Nicole E. Burma, MD, PhD; Taylor E. Woo, MD, MSc; Laurie Parsons, MD, FRCPC

Division of Dermatology, Department of Medicine, University of Calgary, Calgary, AB, Canada

Conflict of interest:
The authors have no conflicts of interest to declare.

The pathogenesis of acne is multifactorial and involves inflammation, bacterial dysbiosis, and androgen stimulation. Existing systemic therapies target hormonal pathways to mitigate acne lesions; however, their use is limited to the female population and associated with systemic adverse effects. Clascoterone is the first topical therapy to target the hormonal pathogenesis of acne approved to treat acne vulgaris. In two identical phase 3 trials, clascoterone showed favorable efficacy over placebo in treating acne, with higher treatment success and a greater reduction in acne lesions. Large scale trials are required to assess the efficacy of clascoterone against its comparators and in combination with existing acne therapies; however, results from the current phase 3 trials support the therapeutic value of clascoterone, suggesting that this novel topical androgen inhibitor represents a valuable addition to the catalogue of acne therapy.

Key Words:
acne, clascoterone, androgen inhibitor, topical acne therapy


Acne vulgaris is a common skin condition that impacts 85% of adolescents and young adults.1,2 Acne prevalence decreases with age, yet many patients are burdened by acne throughout adulthood leading to known psychosocial impact and associated morbidity, including anxiety, depression, and low self-esteem.3,4 The pathogenesis of acne is multifactorial and influenced by androgen stimulation, host microbiome, immune responses, genetics, and diet.5-7 Androgens and other sebogenic hormones stimulate sebum production within the pilosebaceous unit, which enhances the proliferation and dysbiosis of Cutibacterium acnes (C. acnes) leading to inflammation and follicular hyperkeratinization8 (Figure 1). Acne onset is typically observed at adrenarche, and is rare in the prepubertal period when levels of sebogenic hormones are low.9 Associations also exist between acne and conditions with known androgen excess, such as polycystic ovarian syndrome (PCOS), congenital adrenal hyperplasia, and adrenal or ovarian tumors.10-12

Common first-line acne therapies include topical retinoids, benzoyl peroxide, and topical or oral antibiotics.13 Combined oral contraceptives (containing estrogen and progesterone) and spironolactone effectively target the hormonal pathogenesis of acne.14 However, their use is limited to the female population and carries the potential risk of systemic adverse effects, such as thromboembolism or hyperkalemia.15,16 Notably, there are no existing topical acne therapies that target hormonal factors involved in acne.

Topical Clascoterone for Acne Vulgaris - image
Figure 1: Proposed mechanism of action for clascoterone in acne therapy.
Acne is an inflammatory condition of the pilosebaceous unit, driven by proliferation and dysbiosis of Cutibacterium acnes, follicular hyperkeratinization, inflammation due to innate and cellular immune responses, and increased sebum production by sebaceous glands.8 Circulating androgens are taken up by sebocytes (sebumproducing epithelial cells that reside within the sebaceous gland), and are converted to dihydrotestosterone (DHT) within the cytosol.24 DHT subsequently binds to androgen receptors, and the ligand-receptor complex dimerizes before translocating to the nucleus.25 Dimerized androgen receptors promote the transcription of genes involved in acne pathogenesis, including inflammatory cytokines and sebum.18 Clascoterone is postulated to competitively bind to androgen receptors at the site of application, competing with the endogenous ligand DHT and reducing downstream signalling cascades involved in acne pathogenesis.18 This ultimately reduces the production of sebum and release of proinflammatory cytokines implicated in acne lesions. The effects of clascoterone remain localized to site of application, due to the presence of esterases found in the skin and plasma.19

Novel Therapy for Acne Vulgaris

In August 2020, the US FDA approved clascoterone 1% cream as a novel therapy for the treatment of acne vulgaris in individuals aged 12 or older. Two identical randomized phase 3 trials (n=708 and n=732) demonstrated that clascoterone 1% cream showed favorable efficacy compared to vehicle cream at achieving treatment success for acne vulgaris with minimal side effects.17

Mechanism of Action

Clascoterone (cortexolone 17a-propionate) is a novel topical androgen receptor inhibitor. Clascoterone competitively binds to the androgen receptor with high affinity, competing with the endogenous ligand dihydrotestosterone (DHT) at the site of application18 (Figure 1). In vitro studies revealed that clascoterone decreases the downstream signaling events from androgen receptors, thereby reducing the transcription of androgenregulated genes and downstream lipid and proinflammatory cytokine production.18 Ultimately, this decreases sebum production and inflammation of the pilosebaceous unit.18 Esterases present in the skin and plasma hydrolyze clascoterone into its inactive parent form (cortexolone), resulting in a localized effect of clascoterone to the site of topical application and minimizing systemic antiandrogenic effects.19 Small dosefinding phase 2a studies showed that steady-state plasma concentrations of clascoterone were achieved by day 5 at 4.5 ng/mL, which was an approximate two-fold increase compared with the first dose.20 Plasma concentrations of cortexolone (the inactive metabolite of clascoterone) were undetectable (<0.5 ng/mL).

Clinical Trials

Initial pilot studies demonstrated that 1% topical clascoterone cream was more effective than placebo cream at reducing the total number of acne lesions, inflammatory lesions and acne severity.21 The small pilot study also suggested that clascoterone was similar or more clinically effective than its comparator, 0.05% tretinoin cream.21 Phase 2 studies revealed that clascoterone 0.1%, 0.5% and 1% cream were safe and welltolerated in male and female adolescent and adult populations, with application of clascoterone 1% twice daily showing the most favorable clinical results.20,22

The efficacy and safety of clascoterone 1% cream was further assessed in two identical randomized placebo-controlled double-blind phase 3 studies in patients over the age of 9 with moderate to severe facial acne ( Identifiers: NCT02608450 and NCT02608476).17 Subjects enrolled in the study had between 30-75 inflammatory acne lesions and 30-100 non-inflammatory acne lesions. Subjects were excluded if they expressed 2 or more facial nodules on assessment.

Severity of patient acne was scored using the 5-point category Investigator’s Global Assessment (IGA) scale (0=clear, 1=trace, 2=mild, 3=moderate, 4=severe). Composite treatment success was defined as a ≥2 point reduction in IGA score from baseline, and a score of 0 (clear) or 1 (almost clear) at 12 weeks. Three coprimary efficacy endpoints assessed during the trial included: (1) proportion of subjects that achieved treatment success at 12 weeks, and absolute change in number of (2) non-inflammatory and (3) inflammatory acne lesions at week 12 of the study. Secondary endpoints addressed changes in total lesion count, including percentage and absolute changes in lesion number from baseline at 12 weeks.

A total of 1440 subjects were randomized 1:1 to receive clascoterone 1% cream (n=722) or vehicle (n=718) in two identical multicentre trials (n=708, n=732). Approximately 1 gram of clascoterone or vehicle cream was applied to the whole face twice daily for 12 weeks. The subjects included male and non-pregnant female patients, with a median age of 18 years (range 9-58 years) and a slight female predominance (60.6%-65.9% female across all groups). The main phototypes were Fitzpatrick types II, III, and IV, with the majority of subjects being White (>83%) with lesser representation of Black, Asian or other races.

At 12 weeks, subjects assigned to the clascoterone groups achieved significantly more treatment success compared to vehicle controls. In the clascoterone groups, 18.4% (trial 1) and 20.3% (trial 2) obtained treatment success at week 12, compared to only 9.0% (trial 1) and 6.5% (trial 2) of vehicle groups (p<0.001 for both trials). There was also a significant reduction in the absolute number of inflammatory (trial 1, p=0.003; trial 2, p<0.001) and non-inflammatory acne lesions (p<0.001 for both trials) in the clascoterone group compared to vehicle at week 12. As a result, both phase 3 trials met the three coprimary efficacy endpoints. Secondary endpoints, including percentage change in total, inflammatory and non-inflammatory lesion counts from baseline, also favored clascoterone treatment over vehicle in both trials (percentage change in total lesion count: trial 1 p=0.001, trial 2 p<0.001; inflammatory lesion count: trial 1 p=0.005, trial 2 p<0.001; non-inflammatory lesion count: trial 1 p=0.009, trial 2 p<0.001).

Safety Profile

In the phase 3 trials, clascoterone was well-tolerated and maintained a safety profile similar to vehicle.17 The most common local skin reactions were erythema (11.3%-13.1% clascoterone, 14.8%-15.7% vehicle), xerosis (8.8%-12.2% clascoterone, 7.6%-13% vehicle), and local pruritus (5.1%-5.4% clascoterone, 5.2%-6.0% vehicle); while the most common treatment emergent adverse events included nasopharyngitis (1.4% clascoterone, 2.7% vehicle), oropharyngeal pain (0.06% clascoterone, 0.04% vehicle) and headache (0.08% clascoterone, 0.06% vehicle). No electrocardiogram changes or systemic adverse effects were observed in the phase 3 trials. Most reported adverse events were mild in severity, and 76.8% had resolved by conclusion of the study.22 Notably, topical clascoterone did not demonstrate side effects associated with systemic spironolactone use, such as hyperkalemia, abnormal uterine bleeding, hypotension, and renal disturbance.23 In the phase 2a dose-finding study, 7% of subjects (3/42) exhibited an abnormal hypothalamic-pituitary-adrenal (HPA) axis response with elevated serum cortisol levels on day 14 of the study (range 14.9-17.7 μg/dL).20 Follow-up 4 weeks after study conclusion revealed normal cortisol concentrations without evidence of adrenal suppression. In the phase 3 studies, no symptoms of adrenal suppression were observed.17 It should be noted that no studies were performed to assess the long-term safety of clascoterone use, or the safety of clascoterone use in combination with other existing anti-acne therapies (topical or systemic).


Clascoterone 1% cream represents a novel and promising therapeutic agent in the management of acne vulgaris for individuals ≥12 years of age. Evidence surrounding its use demonstrates that clascoterone is an efficacious treatment with a reassuring safety profile, where the most common side effects include erythema, xerosis, and pruritus.17 Notably, this topical agent was not observed to have significant systemic effects seen with systemic anti-androgenic agents. No evidence exists regarding the safety of clascoterone use during pregnancy or lactation, or its efficacy in combination with or compared to existing topical and systemic acne therapies. Indeed, a previous small study (n=77) indicated that clascoterone 1% cream had similar, if not better, efficacy than its comparator tretinoin 0.05% cream,21 yet these findings remain to be substantiated in larger scale trials. Further studies on the long-term safety and efficacy of clascoterone in combination with other therapies are warranted, and subgroup analyses may help guide the clinical utility of clascoterone in specific patient populations.


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