Blood Cancer Drug Decreases Levels of Anti-Fungal Medication

Tibsovo (ivosidenib), which is used to treat patients with IDH1-mutant acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS) — both of which are types of blood cancer — increases the way that the body processes certain anti-fungal drugs, leading to a decreased concentration of these medications in the body, according to recent research published in the journal, Cancer.

The researchers took 78 samples from 31 patients who were taking Tibsovo and an antifungal medication (Noxafil [Posaconazole] or Vfend [voriconazole]). Findings showed that 47 samples (60%) had subtherapeutic levels of Noxafil or Vfend, indicating that the levels in the blood were lower than what was prescribed to effectively treat or prevent infection.

According to the American Cancer Society, infection is one of the major risks for patients with cancer, as both the disease and its treatments can negatively impact the immune system, making patients more susceptible to becoming infected.

READ MORE:Follow-Ups Help Prevent ‘Dangerous’ Outcomes in Blood Cancer Survivors

CURE® recently spoke with study author, Dr. Caitlin Rausch, a clinical pharmacy specialist at The University of Texas MD Anderson Cancer Center, about what patients with MDS or AML need to know about these findings.

CURE®: Can you give a patient-friendly overview of your study, and why it was important to conduct?

Rausch: This study looked at whether [Tibsovo], a targeted therapy used for patients with AML with an IDH1 mutation, interacted with two antifungal medications commonly used in this population, [Vfend] and [Noxafil]. Patients with AML are frequently prescribed [Vfend] or [Noxafil] either for the treatment or prevention of invasive fungal infections. Serum levels of each of these medications are checked to ensure they are within the range necessary for the prevention or treatment of infection.

[Tibsovo] can reduce the amount of these medications in a patient’s body by increasing the metabolism of these medications. We evaluated serum levels of these medications in patients who were receiving [Tibsovo] and those who were not to see if concomitant use of [Tibsovo] significantly reduced serum levels. It is valuable to understand the severity of this interaction so we can know which antifungal is most appropriate to use while patients are receiving [Tibsovo].

Do patients with MDS/AML already have an increased risk for fungal infections? Why?

Yes, patients with newly diagnosed AML receiving intensive chemotherapy and those with relapsed disease are at an increased risk for fungal infections. These patients experience prolonged periods of neutropenia, a specific component of our white blood cells important for fighting disease, as a result of their chemotherapy as well as their underlying disease. Patients with high-risk MDS are at a similarly increased risk if their disease is being treated with AML-like therapy.

With these findings, what do patients now need to know about their risk of fungal infections while being treated with [Tibsovo]?

Treatment with [Tibsovo] itself does not increase the risk of fungal infections in these patients. If patients are receiving [Tibsovo] in combination with an antifungal, they should make sure their antifungal levels are being monitored and in the range their treating team is aiming for.

This research illustrates the complexity of drug interactions with both chemotherapy and other medications. It is important for patients to reach out to their oncology teams if they are prescribed or wish to start any new prescription medication or herbal supplement to ensure there are no known interactions.

For more news on cancer updates, research and education, don’t forget to subscribe to CURE®’s newsletters here.