A Clinical Study of MK-1045 in People With Lupus or Rheumatoid Arthritis (MK-1045-004)

A Dose Escalation Clinical Study to Evaluate the Safety, Tolerability, Pharmacokinetics and Pharmacodynamics of MK-1045 in Participants With Systemic Lupus Erythematosus and Rheumatoid Arthritis

This study looks at a study medicine called MK-1045 in people with lupus and rheumatoid arthritis (RA). The main goal of the study is to learn about the safety of MK-1045 and if people tolerate it when they receive it at different dose levels (amounts).

Study Overview

• Status: Recruiting
• Conditions: Rheumatoid Arthritis; Systemic Lupus Erythematosus
• Intervention / Treatment: Biological: MK-1045

• Study Type: Interventional
• Enrollment (Estimated): 21
• Phase: Phase 1

Contacts and Locations

• Study Contact: Name: Toll Free Number; Phone Number: 1-888-577-8839; Email: Trialsites@msd.com

Study Locations

• Australia
  • Queensland
    • Southport, Queensland, Australia, 4215
      • Recruiting
      • Gold Coast University Hospital ( Site 1601)
      • Contact: Study Coordinator; Phone Number: +611300744284
• Belgium
  • Limburg
    • Diepenbeek, Limburg, Belgium, 3590
      • Recruiting
      • Anima Diepenbeek ( Site 0601)
      • Contact: Study Coordinator; Phone Number: +3211949115
  • Oost-Vlaanderen
    • Ghent, Oost-Vlaanderen, Belgium, 9000
      • Recruiting
      • UZ Gent ( Site 0602)
      • Contact: Study Coordinator; Phone Number: +3293322863
• China
  • Beijing Municipality
    • Beijing, Beijing Municipality, China, 100005
      • Recruiting
      • Chinese Academy of Medical Science Peking Union Medical College Hospital ( Site 1501)
      • Contact: Study Coordinator; Phone Number: 010-69151188
  • Hubei
    • Wuhan, Hubei, China, 430058
      • Recruiting
      • Union Hospital Tongji Medical College Huazhong University of Science and Technology ( Site 1504)
      • Contact: Study Coordinator; Phone Number: 027-84397521
• Georgia
  • Tbilisi, Georgia, 0112
    • Recruiting
    • Arensia Exploartory Medicine ( Site 1301)
    • Contact: Study Coordinator; Phone Number: +995568404374
• Italy
  • Milano
    • Rozzano, Milano, Italy, 20089
      • Recruiting
      • Istituto Clinico Humanitas- IRCCS ( Site 1902)
      • Contact: Study Coordinator; Phone Number: +390282247421
• Japan
  • Tokyo
    • Bunkyo, Tokyo, Japan, 113-8655
      • Recruiting
      • The University of Tokyo Hospital ( Site 0301)
      • Contact: Study Coordinator; Phone Number: +81-3-3815-5411
    • Shinjyuku, Tokyo, Japan, 160-8582
      • Recruiting
      • Keio University Hospital ( Site 0302)
      • Contact: Study Coordinator; Phone Number: +81-3-3353-1211
• Moldova
  • Chisinau, Moldova, 2025
    • Recruiting
    • PMSI Republican Clinical Hospital "T.Mosneaga" ( Site 1001)
    • Contact: Study Coordinator; Phone Number: +37379638895
• Romania
  • Bucharest
    • Bucharest, Bucharest, Romania, 011658
      • Recruiting
      • ARENSIA Clinics ( Site 0902)
      • Contact: Study Coordinator; Phone Number: 40722604155
  • Cluj
    • Cluj-Napoca, Cluj, Romania, 400006
      • Recruiting
      • ARENSIA Exploratory Medicine-Country Emergency Hospital- Arensia,Cluj-Napoca ( Site 0901)
      • Contact: Study Coordinator; Phone Number: +40745381603

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Has a body mass index between 18 and 32 kg/m^2, inclusive
• Systemic lupus erythematosus (SLE): Has a diagnosis of SLE for at least 6 months and met the European Alliance of Associations for Rheumatology (EULAR)/ American College of Rheumatology (ACR) 2019 classification criteria
• SLE: Is taking at least one background therapy for SLE
• RA: Has a diagnosis of RA for at least 6 months and meets the 2010 ACR-EULAR classification criteria for RA

Exclusion Criteria:

• Has a known active infection (excluding fungal infection of nail beds), or any major episode of infection requiring hospitalization or treatment with anti-infectives within 8 weeks prior to the Day 1 dosing
• History of serious recurrent or chronic infection
• Is known to be infected with hepatitis B virus, hepatitis C virus, or human immunodeficiency virus
• Has evidence of active tuberculosis (TB), latent TB, or inadequately treated TB
• Has a significant or uncontrolled medical disease in any organ system not related to RA or SLE
• For RA participants, has a history of any arthritis with onset before age 17 years
• Has a current inflammatory condition other than SLE or RA that could interfere with disease activity assessments
• History of cancer (except fully treated nonmelanoma skin cancers or cervical carcinoma in situ after complete surgical removal) and is disease free for <5 years before Day 1 dosing
• Has had a major surgery within 3 months prior to Screening or has a major surgery planned during the study.
• Has symptomatic heart failure (New York Heart Association class III or IV) or myocardial infarction or unstable angina pectoris within 6 months prior to Screening
• Has a severe chronic pulmonary disease requiring oxygen therapy
• Has current active lymphoproliferative disease, including lymphoma, or signs and symptoms suggestive of possible lymphoproliferative disease

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Sequential Assignment
• Masking: None (Open Label)

Number of Arms

3

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Part 1 Prime Dose Escalation Panels; Participants will receive single intravenous (IV) doses of MK-1045 at varying dose levels.	Biological: MK-1045; IV infusion; Other Names: CN201
Experimental: Part 2 Step-up Dose Escalation Panels; Participants will receive 3 step up doses of MK-1045 as a prime, step-up and target dose over a 3-week dosing interval.	Biological: MK-1045; IV infusion; Other Names: CN201
Experimental: Part 3 Dose Expansion Panels (Optional); Participants will receive 3 step up doses of MK-1045 as a prime, step-up and target dose over a 3-week dosing interval.	Biological: MK-1045; IV infusion; Other Names: CN201

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Part 1: Number of Participants with One or More Adverse Events (AEs)	An AE is defined as any unfavorable and unintended sign, symptom, disease, or worsening of preexisting condition temporally associated with study treatment and irrespective of causality to study treatment.	Up to approximately 12 weeks
Part 1: Number of Participants who Discontinue Study Drug Due to an AE	An AE is defined as any unfavorable and unintended sign, symptom, disease, or worsening of preexisting condition temporally associated with study treatment and irrespective of causality to study treatment.	Up to approximately 4 weeks
Part 2 and Part 3: Number of Participants with One or More AEs	An AE is defined as any unfavorable and unintended sign, symptom, disease, or worsening of preexisting condition temporally associated with study treatment and irrespective of causality to study treatment.	Up to approximately 52 weeks
Part 2 and Part 3: Number of Participants who Discontinue Study Drug Due to an AE	An AE is defined as any unfavorable and unintended sign, symptom, disease, or worsening of preexisting condition temporally associated with study treatment and irrespective of causality to study treatment.	Up to approximately 2 weeks

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Part 1: Maximum Serum Concentration (Cmax) of MK-1045	Blood samples will be collected to determine the Cmax, obtained directly from the measured value of the plasma concentration-time curve.	At designated time points up to 12 weeks
Part 1: Area Under the Concentration-Time Curve from Time 0 to Infinity (AUC0-Inf) of MK-1045	Blood samples will be collected to determine the AUC0-Inf of MK-1045.	At designated time points up to 12 weeks
Part 1: Percentage of Participants with a Peripheral B Cell Count Less Than the Lower Limit of Quantitation (LLOQ) at the End of Each Treatment Period	Blood samples will be collected to determine the B cell depletion in peripheral blood after treatment with MK-1045.	At designated time points up to 12 weeks
Part 2 and Part 3: Cmax of MK-1045	Blood samples will be collected to determine the Cmax, obtained directly from the measured value of the plasma concentration-time curve.	At designated time points up to 52 weeks
Part 2 and Part 3: Area Under the Concentration-Time Curve From Time 0 to the End of the Dosing Interval (AUCtau) of MK-1045	Blood samples will be collected to determine the AUCtau of MK-1045.	At designated time points up to 52 weeks
Part 2 and Part 3: Percentage of Participants with a Peripheral B Cell Count Less Than the LLOQ at the End of the Treatment Period	Blood samples will be collected to determine the B cell depletion in peripheral blood after treatment with MK-1045.	At designated time points up to 52 weeks

Collaborators and Investigators

• Sponsor: Merck Sharp & Dohme LLC
• Investigators: Study Director: Medical Director, Merck Sharp & Dohme LLC

Publications and helpful links

Helpful Links

• Merck Clinical Trials Information
• Plain Language Summary

Study record dates

Study Major Dates

• Study Start (Actual): February 19, 2026
• Primary Completion (Estimated): July 16, 2029
• Study Completion (Estimated): July 16, 2029

Study Registration Dates

• First Submitted: January 16, 2026
• First Submitted That Met QC Criteria: January 16, 2026
• First Posted (Actual): January 23, 2026

Study Record Updates

• Last Update Posted (Actual): May 29, 2026
• Last Update Submitted That Met QC Criteria: May 28, 2026
• Last Verified: May 1, 2026

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Musculoskeletal Diseases; Arthritis; Joint Diseases; Rheumatic Diseases; Connective Tissue Diseases; Autoimmune Diseases; Immune System Diseases; Skin and Connective Tissue Diseases; Lupus Erythematosus, Systemic; Arthritis, Rheumatoid
• Other Study ID Numbers: 1045-004; U1111-1326-4816 (Registry Identifier: UTN); 2025-523412-36-00 (Registry Identifier: EU CT); MK-1045-004 (Other Identifier: MSD); jRCT2031250748 (Registry Identifier: Japan Registry of Clinical Trials (jRCT))

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: https://trialstransparency.msdclinicaltrials.com/pdf/ProcedureAccessClinicalTrialData.pdf

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: Yes
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: Yes