Beyond raising platelet counts, the newly approved BTK inhibitor rilzabrutinib provides dramatic improvements in the fatigue associated with ITP. This unique benefit, likely due to its anti-inflammatory properties, makes it a strong consideration for patients where fatigue is a primary quality of life issue.
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Non-covalent BTK inhibitors like pirtobrutinib are currently approved for use after covalent BTK inhibitors fail. Moving them to the frontline setting, as studied in BRUIN-313, disrupts the established treatment pathway and creates uncertainty for managing relapsed disease, as the standard 'next step' is removed.
The target platelet count for ITP patients should be tailored to their lifestyle, bleeding history, and quality of life goals. A normal platelet count is not necessary, and different thresholds are appropriate for different patients (e.g., someone planning a ski trip versus a sedentary individual).
BTK inhibitors function as highly potent antiplatelet agents, an 'on-target' effect. Many surgeons are unaware, leading to significant post-operative bleeding if the drug isn't stopped. Patients must be educated to inform their surgical teams and advocate for themselves.
ITP caused by immune checkpoint inhibitors (ICIs) is rare (0.25% incidence) but generally has a good prognosis. Most patients respond to standard first-line ITP therapies, and approximately 70% of those re-challenged with the ICI can continue treatment without a recurrence of ITP.
The treatment paradigm for ITP is shifting towards early combination therapy. Recent clinical trials are investigating augmented first- and second-line regimens, such as combining dexamethasone with rituximab or romiplostim, to achieve more durable, treatment-free responses than monotherapy.
Pirtobrutinib is the first BTK inhibitor to show a rate of atrial fibrillation equivalent to a chemoimmunotherapy control arm in a randomized trial. This uniquely safe cardiovascular profile makes it a strong first-line candidate for older Chronic Lymphocytic Leukemia (CLL) patients or those with significant heart-related comorbidities.
Early data from the CLL 314 study shows a progression-free survival benefit for pirtobrutinib over ibrutinib in frontline CLL patients. This finding suggests a potential future shift where non-covalent BTK inhibitors could become the initial standard of care.
Patients with ITP who fail or are intolerant to one TPO receptor agonist (e.g., eltrombopag) should not be considered a class failure. Switching to another TPO agent is a viable strategy that can induce a response in nearly half of these cases, particularly for intolerance.
Pirtobrutinib's reduced side effects, like atrial fibrillation, stem from its precise targeting of BTK with minimal 'binding promiscuity' to other kinases. This makes it a safer option for patients who have already been on a less-targeted BTK inhibitor.
In cases of severe ITP unresponsive to standard therapies, the anti-CD38 monoclonal antibody daratumumab can be highly effective. It works by eliminating the long-lived plasma cells responsible for secreting platelet autoantibodies, a mechanism distinct from other ITP treatments.