Long-Term Extension Data Support Durable Benefit of Rilzabrutinib in Persistent, Chronic ITP: David Kuter, MD, DPhil

Last August, the FDA approved rilzabrutinib (Wayrilz; Sanofi) as a first-in-class treatment for immune thrombocytopenia (ITP), a rare autoimmune disorder characterized by platelet counts below 100,000/μL, driven by both increased platelet destruction and decreased production.

Rilzabrutinib is an oral, reversible covalent Bruton tyrosine kinase (BTK) inhibitor. By selectively inhibiting BTK, rilzabrutinib may reduce disease activity while minimizing the risk of off-target adverse effects.

The decision was based on results from the randomized, multicenter phase 3 LUNA 3 study (NCT04562766), which evaluated the efficacy and safety of rilzabrutinib vs placebo in adults and adolescents with persistent or chronic ITP. Findings demonstrated rilzabrutinib's superiority over placebo, with a 29% durable platelet response rate and improved quality-of-life metrics.

At the European Hematology Association 2026 Congress in Stockholm, Sweden, David Kuter, MD, DPhil, LUNA3 investigator and director of clinical hematology at Massachusetts General Hospital, will present long-term extension (LTE) data from the LUNA3 trial. Ahead of the meeting, he spoke with The American Journal of Managed Care^® about the findings and their impact.

In a population that had lived with ITP for an average of 10 years and failed multiple prior therapies, the LTE data show that 23% to 28% of patients achieved meaningful platelet count elevations that were sustained throughout the observation period, with a median follow-up of approximately 600 days across the extension cohort.

Beyond platelet counts, Kuter noted that the drug reduced bleeding risk and produced clinically meaningful improvements in fatigue, which he considers an underappreciated burden in ITP. A notable secondary finding was that many patients were able to taper or discontinue concurrent ITP therapies, including steroids and thrombopoietin receptor agonists (TPO-RAs), during the open-label extension phase. This was not protocol mandated; rather, Kuter said it reflected real-world clinical decisions by investigators and patients, suggesting rilzabrutinib can sustain its effect as monotherapy.

The safety profile remained consistent with earlier, shorter-duration studies. No new adverse events emerged over the extended follow-up, and no patients discontinued due to toxicity. Compliance reached 99%, which Kuter attributed to tolerability, as patients who are not troubled by a medication tend to stay on it.

He drew particular attention to the implications for earlier-stage disease. Because the LUNA3 population represented the most refractory patients, responses in earlier disease, such as the persistent phase (3-12 months), are expected to be at least as robust. Preliminary data already suggest response rates exceeding 50% in persistent ITP; prospective studies in that population are ongoing.

Kuter emphasized that 2 features may position rilzabrutinib favorably against existing standards of care: a median time to response of approximately 12 days, which is notably faster than some agents currently in development, and activity that appears comparable with TPO-RAs in earlier-phase patients. Together, he argued, the LTE findings and emerging data in less refractory populations suggest rilzabrutinib could offer a durable, well-tolerated option across the ITP disease continuum.

“If response rates are as robust as they appear to be in our brief vignette… I expect this medication to have response rates that are equivalent to the current standard of care, which are TPO-RAs,” he concluded. “Furthermore, this drug's time to response, which is a median of 12 days, shows that it works rapidly, whereas other medications under development may take weeks or months to show an effect.”