1 Introduction
The pathogenesis of acne, one of the most common dermatologic disorders, is a multifactorial process involving follicular proliferation of
Cutibacterium acnes (formerly
Propionibacterium acnes), abnormal keratinization, and increased sebum production and inflammation [
1,
2]. Effective treatment, which requires pharmacologic targeting of one or more of these pathophysiologic mechanisms, includes various prescription oral and topical treatments such as benzoyl peroxide (BPO), retinoids (topical tretinoin, adapalene, tazarotene, trifarotene; oral isotretinoin), antibiotics (e.g., erythromycin, clindamycin, minocycline, doxycycline, sarecycline), and hormonal therapies [
2]. Adherence rates to oral or topical acne treatments, however, are typically poor and reasons for low adherence include complex regimens, lack of efficacy, and adverse effects [
3,
4]. Combining treatments in an easy-to-use, fixed-dose formulation can improve treatment adherence by reducing complex drug regimens [
3,
5]. Furthermore, combining topical treatments that target multiple processes of acne pathogenesis may improve efficacy [
6] and is a recommended treatment strategy for the majority of patients with acne per the US treatment guidelines published in 2016 [
2].
Clindamycin phosphate 1.2%/BPO 3.1%/adapalene 0.15% gel (IDP-126), once approved, will be the first triple-combination fixed-dose topical acne treatment. Formulated as an aqueous gel, with no alcohol, preservatives, occlusive agents, or surfactants, it is pH balanced for the skin and contains propylene glycol, a hydrating humectant. As a smaller particle size allows for better penetration of the pilosebaceous unit [
7,
8], BPO and adapalene have been micronized. Additionally, all ingredients are contained within a polymeric gel to allow for even distribution on the skin. As vehicle formulation can affect the tolerability of topical treatments [
7], the use of micronized ingredients contained within a polymeric gel may also provide better tolerability. Although combining multiple acne treatments into one formulation can be difficult, as some retinoids, such as tretinoin, are more susceptible to oxidative breakdown in the presence of BPO, adapalene is more stable than tretinoin under such conditions [
9].
Several dyad formulations containing BPO/adapalene or BPO/clindamycin have been approved in the USA [
10], but IDP-126 will be the first to combine all three ingredients. While the dyad combinations of BPO with adapalene or clindamycin result in greater lesion reductions than the individual treatments alone, irritation may be an issue with certain combinations [
11‐
14]. Improved efficacy has also been demonstrated following the use of BPO/clindamycin in the morning with the retinoid tazarotene in the evening [
15], though complex regimens can impact patient adherence. The objective of this phase II study was to evaluate the efficacy, safety, and tolerability of IDP-126, a novel once-daily clindamycin phosphate 1.2%/BPO 3.1%/adapalene 0.15% fixed-dose gel, in patients with moderate-to-severe acne.
2 Methods
2.1 Study Design
In this phase II, multicenter, randomized, double-blind, parallel-group, vehicle-controlled study, participants 9 years of age or older with moderate (Evaluator’s Global Severity Score [EGSS] 3) or severe (EGSS 4) acne were enrolled from 31 study centers in the USA and four in Canada. Eligible participants also needed to have the following facial lesions: ≥ 30 to ≤ 100 inflammatory (pustules, papules, and nodules), ≥ 35 to ≤ 150 noninflammatory (closed and open comedones), and two or fewer nodules. Ranges were selected to enroll patients with a baseline number of lesions while minimizing large variations across the treatment arms. CeraVe® hydrating cleanser, CeraVe® moisturizing lotion (L’Oreal, New York, NY, USA), and sunscreen were provided as needed for optimal moisturization/cleaning of the skin.
Participants were equally randomized to receive one of five treatments to be applied to the face once daily for 12 weeks: clindamycin phosphate 1.2%/BPO 3.1%/adapalene 0.15% gel (IDP-126); one of the three component dyads formulated with the same active drug concentration and within the same vehicle as IDP-126 (BPO 3.1%/adapalene 0.15% gel; clindamycin phosphate 1.2%/BPO 3.1% gel; clindamycin phosphate 1.2%/adapalene 0.15% gel); or vehicle gel. Identically labeled/packaged study drug kits were dispensed to participants at baseline and weeks 4 and 8 by study center staff, based on a randomization code assigned by the central randomization system. This study was carried out in accordance with principles of Good Clinical Practice and the Declaration of Helsinki. At all investigational sites, the study protocol was approved by the relevant independent ethics committees or institutional review boards. All participants or their legal guardians provided written informed consent.
2.2 Study Assessments
Efficacy evaluations comprised counts of inflammatory and noninflammatory lesions and treatment success, defined as the proportion of participants achieving a ≥ 2-grade reduction from baseline in EGSS and a score of 0 (clear) or 1 (almost clear). Assessments were performed at screening, baseline, and weeks 2, 4, 8, and 12 (treatment end). The EGSS was scored as follows: 0 = Normal, clear skin with no evidence of acne; 1 = Rare noninflammatory lesions present, with rare noninflamed papules (papules must be resolving and may be hyperpigmented, though not pink-red); 2 = Some noninflammatory lesions are present, with few inflammatory lesions (papules/pustules only; no nodulocystic lesions); 3 = Noninflammatory lesions predominate, with multiple inflammatory lesions evident: several to many comedones and papules/pustules, and there may or may not be one nodulocystic lesion; 4 = Inflammatory lesions are more apparent, many comedones and papules/pustules, there may or may not be up to two nodulocystic lesions. Participants also completed an Acne-Specific Quality of Life (Acne-QoL) questionnaire covering four domains (self-perception, role-emotional, role-social, and acne symptoms) at baseline and week 12; a higher score in any domain indicates improved health-related quality of life [
16]. Investigator-assessed cutaneous safety (scaling, erythema, hypopigmentation, and hyperpigmentation) and participant-reported tolerability (itching, burning, and stinging) were evaluated via a 4-point scale where 0 = none and 3 = severe. Treatment compliance was defined as participants missing ≤ 5 consecutive days of dosing and applying 80–120% of expected applications. Adverse events (AEs) were evaluated throughout the study.
2.3 Statistical Analyses
The coprimary endpoints were the percentage of participants achieving treatment success at week 12 and the absolute changes from baseline to week 12 in inflammatory and noninflammatory lesion counts. Treatment success at week 12 was analyzed using a logistic regression test with factors of treatment group and analysis center. Significant skewness was observed in the change from baseline analyses of noninflammatory and inflammatory lesions, and as such, a nonparametric method was used to rank transform the data prior to the analysis of covariance. For the analysis of covariance, treatment and analysis center were factors and the respective baseline lesion counts were a covariate.
Secondary and post hoc analyses included treatment success and a ≥ 2-grade reduction in EGSS by study visit, percent changes from baseline in inflammatory and noninflammatory lesion counts by study visit, and quality-of-life assessments at week 12. For all post hoc analyses of treatment success and a ≥ 2-grade EGSS reduction, the Firth option was added (used to apply Firth’s Penalized Likelihood to the logistic regression) because of convergence issues.
For all efficacy assessments, values were adjusted for multiple imputations and pairwise tests were performed to compare IDP-126 with the three component dyads (BPO/adapalene, clindamycin/BPO, clindamycin/adapalene) and vehicle gel. Missing efficacy data were handled based on estimation using the Markov Chain Monte Carlo multiple imputation method. Acne-QoL questionnaire results and cutaneous safety and tolerability assessments were summarized using descriptive statistics with no imputation of missing values.
No formal sample size calculation was performed for this study as the sample size was based only on clinical considerations and the numbers of participants enrolled in each treatment arm were considered sufficient to evaluate the safety and tolerability of IDP-126 vs the dyads or vehicle. All statistical analyses were conducted using SAS® software, version 9.3 or later (Cary, NC, USA). Statistical significance was based on two-tailed tests of the null hypothesis resulting in P ≤ 0.05. Adverse events were classified using the Medical Dictionary for Regulatory Activities terminology for the safety population. No interim analyses were performed. The intent-to-treat population consisted of all randomized participants who received the study drug. The safety population was defined as all randomized participants who used the study drug at least once and had at least one post-baseline safety evaluation.
4 Discussion
In this phase II study, IDP-126, the novel fixed-dose triple-combination clindamycin phosphate 1.2%/BPO 3.1%/adapalene 0.15% gel, was evaluated over 12 weeks in participants with moderate-to-severe acne. IDP-126 demonstrated superior efficacy on all three coprimary endpoints compared with the three dyad component combinations and vehicle gel and was well tolerated.
The three drugs that make up IDP-126 were chosen in order to target the multiple processes of acne pathogenesis. Topical retinoids, such as adapalene, are a mainstay of acne treatment; they normalize keratinocyte proliferation, block several inflammatory pathways, promote comedolysis, and reduce microcomedonal formation. While they are generally well tolerated, their use can be limited by dryness, irritation, and erythema [
8,
17]. Adapalene—a third-generation retinoid that modulates cellular keratinization, differentiation, and proliferation [
8,
18]—has the advantage of being one of the most tolerable retinoids [
19] that also retains its stability in the presence of BPO [
9]. Benzoyl peroxide is an antibacterial agent with mild comedolytic activity, keratolytic effects, and good efficacy and tolerability [
2,
20‐
22]; it is unaffected by
C. acnes resistance, [
20] and has been used in combination with topical and oral antibiotics because of its ability to reduce resistant
C. acnes populations [
23]. Topical or oral antibiotics reduce
C. acnes colonization and proliferation [
24], and clindamycin, a lincosamide, is a widely studied and commonly used antibiotic with anti-inflammatory effects [
1]. It has been used for acne treatment for over 30 years [
1] and has shown better efficacy in comparison to erythromycin [
2]. The addition of clindamycin to BPO not only increases antibiotic activity [
22], but may also moderate the irritating effects or withdrawals from AEs observed with BPO [
12,
14]. Altogether, the combination of these three acne treatments targets three of the four acne pathogenic pathways and may reduce the antibiotic resistance and adverse cutaneous effects observed with monotherapy.
In the present study, over half of IDP-126-treated participants achieved treatment success at week 12, with a rate that was 1.7–1.8 times greater than with the component dyads. The inclusion of all dyad combinations within the same vehicle formulation as IDP-126 was a strength in this study, in that it allowed for assessing the contribution of the active drug components while minimizing study arms. However, the exclusion of the component monads prevented the determination of the direct contributions of each active treatment to calculate the synergistic treatment effect. Though synergy cannot be directly assessed in this study, treatment success rates with IDP-126 appeared to be greater than the expected additive effect, as each of the dyad combinations had rates less than two-thirds of IDP-126.
At week 12, IDP-126 demonstrated over 70% reductions in acne lesions. Significantly greater percent reductions in inflammatory and noninflammatory lesions were observed as early as week 2 with IDP-126 vs vehicle gel, suggesting a fast therapeutic action. As BPO, retinoids, and antibiotics act primarily as antibacterial and/or anti-inflammatory agents, it would be expected that inflammatory lesions would be reduced more than noninflammatory lesions with IDP-126. In this study, however, there were similar reductions in both inflammatory and noninflammatory acne. This may be due to the comedolytic properties of BPO as well as the ability of clindamycin to reduce
C. acnes populations. It is likely that using these products together with adapalene targets both inflammatory and noninflammatory acne. Similar results were observed in a 12-week acne study where clindamycin/BPO gel was applied in the morning and tazarotene 0.1% cream was also applied at night [
25].
In context with other 10-week to 12-week clinical studies that examined various combinations and dosages of commercially available dyads containing BPO and clindamycin or adapalene, IDP-126 had greater numeric percent changes in inflammatory and noninflammatory lesions (− 76.4% and − 71.0%, respectively) than the other dyads (range − 42% to − 68.7% and − 21.9% to − 68.3%) [
11‐
13,
26‐
31]. IDP-126 treatment success rates were also numerically greater than dyads in other 12-week clinical studies (52.5% vs a range of 21.5–33.7%) [
13,
26‐
29]. As expected, the component dyads in the present study performed comparably to other commercially available dyads, which further highlights the efficacy of the triple-combination IDP-126 gel. Direct comparisons, however, cannot be made between IDP-126 and other currently approved dyad treatments, as no head-to-head or facial-splitting studies were conducted. Further, there were design differences across the studies (phase II or phase III; differing percentages of participants with moderate or severe acne and other patient backgrounds; differing definitions of treatment success), as well as differences in the drug dosages, combinations, and vehicle formulations.
Limitations of this study and its design are similar to other clinical trials of acne. Assessments of acne severity via the EGSS may result in inter-observer bias or variation. Treatment duration in the study was limited to 12 weeks, and longer treatment would better reflect real-world patient experiences. Finally, results from this study may not be generalizable to diverse real-world practice populations, which may differ in race, age, and sex. Future post hoc analyses evaluating these populations of interest can address this limitation.
In the past, there has not been a formulation containing BPO, a retinoid, and a topical antibiotic—possibly because of concerns regarding tolerability (BPO and retinoids) and/or antibacterial resistance (antibiotics). In the present study, this triple combination demonstrated good tolerability with once-daily use. As expected, there were slight increases from baseline to week 12 in scaling, burning, and stinging mean scores with IDP-126. Transient increases at weeks 2 and 4, however, were lower with IDP-126 than the BPO/adapalene dyad. Furthermore, there were no instances of severe scaling, erythema, or itching with IDP-126, whereas the BPO/adapalene or clindamycin/adapalene dyads had instances of severe ratings; IDP-126 also had fewer severe cases of burning and stinging than BPO/adapalene. Rates of discontinuations because of TEAEs were at least twofold higher with BPO/adapalene than any of the other treatment groups.
The combination of clindamycin, BPO, and adapalene in IDP-126 appears to have a slightly better safety and tolerability profile than the BPO/adapalene combination. This may be a result of the IDP-126 vehicle formulation, the combination of active ingredients, or both. In terms of vehicle formulation, as noted previously, IDP-126 is a gel that uses a polymeric technology to provide a more uniform distribution of all ingredients. It is also possible that the multiple anti-inflammatory properties of clindamycin [
1] can provide a moderating effect on the cutaneous safety and tolerability of BPO and adapalene. This rationale is supported by a meta-analysis that showed clindamycin combined with BPO had lower odds of patient withdrawal/discontinuation because of AEs than BPO alone or BPO/adapalene combinations [
14]. These results are supported by the AEs and AE-related discontinuations reported in this phase II study, as well as the cutaneous safety/tolerability data, as the lowest rates of related AEs were observed with clindamycin/BPO and the highest rates with BPO/adapalene. In addition, topical antibiotics such as clindamycin are an attractive treatment option as they may reduce the risk of systemic side effects that are seen with oral antibiotics [
2]. Though cases of diarrhea, bloody diarrhea, and colitis have been reported with the use of clindamycin (oral or topical) [
32], instances of gastrointestinal AEs were rare in the present study and none were deemed related to treatment.
An issue with common antibiotic acne treatments such as erythromycin, clindamycin, and tetracyclines is the development of
C. acnes resistance [
2,
33]. While a topical minocycline 4% foam (approved in the USA for monotherapy) has been introduced as having a decreased risk for the development of resistance, more research is needed to determine the potential for the development of drug-resistant bacteria with this formulation [
34]. To prevent the development of resistance, antibiotic monotherapy is not recommended [
2,
35]. However, combining an antibiotic with BPO is recommended, as studies have shown that BPO reduces the risk of antibiotic resistance [
2,
23].
While there are many treatment options available, acne is a chronic disease that requires long-term treatment [
2,
4]. Regimens with side effects, low efficacy, or high complexity (e.g., using several treatments at one time, taking multiple doses in a day) can adversely affect treatment adherence [
3,
4]. The results from the present study have demonstrated that IDP-126 was not only well tolerated with low rates of discontinuations due to TEAEs, it was also efficacious and fast acting, providing significantly greater lesion reductions vs vehicle as early as week 2. Together with the simple once-daily treatment regimen, this fixed-dose triple-combination may also help improve treatment adherence.
Declarations
Conflict of interest
Linda Stein Gold has served as an investigator/consultant or speaker for Ortho Dermatologics, LEO Pharma, Dermavant, Incyte, Novartis, AbbVie, Pfizer, Sun Pharma, UCB, Arcutis, and Lilly. Hilary Baldwin has served as an advisor or investigator and on speakers’ bureaus for Almirall, Cassiopea, Foamix, Galderma, Ortho Dermatologics, Sol Gel, and Sun Pharma. Leon H. Kircik has acted as an investigator, advisor, speaker, and consultant for Ortho Dermatologics. Jonathan S. Weiss is a consultant, speaker, advisor, and/or researcher for AbbVie, Ortho Dermatologics, Janssen Biotech, Dermira, Almirall, Brickell Biotech, DermTech, and Scynexis. David M. Pariser has served as a consultant to Atacama Therapeutics, Bickel Biotechnology, Biofrontera AG, Celgene, Dermira, LEO Pharma, Regeneron, Sanofi, TDM SurgiTech, TheraVida, and Ortho Dermatologics; an investigator for Abbott Laboratories, Almirall, Amgen, AOBiome, Asana Biosciences, Bickel Biotechnology, Celgene, Dermavant, Dermira, Eli Lilly, LEO Pharma, Menlo Therapeutics, Merck & Co., Novartis, Novo Nordisk A/S, Ortho Dermatologics, Pfizer, Regeneron, and Stiefel; on the advisory board for Pfizer; and on the data monitoring board for BMS. Valerie Callender has served as an investigator, consultant, or speaker for AbbVie, Galderma, L’Oréal, Ortho Dermatologics, and Vyne. Edward Lain has nothing to disclose. Michael Gold has acted as an investigator, advisor, speaker, and consultant for Ortho Dermatologics. Kenneth Beer has received funding from Allergan, Galderma, Evolus, and Revance. Zoe Draelos received research funding from Ortho Dermatologics. Neil Sadick has served on advisory boards, as a consultant, investigator, speaker, and/or other and has received honoraria and/or grants/research funding from Almirall, Actavis, Allergan, Anacor Pharmaceuticals, Auxilium Pharmaceuticals, Bausch Health, Bayer, Biorasi, BTG, Carma Laboratories, Cassiopea, Celgene Corporation, Cutera, Cynosure, DUSA Pharmaceuticals, Eclipse Medical, Eli Lilly and Company, Endo International, EndyMed Medical, Ferndale Laboratories, Galderma, Gerson Lehrman Group, Hydropeptide, Merz Aesthetics, Neostrata, Novartis, Nutraceutical Wellness, Palomar Medical Technologies, Prescriber’s Choice, Regeneron, Roche Laboratories, Samumed, Solta Medical, Storz Medical AG, Suneva Medical, Vanda Pharmaceuticals, and Venus Concept. Radhakrishnan Pillai and Varsha Bhatt are employees of Bausch Health US, LLC and may hold stock and/or stock options in its parent company. Emil A. Tanghetti has served as a speaker for Novartis, Ortho Dermatologics, Sun Pharma, Lilly, Galderma, AbbVie, and Dermira; served as a consultant in clinical studies for Hologic, Ortho Dermatologics, and Galderma; and is a stockholder for Accure.