Pharmacokinetics of daclizumab



Daclizumab high-yield process (DAC HYP), a humanized immunoglobulin G1 monoclonal antibody specific for the α subunit (CD25) of the high-affinity interleukin-2 receptor, has demonstrated efficacy for treatment of relapsing forms of multiple sclerosisin Phase II and III clinical trials.


To characterize the pharmacokinetics (PK) of DAC HYP following repeated administration of the 150 mg subcutaneous (SC) dose every 4 weeks (q4wk), the proposed clinical regimen in patients with relapsing-remitting multiple sclerosis (RRMS).


Twenty-six patients with RRMS received DAC HYP 150 mg SC q4wk for a total of six doses. Serial PK blood samples were collected over the first and last dosing intervals and trough PK samples were collected between these doses. Blood samples for immunogenicity assessment were collected throughout the study. Serum DAC HYP levels and anti-DAC HYP antibodies were characterized using validated immunoassays. PK parameters were estimated using noncompartmental analysis.


DAC HYP showed slow SC absorption with a median time to reach maximum observed concentration (Cmax) value of ~1 week. Steady state was reached by the fourth injection. At steady state, DAC HYP mean serum Cmax, minimum observed concentration (Cmin), and area under the concentration-time curve within a dosing interval (AUCtau) values were 29.1 µg/mL, 14.9 µg/mL, and 638 µg · day/mL, respectively, with intersubject variability of 35%-40%. The AUC accumulation ratio was ~2.5 at steady state. DAC HYP had a long elimination half-life of ~22 days and low apparent clearance (0.274 L/day). Nine patients tested positive for anti-DAC HYP antibodies, with no impact on DAC HYP clearance in this limited data set.


The PK of DAC HYP in patients with RRMS are consistent with those previously reported in healthy volunteers. The half-life of ~3 weeks and the low fluctuations in peak and trough concentrations of serum DAC HYP support the once-monthly SC dosing regimen.

So there you have it when Daclizimab HYP arrives it will be once a month under the skin and in six doses 9/35 (34%) people made an antibody response. Whilst it is said these had no impact on clearence it will be interesting to see if skin reactions are an issue. If the antibodies hit the binding site then they could neutralise the response. It is interesting that these so called humanised antibodies are immunogenic and create an immune response against themselves. 34% in 6 months is small fry in comparison to alemtuzumab where 30% of people make antibodies with the first month and 75% of people make antibodies within the year. This is staggering for a humanized protein. I wonder if it says something about the antibody and maybe autoantibodies to the drug itself is similar to the autoantibodies to the human tissues casing autoimmunity.

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  • MD, thanks for very interesting, thought-provoking comments. The immune system likes multiple triggers, T cell activation is the obvious example. I have not seen multiple antibodies in a similar context, but after all, in MS, the antibody bands are OLIGOclonal. Don't know what it means, but it may be somehow relevant to the lack of an identifiable single antigen.

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