Generic name: treosulfran
Dosage form: vial lyophilized powder (1g/vial, 5g/vial)
Drug class: Alkylating agents

Medically reviewed by Melisa Puckey, BPharm. Last updated on Mar 31, 2025.

What is Grafapex?

Grafapex (treosulfan) is a medicine used as a preparation treatment before stem cell transplantation (allogeneic hematopoietic) in patients with acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS). It is used in combination with fludarabine. Grafapex helps destroy any remaining cancer cells in the body and weakens the patient's immune system so that the donor stem cells are not rejected. Allogeneic hematopoietic stem cell transplantation (alloHSCT) is when you receive stem cells from the blood or bone marrow from a donor who is genetically similar to you.  

Grafapex is given as an intravenous infusion that is given daily for three days, beginning on Day - 4 before the transplantation (Day 0 is the day you will have your stem cell infusion), it is used in combination with fludarabine therapy.

Grafapex FDA approval was granted on January 22, 2025, as a preparative regimen for allogeneic hematopoietic stem cell transplantation (alloHSCT) in adult and pediatric patients 1 year of age with:

• acute myeloid leukemia (AML)
• myelodysplastic syndrome (MDS).

How does Grafapex work?

Grafapex mechanism of action is an alkylating agent that works by adding an alkyl group to DNA structure to kill cells, which results in depleting hematopoietic stem cells, antitumor activity, and its immunosuppressive effects.

How well does Grafapex work?

Grafapex was FDA-approved after positive results from the clinical trial MC-FludT.14/L Trial II (NCT00822393) which demonstrated an increase in overall survival (OS) for Grafapex compared to busulfan. 

The hazard ratio for OS (stratified by donor type and risk group) comparing Grafapex to busulfan was: 

• 0.67 (95% CI: 0.51, 0.90) in the randomized population
• 0.73 (95% CI: 0.51, 1.06) in patients with AML
• 0.64 (95% CI: 0.40, 1.02) in patients with MDS.

The hazard ratio of less than one means that Grafapex patients' survival time was better than the busulfan group.

Grafapex side effects

The common Grafapex side effects are: 

• Muscle and joint pain (39%) 
• Inflammation of mouth or lips (38%) stomatitis 
• Fever (34%)
• Nausea (33%)
• Edema (29%)
• Infection (23%) 
• Vomiting (22%)
• Rash (17%)
• Diarrhea (17%)
• Headache (16%)
• Febrile neutropenia (15%)
• Abdominal pain (15%).

The above common side effects are the side effects that occurred in 15% or more of Grafapex patients in Study MC-FludT.14/L Trial II.

This medicine also has caused nonhematological laboratory abnormalities (grades 3-4), including increases in alanine aminotransferase, gamma-glutamyl transferase (GGT), bilirubin, aspartate aminotransferase, and creatinine.

Also, see the Warnings section.

This is not a complete list of side effects, and others may occur. Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088

Related/similar drugs

Warnings

Grafapex warnings and precautions

• Bone marrow suppression, you will have regular blood cell counts and be monitored for infections, anemia, and thrombocytopenia (low platelets)
• Seizures
• Injection site reactions that may cause tissue death
• Skin disorders
• Secondary cancers
• Increased early morbidity and mortality and higher doses than the recommended dose
• Embryo-fetal toxicity - It can cause fetal harm. Patients of reproductive potential should use effective contraception. See the Pregnancy section below for more details for males and females.

Who should not take this medicine?

You should not use this medicine if you have a hypersensitivity or allergy to any of the ingredients in this medication.

Before taking this medicine

Before taking this medicine tell your doctor or prescriber about all of your medical conditions.

Pregnancy

Tell your doctor or healthcare provider if you are pregnant or planning a pregnancy as this medicine can cause fetal harm due to its toxic effects, it may be embryotoxic and teratogenic. 

Patients who are able to become pregnant should use effective contraception during treatment and for up to 6 months after treatment, and have a negative pregnancy test 7 days before starting  this medicine

Males with female partners who are able to become pregnant. Males should use effective contraception during treatment and until 3 months after the last dose. 

Infertility. This medicine can impair fertility in females and males and may cause temporary or permanent infertility.

Breastfeeding

You should not breastfeed during treatment with this medicine and for 1 week after, due to the potential for serious adverse reactions in breastfed children.

How will I receive this medication?

Grafapex is given as an intravenous infusion every 3 days starting on Day -4 (Day 0 is the day you will have your stem cell infusion).

• Grafapex and fludarabine infusions are given before your allogeneic hematopoietic stem cell infusion. 
• Grafapex infusion is 3 doses given from day -4 to day -2.
• Fludarabine infusion is 5 doses given from day -6 to day -2.
• You have your hematopoietic stem cell transplantation on day 0.
• You will usually be prescribed an anti-nausea medicine before your first dose of Grafapex and continue until your last dose. 

Grafapex treatment regime

Dosing information

Recommended Grafapex dose is 10 g/㎡ by intravenous infusion daily for 3 days starting on Day -4. It is infused over 2 hours. Day 0 is the day of stem cell infusion.

Grafapex is available as 1g/vial and 5 g/vial treosulfan as a lyophilized powder in a single-dose vial that needs to be reconstituted.

Interactions

Effect of Grafapex on other medicines:

Certain CYP2C19 and CYP3A4 substrates. If minimal concentration changes may cause serious or life-threatening toxicities you may need to reduce the dosage as needed.

Grafapex is a CYP2C19 and CYP3A4 inhibitor. Using Grafapex is predicted to increase the exposure of CYP2C19 and CYP3A4 substrates and may increase the risk of their side effects

This list is not complete. Many other drugs may interact with this medicine including prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible interactions are listed in this medication guide.

Grafapex Prescribing Information  

HCPs and patients often use the Grafapex Prescribing Information (PI) for more detailed information about this medicine. The Grafapex Prescribing Information contains more comprehensive information on Indications and Usage, Dosage and Administration, Clinical Pharmacology, Clinical Studies, Drug Interaction, and more. Discuss any medical questions you have with your HCP (health care professional). This is not all the information you need to know about this medicine for safe and effective use, and it does not take the place of talking to your doctor about your treatment.

The Package Insert is sometimes called Grafapex Package Insert or FDA label.

Storage

Vials: 

• 20°C to 25°C with exclusions permitted between 15°C and 30°C.

Reconstituted solution: 

• room temperature 20°C to 25°C (68°F to 77°F) for up to 24 hours. 
• Do not use if the solution contains precipitate. 
• Do not refrigerate.

Company

Medexus Pharma, Inc., Chicago, Illinois 60606 USA.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Medical Disclaimer