Acne Vulgaris:  
Establishing Effectiveness 
of Drugs Intended for 
Treatment 
Guidance for Industry 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
U.S. Department of Health and Human Services 
Food and Drug Administration 
Center for Drug Evaluation and Research (CDER) 
 
May 2018 
Clinical/Medical 
 
   
Acne Vulgaris:  
Establishing Effectiveness 
of Drugs Intended for 
Treatment 
Guidance for Industry 
 
 
 
Additional copies are available from: 
 
Office of Communications, Division of Drug Information 
Center for Drug Evaluation and Research 
Food and Drug Administration 
10001 New Hampshire Ave., Hillandale Bldg., 4th Floor  
Silver Spring, MD  20993-0002  
Phone: 855-543-3784 or 301-796-3400; Fax: 301-431-6353; Email: druginfo@fda.hhs.gov 
https://www.fda.gov/Drugs/GuidanceComplianceRegulatoryInformation/Guidances/default.htm 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
U.S. Department of Health and Human Services 
Food and Drug Administration 
Center for Drug Evaluation and Research (CDER) 
 
May 2018 
Clinical/Medical 
   
TABLE OF CONTENTS 
 
I.  INTRODUCTION............................................................................................................. 1 
II.  BACKGROUND ............................................................................................................... 1 
III.  CLINICAL TRIAL DESIGN FEATURES  KEY CONSIDERATIONS ................ 2 
A.  Enrollment Criteria ....................................................................................................................... 2 
B.  Study Design and Efficacy Endpoints .......................................................................................... 2 
C.  General Analysis Considerations .................................................................................................. 3 
  Contains Nonbinding Recommendations 
Acne Vulgaris:  Establishing Effectiveness of  
Drugs Intended for Treatment 
Guidance for Industry1 
 
 
 
 
This guidance represents the current thinking of the Food and Drug Administration (FDA or Agency) on 
this topic.  It does not establish any rights for any person and is not binding on FDA or the public.  You 
can use an alternative approach if it satisfies the requirements of the applicable statutes and regulations.  
To discuss an alternative approach, contact the FDA office responsible for this guidance as listed on the 
title page.   
 
 
 
 
I.  INTRODUCTION  
 
The purpose of this guidance is to provide recommendations to industry for establishing clinical 
effectiveness of drugs for the treatment of acne vulgaris (acne).2  The recommendations in this 
guidance are based on the FDAs assessment of issues raised in the review of clinical trials for 
acne. 
 
This guidance does not address systemic retinoid therapies because they may not have 
appropriate risk-benefit profiles for non-nodular acne therapy.  Sponsors should discuss 
development programs for systemic retinoids with the review division before trial initiation.  
This guidance also does not address clinical safety, clinical pharmacokinetics, nonclinical issues, 
or chemistry, manufacturing, and controls issues.   
 
In general, FDAs guidance documents do not establish legally enforceable responsibilities.  
Instead, guidances describe the Agencys current thinking on a topic and should be viewed only 
as recommendations, unless specific regulatory or statutory requirements are cited.  The use of 
the word should in Agency guidances means that something is suggested or recommended, but 
not required.  
 
 
II.  BACKGROUND 
 
Acne is a chronic disease of sebaceous follicles that is multifactorial in etiology.  It can wax and 
wane in severity according to lesion types, numbers, and extent of involvement and can result in 
                                                 
1 This guidance has been prepared by the Division of Dermatology and Dental Products in the Center for Drug 
Evaluation and Research at the Food and Drug Administration.  
 
2 For the purposes of this guidance, all references to drugs include human drugs and not therapeutic biological 
products unless otherwise specified. 
  1 Contains Nonbinding Recommendations 
scarring.  Acne occurs more frequently on the face, but can also occur on nonfacial skin (e.g., 
trunk). 
 
There are two major types of acne lesions: 
 
1.  Noninflammatory:  Noninflammatory lesions are the open (blackheads) or closed 
(whiteheads) comedones. 
 
2.  Inflammatory:  Inflammatory lesions include papules, pustules, and nodules. 
 
Although most drug products for acne are intended for the broad indication of acne vulgaris, 
some drug products have been developed that only target one of these two lesion subsets. 
 
Acne is primarily a disease of adolescence and young adulthood, but can persist past the third 
decade of life. 
 
 
III.  CLINICAL TRIAL DESIGN FEATURES  KEY CONSIDERATIONS 
 
A.  Enrollment Criteria 
 
The study population should be defined by the following criteria: 
 
  A minimum number of each type of lesion:  inflammatory and noninflammatory. 
 
  A baseline score on an Investigators Global Assessment (IGA) severity scale that is 
consistent with the baseline lesion counts. 
 
  An age of enrollment reflective of the onset of acne relative to adrenarche.  
 
B.  Study Design and Efficacy Endpoints 
 
In the assessment of efficacy, sponsors should consider the following: 
 
  To demonstrate efficacy, we recommend conducting randomized, double-blind, well-
controlled trials that include a placebo arm.  
 
  Although acne occurs on the face and trunk, efficacy assessment should be limited to the 
face because it is the most frequent site of involvement.  However, topical drug products 
can be applied to all affected areas during clinical trials.  
 
  We recommend that the IGA be a static evaluation of overall acne severity.  
 
  The IGA should be an ordinal scale with approximately five severity grades (reported 
only in whole numbers (e.g., 0 to 4)).  Each grade should be defined by a distinct and 
clinically relevant morphologic description to minimize interobserver variability.  The 
  2 Contains Nonbinding Recommendations 
definitions of the severity grades should not include numerical ranges of lesions 
because the IGA scale is intended to be a qualitative assessment of the subjects 
condition.  
 
  The IGA scale should be dichotomized to success or failure, with success defined as 
clear or almost clear (grade 0 or 1) and at least a two-grade improvement from 
baseline; this represents a clinically meaningful outcome.  
 
  There is no single, standardized grading system for severity of acne.  We encourage 
sponsors to discuss their IGA scales and study designs with the FDA before trial 
implementation.  
 
  Inflammatory and noninflammatory lesions should be counted and reported separately.  
All lesions on the face should be counted, including those on the nose.  
 
  The assessment of treatment effect should be based on both changes in lesion counts and 
success on the IGA.  Endpoints based on changes in lesion counts and IGA success 
provide both quantitative and qualitative assessments of acne, and thus provide useful 
complementary information. 
 
  A reduction in lesion counts may indicate improvement of acne severity; however, it 
does not account for the variable expression of acne (e.g., size of lesions, intensity of 
inflammation, and location of lesions).  The IGA considers the quality and quantity of 
the acne lesions.  
 
  Although subjects are considered as success or failure based on the IGA with 
improvement of two grades, this endpoint is not a precise measure of the magnitude 
of improvement.  The changes from baseline in lesion counts provide a quantitative 
assessment of the improvement. 
 
C.  General Analysis Considerations 
 
The statistical analysis should address the following: 
 
  The analysis of lesion counts can be influenced by a few extreme outliers, which may 
cause difficulty in interpretation of the clinical trial findings.  The statistical analysis plan 
should consider alternative approaches for analysis of lesion counts if extreme outliers 
are anticipated (such as analyses based on ranks).  
 
  For assessment of the treatment effect on inflammatory and noninflammatory lesion 
counts, analysis of absolute change and percentage change from baseline are both 
relevant and complementary.  Absolute change in lesion counts can be affected by 
subjects with large numbers of lesions at baseline, while percent change in lesion counts 
can be affected by subjects with relatively small numbers of lesions at baseline.  The 
absolute change in lesion counts is expected to have better analysis properties, such as a 
less skewed distribution.  Therefore, we recommend absolute change in lesion counts for 
  3 Contains Nonbinding Recommendations 
the primary endpoint analysis, and percentage change in lesion counts for the secondary 
endpoint analysis. 
 
  4