Duration of Platelet Recovery With TPO-RAs

James B. Bussel, MD:Time of response to a TPO-RA is a little bit of a complicated question. With eltrombopag, you typically start, as this patient did, with 50 mg daily. And chances are if the patient is going to respond, they’ll respond within about 2 weeks. If not, they can go to the maximum dose, which is 75 mg daily, and then if they’re going to respond, they would respond within another 2 weeks or perhaps 3 at the most. This is my opinion. I’m not sure there are perfect data on time to response in groups. In groups of patients, when you look at time to response, it’s within 2 weeks. But if you’re asking how long will it take all patients to respond, it might take up to 4 to 5 weeks for those who are going to respond to respond.

With romiplostim, it depends on how you dose. I believe the package insert still says to start with 1 mcg/kg and then go to 2 mcg/kg and then to 3 mcg/kg and then to 4 mcg/kg. So, it could take you 9 weeks or 10 weeks, depending on how you count it, to get to 10 mcg/kg, which is the maximum dose. Most people with experience in practice don’t follow the package insert and start at 3 mcg/kg and then maybe go to 5 mcg/kg and 7 mcg/kg and 10 mcg/kg. So, again, the platelet count should go up in about the same timeframe, let’s say 2 to 5 weeks, if it’s going to go up. Responders receiving a dose to which they’ll respond of either eltrombopag or romiplostim will probably have their count begin to rise at day 4 or 5 and will be obviously higher than baseline by day 7.

Transcript edited for clarity.

Case: A 48-year-old woman presenting with unusual bruising

October 2017

• A 48-year-old woman presents with complaints of bruising after minor bumps, bleeding gums despite regular tooth cleaning, and a recent spontaneous bloody nose; symptom onset about 1 year ago
• Physical evaluation reveals a woman of normal weight and average height, afebrile, no splenomegaly
• No personal or family history of cancer, autoimmune disease; no recent viral illnesses; no bone pain or night sweats
• Current medications: ibuprofen as needed, generic hydrochlorothiazide (HCTZ)
• Laboratory findings:
  • CBC reveals platelets 28 X 10⁹/L
  • WBCs within normal
  • Renal and hepatic function within normal
• Diagnosis: idiopathic thrombocytopenic purpura
• Patient started on a course of prednisone 1 mg/kg for 21 days, then tapered off
  • Platelets: 29 X 10⁹/L
  • Second course of prednisone 1 mg/kg for 21 days

April 2018

• After 2 courses of prednisone, patient’s platelets have not recovered
  • CBC shows platelets at 28 X 10⁹/L
• Symptoms of easy bruising and bleeding from gums continue
• After discussion with patient, she is started on the thrombopoietin receptor agonist (TPO-RA) eltrombopag (PROMACTA), at a dose of 50 mg/day
  • Dose increased to 75 mg/day; last platelet count, 65 X 10⁹/L