A Phase 2/3 Study in Adult and Adolescent Participants With SCD

March 19, 2026 updated by: Pfizer

A Phase 2/3 Randomized, Multicenter Study of Osivelotor Administered Orally to Adult and Adolescent Participants With Sickle Cell Disease

The purpose of this study is to evaluate the safety, tolerability, efficacy, pharmacokinetics and pharmacodynamics of osivelotor.

Study Overview

Status

Recruiting

Conditions

Intervention / Treatment

Detailed Description

This is a three-part, multicenter, Phase 2/3 study of orally administered osivelotor in participants with sickle cell disease (SCD).

Part A will evaluate the safety, tolerability, and efficacy of osivelotor in adult participants with SCD to determine an optimal dose.

Part B will evaluate the efficacy of osivelotor versus placebo in adult and adolescent participants with SCD for 48 weeks.

Open Label Extension (OLE) will evaluate the long-term safety and hematologic responses of open-label osivelotor in adult and adolescent participants having completed Part B.

Study Type

Interventional

Enrollment (Estimated)

389

Phase

  • Phase 2
  • Phase 3

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 Locations

  • Brazil
      • Rio de Janeiro, Brazil, 20211-030
        • Not yet recruiting
        • Instituto Estadual de Hematologia Arthur Siqueira Cavalcanti - HEMORIO
      • São Paulo, Brazil, 01321-001
        • Not yet recruiting
        • Real E Benemerita Associacao Portuguesa de Sao Paulo
      • São Paulo, Brazil, 05403-000
        • Active, not recruiting
        • Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo
      • São Paulo, Brazil, 05403-010
        • Active, not recruiting
        • Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo
      • São Paulo, Brazil, 01232-010
        • Not yet recruiting
        • ESHO Empresa De Servicos Hospitalares S A
    • Estado de Bahia
      • Salvador, Estado de Bahia, Brazil, 40110-060
        • Not yet recruiting
        • Hospital Universitario Professor Edgar Santos
    • Pernambuco
      • Recife, Pernambuco, Brazil, 50070-460
        • Not yet recruiting
        • Multihemo Servicos Medicos S/A
    • SÃO Paulo- Brasil
      • São Paulo, SÃO Paulo- Brasil, Brazil, 01232-011
        • Not yet recruiting
        • ESHO Empresa De Servicos Hospitalares S A
    • São Paulo
      • Ribeirão Preto, São Paulo, Brazil, 14051-140
        • Not yet recruiting
        • Hospital das Clínicas da Faculdade de Medicina de Ribeirão Preto - USP
      • São José do Rio Preto, São Paulo, Brazil, 15090-000
        • Not yet recruiting
        • Fundacao Faculdade Regional de Medicina de Sao Jose do Rio Preto
      • São Paulo, São Paulo, Brazil, 08270-070
        • Not yet recruiting
        • Casa de Saude Santa Marcelina
      • São Paulo, São Paulo, Brazil, 08270-120
        • Not yet recruiting
        • Casa de Saude Santa Marcelina
      • São Paulo, São Paulo, Brazil, 01321 001
        • Not yet recruiting
        • BP A Beneficencia Portuguesa de Sao Paulo
      • São Paulo, São Paulo, Brazil, 01323-900
        • Not yet recruiting
        • BP - A Beneficencia Portuguesa de São Paulo
  • India
    • Gujarat
      • Surat, Gujarat, India, 395002
        • Active, not recruiting
        • Nirmal Hospital Pvt Ltd
    • Maharashtra
      • Nashik, Maharashtra, India, 422005
        • Active, not recruiting
        • Chopda Medicare & Research Centre Pvt. Ltd: Magnum Heart Institute
  • Kenya
      • Nairobi, Kenya, 00100
        • Not yet recruiting
        • Gertrude's Children's Hospital
      • Nairobi, Kenya, 00100
        • Not yet recruiting
        • Kenya Medical Research Institute - Centre for Respiratory Disease Research
      • Nairobi, Kenya, 00200
        • Not yet recruiting
        • Center for Research In Therapeutic Sciences (CREATES), Strathmore University Medical Centre
    • Siaya County
      • Kisumu, Siaya County, Kenya, 40600
        • Not yet recruiting
        • KEMRI/CRDR, Siaya, KEMRI Clinical Research Annex
  • Nigeria
      • Kano, Nigeria, 700233
        • Active, not recruiting
        • Aminu Kano Teaching Hospital
      • Lagos, Nigeria, 100254
        • Active, not recruiting
        • Lagos University Teaching Hospital
    • Oyo/ibadan North
      • Ibadan, Oyo/ibadan North, Nigeria, 200212
        • Active, not recruiting
        • University College Hospital Ibadan
  • United Kingdom
      • Bristol, United Kingdom, BS2 8ED
        • Not yet recruiting
        • University Hospitals Bristol and Weston NHS Foundation Trust
      • Bristol, United Kingdom, BS2 8EX
        • Not yet recruiting
        • Bristol Royal Infirmary
  • United States
    • Connecticut
      • New Haven, Connecticut, United States, 06511
        • Not yet recruiting
        • Smilow Cancer Hospital
    • Florida
      • Plantation, Florida, United States, 33317
        • Recruiting
        • Edward Jenner Research Group Center LLC
      • West Palm Beach, Florida, United States, 33407
        • Not yet recruiting
        • St. Mary's Medical Center
      • West Palm Beach, Florida, United States, 33407
        • Not yet recruiting
        • Pediatric Hematology / Oncology a division of Kidz Medical services
    • Georgia
      • Dunwoody, Georgia, United States, 30350
        • Active, not recruiting
        • Alpha Clinical Research Georgia
      • Riverdale, Georgia, United States, 30274
        • Active, not recruiting
        • Sonar Clinical Research
    • Illinois
      • Chicago, Illinois, United States, 60612
        • Not yet recruiting
        • University of Illinois at Chicago Clinical Research Center
      • Chicago, Illinois, United States, 60612
        • Not yet recruiting
        • University of Illinois Hospital and Health Sciences System - Investigational Drug Services (IDS)
      • Chicago, Illinois, United States, 60612
        • Not yet recruiting
        • University of Illinois Hospital and Health Sciences System
    • Louisiana
      • Baton Rouge, Louisiana, United States, 70805
        • Active, not recruiting
        • LSU Health Baton Rouge-North Clinic
      • Baton Rouge, Louisiana, United States, 70808
        • Active, not recruiting
        • Our Lady of the Lake Hospital, Inc.
      • Baton Rouge, Louisiana, United States, 70808
        • Active, not recruiting
        • Our Lady of the Lake Hospital
      • New Orleans, Louisiana, United States, 70112
        • Active, not recruiting
        • University Medical Center New Orleans
    • Mississippi
      • Madison, Mississippi, United States, 39110
        • Active, not recruiting
        • Mississippi Center for Advanced Medicine
    • Missouri
      • Kansas City, Missouri, United States, 64108
        • Not yet recruiting
        • University Health
    • North Carolina
      • Chapel Hill, North Carolina, United States, 27514
        • Not yet recruiting
        • UNC Health
      • Chapel Hill, North Carolina, United States, 27514
        • Not yet recruiting
        • Clinical & Translational Research Center (CTRC)
      • Chapel Hill, North Carolina, United States, 27517
        • Not yet recruiting
        • UNC Eastowne Medical Office Building - Consent Only
      • Morrisville, North Carolina, United States, 27560
        • Not yet recruiting
        • UNC IDS
    • Texas
      • Houston, Texas, United States, 77030
        • Active, not recruiting
        • The University of Texas Health Science Center at Houston
      • Houston, Texas, United States, 77030
        • Active, not recruiting
        • McGovern Medical School at UTHealth
      • Houston, Texas, United States, 77030
        • Active, not recruiting
        • Memorial Hermann Hospital, Texas Medical Center - Clinical Research Unit (CRU)
      • Houston, Texas, United States, 77030
        • Active, not recruiting
        • UT Physicians Comprehensive Sickle Cell Clinic
    • Virginia
      • Fairfax, Virginia, United States, 22031
        • Recruiting
        • Inova Schar Cancer Institute

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

6 months to 65 years (Child, Adult, Older Adult)

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

Part A, Part B, and OLE:

  • Male or female with SCD
  • Participants with stable Hb value as judged by the Investigator
  • For participants taking hydroxyurea and/or L-glutamine, the dose must be stable for at least 90 days prior to signing the ICF or assent and with no anticipated need for dose adjustments during the study in the opinion of the Investigator.

Part B:

  • Participants with SCD ages 12 to 65 years, inclusive
  • Participants with more than or equal to 2 and ≤ 10 VOCs within 12 months of Screening.

OLE:

- Participants who have completed the Part B will be eligible.

Exclusion Criteria:

Part A, Part B, and OLE:

  • Participants who had more than 10 VOC within 12 months of screening
  • Female participant who is breastfeeding or pregnant
  • Participants who receive RBC transfusion therapy regularly or received an RBC transfusion ---for any reason within 90 days of Day 1
  • Participants hospitalized for sickle cell crisis or other vaso-occlusive event within 14 days of signing the ICF or anytime during the screening period.

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: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: Quadruple

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Active Comparator: Part A

Initially, participants will be randomized 1:1 to 100 mg and 150 mg daily. Upon review of the 150 mg safety data from at least 6 participants, there will be 1:1:1 randomization: 100 mg, 150 mg, and up to 200 mg.

Participants will then receive maintenance once daily doses through Week 12.
Drug: Osivelotor
Tablets which contain drug substance
Other Names:
  • PF-07940367 or GBT021601
Placebo Comparator: Part B

Study drug arm: Adult participants will receive osivelotor at 300 mg QD loading dose for 7 days followed by 150 mg QD through Week 48.

Adolescent participant dose will be defined in a future protocol amendment.

Placebo arm: Participants will receive placebo tablets for 48 weeks.
Drug: Osivelotor
Tablets which contain drug substance
Other Names:
  • PF-07940367 or GBT021601
Experimental: OLE

Adult Participants will receive 150 mg open-label osivelotor up to 2 years after the last participant's visit in Part B or when the drug is commercially available in that region.

The appropriate doses for adolescents will be defined in a future protocol amendment.
Drug: Osivelotor
Tablets which contain drug substance
Other Names:
  • PF-07940367 or GBT021601

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Part A
Time Frame: Through week 12
Number of adult participants with change from baseline in hemoglobin (Hb) through week 12 as measured by change in osivelotor concentrations from baseline or percentage change from baseline of clinical measures of anemia Hb and hemolysis (including indirect bilirubin, reticulocytes and lactate dehydrogenase).
Through week 12
Part B
Time Frame: Through week 48

Co-primary endpoints: Hb response (increase from baseline of >1 g/dL) at Week 48 (based on average of Hb levels at Week 40 and Week 48) and the Annualized rate of VOC through end of Week 48.

A VOC is defined as an acute episode of pain that:

  • Has no medically determined cause other than a vaso-occlusive event, and
  • Results in a visit to a medical facility (hospitalization, emergency department, urgent care center, outpatient clinic, or infusion center), and
  • Requires parenteral narcotic agents, parenteral nonsteroidal anti-inflammatory drugs (NSAIDs), or an increase in treatment with oral narcotics.

Complicated VOCs of acute chest syndrome (ACS), hepatic sequestration, splenic sequestration, priapism, and dactylitis that meet the requirements listed above will be included in this co-primary endpoint.
Through week 48
OLE
Time Frame: Approximately 24 months after last patient enrolled

Incidence of Treatment Emergent Adverse Events:

  • Incidence of SAEs
  • Incidence of AEs leading to discontinuation
  • Change from baseline in laboratory parameters.
Approximately 24 months after last patient enrolled

Collaborators and Investigators

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

Sponsor

Pfizer

Collaborators

Pfizer

Investigators

  • Study Director: Pfizer CT.gov Call Center, Pfizer

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Helpful Links

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)

September 22, 2022

Primary Completion (Estimated)

December 30, 2030

Study Completion (Estimated)

December 31, 2032

Study Registration Dates

First Submitted

June 21, 2022

First Submitted That Met QC Criteria

June 21, 2022

First Posted (Actual)

June 24, 2022

Study Record Updates

Last Update Posted (Actual)

March 20, 2026

Last Update Submitted That Met QC Criteria

March 19, 2026

Last Verified

March 1, 2026

More Information

Terms related to this study

Additional Relevant MeSH Terms

Other Study ID Numbers

  • GBT021601-021
  • C5351004 (Other Identifier: Alias Study Number)
  • 2023-508766-14-00 (Registry Identifier: CTIS (EU))

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

YES

IPD Plan Description

Pfizer will provide access to individual de-identified participant data and related study documents (e.g. protocol, Statistical Analysis Plan (SAP), Clinical Study Report (CSR)) upon request from qualified researchers, and subject to certain criteria, conditions, and exceptions. Further details on Pfizer's data sharing criteria and process for requesting access can be found at: https://www.pfizer.com/science/clinical_trials/trial_data_and_results/data_requests.

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

Yes

Studies a U.S. FDA-regulated device product

No

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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