Safety of Anumigilimab (CSL324) in Adults With Sickle Cell Disease (SCD)

Phase 2a, Multicenter, Randomized, Double-blind, Placebo-controlled Study to Assess the Safety of Anumigilimab (CSL324) in Adults With Sickle Cell Disease

This is a phase 2a, global, multicenter, randomized, double-blind, placebo-controlled study investigating the safety of anumigilimab administered subcutaneously (SC) at the maximum tolerated dose (MTD) in adult participants with SCD.

The primary aim of the study is to assess the safety of anumigilimab in participants with SCD. Participants will be treated for 64 weeks: for 12 weeks in the dose escalation period, where the dose will be escalated to each participant's individual MTD; and for 52 weeks at the MTD in the maintenance period.

Study Overview

• Status: Recruiting
• Conditions: Sickle Cell Disease
• Intervention / Treatment: Biological: Anumigilimab; Drug: Placebo

• Study Type: Interventional
• Enrollment (Estimated): 63
• Phase: Phase 2

Contacts and Locations

• Study Contact: Name: Trial Registration Coordinator; Phone Number: +1 610-878-4697; Email: clinicaltrials@cslbehring.com

Study Locations

• United States
  • Arkansas
    • Little Rock, Arkansas, United States, 72202
      • Recruiting
      • UAMS Medical Center
  • Florida
    • Hollywood, Florida, United States, 33023-6703
      • Recruiting
      • The Foundation for Sickle Cell Disease
  • Maryland
    • Bethesda, Maryland, United States, 20817
      • Recruiting
      • Center for Cancer and Blood Disorders
  • Mississippi
    • Flowood, Mississippi, United States, 39232
      • Recruiting
      • Southern Specialty Research
  • New York
    • The Bronx, New York, United States, 10461
      • Recruiting
      • Jacobi Medical Center

Participation Criteria

Eligibility Criteria

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

Description

Inclusion Criteria:

• • Adults aged greater than or equal to (>=) 18 years on the day of signing the informed consent form.
• • Confirmed diagnosis of SCD of any genotype.
• • Experienced 1 to 12 VOCs requiring a visit to a medical facility and treatment with parenteral opioids or a parenteral nonsteroidal anti-inflammatory drug within the 12 months before Screening.
• • HU Regimen:
• a. On stable and well-tolerated Hydroxyurea (HU) regimen for at least 30 days before Screening.
• or
• b. HU was discontinued or refused (eg, due to concern of side effects or lack of effect).

Exclusion Criteria:

• • Absolute neutrophil count less than (<) 2.5 ×10^9 cells/Litre at Screening or Baseline (Week 1 Day 1).
• • If on SCD preventive medication, dose is not stable in the 30 days before Screening.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Quadruple

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Anumigilimab; Safety of Anumigilimab (CSL324) in Adults with Sickle Cell Disease (SCD)	Biological: Anumigilimab; Participants will receive anumigilimab, escalated to a maximum dose guided by absolute neutrophil count (ANC) and safety concerns.
Placebo Comparator: Placebo; Participants will receive matching volume of placebo.	Drug: Placebo; Volume matched saline will be administered SC.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Number of participants with Treatment Emergent Adverse Events (TEAEs), Overall and by severity, seriousness and relationship to Investigational Product (IP)		From baseline up to Week 75
Percentage of participants with TEAEs Overall and by severity, seriousness and relationship to IP		From baseline up to Week 75
Number of participants with Adverse Events of Special Interest (AESI)	The following AEs are to be reported as AESI: neutropenia (Common Terminology Criteria for Adverse Events [CTCAE] Grade 3 or 4), severe infection and neutropenic fever.	From baseline up to Week 75
Percentage of participants with AESI	The following AEs are to be reported as AESI: neutropenia (CTCAE Grade 3 or 4), severe infection and neutropenic fever.	From baseline up to Week 75
Number of participants with clinically relevant changes from baseline in laboratory assessments and vital signs		From baseline up to Week 75
Percentage of participants with clinically relevant changes from baseline in laboratory assessments and vital signs		From baseline up to Week 75

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Serum concentration of Anumigilimab		From the first dose of anumigilimab to Week 65
Annualized rate of Vaso-occlusive crisis (VOC) (medical facility)	VOC (medical facility) is defined as VOC that results in a visit to a medical facility and treatment with parenteral opioids or a parenteral nonsteroidal anti-inflammatory drug.	During the maintenance period from Week 13 to Week 65

Collaborators and Investigators

• Sponsor: CSL Behring
• Investigators: Study Director: Study Director, CSL Behring

Study record dates

Study Major Dates

• Study Start (Actual): February 2, 2026
• Primary Completion (Estimated): June 29, 2028
• Study Completion (Estimated): June 29, 2028

Study Registration Dates

• First Submitted: October 31, 2025
• First Submitted That Met QC Criteria: October 31, 2025
• First Posted (Actual): November 4, 2025

Study Record Updates

• Last Update Posted (Actual): May 12, 2026
• Last Update Submitted That Met QC Criteria: May 11, 2026
• Last Verified: May 1, 2026

More Information

Terms related to this study

• Keywords: Anemia; Vaso-occlusive Crises; Genetic Disorder
• Additional Relevant MeSH Terms: Hematologic Diseases; Anemia, Hemolytic, Congenital; Anemia, Hemolytic; Hemoglobinopathies; Congenital, Hereditary, and Neonatal Diseases and Abnormalities; Hemic and Lymphatic Diseases; Genetic Diseases, Inborn; Anemia, Sickle Cell; Anemia; Vaso-Occlusive Crises
• Other Study ID Numbers: CSL324_2002; 2025-521154-42-00 (Ctis)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: CSL will consider on a case-by-case basis requests to share Individual Patient Data (IPD) with external bona-fide, qualified scientific and medical researchers. For information on the process and requirements for submitting a voluntary data sharing request for IPD, please contact CSL at clinicaltrials@cslbehring.com.
• IPD Sharing Time Frame: Requests for IPD will generally be considered once review by major regulatory authorities (i.e. FDA, EMA) is complete and the primary publication is available.

IPD Sharing Access Criteria

Proposed research should seek to answer a previously unanswered important medical or scientific question.

Applicable country specific privacy and other laws and regulations will be considered and may prevent sharing of IPD.

If the request is approved and the researcher has executed an appropriate data sharing agreement, IPD that has been appropriately anonymized will be available.

• IPD Sharing Supporting Information Type: STUDY_PROTOCOL; SAP

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: Yes
• Studies a U.S. FDA-regulated device product: No