Diphenylcyclopropenone: examination for potential contaminants, mechanisms of sensitization, and photochemical stability

Use of Contact Immunotherapy in the Treatment of Skin Diseases Other than Alopecia Areata

For decades, contact immunotherapy with dinitrochlorobenzene, diphencyprone, and squaric acid dibutylester has played an important role in both clinical practice and scientific research. It is listed as the first-line treatment for extensive alopecia areata and was more recently approved for melanoma treatment as an orphan drug in the USA. Moreover, owing to the relative low cost and safety, topical immunotherapy has also been used in many infectious, neoplastic, and inflammatory dermatological diseases. It is especially valuable in vulnerable groups, for cosmetic/pain sensitive areas, or for multiple lesions. In this review, we summarize the current evidence supporting the use of contact immunotherapy for treatment of skin diseases, from articles collected from PubMed database. Owing to space limitation and already numerous studies focusing on alopecia areata, we include only skin diseases other than alopecia areata. In addition to diseases that have been reported to be treated by contact immunotherapy, the hypothesized mechanism, prognosis prediction, efficacy, and safety of these topical agents are discussed.

M-CPOnes: transition metal complexes with cyclopropenone-based ligands for light-triggered carbon monoxide release

A new class of CO-releasing molecules, M-CPOnes, was prepared combining cyclopropenone-based ligands for CO release with the modular scaffold of transition metal complexes. In proof-of-concept studies, M-CPOnes based on Zn^II, Fe^II and Co^II are stable in the dark but undergo light-triggered CO release with the cyclopropenone substituents and metal ions enabling tuning of the photophysical properties. Furthermore, the choice of metal allows the use of different spectroscopic methods to monitor photodecarbonylation from fluorescence spectroscopy to UV/vis spectroscopy and paramagnetic NMR spectroscopy. The modularity of M-CPOnes from the metal ion to the cyclopropenone substitution and potential for further functionalisation of the ligand make M-CPOnes appealing for tailored functionality in applications.

Alopecia areata: a long-term follow-up study of 104 patients

BACKGROUND

Alopecia areata (AA) is a common autoimmune disease that considerably affects the quality of life. Although several studies have investigated the epidemiology, clinical characteristics and treatment of AA, limited recent data are available regarding its long-term course.

OBJECTIVES

To evaluate the long-term course of AA in different age groups.

METHODS

A retrospective evaluation of patients who were newly diagnosed with AA from 2008 to 2011 and had at least 7 years of follow-up. Data regarding the initial episode, treatment given, disease-free interval and relapses were analysed.

RESULTS

A total of 104 cases were analysed: 31 childhood-onset, 63 adult-onset and 10 late-onset. At first episode, 88.5% of patients had mild, 3.8% moderate and 7.7% severe AA. Full or significant re-growth was observed in 74%, 94% and 100% of childhood-onset, adult-onset and late-onset AA patients, respectively. There was no re-growth in 13%, 3% and 0% of childhood-onset, adult-onset and late-onset patients, respectively. The duration of the initial episode and the disease-free interval negatively correlated with age. Systemic steroids were the most effective treatment for the primary episode. The frequency of relapses was high overall (52%, 44% and 30% in childhood-onset, adult-onset and late-onset, respectively), but significantly declined over time with a majority (79%) occurring within the first 4 years. The disease-free interval and relapse rate were not correlated with gender, disease severity at onset or treatment given.

CONCLUSIONS

The prevalence of severe disease, duration of an initial episode and the rate of relapses decreased with an older age at onset. In addition, the outcome and the disease-free interval improved with age at onset. The frequency of relapses declined over time and most appear early on. The current treatment modalities do not seem to influence the long-term outcome.

The Use of Diphenylcyclopropenone in the Treatment of Recalcitrant Warts

Background:

The treatment of recalcitrant palmoplantar and periungual warts using topical immunotherapy with diphenylcyclopropenone (DPC) was reviewed retrospectively over a seven-year period.

Methods:

Two hundred eleven patients were sensitized during this time. The patients consisted of 90 males and 121 females and were between 5 and 78 years old. Twenty-three patients were lost to followup. Of the remaining, 4 were undergoing treatment at the time of evaluation, 1 patient failed sensitization, and 1 patient became pregnant. Four discontinued because of side effects, 3 because of financial reasons, and 18 patients discontinued treatment prior to completing the minimum required applications (defined as 6), producing a dropout rate of 12% (25/211). Three patients had additional treatment during the course of DPC and were not included in the study. The remaining 154 patients were classified as nonresponders or responders.

Results:

The responders consisted of 135 individuals (87.7%) that had complete clearance of warts. Reported adverse effects were local and included with pruritus (15.6%), with blistering (7.1%), and with eczematous reactions (14.2%). The majority of the patients tolerated the treatment very well. One patient developed local impetigo. Patients had an average of 5 treatments over a 6-month period.

Conclusions:

Topical immunotherapy using DPC is an effective treatment option for recalcitrant warts. It should be considered as first-line treatment for warts based on its high response rate, absence of scarring, and painless application.

Alopecia areata: a new treatment plan

Many therapeutic modalities have been used to treat alopecia areata, with variable efficacy and safety profiles. Unfortunately, none of these agents is curative or preventive. Also, many of these therapeutic agents have not been subjected to randomized, controlled trials, and, except for topical immunotherapy, there are few published studies on long-term outcomes. The treatment plan is designed according to the patient's age and extent of disease. In this paper, the therapeutic agents are organized according to their efficacy and safety profiles into first-line, second-line, and third-line options.

Alopecia areata update: part II. Treatment

Various therapeutic agents have been described for the treatment of alopecia areata (AA), but none are curative or preventive. The aim of AA treatment is to suppress the activity of the disease. The high rate of spontaneous remission and the paucity of randomized, double-blind, placebo-controlled studies make the evidence-based assessment of these therapies difficult. The second part of this two-part series on AA discusses treatment options in detail and suggests treatment plans according to specific disease presentation. It also reviews recently reported experimental treatment options and potential directions for future disease management.

LEARNING OBJECTIVES

After completing this learning activity, participants should be able to compare the efficacy and safety of various treatment options, formulate a treatment plan tailored to individual patients, and recognize recently described treatments and potential therapeutic approaches.

Treatment of palmoplantar warts with a diphencyprone and salicylic acid ointment

We report on 50 consecutive suitable patients with one or more palmoplantar warts who were treated with a patient-applied ointment comprising 0.1% diphencyprone and 15% salicylic acid in white soft paraffin. All patients sensitized to diphencyprone were followed up clinically and assessed by patient questionnaire. The intention to treat success rate in this series was 88%. The time to wart clearance ranged from less than 4 weeks to 4 months. In our patient group, 90% rated their treatment as 'excellent' or 'good', whereas 10% stated that the reaction induced by diphencyprone was 'too severe'. Our results are compared with those previously published using diphencyprone in the treatment of palmoplantar warts.

Langerhans cells that express matrix metalloproteinase 9 increase in human dermis during sensitization to diphenylcyclopropenone in patients with alopecia areata

BACKGROUND

We know little of the initial events during the sensitization phase of contact allergy in humans. Alopecia areata (AA), a disease of unknown pathogenesis characterized by patchy hair loss, may be treated by inducing contact allergy to diphenylcyclopropenone (DPC), later followed by its topical application.

OBJECTIVES

To learn more about the initial events during sensitization in human skin, we studied the early events during induction of contact allergy to DPC in patients with AA.

METHODS

DPC 2% and sodium lauryl sulphate (SLS) 4% were applied on the backs of eight patients with AA. Punch biopsies were taken 6 and 24 h after application. The biopsies were snap-frozen and cryostat sections were evaluated with immunohistochemistry using antibodies against CD1a, HLA-DR, CD3, CD54 and matrix metalloproteinase 9 (MMP-9).

RESULTS

After 24 h all subjects exhibited erythema on the DPC-treated areas. Histological evaluation of biopsies from these areas showed hydropic degeneration and a significantly increased number of MMP-9+ cells in the dermis (P < 0.0005). The MMP-9+ cells were identified with double immunofluorescence staining as CD1a + Langerhans cells. The expression of the other markers studied remained unaltered irrespective of treatment, including treatment with SLS.

CONCLUSIONS

Our findings show that DPC induces an irritant reaction leading to an increased number of MMP-9+ CD1a+ cells in the dermis during the initial phase of sensitization.

An interesting response to diphencyprone (DPC) sensitization on facial warts: review of DPC treatment for viral warts

BACKGROUND

This paper highlights the sometimes impressive effect of diphencyprone (DPC) sensitization on warts resistant to other treatments and is interesting in view of the fact that all the warts apparently responded, despite only a very small area being treated.

METHODS

A 31-year-old woman with a 5-year history of widespread facial plane warts that had proved resistant to repeated treatments with cryotherapy and topical preparations was sensitized to diphencyprone.

RESULTS

After application of DPC to the warts within only a 1-cm(2) area of the face, all the facial warts became inflamed and resolved, including those not actively treated. Complete clearance occurred with no recurrence.

CONCLUSION

DPC appears to be a valuable, safe and well-tolerated treatment for resistant viral warts and can be considered as a first line treatment. We review its use and action in this paper

The therapeutic use of topical contact sensitizers in benign dermatoses

Topical therapy using contact sensitizers has been practised since the 1960s to treat conditions associated with an altered immunological state. Dinitrochlorobenzene, squaric acid dibutyl ester and diphencyprone are most commonly employed in the therapy of alopecia areata and viral warts. Few dermatology departments in the U.K. provide such treatment. This systematic review discusses the various contact sensitizers used for topical immunotherapy, the methodology of treatment, factors influencing efficacy and likely adverse effects.

The use of topical diphenylcyclopropenone for the treatment of extensive alopecia areata

BACKGROUND

Highly variable results of topical diphenylcyclopropenone (DPCP) in the treatment of alopecia areata have been reported so far.

OBJECTIVE

The purposes of our study were to evaluate the efficacy and tolerability of DPCP in the treatment of chronic, extensive alopecia areata and to assess the long-term overall benefit of treatment.

METHODS

Fifty-six patients with chronic, extensive alopecia areata were enrolled in an open-label clinical trial. After sensitization with 2% DPCP, progressively higher concentrations beginning at 0.001% were applied weekly for 6 to 12 months to one side of the scalp.

RESULTS

Fifty-two of 56 patients completed therapy. Total regrowth of terminal hair was achieved in 25 of 52 patients (48%) at 6 months. The most frequent side effect was an eczematous reaction at the site of application. Notably, persistent response was observed in 60% of these patients after 6 to 18 months of follow-up (mean, 12 months).

CONCLUSION

Topical DPCP treatment for alopecia areata is effective and well tolerated and provides prolonged therapeutic benefits.

Alopecia areata update

Alopecia areata (AA) is a nonscarring hair loss condition. Among the many factors under investigation in the pathogenesis of AA, the main areas of concentration have been genetic constitution as well as nonspecific immune and organ-specific autoimmune reactions. Treatment with intralesional corticosteroid injections for localized patchy AA and topical immunotherapy for extensive AA have proven successful in the majority of patients, although all treatments are palliative and do not change the prognosis of the disease.

Squaric acid immunotherapy for warts in children

BACKGROUND

Warts are a common pediatric skin infection caused by human papillomavirus (HPV). Spontaneous clearance of warts involves anti-HPV immunity, which may be enhanced by contact sensitizers. Squaric acid dibutylester (SADBE) is a nonmutagenic sensitizing agent useful for immunotherapy of alopecia areata.

OBJECTIVE

We hypothesized that SADBE home application might be effective therapy for warts.

METHODS

An open-label, retrospective study of 61 children with warts was performed. Sensitization with 2% SADBE on the forearm was followed with home application of 0.2% SADBE to warts 3 to 7 nights per week for at least 3 months.

RESULTS

Complete clearing occurred in 34 patients (58%), with a mean duration of therapy of 7 weeks. Partial clearing occurred in 11 (18%), and no response in 14 (24%). Clearance correlated with plantar distribution, wart duration under 2 years (P <.05), and first-line therapy with SADBE. Mild side effects occurred in one third of patients, were limited most commonly to mild erythema at the site of sensitization, and necessitated discontinuation of therapy in only 2 patients.

CONCLUSION

SADBE topical immunotherapy is a safe, effective option for home therapy of warts in children.

Efficacy of topical sensitizers in the treatment of alopecia areata

It has been more than 2 decades since the first report of the use of dinitrochlorobenzene to induce hair growth in 2 patients with alopecia areata. Other topical sensitizers, namely squaric acid dibutylester and diphenylcyclopropenone, have been used with variable success. This article reviews the efficacy and safety of the use of topical sensitizers in the treatment of alopecia areata.

Hair regrowth. Therapeutic agents

Today there are new classes of hair growth promotors with proven efficacy. This article reviews the current state of the art agents for treatment of two of the most common forms of hair loss encountered in clinical practice, androgenetic alopecia and alopecia areata. Current therapeutic strategies are based on recent advances in the understanding of disordered hair growth. Practical treatment protocols are presented.

Treatment of chronic severe alopecia areata with topical diphenylcyclopropenone and 5% minoxidil: a clinical and immunopathologic evaluation

BACKGROUND

Topical diphenylcyclopropenone (DPCP) and minoxidil have been used in the treatment of alopecia areata with variable results.

OBJECTIVE

This study was designed to evaluate the efficacy of DPCP alone or in combination with topical 5% minoxidil for the treatment of chronic severe alopecia areata. The effect of therapy on cutaneous T-cell and Langerhans cell subpopulations and intercellular adhesion molecule-1 (ICAM-1) expression was also examined.

METHODS

Fifteen patients with chronic (more than 2 years), severe (more than 50% scalp involvement) alopecia areata participated in a 24-week trial. Half of the scalp was treated with DPCP once weekly and with either 5% minoxidil solution or a vehicle solution twice daily in a randomized double-blind design. Skin biopsy specimens from each half of the scalp were obtained before therapy and after 12 and 24 weeks of therapy for histologic and immunophenotypic analysis.

RESULTS

Thirteen patients completed the study. Five of 13 patients (38%) showed marked regrowth of coarse terminal hair after 24 weeks of treatment with DPCP. The addition of topical 5% minoxidil did not produce any significant clinical benefit in this 24-week trial. Immunophenotypic analysis showed no differences between responders and nonresponders at baseline. During treatment, Leu-4, Leu-2, Leu-3, and keratinocyte ICAM-1 expression were significantly reduced in biopsy specimens of responders versus nonresponders.

CONCLUSION

DPCP treatment showed a 38% success rate in producing cosmetically acceptable regrowth in patients with chronic severe alopecia areata.

Alopecia areata in children: response to treatment with diphencyprone

Twelve children with extensive alopecia areata or alopecia totalis were treated with the contact allergen diphencyprone. The duration of treatment ranged from 5 months to 1 year. Eight of the 12 (67%) regrew scalp hair and in four (33%) there was a complete regrowth. Six months after treatment was discontinued three of the four children with complete regrowth maintained their hair, one had lost all the regrowth and a further child with patchy regrowth at the end of treatment subsequently regrew hair completely while off therapy.

Treatment of alopecia areata with diphenylcyclopropenone

One hundred thirty-nine patients with severe alopecia areata (the majority with the subtotal, total, or universalis type) were treated with topical immunotherapy (diphenylcyclopropenone). Patients were initially treated unilaterally; the other side of the scalp served as a control. In 50.4% of the patients the response was either excellent (total regrowth) or satisfactory (subtotal regrowth with only a few remaining bald patches). The most frequent side effects were eczematous reactions with blistering, spreading of the induced contact eczema, and sleep disturbances.

Allergic and irritant contact dermatitis compared in the treatment of alopecia totalis and universalis. A comparison of the value of topical diphencyprone and tretinoin gel

Diphencyprone is a potent topical sensitizer, but is non-mutagenic in the Ames test (unlike dinitroclorobenzene) and remains relatively stable in solution (unlike squaric acid dibutyl ester). Seventeen patients with total loss of scalp hair (eight alopecia totalis, nine alopecia universalis) were treated by maintaining on one side of the scalp an allergic contact dermatitis induced by 2,3 diphenylcyclopropenone-I ('diphencyprone'), and on the other side an irritant contact dermatitis using tretinoin gel (Retin A). After 20 weeks, treatment with tretinoin was stopped and diphencyprone was applied bilaterally for a further 10 weeks. Satisfactory regrowth of terminal hair on the scalp was achieved in only one patient. Eyebrow, eyelash and beard regrowth was achieved in one individual whilst in another, moderate, but not cosmetically satisfactory, scalp regrowth took place. In no patient did regrowth take place at tretinoin treated sites until after diphencyprone was substituted.

Contact immunotherapy of resistant warts

Contact immunotherapy has been proved effective in the treatment of resistant warts. This report chronicles our experience with a new contact immunotherapy agent, diphenylcyclopropenone. We have achieved a cure rate of 62% in 45 patients with resistant warts of all types who came to our general dermatology clinic. Cure rates may be lower in patients who have experienced multiple treatment failures. The majority of cures were obtained within 3 to 4 months. Although it appears somewhat less effective than published reports of dinitrochlorobenzene contact immunotherapy, diphenylcyclopropenone contact immunotherapy is an effective treatment for resistant warts and avoids any potential problems from mutagenicity.

Assessment of diphenylcyclopropenone for photochemically induced mutagenicity in the Ames assay

The photochemical conversion of diphenylcyclopropenone to diphenylacetylene has recently been reported. Diphenylcyclopropenone is used in the treatment of alopecia areata and is nonmutagenic in a limited Ames assay. We examined diphenylcyclopropenone and diphenylacetylene, as well as synthetic precursors of diphenylcyclopropenone--dibenzylketone and alpha,alpha'-dibromodibenzylketone--for mutagenicity against TA100, TA98, TA102, UTH8413, and UTH8414. All compounds were nonmutagenic except alpha,alpha'-dibromodibenzylketone, which was a potent mutagen in TA100 with and without S-9 activation. The effect of photochemical activation of diphenylcyclopropenone in the presence of bacteria demonstrated mutagenicity in UTH8413 (two times background) at 10 micrograms/plate with S-9 microsomal activation. 8-Methoxypsoralen produces a mutagenic response in TA102 at 0.1 microgram/plate with 60 seconds of exposure to 350 nm light. In vitro photochemically activated Ames assay with S-9 microsomal fraction may enhance the trapping of short-lived photochemically produced high-energy mutagenic intermediates. This technique offers exciting opportunities to trap high-energy intermediates that may play an important role in mutagenesis. This method can be applied to a variety of topically applied dermatologic agents, potentially subjected to photochemical changes in normal use.