“Janus kinase (JAK) inhibitors, a type of medication that suppresses the activity of Janus kinase family of enzymes, could delay the natural progress of a rare disease called polycythemia vera (PV).”

So said Claire Harrison, a hematology consultant at Guy’s and St. Thomas’s NHS Foundation Trust, London, U.K., while explaining what JAK inhibitors could do in PV patients, at a media education session provided by Novartis Korea in Yeouido, Seoul, Thursday.

PV is a blood cancer in which bone marrow makes too many red blood cells. Excessive red blood cells cause various symptoms, and in severe cases, they can include dizziness, ear noise, headache, and failing of eyesight. PV also causes serious cardiovascular complications such as thrombosis, stroke, and heart attack.

PV is a rare disease that occurs in two or three people per 100,000 annually, mainly in the 60-89 age group.

Claire Harrison, a hematology consultant at Guy’s and St. Thomas’s NHS Foundation Trust, London, U.K., speaks at a media education session provided by Novartis Korea in Yeouido, Seoul, Thursday.

“Among PV patients, 80 percent of them get medications, but one in three patients of them develops resistance to existing medicines or suffer toxicity problem,” Harrison said. “The bigger problem is that physicians don’t ask about the quality of life of PV patients. It is important to keep the symptoms from getting worse.”

She introduced the results of the study on Novartis’ treatment Jakavi (ruxolitinib), saying JAK inhibitors will not only improve PV patients’ quality of life but help prolong their lives.

According to the RESPONSE study in PV patients, 60 percent of the group treated with Jakavi maintained the hematocrit control at the 32nd week. Thirty-eight percent of the patients had at least a 35 percent reduction in spleen volume.

In contrast, in the patient group treated with the best available therapy (BAT), or the standard treatment, only 1 percent of the patients had the hematocrit control and a reduction in spleen volume. After the 32nd week, 99.1 percent of the BAT group (111 out of 112) discontinued the standard treatment due to insufficient efficacy and 98 of them switched to Jakabi treatment. After 32 weeks, 79.2 percent of the patients did not undergo phlebotomy, and 18.8 percent of them had a more than 35 percent reduction in spleen volume, compared to the baseline.

At the 208th week, 37 percent of patients treated with Jakavi and those who switched to Jakavi continued the treatment, and 30 percent of patients completed the therapy.

“I think that JAK inhibitors can even control the natural progress of the disease because JAK inhibitors already proved that they could lower mortality by five or six times in patients with severe PV who had failed in the (commonly used) hydroxyurea treatment,” Harrison said. “If we can use JAK inhibitors at an early stage, before using hydroxyurea, we could curb the worsening of the disease.”

Researchers in Europe are conducting a large-size study to evaluate the effectiveness of the early use of JAK inhibitors, she added.

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