- Myelofibrosis patients have an increased risk of low platelet count.
- Scientists conduct clinical trials to study the efficacy and safety of pacritinib drug for myelofibrosis by comparing it with standard therapies.
- Pacritinib drug shows potential advantage in reducing the spleen size and symptoms of myelofibrosis.
Pacritinib drug was found to significantly reduce the spleen size in myelofibrosis patients, who are with very low levels of platelets. A recent study compared the effectiveness of pacritinib with standard therapy in treating myelofibrosis patients.
The research study was presented at the 58th American Society of Hematology (ASH) Annual Meeting and Exposition in San Diego, California.
The researchers also found that patients who took twice daily dose of oral multikinase inhibitor drug show improvement in symptoms.
Patients with an enlarged spleen are at a higher risk of infection, anemia, bleeding, weight loss and abdominal discomfort. Effective treatment options for reducing the spleen size is required for these patients.
A Phase III clinical trial study was carried out to compare the efficacy and safety of pacritinib drug along with standard therapies like ruxolitinib drug.
Ruxolitinib is a JAK2 inhibitor which was approved by the FDA for high risk myelofibrosis. However the drug may lead to complications when used by patients with low platelet counts (under 50,000 per microliter).
John Mascarenhas, MD of Tisch Cancer Institute, Icahn School of Medicine at Mount SInai, New York said "Despite the fact that these patients have very low platelet counts and in approximately 45 percent of the cases had previously been treated with ruxolitinib, we were able to administer this drug effectively, thereby significantly reducing spleen volume and also significantly improving symptoms in a subset of patients who received pacritinib twice daily."
"This is a very vulnerable patient population. My hope is that pacritinib might become an option for them because even though ruxolitinib is well tolerated, one of the downsides is often myelosuppression, and many patients with myelofibrosis start with low baseline platelet counts."
The research team aims to provide more data to optimize dose for pacritinib drug. The FDA also imposed clinical trials on the drug to control the risk of bleeding and heart events.
The data analysis found 10, 15 and 14 patients died in pacritinib twice daily, once daily and best available treatment options respectively. And the effects of cardiac and bleeding events were found to be rare and comparable.
Dr. Mascarenhas, said, "The safety profile remains reasonable given the fact that we are treating patients with low platelet counts who are already at risk for both bleeding and cardiac events."
The research study was conducted on 221 patients from the intended 311 patients with platelet count of 100,000 microliter. These patients were randomly given pacritinib drug 200mg twice daily, 400mg once daily or best available therapy.
Around half of the patients who took part in the study, had a platelet count of less than 50,000 microliter. 41% of pacritinib group and 46% of best available therapy group were found to be the proportion of patients who took ruxolitinib drug.
The percentage of patients having a 35% or a greater reduction in spleen size was measured using a MRI or CT scan. Improvement of symptoms for fatigue, bone pain, abdominal pain were also noted.
The findings show 18% of patients who took pacritinib drug to achieve a 35% greater reduction in spleen size compared to the 3% from best available therapy.
32 % of patients who took twice daily of pacritinib drug were found to show a 50% or more reduction in symptoms when compared to 14% of the patients from best available therapy.
Pacritinib drug inhibits JAK 2 and FLT3 enzymes which may influence the clinical efficacy and side effects.
Dr. Mascarenhas said, "The fact that there are other kinases that are inhibited beyond JAK2 may potentially explain why, for example, we saw 25 percent anemia response in PERSIST-1 with this drug that was not seen with ruxolitinib."
Common side effects of pacritinib drug include
- Low platelet count