Wayrilz (rilzabrutinib)

Wayrilz is for adults whose ITP did not respond well enough to an earlier treatment. It acts on the immune attack on platelets, while TPO receptor agonists work by boosting platelet production. Its approval rested on a placebo-controlled trial, so the label has no head-to-head data against other ITP drugs.

In ITP, the immune system makes antibodies that coat platelets. Immune cells in the spleen and liver grab the coated platelets through receptors called Fc-gamma receptors and destroy them, while B cells keep producing the antibodies. Both processes rely on an enzyme called Bruton's tyrosine kinase (BTK). Rilzabrutinib blocks BTK, which the label says both dampens B cell activation and interrupts the destruction of antibody-coated cells in the spleen and liver. It leaves the bloodstream within hours, but because it lets go of BTK slowly, its effect on the target lasts through the day^[1].

Wayrilz has no boxed warning and no contraindications. In the LUNA 3 trial, the most common side effects against placebo were diarrhea (32% against 10%), nausea (20% against 6%), headache (18% against 7%), abdominal pain (14% against 1%) and COVID-19 (14% against 4%). The stomach and bowel side effects were all mild to moderate, and with supportive care they settled while treatment continued in 91% of patients with diarrhea, 85% with nausea and 79% with abdominal pain. Mild to moderate neutropenia, a low count of infection-fighting white blood cells, occurred in 11%. Side effects led 4.5% to stop. The label warns about serious infections (1 trial patient died of pneumonia), liver injury, which can be severe or fatal with BTK inhibitors, and possible harm to an unborn baby based on animal studies^[1].

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Approved for adults with persistent or chronic ITP who had an insufficient response to a previous treatment. Safety and effectiveness in children have not been established; the adolescent part of LUNA 3 was still ongoing at approval. Not recommended with moderate or severe liver impairment or severe kidney impairment. LUNA 3 enrolled people whose response to IVIG, anti-D or steroids did not last, or who had an insufficient response to or could not tolerate other standard ITP therapy.

Source: HemAssist Sanofi Support for Wayrilz

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LUNA 3 (NCT04562766) randomized 202 adults with persistent or chronic ITP, 2 to 1, to Wayrilz 400 mg twice daily or placebo for up to 24 weeks. Most had long-standing disease (93% chronic, median 7.7 years since diagnosis), had tried a median of 4 earlier therapies, and started with a median platelet count of about 15,000 per microliter; 60% of the Wayrilz group also took stable doses of oral steroids or TPO receptor agonists. A durable platelet response, meaning weekly counts of at least 50,000 in at least two-thirds of checks during the last 12 weeks without rescue treatment, occurred in 23% (31 of 133) on Wayrilz against 0% (0 of 69) on placebo. Patients on Wayrilz had a platelet response for 7.2 of 24 weeks on average against 0.7 weeks on placebo, reached a first response in a median of 36 days, and needed rescue medicine less often (33% against 58%)^[1][5].

Principia Biopharma developed rilzabrutinib under the code PRN1008 and is now listed as a Sanofi company^[6]; Sanofi agreed to acquire Principia in August 2020, naming rilzabrutinib among the drugs it would gain^[4]. The FDA received the Wayrilz application on August 29, 2024 and approved it on August 29, 2025 for adults with persistent or chronic ITP who had an insufficient response to a previous treatment^[2]. Sanofi said it had FDA Fast Track and orphan drug designations for ITP, and that rilzabrutinib is also being studied in warm autoimmune hemolytic anemia, IgG4-related disease and sickle cell disease^[3].