. 41. von Krogh G. Penile condylomata acuminata: an experimental model for evaluation of topical self-treatment with 0.5-1.0% ethanolic preparations of podophyllotoxin for three days. Sex Transm Dis 1981;8:179-86. 42. Reichman RC, Oakes D, Bonnez W, Greisberger C,
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Tyring S, Miller L, et al. Treatment of condyloma acuminatum with three different interferons administered intralesionally: a double-blind, placebo-controlled trial. Ann Intern Med 1988;108:675-9. 43. Parronchi P, De Carli M, Manetti R, Simonelli C, Sampognaro S, Piccinni MP, et al. IL-4 and IFN (α and γ) exert opposite regulatory effects on the development of cytolytic potential by Th1 or Th2 human T cell clones. J Immunol 1992;I49:2977-83.
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44. McKenzie RC, Sauder DN. Keratinocyte cytokines and growth factors: functions in skin immunity and homeostasis. Dermatol Clin 1990;8:649-54. 45. Griffiths CEM, Voorhees JJ, Nickoloff BJ. Characterization of intercellular adhesion molecule-1 and HLA-DR expression in normal and inflamed skin: modulation by recombinant gamma interferon and tumor necrosis factor. J Am Acad Dermatol 1989;20:617-29.
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