Open-Label Extension Study to Pioneer Study 6058-SCD-101

An Open-Label Extension Study to Evaluate Long-Term Safety and Tolerability of Pociredir in Participants With Sickle Cell Disease (SCD) Who Have Participated in a Pociredir Study

This is an open-label study to evaluate the safety and tolerability of long-term treatment with pociredir without a comparator in participants with SCD who have previously been treated and shown benefit with pociredir in feeder study 6058-SCD-101 (NCT05169580). Participants in this study will receive once daily doses of pociredir for up to 48 months.

Study Overview

• Status: Enrolling by invitation
• Conditions: Sickle Cell Disease
• Intervention / Treatment: Drug: Pociredir

Detailed Description

The first dose of study drug will be administered on Day 1 in the clinic and participants will continue at home dosing once daily (QD). Dosing will occur in the clinic on days where there are clinic visits. Treatment Period clinic visits are planned every other week through Week 12 (Weeks 2, 4, 6, 8, 10, and 12), monthly through Week 24 (Weeks 16, 20, and 24), and then every 12 weeks from Week 24 through Week 192. A final follow-up visit (Week 196) will occur 4 weeks after the final dose of study drug at Week 192.

Participants will receive pociredir at the dose level they received in Study 6058-SCD-101 through Week 192, unless data from that study indicates a change to a different optimized dose.

• Study Type: Interventional
• Enrollment (Estimated): 50
• Phase: Phase 2

Contacts and Locations

Study Locations

• United States
  • Arkansas
    • Little Rock, Arkansas, United States, 72205
      • University of Arkansas for Medical Sciences
  • California
    • Los Angeles, California, United States, 90095
      • University of California, Los Angeles
  • Louisiana
    • Baton Rouge, Louisiana, United States, 70808
      • Our Lady of the Lake Hospital
  • Massachusetts
    • Boston, Massachusetts, United States, 02118
      • Boston Medical Center
  • New York
    • Jamaica, New York, United States, 11432
      • Queens Hospital Cancer Center
    • The Bronx, New York, United States, 10461
      • Jacobi Medical Center
  • Texas
    • Houston, Texas, United States, 77030
      • University of Texas Houston
  • Virginia
    • Fairfax, Virginia, United States, 22031
      • Inova Schar Cancer Institute

Participation Criteria

Eligibility Criteria

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

Description

Inclusion Criteria:

• Participants aged ≥18 years and older must have previously participated in and successfully completed Study 6058-SCD-101.
• Participant has signed and dated the informed consent form (ICF) before any study-specific procedures are performed and is willing and able to comply with the study procedures and restrictions.
• Participants who meet all other inclusion and exclusion criteria for this study, and per Investigator's recommendation may continue standard of care as indicated with the exception of hydroxyurea (HU). Participants may continue crizanlizumab, and/or L-glutamine, but must be on a stable dose for at least 6 months.
• Participants, who if female and of childbearing potential, agree to use 2 effective methods of contraception, 1 of which must be highly effective, or practice abstinence starting at the time of the ICF signing to 90 days after the last dose of study drug, and, who if male, should use condoms or practice abstinence from the time of ICF signing to 90 days after the last dose of study drug.
• Documented HbF benefit, as judged by the Investigator, from prior study.

• Participant must meet both of the following laboratory values during Screening:

  1. Absolute neutrophil count ≥ 1.5 × 10^9/liter,
  2. Platelets ≥ 80 × 10^9/liter
• Absolute reticulocyte count during Screening > 100 × 10^9/liter.

Exclusion Criteria:

• Major surgery, serious illness (acute or chronic), infection (clinically significant bacterial, fungal, parasitic or viral infection which requires therapy), fever not resolved within 3 days of onset and requiring treatment, significant bleeding, cerebrovascular accident, or seizure within 14 days prior to signing the ICF and 14 days prior to starting study drug.
• Sickle cell complication requiring more than 24-hour care from a medical provider in hospital or emergency care setting in the 14 days prior to starting study drug.
• Use of medications that are moderate or strong inducers or inhibitors of cytochrome P450 (CYP) 3A4 or CYP2C8, inhibit P-glycoprotein, breast cancer resistance protein, or multidrug and toxin extrusion protein 2-K, or are substrates of CYP2B6 within 14 days prior to first dose of study drug or anticipated need for any of these medications during the study.
• Participation in any other study with an investigational agent other than pociredir within the past 60 days prior to the first dose of study drug.
• History of bone marrow transplant or hematopoietic stem cell transplant or gene therapies.
• Vaccination in the previous 7 days prior to the first dose of study drug.

Note: Other protocol specified criteria may apply

Study Plan

How is the study designed?

Design Details

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

Number of Arms

1

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Pociredir; Participants will receive Pociredir orally once daily (QD)	Drug: Pociredir; Pociredir Oral Capsules will be administered; Other Names: FTX-6058

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Number of participants reporting Treatment Emergent Adverse Events (TEAEs)		Up to Week 196
Number of participants with clinically significant changes in 12-lead Electrocardiogram (ECGs)		Up to Week 196
Number of participants with clinically significant changes in Vital signs		Up to Week 196
Number of participants with clinically significant changes in Clinical laboratory tests	Laboratory assessments including hematology, coagulation, serum chemistry and electrolytes, lipid panel, SCD characterization, serology, urinalysis and pregnancy tests will be performed.	Up to Week 196

Secondary Outcome Measures

Outcome Measure	Time Frame
Change from Baseline in percent Fetal hemoglobin (HbF)	Baseline (Day 1), and Up to Week 192
Change from Baseline in percent Reticulocytes	Baseline (Day 1), and Up to Week 192
Change from Baseline in Red cell distribution width	Baseline (Day 1), and Up to Week 192
Change from Baseline in Unconjugated bilirubin	Baseline (Day 1), and Up to Week 192
Change from Baseline in Lactate dehydrogenase (LDH)	Baseline (Day 1), and Up to Week 192
Change from Baseline in Haptoglobin	Baseline (Day 1), and Up to Week 192
Change from Baseline in Reticulocyte count	Baseline (Day 1), and Up to Week 192
Number of participants reporting SCD-related complications	Up to Week 192
Annualized rate of Vaso-occlusive episode (VOE)	through end of month 48

Collaborators and Investigators

• Sponsor: Fulcrum Therapeutics

Study record dates

Study Major Dates

• Study Start (Estimated): March 30, 2026
• Primary Completion (Estimated): February 4, 2030
• Study Completion (Estimated): July 5, 2030

Study Registration Dates

• First Submitted: January 28, 2026
• First Submitted That Met QC Criteria: February 6, 2026
• First Posted (Actual): February 11, 2026

Study Record Updates

• Last Update Posted (Actual): April 14, 2026
• Last Update Submitted That Met QC Criteria: April 13, 2026
• Last Verified: April 1, 2026

More Information

Terms related to this study

• Keywords: Open-label; Sickle Cell Disease; Anemia, Sickle Cell; Fetal hemoglobin; Hematologic diseases; FTX-6058; Pociredir
• Additional Relevant MeSH Terms: Genetic Diseases, Inborn; Anemia, Hemolytic, Congenital; Anemia, Hemolytic; Anemia; Hemoglobinopathies; Thalassemia; Congenital, Hereditary, and Neonatal Diseases and Abnormalities; Hemic and Lymphatic Diseases; Anemia, Sickle Cell; beta-Thalassemia; Hematologic Diseases
• Other Study ID Numbers: 6058-SCD-102

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

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