Skip to content
Clinical Trials – home

Rare diseases

Investigational molecules

Locations

Our offerNewsroom

Not yet recruitingRare disease

Study of GBT021601 for Adults and Children with Sickle Cell Disease

Verified siteInvestigational
Clinical Trials Concierge

Prefer not to search? Our Concierge searches the trials for you.

What is this trial about?

A plain-language summary of the goals, design and what participants do

This clinical trial is focused on studying Sickle Cell Disease, a genetic condition that affects the shape and function of red blood cells. The study will evaluate a treatment called Osivelotor, which is taken orally in the form of a tablet. The purpose of the study is to understand how Osivelotor affects patients with sickle cell disease, particularly looking at changes in hemoglobin levels, which is a protein in red blood cells that carries oxygen throughout the body.

The study is divided into different parts. In one part, adult participants will receive osivelotor to see how it changes their hemoglobin levels over a period of time. Another part of the study will compare the effects of osivelotor to a placebo in both adult and adolescent participants, focusing on hemoglobin response and the frequency of painful episodes known as vaso-occlusive crises. Additionally, there is an open-label part of the study that will look at how osivelotor is processed in the bodies of pediatric participants, which means the participants and researchers know what treatment is being given.

Participants in the study will take the medication for a maximum of 48 weeks, and the effects will be monitored through regular check-ups and tests. The study aims to provide valuable information on the safety and effectiveness of osivelotor for treating sickle cell disease, potentially leading to improved management of this condition in the future.

The research process

The trial runs in 6 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Joining the study

    Upon joining the study, eligibility is confirmed based on specific criteria related to sickle cell disease (SCD).

    Participants are grouped into different parts of the study based on age and health status.

  2. Step 2

    Part A: Initial treatment phase

    Participants receive the medication osivelotor orally.

    The primary goal is to observe changes in hemoglobin (Hb) levels over 12 weeks.

  3. Step 3

    Part B: Comparative treatment phase

    Participants aged 12 and older receive either osivelotor at a dose of 150 mg once daily or a placebo.

    The study measures Hb response and the rate of vaso-occlusive crisis (VOC) events over 48 weeks.

  4. Step 4

    Part C: Pediatric study phase

    Pediatric participants are divided into cohorts based on age, ranging from 6 months to 18 years.

    The study assesses the pharmacokinetics (PK) of osivelotor, which involves understanding how the drug is absorbed, distributed, metabolized, and excreted in the body.

  5. Step 5

    Monitoring and assessments

    Throughout the study, participants undergo regular monitoring of Hb levels, reticulocyte counts, and other health indicators.

    The study also tracks any adverse events and changes in laboratory assessments, electrocardiograms (ECGs), and vital signs.

  6. Step 6

    Completion of study

    The study is expected to conclude by April 2027.

    Final assessments are conducted to evaluate the overall effects of the treatment on participants.

Who can join the trial?

10 criteria

  • The participant must have Sickle Cell Disease (SCD). This means they have a specific type of blood disorder.
  • The participant's SCD genotype must be either HbSS or HbSB. This refers to the specific genetic type of SCD they have, which can be confirmed by a lab test.
  • For Part B, the participant must be 12 years or older. Those aged 12 to under 18 will be included only after safety is checked in younger groups.
  • The participant must have had 2 to 10 VOCs in the past year. VOCs are episodes of pain caused by blocked blood flow.
  • The participant's hemoglobin (Hb) level must be between 5.5 and 10.5 g/dL during the screening. Hemoglobin is a protein in red blood cells that carries oxygen.
  • If the participant is taking hydroxyurea or L-glutamine, their dose must have been stable for at least 90 days before joining the study. These are medications used to treat SCD.
  • For Part C, the participant's age must fit into specific groups:
    • Cohort C1: 12 to under 18 years
    • Cohort C2: 6 to under 12 years
    • Cohort C3: 2 to under 6 years
    • Cohort C4: 6 months to under 2 years

Who cannot join the trial?

8 criteria

  • Participants who do not have Sickle Cell Disease cannot join the study. Sickle Cell Disease is a condition where red blood cells, which carry oxygen, are shaped like a sickle or crescent, causing various health issues.
  • Participants who are not within the specified age range for the study cannot participate. The study includes certain age groups, so those outside these groups are excluded.
  • Participants who are not willing or able to follow the study procedures and requirements cannot take part in the study.
  • Participants who have other medical conditions that might interfere with the study or its results cannot participate.
  • Participants who are currently taking medications that might affect the study outcomes cannot join the study.
  • Participants who are pregnant or breastfeeding cannot participate in the study.
  • Participants who have participated in another clinical trial recently may not be eligible to join this study.
  • Participants who have a history of allergic reactions to the study medication or similar medications cannot take part in the study.
Clinical Trials Concierge

Prefer not to search? Our Concierge searches the trials for you.

Tell us about your condition – we search every trial in Europe and connect you with the right site.

We usually reply within a few days

Verified sites

All sites with verified contact details – recruitment status may not be available; ask directly

Trial locations

Where you can join this trial

Countries are shaded by recruitment status. Click a recruiting country to ask about joining there.

Not yet recruiting
Not finding your country?

Not sure what to do next?

Joining a clinical trial can seem overwhelming. We guide you step by step, so you know exactly what to expect and how we support you through the process.

See the full process and FAQ

Investigated drugs

Osivelotor is a medication being studied for its effects on individuals with Sickle Cell Disease (SCD). It is taken orally and is being evaluated for its ability to improve hemoglobin levels in adults and adolescents with SCD. The study also looks at how the medication affects the frequency of vaso-occlusive crisis (VOC) events, which are painful episodes common in SCD. Additionally, the trial includes a part that examines how the body processes the medication in pediatric participants.

What is already known about the treatment

Osivelotor – Osivelotor is administered orally and is currently being studied in clinical trials for its potential use in treating sickle cell disease. It is in the phase 2/3 stage of clinical trials, indicating that it is being evaluated for both efficacy and safety in a larger group of participants. The main therapeutic indication for osivelotor is sickle cell disease, a genetic blood disorder. At the molecular level, osivelotor works by increasing hemoglobin levels, which may help reduce the frequency of vaso-occlusive crises, a common complication of sickle cell disease. It is classified pharmacologically as a hemoglobin modulator.

Investigated diseases

Sickle Cell Disease – Sickle Cell Disease is a genetic disorder that affects the shape and function of red blood cells. Normally, red blood cells are round and flexible, allowing them to move easily through blood vessels. In Sickle Cell Disease, the red blood cells become rigid and shaped like a crescent or sickle. These sickle-shaped cells can get stuck in small blood vessels, which can slow or block blood flow and oxygen to parts of the body. This can lead to episodes of pain, known as vaso-occlusive crises, and can cause damage to organs over time. The disease is chronic and can vary in severity among individuals.
Trial detailsLast updated 2 Oct 2026
Age18+ yearsPhasePhase IVTrial ID2023-508766-14-00Protocol codeC5351004Estimated enrolment436 patientsSponsorGlobal Blood Therapeutics Inc.

sourced from the EU Clinical Trials Register and site verification

Want to learn more about this trial or check if you can participate?

Clinical Trials Concierge

Prefer not to search? Our Concierge searches the trials for you.

Tell us about your condition – we search every trial in Europe and connect you with the right site.