NCT05431088 · Pfizer
A Phase 2/3 Study in Adult and Adolescent Participants With SCD
What this study is about
The purpose of this study is to evaluate the safety, tolerability, effectiveness, how the drug moves through the body and how the drug affects the body of osivelotor.
View original scientific description
The purpose of this study is to evaluate the safety, tolerability, efficacy, pharmacokinetics and pharmacodynamics of osivelotor.
Interventions
DRUG
Osivelotor
Tablets which contain drug substance
Primary outcome measures
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).
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.
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.
Who can participate
This study lists these criteria on ClinicalTrials.gov. A study coordinator reviews eligibility during screening — this page does not determine whether you qualify.
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.
Where
- Mobile, Alabama
- Hartford, Connecticut
- New Haven, Connecticut
- Plantation, Florida
- West Palm Beach, Florida
- Atlanta, Georgia
- Dunwoody, Georgia
- Riverdale, Georgia
- Chicago, Illinois
- Baton Rouge, Louisiana
- New Orleans, Louisiana
- Detroit, Michigan
And 18 more locations — see the full list below.
Related conditions & keywords
Frequently asked questions
What is a clinical trial?
A clinical trial is a research study that tests new medical treatments, drugs, devices, or procedures to determine their safety and effectiveness. Trials are carefully designed and monitored to protect participants while advancing medical knowledge.
Is it safe to participate?
Clinical trials follow strict safety guidelines and ethical standards. Trials must be reviewed and approved, and participants are closely monitored by medical professionals throughout the study. You can withdraw at any time if you choose.
Will I be compensated?
Many clinical trials offer compensation for your time, travel expenses, and inconvenience. The specific compensation varies by study and will be discussed during the screening process. All study-related medical care is typically provided at no cost to participants.
Will I receive a placebo instead of treatment?
When effective treatment exists, participants typically receive either the standard treatment plus the study intervention, or the standard treatment plus placebo. You would not be denied effective care. Placebos are primarily used when no proven treatment is available, or in addition to standard care. Your trial consent form will clearly explain what treatments you may receive.
Can I leave a trial if I change my mind?
Absolutely. Participation in clinical trials is completely voluntary. You have the right to withdraw from the study at any time, for any reason, without penalty or loss of benefits to which you are otherwise entitled.
How long does a clinical trial last?
Trial duration varies widely depending on the study design and purpose. Some trials last just a few weeks, while others may continue for months or years. The study coordinator will provide specific timeline information during your screening call.
Data: ClinicalTrials.gov · synced Aug 18, 2026 · Source of record for eligibility and locations