ACKNOWLEDGEMENTS: Medical writing support was provided by Prescott Medical Communications Group (Chicago, IL) with financial support from Ortho Dermatologics; Ortho Dermatologics is a division of Bausch Health US, LLC • Presented at the Fall Clinical Dermatology Conference for PAs and NPs • June 9-11, 2023 • Orlando, FL

BACKGROUND AND 
RATIONALE

 � For acne vulgaris, the recommended 
first-line treatments are topical benzoyl 
peroxide (BPO) or retinoids as 
monotherapy, or in combination with 
each other and/or an antibiotic1 

 � Cutaneous irritation or dermatitis—either 
irritant (occurs rapidly post-contact) or 
allergic (a less common, delayed immune-
mediated response)—may limit use of 
BPO or retinoids2,3

 � IDP-126 polymeric mesh gel (clindamycin 
phosphate 1.2%/BPO 3.1%/adapalene 0.15%) 
is the first triple-combination, fixed-dose 
topical acne product in development and 
it addresses major acne 
pathophysiological processes 

 � In a phase 2 and two phase 3 studies in 
participants with moderate-to-severe 
acne, IDP-126 resulted in over 70% 
reductions of inflammatory and 
noninflammatory lesions at week 12,  
with good safety/tolerability4

OBJECTIVES

 � To assess dermal irritation/sensitization 
and safety of IDP-126 gel in two phase 1 
studies

 � To compare irritancy of IDP-126 gel and 
commercially available BPO 2.5%/
adapalene 0.3% gel in one phase 1 study 
of healthy participants

METHODS

 � Two phase 1, randomized, evaluator-
blinded, within-participant, dermal safety 
studies enrolled healthy participants aged 
≥18 years (Figure 1)

 � Patches were applied to participants’ 
upper back multiple times over 6-8 weeks 
(RIPT) or every 24 hours for 21 days (CIPT; 
Figure 1)

• Participants in each study received all 
treatments

 � Endpoints comprised sensitization 
potential (allergic; RIPT only), mean 
cumulative/total irritation scores, and 
treatment-emergent adverse events 
(TEAEs)

• Clinical grading of irritation consisted of 
a combination of letter and numerical 
grades (see table at bottom in Figure 2)

FIGURE 1.  Study Designs for the RIPT and CIPT Studies2,5,6

Repeat Insult Patch Test (RIPT)

IDP-126 gel

Vehicle gel

Saline 0.9%
(negative control)

Patch Applications
(for 48-72 h; 3x/wk)b

In induction and challenge phases, patches were applied 10 times to left or 
right upper back over 6-8 weeks. If re-challenge

a
 was required, patches were 

applied 11 additional times.

All who 
received study 

treatment

Safety 
Population

All who 
completed 

Challenge Phase

Sensitization 
Population

All who 
completed 

Induction Phase

Cumulative 
Irritancy 

Population

Study Populations

Determines the potential of a topical treatment to induce sensitization
(allergic potential) via repeated applications

Cumulative Irritancy Patch Test (CIPT)

Patch Applications
(once daily)b

Over 21 days, patches were applied once daily to the left or right upper back 
for 24h.

All who 
received study 

treatment

Safety 
Population

Study Populations

Evaluates a topical treatment’s irritancy potential as a result of direct 
damage to the epidermal cells (without involvement of allergic or 
immunologic mechanism) via repeated applications

IDP-126 gel

Vehicle gel

Saline 0.9%
(negative control)

Sodium lauryl sulfate 0.5%
(positive control)

BPO 2.5%/ADAP 0.3% gel
(active comparator)

aParticipants were only re-challenged to a study material if there were signs suggestive of contact sensitization 
observed at any challenge evaluations or at the investigator’s discretion. 
bTreatment patch placement was randomized for each participant.  
ADAP, adapalene; BPO, benzoyl peroxide; IDP-126, clindamycin phosphate 1.2%/benzoyl peroxide  
3.1%/adapalene 0.15%. 

Dermal Irritation, Sensitization, and Safety of Fixed-Dose Triple-Combination 
Clindamycin Phosphate 1.2%/Benzoyl Peroxide 3.1%/Adapalene 0.15% Gel in Healthy Participants 

Zoe D Draelos, MD,1 Emil A Tanghetti, MD,2 Linda Stein Gold, MD,3 Leon H Kircik, MD,4-6 Neal Bhatia, MD,7 Joshua A Zeichner, MD,4 Jeffrey L Sugarman, MD, PhD8
1Dermatology Consulting Services, PLLC, High Point, NC; 2Center for Dermatology and Laser Surgery, Sacramento, CA; 3Henry Ford Hospital, Detroit, MI; 4Icahn School of Medicine at Mount Sinai, New York, NY; 5Indiana University Medical Center, Indianapolis, IN; 6Physicians Skin Care, PLLC, DermResearch, PLLC, and Skin Sciences, PLLC, Louisville, KY; 7Therapeutics Clinical Research, San Diego, CA; 
8University of California, San Francisco, CA

FIGURE 2.  Mean Cumulative Irritation Scores (RIPT Cumulative 
Irritancy Population; CIPT Safety Population)

0.37

0.07
0.05

0

1

2

3

M
ea

n 
S

co
re

 ±
S

D
 1.29

0.32 0.30

1.17

1.96

0

1

2

3

***

***

***

***
***

G
re

at
er

 ir
ri

ta
tio

n

CIPT (n=44)RIPT (n=209)

IDP-126 Vehicle
gel

Saline
0.9%

IDP-126 SLS
0.5%

BPO 2.5%/
ADAP 0.3%

Vehicle
gel

Saline
0.9%

***P<0.001 vs IDP-126 gel. 
Saline 0.9%=negative control; SLS 0.5%=positive control; BPO 2.5%/ADAP 0.3%=active comparator. 
BPO 2.5%/ADAP 0.3%, benzoyl peroxide 2.5%/adapalene 0.3% gel; CIPT, cumulative irritancy patch test;  
IDP-126, clindamycin phosphate 1.2%/benzoyl peroxide 3.1%/adapalene 0.15% gel; RIPT, repeat insult patch test;  
SD, standard deviation; SLS, sodium lauryl sulfate.

FIGURE 3.  Normalized Total Irritation Scores (CIPT Safety Population)

264

66 63

232

401

0

100

200

300

400

500

600

*** ***

***

N
or

m
al

iz
ed

 T
ot

al
 Ir

ri
ta

tio
n 

S
co

re

No significant 
irritation

Slightly 
irritating

Moderately
irritating

Highly
irritating

IDP-126 Vehicle
gel

Saline
0.9%

SLS
0.5%

CIPT (n=44)

To determine irritation 
classification of each treatment, 
a normalized total score for 
each patch was calculated by 
multiplying the mean total 
irritation score by a factor of 10 
• 0–49 = no significant irritation
• 50–199 = slightly irritating
• 200–449 = moderately irritating
• 450–630 = highly irritating

BPO 2.5%/
ADAP 0.3%

***P<0.001 vs IDP-126 gel. 
Saline 0.9%=negative control; SLS 0.5%=positive control; BPO 2.5%/ADAP 0.3%=active comparator. 
BPO 2.5%/ADAP 0.3%, benzoyl peroxide 2.5%/adapalene 0.3% gel; CIPT, cumulative irritancy patch test;  
IDP-126, clindamycin phosphate 1.2%/benzoyl peroxide 3.1%/adapalene 0.15% gel; SLS, sodium lauryl sulfate.

RESULTS

Participants
 � A total of 279 participants were 
randomized 

 � RIPT populations: safety, N=234; 
cumulative irritancy, n=209; 
sensitization, n=206

• A total of 210 participants completed 
the induction phase and received the 
challenge phase applications, and 
206 (88.0%) completed the study 

 � CIPT population: safety, N=45 

• A total of 44 participants were included 
in the irritation analysis, and 42 (93.3%) 
completed the study 

 � In both studies, the mean age of 
participants was ~55 years, and the 
majority were female (RIPT: 71.4%; 
CIPT: 77.8%), Black (RIPT/CIPT: ~68%), and 
non-Hispanic (89.3%; 91.1%), with a 
Fitzpatrick skin type of IV-VI (65.4%; 
80.0%)

Dermal Sensitization and Irritation
 � Overall, irritation with IDP-126 was 
moderate and not clinically significant

 � RIPT: No participants had investigator-
confirmed sensitization to any treatments

• As expected, mean cumulative irritation 
scores were higher with IDP-126 vs 
vehicle or saline 0.9% (P<0.001, both; 
Figure 2)

• IDP-126 gel, vehicle gel, and saline 0.9% 
were all classified as not causing 
clinically significant irritation

 � CIPT: IDP-126 had a score of “moderately 
irritating,” but was significantly less 
irritating than BPO 2.5%/adapalene 0.3% 
(P<0.001; Figures 2 and 3)
• The highest normalized total irritation 

score was observed for BPO 2.5%/
adapalene 0.3% gel, which was 
significantly greater than  
IDP-126 (401 vs 264; P<0.001; Figure 3)

Adverse Events
 � In both studies, most TEAEs were of 
mild-moderate severity, and <3% of 
participants discontinued due to  
AEs/TEAEs (Table 1)

 � No TEAEs/serious AEs were related to 
treatment 

 � There was no contact dermatitis or 
discontinuation of patch applications due 
to irritation

TABLE 1.  Treatment-Emergent Adverse Events  
(Safety Populations)

n (%)
RIPT

(n=234)
CIPT

(n=45)

Participants reporting any TEAE 4 (1.7) 1 (2.2)

Participants reporting any SAEa 1 (0.4) 1 (2.2)

Participants discontinuing due to AE/TEAEb 3 (1.3) 1 (2.2)

Deaths 1 (0.4)c 0

Severity of TEAEs

Mild 2 (0.9) 0

Moderate 1 (0.4) 1 (2.2)

Severe 1 (0.4) 0

Relationship to study drug

Related 0 0

Unrelated 4 (1.7) 1 (2.2)
aNone of the participants had SAEs that were considered treatment related.  
bDiscontinuing from the study or study drug; none of the AEs were deemed related to treatment.  
cPatient died during hospitalization for suspected COVID-19; no proof of death could be obtained. 
AE, adverse event; CIPT, cumulative irritancy patch test; RIPT, repeat insult patch test; SAE, serious 
adverse event; TEAE, treatment-emergent adverse event.

CONCLUSIONS
 � In two phase 1 studies, fixed-dose, triple-
combination IDP-126 polymeric mesh gel had 
moderate irritancy and no confirmed sensitization 
(ie, allergic potential) in healthy participants

 � Additionally, IDP-126 gel demonstrated significantly 
less irritation versus commercially available, branded 
BPO 2.5%/adapalene 0.3% gel

 � IDP-126 was well tolerated, with most TEAEs of 
mild-moderate severity 

 � Overall, IDP-126 demonstrated good safety and 
tolerability, mirroring the phase 2 and phase 3 study 
results4

REFERENCES
1. Zaenglein, A.L. J Am Acad Dermatol. 2016;74(5):945-73.
2. Nguyen, H.L. Clin Rev Allergy Immunol. 2019;56(1):41-59.
3. Foti, C. Dermatol Ther. 2015;28(5):323-9.
4. Stein Gold, L. J Am Acad Dermatol. 2022;87(3):sAB50.
5. Jordan, W.P. Contact Dermatitis. 1980;6(2):151-2.
6. Berger, R.S. J Toxicol, Cutan Ocul Toxicol. 1982;1(2):109-115.

AUTHOR DISCLOSURES
ZDD has received funding from Ortho Dermatologics. EAT has served as speaker for 
Novartis, Ortho Dermatologics, Sun Pharma, Lilly, Galderma, AbbVie, and Dermira; served 
as a consultant/clinical studies for Hologic, Ortho Dermatologics, and Galderma; and is 
a stockholder for Accure. LSG has served as investigator/consultant or speaker for Ortho 
Dermatologics, LEO Pharma, Dermavant, Incyte, Novartis, AbbVie, Pfizer, Sun Pharma, UCB, 
Arcutis, and Lilly. LHK has acted as an investigator, advisor, speaker, and consultant for Ortho 
Dermatologics. NB has served as advisor, consultant, and investigator for AbbVie, Almirall, 
Biofrontera, BI, Brickell, BMS, EPI Health, Ferndale, Galderma, InCyte, ISDIN, J&J, LaRoche-
Posay, LEO Pharma, Ortho Dermatologics, Regeneron, Sanofi, SunPharma, Verrica, and Vyne. 
JAZ has served as advisor, consultant, or speaker for AbbVie, Allergan, Dermavant, Dermira, 
EPI Health, Galderma, Incyte, Johnson and Johnson, L’Oreal, Ortho Dermatologics, Pfizer, 
Procter and Gamble, Regeneron, Sun Pharma, UCB, Unilever, and Vyne. JLS is a consultant for 
Ortho Dermatologics, Bausch Health, Regeneron, Sanofi, Verrica, and Pfizer.

Numerical grade
0 No evidence of irritation
1 Minimal erythema; barely perceptible

2 Definite erythema, readily visible; or minimal edema; or minimal papular response

3 Erythema, edema, and/or papules; vesicular eruption; or strong spreading reaction

Letter grade (converted to numbers)
0 Slight glazed appearance

1 Marked glazing

2 Glazing with peeling and cracking

3 Glazing with fissures; film of dried serous exudate; or small petechial erosions 

CUMUL ATIVE IRRITATION SCORE 
NUMERICAL GR ADE + LET TER GR ADE 

MA X WORST SCORE = 6