AMSTERDAM – Rozanolixizumab, a subcutaneous antibody for the human neonatal Fc receptor, provides clinically meaningful improvements in platelet count for patients with primary immune thrombocytopenia, according to results from a recent phase 2 trial.
Dr. Tadeusz Robak
Rozanolixizumab was well tolerated across all dose groups, with higher doses delivering faster responses, reported lead author Tadeusz Robak, MD, PhD, of the Medical University of Lodz (Poland).
Targeting the Fc receptor interrupts recirculation of IgG, a key autoantibody in immune thrombocytopenia (ITP) pathogenesis, Dr. Robak explained during a presentation at the annual congress of the European Hematology Association. This approach represents an emerging treatment paradigm, he said, noting that rozanolixizumab is also being studied for the treatment of other IgG-driven autoimmune diseases, such as myasthenia gravis and chronic inflammatory demyelinating polyneuropathy.
The present open-label, dose-escalation study involved 54 adult patients with primary ITP of at least 3 months duration and platelet counts of less than 30 x 109/L at screening and 35 x 109/L at baseline. Eligibility required a previous response to ITP therapy. Enrolled patients were randomized into four dose groups: 4 mg/kg (five doses), 7 mg/kg (three doses), 10 mg/kg (two doses), or 15 mg/kg (one dose). After dosing, patients were followed for 8 weeks. Clinically relevant efficacy was defined as a platelet count of at least 50 x 109/L. Decreases in IgG were also reported.
A safety analysis showed that the regimen was well tolerated across all dose groups. In total, 20.4% of patients experienced at least one treatment-related adverse event. The most common adverse events were headache (31.5%), diarrhea (11.1%), and vomiting (3.7%); all of which were mild or moderate. Headache appeared to be dose related, as 42% of patients in the 15-mg/kg group reported headache, compared with 8% in the 10-mg/kg group, 7% in the 7-mg/kg group, and none in the 4-mg/kg group. Out of four reported serious adverse events, none were considered treatment related.
Concerning efficacy, higher doses were associated with higher response rates and faster response times. In the 4-mg/kg group, 33% of patients achieved a platelet count of at least 50 x 109/L, compared with 33% of the 7-mg/kg group, 50% of the 10-mg/kg group, and 67% of the 15-mg/kg group. Of the patients that achieved clinically meaningful responses, 20% of the 4-mg/kg group did so within 8 days, compared with 40% of 7-mg/kg responders, 50% of 10-mg/kg responders, and 87.5% of 15-mg/kg responders. Additional observations included dose-dependent decreases in IgG titer and longer response durations after multiple lower doses.
“Data from this study indicate that we can achieve effective increases in platelet levels, we can observe decreasing IgG levels, and the treatment was safe for the patients,” Dr. Robak said.
When asked about the intended clinical application of rozanolixizumab, Dr. Robak suggested that the agent may have a role in the postacute care setting. “We should develop a method of prolonged administration of [rozanolixizumab], as we saw that lower, multiple doses gave longer response durations.”
Still, he noted that more research is needed, since responses in diverse patient populations remain unknown. “We do not know how the drug will be active in truly refractory patients and we need this response before we establish the indication for the drug.”
The investigators reported financial relationships with Celgene, Roche, GlaxoSmithKline, Amgen, AbbVie, and other companies.
SOURCE: Robak T et al. EHA Congress, Abstract S850.