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ATI-450

Phase 2

Hidradenitis Suppurativa | Small molecule | Dermatology |Aclaris Therapeutics, Inc.|Trials Updated: Oct 13, 2026

ATI-450 development status

Highest phase Phase 2
Registered trials 6 across 2 sponsors since Jan 2020

ATI-450 target and mechanism

Molecular targetJAK3
Target classKinase
ModalitySmall molecule

Also known as Zunsemetinib, CDD-450, Zumsemetinib

Success Probability

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Market & Valuation

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Trial Design

RandomizedDouble-BlindCONTROLLEDDMC
Total Trials5
Total Enrollment574

FDA Designations

No designations recorded

ATI-450 clinical trials

ATI-450 · 5 trials · 6 indications

Phase 2 3Phase 1 2
NCT05279417ATI-450 Plus Methotrexate (MTX) Versus Placebo Plus MTX in Participants With Moderate to Severe Active Rheumatoid Arthritis (RA)Rheumatoid Arthritis
COMPLETED251 Analytics
NCT05216224ATI-450 vs Placebo in Participants With Moderate to Severe Hidradenitis Suppurativa (HS)Hidradenitis Suppurativa
COMPLETED95 Analytics
NCT04247815Study of ATI-450 Plus Methotrexate (MTX) vs MTX Alone in Patients With Moderate to Severe RARheumatoid Arthritis
COMPLETED25 Analytics
PHASE2COMPLETED
ATI-450 Plus Methotrexate (MTX) Versus Placebo Plus MTX in Participants With Moderate to Severe Active Rheumatoid Arthritis (RA)
Rheumatoid ArthritisUnlock trial analytics
PHASE2COMPLETED
ATI-450 vs Placebo in Participants With Moderate to Severe Hidradenitis Suppurativa (HS)
Hidradenitis SuppurativaUnlock trial analytics
PHASE2COMPLETED
Study of ATI-450 Plus Methotrexate (MTX) vs MTX Alone in Patients With Moderate to Severe RA
Rheumatoid ArthritisUnlock trial analytics

Study Endpoints

Primary Endpoints

Percentage of Participants Achieving ACR20 at Week 12
Week 12

Participants achieving American College of Rheumatology (ACR) 20 (responders) were defined as having ≥20% improvement in both the number of swollen and tender joints (66/68 joint counts) and ≥20% improvement in ≥3 of the following 5 measures: Patient's Global Assessment of Disease Activity (VAS), Patient's Assessment of Arthritis Pain (VAS), Health Assessment Questionnaire-Disability Index (HAQ-DI), Physician's Global Assessment of Disease Activity (VAS), and acute phase reactant as measured by hsCRP. Model-based estimates and 95% confidence intervals (CIs) were produced.

Change From Baseline in Abscess and Inflammatory Nodule (AN) Count at Week 12
Baseline, Week 12

AN count was the sum of number of abscess and inflammatory nodules across anatomical regions. The least square (LS) mean change from baseline in the count at Week 12 was estimated from the Mixed Model Repeated Measures (MMRM) model.

The Primary Outcome Measure is the Determination of the Safety and Tolerability of ATI-450 Plus Methotrexate in Patients With Moderate to Severe Rheumatoid Arthritis: Adverse Events (AEs)
Baseline through Day 114

Safety and tolerability reported as Adverse Events (AEs). AEs will be coded with the Medical Dictionary for Regulatory Activities (MedDRA) version 23.0. AEs will be presented by system organ class and preferred term in frequency tables.

Recommended phase II dose (RP2D) of zunsemetinib in combination with mFOLFIRINOX (Dose Escalation Only)
Completion of 2 cycles (each cycle is 2 weeks - estimated to be 4 weeks)
Number of participants with dose-limiting toxicities (DLTs) (Dose Escalation only)
Completion of 2 cycles (each cycle is 2 weeks - estimated to be 4 weeks)
Number of participants with adverse events (Phase Ib only)
From start of treatment through 30 days after end of treatment (estimated to be 11 months)
Recommended phase II dose of zunsemetinib (Phase Ib only)
Through end of 1st cycle (each cycle is 21 days)
Number of participants with dose-limiting toxicities (Phase Ib only)
Through end of 1st cycle (each cycle is 21 days)
Percent change in serum CTX (Phase II only)
Baseline and Day 1 of week 7
Progression-free survival (PFS) (Phase II only)
From start of treatment through completion of follow-up (estimated to be 3 years and 10 months)

Secondary Endpoints

Percentage of Participants Achieving ACR50 at Week 12
Week 12
Percentage of Participants Achieving ACR70 at Week 12
Week 12
Change From Baseline in DAS28-CRP at Week 12
Baseline, Week 12
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Study Design & Arms

AllocationRANDOMIZED
MaskingQUADRUPLE
ModelPARALLEL
PurposeTREATMENT

Treatment Arms

ArmTypeDescription
ATI-450 20 mg BID plus MethotrexateEXPERIMENTALATI-450 20 mg oral tablet twice daily (BID) with a stable weekly dose of methotrexate for 12 weeks
ATI-450 50 mg BID plus MethotrexateEXPERIMENTALATI-450 50 mg oral tablet BID with a stable weekly dose of methotrexate for 12 weeks
Placebo plus MethotrexatePLACEBO_COMPARATORPlacebo oral tablet BID with a stable weekly dose of methotrexate for 12 weeks
ATI-450EXPERIMENTALATI-450 50 milligrams (mg) oral tablet twice daily (BID)
PlaceboEXPERIMENTALPlacebo oral tablet BID
ATI-450 plus MethotrexateEXPERIMENTALATI-450 50mg oral tablet BID with a stable weekly dose of Methotrexate
Dose escalation phase (zunsemetinib + mFOLFIRNOX)EXPERIMENTALThe dose of zunsemetinib will be determined by the dose level assigned and will be taken by mouth either once or twice daily depending on assigned dose level. mFOLFIRINOX will be 85 mg/m\^2 of oxaliplatin intravenous (IV) on day 1 of each cycle, 150 mg/m\^2 of irinotecan IV on day 1 of each cycle, 400 mg/m\^2 of leucovorin IV on day 1 of each cycle, and 2400 mg/m\^2 continuous infusion starting on day 1 of each cycle and continuing for 46 hours. Each cycle is 2 weeks in length.
Dose expansion phase (zunsemetinib + mFOLFIRNOX)EXPERIMENTALThe dose of zunsemetinib will be determined during the dose escalation phase of the trial. mFOLFIRINOX will be 85 mg/m\^2 of oxaliplatin intravenous (IV) on day 1 of each cycle, 150 mg/m\^2 of irinotecan IV on day 1 of each cycle, 400 mg/m\^2 of leucovorin IV on day 1 of each cycle, and 2400 mg/m\^2 continuous infusion starting on day 1 of each cycle and continuing for 46 hours. Each cycle is 2 weeks in length.
Phase Ib: Zunsemetinib + CapecitabineEXPERIMENTALPatients will receive zunsemetinib by mouth (PO) twice per day (BID) at an assigned dose along with capecitabine (1000 mg/m\^2 PO BID on Days 1-14 an every 21-day cycle). For patients enrolled in phase Ib, capecitabine is dosed on days 2-15 during cycles 1-2. Dose escalation of zunsemetinib will utilize a 3+3 design. A maximum of 3 dose levels of zunsemetinib will be tested, and the two highest dose levels which did not lead to more than 1 of 6 patients with DLT in cycle 1 will be chosen as the RP2D-L1 and RP2D-L2 for Phase II. If only one dose level of zunsemetinib was found tolerable, then only one RP2D will be chosen for Phase II.
Phase II Arm 1: Standard of care anti-resorptive + CapecitabineACTIVE_COMPARATORStandard of care anti-resorptives will consist of bisphosphonate (zoledronic acid) is to be administered every 4-12 weeks, or denosumab is to be administered every 4-6 weeks, as per physician choice and institutional practice. In general, capecitabine will be taken twice daily at a dose of 1000 mg/m\^2 on Days 1 through 14 of every 21-day cycle. The first 4 patients enrolling to phase II will take capecitabine on a different schedule for PK purposes in Cycles 1 and 2 ONLY. Patients will take capecitabine at a dose of 1000mg/m\^2 on Days 2 through 15 of Cycles 1 and 2, and then on Days 1 through 14 starting with Cycle 3.
Phase II Arm 2: Zunsemetinib (RP2D-L1) + CapecitabineEXPERIMENTALPatients will receive zunsemetinib by mouth (PO) twice per day (BID) at an assigned dose. In general, capecitabine will be taken twice daily at a dose of 1000 mg/m\^2 on Days 1 through 14 of every 21-day cycle. The first 4 patients enrolling to phase II will take capecitabine on a different schedule for PK purposes in Cycles 1 and 2 ONLY. Patients will take capecitabine at a dose of 1000mg/m\^2 on Days 2 through 15 of Cycles 1 and 2, and then on Days 1 through 14 starting with Cycle 3.
Phase II Arm 3: Zunsemetinib (RP2D-L2) + CapecitabineEXPERIMENTALPatients will receive zunsemetinib by mouth (PO) twice per day (BID) at an assigned dose. In general, capecitabine will be taken twice daily at a dose of 1000 mg/m\^2 on Days 1 through 14 of every 21-day cycle. The first 4 patients enrolling to phase II will take capecitabine on a different schedule for PK purposes in Cycles 1 and 2 ONLY. Patients will take capecitabine at a dose of 1000mg/m\^2 on Days 2 through 15 of Cycles 1 and 2, and then on Days 1 through 14 starting with Cycle 3. If only one dose level of zunsemetinib plus capecitabine was found tolerable in phase Ib testing, the phase II trial will proceed with 2:1 two-arm randomization with Arm 2 of capecitabine plus zunsemetinib and Arm 1 of capecitabine plus standard of care anti-resorptive agent.

Interventions

NameTypeDescription
ATI-450 50 mg oral tablet BIDDRUGOral, small molecule MK2 inhibitor
Placebo oral tabletDRUGPlacebo tablet manufactured to match ATI-450 in appearance
MethotrexateDRUG15 mg to 25 mg weekly
ATI-450 20 mg oral tablet BIDDRUGOral, small molecule MK2 inhibitor
ATI-450DRUGOral, small molecule MK2 inhibitor
ZunsemetinibDRUGPatients should take zunsemetinib approximately 12 hours apart (if twice daily dosing) or 24 hours apart (if once daily dosing) at the same time(s) every day, with 8 oz of water.
mFOLFIRINOXDRUGIncludes oxaliplatin, irinotecan, leucovorin, and 5-FU.
ZumsemetinibDRUGPatients should take zunsemetinib at approximately the same times every day, with or without food with 8 oz of water.
CapecitabineDRUGPatients should take capecitabine at approximately the same times every day, within 30 minutes after a meal.
Zoledronic acidDRUGStandard of care. Will receive zoledronic acid or denosumab.
DenosumabDRUGStandard of care. Will receive zoledronic acid or denosumab.
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Eligibility Criteria

Age Range18 Years to 75 Years
SexALL
Healthy VolunteersNo
Study Sites50

Inclusion Criteria: * Able to comprehend and be willing to sign the Institutional Review Board (IRB)/Independent Ethics Committee (IEC) approved participant ICF prior to administration of any study-related procedures. * Diagnosis of adult-onset RA as defined by the 2010 American College of Rheumato...

Countries:United StatesBulgariaCzechiaPoland
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Recent Changes (Last 90 Days)

LOWOct 13, 2026NCT06374459lastUpdatePostDate: changed
LOWOct 13, 2026NCT06374459lastUpdatePostDate: changed

Frequently asked questions about ATI-450

What is ATI-450 used for?

ATI-450 is an investigational oral small molecule being studied for the treatment of moderate to severe hidradenitis suppurativa and moderate to severe active rheumatoid arthritis. It has been evaluated in Phase 2 clinical trials in both indications, including studies where it was added to methotrexate in patients with rheumatoid arthritis.

What does ATI-450 target?

ATI-450 targets JAK3, a kinase enzyme involved in immune signaling. By inhibiting JAK3, ATI-450 is designed to modulate inflammatory pathways. This mechanism underlies its investigation in inflammatory conditions such as rheumatoid arthritis and hidradenitis suppurativa.

Who is developing ATI-450?

ATI-450 is being developed by Aclaris Therapeutics, Inc., which trades on the Nasdaq under the ticker ACRS. The company is responsible for the clinical development program of ATI-450 in hidradenitis suppurativa and rheumatoid arthritis.

What phase is ATI-450 in?

ATI-450 is in Phase 2 clinical development. It has completed two Phase 2 trials, one in rheumatoid arthritis and one in hidradenitis suppurativa, and is not currently approved by the FDA for any indication.

What clinical trials is ATI-450 in?

ATI-450 has been studied in three completed Phase 2 trials: NCT05279417 in rheumatoid arthritis with 251 participants, NCT05216224 in hidradenitis suppurativa with 95 participants, and NCT04247815 in rheumatoid arthritis with 25 participants. All trials were randomized, double-blind, and controlled.