Self-administered Topical 5% Imiquimod Cream for External Anogenital Warts FREE

ALTHOUGH GENITAL warts are common, therapy is generally painful, prolonged, variably effective, and characterized by recurrence. One reason for these therapeutic problems is that most current therapies depend on physical destruction of the tumor rather than direct antiviral activity against the causative agent, human papillomavirus. A treatment for anogenital warts that is specifically antiviral and nondestructive would represent a significant advancement.

Imiquimod is a recently developed imidazoquinolin heterocyclic amine that is an immune response modifier. It has been shown to exhibit antiviral^1- 2 and antitumor³ properties in animal models, at least partly on the basis of its ability to induce the production of interferon alpha.⁴ Interferon alfa is known to be effective in the treatment of anogenital warts, but therapy with this medication is expensive and unwieldy. Interferon alfa is not absorbed topically and must be administered intralesionally or sublesionally in a standard dosing schedule requiring 9 injections during 3 weeks for each wart or cluster of warts.^5- 6 In addition, adverse effects generally limit therapy to a maximum of 5 warts concurrently.^5- 6 Because interferon is active against these warts and because imiquimod is active when applied topically, imiquimod has been examined as a potential treatment for anogenital warts with encouraging preliminary results.⁷ This multicenter study compares the effectiveness and safety of 1% imiquimod cream, 5% imiquimod cream, and vehicle cream in the treatment of external anogenital warts.

Healthy men and women aged 18 years or older participated in this trial. Patients had a diagnosis of anogenital warts, with a minimum of 2 and a maximum of 50 external lesions. The total wart area was no less than 10 mm².

Patients were enrolled only when judged to be healthy after a medical history taking, physical examination, and laboratory testing yielded no significant positive or abnormal findings.

Laboratory tests included a complete blood cell count, a serum screening multiphasic chemistry panel, serum pregnancy test (women), a urinalysis, and a determination of human immunodeficiency virus status. A Papanicolaou smear was performed on all women, and patients with abnormalities underwent colposcopy. Those patients found to have high-grade squamous intraepithelial lesions (greater than moderate dysplasia) were excluded. Patients immunosuppressed by virtue of disease or use of medication were excluded, as were pregnant or lactating women, and women not using contraception. Patients with current chemical or alcohol dependency were not enrolled.

Patients underwent a baseline skin biopsy test that was interpreted as diagnostic or suggestive of anogenital warts and without evidence of dysplasia.

Patients could not have treated their warts within 4 weeks before enrollment, and the skin must have returned to normal following any previous therapy. Patients with skin disease in the area to be treated, including frequently recurrent herpes simplex virus infection, were excluded. Patients having used any local medications for any purpose, including topical corticosteroids, in the target area during the 2 weeks prior to enrollment were excluded.

Patients signed consent forms approved by the respective institutional review boards.

At the initiation visit, anogenital warts were photographed, measured, and mapped and patients were randomized to use 1 of 3 treatments: 1% imiquimod cream, 5% imiquimod cream, or vehicle cream. Patients were instructed carefully in the use of the test medication, and they were asked to maintain diaries to record dosing and to ensure compliance. They were told first to clean and dry the area. They were then to apply test cream to all external lesions in an amount that could be rubbed in until the cream disappeared. They were instructed to allow the cream to dry before dressing, and to leave the medication on during their normal sleeping time. The test medication was to be washed off with soap and water after an allowable application time of 6 to 10 hours. The medication was to be used 3 times each week until all baseline warts were confirmed to have disappeared or for 16 weeks, whichever occurred first. Medication was to be applied every other day for 3 doses per week with individual applications separated by no less than 36 hours and no more than 96 hours. After the third dose, there was a 2-day pause (60-120 hours) before the next week's dosing. No other topical preparations of any kind were allowed during the treatment period.

At any time during the treatment phase that warts were no longer visible, use of the test cream was stopped, and the patient was entered into the follow-up phase of the study to investigate recurrence. Patients whose warts did not disappear during the 16-week treatment phase did not enter the follow-up phase. New warts appearing during the treatment period could be treated with the study drug; however, those new warts were tracked separately and were not included in the analysis of baseline warts.

During the treatment phase of the trial, patients were seen weekly for 2 weeks and then biweekly until their warts cleared or for the remainder of the 16-week treatment period. At these visits, patient diaries were checked and patients were questioned for the development of adverse reactions. Warts were measured and photographed, and the area was examined for signs and symptoms of local inflammation.

Patients whose initially identified and treated warts disappeared by 16 weeks were entered, as clearing of the warts occurred, into a 12-week treatment-free follow-up phase. New warts that had appeared during the follow-up phase in these patients could be treated with conventional wart therapy. During this follow-up phase, patients were then seen biweekly to evaluate for recurrence of warts. Similar procedures were performed as were done during the treatment phase. Participation in the study was ended at completion of the 12-week follow-up period or on recurrence of a baseline wart, whichever occurred first.

Anogenital warts were measured, mapped, and photographed after the biopsy procedure but before institution of therapy, and every 2 weeks during the treatment and follow-up phases. Wart size was expressed as total area in square meters and determined by the product of the 2 longest perpendicular dimensions.

Patients who had lesions remaining after therapy underwent biopsy if there was any suspicion that the remaining lesion(s) may not have represented a wart.

Laboratory testing consisting of a complete blood cell count, serum multiphasic screening chemistry panels, and a urinalysis was performed at the beginning of the study and again after 8 weeks of therapy. These laboratory tests, as well as a second physical examination, were performed at the conclusion of each patient's participation. A Papanicolaou smear and, if indicated, colposcopy were repeated at the end of treatment if the time elapsed since the baseline testing was longer than 1 month. These were again repeated at the end of participation in the follow-up period if the time elapsed since the most recent Papanicolaou smear was longer than 1 month.

Patients were interviewed at each visit to identify symptoms possibly caused by use of study medication, and the treatment site was examined for local inflammation. Local reactions were graded independently by the patient and the investigator using the following scale: none, mild (visible irritation with minimal or no discomfort that did not disrupt daily activity), moderate (caused considerable discomfort but did not disrupt normal activities), or severe (substantially interfered with the patient's normal daily activities).

A total of 311 patients at 11 clinical centers were enrolled in this trial, including 131 women (42%) and 180 men (58%). One hundred nine patients were randomized to receive 5% imiquimod cream, 102 patients to receive 1% imiquimod cream, and 100 patients to receive vehicle cream. Patient characteristics can be seen in Table 1. There were no significant differences among the 3 groups for age, sex, race, height, weight, smoking habits, or extent of disease. Although the baseline wart area tended to be smaller for women in each group than for men, there was not a statistically significant difference among treatment groups for either sex (men, P>.50; women, P>.50). Also, the reported duration of the current outbreak of anogenital warts in women in each group was shorter than that of men; the difference in duration of warts among treatment groups for men was statistically significant (P=.01). Median duration of warts in the current outbreak for women was 3.4 months (5% imiquimod group), 3.1 months (1% imiquimod group), and 4.4 months (vehicle group). The reported median duration of warts for men was 6.7 months (5% imiquimod group), 26.4 months (1% imiquimod group), and 7.9 months (vehicle group).

Seventy-seven patients discontinued use of medication during the study, and the discontinuation rate was similar for each group. Nineteen patients (17%) in the 5% imiquimod group stopped use of medication, compared with 31 patients (30%) in the 1% imiquimod group and 27 patients (27%) in the vehicle group. Of the 77 patients who withdrew participation in the study, 4 patients discontinued participation because of adverse reactions and 18 patients for lack of therapeutic effect. These patients were classified as treatment failures. The treatment failures included 6 patients (6%) in the 5% imiquimod group, 8 patients (8%) in the 1% imiquimod group, and 8 patients (8%) in the vehicle group. Fifty-five participants did not complete the study because of noncompliance, personal reasons, or unavailability for follow-up. Because these patients were removed for reasons assumed to be unrelated to adverse reactions or lack of efficacy, they were not included in the treatment failures analysis of clearance rates. In this analysis, 13 patients (12%) in the 5% imiquimod group, 23 patients (23%) in the 1% imiquimod group, and 19 patients (19%) in the vehicle group were excluded. The intent-to-treat analysis included all randomized patients.

A total of 33 (31%) of 106 patients using 5% imiquimod cream developed new warts (not present at baseline) during the study. This rate compares with 44 (42%) of 97 patients using 1% imiquimod cream and 41% of patients using vehicle cream (P=.20).

An intent-to-treat analysis was performed (Table 2). In this analysis, 54 (50%) of 109 patients using 5% imiquimod cream achieved total wart clearance, compared with 21 (21%) of 102 patients using 1% imiquimod cream and 11 (11%) of 100 patients using vehicle cream (P<.001). Thirty-three (72%) of 46 female patients experienced complete clearance, as did 21 (33%) of 63 men.

In the treatment failures analysis, 54 (56%) of 96 patients who received 5% imiquimod cream experienced clearing of all original warts, compared with 21 (27%) of 79 of those using 1% imiquimod cream and 11 (14%) of 81 patients who received vehicle cream (Table 3). The difference between the groups using 5% imiquimod and vehicle cream was statistically significant (P<.001), as was the difference between the groups using 5% and 1% imiquimod cream (P<.001), but there was no significant difference between the groups using 1% imiquimod cream and the vehicle cream. In addition to those patients whose warts were completely eradicated by using the 5% imiquimod cream, many other patients experienced a significant decrease in wart area. A 50% or greater reduction in total wart area occurred in 81% of these patients. Of those patients whose warts disappeared while using 5% imiquimod cream, 44% were clear by 8 weeks of therapy and 69% were clear by 12 weeks.

Seventy-seven percent of women and 40% of men using 5% imiquimod cream experienced complete wart clearance. A higher response in women was present in the groups using 1% imiquimod and vehicle cream as well.

Recurrence of at least 1 wart in the treated area occurred in 6 (13%) of 45 patients using 5% imiquimod cream. This rate is conservative since those who discontinued participation were not included in either the numerator or the denominator. A total of 54 patients using 5% imiquimod cream had their warts cleared and 9 discontinued participation during follow-up, leaving 45 assessable patients. Six of these patients had recurrences; thus, the recurrence rate was 13%. Recurrence rates for patients using 1% imiquimod cream and vehicle cream were 0 (0%) of 18 and 1 (10%) of 10, respectively. These were not significantly different, and recurrence rates did not differ by sex.

There was no difference in incidences of flulike symptoms among groups by interview, laboratory testing, or physical examination. One patient was removed from the study because of rhabdomyolysis that was later found to be familial, and another patient for symptoms of lightheadedness, insomnia, and fatigue. This patient received a total dose of topical imiquimod far below that known to produce adverse reactions even when given systemically.

Local inflammatory reactions were the most common adverse events but these were generally well tolerated (Table 4). There was good correlation between the investigators' and the patients' descriptions as to the presence and severity of local inflammation, although patients tended to assess their reactions as less severe. The most common local inflammatory reaction was erythema, occurring, by investigators' judgment, in 71 (67.0%) of 106 patients treated with 5% imiquimod cream. The erythema was severe at some point in 6 patients (5.7%) and moderate in 36 patients (34.0%). There was correspondingly less erythema in those treated with 1% imiquimod cream (25 patients, or 25.8%) or vehicle cream (23 patients, or 24.2%), with only 4 and 3 patients, respectively, developing moderate redness and no patients experiencing severe redness. There were no other severe reactions of any kind at any time in more than 1 patient in any group. The 1% imiquimod cream and vehicle cream were both associated with less severe local inflammatory reactions. In addition, less than 25% of these patients experienced any local inflammation. The majority of patients in each of the 3 treatment groups experienced no flaking, erosion, edema, scabbing, induration, vesicles, or ulceration. Only 2 patients (both using 5% imiquimod cream) were excluded from the study by investigators because of local reactions.

Anogenital warts are benign tumors induced by any of multiple different types of the human papillomavirus. During the last decade, the prevalence has increased dramatically so that now an estimated 2% of sexually active people are reported to have clinically visible anogenital warts, although far more have evidence of the human papillomavirus when evaluated by the polymerase chain reaction technique.^8- 9

Rapidly effective therapies such as cryotherapy, laser vaporization, electrocautery, and excision are painful as well as expensive to varying degrees and although efficient, recurrences are common. Less destructive therapies include the application of podophyllin, and bichloroacetic and trichloroacetic acids. These medications require multiple applications in the office and regularly produce local inflammation that includes erythema, erosion, and crusting. The only medication appropriate for home use is podofilox, a purified podophyllin, which produces erosions and burning in the majority of patients.¹⁰ Although not approved by the US Food and Drug Administration, 5-fluorouracil is sometimes applied topically at home for external anogenital warts, but the severe irritation is limiting.¹¹ However, none of these therapies provides predictable, long-lasting, comfortable removal of visible disease, with a low recurrence rate.^12- 13

The introduction of interferon alfa for the treatment of anogenital warts raised hopes for a therapy that would eliminate both the wart tumor and the virus itself by immunological enhancement or a precise antiviral mechanism rather than nonspecific destruction. However, use of this medication requires administration by multiple injections, and, although producing clearing rates of 36% to 62% without destruction of underlying skin, it is also associated with a significant recurrence rate of visible warts.^5- 6 In addition, this therapy is expensive, produces systemic adverse effects, and requires multiple office visits.

If interferon alfa could be applied topically, some of the practical obstacles would be eliminated. The interferon molecule, however, is not well absorbed. Imiquimod, developed by 3M Pharmaceuticals, St Paul, Minn, is an immune response modifier. It is an inducer of interferon alfa that is active when applied topically. Interferon alfa subtypes 1, 2, 5, 6, and 8 are produced by human peripheral blood mononuclear cells in vitro in response to imiquimod.¹⁴ In addition, imiquimod induces the production by monocytes and macrophages of other immunologically active cytokines independent of induction by interferon.¹⁵ These cytokines include the following: interleukins 1, 6, and 8; interleukin 1 receptor antagonist; and tumor necrosis factor α.¹⁶ Although the exact mechanism of action of imiquimod is not known, imiquimod apparently exerts its in vivo antiviral, immune-enhancing, and antitumor effects by 1 or a combination of these immune mechanisms, and not by nonspecific tissue destruction.

This study confirms the data from preliminary clinical trials indicating that topical 5% imiquimod cream exerts a beneficial effect on anogenital warts and is well tolerated when applied 3 times a week overnight for up to 16 weeks. The complete eradication of baseline warts in 56% of patients and the dramatic reduction of wart area in even more patients compares well with the effects of more destructive and irritating existing therapies on anogenital warts. Reports include eradication of all treated warts in 32% to 80% of patients receiving podophyllin and 45% to 88% of those using podofilox,¹² 69% to 79% of those receiving cryosurgery,^12,17- 18 and up to 80% of those using bichloroacetic and trichloroacetic acids.^12,18 Reported wart recurrence rates are 30% to 60% following therapy with topical chemotherapies such as podophyllin and bichloroacetic and trichloroacetic acids.¹³ Although excision, electrocautery, and laser vaporization can be used to remove warts quickly, these are painful, destructive therapies and recurrences are common (ie, occurring in 9%-72% of warts treated with ablative laser therapy).¹² In comparison, imiquimod produces much less local tissue destruction and inflammation and has the great advantage of home use over all treatments except podofilox. Although recurrences occur with imiquimod, these rates are lower than those historically associated with other therapies for genital warts. The extremely low recurrence rates in patients whose warts were eliminated while using 1% imiquimod cream and vehicle cream are not surprising, since these warts were probably eradicated by the patient's own immunological mechanisms. The higher clearing of anogenital warts in women in each group compared with men may be attributable to the shorter duration of the warts.

This study shows that 5% imiquimod cream is effective in the treatment of anogenital warts when applied overnight 3 times weekly for up to 16 weeks, and it is associated with a lower recurrence rate than those found with other existing standard therapies. Use of this medication is safe, producing well-tolerated local inflammatory reactions in up to 70% of patients at some time during therapy. Five percent imiquimod cream represents a significant addition to the available armamentarium for the treatment of anogenital warts.

Accepted for publication August 4, 1997.

Members of the Human Papillomavirus Study Group are David Baker, MD, Stony Brook, NY; Libby Edwards, MD, Charlotte, NC; Lawrence Eron, MD, Lihue, Hawaii; Alex Ferenczy, MD, Montreal, Quebec; Brian Kunimoto, MD, Vancouver, British Columbia; James McCarty, MD, Fresno, Calif; Peter Pappas, MD, Birmingham, Ala; Richard Reichman, MD, Rochester, NY; Daniel Sauder, MD, Toronto, Ontario; Thomas Sedlacek, MD, Philadelphia, Pa; and Robert Skinner, MD, Memphis, Tenn.

The following study personnel also participated in this study: Mike Gagel; Frances Maddin, MA; Sherry Phillips; Joann Crawford; Melissa Holloway; A. Bailey-Farcione; Julie Ditzel, RN; Debbie Ellard, RN; Liz Harding, RN; Randy Hutchins, PA-C; Carol Distretti, RN; Marrise Phillips; Angela Vomero; Bernard Bourgault, RN; Joan Fethiere; Mary Beth Alder, MSN, ANP; Jeanette O'Rourke, LPN; and Glenda L. Siegrist, MSN, ANP. The 3M Pharmaceuticals personnel who participated in the study include Mary Jane Maser; Mary L. Mathisen; Diane C. Pietig; Sheri L. Smith, MS; Mark C. Vollmer; Carmen J. Thorvaldson; Winifred C. Wu, RPH; Barb L. Burnett, LPN; Mary M. Fleming, RN; John P. Lagus, MS; Sally E. McCarville, MS; Nancy Prochnow; Lucia M. Struck; and Kathy A. Wagenknecht, LPN.

Presented at the Eighth International Conference of the International Society of Antiviral Research, Santa Fe, NM, April 25, 1995; Society for Investigative Dermatology Annual Meeting, Chicago, Ill, May 25, 1995; International Conference on Chemotherapy, Montreal, Quebec, July 18, 1995; 14th International Papillomavirus Conference, Quebec City, Montreal, Quebec, July 26, 1995; 53rd Annual Meeting of the American Academy of Dermatology, Chicago, Ill, July 26-30, 1995; Annual Meeting of the Infectious Diseases Society of Obstetrics and Gynecology, Traverse City, Mich, August 4, 1995; 11th Meeting of the International Society for STD Research, New Orleans, La, August 29, 1995; Meeting of the Infectious Diseases Society of America, San Francisco, Calif, September 16-17, 1995; 13th World Congress of the International Society for the Study of Vulvovaginal Disease, Iguazu, Argentina, September 17, 1995; 54th Annual Meeting of the American Academy of Dermatology, Washington, DC, February 10-14, 1996; 44th Annual Clinical Meeting of the American College of Obstetricians and Gynecologists, Denver, Colo, April 29, 1996; Meeting of the Clinical Dermatology 2000, Vancouver, British Columbia, May 28-31, 1996; 55th Annual Meeting of the American Academy of Dermatology, San Francisco, Calif, March 21-26, 1997; Eurogin Third International Congress on Lower Genital Tract Infections and Neoplasia Papillomavirus in Human Pathology, Paris, France, March 25, 1997; and the 19th World Congress of Dermatology, Sydney, Australia, June 20, 1997.

All biopsy and cervical cytology specimens were interpreted by Mark H. Stoler, MD, Charlottesville, Va.

Reprints: Libby Edwards, MD, Department of Internal Medicine, Carolinas Medical Center, 1000 Blythe Blvd, Charlotte, NC 28203.