David Saperstein, MD
Co-Director GBS/CIDP Center of Excellence
Phoenix Neurological Associates
Intravenous immunoglobulin (IVIg) is one of the main therapies used to treat CIDP. This therapy can be very effective but there are drawbacks. Some people experience headaches related to the intravenous infusions. Some people have difficulty with IV access. Also, the need for IV infusions lasting several hours one or more days every month can prove burdensome with respect to work or travel. In recent years there has been growing interest in infusing immunoglobulin through the skin in a process called subcutaneous administration (subcutaneous immunoglobulin, or SCIg). SCIg is commonly used in patients with immunodeficiency. SCIg is administered by patients themselves at home. Infusions are generally given in the fat under the skin in the stomach or thighs. Over the last few years there have been small studies of SCIg in patients with CIDP. It has become a popular strategy for treating CIDP in Europe and has been used in some patients in the United States. Several brands of IVIg can be given subcutaneously, but there are a couple of products made specifically for subcutaneous administration. These are 20% in concentration, in contrast to most IVIg products which are 10%. The more concentrated 20% products allow infusions to be completed in just a couple of hours one or two days each week. Unlike IVIg which is usually given in a big dose several weeks apart, SCIg must be administered every week).
The FDA recently approved a 20% formulation of SCIg called Hizentra for maintenance treatment of CIDP. This is based on the results of a large international study of Hizentra called the PATH study (for polyneuropathy and treatment with Hizentra). One hundred and seventy-two patients from North America, Europe, and Asia were studied. These were all patients who were receiving regular maintenance treatment with IVIg. To be eligible to participate in the PATH study, patients had to demonstrate that they needed regular treatment with IVIg. This required them to come off of IVIg and display objective worsening within 12 weeks. Of 245 patients taken off of IVIg, all but 28 worsened within 12 weeks. Ultimately, 172 patients were enrolled. 57 received low dose SCIg (0.2 grams per kilogram per week), 58 received high dose SCIg (0.4 grams per kilogram per week) and 57 received placebo (albumin protein solution). The patients were watched closely over the next 6 months. The main outcome was to see how many patients in each group worsened. Since each patient in the study had already shown that they worsened when coming off of regular IVIg treatments it was assumed that most of the patients in the placebo group would worsen. Interestingly, only 63% did. It is not clear why more did not. Nevertheless, many more patients in the placebo group relapsed over 6 months compared to patients who got SCIg (39% in the low dose group and 33% in the high dose group). Both dose groups did significantly better than placebo, but there was no significant difference between the low and high dose groups. Not surprisingly, the patients receiving SCIg had more skin irritation than patients getting placebo (19% in the low dose group, 29% in the high dose group and 7% in the placebo group). However, much fewer patients experienced reactions to Hizentra than they did to IVIg.
Approximately 90% of subjects rated the SCIg injection process as being easy to learn. About 53% of patients receiving SCIg preferred this treatment to IVIg, citing increased independence and less side effects.
Anybody with CIDP currently receiving IVIg could potentially be switched to SCIg. Of course, if the IVIg is working fine there is no reason to change anything. SCIg is a particularly appealing option for patients who get side-effects such and headaches or nausea from IVIg, who have trouble with IV access, or who prefer to have control of their treatment. Another advantage of SCIg is that it can be stored at room temperature, so people can easily take it with them if they are travelling.