Catalyst Biosciences provides update on the ongoing Phase 1/2 trial investigating its next generation Factor IX candidate CB 2679d/ISU304 for the treatment of severe hemophilia B
- In April 2018, the Phase 1/2 trial, which is being conducted by Catalyst's collaborator ISU Abxis in South Korea, was amended to add a Cohort 6. In this cohort, each patient receives a single loading dose of 75 IU/kg CB 2679d/ISU304 given intravenously, followed by nine daily subcutaneous doses of 150 IU/kg CB 2679d/ISU304, starting half an hour after the intravenous dose. To date, Cohort 6 has enrolled two patients out of a planned three to five and has shown promising efficacy in both. During the treatment period, FIX activity levels always remained above 20% after the IV loading dose in both patients. The first patient then had a progressive increase in trough FIX activity level to 34% and the second patient to a trough activity level of 31%. Patients with FIX levels between 5% and 40% are considered to have mild hemophilia, according to the World Federation of Hemophilia.
- Subsequent blood samples showed the presence of a transient neutralizing antibody in one patient and a neutralizing antibody in the second. Importantly from a safety perspective, the antibodies do not bind to wildtype FIX allowing both patients to successfully resume treatment with their prescribed intravenous FIX prophylaxis therapies; the patients have not experienced any bleeds or other safety issues and are being closely monitored. Prior to Cohort 6, no CB 2679d neutralizing antibodies had been detected in any of the patients treated with CB 2679d/ISU304, including both patients in Cohort 6 who had also participated in Cohort 5.
- Catalyst is conducting an analysis to assess the cause and impact of the antibody observations prior to dosing any further subjects in Cohort 6.
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