A Phase 1b Open-label Study to Evaluate Safety of Plamotamab in Participants With Rheumatoid Arthritis

April 9, 2026 updated by: Xencor, Inc.

A Phase 1b, Open-label, Dose-Escalation Trial to Evaluate Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics of Plamotamab in Participants With Rheumatoid Arthritis

The purpose of this study is to determine the safety and tolerability of plamotamab in patients with rheumatoid arthritis. Participants will be given XmAb13676 subcutaneously (SC) by injection under the skin.

Study Overview

Status

Recruiting

Conditions

Intervention / Treatment

Detailed Description

This is a Phase 1b study to determine the safety, tolerability, pharmacokinetic (PK), and pharmacodynamics (PD), and immunogenicity of plamotamab in adult participants with moderately to severely active RA. This is an open label dose optimization trial with approximately 68 participants assigned to different dose escalation cohorts.

Study Type

Interventional

Enrollment (Estimated)

68

Phase

  • Phase 1

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact Backup

Study Locations

  • Georgia
      • Tbilisi, Georgia
        • Recruiting
        • Xencor Investigative Site
  • Moldova
      • Chisinau, Moldova
        • Recruiting
        • Xencor Investigative Site
  • New Zealand
      • Auckland, New Zealand
        • Recruiting
        • Xencor Investigative Site

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Description

Inclusion Criteria: Adult participants with moderately to severely active RA.

  • Documented diagnosis of RA and meeting the 2010 American College of Rheumatology/European Alliance of Associations for Rheumatology classification criteria for RA at least 3 months prior to screening
  • Inadequate response to, loss of response to, or intolerance to available RA therapies.
  • Stable doses of RA medications prior to screening
  • Use of highly effective methods of contraception

Exclusion Criteria:

  • Major surgery within 12 weeks prior to screening or planned within 12 months after dosing
  • Recurrent infections or active clinically significant infection
  • Active or untreated latent tuberculosis
  • Cancer or history of cancer or lymphoproliferative disease within the previous 5 years
  • Uncontrolled cardiovascular, pulmonary, renal, hepatic, endocrine, or gastrointestinal disease

Note: Additional, more specific inclusion/exclusion criteria are defined in the protocol.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: N/A
  • Interventional Model: Single Group Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: Dose Escalation
Plamotamab administered SC
Biological: Plamotamab
Biological

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Primary
Time Frame: Through Week 52
Percentage of participants with treatment emergent adverse events (TEAEs) and serious adverse events (SAEs)
Through Week 52

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Secondary
Time Frame: Through Week 52
Serum concentration of plamotamab
Through Week 52

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Xencor, Inc.

Investigators

  • Study Director: Mark Osterman, MD, MS, Xencor, Inc.

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

October 21, 2025

Primary Completion (Estimated)

June 1, 2028

Study Completion (Estimated)

June 1, 2028

Study Registration Dates

First Submitted

October 1, 2025

First Submitted That Met QC Criteria

November 14, 2025

First Posted (Actual)

November 17, 2025

Study Record Updates

Last Update Posted (Actual)

April 14, 2026

Last Update Submitted That Met QC Criteria

April 9, 2026

Last Verified

April 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • XmAb13676-06

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

product manufactured in and exported from the U.S.

Yes

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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